1 Jan
2010
1 Jan
'10
6:54 p.m.
On 01/01/2010 11:48 AM, Antonio Goméz Soto wrote:
Right. I see now. It can only send out requests which
it has received,
and not create new ones.
But on the other hand, kamailio *does* keep dialog state, so might it be
possible to create some add-on module, that injects fake messages into
the input stream? Using info that is in the dialog state?
Or.. come to think of it, would that mess up the dialog between the
endpoint, because it would increment counters that are maintained by
the endpoint?
Yes, it would most likely interfere with the statekeeping done by the
endpoints.
The question you are asking is a technical one, but the answer is
really philosophical and conceptual one (i.e. in terms of how RFC 3261
defines various types of SIP elements). Is it theoretically possible
to add some hacks to a SIP proxy to make it behave as something other
than a proxy by spoofing messages in a convincing way? Yes, it is -
with enough ambition; in fact, Kamailio has a number of such hacks
internally, such as the dialog module's timeout attribute which can
spoof a BYE in both directions after a certain amount of time has
passed. But that's what they are - hacks. Useful, perhaps, but they
are departures from what a proxy is supposed to do that break proxy
purity.
So, yes, you could hack the source to inject messages asynchronously.
But when you do that, you no longer have a proxy, but something
else, so it really comes down to (a) what you want and (b) what the
product is intended to be. At the moment - several clever hacks
notwithstanding, and some UAS functionality (e.g. registrar)
notwithstanding as well - it's a proxy. As long as the intent of the
product is to continue to be a proxy, it is largely limited to the
sort of things a proxy can do, formally speaking.
To do the kinds of things you're wanting to do in a way that is
accommodated by the specifications and the protocol mechanics of SIP,
what you're really looking for is something that can behave as a user
agent in its own right.
--
Alex Balashov - Principal
Evariste Systems
Web : http://www.evaristesys.com/
Tel : (+1) (678) 954-0670
Direct : (+1) (678) 954-0671