resolv/inet_ntop.c

   1 /*
   2  * Copyright (c) 1996-1999 by Internet Software Consortium.
   3  *
   4  * Permission to use, copy, modify, and distribute this software for any
   5  * purpose with or without fee is hereby granted, provided that the above
   6  * copyright notice and this permission notice appear in all copies.
   7  *
   8  * THE SOFTWARE IS PROVIDED "AS IS" AND INTERNET SOFTWARE CONSORTIUM DISCLAIMS
   9  * ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES
  10  * OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL INTERNET SOFTWARE
  11  * CONSORTIUM BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL
  12  * DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
  13  * PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
  14  * ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
  15  * SOFTWARE.
  16  */
  17
  18 #if defined(LIBC_SCCS) && !defined(lint)
  19 static const char rcsid[] = "$BINDId: inet_ntop.c,v 1.8 1999/10/13 16:39:28 vixie Exp $";
  20 #endif /* LIBC_SCCS and not lint */
  21
  22 #include <sys/param.h>
  23 #include <sys/types.h>
  24 #include <sys/socket.h>
  25
  26 #include <netinet/in.h>
  27 #include <arpa/inet.h>
  28 #include <arpa/nameser.h>
  29
  30 #include <errno.h>
  31 #include <stdio.h>
  32 #include <string.h>
  33
  34 #ifdef SPRINTF_CHAR
  35 # define SPRINTF(x) strlen(sprintf/**/x)
  36 #else
  37 # define SPRINTF(x) ((size_t)sprintf x)
  38 #endif
  39
  40 /*
  41  * WARNING: Don't even consider trying to compile this on a system where
  42  * sizeof(int) < 4.  sizeof(int) > 4 is fine; all the world's not a VAX.
  43  */
  44
  45 static const char *inet_ntop4 (const u_char *src, char *dst, socklen_t size)
  46      internal_function;
  47 static const char *inet_ntop6 (const u_char *src, char *dst, socklen_t size)
  48      internal_function;
  49
  50 /* char *
  51  * inet_ntop(af, src, dst, size)
  52  *      convert a network format address to presentation format.
  53  * return:
  54  *      pointer to presentation format address (`dst'), or NULL (see errno).
  55  * author:
  56  *      Paul Vixie, 1996.
  57  */
  58 const char *
  59 inet_ntop(af, src, dst, size)
  60         int af;
  61         const void *src;
  62         char *dst;
  63         socklen_t size;
  64 {
  65         switch (af) {
  66         case AF_INET:
  67                 return (inet_ntop4(src, dst, size));
  68         case AF_INET6:
  69                 return (inet_ntop6(src, dst, size));
  70         default:
  71                 __set_errno (EAFNOSUPPORT);
  72                 return (NULL);
  73         }
  74         /* NOTREACHED */
  75 }
  76
  77 /* const char *
  78  * inet_ntop4(src, dst, size)
  79  *      format an IPv4 address
  80  * return:
  81  *      `dst' (as a const)
  82  * notes:
  83  *      (1) uses no statics
  84  *      (2) takes a u_char* not an in_addr as input
  85  * author:
  86  *      Paul Vixie, 1996.
  87  */
  88 static const char *
  89 internal_function
  90 inet_ntop4(src, dst, size)
  91         const u_char *src;
  92         char *dst;
  93         socklen_t size;
  94 {
  95         static const char fmt[] = "%u.%u.%u.%u";
  96         char tmp[sizeof "255.255.255.255"];
  97
  98         if (SPRINTF((tmp, fmt, src[0], src[1], src[2], src[3])) > size) {
  99                 __set_errno (ENOSPC);
 100                 return (NULL);
 101         }
 102         return strcpy(dst, tmp);
 103 }
 104
 105 /* const char *
 106  * inet_ntop6(src, dst, size)
 107  *      convert IPv6 binary address into presentation (printable) format
 108  * author:
 109  *      Paul Vixie, 1996.
 110  */
 111 static const char *
 112 internal_function
 113 inet_ntop6(src, dst, size)
 114         const u_char *src;
 115         char *dst;
 116         socklen_t size;
 117 {
 118         /*
 119          * Note that int32_t and int16_t need only be "at least" large enough
 120          * to contain a value of the specified size.  On some systems, like
 121          * Crays, there is no such thing as an integer variable with 16 bits.
 122          * Keep this in mind if you think this function should have been coded
 123          * to use pointer overlays.  All the world's not a VAX.
 124          */
 125         char tmp[sizeof "ffff:ffff:ffff:ffff:ffff:ffff:255.255.255.255"], *tp;
 126         struct { int base, len; } best, cur;
 127         u_int words[NS_IN6ADDRSZ / NS_INT16SZ];
 128         int i;
 129
 130         /*
 131          * Preprocess:
 132          *      Copy the input (bytewise) array into a wordwise array.
 133          *      Find the longest run of 0x00's in src[] for :: shorthanding.
 134          */
 135         memset(words, '\0', sizeof words);
 136         for (i = 0; i < NS_IN6ADDRSZ; i += 2)
 137                 words[i / 2] = (src[i] << 8) | src[i + 1];
 138         best.base = -1;
 139         cur.base = -1;
 140         for (i = 0; i < (NS_IN6ADDRSZ / NS_INT16SZ); i++) {
 141                 if (words[i] == 0) {
 142                         if (cur.base == -1)
 143                                 cur.base = i, cur.len = 1;
 144                         else
 145                                 cur.len++;
 146                 } else {
 147                         if (cur.base != -1) {
 148                                 if (best.base == -1 || cur.len > best.len)
 149                                         best = cur;
 150                                 cur.base = -1;
 151                         }
 152                 }
 153         }
 154         if (cur.base != -1) {
 155                 if (best.base == -1 || cur.len > best.len)
 156                         best = cur;
 157         }
 158         if (best.base != -1 && best.len < 2)
 159                 best.base = -1;
 160
 161         /*
 162          * Format the result.
 163          */
 164         tp = tmp;
 165         for (i = 0; i < (NS_IN6ADDRSZ / NS_INT16SZ); i++) {
 166                 /* Are we inside the best run of 0x00's? */
 167                 if (best.base != -1 && i >= best.base &&
 168                     i < (best.base + best.len)) {
 169                         if (i == best.base)
 170                                 *tp++ = ':';
 171                         continue;
 172                 }
 173                 /* Are we following an initial run of 0x00s or any real hex? */
 174                 if (i != 0)
 175                         *tp++ = ':';
 176                 /* Is this address an encapsulated IPv4? */
 177                 if (i == 6 && best.base == 0 &&
 178                     (best.len == 6 || (best.len == 5 && words[5] == 0xffff))) {
 179                         if (!inet_ntop4(src+12, tp, sizeof tmp - (tp - tmp)))
 180                                 return (NULL);
 181                         tp += strlen(tp);
 182                         break;
 183                 }
 184                 tp += SPRINTF((tp, "%x", words[i]));
 185         }
 186         /* Was it a trailing run of 0x00's? */
 187         if (best.base != -1 && (best.base + best.len) ==
 188             (NS_IN6ADDRSZ / NS_INT16SZ))
 189                 *tp++ = ':';
 190         *tp++ = '\0';
 191
 192         /*
 193          * Check for overflow, copy, and we're done.
 194          */
 195         if ((socklen_t)(tp - tmp) > size) {
 196                 __set_errno (ENOSPC);
 197                 return (NULL);
 198         }
 199         return strcpy(dst, tmp);
 200 }