1 | // SPDX-License-Identifier: GPL-2.0 |
2 | #include <string.h> |
3 | #include <stdbool.h> |
4 | |
5 | #include <linux/bpf.h> |
6 | #include <linux/in.h> |
7 | #include <linux/in6.h> |
8 | #include <sys/socket.h> |
9 | |
10 | #include <bpf/bpf_helpers.h> |
11 | #include <bpf/bpf_endian.h> |
12 | |
13 | #include <bpf_sockopt_helpers.h> |
14 | |
15 | char _license[] SEC("license" ) = "GPL" ; |
16 | |
17 | struct svc_addr { |
18 | __be32 addr; |
19 | __be16 port; |
20 | }; |
21 | |
22 | struct { |
23 | __uint(type, BPF_MAP_TYPE_SK_STORAGE); |
24 | __uint(map_flags, BPF_F_NO_PREALLOC); |
25 | __type(key, int); |
26 | __type(value, struct svc_addr); |
27 | } service_mapping SEC(".maps" ); |
28 | |
29 | SEC("cgroup/connect4" ) |
30 | int connect4(struct bpf_sock_addr *ctx) |
31 | { |
32 | struct sockaddr_in sa = {}; |
33 | struct svc_addr *orig; |
34 | |
35 | /* Force local address to 127.0.0.1:22222. */ |
36 | sa.sin_family = AF_INET; |
37 | sa.sin_port = bpf_htons(22222); |
38 | sa.sin_addr.s_addr = bpf_htonl(0x7f000001); |
39 | |
40 | if (bpf_bind(ctx, (struct sockaddr *)&sa, sizeof(sa)) != 0) |
41 | return 0; |
42 | |
43 | /* Rewire service 1.2.3.4:60000 to backend 127.0.0.1:60123. */ |
44 | if (ctx->user_port == bpf_htons(60000)) { |
45 | orig = bpf_sk_storage_get(&service_mapping, ctx->sk, 0, |
46 | BPF_SK_STORAGE_GET_F_CREATE); |
47 | if (!orig) |
48 | return 0; |
49 | |
50 | orig->addr = ctx->user_ip4; |
51 | orig->port = ctx->user_port; |
52 | |
53 | ctx->user_ip4 = bpf_htonl(0x7f000001); |
54 | ctx->user_port = bpf_htons(60123); |
55 | } |
56 | return 1; |
57 | } |
58 | |
59 | SEC("cgroup/getsockname4" ) |
60 | int getsockname4(struct bpf_sock_addr *ctx) |
61 | { |
62 | if (!get_set_sk_priority(ctx)) |
63 | return 1; |
64 | |
65 | /* Expose local server as 1.2.3.4:60000 to client. */ |
66 | if (ctx->user_port == bpf_htons(60123)) { |
67 | ctx->user_ip4 = bpf_htonl(0x01020304); |
68 | ctx->user_port = bpf_htons(60000); |
69 | } |
70 | return 1; |
71 | } |
72 | |
73 | SEC("cgroup/getpeername4" ) |
74 | int getpeername4(struct bpf_sock_addr *ctx) |
75 | { |
76 | struct svc_addr *orig; |
77 | |
78 | if (!get_set_sk_priority(ctx)) |
79 | return 1; |
80 | |
81 | /* Expose service 1.2.3.4:60000 as peer instead of backend. */ |
82 | if (ctx->user_port == bpf_htons(60123)) { |
83 | orig = bpf_sk_storage_get(&service_mapping, ctx->sk, 0, 0); |
84 | if (orig) { |
85 | ctx->user_ip4 = orig->addr; |
86 | ctx->user_port = orig->port; |
87 | } |
88 | } |
89 | return 1; |
90 | } |
91 | |