Upon timeout, we move directly to NACC_ST_TX_CELL_CHG_CONTINUE in order
to submit a Cell Change Continue against the MS without providing any
Packet Neighbor Cell Data beforehand, as per spec that's probably the
best we can do in this scenario (TS 44.060):
"""
1) The network responds with a PACKET CELL CHANGE CONTINUE message.
If a mobile station as response to a PACKET CELL CHANGE NOTIFICATION
message receives a PACKET CELL CHANGE CONTINUE message without receiving
any neighbour cell system information, the mobile station shall stop timer
T3208, stop timer T3210 if still running, leave CCN mode and continue cell
reselection in NC0/NC1 mode.
"""
Related: SYS#4909
Change-Id: Ia9932ab082ec095294e85dc4d532046970e17986
This way, we don't open a socket and do the IPA handshake in the event
the request is already cached.
Related: SYS#4909
Change-Id: Ib1ea85e1196c8b9dc40c8837ab5d4a54f2a1f2d4
Older versions of osmo_ctrl_conn_alloc() may not properly initialize
write_queue.bfd.fd to -1, which means if osmo_sock_init2_ofd() failed
during nacc_fsm_alloc(), the destructor would wrongly enter the conditon
where the whole structure is set and unregister the unregistered fd.
Related: libosmocore Change-Id I98f744d2880fbb883719cdf1d3eb31f2b22a13b6
Related: SYS#4909
Change-Id: I253bd9087b1f7ab039aa1127e9dc586f5106905a
A new nacc_fsm is introduced per MS object, with its partner priv
structure struct nacc_fsm_ctx, which exists and is available in the MS
object only during the duration of the NACC procedure.
The NACC context is created on an MS whenever a Pkt Cell Change
Notification is received on Uplink RLCMAC, which asks for neighbor
information of a given ARFCN+BSIC.
First, the target ARFCN+BSIC needs to be translated into a CGI-PS
(RAC+CI) address. That's done by asking the BSC through the Neighbour
Resolution Service available in osmo-bsc using the CTRL interface.
Once the CGI-PS of the target cell is known, PCU starts a RIM RAN-INFO
request against the SGSN (which will route the request as needed), and
wait for a response containing the SI bits from the target cell.
After the SI are received, the scheduler is instructed to eventually
poll a TBF for the MS originating the CCN, so that we can send the SI
encapsulated into multiple Packet Neighbor Cell Data messages on the
downlink.
One all the SI bits are sent, the scheduler is instructed to send a
Packet Cell Change Continue message.
Once the message above has been sent, the FSM autodestroys itself.
Caches are also introduced in this patch which allows for re-using
recently known translations ARFCN+BSIC -> CGI-PS and CGI-PS -> SI_INFO
respectively.
Change-Id: Id35f40d05f3e081f32fddbf1fa34cb338db452ca
Pau Espin