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 congestion control to dctcp when both hosts are
 8 * in the same datacenter (as deteremined by IPv6 prefix).
 9 *
10 * Use load_sock_ops to load this BPF program.
11 */
12
13#include <uapi/linux/bpf.h>
14#include <uapi/linux/tcp.h>
15#include <uapi/linux/if_ether.h>
16#include <uapi/linux/if_packet.h>
17#include <uapi/linux/ip.h>
18#include <linux/socket.h>
19#include "bpf_helpers.h"
20#include "bpf_endian.h"
21
22#define DEBUG 1
23
24#define bpf_printk(fmt, ...)					\
25({								\
26	       char ____fmt[] = fmt;				\
27	       bpf_trace_printk(____fmt, sizeof(____fmt),	\
28				##__VA_ARGS__);			\
29})
30
31SEC("sockops")
32int bpf_cong(struct bpf_sock_ops *skops)
33{
34	char cong[] = "dctcp";
35	int rv = 0;
36	int op;
37
38	/* For testing purposes, only execute rest of BPF program
39	 * if neither port numberis 55601
40	 */
41	if (bpf_ntohl(skops->remote_port) != 55601 &&
42	    skops->local_port != 55601) {
43		skops->reply = -1;
44		return 1;
45	}
46
47	op = (int) skops->op;
48
49#ifdef DEBUG
50	bpf_printk("BPF command: %d\n", op);
51#endif
52
53	/* Check if both hosts are in the same datacenter. For this
54	 * example they are if the 1st 5.5 bytes in the IPv6 address
55	 * are the same.
56	 */
57	if (skops->family == AF_INET6 &&
58	    skops->local_ip6[0] == skops->remote_ip6[0] &&
59	    (bpf_ntohl(skops->local_ip6[1]) & 0xfff00000) ==
60	    (bpf_ntohl(skops->remote_ip6[1]) & 0xfff00000)) {
61		switch (op) {
62		case BPF_SOCK_OPS_NEEDS_ECN:
63			rv = 1;
64			break;
65		case BPF_SOCK_OPS_ACTIVE_ESTABLISHED_CB:
66			rv = bpf_setsockopt(skops, SOL_TCP, TCP_CONGESTION,
67					    cong, sizeof(cong));
68			break;
69		case BPF_SOCK_OPS_PASSIVE_ESTABLISHED_CB:
70			rv = bpf_setsockopt(skops, SOL_TCP, TCP_CONGESTION,
71					    cong, sizeof(cong));
72			break;
73		default:
74			rv = -1;
75		}
76	} else {
77		rv = -1;
78	}
79#ifdef DEBUG
80	bpf_printk("Returning %d\n", rv);
81#endif
82	skops->reply = rv;
83	return 1;
84}
85char _license[] SEC("license") = "GPL";