1
2
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))
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
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
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
191 if (ctx->type == SOCK_STREAM && set_cc(ctx))
192 return 0;
193
194
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
