From: Ralf Spenneberg <lists@spenneberg.org>
To: Abraham van der Merwe <abz@frogfoot.net>
Cc: Netfilter Discussions <netfilter@lists.netfilter.org>
Subject: Re: clearing dont-fragment bit
Date: 10 Oct 2003 07:13:06 +0200 [thread overview]
Message-ID: <1065762785.1650.17.camel@kermit> (raw)
In-Reply-To: <20031009181123.GA8403@oasis.frogfoot.net>
Am Don, 2003-10-09 um 20.11 schrieb Abraham van der Merwe:
> Yes, I know, but as long as all the fragments have unique ids it shouldn't
> matter. Also, if the packet is fragmented along the way under normal
> circumstances (i.e. DF=0), then the IP-ID field would have to be incremented
> by the router fragmenting the packet.
True but Linux 2.4 clears the IP-ID field when sending a packet with the
DF-Bit set. You have to manually recreate a unique IP-ID field when
clearing the DF-Bit on the firewall. Even when the router increments
this field all packets will have the ID of 1. When defragmenting the
receiver does not know which fragment belongs to which packet.
Linux 2.4 is the only operating system I know of that shows this
behavior.
Cheers,
Ralf
--
Ralf Spenneberg
RHCE, RHCX
Book: Intrusion Detection für Linux Server http://www.spenneberg.com
IPsec-Howto http://www.ipsec-howto.org
Honeynet Project Mirror: http://honeynet.spenneberg.org
next prev parent reply other threads:[~2003-10-10 5:13 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-10-09 13:43 clearing dont-fragment bit Abraham van der Merwe
2003-10-09 14:03 ` Maciej Soltysiak
2003-10-09 14:08 ` Abraham van der Merwe
2003-10-09 14:43 ` Ramin Dousti
2003-10-09 14:52 ` Abraham van der Merwe
2003-10-09 15:49 ` Ramin Dousti
2003-10-09 16:13 ` Abraham van der Merwe
2003-10-09 19:44 ` Ramin Dousti
2003-10-09 16:23 ` Ralf Spenneberg
2003-10-09 16:50 ` Abraham van der Merwe
2003-10-09 17:12 ` Ralf Spenneberg
2003-10-09 18:11 ` Abraham van der Merwe
2003-10-10 5:13 ` Ralf Spenneberg [this message]
2003-10-10 8:17 ` Abraham van der Merwe
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