1 /* 2 * Copyright (c) 1998-1999, Craig Metz, All rights reserved. 3 * 4 * Redistribution and use in source and binary forms, with or without 5 * modification, are permitted provided that the following conditions 6 * are met: 7 * 1. Redistributions of source code must retain the above copyright 8 * notice, this list of conditions and the following disclaimer. 9 * 2. Redistributions in binary form must reproduce the above copyright 10 * notice, this list of conditions and the following disclaimer in the 11 * documentation and/or other materials provided with the distribution. 12 * 3. All advertising materials mentioning features or use of this software 13 * must display the following acknowledgement: 14 * This product includes software developed by Craig Metz and 15 * by other contributors. 16 * 4. Neither the name of the author nor the names of contributors 17 * may be used to endorse or promote products derived from this software 18 * without specific prior written permission. 19 * 20 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 21 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 24 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30 * SUCH DAMAGE. 31 */ 32 33 #include <sys/types.h> 34 #include <stdlib.h> 35 #include <sys/socket.h> 36 #include <sys/ioctl.h> 37 #include <net/if.h> 38 #include <net/if_dl.h> 39 #include <errno.h> 40 #include <unistd.h> 41 #include <string.h> 42 43 static char __name[IFNAMSIZ]; 44 45 char * 46 if_indextoname(unsigned int index, char *name) 47 { 48 int i, fd = -1, extra, len = 0; 49 struct ifconf ifconf; 50 char lastname[IFNAMSIZ], iname[IFNAMSIZ], *retname = NULL, *inbuf; 51 struct sockaddr *sa; 52 void *p; 53 54 ifconf.ifc_buf = 0; 55 56 if (!name) 57 name = __name; 58 59 if ((fd = socket(PF_INET, SOCK_DGRAM, 0)) < 0) 60 goto ret; 61 62 /* 63 * Try ifc_len == 0 hack first, to get the actual length. 64 * If that fails, revert to a loop which grows the ifc_buf 65 * until it is sufficiently large. 66 */ 67 extra = sizeof(struct ifreq); 68 while (1) { 69 ifconf.ifc_len = len; 70 if (ioctl(fd, SIOCGIFCONF, (void *) &ifconf) == -1 && 71 ifconf.ifc_buf) 72 goto ret; 73 if (ifconf.ifc_buf && 74 ifconf.ifc_len + extra < len) 75 break; 76 if (ifconf.ifc_buf) { 77 if (len == 0) 78 len = 4096; 79 ifconf.ifc_len = len *= 2; 80 } else { 81 len = ifconf.ifc_len; 82 extra = 0; 83 } 84 inbuf = realloc(ifconf.ifc_buf, ifconf.ifc_len); 85 if (inbuf == NULL) 86 goto ret; 87 ifconf.ifc_buf = inbuf; 88 } 89 90 i = 0; 91 p = ifconf.ifc_buf; 92 len = ifconf.ifc_len; 93 lastname[0] = 0; 94 lastname[sizeof(lastname)-1] = 0; 95 iname[0] = 0; 96 97 while (len > 0) { 98 if (len < (IFNAMSIZ + sizeof(struct sockaddr))) 99 goto ret; 100 if (strncmp(lastname, p, IFNAMSIZ)) { 101 if (i == index) 102 memcpy(iname, lastname, sizeof(iname)); 103 strlcpy(lastname, p, sizeof(lastname)); 104 i++; 105 } 106 len -= IFNAMSIZ; 107 p += IFNAMSIZ; 108 sa = p; 109 110 if (sa->sa_family == AF_LINK) { 111 struct sockaddr_dl *sd = p; 112 113 if (sd->sdl_index == index) { 114 strlcpy(name, lastname, IFNAMSIZ); 115 retname = name; 116 goto ret; 117 } 118 } 119 120 if (len < sa->sa_len) 121 goto ret; 122 len -= sa->sa_len; 123 p += sa->sa_len; 124 } 125 126 if (i == index) 127 strlcpy(iname, lastname, sizeof(iname)); 128 129 if (iname[0]) { 130 strlcpy(name, iname, IFNAMSIZ); 131 retname = name; 132 } 133 ret: 134 if (fd != -1) 135 close(fd); 136 if (ifconf.ifc_buf) 137 free(ifconf.ifc_buf); 138 return (retname); 139 } 140