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
25SEC("sockops")
26int 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}
97char _license[] SEC("license") = "GPL";
98