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")
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")
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")
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
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