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6967 lines
199 KiB
6967 lines
199 KiB
// SPDX-License-Identifier: GPL-2.0 |
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/* |
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* INET An implementation of the TCP/IP protocol suite for the LINUX |
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* operating system. INET is implemented using the BSD Socket |
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* interface as the means of communication with the user level. |
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* |
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* Implementation of the Transmission Control Protocol(TCP). |
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* |
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* Authors: Ross Biro |
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* Fred N. van Kempen, <[email protected]> |
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* Mark Evans, <[email protected]> |
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* Corey Minyard <[email protected]> |
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* Florian La Roche, <[email protected]> |
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* Charles Hedrick, <[email protected]> |
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* Linus Torvalds, <[email protected]> |
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* Alan Cox, <[email protected]> |
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* Matthew Dillon, <[email protected]> |
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* Arnt Gulbrandsen, <[email protected]> |
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* Jorge Cwik, <[email protected]> |
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*/ |
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|
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/* |
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* Changes: |
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* Pedro Roque : Fast Retransmit/Recovery. |
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* Two receive queues. |
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* Retransmit queue handled by TCP. |
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* Better retransmit timer handling. |
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* New congestion avoidance. |
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* Header prediction. |
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* Variable renaming. |
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* |
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* Eric : Fast Retransmit. |
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* Randy Scott : MSS option defines. |
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* Eric Schenk : Fixes to slow start algorithm. |
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* Eric Schenk : Yet another double ACK bug. |
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* Eric Schenk : Delayed ACK bug fixes. |
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* Eric Schenk : Floyd style fast retrans war avoidance. |
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* David S. Miller : Don't allow zero congestion window. |
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* Eric Schenk : Fix retransmitter so that it sends |
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* next packet on ack of previous packet. |
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* Andi Kleen : Moved open_request checking here |
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* and process RSTs for open_requests. |
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* Andi Kleen : Better prune_queue, and other fixes. |
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* Andrey Savochkin: Fix RTT measurements in the presence of |
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* timestamps. |
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* Andrey Savochkin: Check sequence numbers correctly when |
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* removing SACKs due to in sequence incoming |
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* data segments. |
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* Andi Kleen: Make sure we never ack data there is not |
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* enough room for. Also make this condition |
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* a fatal error if it might still happen. |
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* Andi Kleen: Add tcp_measure_rcv_mss to make |
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* connections with MSS<min(MTU,ann. MSS) |
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* work without delayed acks. |
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* Andi Kleen: Process packets with PSH set in the |
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* fast path. |
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* J Hadi Salim: ECN support |
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* Andrei Gurtov, |
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* Pasi Sarolahti, |
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* Panu Kuhlberg: Experimental audit of TCP (re)transmission |
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* engine. Lots of bugs are found. |
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* Pasi Sarolahti: F-RTO for dealing with spurious RTOs |
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*/ |
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|
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#define pr_fmt(fmt) "TCP: " fmt |
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|
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#include <linux/mm.h> |
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#include <linux/slab.h> |
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#include <linux/module.h> |
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#include <linux/sysctl.h> |
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#include <linux/kernel.h> |
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#include <linux/prefetch.h> |
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#include <net/dst.h> |
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#include <net/tcp.h> |
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#include <net/inet_common.h> |
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#include <linux/ipsec.h> |
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#include <asm/unaligned.h> |
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#include <linux/errqueue.h> |
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#include <trace/events/tcp.h> |
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#include <linux/jump_label_ratelimit.h> |
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#include <net/busy_poll.h> |
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#include <net/mptcp.h> |
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|
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int sysctl_tcp_max_orphans __read_mostly = NR_FILE; |
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|
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#define FLAG_DATA 0x01 /* Incoming frame contained data. */ |
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#define FLAG_WIN_UPDATE 0x02 /* Incoming ACK was a window update. */ |
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#define FLAG_DATA_ACKED 0x04 /* This ACK acknowledged new data. */ |
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#define FLAG_RETRANS_DATA_ACKED 0x08 /* "" "" some of which was retransmitted. */ |
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#define FLAG_SYN_ACKED 0x10 /* This ACK acknowledged SYN. */ |
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#define FLAG_DATA_SACKED 0x20 /* New SACK. */ |
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#define FLAG_ECE 0x40 /* ECE in this ACK */ |
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#define FLAG_LOST_RETRANS 0x80 /* This ACK marks some retransmission lost */ |
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#define FLAG_SLOWPATH 0x100 /* Do not skip RFC checks for window update.*/ |
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#define FLAG_ORIG_SACK_ACKED 0x200 /* Never retransmitted data are (s)acked */ |
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#define FLAG_SND_UNA_ADVANCED 0x400 /* Snd_una was changed (!= FLAG_DATA_ACKED) */ |
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#define FLAG_DSACKING_ACK 0x800 /* SACK blocks contained D-SACK info */ |
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#define FLAG_SET_XMIT_TIMER 0x1000 /* Set TLP or RTO timer */ |
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#define FLAG_SACK_RENEGING 0x2000 /* snd_una advanced to a sacked seq */ |
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#define FLAG_UPDATE_TS_RECENT 0x4000 /* tcp_replace_ts_recent() */ |
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#define FLAG_NO_CHALLENGE_ACK 0x8000 /* do not call tcp_send_challenge_ack() */ |
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#define FLAG_ACK_MAYBE_DELAYED 0x10000 /* Likely a delayed ACK */ |
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#define FLAG_DSACK_TLP 0x20000 /* DSACK for tail loss probe */ |
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|
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#define FLAG_ACKED (FLAG_DATA_ACKED|FLAG_SYN_ACKED) |
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#define FLAG_NOT_DUP (FLAG_DATA|FLAG_WIN_UPDATE|FLAG_ACKED) |
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#define FLAG_CA_ALERT (FLAG_DATA_SACKED|FLAG_ECE|FLAG_DSACKING_ACK) |
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#define FLAG_FORWARD_PROGRESS (FLAG_ACKED|FLAG_DATA_SACKED) |
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|
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#define TCP_REMNANT (TCP_FLAG_FIN|TCP_FLAG_URG|TCP_FLAG_SYN|TCP_FLAG_PSH) |
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#define TCP_HP_BITS (~(TCP_RESERVED_BITS|TCP_FLAG_PSH)) |
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|
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#define REXMIT_NONE 0 /* no loss recovery to do */ |
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#define REXMIT_LOST 1 /* retransmit packets marked lost */ |
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#define REXMIT_NEW 2 /* FRTO-style transmit of unsent/new packets */ |
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|
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#if IS_ENABLED(CONFIG_TLS_DEVICE) |
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static DEFINE_STATIC_KEY_DEFERRED_FALSE(clean_acked_data_enabled, HZ); |
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|
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void clean_acked_data_enable(struct inet_connection_sock *icsk, |
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void (*cad)(struct sock *sk, u32 ack_seq)) |
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{ |
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icsk->icsk_clean_acked = cad; |
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static_branch_deferred_inc(&clean_acked_data_enabled); |
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} |
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EXPORT_SYMBOL_GPL(clean_acked_data_enable); |
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|
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void clean_acked_data_disable(struct inet_connection_sock *icsk) |
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{ |
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static_branch_slow_dec_deferred(&clean_acked_data_enabled); |
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icsk->icsk_clean_acked = NULL; |
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} |
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EXPORT_SYMBOL_GPL(clean_acked_data_disable); |
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|
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void clean_acked_data_flush(void) |
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{ |
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static_key_deferred_flush(&clean_acked_data_enabled); |
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} |
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EXPORT_SYMBOL_GPL(clean_acked_data_flush); |
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#endif |
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|
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#ifdef CONFIG_CGROUP_BPF |
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static void bpf_skops_parse_hdr(struct sock *sk, struct sk_buff *skb) |
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{ |
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bool unknown_opt = tcp_sk(sk)->rx_opt.saw_unknown && |
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BPF_SOCK_OPS_TEST_FLAG(tcp_sk(sk), |
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BPF_SOCK_OPS_PARSE_UNKNOWN_HDR_OPT_CB_FLAG); |
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bool parse_all_opt = BPF_SOCK_OPS_TEST_FLAG(tcp_sk(sk), |
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BPF_SOCK_OPS_PARSE_ALL_HDR_OPT_CB_FLAG); |
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struct bpf_sock_ops_kern sock_ops; |
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|
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if (likely(!unknown_opt && !parse_all_opt)) |
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return; |
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|
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/* The skb will be handled in the |
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* bpf_skops_established() or |
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* bpf_skops_write_hdr_opt(). |
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*/ |
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switch (sk->sk_state) { |
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case TCP_SYN_RECV: |
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case TCP_SYN_SENT: |
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case TCP_LISTEN: |
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return; |
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} |
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|
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sock_owned_by_me(sk); |
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|
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memset(&sock_ops, 0, offsetof(struct bpf_sock_ops_kern, temp)); |
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sock_ops.op = BPF_SOCK_OPS_PARSE_HDR_OPT_CB; |
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sock_ops.is_fullsock = 1; |
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sock_ops.sk = sk; |
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bpf_skops_init_skb(&sock_ops, skb, tcp_hdrlen(skb)); |
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|
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BPF_CGROUP_RUN_PROG_SOCK_OPS(&sock_ops); |
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} |
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static void bpf_skops_established(struct sock *sk, int bpf_op, |
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struct sk_buff *skb) |
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{ |
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struct bpf_sock_ops_kern sock_ops; |
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|
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sock_owned_by_me(sk); |
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|
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memset(&sock_ops, 0, offsetof(struct bpf_sock_ops_kern, temp)); |
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sock_ops.op = bpf_op; |
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sock_ops.is_fullsock = 1; |
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sock_ops.sk = sk; |
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/* sk with TCP_REPAIR_ON does not have skb in tcp_finish_connect */ |
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if (skb) |
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bpf_skops_init_skb(&sock_ops, skb, tcp_hdrlen(skb)); |
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|
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BPF_CGROUP_RUN_PROG_SOCK_OPS(&sock_ops); |
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} |
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#else |
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static void bpf_skops_parse_hdr(struct sock *sk, struct sk_buff *skb) |
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{ |
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} |
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|
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static void bpf_skops_established(struct sock *sk, int bpf_op, |
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struct sk_buff *skb) |
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{ |
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} |
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#endif |
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|
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static void tcp_gro_dev_warn(struct sock *sk, const struct sk_buff *skb, |
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unsigned int len) |
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{ |
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static bool __once __read_mostly; |
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|
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if (!__once) { |
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struct net_device *dev; |
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|
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__once = true; |
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rcu_read_lock(); |
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dev = dev_get_by_index_rcu(sock_net(sk), skb->skb_iif); |
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if (!dev || len >= dev->mtu) |
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pr_warn("%s: Driver has suspect GRO implementation, TCP performance may be compromised.\n", |
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dev ? dev->name : "Unknown driver"); |
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rcu_read_unlock(); |
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} |
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} |
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|
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/* Adapt the MSS value used to make delayed ack decision to the |
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* real world. |
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*/ |
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static void tcp_measure_rcv_mss(struct sock *sk, const struct sk_buff *skb) |
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{ |
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struct inet_connection_sock *icsk = inet_csk(sk); |
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const unsigned int lss = icsk->icsk_ack.last_seg_size; |
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unsigned int len; |
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icsk->icsk_ack.last_seg_size = 0; |
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|
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/* skb->len may jitter because of SACKs, even if peer |
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* sends good full-sized frames. |
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*/ |
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len = skb_shinfo(skb)->gso_size ? : skb->len; |
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if (len >= icsk->icsk_ack.rcv_mss) { |
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icsk->icsk_ack.rcv_mss = min_t(unsigned int, len, |
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tcp_sk(sk)->advmss); |
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/* Account for possibly-removed options */ |
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if (unlikely(len > icsk->icsk_ack.rcv_mss + |
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MAX_TCP_OPTION_SPACE)) |
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tcp_gro_dev_warn(sk, skb, len); |
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} else { |
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/* Otherwise, we make more careful check taking into account, |
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* that SACKs block is variable. |
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* |
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* "len" is invariant segment length, including TCP header. |
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*/ |
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len += skb->data - skb_transport_header(skb); |
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if (len >= TCP_MSS_DEFAULT + sizeof(struct tcphdr) || |
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/* If PSH is not set, packet should be |
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* full sized, provided peer TCP is not badly broken. |
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* This observation (if it is correct 8)) allows |
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* to handle super-low mtu links fairly. |
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*/ |
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(len >= TCP_MIN_MSS + sizeof(struct tcphdr) && |
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!(tcp_flag_word(tcp_hdr(skb)) & TCP_REMNANT))) { |
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/* Subtract also invariant (if peer is RFC compliant), |
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* tcp header plus fixed timestamp option length. |
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* Resulting "len" is MSS free of SACK jitter. |
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*/ |
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len -= tcp_sk(sk)->tcp_header_len; |
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icsk->icsk_ack.last_seg_size = len; |
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if (len == lss) { |
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icsk->icsk_ack.rcv_mss = len; |
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return; |
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} |
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} |
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if (icsk->icsk_ack.pending & ICSK_ACK_PUSHED) |
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icsk->icsk_ack.pending |= ICSK_ACK_PUSHED2; |
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icsk->icsk_ack.pending |= ICSK_ACK_PUSHED; |
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} |
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} |
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static void tcp_incr_quickack(struct sock *sk, unsigned int max_quickacks) |
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{ |
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struct inet_connection_sock *icsk = inet_csk(sk); |
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unsigned int quickacks = tcp_sk(sk)->rcv_wnd / (2 * icsk->icsk_ack.rcv_mss); |
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if (quickacks == 0) |
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quickacks = 2; |
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quickacks = min(quickacks, max_quickacks); |
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if (quickacks > icsk->icsk_ack.quick) |
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icsk->icsk_ack.quick = quickacks; |
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} |
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void tcp_enter_quickack_mode(struct sock *sk, unsigned int max_quickacks) |
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{ |
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struct inet_connection_sock *icsk = inet_csk(sk); |
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|
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tcp_incr_quickack(sk, max_quickacks); |
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inet_csk_exit_pingpong_mode(sk); |
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icsk->icsk_ack.ato = TCP_ATO_MIN; |
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} |
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EXPORT_SYMBOL(tcp_enter_quickack_mode); |
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|
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/* Send ACKs quickly, if "quick" count is not exhausted |
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* and the session is not interactive. |
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*/ |
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static bool tcp_in_quickack_mode(struct sock *sk) |
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{ |
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const struct inet_connection_sock *icsk = inet_csk(sk); |
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const struct dst_entry *dst = __sk_dst_get(sk); |
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|
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return (dst && dst_metric(dst, RTAX_QUICKACK)) || |
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(icsk->icsk_ack.quick && !inet_csk_in_pingpong_mode(sk)); |
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} |
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static void tcp_ecn_queue_cwr(struct tcp_sock *tp) |
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{ |
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if (tp->ecn_flags & TCP_ECN_OK) |
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tp->ecn_flags |= TCP_ECN_QUEUE_CWR; |
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} |
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|
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static void tcp_ecn_accept_cwr(struct sock *sk, const struct sk_buff *skb) |
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{ |
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if (tcp_hdr(skb)->cwr) { |
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tcp_sk(sk)->ecn_flags &= ~TCP_ECN_DEMAND_CWR; |
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|
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/* If the sender is telling us it has entered CWR, then its |
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* cwnd may be very low (even just 1 packet), so we should ACK |
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* immediately. |
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*/ |
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if (TCP_SKB_CB(skb)->seq != TCP_SKB_CB(skb)->end_seq) |
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inet_csk(sk)->icsk_ack.pending |= ICSK_ACK_NOW; |
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} |
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} |
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|
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static void tcp_ecn_withdraw_cwr(struct tcp_sock *tp) |
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{ |
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tp->ecn_flags &= ~TCP_ECN_QUEUE_CWR; |
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} |
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|
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static void __tcp_ecn_check_ce(struct sock *sk, const struct sk_buff *skb) |
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{ |
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struct tcp_sock *tp = tcp_sk(sk); |
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|
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switch (TCP_SKB_CB(skb)->ip_dsfield & INET_ECN_MASK) { |
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case INET_ECN_NOT_ECT: |
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/* Funny extension: if ECT is not set on a segment, |
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* and we already seen ECT on a previous segment, |
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* it is probably a retransmit. |
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*/ |
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if (tp->ecn_flags & TCP_ECN_SEEN) |
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tcp_enter_quickack_mode(sk, 2); |
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break; |
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case INET_ECN_CE: |
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if (tcp_ca_needs_ecn(sk)) |
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tcp_ca_event(sk, CA_EVENT_ECN_IS_CE); |
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|
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if (!(tp->ecn_flags & TCP_ECN_DEMAND_CWR)) { |
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/* Better not delay acks, sender can have a very low cwnd */ |
