gl/inet_ntop.c

   1 /* inet_ntop.c -- convert IPv4 and IPv6 addresses from binary to text form
   2    Copyright (c) 2005, 2006  Free Software Foundation, Inc.
   3
   4    This program is free software; you can redistribute it and/or modify
   5    it under the terms of the GNU General Public License as published by
   6    the Free Software Foundation; either version 2, or (at your option)
   7    any later version.
   8
   9    This program is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12    GNU General Public License for more details.
  13
  14    You should have received a copy of the GNU General Public License
  15    along with this program; if not, write to the Free Software Foundation,
  16    Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.  */
  17
  18 /*
  19  * Copyright (c) 1996-1999 by Internet Software Consortium.
  20  *
  21  * Permission to use, copy, modify, and distribute this software for any
  22  * purpose with or without fee is hereby granted, provided that the above
  23  * copyright notice and this permission notice appear in all copies.
  24  *
  25  * THE SOFTWARE IS PROVIDED "AS IS" AND INTERNET SOFTWARE CONSORTIUM DISCLAIMS
  26  * ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES
  27  * OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL INTERNET SOFTWARE
  28  * CONSORTIUM BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL
  29  * DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
  30  * PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
  31  * ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
  32  * SOFTWARE.
  33  */
  34
  35 #ifdef HAVE_CONFIG_H
  36 # include <config.h>
  37 #endif
  38
  39 /* Specification.  */
  40 #include "inet_ntop.h"
  41
  42 #include <stdio.h>
  43 #include <string.h>
  44 #include <errno.h>
  45
  46 #ifndef EAFNOSUPPORT
  47 # define EAFNOSUPPORT EINVAL
  48 #endif
  49
  50 #define NS_IN6ADDRSZ 16
  51 #define NS_INT16SZ 2
  52
  53 /*
  54  * WARNING: Don't even consider trying to compile this on a system where
  55  * sizeof(int) < 4.  sizeof(int) > 4 is fine; all the world's not a VAX.
  56  */
  57 typedef int verify_int_size[2 * sizeof (int) - 7];
  58
  59 static const char *inet_ntop4 (const unsigned char *src, char *dst, socklen_t size);
  60 #if HAVE_IPV6
  61 static const char *inet_ntop6 (const unsigned char *src, char *dst, socklen_t size);
  62 #endif
  63
  64
  65 /* char *
  66  * inet_ntop(af, src, dst, size)
  67  *      convert a network format address to presentation format.
  68  * return:
  69  *      pointer to presentation format address (`dst'), or NULL (see errno).
  70  * author:
  71  *      Paul Vixie, 1996.
  72  */
  73 const char *
  74 inet_ntop (int af, const void *restrict src,
  75            char *restrict dst, socklen_t cnt)
  76 {
  77   switch (af)
  78     {
  79 #if HAVE_IPV4
  80     case AF_INET:
  81       return (inet_ntop4 (src, dst, cnt));
  82 #endif
  83
  84 #if HAVE_IPV6
  85     case AF_INET6:
  86       return (inet_ntop6 (src, dst, cnt));
  87 #endif
  88
  89     default:
  90       errno = EAFNOSUPPORT;
  91       return (NULL);
  92     }
  93   /* NOTREACHED */
  94 }
  95
  96 /* const char *
  97  * inet_ntop4(src, dst, size)
  98  *      format an IPv4 address
  99  * return:
 100  *      `dst' (as a const)
 101  * notes:
 102  *      (1) uses no statics
 103  *      (2) takes a u_char* not an in_addr as input
 104  * author:
 105  *      Paul Vixie, 1996.
 106  */
 107 static const char *
 108 inet_ntop4 (const unsigned char *src, char *dst, socklen_t size)
 109 {
 110   char tmp[sizeof "255.255.255.255"];
 111   int len;
 112
 113   len = sprintf (tmp, "%u.%u.%u.%u", src[0], src[1], src[2], src[3]);
 114   if (len < 0)
 115     return NULL;
 116
 117   if (len > size)
 118     {
 119       errno = ENOSPC;
 120       return NULL;
 121     }
 122
 123   return strcpy (dst, tmp);
 124 }
 125
 126 #if HAVE_IPV6
 127
 128 /* const char *
 129  * inet_ntop6(src, dst, size)
 130  *      convert IPv6 binary address into presentation (printable) format
 131  * author:
 132  *      Paul Vixie, 1996.
