1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * Copyright (c) 2018 Facebook
4 *
5 * BPF program to automatically reflect TOS option from received syn packet
6 *
7 * Use "bpftool cgroup attach $cg sock_ops $prog" to load this BPF program.
8 */
9
10 #include <uapi/linux/bpf.h>
11 #include <uapi/linux/tcp.h>
12 #include <uapi/linux/if_ether.h>
13 #include <uapi/linux/if_packet.h>
14 #include <uapi/linux/ip.h>
15 #include <uapi/linux/ipv6.h>
16 #include <uapi/linux/in.h>
17 #include <linux/socket.h>
18 #include <bpf/bpf_helpers.h>
19 #include <bpf/bpf_endian.h>
20
21 #define DEBUG 1
22
23 SEC("sockops")
24 int bpf_basertt(struct bpf_sock_ops *skops)
25 {
26 char header[sizeof(struct ipv6hdr)];
27 struct ipv6hdr *hdr6;
28 struct iphdr *hdr;
29 int hdr_size = 0;
30 int save_syn = 1;
31 int tos = 0;
32 int rv = 0;
33 int op;
34
35 op = (int) skops->op;
36
37 #ifdef DEBUG
38 bpf_printk("BPF command: %d\n", op);
39 #endif
40 switch (op) {
41 case BPF_SOCK_OPS_TCP_LISTEN_CB:
42 rv = bpf_setsockopt(skops, SOL_TCP, TCP_SAVE_SYN,
43 &save_syn, sizeof(save_syn));
44 break;
45 case BPF_SOCK_OPS_PASSIVE_ESTABLISHED_CB:
46 if (skops->family == AF_INET)
47 hdr_size = sizeof(struct iphdr);
48 else
49 hdr_size = sizeof(struct ipv6hdr);
50 rv = bpf_getsockopt(skops, SOL_TCP, TCP_SAVED_SYN,
51 header, hdr_size);
52 if (!rv) {
53 if (skops->family == AF_INET) {
54 hdr = (struct iphdr *) header;
55 tos = hdr->tos;
56 if (tos != 0)
57 bpf_setsockopt(skops, SOL_IP, IP_TOS,
58 &tos, sizeof(tos));
59 } else {
60 hdr6 = (struct ipv6hdr *) header;
61 tos = ((hdr6->priority) << 4 |
62 (hdr6->flow_lbl[0]) >> 4);
63 if (tos)
64 bpf_setsockopt(skops, SOL_IPV6,
65 IPV6_TCLASS,
66 &tos, sizeof(tos));
67 }
68 rv = 0;
69 }
70 break;
71 default:
72 rv = -1;
73 }
74 #ifdef DEBUG
75 bpf_printk("Returning %d\n", rv);
76 #endif
77 skops->reply = rv;
78 return 1;
79 }
80 char _license[] SEC("license") = "GPL";
81
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