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tcp_enter_quickack_mode(sk, 2); |
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tp->ecn_flags |= TCP_ECN_DEMAND_CWR; |
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} |
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tp->ecn_flags |= TCP_ECN_SEEN; |
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break; |
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default: |
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if (tcp_ca_needs_ecn(sk)) |
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tcp_ca_event(sk, CA_EVENT_ECN_NO_CE); |
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tp->ecn_flags |= TCP_ECN_SEEN; |
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break; |
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} |
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} |
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|
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static void tcp_ecn_check_ce(struct sock *sk, const struct sk_buff *skb) |
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{ |
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if (tcp_sk(sk)->ecn_flags & TCP_ECN_OK) |
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__tcp_ecn_check_ce(sk, skb); |
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} |
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|
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static void tcp_ecn_rcv_synack(struct tcp_sock *tp, const struct tcphdr *th) |
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{ |
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if ((tp->ecn_flags & TCP_ECN_OK) && (!th->ece || th->cwr)) |
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tp->ecn_flags &= ~TCP_ECN_OK; |
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} |
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|
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static void tcp_ecn_rcv_syn(struct tcp_sock *tp, const struct tcphdr *th) |
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{ |
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if ((tp->ecn_flags & TCP_ECN_OK) && (!th->ece || !th->cwr)) |
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tp->ecn_flags &= ~TCP_ECN_OK; |
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} |
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|
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static bool tcp_ecn_rcv_ecn_echo(const struct tcp_sock *tp, const struct tcphdr *th) |
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{ |
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if (th->ece && !th->syn && (tp->ecn_flags & TCP_ECN_OK)) |
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return true; |
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return false; |
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} |
|
|
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/* Buffer size and advertised window tuning. |
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* |
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* 1. Tuning sk->sk_sndbuf, when connection enters established state. |
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*/ |
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|
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static void tcp_sndbuf_expand(struct sock *sk) |
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{ |
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const struct tcp_sock *tp = tcp_sk(sk); |
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const struct tcp_congestion_ops *ca_ops = inet_csk(sk)->icsk_ca_ops; |
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int sndmem, per_mss; |
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u32 nr_segs; |
|
|
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/* Worst case is non GSO/TSO : each frame consumes one skb |
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* and skb->head is kmalloced using power of two area of memory |
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*/ |
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per_mss = max_t(u32, tp->rx_opt.mss_clamp, tp->mss_cache) + |
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MAX_TCP_HEADER + |
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SKB_DATA_ALIGN(sizeof(struct skb_shared_info)); |
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|
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per_mss = roundup_pow_of_two(per_mss) + |
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SKB_DATA_ALIGN(sizeof(struct sk_buff)); |
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|
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nr_segs = max_t(u32, TCP_INIT_CWND, tp->snd_cwnd); |
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nr_segs = max_t(u32, nr_segs, tp->reordering + 1); |
|
|
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/* Fast Recovery (RFC 5681 3.2) : |
|
* Cubic needs 1.7 factor, rounded to 2 to include |
|
* extra cushion (application might react slowly to EPOLLOUT) |
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*/ |
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sndmem = ca_ops->sndbuf_expand ? ca_ops->sndbuf_expand(sk) : 2; |
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sndmem *= nr_segs * per_mss; |
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|
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if (sk->sk_sndbuf < sndmem) |
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WRITE_ONCE(sk->sk_sndbuf, |
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min(sndmem, sock_net(sk)->ipv4.sysctl_tcp_wmem[2])); |
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} |
|
|
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/* 2. Tuning advertised window (window_clamp, rcv_ssthresh) |
|
* |
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* All tcp_full_space() is split to two parts: "network" buffer, allocated |
|
* forward and advertised in receiver window (tp->rcv_wnd) and |
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* "application buffer", required to isolate scheduling/application |
|
* latencies from network. |
|
* window_clamp is maximal advertised window. It can be less than |
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* tcp_full_space(), in this case tcp_full_space() - window_clamp |
|
* is reserved for "application" buffer. The less window_clamp is |
|
* the smoother our behaviour from viewpoint of network, but the lower |
|
* throughput and the higher sensitivity of the connection to losses. 8) |
|
* |
|
* rcv_ssthresh is more strict window_clamp used at "slow start" |
|
* phase to predict further behaviour of this connection. |
|
* It is used for two goals: |
|
* - to enforce header prediction at sender, even when application |
|
* requires some significant "application buffer". It is check #1. |
|
* - to prevent pruning of receive queue because of misprediction |
|
* of receiver window. Check #2. |
|
* |
|
* The scheme does not work when sender sends good segments opening |
|
* window and then starts to feed us spaghetti. But it should work |
|
* in common situations. Otherwise, we have to rely on queue collapsing. |
|
*/ |
|
|
|
/* Slow part of check#2. */ |
|
static int __tcp_grow_window(const struct sock *sk, const struct sk_buff *skb, |
|
unsigned int skbtruesize) |
|
{ |
|
struct tcp_sock *tp = tcp_sk(sk); |
|
/* Optimize this! */ |
|
int truesize = tcp_win_from_space(sk, skbtruesize) >> 1; |
|
int window = tcp_win_from_space(sk, sock_net(sk)->ipv4.sysctl_tcp_rmem[2]) >> 1; |
|
|
|
while (tp->rcv_ssthresh <= window) { |
|
if (truesize <= skb->len) |
|
return 2 * inet_csk(sk)->icsk_ack.rcv_mss; |
|
|
|
truesize >>= 1; |
|
window >>= 1; |
|
} |
|
return 0; |
|
} |
|
|
|
/* Even if skb appears to have a bad len/truesize ratio, TCP coalescing |
|
* can play nice with us, as sk_buff and skb->head might be either |
|
* freed or shared with up to MAX_SKB_FRAGS segments. |
|
* Only give a boost to drivers using page frag(s) to hold the frame(s), |
|
* and if no payload was pulled in skb->head before reaching us. |
|
*/ |
|
static u32 truesize_adjust(bool adjust, const struct sk_buff *skb) |
|
{ |
|
u32 truesize = skb->truesize; |
|
|
|
if (adjust && !skb_headlen(skb)) { |
|
truesize -= SKB_TRUESIZE(skb_end_offset(skb)); |
|
/* paranoid check, some drivers might be buggy */ |
|
if (unlikely((int)truesize < (int)skb->len)) |
|
truesize = skb->truesize; |
|
} |
|
return truesize; |
|
} |
|
|
|
static void tcp_grow_window(struct sock *sk, const struct sk_buff *skb, |
|
bool adjust) |
|
{ |
|
struct tcp_sock *tp = tcp_sk(sk); |
|
int room; |
|
|
|
room = min_t(int, tp->window_clamp, tcp_space(sk)) - tp->rcv_ssthresh; |
|
|
|
if (room <= 0) |
|
return; |
|
|
|
/* Check #1 */ |
|
if (!tcp_under_memory_pressure(sk)) { |
|
unsigned int truesize = truesize_adjust(adjust, skb); |
|
int incr; |
|
|
|
/* Check #2. Increase window, if skb with such overhead |
|
* will fit to rcvbuf in future. |
|
*/ |
|
if (tcp_win_from_space(sk, truesize) <= skb->len) |
|
incr = 2 * tp->advmss; |
|
else |
|
incr = __tcp_grow_window(sk, skb, truesize); |
|
|
|
if (incr) { |
|
incr = max_t(int, incr, 2 * skb->len); |
|
tp->rcv_ssthresh += min(room, incr); |
|
inet_csk(sk)->icsk_ack.quick |= 1; |
|
} |
|
} else { |
|
/* Under pressure: |
|
* Adjust rcv_ssthresh according to reserved mem |
|
*/ |
|
tcp_adjust_rcv_ssthresh(sk); |
|
} |
|
} |
|
|
|
/* 3. Try to fixup all. It is made immediately after connection enters |
|
* established state. |
|
*/ |
|
static void tcp_init_buffer_space(struct sock *sk) |
|
{ |
|
int tcp_app_win = sock_net(sk)->ipv4.sysctl_tcp_app_win; |
|
struct tcp_sock *tp = tcp_sk(sk); |
|
int maxwin; |
|
|
|
if (!(sk->sk_userlocks & SOCK_SNDBUF_LOCK)) |
|
tcp_sndbuf_expand(sk); |
|
|
|
tcp_mstamp_refresh(tp); |
|
tp->rcvq_space.time = tp->tcp_mstamp; |
|
tp->rcvq_space.seq = tp->copied_seq; |
|
|
|
maxwin = tcp_full_space(sk); |
|
|
|
if (tp->window_clamp >= maxwin) { |
|
tp->window_clamp = maxwin; |
|
|
|
if (tcp_app_win && maxwin > 4 * tp->advmss) |
|
tp->window_clamp = max(maxwin - |
|
(maxwin >> tcp_app_win), |
|
4 * tp->advmss); |
|
} |
|
|
|
/* Force reservation of one segment. */ |
|
if (tcp_app_win && |
|
tp->window_clamp > 2 * tp->advmss && |
|
tp->window_clamp + tp->advmss > maxwin) |
|
tp->window_clamp = max(2 * tp->advmss, maxwin - tp->advmss); |
|
|
|
tp->rcv_ssthresh = min(tp->rcv_ssthresh, tp->window_clamp); |
|
tp->snd_cwnd_stamp = tcp_jiffies32; |
|
tp->rcvq_space.space = min3(tp->rcv_ssthresh, tp->rcv_wnd, |
|
(u32)TCP_INIT_CWND * tp->advmss); |
|
} |
|
|
|
/* 4. Recalculate window clamp after socket hit its memory bounds. */ |
|
static void tcp_clamp_window(struct sock *sk) |
|
{ |
|
struct tcp_sock *tp = tcp_sk(sk); |
|
struct inet_connection_sock *icsk = inet_csk(sk); |
|
struct net *net = sock_net(sk); |
|
|
|
icsk->icsk_ack.quick = 0; |
|
|
|
if (sk->sk_rcvbuf < net->ipv4.sysctl_tcp_rmem[2] && |
|
!(sk->sk_userlocks & SOCK_RCVBUF_LOCK) && |
|
!tcp_under_memory_pressure(sk) && |
|
sk_memory_allocated(sk) < sk_prot_mem_limits(sk, 0)) { |
|
WRITE_ONCE(sk->sk_rcvbuf, |
|
min(atomic_read(&sk->sk_rmem_alloc), |
|
net->ipv4.sysctl_tcp_rmem[2])); |
|
} |
|
if (atomic_read(&sk->sk_rmem_alloc) > sk->sk_rcvbuf) |
|
tp->rcv_ssthresh = min(tp->window_clamp, 2U * tp->advmss); |
|
} |
|
|
|
/* Initialize RCV_MSS value. |
|
* RCV_MSS is an our guess about MSS used by the peer. |
|
* We haven't any direct information about the MSS. |
|
* It's better to underestimate the RCV_MSS rather than overestimate. |
|
* Overestimations make us ACKing less frequently than needed. |
|
* Underestimations are more easy to detect and fix by tcp_measure_rcv_mss(). |
|
*/ |
|
void tcp_initialize_rcv_mss(struct sock *sk) |
|
{ |
|
const struct tcp_sock *tp = tcp_sk(sk); |
|
unsigned int hint = min_t(unsigned int, tp->advmss, tp->mss_cache); |
|
|
|
hint = min(hint, tp->rcv_wnd / 2); |
|
hint = min(hint, TCP_MSS_DEFAULT); |
|
hint = max(hint, TCP_MIN_MSS); |
|
|
|
inet_csk(sk)->icsk_ack.rcv_mss = hint; |
|
} |
|
EXPORT_SYMBOL(tcp_initialize_rcv_mss); |
|
|
|
/* Receiver "autotuning" code. |
|
* |
|
* The algorithm for RTT estimation w/o timestamps is based on |
|
* Dynamic Right-Sizing (DRS) by Wu Feng and Mike Fisk of LANL. |
|
* <https://public.lanl.gov/radiant/pubs.html#DRS> |
|
* |
|
* More detail on this code can be found at |
|
* <http://staff.psc.edu/jheffner/>, |
|
* though this reference is out of date. A new paper |
|
* is pending. |
|
*/ |
|
static void tcp_rcv_rtt_update(struct tcp_sock *tp, u32 sample, int win_dep) |
|
{ |
|
u32 new_sample = tp->rcv_rtt_est.rtt_us; |
|
long m = sample; |
|
|
|
if (new_sample != 0) { |
|
/* If we sample in larger samples in the non-timestamp |
|
* case, we could grossly overestimate the RTT especially |
|
* with chatty applications or bulk transfer apps which |
|
* are stalled on filesystem I/O. |
|
* |
|
* Also, since we are only going for a minimum in the |
|
* non-timestamp case, we do not smooth things out |
|
* else with timestamps disabled convergence takes too |
|
* long. |
|
*/ |
|
if (!win_dep) { |
|
m -= (new_sample >> 3); |
|
new_sample += m; |
|
} else { |
|
m <<= 3; |
|
if (m < new_sample) |
|
new_sample = m; |
|
} |
|
} else { |
|
/* No previous measure. */ |
|
new_sample = m << 3; |
|
} |
|
|
|
tp->rcv_rtt_est.rtt_us = new_sample; |
|
} |
|
|
|
static inline void tcp_rcv_rtt_measure(struct tcp_sock *tp) |
|
{ |
|
u32 delta_us; |
|
|
|
if (tp->rcv_rtt_est.time == 0) |
|
goto new_measure; |
|
if (before(tp->rcv_nxt, tp->rcv_rtt_est.seq)) |
|
return; |
|
delta_us = tcp_stamp_us_delta(tp->tcp_mstamp, tp->rcv_rtt_est.time); |
|
if (!delta_us) |
|
delta_us = 1; |
|
tcp_rcv_rtt_update(tp, delta_us, 1); |
|
|
|
new_measure: |
|
tp->rcv_rtt_est.seq = tp->rcv_nxt + tp->rcv_wnd; |
|
tp->rcv_rtt_est.time = tp->tcp_mstamp; |
|
} |
|
|
|
static inline void tcp_rcv_rtt_measure_ts(struct sock *sk, |
|
const struct sk_buff *skb) |
|
{ |
|
struct tcp_sock *tp = tcp_sk(sk); |
|
|
|
if (tp->rx_opt.rcv_tsecr == tp->rcv_rtt_last_tsecr) |
|
return; |
|
tp->rcv_rtt_last_tsecr = tp->rx_opt.rcv_tsecr; |
|
|
|
if (TCP_SKB_CB(skb)->end_seq - |
|
TCP_SKB_CB(skb)->seq >= inet_csk(sk)->icsk_ack.rcv_mss) { |
|
u32 delta = tcp_time_stamp(tp) - tp->rx_opt.rcv_tsecr; |
|
u32 delta_us; |
|
|
|
if (likely(delta < INT_MAX / (USEC_PER_SEC / TCP_TS_HZ))) { |
|
if (!delta) |
|
delta = 1; |
|
delta_us = delta * (USEC_PER_SEC / TCP_TS_HZ); |
|
tcp_rcv_rtt_update(tp, delta_us, 0); |
|
} |
|
} |
|
} |
|
|
|
/* |
|
* This function should be called every time data is copied to user space. |
|
* It calculates the appropriate TCP receive buffer space. |
|
*/ |
|
void tcp_rcv_space_adjust(struct sock *sk) |
|
{ |
|
struct tcp_sock *tp = tcp_sk(sk); |
|
u32 copied; |
|
int time; |
|
|
|
trace_tcp_rcv_space_adjust(sk); |
|
|
|
tcp_mstamp_refresh(tp); |
|
time = tcp_stamp_us_delta(tp->tcp_mstamp, tp->rcvq_space.time); |
|
if (time < (tp->rcv_rtt_est.rtt_us >> 3) || tp->rcv_rtt_est.rtt_us == 0) |
|
return; |
|
|
|
/* Number of bytes copied to user in last RTT */ |
|
copied = tp->copied_seq - tp->rcvq_space.seq; |
|
if (copied <= tp->rcvq_space.space) |
|
goto new_measure; |
|
|
|
/* A bit of theory : |
|
* copied = bytes received in previous RTT, our base window |
|
* To cope with packet losses, we need a 2x factor |
|
* To cope with slow start, and sender growing its cwin by 100 % |
|
* every RTT, we need a 4x factor, because the ACK we are sending |
|
* now is for the next RTT, not the current one : |
|
* <prev RTT . ><current RTT .. ><next RTT .... > |
|
*/ |
|
|
|
if (sock_net(sk)->ipv4.sysctl_tcp_moderate_rcvbuf && |
|
!(sk->sk_userlocks & SOCK_RCVBUF_LOCK)) { |
|
int rcvmem, rcvbuf; |
|
u64 rcvwin, grow; |
|
|
|
/* minimal window to cope with packet losses, assuming |
|
* steady state. Add some cushion because of small variations. |
|
*/ |
|
rcvwin = ((u64)copied << 1) + 16 * tp->advmss; |
|
|
|
/* Accommodate for sender rate increase (eg. slow start) */ |
|
grow = rcvwin * (copied - tp->rcvq_space.space); |
|
do_div(grow, tp->rcvq_space.space); |
|
rcvwin += (grow << 1); |
|
|
|
rcvmem = SKB_TRUESIZE(tp->advmss + MAX_TCP_HEADER); |
|
while (tcp_win_from_space(sk, rcvmem) < tp->advmss) |
|
rcvmem += 128; |
|
|
|
do_div(rcvwin, tp->advmss); |
|
rcvbuf = min_t(u64, rcvwin * rcvmem, |
|
sock_net(sk)->ipv4.sysctl_tcp_rmem[2]); |
|
if (rcvbuf > sk->sk_rcvbuf) { |
|
WRITE_ONCE(sk->sk_rcvbuf, rcvbuf); |
|
|
|
/* Make the window clamp follow along. */ |
|
tp->window_clamp = tcp_win_from_space(sk, rcvbuf); |
|
} |
|
} |
|
tp->rcvq_space.space = copied; |
|
|
|
new_measure: |
|
tp->rcvq_space.seq = tp->copied_seq; |
|
tp->rcvq_space.time = tp->tcp_mstamp; |
|
} |
|
|
|
/* There is something which you must keep in mind when you analyze the |
|
* behavior of the tp->ato delayed ack timeout interval. When a |
|
* connection starts up, we want to ack as quickly as possible. The |
|
* problem is that "good" TCP's do slow start at the beginning of data |
|
* transmission. The means that until we send the first few ACK's the |
|
* sender will sit on his end and only queue most of his data, because |
|
* he can only send snd_cwnd unacked packets at any given time. For |
|
* each ACK we send, he increments snd_cwnd and transmits more of his |
|
* queue. -DaveM |
|
*/ |
|
static void tcp_event_data_recv(struct sock *sk, struct sk_buff *skb) |
|
{ |
|
struct tcp_sock *tp = tcp_sk(sk); |
|
struct inet_connection_sock *icsk = inet_csk(sk); |
|
u32 now; |
|
|
|
inet_csk_schedule_ack(sk); |
|
|
|
tcp_measure_rcv_mss(sk, skb); |
|
|
|
tcp_rcv_rtt_measure(tp); |
|
|
|
now = tcp_jiffies32; |
|
|
|
if (!icsk->icsk_ack.ato) { |
|
/* The _first_ data packet received, initialize |
|
* delayed ACK engine. |
|
*/ |
|
tcp_incr_quickack(sk, TCP_MAX_QUICKACKS); |
|
icsk->icsk_ack.ato = TCP_ATO_MIN; |
|
} else { |
|
int m = now - icsk->icsk_ack.lrcvtime; |
|
|
|
if (m <= TCP_ATO_MIN / 2) { |
|
/* The fastest case is the first. */ |
|
icsk->icsk_ack.ato = (icsk->icsk_ack.ato >> 1) + TCP_ATO_MIN / 2; |
|
} else if (m < icsk->icsk_ack.ato) { |
|
icsk->icsk_ack.ato = (icsk->icsk_ack.ato >> 1) + m; |
|
if (icsk->icsk_ack.ato > icsk->icsk_rto) |
|
icsk->icsk_ack.ato = icsk->icsk_rto; |
|
} else if (m > icsk->icsk_rto) { |
|
/* Too long gap. Apparently sender failed to |
|
* restart window, so that we send ACKs quickly. |
|
*/ |
|
tcp_incr_quickack(sk, TCP_MAX_QUICKACKS); |
|
sk_mem_reclaim(sk); |
|
} |
|
} |
|
icsk->icsk_ack.lrcvtime = now; |
|
|
|
tcp_ecn_check_ce(sk, skb); |
|
|
|
if (skb->len >= 128) |
|
tcp_grow_window(sk, skb, true); |
|
} |
|
|
|
/* Called to compute a smoothed rtt estimate. The data fed to this |
|
* routine either comes from timestamps, or from segments that were |
|
* known _not_ to have been retransmitted [see Karn/Partridge |
|
* Proceedings SIGCOMM 87]. The algorithm is from the SIGCOMM 88 |
|
* piece by Van Jacobson. |
|
* NOTE: the next three routines used to be one big routine. |
|
* To save cycles in the RFC 1323 implementation it was better to break |
|
* it up into three procedures. -- erics |
|
*/ |
|
static void tcp_rtt_estimator(struct sock *sk, long mrtt_us) |
|
{ |
|
struct tcp_sock *tp = tcp_sk(sk); |
|
long m = mrtt_us; /* RTT */ |
|
u32 srtt = tp->srtt_us; |
|
|
|
/* The following amusing code comes from Jacobson's |
|
* article in SIGCOMM '88. Note that rtt and mdev |
|
* are scaled versions of rtt and mean deviation. |
|
* This is designed to be as fast as possible |
|
* m stands for "measurement". |
|
* |
|
* On a 1990 paper the rto value is changed to: |
|
* RTO = rtt + 4 * mdev |
|
* |
|
* Funny. This algorithm seems to be very broken. |
|
* These formulae increase RTO, when it should be decreased, increase |
|
* too slowly, when it should be increased quickly, decrease too quickly |
|
* etc. I guess in BSD RTO takes ONE value, so that it is absolutely |
|
* does not matter how to _calculate_ it. Seems, it was trap |
|
* that VJ failed to avoid. 8) |
|
*/ |
|
if (srtt != 0) { |
|
m -= (srtt >> 3); /* m is now error in rtt est */ |
|
srtt += m; /* rtt = 7/8 rtt + 1/8 new */ |
|
if (m < 0) { |
|
m = -m; /* m is now abs(error) */ |
|
m -= (tp->mdev_us >> 2); /* similar update on mdev */ |
|
/* This is similar to one of Eifel findings. |
|
* Eifel blocks mdev updates when rtt decreases. |
|
* This solution is a bit different: we use finer gain |
|
* for mdev in this case (alpha*beta). |
|
* Like Eifel it also prevents growth of rto, |
|
* but also it limits too fast rto decreases, |
|
* happening in pure Eifel. |
|
*/ |
|
if (m > 0) |
|
m >>= 3; |
|
} else { |
|
m -= (tp->mdev_us >> 2); /* similar update on mdev */ |
|
} |
|
tp->mdev_us += m; /* mdev = 3/4 mdev + 1/4 new */ |
|
if (tp->mdev_us > tp->mdev_max_us) { |
|
tp->mdev_max_us = tp->mdev_us; |
|
if (tp->mdev_max_us > tp->rttvar_us) |
|
tp->rttvar_us = tp->mdev_max_us; |
|
} |
|
if (after(tp->snd_una, tp->rtt_seq)) { |
|
if (tp->mdev_max_us < tp->rttvar_us) |
|
tp->rttvar_us -= (tp->rttvar_us - tp->mdev_max_us) >> 2; |
|
tp->rtt_seq = tp->snd_nxt; |
|
tp->mdev_max_us = tcp_rto_min_us(sk); |
|
|
|
tcp_bpf_rtt(sk); |
|
} |
|
} else { |
|
/* no previous measure. */ |
|
srtt = m << 3; /* take the measured time to be rtt */ |
|
tp->mdev_us = m << 1; /* make sure rto = 3*rtt */ |
|
tp->rttvar_us = max(tp->mdev_us, tcp_rto_min_us(sk)); |
|
tp->mdev_max_us = tp->rttvar_us; |
|
tp->rtt_seq = tp->snd_nxt; |
|
|
|
tcp_bpf_rtt(sk); |
|
} |
|
tp->srtt_us = max(1U, srtt); |
|
} |
|
|
|
static void tcp_update_pacing_rate(struct sock *sk) |
|
{ |
|
const struct tcp_sock *tp = tcp_sk(sk); |
|
u64 rate; |
|
|
|
/* set sk_pacing_rate to 200 % of current rate (mss * cwnd / srtt) */ |
|
rate = (u64)tp->mss_cache * ((USEC_PER_SEC / 100) << 3); |
|
|
|
/* current rate is (cwnd * mss) / srtt |
|
* In Slow Start [1], set sk_pacing_rate to 200 % the current rate. |
|
* In Congestion Avoidance phase, set it to 120 % the current rate. |
|
* |
|
* [1] : Normal Slow Start condition is (tp->snd_cwnd < tp->snd_ssthresh) |
|
* If snd_cwnd >= (tp->snd_ssthresh / 2), we are approaching |
|
* end of slow start and should slow down. |
|
*/ |
|
if (tp->snd_cwnd < tp->snd_ssthresh / 2) |
|
rate *= sock_net(sk)->ipv4.sysctl_tcp_pacing_ss_ratio; |
|
else |
|
rate *= sock_net(sk)->ipv4.sysctl_tcp_pacing_ca_ratio; |
|
|
|
rate *= max(tp->snd_cwnd, tp->packets_out); |
|
|
|
if (likely(tp->srtt_us)) |
|
do_div(rate, tp->srtt_us); |
|
|
|
/* WRITE_ONCE() is needed because sch_fq fetches sk_pacing_rate |
|
* without any lock. We want to make sure compiler wont store |
|
* intermediate values in this location. |
|
*/ |
|
WRITE_ONCE(sk->sk_pacing_rate, min_t(u64, rate, |
|
sk->sk_max_pacing_rate)); |
|
} |
|
|
|
/* Calculate rto without backoff. This is the second half of Van Jacobson's |
|
* routine referred to above. |
|
*/ |
|
static void tcp_set_rto(struct sock *sk) |
|
{ |
|
const struct tcp_sock *tp = tcp_sk(sk); |
|
/* Old crap is replaced with new one. 8) |
|
* |
|
* More seriously: |
|
* 1. If rtt variance happened to be less 50msec, it is hallucination. |
|
* It cannot be less due to utterly erratic ACK generation made |
|
* at least by solaris and freebsd. "Erratic ACKs" has _nothing_ |
|
* to do with delayed acks, because at cwnd>2 true delack timeout |
|
* is invisible. Actually, Linux-2.4 also generates erratic |
|
* ACKs in some circumstances. |
|
*/ |
|
inet_csk(sk)->icsk_rto = __tcp_set_rto(tp); |
|
|
|
/* 2. Fixups made earlier cannot be right. |
|
* If we do not estimate RTO correctly without them, |
|
* all the algo is pure shit and should be replaced |
|
* with correct one. It is exactly, which we pretend to do. |
|
*/ |
|
|
|
/* NOTE: clamping at TCP_RTO_MIN is not required, current algo |
|
* guarantees that rto is higher. |
|
*/ |
|
tcp_bound_rto(sk); |
|
} |
|
|
|
__u32 tcp_init_cwnd(const struct tcp_sock *tp, const struct dst_entry *dst) |
|
{ |
|
__u32 cwnd = (dst ? dst_metric(dst, RTAX_INITCWND) : 0); |
|
|
|
if (!cwnd) |
|
cwnd = TCP_INIT_CWND; |
|
return min_t(__u32, cwnd, tp->snd_cwnd_clamp); |
|
} |
|
|
|
struct tcp_sacktag_state { |
|
/* Timestamps for earliest and latest never-retransmitted segment |
|
* that was SACKed. RTO needs the earliest RTT to stay conservative, |
|
* but congestion control should still get an accurate delay signal. |
|
*/ |
|
u64 first_sackt; |
|
u64 last_sackt; |
|
u32 reord; |
|
u32 sack_delivered; |
|
int flag; |
|
unsigned int mss_now; |
|
struct rate_sample *rate; |
|
}; |
|
|
|
/* Take a notice that peer is sending D-SACKs. Skip update of data delivery |
|
* and spurious retransmission information if this DSACK is unlikely caused by |
|
* sender's action: |
|
* - DSACKed sequence range is larger than maximum receiver's window. |
|
* - Total no. of DSACKed segments exceed the total no. of retransmitted segs. |
|
*/ |
|
static u32 tcp_dsack_seen(struct tcp_sock *tp, u32 start_seq, |
|
u32 end_seq, struct tcp_sacktag_state *state) |
|
{ |
|
u32 seq_len, dup_segs = 1; |
|
|
|
if (!before(start_seq, end_seq)) |
|
return 0; |
|
|
|
seq_len = end_seq - start_seq; |
|
/* Dubious DSACK: DSACKed range greater than maximum advertised rwnd */ |
|
if (seq_len > tp->max_window) |
|
return 0; |
|
if (seq_len > tp->mss_cache) |
|
dup_segs = DIV_ROUND_UP(seq_len, tp->mss_cache); |
|
else if (tp->tlp_high_seq && tp->tlp_high_seq == end_seq) |
|
state->flag |= FLAG_DSACK_TLP; |
|
|
|
tp->dsack_dups += dup_segs; |
|
/* Skip the DSACK if dup segs weren't retransmitted by sender */ |
|
if (tp->dsack_dups > tp->total_retrans) |
|
return 0; |
|
|
|
tp->rx_opt.sack_ok |= TCP_DSACK_SEEN; |
|
/* We increase the RACK ordering window in rounds where we receive |
|
* DSACKs that may have been due to reordering causing RACK to trigger |
|
* a spurious fast recovery. Thus RACK ignores DSACKs that happen |
|
* without having seen reordering, or that match TLP probes (TLP |
|
* is timer-driven, not triggered by RACK). |
|
*/ |
|
if (tp->reord_seen && !(state->flag & FLAG_DSACK_TLP)) |
|
tp->rack.dsack_seen = 1; |
|
|
|
state->flag |= FLAG_DSACKING_ACK; |
|
/* A spurious retransmission is delivered */ |
|
state->sack_delivered += dup_segs; |
|
|
|
return dup_segs; |
|
} |
|
|
|
/* It's reordering when higher sequence was delivered (i.e. sacked) before |
|
* some lower never-retransmitted sequence ("low_seq"). The maximum reordering |
|
* distance is approximated in full-mss packet distance ("reordering"). |
|
*/ |
|
static void tcp_check_sack_reordering(struct sock *sk, const u32 low_seq, |
|
const int ts) |
|
{ |
|
struct tcp_sock *tp = tcp_sk(sk); |
|
const u32 mss = tp->mss_cache; |
|
u32 fack, metric; |
|
|
|
fack = tcp_highest_sack_seq(tp); |
|
if (!before(low_seq, fack)) |
|
return; |
|
|
|
metric = fack - low_seq; |
|
if ((metric > tp->reordering * mss) && mss) { |
|
#if FASTRETRANS_DEBUG > 1 |
|
pr_debug("Disorder%d %d %u f%u s%u rr%d\n", |
|
tp->rx_opt.sack_ok, inet_csk(sk)->icsk_ca_state, |
|
tp->reordering, |
|
0, |
|
tp->sacked_out, |
|
tp->undo_marker ? tp->undo_retrans : 0); |
|
#endif |
|
tp->reordering = min_t(u32, (metric + mss - 1) / mss, |
|
sock_net(sk)->ipv4.sysctl_tcp_max_reordering); |
|
} |
|
|
|
/* This exciting event is worth to be remembered. 8) */ |
|
tp->reord_seen++; |
|
NET_INC_STATS(sock_net(sk), |
|
ts ? LINUX_MIB_TCPTSREORDER : LINUX_MIB_TCPSACKREORDER); |
|
} |
|
|
|
/* This must be called before lost_out or retrans_out are updated |
|
* on a new loss, because we want to know if all skbs previously |
|
* known to be lost have already been retransmitted, indicating |
|
* that this newly lost skb is our next skb to retransmit. |
|
*/ |
|
static void tcp_verify_retransmit_hint(struct tcp_sock *tp, struct sk_buff *skb) |
|
{ |
|
if ((!tp->retransmit_skb_hint && tp->retrans_out >= tp->lost_out) || |
|
(tp->retransmit_skb_hint && |
|
before(TCP_SKB_CB(skb)->seq, |
|
TCP_SKB_CB(tp->retransmit_skb_hint)->seq))) |
|
tp->retransmit_skb_hint = skb; |
|
} |
|
|
|
/* Sum the number of packets on the wire we have marked as lost, and |
|
* notify the congestion control module that the given skb was marked lost. |
|
*/ |
|
static void tcp_notify_skb_loss_event(struct tcp_sock *tp, const struct sk_buff *skb) |
|
{ |
|
tp->lost += tcp_skb_pcount(skb); |
|
} |
|
|
|
void tcp_mark_skb_lost(struct sock *sk, struct sk_buff *skb) |
|
{ |
|
__u8 sacked = TCP_SKB_CB(skb)->sacked; |
|
struct tcp_sock *tp = tcp_sk(sk); |
|
|
|
if (sacked & TCPCB_SACKED_ACKED) |
|
return; |
|
|
|
tcp_verify_retransmit_hint(tp, skb); |
|
if (sacked & TCPCB_LOST) { |
|
if (sacked & TCPCB_SACKED_RETRANS) { |
|
/* Account for retransmits that are lost again */ |
|
TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS; |
|
tp->retrans_out -= tcp_skb_pcount(skb); |
|
NET_ADD_STATS(sock_net(sk), LINUX_MIB_TCPLOSTRETRANSMIT, |
|
tcp_skb_pcount(skb)); |
|
tcp_notify_skb_loss_event(tp, skb); |
|
} |
|
} else { |
|
tp->lost_out += tcp_skb_pcount(skb); |
|
TCP_SKB_CB(skb)->sacked |= TCPCB_LOST; |
|
tcp_notify_skb_loss_event(tp, skb); |
|
} |
|
} |
|
|
|
/* Updates the delivered and delivered_ce counts */ |
|
static void tcp_count_delivered(struct tcp_sock *tp, u32 delivered, |
|
bool ece_ack) |
|
{ |
|
tp->delivered += delivered; |
|
if (ece_ack) |
|
tp->delivered_ce += delivered; |
|
} |
|
|
|
/* This procedure tags the retransmission queue when SACKs arrive. |
|
* |
|
* We have three tag bits: SACKED(S), RETRANS(R) and LOST(L). |
|
* Packets in queue with these bits set are counted in variables |
|
* sacked_out, retrans_out and lost_out, correspondingly. |
|
* |
|
* Valid combinations are: |
|
* Tag InFlight Description |
|
* 0 1 - orig segment is in flight. |
|
* S 0 - nothing flies, orig reached receiver. |
|
* L 0 - nothing flies, orig lost by net. |
|
* R 2 - both orig and retransmit are in flight. |
|
* L|R 1 - orig is lost, retransmit is in flight. |
|
* S|R 1 - orig reached receiver, retrans is still in flight. |
|
* (L|S|R is logically valid, it could occur when L|R is sacked, |
|
* but it is equivalent to plain S and code short-curcuits it to S. |
