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")
bpf_basertt(struct bpf_sock_ops * skops)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