1 // SPDX-License-Identifier: GPL-2.0
2
3 #include <string.h>
4
5 #include <linux/stddef.h>
6 #include <linux/bpf.h>
7 #include <linux/in.h>
8 #include <linux/in6.h>
9 #include <linux/if.h>
10 #include <errno.h>
11
12 #include <bpf/bpf_helpers.h>
13 #include <bpf/bpf_endian.h>
14
15 #define SERV4_IP 0xc0a801feU /* 192.168.1.254 */
16 #define SERV4_PORT 4040
17 #define SERV4_REWRITE_IP 0x7f000001U /* 127.0.0.1 */
18 #define SERV4_REWRITE_PORT 4444
19
20 #ifndef IFNAMSIZ
21 #define IFNAMSIZ 16
22 #endif
23
bind_to_device(struct bpf_sock_addr * ctx)24 static __inline int bind_to_device(struct bpf_sock_addr *ctx)
25 {
26 char veth1[IFNAMSIZ] = "test_sock_addr1";
27 char veth2[IFNAMSIZ] = "test_sock_addr2";
28 char missing[IFNAMSIZ] = "nonexistent_dev";
29 char del_bind[IFNAMSIZ] = "";
30 int veth1_idx, veth2_idx;
31
32 if (bpf_setsockopt(ctx, SOL_SOCKET, SO_BINDTODEVICE,
33 &veth1, sizeof(veth1)))
34 return 1;
35 if (bpf_getsockopt(ctx, SOL_SOCKET, SO_BINDTOIFINDEX,
36 &veth1_idx, sizeof(veth1_idx)) || !veth1_idx)
37 return 1;
38 if (bpf_setsockopt(ctx, SOL_SOCKET, SO_BINDTODEVICE,
39 &veth2, sizeof(veth2)))
40 return 1;
41 if (bpf_getsockopt(ctx, SOL_SOCKET, SO_BINDTOIFINDEX,
42 &veth2_idx, sizeof(veth2_idx)) || !veth2_idx ||
43 veth1_idx == veth2_idx)
44 return 1;
45 if (bpf_setsockopt(ctx, SOL_SOCKET, SO_BINDTODEVICE,
46 &missing, sizeof(missing)) != -ENODEV)
47 return 1;
48 if (bpf_setsockopt(ctx, SOL_SOCKET, SO_BINDTOIFINDEX,
49 &veth1_idx, sizeof(veth1_idx)))
50 return 1;
51 if (bpf_setsockopt(ctx, SOL_SOCKET, SO_BINDTODEVICE,
52 &del_bind, sizeof(del_bind)))
53 return 1;
54
55 return 0;
56 }
57
bind_reuseport(struct bpf_sock_addr * ctx)58 static __inline int bind_reuseport(struct bpf_sock_addr *ctx)
59 {
60 int val = 1;
61
62 if (bpf_setsockopt(ctx, SOL_SOCKET, SO_REUSEPORT,
63 &val, sizeof(val)))
64 return 1;
65 if (bpf_getsockopt(ctx, SOL_SOCKET, SO_REUSEPORT,
66 &val, sizeof(val)) || !val)
67 return 1;
68 val = 0;
69 if (bpf_setsockopt(ctx, SOL_SOCKET, SO_REUSEPORT,
70 &val, sizeof(val)))
71 return 1;
72 if (bpf_getsockopt(ctx, SOL_SOCKET, SO_REUSEPORT,
73 &val, sizeof(val)) || val)
74 return 1;
75
76 return 0;
77 }
78
misc_opts(struct bpf_sock_addr * ctx,int opt)79 static __inline int misc_opts(struct bpf_sock_addr *ctx, int opt)
80 {
81 int old, tmp, new = 0xeb9f;
82
83 /* Socket in test case has guarantee that old never equals to new. */
84 if (bpf_getsockopt(ctx, SOL_SOCKET, opt, &old, sizeof(old)) ||
85 old == new)
86 return 1;
87 if (bpf_setsockopt(ctx, SOL_SOCKET, opt, &new, sizeof(new)))
88 return 1;
89 if (bpf_getsockopt(ctx, SOL_SOCKET, opt, &tmp, sizeof(tmp)) ||
90 tmp != new)
91 return 1;
92 if (bpf_setsockopt(ctx, SOL_SOCKET, opt, &old, sizeof(old)))
93 return 1;
94
95 return 0;
96 }
97
98 SEC("cgroup/bind4")
bind_v4_prog(struct bpf_sock_addr * ctx)99 int bind_v4_prog(struct bpf_sock_addr *ctx)
100 {
101 struct bpf_sock *sk;
102 __u32 user_ip4;
103 __u16 user_port;
104
105 sk = ctx->sk;
106 if (!sk)
107 return 0;
108
109 if (sk->family != AF_INET)
110 return 0;
111
112 if (ctx->type != SOCK_STREAM && ctx->type != SOCK_DGRAM)
113 return 0;
114
115 if (ctx->user_ip4 != bpf_htonl(SERV4_IP) ||
116 ctx->user_port != bpf_htons(SERV4_PORT))
117 return 0;
118
119 // u8 narrow loads:
120 user_ip4 = 0;
121 user_ip4 |= ((volatile __u8 *)&ctx->user_ip4)[0] << 0;
122 user_ip4 |= ((volatile __u8 *)&ctx->user_ip4)[1] << 8;
123 user_ip4 |= ((volatile __u8 *)&ctx->user_ip4)[2] << 16;
124 user_ip4 |= ((volatile __u8 *)&ctx->user_ip4)[3] << 24;
125 if (ctx->user_ip4 != user_ip4)
126 return 0;
127
128 user_port = 0;
129 user_port |= ((volatile __u8 *)&ctx->user_port)[0] << 0;
130 user_port |= ((volatile __u8 *)&ctx->user_port)[1] << 8;
131 if (ctx->user_port != user_port)
132 return 0;
133
134 // u16 narrow loads:
135 user_ip4 = 0;
136 user_ip4 |= ((volatile __u16 *)&ctx->user_ip4)[0] << 0;
137 user_ip4 |= ((volatile __u16 *)&ctx->user_ip4)[1] << 16;
138 if (ctx->user_ip4 != user_ip4)
139 return 0;
140
141 /* Bind to device and unbind it. */
142 if (bind_to_device(ctx))
143 return 0;
144
145 /* Test for misc socket options. */
146 if (misc_opts(ctx, SO_MARK) || misc_opts(ctx, SO_PRIORITY))
147 return 0;
148
149 /* Set reuseport and unset */
150 if (bind_reuseport(ctx))
151 return 0;
152
153 ctx->user_ip4 = bpf_htonl(SERV4_REWRITE_IP);
154 ctx->user_port = bpf_htons(SERV4_REWRITE_PORT);
155
156 return 1;
157 }
158
159 char _license[] SEC("license") = "GPL";
160