|
* L|S is logically invalid, it would mean -1 packet in flight 8)) |
|
* |
|
* These 6 states form finite state machine, controlled by the following events: |
|
* 1. New ACK (+SACK) arrives. (tcp_sacktag_write_queue()) |
|
* 2. Retransmission. (tcp_retransmit_skb(), tcp_xmit_retransmit_queue()) |
|
* 3. Loss detection event of two flavors: |
|
* A. Scoreboard estimator decided the packet is lost. |
|
* A'. Reno "three dupacks" marks head of queue lost. |
|
* B. SACK arrives sacking SND.NXT at the moment, when the |
|
* segment was retransmitted. |
|
* 4. D-SACK added new rule: D-SACK changes any tag to S. |
|
* |
|
* It is pleasant to note, that state diagram turns out to be commutative, |
|
* so that we are allowed not to be bothered by order of our actions, |
|
* when multiple events arrive simultaneously. (see the function below). |
|
* |
|
* Reordering detection. |
|
* -------------------- |
|
* Reordering metric is maximal distance, which a packet can be displaced |
|
* in packet stream. With SACKs we can estimate it: |
|
* |
|
* 1. SACK fills old hole and the corresponding segment was not |
|
* ever retransmitted -> reordering. Alas, we cannot use it |
|
* when segment was retransmitted. |
|
* 2. The last flaw is solved with D-SACK. D-SACK arrives |
|
* for retransmitted and already SACKed segment -> reordering.. |
|
* Both of these heuristics are not used in Loss state, when we cannot |
|
* account for retransmits accurately. |
|
* |
|
* SACK block validation. |
|
* ---------------------- |
|
* |
|
* SACK block range validation checks that the received SACK block fits to |
|
* the expected sequence limits, i.e., it is between SND.UNA and SND.NXT. |
|
* Note that SND.UNA is not included to the range though being valid because |
|
* it means that the receiver is rather inconsistent with itself reporting |
|
* SACK reneging when it should advance SND.UNA. Such SACK block this is |
|
* perfectly valid, however, in light of RFC2018 which explicitly states |
|
* that "SACK block MUST reflect the newest segment. Even if the newest |
|
* segment is going to be discarded ...", not that it looks very clever |
|
* in case of head skb. Due to potentional receiver driven attacks, we |
|
* choose to avoid immediate execution of a walk in write queue due to |
|
* reneging and defer head skb's loss recovery to standard loss recovery |
|
* procedure that will eventually trigger (nothing forbids us doing this). |
|
* |
|
* Implements also blockage to start_seq wrap-around. Problem lies in the |
|
* fact that though start_seq (s) is before end_seq (i.e., not reversed), |
|
* there's no guarantee that it will be before snd_nxt (n). The problem |
|
* happens when start_seq resides between end_seq wrap (e_w) and snd_nxt |
|
* wrap (s_w): |
|
* |
|
* <- outs wnd -> <- wrapzone -> |
|
* u e n u_w e_w s n_w |
|
* | | | | | | | |
|
* |<------------+------+----- TCP seqno space --------------+---------->| |
|
* ...-- <2^31 ->| |<--------... |
|
* ...---- >2^31 ------>| |<--------... |
|
* |
|
* Current code wouldn't be vulnerable but it's better still to discard such |
|
* crazy SACK blocks. Doing this check for start_seq alone closes somewhat |
|
* similar case (end_seq after snd_nxt wrap) as earlier reversed check in |
|
* snd_nxt wrap -> snd_una region will then become "well defined", i.e., |
|
* equal to the ideal case (infinite seqno space without wrap caused issues). |
|
* |
|
* With D-SACK the lower bound is extended to cover sequence space below |
|
* SND.UNA down to undo_marker, which is the last point of interest. Yet |
|
* again, D-SACK block must not to go across snd_una (for the same reason as |
|
* for the normal SACK blocks, explained above). But there all simplicity |
|
* ends, TCP might receive valid D-SACKs below that. As long as they reside |
|
* fully below undo_marker they do not affect behavior in anyway and can |
|
* therefore be safely ignored. In rare cases (which are more or less |
|
* theoretical ones), the D-SACK will nicely cross that boundary due to skb |
|
* fragmentation and packet reordering past skb's retransmission. To consider |
|
* them correctly, the acceptable range must be extended even more though |
|
* the exact amount is rather hard to quantify. However, tp->max_window can |
|
* be used as an exaggerated estimate. |
|
*/ |
|
static bool tcp_is_sackblock_valid(struct tcp_sock *tp, bool is_dsack, |
|
u32 start_seq, u32 end_seq) |
|
{ |
|
/* Too far in future, or reversed (interpretation is ambiguous) */ |
|
if (after(end_seq, tp->snd_nxt) || !before(start_seq, end_seq)) |
|
return false; |
|
|
|
/* Nasty start_seq wrap-around check (see comments above) */ |
|
if (!before(start_seq, tp->snd_nxt)) |
|
return false; |
|
|
|
/* In outstanding window? ...This is valid exit for D-SACKs too. |
|
* start_seq == snd_una is non-sensical (see comments above) |
|
*/ |
|
if (after(start_seq, tp->snd_una)) |
|
return true; |
|
|
|
if (!is_dsack || !tp->undo_marker) |
|
return false; |
|
|
|
/* ...Then it's D-SACK, and must reside below snd_una completely */ |
|
if (after(end_seq, tp->snd_una)) |
|
return false; |
|
|
|
if (!before(start_seq, tp->undo_marker)) |
|
return true; |
|
|
|
/* Too old */ |
|
if (!after(end_seq, tp->undo_marker)) |
|
return false; |
|
|
|
/* Undo_marker boundary crossing (overestimates a lot). Known already: |
|
* start_seq < undo_marker and end_seq >= undo_marker. |
|
*/ |
|
return !before(start_seq, end_seq - tp->max_window); |
|
} |
|
|
|
static bool tcp_check_dsack(struct sock *sk, const struct sk_buff *ack_skb, |
|
struct tcp_sack_block_wire *sp, int num_sacks, |
|
u32 prior_snd_una, struct tcp_sacktag_state *state) |
|
{ |
|
struct tcp_sock *tp = tcp_sk(sk); |
|
u32 start_seq_0 = get_unaligned_be32(&sp[0].start_seq); |
|
u32 end_seq_0 = get_unaligned_be32(&sp[0].end_seq); |
|
u32 dup_segs; |
|
|
|
if (before(start_seq_0, TCP_SKB_CB(ack_skb)->ack_seq)) { |
|
NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPDSACKRECV); |
|
} else if (num_sacks > 1) { |
|
u32 end_seq_1 = get_unaligned_be32(&sp[1].end_seq); |
|
u32 start_seq_1 = get_unaligned_be32(&sp[1].start_seq); |
|
|
|
if (after(end_seq_0, end_seq_1) || before(start_seq_0, start_seq_1)) |
|
return false; |
|
NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPDSACKOFORECV); |
|
} else { |
|
return false; |
|
} |
|
|
|
dup_segs = tcp_dsack_seen(tp, start_seq_0, end_seq_0, state); |
|
if (!dup_segs) { /* Skip dubious DSACK */ |
|
NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPDSACKIGNOREDDUBIOUS); |
|
return false; |
|
} |
|
|
|
NET_ADD_STATS(sock_net(sk), LINUX_MIB_TCPDSACKRECVSEGS, dup_segs); |
|
|
|
/* D-SACK for already forgotten data... Do dumb counting. */ |
|
if (tp->undo_marker && tp->undo_retrans > 0 && |
|
!after(end_seq_0, prior_snd_una) && |
|
after(end_seq_0, tp->undo_marker)) |
|
tp->undo_retrans = max_t(int, 0, tp->undo_retrans - dup_segs); |
|
|
|
return true; |
|
} |
|
|
|
/* Check if skb is fully within the SACK block. In presence of GSO skbs, |
|
* the incoming SACK may not exactly match but we can find smaller MSS |
|
* aligned portion of it that matches. Therefore we might need to fragment |
|
* which may fail and creates some hassle (caller must handle error case |
|
* returns). |
|
* |
|
* FIXME: this could be merged to shift decision code |
|
*/ |
|
static int tcp_match_skb_to_sack(struct sock *sk, struct sk_buff *skb, |
|
u32 start_seq, u32 end_seq) |
|
{ |
|
int err; |
|
bool in_sack; |
|
unsigned int pkt_len; |
|
unsigned int mss; |
|
|
|
in_sack = !after(start_seq, TCP_SKB_CB(skb)->seq) && |
|
!before(end_seq, TCP_SKB_CB(skb)->end_seq); |
|
|
|
if (tcp_skb_pcount(skb) > 1 && !in_sack && |
|
after(TCP_SKB_CB(skb)->end_seq, start_seq)) { |
|
mss = tcp_skb_mss(skb); |
|
in_sack = !after(start_seq, TCP_SKB_CB(skb)->seq); |
|
|
|
if (!in_sack) { |
|
pkt_len = start_seq - TCP_SKB_CB(skb)->seq; |
|
if (pkt_len < mss) |
|
pkt_len = mss; |
|
} else { |
|
pkt_len = end_seq - TCP_SKB_CB(skb)->seq; |
|
if (pkt_len < mss) |
|
return -EINVAL; |
|
} |
|
|
|
/* Round if necessary so that SACKs cover only full MSSes |
|
* and/or the remaining small portion (if present) |
|
*/ |
|
if (pkt_len > mss) { |
|
unsigned int new_len = (pkt_len / mss) * mss; |
|
if (!in_sack && new_len < pkt_len) |
|
new_len += mss; |
|
pkt_len = new_len; |
|
} |
|
|
|
if (pkt_len >= skb->len && !in_sack) |
|
return 0; |
|
|
|
err = tcp_fragment(sk, TCP_FRAG_IN_RTX_QUEUE, skb, |
|
pkt_len, mss, GFP_ATOMIC); |
|
if (err < 0) |
|
return err; |
|
} |
|
|
|
return in_sack; |
|
} |
|
|
|
/* Mark the given newly-SACKed range as such, adjusting counters and hints. */ |
|
static u8 tcp_sacktag_one(struct sock *sk, |
|
struct tcp_sacktag_state *state, u8 sacked, |
|
u32 start_seq, u32 end_seq, |
|
int dup_sack, int pcount, |
|
u64 xmit_time) |
|
{ |
|
struct tcp_sock *tp = tcp_sk(sk); |
|
|
|
/* Account D-SACK for retransmitted packet. */ |
|
if (dup_sack && (sacked & TCPCB_RETRANS)) { |
|
if (tp->undo_marker && tp->undo_retrans > 0 && |
|
after(end_seq, tp->undo_marker)) |
|
tp->undo_retrans = max_t(int, 0, tp->undo_retrans - pcount); |
|
if ((sacked & TCPCB_SACKED_ACKED) && |
|
before(start_seq, state->reord)) |
|
state->reord = start_seq; |
|
} |
|
|
|
/* Nothing to do; acked frame is about to be dropped (was ACKed). */ |
|
if (!after(end_seq, tp->snd_una)) |
|
return sacked; |
|
|
|
if (!(sacked & TCPCB_SACKED_ACKED)) { |
|
tcp_rack_advance(tp, sacked, end_seq, xmit_time); |
|
|
|
if (sacked & TCPCB_SACKED_RETRANS) { |
|
/* If the segment is not tagged as lost, |
|
* we do not clear RETRANS, believing |
|
* that retransmission is still in flight. |
|
*/ |
|
if (sacked & TCPCB_LOST) { |
|
sacked &= ~(TCPCB_LOST|TCPCB_SACKED_RETRANS); |
|
tp->lost_out -= pcount; |
|
tp->retrans_out -= pcount; |
|
} |
|
} else { |
|
if (!(sacked & TCPCB_RETRANS)) { |
|
/* New sack for not retransmitted frame, |
|
* which was in hole. It is reordering. |
|
*/ |
|
if (before(start_seq, |
|
tcp_highest_sack_seq(tp)) && |
|
before(start_seq, state->reord)) |
|
state->reord = start_seq; |
|
|
|
if (!after(end_seq, tp->high_seq)) |
|
state->flag |= FLAG_ORIG_SACK_ACKED; |
|
if (state->first_sackt == 0) |
|
state->first_sackt = xmit_time; |
|
state->last_sackt = xmit_time; |
|
} |
|
|
|
if (sacked & TCPCB_LOST) { |
|
sacked &= ~TCPCB_LOST; |
|
tp->lost_out -= pcount; |
|
} |
|
} |
|
|
|
sacked |= TCPCB_SACKED_ACKED; |
|
state->flag |= FLAG_DATA_SACKED; |
|
tp->sacked_out += pcount; |
|
/* Out-of-order packets delivered */ |
|
state->sack_delivered += pcount; |
|
|
|
/* Lost marker hint past SACKed? Tweak RFC3517 cnt */ |
|
if (tp->lost_skb_hint && |
|
before(start_seq, TCP_SKB_CB(tp->lost_skb_hint)->seq)) |
|
tp->lost_cnt_hint += pcount; |
|
} |
|
|
|
/* D-SACK. We can detect redundant retransmission in S|R and plain R |
|
* frames and clear it. undo_retrans is decreased above, L|R frames |
|
* are accounted above as well. |
|
*/ |
|
if (dup_sack && (sacked & TCPCB_SACKED_RETRANS)) { |
|
sacked &= ~TCPCB_SACKED_RETRANS; |
|
tp->retrans_out -= pcount; |
|
} |
|
|
|
return sacked; |
|
} |
|
|
|
/* Shift newly-SACKed bytes from this skb to the immediately previous |
|
* already-SACKed sk_buff. Mark the newly-SACKed bytes as such. |
|
*/ |
|
static bool tcp_shifted_skb(struct sock *sk, struct sk_buff *prev, |
|
struct sk_buff *skb, |
|
struct tcp_sacktag_state *state, |
|
unsigned int pcount, int shifted, int mss, |
|
bool dup_sack) |
|
{ |
|
struct tcp_sock *tp = tcp_sk(sk); |
|
u32 start_seq = TCP_SKB_CB(skb)->seq; /* start of newly-SACKed */ |
|
u32 end_seq = start_seq + shifted; /* end of newly-SACKed */ |
|
|
|
BUG_ON(!pcount); |
|
|
|
/* Adjust counters and hints for the newly sacked sequence |
|
* range but discard the return value since prev is already |
|
* marked. We must tag the range first because the seq |
|
* advancement below implicitly advances |
|
* tcp_highest_sack_seq() when skb is highest_sack. |
|
*/ |
|
tcp_sacktag_one(sk, state, TCP_SKB_CB(skb)->sacked, |
|
start_seq, end_seq, dup_sack, pcount, |
|
tcp_skb_timestamp_us(skb)); |
|
tcp_rate_skb_delivered(sk, skb, state->rate); |
|
|
|
if (skb == tp->lost_skb_hint) |
|
tp->lost_cnt_hint += pcount; |
|
|
|
TCP_SKB_CB(prev)->end_seq += shifted; |
|
TCP_SKB_CB(skb)->seq += shifted; |
|
|
|
tcp_skb_pcount_add(prev, pcount); |
|
WARN_ON_ONCE(tcp_skb_pcount(skb) < pcount); |
|
tcp_skb_pcount_add(skb, -pcount); |
|
|
|
/* When we're adding to gso_segs == 1, gso_size will be zero, |
|
* in theory this shouldn't be necessary but as long as DSACK |
|
* code can come after this skb later on it's better to keep |
|
* setting gso_size to something. |
|
*/ |
|
if (!TCP_SKB_CB(prev)->tcp_gso_size) |
|
TCP_SKB_CB(prev)->tcp_gso_size = mss; |
|
|
|
/* CHECKME: To clear or not to clear? Mimics normal skb currently */ |
|
if (tcp_skb_pcount(skb) <= 1) |
|
TCP_SKB_CB(skb)->tcp_gso_size = 0; |
|
|
|
/* Difference in this won't matter, both ACKed by the same cumul. ACK */ |
|
TCP_SKB_CB(prev)->sacked |= (TCP_SKB_CB(skb)->sacked & TCPCB_EVER_RETRANS); |
|
|
|
if (skb->len > 0) { |
|
BUG_ON(!tcp_skb_pcount(skb)); |
|
NET_INC_STATS(sock_net(sk), LINUX_MIB_SACKSHIFTED); |
|
return false; |
|
} |
|
|
|
/* Whole SKB was eaten :-) */ |
|
|
|
if (skb == tp->retransmit_skb_hint) |
|
tp->retransmit_skb_hint = prev; |
|
if (skb == tp->lost_skb_hint) { |
|
tp->lost_skb_hint = prev; |
|
tp->lost_cnt_hint -= tcp_skb_pcount(prev); |
|
} |
|
|
|
TCP_SKB_CB(prev)->tcp_flags |= TCP_SKB_CB(skb)->tcp_flags; |
|
TCP_SKB_CB(prev)->eor = TCP_SKB_CB(skb)->eor; |
|
if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN) |
|
TCP_SKB_CB(prev)->end_seq++; |
|
|
|
if (skb == tcp_highest_sack(sk)) |
|
tcp_advance_highest_sack(sk, skb); |
|
|
|
tcp_skb_collapse_tstamp(prev, skb); |
|
if (unlikely(TCP_SKB_CB(prev)->tx.delivered_mstamp)) |
|
TCP_SKB_CB(prev)->tx.delivered_mstamp = 0; |
|
|
|
tcp_rtx_queue_unlink_and_free(skb, sk); |
|
|
|
NET_INC_STATS(sock_net(sk), LINUX_MIB_SACKMERGED); |
|
|
|
return true; |
|
} |
|
|
|
/* I wish gso_size would have a bit more sane initialization than |
|
* something-or-zero which complicates things |
|
*/ |
|
static int tcp_skb_seglen(const struct sk_buff *skb) |
|
{ |
|
return tcp_skb_pcount(skb) == 1 ? skb->len : tcp_skb_mss(skb); |
|
} |
|
|
|
/* Shifting pages past head area doesn't work */ |
|
static int skb_can_shift(const struct sk_buff *skb) |
|
{ |
|
return !skb_headlen(skb) && skb_is_nonlinear(skb); |
|
} |
|
|
|
int tcp_skb_shift(struct sk_buff *to, struct sk_buff *from, |
|
int pcount, int shiftlen) |
|
{ |
|
/* TCP min gso_size is 8 bytes (TCP_MIN_GSO_SIZE) |
|
* Since TCP_SKB_CB(skb)->tcp_gso_segs is 16 bits, we need |
|
* to make sure not storing more than 65535 * 8 bytes per skb, |
|
* even if current MSS is bigger. |
|
*/ |
|
if (unlikely(to->len + shiftlen >= 65535 * TCP_MIN_GSO_SIZE)) |
|
return 0; |
|
if (unlikely(tcp_skb_pcount(to) + pcount > 65535)) |
|
return 0; |
|
return skb_shift(to, from, shiftlen); |
|
} |
|
|
|
/* Try collapsing SACK blocks spanning across multiple skbs to a single |
|
* skb. |
|
*/ |
|
static struct sk_buff *tcp_shift_skb_data(struct sock *sk, struct sk_buff *skb, |
|
struct tcp_sacktag_state *state, |
|
u32 start_seq, u32 end_seq, |
|
bool dup_sack) |
|
{ |
|
struct tcp_sock *tp = tcp_sk(sk); |
|
struct sk_buff *prev; |
|
int mss; |
|
int pcount = 0; |
|
int len; |
|
int in_sack; |
|
|
|
/* Normally R but no L won't result in plain S */ |
|
if (!dup_sack && |
|
(TCP_SKB_CB(skb)->sacked & (TCPCB_LOST|TCPCB_SACKED_RETRANS)) == TCPCB_SACKED_RETRANS) |
|
goto fallback; |
|
if (!skb_can_shift(skb)) |
|
goto fallback; |
|
/* This frame is about to be dropped (was ACKed). */ |
|
if (!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una)) |
|
goto fallback; |
|
|
|
/* Can only happen with delayed DSACK + discard craziness */ |
|
prev = skb_rb_prev(skb); |
|
if (!prev) |
|
goto fallback; |
|
|
|
if ((TCP_SKB_CB(prev)->sacked & TCPCB_TAGBITS) != TCPCB_SACKED_ACKED) |
|
goto fallback; |
|
|
|
if (!tcp_skb_can_collapse(prev, skb)) |
|
goto fallback; |
|
|
|
in_sack = !after(start_seq, TCP_SKB_CB(skb)->seq) && |
|
!before(end_seq, TCP_SKB_CB(skb)->end_seq); |
|
|
|
if (in_sack) { |
|
len = skb->len; |
|
pcount = tcp_skb_pcount(skb); |
|
mss = tcp_skb_seglen(skb); |
|
|
|
/* TODO: Fix DSACKs to not fragment already SACKed and we can |
|
* drop this restriction as unnecessary |
|
*/ |
|
if (mss != tcp_skb_seglen(prev)) |
|
goto fallback; |
|
} else { |
|
if (!after(TCP_SKB_CB(skb)->end_seq, start_seq)) |
|
goto noop; |
|
/* CHECKME: This is non-MSS split case only?, this will |
|
* cause skipped skbs due to advancing loop btw, original |
|
* has that feature too |
|
*/ |
|
if (tcp_skb_pcount(skb) <= 1) |
|
goto noop; |
|
|
|
in_sack = !after(start_seq, TCP_SKB_CB(skb)->seq); |
|
if (!in_sack) { |
|
/* TODO: head merge to next could be attempted here |
|
* if (!after(TCP_SKB_CB(skb)->end_seq, end_seq)), |
|
* though it might not be worth of the additional hassle |
|
* |
|
* ...we can probably just fallback to what was done |
|
* previously. We could try merging non-SACKed ones |
|
* as well but it probably isn't going to buy off |
|
* because later SACKs might again split them, and |
|
* it would make skb timestamp tracking considerably |
|
* harder problem. |
|
*/ |
|
goto fallback; |
|
} |
|
|
|
len = end_seq - TCP_SKB_CB(skb)->seq; |
|
BUG_ON(len < 0); |
|
BUG_ON(len > skb->len); |
|
|
|
/* MSS boundaries should be honoured or else pcount will |
|
* severely break even though it makes things bit trickier. |
|
* Optimize common case to avoid most of the divides |
|
*/ |
|
mss = tcp_skb_mss(skb); |
|
|
|
/* TODO: Fix DSACKs to not fragment already SACKed and we can |
|
* drop this restriction as unnecessary |
|
*/ |
|
if (mss != tcp_skb_seglen(prev)) |
|
goto fallback; |
|
|
|
if (len == mss) { |
|
pcount = 1; |
|
} else if (len < mss) { |
|
goto noop; |
|
} else { |
|
pcount = len / mss; |
|
len = pcount * mss; |
|
} |
|
} |
|
|
|
/* tcp_sacktag_one() won't SACK-tag ranges below snd_una */ |
|
if (!after(TCP_SKB_CB(skb)->seq + len, tp->snd_una)) |
|
goto fallback; |
|
|
|
if (!tcp_skb_shift(prev, skb, pcount, len)) |
|
goto fallback; |
|
if (!tcp_shifted_skb(sk, prev, skb, state, pcount, len, mss, dup_sack)) |
|
goto out; |
|
|
|
/* Hole filled allows collapsing with the next as well, this is very |
|
* useful when hole on every nth skb pattern happens |
|
*/ |
|
skb = skb_rb_next(prev); |
|
if (!skb) |
|
goto out; |
|
|
|
if (!skb_can_shift(skb) || |
|
((TCP_SKB_CB(skb)->sacked & TCPCB_TAGBITS) != TCPCB_SACKED_ACKED) || |
|
(mss != tcp_skb_seglen(skb))) |
|
goto out; |
|
|
|
if (!tcp_skb_can_collapse(prev, skb)) |
|
goto out; |
|
len = skb->len; |
|
pcount = tcp_skb_pcount(skb); |
|
if (tcp_skb_shift(prev, skb, pcount, len)) |
|
tcp_shifted_skb(sk, prev, skb, state, pcount, |
|
len, mss, 0); |
|
|
|
out: |
|
return prev; |
|
|
|
noop: |
|
return skb; |
|
|
|
fallback: |
|
NET_INC_STATS(sock_net(sk), LINUX_MIB_SACKSHIFTFALLBACK); |
|
return NULL; |
|
} |
|
|
|
static struct sk_buff *tcp_sacktag_walk(struct sk_buff *skb, struct sock *sk, |
|
struct tcp_sack_block *next_dup, |
|
struct tcp_sacktag_state *state, |
|
u32 start_seq, u32 end_seq, |
|
bool dup_sack_in) |
|
{ |
|
struct tcp_sock *tp = tcp_sk(sk); |
|
struct sk_buff *tmp; |
|
|
|
skb_rbtree_walk_from(skb) { |
|
int in_sack = 0; |
|
bool dup_sack = dup_sack_in; |
|
|
|
/* queue is in-order => we can short-circuit the walk early */ |
|
if (!before(TCP_SKB_CB(skb)->seq, end_seq)) |
|
break; |
|
|
|
if (next_dup && |
|
before(TCP_SKB_CB(skb)->seq, next_dup->end_seq)) { |
|
in_sack = tcp_match_skb_to_sack(sk, skb, |
|
next_dup->start_seq, |
|
next_dup->end_seq); |
|
if (in_sack > 0) |
|
dup_sack = true; |
|
} |
|
|
|
/* skb reference here is a bit tricky to get right, since |
|
* shifting can eat and free both this skb and the next, |
|
* so not even _safe variant of the loop is enough. |
|
*/ |
|
if (in_sack <= 0) { |
|
tmp = tcp_shift_skb_data(sk, skb, state, |
|
start_seq, end_seq, dup_sack); |
|
if (tmp) { |
|
if (tmp != skb) { |
|
skb = tmp; |
|
continue; |
|
} |
|
|
|
in_sack = 0; |
|
} else { |
|
in_sack = tcp_match_skb_to_sack(sk, skb, |
|
start_seq, |
|
end_seq); |
|
} |
|
} |
|
|
|
if (unlikely(in_sack < 0)) |
|
break; |
|
|
|
if (in_sack) { |
|
TCP_SKB_CB(skb)->sacked = |
|
tcp_sacktag_one(sk, |
|
state, |
|
TCP_SKB_CB(skb)->sacked, |
|
TCP_SKB_CB(skb)->seq, |
|
TCP_SKB_CB(skb)->end_seq, |
|
dup_sack, |
|
tcp_skb_pcount(skb), |
|
tcp_skb_timestamp_us(skb)); |
|
tcp_rate_skb_delivered(sk, skb, state->rate); |
|
if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED) |
|
list_del_init(&skb->tcp_tsorted_anchor); |
|
|
|
if (!before(TCP_SKB_CB(skb)->seq, |
|
tcp_highest_sack_seq(tp))) |
|
tcp_advance_highest_sack(sk, skb); |
|
} |
|
} |
|
return skb; |
|
} |
|
|
|
static struct sk_buff *tcp_sacktag_bsearch(struct sock *sk, u32 seq) |
|
{ |
|
struct rb_node *parent, **p = &sk->tcp_rtx_queue.rb_node; |
|
struct sk_buff *skb; |
|
|
|
while (*p) { |
|
parent = *p; |
|
skb = rb_to_skb(parent); |
|
if (before(seq, TCP_SKB_CB(skb)->seq)) { |
|
p = &parent->rb_left; |
|
continue; |
|
} |
|
if (!before(seq, TCP_SKB_CB(skb)->end_seq)) { |
|
p = &parent->rb_right; |
|
continue; |
|
} |
|
return skb; |
|
} |
|
return NULL; |
|
} |
|
|
|
static struct sk_buff *tcp_sacktag_skip(struct sk_buff *skb, struct sock *sk, |
|
u32 skip_to_seq) |
|
{ |
|
if (skb && after(TCP_SKB_CB(skb)->seq, skip_to_seq)) |
|
return skb; |
|
|
|
return tcp_sacktag_bsearch(sk, skip_to_seq); |
|
} |
|
|
|
static struct sk_buff *tcp_maybe_skipping_dsack(struct sk_buff *skb, |
|
struct sock *sk, |
|
struct tcp_sack_block *next_dup, |
|
struct tcp_sacktag_state *state, |
|
u32 skip_to_seq) |
|
{ |
|
if (!next_dup) |
|
return skb; |
|
|
|
if (before(next_dup->start_seq, skip_to_seq)) { |
|
skb = tcp_sacktag_skip(skb, sk, next_dup->start_seq); |
|
skb = tcp_sacktag_walk(skb, sk, NULL, state, |
|
next_dup->start_seq, next_dup->end_seq, |
|
1); |
|
} |
|
|
|
return skb; |
|
} |
|
|
|
static int tcp_sack_cache_ok(const struct tcp_sock *tp, const struct tcp_sack_block *cache) |
|
{ |
|
return cache < tp->recv_sack_cache + ARRAY_SIZE(tp->recv_sack_cache); |
|
} |
|
|
|
static int |
|
tcp_sacktag_write_queue(struct sock *sk, const struct sk_buff *ack_skb, |
|
u32 prior_snd_una, struct tcp_sacktag_state *state) |
|
{ |
|
struct tcp_sock *tp = tcp_sk(sk); |
|
const unsigned char *ptr = (skb_transport_header(ack_skb) + |
|
TCP_SKB_CB(ack_skb)->sacked); |
|
struct tcp_sack_block_wire *sp_wire = (struct tcp_sack_block_wire *)(ptr+2); |
|
struct tcp_sack_block sp[TCP_NUM_SACKS]; |
|
struct tcp_sack_block *cache; |
|
struct sk_buff *skb; |
|
int num_sacks = min(TCP_NUM_SACKS, (ptr[1] - TCPOLEN_SACK_BASE) >> 3); |
|
int used_sacks; |
|
bool found_dup_sack = false; |
|
int i, j; |
|
int first_sack_index; |
|
|
|
state->flag = 0; |
|
state->reord = tp->snd_nxt; |
|
|
|
if (!tp->sacked_out) |
|
tcp_highest_sack_reset(sk); |
|
|
|
found_dup_sack = tcp_check_dsack(sk, ack_skb, sp_wire, |
|
num_sacks, prior_snd_una, state); |
|
|
|
/* Eliminate too old ACKs, but take into |
|
* account more or less fresh ones, they can |
|
* contain valid SACK info. |
|
*/ |
|
if (before(TCP_SKB_CB(ack_skb)->ack_seq, prior_snd_una - tp->max_window)) |
|
return 0; |
|
|
|
if (!tp->packets_out) |
|
goto out; |
|
|
|
used_sacks = 0; |
|
first_sack_index = 0; |
|
for (i = 0; i < num_sacks; i++) { |
|
bool dup_sack = !i && found_dup_sack; |
|
|
|
sp[used_sacks].start_seq = get_unaligned_be32(&sp_wire[i].start_seq); |
|
sp[used_sacks].end_seq = get_unaligned_be32(&sp_wire[i].end_seq); |
|
|
|
if (!tcp_is_sackblock_valid(tp, dup_sack, |
|
sp[used_sacks].start_seq, |
|
sp[used_sacks].end_seq)) { |
|
int mib_idx; |
|
|
|
if (dup_sack) { |
|
if (!tp->undo_marker) |
|
mib_idx = LINUX_MIB_TCPDSACKIGNOREDNOUNDO; |
|
else |
|
mib_idx = LINUX_MIB_TCPDSACKIGNOREDOLD; |
|
} else { |
|
/* Don't count olds caused by ACK reordering */ |
|
if ((TCP_SKB_CB(ack_skb)->ack_seq != tp->snd_una) && |
|
!after(sp[used_sacks].end_seq, tp->snd_una)) |
|
continue; |
|
mib_idx = LINUX_MIB_TCPSACKDISCARD; |
|
} |
|
|
|
NET_INC_STATS(sock_net(sk), mib_idx); |
|
if (i == 0) |
|
first_sack_index = -1; |
|
continue; |
|
} |
|
|
|
/* Ignore very old stuff early */ |
|
if (!after(sp[used_sacks].end_seq, prior_snd_una)) { |
|
if (i == 0) |
|
first_sack_index = -1; |
|
continue; |
|
} |
|
|
|
used_sacks++; |
|
} |
|
|
|
/* order SACK blocks to allow in order walk of the retrans queue */ |
|
for (i = used_sacks - 1; i > 0; i--) { |
|
for (j = 0; j < i; j++) { |
|
if (after(sp[j].start_seq, sp[j + 1].start_seq)) { |
|
swap(sp[j], sp[j + 1]); |
|
|
|
/* Track where the first SACK block goes to */ |
|
if (j == first_sack_index) |
|
first_sack_index = j + 1; |
|
} |
|
} |
|
} |
|
|
|
state->mss_now = tcp_current_mss(sk); |
|
skb = NULL; |
|
i = 0; |
|
|
|
if (!tp->sacked_out) { |
|
/* It's already past, so skip checking against it */ |
|
cache = tp->recv_sack_cache + ARRAY_SIZE(tp->recv_sack_cache); |
|
} else { |
|
cache = tp->recv_sack_cache; |
|
/* Skip empty blocks in at head of the cache */ |
|
while (tcp_sack_cache_ok(tp, cache) && !cache->start_seq && |
|
!cache->end_seq) |
|
cache++; |
|
} |
|
|
|
while (i < used_sacks) { |
|
u32 start_seq = sp[i].start_seq; |
|
u32 end_seq = sp[i].end_seq; |
|
bool dup_sack = (found_dup_sack && (i == first_sack_index)); |
|
struct tcp_sack_block *next_dup = NULL; |
|
|
|
if (found_dup_sack && ((i + 1) == first_sack_index)) |
|
next_dup = &sp[i + 1]; |
|
|
|
/* Skip too early cached blocks */ |
|
while (tcp_sack_cache_ok(tp, cache) && |
|
!before(start_seq, cache->end_seq)) |
|
cache++; |
|
|
|
/* Can skip some work by looking recv_sack_cache? */ |
|
if (tcp_sack_cache_ok(tp, cache) && !dup_sack && |
|
after(end_seq, cache->start_seq)) { |
|
|
|
/* Head todo? */ |
|
if (before(start_seq, cache->start_seq)) { |
|
skb = tcp_sacktag_skip(skb, sk, start_seq); |
|
skb = tcp_sacktag_walk(skb, sk, next_dup, |
|
state, |
|
start_seq, |
|
cache->start_seq, |
|
dup_sack); |
|
} |
|
|
|
/* Rest of the block already fully processed? */ |
|
if (!after(end_seq, cache->end_seq)) |
|
goto advance_sp; |
|
|
|
skb = tcp_maybe_skipping_dsack(skb, sk, next_dup, |
|
state, |
|
cache->end_seq); |
|
|
|
/* ...tail remains todo... */ |
|
if (tcp_highest_sack_seq(tp) == cache->end_seq) { |
|
/* ...but better entrypoint exists! */ |
|
skb = tcp_highest_sack(sk); |
|
if (!skb) |
|
break; |
|
cache++; |
|
goto walk; |
|
} |
|
|
|
skb = tcp_sacktag_skip(skb, sk, cache->end_seq); |
|
/* Check overlap against next cached too (past this one already) */ |
|
cache++; |
|
continue; |
|
} |
|
|
|
if (!before(start_seq, tcp_highest_sack_seq(tp))) { |
|
skb = tcp_highest_sack(sk); |
|
if (!skb) |
|
break; |
|
} |
|
skb = tcp_sacktag_skip(skb, sk, start_seq); |
|
|
|
walk: |
|
skb = tcp_sacktag_walk(skb, sk, next_dup, state, |
|
start_seq, end_seq, dup_sack); |
|
|
|
advance_sp: |
|
i++; |
|
} |
|
|
|
/* Clear the head of the cache sack blocks so we can skip it next time */ |
|
for (i = 0; i < ARRAY_SIZE(tp->recv_sack_cache) - used_sacks; i++) { |
|
tp->recv_sack_cache[i].start_seq = 0; |
|
tp->recv_sack_cache[i].end_seq = 0; |
|
} |
|
for (j = 0; j < used_sacks; j++) |
|
tp->recv_sack_cache[i++] = sp[j]; |
|
|
|
if (inet_csk(sk)->icsk_ca_state != TCP_CA_Loss || tp->undo_marker) |
|
tcp_check_sack_reordering(sk, state->reord, 0); |
|
|
|
tcp_verify_left_out(tp); |
|
out: |
|
|
|
#if FASTRETRANS_DEBUG > 0 |
|
WARN_ON((int)tp->sacked_out < 0); |
|
WARN_ON((int)tp->lost_out < 0); |
|
WARN_ON((int)tp->retrans_out < 0); |
|
WARN_ON((int)tcp_packets_in_flight(tp) < 0); |
|
#endif |
|
return state->flag; |
|
} |
|
|
|
/* Limits sacked_out so that sum with lost_out isn't ever larger than |
|
* packets_out. Returns false if sacked_out adjustement wasn't necessary. |
|
*/ |
|
static bool tcp_limit_reno_sacked(struct tcp_sock *tp) |
|
{ |
|
u32 holes; |
|
|
|
holes = max(tp->lost_out, 1U); |
|
holes = min(holes, tp->packets_out); |
|
|
|
if ((tp->sacked_out + holes) > tp->packets_out) { |
|
tp->sacked_out = tp->packets_out - holes; |
|
return true; |
|
} |
|
return false; |
|
} |
|
|
|
/* If we receive more dupacks than we expected counting segments |
|
* in assumption of absent reordering, interpret this as reordering. |
|
* The only another reason could be bug in receiver TCP. |
|
*/ |
|
static void tcp_check_reno_reordering(struct sock *sk, const int addend) |
|
{ |
|
struct tcp_sock *tp = tcp_sk(sk); |
|
|
|
if (!tcp_limit_reno_sacked(tp)) |
|
return; |
|
|
|
tp->reordering = min_t(u32, tp->packets_out + addend, |
|
sock_net(sk)->ipv4.sysctl_tcp_max_reordering); |
|
tp->reord_seen++; |
|
NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPRENOREORDER); |
|
} |
|
|
|
/* Emulate SACKs for SACKless connection: account for a new dupack. */ |
|
|
|
static void tcp_add_reno_sack(struct sock *sk, int num_dupack, bool ece_ack) |
|
{ |
|
if (num_dupack) { |
|
struct tcp_sock *tp = tcp_sk(sk); |
|
u32 prior_sacked = tp->sacked_out; |
|
s32 delivered; |
|
|
|
tp->sacked_out += num_dupack; |
|
tcp_check_reno_reordering(sk, 0); |
|
delivered = tp->sacked_out - prior_sacked; |
|
if (delivered > 0) |
|
tcp_count_delivered(tp, delivered, ece_ack); |
|
tcp_verify_left_out(tp); |
|
} |
|
} |
|
|
|
/* Account for ACK, ACKing some data in Reno Recovery phase. */ |
|
|
|
static void tcp_remove_reno_sacks(struct sock *sk, int acked, bool ece_ack) |
|
{ |
|
struct tcp_sock *tp = tcp_sk(sk); |
|
|
|
if (acked > 0) { |
|
/* One ACK acked hole. The rest eat duplicate ACKs. */ |
|
tcp_count_delivered(tp, max_t(int, acked - tp->sacked_out, 1), |
|
ece_ack); |
|
if (acked - 1 >= tp->sacked_out) |
|
tp->sacked_out = 0; |
|
else |
|
tp->sacked_out -= acked - 1; |
|
} |
|
tcp_check_reno_reordering(sk, acked); |
|
tcp_verify_left_out(tp); |
|
} |
|
|
|
static inline void tcp_reset_reno_sack(struct tcp_sock *tp) |
|
{ |
|
tp->sacked_out = 0; |
|
} |
|
|
|
void tcp_clear_retrans(struct tcp_sock *tp) |
|
{ |
|
tp->retrans_out = 0; |
|
tp->lost_out = 0; |
|
tp->undo_marker = 0; |
|
tp->undo_retrans = -1; |
|
tp->sacked_out = 0; |
|
} |
|
|
|
