1// SPDX-License-Identifier: GPL-2.0
2// Copyright (c) 2018 Facebook
3
4#include <string.h>
5
6#include <linux/stddef.h>
7#include <linux/bpf.h>
8#include <linux/in.h>
9#include <linux/in6.h>
10#include <sys/socket.h>
11#include <netinet/tcp.h>
12#include <linux/if.h>
13#include <errno.h>
14
15#include <bpf/bpf_helpers.h>
16#include <bpf/bpf_endian.h>
17
18#define SRC_REWRITE_IP4		0x7f000004U
19#define DST_REWRITE_IP4		0x7f000001U
20#define DST_REWRITE_PORT4	4444
21
22#ifndef TCP_CA_NAME_MAX
23#define TCP_CA_NAME_MAX 16
24#endif
25
26#ifndef TCP_NOTSENT_LOWAT
27#define TCP_NOTSENT_LOWAT 25
28#endif
29
30#ifndef IFNAMSIZ
31#define IFNAMSIZ 16
32#endif
33
34int _version SEC("version") = 1;
35
36__attribute__ ((noinline)) __weak
37int do_bind(struct bpf_sock_addr *ctx)
38{
39	struct sockaddr_in sa = {};
40
41	sa.sin_family = AF_INET;
42	sa.sin_port = bpf_htons(0);
43	sa.sin_addr.s_addr = bpf_htonl(SRC_REWRITE_IP4);
44
45	if (bpf_bind(ctx, (struct sockaddr *)&sa, sizeof(sa)) != 0)
46		return 0;
47
48	return 1;
49}
50
51static __inline int verify_cc(struct bpf_sock_addr *ctx,
52			      char expected[TCP_CA_NAME_MAX])
53{
54	char buf[TCP_CA_NAME_MAX];
55	int i;
56
57	if (bpf_getsockopt(ctx, SOL_TCP, TCP_CONGESTION, &buf, sizeof(buf)))
58		return 1;
59
60	for (i = 0; i < TCP_CA_NAME_MAX; i++) {
61		if (buf[i] != expected[i])
62			return 1;
63		if (buf[i] == 0)
64			break;
65	}
66
67	return 0;
68}
69
70static __inline int set_cc(struct bpf_sock_addr *ctx)
71{
72	char reno[TCP_CA_NAME_MAX] = "reno";
73	char cubic[TCP_CA_NAME_MAX] = "cubic";
74
75	if (bpf_setsockopt(ctx, SOL_TCP, TCP_CONGESTION, &reno, sizeof(reno)))
76		return 1;
77	if (verify_cc(ctx, reno))
78		return 1;
79
80	if (bpf_setsockopt(ctx, SOL_TCP, TCP_CONGESTION, &cubic, sizeof(cubic)))
81		return 1;
82	if (verify_cc(ctx, cubic))
83		return 1;
84
85	return 0;
86}
87
88static __inline int bind_to_device(struct bpf_sock_addr *ctx)
89{
90	char veth1[IFNAMSIZ] = "test_sock_addr1";
91	char veth2[IFNAMSIZ] = "test_sock_addr2";
92	char missing[IFNAMSIZ] = "nonexistent_dev";
93	char del_bind[IFNAMSIZ] = "";
94
95	if (bpf_setsockopt(ctx, SOL_SOCKET, SO_BINDTODEVICE,
96				&veth1, sizeof(veth1)))
97		return 1;
98	if (bpf_setsockopt(ctx, SOL_SOCKET, SO_BINDTODEVICE,
99				&veth2, sizeof(veth2)))
100		return 1;
101	if (bpf_setsockopt(ctx, SOL_SOCKET, SO_BINDTODEVICE,
102				&missing, sizeof(missing)) != -ENODEV)
103		return 1;
104	if (bpf_setsockopt(ctx, SOL_SOCKET, SO_BINDTODEVICE,
105				&del_bind, sizeof(del_bind)))
106		return 1;
107
108	return 0;
