Nmap Development mailing list archives
Re: Timing related problem with nmap > 3.20?
From: Fyodor <fyodor () insecure org>
Date: Tue, 10 Jun 2003 22:37:42 -0700
On Wed, Jun 04, 2003 at 10:22:24AM +0100, Richard Moore wrote:
Hi all, I recently upgraded to nmap 3.27 and I seem to be hitting a problem - I get the message: Serious time computation problem in adjust_timeout ... received = (1054717924, 348069) sent=(1054717924,350690) delta = 0 srtt = -2621 rttvar = 5000 to = 300000 QUITTING!
Thanks for the report. This is a strange problem dealing with clock inconsistencies of some sort. I have implemented a workaround for the next version of Nmap. Here is a description which will be in the CHANGELOG: o Fixed (I hope) an issue that would cause Nmap to print "Serious time computation problem in adjust_timeout ..." and quit. The ultimate cause was demonstrated by this --packet_trace snippet that Russel Miller (rmiller(a)duskglow.com) sent me: SENT (0.0500s) ICMP 0.0.0.0 > 127.0.0.1 Echo request (type=8/code=0) ... RCVD (0.0450s) ICMP 127.0.0.1 > 127.0.0.1 Echo reply (type=0/code=0) ... As you can see, the ping reply appears to come BEFORE the request was sent(!). This sort of thing happens on at least Linux and Windows. The send time is obtained from gettimeofday(NULL), while receive time libpcap packet header. If anyone knows why this occurs, or (even better) knows a good way to fix it, let me know. For now, I am allowing the response to come up to .05s "before" the request. That is gross. Cheers, -F --------------------------------------------------------------------- For help using this (nmap-dev) mailing list, send a blank email to nmap-dev-help () insecure org . List run by ezmlm-idx (www.ezmlm.org).
Current thread:
- Timing related problem with nmap > 3.20? Richard Moore (Jun 04)
- Re: Timing related problem with nmap > 3.20? Fyodor (Jun 10)