Re: stateful UDP with unknown source port on INPUT?

[Robert Nichols <rnicholsNOSPAM@comcast.net>]

I wrote:
> noa levy wrote:
> 
>> Thanks!
>> I forgot to mention, though, that my source port for the SNMP informs 
>> is also random, so I can't match against the destination port for the 
>> incoming packet - does the recent target also maintain a port list or 
>> is it IP addresses only?
> 
> 
> How about something like this:
> 
> iptables -t nat -A POSTROUTING -p udp --dport 162 -j SNAT --to-source :29999
> iptables -t mangle -A PREROUTING -p udp --dport 29999 -j MARK --set-mark 99
> iptables -A input -p udp -dport ! 29999 -m mark --mark 99 -j ACCEPT

Which, of course, won't work because de-SNAT won't recognize the reply
packets coming from a random port.  I really shouldn't try to post
something that complex, and untested, late at night.  Sorry.

-- 
Bob Nichols         Yes, "NOSPAM" is really part of my email address.