[OpenSER-Users] nat_uac_test("31") not enough to detect with some consumer voip passthrough routers

[Klaus Darilion]

Hi Mike!

Dealing with SIP ALGs is really PITA. Currently I do not use any NAT 
tests at all but always do NAT traversal (except I know for sure that 
the client is asymmetric).

Another useful approach is to open another socket on the SIP proxy with 
non-standard port, as most SIP ALGs trigger on port 5060.

regards
klaus

Mike Fedyk schrieb:
> Hi,
> 
> Some of our customers have been connecting behind NAT routers that mangle
> the sip headers but don't keep the ports open.  I've added checks on the
> source port to catch this case.  Has anyone done something similar or
> better?  It'd be nice if this could be added as a flag to nat_uac_test() if
> it is a common test and there isn't already a better way.
> 
> Here is the code I've used to handle my registers.  I need to do more
> testing once I can get some of these routers in my lab to see how this
> affects call processing, not just registering.
> 
> Mike
> 
> 	if (!search("^Contact:\ +\*") && nat_uac_test("7"))
> 	{
> 		xlog("L_INFO", "M=$rm RURI=$ru F=$fu IP=$si:$sp CS=$cs
> route2: matched nat_uac_test7\n");
> 		xlog("L_NOTICE", "M=$rm RURI=$ru F=$fu IP=$si:$sp CS=$cs
> route2: setbflag(6)\n");
> 		setbflag(6);
> 		xlog("L_NOTICE", "M=$rm RURI=$ru F=$fu IP=$si:$sp CS=$cs
> route2: fix_natted_register()\n");
> 		fix_nated_register();
> 		#xlog("L_INFO", "M=$rm RURI=$ru F=$fu IP=$si:$sp CS=$cs
> route2: force_rport()\n");
> 		#force_rport();
> 	};
> 	#Some NAT devices modify SIP headers to but do not keep the port
> mappings open, also some UAs detect report the 
> 	#public IP address.  In both cases we need nat ping.  Exceptions for
> default ports.  These ports if used as 
> 	#source ports can be assumed to be at the very least port forwarded.
> 	if (!isbflagset(6) && $sp != '5060' && $sp != '5061')
> 	{
> 		xlog("L_NOTICE", "M=$rm RURI=$ru F=$fu IP=$si:$sp CS=$cs
> route2: matched !isbflagset(6) && ($sp != '5060' && $sp != '5061')\n");
> 		setbflag(6);
> 	};
> 
> 
> 
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