If eg. PCRF or AAA diameter link is not yet ready (eg. PCRF crashed),
and a client sends a CreateSessionRequest announcing its ow F-TEID,
then open5gs-smfd answers with Create Session Response Cause="Remote peer not responding",
but it is not setting the received F-TEID in the header of the response,
instead it sends with TEID=0.
As a result, the peer cannot match the CreateSessionResponse,
and needs to rely on its own timeout timer to figure out
that specific request failed.
See 3GPP TS 29.274 5.5 Usage of the GTPv2-C Header:
```
Bit 4 represents a "T" flag, which indicates if TEID field is present in the GTP-C header or not. If the "T" flag is
set to 0, then the TEID field shall not be present in the GTP-C header. If the "T" flag is set to 1, then the TEID
field shall immediately follow the Length field, in octets 5 to 8. Apart from the Echo Request, Echo Response
and Version Not Supported Indication messages, in all EPC specific messages the value of the "T" flag shall be
set to "1".
```
This happens with Delete Session Requests and can happen with any PFCP message.
I've fixed TEID/SEID to send the value in the reponse message as is if it was received.
'node_timeout' and some other functions can remove a smf_sess_t
while that session is still waiting for a PFCP reply
and has an active PFCP xact.
In this case, xact->data points to the deleted session
and xact's timeout function (sess_5gc_timeout for example)
eventually refers to this already freed session.
This fix prevents duplicate deletes from occurring by checking to see
if the session context has already been deleted when the timeout occurs.
Additionally, it moves session deletions out of timer callbacks into
state machine by reselect_upf().
Due to the way 'ogs_timer_mgr_expire' calls timer callbacks,
one must not stop or expire timers from within a timer callback.
And now one must not remove sessions from within a timer callback.
TS23.007 17.4.1
19A PFCP based restart procedures
After a PFCP entity has restarted, it shall immediately update all local Recovery Time Stamps and shall clear all remote
Recovery Time Stamps. When peer PFCP entities information is available, i.e. when the PFCP Association is still alive,
the restarted PFCP entity shall send its updated Recovery Time Stamps in a Heartbeat Request message to the peer
PFCP entities before initiating any PFCP session signalling.
- Set the number of UEs in units of AMF/MME instead of gNB/eNB.
- See default value as shown below
Number of UEs per AMF/MME : 4,096
Number of gNB/eNB per AMF/MME : 32
Sukchan Lee
Spencer Sevilla
Pau Espin