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(dst, iface) 51 struct in_addr *dst; 52 struct in_addr *iface; 53 { 54 static struct sockaddr_in local; 55 struct sockaddr_in remote; 56 socklen_t namelen; 57 int s, rv; 58 59 memcpy(&remote.sin_addr, dst, sizeof remote.sin_addr); 60 remote.sin_port = htons(60000); 61 remote.sin_family = AF_INET; 62 remote.sin_len = sizeof remote; 63 64 local.sin_addr.s_addr = htonl(INADDR_ANY); 65 local.sin_port = htons(60000); 66 local.sin_family = AF_INET; 67 local.sin_len = sizeof local; 68 69 s = socket(PF_INET, SOCK_DGRAM, 0); 70 if (s < 0) 71 return -1; 72 73 do { 74 rv = bind(s, (struct sockaddr *)&local, sizeof local); 75 local.sin_port = htons(ntohs(local.sin_port) + 1); 76 } while(rv < 0 && errno == EADDRINUSE); 77 78 if (rv < 0) { 79 close(s); 80 return -1; 81 } 82 83 do { 84 rv = connect(s, (struct sockaddr *)&remote, sizeof remote); 85 remote.sin_port = htons(ntohs(remote.sin_port) + 1); 86 } while(rv < 0 && errno == EADDRINUSE); 87 88 if (rv < 0) { 89 close(s); 90 return -1; 91 } 92 93 namelen = sizeof local; 94 rv = getsockname(s, (struct sockaddr *)&local, &namelen); 95 close(s); 96 if (rv < 0) 97 return -1; 98 99 memcpy(iface, &local.sin_addr, sizeof local.sin_addr); 100 return 0; 101 } 102