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arping

    1: /* arping/src/findif_linux.c
    2:  *
    3:  *  Copyright (C) 2000-2009 Thomas Habets <thomas@habets.pp.se>
    4:  *
    5:  *  This library is free software; you can redistribute it and/or
    6:  *  modify it under the terms of the GNU General Public
    7:  *  License as published by the Free Software Foundation; either
    8:  *  version 2 of the License, or (at your option) any later version.
    9:  *
   10:  *  This library 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 GNU
   13:  *  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: #if HAVE_CONFIG_H
   20: #include "config.h"
   21: #endif
   22: 
   23: #include <stdio.h>
   24: #include <string.h>
   25: 
   26: #include "arping.h"
   27: 
   28: /**
   29:  * WARNING: non-reentrant
   30:  */
   31: const char *
   32: arping_lookupdev(const char *ifname,
   33:                  uint32_t srcip,
   34:                  uint32_t dstip,
   35:                  char *ebuf)
   36: {
   37: 	FILE *f;
   38: 	static char buf[1024];
   39: 	char buf1[1024];
   40: 	char buf2[1024];
   41: 	char *p,*p2;
   42: 	int n;
   43: 
   44: 	do_libnet_init(ifname);
   45: 	libnet_addr2name4_r(dstip,0,buf2,1024);
   46: 	libnet_addr2name4_r(srcip,0,buf1,1024);
   47: 
   48: 	/*
   49: 	 * Construct and run command
   50: 	 */
   51: 	snprintf(buf, 1023, "/sbin/ip route get %s from %s 2>&1",
   52: 		 buf2, buf1);
   53: 	if (!(f = popen(buf, "r"))) {
   54: 		goto failed;
   55: 	}
   56: 	if (0>(n = fread(buf, 1, sizeof(buf)-1, f))) {
   57: 		pclose(f);
   58: 		goto failed;
   59: 	}
   60: 	buf[n] = 0;
   61: 	if (-1 == pclose(f)) {
   62: 		perror("arping: pclose()");
   63: 		goto failed;
   64: 	}
   65: 
   66: 	/*
   67: 	 * Parse interface name
   68: 	 */
   69: 	p = strstr(buf, "dev ");
   70: 	if (!p) {
   71: 		goto failed;
   72: 	}
   73: 
   74: 	p+=4;
   75: 
   76: 	p2 = strchr(p, ' ');
   77: 	if (!p2) {
   78: 		goto failed;
   79: 	}
   80: 	*p2 = 0;
   81: 	return p;
   82:  failed:
   83: 	return arping_lookupdev_default(ifname,srcip,dstip,ebuf);
   84: }