timing.cc

Ubuntu packages of security software。 相当不错的源码

/***************************************************************************
 * timing.cc -- Functions related to computing scan timing (such as        *
 * keeping track of and adjusting smoothed round trip times, statistical   *
 * deviations, timeout values, etc.  Various user options (such as the     *
 * timing policy (-T)) also play a role in these calculations              *
 *                                                                         *
 ***********************IMPORTANT NMAP LICENSE TERMS************************
 *                                                                         *
 * The Nmap Security Scanner is (C) 1996-2008 Insecure.Com LLC. Nmap is    *
 * 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  *
 * GNU General Public License as published by the Free Software            *
 * Foundation; Version 2 with the clarifications and exceptions described  *
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 * license Nmap technology such as host discovery, port scanning, OS       *
 * detection, and version detection.                                       *
 *                                                                         *
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 *                                                                         *
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 *                                                                         *
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 *                                                                         *
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 *                                                                         *
 * Source is provided to this software because we believe users have a     *
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 * This also allows you to audit the software for security holes (none     *
 * have been found so far).                                                *
 *                                                                         *
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 * distribution.  By sending these changes to Fyodor or one the            *
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 *                                                                         *
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 * General Public License for more details at                              *
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 * with Nmap.                                                              *
 *                                                                         *
 ***************************************************************************/

/* $Id: timing.cc 6633 2007-12-22 06:32:03Z fyodor $ */

#include "timing.h"
#include "NmapOps.h"
#include "utils.h"

extern NmapOps o;

/* Call this function on a newly allocated struct timeout_info to
   initialize the values appropriately */
void initialize_timeout_info(struct timeout_info *to) {
  to->srtt = -1;
  to->rttvar = -1;
  to->timeout = o.initialRttTimeout() * 1000;
}

/* Adjust our timeout values based on the time the latest probe took for a 
   response.  We update our RTT averages, etc. */
void adjust_timeouts(struct timeval sent, struct timeout_info *to) {
  struct timeval received;
  gettimeofday(&received, NULL);

  adjust_timeouts2(&sent, &received, to);
  return;
}

/* Same as adjust_timeouts(), except this one allows you to specify
 the receive time too (which could be because it was received a while
 back or it could be for efficiency because the caller already knows
 the current time */
void adjust_timeouts2(const struct timeval *sent, 
		      const struct timeval *received, 
		      struct timeout_info *to) {
  long delta = 0;

  if (o.debugging > 3) {
    log_write(LOG_STDOUT, "Timeout vals: srtt: %d rttvar: %d to: %d ", to->srtt, to->rttvar, to->timeout);
  }

  delta = TIMEVAL_SUBTRACT(*received, *sent);

  /* Argh ... pcap receive time is sometimes a little off my
     getimeofday() results on various platforms :(.  So a packet may
     appear to be received as much as a hundredth of a second before
     it was sent.  So I will allow small negative RTT numbers */
  if (delta < 0 && delta > -50000) {
    if (o.debugging > 2)
      log_write(LOG_STDOUT, "Small negative delta (probably due to libpcap time / gettimeofday() discrepancy) - adjusting from %lius to %dus\n", delta, 10000);
    delta = 10000;
  }


  if (to->srtt == -1 && to->rttvar == -1) {
    /* We need to initialize the sucker ... */
    to->srtt = delta;
    to->rttvar = MAX(5000, MIN(to->srtt, 2000000));
    to->timeout = to->srtt + (to->rttvar << 2);
  }
  else {
    if (delta >= 8000000 || delta < 0) {
      if (o.verbose)
	error("%s: packet supposedly had rtt of %lu microseconds.  Ignoring time.", __func__, delta);
      return;
    }
    delta -= to->srtt;
    /* sanity check 2*/
    if (delta > 1500000 && delta > 3 * to->srtt + 2 * to->rttvar) {
      /* WANKER ALERT! */
      if (o.debugging) {
	log_write(LOG_STDOUT, "Bogus delta: %ld (srtt %d) ... ignoring\n", delta, to->srtt);
      }
      return;
    }
    to->srtt += delta >> 3;
    to->rttvar += (ABS(delta) - to->rttvar) >> 2;
    to->timeout = to->srtt + (to->rttvar << 2);  
  }
  if (to->rttvar > 2300000) {
    error("RTTVAR has grown to over 2.3 seconds, decreasing to 2.0");
    to->rttvar = 2000000;
  }
  
  /* It hurts to do this ... it really does ... but otherwise we are being
     too risky */
  to->timeout = box(o.minRttTimeout() * 1000, o.maxRttTimeout() * 1000,  
		    to->timeout);

  if (o.scan_delay)
    to->timeout = MAX((unsigned) to->timeout, o.scan_delay * 1000);

  if (o.debugging > 3) {
    log_write(LOG_STDOUT, "delta %ld ==> srtt: %d rttvar: %d to: %d\n", delta, to->srtt, to->rttvar, to->timeout);
  }

  /* if (to->srtt < 0 || to->rttvar < 0 || to->timeout < 0 || delta < -50000000 || 
      sent->tv_sec == 0 || received->tv_sec == 0 ) {
    fatal("Serious time computation problem in adjust_timeout ... received = (%ld, %ld) sent=(%ld,%ld) delta = %ld srtt = %d rttvar = %d to = %d", (long) received->tv_sec, (long)received->tv_usec, (long) sent->tv_sec, (long) sent->tv_usec, delta, to->srtt, to->rttvar, to->timeout);
  } */
}

/* Sleeps if necessary to ensure that it isn't called twice within less
   time than o.send_delay.  If it is passed a non-null tv, the POST-SLEEP
   time is recorded in it */
void enforce_scan_delay(struct timeval *tv) {
  static int init = -1;
  static struct timeval lastcall;
  struct timeval now;
  int time_diff;

  if (!o.scan_delay) {
    if (tv) gettimeofday(tv, NULL);
    return;
  }

  if (init == -1) {
    gettimeofday(&lastcall, NULL);
    init = 0;
    if (tv)
      memcpy(tv, &lastcall, sizeof(struct timeval));
    return;
  }