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: 09 Oct 2003 18:23:06 +0200 [thread overview]
Message-ID: <1065716586.5873.23.camel@kermit> (raw)
In-Reply-To: <20031009134311.GA25685@oasis.frogfoot.net>
Am Don, 2003-10-09 um 15.43 schrieb Abraham van der Merwe:
> Hi!
>
> Are there any iptables extensions out there that allow you to clear the DF
> (Dont Fragment) bit in ip headers?
If you clear the DF-Bit and use Linux on either side of the tunnel where
the packets are fragmented you are in deep trouble, because Linux 2.4
(when using PMTU) not only sets the DF-Bit but also clears the IP-ID
which is needed to defragment the packets again. So, when clearing the
DF-Bit you have to ensure unique numbers in the IP-ID field, too.
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:[~2003-10-09 16:23 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 [this message]
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
2003-10-10 8:17 ` Abraham van der Merwe
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