lib/inet_ntop.c

   1 /* inet_ntop.c -- convert IPv4 and IPv6 addresses from binary to text form
   2
   3    Copyright (C) 2005-2006, 2008-2020 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, see <https://www.gnu.org/licenses/>.  */
  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 #include <config.h>
  36
  37 /* Specification.  */
  38 #include <arpa/inet.h>
  39
  40 /* Use this to suppress gcc's "...may be used before initialized" warnings.
  41    Beware: The Code argument must not contain commas.  */
  42 #ifndef IF_LINT
  43 # if defined GCC_LINT || defined lint
  44 #  define IF_LINT(Code) Code
  45 # else
  46 #  define IF_LINT(Code) /* empty */
  47 # endif
  48 #endif
  49
  50 #if HAVE_DECL_INET_NTOP
  51
  52 # undef inet_ntop
  53
  54 const char *
  55 rpl_inet_ntop (int af, const void *restrict src,
  56                char *restrict dst, socklen_t cnt)
  57 {
  58   return inet_ntop (af, src, dst, cnt);
  59 }
  60
  61 #else
  62
  63 # include <stdio.h>
  64 # include <string.h>
  65 # include <errno.h>
  66
  67 # define NS_IN6ADDRSZ 16
  68 # define NS_INT16SZ 2
  69
  70 /*
  71  * WARNING: Don't even consider trying to compile this on a system where
  72  * sizeof(int) < 4.  sizeof(int) > 4 is fine; all the world's not a VAX.
  73  */
  74 typedef int verify_int_size[4 <= sizeof (int) ? 1 : -1];
  75
  76 static const char *inet_ntop4 (const unsigned char *src, char *dst, socklen_t size);
  77 # if HAVE_IPV6
  78 static const char *inet_ntop6 (const unsigned char *src, char *dst, socklen_t size);
  79 # endif
  80
  81
  82 /* char *
  83  * inet_ntop(af, src, dst, size)
  84  *      convert a network format address to presentation format.
  85  * return:
  86  *      pointer to presentation format address ('dst'), or NULL (see errno).
  87  * author:
  88  *      Paul Vixie, 1996.
  89  */
  90 const char *
  91 inet_ntop (int af, const void *restrict src,
  92            char *restrict dst, socklen_t cnt)
  93 {
  94   switch (af)
  95     {
  96 # if HAVE_IPV4
  97     case AF_INET:
  98       return (inet_ntop4 (src, dst, cnt));
  99 # endif
 100
 101 # if HAVE_IPV6
 102     case AF_INET6:
 103       return (inet_ntop6 (src, dst, cnt));
 104 # endif
 105
 106     default:
 107       errno = EAFNOSUPPORT;
 108       return (NULL);
 109     }
 110   /* NOTREACHED */
 111 }
 112
 113 /* const char *
 114  * inet_ntop4(src, dst, size)
 115  *      format an IPv4 address
 116  * return:
 117  *      'dst' (as a const)
 118  * notes:
 119  *      (1) uses no statics
 120  *      (2) takes a u_char* not an in_addr as input
 121  * author:
 122  *      Paul Vixie, 1996.
 123  */
 124 static const char *
 125 inet_ntop4 (const unsigned char *src, char *dst, socklen_t size)
 126 {
 127   char tmp[sizeof "255.255.255.255"];
 128   int len;
 129
 130   len = sprintf (tmp, "%u.%u.%u.%u", src[0], src[1], src[2], src[3]);
 131   if (len < 0)
 132     return NULL;
 133
 134   if (len > size)
 135     {
 136       errno = ENOSPC;
 137       return NULL;
 138     }
 139
 140   return strcpy (dst, tmp);
 141 }
 142
 143 # if HAVE_IPV6
 144
 145 /* const char *
 146  * inet_ntop6(src, dst, size)
 147  *      convert IPv6 binary address into presentation (printable) format
 148  * author:
 149  *      Paul Vixie, 1996.
