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 #include <sys/param.h>
  19 #include <sys/types.h>
  20 #include <sys/socket.h>
  21
  22 #include <netinet/in.h>
  23 #include <arpa/inet.h>
  24 #include <arpa/nameser.h>
  25
  26 #include <errno.h>
  27 #include <stdio.h>
  28 #include <string.h>
  29
  30 #ifdef SPRINTF_CHAR
  31 # define SPRINTF(x) strlen(sprintf/**/x)
  32 #else
  33 # define SPRINTF(x) ((size_t)sprintf x)
  34 #endif
  35
  36 /*
  37  * WARNING: Don't even consider trying to compile this on a system where
  38  * sizeof(int) < 4.  sizeof(int) > 4 is fine; all the world's not a VAX.
  39  */
  40
  41 static const char *inet_ntop4 (const u_char *src, char *dst, socklen_t size)
  42      internal_function;
  43 static const char *inet_ntop6 (const u_char *src, char *dst, socklen_t size)
  44      internal_function;
  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 (int af, const void *src, char *dst, socklen_t size)
  56 {
  57         switch (af) {
  58         case AF_INET:
  59                 return (inet_ntop4(src, dst, size));
  60         case AF_INET6:
  61                 return (inet_ntop6(src, dst, size));
  62         default:
  63                 __set_errno (EAFNOSUPPORT);
  64                 return (NULL);
  65         }
  66         /* NOTREACHED */
  67 }
  68 libc_hidden_def (inet_ntop)
  69
  70 /* const char *
  71  * inet_ntop4(src, dst, size)
  72  *      format an IPv4 address
  73  * return:
  74  *      `dst' (as a const)
  75  * notes:
  76  *      (1) uses no statics
  77  *      (2) takes a u_char* not an in_addr as input
  78  * author:
  79  *      Paul Vixie, 1996.
  80  */
  81 static const char *
  82 internal_function
  83 inet_ntop4 (const u_char *src, char *dst, socklen_t size)
  84 {
  85         static const char fmt[] = "%u.%u.%u.%u";
  86         char tmp[sizeof "255.255.255.255"];
  87
  88         if (SPRINTF((tmp, fmt, src[0], src[1], src[2], src[3])) >= size) {
  89                 __set_errno (ENOSPC);
  90                 return (NULL);
  91         }
  92         return strcpy(dst, tmp);
  93 }
  94
  95 /* const char *
  96  * inet_ntop6(src, dst, size)
  97  *      convert IPv6 binary address into presentation (printable) format
  98  * author:
  99  *      Paul Vixie, 1996.
 100  */
 101 static const char *
 102 internal_function
 103 inet_ntop6 (const u_char *src, char *dst, socklen_t size)
 104 {
 105         /*
 106          * Note that int32_t and int16_t need only be "at least" large enough
 107          * to contain a value of the specified size.  On some systems, like
 108          * Crays, there is no such thing as an integer variable with 16 bits.
 109          * Keep this in mind if you think this function should have been coded
 110          * to use pointer overlays.  All the world's not a VAX.
 111          */
 112         char tmp[sizeof "ffff:ffff:ffff:ffff:ffff:ffff:255.255.255.255"], *tp;
 113         struct { int base, len; } best, cur;
 114         u_int words[NS_IN6ADDRSZ / NS_INT16SZ];
 115         int i;
 116
 117         /*
 118          * Preprocess:
 119          *      Copy the input (bytewise) array into a wordwise array.
 120          *      Find the longest run of 0x00's in src[] for :: shorthanding.
 121          */
 122         memset(words, '\0', sizeof words);
 123         for (i = 0; i < NS_IN6ADDRSZ; i += 2)
 124                 words[i / 2] = (src[i] << 8) | src[i + 1];
 125         best.base = -1;
 126         cur.base = -1;
 127         best.len = 0;
 128         cur.len = 0;
 129         for (i = 0; i < (NS_IN6ADDRSZ / NS_INT16SZ); i++) {
 130                 if (words[i] == 0) {
 131                         if (cur.base == -1)
 132                                 cur.base = i, cur.len = 1;
 133                         else
 134                                 cur.len++;
 135                 } else {
 136                         if (cur.base != -1) {
 137                                 if (best.base == -1 || cur.len > best.len)
 138                                         best = cur;
 139                                 cur.base = -1;
 140                         }
 141                 }
 142         }
 143         if (cur.base != -1) {
 144                 if (best.base == -1 || cur.len > best.len)
 145                         best = cur;
 146         }
 147         if (best.base != -1 && best.len < 2)
 148                 best.base = -1;
 149
 150         /*
 151          * Format the result.
 152          */
 153         tp = tmp;
 154         for (i = 0; i < (NS_IN6ADDRSZ / NS_INT16SZ); i++) {
 155                 /* Are we inside the best run of 0x00's? */
 156                 if (best.base != -1 && i >= best.base &&
 157                     i < (best.base + best.len)) {
 158                         if (i == best.base)
 159                                 *tp++ = ':';
 160                         continue;
 161                 }
 162                 /* Are we following an initial run of 0x00s or any real hex? */
 163                 if (i != 0)
 164                         *tp++ = ':';
 165                 /* Is this address an encapsulated IPv4? */
 166                 if (i == 6 && best.base == 0 &&
 167                     (best.len == 6 || (best.len == 5 && words[5] == 0xffff))) {
 168                         if (!inet_ntop4(src+12, tp, sizeof tmp - (tp - tmp)))
 169                                 return (NULL);
 170                         tp += strlen(tp);
 171                         break;
 172                 }
 173                 tp += SPRINTF((tp, "%x", words[i]));
 174         }
 175         /* Was it a trailing run of 0x00's? */
 176         if (best.base != -1 && (best.base + best.len) ==
 177             (NS_IN6ADDRSZ / NS_INT16SZ))
 178                 *tp++ = ':';
 179         *tp++ = '\0';
 180
 181         /*
 182          * Check for overflow, copy, and we're done.
 183          */
 184         if ((socklen_t)(tp - tmp) > size) {
 185                 __set_errno (ENOSPC);
 186                 return (NULL);
 187         }
 188         return strcpy(dst, tmp);
 189 }