[dns-operations] Strange problem with fragmented DNS responses from b.iana-servers.net

Mark Andrews Mark_Andrews at isc.org
Wed Dec 10 23:02:19 UTC 2008

In message <82fxkwksz2.fsf at mid.bfk.de>, Florian Weimer writes:
> > I receive (fragmented) replies both from B and C. Very occasionally
> > the reply from B is reordered on the way, i.e. I receive the second
> > fragment (which doesn't contain port numbers) first. Such a reordering
> > could presumably cause problems for stateful firewalls...
> Not likely.  There are some stacks which consistently send the
> fragment at the highest offset first.

	And there are some middleware boxes that can't handle
	fragmented responses where the first fragment is not recieved
	first.  I know they exist as one of them is running the X
	server I'm using right at this moment.   It handles fragmented
	packets that terminate on it.  It doesn't handle fragmented
	packets that are in response to NATed traffic.

> -- =
> Florian Weimer                <fweimer at bfk.de>
> BFK edv-consulting GmbH       http://www.bfk.de/
> Kriegsstra=DFe 100              tel: +49-721-96201-1
> D-76133 Karlsruhe             fax: +49-721-96201-99
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Mark Andrews, ISC
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742                 INTERNET: Mark_Andrews at isc.org

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