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
23SEC("sockops")
24int 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}
80char _license[] SEC("license") = "GPL";