 150  */
 151 static const char *
 152 inet_ntop6 (const unsigned char *src, char *dst, socklen_t size)
 153 {
 154   /*
 155    * Note that int32_t and int16_t need only be "at least" large enough
 156    * to contain a value of the specified size.  On some systems, like
 157    * Crays, there is no such thing as an integer variable with 16 bits.
 158    * Keep this in mind if you think this function should have been coded
 159    * to use pointer overlays.  All the world's not a VAX.
 160    */
 161   char tmp[sizeof "ffff:ffff:ffff:ffff:ffff:ffff:255.255.255.255"], *tp;
 162   struct
 163   {
 164     int base, len;
 165   } best, cur;
 166   unsigned int words[NS_IN6ADDRSZ / NS_INT16SZ];
 167   int i;
 168
 169   /*
 170    * Preprocess:
 171    *      Copy the input (bytewise) array into a wordwise array.
 172    *      Find the longest run of 0x00's in src[] for :: shorthanding.
 173    */
 174   memset (words, '\0', sizeof words);
 175   for (i = 0; i < NS_IN6ADDRSZ; i += 2)
 176     words[i / 2] = (src[i] << 8) | src[i + 1];
 177   best.base = -1;
 178   cur.base = -1;
 179   IF_LINT(best.len = 0);
 180   IF_LINT(cur.len = 0);
 181   for (i = 0; i < (NS_IN6ADDRSZ / NS_INT16SZ); i++)
 182     {
 183       if (words[i] == 0)
 184         {
 185           if (cur.base == -1)
 186             cur.base = i, cur.len = 1;
 187           else
 188             cur.len++;
 189         }
 190       else
 191         {
 192           if (cur.base != -1)
 193             {
 194               if (best.base == -1 || cur.len > best.len)
 195                 best = cur;
 196               cur.base = -1;
 197             }
 198         }
 199     }
 200   if (cur.base != -1)
 201     {
 202       if (best.base == -1 || cur.len > best.len)
 203         best = cur;
 204     }
 205   if (best.base != -1 && best.len < 2)
 206     best.base = -1;
 207
 208   /*
 209    * Format the result.
 210    */
 211   tp = tmp;
 212   for (i = 0; i < (NS_IN6ADDRSZ / NS_INT16SZ); i++)
 213     {
 214       /* Are we inside the best run of 0x00's? */
 215       if (best.base != -1 && i >= best.base && i < (best.base + best.len))
 216         {
 217           if (i == best.base)
 218             *tp++ = ':';
 219           continue;
 220         }
 221       /* Are we following an initial run of 0x00s or any real hex? */
 222       if (i != 0)
 223         *tp++ = ':';
 224       /* Is this address an encapsulated IPv4? */
 225       if (i == 6 && best.base == 0 &&
 226           (best.len == 6 || (best.len == 5 && words[5] == 0xffff)))
 227         {
 228           if (!inet_ntop4 (src + 12, tp, sizeof tmp - (tp - tmp)))
 229             return (NULL);
 230           tp += strlen (tp);
 231           break;
 232         }
 233       {
 234         int len = sprintf (tp, "%x", words[i]);
 235         if (len < 0)
 236           return NULL;
 237         tp += len;
 238       }
 239     }
 240   /* Was it a trailing run of 0x00's? */
 241   if (best.base != -1 && (best.base + best.len) ==
 242       (NS_IN6ADDRSZ / NS_INT16SZ))
 243     *tp++ = ':';
 244   *tp++ = '\0';
 245
 246   /*
 247    * Check for overflow, copy, and we're done.
 248    */
 249   if ((socklen_t) (tp - tmp) > size)
 250     {
 251       errno = ENOSPC;
 252       return NULL;
 253     }
 254
 255   return strcpy (dst, tmp);
 256 }
 257
 258 # endif
 259
 260 #endif