resolv/inet_ntop.c

   1 /* Copyright (c) 1996 by Internet Software Consortium.
   2  *
   3  * Permission to use, copy, modify, and distribute this software for any
   4  * purpose with or without fee is hereby granted, provided that the above
   5  * copyright notice and this permission notice appear in all copies.
   6  *
   7  * THE SOFTWARE IS PROVIDED "AS IS" AND INTERNET SOFTWARE CONSORTIUM DISCLAIMS
   8  * ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES
   9  * OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL INTERNET SOFTWARE
  10  * CONSORTIUM BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL
  11  * DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
  12  * PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
  13  * ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
  14  * SOFTWARE.
  15  */
  16
  17 #if defined(LIBC_SCCS) && !defined(lint)
  18 static char rcsid[] = "$Id$";
  19 #endif /* LIBC_SCCS and not lint */
  20
  21 #include <sys/param.h>
  22 #include <sys/types.h>
  23 #include <sys/socket.h>
  24 #include <netinet/in.h>
  25 #include <arpa/inet.h>
  26 #include <arpa/nameser.h>
  27 #include <string.h>
  28 #include <errno.h>
  29 #include <stdio.h>
  30 #include "../conf/portability.h"
  31
  32 #ifdef SPRINTF_CHAR
  33 # define SPRINTF(x) strlen(sprintf/**/x)
  34 #else
  35 # define SPRINTF(x) ((size_t)sprintf x)
  36 #endif
  37
  38 /*
  39  * WARNING: Don't even consider trying to compile this on a system where
  40  * sizeof(int) < 4.  sizeof(int) > 4 is fine; all the world's not a VAX.
  41  */
  42
  43 static const char *inet_ntop4 __P((const u_char *src, char *dst, size_t size))
  44      internal_function;
  45 static const char *inet_ntop6 __P((const u_char *src, char *dst, size_t size))
  46      internal_function;
  47
  48 /* char *
  49  * inet_ntop(af, src, dst, size)
  50  *      convert a network format address to presentation format.
  51  * return:
  52  *      pointer to presentation format address (`dst'), or NULL (see errno).
  53  * author:
  54  *      Paul Vixie, 1996.
  55  */
  56 const char *
  57 inet_ntop(af, src, dst, size)
  58         int af;
  59         const void *src;
  60         char *dst;
  61         size_t size;
  62 {
  63         switch (af) {
  64         case AF_INET:
  65                 return (inet_ntop4(src, dst, size));
  66         case AF_INET6:
  67                 return (inet_ntop6(src, dst, size));
  68         default:
  69                 __set_errno (EAFNOSUPPORT);
  70                 return (NULL);
  71         }
  72         /* NOTREACHED */
  73 }
  74
  75 /* const char *
  76  * inet_ntop4(src, dst, size)
  77  *      format an IPv4 address, more or less like inet_ntoa()
  78  * return:
  79  *      `dst' (as a const)
  80  * notes:
  81  *      (1) uses no statics
  82  *      (2) takes a u_char* not an in_addr as input
  83  * author:
  84  *      Paul Vixie, 1996.
  85  */
  86 static const char *
  87 internal_function
  88 inet_ntop4(src, dst, size)
  89         const u_char *src;
  90         char *dst;
  91         size_t size;
  92 {
  93         static const char fmt[] = "%u.%u.%u.%u";
  94         char tmp[sizeof "255.255.255.255"];
  95
  96         if (SPRINTF((tmp, fmt, src[0], src[1], src[2], src[3])) > size) {
  97                 __set_errno (ENOSPC);
  98                 return (NULL);
  99         }
 100         return strcpy(dst, tmp);
 101 }
 102
 103 /* const char *
 104  * inet_ntop6(src, dst, size)
 105  *      convert IPv6 binary address into presentation (printable) format
 106  * author:
 107  *      Paul Vixie, 1996.
 108  */
 109 static const char *
 110 internal_function
 111 inet_ntop6(src, dst, size)
 112         const u_char *src;
 113         char *dst;
 114         size_t size;
 115 {
 116         /*
 117          * Note that int32_t and int16_t need only be "at least" large enough
 118          * to contain a value of the specified size.  On some systems, like
 119          * Crays, there is no such thing as an integer variable with 16 bits.
 120          * Keep this in mind if you think this function should have been coded
 121          * to use pointer overlays.  All the world's not a VAX.
 122          */
 123         char tmp[sizeof "ffff:ffff:ffff:ffff:ffff:ffff:255.255.255.255"], *tp;
 124         struct { int base, len; } best, cur;
 125         u_int words[IN6ADDRSZ / INT16SZ];
 126         int i;
 127
 128         /*
 129          * Preprocess:
 130          *      Copy the input (bytewise) array into a wordwise array.
 131          *      Find the longest run of 0x00's in src[] for :: shorthanding.
 132          */
 133         memset(words, '\0', sizeof words);
 134         for (i = 0; i < IN6ADDRSZ; i += 2)
 135                 words[i / 2] = (src[i] << 8) | src[i + 1];
 136         best.base = -1;
 137         cur.base = -1;
 138         for (i = 0; i < (IN6ADDRSZ / INT16SZ); i++) {
 139                 if (words[i] == 0) {
 140                         if (cur.base == -1)
 141                                 cur.base = i, cur.len = 1;
 142                         else
 143                                 cur.len++;
 144                 } else {
 145                         if (cur.base != -1) {
 146                                 if (best.base == -1 || cur.len > best.len)
 147                                         best = cur;
 148                                 cur.base = -1;
 149                         }
 150                 }
 151         }
 152         if (cur.base != -1) {
 153                 if (best.base == -1 || cur.len > best.len)
 154                         best = cur;
 155         }
 156         if (best.base != -1 && best.len < 2)
 157                 best.base = -1;
 158
 159         /*
 160          * Format the result.
 161          */
 162         tp = tmp;
 163         for (i = 0; i < (IN6ADDRSZ / INT16SZ); i++) {
 164                 /* Are we inside the best run of 0x00's? */
 165                 if (best.base != -1 && i >= best.base &&
 166                     i < (best.base + best.len)) {
 167                         if (i == best.base)
 168                                 *tp++ = ':';
 169                         continue;
 170                 }
 171                 /* Are we following an initial run of 0x00s or any real hex? */
 172                 if (i != 0)
 173                         *tp++ = ':';
 174                 /* Is this address an encapsulated IPv4? */
 175                 if (i == 6 && best.base == 0 &&
 176                     (best.len == 6 || (best.len == 5 && words[5] == 0xffff))) {
 177                         if (!inet_ntop4(src+12, tp, sizeof tmp - (tp - tmp)))
 178                                 return (NULL);
 179                         tp += strlen(tp);
 180                         break;
 181                 }
 182                 tp += SPRINTF((tp, "%x", words[i]));
 183         }
 184         /* Was it a trailing run of 0x00's? */
 185         if (best.base != -1 && (best.base + best.len) == (IN6ADDRSZ / INT16SZ))
 186                 *tp++ = ':';
 187         *tp++ = '\0';
 188
 189         /*
 190          * Check for overflow, copy, and we're done.
 191          */
 192         if ((size_t)(tp - tmp) > size) {
 193                 __set_errno (ENOSPC);
 194                 return (NULL);
 195         }
 196         return strcpy(dst, tmp);
 197 }