this patch adds a check to drop all PDCP control PDUs
in order to prevent handling them as data PDUs.
This could happen when the size exceeded the arbitrary length check.
This should fix#1787
* add locked and unlocked version of has_data() since one is
called from stack and one from PHY threads
* add comments in each interface section as to why locking
is required or not
* remove RLC rwlock when not required
* move calls only used by RRC to RRC section
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
This lock was removed in 1cbf7eac because it was considered unneeded.
However, as can be seen in issue #1503, we need to protect the access
to rx_window, for example.
Issue #1503 shows a stack trace where a PHY worker generates a status PDU.
While holding the mutex to access rx_window, the stack thread on the
other hand, happily accesses the rx_window member without acquiring
the lock. This commit protects all handle_*() functions in write_pdu().
This reverts commit 1cbf7eac04.
instead of logging PDU received from below, and SDU that is forwarded
to above, only log the PDU in rx in info mode.
The next layer will do the same and log the PDU received (which is the SDU coming from here)
so there is now loss of information in the logs.
during the PDU packing it could happen that a new SDU segment
was added but the resulting larger header was so big that not even
a single byte of the new PDU could be added. because this
corner case wasn't handled correctly an invalid PDU was transmitted.
the solution is to revert the addition of the new SDU.