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658 lines
15 KiB
658 lines
15 KiB
// SPDX-License-Identifier: GPL-2.0-only |
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/* Copyright (c) 2016 Thomas Graf <[email protected]> |
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*/ |
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#include <linux/kernel.h> |
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#include <linux/module.h> |
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#include <linux/skbuff.h> |
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#include <linux/types.h> |
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#include <linux/bpf.h> |
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#include <net/lwtunnel.h> |
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#include <net/gre.h> |
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#include <net/ip6_route.h> |
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#include <net/ipv6_stubs.h> |
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struct bpf_lwt_prog { |
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struct bpf_prog *prog; |
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char *name; |
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}; |
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struct bpf_lwt { |
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struct bpf_lwt_prog in; |
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struct bpf_lwt_prog out; |
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struct bpf_lwt_prog xmit; |
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int family; |
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}; |
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#define MAX_PROG_NAME 256 |
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static inline struct bpf_lwt *bpf_lwt_lwtunnel(struct lwtunnel_state *lwt) |
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{ |
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return (struct bpf_lwt *)lwt->data; |
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} |
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#define NO_REDIRECT false |
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#define CAN_REDIRECT true |
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static int run_lwt_bpf(struct sk_buff *skb, struct bpf_lwt_prog *lwt, |
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struct dst_entry *dst, bool can_redirect) |
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{ |
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int ret; |
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|
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/* Migration disable and BH disable are needed to protect per-cpu |
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* redirect_info between BPF prog and skb_do_redirect(). |
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*/ |
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migrate_disable(); |
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local_bh_disable(); |
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bpf_compute_data_pointers(skb); |
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ret = bpf_prog_run_save_cb(lwt->prog, skb); |
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switch (ret) { |
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case BPF_OK: |
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case BPF_LWT_REROUTE: |
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break; |
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case BPF_REDIRECT: |
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if (unlikely(!can_redirect)) { |
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pr_warn_once("Illegal redirect return code in prog %s\n", |
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lwt->name ? : "<unknown>"); |
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ret = BPF_OK; |
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} else { |
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skb_reset_mac_header(skb); |
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ret = skb_do_redirect(skb); |
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if (ret == 0) |
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ret = BPF_REDIRECT; |
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} |
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break; |
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case BPF_DROP: |
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kfree_skb(skb); |
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ret = -EPERM; |
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break; |
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default: |
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pr_warn_once("bpf-lwt: Illegal return value %u, expect packet loss\n", ret); |
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kfree_skb(skb); |
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ret = -EINVAL; |
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break; |
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} |
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local_bh_enable(); |
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migrate_enable(); |
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return ret; |
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} |
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static int bpf_lwt_input_reroute(struct sk_buff *skb) |
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{ |
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int err = -EINVAL; |
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if (skb->protocol == htons(ETH_P_IP)) { |
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struct net_device *dev = skb_dst(skb)->dev; |
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struct iphdr *iph = ip_hdr(skb); |
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dev_hold(dev); |
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skb_dst_drop(skb); |
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err = ip_route_input_noref(skb, iph->daddr, iph->saddr, |
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iph->tos, dev); |
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dev_put(dev); |
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} else if (skb->protocol == htons(ETH_P_IPV6)) { |
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skb_dst_drop(skb); |
