8 Jul
2010
8 Jul
'10
4:09 p.m.
Hey,
OK, so after further research, I found that the trouble was not in fact
in the transaction, the trouble was with fix_nated_contact();
So I setup a spiral SIP path. I have a public server that is used by a
bunch of different phones, and I have a alg server ( one public and one
private).
The public server often handles NATed users and the private alg server
handles NAT for a particular user set ( the users on that particular
network) .
The trouble is that the ALG does not rewrite the contact, rather it adds
a Route: header with Record-Route. The trouble was the public server was
calling fix_nated_contact on these users' requests, so when it came back
and the last route header was parsed, the packet could not be delivered
because the fix_nated_contact was changing the contact to the alg proxy
server.
I added a custom header called "X-Ignore-NAT", and when I do the nat
tests ( nac_uac_test ), I also check that the X-Ignore-NAT header was
not present.
So I misdiagnosed the problem that I described in my message. I did my
traces on the end point, so when I did not see the final packet arrive
to the device, I thought it was being reabsorbed.
Is the custom header I used a good solution?
David
On 10-07-08 07:04 AM, Klaus Darilion wrote:
Am 08.07.2010 00:53, schrieb David:
Hey,
I do not do anything IP level forwarding. All my forwarding is done
using Kamailio. It looks like what I am doing is called hairpin routing.
I think the correct term is "spiral" - at least the RFC uses this term.
How do you forward the request - t_relay()? If yes, then tm module
should treat the request as a new transaction.
Post a trace (you can rewrite IP addresses):
ngrep -t -q -W byline -d any -P "" port 5060 or 5061
regards
Klaus
>
> Thanks,
>
> David
>
> On 2010-07-07 18:48, Timo Reimann wrote:
>> Hi,
>>
>>
>> David wrote:
>>> I have setup two Kamailio servers, my INVITEs will go through
>>> server A,
>>> which forwards to server B which forwards it back to server A.
>>>
>>> This is intential, the trouble is when the packet comes back through
>>> server B, nothing has changed so TM sees it as a retransmission.
>>>
>>> The difference between the first time through and the second time
>>> is the
>>> port 5061 instead of 5060.
>> If you forward the INVITE from B to A SIP-wise (e.g., by calling
>> forward()) a new Via header should be added which prevents the spiraled
>> INVITE message from being considered a retransmission on A.
>>
>> Do you perform forwarding on a lower level, like IP?
>>
>>
>> Cheers,
>>
>> --Timo
>
>
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