xref: /openbmc/linux/samples/bpf/tcp_bufs_kern.c (revision 5d0e4d78)
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 
32 SEC("sockops")
33 int 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 		return -1;
46 
47 	op = (int) skops->op;
48 
49 #ifdef DEBUG
50 	bpf_printk("Returning %d\n", rv);
51 #endif
52 
53 	/* Usually there would be a check to insure the hosts are far
54 	 * from each other so it makes sense to increase buffer sizes
55 	 */
56 	switch (op) {
57 	case BPF_SOCK_OPS_RWND_INIT:
58 		rv = rwnd_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, &bufsize,
63 				    sizeof(bufsize));
64 		rv = rv*100 + bpf_setsockopt(skops, SOL_SOCKET, SO_RCVBUF,
65 					     &bufsize, sizeof(bufsize));
66 		break;
67 	case BPF_SOCK_OPS_ACTIVE_ESTABLISHED_CB:
68 		/* Nothing to do */
69 		break;
70 	case BPF_SOCK_OPS_PASSIVE_ESTABLISHED_CB:
71 		/* Set sndbuf and rcvbuf of passive connections */
72 		rv = bpf_setsockopt(skops, SOL_SOCKET, SO_SNDBUF, &bufsize,
73 				    sizeof(bufsize));
74 		rv = rv*100 + bpf_setsockopt(skops, SOL_SOCKET, SO_RCVBUF,
75 					     &bufsize, sizeof(bufsize));
76 		break;
77 	default:
78 		rv = -1;
79 	}
80 #ifdef DEBUG
81 	bpf_printk("Returning %d\n", rv);
82 #endif
83 	skops->reply = rv;
84 	return 1;
85 }
86 char _license[] SEC("license") = "GPL";
87