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      1 /*
      2  * Copyright (c) 2014-2015 Dmitry V. Levin <ldv (at) 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 
     36 static int
     37 send_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 
     71 static int
     72 check_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 
     99 int 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