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 * nbase_misc.c -- Some small miscelaneous utility/compatability           *
 * functions.                                                              *
 *                                                                         *
 ***********************IMPORTANT NMAP LICENSE TERMS************************
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 * also a registered trademark of Insecure.Com LLC.  This program is free  *
 * software; you may redistribute and/or modify it under the terms of the  *
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 *                                                                         *

/* $Id: nbase_misc.c 7896 2008-06-03 15:58:02Z michael $ */

#ifndef WIN32
#include <errno.h>
#ifndef errno
extern int errno;
#include <winsock2.h>

#include "nbase.h"
#include "nbase_ipv6.h"

#include <assert.h>


/* Returns the UNIX/Windows errno-equivalent.  Note that the Windows
   call is socket/networking specific.  The windows error number
   returned is like WSAMSGSIZE, but nbase.h includes #defines to
   correlate many of the common UNIX errors with their closest Windows
   equivalents.  So you can use EMSGSIZE or EINTR. */
int socket_errno() {
#ifdef WIN32
      return WSAGetLastError();
      return errno;

/* This function is an easier version of inet_ntop because you don't
   need to pass a dest buffer.  Instead, it returns a static buffer that
   you can use until the function is called again (by the same or another
   thread in the process).  If there is a wierd error (like sslen being
   too short) then NULL will be returned. */
const char *inet_ntop_ez(struct sockaddr_storage *ss, size_t sslen) {

  struct sockaddr_in *sin = (struct sockaddr_in *) ss;
  static char str[INET6_ADDRSTRLEN];
  struct sockaddr_in6 *sin6 = (struct sockaddr_in6 *) ss;

  str[0] = '\0';

  if (sin->sin_family == AF_INET) {
    if (sslen < sizeof(struct sockaddr_in))
      return NULL;
    return inet_ntop(AF_INET, &sin->sin_addr, str, sizeof(str));
  else if(sin->sin_family == AF_INET6) {
    if (sslen < sizeof(struct sockaddr_in6))
      return NULL;
    return inet_ntop(AF_INET6, &sin6->sin6_addr, str, sizeof(str));
  //Some laptops report the ip and address family of disabled wifi cards as null
  //so yes, we will hit this sometimes.
  return NULL;

 * CRC16 Cyclic Redundancy Check
 * simply copied from http://www.ptb.de/de/org/1/11/112/infos/crc16.htm

/* Table of CRCs of all 8-bit messages. */
static unsigned long crc_table[256];

/* Flag: has the table been computed? Initially false. */
static int crc_table_computed = 0;

/* Make the table for a fast CRC. */
static void make_crc_table(void)
  unsigned long c;
  int n, k;

  for (n = 0; n < 256; n++) {
    c = (unsigned long) n;
    for (k = 0; k < 8; k++) {
      if (c & 1) {
        c = 0xedb88320L ^ (c >> 1);
      } else {
        c = c >> 1;
    crc_table[n] = c;
  crc_table_computed = 1;

   Update a running crc with the bytes buf[0..len-1] and return
 the updated crc. The crc should be initialized to zero. Pre- and
 post-conditioning (one's complement) is performed within this
 function so it shouldn't be done by the caller. Usage example:

   unsigned long crc = 0L;

   while (read_buffer(buffer, length) != EOF) {
     crc = update_crc(crc, buffer, length);
   if (crc != original_crc) error();
static unsigned long update_crc(unsigned long crc,
                unsigned char *buf, int len)
  unsigned long c = crc ^ 0xffffffffL;
  int n;

  if (!crc_table_computed)
  for (n = 0; n < len; n++) {
    c = crc_table[(c ^ buf[n]) & 0xff] ^ (c >> 8);
  return c ^ 0xffffffffL;

/* Return the CRC of the bytes buf[0..len-1]. */
unsigned long crc16(unsigned char *buf, int len)
  return update_crc(0L, buf, len);

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