static inline void tcp_init_undo(struct tcp_sock *tp) |
|
{ |
|
tp->undo_marker = tp->snd_una; |
|
/* Retransmission still in flight may cause DSACKs later. */ |
|
tp->undo_retrans = tp->retrans_out ? : -1; |
|
} |
|
|
|
static bool tcp_is_rack(const struct sock *sk) |
|
{ |
|
return sock_net(sk)->ipv4.sysctl_tcp_recovery & TCP_RACK_LOSS_DETECTION; |
|
} |
|
|
|
/* If we detect SACK reneging, forget all SACK information |
|
* and reset tags completely, otherwise preserve SACKs. If receiver |
|
* dropped its ofo queue, we will know this due to reneging detection. |
|
*/ |
|
static void tcp_timeout_mark_lost(struct sock *sk) |
|
{ |
|
struct tcp_sock *tp = tcp_sk(sk); |
|
struct sk_buff *skb, *head; |
|
bool is_reneg; /* is receiver reneging on SACKs? */ |
|
|
|
head = tcp_rtx_queue_head(sk); |
|
is_reneg = head && (TCP_SKB_CB(head)->sacked & TCPCB_SACKED_ACKED); |
|
if (is_reneg) { |
|
NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPSACKRENEGING); |
|
tp->sacked_out = 0; |
|
/* Mark SACK reneging until we recover from this loss event. */ |
|
tp->is_sack_reneg = 1; |
|
} else if (tcp_is_reno(tp)) { |
|
tcp_reset_reno_sack(tp); |
|
} |
|
|
|
skb = head; |
|
skb_rbtree_walk_from(skb) { |
|
if (is_reneg) |
|
TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_ACKED; |
|
else if (tcp_is_rack(sk) && skb != head && |
|
tcp_rack_skb_timeout(tp, skb, 0) > 0) |
|
continue; /* Don't mark recently sent ones lost yet */ |
|
tcp_mark_skb_lost(sk, skb); |
|
} |
|
tcp_verify_left_out(tp); |
|
tcp_clear_all_retrans_hints(tp); |
|
} |
|
|
|
/* Enter Loss state. */ |
|
void tcp_enter_loss(struct sock *sk) |
|
{ |
|
const struct inet_connection_sock *icsk = inet_csk(sk); |
|
struct tcp_sock *tp = tcp_sk(sk); |
|
struct net *net = sock_net(sk); |
|
bool new_recovery = icsk->icsk_ca_state < TCP_CA_Recovery; |
|
|
|
tcp_timeout_mark_lost(sk); |
|
|
|
/* Reduce ssthresh if it has not yet been made inside this window. */ |
|
if (icsk->icsk_ca_state <= TCP_CA_Disorder || |
|
!after(tp->high_seq, tp->snd_una) || |
|
(icsk->icsk_ca_state == TCP_CA_Loss && !icsk->icsk_retransmits)) { |
|
tp->prior_ssthresh = tcp_current_ssthresh(sk); |
|
tp->prior_cwnd = tp->snd_cwnd; |
|
tp->snd_ssthresh = icsk->icsk_ca_ops->ssthresh(sk); |
|
tcp_ca_event(sk, CA_EVENT_LOSS); |
|
tcp_init_undo(tp); |
|
} |
|
tp->snd_cwnd = tcp_packets_in_flight(tp) + 1; |
|
tp->snd_cwnd_cnt = 0; |
|
tp->snd_cwnd_stamp = tcp_jiffies32; |
|
|
|
/* Timeout in disordered state after receiving substantial DUPACKs |
|
* suggests that the degree of reordering is over-estimated. |
|
*/ |
|
if (icsk->icsk_ca_state <= TCP_CA_Disorder && |
|
tp->sacked_out >= net->ipv4.sysctl_tcp_reordering) |
|
tp->reordering = min_t(unsigned int, tp->reordering, |
|
net->ipv4.sysctl_tcp_reordering); |
|
tcp_set_ca_state(sk, TCP_CA_Loss); |
|
tp->high_seq = tp->snd_nxt; |
|
tcp_ecn_queue_cwr(tp); |
|
|
|
/* F-RTO RFC5682 sec 3.1 step 1: retransmit SND.UNA if no previous |
|
* loss recovery is underway except recurring timeout(s) on |
|
* the same SND.UNA (sec 3.2). Disable F-RTO on path MTU probing |
|
*/ |
|
tp->frto = net->ipv4.sysctl_tcp_frto && |
|
(new_recovery || icsk->icsk_retransmits) && |
|
!inet_csk(sk)->icsk_mtup.probe_size; |
|
} |
|
|
|
/* If ACK arrived pointing to a remembered SACK, it means that our |
|
* remembered SACKs do not reflect real state of receiver i.e. |
|
* receiver _host_ is heavily congested (or buggy). |
|
* |
|
* To avoid big spurious retransmission bursts due to transient SACK |
|
* scoreboard oddities that look like reneging, we give the receiver a |
|
* little time (max(RTT/2, 10ms)) to send us some more ACKs that will |
|
* restore sanity to the SACK scoreboard. If the apparent reneging |
|
* persists until this RTO then we'll clear the SACK scoreboard. |
|
*/ |
|
static bool tcp_check_sack_reneging(struct sock *sk, int flag) |
|
{ |
|
if (flag & FLAG_SACK_RENEGING) { |
|
struct tcp_sock *tp = tcp_sk(sk); |
|
unsigned long delay = max(usecs_to_jiffies(tp->srtt_us >> 4), |
|
msecs_to_jiffies(10)); |
|
|
|
inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, |
|
delay, TCP_RTO_MAX); |
|
return true; |
|
} |
|
return false; |
|
} |
|
|
|
/* Heurestics to calculate number of duplicate ACKs. There's no dupACKs |
|
* counter when SACK is enabled (without SACK, sacked_out is used for |
|
* that purpose). |
|
* |
|
* With reordering, holes may still be in flight, so RFC3517 recovery |
|
* uses pure sacked_out (total number of SACKed segments) even though |
|
* it violates the RFC that uses duplicate ACKs, often these are equal |
|
* but when e.g. out-of-window ACKs or packet duplication occurs, |
|
* they differ. Since neither occurs due to loss, TCP should really |
|
* ignore them. |
|
*/ |
|
static inline int tcp_dupack_heuristics(const struct tcp_sock *tp) |
|
{ |
|
return tp->sacked_out + 1; |
|
} |
|
|
|
/* Linux NewReno/SACK/ECN state machine. |
|
* -------------------------------------- |
|
* |
|
* "Open" Normal state, no dubious events, fast path. |
|
* "Disorder" In all the respects it is "Open", |
|
* but requires a bit more attention. It is entered when |
|
* we see some SACKs or dupacks. It is split of "Open" |
|
* mainly to move some processing from fast path to slow one. |
|
* "CWR" CWND was reduced due to some Congestion Notification event. |
|
* It can be ECN, ICMP source quench, local device congestion. |
|
* "Recovery" CWND was reduced, we are fast-retransmitting. |
|
* "Loss" CWND was reduced due to RTO timeout or SACK reneging. |
|
* |
|
* tcp_fastretrans_alert() is entered: |
|
* - each incoming ACK, if state is not "Open" |
|
* - when arrived ACK is unusual, namely: |
|
* * SACK |
|
* * Duplicate ACK. |
|
* * ECN ECE. |
|
* |
|
* Counting packets in flight is pretty simple. |
|
* |
|
* in_flight = packets_out - left_out + retrans_out |
|
* |
|
* packets_out is SND.NXT-SND.UNA counted in packets. |
|
* |
|
* retrans_out is number of retransmitted segments. |
|
* |
|
* left_out is number of segments left network, but not ACKed yet. |
|
* |
|
* left_out = sacked_out + lost_out |
|
* |
|
* sacked_out: Packets, which arrived to receiver out of order |
|
* and hence not ACKed. With SACKs this number is simply |
|
* amount of SACKed data. Even without SACKs |
|
* it is easy to give pretty reliable estimate of this number, |
|
* counting duplicate ACKs. |
|
* |
|
* lost_out: Packets lost by network. TCP has no explicit |
|
* "loss notification" feedback from network (for now). |
|
* It means that this number can be only _guessed_. |
|
* Actually, it is the heuristics to predict lossage that |
|
* distinguishes different algorithms. |
|
* |
|
* F.e. after RTO, when all the queue is considered as lost, |
|
* lost_out = packets_out and in_flight = retrans_out. |
|
* |
|
* Essentially, we have now a few algorithms detecting |
|
* lost packets. |
|
* |
|
* If the receiver supports SACK: |
|
* |
|
* RFC6675/3517: It is the conventional algorithm. A packet is |
|
* considered lost if the number of higher sequence packets |
|
* SACKed is greater than or equal the DUPACK thoreshold |
|
* (reordering). This is implemented in tcp_mark_head_lost and |
|
* tcp_update_scoreboard. |
|
* |
|
* RACK (draft-ietf-tcpm-rack-01): it is a newer algorithm |
|
* (2017-) that checks timing instead of counting DUPACKs. |
|
* Essentially a packet is considered lost if it's not S/ACKed |
|
* after RTT + reordering_window, where both metrics are |
|
* dynamically measured and adjusted. This is implemented in |
|
* tcp_rack_mark_lost. |
|
* |
|
* If the receiver does not support SACK: |
|
* |
|
* NewReno (RFC6582): in Recovery we assume that one segment |
|
* is lost (classic Reno). While we are in Recovery and |
|
* a partial ACK arrives, we assume that one more packet |
|
* is lost (NewReno). This heuristics are the same in NewReno |
|
* and SACK. |
|
* |
|
* Really tricky (and requiring careful tuning) part of algorithm |
|
* is hidden in functions tcp_time_to_recover() and tcp_xmit_retransmit_queue(). |
|
* The first determines the moment _when_ we should reduce CWND and, |
|
* hence, slow down forward transmission. In fact, it determines the moment |
|
* when we decide that hole is caused by loss, rather than by a reorder. |
|
* |
|
* tcp_xmit_retransmit_queue() decides, _what_ we should retransmit to fill |
|
* holes, caused by lost packets. |
|
* |
|
* And the most logically complicated part of algorithm is undo |
|
* heuristics. We detect false retransmits due to both too early |
|
* fast retransmit (reordering) and underestimated RTO, analyzing |
|
* timestamps and D-SACKs. When we detect that some segments were |
|
* retransmitted by mistake and CWND reduction was wrong, we undo |
|
* window reduction and abort recovery phase. This logic is hidden |
|
* inside several functions named tcp_try_undo_<something>. |
|
*/ |
|
|
|
/* This function decides, when we should leave Disordered state |
|
* and enter Recovery phase, reducing congestion window. |
|
* |
|
* Main question: may we further continue forward transmission |
|
* with the same cwnd? |
|
*/ |
|
static bool tcp_time_to_recover(struct sock *sk, int flag) |
|
{ |
|
struct tcp_sock *tp = tcp_sk(sk); |
|
|
|
/* Trick#1: The loss is proven. */ |
|
if (tp->lost_out) |
|
return true; |
|
|
|
/* Not-A-Trick#2 : Classic rule... */ |
|
if (!tcp_is_rack(sk) && tcp_dupack_heuristics(tp) > tp->reordering) |
|
return true; |
|
|
|
return false; |
|
} |
|
|
|
/* Detect loss in event "A" above by marking head of queue up as lost. |
|
* For RFC3517 SACK, a segment is considered lost if it |
|
* has at least tp->reordering SACKed seqments above it; "packets" refers to |
|
* the maximum SACKed segments to pass before reaching this limit. |
|
*/ |
|
static void tcp_mark_head_lost(struct sock *sk, int packets, int mark_head) |
|
{ |
|
struct tcp_sock *tp = tcp_sk(sk); |
|
struct sk_buff *skb; |
|
int cnt; |
|
/* Use SACK to deduce losses of new sequences sent during recovery */ |
|
const u32 loss_high = tp->snd_nxt; |
|
|
|
WARN_ON(packets > tp->packets_out); |
|
skb = tp->lost_skb_hint; |
|
if (skb) { |
|
/* Head already handled? */ |
|
if (mark_head && after(TCP_SKB_CB(skb)->seq, tp->snd_una)) |
|
return; |
|
cnt = tp->lost_cnt_hint; |
|
} else { |
|
skb = tcp_rtx_queue_head(sk); |
|
cnt = 0; |
|
} |
|
|
|
skb_rbtree_walk_from(skb) { |
|
/* TODO: do this better */ |
|
/* this is not the most efficient way to do this... */ |
|
tp->lost_skb_hint = skb; |
|
tp->lost_cnt_hint = cnt; |
|
|
|
if (after(TCP_SKB_CB(skb)->end_seq, loss_high)) |
|
break; |
|
|
|
if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED) |
|
cnt += tcp_skb_pcount(skb); |
|
|
|
if (cnt > packets) |
|
break; |
|
|
|
if (!(TCP_SKB_CB(skb)->sacked & TCPCB_LOST)) |
|
tcp_mark_skb_lost(sk, skb); |
|
|
|
if (mark_head) |
|
break; |
|
} |
|
tcp_verify_left_out(tp); |
|
} |
|
|
|
/* Account newly detected lost packet(s) */ |
|
|
|
static void tcp_update_scoreboard(struct sock *sk, int fast_rexmit) |
|
{ |
|
struct tcp_sock *tp = tcp_sk(sk); |
|
|
|
if (tcp_is_sack(tp)) { |
|
int sacked_upto = tp->sacked_out - tp->reordering; |
|
if (sacked_upto >= 0) |
|
tcp_mark_head_lost(sk, sacked_upto, 0); |
|
else if (fast_rexmit) |
|
tcp_mark_head_lost(sk, 1, 1); |
|
} |
|
} |
|
|
|
static bool tcp_tsopt_ecr_before(const struct tcp_sock *tp, u32 when) |
|
{ |
|
return tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr && |
|
before(tp->rx_opt.rcv_tsecr, when); |
|
} |
|
|
|
/* skb is spurious retransmitted if the returned timestamp echo |
|
* reply is prior to the skb transmission time |
|
*/ |
|
static bool tcp_skb_spurious_retrans(const struct tcp_sock *tp, |
|
const struct sk_buff *skb) |
|
{ |
|
return (TCP_SKB_CB(skb)->sacked & TCPCB_RETRANS) && |
|
tcp_tsopt_ecr_before(tp, tcp_skb_timestamp(skb)); |
|
} |
|
|
|
/* Nothing was retransmitted or returned timestamp is less |
|
* than timestamp of the first retransmission. |
|
*/ |
|
static inline bool tcp_packet_delayed(const struct tcp_sock *tp) |
|
{ |
|
return tp->retrans_stamp && |
|
tcp_tsopt_ecr_before(tp, tp->retrans_stamp); |
|
} |
|
|
|
/* Undo procedures. */ |
|
|
|
/* We can clear retrans_stamp when there are no retransmissions in the |
|
* window. It would seem that it is trivially available for us in |
|
* tp->retrans_out, however, that kind of assumptions doesn't consider |
|
* what will happen if errors occur when sending retransmission for the |
|
* second time. ...It could the that such segment has only |
|
* TCPCB_EVER_RETRANS set at the present time. It seems that checking |
|
* the head skb is enough except for some reneging corner cases that |
|
* are not worth the effort. |
|
* |
|
* Main reason for all this complexity is the fact that connection dying |
|
* time now depends on the validity of the retrans_stamp, in particular, |
|
* that successive retransmissions of a segment must not advance |
|
* retrans_stamp under any conditions. |
|
*/ |
|
static bool tcp_any_retrans_done(const struct sock *sk) |
|
{ |
|
const struct tcp_sock *tp = tcp_sk(sk); |
|
struct sk_buff *skb; |
|
|
|
if (tp->retrans_out) |
|
return true; |
|
|
|
skb = tcp_rtx_queue_head(sk); |
|
if (unlikely(skb && TCP_SKB_CB(skb)->sacked & TCPCB_EVER_RETRANS)) |
|
return true; |
|
|
|
return false; |
|
} |
|
|
|
static void DBGUNDO(struct sock *sk, const char *msg) |
|
{ |
|
#if FASTRETRANS_DEBUG > 1 |
|
struct tcp_sock *tp = tcp_sk(sk); |
|
struct inet_sock *inet = inet_sk(sk); |
|
|
|
if (sk->sk_family == AF_INET) { |
|
pr_debug("Undo %s %pI4/%u c%u l%u ss%u/%u p%u\n", |
|
msg, |
|
&inet->inet_daddr, ntohs(inet->inet_dport), |
|
tp->snd_cwnd, tcp_left_out(tp), |
|
tp->snd_ssthresh, tp->prior_ssthresh, |
|
tp->packets_out); |
|
} |
|
#if IS_ENABLED(CONFIG_IPV6) |
|
else if (sk->sk_family == AF_INET6) { |
|
pr_debug("Undo %s %pI6/%u c%u l%u ss%u/%u p%u\n", |
|
msg, |
|
&sk->sk_v6_daddr, ntohs(inet->inet_dport), |
|
tp->snd_cwnd, tcp_left_out(tp), |
|
tp->snd_ssthresh, tp->prior_ssthresh, |
|
tp->packets_out); |
|
} |
|
#endif |
|
#endif |
|
} |
|
|
|
static void tcp_undo_cwnd_reduction(struct sock *sk, bool unmark_loss) |
|
{ |
|
struct tcp_sock *tp = tcp_sk(sk); |
|
|
|
if (unmark_loss) { |
|
struct sk_buff *skb; |
|
|
|
skb_rbtree_walk(skb, &sk->tcp_rtx_queue) { |
|
TCP_SKB_CB(skb)->sacked &= ~TCPCB_LOST; |
|
} |
|
tp->lost_out = 0; |
|
tcp_clear_all_retrans_hints(tp); |
|
} |
|
|
|
if (tp->prior_ssthresh) { |
|
const struct inet_connection_sock *icsk = inet_csk(sk); |
|
|
|
tp->snd_cwnd = icsk->icsk_ca_ops->undo_cwnd(sk); |
|
|
|
if (tp->prior_ssthresh > tp->snd_ssthresh) { |
|
tp->snd_ssthresh = tp->prior_ssthresh; |
|
tcp_ecn_withdraw_cwr(tp); |
|
} |
|
} |
|
tp->snd_cwnd_stamp = tcp_jiffies32; |
|
tp->undo_marker = 0; |
|
tp->rack.advanced = 1; /* Force RACK to re-exam losses */ |
|
} |
|
|
|
static inline bool tcp_may_undo(const struct tcp_sock *tp) |
|
{ |
|
return tp->undo_marker && (!tp->undo_retrans || tcp_packet_delayed(tp)); |
|
} |
|
|
|
/* People celebrate: "We love our President!" */ |
|
static bool tcp_try_undo_recovery(struct sock *sk) |
|
{ |
|
struct tcp_sock *tp = tcp_sk(sk); |
|
|
|
if (tcp_may_undo(tp)) { |
|
int mib_idx; |
|
|
|
/* Happy end! We did not retransmit anything |
|
* or our original transmission succeeded. |
|
*/ |
|
DBGUNDO(sk, inet_csk(sk)->icsk_ca_state == TCP_CA_Loss ? "loss" : "retrans"); |
|
tcp_undo_cwnd_reduction(sk, false); |
|
if (inet_csk(sk)->icsk_ca_state == TCP_CA_Loss) |
|
mib_idx = LINUX_MIB_TCPLOSSUNDO; |
|
else |
|
mib_idx = LINUX_MIB_TCPFULLUNDO; |
|
|
|
NET_INC_STATS(sock_net(sk), mib_idx); |
|
} else if (tp->rack.reo_wnd_persist) { |
|
tp->rack.reo_wnd_persist--; |
|
} |
|
if (tp->snd_una == tp->high_seq && tcp_is_reno(tp)) { |
|
/* Hold old state until something *above* high_seq |
|
* is ACKed. For Reno it is MUST to prevent false |
|
* fast retransmits (RFC2582). SACK TCP is safe. */ |
|
if (!tcp_any_retrans_done(sk)) |
|
tp->retrans_stamp = 0; |
|
return true; |
|
} |
|
tcp_set_ca_state(sk, TCP_CA_Open); |
|
tp->is_sack_reneg = 0; |
|
return false; |
|
} |
|
|
|
/* Try to undo cwnd reduction, because D-SACKs acked all retransmitted data */ |
|
static bool tcp_try_undo_dsack(struct sock *sk) |
|
{ |
|
struct tcp_sock *tp = tcp_sk(sk); |
|
|
|
if (tp->undo_marker && !tp->undo_retrans) { |
|
tp->rack.reo_wnd_persist = min(TCP_RACK_RECOVERY_THRESH, |
|
tp->rack.reo_wnd_persist + 1); |
|
DBGUNDO(sk, "D-SACK"); |
|
tcp_undo_cwnd_reduction(sk, false); |
|
NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPDSACKUNDO); |
|
return true; |
|
} |
|
return false; |
|
} |
|
|
|
/* Undo during loss recovery after partial ACK or using F-RTO. */ |
|
static bool tcp_try_undo_loss(struct sock *sk, bool frto_undo) |
|
{ |
|
struct tcp_sock *tp = tcp_sk(sk); |
|
|
|
if (frto_undo || tcp_may_undo(tp)) { |
|
tcp_undo_cwnd_reduction(sk, true); |
|
|
|
DBGUNDO(sk, "partial loss"); |
|
NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPLOSSUNDO); |
|
if (frto_undo) |
|
NET_INC_STATS(sock_net(sk), |
|
LINUX_MIB_TCPSPURIOUSRTOS); |
|
inet_csk(sk)->icsk_retransmits = 0; |
|
if (frto_undo || tcp_is_sack(tp)) { |
|
tcp_set_ca_state(sk, TCP_CA_Open); |
|
tp->is_sack_reneg = 0; |
|
} |
|
return true; |
|
} |
|
return false; |
|
} |
|
|
|
/* The cwnd reduction in CWR and Recovery uses the PRR algorithm in RFC 6937. |
|
* It computes the number of packets to send (sndcnt) based on packets newly |
|
* delivered: |
|
* 1) If the packets in flight is larger than ssthresh, PRR spreads the |
|
* cwnd reductions across a full RTT. |
|
* 2) Otherwise PRR uses packet conservation to send as much as delivered. |
|
* But when SND_UNA is acked without further losses, |
|
* slow starts cwnd up to ssthresh to speed up the recovery. |
|
*/ |
|
static void tcp_init_cwnd_reduction(struct sock *sk) |
|
{ |
|
struct tcp_sock *tp = tcp_sk(sk); |
|
|
|
tp->high_seq = tp->snd_nxt; |
|
tp->tlp_high_seq = 0; |
|
tp->snd_cwnd_cnt = 0; |
|
tp->prior_cwnd = tp->snd_cwnd; |
|
tp->prr_delivered = 0; |
|
tp->prr_out = 0; |
|
tp->snd_ssthresh = inet_csk(sk)->icsk_ca_ops->ssthresh(sk); |
|
tcp_ecn_queue_cwr(tp); |
|
} |
|
|
|
void tcp_cwnd_reduction(struct sock *sk, int newly_acked_sacked, int newly_lost, int flag) |
|
{ |
|
struct tcp_sock *tp = tcp_sk(sk); |
|
int sndcnt = 0; |
|
int delta = tp->snd_ssthresh - tcp_packets_in_flight(tp); |
|
|
|
if (newly_acked_sacked <= 0 || WARN_ON_ONCE(!tp->prior_cwnd)) |
|
return; |
|
|
|
tp->prr_delivered += newly_acked_sacked; |
|
if (delta < 0) { |
|
u64 dividend = (u64)tp->snd_ssthresh * tp->prr_delivered + |
|
tp->prior_cwnd - 1; |
|
sndcnt = div_u64(dividend, tp->prior_cwnd) - tp->prr_out; |
|
} else if (flag & FLAG_SND_UNA_ADVANCED && !newly_lost) { |
|
sndcnt = min_t(int, delta, |
|
max_t(int, tp->prr_delivered - tp->prr_out, |
|
newly_acked_sacked) + 1); |
|
} else { |
|
sndcnt = min(delta, newly_acked_sacked); |
|
} |
|
/* Force a fast retransmit upon entering fast recovery */ |
|
sndcnt = max(sndcnt, (tp->prr_out ? 0 : 1)); |
|
tp->snd_cwnd = tcp_packets_in_flight(tp) + sndcnt; |
|
} |
|
|
|
static inline void tcp_end_cwnd_reduction(struct sock *sk) |
|
{ |
|
struct tcp_sock *tp = tcp_sk(sk); |
|
|
|
if (inet_csk(sk)->icsk_ca_ops->cong_control) |
|
return; |
|
|
|
/* Reset cwnd to ssthresh in CWR or Recovery (unless it's undone) */ |
|
if (tp->snd_ssthresh < TCP_INFINITE_SSTHRESH && |
|
(inet_csk(sk)->icsk_ca_state == TCP_CA_CWR || tp->undo_marker)) { |
|
tp->snd_cwnd = tp->snd_ssthresh; |
|
tp->snd_cwnd_stamp = tcp_jiffies32; |
|
} |
|
tcp_ca_event(sk, CA_EVENT_COMPLETE_CWR); |
|
} |
|
|
|
/* Enter CWR state. Disable cwnd undo since congestion is proven with ECN */ |
|
void tcp_enter_cwr(struct sock *sk) |
|
{ |
|
struct tcp_sock *tp = tcp_sk(sk); |
|
|
|
tp->prior_ssthresh = 0; |
|
if (inet_csk(sk)->icsk_ca_state < TCP_CA_CWR) { |
|
tp->undo_marker = 0; |
|
tcp_init_cwnd_reduction(sk); |
|
tcp_set_ca_state(sk, TCP_CA_CWR); |
|
} |
|
} |
|
EXPORT_SYMBOL(tcp_enter_cwr); |
|
|
|
static void tcp_try_keep_open(struct sock *sk) |
|
{ |
|
struct tcp_sock *tp = tcp_sk(sk); |
|
int state = TCP_CA_Open; |
|
|
|
if (tcp_left_out(tp) || tcp_any_retrans_done(sk)) |
|
state = TCP_CA_Disorder; |
|
|
|
if (inet_csk(sk)->icsk_ca_state != state) { |
|
tcp_set_ca_state(sk, state); |
|
tp->high_seq = tp->snd_nxt; |
|
} |
|
} |
|
|
|
static void tcp_try_to_open(struct sock *sk, int flag) |
|
{ |
|
struct tcp_sock *tp = tcp_sk(sk); |
|
|
|
tcp_verify_left_out(tp); |
|
|
|
if (!tcp_any_retrans_done(sk)) |
|
tp->retrans_stamp = 0; |
|
|
|
if (flag & FLAG_ECE) |
|
tcp_enter_cwr(sk); |
|
|
|
if (inet_csk(sk)->icsk_ca_state != TCP_CA_CWR) { |
|
tcp_try_keep_open(sk); |
|
} |
|
} |
|
|
|
static void tcp_mtup_probe_failed(struct sock *sk) |
|
{ |
|
struct inet_connection_sock *icsk = inet_csk(sk); |
|
|
|
icsk->icsk_mtup.search_high = icsk->icsk_mtup.probe_size - 1; |
|
icsk->icsk_mtup.probe_size = 0; |
|
NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPMTUPFAIL); |
|
} |
|
|
|
static void tcp_mtup_probe_success(struct sock *sk) |
|
{ |
|
struct tcp_sock *tp = tcp_sk(sk); |
|
struct inet_connection_sock *icsk = inet_csk(sk); |
|
|
|
/* FIXME: breaks with very large cwnd */ |
|
tp->prior_ssthresh = tcp_current_ssthresh(sk); |
|
tp->snd_cwnd = tp->snd_cwnd * |
|
tcp_mss_to_mtu(sk, tp->mss_cache) / |
|
icsk->icsk_mtup.probe_size; |
|
tp->snd_cwnd_cnt = 0; |
|
tp->snd_cwnd_stamp = tcp_jiffies32; |
|
tp->snd_ssthresh = tcp_current_ssthresh(sk); |
|
|
|
icsk->icsk_mtup.search_low = icsk->icsk_mtup.probe_size; |
|
icsk->icsk_mtup.probe_size = 0; |
|
tcp_sync_mss(sk, icsk->icsk_pmtu_cookie); |
|
NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPMTUPSUCCESS); |
|
} |
|
|
|
/* Do a simple retransmit without using the backoff mechanisms in |
|
* tcp_timer. This is used for path mtu discovery. |
|
* The socket is already locked here. |
|
*/ |
|
void tcp_simple_retransmit(struct sock *sk) |
|
{ |
|
const struct inet_connection_sock *icsk = inet_csk(sk); |
|
struct tcp_sock *tp = tcp_sk(sk); |
|
struct sk_buff *skb; |
|
int mss; |
|
|
|
/* A fastopen SYN request is stored as two separate packets within |
|
* the retransmit queue, this is done by tcp_send_syn_data(). |
|
* As a result simply checking the MSS of the frames in the queue |
|
* will not work for the SYN packet. |
|
* |
|
* Us being here is an indication of a path MTU issue so we can |
|
* assume that the fastopen SYN was lost and just mark all the |
|
* frames in the retransmit queue as lost. We will use an MSS of |
|
* -1 to mark all frames as lost, otherwise compute the current MSS. |
|
*/ |
|
if (tp->syn_data && sk->sk_state == TCP_SYN_SENT) |
|
mss = -1; |
|
else |
|
mss = tcp_current_mss(sk); |
|
|
|
skb_rbtree_walk(skb, &sk->tcp_rtx_queue) { |
|
if (tcp_skb_seglen(skb) > mss) |
|
tcp_mark_skb_lost(sk, skb); |
|
} |
|
|
|
tcp_clear_retrans_hints_partial(tp); |
|
|
|
if (!tp->lost_out) |
|
return; |
|
|
|
if (tcp_is_reno(tp)) |
|
tcp_limit_reno_sacked(tp); |
|
|
|
tcp_verify_left_out(tp); |
|
|
|
/* Don't muck with the congestion window here. |
|
* Reason is that we do not increase amount of _data_ |
|
* in network, but units changed and effective |
|
* cwnd/ssthresh really reduced now. |
|
*/ |
|
if (icsk->icsk_ca_state != TCP_CA_Loss) { |
|
tp->high_seq = tp->snd_nxt; |
|
tp->snd_ssthresh = tcp_current_ssthresh(sk); |
|
tp->prior_ssthresh = 0; |
|
tp->undo_marker = 0; |
|
tcp_set_ca_state(sk, TCP_CA_Loss); |
|
} |
|
tcp_xmit_retransmit_queue(sk); |
|
} |
|
EXPORT_SYMBOL(tcp_simple_retransmit); |
|
|
|
void tcp_enter_recovery(struct sock *sk, bool ece_ack) |
|
{ |
|
struct tcp_sock *tp = tcp_sk(sk); |
|
int mib_idx; |
|
|
|
if (tcp_is_reno(tp)) |
|
mib_idx = LINUX_MIB_TCPRENORECOVERY; |
|
else |
|
mib_idx = LINUX_MIB_TCPSACKRECOVERY; |
|
|
|
NET_INC_STATS(sock_net(sk), mib_idx); |
|
|
|
tp->prior_ssthresh = 0; |
|
tcp_init_undo(tp); |
|
|
|
if (!tcp_in_cwnd_reduction(sk)) { |
|
if (!ece_ack) |
|
tp->prior_ssthresh = tcp_current_ssthresh(sk); |
|
tcp_init_cwnd_reduction(sk); |
|
} |
|
tcp_set_ca_state(sk, TCP_CA_Recovery); |
|
} |
|
|
|
/* Process an ACK in CA_Loss state. Move to CA_Open if lost data are |
|
* recovered or spurious. Otherwise retransmits more on partial ACKs. |
|
*/ |
|
static void tcp_process_loss(struct sock *sk, int flag, int num_dupack, |
|
int *rexmit) |
|
{ |
|
struct tcp_sock *tp = tcp_sk(sk); |
|
bool recovered = !before(tp->snd_una, tp->high_seq); |
|
|
|
if ((flag & FLAG_SND_UNA_ADVANCED || rcu_access_pointer(tp->fastopen_rsk)) && |
|
tcp_try_undo_loss(sk, false)) |
|
return; |
|
|
|
if (tp->frto) { /* F-RTO RFC5682 sec 3.1 (sack enhanced version). */ |
|
/* Step 3.b. A timeout is spurious if not all data are |
|
* lost, i.e., never-retransmitted data are (s)acked. |
|
*/ |
|
if ((flag & FLAG_ORIG_SACK_ACKED) && |
|
tcp_try_undo_loss(sk, true)) |
|
return; |
|
|
|
if (after(tp->snd_nxt, tp->high_seq)) { |
|
if (flag & FLAG_DATA_SACKED || num_dupack) |
|
tp->frto = 0; /* Step 3.a. loss was real */ |
|
} else if (flag & FLAG_SND_UNA_ADVANCED && !recovered) { |
|
tp->high_seq = tp->snd_nxt; |
|
/* Step 2.b. Try send new data (but deferred until cwnd |
|
* is updated in tcp_ack()). Otherwise fall back to |
|
* the conventional recovery. |
|
*/ |
|
if (!tcp_write_queue_empty(sk) && |
|
after(tcp_wnd_end(tp), tp->snd_nxt)) { |
|
*rexmit = REXMIT_NEW; |
|
return; |
|
} |
|
tp->frto = 0; |
|
} |
|
} |
|
|
|
if (recovered) { |
|
/* F-RTO RFC5682 sec 3.1 step 2.a and 1st part of step 3.a */ |
|
tcp_try_undo_recovery(sk); |
|
return; |
|
} |
|
if (tcp_is_reno(tp)) { |
|
/* A Reno DUPACK means new data in F-RTO step 2.b above are |
|
* delivered. Lower inflight to clock out (re)tranmissions. |
|
*/ |
|
if (after(tp->snd_nxt, tp->high_seq) && num_dupack) |
|
tcp_add_reno_sack(sk, num_dupack, flag & FLAG_ECE); |
|
else if (flag & FLAG_SND_UNA_ADVANCED) |
|
tcp_reset_reno_sack(tp); |
|
} |
|
*rexmit = REXMIT_LOST; |
|
} |
|
|
|
static bool tcp_force_fast_retransmit(struct sock *sk) |
|
{ |
|
struct tcp_sock *tp = tcp_sk(sk); |
|
|
|
return after(tcp_highest_sack_seq(tp), |
|
tp->snd_una + tp->reordering * tp->mss_cache); |
|
} |
|
|
|
/* Undo during fast recovery after partial ACK. */ |
|
static bool tcp_try_undo_partial(struct sock *sk, u32 prior_snd_una, |
|
bool *do_lost) |
|
{ |
|
struct tcp_sock *tp = tcp_sk(sk); |
|
|
|
if (tp->undo_marker && tcp_packet_delayed(tp)) { |
|
/* Plain luck! Hole if filled with delayed |
|
* packet, rather than with a retransmit. Check reordering. |
|
*/ |
|
tcp_check_sack_reordering(sk, prior_snd_una, 1); |
|
|
|
/* We are getting evidence that the reordering degree is higher |
|
* than we realized. If there are no retransmits out then we |
|
* can undo. Otherwise we clock out new packets but do not |
|
* mark more packets lost or retransmit more. |
|
*/ |
|
if (tp->retrans_out) |
|
return true; |
|
|
|
if (!tcp_any_retrans_done(sk)) |
|
tp->retrans_stamp = 0; |
|
|
|
DBGUNDO(sk, "partial recovery"); |
|
tcp_undo_cwnd_reduction(sk, true); |
|
NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPPARTIALUNDO); |
|
tcp_try_keep_open(sk); |
|
} else { |
|
/* Partial ACK arrived. Force fast retransmit. */ |
|
*do_lost = tcp_force_fast_retransmit(sk); |
|
} |
|
return false; |
|
} |
|
|
|
static void tcp_identify_packet_loss(struct sock *sk, int *ack_flag) |
|
{ |
|
struct tcp_sock *tp = tcp_sk(sk); |
|
|
|
if (tcp_rtx_queue_empty(sk)) |
|
return; |
|
|
|
if (unlikely(tcp_is_reno(tp))) { |
|
tcp_newreno_mark_lost(sk, *ack_flag & FLAG_SND_UNA_ADVANCED); |
|
} else if (tcp_is_rack(sk)) { |
|
u32 prior_retrans = tp->retrans_out; |
|
|
|
if (tcp_rack_mark_lost(sk)) |
|
*ack_flag &= ~FLAG_SET_XMIT_TIMER; |
|
if (prior_retrans > tp->retrans_out) |
|
*ack_flag |= FLAG_LOST_RETRANS; |
|
} |
|
} |
|
|
|
/* Process an event, which can update packets-in-flight not trivially. |
|
* Main goal of this function is to calculate new estimate for left_out, |
|
* taking into account both packets sitting in receiver's buffer and |
|
* packets lost by network. |
|
* |
|
* Besides that it updates the congestion state when packet loss or ECN |
|
* is detected. But it does not reduce the cwnd, it is done by the |
|
* congestion control later. |
|
* |
|
* It does _not_ decide what to send, it is made in function |
|
* tcp_xmit_retransmit_queue(). |
|
*/ |
|
static void tcp_fastretrans_alert(struct sock *sk, const u32 prior_snd_una, |
|
int num_dupack, int *ack_flag, int *rexmit) |
|
{ |
|
struct inet_connection_sock *icsk = inet_csk(sk); |
|
struct tcp_sock *tp = tcp_sk(sk); |
|
int fast_rexmit = 0, flag = *ack_flag; |
|
bool ece_ack = flag & FLAG_ECE; |
|
bool do_lost = num_dupack || ((flag & FLAG_DATA_SACKED) && |
|
tcp_force_fast_retransmit(sk)); |
|
|
|
if (!tp->packets_out && tp->sacked_out) |
|
tp->sacked_out = 0; |
|
|
|
/* Now state machine starts. |
|
* A. ECE, hence prohibit cwnd undoing, the reduction is required. */ |
|
if (ece_ack) |
|
tp->prior_ssthresh = 0; |
|
|
|
/* B. In all the states check for reneging SACKs. */ |
|
if (tcp_check_sack_reneging(sk, flag)) |
|
return; |
|
|
|
/* C. Check consistency of the current state. */ |
|
tcp_verify_left_out(tp); |
|
|
|
/* D. Check state exit conditions. State can be terminated |
|
* when high_seq is ACKed. */ |
|
if (icsk->icsk_ca_state == TCP_CA_Open) { |
|
WARN_ON(tp->retrans_out != 0 && !tp->syn_data); |
|
tp->retrans_stamp = 0; |
|
} else if (!before(tp->snd_una, tp->high_seq)) { |
|
switch (icsk->icsk_ca_state) { |
|
case TCP_CA_CWR: |
|
/* CWR is to be held something *above* high_seq |
|
* is ACKed for CWR bit to reach receiver. */ |
|
if (tp->snd_una != tp->high_seq) { |
|
tcp_end_cwnd_reduction(sk); |
|
tcp_set_ca_state(sk, TCP_CA_Open); |
|
} |
|
break; |
|
|
|
case TCP_CA_Recovery: |
|
if (tcp_is_reno(tp)) |
|
tcp_reset_reno_sack(tp); |
|
if (tcp_try_undo_recovery(sk)) |
|
return; |
|
tcp_end_cwnd_reduction(sk); |
|
break; |
|
} |
|
} |
|
|
|
/* E. Process state. */ |
|
switch (icsk->icsk_ca_state) { |
|
case TCP_CA_Recovery: |
|
if (!(flag & FLAG_SND_UNA_ADVANCED)) { |
|
if (tcp_is_reno(tp)) |
|
tcp_add_reno_sack(sk, num_dupack, ece_ack); |
|
} else if (tcp_try_undo_partial(sk, prior_snd_una, &do_lost)) |
|
return; |
|
|
|
if (tcp_try_undo_dsack(sk)) |
|
tcp_try_keep_open(sk); |
