Subject: Bad handling of DNS responses over TCP.

From: Mark Andrews <[email-masked]>
Date: Thu, 03 Aug 2006 11:00:46 +1000

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	There appears to be a nameserver (just released?) that
	mishandles TCP responses by closing the TCP connection
	immediately after sending the response (no SO_LINGER set).
	This triggers TCP resets rather than allowing response to
	get through.

	Normal TCP DNS client model.

	client		server
	======		======
			listen
	connect
			accept
	send query
			read query
			send response
	read response
	close
			close

	Abnormal Model

	client		server
	======		======
			listen
	connect
			accept
	send query
			read query
			send response
			close
			(TCP RST sent here)
	close

	Server side initiated closes should normally only be done
	after sufficient time has elaspsed for the response to get
	through.  This includes sending REFUSED.

	Mark
-- 
Mark Andrews, ISC
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE:	+61 2 9871 4742		         INTERNET: [email-masked]

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