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Date: Sat, 31 Aug 2002 02:50:09 -0700 (PDT)
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To: freebsd-bugs@FreeBSD.org
Cc: 
From: Martin.Kaeske@Stud.TU-Ilmenau.DE
Subject: Re: kern/42137: Path MTU broken - initial too-large pa
Reply-To: Martin.Kaeske@Stud.TU-Ilmenau.DE
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The following reply was made to PR kern/42137; it has been noted by GNATS.

From: Martin.Kaeske@Stud.TU-Ilmenau.DE
To: freebsd-gnats-submit@FreeBSD.org, jeff@expertcity.com
Cc:  
Subject: Re: kern/42137: Path MTU broken - initial too-large pa
Date: 31 Aug 2002 09:46:44 -0000

 Hello,
 I have an OpenBSD-2.9 machine (with ipfilter-3.4.16) acting as a router
 for my LAN and i have similar problems (MTU is lowered but FBSD keeps
 sending too large packets). I found out that it's not FreeBSDs fault
 it's the router sending wrong ICMP messages. The ICMP message should
 contain the IP-header and the first 8 bytes of data from the IP-packet
 that caused the error but OpenBSD doesn't include the 8 bytes. Since
 FreeBSD seems to need src/dst ip-address _and_ port number to react
 properly to the ICMP message and since src/dst port number are located
 in this 8 bytes FBSD keeps sending to large packets.
 Once i disabled ipfilter in OpenBSD (build a kernel without 'options
 IPFILTER') the problem disappeared (that means the ICMP messages are
 correct).
 
 Can you check if you're also getting such wrong ICMP-messages?
 
 Martin

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