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err = ipv6_stub->ipv6_route_input(skb); |
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} else { |
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err = -EAFNOSUPPORT; |
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} |
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if (err) |
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goto err; |
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return dst_input(skb); |
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err: |
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kfree_skb(skb); |
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return err; |
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} |
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static int bpf_input(struct sk_buff *skb) |
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{ |
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struct dst_entry *dst = skb_dst(skb); |
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struct bpf_lwt *bpf; |
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int ret; |
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bpf = bpf_lwt_lwtunnel(dst->lwtstate); |
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if (bpf->in.prog) { |
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ret = run_lwt_bpf(skb, &bpf->in, dst, NO_REDIRECT); |
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if (ret < 0) |
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return ret; |
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if (ret == BPF_LWT_REROUTE) |
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return bpf_lwt_input_reroute(skb); |
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} |
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if (unlikely(!dst->lwtstate->orig_input)) { |
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kfree_skb(skb); |
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return -EINVAL; |
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} |
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return dst->lwtstate->orig_input(skb); |
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} |
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static int bpf_output(struct net *net, struct sock *sk, struct sk_buff *skb) |
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{ |
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struct dst_entry *dst = skb_dst(skb); |
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struct bpf_lwt *bpf; |
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int ret; |
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bpf = bpf_lwt_lwtunnel(dst->lwtstate); |
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if (bpf->out.prog) { |
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ret = run_lwt_bpf(skb, &bpf->out, dst, NO_REDIRECT); |
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if (ret < 0) |
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return ret; |
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} |
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if (unlikely(!dst->lwtstate->orig_output)) { |
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pr_warn_once("orig_output not set on dst for prog %s\n", |
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bpf->out.name); |
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kfree_skb(skb); |
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return -EINVAL; |
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} |
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return dst->lwtstate->orig_output(net, sk, skb); |
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} |
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static int xmit_check_hhlen(struct sk_buff *skb) |
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{ |
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int hh_len = skb_dst(skb)->dev->hard_header_len; |
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if (skb_headroom(skb) < hh_len) { |
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int nhead = HH_DATA_ALIGN(hh_len - skb_headroom(skb)); |
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if (pskb_expand_head(skb, nhead, 0, GFP_ATOMIC)) |
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return -ENOMEM; |
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} |
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return 0; |
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} |
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static int bpf_lwt_xmit_reroute(struct sk_buff *skb) |
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{ |
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struct net_device *l3mdev = l3mdev_master_dev_rcu(skb_dst(skb)->dev); |
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int oif = l3mdev ? l3mdev->ifindex : 0; |
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struct dst_entry *dst = NULL; |
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int err = -EAFNOSUPPORT; |
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struct sock *sk; |
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struct net *net; |
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bool ipv4; |
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if (skb->protocol == htons(ETH_P_IP)) |
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ipv4 = true; |
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else if (skb->protocol == htons(ETH_P_IPV6)) |
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ipv4 = false; |
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else |
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goto err; |
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sk = sk_to_full_sk(skb->sk); |
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if (sk) { |
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if (sk->sk_bound_dev_if) |
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oif = sk->sk_bound_dev_if; |
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net = sock_net(sk); |
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} else { |
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net = dev_net(skb_dst(skb)->dev); |
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} |
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if (ipv4) { |
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struct iphdr *iph = ip_hdr(skb); |
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struct flowi4 fl4 = {}; |