|
|
|
tcp_identify_packet_loss(sk, ack_flag); |
|
if (icsk->icsk_ca_state != TCP_CA_Recovery) { |
|
if (!tcp_time_to_recover(sk, flag)) |
|
return; |
|
/* Undo reverts the recovery state. If loss is evident, |
|
* starts a new recovery (e.g. reordering then loss); |
|
*/ |
|
tcp_enter_recovery(sk, ece_ack); |
|
} |
|
break; |
|
case TCP_CA_Loss: |
|
tcp_process_loss(sk, flag, num_dupack, rexmit); |
|
tcp_identify_packet_loss(sk, ack_flag); |
|
if (!(icsk->icsk_ca_state == TCP_CA_Open || |
|
(*ack_flag & FLAG_LOST_RETRANS))) |
|
return; |
|
/* Change state if cwnd is undone or retransmits are lost */ |
|
fallthrough; |
|
default: |
|
if (tcp_is_reno(tp)) { |
|
if (flag & FLAG_SND_UNA_ADVANCED) |
|
tcp_reset_reno_sack(tp); |
|
tcp_add_reno_sack(sk, num_dupack, ece_ack); |
|
} |
|
|
|
if (icsk->icsk_ca_state <= TCP_CA_Disorder) |
|
tcp_try_undo_dsack(sk); |
|
|
|
tcp_identify_packet_loss(sk, ack_flag); |
|
if (!tcp_time_to_recover(sk, flag)) { |
|
tcp_try_to_open(sk, flag); |
|
return; |
|
} |
|
|
|
/* MTU probe failure: don't reduce cwnd */ |
|
if (icsk->icsk_ca_state < TCP_CA_CWR && |
|
icsk->icsk_mtup.probe_size && |
|
tp->snd_una == tp->mtu_probe.probe_seq_start) { |
|
tcp_mtup_probe_failed(sk); |
|
/* Restores the reduction we did in tcp_mtup_probe() */ |
|
tp->snd_cwnd++; |
|
tcp_simple_retransmit(sk); |
|
return; |
|
} |
|
|
|
/* Otherwise enter Recovery state */ |
|
tcp_enter_recovery(sk, ece_ack); |
|
fast_rexmit = 1; |
|
} |
|
|
|
if (!tcp_is_rack(sk) && do_lost) |
|
tcp_update_scoreboard(sk, fast_rexmit); |
|
*rexmit = REXMIT_LOST; |
|
} |
|
|
|
static void tcp_update_rtt_min(struct sock *sk, u32 rtt_us, const int flag) |
|
{ |
|
u32 wlen = sock_net(sk)->ipv4.sysctl_tcp_min_rtt_wlen * HZ; |
|
struct tcp_sock *tp = tcp_sk(sk); |
|
|
|
if ((flag & FLAG_ACK_MAYBE_DELAYED) && rtt_us > tcp_min_rtt(tp)) { |
|
/* If the remote keeps returning delayed ACKs, eventually |
|
* the min filter would pick it up and overestimate the |
|
* prop. delay when it expires. Skip suspected delayed ACKs. |
|
*/ |
|
return; |
|
} |
|
minmax_running_min(&tp->rtt_min, wlen, tcp_jiffies32, |
|
rtt_us ? : jiffies_to_usecs(1)); |
|
} |
|
|
|
static bool tcp_ack_update_rtt(struct sock *sk, const int flag, |
|
long seq_rtt_us, long sack_rtt_us, |
|
long ca_rtt_us, struct rate_sample *rs) |
|
{ |
|
const struct tcp_sock *tp = tcp_sk(sk); |
|
|
|
/* Prefer RTT measured from ACK's timing to TS-ECR. This is because |
|
* broken middle-boxes or peers may corrupt TS-ECR fields. But |
|
* Karn's algorithm forbids taking RTT if some retransmitted data |
|
* is acked (RFC6298). |
|
*/ |
|
if (seq_rtt_us < 0) |
|
seq_rtt_us = sack_rtt_us; |
|
|
|
/* RTTM Rule: A TSecr value received in a segment is used to |
|
* update the averaged RTT measurement only if the segment |
|
* acknowledges some new data, i.e., only if it advances the |
|
* left edge of the send window. |
|
* See draft-ietf-tcplw-high-performance-00, section 3.3. |
|
*/ |
|
if (seq_rtt_us < 0 && tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr && |
|
flag & FLAG_ACKED) { |
|
u32 delta = tcp_time_stamp(tp) - tp->rx_opt.rcv_tsecr; |
|
|
|
if (likely(delta < INT_MAX / (USEC_PER_SEC / TCP_TS_HZ))) { |
|
if (!delta) |
|
delta = 1; |
|
seq_rtt_us = delta * (USEC_PER_SEC / TCP_TS_HZ); |
|
ca_rtt_us = seq_rtt_us; |
|
} |
|
} |
|
rs->rtt_us = ca_rtt_us; /* RTT of last (S)ACKed packet (or -1) */ |
|
if (seq_rtt_us < 0) |
|
return false; |
|
|
|
/* ca_rtt_us >= 0 is counting on the invariant that ca_rtt_us is |
|
* always taken together with ACK, SACK, or TS-opts. Any negative |
|
* values will be skipped with the seq_rtt_us < 0 check above. |
|
*/ |
|
tcp_update_rtt_min(sk, ca_rtt_us, flag); |
|
tcp_rtt_estimator(sk, seq_rtt_us); |
|
tcp_set_rto(sk); |
|
|
|
/* RFC6298: only reset backoff on valid RTT measurement. */ |
|
inet_csk(sk)->icsk_backoff = 0; |
|
return true; |
|
} |
|
|
|
/* Compute time elapsed between (last) SYNACK and the ACK completing 3WHS. */ |
|
void tcp_synack_rtt_meas(struct sock *sk, struct request_sock *req) |
|
{ |
|
struct rate_sample rs; |
|
long rtt_us = -1L; |
|
|
|
if (req && !req->num_retrans && tcp_rsk(req)->snt_synack) |
|
rtt_us = tcp_stamp_us_delta(tcp_clock_us(), tcp_rsk(req)->snt_synack); |
|
|
|
tcp_ack_update_rtt(sk, FLAG_SYN_ACKED, rtt_us, -1L, rtt_us, &rs); |
|
} |
|
|
|
|
|
static void tcp_cong_avoid(struct sock *sk, u32 ack, u32 acked) |
|
{ |
|
const struct inet_connection_sock *icsk = inet_csk(sk); |
|
|
|
icsk->icsk_ca_ops->cong_avoid(sk, ack, acked); |
|
tcp_sk(sk)->snd_cwnd_stamp = tcp_jiffies32; |
|
} |
|
|
|
/* Restart timer after forward progress on connection. |
|
* RFC2988 recommends to restart timer to now+rto. |
|
*/ |
|
void tcp_rearm_rto(struct sock *sk) |
|
{ |
|
const struct inet_connection_sock *icsk = inet_csk(sk); |
|
struct tcp_sock *tp = tcp_sk(sk); |
|
|
|
/* If the retrans timer is currently being used by Fast Open |
|
* for SYN-ACK retrans purpose, stay put. |
|
*/ |
|
if (rcu_access_pointer(tp->fastopen_rsk)) |
|
return; |
|
|
|
if (!tp->packets_out) { |
|
inet_csk_clear_xmit_timer(sk, ICSK_TIME_RETRANS); |
|
} else { |
|
u32 rto = inet_csk(sk)->icsk_rto; |
|
/* Offset the time elapsed after installing regular RTO */ |
|
if (icsk->icsk_pending == ICSK_TIME_REO_TIMEOUT || |
|
icsk->icsk_pending == ICSK_TIME_LOSS_PROBE) { |
|
s64 delta_us = tcp_rto_delta_us(sk); |
|
/* delta_us may not be positive if the socket is locked |
|
* when the retrans timer fires and is rescheduled. |
|
*/ |
|
rto = usecs_to_jiffies(max_t(int, delta_us, 1)); |
|
} |
|
tcp_reset_xmit_timer(sk, ICSK_TIME_RETRANS, rto, |
|
TCP_RTO_MAX); |
|
} |
|
} |
|
|
|
/* Try to schedule a loss probe; if that doesn't work, then schedule an RTO. */ |
|
static void tcp_set_xmit_timer(struct sock *sk) |
|
{ |
|
if (!tcp_schedule_loss_probe(sk, true)) |
|
tcp_rearm_rto(sk); |
|
} |
|
|
|
/* If we get here, the whole TSO packet has not been acked. */ |
|
static u32 tcp_tso_acked(struct sock *sk, struct sk_buff *skb) |
|
{ |
|
struct tcp_sock *tp = tcp_sk(sk); |
|
u32 packets_acked; |
|
|
|
BUG_ON(!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una)); |
|
|
|
packets_acked = tcp_skb_pcount(skb); |
|
if (tcp_trim_head(sk, skb, tp->snd_una - TCP_SKB_CB(skb)->seq)) |
|
return 0; |
|
packets_acked -= tcp_skb_pcount(skb); |
|
|
|
if (packets_acked) { |
|
BUG_ON(tcp_skb_pcount(skb) == 0); |
|
BUG_ON(!before(TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq)); |
|
} |
|
|
|
return packets_acked; |
|
} |
|
|
|
static void tcp_ack_tstamp(struct sock *sk, struct sk_buff *skb, |
|
const struct sk_buff *ack_skb, u32 prior_snd_una) |
|
{ |
|
const struct skb_shared_info *shinfo; |
|
|
|
/* Avoid cache line misses to get skb_shinfo() and shinfo->tx_flags */ |
|
if (likely(!TCP_SKB_CB(skb)->txstamp_ack)) |
|
return; |
|
|
|
shinfo = skb_shinfo(skb); |
|
if (!before(shinfo->tskey, prior_snd_una) && |
|
before(shinfo->tskey, tcp_sk(sk)->snd_una)) { |
|
tcp_skb_tsorted_save(skb) { |
|
__skb_tstamp_tx(skb, ack_skb, NULL, sk, SCM_TSTAMP_ACK); |
|
} tcp_skb_tsorted_restore(skb); |
|
} |
|
} |
|
|
|
/* Remove acknowledged frames from the retransmission queue. If our packet |
|
* is before the ack sequence we can discard it as it's confirmed to have |
|
* arrived at the other end. |
|
*/ |
|
static int tcp_clean_rtx_queue(struct sock *sk, const struct sk_buff *ack_skb, |
|
u32 prior_fack, u32 prior_snd_una, |
|
struct tcp_sacktag_state *sack, bool ece_ack) |
|
{ |
|
const struct inet_connection_sock *icsk = inet_csk(sk); |
|
u64 first_ackt, last_ackt; |
|
struct tcp_sock *tp = tcp_sk(sk); |
|
u32 prior_sacked = tp->sacked_out; |
|
u32 reord = tp->snd_nxt; /* lowest acked un-retx un-sacked seq */ |
|
struct sk_buff *skb, *next; |
|
bool fully_acked = true; |
|
long sack_rtt_us = -1L; |
|
long seq_rtt_us = -1L; |
|
long ca_rtt_us = -1L; |
|
u32 pkts_acked = 0; |
|
bool rtt_update; |
|
int flag = 0; |
|
|
|
first_ackt = 0; |
|
|
|
for (skb = skb_rb_first(&sk->tcp_rtx_queue); skb; skb = next) { |
|
struct tcp_skb_cb *scb = TCP_SKB_CB(skb); |
|
const u32 start_seq = scb->seq; |
|
u8 sacked = scb->sacked; |
|
u32 acked_pcount; |
|
|
|
/* Determine how many packets and what bytes were acked, tso and else */ |
|
if (after(scb->end_seq, tp->snd_una)) { |
|
if (tcp_skb_pcount(skb) == 1 || |
|
!after(tp->snd_una, scb->seq)) |
|
break; |
|
|
|
acked_pcount = tcp_tso_acked(sk, skb); |
|
if (!acked_pcount) |
|
break; |
|
fully_acked = false; |
|
} else { |
|
acked_pcount = tcp_skb_pcount(skb); |
|
} |
|
|
|
if (unlikely(sacked & TCPCB_RETRANS)) { |
|
if (sacked & TCPCB_SACKED_RETRANS) |
|
tp->retrans_out -= acked_pcount; |
|
flag |= FLAG_RETRANS_DATA_ACKED; |
|
} else if (!(sacked & TCPCB_SACKED_ACKED)) { |
|
last_ackt = tcp_skb_timestamp_us(skb); |
|
WARN_ON_ONCE(last_ackt == 0); |
|
if (!first_ackt) |
|
first_ackt = last_ackt; |
|
|
|
if (before(start_seq, reord)) |
|
reord = start_seq; |
|
if (!after(scb->end_seq, tp->high_seq)) |
|
flag |= FLAG_ORIG_SACK_ACKED; |
|
} |
|
|
|
if (sacked & TCPCB_SACKED_ACKED) { |
|
tp->sacked_out -= acked_pcount; |
|
} else if (tcp_is_sack(tp)) { |
|
tcp_count_delivered(tp, acked_pcount, ece_ack); |
|
if (!tcp_skb_spurious_retrans(tp, skb)) |
|
tcp_rack_advance(tp, sacked, scb->end_seq, |
|
tcp_skb_timestamp_us(skb)); |
|
} |
|
if (sacked & TCPCB_LOST) |
|
tp->lost_out -= acked_pcount; |
|
|
|
tp->packets_out -= acked_pcount; |
|
pkts_acked += acked_pcount; |
|
tcp_rate_skb_delivered(sk, skb, sack->rate); |
|
|
|
/* Initial outgoing SYN's get put onto the write_queue |
|
* just like anything else we transmit. It is not |
|
* true data, and if we misinform our callers that |
|
* this ACK acks real data, we will erroneously exit |
|
* connection startup slow start one packet too |
|
* quickly. This is severely frowned upon behavior. |
|
*/ |
|
if (likely(!(scb->tcp_flags & TCPHDR_SYN))) { |
|
flag |= FLAG_DATA_ACKED; |
|
} else { |
|
flag |= FLAG_SYN_ACKED; |
|
tp->retrans_stamp = 0; |
|
} |
|
|
|
if (!fully_acked) |
|
break; |
|
|
|
tcp_ack_tstamp(sk, skb, ack_skb, prior_snd_una); |
|
|
|
next = skb_rb_next(skb); |
|
if (unlikely(skb == tp->retransmit_skb_hint)) |
|
tp->retransmit_skb_hint = NULL; |
|
if (unlikely(skb == tp->lost_skb_hint)) |
|
tp->lost_skb_hint = NULL; |
|
tcp_highest_sack_replace(sk, skb, next); |
|
tcp_rtx_queue_unlink_and_free(skb, sk); |
|
} |
|
|
|
if (!skb) |
|
tcp_chrono_stop(sk, TCP_CHRONO_BUSY); |
|
|
|
if (likely(between(tp->snd_up, prior_snd_una, tp->snd_una))) |
|
tp->snd_up = tp->snd_una; |
|
|
|
if (skb) { |
|
tcp_ack_tstamp(sk, skb, ack_skb, prior_snd_una); |
|
if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED) |
|
flag |= FLAG_SACK_RENEGING; |
|
} |
|
|
|
if (likely(first_ackt) && !(flag & FLAG_RETRANS_DATA_ACKED)) { |
|
seq_rtt_us = tcp_stamp_us_delta(tp->tcp_mstamp, first_ackt); |
|
ca_rtt_us = tcp_stamp_us_delta(tp->tcp_mstamp, last_ackt); |
|
|
|
if (pkts_acked == 1 && fully_acked && !prior_sacked && |
|
(tp->snd_una - prior_snd_una) < tp->mss_cache && |
|
sack->rate->prior_delivered + 1 == tp->delivered && |
|
!(flag & (FLAG_CA_ALERT | FLAG_SYN_ACKED))) { |
|
/* Conservatively mark a delayed ACK. It's typically |
|
* from a lone runt packet over the round trip to |
|
* a receiver w/o out-of-order or CE events. |
|
*/ |
|
flag |= FLAG_ACK_MAYBE_DELAYED; |
|
} |
|
} |
|
if (sack->first_sackt) { |
|
sack_rtt_us = tcp_stamp_us_delta(tp->tcp_mstamp, sack->first_sackt); |
|
ca_rtt_us = tcp_stamp_us_delta(tp->tcp_mstamp, sack->last_sackt); |
|
} |
|
rtt_update = tcp_ack_update_rtt(sk, flag, seq_rtt_us, sack_rtt_us, |
|
ca_rtt_us, sack->rate); |
|
|
|
if (flag & FLAG_ACKED) { |
|
flag |= FLAG_SET_XMIT_TIMER; /* set TLP or RTO timer */ |
|
if (unlikely(icsk->icsk_mtup.probe_size && |
|
!after(tp->mtu_probe.probe_seq_end, tp->snd_una))) { |
|
tcp_mtup_probe_success(sk); |
|
} |
|
|
|
if (tcp_is_reno(tp)) { |
|
tcp_remove_reno_sacks(sk, pkts_acked, ece_ack); |
|
|
|
/* If any of the cumulatively ACKed segments was |
|
* retransmitted, non-SACK case cannot confirm that |
|
* progress was due to original transmission due to |
|
* lack of TCPCB_SACKED_ACKED bits even if some of |
|
* the packets may have been never retransmitted. |
|
*/ |
|
if (flag & FLAG_RETRANS_DATA_ACKED) |
|
flag &= ~FLAG_ORIG_SACK_ACKED; |
|
} else { |
|
int delta; |
|
|
|
/* Non-retransmitted hole got filled? That's reordering */ |
|
if (before(reord, prior_fack)) |
|
tcp_check_sack_reordering(sk, reord, 0); |
|
|
|
delta = prior_sacked - tp->sacked_out; |
|
tp->lost_cnt_hint -= min(tp->lost_cnt_hint, delta); |
|
} |
|
} else if (skb && rtt_update && sack_rtt_us >= 0 && |
|
sack_rtt_us > tcp_stamp_us_delta(tp->tcp_mstamp, |
|
tcp_skb_timestamp_us(skb))) { |
|
/* Do not re-arm RTO if the sack RTT is measured from data sent |
|
* after when the head was last (re)transmitted. Otherwise the |
|
* timeout may continue to extend in loss recovery. |
|
*/ |
|
flag |= FLAG_SET_XMIT_TIMER; /* set TLP or RTO timer */ |
|
} |
|
|
|
if (icsk->icsk_ca_ops->pkts_acked) { |
|
struct ack_sample sample = { .pkts_acked = pkts_acked, |
|
.rtt_us = sack->rate->rtt_us }; |
|
|
|
sample.in_flight = tp->mss_cache * |
|
(tp->delivered - sack->rate->prior_delivered); |
|
icsk->icsk_ca_ops->pkts_acked(sk, &sample); |
|
} |
|
|
|
#if FASTRETRANS_DEBUG > 0 |
|
WARN_ON((int)tp->sacked_out < 0); |
|
WARN_ON((int)tp->lost_out < 0); |
|
WARN_ON((int)tp->retrans_out < 0); |
|
if (!tp->packets_out && tcp_is_sack(tp)) { |
|
icsk = inet_csk(sk); |
|
if (tp->lost_out) { |
|
pr_debug("Leak l=%u %d\n", |
|
tp->lost_out, icsk->icsk_ca_state); |
|
tp->lost_out = 0; |
|
} |
|
if (tp->sacked_out) { |
|
pr_debug("Leak s=%u %d\n", |
|
tp->sacked_out, icsk->icsk_ca_state); |
|
tp->sacked_out = 0; |
|
} |
|
if (tp->retrans_out) { |
|
pr_debug("Leak r=%u %d\n", |
|
tp->retrans_out, icsk->icsk_ca_state); |
|
tp->retrans_out = 0; |
|
} |
|
} |
|
#endif |
|
return flag; |
|
} |
|
|
|
static void tcp_ack_probe(struct sock *sk) |
|
{ |
|
struct inet_connection_sock *icsk = inet_csk(sk); |
|
struct sk_buff *head = tcp_send_head(sk); |
|
const struct tcp_sock *tp = tcp_sk(sk); |
|
|
|
/* Was it a usable window open? */ |
|
if (!head) |
|
return; |
|
if (!after(TCP_SKB_CB(head)->end_seq, tcp_wnd_end(tp))) { |
|
icsk->icsk_backoff = 0; |
|
icsk->icsk_probes_tstamp = 0; |
|
inet_csk_clear_xmit_timer(sk, ICSK_TIME_PROBE0); |
|
/* Socket must be waked up by subsequent tcp_data_snd_check(). |
|
* This function is not for random using! |
|
*/ |
|
} else { |
|
unsigned long when = tcp_probe0_when(sk, TCP_RTO_MAX); |
|
|
|
when = tcp_clamp_probe0_to_user_timeout(sk, when); |
|
tcp_reset_xmit_timer(sk, ICSK_TIME_PROBE0, when, TCP_RTO_MAX); |
|
} |
|
} |
|
|
|
static inline bool tcp_ack_is_dubious(const struct sock *sk, const int flag) |
|
{ |
|
return !(flag & FLAG_NOT_DUP) || (flag & FLAG_CA_ALERT) || |
|
inet_csk(sk)->icsk_ca_state != TCP_CA_Open; |
|
} |
|
|
|
/* Decide wheather to run the increase function of congestion control. */ |
|
static inline bool tcp_may_raise_cwnd(const struct sock *sk, const int flag) |
|
{ |
|
/* If reordering is high then always grow cwnd whenever data is |
|
* delivered regardless of its ordering. Otherwise stay conservative |
|
* and only grow cwnd on in-order delivery (RFC5681). A stretched ACK w/ |
|
* new SACK or ECE mark may first advance cwnd here and later reduce |
|
* cwnd in tcp_fastretrans_alert() based on more states. |
|
*/ |
|
if (tcp_sk(sk)->reordering > sock_net(sk)->ipv4.sysctl_tcp_reordering) |
|
return flag & FLAG_FORWARD_PROGRESS; |
|
|
|
return flag & FLAG_DATA_ACKED; |
|
} |
|
|
|
/* The "ultimate" congestion control function that aims to replace the rigid |
|
* cwnd increase and decrease control (tcp_cong_avoid,tcp_*cwnd_reduction). |
|
* It's called toward the end of processing an ACK with precise rate |
|
* information. All transmission or retransmission are delayed afterwards. |
|
*/ |
|
static void tcp_cong_control(struct sock *sk, u32 ack, u32 acked_sacked, |
|
int flag, const struct rate_sample *rs) |
|
{ |
|
const struct inet_connection_sock *icsk = inet_csk(sk); |
|
|
|
if (icsk->icsk_ca_ops->cong_control) { |
|
icsk->icsk_ca_ops->cong_control(sk, rs); |
|
return; |
|
} |
|
|
|
if (tcp_in_cwnd_reduction(sk)) { |
|
/* Reduce cwnd if state mandates */ |
|
tcp_cwnd_reduction(sk, acked_sacked, rs->losses, flag); |
|
} else if (tcp_may_raise_cwnd(sk, flag)) { |
|
/* Advance cwnd if state allows */ |
|
tcp_cong_avoid(sk, ack, acked_sacked); |
|
} |
|
tcp_update_pacing_rate(sk); |
|
} |
|
|
|
/* Check that window update is acceptable. |
|
* The function assumes that snd_una<=ack<=snd_next. |
|
*/ |
|
static inline bool tcp_may_update_window(const struct tcp_sock *tp, |
|
const u32 ack, const u32 ack_seq, |
|
const u32 nwin) |
|
{ |
|
return after(ack, tp->snd_una) || |
|
after(ack_seq, tp->snd_wl1) || |
|
(ack_seq == tp->snd_wl1 && nwin > tp->snd_wnd); |
|
} |
|
|
|
/* If we update tp->snd_una, also update tp->bytes_acked */ |
|
static void tcp_snd_una_update(struct tcp_sock *tp, u32 ack) |
|
{ |
|
u32 delta = ack - tp->snd_una; |
|
|
|
sock_owned_by_me((struct sock *)tp); |
|
tp->bytes_acked += delta; |
|
tp->snd_una = ack; |
|
} |
|
|
|
/* If we update tp->rcv_nxt, also update tp->bytes_received */ |
|
static void tcp_rcv_nxt_update(struct tcp_sock *tp, u32 seq) |
|
{ |
|
u32 delta = seq - tp->rcv_nxt; |
|
|
|
sock_owned_by_me((struct sock *)tp); |
|
tp->bytes_received += delta; |
|
WRITE_ONCE(tp->rcv_nxt, seq); |
|
} |
|
|
|
/* Update our send window. |
|
* |
|
* Window update algorithm, described in RFC793/RFC1122 (used in linux-2.2 |
|
* and in FreeBSD. NetBSD's one is even worse.) is wrong. |
|
*/ |
|
static int tcp_ack_update_window(struct sock *sk, const struct sk_buff *skb, u32 ack, |
|
u32 ack_seq) |
|
{ |
|
struct tcp_sock *tp = tcp_sk(sk); |
|
int flag = 0; |
|
u32 nwin = ntohs(tcp_hdr(skb)->window); |
|
|
|
if (likely(!tcp_hdr(skb)->syn)) |
|
nwin <<= tp->rx_opt.snd_wscale; |
|
|
|
if (tcp_may_update_window(tp, ack, ack_seq, nwin)) { |
|
flag |= FLAG_WIN_UPDATE; |
|
tcp_update_wl(tp, ack_seq); |
|
|
|
if (tp->snd_wnd != nwin) { |
|
tp->snd_wnd = nwin; |
|
|
|
/* Note, it is the only place, where |
|
* fast path is recovered for sending TCP. |
|
*/ |
|
tp->pred_flags = 0; |
|
tcp_fast_path_check(sk); |
|
|
|
if (!tcp_write_queue_empty(sk)) |
|
tcp_slow_start_after_idle_check(sk); |
|
|
|
if (nwin > tp->max_window) { |
|
tp->max_window = nwin; |
|
tcp_sync_mss(sk, inet_csk(sk)->icsk_pmtu_cookie); |
|
} |
|
} |
|
} |
|
|
|
tcp_snd_una_update(tp, ack); |
|
|
|
return flag; |
|
} |
|
|
|
static bool __tcp_oow_rate_limited(struct net *net, int mib_idx, |
|
u32 *last_oow_ack_time) |
|
{ |
|
if (*last_oow_ack_time) { |
|
s32 elapsed = (s32)(tcp_jiffies32 - *last_oow_ack_time); |
|
|
|
if (0 <= elapsed && elapsed < net->ipv4.sysctl_tcp_invalid_ratelimit) { |
|
NET_INC_STATS(net, mib_idx); |
|
return true; /* rate-limited: don't send yet! */ |
|
} |
|
} |
|
|
|
*last_oow_ack_time = tcp_jiffies32; |
|
|
|
return false; /* not rate-limited: go ahead, send dupack now! */ |
|
} |
|
|
|
/* Return true if we're currently rate-limiting out-of-window ACKs and |
|
* thus shouldn't send a dupack right now. We rate-limit dupacks in |
|
* response to out-of-window SYNs or ACKs to mitigate ACK loops or DoS |
|
* attacks that send repeated SYNs or ACKs for the same connection. To |
|
* do this, we do not send a duplicate SYNACK or ACK if the remote |
|
* endpoint is sending out-of-window SYNs or pure ACKs at a high rate. |
|
*/ |
|
bool tcp_oow_rate_limited(struct net *net, const struct sk_buff *skb, |
|
int mib_idx, u32 *last_oow_ack_time) |
|
{ |
|
/* Data packets without SYNs are not likely part of an ACK loop. */ |
|
if ((TCP_SKB_CB(skb)->seq != TCP_SKB_CB(skb)->end_seq) && |
|
!tcp_hdr(skb)->syn) |
|
return false; |
|
|
|
return __tcp_oow_rate_limited(net, mib_idx, last_oow_ack_time); |
|
} |
|
|
|
/* RFC 5961 7 [ACK Throttling] */ |
|
static void tcp_send_challenge_ack(struct sock *sk) |
|
{ |
|
/* unprotected vars, we dont care of overwrites */ |
|
static u32 challenge_timestamp; |
|
static unsigned int challenge_count; |
|
struct tcp_sock *tp = tcp_sk(sk); |
|
struct net *net = sock_net(sk); |
|
u32 count, now; |
|
|
|
/* First check our per-socket dupack rate limit. */ |
|
if (__tcp_oow_rate_limited(net, |
|
LINUX_MIB_TCPACKSKIPPEDCHALLENGE, |
|
&tp->last_oow_ack_time)) |
|
return; |
|
|
|
/* Then check host-wide RFC 5961 rate limit. */ |
|
now = jiffies / HZ; |
|
if (now != challenge_timestamp) { |
|
u32 ack_limit = net->ipv4.sysctl_tcp_challenge_ack_limit; |
|
u32 half = (ack_limit + 1) >> 1; |
|
|
|
challenge_timestamp = now; |
|
WRITE_ONCE(challenge_count, half + prandom_u32_max(ack_limit)); |
|
} |
|
count = READ_ONCE(challenge_count); |
|
if (count > 0) { |
|
WRITE_ONCE(challenge_count, count - 1); |
|
NET_INC_STATS(net, LINUX_MIB_TCPCHALLENGEACK); |
|
tcp_send_ack(sk); |
|
} |
|
} |
|
|
|
static void tcp_store_ts_recent(struct tcp_sock *tp) |
|
{ |
|
tp->rx_opt.ts_recent = tp->rx_opt.rcv_tsval; |
|
tp->rx_opt.ts_recent_stamp = ktime_get_seconds(); |
|
} |
|
|
|
static void tcp_replace_ts_recent(struct tcp_sock *tp, u32 seq) |
|
{ |
|
if (tp->rx_opt.saw_tstamp && !after(seq, tp->rcv_wup)) { |
|
/* PAWS bug workaround wrt. ACK frames, the PAWS discard |
|
* extra check below makes sure this can only happen |
|
* for pure ACK frames. -DaveM |
|
* |
|
* Not only, also it occurs for expired timestamps. |
|
*/ |
|
|
|
if (tcp_paws_check(&tp->rx_opt, 0)) |
|
tcp_store_ts_recent(tp); |
|
} |
|
} |
|
|
|
/* This routine deals with acks during a TLP episode and ends an episode by |
|
* resetting tlp_high_seq. Ref: TLP algorithm in draft-ietf-tcpm-rack |
|
*/ |
|
static void tcp_process_tlp_ack(struct sock *sk, u32 ack, int flag) |
|
{ |
|
struct tcp_sock *tp = tcp_sk(sk); |
|
|
|
if (before(ack, tp->tlp_high_seq)) |
|
return; |
|
|
|
if (!tp->tlp_retrans) { |
|
/* TLP of new data has been acknowledged */ |
|
tp->tlp_high_seq = 0; |
|
} else if (flag & FLAG_DSACK_TLP) { |
|
/* This DSACK means original and TLP probe arrived; no loss */ |
|
tp->tlp_high_seq = 0; |
|
} else if (after(ack, tp->tlp_high_seq)) { |
|
/* ACK advances: there was a loss, so reduce cwnd. Reset |
|
* tlp_high_seq in tcp_init_cwnd_reduction() |
|
*/ |
|
tcp_init_cwnd_reduction(sk); |
|
tcp_set_ca_state(sk, TCP_CA_CWR); |
|
tcp_end_cwnd_reduction(sk); |
|
tcp_try_keep_open(sk); |
|
NET_INC_STATS(sock_net(sk), |
|
LINUX_MIB_TCPLOSSPROBERECOVERY); |
|
} else if (!(flag & (FLAG_SND_UNA_ADVANCED | |
|
FLAG_NOT_DUP | FLAG_DATA_SACKED))) { |
|
/* Pure dupack: original and TLP probe arrived; no loss */ |
|
tp->tlp_high_seq = 0; |
|
} |
|
} |
|
|
|
static inline void tcp_in_ack_event(struct sock *sk, u32 flags) |
|
{ |
|
const struct inet_connection_sock *icsk = inet_csk(sk); |
|
|
|
if (icsk->icsk_ca_ops->in_ack_event) |
|
icsk->icsk_ca_ops->in_ack_event(sk, flags); |
|
} |
|
|
|
/* Congestion control has updated the cwnd already. So if we're in |
|
* loss recovery then now we do any new sends (for FRTO) or |
|
* retransmits (for CA_Loss or CA_recovery) that make sense. |
|
*/ |
|
static void tcp_xmit_recovery(struct sock *sk, int rexmit) |
|
{ |
|
struct tcp_sock *tp = tcp_sk(sk); |
|
|
|
if (rexmit == REXMIT_NONE || sk->sk_state == TCP_SYN_SENT) |
|
return; |
|
|
|
if (unlikely(rexmit == REXMIT_NEW)) { |
|
__tcp_push_pending_frames(sk, tcp_current_mss(sk), |
|
TCP_NAGLE_OFF); |
|
if (after(tp->snd_nxt, tp->high_seq)) |
|
return; |
|
tp->frto = 0; |
|
} |
|
tcp_xmit_retransmit_queue(sk); |
|
} |
|
|
|
/* Returns the number of packets newly acked or sacked by the current ACK */ |
|
static u32 tcp_newly_delivered(struct sock *sk, u32 prior_delivered, int flag) |
|
{ |
|
const struct net *net = sock_net(sk); |
|
struct tcp_sock *tp = tcp_sk(sk); |
|
u32 delivered; |
|
|
|
delivered = tp->delivered - prior_delivered; |
|
NET_ADD_STATS(net, LINUX_MIB_TCPDELIVERED, delivered); |
|
if (flag & FLAG_ECE) |
|
NET_ADD_STATS(net, LINUX_MIB_TCPDELIVEREDCE, delivered); |
|
|
|
return delivered; |
|
} |
|
|
|
/* This routine deals with incoming acks, but not outgoing ones. */ |
|
static int tcp_ack(struct sock *sk, const struct sk_buff *skb, int flag) |
|
{ |
|
struct inet_connection_sock *icsk = inet_csk(sk); |
|
struct tcp_sock *tp = tcp_sk(sk); |
|
struct tcp_sacktag_state sack_state; |
|
struct rate_sample rs = { .prior_delivered = 0 }; |
|
u32 prior_snd_una = tp->snd_una; |
|
bool is_sack_reneg = tp->is_sack_reneg; |
|
u32 ack_seq = TCP_SKB_CB(skb)->seq; |
|
u32 ack = TCP_SKB_CB(skb)->ack_seq; |
|
int num_dupack = 0; |
|
int prior_packets = tp->packets_out; |
|
u32 delivered = tp->delivered; |
|
u32 lost = tp->lost; |
|
int rexmit = REXMIT_NONE; /* Flag to (re)transmit to recover losses */ |
|
u32 prior_fack; |
|
|
|
sack_state.first_sackt = 0; |
|
sack_state.rate = &rs; |
|
sack_state.sack_delivered = 0; |
|
|
|
/* We very likely will need to access rtx queue. */ |
|
prefetch(sk->tcp_rtx_queue.rb_node); |
|
|
|
/* If the ack is older than previous acks |
|
* then we can probably ignore it. |
|
*/ |
|
if (before(ack, prior_snd_una)) { |
|
/* RFC 5961 5.2 [Blind Data Injection Attack].[Mitigation] */ |
|
if (before(ack, prior_snd_una - tp->max_window)) { |
|
if (!(flag & FLAG_NO_CHALLENGE_ACK)) |
|
tcp_send_challenge_ack(sk); |
|
return -1; |
|
} |
|
goto old_ack; |
|
} |
|
|
|
/* If the ack includes data we haven't sent yet, discard |
|
* this segment (RFC793 Section 3.9). |
|
*/ |
|
if (after(ack, tp->snd_nxt)) |
|
return -1; |
|
|
|
if (after(ack, prior_snd_una)) { |
|
flag |= FLAG_SND_UNA_ADVANCED; |
|
icsk->icsk_retransmits = 0; |
|
|
|
#if IS_ENABLED(CONFIG_TLS_DEVICE) |
|
if (static_branch_unlikely(&clean_acked_data_enabled.key)) |
|
if (icsk->icsk_clean_acked) |
|
icsk->icsk_clean_acked(sk, ack); |
|
#endif |
|
} |
|
|
|
prior_fack = tcp_is_sack(tp) ? tcp_highest_sack_seq(tp) : tp->snd_una; |
|
rs.prior_in_flight = tcp_packets_in_flight(tp); |
|
|
|
/* ts_recent update must be made after we are sure that the packet |
|
* is in window. |
|
*/ |
|
if (flag & FLAG_UPDATE_TS_RECENT) |
|
tcp_replace_ts_recent(tp, TCP_SKB_CB(skb)->seq); |
|
|
|
if ((flag & (FLAG_SLOWPATH | FLAG_SND_UNA_ADVANCED)) == |
|
FLAG_SND_UNA_ADVANCED) { |
|
/* Window is constant, pure forward advance. |
|
* No more checks are required. |
|
* Note, we use the fact that SND.UNA>=SND.WL2. |
|
*/ |
|
tcp_update_wl(tp, ack_seq); |
|
tcp_snd_una_update(tp, ack); |
|
flag |= FLAG_WIN_UPDATE; |
|
|
|
tcp_in_ack_event(sk, CA_ACK_WIN_UPDATE); |
|
|
|
NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPHPACKS); |
|
} else { |
|
u32 ack_ev_flags = CA_ACK_SLOWPATH; |
|
|
|
if (ack_seq != TCP_SKB_CB(skb)->end_seq) |
|
flag |= FLAG_DATA; |
|
else |
|
NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPPUREACKS); |
|
|
|
flag |= tcp_ack_update_window(sk, skb, ack, ack_seq); |
|
|
|
if (TCP_SKB_CB(skb)->sacked) |
|
flag |= tcp_sacktag_write_queue(sk, skb, prior_snd_una, |
|
&sack_state); |
|
|
|
if (tcp_ecn_rcv_ecn_echo(tp, tcp_hdr(skb))) { |
|
flag |= FLAG_ECE; |
|
ack_ev_flags |= CA_ACK_ECE; |
|
} |
|
|
|
if (sack_state.sack_delivered) |
|
tcp_count_delivered(tp, sack_state.sack_delivered, |
|
flag & FLAG_ECE); |
|
|
|
if (flag & FLAG_WIN_UPDATE) |
|
ack_ev_flags |= CA_ACK_WIN_UPDATE; |
|
|
|
tcp_in_ack_event(sk, ack_ev_flags); |
|
} |
|
|
|
/* This is a deviation from RFC3168 since it states that: |
|
* "When the TCP data sender is ready to set the CWR bit after reducing |
|
* the congestion window, it SHOULD set the CWR bit only on the first |
|
* new data packet that it transmits." |
|
* We accept CWR on pure ACKs to be more robust |
|
* with widely-deployed TCP implementations that do this. |
|
*/ |
|
tcp_ecn_accept_cwr(sk, skb); |
|
|
|
/* We passed data and got it acked, remove any soft error |
|
* log. Something worked... |
|
*/ |
|
sk->sk_err_soft = 0; |
|
icsk->icsk_probes_out = 0; |
|
tp->rcv_tstamp = tcp_jiffies32; |
|
if (!prior_packets) |
|
goto no_queue; |
|
|
|
/* See if we can take anything off of the retransmit queue. */ |
|
flag |= tcp_clean_rtx_queue(sk, skb, prior_fack, prior_snd_una, |
|
&sack_state, flag & FLAG_ECE); |
|
|
|
tcp_rack_update_reo_wnd(sk, &rs); |
|
|
|
if (tp->tlp_high_seq) |
|
tcp_process_tlp_ack(sk, ack, flag); |
|
|
|
if (tcp_ack_is_dubious(sk, flag)) { |
|
if (!(flag & (FLAG_SND_UNA_ADVANCED | FLAG_NOT_DUP))) { |
|
num_dupack = 1; |
|
/* Consider if pure acks were aggregated in tcp_add_backlog() */ |
|
if (!(flag & FLAG_DATA)) |
|
num_dupack = max_t(u16, 1, skb_shinfo(skb)->gso_segs); |
|
} |
|
tcp_fastretrans_alert(sk, prior_snd_una, num_dupack, &flag, |
|
&rexmit); |
|
} |
|
|
|
/* If needed, reset TLP/RTO timer when RACK doesn't set. */ |
|
if (flag & FLAG_SET_XMIT_TIMER) |
|
tcp_set_xmit_timer(sk); |
|
|
|
if ((flag & FLAG_FORWARD_PROGRESS) || !(flag & FLAG_NOT_DUP)) |
|
sk_dst_confirm(sk); |
|
|
|
delivered = tcp_newly_delivered(sk, delivered, flag); |
|
lost = tp->lost - lost; /* freshly marked lost */ |
|
rs.is_ack_delayed = !!(flag & FLAG_ACK_MAYBE_DELAYED); |
|
tcp_rate_gen(sk, delivered, lost, is_sack_reneg, sack_state.rate); |
|
tcp_cong_control(sk, ack, delivered, flag, sack_state.rate); |
|
tcp_xmit_recovery(sk, rexmit); |
|
return 1; |
|
|
|
no_queue: |
|
/* If data was DSACKed, see if we can undo a cwnd reduction. */ |
|
if (flag & FLAG_DSACKING_ACK) { |
|
tcp_fastretrans_alert(sk, prior_snd_una, num_dupack, &flag, |
|
&rexmit); |
|
tcp_newly_delivered(sk, delivered, flag); |
|
} |
|
/* If this ack opens up a zero window, clear backoff. It was |
|
* being used to time the probes, and is probably far higher than |
|
* it needs to be for normal retransmission. |
|
*/ |
|
tcp_ack_probe(sk); |
|
|
|
if (tp->tlp_high_seq) |
|
tcp_process_tlp_ack(sk, ack, flag); |
|
return 1; |
|
|
|
old_ack: |
|
/* If data was SACKed, tag it and see if we should send more data. |
|
* If data was DSACKed, see if we can undo a cwnd reduction. |
|
*/ |
|
if (TCP_SKB_CB(skb)->sacked) { |
|
flag |= tcp_sacktag_write_queue(sk, skb, prior_snd_una, |
|
&sack_state); |
|
tcp_fastretrans_alert(sk, prior_snd_una, num_dupack, &flag, |
|
&rexmit); |
|
tcp_newly_delivered(sk, delivered, flag); |
|
tcp_xmit_recovery(sk, rexmit); |
