Hi

> You don't want the above -- it accepts *ALL* tcp connection requests.

Agreed, sorry that was cut and paste, I actually used "CONTINUE" in an 
action


> In the NEW section, simply place this rule:
>
> NotSyn(REJECT)        all     all     tcp

Aha, splendid.  Didn't see that!  Just what I need

So for the benefit of Google, the above allows effectively rejecting 
"in-progress" connections that conntrack is trying to recreate. 
Effectively reject any (tcp) connection in state NEW that isn't a SYN 
packet.

Note: Beware that shorewall can also send untracked and invalid packets 
into the NEW section (depending on xx_DISPOSITION variables). I created 
an action so I could ignore (CONTINUE) untracked connections

I only use this for PPP links (where the IP will change), this means I 
can reboot the firewall without terminating in-progress connections 
through the LAN, but it will terminate PPP connections (and avoid them 
hanging).  I also have some PPP ip-down.d scripts which clear those 
conntrack entries to achieve the same on dropped links.

Many thanks!

Ed W


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