[LARTC] Another newbyish question I'm afraid, -m state --state

[Arthur van Leeuwen arthurvl@sci.kun.nl]

<PRE>On Wed, 28 Feb 2001, Paul Wouters wrote:

&gt;<i> I'd like to be able to deny all new connections to a firewall, with the
</I>&gt;<i> exception of port 22 (sshd) and some ports I'd like to forward internally.
</I>
&gt;<i> However, it seems I can't make a rule that is using the state
</I>&gt;<i> AND a source/dest port in there. Eg the following won't work:
</I>&gt;<i>
</I>&gt;<i> iptables -A INPUT -i eth0 -m state --state NEW,INVALID --dport 22 -j DROP
</I>&gt;<i> iptables -A INPUT -i eth0 -m state --state NEW,INVALID -j DROP
</I>&gt;<i> iptables -A FORWARD -i eth0 -m state --state NEW,INVALID --dport 25 -j ACCEPT
</I>&gt;<i> iptables -A FORWARD -i eth0 -m state --state NEW,INVALID -j DROP
</I>&gt;<i>
</I>&gt;<i> Anyone? :)
</I>
iptables -A INPUT -i eth0 -p tcp --dport 22 -m state --state NEW,INVALID -j DROP
iptables -A INPUT -i eth0 -m state --state NEW,INVALID -j DROP
iptables -A FORWARD -i eth0 -p tcp --dport 25 -m state --state NEW,INVALID -j ACCEPT
iptables -A FORWARD -i eth0 -m state --state NEW,INVALID -j DROP

--sport and --dport need the -p tcp or -p udp flags to be set, as source and
destination ports may not make sense for certain protocols, most notably
ICMP.

Doei, Arthur.

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</PRE>