|
} |
|
|
|
return 0; |
|
} |
|
|
|
static void tcp_parse_fastopen_option(int len, const unsigned char *cookie, |
|
bool syn, struct tcp_fastopen_cookie *foc, |
|
bool exp_opt) |
|
{ |
|
/* Valid only in SYN or SYN-ACK with an even length. */ |
|
if (!foc || !syn || len < 0 || (len & 1)) |
|
return; |
|
|
|
if (len >= TCP_FASTOPEN_COOKIE_MIN && |
|
len <= TCP_FASTOPEN_COOKIE_MAX) |
|
memcpy(foc->val, cookie, len); |
|
else if (len != 0) |
|
len = -1; |
|
foc->len = len; |
|
foc->exp = exp_opt; |
|
} |
|
|
|
static bool smc_parse_options(const struct tcphdr *th, |
|
struct tcp_options_received *opt_rx, |
|
const unsigned char *ptr, |
|
int opsize) |
|
{ |
|
#if IS_ENABLED(CONFIG_SMC) |
|
if (static_branch_unlikely(&tcp_have_smc)) { |
|
if (th->syn && !(opsize & 1) && |
|
opsize >= TCPOLEN_EXP_SMC_BASE && |
|
get_unaligned_be32(ptr) == TCPOPT_SMC_MAGIC) { |
|
opt_rx->smc_ok = 1; |
|
return true; |
|
} |
|
} |
|
#endif |
|
return false; |
|
} |
|
|
|
/* Try to parse the MSS option from the TCP header. Return 0 on failure, clamped |
|
* value on success. |
|
*/ |
|
static u16 tcp_parse_mss_option(const struct tcphdr *th, u16 user_mss) |
|
{ |
|
const unsigned char *ptr = (const unsigned char *)(th + 1); |
|
int length = (th->doff * 4) - sizeof(struct tcphdr); |
|
u16 mss = 0; |
|
|
|
while (length > 0) { |
|
int opcode = *ptr++; |
|
int opsize; |
|
|
|
switch (opcode) { |
|
case TCPOPT_EOL: |
|
return mss; |
|
case TCPOPT_NOP: /* Ref: RFC 793 section 3.1 */ |
|
length--; |
|
continue; |
|
default: |
|
if (length < 2) |
|
return mss; |
|
opsize = *ptr++; |
|
if (opsize < 2) /* "silly options" */ |
|
return mss; |
|
if (opsize > length) |
|
return mss; /* fail on partial options */ |
|
if (opcode == TCPOPT_MSS && opsize == TCPOLEN_MSS) { |
|
u16 in_mss = get_unaligned_be16(ptr); |
|
|
|
if (in_mss) { |
|
if (user_mss && user_mss < in_mss) |
|
in_mss = user_mss; |
|
mss = in_mss; |
|
} |
|
} |
|
ptr += opsize - 2; |
|
length -= opsize; |
|
} |
|
} |
|
return mss; |
|
} |
|
|
|
/* Look for tcp options. Normally only called on SYN and SYNACK packets. |
|
* But, this can also be called on packets in the established flow when |
|
* the fast version below fails. |
|
*/ |
|
void tcp_parse_options(const struct net *net, |
|
const struct sk_buff *skb, |
|
struct tcp_options_received *opt_rx, int estab, |
|
struct tcp_fastopen_cookie *foc) |
|
{ |
|
const unsigned char *ptr; |
|
const struct tcphdr *th = tcp_hdr(skb); |
|
int length = (th->doff * 4) - sizeof(struct tcphdr); |
|
|
|
ptr = (const unsigned char *)(th + 1); |
|
opt_rx->saw_tstamp = 0; |
|
opt_rx->saw_unknown = 0; |
|
|
|
while (length > 0) { |
|
int opcode = *ptr++; |
|
int opsize; |
|
|
|
switch (opcode) { |
|
case TCPOPT_EOL: |
|
return; |
|
case TCPOPT_NOP: /* Ref: RFC 793 section 3.1 */ |
|
length--; |
|
continue; |
|
default: |
|
if (length < 2) |
|
return; |
|
opsize = *ptr++; |
|
if (opsize < 2) /* "silly options" */ |
|
return; |
|
if (opsize > length) |
|
return; /* don't parse partial options */ |
|
switch (opcode) { |
|
case TCPOPT_MSS: |
|
if (opsize == TCPOLEN_MSS && th->syn && !estab) { |
|
u16 in_mss = get_unaligned_be16(ptr); |
|
if (in_mss) { |
|
if (opt_rx->user_mss && |
|
opt_rx->user_mss < in_mss) |
|
in_mss = opt_rx->user_mss; |
|
opt_rx->mss_clamp = in_mss; |
|
} |
|
} |
|
break; |
|
case TCPOPT_WINDOW: |
|
if (opsize == TCPOLEN_WINDOW && th->syn && |
|
!estab && net->ipv4.sysctl_tcp_window_scaling) { |
|
__u8 snd_wscale = *(__u8 *)ptr; |
|
opt_rx->wscale_ok = 1; |
|
if (snd_wscale > TCP_MAX_WSCALE) { |
|
net_info_ratelimited("%s: Illegal window scaling value %d > %u received\n", |
|
__func__, |
|
snd_wscale, |
|
TCP_MAX_WSCALE); |
|
snd_wscale = TCP_MAX_WSCALE; |
|
} |
|
opt_rx->snd_wscale = snd_wscale; |
|
} |
|
break; |
|
case TCPOPT_TIMESTAMP: |
|
if ((opsize == TCPOLEN_TIMESTAMP) && |
|
((estab && opt_rx->tstamp_ok) || |
|
(!estab && net->ipv4.sysctl_tcp_timestamps))) { |
|
opt_rx->saw_tstamp = 1; |
|
opt_rx->rcv_tsval = get_unaligned_be32(ptr); |
|
opt_rx->rcv_tsecr = get_unaligned_be32(ptr + 4); |
|
} |
|
break; |
|
case TCPOPT_SACK_PERM: |
|
if (opsize == TCPOLEN_SACK_PERM && th->syn && |
|
!estab && net->ipv4.sysctl_tcp_sack) { |
|
opt_rx->sack_ok = TCP_SACK_SEEN; |
|
tcp_sack_reset(opt_rx); |
|
} |
|
break; |
|
|
|
case TCPOPT_SACK: |
|
if ((opsize >= (TCPOLEN_SACK_BASE + TCPOLEN_SACK_PERBLOCK)) && |
|
!((opsize - TCPOLEN_SACK_BASE) % TCPOLEN_SACK_PERBLOCK) && |
|
opt_rx->sack_ok) { |
|
TCP_SKB_CB(skb)->sacked = (ptr - 2) - (unsigned char *)th; |
|
} |
|
break; |
|
#ifdef CONFIG_TCP_MD5SIG |
|
case TCPOPT_MD5SIG: |
|
/* |
|
* The MD5 Hash has already been |
|
* checked (see tcp_v{4,6}_do_rcv()). |
|
*/ |
|
break; |
|
#endif |
|
case TCPOPT_FASTOPEN: |
|
tcp_parse_fastopen_option( |
|
opsize - TCPOLEN_FASTOPEN_BASE, |
|
ptr, th->syn, foc, false); |
|
break; |
|
|
|
case TCPOPT_EXP: |
|
/* Fast Open option shares code 254 using a |
|
* 16 bits magic number. |
|
*/ |
|
if (opsize >= TCPOLEN_EXP_FASTOPEN_BASE && |
|
get_unaligned_be16(ptr) == |
|
TCPOPT_FASTOPEN_MAGIC) { |
|
tcp_parse_fastopen_option(opsize - |
|
TCPOLEN_EXP_FASTOPEN_BASE, |
|
ptr + 2, th->syn, foc, true); |
|
break; |
|
} |
|
|
|
if (smc_parse_options(th, opt_rx, ptr, opsize)) |
|
break; |
|
|
|
opt_rx->saw_unknown = 1; |
|
break; |
|
|
|
default: |
|
opt_rx->saw_unknown = 1; |
|
} |
|
ptr += opsize-2; |
|
length -= opsize; |
|
} |
|
} |
|
} |
|
EXPORT_SYMBOL(tcp_parse_options); |
|
|
|
static bool tcp_parse_aligned_timestamp(struct tcp_sock *tp, const struct tcphdr *th) |
|
{ |
|
const __be32 *ptr = (const __be32 *)(th + 1); |
|
|
|
if (*ptr == htonl((TCPOPT_NOP << 24) | (TCPOPT_NOP << 16) |
|
| (TCPOPT_TIMESTAMP << 8) | TCPOLEN_TIMESTAMP)) { |
|
tp->rx_opt.saw_tstamp = 1; |
|
++ptr; |
|
tp->rx_opt.rcv_tsval = ntohl(*ptr); |
|
++ptr; |
|
if (*ptr) |
|
tp->rx_opt.rcv_tsecr = ntohl(*ptr) - tp->tsoffset; |
|
else |
|
tp->rx_opt.rcv_tsecr = 0; |
|
return true; |
|
} |
|
return false; |
|
} |
|
|
|
/* Fast parse options. This hopes to only see timestamps. |
|
* If it is wrong it falls back on tcp_parse_options(). |
|
*/ |
|
static bool tcp_fast_parse_options(const struct net *net, |
|
const struct sk_buff *skb, |
|
const struct tcphdr *th, struct tcp_sock *tp) |
|
{ |
|
/* In the spirit of fast parsing, compare doff directly to constant |
|
* values. Because equality is used, short doff can be ignored here. |
|
*/ |
|
if (th->doff == (sizeof(*th) / 4)) { |
|
tp->rx_opt.saw_tstamp = 0; |
|
return false; |
|
} else if (tp->rx_opt.tstamp_ok && |
|
th->doff == ((sizeof(*th) + TCPOLEN_TSTAMP_ALIGNED) / 4)) { |
|
if (tcp_parse_aligned_timestamp(tp, th)) |
|
return true; |
|
} |
|
|
|
tcp_parse_options(net, skb, &tp->rx_opt, 1, NULL); |
|
if (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr) |
|
tp->rx_opt.rcv_tsecr -= tp->tsoffset; |
|
|
|
return true; |
|
} |
|
|
|
#ifdef CONFIG_TCP_MD5SIG |
|
/* |
|
* Parse MD5 Signature option |
|
*/ |
|
const u8 *tcp_parse_md5sig_option(const struct tcphdr *th) |
|
{ |
|
int length = (th->doff << 2) - sizeof(*th); |
|
const u8 *ptr = (const u8 *)(th + 1); |
|
|
|
/* If not enough data remaining, we can short cut */ |
|
while (length >= TCPOLEN_MD5SIG) { |
|
int opcode = *ptr++; |
|
int opsize; |
|
|
|
switch (opcode) { |
|
case TCPOPT_EOL: |
|
return NULL; |
|
case TCPOPT_NOP: |
|
length--; |
|
continue; |
|
default: |
|
opsize = *ptr++; |
|
if (opsize < 2 || opsize > length) |
|
return NULL; |
|
if (opcode == TCPOPT_MD5SIG) |
|
return opsize == TCPOLEN_MD5SIG ? ptr : NULL; |
|
} |
|
ptr += opsize - 2; |
|
length -= opsize; |
|
} |
|
return NULL; |
|
} |
|
EXPORT_SYMBOL(tcp_parse_md5sig_option); |
|
#endif |
|
|
|
/* Sorry, PAWS as specified is broken wrt. pure-ACKs -DaveM |
|
* |
|
* It is not fatal. If this ACK does _not_ change critical state (seqs, window) |
|
* it can pass through stack. So, the following predicate verifies that |
|
* this segment is not used for anything but congestion avoidance or |
|
* fast retransmit. Moreover, we even are able to eliminate most of such |
|
* second order effects, if we apply some small "replay" window (~RTO) |
|
* to timestamp space. |
|
* |
|
* All these measures still do not guarantee that we reject wrapped ACKs |
|
* on networks with high bandwidth, when sequence space is recycled fastly, |
|
* but it guarantees that such events will be very rare and do not affect |
|
* connection seriously. This doesn't look nice, but alas, PAWS is really |
|
* buggy extension. |
|
* |
|
* [ Later note. Even worse! It is buggy for segments _with_ data. RFC |
|
* states that events when retransmit arrives after original data are rare. |
|
* It is a blatant lie. VJ forgot about fast retransmit! 8)8) It is |
|
* the biggest problem on large power networks even with minor reordering. |
|
* OK, let's give it small replay window. If peer clock is even 1hz, it is safe |
|
* up to bandwidth of 18Gigabit/sec. 8) ] |
|
*/ |
|
|
|
static int tcp_disordered_ack(const struct sock *sk, const struct sk_buff *skb) |
|
{ |
|
const struct tcp_sock *tp = tcp_sk(sk); |
|
const struct tcphdr *th = tcp_hdr(skb); |
|
u32 seq = TCP_SKB_CB(skb)->seq; |
|
u32 ack = TCP_SKB_CB(skb)->ack_seq; |
|
|
|
return (/* 1. Pure ACK with correct sequence number. */ |
|
(th->ack && seq == TCP_SKB_CB(skb)->end_seq && seq == tp->rcv_nxt) && |
|
|
|
/* 2. ... and duplicate ACK. */ |
|
ack == tp->snd_una && |
|
|
|
/* 3. ... and does not update window. */ |
|
!tcp_may_update_window(tp, ack, seq, ntohs(th->window) << tp->rx_opt.snd_wscale) && |
|
|
|
/* 4. ... and sits in replay window. */ |
|
(s32)(tp->rx_opt.ts_recent - tp->rx_opt.rcv_tsval) <= (inet_csk(sk)->icsk_rto * 1024) / HZ); |
|
} |
|
|
|
static inline bool tcp_paws_discard(const struct sock *sk, |
|
const struct sk_buff *skb) |
|
{ |
|
const struct tcp_sock *tp = tcp_sk(sk); |
|
|
|
return !tcp_paws_check(&tp->rx_opt, TCP_PAWS_WINDOW) && |
|
!tcp_disordered_ack(sk, skb); |
|
} |
|
|
|
/* Check segment sequence number for validity. |
|
* |
|
* Segment controls are considered valid, if the segment |
|
* fits to the window after truncation to the window. Acceptability |
|
* of data (and SYN, FIN, of course) is checked separately. |
|
* See tcp_data_queue(), for example. |
|
* |
|
* Also, controls (RST is main one) are accepted using RCV.WUP instead |
|
* of RCV.NXT. Peer still did not advance his SND.UNA when we |
|
* delayed ACK, so that hisSND.UNA<=ourRCV.WUP. |
|
* (borrowed from freebsd) |
|
*/ |
|
|
|
static inline bool tcp_sequence(const struct tcp_sock *tp, u32 seq, u32 end_seq) |
|
{ |
|
return !before(end_seq, tp->rcv_wup) && |
|
!after(seq, tp->rcv_nxt + tcp_receive_window(tp)); |
|
} |
|
|
|
/* When we get a reset we do this. */ |
|
void tcp_reset(struct sock *sk, struct sk_buff *skb) |
|
{ |
|
trace_tcp_receive_reset(sk); |
|
|
|
/* mptcp can't tell us to ignore reset pkts, |
|
* so just ignore the return value of mptcp_incoming_options(). |
|
*/ |
|
if (sk_is_mptcp(sk)) |
|
mptcp_incoming_options(sk, skb); |
|
|
|
/* We want the right error as BSD sees it (and indeed as we do). */ |
|
switch (sk->sk_state) { |
|
case TCP_SYN_SENT: |
|
sk->sk_err = ECONNREFUSED; |
|
break; |
|
case TCP_CLOSE_WAIT: |
|
sk->sk_err = EPIPE; |
|
break; |
|
case TCP_CLOSE: |
|
return; |
|
default: |
|
sk->sk_err = ECONNRESET; |
|
} |
|
/* This barrier is coupled with smp_rmb() in tcp_poll() */ |
|
smp_wmb(); |
|
|
|
tcp_write_queue_purge(sk); |
|
tcp_done(sk); |
|
|
|
if (!sock_flag(sk, SOCK_DEAD)) |
|
sk_error_report(sk); |
|
} |
|
|
|
/* |
|
* Process the FIN bit. This now behaves as it is supposed to work |
|
* and the FIN takes effect when it is validly part of sequence |
|
* space. Not before when we get holes. |
|
* |
|
* If we are ESTABLISHED, a received fin moves us to CLOSE-WAIT |
|
* (and thence onto LAST-ACK and finally, CLOSE, we never enter |
|
* TIME-WAIT) |
|
* |
|
* If we are in FINWAIT-1, a received FIN indicates simultaneous |
|
* close and we go into CLOSING (and later onto TIME-WAIT) |
|
* |
|
* If we are in FINWAIT-2, a received FIN moves us to TIME-WAIT. |
|
*/ |
|
void tcp_fin(struct sock *sk) |
|
{ |
|
struct tcp_sock *tp = tcp_sk(sk); |
|
|
|
inet_csk_schedule_ack(sk); |
|
|
|
sk->sk_shutdown |= RCV_SHUTDOWN; |
|
sock_set_flag(sk, SOCK_DONE); |
|
|
|
switch (sk->sk_state) { |
|
case TCP_SYN_RECV: |
|
case TCP_ESTABLISHED: |
|
/* Move to CLOSE_WAIT */ |
|
tcp_set_state(sk, TCP_CLOSE_WAIT); |
|
inet_csk_enter_pingpong_mode(sk); |
|
break; |
|
|
|
case TCP_CLOSE_WAIT: |
|
case TCP_CLOSING: |
|
/* Received a retransmission of the FIN, do |
|
* nothing. |
|
*/ |
|
break; |
|
case TCP_LAST_ACK: |
|
/* RFC793: Remain in the LAST-ACK state. */ |
|
break; |
|
|
|
case TCP_FIN_WAIT1: |
|
/* This case occurs when a simultaneous close |
|
* happens, we must ack the received FIN and |
|
* enter the CLOSING state. |
|
*/ |
|
tcp_send_ack(sk); |
|
tcp_set_state(sk, TCP_CLOSING); |
|
break; |
|
case TCP_FIN_WAIT2: |
|
/* Received a FIN -- send ACK and enter TIME_WAIT. */ |
|
tcp_send_ack(sk); |
|
tcp_time_wait(sk, TCP_TIME_WAIT, 0); |
|
break; |
|
default: |
|
/* Only TCP_LISTEN and TCP_CLOSE are left, in these |
|
* cases we should never reach this piece of code. |
|
*/ |
|
pr_err("%s: Impossible, sk->sk_state=%d\n", |
|
__func__, sk->sk_state); |
|
break; |
|
} |
|
|
|
/* It _is_ possible, that we have something out-of-order _after_ FIN. |
|
* Probably, we should reset in this case. For now drop them. |
|
*/ |
|
skb_rbtree_purge(&tp->out_of_order_queue); |
|
if (tcp_is_sack(tp)) |
|
tcp_sack_reset(&tp->rx_opt); |
|
sk_mem_reclaim(sk); |
|
|
|
if (!sock_flag(sk, SOCK_DEAD)) { |
|
sk->sk_state_change(sk); |
|
|
|
/* Do not send POLL_HUP for half duplex close. */ |
|
if (sk->sk_shutdown == SHUTDOWN_MASK || |
|
sk->sk_state == TCP_CLOSE) |
|
sk_wake_async(sk, SOCK_WAKE_WAITD, POLL_HUP); |
|
else |
|
sk_wake_async(sk, SOCK_WAKE_WAITD, POLL_IN); |
|
} |
|
} |
|
|
|
static inline bool tcp_sack_extend(struct tcp_sack_block *sp, u32 seq, |
|
u32 end_seq) |
|
{ |
|
if (!after(seq, sp->end_seq) && !after(sp->start_seq, end_seq)) { |
|
if (before(seq, sp->start_seq)) |
|
sp->start_seq = seq; |
|
if (after(end_seq, sp->end_seq)) |
|
sp->end_seq = end_seq; |
|
return true; |
|
} |
|
return false; |
|
} |
|
|
|
static void tcp_dsack_set(struct sock *sk, u32 seq, u32 end_seq) |
|
{ |
|
struct tcp_sock *tp = tcp_sk(sk); |
|
|
|
if (tcp_is_sack(tp) && sock_net(sk)->ipv4.sysctl_tcp_dsack) { |
|
int mib_idx; |
|
|
|
if (before(seq, tp->rcv_nxt)) |
|
mib_idx = LINUX_MIB_TCPDSACKOLDSENT; |
|
else |
|
mib_idx = LINUX_MIB_TCPDSACKOFOSENT; |
|
|
|
NET_INC_STATS(sock_net(sk), mib_idx); |
|
|
|
tp->rx_opt.dsack = 1; |
|
tp->duplicate_sack[0].start_seq = seq; |
|
tp->duplicate_sack[0].end_seq = end_seq; |
|
} |
|
} |
|
|
|
static void tcp_dsack_extend(struct sock *sk, u32 seq, u32 end_seq) |
|
{ |
|
struct tcp_sock *tp = tcp_sk(sk); |
|
|
|
if (!tp->rx_opt.dsack) |
|
tcp_dsack_set(sk, seq, end_seq); |
|
else |
|
tcp_sack_extend(tp->duplicate_sack, seq, end_seq); |
|
} |
|
|
|
static void tcp_rcv_spurious_retrans(struct sock *sk, const struct sk_buff *skb) |
|
{ |
|
/* When the ACK path fails or drops most ACKs, the sender would |
|
* timeout and spuriously retransmit the same segment repeatedly. |
|
* The receiver remembers and reflects via DSACKs. Leverage the |
|
* DSACK state and change the txhash to re-route speculatively. |
|
*/ |
|
if (TCP_SKB_CB(skb)->seq == tcp_sk(sk)->duplicate_sack[0].start_seq && |
|
sk_rethink_txhash(sk)) |
|
NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPDUPLICATEDATAREHASH); |
|
} |
|
|
|
static void tcp_send_dupack(struct sock *sk, const struct sk_buff *skb) |
|
{ |
|
struct tcp_sock *tp = tcp_sk(sk); |
|
|
|
if (TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq && |
|
before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) { |
|
NET_INC_STATS(sock_net(sk), LINUX_MIB_DELAYEDACKLOST); |
|
tcp_enter_quickack_mode(sk, TCP_MAX_QUICKACKS); |
|
|
|
if (tcp_is_sack(tp) && sock_net(sk)->ipv4.sysctl_tcp_dsack) { |
|
u32 end_seq = TCP_SKB_CB(skb)->end_seq; |
|
|
|
tcp_rcv_spurious_retrans(sk, skb); |
|
if (after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt)) |
|
end_seq = tp->rcv_nxt; |
|
tcp_dsack_set(sk, TCP_SKB_CB(skb)->seq, end_seq); |
|
} |
|
} |
|
|
|
tcp_send_ack(sk); |
|
} |
|
|
|
/* These routines update the SACK block as out-of-order packets arrive or |
|
* in-order packets close up the sequence space. |
|
*/ |
|
static void tcp_sack_maybe_coalesce(struct tcp_sock *tp) |
|
{ |
|
int this_sack; |
|
struct tcp_sack_block *sp = &tp->selective_acks[0]; |
|
struct tcp_sack_block *swalk = sp + 1; |
|
|
|
/* See if the recent change to the first SACK eats into |
|
* or hits the sequence space of other SACK blocks, if so coalesce. |
|
*/ |
|
for (this_sack = 1; this_sack < tp->rx_opt.num_sacks;) { |
|
if (tcp_sack_extend(sp, swalk->start_seq, swalk->end_seq)) { |
|
int i; |
|
|
|
/* Zap SWALK, by moving every further SACK up by one slot. |
|
* Decrease num_sacks. |
|
*/ |
|
tp->rx_opt.num_sacks--; |
|
for (i = this_sack; i < tp->rx_opt.num_sacks; i++) |
|
sp[i] = sp[i + 1]; |
|
continue; |
|
} |
|
this_sack++; |
|
swalk++; |
|
} |
|
} |
|
|
|
static void tcp_sack_compress_send_ack(struct sock *sk) |
|
{ |
|
struct tcp_sock *tp = tcp_sk(sk); |
|
|
|
if (!tp->compressed_ack) |
|
return; |
|
|
|
if (hrtimer_try_to_cancel(&tp->compressed_ack_timer) == 1) |
|
__sock_put(sk); |
|
|
|
/* Since we have to send one ack finally, |
|
* substract one from tp->compressed_ack to keep |
|
* LINUX_MIB_TCPACKCOMPRESSED accurate. |
|
*/ |
|
NET_ADD_STATS(sock_net(sk), LINUX_MIB_TCPACKCOMPRESSED, |
|
tp->compressed_ack - 1); |
|
|
|
tp->compressed_ack = 0; |
|
tcp_send_ack(sk); |
|
} |
|
|
|
/* Reasonable amount of sack blocks included in TCP SACK option |
|
* The max is 4, but this becomes 3 if TCP timestamps are there. |
|
* Given that SACK packets might be lost, be conservative and use 2. |
|
*/ |
|
#define TCP_SACK_BLOCKS_EXPECTED 2 |
|
|
|
static void tcp_sack_new_ofo_skb(struct sock *sk, u32 seq, u32 end_seq) |
|
{ |
|
struct tcp_sock *tp = tcp_sk(sk); |
|
struct tcp_sack_block *sp = &tp->selective_acks[0]; |
|
int cur_sacks = tp->rx_opt.num_sacks; |
|
int this_sack; |
|
|
|
if (!cur_sacks) |
|
goto new_sack; |
|
|
|
for (this_sack = 0; this_sack < cur_sacks; this_sack++, sp++) { |
|
if (tcp_sack_extend(sp, seq, end_seq)) { |
|
if (this_sack >= TCP_SACK_BLOCKS_EXPECTED) |
|
tcp_sack_compress_send_ack(sk); |
|
/* Rotate this_sack to the first one. */ |
|
for (; this_sack > 0; this_sack--, sp--) |
|
swap(*sp, *(sp - 1)); |
|
if (cur_sacks > 1) |
|
tcp_sack_maybe_coalesce(tp); |
|
return; |
|
} |
|
} |
|
|
|
if (this_sack >= TCP_SACK_BLOCKS_EXPECTED) |
|
tcp_sack_compress_send_ack(sk); |
|
|
|
/* Could not find an adjacent existing SACK, build a new one, |
|
* put it at the front, and shift everyone else down. We |
|
* always know there is at least one SACK present already here. |
|
* |
|
* If the sack array is full, forget about the last one. |
|
*/ |
|
if (this_sack >= TCP_NUM_SACKS) { |
|
this_sack--; |
|
tp->rx_opt.num_sacks--; |
|
sp--; |
|
} |
|
for (; this_sack > 0; this_sack--, sp--) |
|
*sp = *(sp - 1); |
|
|
|
new_sack: |
|
/* Build the new head SACK, and we're done. */ |
|
sp->start_seq = seq; |
|
sp->end_seq = end_seq; |
|
tp->rx_opt.num_sacks++; |
|
} |
|
|
|
/* RCV.NXT advances, some SACKs should be eaten. */ |
|
|
|
static void tcp_sack_remove(struct tcp_sock *tp) |
|
{ |
|
struct tcp_sack_block *sp = &tp->selective_acks[0]; |
|
int num_sacks = tp->rx_opt.num_sacks; |
|
int this_sack; |
|
|
|
/* Empty ofo queue, hence, all the SACKs are eaten. Clear. */ |
|
if (RB_EMPTY_ROOT(&tp->out_of_order_queue)) { |
|
tp->rx_opt.num_sacks = 0; |
|
return; |
|
} |
|
|
|
for (this_sack = 0; this_sack < num_sacks;) { |
|
/* Check if the start of the sack is covered by RCV.NXT. */ |
|
if (!before(tp->rcv_nxt, sp->start_seq)) { |
|
int i; |
|
|
|
/* RCV.NXT must cover all the block! */ |
|
WARN_ON(before(tp->rcv_nxt, sp->end_seq)); |
|
|
|
/* Zap this SACK, by moving forward any other SACKS. */ |
|
for (i = this_sack+1; i < num_sacks; i++) |
|
tp->selective_acks[i-1] = tp->selective_acks[i]; |
|
num_sacks--; |
|
continue; |
|
} |
|
this_sack++; |
|
sp++; |
|
} |
|
tp->rx_opt.num_sacks = num_sacks; |
|
} |
|
|
|
/** |
|
* tcp_try_coalesce - try to merge skb to prior one |
|
* @sk: socket |
|
* @to: prior buffer |
|
* @from: buffer to add in queue |
|
* @fragstolen: pointer to boolean |
|
* |
|
* Before queueing skb @from after @to, try to merge them |
|
* to reduce overall memory use and queue lengths, if cost is small. |
|
* Packets in ofo or receive queues can stay a long time. |
|
* Better try to coalesce them right now to avoid future collapses. |
|
* Returns true if caller should free @from instead of queueing it |
|
*/ |
|
static bool tcp_try_coalesce(struct sock *sk, |
|
struct sk_buff *to, |
|
struct sk_buff *from, |
|
bool *fragstolen) |
|
{ |
|
int delta; |
|
|
|
*fragstolen = false; |
|
|
|
/* Its possible this segment overlaps with prior segment in queue */ |
|
if (TCP_SKB_CB(from)->seq != TCP_SKB_CB(to)->end_seq) |
|
return false; |
|
|
|
if (!mptcp_skb_can_collapse(to, from)) |
|
return false; |
|
|
|
#ifdef CONFIG_TLS_DEVICE |
|
if (from->decrypted != to->decrypted) |
|
return false; |
|
#endif |
|
|
|
if (!skb_try_coalesce(to, from, fragstolen, &delta)) |
|
return false; |
|
|
|
atomic_add(delta, &sk->sk_rmem_alloc); |
|
sk_mem_charge(sk, delta); |
|
NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPRCVCOALESCE); |
|
TCP_SKB_CB(to)->end_seq = TCP_SKB_CB(from)->end_seq; |
|
TCP_SKB_CB(to)->ack_seq = TCP_SKB_CB(from)->ack_seq; |
|
TCP_SKB_CB(to)->tcp_flags |= TCP_SKB_CB(from)->tcp_flags; |
|
|
|
if (TCP_SKB_CB(from)->has_rxtstamp) { |
|
TCP_SKB_CB(to)->has_rxtstamp = true; |
|
to->tstamp = from->tstamp; |
|
skb_hwtstamps(to)->hwtstamp = skb_hwtstamps(from)->hwtstamp; |
|
} |
|
|
|
return true; |
|
} |
|
|
|
static bool tcp_ooo_try_coalesce(struct sock *sk, |
|
struct sk_buff *to, |
|
struct sk_buff *from, |
|
bool *fragstolen) |
|
{ |
|
bool res = tcp_try_coalesce(sk, to, from, fragstolen); |
|
|
|
/* In case tcp_drop() is called later, update to->gso_segs */ |
|
if (res) { |
|
u32 gso_segs = max_t(u16, 1, skb_shinfo(to)->gso_segs) + |
|
max_t(u16, 1, skb_shinfo(from)->gso_segs); |
|
|
|
skb_shinfo(to)->gso_segs = min_t(u32, gso_segs, 0xFFFF); |
|
} |
|
return res; |
|
} |
|
|
|
static void tcp_drop(struct sock *sk, struct sk_buff *skb) |
|
{ |
|
sk_drops_add(sk, skb); |
|
__kfree_skb(skb); |
|
} |
|
|
|
/* This one checks to see if we can put data from the |
|
* out_of_order queue into the receive_queue. |
|
*/ |
|
static void tcp_ofo_queue(struct sock *sk) |
|
{ |
|
struct tcp_sock *tp = tcp_sk(sk); |
|
__u32 dsack_high = tp->rcv_nxt; |
|
bool fin, fragstolen, eaten; |
|
struct sk_buff *skb, *tail; |
|
struct rb_node *p; |
|
|
|
p = rb_first(&tp->out_of_order_queue); |
|
while (p) { |
|
skb = rb_to_skb(p); |
|
if (after(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) |
|
break; |
|
|
|
if (before(TCP_SKB_CB(skb)->seq, dsack_high)) { |
|
__u32 dsack = dsack_high; |
|
if (before(TCP_SKB_CB(skb)->end_seq, dsack_high)) |
|
dsack_high = TCP_SKB_CB(skb)->end_seq; |
|
tcp_dsack_extend(sk, TCP_SKB_CB(skb)->seq, dsack); |
|
} |
|
p = rb_next(p); |
|
rb_erase(&skb->rbnode, &tp->out_of_order_queue); |
|
|
|
if (unlikely(!after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt))) { |
|
tcp_drop(sk, skb); |
|
continue; |
|
} |
|
|
|
tail = skb_peek_tail(&sk->sk_receive_queue); |
|
eaten = tail && tcp_try_coalesce(sk, tail, skb, &fragstolen); |
|
tcp_rcv_nxt_update(tp, TCP_SKB_CB(skb)->end_seq); |
|
fin = TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN; |
|
if (!eaten) |
|
__skb_queue_tail(&sk->sk_receive_queue, skb); |
|
else |
|
kfree_skb_partial(skb, fragstolen); |
|
|
|
if (unlikely(fin)) { |
|
tcp_fin(sk); |
|
/* tcp_fin() purges tp->out_of_order_queue, |
|
* so we must end this loop right now. |
|
*/ |
|
break; |
|
} |
|
} |
|
} |
|
|
|
static bool tcp_prune_ofo_queue(struct sock *sk); |
|
static int tcp_prune_queue(struct sock *sk); |
|
|
|
static int tcp_try_rmem_schedule(struct sock *sk, struct sk_buff *skb, |
|
unsigned int size) |
|
{ |
|
if (atomic_read(&sk->sk_rmem_alloc) > sk->sk_rcvbuf || |
|
!sk_rmem_schedule(sk, skb, size)) { |
|
|
|
if (tcp_prune_queue(sk) < 0) |
|
return -1; |
|
|
|
while (!sk_rmem_schedule(sk, skb, size)) { |
|
if (!tcp_prune_ofo_queue(sk)) |
|
return -1; |
|
} |
|
} |
|
return 0; |
|
} |
|
|
|
static void tcp_data_queue_ofo(struct sock *sk, struct sk_buff *skb) |
|
{ |
|
struct tcp_sock *tp = tcp_sk(sk); |
|
struct rb_node **p, *parent; |
|
struct sk_buff *skb1; |
|
u32 seq, end_seq; |
|
bool fragstolen; |
|
|
|
tcp_ecn_check_ce(sk, skb); |
|
|
|
if (unlikely(tcp_try_rmem_schedule(sk, skb, skb->truesize))) { |
|
NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPOFODROP); |
|
sk->sk_data_ready(sk); |
|
tcp_drop(sk, skb); |
|
return; |
|
} |
|
|
|
/* Disable header prediction. */ |
|
tp->pred_flags = 0; |
|
inet_csk_schedule_ack(sk); |
|
|
|
tp->rcv_ooopack += max_t(u16, 1, skb_shinfo(skb)->gso_segs); |
|
NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPOFOQUEUE); |
|
seq = TCP_SKB_CB(skb)->seq; |
|
end_seq = TCP_SKB_CB(skb)->end_seq; |
|
|
|
p = &tp->out_of_order_queue.rb_node; |
|
if (RB_EMPTY_ROOT(&tp->out_of_order_queue)) { |
|
/* Initial out of order segment, build 1 SACK. */ |
|
if (tcp_is_sack(tp)) { |
|
tp->rx_opt.num_sacks = 1; |
|
tp->selective_acks[0].start_seq = seq; |
|
tp->selective_acks[0].end_seq = end_seq; |
|
} |
|
rb_link_node(&skb->rbnode, NULL, p); |
|
rb_insert_color(&skb->rbnode, &tp->out_of_order_queue); |
|
tp->ooo_last_skb = skb; |
|
goto end; |
|
} |
|
|
|
/* In the typical case, we are adding an skb to the end of the list. |
|
* Use of ooo_last_skb avoids the O(Log(N)) rbtree lookup. |
|
*/ |
|
if (tcp_ooo_try_coalesce(sk, tp->ooo_last_skb, |
|
skb, &fragstolen)) { |
|
coalesce_done: |
|
/* For non sack flows, do not grow window to force DUPACK |
|
* and trigger fast retransmit. |
|
*/ |
|
if (tcp_is_sack(tp)) |
|
tcp_grow_window(sk, skb, true); |
|
kfree_skb_partial(skb, fragstolen); |
|
skb = NULL; |
|
goto add_sack; |
|
} |
|
/* Can avoid an rbtree lookup if we are adding skb after ooo_last_skb */ |
|
if (!before(seq, TCP_SKB_CB(tp->ooo_last_skb)->end_seq)) { |
|
parent = &tp->ooo_last_skb->rbnode; |
|
p = &parent->rb_right; |
|
goto insert; |
|
} |
|
|
|
/* Find place to insert this segment. Handle overlaps on the way. */ |
|
parent = NULL; |
|
while (*p) { |
|
parent = *p; |
|
skb1 = rb_to_skb(parent); |
|
if (before(seq, TCP_SKB_CB(skb1)->seq)) { |
|
p = &parent->rb_left; |
|
continue; |
|
} |
|
if (before(seq, TCP_SKB_CB(skb1)->end_seq)) { |
|
if (!after(end_seq, TCP_SKB_CB(skb1)->end_seq)) { |
|
/* All the bits are present. Drop. */ |
|
NET_INC_STATS(sock_net(sk), |
|
LINUX_MIB_TCPOFOMERGE); |
|
tcp_drop(sk, skb); |
|
skb = NULL; |
|
tcp_dsack_set(sk, seq, end_seq); |
|
goto add_sack; |
|
} |
|
if (after(seq, TCP_SKB_CB(skb1)->seq)) { |
|
/* Partial overlap. */ |
|
tcp_dsack_set(sk, seq, TCP_SKB_CB(skb1)->end_seq); |
|
} else { |
|
/* skb's seq == skb1's seq and skb covers skb1. |
|
* Replace skb1 with skb. |
|
*/ |
|
rb_replace_node(&skb1->rbnode, &skb->rbnode, |
|
&tp->out_of_order_queue); |
|
tcp_dsack_extend(sk, |
|
TCP_SKB_CB(skb1)->seq, |
|
TCP_SKB_CB(skb1)->end_seq); |
|
NET_INC_STATS(sock_net(sk), |
|
LINUX_MIB_TCPOFOMERGE); |
|
tcp_drop(sk, skb1); |
|
goto merge_right; |
|
} |
|
} else if (tcp_ooo_try_coalesce(sk, skb1, |
|
skb, &fragstolen)) { |
|
goto coalesce_done; |
|
} |
|
p = &parent->rb_right; |
|
} |
|
insert: |
|
/* Insert segment into RB tree. */ |
|
rb_link_node(&skb->rbnode, parent, p); |
|
rb_insert_color(&skb->rbnode, &tp->out_of_order_queue); |
|
|
|
merge_right: |
|
/* Remove other segments covered by skb. */ |
|
while ((skb1 = skb_rb_next(skb)) != NULL) { |
|
if (!after(end_seq, TCP_SKB_CB(skb1)->seq)) |
|
break; |
|
if (before(end_seq, TCP_SKB_CB(skb1)->end_seq)) { |
|
tcp_dsack_extend(sk, TCP_SKB_CB(skb1)->seq, |
|
end_seq); |
|
break; |
|
} |
|
rb_erase(&skb1->rbnode, &tp->out_of_order_queue); |
|
tcp_dsack_extend(sk, TCP_SKB_CB(skb1)->seq, |
|
TCP_SKB_CB(skb1)->end_seq); |
|
NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPOFOMERGE); |
|
tcp_drop(sk, skb1); |
|
} |
|
/* If there is no skb after us, we are the last_skb ! */ |
|
if (!skb1) |
|
tp->ooo_last_skb = skb; |
|
|
|
add_sack: |
|
if (tcp_is_sack(tp)) |
|
tcp_sack_new_ofo_skb(sk, seq, end_seq); |
|
end: |
|
if (skb) { |
|
/* For non sack flows, do not grow window to force DUPACK |
|
* and trigger fast retransmit. |
|
*/ |
|
if (tcp_is_sack(tp)) |
|
tcp_grow_window(sk, skb, false); |
|
skb_condense(skb); |
|
skb_set_owner_r(skb, sk); |
|
} |
|
} |
|
|
|
static int __must_check tcp_queue_rcv(struct sock *sk, struct sk_buff *skb, |
|
bool *fragstolen) |
|
{ |
|
int eaten; |
|
struct sk_buff *tail = skb_peek_tail(&sk->sk_receive_queue); |
|
|
|
eaten = (tail && |
|
tcp_try_coalesce(sk, tail, |
|
skb, fragstolen)) ? 1 : 0; |
|
tcp_rcv_nxt_update(tcp_sk(sk), TCP_SKB_CB(skb)->end_seq); |
|
if (!eaten) { |
|
__skb_queue_tail(&sk->sk_receive_queue, skb); |
|
skb_set_owner_r(skb, sk); |
|
} |
|
return eaten; |
|
} |
|
|
|
int tcp_send_rcvq(struct sock *sk, struct msghdr *msg, size_t size) |
|
{ |
|
struct sk_buff *skb; |
|
int err = -ENOMEM; |
|
int data_len = 0; |
|
bool fragstolen; |
|
|
|
if (size == 0) |
|
return 0; |
|
|
|
if (size > PAGE_SIZE) { |
|
int npages = min_t(size_t, size >> PAGE_SHIFT, MAX_SKB_FRAGS); |
|
|
|
data_len = npages << PAGE_SHIFT; |
|
size = data_len + (size & ~PAGE_MASK); |
|
} |
|
skb = alloc_skb_with_frags(size - data_len, data_len, |
|
PAGE_ALLOC_COSTLY_ORDER, |
|
&err, sk->sk_allocation); |
|
if (!skb) |
|
goto err; |
|
|
|
skb_put(skb, size - data_len); |
|
skb->data_len = data_len; |
|
skb->len = size; |
|
|
|
if (tcp_try_rmem_schedule(sk, skb, skb->truesize)) { |
|
NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPRCVQDROP); |
|
goto err_free; |
|
} |
|
|
|
err = skb_copy_datagram_from_iter(skb, 0, &msg->msg_iter, size); |
|
if (err) |
|
goto err_free; |
