lib/libc/inet/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 1.5 2005/11/03 22:59:52 marka Exp $";
  20 #endif /* LIBC_SCCS and not lint */
  21 #include <sys/cdefs.h>
  22 __FBSDID("$FreeBSD$");
  23
  24 #include "port_before.h"
  25
  26 #include <sys/param.h>
  27 #include <sys/socket.h>
  28
  29 #include <netinet/in.h>
  30 #include <arpa/inet.h>
  31 #include <arpa/nameser.h>
  32
  33 #include <errno.h>
  34 #include <stdio.h>
  35 #include <string.h>
  36
  37 #include "port_after.h"
  38
  39 /*%
  40  * WARNING: Don't even consider trying to compile this on a system where
  41  * sizeof(int) < 4.  sizeof(int) > 4 is fine; all the world's not a VAX.
  42  */
  43
  44 static const char *inet_ntop4(const u_char *src, char *dst, socklen_t size);
  45 static const char *inet_ntop6(const u_char *src, char *dst, socklen_t size);
  46
  47 /* const char *
  48  * inet_ntop(af, src, dst, size)
  49  *      convert a network format address to presentation format.
  50  * return:
  51  *      pointer to presentation format address (`dst'), or NULL (see errno).
  52  * author:
  53  *      Paul Vixie, 1996.
  54  */
  55 const char *
  56 inet_ntop(int af, const void * __restrict src, char * __restrict dst,
  57     socklen_t size)
  58 {
  59         switch (af) {
  60         case AF_INET:
  61                 return (inet_ntop4(src, dst, size));
  62         case AF_INET6:
  63                 return (inet_ntop6(src, dst, size));
  64         default:
  65                 errno = EAFNOSUPPORT;
  66                 return (NULL);
  67         }
  68         /* NOTREACHED */
  69 }
  70
  71 /* const char *
  72  * inet_ntop4(src, dst, size)
  73  *      format an IPv4 address
  74  * return:
  75  *      `dst' (as a const)
  76  * notes:
  77  *      (1) uses no statics
  78  *      (2) takes a u_char* not an in_addr as input
  79  * author:
  80  *      Paul Vixie, 1996.
  81  */
  82 static const char *
  83 inet_ntop4(const u_char *src, char *dst, socklen_t size)
  84 {
  85         static const char fmt[] = "%u.%u.%u.%u";
  86         char tmp[sizeof "255.255.255.255"];
  87         int l;
  88
  89         l = snprintf(tmp, sizeof(tmp), fmt, src[0], src[1], src[2], src[3]);
  90         if (l <= 0 || (socklen_t) l >= size) {
  91                 errno = ENOSPC;
  92                 return (NULL);
  93         }
  94         strlcpy(dst, tmp, size);
  95         return (dst);
  96 }
  97
  98 /* const char *
  99  * inet_ntop6(src, dst, size)
 100  *      convert IPv6 binary address into presentation (printable) format
 101  * author:
 102  *      Paul Vixie, 1996.
 103  */
 104 static const char *
 105 inet_ntop6(const u_char *src, char *dst, socklen_t size)
 106 {
 107         /*
 108          * Note that int32_t and int16_t need only be "at least" large enough
 109          * to contain a value of the specified size.  On some systems, like
 110          * Crays, there is no such thing as an integer variable with 16 bits.
 111          * Keep this in mind if you think this function should have been coded
 112          * to use pointer overlays.  All the world's not a VAX.
 113          */
 114         char tmp[sizeof "ffff:ffff:ffff:ffff:ffff:ffff:255.255.255.255"], *tp;
 115         struct { int base, len; } best, cur;
 116         u_int words[NS_IN6ADDRSZ / NS_INT16SZ];
 117         int i;
 118
 119         /*
 120          * Preprocess:
 121          *      Copy the input (bytewise) array into a wordwise array.
 122          *      Find the longest run of 0x00's in src[] for :: shorthanding.
 123          */
 124         memset(words, '\0', sizeof words);
 125         for (i = 0; i < NS_IN6ADDRSZ; i++)
 126                 words[i / 2] |= (src[i] << ((1 - (i % 2)) << 3));
 127         best.base = -1;
 128         best.len = 0;
 129         cur.base = -1;
 130         cur.len = 0;
 131         for (i = 0; i < (NS_IN6ADDRSZ / NS_INT16SZ); i++) {
 132                 if (words[i] == 0) {
 133                         if (cur.base == -1)
 134                                 cur.base = i, cur.len = 1;
 135                         else
 136                                 cur.len++;
 137                 } else {
 138                         if (cur.base != -1) {
 139                                 if (best.base == -1 || cur.len > best.len)
 140                                         best = cur;
 141                                 cur.base = -1;
 142                         }
 143                 }
 144         }
 145         if (cur.base != -1) {
 146                 if (best.base == -1 || cur.len > best.len)
 147                         best = cur;
 148         }
 149         if (best.base != -1 && best.len < 2)
 150                 best.base = -1;
 151
 152         /*
 153          * Format the result.
 154          */
 155         tp = tmp;
 156         for (i = 0; i < (NS_IN6ADDRSZ / NS_INT16SZ); i++) {
 157                 /* Are we inside the best run of 0x00's? */
 158                 if (best.base != -1 && i >= best.base &&
 159                     i < (best.base + best.len)) {
 160                         if (i == best.base)
 161                                 *tp++ = ':';
 162                         continue;
 163                 }
 164                 /* Are we following an initial run of 0x00s or any real hex? */
 165                 if (i != 0)
 166                         *tp++ = ':';
 167                 /* Is this address an encapsulated IPv4? */
 168                 if (i == 6 && best.base == 0 && (best.len == 6 ||
 169                     (best.len == 7 && words[7] != 0x0001) ||
 170                     (best.len == 5 && words[5] == 0xffff))) {
 171                         if (!inet_ntop4(src+12, tp, sizeof tmp - (tp - tmp))) {
 172                                 errno = ENOSPC;
 173                                 return (NULL);
 174                         }
 175                         tp += strlen(tp);
 176                         break;
 177                 }
 178                 tp += sprintf(tp, "%x", words[i]);
 179         }
 180         /* Was it a trailing run of 0x00's? */
 181         if (best.base != -1 && (best.base + best.len) ==
 182             (NS_IN6ADDRSZ / NS_INT16SZ))
 183                 *tp++ = ':';
 184         *tp++ = '\0';
 185
 186         /*
 187          * Check for overflow, copy, and we're done.
 188          */
 189         if ((socklen_t)(tp - tmp) > size) {
 190                 errno = ENOSPC;
 191                 return (NULL);
 192         }
 193         strcpy(dst, tmp);
 194         return (dst);
 195 }
 196
 197 /*
 198  * Weak aliases for applications that use certain private entry points,
 199  * and fail to include <arpa/inet.h>.
 200  */
 201 #undef inet_ntop
 202 __weak_reference(__inet_ntop, inet_ntop);
 203
 204 /*! \file */