[Users] nathelper and flag 2

Klaus Darilion klaus.mailinglists at pernau.at
Tue Feb 13 17:50:04 CET 2007


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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