|
|
|
TCP_SKB_CB(skb)->seq = tcp_sk(sk)->rcv_nxt; |
|
TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(skb)->seq + size; |
|
TCP_SKB_CB(skb)->ack_seq = tcp_sk(sk)->snd_una - 1; |
|
|
|
if (tcp_queue_rcv(sk, skb, &fragstolen)) { |
|
WARN_ON_ONCE(fragstolen); /* should not happen */ |
|
__kfree_skb(skb); |
|
} |
|
return size; |
|
|
|
err_free: |
|
kfree_skb(skb); |
|
err: |
|
return err; |
|
|
|
} |
|
|
|
void tcp_data_ready(struct sock *sk) |
|
{ |
|
if (tcp_epollin_ready(sk, sk->sk_rcvlowat) || sock_flag(sk, SOCK_DONE)) |
|
sk->sk_data_ready(sk); |
|
} |
|
|
|
static void tcp_data_queue(struct sock *sk, struct sk_buff *skb) |
|
{ |
|
struct tcp_sock *tp = tcp_sk(sk); |
|
bool fragstolen; |
|
int eaten; |
|
|
|
/* If a subflow has been reset, the packet should not continue |
|
* to be processed, drop the packet. |
|
*/ |
|
if (sk_is_mptcp(sk) && !mptcp_incoming_options(sk, skb)) { |
|
__kfree_skb(skb); |
|
return; |
|
} |
|
|
|
if (TCP_SKB_CB(skb)->seq == TCP_SKB_CB(skb)->end_seq) { |
|
__kfree_skb(skb); |
|
return; |
|
} |
|
skb_dst_drop(skb); |
|
__skb_pull(skb, tcp_hdr(skb)->doff * 4); |
|
|
|
tp->rx_opt.dsack = 0; |
|
|
|
/* Queue data for delivery to the user. |
|
* Packets in sequence go to the receive queue. |
|
* Out of sequence packets to the out_of_order_queue. |
|
*/ |
|
if (TCP_SKB_CB(skb)->seq == tp->rcv_nxt) { |
|
if (tcp_receive_window(tp) == 0) { |
|
NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPZEROWINDOWDROP); |
|
goto out_of_window; |
|
} |
|
|
|
/* Ok. In sequence. In window. */ |
|
queue_and_out: |
|
if (skb_queue_len(&sk->sk_receive_queue) == 0) |
|
sk_forced_mem_schedule(sk, skb->truesize); |
|
else if (tcp_try_rmem_schedule(sk, skb, skb->truesize)) { |
|
NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPRCVQDROP); |
|
sk->sk_data_ready(sk); |
|
goto drop; |
|
} |
|
|
|
eaten = tcp_queue_rcv(sk, skb, &fragstolen); |
|
if (skb->len) |
|
tcp_event_data_recv(sk, skb); |
|
if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN) |
|
tcp_fin(sk); |
|
|
|
if (!RB_EMPTY_ROOT(&tp->out_of_order_queue)) { |
|
tcp_ofo_queue(sk); |
|
|
|
/* RFC5681. 4.2. SHOULD send immediate ACK, when |
|
* gap in queue is filled. |
|
*/ |
|
if (RB_EMPTY_ROOT(&tp->out_of_order_queue)) |
|
inet_csk(sk)->icsk_ack.pending |= ICSK_ACK_NOW; |
|
} |
|
|
|
if (tp->rx_opt.num_sacks) |
|
tcp_sack_remove(tp); |
|
|
|
tcp_fast_path_check(sk); |
|
|
|
if (eaten > 0) |
|
kfree_skb_partial(skb, fragstolen); |
|
if (!sock_flag(sk, SOCK_DEAD)) |
|
tcp_data_ready(sk); |
|
return; |
|
} |
|
|
|
if (!after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt)) { |
|
tcp_rcv_spurious_retrans(sk, skb); |
|
/* A retransmit, 2nd most common case. Force an immediate ack. */ |
|
NET_INC_STATS(sock_net(sk), LINUX_MIB_DELAYEDACKLOST); |
|
tcp_dsack_set(sk, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq); |
|
|
|
out_of_window: |
|
tcp_enter_quickack_mode(sk, TCP_MAX_QUICKACKS); |
|
inet_csk_schedule_ack(sk); |
|
drop: |
|
tcp_drop(sk, skb); |
|
return; |
|
} |
|
|
|
/* Out of window. F.e. zero window probe. */ |
|
if (!before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt + tcp_receive_window(tp))) |
|
goto out_of_window; |
|
|
|
if (before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) { |
|
/* Partial packet, seq < rcv_next < end_seq */ |
|
tcp_dsack_set(sk, TCP_SKB_CB(skb)->seq, tp->rcv_nxt); |
|
|
|
/* If window is closed, drop tail of packet. But after |
|
* remembering D-SACK for its head made in previous line. |
|
*/ |
|
if (!tcp_receive_window(tp)) { |
|
NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPZEROWINDOWDROP); |
|
goto out_of_window; |
|
} |
|
goto queue_and_out; |
|
} |
|
|
|
tcp_data_queue_ofo(sk, skb); |
|
} |
|
|
|
static struct sk_buff *tcp_skb_next(struct sk_buff *skb, struct sk_buff_head *list) |
|
{ |
|
if (list) |
|
return !skb_queue_is_last(list, skb) ? skb->next : NULL; |
|
|
|
return skb_rb_next(skb); |
|
} |
|
|
|
static struct sk_buff *tcp_collapse_one(struct sock *sk, struct sk_buff *skb, |
|
struct sk_buff_head *list, |
|
struct rb_root *root) |
|
{ |
|
struct sk_buff *next = tcp_skb_next(skb, list); |
|
|
|
if (list) |
|
__skb_unlink(skb, list); |
|
else |
|
rb_erase(&skb->rbnode, root); |
|
|
|
__kfree_skb(skb); |
|
NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPRCVCOLLAPSED); |
|
|
|
return next; |
|
} |
|
|
|
/* Insert skb into rb tree, ordered by TCP_SKB_CB(skb)->seq */ |
|
void tcp_rbtree_insert(struct rb_root *root, struct sk_buff *skb) |
|
{ |
|
struct rb_node **p = &root->rb_node; |
|
struct rb_node *parent = NULL; |
|
struct sk_buff *skb1; |
|
|
|
while (*p) { |
|
parent = *p; |
|
skb1 = rb_to_skb(parent); |
|
if (before(TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb1)->seq)) |
|
p = &parent->rb_left; |
|
else |
|
p = &parent->rb_right; |
|
} |
|
rb_link_node(&skb->rbnode, parent, p); |
|
rb_insert_color(&skb->rbnode, root); |
|
} |
|
|
|
/* Collapse contiguous sequence of skbs head..tail with |
|
* sequence numbers start..end. |
|
* |
|
* If tail is NULL, this means until the end of the queue. |
|
* |
|
* Segments with FIN/SYN are not collapsed (only because this |
|
* simplifies code) |
|
*/ |
|
static void |
|
tcp_collapse(struct sock *sk, struct sk_buff_head *list, struct rb_root *root, |
|
struct sk_buff *head, struct sk_buff *tail, u32 start, u32 end) |
|
{ |
|
struct sk_buff *skb = head, *n; |
|
struct sk_buff_head tmp; |
|
bool end_of_skbs; |
|
|
|
/* First, check that queue is collapsible and find |
|
* the point where collapsing can be useful. |
|
*/ |
|
restart: |
|
for (end_of_skbs = true; skb != NULL && skb != tail; skb = n) { |
|
n = tcp_skb_next(skb, list); |
|
|
|
/* No new bits? It is possible on ofo queue. */ |
|
if (!before(start, TCP_SKB_CB(skb)->end_seq)) { |
|
skb = tcp_collapse_one(sk, skb, list, root); |
|
if (!skb) |
|
break; |
|
goto restart; |
|
} |
|
|
|
/* The first skb to collapse is: |
|
* - not SYN/FIN and |
|
* - bloated or contains data before "start" or |
|
* overlaps to the next one and mptcp allow collapsing. |
|
*/ |
|
if (!(TCP_SKB_CB(skb)->tcp_flags & (TCPHDR_SYN | TCPHDR_FIN)) && |
|
(tcp_win_from_space(sk, skb->truesize) > skb->len || |
|
before(TCP_SKB_CB(skb)->seq, start))) { |
|
end_of_skbs = false; |
|
break; |
|
} |
|
|
|
if (n && n != tail && mptcp_skb_can_collapse(skb, n) && |
|
TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(n)->seq) { |
|
end_of_skbs = false; |
|
break; |
|
} |
|
|
|
/* Decided to skip this, advance start seq. */ |
|
start = TCP_SKB_CB(skb)->end_seq; |
|
} |
|
if (end_of_skbs || |
|
(TCP_SKB_CB(skb)->tcp_flags & (TCPHDR_SYN | TCPHDR_FIN))) |
|
return; |
|
|
|
__skb_queue_head_init(&tmp); |
|
|
|
while (before(start, end)) { |
|
int copy = min_t(int, SKB_MAX_ORDER(0, 0), end - start); |
|
struct sk_buff *nskb; |
|
|
|
nskb = alloc_skb(copy, GFP_ATOMIC); |
|
if (!nskb) |
|
break; |
|
|
|
memcpy(nskb->cb, skb->cb, sizeof(skb->cb)); |
|
#ifdef CONFIG_TLS_DEVICE |
|
nskb->decrypted = skb->decrypted; |
|
#endif |
|
TCP_SKB_CB(nskb)->seq = TCP_SKB_CB(nskb)->end_seq = start; |
|
if (list) |
|
__skb_queue_before(list, skb, nskb); |
|
else |
|
__skb_queue_tail(&tmp, nskb); /* defer rbtree insertion */ |
|
skb_set_owner_r(nskb, sk); |
|
mptcp_skb_ext_move(nskb, skb); |
|
|
|
/* Copy data, releasing collapsed skbs. */ |
|
while (copy > 0) { |
|
int offset = start - TCP_SKB_CB(skb)->seq; |
|
int size = TCP_SKB_CB(skb)->end_seq - start; |
|
|
|
BUG_ON(offset < 0); |
|
if (size > 0) { |
|
size = min(copy, size); |
|
if (skb_copy_bits(skb, offset, skb_put(nskb, size), size)) |
|
BUG(); |
|
TCP_SKB_CB(nskb)->end_seq += size; |
|
copy -= size; |
|
start += size; |
|
} |
|
if (!before(start, TCP_SKB_CB(skb)->end_seq)) { |
|
skb = tcp_collapse_one(sk, skb, list, root); |
|
if (!skb || |
|
skb == tail || |
|
!mptcp_skb_can_collapse(nskb, skb) || |
|
(TCP_SKB_CB(skb)->tcp_flags & (TCPHDR_SYN | TCPHDR_FIN))) |
|
goto end; |
|
#ifdef CONFIG_TLS_DEVICE |
|
if (skb->decrypted != nskb->decrypted) |
|
goto end; |
|
#endif |
|
} |
|
} |
|
} |
|
end: |
|
skb_queue_walk_safe(&tmp, skb, n) |
|
tcp_rbtree_insert(root, skb); |
|
} |
|
|
|
/* Collapse ofo queue. Algorithm: select contiguous sequence of skbs |
|
* and tcp_collapse() them until all the queue is collapsed. |
|
*/ |
|
static void tcp_collapse_ofo_queue(struct sock *sk) |
|
{ |
|
struct tcp_sock *tp = tcp_sk(sk); |
|
u32 range_truesize, sum_tiny = 0; |
|
struct sk_buff *skb, *head; |
|
u32 start, end; |
|
|
|
skb = skb_rb_first(&tp->out_of_order_queue); |
|
new_range: |
|
if (!skb) { |
|
tp->ooo_last_skb = skb_rb_last(&tp->out_of_order_queue); |
|
return; |
|
} |
|
start = TCP_SKB_CB(skb)->seq; |
|
end = TCP_SKB_CB(skb)->end_seq; |
|
range_truesize = skb->truesize; |
|
|
|
for (head = skb;;) { |
|
skb = skb_rb_next(skb); |
|
|
|
/* Range is terminated when we see a gap or when |
|
* we are at the queue end. |
|
*/ |
|
if (!skb || |
|
after(TCP_SKB_CB(skb)->seq, end) || |
|
before(TCP_SKB_CB(skb)->end_seq, start)) { |
|
/* Do not attempt collapsing tiny skbs */ |
|
if (range_truesize != head->truesize || |
|
end - start >= SKB_WITH_OVERHEAD(SK_MEM_QUANTUM)) { |
|
tcp_collapse(sk, NULL, &tp->out_of_order_queue, |
|
head, skb, start, end); |
|
} else { |
|
sum_tiny += range_truesize; |
|
if (sum_tiny > sk->sk_rcvbuf >> 3) |
|
return; |
|
} |
|
goto new_range; |
|
} |
|
|
|
range_truesize += skb->truesize; |
|
if (unlikely(before(TCP_SKB_CB(skb)->seq, start))) |
|
start = TCP_SKB_CB(skb)->seq; |
|
if (after(TCP_SKB_CB(skb)->end_seq, end)) |
|
end = TCP_SKB_CB(skb)->end_seq; |
|
} |
|
} |
|
|
|
/* |
|
* Clean the out-of-order queue to make room. |
|
* We drop high sequences packets to : |
|
* 1) Let a chance for holes to be filled. |
|
* 2) not add too big latencies if thousands of packets sit there. |
|
* (But if application shrinks SO_RCVBUF, we could still end up |
|
* freeing whole queue here) |
|
* 3) Drop at least 12.5 % of sk_rcvbuf to avoid malicious attacks. |
|
* |
|
* Return true if queue has shrunk. |
|
*/ |
|
static bool tcp_prune_ofo_queue(struct sock *sk) |
|
{ |
|
struct tcp_sock *tp = tcp_sk(sk); |
|
struct rb_node *node, *prev; |
|
int goal; |
|
|
|
if (RB_EMPTY_ROOT(&tp->out_of_order_queue)) |
|
return false; |
|
|
|
NET_INC_STATS(sock_net(sk), LINUX_MIB_OFOPRUNED); |
|
goal = sk->sk_rcvbuf >> 3; |
|
node = &tp->ooo_last_skb->rbnode; |
|
do { |
|
prev = rb_prev(node); |
|
rb_erase(node, &tp->out_of_order_queue); |
|
goal -= rb_to_skb(node)->truesize; |
|
tcp_drop(sk, rb_to_skb(node)); |
|
if (!prev || goal <= 0) { |
|
sk_mem_reclaim(sk); |
|
if (atomic_read(&sk->sk_rmem_alloc) <= sk->sk_rcvbuf && |
|
!tcp_under_memory_pressure(sk)) |
|
break; |
|
goal = sk->sk_rcvbuf >> 3; |
|
} |
|
node = prev; |
|
} while (node); |
|
tp->ooo_last_skb = rb_to_skb(prev); |
|
|
|
/* Reset SACK state. A conforming SACK implementation will |
|
* do the same at a timeout based retransmit. When a connection |
|
* is in a sad state like this, we care only about integrity |
|
* of the connection not performance. |
|
*/ |
|
if (tp->rx_opt.sack_ok) |
|
tcp_sack_reset(&tp->rx_opt); |
|
return true; |
|
} |
|
|
|
/* Reduce allocated memory if we can, trying to get |
|
* the socket within its memory limits again. |
|
* |
|
* Return less than zero if we should start dropping frames |
|
* until the socket owning process reads some of the data |
|
* to stabilize the situation. |
|
*/ |
|
static int tcp_prune_queue(struct sock *sk) |
|
{ |
|
struct tcp_sock *tp = tcp_sk(sk); |
|
|
|
NET_INC_STATS(sock_net(sk), LINUX_MIB_PRUNECALLED); |
|
|
|
if (atomic_read(&sk->sk_rmem_alloc) >= sk->sk_rcvbuf) |
|
tcp_clamp_window(sk); |
|
else if (tcp_under_memory_pressure(sk)) |
|
tcp_adjust_rcv_ssthresh(sk); |
|
|
|
if (atomic_read(&sk->sk_rmem_alloc) <= sk->sk_rcvbuf) |
|
return 0; |
|
|
|
tcp_collapse_ofo_queue(sk); |
|
if (!skb_queue_empty(&sk->sk_receive_queue)) |
|
tcp_collapse(sk, &sk->sk_receive_queue, NULL, |
|
skb_peek(&sk->sk_receive_queue), |
|
NULL, |
|
tp->copied_seq, tp->rcv_nxt); |
|
sk_mem_reclaim(sk); |
|
|
|
if (atomic_read(&sk->sk_rmem_alloc) <= sk->sk_rcvbuf) |
|
return 0; |
|
|
|
/* Collapsing did not help, destructive actions follow. |
|
* This must not ever occur. */ |
|
|
|
tcp_prune_ofo_queue(sk); |
|
|
|
if (atomic_read(&sk->sk_rmem_alloc) <= sk->sk_rcvbuf) |
|
return 0; |
|
|
|
/* If we are really being abused, tell the caller to silently |
|
* drop receive data on the floor. It will get retransmitted |
|
* and hopefully then we'll have sufficient space. |
|
*/ |
|
NET_INC_STATS(sock_net(sk), LINUX_MIB_RCVPRUNED); |
|
|
|
/* Massive buffer overcommit. */ |
|
tp->pred_flags = 0; |
|
return -1; |
|
} |
|
|
|
static bool tcp_should_expand_sndbuf(struct sock *sk) |
|
{ |
|
const struct tcp_sock *tp = tcp_sk(sk); |
|
|
|
/* If the user specified a specific send buffer setting, do |
|
* not modify it. |
|
*/ |
|
if (sk->sk_userlocks & SOCK_SNDBUF_LOCK) |
|
return false; |
|
|
|
/* If we are under global TCP memory pressure, do not expand. */ |
|
if (tcp_under_memory_pressure(sk)) { |
|
int unused_mem = sk_unused_reserved_mem(sk); |
|
|
|
/* Adjust sndbuf according to reserved mem. But make sure |
|
* it never goes below SOCK_MIN_SNDBUF. |
|
* See sk_stream_moderate_sndbuf() for more details. |
|
*/ |
|
if (unused_mem > SOCK_MIN_SNDBUF) |
|
WRITE_ONCE(sk->sk_sndbuf, unused_mem); |
|
|
|
return false; |
|
} |
|
|
|
/* If we are under soft global TCP memory pressure, do not expand. */ |
|
if (sk_memory_allocated(sk) >= sk_prot_mem_limits(sk, 0)) |
|
return false; |
|
|
|
/* If we filled the congestion window, do not expand. */ |
|
if (tcp_packets_in_flight(tp) >= tp->snd_cwnd) |
|
return false; |
|
|
|
return true; |
|
} |
|
|
|
static void tcp_new_space(struct sock *sk) |
|
{ |
|
struct tcp_sock *tp = tcp_sk(sk); |
|
|
|
if (tcp_should_expand_sndbuf(sk)) { |
|
tcp_sndbuf_expand(sk); |
|
tp->snd_cwnd_stamp = tcp_jiffies32; |
|
} |
|
|
|
INDIRECT_CALL_1(sk->sk_write_space, sk_stream_write_space, sk); |
|
} |
|
|
|
static void tcp_check_space(struct sock *sk) |
|
{ |
|
/* pairs with tcp_poll() */ |
|
smp_mb(); |
|
if (sk->sk_socket && |
|
test_bit(SOCK_NOSPACE, &sk->sk_socket->flags)) { |
|
tcp_new_space(sk); |
|
if (!test_bit(SOCK_NOSPACE, &sk->sk_socket->flags)) |
|
tcp_chrono_stop(sk, TCP_CHRONO_SNDBUF_LIMITED); |
|
} |
|
} |
|
|
|
static inline void tcp_data_snd_check(struct sock *sk) |
|
{ |
|
tcp_push_pending_frames(sk); |
|
tcp_check_space(sk); |
|
} |
|
|
|
/* |
|
* Check if sending an ack is needed. |
|
*/ |
|
static void __tcp_ack_snd_check(struct sock *sk, int ofo_possible) |
|
{ |
|
struct tcp_sock *tp = tcp_sk(sk); |
|
unsigned long rtt, delay; |
|
|
|
/* More than one full frame received... */ |
|
if (((tp->rcv_nxt - tp->rcv_wup) > inet_csk(sk)->icsk_ack.rcv_mss && |
|
/* ... and right edge of window advances far enough. |
|
* (tcp_recvmsg() will send ACK otherwise). |
|
* If application uses SO_RCVLOWAT, we want send ack now if |
|
* we have not received enough bytes to satisfy the condition. |
|
*/ |
|
(tp->rcv_nxt - tp->copied_seq < sk->sk_rcvlowat || |
|
__tcp_select_window(sk) >= tp->rcv_wnd)) || |
|
/* We ACK each frame or... */ |
|
tcp_in_quickack_mode(sk) || |
|
/* Protocol state mandates a one-time immediate ACK */ |
|
inet_csk(sk)->icsk_ack.pending & ICSK_ACK_NOW) { |
|
send_now: |
|
tcp_send_ack(sk); |
|
return; |
|
} |
|
|
|
if (!ofo_possible || RB_EMPTY_ROOT(&tp->out_of_order_queue)) { |
|
tcp_send_delayed_ack(sk); |
|
return; |
|
} |
|
|
|
if (!tcp_is_sack(tp) || |
|
tp->compressed_ack >= sock_net(sk)->ipv4.sysctl_tcp_comp_sack_nr) |
|
goto send_now; |
|
|
|
if (tp->compressed_ack_rcv_nxt != tp->rcv_nxt) { |
|
tp->compressed_ack_rcv_nxt = tp->rcv_nxt; |
|
tp->dup_ack_counter = 0; |
|
} |
|
if (tp->dup_ack_counter < TCP_FASTRETRANS_THRESH) { |
|
tp->dup_ack_counter++; |
|
goto send_now; |
|
} |
|
tp->compressed_ack++; |
|
if (hrtimer_is_queued(&tp->compressed_ack_timer)) |
|
return; |
|
|
|
/* compress ack timer : 5 % of rtt, but no more than tcp_comp_sack_delay_ns */ |
|
|
|
rtt = tp->rcv_rtt_est.rtt_us; |
|
if (tp->srtt_us && tp->srtt_us < rtt) |
|
rtt = tp->srtt_us; |
|
|
|
delay = min_t(unsigned long, sock_net(sk)->ipv4.sysctl_tcp_comp_sack_delay_ns, |
|
rtt * (NSEC_PER_USEC >> 3)/20); |
|
sock_hold(sk); |
|
hrtimer_start_range_ns(&tp->compressed_ack_timer, ns_to_ktime(delay), |
|
sock_net(sk)->ipv4.sysctl_tcp_comp_sack_slack_ns, |
|
HRTIMER_MODE_REL_PINNED_SOFT); |
|
} |
|
|
|
static inline void tcp_ack_snd_check(struct sock *sk) |
|
{ |
|
if (!inet_csk_ack_scheduled(sk)) { |
|
/* We sent a data segment already. */ |
|
return; |
|
} |
|
__tcp_ack_snd_check(sk, 1); |
|
} |
|
|
|
/* |
|
* This routine is only called when we have urgent data |
|
* signaled. Its the 'slow' part of tcp_urg. It could be |
|
* moved inline now as tcp_urg is only called from one |
|
* place. We handle URGent data wrong. We have to - as |
|
* BSD still doesn't use the correction from RFC961. |
|
* For 1003.1g we should support a new option TCP_STDURG to permit |
|
* either form (or just set the sysctl tcp_stdurg). |
|
*/ |
|
|
|
static void tcp_check_urg(struct sock *sk, const struct tcphdr *th) |
|
{ |
|
struct tcp_sock *tp = tcp_sk(sk); |
|
u32 ptr = ntohs(th->urg_ptr); |
|
|
|
if (ptr && !sock_net(sk)->ipv4.sysctl_tcp_stdurg) |
|
ptr--; |
|
ptr += ntohl(th->seq); |
|
|
|
/* Ignore urgent data that we've already seen and read. */ |
|
if (after(tp->copied_seq, ptr)) |
|
return; |
|
|
|
/* Do not replay urg ptr. |
|
* |
|
* NOTE: interesting situation not covered by specs. |
|
* Misbehaving sender may send urg ptr, pointing to segment, |
|
* which we already have in ofo queue. We are not able to fetch |
|
* such data and will stay in TCP_URG_NOTYET until will be eaten |
|
* by recvmsg(). Seems, we are not obliged to handle such wicked |
|
* situations. But it is worth to think about possibility of some |
|
* DoSes using some hypothetical application level deadlock. |
|
*/ |
|
if (before(ptr, tp->rcv_nxt)) |
|
return; |
|
|
|
/* Do we already have a newer (or duplicate) urgent pointer? */ |
|
if (tp->urg_data && !after(ptr, tp->urg_seq)) |
|
return; |
|
|
|
/* Tell the world about our new urgent pointer. */ |
|
sk_send_sigurg(sk); |
|
|
|
/* We may be adding urgent data when the last byte read was |
|
* urgent. To do this requires some care. We cannot just ignore |
|
* tp->copied_seq since we would read the last urgent byte again |
|
* as data, nor can we alter copied_seq until this data arrives |
|
* or we break the semantics of SIOCATMARK (and thus sockatmark()) |
|
* |
|
* NOTE. Double Dutch. Rendering to plain English: author of comment |
|
* above did something sort of send("A", MSG_OOB); send("B", MSG_OOB); |
|
* and expect that both A and B disappear from stream. This is _wrong_. |
|
* Though this happens in BSD with high probability, this is occasional. |
|
* Any application relying on this is buggy. Note also, that fix "works" |
|
* only in this artificial test. Insert some normal data between A and B and we will |
|
* decline of BSD again. Verdict: it is better to remove to trap |
|
* buggy users. |
|
*/ |
|
if (tp->urg_seq == tp->copied_seq && tp->urg_data && |
|
!sock_flag(sk, SOCK_URGINLINE) && tp->copied_seq != tp->rcv_nxt) { |
|
struct sk_buff *skb = skb_peek(&sk->sk_receive_queue); |
|
tp->copied_seq++; |
|
if (skb && !before(tp->copied_seq, TCP_SKB_CB(skb)->end_seq)) { |
|
__skb_unlink(skb, &sk->sk_receive_queue); |
|
__kfree_skb(skb); |
|
} |
|
} |
|
|
|
WRITE_ONCE(tp->urg_data, TCP_URG_NOTYET); |
|
WRITE_ONCE(tp->urg_seq, ptr); |
|
|
|
/* Disable header prediction. */ |
|
tp->pred_flags = 0; |
|
} |
|
|
|
/* This is the 'fast' part of urgent handling. */ |
|
static void tcp_urg(struct sock *sk, struct sk_buff *skb, const struct tcphdr *th) |
|
{ |
|
struct tcp_sock *tp = tcp_sk(sk); |
|
|
|
/* Check if we get a new urgent pointer - normally not. */ |
|
if (unlikely(th->urg)) |
|
tcp_check_urg(sk, th); |
|
|
|
/* Do we wait for any urgent data? - normally not... */ |
|
if (unlikely(tp->urg_data == TCP_URG_NOTYET)) { |
|
u32 ptr = tp->urg_seq - ntohl(th->seq) + (th->doff * 4) - |
|
th->syn; |
|
|
|
/* Is the urgent pointer pointing into this packet? */ |
|
if (ptr < skb->len) { |
|
u8 tmp; |
|
if (skb_copy_bits(skb, ptr, &tmp, 1)) |
|
BUG(); |
|
WRITE_ONCE(tp->urg_data, TCP_URG_VALID | tmp); |
|
if (!sock_flag(sk, SOCK_DEAD)) |
|
sk->sk_data_ready(sk); |
|
} |
|
} |
|
} |
|
|
|
/* Accept RST for rcv_nxt - 1 after a FIN. |
|
* When tcp connections are abruptly terminated from Mac OSX (via ^C), a |
|
* FIN is sent followed by a RST packet. The RST is sent with the same |
|
* sequence number as the FIN, and thus according to RFC 5961 a challenge |
|
* ACK should be sent. However, Mac OSX rate limits replies to challenge |
|
* ACKs on the closed socket. In addition middleboxes can drop either the |
|
* challenge ACK or a subsequent RST. |
|
*/ |
|
static bool tcp_reset_check(const struct sock *sk, const struct sk_buff *skb) |
|
{ |
|
struct tcp_sock *tp = tcp_sk(sk); |
|
|
|
return unlikely(TCP_SKB_CB(skb)->seq == (tp->rcv_nxt - 1) && |
|
(1 << sk->sk_state) & (TCPF_CLOSE_WAIT | TCPF_LAST_ACK | |
|
TCPF_CLOSING)); |
|
} |
|
|
|
/* Does PAWS and seqno based validation of an incoming segment, flags will |
|
* play significant role here. |
|
*/ |
|
static bool tcp_validate_incoming(struct sock *sk, struct sk_buff *skb, |
|
const struct tcphdr *th, int syn_inerr) |
|
{ |
|
struct tcp_sock *tp = tcp_sk(sk); |
|
bool rst_seq_match = false; |
|
|
|
/* RFC1323: H1. Apply PAWS check first. */ |
|
if (tcp_fast_parse_options(sock_net(sk), skb, th, tp) && |
|
tp->rx_opt.saw_tstamp && |
|
tcp_paws_discard(sk, skb)) { |
|
if (!th->rst) { |
|
NET_INC_STATS(sock_net(sk), LINUX_MIB_PAWSESTABREJECTED); |
|
if (!tcp_oow_rate_limited(sock_net(sk), skb, |
|
LINUX_MIB_TCPACKSKIPPEDPAWS, |
|
&tp->last_oow_ack_time)) |
|
tcp_send_dupack(sk, skb); |
|
goto discard; |
|
} |
|
/* Reset is accepted even if it did not pass PAWS. */ |
|
} |
|
|
|
/* Step 1: check sequence number */ |
|
if (!tcp_sequence(tp, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq)) { |
|
/* RFC793, page 37: "In all states except SYN-SENT, all reset |
|
* (RST) segments are validated by checking their SEQ-fields." |
|
* And page 69: "If an incoming segment is not acceptable, |
|
* an acknowledgment should be sent in reply (unless the RST |
|
* bit is set, if so drop the segment and return)". |
|
*/ |
|
if (!th->rst) { |
|
if (th->syn) |
|
goto syn_challenge; |
|
if (!tcp_oow_rate_limited(sock_net(sk), skb, |
|
LINUX_MIB_TCPACKSKIPPEDSEQ, |
|
&tp->last_oow_ack_time)) |
|
tcp_send_dupack(sk, skb); |
|
} else if (tcp_reset_check(sk, skb)) { |
|
tcp_reset(sk, skb); |
|
} |
|
goto discard; |
|
} |
|
|
|
/* Step 2: check RST bit */ |
|
if (th->rst) { |
|
/* RFC 5961 3.2 (extend to match against (RCV.NXT - 1) after a |
|
* FIN and SACK too if available): |
|
* If seq num matches RCV.NXT or (RCV.NXT - 1) after a FIN, or |
|
* the right-most SACK block, |
|
* then |
|
* RESET the connection |
|
* else |
|
* Send a challenge ACK |
|
*/ |
|
if (TCP_SKB_CB(skb)->seq == tp->rcv_nxt || |
|
tcp_reset_check(sk, skb)) { |
|
rst_seq_match = true; |
|
} else if (tcp_is_sack(tp) && tp->rx_opt.num_sacks > 0) { |
|
struct tcp_sack_block *sp = &tp->selective_acks[0]; |
|
int max_sack = sp[0].end_seq; |
|
int this_sack; |
|
|
|
for (this_sack = 1; this_sack < tp->rx_opt.num_sacks; |
|
++this_sack) { |
|
max_sack = after(sp[this_sack].end_seq, |
|
max_sack) ? |
|
sp[this_sack].end_seq : max_sack; |
|
} |
|
|
|
if (TCP_SKB_CB(skb)->seq == max_sack) |
|
rst_seq_match = true; |
|
} |
|
|
|
if (rst_seq_match) |
|
tcp_reset(sk, skb); |
|
else { |
|
/* Disable TFO if RST is out-of-order |
|
* and no data has been received |
|
* for current active TFO socket |
|
*/ |
|
if (tp->syn_fastopen && !tp->data_segs_in && |
|
sk->sk_state == TCP_ESTABLISHED) |
|
tcp_fastopen_active_disable(sk); |
|
tcp_send_challenge_ack(sk); |
|
} |
|
goto discard; |
|
} |
|
|
|
/* step 3: check security and precedence [ignored] */ |
|
|
|
/* step 4: Check for a SYN |
|
* RFC 5961 4.2 : Send a challenge ack |
|
*/ |
|
if (th->syn) { |
|
syn_challenge: |
|
if (syn_inerr) |
|
TCP_INC_STATS(sock_net(sk), TCP_MIB_INERRS); |
|
NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPSYNCHALLENGE); |
|
tcp_send_challenge_ack(sk); |
|
goto discard; |
|
} |
|
|
|
bpf_skops_parse_hdr(sk, skb); |
|
|
|
return true; |
|
|
|
discard: |
|
tcp_drop(sk, skb); |
|
return false; |
|
} |
|
|
|
/* |
|
* TCP receive function for the ESTABLISHED state. |
|
* |
|
* It is split into a fast path and a slow path. The fast path is |
|
* disabled when: |
|
* - A zero window was announced from us - zero window probing |
|
* is only handled properly in the slow path. |
|
* - Out of order segments arrived. |
|
* - Urgent data is expected. |
|
* - There is no buffer space left |
|
* - Unexpected TCP flags/window values/header lengths are received |
|
* (detected by checking the TCP header against pred_flags) |
|
* - Data is sent in both directions. Fast path only supports pure senders |
|
* or pure receivers (this means either the sequence number or the ack |
|
* value must stay constant) |
|
* - Unexpected TCP option. |
|
* |
|
* When these conditions are not satisfied it drops into a standard |
|
* receive procedure patterned after RFC793 to handle all cases. |
|
* The first three cases are guaranteed by proper pred_flags setting, |
|
* the rest is checked inline. Fast processing is turned on in |
|
* tcp_data_queue when everything is OK. |
|
*/ |
|
void tcp_rcv_established(struct sock *sk, struct sk_buff *skb) |
|
{ |
|
const struct tcphdr *th = (const struct tcphdr *)skb->data; |
|
struct tcp_sock *tp = tcp_sk(sk); |
|
unsigned int len = skb->len; |
|
|
|
/* TCP congestion window tracking */ |
|
trace_tcp_probe(sk, skb); |
|
|
|
tcp_mstamp_refresh(tp); |
|
if (unlikely(!rcu_access_pointer(sk->sk_rx_dst))) |
|
inet_csk(sk)->icsk_af_ops->sk_rx_dst_set(sk, skb); |
|
/* |
|
* Header prediction. |
|
* The code loosely follows the one in the famous |
|
* "30 instruction TCP receive" Van Jacobson mail. |
|
* |
|
* Van's trick is to deposit buffers into socket queue |
|
* on a device interrupt, to call tcp_recv function |
|
* on the receive process context and checksum and copy |
|
* the buffer to user space. smart... |
|
* |
|
* Our current scheme is not silly either but we take the |
|
* extra cost of the net_bh soft interrupt processing... |
|
* We do checksum and copy also but from device to kernel. |
|
*/ |
|
|
|
tp->rx_opt.saw_tstamp = 0; |
|
|
|
/* pred_flags is 0xS?10 << 16 + snd_wnd |
|
* if header_prediction is to be made |
|
* 'S' will always be tp->tcp_header_len >> 2 |
|
* '?' will be 0 for the fast path, otherwise pred_flags is 0 to |
|
* turn it off (when there are holes in the receive |
|
* space for instance) |
|
* PSH flag is ignored. |
|
*/ |
|
|
|
if ((tcp_flag_word(th) & TCP_HP_BITS) == tp->pred_flags && |
|
TCP_SKB_CB(skb)->seq == tp->rcv_nxt && |
|
!after(TCP_SKB_CB(skb)->ack_seq, tp->snd_nxt)) { |
|
int tcp_header_len = tp->tcp_header_len; |
|
|
|
/* Timestamp header prediction: tcp_header_len |
|
* is automatically equal to th->doff*4 due to pred_flags |
|
* match. |
|
*/ |
|
|
|
/* Check timestamp */ |
|
if (tcp_header_len == sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED) { |
|
/* No? Slow path! */ |
|
if (!tcp_parse_aligned_timestamp(tp, th)) |
|
goto slow_path; |
|
|
|
/* If PAWS failed, check it more carefully in slow path */ |
|
if ((s32)(tp->rx_opt.rcv_tsval - tp->rx_opt.ts_recent) < 0) |
|
goto slow_path; |
|
|
|
/* DO NOT update ts_recent here, if checksum fails |
|
* and timestamp was corrupted part, it will result |
|
* in a hung connection since we will drop all |
|
* future packets due to the PAWS test. |
|
*/ |
|
} |
|
|
|
if (len <= tcp_header_len) { |
|
/* Bulk data transfer: sender */ |
|
if (len == tcp_header_len) { |
|
/* Predicted packet is in window by definition. |
|
* seq == rcv_nxt and rcv_wup <= rcv_nxt. |
|
* Hence, check seq<=rcv_wup reduces to: |
|
*/ |
|
if (tcp_header_len == |
|
(sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED) && |
|
tp->rcv_nxt == tp->rcv_wup) |
|
tcp_store_ts_recent(tp); |
|
|
|
/* We know that such packets are checksummed |
|
* on entry. |
|
*/ |
|
tcp_ack(sk, skb, 0); |
|
__kfree_skb(skb); |
|
tcp_data_snd_check(sk); |
|
/* When receiving pure ack in fast path, update |
|
* last ts ecr directly instead of calling |
|
* tcp_rcv_rtt_measure_ts() |
|
*/ |
|
tp->rcv_rtt_last_tsecr = tp->rx_opt.rcv_tsecr; |
|
return; |
|
} else { /* Header too small */ |
|
TCP_INC_STATS(sock_net(sk), TCP_MIB_INERRS); |
|
goto discard; |
|
} |
|
} else { |
|
int eaten = 0; |
|
bool fragstolen = false; |
|
|
|
if (tcp_checksum_complete(skb)) |
|
goto csum_error; |
|
|
|
if ((int)skb->truesize > sk->sk_forward_alloc) |
|
goto step5; |
|
|
|
/* Predicted packet is in window by definition. |
|
* seq == rcv_nxt and rcv_wup <= rcv_nxt. |
|
* Hence, check seq<=rcv_wup reduces to: |
|
*/ |
|
if (tcp_header_len == |
|
(sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED) && |
|
tp->rcv_nxt == tp->rcv_wup) |
|
tcp_store_ts_recent(tp); |
|
|
|
tcp_rcv_rtt_measure_ts(sk, skb); |
|
|
|
NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPHPHITS); |
|
|
|
/* Bulk data transfer: receiver */ |
|
__skb_pull(skb, tcp_header_len); |
|
eaten = tcp_queue_rcv(sk, skb, &fragstolen); |
|
|
|
tcp_event_data_recv(sk, skb); |
|
|
|
if (TCP_SKB_CB(skb)->ack_seq != tp->snd_una) { |
|
/* Well, only one small jumplet in fast path... */ |
|
tcp_ack(sk, skb, FLAG_DATA); |
|
tcp_data_snd_check(sk); |
|
if (!inet_csk_ack_scheduled(sk)) |
|
goto no_ack; |
|
} else { |
|
tcp_update_wl(tp, TCP_SKB_CB(skb)->seq); |
|
} |
|
|
|
__tcp_ack_snd_check(sk, 0); |
|
no_ack: |
|
if (eaten) |
|
kfree_skb_partial(skb, fragstolen); |
|
tcp_data_ready(sk); |
|
return; |
|
} |
|
} |
|
|
|
slow_path: |
|
if (len < (th->doff << 2) || tcp_checksum_complete(skb)) |
|
goto csum_error; |
|
|
|
if (!th->ack && !th->rst && !th->syn) |
|
goto discard; |
|
|
|
/* |
|
* Standard slow path. |
|
*/ |
|
|
|
if (!tcp_validate_incoming(sk, skb, th, 1)) |
|
return; |
