PDCP PDUs. This includes:
- Modifying the byte_buffer_t to include PDCP SN meta-data. This way,
the RLC can keep track of the ack'ed bytes for a specific PDCP PDU.
- Added in the RLC an `undelivered_sdu_info queue`, to keep track of the
amount of ack'ed bytes and the total size of the PDCP PDU,
so the RLC can know when delivery is finished.
- Added an interface between the PDCP and the RLC so that the RLC can
notify the PDCP when it receives an ack from the status PDUs. The RLC
passes to the PDCP a vector of all the ack'ed pdus in a rx'ed status PDU.
- Added some tests to the notify functionality. This includes some tests
where the PDUs are acked imediatly, and one test where the PDU is
retx'ed.
this patch refactors the SDU queuing and dropping policy of the RLC and PDCP layer.
the previous design had issues when packets have been generated at a higher
rate above the PDCP than they could be consumed below the RLC.
When the RLC SDU queues were full, we allowed two policies, one to block on the write
and the other to drop the SDU. Both options are not ideal because they either
lead to a blocking stack thread or to lost PDCP PDUs.
To avoid this, this patch makes the following changes:
* PDCP monitors RLC's SDU queue and drops packets on its north-bound SAP if queues are full
* a new method sdu_queue_is_full() has been added to the RLC interface for PDCP
* remove blocking write from pdcp and rlc write_sdu() interface
* all writes into queues need to be non-blocking
* if Tx queues are overflowing, SDUs are dropped above PDCP, not RLC
* log warning if RLC still needs to drop SDUs
* this case should be avoided with the monitoring mechanism
Pedro Alvarez
Andre Puschmann
Francisco Paisana