1/*
2 * Copyright (c) 2014-2015 Dmitry V. Levin <ldv@altlinux.org>
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 *    notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 *    notice, this list of conditions and the following disclaimer in the
12 *    documentation and/or other materials provided with the distribution.
13 * 3. The name of the author may not be used to endorse or promote products
14 *    derived from this software without specific prior written permission.
15 *
16 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
17 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
18 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
19 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
20 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
21 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
22 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
23 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
24 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
25 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
26 */
27
28#include <assert.h>
29#include <string.h>
30#include <unistd.h>
31#include <netinet/in.h>
32#include <linux/netlink.h>
33#include <linux/sock_diag.h>
34#include <linux/inet_diag.h>
35
36static int
37send_query(const int fd, const int family, const int proto)
38{
39	struct sockaddr_nl nladdr = {
40		.nl_family = AF_NETLINK
41	};
42	struct {
43		struct nlmsghdr nlh;
44		struct inet_diag_req_v2 idr;
45	} req = {
46		.nlh = {
47			.nlmsg_len = sizeof(req),
48			.nlmsg_type = SOCK_DIAG_BY_FAMILY,
49			.nlmsg_flags = NLM_F_DUMP | NLM_F_REQUEST
50		},
51		.idr = {
52			.sdiag_family = family,
53			.sdiag_protocol = proto,
54			.idiag_states = -1
55		}
56	};
57	struct iovec iov = {
58		.iov_base = &req,
59		.iov_len = sizeof(req)
60	};
61	struct msghdr msg = {
62		.msg_name = (void*)&nladdr,
63		.msg_namelen = sizeof(nladdr),
64		.msg_iov = &iov,
65		.msg_iovlen = 1
66	};
67
68	return sendmsg(fd, &msg, 0) > 0;
69}
70
71static int
72check_responses(const int fd)
73{
74	static char buf[8192];
75	struct sockaddr_nl nladdr = {
76		.nl_family = AF_NETLINK
77	};
78	struct iovec iov = {
79		.iov_base = buf,
80		.iov_len = sizeof(buf)
81	};
82	struct msghdr msg = {
83		.msg_name = (void*)&nladdr,
84		.msg_namelen = sizeof(nladdr),
85		.msg_iov = &iov,
86		.msg_iovlen = 1
87	};
88
89	ssize_t ret = recvmsg(fd, &msg, 0);
90	if (ret <= 0)
91		return 0;
92
93	struct nlmsghdr *h = (struct nlmsghdr*)buf;
94	return (NLMSG_OK(h, ret) &&
95		h->nlmsg_type != NLMSG_ERROR &&
96		h->nlmsg_type != NLMSG_DONE) ? 1 : 0;
97}
98
99int main(void)
100{
101	struct sockaddr_in addr;
102	socklen_t len = sizeof(addr);
103
104	memset(&addr, 0, sizeof(addr));
105	addr.sin_family = AF_INET;
106	addr.sin_addr.s_addr = htonl(INADDR_LOOPBACK);
107
108	close(0);
109	close(1);
110
111	if (socket(PF_INET, SOCK_STREAM, 0) ||
112	    bind(0, (struct sockaddr *) &addr, len) ||
113	    listen(0, 5) ||
114	    socket(AF_NETLINK, SOCK_RAW, NETLINK_INET_DIAG) != 1)
115		return 77;
116
117	return (send_query(1, AF_INET, IPPROTO_TCP) &&
118		check_responses(1)) ? 0 : 77;
119}
120