The Tcpdump Group git mirrors - tcpdump/blob - addrtostr.c

   1 /*
   2  * Copyright (c) 1999 Kungliga Tekniska Högskolan
   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  *      Högskolan 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 #include <config.h>
  40
  41 #include "netdissect-stdinc.h"
  42 #include "addrtostr.h"
  43
  44 #include <stdio.h>
  45 #include <string.h>
  46
  47 /*
  48  *
  49  */
  50
  51 #ifndef IN6ADDRSZ
  52 #define IN6ADDRSZ   16   /* IPv6 T_AAAA */
  53 #endif
  54
  55 #ifndef INT16SZ
  56 #define INT16SZ     2    /* word size */
  57 #endif
  58
  59 const char *
  60 addrtostr (const void *src, char *dst, size_t size)
  61 {
  62     const u_char *srcaddr = (const u_char *)src;
  63     const char digits[] = "0123456789";
  64     int i;
  65     const char *orig_dst = dst;
  66
  67     if (size < INET_ADDRSTRLEN) {
  68         errno = ENOSPC;
  69         return NULL;
  70     }
  71     for (i = 0; i < 4; ++i) {
  72         int n = *srcaddr++;
  73         int non_zerop = 0;
  74
  75         if (non_zerop || n / 100 > 0) {
  76             *dst++ = digits[n / 100];
  77             n %= 100;
  78             non_zerop = 1;
  79         }
  80         if (non_zerop || n / 10 > 0) {
  81             *dst++ = digits[n / 10];
  82             n %= 10;
  83             non_zerop = 1;
  84         }
  85         *dst++ = digits[n];
  86         if (i != 3)
  87             *dst++ = '.';
  88     }
  89     *dst++ = '\0';
  90     return orig_dst;
  91 }
  92
  93 /*
  94  * Convert IPv6 binary address into presentation (printable) format.
  95  */
  96 const char *
  97 addrtostr6 (const void *src, char *dst, size_t size)
  98 {
  99   /*
 100    * Note that int32_t and int16_t need only be "at least" large enough
 101    * to contain a value of the specified size.  On some systems, like
 102    * Crays, there is no such thing as an integer variable with 16 bits.
 103    * Keep this in mind if you think this function should have been coded
 104    * to use pointer overlays.  All the world's not a VAX.
 105    */
 106   const u_char *srcaddr = (const u_char *)src;
 107   char *dp;
 108   size_t space_left, added_space;
 109   int snprintfed;
 110   struct {
 111     int base;
 112     int len;
 113   } best, cur;
 114   uint16_t words [IN6ADDRSZ / INT16SZ];
 115   int  i;
 116
 117   /* Preprocess:
 118    *  Copy the input (bytewise) array into a wordwise array.
 119    *  Find the longest run of 0x00's in src[] for :: shorthanding.
 120    */
 121   for (i = 0; i < (IN6ADDRSZ / INT16SZ); i++)
 122       words[i] = (srcaddr[2*i] << 8) | srcaddr[2*i + 1];
 123
 124   best.len = 0;
 125   best.base = -1;
 126   cur.len = 0;
 127   cur.base  = -1;
 128   for (i = 0; i < (IN6ADDRSZ / INT16SZ); i++) {
 129     if (words[i] == 0) {
 130       if (cur.base == -1)
 131            cur.base = i, cur.len = 1;
 132       else cur.len++;
 133     } else if (cur.base != -1) {
 134       if (best.base == -1 || cur.len > best.len)
 135          best = cur;
 136       cur.base = -1;
 137     }
 138   }
 139   if ((cur.base != -1) && (best.base == -1 || cur.len > best.len))
 140      best = cur;
 141   if (best.base != -1 && best.len < 2)
 142      best.base = -1;
 143
 144   /* Format the result.
 145    */
 146   dp = dst;
 147   space_left = size;
 148 #define APPEND_CHAR(c) \
 149     { \
 150         if (space_left == 0) { \
 151             errno = ENOSPC; \
 152             return (NULL); \
 153         } \
 154         *dp++ = c; \
 155         space_left--; \
 156     }
 157   for (i = 0; i < (IN6ADDRSZ / INT16SZ); i++) {
 158     /* Are we inside the best run of 0x00's?
 159      */
 160     if (best.base != -1 && i >= best.base && i < (best.base + best.len)) {
 161       if (i == best.base)
 162           APPEND_CHAR(':');
 163       continue;
 164     }
 165
 166     /* Are we following an initial run of 0x00s or any real hex?
 167      */
 168     if (i != 0)
 169        APPEND_CHAR(':');
 170
 171     /* Is this address an encapsulated IPv4?
 172      */
 173     if (i == 6 && best.base == 0 &&
 174         (best.len == 6 || (best.len == 5 && words[5] == 0xffff)))
 175     {
 176       if (!addrtostr(srcaddr+12, dp, space_left)) {
 177         errno = ENOSPC;
 178         return (NULL);
 179       }
 180       added_space = strlen(dp);
 181       dp += added_space;
 182       space_left -= added_space;
 183       break;
 184     }
 185     snprintfed = snprintf (dp, space_left, "%x", words[i]);
 186     if (snprintfed < 0)
 187         return (NULL);
 188     if ((size_t) snprintfed >= space_left) {
 189         errno = ENOSPC;
 190         return (NULL);
 191     }
 192     dp += snprintfed;
 193     space_left -= snprintfed;
 194   }
 195
 196   /* Was it a trailing run of 0x00's?
 197    */
 198   if (best.base != -1 && (best.base + best.len) == (IN6ADDRSZ / INT16SZ))
 199      APPEND_CHAR(':');
 200   APPEND_CHAR('\0');
 201
 202   return (dst);
 203 }