[Users] nathelper and flag 2

Andreas Granig andreas.granig at inode.info
Tue Feb 13 17:58:48 CET 2007


Hi Klaus,

I have nearly the same approach. Problem is, that I have to do 
fix_nated_sdp if the client is nated to pass the right media IP to 
mediaproxy-dispatcher. In this special case, SIP came from 1.2.3.4 and 
RTP from 1.2.3.5 (announced in SDP), but since NAT was detected, it was 
"fixed" to 1.2.3.4 by fix_nated_sdp, so my RTP-Proxy silently dropped 
packets from 1.2.3.5.

If RTP and SIP both always come from the same IP, this problem may 
remain undetected, but here it popped up due to the different IP addresses.

Andreas

Klaus Darilion wrote:
> Probably not solving your problem but this is my newest pragmatic aproach:
> 
> A client should support symmetric SIP. Thus, I use force_rport for all
> local clients. As usually also all SIP proxies are symmetric I also do
> force_port for requests from external nodes.
> 
> For REGISTER I do not trust the information in the Contact header at all -
> I always use fix_nated_register. Further, I always use fix_nated_contact
> for local SIP users - thus for SIP NAT traversal I do not need any tests.
> 
> Regarding RTP NAT traversal - if you want to save bandwidth on your RTP
> proxy - of course you still need a nat-test.
> 
> regards
> klaus
> 
> 
> On Tue, February 13, 2007 17:36, Andreas Granig said:
>> Hi,
>>
>> Today I found a UAC which is *not* located behind NAT (public IP
>> 1.2.3.4) and sends this Via-Header, which seems perfectly valid
>> according to RFC3261:
>>
>> SIP/2.0/UDP VINNASUP06C:5060;maddr=1.2.3.4;branch=z9hG4bK-2198d2
>>
>> I used to check for nated clients using nat_uac_test("3"), which detects
>> NAT in this case, because the host-part doesn't match the
>> received-address. So is the test-flag "2" useless, since the host-part
>> can be "hostname / IPv4address / IPv6reference", or should this
>> particular test be extended to also check for the maddr-parameter?
>>
>> In the meanwhile, I've changed my nat-test to "17" for only testing
>> Contact and Via-Port instead of Contact and Via-Address, but it's still
>> not optimal.
>>
>> Any opinions on this?
>>
>> Andreas
>>
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> 


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