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 <linux/tcp.h>
11#include <linux/if.h>
12#include <errno.h>
13
14#include <bpf/bpf_helpers.h>
15#include <bpf/bpf_endian.h>
16
17#define SRC_REWRITE_IP4		0x7f000004U
18#define DST_REWRITE_IP4		0x7f000001U
19#define DST_REWRITE_PORT4	4444
20
21#ifndef TCP_CA_NAME_MAX
22#define TCP_CA_NAME_MAX 16
23#endif
24
25#ifndef TCP_NOTSENT_LOWAT
26#define TCP_NOTSENT_LOWAT 25
27#endif
28
29#ifndef IFNAMSIZ
30#define IFNAMSIZ 16
31#endif
32
33#ifndef SOL_TCP
34#define SOL_TCP 6
35#endif
36
37__attribute__ ((noinline)) __weak
38int do_bind(struct bpf_sock_addr *ctx)
39{
40	struct sockaddr_in sa = {};
41
42	sa.sin_family = AF_INET;
43	sa.sin_port = bpf_htons(0);
44	sa.sin_addr.s_addr = bpf_htonl(SRC_REWRITE_IP4);
45
46	if (bpf_bind(ctx, (struct sockaddr *)&sa, sizeof(sa)) != 0)
47		return 0;
48
49	return 1;
50}
51
52static __inline int verify_cc(struct bpf_sock_addr *ctx,
53			      char expected[TCP_CA_NAME_MAX])
54{
55	char buf[TCP_CA_NAME_MAX];
56	int i;
57
58	if (bpf_getsockopt(ctx, SOL_TCP, TCP_CONGESTION, &buf, sizeof(buf)))
59		return 1;
60
61	for (i = 0; i < TCP_CA_NAME_MAX; i++) {
62		if (buf[i] != expected[i])
63			return 1;
64		if (buf[i] == 0)
65			break;
66	}
67
68	return 0;
69}
70
71static __inline int set_cc(struct bpf_sock_addr *ctx)
72{
73	char reno[TCP_CA_NAME_MAX] = "reno";
74	char cubic[TCP_CA_NAME_MAX] = "cubic";
75
76	if (bpf_setsockopt(ctx, SOL_TCP, TCP_CONGESTION, &reno, sizeof(reno)))
77		return 1;
78	if (verify_cc(ctx, reno))
79		return 1;
80
81	if (bpf_setsockopt(ctx, SOL_TCP, TCP_CONGESTION, &cubic, sizeof(cubic)))
82		return 1;
83	if (verify_cc(ctx, cubic))
84		return 1;
85
86	return 0;
87}
88
89static __inline int bind_to_device(struct bpf_sock_addr *ctx)
90{
91	char veth1[IFNAMSIZ] = "test_sock_addr1";
92	char veth2[IFNAMSIZ] = "test_sock_addr2";
93	char missing[IFNAMSIZ] = "nonexistent_dev";
94	char del_bind[IFNAMSIZ] = "";
95
96	if (bpf_setsockopt(ctx, SOL_SOCKET, SO_BINDTODEVICE,
97				&veth1, sizeof(veth1)))
98		return 1;
99	if (bpf_setsockopt(ctx, SOL_SOCKET, SO_BINDTODEVICE,
100				&veth2, sizeof(veth2)))
101		return 1;
102	if (bpf_setsockopt(ctx, SOL_SOCKET, SO_BINDTODEVICE,
103				&missing, sizeof(missing)) != -ENODEV)
104		return 1;
105	if (bpf_setsockopt(ctx, SOL_SOCKET, SO_BINDTODEVICE,
106				&del_bind, sizeof(del_bind)))
107		return 1;
108
109	return 0;
110}
111
112static __inline int set_keepalive(struct bpf_sock_addr *ctx)
113{
114	int zero = 0, one = 1;
115
116	if (bpf_setsockopt(ctx, SOL_SOCKET, SO_KEEPALIVE, &one, sizeof(one)))
117		return 1;
118	if (ctx->type == SOCK_STREAM) {
119		if (bpf_setsockopt(ctx, SOL_TCP, TCP_KEEPIDLE, &one, sizeof(one)))
120			return 1;
121		if (bpf_setsockopt(ctx, SOL_TCP, TCP_KEEPINTVL, &one, sizeof(one)))
122			return 1;
123		if (bpf_setsockopt(ctx, SOL_TCP, TCP_KEEPCNT, &one, sizeof(one)))
124			return 1;
125		if (bpf_setsockopt(ctx, SOL_TCP, TCP_SYNCNT, &one, sizeof(one)))
126			return 1;
127		if (bpf_setsockopt(ctx, SOL_TCP, TCP_USER_TIMEOUT, &one, sizeof(one)))
128			return 1;
129	}
130	if (bpf_setsockopt(ctx, SOL_SOCKET, SO_KEEPALIVE, &zero, sizeof(zero)))
131		return 1;
132
133	return 0;
134}
135
136static __inline int set_notsent_lowat(struct bpf_sock_addr *ctx)
137{
138	int lowat = 65535;
139
140	if (ctx->type == SOCK_STREAM) {
141		if (bpf_setsockopt(ctx, SOL_TCP, TCP_NOTSENT_LOWAT, &lowat, sizeof(lowat)))
142			return 1;
143	}
144
145	return 0;
146}
147
148SEC("cgroup/connect4")
149int connect_v4_prog(struct bpf_sock_addr *ctx)
150{
151	struct bpf_sock_tuple tuple = {};
152	struct bpf_sock *sk;
153
154	/* Verify that new destination is available. */
155	memset(&tuple.ipv4.saddr, 0, sizeof(tuple.ipv4.saddr));
156	memset(&tuple.ipv4.sport, 0, sizeof(tuple.ipv4.sport));
157
158	tuple.ipv4.daddr = bpf_htonl(DST_REWRITE_IP4);
159	tuple.ipv4.dport = bpf_htons(DST_REWRITE_PORT4);
160
161	/* Bind to device and unbind it. */
162	if (bind_to_device(ctx))
163		return 0;
164
165	if (set_keepalive(ctx))
166		return 0;
167
168	if (set_notsent_lowat(ctx))
169		return 0;
170
171	if (ctx->type != SOCK_STREAM && ctx->type != SOCK_DGRAM)
172		return 0;
173	else if (ctx->type == SOCK_STREAM)
174		sk = bpf_sk_lookup_tcp(ctx, &tuple, sizeof(tuple.ipv4),
175				       BPF_F_CURRENT_NETNS, 0);
176	else
177		sk = bpf_sk_lookup_udp(ctx, &tuple, sizeof(tuple.ipv4),
178				       BPF_F_CURRENT_NETNS, 0);
179
180	if (!sk)
181		return 0;
182
183	if (sk->src_ip4 != tuple.ipv4.daddr ||
184	    sk->src_port != DST_REWRITE_PORT4) {
185		bpf_sk_release(sk);
186		return 0;
187	}
188
189	bpf_sk_release(sk);
190
191	/* Rewrite congestion control. */
192	if (ctx->type == SOCK_STREAM && set_cc(ctx))
193		return 0;
194
195	/* Rewrite destination. */
196	ctx->user_ip4 = bpf_htonl(DST_REWRITE_IP4);
197	ctx->user_port = bpf_htons(DST_REWRITE_PORT4);
198
199	return do_bind(ctx) ? 1 : 0;
200}
201
202SEC("cgroup/connect4")
203int connect_v4_deny_prog(struct bpf_sock_addr *ctx)
204{
205	return 0;
206}
207
208char _license[] SEC("license") = "GPL";
209