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 
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 
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 
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")
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