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acb4ea9564
Sample program which shows TCP_SAVE_SYN/TCP_SAVED_SYN usage example: bpf program which is doing TOS/TCLASS reflection (server would reply with a same TOS/TCLASS as client). Signed-off-by: Nikita V. Shirokov <tehnerd@fb.com> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
88 lines
1.9 KiB
C
88 lines
1.9 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* Copyright (c) 2018 Facebook
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*
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* BPF program to automatically reflect TOS option from received syn packet
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*
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* Use load_sock_ops to load this BPF program.
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*/
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#include <uapi/linux/bpf.h>
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#include <uapi/linux/tcp.h>
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#include <uapi/linux/if_ether.h>
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#include <uapi/linux/if_packet.h>
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#include <uapi/linux/ip.h>
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#include <uapi/linux/ipv6.h>
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#include <uapi/linux/in.h>
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#include <linux/socket.h>
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#include "bpf_helpers.h"
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#include "bpf_endian.h"
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#define DEBUG 1
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#define bpf_printk(fmt, ...) \
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({ \
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char ____fmt[] = fmt; \
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bpf_trace_printk(____fmt, sizeof(____fmt), \
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##__VA_ARGS__); \
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})
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SEC("sockops")
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int bpf_basertt(struct bpf_sock_ops *skops)
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{
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char header[sizeof(struct ipv6hdr)];
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struct ipv6hdr *hdr6;
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struct iphdr *hdr;
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int hdr_size = 0;
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int save_syn = 1;
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int tos = 0;
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int rv = 0;
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int op;
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op = (int) skops->op;
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#ifdef DEBUG
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bpf_printk("BPF command: %d\n", op);
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#endif
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switch (op) {
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case BPF_SOCK_OPS_TCP_LISTEN_CB:
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rv = bpf_setsockopt(skops, SOL_TCP, TCP_SAVE_SYN,
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&save_syn, sizeof(save_syn));
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break;
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case BPF_SOCK_OPS_PASSIVE_ESTABLISHED_CB:
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if (skops->family == AF_INET)
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hdr_size = sizeof(struct iphdr);
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else
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hdr_size = sizeof(struct ipv6hdr);
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rv = bpf_getsockopt(skops, SOL_TCP, TCP_SAVED_SYN,
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header, hdr_size);
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if (!rv) {
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if (skops->family == AF_INET) {
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hdr = (struct iphdr *) header;
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tos = hdr->tos;
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if (tos != 0)
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bpf_setsockopt(skops, SOL_IP, IP_TOS,
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&tos, sizeof(tos));
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} else {
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hdr6 = (struct ipv6hdr *) header;
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tos = ((hdr6->priority) << 4 |
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(hdr6->flow_lbl[0]) >> 4);
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if (tos)
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bpf_setsockopt(skops, SOL_IPV6,
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IPV6_TCLASS,
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&tos, sizeof(tos));
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}
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rv = 0;
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}
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break;
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default:
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rv = -1;
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}
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#ifdef DEBUG
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bpf_printk("Returning %d\n", rv);
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#endif
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skops->reply = rv;
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return 1;
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}
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char _license[] SEC("license") = "GPL";
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