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So it turns out rack has a shortcoming in dup-ack counting. It counts the dupacks but

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then does not properly respond to them. This is because a few missing bits are not present.
BBR actually does properly respond (though it also sends a TLP which is interesting and
maybe something to fix)..

Sponsored by:	Netflix Inc.
Differential Revision:	https://reviews.freebsd.org/D25294
This commit is contained in:
Randall Stewart 2020-06-16 12:26:23 +00:00
parent c120c5646d
commit 4d418f8da8
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=362225
1 changed files with 5 additions and 3 deletions
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8
sys/netinet/tcp_stacks/rack.c
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@ -4588,7 +4588,7 @@ rack_timer_start(struct tcpcb *tp, struct tcp_rack *rack, uint32_t cts, int sup_
goto activate_rxt;
}
/* Convert from ms to usecs */
if (rsm->r_flags & RACK_SACK_PASSED) {
if ((rsm->r_flags & RACK_SACK_PASSED) || (rsm->r_dupack >= DUP_ACK_THRESHOLD)) {
if ((tp->t_flags & TF_SENTFIN) &&
((tp->snd_max - tp->snd_una) == 1) &&
(rsm->r_flags & RACK_HAS_FIN)) {
@ -6237,7 +6237,7 @@ rack_log_output(struct tcpcb *tp, struct tcpopt *to, int32_t len,
* or FIN if seq_out is adding more on and a FIN is present
* (and we are not resending).
*/
if ((th_flags & TH_SYN) && (seq_out == tp->iss))
if ((th_flags & TH_SYN) && (seq_out == tp->iss))
len++;
if (th_flags & TH_FIN)
len++;
@ -8190,6 +8190,7 @@ rack_strike_dupack(struct tcp_rack *rack)
rsm->r_dupack++;
if (rsm->r_dupack >= DUP_ACK_THRESHOLD) {
rack->r_wanted_output = 1;
rack->r_timer_override = 1;
rack_log_retran_reason(rack, rsm, __LINE__, 1, 3);
} else {
rack_log_retran_reason(rack, rsm, __LINE__, 0, 3);
@ -11359,7 +11360,8 @@ tcp_rack_output(struct tcpcb *tp, struct tcp_rack *rack, uint32_t tsused)
if (rsm->r_flags & RACK_ACKED) {
return (NULL);
}
if ((rsm->r_flags & RACK_SACK_PASSED) == 0) {
if (((rsm->r_flags & RACK_SACK_PASSED) == 0) &&
(rsm->r_dupack < DUP_ACK_THRESHOLD)) {
/* Its not yet ready */
return (NULL);
}