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 * Sample BPF program to set send and receive buffers to 150KB, sndcwnd clamp
8 * to 100 packets and SYN and SYN_ACK RTOs to 10ms when both hosts are within
9 * the same datacenter. For his example, we assume they are within the same
10 * datacenter when the first 5.5 bytes of their IPv6 addresses are the same.
11 *
12 * Use "bpftool cgroup attach $cg sock_ops $prog" to load this BPF program.
13 */
14
15 #include <uapi/linux/bpf.h>
16 #include <uapi/linux/if_ether.h>
17 #include <uapi/linux/if_packet.h>
18 #include <uapi/linux/ip.h>
19 #include <linux/socket.h>
20 #include <bpf/bpf_helpers.h>
21 #include <bpf/bpf_endian.h>
22
23 #define DEBUG 1
24
25 SEC("sockops")
bpf_clamp(struct bpf_sock_ops * skops)26 int bpf_clamp(struct bpf_sock_ops *skops)
27 {
28 int bufsize = 150000;
29 int to_init = 10;
30 int clamp = 100;
31 int rv = 0;
32 int op;
33
34 /* For testing purposes, only execute rest of BPF program
35 * if neither port numberis 55601
36 */
37 if (bpf_ntohl(skops->remote_port) != 55601 && skops->local_port != 55601) {
38 skops->reply = -1;
39 return 0;
40 }
41
42 op = (int) skops->op;
43
44 #ifdef DEBUG
45 bpf_printk("BPF command: %d\n", op);
46 #endif
47
48 /* Check that both hosts are within same datacenter. For this example
49 * it is the case when the first 5.5 bytes of their IPv6 addresses are
50 * the same.
51 */
52 if (skops->family == AF_INET6 &&
53 skops->local_ip6[0] == skops->remote_ip6[0] &&
54 (bpf_ntohl(skops->local_ip6[1]) & 0xfff00000) ==
55 (bpf_ntohl(skops->remote_ip6[1]) & 0xfff00000)) {
56 switch (op) {
57 case BPF_SOCK_OPS_TIMEOUT_INIT:
58 rv = to_init;
59 break;
60 case BPF_SOCK_OPS_TCP_CONNECT_CB:
61 /* Set sndbuf and rcvbuf of active connections */
62 rv = bpf_setsockopt(skops, SOL_SOCKET, SO_SNDBUF,
63 &bufsize, sizeof(bufsize));
64 rv += bpf_setsockopt(skops, SOL_SOCKET,
65 SO_RCVBUF, &bufsize,
66 sizeof(bufsize));
67 break;
68 case BPF_SOCK_OPS_ACTIVE_ESTABLISHED_CB:
69 rv = bpf_setsockopt(skops, SOL_TCP,
70 TCP_BPF_SNDCWND_CLAMP,
71 &clamp, sizeof(clamp));
72 break;
73 case BPF_SOCK_OPS_PASSIVE_ESTABLISHED_CB:
74 /* Set sndbuf and rcvbuf of passive connections */
75 rv = bpf_setsockopt(skops, SOL_TCP,
76 TCP_BPF_SNDCWND_CLAMP,
77 &clamp, sizeof(clamp));
78 rv += bpf_setsockopt(skops, SOL_SOCKET,
79 SO_SNDBUF, &bufsize,
80 sizeof(bufsize));
81 rv += bpf_setsockopt(skops, SOL_SOCKET,
82 SO_RCVBUF, &bufsize,
83 sizeof(bufsize));
84 break;
85 default:
86 rv = -1;
87 }
88 } else {
89 rv = -1;
90 }
91 #ifdef DEBUG
92 bpf_printk("Returning %d\n", rv);
93 #endif
94 skops->reply = rv;
95 return 1;
96 }
97 char _license[] SEC("license") = "GPL";
98