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      1 /*
      2  * Copyright (c) 1999 Kungliga Tekniska Hgskolan
      3  * (Royal Institute of Technology, Stockholm, Sweden).
      4  * All rights reserved.
      5  *
      6  * Redistribution and use in source and binary forms, with or without
      7  * modification, are permitted provided that the following conditions
      8  * are met:
      9  *
     10  * 1. Redistributions of source code must retain the above copyright
     11  *    notice, this list of conditions and the following disclaimer.
     12  *
     13  * 2. Redistributions in binary form must reproduce the above copyright
     14  *    notice, this list of conditions and the following disclaimer in the
     15  *    documentation and/or other materials provided with the distribution.
     16  *
     17  * 3. All advertising materials mentioning features or use of this software
     18  *    must display the following acknowledgement:
     19  *      This product includes software developed by the Kungliga Tekniska
     20  *      Hgskolan and its contributors.
     21  *
     22  * 4. Neither the name of the Institute nor the names of its contributors
     23  *    may be used to endorse or promote products derived from this software
     24  *    without specific prior written permission.
     25  *
     26  * THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
     27  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     28  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     29  * ARE DISCLAIMED.  IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
     30  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     31  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     32  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     33  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     34  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     35  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     36  * SUCH DAMAGE.
     37  */
     38 
     39 /* $Id: inet_ntop.c,v 1.8 2005/02/09 02:25:46 guy Exp $ */
     40 
     41 #ifndef lint
     42 static const char rcsid[] _U_ =
     43      "@(#) $Header: /tcpdump/master/tcpdump/missing/inet_ntop.c,v 1.8 2005/02/09 02:25:46 guy Exp $";
     44 #endif
     45 
     46 #include <tcpdump-stdinc.h>
     47 
     48 #include <stdio.h>
     49 #include <errno.h>
     50 
     51 /*
     52  *
     53  */
     54 
     55 #ifndef IN6ADDRSZ
     56 #define IN6ADDRSZ   16   /* IPv6 T_AAAA */
     57 #endif
     58 
     59 #ifndef INT16SZ
     60 #define INT16SZ     2    /* word size */
     61 #endif
     62 
     63 static const char *
     64 inet_ntop_v4 (const void *src, char *dst, size_t size)
     65 {
     66     const char digits[] = "0123456789";
     67     int i;
     68     struct in_addr *addr = (struct in_addr *)src;
     69     u_long a = ntohl(addr->s_addr);
     70     const char *orig_dst = dst;
     71 
     72     if (size < INET_ADDRSTRLEN) {
     73 	errno = ENOSPC;
     74 	return NULL;
     75     }
     76     for (i = 0; i < 4; ++i) {
     77 	int n = (a >> (24 - i * 8)) & 0xFF;
     78 	int non_zerop = 0;
     79 
     80 	if (non_zerop || n / 100 > 0) {
     81 	    *dst++ = digits[n / 100];
     82 	    n %= 100;
     83 	    non_zerop = 1;
     84 	}
     85 	if (non_zerop || n / 10 > 0) {
     86 	    *dst++ = digits[n / 10];
     87 	    n %= 10;
     88 	    non_zerop = 1;
     89 	}
     90 	*dst++ = digits[n];
     91 	if (i != 3)
     92 	    *dst++ = '.';
     93     }
     94     *dst++ = '\0';
     95     return orig_dst;
     96 }
     97 
     98 #ifdef INET6
     99 /*
    100  * Convert IPv6 binary address into presentation (printable) format.
    101  */
    102 static const char *
    103 inet_ntop_v6 (const u_char *src, char *dst, size_t size)
    104 {
    105   /*
    106    * Note that int32_t and int16_t need only be "at least" large enough
    107    * to contain a value of the specified size.  On some systems, like
    108    * Crays, there is no such thing as an integer variable with 16 bits.
    109    * Keep this in mind if you think this function should have been coded
    110    * to use pointer overlays.  All the world's not a VAX.
    111    */
    112   char  tmp [INET6_ADDRSTRLEN+1];
    113   char *tp;
    114   struct {
    115     long base;
    116     long len;
    117   } best, cur;
    118   u_long words [IN6ADDRSZ / INT16SZ];
    119   int    i;
    120 
    121   /* Preprocess:
    122    *  Copy the input (bytewise) array into a wordwise array.
    123    *  Find the longest run of 0x00's in src[] for :: shorthanding.
    124    */
    125   memset (words, 0, sizeof(words));
    126   for (i = 0; i < IN6ADDRSZ; i++)
    127       words[i/2] |= (src[i] << ((1 - (i % 2)) << 3));
    128 
    129   best.base = -1;
    130   cur.base  = -1;
    131   for (i = 0; i < (IN6ADDRSZ / INT16SZ); i++)
    132   {
    133     if (words[i] == 0)
    134     {
    135       if (cur.base == -1)
    136            cur.base = i, cur.len = 1;
    137       else cur.len++;
    138     }
    139     else if (cur.base != -1)
    140     {
    141       if (best.base == -1 || cur.len > best.len)
    142          best = cur;
    143       cur.base = -1;
    144     }
    145   }
    146   if ((cur.base != -1) && (best.base == -1 || cur.len > best.len))
    147      best = cur;
    148   if (best.base != -1 && best.len < 2)
    149      best.base = -1;
    150 
    151   /* Format the result.
    152    */
    153   tp = tmp;
    154   for (i = 0; i < (IN6ADDRSZ / INT16SZ); i++)
    155   {
    156     /* Are we inside the best run of 0x00's?
    157      */
    158     if (best.base != -1 && i >= best.base && i < (best.base + best.len))
    159     {
    160       if (i == best.base)
    161          *tp++ = ':';
    162       continue;
    163     }
    164 
    165     /* Are we following an initial run of 0x00s or any real hex?
    166      */
    167     if (i != 0)
    168        *tp++ = ':';
    169 
    170     /* Is this address an encapsulated IPv4?
    171      */
    172     if (i == 6 && best.base == 0 &&
    173         (best.len == 6 || (best.len == 5 && words[5] == 0xffff)))
    174     {
    175       if (!inet_ntop_v4(src+12, tp, sizeof(tmp) - (tp - tmp)))
    176       {
    177         errno = ENOSPC;
    178         return (NULL);
    179       }
    180       tp += strlen(tp);
    181       break;
    182     }
    183     tp += sprintf (tp, "%lX", words[i]);
    184   }
    185 
    186   /* Was it a trailing run of 0x00's?
    187    */
    188   if (best.base != -1 && (best.base + best.len) == (IN6ADDRSZ / INT16SZ))
    189      *tp++ = ':';
    190   *tp++ = '\0';
    191 
    192   /* Check for overflow, copy, and we're done.
    193    */
    194   if ((size_t)(tp - tmp) > size)
    195   {
    196     errno = ENOSPC;
    197     return (NULL);
    198   }
    199   return strcpy (dst, tmp);
    200   return (NULL);
    201 }
    202 #endif   /* INET6 */
    203 
    204 
    205 const char *
    206 inet_ntop(int af, const void *src, char *dst, size_t size)
    207 {
    208     switch (af) {
    209     case AF_INET :
    210 	return inet_ntop_v4 (src, dst, size);
    211 #ifdef INET6
    212     case AF_INET6:
    213          return inet_ntop_v6 ((const u_char*)src, dst, size);
    214 #endif
    215     default :
    216 	errno = EAFNOSUPPORT;
    217 	return NULL;
    218     }
    219 }
    220