lib/inet_ntop.c

   1 /*
   2  * Copyright (C) 1996-2001  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
   9  * DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL
  10  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL
  11  * INTERNET SOFTWARE CONSORTIUM BE LIABLE FOR ANY SPECIAL, DIRECT,
  12  * INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING
  13  * FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT,
  14  * NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION
  15  * WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  16  */
  17
  18
  19 #include "rsync.h"
  20
  21 #define NS_INT16SZ       2
  22 #define NS_IN6ADDRSZ    16
  23
  24 /*
  25  * WARNING: Don't even consider trying to compile this on a system where
  26  * sizeof(int) < 4.  sizeof(int) > 4 is fine; all the world's not a VAX.
  27  */
  28
  29 static const char *inet_ntop4(const unsigned char *src, char *dst,
  30                               size_t size);
  31
  32 #ifdef AF_INET6
  33 static const char *inet_ntop6(const unsigned char *src, char *dst,
  34                               size_t size);
  35 #endif
  36
  37 /* char *
  38  * isc_net_ntop(af, src, dst, size)
  39  *      convert a network format address to presentation format.
  40  * return:
  41  *      pointer to presentation format address (`dst'), or NULL (see errno).
  42  * author:
  43  *      Paul Vixie, 1996.
  44  */
  45 const char *
  46 inet_ntop(int af, const void *src, char *dst, size_t size)
  47 {
  48         switch (af) {
  49         case AF_INET:
  50                 return (inet_ntop4(src, dst, size));
  51 #ifdef AF_INET6
  52         case AF_INET6:
  53                 return (inet_ntop6(src, dst, size));
  54 #endif
  55         default:
  56                 errno = EAFNOSUPPORT;
  57                 return (NULL);
  58         }
  59         /* NOTREACHED */
  60 }
  61
  62 /* const char *
  63  * inet_ntop4(src, dst, size)
  64  *      format an IPv4 address
  65  * return:
  66  *      `dst' (as a const)
  67  * notes:
  68  *      (1) uses no statics
  69  *      (2) takes a unsigned char* not an in_addr as input
  70  * author:
  71  *      Paul Vixie, 1996.
  72  */
  73 static const char *
  74 inet_ntop4(const unsigned char *src, char *dst, size_t size)
  75 {
  76         static const char *fmt = "%u.%u.%u.%u";
  77         char tmp[sizeof "255.255.255.255"];
  78         size_t len;
  79
  80         len = snprintf(tmp, sizeof tmp, fmt, src[0], src[1], src[2], src[3]);
  81         if (len >= size) {
  82                 errno = ENOSPC;
  83                 return (NULL);
  84         }
  85         memcpy(dst, tmp, len + 1);
  86
  87         return (dst);
  88 }
  89
  90 /* const char *
  91  * isc_inet_ntop6(src, dst, size)
  92  *      convert IPv6 binary address into presentation (printable) format
  93  * author:
  94  *      Paul Vixie, 1996.
  95  */
  96 #ifdef AF_INET6
  97 static const char *
  98 inet_ntop6(const unsigned char *src, char *dst, size_t size)
  99 {
 100         /*
 101          * Note that int32_t and int16_t need only be "at least" large enough
 102          * to contain a value of the specified size.  On some systems, like
 103          * Crays, there is no such thing as an integer variable with 16 bits.
 104          * Keep this in mind if you think this function should have been coded
 105          * to use pointer overlays.  All the world's not a VAX.
 106          */
 107         char tmp[sizeof "ffff:ffff:ffff:ffff:ffff:ffff:255.255.255.255"], *tp;
 108         struct { int base, len; } best, cur;
 109         unsigned int words[NS_IN6ADDRSZ / NS_INT16SZ];
 110         int i, inc;
 111
 112         /*
 113          * Preprocess:
 114          *      Copy the input (bytewise) array into a wordwise array.
 115          *      Find the longest run of 0x00's in src[] for :: shorthanding.
 116          */
 117         memset(words, '\0', sizeof words);
 118         for (i = 0; i < NS_IN6ADDRSZ; i++)
 119                 words[i / 2] |= (src[i] << ((1 - (i % 2)) << 3));
 120         best.base = -1;
 121         cur.base = -1;
 122         for (i = 0; i < (NS_IN6ADDRSZ / NS_INT16SZ); i++) {
 123                 if (words[i] == 0) {
 124                         if (cur.base == -1)
 125                                 cur.base = i, cur.len = 1;
 126                         else
 127                                 cur.len++;
 128                 } else {
 129                         if (cur.base != -1) {
 130                                 if (best.base == -1 || cur.len > best.len)
 131                                         best = cur;
 132                                 cur.base = -1;
 133                         }
 134                 }
 135         }
 136         if (cur.base != -1) {
 137                 if (best.base == -1 || cur.len > best.len)
 138                         best = cur;
 139         }
 140         if (best.base != -1 && best.len < 2)
 141                 best.base = -1;
 142
 143         /*
 144          * Format the result.
 145          */
 146         tp = tmp;
 147         for (i = 0; i < (NS_IN6ADDRSZ / NS_INT16SZ); i++) {
 148                 /* Are we inside the best run of 0x00's? */
 149                 if (best.base != -1 && i >= best.base &&
 150                     i < (best.base + best.len)) {
 151                         if (i == best.base)
 152                                 *tp++ = ':';
 153                         continue;
 154                 }
 155                 /* Are we following an initial run of 0x00s or any real hex? */
 156                 if (i != 0)
 157                         *tp++ = ':';
 158                 /* Is this address an encapsulated IPv4? */
 159                 if (i == 6 && best.base == 0 &&
 160                     (best.len == 6 || (best.len == 5 && words[5] == 0xffff))) {
 161                         if (!inet_ntop4(src+12, tp, sizeof tmp - (tp - tmp)))
 162                                 return (NULL);
 163                         tp += strlen(tp);
 164                         break;
 165                 }
 166                 inc = snprintf(tp, 5, "%x", words[i]);
 167                 assert(inc < 5);
 168                 tp += inc;
 169         }
 170         /* Was it a trailing run of 0x00's? */
 171         if (best.base != -1 && (best.base + best.len) ==
 172             (NS_IN6ADDRSZ / NS_INT16SZ))
 173                 *tp++ = ':';
 174         *tp++ = '\0';
 175
 176         /*
 177          * Check for overflow, copy, and we're done.
 178          */
 179         if ((size_t)(tp - tmp) > size) {
 180                 errno = ENOSPC;
 181                 return (NULL);
 182         }
 183         memcpy(dst, tmp, tp - tmp);
 184         return (dst);
 185 }
 186 #endif /* AF_INET6 */