ouroboros/src/lib/rxmwheel.c, branch master

lib: Complete retransmission logic

2020-09-25T09:52:51+00:00

This completes the retransmission (automated repeat-request, ARQ) logic, sending (delayed) ACK messages when needed. On deallocation, flows will ACK try to retransmit any remaining unacknowledged messages (unless the FRCTFLINGER flag is turned off; this is on by default). Applications can safely shut down as soon as everything is ACK'd (i.e. the current Delta-t run is done). The activity timeout is now passed to the IPCP for it to sleep before completing deallocation (and releasing the flow_id). That should be moved to the IRMd in due time. The timerwheel is revised to be multi-level to reduce memory consumption. The resolution bumps by a factor of 1 << RXMQ_BUMP (16) and each level has RXMQ_SLOTS (1 << 8) slots. The lowest level has a resolution of (1 << RXMQ_RES) (20) ns, which is roughly a millisecond. Currently, 3 levels are defined, so the largest delay we can schedule at each level is: Level 0: 256ms Level 1: 4s Level 2: about a minute. Signed-off-by: Dimitri Staessens Signed-off-by: Sander Vrijders

lib: Allow pure acknowledgment packets in FRCT

2020-06-06T16:29:14+00:00

This adds the logic to send a pure acknowledgment packet without any data to send. This needed the event filter for the fqueue, as these non-data packets should not trigger application PKT events. The default timeout is now 10ms, until we have FRCP tuning as part of fccntl. Karn's algorithm seems to be very unstable with low (sub-ms) RTT estimates. Doubling RTO (every RTO) seems still too slow to prevent rtx storms when the measured rtt suddenly spikes several orders of magnitude. Just assuming the ACK'd packet is the last one transmitted seems to be a lot more stable. It can lead to temporary underestimation, but this is not a throughput-killer in FRCP. Changes most time units to nanoseconds for faster computation. Signed-off-by: Dimitri Staessens Signed-off-by: Sander Vrijders

lib: Fix retransmission DRF update

2020-05-02T09:34:28+00:00

The retransmission was always disabling the DRF flag. This caused problems with the loss of the first packet, which of course needs a DRF flag set. The retransmitted packet will now contain a the original DRF flag and an updated ack number. Signed-off-by: Dimitri Staessens Signed-off-by: Sander Vrijders

lib: Create an rxmwheel per flow

2020-05-02T09:34:28+00:00

The single retransmission wheel caused locking headaches as the calls for different flows could block on the same rxmwheel. This stabilizes the stack, but if the rdrbuff gets full there can now be big delays. Signed-off-by: Dimitri Staessens Signed-off-by: Sander Vrijders

lib: Fix updating retransmission wheel

2020-05-01T08:13:10+00:00

Fixes infinite rescheduling with RTO getting lower than the timerwheel resolution. For very low RTO values we'd need a big packet buffer with the current memory allocator implementation (rdrbuff). Setting a (configurable) minimum RTO (250 us) reduces this need. Signed-off-by: Dimitri Staessens Signed-off-by: Sander Vrijders

lib: Stabilize FRCP under packet loss conditions

2020-04-30T09:54:44+00:00

There were a bunch of bugs in FRCP that urgently needed fixing. Now data QoS is usable even with heavy packet loss (within some parameters). The current RTT estimator is the IETF one. It should be updated to the improved one used in the Linux kernel once the A-timer (ACKs without data) and graceful shutdown are implemented. Signed-off-by: Dimitri Staessens Signed-off-by: Sander Vrijders

build: Update copyright to 2020

2020-01-02T14:07:36+00:00

Signed-off-by: Dimitri Staessens Signed-off-by: Sander Vrijders

lib: Add initial rtt estimator to FRCT

2019-02-08T11:39:23+00:00

This adds a simple round-trip time estimator to FRCT. The estimate is a weighted average with deviation. The retransmission is scheduled after rtt + 2 times the deviation. A retransmit doubles the rtt estimate to avoid the no-update case when rtt suddenly increases. The rtt is estimated in microseconds and the granularity for retransmits is 256 microseconds. Signed-off-by: Dimitri Staessens Signed-off-by: Sander Vrijders

2019-02-05T08:58:08+00:00

Updates the copyright notice in all sources to 2019. Signed-off-by: Dimitri Staessens Signed-off-by: Sander Vrijders

lib: Remove CRC flag from FRCT

2018-10-15T11:30:56+00:00

The integrity check mechanism was split from FRCT, this flag is not needed anymore. Signed-off-by: Dimitri Staessens Signed-off-by: Sander Vrijders