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
25SEC("sockops")
26int 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}
83char _license[] SEC("license") = "GPL";
84