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158 lines
4.5 KiB
158 lines
4.5 KiB
// SPDX-License-Identifier: GPL-2.0 |
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/* Copyright (c) 2017-18 David Ahern <[email protected]> |
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* |
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* This program is free software; you can redistribute it and/or |
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* modify it under the terms of version 2 of the GNU General Public |
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* License as published by the Free Software Foundation. |
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* |
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* This program is distributed in the hope that it will be useful, but |
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* WITHOUT ANY WARRANTY; without even the implied warranty of |
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
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* General Public License for more details. |
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*/ |
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#define KBUILD_MODNAME "foo" |
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#include <uapi/linux/bpf.h> |
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#include <linux/in.h> |
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#include <linux/if_ether.h> |
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#include <linux/if_packet.h> |
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#include <linux/if_vlan.h> |
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#include <linux/ip.h> |
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#include <linux/ipv6.h> |
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#include <bpf/bpf_helpers.h> |
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#define IPV6_FLOWINFO_MASK cpu_to_be32(0x0FFFFFFF) |
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struct { |
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__uint(type, BPF_MAP_TYPE_DEVMAP); |
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__uint(key_size, sizeof(int)); |
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__uint(value_size, sizeof(int)); |
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__uint(max_entries, 64); |
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} xdp_tx_ports SEC(".maps"); |
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/* from include/net/ip.h */ |
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static __always_inline int ip_decrease_ttl(struct iphdr *iph) |
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{ |
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u32 check = (__force u32)iph->check; |
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check += (__force u32)htons(0x0100); |
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iph->check = (__force __sum16)(check + (check >= 0xFFFF)); |
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return --iph->ttl; |
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} |
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static __always_inline int xdp_fwd_flags(struct xdp_md *ctx, u32 flags) |
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{ |
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void *data_end = (void *)(long)ctx->data_end; |
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void *data = (void *)(long)ctx->data; |
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struct bpf_fib_lookup fib_params; |
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struct ethhdr *eth = data; |
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struct ipv6hdr *ip6h; |
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struct iphdr *iph; |
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u16 h_proto; |
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u64 nh_off; |
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int rc; |
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nh_off = sizeof(*eth); |
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if (data + nh_off > data_end) |
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return XDP_DROP; |
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__builtin_memset(&fib_params, 0, sizeof(fib_params)); |
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h_proto = eth->h_proto; |
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if (h_proto == htons(ETH_P_IP)) { |
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iph = data + nh_off; |
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if (iph + 1 > data_end) |
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return XDP_DROP; |
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if (iph->ttl <= 1) |
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return XDP_PASS; |
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fib_params.family = AF_INET; |
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fib_params.tos = iph->tos; |
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fib_params.l4_protocol = iph->protocol; |
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fib_params.sport = 0; |
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fib_params.dport = 0; |
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fib_params.tot_len = ntohs(iph->tot_len); |
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fib_params.ipv4_src = iph->saddr; |
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fib_params.ipv4_dst = iph->daddr; |
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} else if (h_proto == htons(ETH_P_IPV6)) { |
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struct in6_addr *src = (struct in6_addr *) fib_params.ipv6_src; |
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struct in6_addr *dst = (struct in6_addr *) fib_params.ipv6_dst; |
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ip6h = data + nh_off; |
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if (ip6h + 1 > data_end) |
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return XDP_DROP; |
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if (ip6h->hop_limit <= 1) |
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return XDP_PASS; |
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fib_params.family = AF_INET6; |
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fib_params.flowinfo = *(__be32 *)ip6h & IPV6_FLOWINFO_MASK; |
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fib_params.l4_protocol = ip6h->nexthdr; |
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fib_params.sport = 0; |
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fib_params.dport = 0; |
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fib_params.tot_len = ntohs(ip6h->payload_len); |
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*src = ip6h->saddr; |
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*dst = ip6h->daddr; |
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} else { |
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return XDP_PASS; |
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} |
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fib_params.ifindex = ctx->ingress_ifindex; |
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rc = bpf_fib_lookup(ctx, &fib_params, sizeof(fib_params), flags); |
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/* |
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* Some rc (return codes) from bpf_fib_lookup() are important, |
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* to understand how this XDP-prog interacts with network stack. |
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* |
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* BPF_FIB_LKUP_RET_NO_NEIGH: |
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* Even if route lookup was a success, then the MAC-addresses are also |
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* needed. This is obtained from arp/neighbour table, but if table is |
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* (still) empty then BPF_FIB_LKUP_RET_NO_NEIGH is returned. To avoid |
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* doing ARP lookup directly from XDP, then send packet to normal |
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* network stack via XDP_PASS and expect it will do ARP resolution. |
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* |
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* BPF_FIB_LKUP_RET_FWD_DISABLED: |
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* The bpf_fib_lookup respect sysctl net.ipv{4,6}.conf.all.forwarding |
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* setting, and will return BPF_FIB_LKUP_RET_FWD_DISABLED if not |
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* enabled this on ingress device. |
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*/ |
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if (rc == BPF_FIB_LKUP_RET_SUCCESS) { |
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/* Verify egress index has been configured as TX-port. |
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* (Note: User can still have inserted an egress ifindex that |
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* doesn't support XDP xmit, which will result in packet drops). |
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* |
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* Note: lookup in devmap supported since 0cdbb4b09a0. |
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* If not supported will fail with: |
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* cannot pass map_type 14 into func bpf_map_lookup_elem#1: |
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*/ |
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if (!bpf_map_lookup_elem(&xdp_tx_ports, &fib_params.ifindex)) |
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return XDP_PASS; |
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if (h_proto == htons(ETH_P_IP)) |
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ip_decrease_ttl(iph); |
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else if (h_proto == htons(ETH_P_IPV6)) |
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ip6h->hop_limit--; |
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memcpy(eth->h_dest, fib_params.dmac, ETH_ALEN); |
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memcpy(eth->h_source, fib_params.smac, ETH_ALEN); |
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return bpf_redirect_map(&xdp_tx_ports, fib_params.ifindex, 0); |
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} |
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return XDP_PASS; |
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} |
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SEC("xdp_fwd") |
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int xdp_fwd_prog(struct xdp_md *ctx) |
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{ |
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return xdp_fwd_flags(ctx, 0); |
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} |
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SEC("xdp_fwd_direct") |
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int xdp_fwd_direct_prog(struct xdp_md *ctx) |
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{ |
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return xdp_fwd_flags(ctx, BPF_FIB_LOOKUP_DIRECT); |
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} |
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char _license[] SEC("license") = "GPL";
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