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arping v2.15

    1: /* arping/src/findif_getifaddrs.c
    2:  *
    3:  *  Copyright (C) 2000-2014 Thomas Habets <thomas@habets.se>
    4:  *
    5:  *  This program is free software; you can redistribute it and/or modify
    6:  *  it under the terms of the GNU General Public License as published by
    7:  *  the Free Software Foundation; either version 2 of the License, or
    8:  *  (at your option) any later version.
    9:  *
   10:  *  This program is distributed in the hope that it will be useful,
   11:  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
   12:  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   13:  *  GNU General Public License for more details.
   14:  *
   15:  *  You should have received a copy of the GNU General Public License along
   16:  *  with this program; if not, write to the Free Software Foundation, Inc.,
   17:  *  51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
   18:  */
   19: /**
   20:  * Most modern systems should have getifaddrs().
   21:  */
   22: #if HAVE_CONFIG_H
   23: #include "config.h"
   24: #endif
   25: 
   26: #include <stdio.h>
   27: #include <string.h>
   28: #include <errno.h>
   29: #include <sys/types.h>
   30: #include <sys/socket.h>
   31: #include <sys/ioctl.h>
   32: #include <ifaddrs.h>
   33: #include <net/if.h>
   34: #include <netinet/in.h>
   35: 
   36: #if HAVE_LIBNET_H
   37: #include <libnet.h>
   38: #endif
   39: 
   40: #include "arping.h"
   41: 
   42: const char *
   43: arping_lookupdev(uint32_t srcip,
   44:                  uint32_t dstip,
   45:                  char *ebuf)
   46: {
   47:         struct ifaddrs *ifa = NULL;
   48:         struct ifaddrs *cur;
   49:         const char *ret = NULL;
   50:         int match_count = 0;     /* Matching interfaces */
   51: 
   52:         /* best match */
   53:         in_addr_t best_mask = 0;
   54:         in_addr_t best_addr;
   55: 
   56:         /* Results */
   57:         static char ifname[IFNAMSIZ];
   58: 
   59:         *ebuf = 0;
   60: 
   61:         if (getifaddrs(&ifa)) {
   62:                 if (verbose) {
   63:                         printf("arping: getifaddrs(): %s\n", strerror(errno));
   64:                 }
   65:                 snprintf(ebuf, LIBNET_ERRBUF_SIZE,
   66:                          "getifaddrs(): %s", strerror(errno));
   67:                 goto out;
   68:         }
   69:         for (cur = ifa; cur; cur = cur->ifa_next) {
   70:                 in_addr_t addr, mask;
   71: 
   72:                 if (!(cur->ifa_flags & IFF_UP)) {
   73:                         continue;
   74:                 }
   75:                 if (!cur->ifa_addr
   76:                     || !cur->ifa_netmask
   77:                     || !cur->ifa_name) {
   78:                         continue;
   79:                 }
   80:                 if (cur->ifa_addr->sa_family != AF_INET) {
   81:                         continue;
   82:                 }
   83:                 if (cur->ifa_flags & (IFF_LOOPBACK|IFF_POINTOPOINT)) {
   84:                         continue;
   85:                 }
   86:                 addr =((struct sockaddr_in*)cur->ifa_addr)->sin_addr.s_addr;
   87:                 mask =((struct sockaddr_in*)cur->ifa_netmask)->sin_addr.s_addr;
   88:                 if ((addr & mask) != (dstip & mask)) {
   89:                         continue;
   90:                 }
   91:                 match_count++;
   92:                 if (ntohl(mask) > ntohl(best_mask)) {
   93:                         memset(ifname, 0, sizeof(ifname));
   94:                         strncpy(ifname, cur->ifa_name, sizeof(ifname)-1);
   95:                         best_addr = addr;
   96:                         best_mask = mask;
   97:                 }
   98:         }
   99:         if (match_count) {
  100:                 ret = ifname;
  101:                 if (verbose) {
  102:                         printf("arping: Autodetected interface %s\n", ret);
  103:                 }
  104:         } else {
  105:                 if (verbose > 1) {
  106:                         printf("arping: Failed to find iface using"
  107:                                " getifaddrs().\n");
  108:                 }
  109:                 snprintf(ebuf, LIBNET_ERRBUF_SIZE,
  110:                          "No matching interface found using getifaddrs().");
  111:         }
  112:  out:
  113:         if (ifa) {
  114:                 freeifaddrs(ifa);
  115:         }
  116:         return ret;
  117: }
  118: /* ---- Emacs Variables ----
  119:  * Local Variables:
  120:  * c-basic-offset: 8
  121:  * indent-tabs-mode: nil
  122:  * End:
  123:  */