lib/libc/net/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  * $FreeBSD: src/lib/libc/net/inet_ntop.c,v 1.6.2.2 2002/12/16 15:19:35 robert Exp $
  17  * $DragonFly: src/lib/libc/net/inet_ntop.c,v 1.4 2005/11/13 02:04:47 swildner Exp $
  18  */
  19
  20 #include <sys/param.h>
  21 #include <sys/types.h>
  22 #include <sys/socket.h>
  23 #include <netinet/in.h>
  24 #include <arpa/inet.h>
  25 #include <arpa/nameser.h>
  26 #include <errno.h>
  27 #include <stdio.h>
  28 #include <string.h>
  29
  30 /*
  31  * WARNING: Don't even consider trying to compile this on a system where
  32  * sizeof(int) < 4.  sizeof(int) > 4 is fine; all the world's not a VAX.
  33  */
  34
  35 static const char *inet_ntop4 (const u_char *src, char *dst, size_t size);
  36 static const char *inet_ntop6 (const u_char *src, char *dst, size_t size);
  37
  38 /* char *
  39  * inet_ntop(af, src, dst, size)
  40  *      convert a network format address to presentation format.
  41  * return:
  42  *      pointer to presentation format address (`dst'), or NULL (see errno).
  43  * author:
  44  *      Paul Vixie, 1996.
  45  */
  46 const char *
  47 inet_ntop(int af, const void *src, char *dst, size_t size)
  48 {
  49         switch (af) {
  50         case AF_INET:
  51                 return (inet_ntop4(src, dst, size));
  52         case AF_INET6:
  53                 return (inet_ntop6(src, dst, size));
  54         default:
  55                 errno = EAFNOSUPPORT;
  56                 return (NULL);
  57         }
  58         /* NOTREACHED */
  59 }
  60
  61 /* const char *
  62  * inet_ntop4(src, dst, size)
  63  *      format an IPv4 address, more or less like inet_ntoa()
  64  * return:
  65  *      `dst' (as a const)
  66  * notes:
  67  *      (1) uses no statics
  68  *      (2) takes a u_char* not an in_addr as input
  69  * author:
  70  *      Paul Vixie, 1996.
  71  */
  72 static const char *
  73 inet_ntop4(const u_char *src, char *dst, size_t size)
  74 {
  75         static const char fmt[] = "%u.%u.%u.%u";
  76
  77         if ((size_t)snprintf(dst, size, fmt, src[0], src[1], src[2], src[3])
  78             >= size) {
  79                 errno = ENOSPC;
  80                 return (NULL);
  81         }
  82         return (dst);
  83 }
  84
  85 /* const char *
  86  * inet_ntop6(src, dst, size)
  87  *      convert IPv6 binary address into presentation (printable) format
  88  * author:
  89  *      Paul Vixie, 1996.
  90  */
  91 static const char *
  92 inet_ntop6(const u_char *src, char *dst, size_t size)
  93 {
  94         /*
  95          * Note that int32_t and int16_t need only be "at least" large enough
  96          * to contain a value of the specified size.  On some systems, like
  97          * Crays, there is no such thing as an integer variable with 16 bits.
  98          * Keep this in mind if you think this function should have been coded
  99          * to use pointer overlays.  All the world's not a VAX.
 100          */
 101         char tmp[sizeof "ffff:ffff:ffff:ffff:ffff:ffff:255.255.255.255"], *tp;
 102         struct { int base, len; } best, cur;
 103         u_int words[NS_IN6ADDRSZ / NS_INT16SZ];
 104         int i;
 105
 106         /*
 107          * Preprocess:
 108          *      Copy the input (bytewise) array into a wordwise array.
 109          *      Find the longest run of 0x00's in src[] for :: shorthanding.
 110          */
 111         memset(words, '\0', sizeof words);
 112         for (i = 0; i < NS_IN6ADDRSZ; i++)
 113                 words[i / 2] |= (src[i] << ((1 - (i % 2)) << 3));
 114         best.base = -1;
 115         cur.base = -1;
 116         for (i = 0; i < (NS_IN6ADDRSZ / NS_INT16SZ); i++) {
 117                 if (words[i] == 0) {
 118                         if (cur.base == -1)
 119                                 cur.base = i, cur.len = 1;
 120                         else
 121                                 cur.len++;
 122                 } else {
 123                         if (cur.base != -1) {
 124                                 if (best.base == -1 || cur.len > best.len)
 125                                         best = cur;
 126                                 cur.base = -1;
 127                         }
 128                 }
 129         }
 130         if (cur.base != -1) {
 131                 if (best.base == -1 || cur.len > best.len)
 132                         best = cur;
 133         }
 134         if (best.base != -1 && best.len < 2)
 135                 best.base = -1;
 136
 137         /*
 138          * Format the result.
 139          */
 140         tp = tmp;
 141         for (i = 0; i < (NS_IN6ADDRSZ / NS_INT16SZ); i++) {
 142                 /* Are we inside the best run of 0x00's? */
 143                 if (best.base != -1 && i >= best.base &&
 144                     i < (best.base + best.len)) {
 145                         if (i == best.base)
 146                                 *tp++ = ':';
 147                         continue;
 148                 }
 149                 /* Are we following an initial run of 0x00s or any real hex? */
 150                 if (i != 0)
 151                         *tp++ = ':';
 152                 /* Is this address an encapsulated IPv4? */
 153                 if (i == 6 && best.base == 0 &&
 154                     (best.len == 6 || (best.len == 5 && words[5] == 0xffff))) {
 155                         if (!inet_ntop4(src+12, tp, sizeof tmp - (tp - tmp)))
 156                                 return (NULL);
 157                         tp += strlen(tp);
 158                         break;
 159                 }
 160                 tp += sprintf(tp, "%x", words[i]);
 161         }
 162         /* Was it a trailing run of 0x00's? */
 163         if (best.base != -1 && (best.base + best.len) ==
 164             (NS_IN6ADDRSZ / NS_INT16SZ))
 165                 *tp++ = ':';
 166         *tp++ = '\0';
 167
 168         /*
 169          * Check for overflow, copy, and we're done.
 170          */
 171         if ((size_t)(tp - tmp) > size) {
 172                 errno = ENOSPC;
 173                 return (NULL);
 174         }
 175         strcpy(dst, tmp);
 176         return (dst);
 177 }
 178
 179 /*
 180  * Weak aliases for applications that use certain private entry points,
 181  * and fail to include <arpa/inet.h>.
 182  */
 183 #undef inet_ntop
 184 __weak_reference(__inet_ntop, inet_ntop);