it turned out that a certain order of events can lead to
a RLC transmitter stalling because even though unacknowledged PDUs
are queued, none of them was actually considered for retx.
This can happen if a pollRetxTimer expires for a SN that, meanwhile,
has already been acknowledged. The positive lead to the deletion of
the SN from the Tx window.
The fix makes sure that when a retx for a unexisting SN is requested,
the sender will consider the next unacknowledged SN instead.
it seems that different SNs should be retransmitted depending
on the actual situation. In case of pollRetx timer expiration,
vt_s - 1 should actually be resent.
This patch prepares the function to accept different SNs but
leaves it to send vt_a by default. The RLC AM test would need
to changed as well to not fail.
if RLC PDUs with certain PDCP SNs were already in flight
when their discard timer at PDCP expires, they weren't
remove from the undelivered_sdu_info_queue causing
indesired log entries like:
08:08:52.455280 [RLC ] [W] PDCP_SN=2103 already marked as undelivered
when the SN was sent again (after wrap around).
The patch makes sure to always try to delete the PDCP SN
from the queue. It should fix (at least partly) #2560
avoiding any allocations.
Each segment stores its own PDCP SN and RLC SN and has two pointers,
one for the next segment of the same RLC PDU, and another for the next segment
of the same PDCP PDU.
previously we were only counting retx if we retx the start of a segment.
this could lead to unwanted behaviour, i.e., not counting retx
correctly and thus not triggering the maxretx attempt, if the receive
always sends NACKs with a SO_start.
The RLC spec is not clear on how this should be handled correctly but
IMHO using an integer number of retx is reasonable, even for segments
that might be retransmitted more often.
The alternative of using a fractional retx counter that may be increamented
proportional to the segment size that is retx is another alternative
but considered too complex to implement (and test correctly).
This was done so it would work when circular buffer holds other things
that are not unique_pointers. Queue and pop_func had to be made public
to be able to call the pop_func when an SDU is discarded.
* Added ability to discard to dyn_block_queue
* Change way of keeping track of SDUs
* Check nullptr in poping callback. Starting to check for nullptr in RLC read_pdu.
* Adding RLC discard tests
* Clearing PDCP info when RLC discard happens
* Read SDUs until they are no longer nullptr
* Changed discard_if to use template argument
the patch refactor the logging when a new PDCP SDU is enqueued for
transmission at RLC.
If the SN is already present, only a warning is logged. From the RLC
perspective operation continues and the SDU will be transmitted.
The patch also changes the order of logs. When the SN cannot be inserted
inside the queue of undelivered SDUs, only one message is logged.
this patch replaces the std::vector type used in the interface between
PDCP and RLC to signal delivery status between both layers. The new
data type is a configurable but fixed-size vector.
The RLC AM doesn't need to dynamically allocate the vector for every SN but
uses the tx_window for storage.
this patch fixes the actions/handling after RLC detected
maxRetx reached for a given SN.
According to the TS, RLC should only inform upper layers and
not try to recover from the event itself.
As a consequence, we won't manipulate the Tx or Rx window.
As a result of this, we might retransmit a SN more than
the specified amount of times.
It's the task of RRC to reestablish the bearer to recover
from that.
* optimize processing of status PDU (SN is removed from window immediately)
* fix maxRetx signaling for segments
* make tx_window_t a template class, rename and use for rx_window as well
this fixes an issue when the RLC bearer isn't reset from RRC.
In this case, the RLC would retransmit the same PDU over and over
again despite the max retx counter being reached.
* Added interfaces for the RLC to notify the PDCP of failure to transmit
SDU
* Limit discard timer to 1500ms, to avoid issues of lingering SDUs in the undeliverd_sdus_queue.
* Fix bug in early exit of notify_delivery and notify_failure
* fix compilation issue in rlc-pdcp notification
Co-authored-by: Francisco <francisco.paisana@softwareradiosystems.com>
* reuse vector capacity for pdcp sn notification
* use an extra lookup data structure to find PDCP SNs that an RLC SN contains
* fix rlc sn->pdcp sn lookup datastructure in rlc
* fix rlc failing test
Andre Puschmann
Francisco
Pedro Alvarez
Codebot
faluco