lib/inet_ntop.c

   1 /* inet_ntop.c -- convert IPv4 and IPv6 addresses from binary to text form
   2
   3    Copyright (C) 2005-2006, 2008-2011 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 Lesser 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 Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser 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 <arpa/inet.h>
  40
  41 #include <stdio.h>
  42 #include <string.h>
  43 #include <errno.h>
  44
  45 #define NS_IN6ADDRSZ 16
  46 #define NS_INT16SZ 2
  47
  48 /*
  49  * WARNING: Don't even consider trying to compile this on a system where
  50  * sizeof(int) < 4.  sizeof(int) > 4 is fine; all the world's not a VAX.
  51  */
  52 typedef int verify_int_size[4 <= sizeof (int) ? 1 : -1];
  53
  54 static const char *inet_ntop4 (const unsigned char *src, char *dst, socklen_t size);
  55 #if HAVE_IPV6
  56 static const char *inet_ntop6 (const unsigned char *src, char *dst, socklen_t size);
  57 #endif
  58
  59
  60 /* char *
  61  * inet_ntop(af, src, dst, size)
  62  *      convert a network format address to presentation format.
  63  * return:
  64  *      pointer to presentation format address (`dst'), or NULL (see errno).
  65  * author:
  66  *      Paul Vixie, 1996.
  67  */
  68 const char *
  69 inet_ntop (int af, const void *restrict src,
  70            char *restrict dst, socklen_t cnt)
  71 {
  72   switch (af)
  73     {
  74 #if HAVE_IPV4
  75     case AF_INET:
  76       return (inet_ntop4 (src, dst, cnt));
  77 #endif
  78
  79 #if HAVE_IPV6
  80     case AF_INET6:
  81       return (inet_ntop6 (src, dst, cnt));
  82 #endif
  83
  84     default:
  85       errno = EAFNOSUPPORT;
  86       return (NULL);
  87     }
  88   /* NOTREACHED */
  89 }
  90
  91 /* const char *
  92  * inet_ntop4(src, dst, size)
  93  *      format an IPv4 address
  94  * return:
  95  *      `dst' (as a const)
  96  * notes:
  97  *      (1) uses no statics
  98  *      (2) takes a u_char* not an in_addr as input
  99  * author:
 100  *      Paul Vixie, 1996.
 101  */
 102 static const char *
 103 inet_ntop4 (const unsigned char *src, char *dst, socklen_t size)
 104 {
 105   char tmp[sizeof "255.255.255.255"];
 106   int len;
 107
 108   len = sprintf (tmp, "%u.%u.%u.%u", src[0], src[1], src[2], src[3]);
 109   if (len < 0)
 110     return NULL;
 111
 112   if (len > size)
 113     {
 114       errno = ENOSPC;
 115       return NULL;
 116     }
 117
 118   return strcpy (dst, tmp);
 119 }
 120
 121 #if HAVE_IPV6
 122
 123 /* const char *
 124  * inet_ntop6(src, dst, size)
 125  *      convert IPv6 binary address into presentation (printable) format
 126  * author:
 127  *      Paul Vixie, 1996.
 128  */
 129 static const char *
 130 inet_ntop6 (const unsigned char *src, char *dst, socklen_t size)
 131 {
 132   /*
 133    * Note that int32_t and int16_t need only be "at least" large enough
 134    * to contain a value of the specified size.  On some systems, like
 135    * Crays, there is no such thing as an integer variable with 16 bits.
 136    * Keep this in mind if you think this function should have been coded
 137    * to use pointer overlays.  All the world's not a VAX.
 138    */
 139   char tmp[sizeof "ffff:ffff:ffff:ffff:ffff:ffff:255.255.255.255"], *tp;
 140   struct
 141   {
 142     int base, len;
 143   } best, cur;
 144   unsigned int words[NS_IN6ADDRSZ / NS_INT16SZ];
 145   int i;
 146
 147   /*
 148    * Preprocess:
 149    *      Copy the input (bytewise) array into a wordwise array.
 150    *      Find the longest run of 0x00's in src[] for :: shorthanding.
 151    */
 152   memset (words, '\0', sizeof words);
 153   for (i = 0; i < NS_IN6ADDRSZ; i += 2)
 154     words[i / 2] = (src[i] << 8) | src[i + 1];
 155   best.base = -1;
 156   cur.base = -1;
 157   for (i = 0; i < (NS_IN6ADDRSZ / NS_INT16SZ); i++)
 158     {
 159       if (words[i] == 0)
 160         {
 161           if (cur.base == -1)
 162             cur.base = i, cur.len = 1;
 163           else
 164             cur.len++;
 165         }
 166       else
 167         {
 168           if (cur.base != -1)
 169             {
 170               if (best.base == -1 || cur.len > best.len)
 171                 best = cur;
 172               cur.base = -1;
 173             }
 174         }
 175     }
 176   if (cur.base != -1)
 177     {
 178       if (best.base == -1 || cur.len > best.len)
 179         best = cur;
 180     }
 181   if (best.base != -1 && best.len < 2)
 182     best.base = -1;
 183
 184   /*
 185    * Format the result.
 186    */
 187   tp = tmp;
 188   for (i = 0; i < (NS_IN6ADDRSZ / NS_INT16SZ); i++)
 189     {
 190       /* Are we inside the best run of 0x00's? */
 191       if (best.base != -1 && i >= best.base && i < (best.base + best.len))
 192         {
 193           if (i == best.base)
 194             *tp++ = ':';
 195           continue;
 196         }
 197       /* Are we following an initial run of 0x00s or any real hex? */
 198       if (i != 0)
 199         *tp++ = ':';
 200       /* Is this address an encapsulated IPv4? */
 201       if (i == 6 && best.base == 0 &&
 202           (best.len == 6 || (best.len == 5 && words[5] == 0xffff)))
 203         {
 204           if (!inet_ntop4 (src + 12, tp, sizeof tmp - (tp - tmp)))
 205             return (NULL);
 206           tp += strlen (tp);
 207           break;
 208         }
 209       {
 210         int len = sprintf (tp, "%x", words[i]);
 211         if (len < 0)
 212           return NULL;
 213         tp += len;
 214       }
 215     }
 216   /* Was it a trailing run of 0x00's? */
 217   if (best.base != -1 && (best.base + best.len) ==
 218       (NS_IN6ADDRSZ / NS_INT16SZ))
 219     *tp++ = ':';
 220   *tp++ = '\0';
 221
 222   /*
 223    * Check for overflow, copy, and we're done.
 224    */
 225   if ((socklen_t) (tp - tmp) > size)
 226     {
 227       errno = ENOSPC;
 228       return NULL;
 229     }
 230
 231   return strcpy (dst, tmp);
 232 }
 233
 234 #endif