We already have a similar function for Neighbor Address Resolution.
This way we keep as much as possible internal state related logic into
the nacc_fsm.c file.
Change-Id: I7378939825cc3ec3280f76bc51233c0a172d8a27
While NACC was initially developed, it became clear there was need for
a way to interact PCU<->BSC in order resolve ARFCN+BSIC into CGI-PS
for later RIM usage.
Hence, this resolution was first (until today) implemented using an out
of bands RPC system using the CTRL interface, which required specific
config to be written and matches in osmo-pcu and osmo-bsc VTY (ip+port
of the CTRL interface to use).
However, this has several shortcomings:
* As explained above, specific configuration is required
* Since recently, we do support BSC redundancy in osmo-bts. Hence the BTS
may switch to a BSC other than first one. If that happened, that'd mean
the CTRL interface would still point to the initially configured one,
which may not be the same currently serving the PCU.
During recent development of ANR related features, a similar need for
PCU<->BSC was required, but this time it was decided to extend the IPA
multiplex of the Abis OML connection to pass PCUIF messages,
transparently forwarded to each side by the BTS.
This has the advantage that connection PCU<->BTS is handled by BTS and
both sides send messages transparently.
Let's switch by default to using this new interface, while still
maintaing the old way for a while (announcing them as deprecated) to
avoid breaking existing deployments until they are upgraded to new
versions of osmo-pcu and osmo-bsc.
Related: SYS#4971
Change-Id: I6ad33c7ab10202840cf804dea9ba595978d0e920
Use the fact that the MS must answer the RRBP of the Pkt Cell Change
Continue with a CTRL ACK to find out whether the message was received
successfuly or a retransmission is potentially required.
3GPP TS 44.060:
"""
When the mobile station receives the PACKET CELL CHANGE ORDER or
the PACKET CELL CHANGE CONTINUE message the mobile station shall
transmit a PACKET CONTROL ACKNOWLEDGMENT message in the specified
uplink radio block if a valid RRBP field is received as part of the
message; the mobile station may then switch to a new cell.
"""
Related: SYS#4909
Change-Id: I7cc28922e71699598da0ef6eb90136a47d3c002f
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
Pau Espin Pedrol