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struct rtable *rt; |
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fl4.flowi4_oif = oif; |
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fl4.flowi4_mark = skb->mark; |
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fl4.flowi4_uid = sock_net_uid(net, sk); |
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fl4.flowi4_tos = RT_TOS(iph->tos); |
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fl4.flowi4_flags = FLOWI_FLAG_ANYSRC; |
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fl4.flowi4_proto = iph->protocol; |
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fl4.daddr = iph->daddr; |
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fl4.saddr = iph->saddr; |
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rt = ip_route_output_key(net, &fl4); |
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if (IS_ERR(rt)) { |
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err = PTR_ERR(rt); |
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goto err; |
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} |
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dst = &rt->dst; |
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} else { |
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struct ipv6hdr *iph6 = ipv6_hdr(skb); |
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struct flowi6 fl6 = {}; |
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fl6.flowi6_oif = oif; |
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fl6.flowi6_mark = skb->mark; |
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fl6.flowi6_uid = sock_net_uid(net, sk); |
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fl6.flowlabel = ip6_flowinfo(iph6); |
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fl6.flowi6_proto = iph6->nexthdr; |
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fl6.daddr = iph6->daddr; |
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fl6.saddr = iph6->saddr; |
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dst = ipv6_stub->ipv6_dst_lookup_flow(net, skb->sk, &fl6, NULL); |
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if (IS_ERR(dst)) { |
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err = PTR_ERR(dst); |
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goto err; |
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} |
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} |
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if (unlikely(dst->error)) { |
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err = dst->error; |
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dst_release(dst); |
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goto err; |
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} |
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/* Although skb header was reserved in bpf_lwt_push_ip_encap(), it |
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* was done for the previous dst, so we are doing it here again, in |
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* case the new dst needs much more space. The call below is a noop |
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* if there is enough header space in skb. |
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*/ |
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err = skb_cow_head(skb, LL_RESERVED_SPACE(dst->dev)); |
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if (unlikely(err)) |
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goto err; |
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skb_dst_drop(skb); |
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skb_dst_set(skb, dst); |
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err = dst_output(dev_net(skb_dst(skb)->dev), skb->sk, skb); |
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if (unlikely(err)) |
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return err; |
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/* ip[6]_finish_output2 understand LWTUNNEL_XMIT_DONE */ |
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return LWTUNNEL_XMIT_DONE; |
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err: |
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kfree_skb(skb); |
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return err; |
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} |
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static int bpf_xmit(struct sk_buff *skb) |
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{ |
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struct dst_entry *dst = skb_dst(skb); |
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struct bpf_lwt *bpf; |
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bpf = bpf_lwt_lwtunnel(dst->lwtstate); |
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if (bpf->xmit.prog) { |
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__be16 proto = skb->protocol; |
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int ret; |
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ret = run_lwt_bpf(skb, &bpf->xmit, dst, CAN_REDIRECT); |
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switch (ret) { |
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case BPF_OK: |
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/* If the header changed, e.g. via bpf_lwt_push_encap, |
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* BPF_LWT_REROUTE below should have been used if the |
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* protocol was also changed. |
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*/ |
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if (skb->protocol != proto) { |
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kfree_skb(skb); |
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return -EINVAL; |
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} |
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/* If the header was expanded, headroom might be too |
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* small for L2 header to come, expand as needed. |
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*/ |
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ret = xmit_check_hhlen(skb); |
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if (unlikely(ret)) |
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return ret; |
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return LWTUNNEL_XMIT_CONTINUE; |
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case BPF_REDIRECT: |
