connect4_prog.c

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