xref: /linux/tools/testing/selftests/bpf/progs/sendmsg4_prog.c (revision 621cde16e49b3ecf7d59a8106a20aaebfb4a59a9)
1  // SPDX-License-Identifier: GPL-2.0
2  // Copyright (c) 2018 Facebook
3  
4  #include <linux/stddef.h>
5  #include <linux/bpf.h>
6  #include <sys/socket.h>
7  
8  #include <bpf/bpf_helpers.h>
9  #include <bpf/bpf_endian.h>
10  
11  #include <bpf_sockopt_helpers.h>
12  
13  #define SRC1_IP4		0xAC100001U /* 172.16.0.1 */
14  #define SRC2_IP4		0x00000000U
15  #define SRC_REWRITE_IP4		0x7f000004U
16  #define DST_IP4			0xC0A801FEU /* 192.168.1.254 */
17  #define DST_REWRITE_IP4		0x7f000001U
18  #define DST_PORT		4040
19  #define DST_REWRITE_PORT4	4444
20  
21  SEC("cgroup/sendmsg4")
sendmsg_v4_prog(struct bpf_sock_addr * ctx)22  int sendmsg_v4_prog(struct bpf_sock_addr *ctx)
23  {
24  	if (ctx->type != SOCK_DGRAM)
25  		return 0;
26  
27  	if (!get_set_sk_priority(ctx))
28  		return 0;
29  
30  	/* Rewrite source. */
31  	if (ctx->msg_src_ip4 == bpf_htonl(SRC1_IP4) ||
32  	    ctx->msg_src_ip4 == bpf_htonl(SRC2_IP4)) {
33  		ctx->msg_src_ip4 = bpf_htonl(SRC_REWRITE_IP4);
34  	} else {
35  		/* Unexpected source. Reject sendmsg. */
36  		return 0;
37  	}
38  
39  	/* Rewrite destination. */
40  	if ((ctx->user_ip4 >> 24) == (bpf_htonl(DST_IP4) >> 24) &&
41  	     ctx->user_port == bpf_htons(DST_PORT)) {
42  		ctx->user_ip4 = bpf_htonl(DST_REWRITE_IP4);
43  		ctx->user_port = bpf_htons(DST_REWRITE_PORT4);
44  	} else {
45  		/* Unexpected source. Reject sendmsg. */
46  		return 0;
47  	}
48  
49  	return 1;
50  }
51  
52  SEC("cgroup/sendmsg4")
sendmsg_v4_deny_prog(struct bpf_sock_addr * ctx)53  int sendmsg_v4_deny_prog(struct bpf_sock_addr *ctx)
54  {
55  	return 0;
56  }
57  
58  char _license[] SEC("license") = "GPL";
59