On 11/15/2022 9:56 AM, Joshua C. Colp wrote:
On Tue, Nov 15, 2022 at 10:50 AM <aster...@phreaknet.org
<mailto:aster...@phreaknet.org>> wrote:
If res_pjsip_pubsub would need to be extended to support this,
would it
reasonable to add a callback to a pubsub module that allows it
access to
the pjsip_tx_data, so it can do whatever it needs to with it,
before the
response gets sent? Or another preferred method of allowing
modules to
add headers?
At a surface it is probably fine.
Thanks, doing that allowed just what I needed to do.
Next limitation... the new_subscribe callback is supposed to return 200
(or some other code) to accept or reject the subscription. The only
arguments are the endpoint name and resource name.
This is not really always sufficient; it may be necessary to approve or
reject the subscription using some information present in the
subscription itself (for example, a header). I think this is all
consequent of the very narrow range of scenarios that res_pjsip_pubsub
was written for originally.
The subscription_established callback is actually perfectly set up for
this. We have a handle on the ast_sip_subscription, and can call
ast_sip_subscription_get_header if needed to get the header.
However, this requires approving all subscriptions with a 200 in the
new_subscribe callback, only to potentially realize it should be
rejected in the subscription_established callback. This is too late
because the 200 OK already gets sent to the endpoint before
subscription_established gets called.
So, the only good solution is to extend new_subscribe to accept a third
argument: rdata, since a subscription hasn't yet been created at that
point so we could not use ast_sip_subscription_get_header to fetch
headers. Yuck, since it's a public API... there could also be a
new_subscribe_with_rdata callback that gets executed instead if a module
defines one. Or maybe we can break ABI and go master only here if that
would be too inelegant.
In any case, the problem could be solved by passing rdata into all of
the functions in res_pjsip_pubsub that call the new_subscribe callback,
since it's not currently available in those functions.
I think the only reason it isn't done this way now is so that
new_subscribe can be unit tested, without having a pjsip_rx_data. The
unit test could simply pass in NULL for rdata, though, since it won't
actually need it for what it does (nor would any existing modules).
Any thoughts/objections?
Thanks!
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