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return LWTUNNEL_XMIT_DONE; |
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case BPF_LWT_REROUTE: |
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return bpf_lwt_xmit_reroute(skb); |
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default: |
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return ret; |
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} |
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} |
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return LWTUNNEL_XMIT_CONTINUE; |
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} |
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static void bpf_lwt_prog_destroy(struct bpf_lwt_prog *prog) |
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{ |
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if (prog->prog) |
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bpf_prog_put(prog->prog); |
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kfree(prog->name); |
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} |
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static void bpf_destroy_state(struct lwtunnel_state *lwt) |
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{ |
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struct bpf_lwt *bpf = bpf_lwt_lwtunnel(lwt); |
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bpf_lwt_prog_destroy(&bpf->in); |
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bpf_lwt_prog_destroy(&bpf->out); |
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bpf_lwt_prog_destroy(&bpf->xmit); |
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} |
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static const struct nla_policy bpf_prog_policy[LWT_BPF_PROG_MAX + 1] = { |
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[LWT_BPF_PROG_FD] = { .type = NLA_U32, }, |
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[LWT_BPF_PROG_NAME] = { .type = NLA_NUL_STRING, |
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.len = MAX_PROG_NAME }, |
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}; |
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static int bpf_parse_prog(struct nlattr *attr, struct bpf_lwt_prog *prog, |
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enum bpf_prog_type type) |
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{ |
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struct nlattr *tb[LWT_BPF_PROG_MAX + 1]; |
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struct bpf_prog *p; |
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int ret; |
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u32 fd; |
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ret = nla_parse_nested_deprecated(tb, LWT_BPF_PROG_MAX, attr, |
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bpf_prog_policy, NULL); |
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if (ret < 0) |
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return ret; |
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if (!tb[LWT_BPF_PROG_FD] || !tb[LWT_BPF_PROG_NAME]) |
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return -EINVAL; |
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prog->name = nla_memdup(tb[LWT_BPF_PROG_NAME], GFP_ATOMIC); |
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if (!prog->name) |
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return -ENOMEM; |
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fd = nla_get_u32(tb[LWT_BPF_PROG_FD]); |
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p = bpf_prog_get_type(fd, type); |
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if (IS_ERR(p)) |
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return PTR_ERR(p); |
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prog->prog = p; |
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return 0; |
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} |
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static const struct nla_policy bpf_nl_policy[LWT_BPF_MAX + 1] = { |
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[LWT_BPF_IN] = { .type = NLA_NESTED, }, |
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[LWT_BPF_OUT] = { .type = NLA_NESTED, }, |
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[LWT_BPF_XMIT] = { .type = NLA_NESTED, }, |
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[LWT_BPF_XMIT_HEADROOM] = { .type = NLA_U32 }, |
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}; |
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static int bpf_build_state(struct net *net, struct nlattr *nla, |
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unsigned int family, const void *cfg, |
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struct lwtunnel_state **ts, |
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struct netlink_ext_ack *extack) |
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{ |
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struct nlattr *tb[LWT_BPF_MAX + 1]; |
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struct lwtunnel_state *newts; |
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struct bpf_lwt *bpf; |
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int ret; |
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if (family != AF_INET && family != AF_INET6) |
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return -EAFNOSUPPORT; |
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ret = nla_parse_nested_deprecated(tb, LWT_BPF_MAX, nla, bpf_nl_policy, |
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extack); |
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if (ret < 0) |
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return ret; |
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if (!tb[LWT_BPF_IN] && !tb[LWT_BPF_OUT] && !tb[LWT_BPF_XMIT]) |
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return -EINVAL; |
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newts = lwtunnel_state_alloc(sizeof(*bpf)); |
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if (!newts) |
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return -ENOMEM; |
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newts->type = LWTUNNEL_ENCAP_BPF; |
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bpf = bpf_lwt_lwtunnel(newts); |
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if (tb[LWT_BPF_IN]) { |
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newts->flags |= LWTUNNEL_STATE_INPUT_REDIRECT; |
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ret = bpf_parse_prog(tb[LWT_BPF_IN], &bpf->in, |
