gl/inet_ntop.c

   1 /* inet_ntop.c -- convert IPv4 and IPv6 addresses from binary to text form
   2
   3    Copyright (C) 2005, 2006  Free Software Foundation, Inc.
   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, or (at your option)
   8    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
  16    along with this program; if not, write to the Free Software Foundation,
  17    Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.  */
  18
  19 /*
  20  * Copyright (c) 1996-1999 by Internet Software Consortium.
  21  *
  22  * Permission to use, copy, modify, and distribute this software for any
  23  * purpose with or without fee is hereby granted, provided that the above
  24  * copyright notice and this permission notice appear in all copies.
  25  *
  26  * THE SOFTWARE IS PROVIDED "AS IS" AND INTERNET SOFTWARE CONSORTIUM DISCLAIMS
  27  * ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES
  28  * OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL INTERNET SOFTWARE
  29  * CONSORTIUM BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL
  30  * DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
  31  * PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
  32  * ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
  33  * SOFTWARE.
  34  */
  35
  36 #include <config.h>
  37
  38 /* Specification.  */
  39 #include "inet_ntop.h"
  40
  41 #include <stdio.h>
  42 #include <string.h>
  43 #include <errno.h>
  44
  45 #ifndef EAFNOSUPPORT
  46 # define EAFNOSUPPORT EINVAL
  47 #endif
  48
  49 #define NS_IN6ADDRSZ 16
  50 #define NS_INT16SZ 2
  51
  52 /*
  53  * WARNING: Don't even consider trying to compile this on a system where
  54  * sizeof(int) < 4.  sizeof(int) > 4 is fine; all the world's not a VAX.
  55  */
  56 typedef int verify_int_size[2 * sizeof (int) - 7];
  57
  58 static const char *inet_ntop4 (const unsigned char *src, char *dst, socklen_t size);
  59 #if HAVE_IPV6
  60 static const char *inet_ntop6 (const unsigned char *src, char *dst, socklen_t size);
  61 #endif
  62
  63
  64 /* char *
  65  * inet_ntop(af, src, dst, size)
  66  *      convert a network format address to presentation format.
  67  * return:
  68  *      pointer to presentation format address (`dst'), or NULL (see errno).
  69  * author:
  70  *      Paul Vixie, 1996.
  71  */
  72 const char *
  73 inet_ntop (int af, const void *restrict src,
  74            char *restrict dst, socklen_t cnt)
  75 {
  76   switch (af)
  77     {
  78 #if HAVE_IPV4
  79     case AF_INET:
  80       return (inet_ntop4 (src, dst, cnt));
  81 #endif
  82
  83 #if HAVE_IPV6
  84     case AF_INET6:
  85       return (inet_ntop6 (src, dst, cnt));
  86 #endif
  87
  88     default:
  89       errno = EAFNOSUPPORT;
  90       return (NULL);
  91     }
  92   /* NOTREACHED */
  93 }
  94
  95 /* const char *
  96  * inet_ntop4(src, dst, size)
  97  *      format an IPv4 address
  98  * return:
  99  *      `dst' (as a const)
 100  * notes:
 101  *      (1) uses no statics
 102  *      (2) takes a u_char* not an in_addr as input
 103  * author:
 104  *      Paul Vixie, 1996.
 105  */
 106 static const char *
 107 inet_ntop4 (const unsigned char *src, char *dst, socklen_t size)
 108 {
 109   char tmp[sizeof "255.255.255.255"];
 110   int len;
 111
 112   len = sprintf (tmp, "%u.%u.%u.%u", src[0], src[1], src[2], src[3]);
 113   if (len < 0)
 114     return NULL;
 115
 116   if (len > size)
 117     {
 118       errno = ENOSPC;
 119       return NULL;
 120     }
 121
 122   return strcpy (dst, tmp);
 123 }
 124
 125 #if HAVE_IPV6
 126
 127 /* const char *
 128  * inet_ntop6(src, dst, size)
 129  *      convert IPv6 binary address into presentation (printable) format
 130  * author:
 131  *      Paul Vixie, 1996.
