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 initial receive window to 40 packets and send
8 * and receive buffers to 1.5MB. This would usually be done after
9 * doing appropriate checks that indicate the hosts are far enough
10 * away (i.e. large RTT).
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_bufs(struct bpf_sock_ops * skops)26 int bpf_bufs(struct bpf_sock_ops *skops)
27 {
28 int bufsize = 1500000;
29 int rwnd_init = 40;
30 int rv = 0;
31 int op;
32
33 /* For testing purposes, only execute rest of BPF program
34 * if neither port numberis 55601
35 */
36 if (bpf_ntohl(skops->remote_port) != 55601 &&
37 skops->local_port != 55601) {
38 skops->reply = -1;
39 return 1;
40 }
41
42 op = (int) skops->op;
43
44 #ifdef DEBUG
45 bpf_printk("Returning %d\n", rv);
46 #endif
47
48 /* Usually there would be a check to insure the hosts are far
49 * from each other so it makes sense to increase buffer sizes
50 */
51 switch (op) {
52 case BPF_SOCK_OPS_RWND_INIT:
53 rv = rwnd_init;
54 break;
55 case BPF_SOCK_OPS_TCP_CONNECT_CB:
56 /* Set sndbuf and rcvbuf of active connections */
57 rv = bpf_setsockopt(skops, SOL_SOCKET, SO_SNDBUF, &bufsize,
58 sizeof(bufsize));
59 rv += bpf_setsockopt(skops, SOL_SOCKET, SO_RCVBUF,
60 &bufsize, sizeof(bufsize));
61 break;
62 case BPF_SOCK_OPS_ACTIVE_ESTABLISHED_CB:
63 /* Nothing to do */
64 break;
65 case BPF_SOCK_OPS_PASSIVE_ESTABLISHED_CB:
66 /* Set sndbuf and rcvbuf of passive connections */
67 rv = bpf_setsockopt(skops, SOL_SOCKET, SO_SNDBUF, &bufsize,
68 sizeof(bufsize));
69 rv += bpf_setsockopt(skops, SOL_SOCKET, SO_RCVBUF,
70 &bufsize, sizeof(bufsize));
71 break;
72 default:
73 rv = -1;
74 }
75 #ifdef DEBUG
76 bpf_printk("Returning %d\n", rv);
77 #endif
78 skops->reply = rv;
79 return 1;
80 }
81 char _license[] SEC("license") = "GPL";
82