GNU Linux-libre 6.6.15-gnu
[releases.git] / samples / bpf / tcp_clamp_kern.c
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")
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";