Problem with P-Access-Network-Info SIP header

[lzisko]

Hi,
I am trying to add P-Access-Network-Info header to REGISTER request using CSIPMessageElements::SetUserHeadersL, but it leaves with -6. If I do that with a fake header name "P-Header", it works ok. The value for that header is "3GPP-GERAN;cgi-3gpp=012345cb21932" which seems to me syntactically ok. Also, can't see reason, why would SIP stack check syntax of user header.
Is P-Access-Network-Info disallowed from user headers? It is not listed in SDK help to CSIPMessageElements as disallowed.
What other way can it be added to REGISTER request?
Thanks for any help in advance.

[jp40]

Certain SIP headers are treated as private and can't be added by application. P-Access-Network-Info is one of them.

[lzisko]

Thanks for the response JP40.
In which sense 'private' do you mean? I know that by the spec this header should go by secured transport, because it carries sensitive info and I use secured transport.
If application can't add this header, can it somehow trigger this header to be added by the SIP stack itself? The header is quite common in IMS world and I would expect that there is a way to add it to the request, just it is not documented anywhere.
Also it's not nice, that the documentation to SetUserHeadersL doesn't mention this limitation.

[jp40]

The header is automatically inserted to SIP requests when IPsec is in use, provided that the network information that is put into the P-Access-Network-Info is also available.

[lzisko]

I use SIP connection over VPN access point and it still doesn't publish the PANI header. How do I tell the SIP Stack programatically, that the IPSec is used?

[jp40]

There is no way to instruct SIP stack to add the header. It does that by itself when IPsec is used and the network and location information are available.

[stenlik]

Hi,

"Certain SIP headers are treated as private and can't be added by application." -- that's the obvious problem with 3rd party solutions... If you cannot manage all aspects of SIP it becomes pain. On the other side the PANI header holds according to the 3GPP information about the access side network, so I guess this should be responsibility of sip stack to add this header automatically if instructed to do... Change to PJSIP and get rid of all such problems

BR
STeN

[lzisko]

Thanks for the offer Stenlik, but it's too risky to redo the core in the middle of a running project.
The JP40's response still doesn't make sense to me. I understand IPsec as secured protocol on IP layer. If this is correct, then the SIP stack should determine that the SIP connection used for Registration Binding uses VPN IAP and should add the PANI header automatically. But it doesn't do that in my case. Is there any other understanding of IPsec in SIP world? Perhaps special SIP transport extension? If yes, how can I enable/trigger its usage? There is a setting in native SIP profile called "use security" which might do that. But I couldn't find anything similar in the API to trigger the security usage programatically.
I am really puzzled here. Please, help me out.

[meskausk]

well, P-ACCESS-NETWORK-INFO is really invented for 3GPP IMS usage and it used only when SIP stack has established an IPSec connection with a trusted P-CSCF (IMS AKA has taken place). VPN is a different story and actually SIP stack does not see that at all.
And the SIP UA must trust the SIP network (the proxy must remove it before forwarding to other SIP domain) as the header is very sensitive.

cheers,
paulius