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/bpf_helpers.h>
13 #include <bpf/bpf_endian.h>
14 
15 #define SRC_REWRITE_IP6_0	0
16 #define SRC_REWRITE_IP6_1	0
17 #define SRC_REWRITE_IP6_2	0
18 #define SRC_REWRITE_IP6_3	6
19 
20 #define DST_REWRITE_IP6_0	0
21 #define DST_REWRITE_IP6_1	0
22 #define DST_REWRITE_IP6_2	0
23 #define DST_REWRITE_IP6_3	1
24 
25 #define DST_REWRITE_PORT6	6666
26 
27 int _version SEC("version") = 1;
28 
29 SEC("cgroup/connect6")
30 int connect_v6_prog(struct bpf_sock_addr *ctx)
31 {
32 	struct bpf_sock_tuple tuple = {};
33 	struct sockaddr_in6 sa;
34 	struct bpf_sock *sk;
35 
36 	/* Verify that new destination is available. */
37 	memset(&tuple.ipv6.saddr, 0, sizeof(tuple.ipv6.saddr));
38 	memset(&tuple.ipv6.sport, 0, sizeof(tuple.ipv6.sport));
39 
40 	tuple.ipv6.daddr[0] = bpf_htonl(DST_REWRITE_IP6_0);
41 	tuple.ipv6.daddr[1] = bpf_htonl(DST_REWRITE_IP6_1);
42 	tuple.ipv6.daddr[2] = bpf_htonl(DST_REWRITE_IP6_2);
43 	tuple.ipv6.daddr[3] = bpf_htonl(DST_REWRITE_IP6_3);
44 
45 	tuple.ipv6.dport = bpf_htons(DST_REWRITE_PORT6);
46 
47 	if (ctx->type != SOCK_STREAM && ctx->type != SOCK_DGRAM)
48 		return 0;
49 	else if (ctx->type == SOCK_STREAM)
50 		sk = bpf_sk_lookup_tcp(ctx, &tuple, sizeof(tuple.ipv6),
51 				       BPF_F_CURRENT_NETNS, 0);
52 	else
53 		sk = bpf_sk_lookup_udp(ctx, &tuple, sizeof(tuple.ipv6),
54 				       BPF_F_CURRENT_NETNS, 0);
55 
56 	if (!sk)
57 		return 0;
58 
59 	if (sk->src_ip6[0] != tuple.ipv6.daddr[0] ||
60 	    sk->src_ip6[1] != tuple.ipv6.daddr[1] ||
61 	    sk->src_ip6[2] != tuple.ipv6.daddr[2] ||
62 	    sk->src_ip6[3] != tuple.ipv6.daddr[3] ||
63 	    sk->src_port != DST_REWRITE_PORT6) {
64 		bpf_sk_release(sk);
65 		return 0;
66 	}
67 
68 	bpf_sk_release(sk);
69 
70 	/* Rewrite destination. */
71 	ctx->user_ip6[0] = bpf_htonl(DST_REWRITE_IP6_0);
72 	ctx->user_ip6[1] = bpf_htonl(DST_REWRITE_IP6_1);
73 	ctx->user_ip6[2] = bpf_htonl(DST_REWRITE_IP6_2);
74 	ctx->user_ip6[3] = bpf_htonl(DST_REWRITE_IP6_3);
75 
76 	ctx->user_port = bpf_htons(DST_REWRITE_PORT6);
77 
78 	/* Rewrite source. */
79 	memset(&sa, 0, sizeof(sa));
80 
81 	sa.sin6_family = AF_INET6;
82 	sa.sin6_port = bpf_htons(0);
83 
84 	sa.sin6_addr.s6_addr32[0] = bpf_htonl(SRC_REWRITE_IP6_0);
85 	sa.sin6_addr.s6_addr32[1] = bpf_htonl(SRC_REWRITE_IP6_1);
86 	sa.sin6_addr.s6_addr32[2] = bpf_htonl(SRC_REWRITE_IP6_2);
87 	sa.sin6_addr.s6_addr32[3] = bpf_htonl(SRC_REWRITE_IP6_3);
88 
89 	if (bpf_bind(ctx, (struct sockaddr *)&sa, sizeof(sa)) != 0)
90 		return 0;
91 
92 	return 1;
93 }
94 
95 char _license[] SEC("license") = "GPL";
96