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BPF_PROG_TYPE_LWT_IN); |
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if (ret < 0) |
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goto errout; |
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} |
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if (tb[LWT_BPF_OUT]) { |
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newts->flags |= LWTUNNEL_STATE_OUTPUT_REDIRECT; |
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ret = bpf_parse_prog(tb[LWT_BPF_OUT], &bpf->out, |
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BPF_PROG_TYPE_LWT_OUT); |
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if (ret < 0) |
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goto errout; |
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} |
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if (tb[LWT_BPF_XMIT]) { |
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newts->flags |= LWTUNNEL_STATE_XMIT_REDIRECT; |
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ret = bpf_parse_prog(tb[LWT_BPF_XMIT], &bpf->xmit, |
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BPF_PROG_TYPE_LWT_XMIT); |
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if (ret < 0) |
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goto errout; |
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} |
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if (tb[LWT_BPF_XMIT_HEADROOM]) { |
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u32 headroom = nla_get_u32(tb[LWT_BPF_XMIT_HEADROOM]); |
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if (headroom > LWT_BPF_MAX_HEADROOM) { |
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ret = -ERANGE; |
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goto errout; |
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} |
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newts->headroom = headroom; |
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} |
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bpf->family = family; |
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*ts = newts; |
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return 0; |
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errout: |
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bpf_destroy_state(newts); |
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kfree(newts); |
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return ret; |
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} |
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static int bpf_fill_lwt_prog(struct sk_buff *skb, int attr, |
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struct bpf_lwt_prog *prog) |
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{ |
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struct nlattr *nest; |
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if (!prog->prog) |
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return 0; |
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nest = nla_nest_start_noflag(skb, attr); |
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if (!nest) |
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return -EMSGSIZE; |
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if (prog->name && |
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nla_put_string(skb, LWT_BPF_PROG_NAME, prog->name)) |
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return -EMSGSIZE; |
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return nla_nest_end(skb, nest); |
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} |
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static int bpf_fill_encap_info(struct sk_buff *skb, struct lwtunnel_state *lwt) |
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{ |
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struct bpf_lwt *bpf = bpf_lwt_lwtunnel(lwt); |
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if (bpf_fill_lwt_prog(skb, LWT_BPF_IN, &bpf->in) < 0 || |
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bpf_fill_lwt_prog(skb, LWT_BPF_OUT, &bpf->out) < 0 || |
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bpf_fill_lwt_prog(skb, LWT_BPF_XMIT, &bpf->xmit) < 0) |
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return -EMSGSIZE; |
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return 0; |
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} |
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static int bpf_encap_nlsize(struct lwtunnel_state *lwtstate) |
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{ |
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int nest_len = nla_total_size(sizeof(struct nlattr)) + |
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nla_total_size(MAX_PROG_NAME) + /* LWT_BPF_PROG_NAME */ |
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0; |
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return nest_len + /* LWT_BPF_IN */ |
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nest_len + /* LWT_BPF_OUT */ |
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nest_len + /* LWT_BPF_XMIT */ |
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0; |
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} |
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static int bpf_lwt_prog_cmp(struct bpf_lwt_prog *a, struct bpf_lwt_prog *b) |
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{ |
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/* FIXME: |
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* The LWT state is currently rebuilt for delete requests which |
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* results in a new bpf_prog instance. Comparing names for now. |
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*/ |
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if (!a->name && !b->name) |
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return 0; |
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if (!a->name || !b->name) |
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return 1; |
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return strcmp(a->name, b->name); |
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} |
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static int bpf_encap_cmp(struct lwtunnel_state *a, struct lwtunnel_state *b) |
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{ |
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struct bpf_lwt *a_bpf = bpf_lwt_lwtunnel(a); |
