libkern/net/inet_ntop.c

   1 /*
   2  * Copyright (c) 2004 by Internet Systems Consortium, Inc. ("ISC")
   3  * Copyright (c) 1996-1999 by Internet Software Consortium.
   4  *
   5  * Permission to use, copy, modify, and distribute this software for any
   6  * purpose with or without fee is hereby granted, provided that the above
   7  * copyright notice and this permission notice appear in all copies.
   8  *
   9  * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES
  10  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
  11  * MERCHANTABILITY AND FITNESS.  IN NO EVENT SHALL ISC BE LIABLE FOR
  12  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
  13  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
  14  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT
  15  * OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  16  */
  17
  18 #if defined(LIBC_SCCS) && !defined(lint)
  19 static const char rcsid[] = "$Id: inet_ntop.c,v 1.3.18.2 2005/11/03 23:02:22 marka Exp $";
  20 #endif /* LIBC_SCCS and not lint */
  21
  22 #include <sys/param.h>
  23 #include <sys/socket.h>
  24 #include <sys/systm.h>
  25
  26 #include <netinet/in.h>
  27
  28 /*%
  29  * WARNING: Don't even consider trying to compile this on a system where
  30  * sizeof(int) < 4.  sizeof(int) > 4 is fine; all the world's not a VAX.
  31  */
  32
  33 static char     *inet_ntop4(const u_char *src, char *dst, socklen_t size);
  34 static char     *inet_ntop6(const u_char *src, char *dst, socklen_t size);
  35
  36 /* char *
  37  * inet_ntop(af, src, dst, size)
  38  *      convert a network format address to presentation format.
  39  * return:
  40  *      pointer to presentation format address (`dst'), or NULL (see errno).
  41  * author:
  42  *      Paul Vixie, 1996.
  43  */
  44 const char *
  45 inet_ntop(int af, const void *src, char *dst, socklen_t size)
  46 {
  47         switch (af) {
  48         case AF_INET:
  49                 return (inet_ntop4(src, dst, size));
  50         case AF_INET6:
  51                 return (inet_ntop6(src, dst, size));
  52         default:
  53                 return (NULL);
  54         }
  55         /* NOTREACHED */
  56 }
  57
  58 /* const char *
  59  * inet_ntop4(src, dst, size)
  60  *      format an IPv4 address
  61  * return:
  62  *      `dst' (as a const)
  63  * notes:
  64  *      (1) uses no statics
  65  *      (2) takes a u_char* not an in_addr as input
  66  * author:
  67  *      Paul Vixie, 1996.
  68  */
  69 static char *
  70 inet_ntop4(const u_char *src, char *dst, socklen_t size)
  71 {
  72         static const char fmt[] = "%u.%u.%u.%u";
  73         char tmp[sizeof "255.255.255.255"];
  74         int l;
  75
  76         l = snprintf(tmp, sizeof(tmp), fmt, src[0], src[1], src[2], src[3]);
  77         if (l <= 0 || (socklen_t) l >= size) {
  78                 return (NULL);
  79         }
  80         strlcpy(dst, tmp, size);
  81         return (dst);
  82 }
  83
  84 /* const char *
  85  * inet_ntop6(src, dst, size)
  86  *      convert IPv6 binary address into presentation (printable) format
  87  * author:
  88  *      Paul Vixie, 1996.
  89  */
  90 static char *
  91 inet_ntop6(const u_char *src, char *dst, socklen_t size)
  92 {
  93         /*
  94          * Note that int32_t and int16_t need only be "at least" large enough
  95          * to contain a value of the specified size.  On some systems, like
  96          * Crays, there is no such thing as an integer variable with 16 bits.
  97          * Keep this in mind if you think this function should have been coded
  98          * to use pointer overlays.  All the world's not a VAX.
  99          */
 100         char tmp[sizeof "ffff:ffff:ffff:ffff:ffff:ffff:255.255.255.255"], *tp;
 101         struct { int base, len; } best, cur;
 102 #define NS_IN6ADDRSZ    16
 103 #define NS_INT16SZ      2
 104         u_int words[NS_IN6ADDRSZ / NS_INT16SZ];
 105         int i;
 106
 107         /*
 108          * Preprocess:
 109          *      Copy the input (bytewise) array into a wordwise array.
 110          *      Find the longest run of 0x00's in src[] for :: shorthanding.
 111          */
 112         memset(words, '\0', sizeof words);
 113         for (i = 0; i < NS_IN6ADDRSZ; i++)
 114                 words[i / 2] |= (src[i] << ((1 - (i % 2)) << 3));
 115         best.base = -1;
 116         best.len = 0;
 117         cur.base = -1;
 118         cur.len = 0;
 119         for (i = 0; i < (NS_IN6ADDRSZ / NS_INT16SZ); i++) {
 120                 if (words[i] == 0) {
 121                         if (cur.base == -1)
 122                                 cur.base = i, cur.len = 1;
 123                         else
 124                                 cur.len++;
 125                 } else {
 126                         if (cur.base != -1) {
 127                                 if (best.base == -1 || cur.len > best.len)
 128                                         best = cur;
 129                                 cur.base = -1;
 130                         }
 131                 }
 132         }
 133         if (cur.base != -1) {
 134                 if (best.base == -1 || cur.len > best.len)
 135                         best = cur;
 136         }
 137         if (best.base != -1 && best.len < 2)
 138                 best.base = -1;
 139
 140         /*
 141          * Format the result.
 142          */
 143         tp = tmp;
 144         for (i = 0; i < (NS_IN6ADDRSZ / NS_INT16SZ); i++) {
 145                 /* Are we inside the best run of 0x00's? */
 146                 if (best.base != -1 && i >= best.base &&
 147                     i < (best.base + best.len)) {
 148                         if (i == best.base)
 149                                 *tp++ = ':';
 150                         continue;
 151                 }
 152                 /* Are we following an initial run of 0x00s or any real hex? */
 153                 if (i != 0)
 154                         *tp++ = ':';
 155                 /* Is this address an encapsulated IPv4? */
 156                 if (i == 6 && best.base == 0 && (best.len == 6 ||
 157                     (best.len == 7 && words[7] != 0x0001) ||
 158                     (best.len == 5 && words[5] == 0xffff))) {
 159                         if (!inet_ntop4(src+12, tp, sizeof tmp - (tp - tmp)))
 160                                 return (NULL);
 161                         tp += strlen(tp);
 162                         break;
 163                 }
 164                 tp += snprintf(tp, sizeof(tmp), "%x", words[i]);
 165         }
 166         /* Was it a trailing run of 0x00's? */
 167         if (best.base != -1 && (best.base + best.len) ==
 168             (NS_IN6ADDRSZ / NS_INT16SZ))
 169                 *tp++ = ':';
 170         *tp++ = '\0';
 171
 172         /*
 173          * Check for overflow, copy, and we're done.
 174          */
 175         if ((socklen_t)(tp - tmp) > size) {
 176                 return (NULL);
 177         }
 178         strlcpy(dst, tmp, size);
 179         return (dst);
 180 }
 181
 182 /*! \file */