1 /* Copyright (c) 2017 Facebook
2 *
3 * This program is free software; you can redistribute it and/or
4 * modify it under the terms of version 2 of the GNU General Public
5 * License as published by the Free Software Foundation.
6 *
7 * BPF program to set congestion control to dctcp when both hosts are
8 * in the same datacenter (as deteremined by IPv6 prefix).
9 *
10 * Use "bpftool cgroup attach $cg sock_ops $prog" to load this BPF program.
11 */
12
13 #include <uapi/linux/bpf.h>
14 #include <uapi/linux/tcp.h>
15 #include <uapi/linux/if_ether.h>
16 #include <uapi/linux/if_packet.h>
17 #include <uapi/linux/ip.h>
18 #include <linux/socket.h>
19 #include <bpf/bpf_helpers.h>
20 #include <bpf/bpf_endian.h>
21
22 #define DEBUG 1
23
24 SEC("sockops")
25 int bpf_cong(struct bpf_sock_ops *skops)
26 {
27 char cong[] = "dctcp";
28 int rv = 0;
29 int op;
30
31 /* For testing purposes, only execute rest of BPF program
32 * if neither port numberis 55601
33 */
34 if (bpf_ntohl(skops->remote_port) != 55601 &&
35 skops->local_port != 55601) {
36 skops->reply = -1;
37 return 1;
38 }
39
40 op = (int) skops->op;
41
42 #ifdef DEBUG
43 bpf_printk("BPF command: %d\n", op);
44 #endif
45
46 /* Check if both hosts are in the same datacenter. For this
47 * example they are if the 1st 5.5 bytes in the IPv6 address
48 * are the same.
49 */
50 if (skops->family == AF_INET6 &&
51 skops->local_ip6[0] == skops->remote_ip6[0] &&
52 (bpf_ntohl(skops->local_ip6[1]) & 0xfff00000) ==
53 (bpf_ntohl(skops->remote_ip6[1]) & 0xfff00000)) {
54 switch (op) {
55 case BPF_SOCK_OPS_NEEDS_ECN:
56 rv = 1;
57 break;
58 case BPF_SOCK_OPS_ACTIVE_ESTABLISHED_CB:
59 rv = bpf_setsockopt(skops, SOL_TCP, TCP_CONGESTION,
60 cong, sizeof(cong));
61 break;
62 case BPF_SOCK_OPS_PASSIVE_ESTABLISHED_CB:
63 rv = bpf_setsockopt(skops, SOL_TCP, TCP_CONGESTION,
64 cong, sizeof(cong));
65 break;
66 default:
67 rv = -1;
68 }
69 } else {
70 rv = -1;
71 }
72 #ifdef DEBUG
73 bpf_printk("Returning %d\n", rv);
74 #endif
75 skops->reply = rv;
76 return 1;
77 }
78 char _license[] SEC("license") = "GPL";
79
Linux® is a registered trademark of Linus Torvalds in the United States and other countries.
TOMOYO® is a registered trademark of NTT DATA CORPORATION.