examples/find_interface/find_interface.c

/* $MidnightBSD$ */
/*
 * Copyright 1994, 1995 Massachusetts Institute of Technology
 *
 * Permission to use, copy, modify, and distribute this software and
 * its documentation for any purpose and without fee is hereby
 * granted, provided that both the above copyright notice and this
 * permission notice appear in all copies, that both the above
 * copyright notice and this permission notice appear in all
 * supporting documentation, and that the name of M.I.T. not be used
 * in advertising or publicity pertaining to distribution of the
 * software without specific, written prior permission.  M.I.T. makes
 * no representations about the suitability of this software for any
 * purpose.  It is provided "as is" without express or implied
 * warranty.
 * 
 * THIS SOFTWARE IS PROVIDED BY M.I.T. ``AS IS''.  M.I.T. DISCLAIMS
 * ALL EXPRESS OR IMPLIED WARRANTIES WITH REGARD TO THIS SOFTWARE,
 * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT
 * SHALL M.I.T. BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 * $FreeBSD: stable/10/share/examples/find_interface/find_interface.c 50476 1999-08-28 00:22:10Z peter $
 */

/*
 * This is a simple program which demonstrates how to query the kernel
 * routing mechanism using only a UDP socket.  Pass it a hostname on
 * the command line (sorry, it doesn't parse dotted decimal) and it will
 * print out an IP address which names the interface over which UDP
 * packets intended for that destination would be sent.
 * A more sophisticated program might use the list obtained from SIOCGIFCONF
 * to match the address with an interface name, but applications programmers
 * much more often need to know the address of the interface rather than
 * the name.
 */
#include <sys/types.h>
#include <sys/socket.h>
#include <unistd.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <stdlib.h>
#include <stdio.h>
#include <netdb.h>
#include <err.h>
#include <errno.h>
#include <string.h>
#include <sysexits.h>

int
main(int argc, char **argv)
{
        struct sockaddr_in local, remote;
        struct hostent *hp;
        int s, rv, namelen;

        argc--, argv++;

        if (!*argv) {
                errx(EX_USAGE, "must supply a hostname");
        }

        hp = gethostbyname(*argv);
        if (!hp) {
                errx(EX_NOHOST, "cannot resolve hostname: %s", *argv);
        }

        memcpy(&remote.sin_addr, hp->h_addr_list[0], sizeof remote.sin_addr);
        remote.sin_port = htons(60000);
        remote.sin_family = AF_INET;
        remote.sin_len = sizeof remote;

        local.sin_addr.s_addr = htonl(INADDR_ANY);
        local.sin_port = htons(60000);
        local.sin_family = AF_INET;
        local.sin_len = sizeof local;

        s = socket(PF_INET, SOCK_DGRAM, 0);
        if (s < 0)
                err(EX_OSERR, "socket");

        do {
                rv = bind(s, (struct sockaddr *)&local, sizeof local);
                local.sin_port = htons(ntohs(local.sin_port) + 1);
        } while(rv < 0 && errno == EADDRINUSE);

        if (rv < 0)
                err(EX_OSERR, "bind");

        do {
                rv = connect(s, (struct sockaddr *)&remote, sizeof remote);
                remote.sin_port = htons(ntohs(remote.sin_port) + 1);
        } while(rv < 0 && errno == EADDRINUSE);

        if (rv < 0)
                err(EX_OSERR, "connect");

        namelen = sizeof local;
        rv = getsockname(s, (struct sockaddr *)&local, &namelen);
        if (rv < 0)
                err(EX_OSERR, "getsockname");

