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[LARTC] Re: iptables rule not matching after stream begins

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Subject: [LARTC] Re: iptables rule not matching after stream begins
From: "Bob Beers" <bob.beers@gmail.com>
Date: Mon, 20 Nov 2006 19:46:00 -0500
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Trying again, after re-subscribing:

On 11/20/06, Bob Beers <bob.beers@gmail.com> wrote:
Hello,

I want to dynamically create DNAT rules for
 RTP streams (port-mapping for a SIP proxy).

If my proxy adds the rule before the first packet
 of the RTP stream hits the port, all is well.  But, if
 the stream begins arriving before my rule is in
 place, it never matches.  I cannot always be
 sure that the info for setting up the rule
 arrives sufficiently ahead of the stream.

I suspect if there is a simple resolution to my
 problem.  Does anyone else see this behavior,
 and will share with me the solution?

Apologies if there is a better place to seek an
 answer to this question, please redirect me as
 necessary.

I am using kernel 2.6.15.4, and iptables 1.3.3.

My rules are similar to this:
iptables -I PREROUTING -t nat -p UDP \
  -d<public_ip> --dport <public_port> \
   -j DNAT --to-destination <private_ip:port>
iptables -I FORWARD -p UDP \
   -d <private_ip> --dport <private_port>

--
-Bob
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