contrib/traceroute/findsaddr-linux.c

   1 /*
   2  * Copyright (c) 2000
   3  *      The Regents of the University of California.  All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  * 1. Redistributions of source code must retain the above copyright
   9  *    notice, this list of conditions and the following disclaimer.
  10  * 2. Redistributions in binary form must reproduce the above copyright
  11  *    notice, this list of conditions and the following disclaimer in the
  12  *    documentation and/or other materials provided with the distribution.
  13  * 3. All advertising materials mentioning features or use of this software
  14  *    must display the following acknowledgement:
  15  *      This product includes software developed by the Computer Systems
  16  *      Engineering Group at Lawrence Berkeley Laboratory.
  17  * 4. Neither the name of the University nor of the Laboratory may be used
  18  *    to endorse or promote products derived from this software without
  19  *    specific prior written permission.
  20  *
  21  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  22  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  23  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  24  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  25  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  26  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  27  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  28  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  29  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  30  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  31  * SUCH DAMAGE.
  32  */
  33
  34 #ifndef lint
  35 static const char rcsid[] =
  36     "@(#) $Id: findsaddr-linux.c,v 1.1 2000/11/23 20:17:12 leres Exp $ (LBL)";
  37 #endif
  38
  39 /* XXX linux is different (as usual) */
  40
  41 #include <sys/param.h>
  42 #include <sys/file.h>
  43 #include <sys/ioctl.h>
  44 #include <sys/socket.h>
  45 #ifdef HAVE_SYS_SOCKIO_H
  46 #include <sys/sockio.h>
  47 #endif
  48 #include <sys/time.h>                           /* concession to AIX */
  49
  50 #if __STDC__
  51 struct mbuf;
  52 struct rtentry;
  53 #endif
  54
  55 #include <net/if.h>
  56 #include <netinet/in.h>
  57
  58 #include <arpa/inet.h>
  59
  60 #include <errno.h>
  61 #include <stdio.h>
  62 #include <stdlib.h>
  63 #include <string.h>
  64 #include <unistd.h>
  65
  66 #include "gnuc.h"
  67 #ifdef HAVE_OS_PROTO_H
  68 #include "os-proto.h"
  69 #endif
  70
  71 #include "findsaddr.h"
  72 #include "ifaddrlist.h"
  73 #include "traceroute.h"
  74
  75 static const char route[] = "/proc/net/route";
  76
  77 /*
  78  * Return the source address for the given destination address
  79  */
  80 const char *
  81 findsaddr(register const struct sockaddr_in *to,
  82     register struct sockaddr_in *from)
  83 {
  84         register int i, n;
  85         register FILE *f;
  86         register u_int32_t mask;
  87         u_int32_t dest, tmask;
  88         struct ifaddrlist *al;
  89         char buf[256], tdevice[256], device[256];
  90         static char errbuf[132];
  91
  92         if ((f = fopen(route, "r")) == NULL) {
  93                 sprintf(errbuf, "open %s: %.128s", route, strerror(errno));
  94                 return (errbuf);
  95         }
  96
  97         /* Find the appropriate interface */
  98         n = 0;
  99         mask = 0;
 100         device[0] = '\0';
 101         while (fgets(buf, sizeof(buf), f) != NULL) {
 102                 ++n;
 103                 if (n == 1 && strncmp(buf, "Iface", 5) == 0)
 104                         continue;
 105                 if ((i = sscanf(buf, "%s %x %*s %*s %*s %*s %*s %x",
 106                     tdevice, &dest, &tmask)) != 3)
 107                         return ("junk in buffer");
 108                 if ((to->sin_addr.s_addr & tmask) == dest &&
 109                     (tmask > mask || mask == 0)) {
 110                         mask = tmask;
 111                         strcpy(device, tdevice);
 112                 }
 113         }
 114         fclose(f);
 115
 116         if (device[0] == '\0')
 117                 return ("Can't find interface");
 118
 119         /* Get the interface address list */
 120         if ((n = ifaddrlist(&al, errbuf)) < 0)
 121                 return (errbuf);
 122
 123         if (n == 0)
 124                 return ("Can't find any network interfaces");
 125
 126         /* Find our appropriate source address */
 127         for (i = n; i > 0; --i, ++al)
 128                 if (strcmp(device, al->device) == 0)
 129                         break;
 130         if (i <= 0) {
 131                 sprintf(errbuf, "Can't find interface \"%.32s\"", device);
 132                 return (errbuf);
 133         }
 134
 135         setsin(from, al->addr);
 136         return (NULL);
 137 }