        printf("Route to %s is out %s\n", *argv, inet_ntoa(local.sin_addr));
        return 0;
}
Revision:	11829
Committed:	Fri Jul 13 00:06:52 2018 UTC (5 years, 9 months ago) by laffer1
Content type:	text/plain
File size:	3766 byte(s)
Log Message:	tag
#	Content
1	/* $MidnightBSD$ */
2	/*
3	* Copyright 1994, 1995 Massachusetts Institute of Technology
4	*
5	* Permission to use, copy, modify, and distribute this software and
6	* its documentation for any purpose and without fee is hereby
7	* granted, provided that both the above copyright notice and this
8	* permission notice appear in all copies, that both the above
9	* copyright notice and this permission notice appear in all
10	* supporting documentation, and that the name of M.I.T. not be used
11	* in advertising or publicity pertaining to distribution of the
12	* software without specific, written prior permission. M.I.T. makes
13	* no representations about the suitability of this software for any
14	* purpose. It is provided "as is" without express or implied
15	* warranty.
16	*
17	* THIS SOFTWARE IS PROVIDED BY M.I.T. ``AS IS''. M.I.T. DISCLAIMS
18	* ALL EXPRESS OR IMPLIED WARRANTIES WITH REGARD TO THIS SOFTWARE,
19	* INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
20	* MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT
21	* SHALL M.I.T. BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
22	* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
23	* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
24	* USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
25	* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
26	* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
27	* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
28	* SUCH DAMAGE.
29	*
30	* $FreeBSD: stable/10/share/examples/find_interface/find_interface.c 50476 1999-08-28 00:22:10Z peter $
31	*/
32
33	/*
34	* This is a simple program which demonstrates how to query the kernel
35	* routing mechanism using only a UDP socket. Pass it a hostname on
36	* the command line (sorry, it doesn't parse dotted decimal) and it will
37	* print out an IP address which names the interface over which UDP
38	* packets intended for that destination would be sent.
39	* A more sophisticated program might use the list obtained from SIOCGIFCONF
40	* to match the address with an interface name, but applications programmers
41	* much more often need to know the address of the interface rather than
42	* the name.
43	*/
44	#include <sys/types.h>
45	#include <sys/socket.h>
46	#include <unistd.h>
47	#include <netinet/in.h>
48	#include <arpa/inet.h>
49	#include <stdlib.h>
50	#include <stdio.h>
51	#include <netdb.h>
52	#include <err.h>
53	#include <errno.h>
54	#include <string.h>
55	#include <sysexits.h>
56
57	int
58	main(int argc, char **argv)
59	{
60	struct sockaddr_in local, remote;
61	struct hostent *hp;
62	int s, rv, namelen;
63
64	argc--, argv++;
65
66	if (!*argv) {
67	errx(EX_USAGE, "must supply a hostname");
68	}
69
70	hp = gethostbyname(*argv);
71	if (!hp) {
72	errx(EX_NOHOST, "cannot resolve hostname: %s", *argv);
73	}
74
75	memcpy(&remote.sin_addr, hp->h_addr_list[0], sizeof remote.sin_addr);
76	remote.sin_port = htons(60000);
77	remote.sin_family = AF_INET;
78	remote.sin_len = sizeof remote;
79
80	local.sin_addr.s_addr = htonl(INADDR_ANY);
81	local.sin_port = htons(60000);
82	local.sin_family = AF_INET;
83	local.sin_len = sizeof local;
84
85	s = socket(PF_INET, SOCK_DGRAM, 0);
86	if (s < 0)
87	err(EX_OSERR, "socket");
88
89	do {
90	rv = bind(s, (struct sockaddr *)&local, sizeof local);
91	local.sin_port = htons(ntohs(local.sin_port) + 1);
92	} while(rv < 0 && errno == EADDRINUSE);
93
94	if (rv < 0)
95	err(EX_OSERR, "bind");
96
97	do {
98	rv = connect(s, (struct sockaddr *)&remote, sizeof remote);
99	remote.sin_port = htons(ntohs(remote.sin_port) + 1);
100	} while(rv < 0 && errno == EADDRINUSE);
101
102	if (rv < 0)
103	err(EX_OSERR, "connect");
104
105	namelen = sizeof local;
106	rv = getsockname(s, (struct sockaddr *)&local, &namelen);
107	if (rv < 0)
108	err(EX_OSERR, "getsockname");
109
110	printf("Route to %s is out %s\n", *argv, inet_ntoa(local.sin_addr));
111	return 0;
112	}