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 load_sock_ops 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_helpers.h"
21#include "bpf_endian.h"
22
23#define DEBUG 1
24
25#define bpf_printk(fmt, ...)					\
26({								\
27	       char ____fmt[] = fmt;				\
28	       bpf_trace_printk(____fmt, sizeof(____fmt),	\
29				##__VA_ARGS__);			\
30})
31
32SEC("sockops")
33int bpf_bufs(struct bpf_sock_ops *skops)
34{
35	int bufsize = 1500000;
36	int rwnd_init = 40;
37	int rv = 0;
38	int op;
39
40	/* For testing purposes, only execute rest of BPF program
41	 * if neither port numberis 55601
42	 */
43	if (bpf_ntohl(skops->remote_port) != 55601 &&
44	    skops->local_port != 55601) {
45		skops->reply = -1;
46		return 1;
47	}
48
49	op = (int) skops->op;
50
51#ifdef DEBUG
52	bpf_printk("Returning %d\n", rv);
53#endif
54
55	/* Usually there would be a check to insure the hosts are far
56	 * from each other so it makes sense to increase buffer sizes
57	 */
58	switch (op) {
59	case BPF_SOCK_OPS_RWND_INIT:
60		rv = rwnd_init;
61		break;
62	case BPF_SOCK_OPS_TCP_CONNECT_CB:
63		/* Set sndbuf and rcvbuf of active connections */
64		rv = bpf_setsockopt(skops, SOL_SOCKET, SO_SNDBUF, &bufsize,
65				    sizeof(bufsize));
66		rv += bpf_setsockopt(skops, SOL_SOCKET, SO_RCVBUF,
67				     &bufsize, sizeof(bufsize));
68		break;
69	case BPF_SOCK_OPS_ACTIVE_ESTABLISHED_CB:
70		/* Nothing to do */
71		break;
72	case BPF_SOCK_OPS_PASSIVE_ESTABLISHED_CB:
73		/* Set sndbuf and rcvbuf of passive connections */
74		rv = bpf_setsockopt(skops, SOL_SOCKET, SO_SNDBUF, &bufsize,
75				    sizeof(bufsize));
76		rv += bpf_setsockopt(skops, SOL_SOCKET, SO_RCVBUF,
77				     &bufsize, sizeof(bufsize));
78		break;
79	default:
80		rv = -1;
81	}
82#ifdef DEBUG
83	bpf_printk("Returning %d\n", rv);
84#endif
85	skops->reply = rv;
86	return 1;
87}
88char _license[] SEC("license") = "GPL";