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 static const char *inet_ntop6 (const u_char *src, char *dst, socklen_t size);
  43
  44 /* char *
  45  * inet_ntop(af, src, dst, size)
  46  *      convert a network format address to presentation format.
  47  * return:
  48  *      pointer to presentation format address (`dst'), or NULL (see errno).
  49  * author:
  50  *      Paul Vixie, 1996.
  51  */
  52 const char *
  53 inet_ntop (int af, const void *src, char *dst, socklen_t size)
  54 {
  55         switch (af) {
  56         case AF_INET:
  57                 return (inet_ntop4(src, dst, size));
  58         case AF_INET6:
  59                 return (inet_ntop6(src, dst, size));
  60         default:
  61                 __set_errno (EAFNOSUPPORT);
  62                 return (NULL);
  63         }
  64         /* NOTREACHED */
  65 }
  66 libc_hidden_def (inet_ntop)
  67
  68 /* const char *
  69  * inet_ntop4(src, dst, size)
  70  *      format an IPv4 address
  71  * return:
  72  *      `dst' (as a const)
  73  * notes:
  74  *      (1) uses no statics
  75  *      (2) takes a u_char* not an in_addr as input
  76  * author:
  77  *      Paul Vixie, 1996.
  78  */
  79 static const char *
  80 inet_ntop4 (const u_char *src, char *dst, socklen_t size)
  81 {
  82         static const char fmt[] = "%u.%u.%u.%u";
  83         char tmp[sizeof "255.255.255.255"];
  84
  85         if (SPRINTF((tmp, fmt, src[0], src[1], src[2], src[3])) >= size) {
  86                 __set_errno (ENOSPC);
  87                 return (NULL);
  88         }
  89         return strcpy(dst, tmp);
  90 }
  91
  92 /* const char *
  93  * inet_ntop6(src, dst, size)
  94  *      convert IPv6 binary address into presentation (printable) format
  95  * author:
  96  *      Paul Vixie, 1996.
  97  */
  98 static const char *
  99 inet_ntop6 (const u_char *src, char *dst, socklen_t size)
 100 {
 101         /*
 102          * Note that int32_t and int16_t need only be "at least" large enough
 103          * to contain a value of the specified size.  On some systems, like
 104          * Crays, there is no such thing as an integer variable with 16 bits.
 105          * Keep this in mind if you think this function should have been coded
 106          * to use pointer overlays.  All the world's not a VAX.
 107          */
 108         char tmp[sizeof "ffff:ffff:ffff:ffff:ffff:ffff:255.255.255.255"], *tp;
 109         struct { int base, len; } best, cur;
 110         u_int words[NS_IN6ADDRSZ / NS_INT16SZ];
 111         int i;
 112
 113         /*
 114          * Preprocess:
 115          *      Copy the input (bytewise) array into a wordwise array.
 116          *      Find the longest run of 0x00's in src[] for :: shorthanding.
 117          */
 118         memset(words, '\0', sizeof words);
 119         for (i = 0; i < NS_IN6ADDRSZ; i += 2)
 120                 words[i / 2] = (src[i] << 8) | src[i + 1];
 121         best.base = -1;
 122         cur.base = -1;
 123         best.len = 0;
 124         cur.len = 0;
 125         for (i = 0; i < (NS_IN6ADDRSZ / NS_INT16SZ); i++) {
 126                 if (words[i] == 0) {
 127                         if (cur.base == -1)
 128                                 cur.base = i, cur.len = 1;
 129                         else
 130                                 cur.len++;
 131                 } else {
 132                         if (cur.base != -1) {
 133                                 if (best.base == -1 || cur.len > best.len)
 134                                         best = cur;
 135                                 cur.base = -1;
 136                         }
 137                 }
 138         }
 139         if (cur.base != -1) {
 140                 if (best.base == -1 || cur.len > best.len)
 141                         best = cur;
 142         }
 143         if (best.base != -1 && best.len < 2)
 144                 best.base = -1;
 145
 146         /*
 147          * Format the result.
 148          */
 149         tp = tmp;
 150         for (i = 0; i < (NS_IN6ADDRSZ / NS_INT16SZ); i++) {
 151                 /* Are we inside the best run of 0x00's? */
 152                 if (best.base != -1 && i >= best.base &&
 153                     i < (best.base + best.len)) {
 154                         if (i == best.base)
 155                                 *tp++ = ':';
 156                         continue;
 157                 }
 158                 /* Are we following an initial run of 0x00s or any real hex? */
 159                 if (i != 0)
 160                         *tp++ = ':';
 161                 /* Is this address an encapsulated IPv4? */
 162                 if (i == 6 && best.base == 0 &&
 163                     (best.len == 6 || (best.len == 5 && words[5] == 0xffff))) {
 164                         if (!inet_ntop4(src+12, tp, sizeof tmp - (tp - tmp)))
 165                                 return (NULL);
 166                         tp += strlen(tp);
 167                         break;
 168                 }
 169                 tp += SPRINTF((tp, "%x", words[i]));
 170         }
 171         /* Was it a trailing run of 0x00's? */
 172         if (best.base != -1 && (best.base + best.len) ==
 173             (NS_IN6ADDRSZ / NS_INT16SZ))
 174                 *tp++ = ':';
 175         *tp++ = '\0';
 176
 177         /*
 178          * Check for overflow, copy, and we're done.
 179          */
 180         if ((socklen_t)(tp - tmp) > size) {
 181                 __set_errno (ENOSPC);
 182                 return (NULL);
 183         }
 184         return strcpy(dst, tmp);
 185 }