Re: how to match connection tracker's flows?

[Abraham van der Merwe <abz@frogfoot.net>]

Hi Eric                                          >@2004.11.03_21:07:48_+0200

> > If I add
> > 
> > # rules to track ftp
> > iptables -t mangle -A POSTROUTING -p tcp -j CONNMARK --restore-mark
> > iptables -t mangle -A POSTROUTING -p tcp -m mark ! --mark 0 -j RETURN
> 
> If packet are marked they return so leave mangle, so if CONNMARK works
> leave mangle.
> 
> > # a rule to see how much ftp traffic is matched
> > iptables -t mangle -A POSTROUTING -m mark --mark 2
> 
> This line is never reached if CONNMARK works.

Ok, sorry I didn't paste the real commands. It is actually:

# rules to send all traffic to user-defined chain
iptables -t mangle -N TRACK
iptables -t mangle -A POSTROUTING -j TRACK

# a rule to see how much ftp traffic is matched
iptables -t mangle -A POSTROUTING -m mark --mark 2

# rules to track ftp
iptables -t mangle -A TRACK -p tcp -j CONNMARK --restore-mark
iptables -t mangle -A TRACK -p tcp -m mark ! --mark 0 -j RETURN
iptables -t mangle -A TRACK -p tcp --dport 21 -j MARK --set-mark 2
iptables -t mangle -A TRACK -j CONNMARK --save-mark

In other words, it returns from a user-defined chain and the mark is in the
top level chain and will always be matched.

With above, it doesn't match all the ftp traffic. It definitely matches
some, but I think it is just the port 21 traffic, not the port 20 (ftp-data)
stuff which should be picked up by the connection tracking.

I also tried a derivative of above scheme which doesn't work properly either:

iptables -t mangle -A POSTROUTING -p tcp --dport 21 \
	-m state --state NEW,ESTABLISHED,RELATED -j MARK --set-mark 2
iptables -t mangle -A POSTROUTING -m mark --mark 2

Above rule have pretty much the same effect.

-- 

Regards
 Abraham

TODAY the Pond!
TOMORROW the World!
                -- Frogs (1972)

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 Abraham vd Merwe - Frogfoot Networks CC
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