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arping v2.15

    1: /* arping/src/findif_linux.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:  * Fallback to ugly solution. This should not actually be used, as
   21:  * modern systems have getifaddrs().
   22:  */
   23: #if HAVE_CONFIG_H
   24: #include "config.h"
   25: #endif
   26: 
   27: #include <stdio.h>
   28: #include <string.h>
   29: 
   30: #if HAVE_LIBNET_H
   31: #include <libnet.h>
   32: #endif
   33: 
   34: #include "arping.h"
   35: 
   36: /**
   37:  * WARNING: non-reentrant
   38:  */
   39: const char *
   40: arping_lookupdev(uint32_t srcip,
   41:                  uint32_t dstip,
   42:                  char *ebuf)
   43: {
   44:         FILE *f = NULL;
   45: 	static char buf[1024];
   46: 	char buf1[1024];
   47: 	char buf2[1024];
   48: 	char *p,*p2;
   49: 	int n;
   50: 
   51:         *ebuf = 0;
   52: 
   53:         do_libnet_init(NULL, 0);
   54: 	libnet_addr2name4_r(dstip,0,buf2,1024);
   55: 	libnet_addr2name4_r(srcip,0,buf1,1024);
   56: 
   57: 	/*
   58: 	 * Construct and run command
   59: 	 */
   60: 	snprintf(buf, 1023, "/sbin/ip route get %s from %s 2>&1",
   61: 		 buf2, buf1);
   62: 	if (!(f = popen(buf, "r"))) {
   63:                 snprintf(ebuf, LIBNET_ERRBUF_SIZE,
   64:                          "popen(/sbin/ip): %s", strerror(errno));
   65: 		goto failed;
   66: 	}
   67: 	if (0>(n = fread(buf, 1, sizeof(buf)-1, f))) {
   68:                 snprintf(ebuf, LIBNET_ERRBUF_SIZE,
   69:                          "fread(/sbin/ip): %s", strerror(errno));
   70: 		goto failed;
   71: 	}
   72: 	buf[n] = 0;
   73: 	if (-1 == pclose(f)) {
   74:                 snprintf(ebuf, LIBNET_ERRBUF_SIZE,
   75:                          "pclose(/sbin/ip): %s", strerror(errno));
   76: 		goto failed;
   77: 	}
   78:         f = NULL;
   79: 
   80: 	/*
   81: 	 * Parse interface name
   82: 	 */
   83:         const char* head = "dev ";
   84:         p = strstr(buf, head);
   85: 	if (!p) {
   86:                 if (verbose) {
   87:                         printf("arping: /sbin/ip output: %s\n", buf);
   88:                 }
   89:                 snprintf(ebuf, LIBNET_ERRBUF_SIZE,
   90:                          "\"dev \" not found in /sbin/ip output.");
   91: 		goto failed;
   92: 	}
   93: 
   94:         p += strlen(head);
   95: 
   96: 	p2 = strchr(p, ' ');
   97: 	if (!p2) {
   98:                 if (verbose) {
   99:                         printf("arping: /sbin/ip output: %s\n", buf);
  100:                 }
  101:                 snprintf(ebuf, LIBNET_ERRBUF_SIZE,
  102:                          "interface not found in /sbin/ip output.");
  103: 		goto failed;
  104: 	}
  105: 	*p2 = 0;
  106: 	return p;
  107:  failed:
  108:         if (f) {
  109:                 pclose(f);
  110:         }
  111: 	return NULL;
  112: }
  113: /* ---- Emacs Variables ----
  114:  * Local Variables:
  115:  * c-basic-offset: 8
  116:  * indent-tabs-mode: nil
  117:  * End:
  118:  */