So it turns out rack has a shortcoming in dup-ack counting. It counts the dupacks but
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
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Notes:
svn2git
2020-12-20 02:59:44 +00:00
svn path=/head/; revision=362225
@ -4588,7 +4588,7 @@ rack_timer_start(struct tcpcb *tp, struct tcp_rack *rack, uint32_t cts, int sup_
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goto activate_rxt;
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}
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/* Convert from ms to usecs */
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if (rsm->r_flags & RACK_SACK_PASSED) {
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if ((rsm->r_flags & RACK_SACK_PASSED) || (rsm->r_dupack >= DUP_ACK_THRESHOLD)) {
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if ((tp->t_flags & TF_SENTFIN) &&
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((tp->snd_max - tp->snd_una) == 1) &&
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(rsm->r_flags & RACK_HAS_FIN)) {
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@ -8190,6 +8190,7 @@ rack_strike_dupack(struct tcp_rack *rack)
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rsm->r_dupack++;
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if (rsm->r_dupack >= DUP_ACK_THRESHOLD) {
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rack->r_wanted_output = 1;
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rack->r_timer_override = 1;
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rack_log_retran_reason(rack, rsm, __LINE__, 1, 3);
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} else {
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rack_log_retran_reason(rack, rsm, __LINE__, 0, 3);
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@ -11359,7 +11360,8 @@ tcp_rack_output(struct tcpcb *tp, struct tcp_rack *rack, uint32_t tsused)
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if (rsm->r_flags & RACK_ACKED) {
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return (NULL);
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}
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if ((rsm->r_flags & RACK_SACK_PASSED) == 0) {
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if (((rsm->r_flags & RACK_SACK_PASSED) == 0) &&
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(rsm->r_dupack < DUP_ACK_THRESHOLD)) {
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/* Its not yet ready */
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return (NULL);
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}
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