1 /* 2 * Copyright 1994, 1995 Massachusetts Institute of Technology 3 * 4 * Permission to use, copy, modify, and distribute this software and 5 * its documentation for any purpose and without fee is hereby 6 * granted, provided that both the above copyright notice and this 7 * permission notice appear in all copies, that both the above 8 * copyright notice and this permission notice appear in all 9 * supporting documentation, and that the name of M.I.T. not be used 10 * in advertising or publicity pertaining to distribution of the 11 * software without specific, written prior permission. M.I.T. makes 12 * no representations about the suitability of this software for any 13 * purpose. It is provided "as is" without express or implied 14 * warranty. 15 * 16 * THIS SOFTWARE IS PROVIDED BY M.I.T. ``AS IS''. M.I.T. DISCLAIMS 17 * ALL EXPRESS OR IMPLIED WARRANTIES WITH REGARD TO THIS SOFTWARE, 18 * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF 19 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT 20 * SHALL M.I.T. BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 21 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 22 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF 23 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND 24 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, 25 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT 26 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 27 * SUCH DAMAGE. 28 * 29 * From: 30 * Id: find_interface.c,v 1.1 1995/08/14 16:08:39 wollman Exp 31 * 32 * $FreeBSD: src/usr.bin/talk/get_iface.c,v 1.7 1999/08/28 01:06:12 peter Exp $ 33 * $DragonFly: src/usr.bin/talk/get_iface.c,v 1.3 2003/10/04 20:36:52 hmp Exp $ 34 */ 35 36 #include <errno.h> 37 #include <string.h> 38 #include "talk.h" 39 40 /* 41 * Try to find the interface address that is used to route an IP 42 * packet to a remote peer. 43 */ 44 45 int 46 get_iface(struct in_addr *dst, struct in_addr *iface) 47 { 48 static struct sockaddr_in local; 49 struct sockaddr_in remote; 50 struct hostent *hp; 51 int s, rv, namelen; 52 53 memcpy(&remote.sin_addr, dst, sizeof remote.sin_addr); 54 remote.sin_port = htons(60000); 55 remote.sin_family = AF_INET; 56 remote.sin_len = sizeof remote; 57 58 local.sin_addr.s_addr = htonl(INADDR_ANY); 59 local.sin_port = htons(60000); 60 local.sin_family = AF_INET; 61 local.sin_len = sizeof local; 62 63 s = socket(PF_INET, SOCK_DGRAM, 0); 64 if (s < 0) 65 return -1; 66 67 do { 68 rv = bind(s, (struct sockaddr *)&local, sizeof local); 69 local.sin_port = htons(ntohs(local.sin_port) + 1); 70 } while(rv < 0 && errno == EADDRINUSE); 71 72 if (rv < 0) { 73 close(s); 74 return -1; 75 } 76 77 do { 78 rv = connect(s, (struct sockaddr *)&remote, sizeof remote); 79 remote.sin_port = htons(ntohs(remote.sin_port) + 1); 80 } while(rv < 0 && errno == EADDRINUSE); 81 82 if (rv < 0) { 83 close(s); 84 return -1; 85 } 86 87 namelen = sizeof local; 88 rv = getsockname(s, (struct sockaddr *)&local, &namelen); 89 close(s); 90 if (rv < 0) 91 return -1; 92 93 memcpy(iface, &local.sin_addr, sizeof local.sin_addr); 94 return 0; 95 } 96