Hi Li,
If I understand correctly, you try to improve the b2b support in
OpenSIPS in order to properly handle that NOTIFY for REFER, right ?
Regards,
Bogdan-Andrei Iancu
OpenSIPS Founder and Developer
https://www.opensips-solutions.com
OpenSIPS Summit 27-30 Sept 2022, Athens
https://www.opensips.org/events/Summit-2022Athens/
On 7/22/22 11:02 PM, Li Cai wrote:
Hi experts,
I’m working on the implementation for ‘2.4.6 Multiple REFER Requests
in a Dialog’ of RFC3515 in a B2B SIP Proxy. Right now, I got stuck
with two problems in the solution. Please see the paragraph from RFC-
A REFER creates an implicit subscription sharing the dialog
identifiers in the REFER request. If more than one REFER is issued
in the same dialog (a second attempt at transferring a call for
example), the dialog identifiers do not provide enough information to
associate the resulting NOTIFYs with the proper REFER.
Thus, for the second and subsequent REFER requests a UA receives in a
given dialog, it MUST include an id parameter[2] in the Event header
field of each NOTIFY containing the sequence number (the number from
the CSeq header field value) of the REFER this NOTIFY is associated
with. This id parameter MAY be included in NOTIFYs to the first
REFER a UA receives in a given dialog. A SUBSCRIBE sent to refresh
or terminate this subscription MUST contain this id parameter.
Different from the definition in RFC, the NOTIFY forwarded by the
proxy contains the same Id in Event header as the other side. Please
see the below chart –
B2BProxy
|
<- REFER 2 (Cseq=2) | <-REFER 1
(Cseq=1003)
. . . | . . .
->NOTIFY 1 (event:*id=2*) | ->NOTIFY 2 (_event*:id=2*)_
The current problem is, the above NOTIFY on the right side should
_include ‘id=1003’ instead of ‘id=2’_.
The solution I’m trying is as in the following flow –
1. get CSeq 1 of REFER 1 in route[b2b_request]{} ->
2. get CSeq 2 of REFER 2 in local_route{}, then save
the pair(key=CSeq2, value=CSeq1) in a map set->
3. get Id from NOTIFY 1 event in route[b2b_request]{} ->
4. use Id as key then get matched CSeq1 from the map
set, use remove_hf() and append_hf() to modify the event header in
local_route{}
My two questions are:
1. To transfer Cseq 1 from step1 to step2, I tried a variable in the
AVP type but it didn’t work. The script variable can work but it
doesn’t fit because the processing is based on per request. Can I
ask if you have any suggest on how to transfer the value from
route[b2b_request]{} to local_route{}?
2. In the step2, I tried to create and operate a JSON map set to save
the CSeq pairs. But the JSON data didn’t work for me.
My source :
$json(csList) = ””; #
Initialize the data set, not sure if it’s correct
$json(csList/”$cs”) = “$avp(csNum)”;
The error I got:
ERROR:core:do_assign: setting PV failed
ERROR:core:do_assign: error at /usr/local//et/opensips/opensips.cfg:531
Thank you very much for the help! Any your suggests are very welcomed.
Thanks,
Li
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