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/*
* 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.
*
* From:
* Id: find_interface.c,v 1.1 1995/08/14 16:08:39 wollman Exp
*
* $Id$
*/
#include <unistd.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include "talk.h"
/*
* Try to find the interface address that is used to route an IP
* packet to a remote peer.
*/
int
get_iface(dst, iface)
struct in_addr *dst;
struct in_addr *iface;
{
static struct sockaddr_in local;
struct sockaddr_in remote;
struct hostent *hp;
int s, rv, namelen;
memcpy(&remote.sin_addr, dst, 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)
return -1;
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) {
close(s);
return -1;
}
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) {
close(s);
return -1;
}
namelen = sizeof local;
rv = getsockname(s, (struct sockaddr *)&local, &namelen);
close(s);
if (rv < 0)
return -1;
memcpy(iface, &local.sin_addr, sizeof local.sin_addr);
return 0;
}
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