1 // SPDX-License-Identifier: GPL-2.0
2 #include <string.h>
3 
4 #include <linux/bpf.h>
5 #include <linux/in.h>
6 #include <linux/in6.h>
7 #include <sys/socket.h>
8 
9 #include <bpf/bpf_helpers.h>
10 #include <bpf/bpf_endian.h>
11 
12 #include <bpf_sockopt_helpers.h>
13 
14 char _license[] SEC("license") = "GPL";
15 
16 struct svc_addr {
17 	__be32 addr[4];
18 	__be16 port;
19 };
20 
21 struct {
22 	__uint(type, BPF_MAP_TYPE_SK_STORAGE);
23 	__uint(map_flags, BPF_F_NO_PREALLOC);
24 	__type(key, int);
25 	__type(value, struct svc_addr);
26 } service_mapping SEC(".maps");
27 
28 SEC("cgroup/connect6")
connect6(struct bpf_sock_addr * ctx)29 int connect6(struct bpf_sock_addr *ctx)
30 {
31 	struct sockaddr_in6 sa = {};
32 	struct svc_addr *orig;
33 
34 	/* Force local address to [::1]:22223. */
35 	sa.sin6_family = AF_INET6;
36 	sa.sin6_port = bpf_htons(22223);
37 	sa.sin6_addr.s6_addr32[3] = bpf_htonl(1);
38 
39 	if (bpf_bind(ctx, (struct sockaddr *)&sa, sizeof(sa)) != 0)
40 		return 0;
41 
42 	/* Rewire service [fc00::1]:60000 to backend [::1]:60124. */
43 	if (ctx->user_port == bpf_htons(60000)) {
44 		orig = bpf_sk_storage_get(&service_mapping, ctx->sk, 0,
45 					  BPF_SK_STORAGE_GET_F_CREATE);
46 		if (!orig)
47 			return 0;
48 
49 		orig->addr[0] = ctx->user_ip6[0];
50 		orig->addr[1] = ctx->user_ip6[1];
51 		orig->addr[2] = ctx->user_ip6[2];
52 		orig->addr[3] = ctx->user_ip6[3];
53 		orig->port = ctx->user_port;
54 
55 		ctx->user_ip6[0] = 0;
56 		ctx->user_ip6[1] = 0;
57 		ctx->user_ip6[2] = 0;
58 		ctx->user_ip6[3] = bpf_htonl(1);
59 		ctx->user_port = bpf_htons(60124);
60 	}
61 	return 1;
62 }
63 
64 SEC("cgroup/getsockname6")
getsockname6(struct bpf_sock_addr * ctx)65 int getsockname6(struct bpf_sock_addr *ctx)
66 {
67 	if (!get_set_sk_priority(ctx))
68 		return 1;
69 
70 	/* Expose local server as [fc00::1]:60000 to client. */
71 	if (ctx->user_port == bpf_htons(60124)) {
72 		ctx->user_ip6[0] = bpf_htonl(0xfc000000);
73 		ctx->user_ip6[1] = 0;
74 		ctx->user_ip6[2] = 0;
75 		ctx->user_ip6[3] = bpf_htonl(1);
76 		ctx->user_port = bpf_htons(60000);
77 	}
78 	return 1;
79 }
80 
81 SEC("cgroup/getpeername6")
getpeername6(struct bpf_sock_addr * ctx)82 int getpeername6(struct bpf_sock_addr *ctx)
83 {
84 	struct svc_addr *orig;
85 
86 	if (!get_set_sk_priority(ctx))
87 		return 1;
88 
89 	/* Expose service [fc00::1]:60000 as peer instead of backend. */
90 	if (ctx->user_port == bpf_htons(60124)) {
91 		orig = bpf_sk_storage_get(&service_mapping, ctx->sk, 0, 0);
92 		if (orig) {
93 			ctx->user_ip6[0] = orig->addr[0];
94 			ctx->user_ip6[1] = orig->addr[1];
95 			ctx->user_ip6[2] = orig->addr[2];
96 			ctx->user_ip6[3] = orig->addr[3];
97 			ctx->user_port = orig->port;
98 		}
99 	}
100 	return 1;
101 }
102