inet_ntop.c   [plain text]


/*
 * Copyright (c) 1999 Kungliga Tekniska Högskolan
 * (Royal Institute of Technology, Stockholm, Sweden).
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *      This product includes software developed by the Kungliga Tekniska
 *      Högskolan and its contributors.
 *
 * 4. Neither the name of the Institute nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

/* $Id: inet_ntop.c,v 1.8 2005-02-09 02:25:46 guy Exp $ */

#ifndef lint
static const char rcsid[] _U_ =
     "@(#) $Header: /tcpdump/master/tcpdump/missing/inet_ntop.c,v 1.8 2005-02-09 02:25:46 guy Exp $";
#endif

#include <tcpdump-stdinc.h>

#include <stdio.h>
#include <errno.h>

/*
 *
 */

#ifndef IN6ADDRSZ
#define IN6ADDRSZ   16   /* IPv6 T_AAAA */
#endif

#ifndef INT16SZ
#define INT16SZ     2    /* word size */
#endif

static const char *
inet_ntop_v4 (const void *src, char *dst, size_t size)
{
    const char digits[] = "0123456789";
    int i;
    struct in_addr *addr = (struct in_addr *)src;
    u_long a = ntohl(addr->s_addr);
    const char *orig_dst = dst;

    if (size < INET_ADDRSTRLEN) {
	errno = ENOSPC;
	return NULL;
    }
    for (i = 0; i < 4; ++i) {
	int n = (a >> (24 - i * 8)) & 0xFF;
	int non_zerop = 0;

	if (non_zerop || n / 100 > 0) {
	    *dst++ = digits[n / 100];
	    n %= 100;
	    non_zerop = 1;
	}
	if (non_zerop || n / 10 > 0) {
	    *dst++ = digits[n / 10];
	    n %= 10;
	    non_zerop = 1;
	}
	*dst++ = digits[n];
	if (i != 3)
	    *dst++ = '.';
    }
    *dst++ = '\0';
    return orig_dst;
}

#ifdef INET6
/*
 * Convert IPv6 binary address into presentation (printable) format.
 */
static const char *
inet_ntop_v6 (const u_char *src, char *dst, size_t size)
{
  /*
   * Note that int32_t and int16_t need only be "at least" large enough
   * to contain a value of the specified size.  On some systems, like
   * Crays, there is no such thing as an integer variable with 16 bits.
   * Keep this in mind if you think this function should have been coded
   * to use pointer overlays.  All the world's not a VAX.
   */
  char  tmp [INET6_ADDRSTRLEN+1];
  char *tp;
  struct {
    long base;
    long len;
  } best, cur;
  u_long words [IN6ADDRSZ / INT16SZ];
  int    i;

  /* Preprocess:
   *  Copy the input (bytewise) array into a wordwise array.
   *  Find the longest run of 0x00's in src[] for :: shorthanding.
   */
  memset (words, 0, sizeof(words));
  for (i = 0; i < IN6ADDRSZ; i++)
      words[i/2] |= (src[i] << ((1 - (i % 2)) << 3));

  best.base = -1;
  cur.base  = -1;
  for (i = 0; i < (IN6ADDRSZ / INT16SZ); i++)
  {
    if (words[i] == 0)
    {
      if (cur.base == -1)
           cur.base = i, cur.len = 1;
      else cur.len++;
    }
    else if (cur.base != -1)
    {
      if (best.base == -1 || cur.len > best.len)
         best = cur;
      cur.base = -1;
    }
  }
  if ((cur.base != -1) && (best.base == -1 || cur.len > best.len))
     best = cur;
  if (best.base != -1 && best.len < 2)
     best.base = -1;

  /* Format the result.
   */
  tp = tmp;
  for (i = 0; i < (IN6ADDRSZ / INT16SZ); i++)
  {
    /* Are we inside the best run of 0x00's?
     */
    if (best.base != -1 && i >= best.base && i < (best.base + best.len))
    {
      if (i == best.base)
         *tp++ = ':';
      continue;
    }

    /* Are we following an initial run of 0x00s or any real hex?
     */
    if (i != 0)
       *tp++ = ':';

    /* Is this address an encapsulated IPv4?
     */
    if (i == 6 && best.base == 0 &&
        (best.len == 6 || (best.len == 5 && words[5] == 0xffff)))
    {
      if (!inet_ntop_v4(src+12, tp, sizeof(tmp) - (tp - tmp)))
      {
        errno = ENOSPC;
        return (NULL);
      }
      tp += strlen(tp);
      break;
    }
    tp += sprintf (tp, "%lX", words[i]);
  }

  /* Was it a trailing run of 0x00's?
   */
  if (best.base != -1 && (best.base + best.len) == (IN6ADDRSZ / INT16SZ))
     *tp++ = ':';
  *tp++ = '\0';

  /* Check for overflow, copy, and we're done.
   */
  if ((size_t)(tp - tmp) > size)
  {
    errno = ENOSPC;
    return (NULL);
  }
  return strcpy (dst, tmp);
  return (NULL);
}
#endif   /* INET6 */


const char *
inet_ntop(int af, const void *src, char *dst, size_t size)
{
    switch (af) {
    case AF_INET :
	return inet_ntop_v4 (src, dst, size);
#ifdef INET6
    case AF_INET6:
         return inet_ntop_v6 ((const u_char*)src, dst, size);
#endif
    default :
	errno = EAFNOSUPPORT;
	return NULL;
    }
}