109}
110
111static __inline int set_keepalive(struct bpf_sock_addr *ctx)
112{
113	int zero = 0, one = 1;
114
115	if (bpf_setsockopt(ctx, SOL_SOCKET, SO_KEEPALIVE, &one, sizeof(one)))
116		return 1;
117	if (ctx->type == SOCK_STREAM) {
118		if (bpf_setsockopt(ctx, SOL_TCP, TCP_KEEPIDLE, &one, sizeof(one)))
119			return 1;
120		if (bpf_setsockopt(ctx, SOL_TCP, TCP_KEEPINTVL, &one, sizeof(one)))
121			return 1;
122		if (bpf_setsockopt(ctx, SOL_TCP, TCP_KEEPCNT, &one, sizeof(one)))
123			return 1;
124		if (bpf_setsockopt(ctx, SOL_TCP, TCP_SYNCNT, &one, sizeof(one)))
125			return 1;
126		if (bpf_setsockopt(ctx, SOL_TCP, TCP_USER_TIMEOUT, &one, sizeof(one)))
127			return 1;
128	}
129	if (bpf_setsockopt(ctx, SOL_SOCKET, SO_KEEPALIVE, &zero, sizeof(zero)))
130		return 1;
131
132	return 0;
133}
134
135static __inline int set_notsent_lowat(struct bpf_sock_addr *ctx)
136{
137	int lowat = 65535;
138
139	if (ctx->type == SOCK_STREAM) {
140		if (bpf_setsockopt(ctx, SOL_TCP, TCP_NOTSENT_LOWAT, &lowat, sizeof(lowat)))
141			return 1;
142	}
143
144	return 0;
145}
146
147SEC("cgroup/connect4")
148int connect_v4_prog(struct bpf_sock_addr *ctx)
149{
150	struct bpf_sock_tuple tuple = {};
151	struct bpf_sock *sk;
152
153	/* Verify that new destination is available. */
154	memset(&tuple.ipv4.saddr, 0, sizeof(tuple.ipv4.saddr));
155	memset(&tuple.ipv4.sport, 0, sizeof(tuple.ipv4.sport));
156
157	tuple.ipv4.daddr = bpf_htonl(DST_REWRITE_IP4);
158	tuple.ipv4.dport = bpf_htons(DST_REWRITE_PORT4);
159
160	/* Bind to device and unbind it. */
161	if (bind_to_device(ctx))
162		return 0;
163
164	if (set_keepalive(ctx))
165		return 0;
166
167	if (set_notsent_lowat(ctx))
168		return 0;
169
170	if (ctx->type != SOCK_STREAM && ctx->type != SOCK_DGRAM)
171		return 0;
172	else if (ctx->type == SOCK_STREAM)
173		sk = bpf_sk_lookup_tcp(ctx, &tuple, sizeof(tuple.ipv4),
174				       BPF_F_CURRENT_NETNS, 0);
175	else
176		sk = bpf_sk_lookup_udp(ctx, &tuple, sizeof(tuple.ipv4),
177				       BPF_F_CURRENT_NETNS, 0);
178
179	if (!sk)
180		return 0;
181
182	if (sk->src_ip4 != tuple.ipv4.daddr ||
183	    sk->src_port != DST_REWRITE_PORT4) {
184		bpf_sk_release(sk);
185		return 0;
186	}
187
188	bpf_sk_release(sk);
189
190	/* Rewrite congestion control. */
191	if (ctx->type == SOCK_STREAM && set_cc(ctx))
192		return 0;
193
194	/* Rewrite destination. */
195	ctx->user_ip4 = bpf_htonl(DST_REWRITE_IP4);
196	ctx->user_port = bpf_htons(DST_REWRITE_PORT4);
197
198	return do_bind(ctx) ? 1 : 0;
199}
200
201char _license[] SEC("license") = "GPL";
202