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iptable_nat seriously b0rken

To: netfilter@xxxxxxxxx, netdev@xxxxxxxxxxx
Subject: iptable_nat seriously b0rken
From: Jan Rekorajski <baggins@xxxxxxxxxxxxxxxxx>
Date: Wed, 5 Jul 2000 01:11:42 +0200
Sender: owner-netdev@xxxxxxxxxxx
Please CC answers to me as I'm not subscribed to the lists.

The problem is simple, iptable_nat kills sit tunnels, see this:

7: sit1@lec0: <POINTOPOINT,MULTICAST,NOARP,UP> mtu 1480 qdisc noqueue 
    link/sit 193.0.97.15 peer 193.219.28.246
    inet6 fe80::c100:610f/128 scope link 
    inet6 3ffe:8010:70::2/126 scope global 

Normal, configured tunnel, local IPv6 is 3ffe:8010:70::2, remote
is 3ffe:8010:70::1

spider /root~# ping6 3ffe:8010:70::1
PING 3ffe:8010:70::1(6bone-gw.icm.edu.pl) 56 data bytes
64 bytes from 6bone-gw.icm.edu.pl: icmp_seq=0 hops=64 time=7.0 ms
64 bytes from 6bone-gw.icm.edu.pl: icmp_seq=1 hops=64 time=6.5 ms
64 bytes from 6bone-gw.icm.edu.pl: icmp_seq=2 hops=64 time=5.1 ms

--- 3ffe:8010:70::1 ping statistics ---
3 packets transmitted, 3 packets received, 0% packet loss
round-trip min/avg/max = 5.1/6.2/7.0 ms

A you can see it works...

spider /root~# modprobe ip_tables

spider /root~# ping6 3ffe:8010:70::1
PING 3ffe:8010:70::1(6bone-gw.icm.edu.pl) 56 data bytes
64 bytes from 6bone-gw.icm.edu.pl: icmp_seq=0 hops=64 time=6.8 ms
64 bytes from 6bone-gw.icm.edu.pl: icmp_seq=1 hops=64 time=7.2 ms

--- 3ffe:8010:70::1 ping statistics ---
2 packets transmitted, 2 packets received, 0% packet loss
round-trip min/avg/max = 6.8/7.0/7.2 ms

...it still works...

spider /root~# modprobe iptable_nat

spider /root~# ping6 3ffe:8010:70::1
PING 3ffe:8010:70::1(6bone-gw.icm.edu.pl) 56 data bytes

--- 3ffe:8010:70::1 ping statistics ---
3 packets transmitted, 0 packets received, 100% packet loss

...and now my tunnel has been converted into /dev/null, _what_ does
iptable_nat do that simple insmod kills the tunnel?

Kernels tested from 2.3.99-pre6 to 2.4.0-test1,
then 2.4.0-test3-pre2/ac2/pre1, 2.4.0-test2-ac19/ac7,
with, or without patches from netfilter CVS.

Jan
-- 
Jan Rękorajski            |  ALL SUSPECTS ARE GUILTY. PERIOD!
baggins<at>mimuw.edu.pl   |  OTHERWISE THEY WOULDN'T BE SUSPECTS, WOULD THEY?
BOFH, type MANIAC         |                   -- TROOPS by Kevin Rubio

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