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Solution to MacDNS problem (keywords MacDNS DNS Macintosh
From: dbrown () CMR GOV (Dan Brown)
Date: Mon, 7 Jul 1997 10:50:42 -0400

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From net-troubleshooting () aggroup com  Mon Jul  7 10:43:29 1997
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Date: Mon, 07 Jul 1997 10:35:07 +0000
From: Matt Leo <Matt () acrcorp com>
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To: Net-Troubleshooting <Net-Troubleshooting () aggroup com>
Subject: Solution to MacDNS problem (keywords MacDNS DNS Macintosh firewall)
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Earlier I posted a problem about MacDNS crashing on a 6100/66. We went
through several machines and O/S upgrades to no avail.

I have since solved the problem, and I am posting the solution here.

The problem turned out to be that the firewall was sending DNS requests
at a sufficiently high rate to crash MacDNS. Among other things, the
firewall attempted to resolve the inverse domain name of every URL
requested by users.  This could amount to bursts of several DNS requests
per second over several seconds.

This may have possibly resulted in some buffer in either the MacOS or
MacDNS being overrun (Warning: this might be used for a D.O.S. attack on
sites using MacDNS) and a subsequent O/S crash.  This problem may or may
not apply to other Mac based DNS products.

The solution is to reconfigure the bastion host to use its own name
resolver.  However, this may expose some internal DNS information to the
outside world;  we are considering using packet filtering to address
this problem.

Dan Brown
dbrown () seismo css gov

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