 132  */
 133 static const char *
 134 inet_ntop6 (const unsigned char *src, char *dst, socklen_t size)
 135 {
 136   /*
 137    * Note that int32_t and int16_t need only be "at least" large enough
 138    * to contain a value of the specified size.  On some systems, like
 139    * Crays, there is no such thing as an integer variable with 16 bits.
 140    * Keep this in mind if you think this function should have been coded
 141    * to use pointer overlays.  All the world's not a VAX.
 142    */
 143   char tmp[sizeof "ffff:ffff:ffff:ffff:ffff:ffff:255.255.255.255"], *tp;
 144   struct
 145   {
 146     int base, len;
 147   } best, cur;
 148   unsigned int words[NS_IN6ADDRSZ / NS_INT16SZ];
 149   int i;
 150
 151   /*
 152    * Preprocess:
 153    *      Copy the input (bytewise) array into a wordwise array.
 154    *      Find the longest run of 0x00's in src[] for :: shorthanding.
 155    */
 156   memset (words, '\0', sizeof words);
 157   for (i = 0; i < NS_IN6ADDRSZ; i += 2)
 158     words[i / 2] = (src[i] << 8) | src[i + 1];
 159   best.base = -1;
 160   cur.base = -1;
 161   for (i = 0; i < (NS_IN6ADDRSZ / NS_INT16SZ); i++)
 162     {
 163       if (words[i] == 0)
 164         {
 165           if (cur.base == -1)
 166             cur.base = i, cur.len = 1;
 167           else
 168             cur.len++;
 169         }
 170       else
 171         {
 172           if (cur.base != -1)
 173             {
 174               if (best.base == -1 || cur.len > best.len)
 175                 best = cur;
 176               cur.base = -1;
 177             }
 178         }
 179     }
 180   if (cur.base != -1)
 181     {
 182       if (best.base == -1 || cur.len > best.len)
 183         best = cur;
 184     }
 185   if (best.base != -1 && best.len < 2)
 186     best.base = -1;
 187
 188   /*
 189    * Format the result.
 190    */
 191   tp = tmp;
 192   for (i = 0; i < (NS_IN6ADDRSZ / NS_INT16SZ); i++)
 193     {
 194       /* Are we inside the best run of 0x00's? */
 195       if (best.base != -1 && i >= best.base && i < (best.base + best.len))
 196         {
 197           if (i == best.base)
 198             *tp++ = ':';
 199           continue;
 200         }
 201       /* Are we following an initial run of 0x00s or any real hex? */
 202       if (i != 0)
 203         *tp++ = ':';
 204       /* Is this address an encapsulated IPv4? */
 205       if (i == 6 && best.base == 0 &&
 206           (best.len == 6 || (best.len == 5 && words[5] == 0xffff)))
 207         {
 208           if (!inet_ntop4 (src + 12, tp, sizeof tmp - (tp - tmp)))
 209             return (NULL);
 210           tp += strlen (tp);
 211           break;
 212         }
 213       {
 214         int len = sprintf (tp, "%x", words[i]);
 215         if (len < 0)
 216           return NULL;
 217         tp += len;
 218       }
 219     }
 220   /* Was it a trailing run of 0x00's? */
 221   if (best.base != -1 && (best.base + best.len) ==
 222       (NS_IN6ADDRSZ / NS_INT16SZ))
 223     *tp++ = ':';
 224   *tp++ = '\0';
 225
 226   /*
 227    * Check for overflow, copy, and we're done.
 228    */
 229   if ((socklen_t) (tp - tmp) > size)
 230     {
 231       errno = ENOSPC;
 232       return NULL;
 233     }
 234
 235   return strcpy (dst, tmp);
 236 }
 237
 238 #endif