tjh.dev
Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
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
13char _license[] SEC("license") = "GPL";
14int _version SEC("version") = 1;
15
16struct svc_addr {
17 __be32 addr;
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/connect4")
29int connect4(struct bpf_sock_addr *ctx)
30{
31 struct sockaddr_in sa = {};
32 struct svc_addr *orig;
33
34 /* Force local address to 127.0.0.1:22222. */
35 sa.sin_family = AF_INET;
36 sa.sin_port = bpf_htons(22222);
37 sa.sin_addr.s_addr = bpf_htonl(0x7f000001);
38
39 if (bpf_bind(ctx, (struct sockaddr *)&sa, sizeof(sa)) != 0)
40 return 0;
41
42 /* Rewire service 1.2.3.4:60000 to backend 127.0.0.1:60123. */
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 = ctx->user_ip4;
50 orig->port = ctx->user_port;
51
52 ctx->user_ip4 = bpf_htonl(0x7f000001);
53 ctx->user_port = bpf_htons(60123);
54 }
55 return 1;
56}
57
58SEC("cgroup/getsockname4")
59int getsockname4(struct bpf_sock_addr *ctx)
60{
61 /* Expose local server as 1.2.3.4:60000 to client. */
62 if (ctx->user_port == bpf_htons(60123)) {
63 ctx->user_ip4 = bpf_htonl(0x01020304);
64 ctx->user_port = bpf_htons(60000);
65 }
66 return 1;
67}
68
69SEC("cgroup/getpeername4")
70int getpeername4(struct bpf_sock_addr *ctx)
71{
72 struct svc_addr *orig;
73
74 /* Expose service 1.2.3.4:60000 as peer instead of backend. */
75 if (ctx->user_port == bpf_htons(60123)) {
76 orig = bpf_sk_storage_get(&service_mapping, ctx->sk, 0, 0);
77 if (orig) {
78 ctx->user_ip4 = orig->addr;
79 ctx->user_port = orig->port;
80 }
81 }
82 return 1;
83}