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serialqueue: Allow a second nak after a retransmit 

If a nak message causes a retransmission then also accept a second nak
message as long as it is for a sequence greater than the first nak.
This should allow faster retransmits when there are multiple
transmission errors in a small time period.

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>
This commit is contained in:
Kevin O'Connor 2017-07-21 23:49:44 -04:00
parent 4655a6bfef
commit d469db84ee
1 changed files with 11 additions and 3 deletions
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14
klippy/serialqueue.c
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@ -347,7 +347,7 @@ struct serialqueue {
double last_receive_sent_time;
// Retransmit support
uint64_t send_seq, receive_seq;
uint64_t retransmit_seq, rtt_sample_seq;
uint64_t ignore_nak_seq, retransmit_seq, rtt_sample_seq;
struct list_head sent_queue;
double srtt, rttvar, rto;
// Pending transmission message queues
@ -492,7 +492,7 @@ handle_message(struct serialqueue *sq, double eventtime, int len)
if (rseq != sq->receive_seq)
// New sequence number
update_receive_seq(sq, eventtime, rseq);
else if (len == MESSAGE_MIN && rseq > sq->retransmit_seq
else if (len == MESSAGE_MIN && rseq > sq->ignore_nak_seq
&& !list_empty(&sq->sent_queue))
// Duplicate sequence number in an empty message is a nak
pollreactor_update_timer(&sq->pr, SQPT_RETRANSMIT, PR_NOW);
@ -581,10 +581,18 @@ retransmit_event(struct serialqueue *sq, double eventtime)
sq->bytes_retransmit += buflen;
// Update rto
if (pollreactor_get_timer(&sq->pr, SQPT_RETRANSMIT) != PR_NOW) {
if (pollreactor_get_timer(&sq->pr, SQPT_RETRANSMIT) == PR_NOW) {
// Retransmit due to nak
sq->ignore_nak_seq = sq->receive_seq;
if (sq->receive_seq < sq->retransmit_seq)
// Second nak for this retransmit - don't allow third
sq->ignore_nak_seq = sq->retransmit_seq;
} else {
// Retransmit due to timeout
sq->rto *= 2.0;
if (sq->rto > MAX_RTO)
sq->rto = MAX_RTO;
sq->ignore_nak_seq = sq->send_seq - 1;
}
sq->retransmit_seq = sq->send_seq - 1;
sq->rtt_sample_seq = 0;