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
14char _license[] SEC("license") = "GPL";
15
16struct svc_addr {
17	__be32 addr[4];
18	__be16 port;
19};
20
21struct {
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
28SEC("cgroup/connect6")
29int 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
64SEC("cgroup/getsockname6")
65int 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
81SEC("cgroup/getpeername6")
82int 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