sys/libkern/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  * $Id: inet_ntop.c,v 1.3.18.2 2005/11/03 23:02:22 marka Exp $
  18  * FreeBSD r213103
  19  */
  20
  21 #include <sys/param.h>
  22 #include <sys/socket.h>
  23 #include <sys/systm.h>
  24
  25 #include <netinet/in.h>
  26
  27 /*%
  28  * WARNING: Don't even consider trying to compile this on a system where
  29  * sizeof(int) < 4.  sizeof(int) > 4 is fine; all the world's not a VAX.
  30  */
  31
  32 static char     *inet_ntop4(const u_char *src, char *dst, socklen_t size);
  33 static char     *inet_ntop6(const u_char *src, char *dst, socklen_t size);
  34
  35 /* char *
  36  * inet_ntop(af, src, dst, size)
  37  *      convert a network format address to presentation format.
  38  * return:
  39  *      pointer to presentation format address (`dst'), or NULL (see errno).
  40  * author:
  41  *      Paul Vixie, 1996.
  42  */
  43 char *
  44 inet_ntop(int af, const void *src, char *dst, socklen_t size)
  45 {
  46         switch (af) {
  47         case AF_INET:
  48                 return (inet_ntop4(src, dst, size));
  49         case AF_INET6:
  50                 return (inet_ntop6(src, dst, size));
  51         default:
  52                 return (NULL);
  53         }
  54         /* NOTREACHED */
  55 }
  56
  57 /* const char *
  58  * inet_ntop4(src, dst, size)
  59  *      format an IPv4 address
  60  * return:
  61  *      `dst' (as a const)
  62  * notes:
  63  *      (1) uses no statics
  64  *      (2) takes a u_char* not an in_addr as input
  65  * author:
  66  *      Paul Vixie, 1996.
  67  */
  68 static char *
  69 inet_ntop4(const u_char *src, char *dst, socklen_t size)
  70 {
  71         static const char fmt[] = "%u.%u.%u.%u";
  72         char tmp[sizeof "255.255.255.255"];
  73         int l;
  74
  75         l = ksnprintf(tmp, sizeof(tmp), fmt, src[0], src[1], src[2], src[3]);
  76         if (l <= 0 || (socklen_t) l >= size) {
  77                 return (NULL);
  78         }
  79         strlcpy(dst, tmp, size);
  80         return (dst);
  81 }
  82
  83 /* const char *
  84  * inet_ntop6(src, dst, size)
  85  *      convert IPv6 binary address into presentation (printable) format
  86  * author:
  87  *      Paul Vixie, 1996.
  88  */
  89 static char *
  90 inet_ntop6(const u_char *src, char *dst, socklen_t size)
  91 {
  92         /*
  93          * Note that int32_t and int16_t need only be "at least" large enough
  94          * to contain a value of the specified size.  On some systems, like
  95          * Crays, there is no such thing as an integer variable with 16 bits.
  96          * Keep this in mind if you think this function should have been coded
  97          * to use pointer overlays.  All the world's not a VAX.
  98          */
  99         char tmp[sizeof "ffff:ffff:ffff:ffff:ffff:ffff:255.255.255.255"], *tp;
 100         struct { int base, len; } best, cur;
 101 #define NS_IN6ADDRSZ    16
 102 #define NS_INT16SZ      2
 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         best.len = 0;
 116         cur.base = -1;
 117         cur.len = 0;
 118         for (i = 0; i < (NS_IN6ADDRSZ / NS_INT16SZ); i++) {
 119                 if (words[i] == 0) {
 120                         if (cur.base == -1)
 121                                 cur.base = i, cur.len = 1;
 122                         else
 123                                 cur.len++;
 124                 } else {
 125                         if (cur.base != -1) {
 126                                 if (best.base == -1 || cur.len > best.len)
 127                                         best = cur;
 128                                 cur.base = -1;
 129                         }
 130                 }
 131         }
 132         if (cur.base != -1) {
 133                 if (best.base == -1 || cur.len > best.len)
 134                         best = cur;
 135         }
 136         if (best.base != -1 && best.len < 2)
 137                 best.base = -1;
 138
 139         /*
 140          * Format the result.
 141          */
 142         tp = tmp;
 143         for (i = 0; i < (NS_IN6ADDRSZ / NS_INT16SZ); i++) {
 144                 /* Are we inside the best run of 0x00's? */
 145                 if (best.base != -1 && i >= best.base &&
 146                     i < (best.base + best.len)) {
 147                         if (i == best.base)
 148                                 *tp++ = ':';
 149                         continue;
 150                 }
 151                 /* Are we following an initial run of 0x00s or any real hex? */
 152                 if (i != 0)
 153                         *tp++ = ':';
 154                 /* Is this address an encapsulated IPv4? */
 155                 if (i == 6 && best.base == 0 && (best.len == 6 ||
 156                     (best.len == 7 && words[7] != 0x0001) ||
 157                     (best.len == 5 && words[5] == 0xffff))) {
 158                         if (!inet_ntop4(src+12, tp, sizeof tmp - (tp - tmp)))
 159                                 return (NULL);
 160                         tp += strlen(tp);
 161                         break;
 162                 }
 163                 tp += ksprintf(tp, "%x", words[i]);
 164         }
 165         /* Was it a trailing run of 0x00's? */
 166         if (best.base != -1 && (best.base + best.len) ==
 167             (NS_IN6ADDRSZ / NS_INT16SZ))
 168                 *tp++ = ':';
 169         *tp++ = '\0';
 170
 171         /*
 172          * Check for overflow, copy, and we're done.
 173          */
 174         if ((socklen_t)(tp - tmp) > size) {
 175                 return (NULL);
 176         }
 177         strcpy(dst, tmp);
 178         return (dst);
 179 }
 180
 181 /*! \file */