1// SPDX-License-Identifier: GPL-2.0
 2// Copyright (c) 2018 Facebook
 3
 4#include <string.h>
 5
 6#include <linux/stddef.h>
 7#include <linux/bpf.h>
 8#include <linux/in.h>
 9#include <linux/in6.h>
10#include <sys/socket.h>
11
12#include "bpf_helpers.h"
13#include "bpf_endian.h"
14
15#define SRC_REWRITE_IP4		0x7f000004U
16#define DST_REWRITE_IP4		0x7f000001U
17#define DST_REWRITE_PORT4	4444
18
19int _version SEC("version") = 1;
20
21SEC("cgroup/connect4")
22int connect_v4_prog(struct bpf_sock_addr *ctx)
23{
24	struct bpf_sock_tuple tuple = {};
25	struct sockaddr_in sa;
26	struct bpf_sock *sk;
27
28	/* Verify that new destination is available. */
29	memset(&tuple.ipv4.saddr, 0, sizeof(tuple.ipv4.saddr));
30	memset(&tuple.ipv4.sport, 0, sizeof(tuple.ipv4.sport));
31
32	tuple.ipv4.daddr = bpf_htonl(DST_REWRITE_IP4);
33	tuple.ipv4.dport = bpf_htons(DST_REWRITE_PORT4);
34
35	if (ctx->type != SOCK_STREAM && ctx->type != SOCK_DGRAM)
36		return 0;
37	else if (ctx->type == SOCK_STREAM)
38		sk = bpf_sk_lookup_tcp(ctx, &tuple, sizeof(tuple.ipv4),
39				       BPF_F_CURRENT_NETNS, 0);
40	else
41		sk = bpf_sk_lookup_udp(ctx, &tuple, sizeof(tuple.ipv4),
42				       BPF_F_CURRENT_NETNS, 0);
43
44	if (!sk)
45		return 0;
46
47	if (sk->src_ip4 != tuple.ipv4.daddr ||
48	    sk->src_port != DST_REWRITE_PORT4) {
49		bpf_sk_release(sk);
50		return 0;
51	}
52
53	bpf_sk_release(sk);
54
55	/* Rewrite destination. */
56	ctx->user_ip4 = bpf_htonl(DST_REWRITE_IP4);
57	ctx->user_port = bpf_htons(DST_REWRITE_PORT4);
58
59	/* Rewrite source. */
60	memset(&sa, 0, sizeof(sa));
61
62	sa.sin_family = AF_INET;
63	sa.sin_port = bpf_htons(0);
64	sa.sin_addr.s_addr = bpf_htonl(SRC_REWRITE_IP4);
65
66	if (bpf_bind(ctx, (struct sockaddr *)&sa, sizeof(sa)) != 0)
67		return 0;
68
69	return 1;
70}
71
72char _license[] SEC("license") = "GPL";