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 congestion window and initial receive
8 * window to 40 packets and send and receive buffers to 1.5MB. This
9 * would usually be done after doing appropriate checks that indicate
10 * the hosts are far enough 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_iw(struct bpf_sock_ops * skops)26 int bpf_iw(struct bpf_sock_ops *skops)
27 {
28 int bufsize = 1500000;
29 int rwnd_init = 40;
30 int iw = 40;
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 &&
38 skops->local_port != 55601) {
39 skops->reply = -1;
40 return 1;
41 }
42
43 op = (int) skops->op;
44
45 #ifdef DEBUG
46 bpf_printk("BPF command: %d\n", op);
47 #endif
48
49 /* Usually there would be a check to insure the hosts are far
50 * from each other so it makes sense to increase buffer sizes
51 */
52 switch (op) {
53 case BPF_SOCK_OPS_RWND_INIT:
54 rv = rwnd_init;
55 break;
56 case BPF_SOCK_OPS_TCP_CONNECT_CB:
57 /* Set sndbuf and rcvbuf of active connections */
58 rv = bpf_setsockopt(skops, SOL_SOCKET, SO_SNDBUF, &bufsize,
59 sizeof(bufsize));
60 rv += bpf_setsockopt(skops, SOL_SOCKET, SO_RCVBUF,
61 &bufsize, sizeof(bufsize));
62 break;
63 case BPF_SOCK_OPS_ACTIVE_ESTABLISHED_CB:
64 rv = bpf_setsockopt(skops, SOL_TCP, TCP_BPF_IW, &iw,
65 sizeof(iw));
66 break;
67 case BPF_SOCK_OPS_PASSIVE_ESTABLISHED_CB:
68 /* Set sndbuf and rcvbuf of passive connections */
69 rv = bpf_setsockopt(skops, SOL_SOCKET, SO_SNDBUF, &bufsize,
70 sizeof(bufsize));
71 rv += bpf_setsockopt(skops, SOL_SOCKET, SO_RCVBUF,
72 &bufsize, sizeof(bufsize));
73 break;
74 default:
75 rv = -1;
76 }
77 #ifdef DEBUG
78 bpf_printk("Returning %d\n", rv);
79 #endif
80 skops->reply = rv;
81 return 1;
82 }
83 char _license[] SEC("license") = "GPL";
84