From: Nigel Metheringham <Nigel.Metheringham@dev.InTechnology.co.uk>
To: Martin Josefsson <gandalf@wlug.westbo.se>
Cc: Netfilter <netfilter@lists.netfilter.org>
Subject: Re: NAT and MTU issues
Date: Mon, 22 Sep 2003 16:08:36 +0100 [thread overview]
Message-ID: <1064243316.6070.85.camel@angua.localnet> (raw)
In-Reply-To: <1064242324.6070.77.camel@angua.localnet>
On Mon, 2003-09-22 at 15:52, Nigel Metheringham wrote:
> On Mon, 2003-09-22 at 13:00, Martin Josefsson wrote:
> > Could you please apply the attached patch and reproduce it again?
> > It's just a small patch that enables a little debugging for this.
>
> Very odd - I am seeing ICMPs generated:-
> # /usr/sbin/tcpdump -n -i eth0 icmp
> tcpdump: listening on eth0
> 15:26:12.146557 192.168.50.119 > 172.16.28.33: icmp: 10.0.2.2
> unreachable - need to frag (mtu 1450) [tos 0xc0]
>
> but no extra chatter in dmesg despite ensuring dmesg -n is turned up.
> Checking the module object file shows the extra log messages in there,
> so its not me doing something completely silly.
>
> Putting a
> iptables -t mangle -A FORWARD -p tcp --syn -j TCPMSS \
> --clamp-mss-to-pmtu
>
> in appears to fix things for me.
Took a closer look.
If I put that mangle rule in then:-
* I see no ICMP packets on the wire between the originating box
and the linux g/w (tested in 2 places to make sure I don't have
any packet sniffing/netfilter interactions). Previously I saw
ICMP need frag packets as quoted above
* those icmp_reply log messages appear to fire on each and every
packet
icmp_reply: outer SRC -> 192.168.50.119
icmp_reply: inner DST -> 192.168.50.119 1500
Nigel.
--
[ Nigel Metheringham Nigel.Metheringham@InTechnology.co.uk ]
[ - Comments in this message are my own and not ITO opinion/policy - ]
next prev parent reply other threads:[~2003-09-22 15:08 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-09-19 15:28 NAT and MTU issues Nigel Metheringham
2003-09-20 9:15 ` n00b question..... How to get details on active connections Paul Gibson
2003-09-20 16:09 ` Nox
2003-09-20 19:04 ` NAT and MTU issues Martin Josefsson
2003-09-22 9:53 ` Nigel Metheringham
2003-09-22 12:00 ` Martin Josefsson
2003-09-22 14:52 ` Nigel Metheringham
2003-09-22 15:03 ` Martin Josefsson
2003-09-22 15:08 ` Nigel Metheringham [this message]
2003-09-22 15:41 ` Martin Josefsson
2003-09-22 15:46 ` Nigel Metheringham
2003-09-22 17:06 ` Martin Josefsson
2003-09-23 12:03 ` Nigel Metheringham
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