|
|
|
step5: |
|
if (tcp_ack(sk, skb, FLAG_SLOWPATH | FLAG_UPDATE_TS_RECENT) < 0) |
|
goto discard; |
|
|
|
tcp_rcv_rtt_measure_ts(sk, skb); |
|
|
|
/* Process urgent data. */ |
|
tcp_urg(sk, skb, th); |
|
|
|
/* step 7: process the segment text */ |
|
tcp_data_queue(sk, skb); |
|
|
|
tcp_data_snd_check(sk); |
|
tcp_ack_snd_check(sk); |
|
return; |
|
|
|
csum_error: |
|
trace_tcp_bad_csum(skb); |
|
TCP_INC_STATS(sock_net(sk), TCP_MIB_CSUMERRORS); |
|
TCP_INC_STATS(sock_net(sk), TCP_MIB_INERRS); |
|
|
|
discard: |
|
tcp_drop(sk, skb); |
|
} |
|
EXPORT_SYMBOL(tcp_rcv_established); |
|
|
|
void tcp_init_transfer(struct sock *sk, int bpf_op, struct sk_buff *skb) |
|
{ |
|
struct inet_connection_sock *icsk = inet_csk(sk); |
|
struct tcp_sock *tp = tcp_sk(sk); |
|
|
|
tcp_mtup_init(sk); |
|
icsk->icsk_af_ops->rebuild_header(sk); |
|
tcp_init_metrics(sk); |
|
|
|
/* Initialize the congestion window to start the transfer. |
|
* Cut cwnd down to 1 per RFC5681 if SYN or SYN-ACK has been |
|
* retransmitted. In light of RFC6298 more aggressive 1sec |
|
* initRTO, we only reset cwnd when more than 1 SYN/SYN-ACK |
|
* retransmission has occurred. |
|
*/ |
|
if (tp->total_retrans > 1 && tp->undo_marker) |
|
tp->snd_cwnd = 1; |
|
else |
|
tp->snd_cwnd = tcp_init_cwnd(tp, __sk_dst_get(sk)); |
|
tp->snd_cwnd_stamp = tcp_jiffies32; |
|
|
|
bpf_skops_established(sk, bpf_op, skb); |
|
/* Initialize congestion control unless BPF initialized it already: */ |
|
if (!icsk->icsk_ca_initialized) |
|
tcp_init_congestion_control(sk); |
|
tcp_init_buffer_space(sk); |
|
} |
|
|
|
void tcp_finish_connect(struct sock *sk, struct sk_buff *skb) |
|
{ |
|
struct tcp_sock *tp = tcp_sk(sk); |
|
struct inet_connection_sock *icsk = inet_csk(sk); |
|
|
|
tcp_set_state(sk, TCP_ESTABLISHED); |
|
icsk->icsk_ack.lrcvtime = tcp_jiffies32; |
|
|
|
if (skb) { |
|
icsk->icsk_af_ops->sk_rx_dst_set(sk, skb); |
|
security_inet_conn_established(sk, skb); |
|
sk_mark_napi_id(sk, skb); |
|
} |
|
|
|
tcp_init_transfer(sk, BPF_SOCK_OPS_ACTIVE_ESTABLISHED_CB, skb); |
|
|
|
/* Prevent spurious tcp_cwnd_restart() on first data |
|
* packet. |
|
*/ |
|
tp->lsndtime = tcp_jiffies32; |
|
|
|
if (sock_flag(sk, SOCK_KEEPOPEN)) |
|
inet_csk_reset_keepalive_timer(sk, keepalive_time_when(tp)); |
|
|
|
if (!tp->rx_opt.snd_wscale) |
|
__tcp_fast_path_on(tp, tp->snd_wnd); |
|
else |
|
tp->pred_flags = 0; |
|
} |
|
|
|
static bool tcp_rcv_fastopen_synack(struct sock *sk, struct sk_buff *synack, |
|
struct tcp_fastopen_cookie *cookie) |
|
{ |
|
struct tcp_sock *tp = tcp_sk(sk); |
|
struct sk_buff *data = tp->syn_data ? tcp_rtx_queue_head(sk) : NULL; |
|
u16 mss = tp->rx_opt.mss_clamp, try_exp = 0; |
|
bool syn_drop = false; |
|
|
|
if (mss == tp->rx_opt.user_mss) { |
|
struct tcp_options_received opt; |
|
|
|
/* Get original SYNACK MSS value if user MSS sets mss_clamp */ |
|
tcp_clear_options(&opt); |
|
opt.user_mss = opt.mss_clamp = 0; |
|
tcp_parse_options(sock_net(sk), synack, &opt, 0, NULL); |
|
mss = opt.mss_clamp; |
|
} |
|
|
|
if (!tp->syn_fastopen) { |
|
/* Ignore an unsolicited cookie */ |
|
cookie->len = -1; |
|
} else if (tp->total_retrans) { |
|
/* SYN timed out and the SYN-ACK neither has a cookie nor |
|
* acknowledges data. Presumably the remote received only |
|
* the retransmitted (regular) SYNs: either the original |
|
* SYN-data or the corresponding SYN-ACK was dropped. |
|
*/ |
|
syn_drop = (cookie->len < 0 && data); |
|
} else if (cookie->len < 0 && !tp->syn_data) { |
|
/* We requested a cookie but didn't get it. If we did not use |
|
* the (old) exp opt format then try so next time (try_exp=1). |
|
* Otherwise we go back to use the RFC7413 opt (try_exp=2). |
|
*/ |
|
try_exp = tp->syn_fastopen_exp ? 2 : 1; |
|
} |
|
|
|
tcp_fastopen_cache_set(sk, mss, cookie, syn_drop, try_exp); |
|
|
|
if (data) { /* Retransmit unacked data in SYN */ |
|
if (tp->total_retrans) |
|
tp->fastopen_client_fail = TFO_SYN_RETRANSMITTED; |
|
else |
|
tp->fastopen_client_fail = TFO_DATA_NOT_ACKED; |
|
skb_rbtree_walk_from(data) |
|
tcp_mark_skb_lost(sk, data); |
|
tcp_xmit_retransmit_queue(sk); |
|
NET_INC_STATS(sock_net(sk), |
|
LINUX_MIB_TCPFASTOPENACTIVEFAIL); |
|
return true; |
|
} |
|
tp->syn_data_acked = tp->syn_data; |
|
if (tp->syn_data_acked) { |
|
NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPFASTOPENACTIVE); |
|
/* SYN-data is counted as two separate packets in tcp_ack() */ |
|
if (tp->delivered > 1) |
|
--tp->delivered; |
|
} |
|
|
|
tcp_fastopen_add_skb(sk, synack); |
|
|
|
return false; |
|
} |
|
|
|
static void smc_check_reset_syn(struct tcp_sock *tp) |
|
{ |
|
#if IS_ENABLED(CONFIG_SMC) |
|
if (static_branch_unlikely(&tcp_have_smc)) { |
|
if (tp->syn_smc && !tp->rx_opt.smc_ok) |
|
tp->syn_smc = 0; |
|
} |
|
#endif |
|
} |
|
|
|
static void tcp_try_undo_spurious_syn(struct sock *sk) |
|
{ |
|
struct tcp_sock *tp = tcp_sk(sk); |
|
u32 syn_stamp; |
|
|
|
/* undo_marker is set when SYN or SYNACK times out. The timeout is |
|
* spurious if the ACK's timestamp option echo value matches the |
|
* original SYN timestamp. |
|
*/ |
|
syn_stamp = tp->retrans_stamp; |
|
if (tp->undo_marker && syn_stamp && tp->rx_opt.saw_tstamp && |
|
syn_stamp == tp->rx_opt.rcv_tsecr) |
|
tp->undo_marker = 0; |
|
} |
|
|
|
static int tcp_rcv_synsent_state_process(struct sock *sk, struct sk_buff *skb, |
|
const struct tcphdr *th) |
|
{ |
|
struct inet_connection_sock *icsk = inet_csk(sk); |
|
struct tcp_sock *tp = tcp_sk(sk); |
|
struct tcp_fastopen_cookie foc = { .len = -1 }; |
|
int saved_clamp = tp->rx_opt.mss_clamp; |
|
bool fastopen_fail; |
|
|
|
tcp_parse_options(sock_net(sk), skb, &tp->rx_opt, 0, &foc); |
|
if (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr) |
|
tp->rx_opt.rcv_tsecr -= tp->tsoffset; |
|
|
|
if (th->ack) { |
|
/* rfc793: |
|
* "If the state is SYN-SENT then |
|
* first check the ACK bit |
|
* If the ACK bit is set |
|
* If SEG.ACK =< ISS, or SEG.ACK > SND.NXT, send |
|
* a reset (unless the RST bit is set, if so drop |
|
* the segment and return)" |
|
*/ |
|
if (!after(TCP_SKB_CB(skb)->ack_seq, tp->snd_una) || |
|
after(TCP_SKB_CB(skb)->ack_seq, tp->snd_nxt)) { |
|
/* Previous FIN/ACK or RST/ACK might be ignored. */ |
|
if (icsk->icsk_retransmits == 0) |
|
inet_csk_reset_xmit_timer(sk, |
|
ICSK_TIME_RETRANS, |
|
TCP_TIMEOUT_MIN, TCP_RTO_MAX); |
|
goto reset_and_undo; |
|
} |
|
|
|
if (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr && |
|
!between(tp->rx_opt.rcv_tsecr, tp->retrans_stamp, |
|
tcp_time_stamp(tp))) { |
|
NET_INC_STATS(sock_net(sk), |
|
LINUX_MIB_PAWSACTIVEREJECTED); |
|
goto reset_and_undo; |
|
} |
|
|
|
/* Now ACK is acceptable. |
|
* |
|
* "If the RST bit is set |
|
* If the ACK was acceptable then signal the user "error: |
|
* connection reset", drop the segment, enter CLOSED state, |
|
* delete TCB, and return." |
|
*/ |
|
|
|
if (th->rst) { |
|
tcp_reset(sk, skb); |
|
goto discard; |
|
} |
|
|
|
/* rfc793: |
|
* "fifth, if neither of the SYN or RST bits is set then |
|
* drop the segment and return." |
|
* |
|
* See note below! |
|
* --ANK(990513) |
|
*/ |
|
if (!th->syn) |
|
goto discard_and_undo; |
|
|
|
/* rfc793: |
|
* "If the SYN bit is on ... |
|
* are acceptable then ... |
|
* (our SYN has been ACKed), change the connection |
|
* state to ESTABLISHED..." |
|
*/ |
|
|
|
tcp_ecn_rcv_synack(tp, th); |
|
|
|
tcp_init_wl(tp, TCP_SKB_CB(skb)->seq); |
|
tcp_try_undo_spurious_syn(sk); |
|
tcp_ack(sk, skb, FLAG_SLOWPATH); |
|
|
|
/* Ok.. it's good. Set up sequence numbers and |
|
* move to established. |
|
*/ |
|
WRITE_ONCE(tp->rcv_nxt, TCP_SKB_CB(skb)->seq + 1); |
|
tp->rcv_wup = TCP_SKB_CB(skb)->seq + 1; |
|
|
|
/* RFC1323: The window in SYN & SYN/ACK segments is |
|
* never scaled. |
|
*/ |
|
tp->snd_wnd = ntohs(th->window); |
|
|
|
if (!tp->rx_opt.wscale_ok) { |
|
tp->rx_opt.snd_wscale = tp->rx_opt.rcv_wscale = 0; |
|
tp->window_clamp = min(tp->window_clamp, 65535U); |
|
} |
|
|
|
if (tp->rx_opt.saw_tstamp) { |
|
tp->rx_opt.tstamp_ok = 1; |
|
tp->tcp_header_len = |
|
sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED; |
|
tp->advmss -= TCPOLEN_TSTAMP_ALIGNED; |
|
tcp_store_ts_recent(tp); |
|
} else { |
|
tp->tcp_header_len = sizeof(struct tcphdr); |
|
} |
|
|
|
tcp_sync_mss(sk, icsk->icsk_pmtu_cookie); |
|
tcp_initialize_rcv_mss(sk); |
|
|
|
/* Remember, tcp_poll() does not lock socket! |
|
* Change state from SYN-SENT only after copied_seq |
|
* is initialized. */ |
|
WRITE_ONCE(tp->copied_seq, tp->rcv_nxt); |
|
|
|
smc_check_reset_syn(tp); |
|
|
|
smp_mb(); |
|
|
|
tcp_finish_connect(sk, skb); |
|
|
|
fastopen_fail = (tp->syn_fastopen || tp->syn_data) && |
|
tcp_rcv_fastopen_synack(sk, skb, &foc); |
|
|
|
if (!sock_flag(sk, SOCK_DEAD)) { |
|
sk->sk_state_change(sk); |
|
sk_wake_async(sk, SOCK_WAKE_IO, POLL_OUT); |
|
} |
|
if (fastopen_fail) |
|
return -1; |
|
if (sk->sk_write_pending || |
|
icsk->icsk_accept_queue.rskq_defer_accept || |
|
inet_csk_in_pingpong_mode(sk)) { |
|
/* Save one ACK. Data will be ready after |
|
* several ticks, if write_pending is set. |
|
* |
|
* It may be deleted, but with this feature tcpdumps |
|
* look so _wonderfully_ clever, that I was not able |
|
* to stand against the temptation 8) --ANK |
|
*/ |
|
inet_csk_schedule_ack(sk); |
|
tcp_enter_quickack_mode(sk, TCP_MAX_QUICKACKS); |
|
inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK, |
|
TCP_DELACK_MAX, TCP_RTO_MAX); |
|
|
|
discard: |
|
tcp_drop(sk, skb); |
|
return 0; |
|
} else { |
|
tcp_send_ack(sk); |
|
} |
|
return -1; |
|
} |
|
|
|
/* No ACK in the segment */ |
|
|
|
if (th->rst) { |
|
/* rfc793: |
|
* "If the RST bit is set |
|
* |
|
* Otherwise (no ACK) drop the segment and return." |
|
*/ |
|
|
|
goto discard_and_undo; |
|
} |
|
|
|
/* PAWS check. */ |
|
if (tp->rx_opt.ts_recent_stamp && tp->rx_opt.saw_tstamp && |
|
tcp_paws_reject(&tp->rx_opt, 0)) |
|
goto discard_and_undo; |
|
|
|
if (th->syn) { |
|
/* We see SYN without ACK. It is attempt of |
|
* simultaneous connect with crossed SYNs. |
|
* Particularly, it can be connect to self. |
|
*/ |
|
tcp_set_state(sk, TCP_SYN_RECV); |
|
|
|
if (tp->rx_opt.saw_tstamp) { |
|
tp->rx_opt.tstamp_ok = 1; |
|
tcp_store_ts_recent(tp); |
|
tp->tcp_header_len = |
|
sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED; |
|
} else { |
|
tp->tcp_header_len = sizeof(struct tcphdr); |
|
} |
|
|
|
WRITE_ONCE(tp->rcv_nxt, TCP_SKB_CB(skb)->seq + 1); |
|
WRITE_ONCE(tp->copied_seq, tp->rcv_nxt); |
|
tp->rcv_wup = TCP_SKB_CB(skb)->seq + 1; |
|
|
|
/* RFC1323: The window in SYN & SYN/ACK segments is |
|
* never scaled. |
|
*/ |
|
tp->snd_wnd = ntohs(th->window); |
|
tp->snd_wl1 = TCP_SKB_CB(skb)->seq; |
|
tp->max_window = tp->snd_wnd; |
|
|
|
tcp_ecn_rcv_syn(tp, th); |
|
|
|
tcp_mtup_init(sk); |
|
tcp_sync_mss(sk, icsk->icsk_pmtu_cookie); |
|
tcp_initialize_rcv_mss(sk); |
|
|
|
tcp_send_synack(sk); |
|
#if 0 |
|
/* Note, we could accept data and URG from this segment. |
|
* There are no obstacles to make this (except that we must |
|
* either change tcp_recvmsg() to prevent it from returning data |
|
* before 3WHS completes per RFC793, or employ TCP Fast Open). |
|
* |
|
* However, if we ignore data in ACKless segments sometimes, |
|
* we have no reasons to accept it sometimes. |
|
* Also, seems the code doing it in step6 of tcp_rcv_state_process |
|
* is not flawless. So, discard packet for sanity. |
|
* Uncomment this return to process the data. |
|
*/ |
|
return -1; |
|
#else |
|
goto discard; |
|
#endif |
|
} |
|
/* "fifth, if neither of the SYN or RST bits is set then |
|
* drop the segment and return." |
|
*/ |
|
|
|
discard_and_undo: |
|
tcp_clear_options(&tp->rx_opt); |
|
tp->rx_opt.mss_clamp = saved_clamp; |
|
goto discard; |
|
|
|
reset_and_undo: |
|
tcp_clear_options(&tp->rx_opt); |
|
tp->rx_opt.mss_clamp = saved_clamp; |
|
return 1; |
|
} |
|
|
|
static void tcp_rcv_synrecv_state_fastopen(struct sock *sk) |
|
{ |
|
struct request_sock *req; |
|
|
|
/* If we are still handling the SYNACK RTO, see if timestamp ECR allows |
|
* undo. If peer SACKs triggered fast recovery, we can't undo here. |
|
*/ |
|
if (inet_csk(sk)->icsk_ca_state == TCP_CA_Loss) |
|
tcp_try_undo_loss(sk, false); |
|
|
|
/* Reset rtx states to prevent spurious retransmits_timed_out() */ |
|
tcp_sk(sk)->retrans_stamp = 0; |
|
inet_csk(sk)->icsk_retransmits = 0; |
|
|
|
/* Once we leave TCP_SYN_RECV or TCP_FIN_WAIT_1, |
|
* we no longer need req so release it. |
|
*/ |
|
req = rcu_dereference_protected(tcp_sk(sk)->fastopen_rsk, |
|
lockdep_sock_is_held(sk)); |
|
reqsk_fastopen_remove(sk, req, false); |
|
|
|
/* Re-arm the timer because data may have been sent out. |
|
* This is similar to the regular data transmission case |
|
* when new data has just been ack'ed. |
|
* |
|
* (TFO) - we could try to be more aggressive and |
|
* retransmitting any data sooner based on when they |
|
* are sent out. |
|
*/ |
|
tcp_rearm_rto(sk); |
|
} |
|
|
|
/* |
|
* This function implements the receiving procedure of RFC 793 for |
|
* all states except ESTABLISHED and TIME_WAIT. |
|
* It's called from both tcp_v4_rcv and tcp_v6_rcv and should be |
|
* address independent. |
|
*/ |
|
|
|
int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb) |
|
{ |
|
struct tcp_sock *tp = tcp_sk(sk); |
|
struct inet_connection_sock *icsk = inet_csk(sk); |
|
const struct tcphdr *th = tcp_hdr(skb); |
|
struct request_sock *req; |
|
int queued = 0; |
|
bool acceptable; |
|
|
|
switch (sk->sk_state) { |
|
case TCP_CLOSE: |
|
goto discard; |
|
|
|
case TCP_LISTEN: |
|
if (th->ack) |
|
return 1; |
|
|
|
if (th->rst) |
|
goto discard; |
|
|
|
if (th->syn) { |
|
if (th->fin) |
|
goto discard; |
|
/* It is possible that we process SYN packets from backlog, |
|
* so we need to make sure to disable BH and RCU right there. |
|
*/ |
|
rcu_read_lock(); |
|
local_bh_disable(); |
|
acceptable = icsk->icsk_af_ops->conn_request(sk, skb) >= 0; |
|
local_bh_enable(); |
|
rcu_read_unlock(); |
|
|
|
if (!acceptable) |
|
return 1; |
|
consume_skb(skb); |
|
return 0; |
|
} |
|
goto discard; |
|
|
|
case TCP_SYN_SENT: |
|
tp->rx_opt.saw_tstamp = 0; |
|
tcp_mstamp_refresh(tp); |
|
queued = tcp_rcv_synsent_state_process(sk, skb, th); |
|
if (queued >= 0) |
|
return queued; |
|
|
|
/* Do step6 onward by hand. */ |
|
tcp_urg(sk, skb, th); |
|
__kfree_skb(skb); |
|
tcp_data_snd_check(sk); |
|
return 0; |
|
} |
|
|
|
tcp_mstamp_refresh(tp); |
|
tp->rx_opt.saw_tstamp = 0; |
|
req = rcu_dereference_protected(tp->fastopen_rsk, |
|
lockdep_sock_is_held(sk)); |
|
if (req) { |
|
bool req_stolen; |
|
|
|
WARN_ON_ONCE(sk->sk_state != TCP_SYN_RECV && |
|
sk->sk_state != TCP_FIN_WAIT1); |
|
|
|
if (!tcp_check_req(sk, skb, req, true, &req_stolen)) |
|
goto discard; |
|
} |
|
|
|
if (!th->ack && !th->rst && !th->syn) |
|
goto discard; |
|
|
|
if (!tcp_validate_incoming(sk, skb, th, 0)) |
|
return 0; |
|
|
|
/* step 5: check the ACK field */ |
|
acceptable = tcp_ack(sk, skb, FLAG_SLOWPATH | |
|
FLAG_UPDATE_TS_RECENT | |
|
FLAG_NO_CHALLENGE_ACK) > 0; |
|
|
|
if (!acceptable) { |
|
if (sk->sk_state == TCP_SYN_RECV) |
|
return 1; /* send one RST */ |
|
tcp_send_challenge_ack(sk); |
|
goto discard; |
|
} |
|
switch (sk->sk_state) { |
|
case TCP_SYN_RECV: |
|
tp->delivered++; /* SYN-ACK delivery isn't tracked in tcp_ack */ |
|
if (!tp->srtt_us) |
|
tcp_synack_rtt_meas(sk, req); |
|
|
|
if (req) { |
|
tcp_rcv_synrecv_state_fastopen(sk); |
|
} else { |
|
tcp_try_undo_spurious_syn(sk); |
|
tp->retrans_stamp = 0; |
|
tcp_init_transfer(sk, BPF_SOCK_OPS_PASSIVE_ESTABLISHED_CB, |
|
skb); |
|
WRITE_ONCE(tp->copied_seq, tp->rcv_nxt); |
|
} |
|
smp_mb(); |
|
tcp_set_state(sk, TCP_ESTABLISHED); |
|
sk->sk_state_change(sk); |
|
|
|
/* Note, that this wakeup is only for marginal crossed SYN case. |
|
* Passively open sockets are not waked up, because |
|
* sk->sk_sleep == NULL and sk->sk_socket == NULL. |
|
*/ |
|
if (sk->sk_socket) |
|
sk_wake_async(sk, SOCK_WAKE_IO, POLL_OUT); |
|
|
|
tp->snd_una = TCP_SKB_CB(skb)->ack_seq; |
|
tp->snd_wnd = ntohs(th->window) << tp->rx_opt.snd_wscale; |
|
tcp_init_wl(tp, TCP_SKB_CB(skb)->seq); |
|
|
|
if (tp->rx_opt.tstamp_ok) |
|
tp->advmss -= TCPOLEN_TSTAMP_ALIGNED; |
|
|
|
if (!inet_csk(sk)->icsk_ca_ops->cong_control) |
|
tcp_update_pacing_rate(sk); |
|
|
|
/* Prevent spurious tcp_cwnd_restart() on first data packet */ |
|
tp->lsndtime = tcp_jiffies32; |
|
|
|
tcp_initialize_rcv_mss(sk); |
|
tcp_fast_path_on(tp); |
|
break; |
|
|
|
case TCP_FIN_WAIT1: { |
|
int tmo; |
|
|
|
if (req) |
|
tcp_rcv_synrecv_state_fastopen(sk); |
|
|
|
if (tp->snd_una != tp->write_seq) |
|
break; |
|
|
|
tcp_set_state(sk, TCP_FIN_WAIT2); |
|
sk->sk_shutdown |= SEND_SHUTDOWN; |
|
|
|
sk_dst_confirm(sk); |
|
|
|
if (!sock_flag(sk, SOCK_DEAD)) { |
|
/* Wake up lingering close() */ |
|
sk->sk_state_change(sk); |
|
break; |
|
} |
|
|
|
if (tp->linger2 < 0) { |
|
tcp_done(sk); |
|
NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTONDATA); |
|
return 1; |
|
} |
|
if (TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq && |
|
after(TCP_SKB_CB(skb)->end_seq - th->fin, tp->rcv_nxt)) { |
|
/* Receive out of order FIN after close() */ |
|
if (tp->syn_fastopen && th->fin) |
|
tcp_fastopen_active_disable(sk); |
|
tcp_done(sk); |
|
NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTONDATA); |
|
return 1; |
|
} |
|
|
|
tmo = tcp_fin_time(sk); |
|
if (tmo > TCP_TIMEWAIT_LEN) { |
|
inet_csk_reset_keepalive_timer(sk, tmo - TCP_TIMEWAIT_LEN); |
|
} else if (th->fin || sock_owned_by_user(sk)) { |
|
/* Bad case. We could lose such FIN otherwise. |
|
* It is not a big problem, but it looks confusing |
|
* and not so rare event. We still can lose it now, |
|
* if it spins in bh_lock_sock(), but it is really |
|
* marginal case. |
|
*/ |
|
inet_csk_reset_keepalive_timer(sk, tmo); |
|
} else { |
|
tcp_time_wait(sk, TCP_FIN_WAIT2, tmo); |
|
goto discard; |
|
} |
|
break; |
|
} |
|
|
|
case TCP_CLOSING: |
|
if (tp->snd_una == tp->write_seq) { |
|
tcp_time_wait(sk, TCP_TIME_WAIT, 0); |
|
goto discard; |
|
} |
|
break; |
|
|
|
case TCP_LAST_ACK: |
|
if (tp->snd_una == tp->write_seq) { |
|
tcp_update_metrics(sk); |
|
tcp_done(sk); |
|
goto discard; |
|
} |
|
break; |
|
} |
|
|
|
/* step 6: check the URG bit */ |
|
tcp_urg(sk, skb, th); |
|
|
|
/* step 7: process the segment text */ |
|
switch (sk->sk_state) { |
|
case TCP_CLOSE_WAIT: |
|
case TCP_CLOSING: |
|
case TCP_LAST_ACK: |
|
if (!before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) { |
|
/* If a subflow has been reset, the packet should not |
|
* continue to be processed, drop the packet. |
|
*/ |
|
if (sk_is_mptcp(sk) && !mptcp_incoming_options(sk, skb)) |
|
goto discard; |
|
break; |
|
} |
|
fallthrough; |
|
case TCP_FIN_WAIT1: |
|
case TCP_FIN_WAIT2: |
|
/* RFC 793 says to queue data in these states, |
|
* RFC 1122 says we MUST send a reset. |
|
* BSD 4.4 also does reset. |
|
*/ |
|
if (sk->sk_shutdown & RCV_SHUTDOWN) { |
|
if (TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq && |
|
after(TCP_SKB_CB(skb)->end_seq - th->fin, tp->rcv_nxt)) { |
|
NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTONDATA); |
|
tcp_reset(sk, skb); |
|
return 1; |
|
} |
|
} |
|
fallthrough; |
|
case TCP_ESTABLISHED: |
|
tcp_data_queue(sk, skb); |
|
queued = 1; |
|
break; |
|
} |
|
|
|
/* tcp_data could move socket to TIME-WAIT */ |
|
if (sk->sk_state != TCP_CLOSE) { |
|
tcp_data_snd_check(sk); |
|
tcp_ack_snd_check(sk); |
|
} |
|
|
|
if (!queued) { |
|
discard: |
|
tcp_drop(sk, skb); |
|
} |
|
return 0; |
|
} |
|
EXPORT_SYMBOL(tcp_rcv_state_process); |
|
|
|
static inline void pr_drop_req(struct request_sock *req, __u16 port, int family) |
|
{ |
|
struct inet_request_sock *ireq = inet_rsk(req); |
|
|
|
if (family == AF_INET) |
|
net_dbg_ratelimited("drop open request from %pI4/%u\n", |
|
&ireq->ir_rmt_addr, port); |
|
#if IS_ENABLED(CONFIG_IPV6) |
|
else if (family == AF_INET6) |
|
net_dbg_ratelimited("drop open request from %pI6/%u\n", |
|
&ireq->ir_v6_rmt_addr, port); |
|
#endif |
|
} |
|
|
|
/* RFC3168 : 6.1.1 SYN packets must not have ECT/ECN bits set |
|
* |
|
* If we receive a SYN packet with these bits set, it means a |
|
* network is playing bad games with TOS bits. In order to |
|
* avoid possible false congestion notifications, we disable |
|
* TCP ECN negotiation. |
|
* |
|
* Exception: tcp_ca wants ECN. This is required for DCTCP |
|
* congestion control: Linux DCTCP asserts ECT on all packets, |
|
* including SYN, which is most optimal solution; however, |
|
* others, such as FreeBSD do not. |
|
* |
|
* Exception: At least one of the reserved bits of the TCP header (th->res1) is |
|
* set, indicating the use of a future TCP extension (such as AccECN). See |
|
* RFC8311 §4.3 which updates RFC3168 to allow the development of such |
|
* extensions. |
|
*/ |
|
static void tcp_ecn_create_request(struct request_sock *req, |
|
const struct sk_buff *skb, |
|
const struct sock *listen_sk, |
|
const struct dst_entry *dst) |
|
{ |
|
const struct tcphdr *th = tcp_hdr(skb); |
|
const struct net *net = sock_net(listen_sk); |
|
bool th_ecn = th->ece && th->cwr; |
|
bool ect, ecn_ok; |
|
u32 ecn_ok_dst; |
|
|
|
if (!th_ecn) |
|
return; |
|
|
|
ect = !INET_ECN_is_not_ect(TCP_SKB_CB(skb)->ip_dsfield); |
|
ecn_ok_dst = dst_feature(dst, DST_FEATURE_ECN_MASK); |
|
ecn_ok = net->ipv4.sysctl_tcp_ecn || ecn_ok_dst; |
|
|
|
if (((!ect || th->res1) && ecn_ok) || tcp_ca_needs_ecn(listen_sk) || |
|
(ecn_ok_dst & DST_FEATURE_ECN_CA) || |
|
tcp_bpf_ca_needs_ecn((struct sock *)req)) |
|
inet_rsk(req)->ecn_ok = 1; |
|
} |
|
|
|
static void tcp_openreq_init(struct request_sock *req, |
|
const struct tcp_options_received *rx_opt, |
|
struct sk_buff *skb, const struct sock *sk) |
|
{ |
|
struct inet_request_sock *ireq = inet_rsk(req); |
|
|
|
req->rsk_rcv_wnd = 0; /* So that tcp_send_synack() knows! */ |
|
tcp_rsk(req)->rcv_isn = TCP_SKB_CB(skb)->seq; |
|
tcp_rsk(req)->rcv_nxt = TCP_SKB_CB(skb)->seq + 1; |
|
tcp_rsk(req)->snt_synack = 0; |
|
tcp_rsk(req)->last_oow_ack_time = 0; |
|
req->mss = rx_opt->mss_clamp; |
|
req->ts_recent = rx_opt->saw_tstamp ? rx_opt->rcv_tsval : 0; |
|
ireq->tstamp_ok = rx_opt->tstamp_ok; |
|
ireq->sack_ok = rx_opt->sack_ok; |
|
ireq->snd_wscale = rx_opt->snd_wscale; |
|
ireq->wscale_ok = rx_opt->wscale_ok; |
|
ireq->acked = 0; |
|
ireq->ecn_ok = 0; |
|
ireq->ir_rmt_port = tcp_hdr(skb)->source; |
|
ireq->ir_num = ntohs(tcp_hdr(skb)->dest); |
|
ireq->ir_mark = inet_request_mark(sk, skb); |
|
#if IS_ENABLED(CONFIG_SMC) |
|
ireq->smc_ok = rx_opt->smc_ok; |
|
#endif |
|
} |
|
|
|
struct request_sock *inet_reqsk_alloc(const struct request_sock_ops *ops, |
|
struct sock *sk_listener, |
|
bool attach_listener) |
|
{ |
|
struct request_sock *req = reqsk_alloc(ops, sk_listener, |
|
attach_listener); |
|
|
|
if (req) { |
|
struct inet_request_sock *ireq = inet_rsk(req); |
|
|
|
ireq->ireq_opt = NULL; |
|
#if IS_ENABLED(CONFIG_IPV6) |
|
ireq->pktopts = NULL; |
|
#endif |
|
atomic64_set(&ireq->ir_cookie, 0); |
|
ireq->ireq_state = TCP_NEW_SYN_RECV; |
|
write_pnet(&ireq->ireq_net, sock_net(sk_listener)); |
|
ireq->ireq_family = sk_listener->sk_family; |
|
} |
|
|
|
return req; |
|
} |
|
EXPORT_SYMBOL(inet_reqsk_alloc); |
|
|
|
/* |
|
* Return true if a syncookie should be sent |
|
*/ |
|
static bool tcp_syn_flood_action(const struct sock *sk, const char *proto) |
|
{ |
|
struct request_sock_queue *queue = &inet_csk(sk)->icsk_accept_queue; |
|
const char *msg = "Dropping request"; |
|
bool want_cookie = false; |
|
struct net *net = sock_net(sk); |
|
|
|
#ifdef CONFIG_SYN_COOKIES |
|
if (net->ipv4.sysctl_tcp_syncookies) { |
|
msg = "Sending cookies"; |
|
want_cookie = true; |
|
__NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPREQQFULLDOCOOKIES); |
|
} else |
|
#endif |
|
__NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPREQQFULLDROP); |
|
|
|
if (!queue->synflood_warned && |
|
net->ipv4.sysctl_tcp_syncookies != 2 && |
|
xchg(&queue->synflood_warned, 1) == 0) |
|
net_info_ratelimited("%s: Possible SYN flooding on port %d. %s. Check SNMP counters.\n", |
|
proto, sk->sk_num, msg); |
|
|
|
return want_cookie; |
|
} |
|
|
|
static void tcp_reqsk_record_syn(const struct sock *sk, |
|
struct request_sock *req, |
|
const struct sk_buff *skb) |
|
{ |
|
if (tcp_sk(sk)->save_syn) { |
|
u32 len = skb_network_header_len(skb) + tcp_hdrlen(skb); |
|
struct saved_syn *saved_syn; |
|
u32 mac_hdrlen; |
|
void *base; |
|
|
|
if (tcp_sk(sk)->save_syn == 2) { /* Save full header. */ |
|
base = skb_mac_header(skb); |
|
mac_hdrlen = skb_mac_header_len(skb); |
|
len += mac_hdrlen; |
|
} else { |
|
base = skb_network_header(skb); |
|
mac_hdrlen = 0; |
|
} |
|
|
|
saved_syn = kmalloc(struct_size(saved_syn, data, len), |
|
GFP_ATOMIC); |
|
if (saved_syn) { |
|
saved_syn->mac_hdrlen = mac_hdrlen; |
|
saved_syn->network_hdrlen = skb_network_header_len(skb); |
|
saved_syn->tcp_hdrlen = tcp_hdrlen(skb); |
|
memcpy(saved_syn->data, base, len); |
|
req->saved_syn = saved_syn; |
|
} |
|
} |
|
} |
|
|
|
/* If a SYN cookie is required and supported, returns a clamped MSS value to be |
|
* used for SYN cookie generation. |
|
*/ |
|
u16 tcp_get_syncookie_mss(struct request_sock_ops *rsk_ops, |
|
const struct tcp_request_sock_ops *af_ops, |
|
struct sock *sk, struct tcphdr *th) |
|
{ |
|
struct tcp_sock *tp = tcp_sk(sk); |
|
u16 mss; |
|
|
|
if (sock_net(sk)->ipv4.sysctl_tcp_syncookies != 2 && |
|
!inet_csk_reqsk_queue_is_full(sk)) |
|
return 0; |
|
|
|
if (!tcp_syn_flood_action(sk, rsk_ops->slab_name)) |
|
return 0; |
|
|
|
if (sk_acceptq_is_full(sk)) { |
|
NET_INC_STATS(sock_net(sk), LINUX_MIB_LISTENOVERFLOWS); |
|
return 0; |
|
} |
|
|
|
mss = tcp_parse_mss_option(th, tp->rx_opt.user_mss); |
|
if (!mss) |
|
mss = af_ops->mss_clamp; |
|
|
|
return mss; |
|
} |
|
EXPORT_SYMBOL_GPL(tcp_get_syncookie_mss); |
|
|
|
int tcp_conn_request(struct request_sock_ops *rsk_ops, |
|
const struct tcp_request_sock_ops *af_ops, |
|
struct sock *sk, struct sk_buff *skb) |
|
{ |
|
struct tcp_fastopen_cookie foc = { .len = -1 }; |
|
__u32 isn = TCP_SKB_CB(skb)->tcp_tw_isn; |
|
struct tcp_options_received tmp_opt; |
|
struct tcp_sock *tp = tcp_sk(sk); |
|
struct net *net = sock_net(sk); |
|
struct sock *fastopen_sk = NULL; |
|
struct request_sock *req; |
|
bool want_cookie = false; |
|
struct dst_entry *dst; |
|
struct flowi fl; |
|
|
|
/* TW buckets are converted to open requests without |
|
* limitations, they conserve resources and peer is |
|
* evidently real one. |
|
*/ |
|
if ((net->ipv4.sysctl_tcp_syncookies == 2 || |
|
inet_csk_reqsk_queue_is_full(sk)) && !isn) { |
|
want_cookie = tcp_syn_flood_action(sk, rsk_ops->slab_name); |
|
if (!want_cookie) |
|
goto drop; |
|
} |
|
|
|
if (sk_acceptq_is_full(sk)) { |
|
NET_INC_STATS(sock_net(sk), LINUX_MIB_LISTENOVERFLOWS); |
|
goto drop; |
|
} |
|
|
|
req = inet_reqsk_alloc(rsk_ops, sk, !want_cookie); |
|
if (!req) |
|
goto drop; |
|
|
|
req->syncookie = want_cookie; |
|
tcp_rsk(req)->af_specific = af_ops; |
|
tcp_rsk(req)->ts_off = 0; |
|
#if IS_ENABLED(CONFIG_MPTCP) |
|
tcp_rsk(req)->is_mptcp = 0; |
|
#endif |
|
|
|
tcp_clear_options(&tmp_opt); |
|
tmp_opt.mss_clamp = af_ops->mss_clamp; |
|
tmp_opt.user_mss = tp->rx_opt.user_mss; |
|
tcp_parse_options(sock_net(sk), skb, &tmp_opt, 0, |
|
want_cookie ? NULL : &foc); |
|
|
|
if (want_cookie && !tmp_opt.saw_tstamp) |
|
tcp_clear_options(&tmp_opt); |
|
|
|
if (IS_ENABLED(CONFIG_SMC) && want_cookie) |
|
tmp_opt.smc_ok = 0; |
|
|
|
tmp_opt.tstamp_ok = tmp_opt.saw_tstamp; |
|
tcp_openreq_init(req, &tmp_opt, skb, sk); |
|
inet_rsk(req)->no_srccheck = inet_sk(sk)->transparent; |
|
|
|
/* Note: tcp_v6_init_req() might override ir_iif for link locals */ |
|
inet_rsk(req)->ir_iif = inet_request_bound_dev_if(sk, skb); |
|
|
|
dst = af_ops->route_req(sk, skb, &fl, req); |
|
if (!dst) |
|
goto drop_and_free; |
|
|
|
if (tmp_opt.tstamp_ok) |
|
tcp_rsk(req)->ts_off = af_ops->init_ts_off(net, skb); |
|
|
|
if (!want_cookie && !isn) { |
|
/* Kill the following clause, if you dislike this way. */ |
|
if (!net->ipv4.sysctl_tcp_syncookies && |
|
(net->ipv4.sysctl_max_syn_backlog - inet_csk_reqsk_queue_len(sk) < |
|
(net->ipv4.sysctl_max_syn_backlog >> 2)) && |
|
!tcp_peer_is_proven(req, dst)) { |
|
/* Without syncookies last quarter of |
|
* backlog is filled with destinations, |
|
* proven to be alive. |
|
* It means that we continue to communicate |
|
* to destinations, already remembered |
|
* to the moment of synflood. |
|
*/ |
|
pr_drop_req(req, ntohs(tcp_hdr(skb)->source), |
|
rsk_ops->family); |
|
goto drop_and_release; |
|
} |
|
|
|
isn = af_ops->init_seq(skb); |
|
} |
|
|
|
tcp_ecn_create_request(req, skb, sk, dst); |
|
|
|
if (want_cookie) { |
|
isn = cookie_init_sequence(af_ops, sk, skb, &req->mss); |
|
if (!tmp_opt.tstamp_ok) |
|
inet_rsk(req)->ecn_ok = 0; |
|
} |
|
|
|
tcp_rsk(req)->snt_isn = isn; |
|
tcp_rsk(req)->txhash = net_tx_rndhash(); |
|
tcp_rsk(req)->syn_tos = TCP_SKB_CB(skb)->ip_dsfield; |
|
tcp_openreq_init_rwin(req, sk, dst); |
|
sk_rx_queue_set(req_to_sk(req), skb); |
|
if (!want_cookie) { |
|
tcp_reqsk_record_syn(sk, req, skb); |
|
fastopen_sk = tcp_try_fastopen(sk, skb, req, &foc, dst); |
|
} |
|
if (fastopen_sk) { |
|
af_ops->send_synack(fastopen_sk, dst, &fl, req, |
|
&foc, TCP_SYNACK_FASTOPEN, skb); |
|
/* Add the child socket directly into the accept queue */ |
|
if (!inet_csk_reqsk_queue_add(sk, req, fastopen_sk)) { |
|
reqsk_fastopen_remove(fastopen_sk, req, false); |
|
bh_unlock_sock(fastopen_sk); |
|
sock_put(fastopen_sk); |
|
goto drop_and_free; |
|
} |
|
sk->sk_data_ready(sk); |
|
bh_unlock_sock(fastopen_sk); |
|
sock_put(fastopen_sk); |
|
} else { |
|
tcp_rsk(req)->tfo_listener = false; |
|
if (!want_cookie) |
|
inet_csk_reqsk_queue_hash_add(sk, req, |
|
tcp_timeout_init((struct sock *)req)); |
|
af_ops->send_synack(sk, dst, &fl, req, &foc, |
|
!want_cookie ? TCP_SYNACK_NORMAL : |
|
TCP_SYNACK_COOKIE, |
|
skb); |
|
if (want_cookie) { |
|
reqsk_free(req); |
|
return 0; |
|
} |
|
} |
|
reqsk_put(req); |
|
return 0; |
|
|
|
drop_and_release: |
|
dst_release(dst); |
|
drop_and_free: |
|
__reqsk_free(req); |
|
drop: |
|
tcp_listendrop(sk); |
|
return 0; |
|
} |
|
EXPORT_SYMBOL(tcp_conn_request);
|
|
|