 133  */
 134 static const char *
 135 inet_ntop6 (const unsigned char *src, char *dst, socklen_t size)
 136 {
 137   /*
 138    * Note that int32_t and int16_t need only be "at least" large enough
 139    * to contain a value of the specified size.  On some systems, like
 140    * Crays, there is no such thing as an integer variable with 16 bits.
 141    * Keep this in mind if you think this function should have been coded
 142    * to use pointer overlays.  All the world's not a VAX.
 143    */
 144   char tmp[sizeof "ffff:ffff:ffff:ffff:ffff:ffff:255.255.255.255"], *tp;
 145   struct
 146   {
 147     int base, len;
 148   } best, cur;
 149   unsigned int words[NS_IN6ADDRSZ / NS_INT16SZ];
 150   int i;
 151
 152   /*
 153    * Preprocess:
 154    *      Copy the input (bytewise) array into a wordwise array.
 155    *      Find the longest run of 0x00's in src[] for :: shorthanding.
 156    */
 157   memset (words, '\0', sizeof words);
 158   for (i = 0; i < NS_IN6ADDRSZ; i += 2)
 159     words[i / 2] = (src[i] << 8) | src[i + 1];
 160   best.base = -1;
 161   cur.base = -1;
 162   for (i = 0; i < (NS_IN6ADDRSZ / NS_INT16SZ); i++)
 163     {
 164       if (words[i] == 0)
 165         {
 166           if (cur.base == -1)
 167             cur.base = i, cur.len = 1;
 168           else
 169             cur.len++;
 170         }
 171       else
 172         {
 173           if (cur.base != -1)
 174             {
 175               if (best.base == -1 || cur.len > best.len)
 176                 best = cur;
 177               cur.base = -1;
 178             }
 179         }
 180     }
 181   if (cur.base != -1)
 182     {
 183       if (best.base == -1 || cur.len > best.len)
 184         best = cur;
 185     }
 186   if (best.base != -1 && best.len < 2)
 187     best.base = -1;
 188
 189   /*
 190    * Format the result.
 191    */
 192   tp = tmp;
 193   for (i = 0; i < (NS_IN6ADDRSZ / NS_INT16SZ); i++)
 194     {
 195       /* Are we inside the best run of 0x00's? */
 196       if (best.base != -1 && i >= best.base && i < (best.base + best.len))
 197         {
 198           if (i == best.base)
 199             *tp++ = ':';
 200           continue;
 201         }
 202       /* Are we following an initial run of 0x00s or any real hex? */
 203       if (i != 0)
 204         *tp++ = ':';
 205       /* Is this address an encapsulated IPv4? */
 206       if (i == 6 && best.base == 0 &&
 207           (best.len == 6 || (best.len == 5 && words[5] == 0xffff)))
 208         {
 209           if (!inet_ntop4 (src + 12, tp, sizeof tmp - (tp - tmp)))
 210             return (NULL);
 211           tp += strlen (tp);
 212           break;
 213         }
 214       {
 215         int len = sprintf (tp, "%x", words[i]);
 216         if (len < 0)
 217           return NULL;
 218         tp += len;
 219       }
 220     }
 221   /* Was it a trailing run of 0x00's? */
 222   if (best.base != -1 && (best.base + best.len) ==
 223       (NS_IN6ADDRSZ / NS_INT16SZ))
 224     *tp++ = ':';
 225   *tp++ = '\0';
 226
 227   /*
 228    * Check for overflow, copy, and we're done.
 229    */
 230   if ((socklen_t) (tp - tmp) > size)
 231     {
 232       errno = ENOSPC;
 233       return NULL;
 234     }
 235
 236   return strcpy (dst, tmp);
 237 }
 238
 239 #endif