[OpenSER-Users] RE: NAT question - sr-users

8 Aug 2007

Hi Inaki,

Why would you leave out the "4" flag test in nat_uac_test() for the replies? 
Of course if I leave out the "2" test then my example works (I have tested it)
but I am afraid that this will break some other NATed senario. And if leave out the
"2" test, should I also leave out the "16" test?

Best regards

George

...
  ------------------------------

 Message: 4
 Date: Wed, 8 Aug 2007 11:53:46 +0200
 From: I?aki Baz Castillo &lt;ibc(a)in.ilimit.es&gt;
 Subject: Re: [OpenSER-Users] NAT question
 To: users(a)openser.org
 Message-ID: &lt;200708081153.46621.ibc(a)in.ilimit.es&gt;
 Content-Type: text/plain;	charset="iso-8859-1"

 El Wednesday 08 August 2007 10:30:54 Papadopoulos Georgios escribiσ:
  Hi Bogdan,

 I understand that 200 OK should not be fixed by proxyA. Maybe what I
 don't understand is what nat_uac_test("2") does and when to use it.

 Following is an example where
 clientA = demo1(a)altecnet.gr
 clientB = sip_test_1(a)i-call.gr
 proxyA = 213.5.43.4
 proxyB = 213.5.43.134

 When proxyA goes in the onreply_route for the 200 OK,  
nat_uac_test("23")
  returns true (I guess because of the
"2" flag) and proxyA fixes the
 contact again which is wrong. So, would it be safe to use
 nat_uac_test("23") for the requests and nat_uac_test("21") for the
 replies? I am afraid this would break the simple case with 2 NATed
 clients and only one proxy:
 clientA ------> proxyA ------> clientC  

 Good point. As I think, the correct NAT test for replies is:
   nat_uac_test("1")
 so we just check if <Contact:> header does contain an RFC1918 
 IP address 
 (private IP address).

 In your case it will work since the <Contact> modified by 
 proxyB will contain 
 a non private IP so the NAT check (nat_uac_test("1")) in 
 proxyA wont detect 
 the repliy as behind NAT.

 Maybe others test could be done, but I think they should no 
 valid test that 
 just compare the received IP with the IP of the contact since 
 both could be 
 public IP but different, in which case shouldn't be 
 applied "fix_nat_contact".

 Regards.

 -- 
 Iρaki Baz Castillo
 ibc(a)in.ilimit.es

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