18 Mar
2010
18 Mar
'10
9:11 a.m.
2010/3/18 Timo Reimann <timo.reimann(a)1und1.de>de>:
Thanks for clarification. More inline:
Yes,
that's the point, the in-dialog requests. The only way is by
inspecting the route-set of the request but this involver ugly SIP
URI comparisons. But this can be really simpliffied using RR-cookies
as RR module already uses, right? If not, the dialog hash_id could be
added to the Record-Route during loose_route().
The dialog module currently supports three modes of matching dialogs
(actually, it's just two because the third mode is a combination of both
were one is used as fallback). See here for a short description:
http://kamailio.org/docs/modules/1.5.x/dialog.html#id2491878
(The modes haven't changed for 3.x.) Matching on SIP elements only employs the Call-ID,
From-tag, and To-tag
currently. Record set is stored but its usage apparently limited to
displaying purposes (i.e., MI interface): dlg_hash.h's match_dialog()
function doesn't show any sign of record set parsing.
Yes sure, note that matching a route-set involves complex SIP URI
comparisons, which would be not very "efficient".
For DID-(cookie-)based matching, a reference to the
hashed dialog
data-structure is attached to the record set by the time the dialog is
created, and later fetched when on-route processing in dlg_onroute()
(called from loose_route()) is performed.
Ok, then this way (using cookie) is the *only* way to properly match
dialogs when an spiral occurs. Do you agree?
Of course, a malicious user could modify such cookie value so kamailio
couldn't match the dialog, or it could match it according to
From/To-tags and Call-ID, but then it's not possible to differentiate
between two dialogs originated due to a spiral (the in-dialog request
matches both if route-set is not inspected).
So the next question would be: do we need two dialog entries to be
created when an INVITE does a spiral? As I understand this is fully
possible as the INVITE after the spiral is a new transaction and
future in-dialog requests would be matched against the appropriate
dialog based on the dialog cookie, right?
Regards.
--
Iñaki Baz Castillo
<ibc(a)aliax.net>