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 30 #include <sys/cdefs.h> 31 32 __FBSDID("$FreeBSD$"); 33 34 /* 35 * From: 36 * Id: find_interface.c,v 1.1 1995/08/14 16:08:39 wollman Exp 37 */ 38 39 #include <errno.h> 40 #include <string.h> 41 42 #include "talk.h" 43 44 /* 45 * Try to find the interface address that is used to route an IP 46 * packet to a remote peer. 47 */ 48 49 int 50 get_iface(struct in_addr *dst, struct in_addr *iface) 51 { 52 static struct sockaddr_in local; 53 struct sockaddr_in remote; 54 socklen_t namelen; 55 int s, rv; 56 57 memcpy(&remote.sin_addr, dst, sizeof remote.sin_addr); 58 remote.sin_port = htons(60000); 59 remote.sin_family = AF_INET; 60 remote.sin_len = sizeof remote; 61 62 local.sin_addr.s_addr = htonl(INADDR_ANY); 63 local.sin_port = htons(60000); 64 local.sin_family = AF_INET; 65 local.sin_len = sizeof local; 66 67 s = socket(PF_INET, SOCK_DGRAM, 0); 68 if (s < 0) 69 return -1; 70 71 do { 72 rv = bind(s, (struct sockaddr *)&local, sizeof local); 73 local.sin_port = htons(ntohs(local.sin_port) + 1); 74 } while(rv < 0 && errno == EADDRINUSE); 75 76 if (rv < 0) { 77 close(s); 78 return -1; 79 } 80 81 do { 82 rv = connect(s, (struct sockaddr *)&remote, sizeof remote); 83 remote.sin_port = htons(ntohs(remote.sin_port) + 1); 84 } while(rv < 0 && errno == EADDRINUSE); 85 86 if (rv < 0) { 87 close(s); 88 return -1; 89 } 90 91 namelen = sizeof local; 92 rv = getsockname(s, (struct sockaddr *)&local, &namelen); 93 close(s); 94 if (rv < 0) 95 return -1; 96 97 memcpy(iface, &local.sin_addr, sizeof local.sin_addr); 98 return 0; 99 } 100