From mboxrd@z Thu Jan  1 00:00:00 1970
From: Mark Hindley <mark@hindley.uklinux.net>
Subject: Firehol DROPping INVALID
Date: Sat, 5 Jun 2004 21:17:39 +0100
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To: netfilter@lists.netfilter.org

Hi,

I have asked this on the Firehol lists, but got no response. Hope you
can help.

I am using kernel 2.6.6 and have firehol setting up a firewall on the
gateway machine with eth0 LAN, ppp0 dial-up link. NAT for hosts on LAN

If the ppp link is down and a host on the LAN sends a packet destined
for the outside world, the icmp-unreacahble packet does not get
returned, so the LAN host has to wait to time out.

The offending command issued by firehol seems to be: 


iptables -A OUTPUT -m state --state INVALID -j DROP

Although the comment says this is recommended in the Netfilter HOWTO, I
cannot find it.

I can get round it by adding

iptables -I OUTPUT 2  -m state --state INVALID -p icmp --icmp-type  destination-unreachable -j ACCEPT

which inserts the ACCEPT before the DROP above and means that hosts on
the LAN get an immediate icmp reply "destination-unreachable" if the
ppp link is down.

Is this wise? secure. Am I missing something.

Thanks for your help

Mark