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      1 /*
      2  * Copyright (C) 2008 The Android Open Source Project
      3  * 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  *  * Redistributions of source code must retain the above copyright
      9  *    notice, this list of conditions and the following disclaimer.
     10  *  * Redistributions in binary form must reproduce the above copyright
     11  *    notice, this list of conditions and the following disclaimer in
     12  *    the documentation and/or other materials provided with the
     13  *    distribution.
     14  *
     15  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
     16  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
     17  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
     18  * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
     19  * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
     20  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
     21  * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
     22  * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
     23  * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
     24  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
     25  * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     26  * SUCH DAMAGE.
     27  */
     28 
     29 #include <string.h>
     30 #include <unistd.h>
     31 #include <linux/sockios.h>
     32 #include <net/if.h>
     33 #include <sys/socket.h>
     34 #include <sys/ioctl.h>
     35 #include <errno.h>
     36 
     37 /*
     38  * Map an interface index into its name.
     39  * Returns NULL on error.
     40  */
     41 char*
     42 if_indextoname(unsigned ifindex, char *ifname)
     43 {
     44     int index;
     45     int ctl_sock;
     46     struct ifreq ifr;
     47     char*  ret = NULL;
     48 
     49     memset(&ifr, 0, sizeof(struct ifreq));
     50     ifr.ifr_ifindex = ifindex;
     51 
     52     if ((ctl_sock = socket(AF_INET, SOCK_DGRAM, 0)) >= 0) {
     53         if (ioctl(ctl_sock, SIOCGIFNAME, &ifr) >= 0) {
     54             ret = strncpy (ifname, ifr.ifr_name, IFNAMSIZ);
     55         } else {
     56             /* Posix requires ENXIO */
     57             if (errno == ENODEV)
     58                 errno = ENXIO;
     59         }
     60         close(ctl_sock);
     61     }
     62     return ret;
     63 }
     64