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98 lines
2.8 KiB
C
98 lines
2.8 KiB
C
/*
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* Copyright 1994, 1995 Massachusetts Institute of Technology
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*
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* Permission to use, copy, modify, and distribute this software and
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* its documentation for any purpose and without fee is hereby
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* granted, provided that both the above copyright notice and this
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* permission notice appear in all copies, that both the above
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* copyright notice and this permission notice appear in all
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* supporting documentation, and that the name of M.I.T. not be used
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* in advertising or publicity pertaining to distribution of the
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* software without specific, written prior permission. M.I.T. makes
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* no representations about the suitability of this software for any
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* purpose. It is provided "as is" without express or implied
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* warranty.
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*
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* THIS SOFTWARE IS PROVIDED BY M.I.T. ``AS IS''. M.I.T. DISCLAIMS
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* ALL EXPRESS OR IMPLIED WARRANTIES WITH REGARD TO THIS SOFTWARE,
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* INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
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* MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT
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* SHALL M.I.T. BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
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* USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
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* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
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* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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/*
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* From:
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* Id: find_interface.c,v 1.1 1995/08/14 16:08:39 wollman Exp
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*/
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#include <errno.h>
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#include <string.h>
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#include <unistd.h>
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#include "talk.h"
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/*
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* Try to find the interface address that is used to route an IP
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* packet to a remote peer.
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*/
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int
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get_iface(struct in_addr *dst, struct in_addr *iface)
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{
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static struct sockaddr_in local;
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struct sockaddr_in remote;
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socklen_t namelen;
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int s, rv;
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memcpy(&remote.sin_addr, dst, sizeof remote.sin_addr);
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remote.sin_port = htons(60000);
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remote.sin_family = AF_INET;
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remote.sin_len = sizeof remote;
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local.sin_addr.s_addr = htonl(INADDR_ANY);
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local.sin_port = htons(60000);
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local.sin_family = AF_INET;
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local.sin_len = sizeof local;
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s = socket(PF_INET, SOCK_DGRAM, 0);
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if (s < 0)
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return -1;
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do {
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rv = bind(s, (struct sockaddr *)&local, sizeof local);
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local.sin_port = htons(ntohs(local.sin_port) + 1);
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} while(rv < 0 && errno == EADDRINUSE);
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if (rv < 0) {
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close(s);
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return -1;
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}
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do {
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rv = connect(s, (struct sockaddr *)&remote, sizeof remote);
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remote.sin_port = htons(ntohs(remote.sin_port) + 1);
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} while(rv < 0 && errno == EADDRINUSE);
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if (rv < 0) {
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close(s);
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return -1;
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}
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namelen = sizeof local;
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rv = getsockname(s, (struct sockaddr *)&local, &namelen);
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close(s);
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if (rv < 0)
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return -1;
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memcpy(iface, &local.sin_addr, sizeof local.sin_addr);
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return 0;
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}
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