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struct bpf_lwt *b_bpf = bpf_lwt_lwtunnel(b); |
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return bpf_lwt_prog_cmp(&a_bpf->in, &b_bpf->in) || |
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bpf_lwt_prog_cmp(&a_bpf->out, &b_bpf->out) || |
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bpf_lwt_prog_cmp(&a_bpf->xmit, &b_bpf->xmit); |
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} |
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static const struct lwtunnel_encap_ops bpf_encap_ops = { |
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.build_state = bpf_build_state, |
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.destroy_state = bpf_destroy_state, |
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.input = bpf_input, |
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.output = bpf_output, |
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.xmit = bpf_xmit, |
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.fill_encap = bpf_fill_encap_info, |
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.get_encap_size = bpf_encap_nlsize, |
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.cmp_encap = bpf_encap_cmp, |
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.owner = THIS_MODULE, |
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}; |
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static int handle_gso_type(struct sk_buff *skb, unsigned int gso_type, |
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int encap_len) |
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{ |
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struct skb_shared_info *shinfo = skb_shinfo(skb); |
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gso_type |= SKB_GSO_DODGY; |
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shinfo->gso_type |= gso_type; |
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skb_decrease_gso_size(shinfo, encap_len); |
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shinfo->gso_segs = 0; |
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return 0; |
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} |
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static int handle_gso_encap(struct sk_buff *skb, bool ipv4, int encap_len) |
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{ |
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int next_hdr_offset; |
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void *next_hdr; |
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__u8 protocol; |
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/* SCTP and UDP_L4 gso need more nuanced handling than what |
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* handle_gso_type() does above: skb_decrease_gso_size() is not enough. |
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* So at the moment only TCP GSO packets are let through. |
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*/ |
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if (!(skb_shinfo(skb)->gso_type & (SKB_GSO_TCPV4 | SKB_GSO_TCPV6))) |
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return -ENOTSUPP; |
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if (ipv4) { |
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protocol = ip_hdr(skb)->protocol; |
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next_hdr_offset = sizeof(struct iphdr); |
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next_hdr = skb_network_header(skb) + next_hdr_offset; |
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} else { |
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protocol = ipv6_hdr(skb)->nexthdr; |
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next_hdr_offset = sizeof(struct ipv6hdr); |
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next_hdr = skb_network_header(skb) + next_hdr_offset; |
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} |
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|
|
switch (protocol) { |
|
case IPPROTO_GRE: |
|
next_hdr_offset += sizeof(struct gre_base_hdr); |
|
if (next_hdr_offset > encap_len) |
|
return -EINVAL; |
|
|
|
if (((struct gre_base_hdr *)next_hdr)->flags & GRE_CSUM) |
|
return handle_gso_type(skb, SKB_GSO_GRE_CSUM, |
|
encap_len); |
|
return handle_gso_type(skb, SKB_GSO_GRE, encap_len); |
|
|
|
case IPPROTO_UDP: |
|
next_hdr_offset += sizeof(struct udphdr); |
|
if (next_hdr_offset > encap_len) |
|
return -EINVAL; |
|
|
|
if (((struct udphdr *)next_hdr)->check) |
|
return handle_gso_type(skb, SKB_GSO_UDP_TUNNEL_CSUM, |
|
encap_len); |
|
return handle_gso_type(skb, SKB_GSO_UDP_TUNNEL, encap_len); |
|
|
|
case IPPROTO_IP: |
|
case IPPROTO_IPV6: |
|
if (ipv4) |
|
return handle_gso_type(skb, SKB_GSO_IPXIP4, encap_len); |
|
else |
|
return handle_gso_type(skb, SKB_GSO_IPXIP6, encap_len); |
|
|
|
default: |
|
return -EPROTONOSUPPORT; |
|
} |
|
} |
|
|
|
int bpf_lwt_push_ip_encap(struct sk_buff *skb, void *hdr, u32 len, bool ingress) |
|
{ |
|
struct iphdr *iph; |
|
bool ipv4; |
|
int err; |
|
|
|
if (unlikely(len < sizeof(struct iphdr) || len > LWT_BPF_MAX_HEADROOM)) |
|
return -EINVAL; |
|
|
|
/* validate protocol and length */ |
|
iph = (struct iphdr *)hdr; |
|
if (iph->version == 4) { |
|
ipv4 = true; |
|
if (unlikely(len < iph->ihl * 4)) |
|
return -EINVAL; |
|
} else if (iph->version == 6) { |
|
ipv4 = false; |
|
if (unlikely(len < sizeof(struct ipv6hdr))) |
|
return -EINVAL; |
|
} else { |
|
return -EINVAL; |
|
} |
|
|
|
if (ingress) |
|
err = skb_cow_head(skb, len + skb->mac_len); |
|
else |
|
err = skb_cow_head(skb, |
|
len + LL_RESERVED_SPACE(skb_dst(skb)->dev)); |
|
if (unlikely(err)) |
|
return err; |
|
|
|
/* push the encap headers and fix pointers */ |
|
skb_reset_inner_headers(skb); |
|
skb_reset_inner_mac_header(skb); /* mac header is not yet set */ |
|
skb_set_inner_protocol(skb, skb->protocol); |
|
skb->encapsulation = 1; |
|
skb_push(skb, len); |
|
if (ingress) |
|
skb_postpush_rcsum(skb, iph, len); |
|
skb_reset_network_header(skb); |
|
memcpy(skb_network_header(skb), hdr, len); |
|
bpf_compute_data_pointers(skb); |
|
skb_clear_hash(skb); |
|
|
|
if (ipv4) { |
|
skb->protocol = htons(ETH_P_IP); |
|
iph = ip_hdr(skb); |
|
|
|
if (!iph->check) |
|
iph->check = ip_fast_csum((unsigned char *)iph, |
|
iph->ihl); |
|
} else { |
|
skb->protocol = htons(ETH_P_IPV6); |
|
} |
|
|
|
if (skb_is_gso(skb)) |
|
return handle_gso_encap(skb, ipv4, len); |
|
|
|
return 0; |
|
} |
|
|
|
static int __init bpf_lwt_init(void) |
|
{ |
|
return lwtunnel_encap_add_ops(&bpf_encap_ops, LWTUNNEL_ENCAP_BPF); |
|
} |
|
|
|
subsys_initcall(bpf_lwt_init)
|
|
|