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
25SEC("sockops")
26int 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}
81char _license[] SEC("license") = "GPL";
82