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 static const char *inet_ntop6 __P((const u_char *src, char *dst, size_t size));
  45
  46 /* char *
  47  * inet_ntop(af, src, dst, size)
  48  *      convert a network format address to presentation format.
  49  * return:
  50  *      pointer to presentation format address (`dst'), or NULL (see errno).
  51  * author:
  52  *      Paul Vixie, 1996.
  53  */
  54 const char *
  55 inet_ntop(af, src, dst, size)
  56         int af;
  57         const void *src;
  58         char *dst;
  59         size_t size;
  60 {
  61         switch (af) {
  62         case AF_INET:
  63                 return (inet_ntop4(src, dst, size));
  64         case AF_INET6:
  65                 return (inet_ntop6(src, dst, size));
  66         default:
  67                 errno = EAFNOSUPPORT;
  68                 return (NULL);
  69         }
  70         /* NOTREACHED */
  71 }
  72
  73 /* const char *
  74  * inet_ntop4(src, dst, size)
  75  *      format an IPv4 address, more or less like inet_ntoa()
  76  * return:
  77  *      `dst' (as a const)
  78  * notes:
  79  *      (1) uses no statics
  80  *      (2) takes a u_char* not an in_addr as input
  81  * author:
  82  *      Paul Vixie, 1996.
  83  */
  84 static const char *
  85 inet_ntop4(src, dst, size)
  86         const u_char *src;
  87         char *dst;
  88         size_t size;
  89 {
  90         static const char fmt[] = "%u.%u.%u.%u";
  91         char tmp[sizeof "255.255.255.255"];
  92
  93         if (SPRINTF((tmp, fmt, src[0], src[1], src[2], src[3])) > size) {
  94                 errno = ENOSPC;
  95                 return (NULL);
  96         }
  97         strcpy(dst, tmp);
  98         return (dst);
  99 }
 100
 101 /* const char *
 102  * inet_ntop6(src, dst, size)
 103  *      convert IPv6 binary address into presentation (printable) format
 104  * author:
 105  *      Paul Vixie, 1996.
 106  */
 107 static const char *
 108 inet_ntop6(src, dst, size)
 109         const u_char *src;
 110         char *dst;
 111         size_t size;
 112 {
 113         /*
 114          * Note that int32_t and int16_t need only be "at least" large enough
 115          * to contain a value of the specified size.  On some systems, like
 116          * Crays, there is no such thing as an integer variable with 16 bits.
 117          * Keep this in mind if you think this function should have been coded
 118          * to use pointer overlays.  All the world's not a VAX.
 119          */
 120         char tmp[sizeof "ffff:ffff:ffff:ffff:ffff:ffff:255.255.255.255"], *tp;
 121         struct { int base, len; } best, cur;
 122         u_int words[IN6ADDRSZ / INT16SZ];
 123         int i;
 124
 125         /*
 126          * Preprocess:
 127          *      Copy the input (bytewise) array into a wordwise array.
 128          *      Find the longest run of 0x00's in src[] for :: shorthanding.
 129          */
 130         memset(words, '\0', sizeof words);
 131         for (i = 0; i < IN6ADDRSZ; i++)
 132                 words[i / 2] |= (src[i] << ((1 - (i % 2)) << 3));
 133         best.base = -1;
 134         cur.base = -1;
 135         for (i = 0; i < (IN6ADDRSZ / INT16SZ); i++) {
 136                 if (words[i] == 0) {
 137                         if (cur.base == -1)
 138                                 cur.base = i, cur.len = 1;
 139                         else
 140                                 cur.len++;
 141                 } else {
 142                         if (cur.base != -1) {
 143                                 if (best.base == -1 || cur.len > best.len)
 144                                         best = cur;
 145                                 cur.base = -1;
 146                         }
 147                 }
 148         }
 149         if (cur.base != -1) {
 150                 if (best.base == -1 || cur.len > best.len)
 151                         best = cur;
 152         }
 153         if (best.base != -1 && best.len < 2)
 154                 best.base = -1;
 155
 156         /*
 157          * Format the result.
 158          */
 159         tp = tmp;
 160         for (i = 0; i < (IN6ADDRSZ / INT16SZ); i++) {
 161                 /* Are we inside the best run of 0x00's? */
 162                 if (best.base != -1 && i >= best.base &&
 163                     i < (best.base + best.len)) {
 164                         if (i == best.base)
 165                                 *tp++ = ':';
 166                         continue;
 167                 }
 168                 /* Are we following an initial run of 0x00s or any real hex? */
 169                 if (i != 0)
 170                         *tp++ = ':';
 171                 /* Is this address an encapsulated IPv4? */
 172                 if (i == 6 && best.base == 0 &&
 173                     (best.len == 6 || (best.len == 5 && words[5] == 0xffff))) {
 174                         if (!inet_ntop4(src+12, tp, sizeof tmp - (tp - tmp)))
 175                                 return (NULL);
 176                         tp += strlen(tp);
 177                         break;
 178                 }
 179                 tp += SPRINTF((tp, "%x", words[i]));
 180         }
 181         /* Was it a trailing run of 0x00's? */
 182         if (best.base != -1 && (best.base + best.len) == (IN6ADDRSZ / INT16SZ))
 183                 *tp++ = ':';
 184         *tp++ = '\0';
 185
 186         /*
 187          * Check for overflow, copy, and we're done.
 188          */
 189         if ((size_t)(tp - tmp) > size) {
 190                 errno = ENOSPC;
 191                 return (NULL);
 192         }
 193         strcpy(dst, tmp);
 194         return (dst);
 195 }