xref: /linux/samples/bpf/tcp_bufs_kern.c (revision 8dd06ef34b6e2f41b29fbf5fc1663780f2524285)
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 
25 SEC("sockops")
bpf_bufs(struct bpf_sock_ops * skops)26 int 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 }
81 char _license[] SEC("license") = "GPL";
82