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tcp: move cc_post_recovery past snd_una update

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The RFC6675 pipe calculation (sack.revised, enabled
by default since D28702), uses outdated information,
while the previous default calculated it correctly
with up-to-date information from the incoming ACK.

This difference can become as large as the receive
window (not the congestion window previously),
potentially triggering a massive burst of new packets.

MFC after:             1 week
Reviewed By:           tuexen, #transport
Sponsored by:          NetApp, Inc.
Differential Revision: https://reviews.freebsd.org/D43520
This commit is contained in:
Richard Scheffenegger 2024-01-28 00:16:59 +01:00
parent 7b707e797b
commit 0b3f9e435f
1 changed files with 22 additions and 28 deletions
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50
sys/netinet/tcp_input.c
View file

@ -474,13 +474,12 @@ cc_post_recovery(struct tcpcb *tp, struct tcphdr *th)
{
INP_WLOCK_ASSERT(tptoinpcb(tp));
/* XXXLAS: KASSERT that we're in recovery? */
if (CC_ALGO(tp)->post_recovery != NULL) {
tp->t_ccv.curack = th->th_ack;
CC_ALGO(tp)->post_recovery(&tp->t_ccv);
}
/* XXXLAS: EXIT_RECOVERY ? */
EXIT_RECOVERY(tp->t_flags);
tp->t_bytes_acked = 0;
tp->sackhint.delivered_data = 0;
tp->sackhint.prr_delivered = 0;
@ -2813,11 +2812,13 @@ tcp_do_segment(struct tcpcb *tp, struct mbuf *m, struct tcphdr *th,
* If the congestion window was inflated to account
* for the other side's cached packets, retract it.
*/
if (IN_FASTRECOVERY(tp->t_flags)) {
if (SEQ_LT(th->th_ack, tp->snd_recover)) {
if (SEQ_LT(th->th_ack, tp->snd_recover)) {
if (IN_FASTRECOVERY(tp->t_flags)) {
if (tp->t_flags & TF_SACK_PERMIT) {
if (V_tcp_do_prr && to.to_flags & TOF_SACK) {
tcp_timer_activate(tp, TT_REXMT, 0);
if (V_tcp_do_prr &&
(to.to_flags & TOF_SACK)) {
tcp_timer_activate(tp,
TT_REXMT, 0);
tp->t_rtttime = 0;
tcp_do_prr_ack(tp, th, &to,
sack_changed, &maxseg);
@ -2830,24 +2831,18 @@ tcp_do_segment(struct tcpcb *tp, struct mbuf *m, struct tcphdr *th,
} else {
tcp_newreno_partial_ack(tp, th);
}
} else {
cc_post_recovery(tp, th);
}
} else if (IN_CONGRECOVERY(tp->t_flags)) {
if (SEQ_LT(th->th_ack, tp->snd_recover)) {
if (V_tcp_do_prr) {
tp->sackhint.delivered_data = BYTES_THIS_ACK(tp, th);
tp->snd_fack = th->th_ack;
/*
* During ECN cwnd reduction
* always use PRR-SSRB
*/
tcp_do_prr_ack(tp, th, &to, SACK_CHANGE,
&maxseg);
(void) tcp_output(tp);
}
} else {
cc_post_recovery(tp, th);
} else if (IN_CONGRECOVERY(tp->t_flags) &&
(V_tcp_do_prr)) {
tp->sackhint.delivered_data =
BYTES_THIS_ACK(tp, th);
tp->snd_fack = th->th_ack;
/*
* During ECN cwnd reduction
* always use PRR-SSRB
*/
tcp_do_prr_ack(tp, th, &to, SACK_CHANGE,
&maxseg);
(void) tcp_output(tp);
}
}
/*
@ -2999,12 +2994,11 @@ tcp_do_segment(struct tcpcb *tp, struct mbuf *m, struct tcphdr *th,
SEQ_GT(tp->snd_una, tp->snd_recover) &&
SEQ_LEQ(th->th_ack, tp->snd_recover))
tp->snd_recover = th->th_ack - 1;
/* XXXLAS: Can this be moved up into cc_post_recovery? */
tp->snd_una = th->th_ack;
if (IN_RECOVERY(tp->t_flags) &&
SEQ_GEQ(th->th_ack, tp->snd_recover)) {
EXIT_RECOVERY(tp->t_flags);
cc_post_recovery(tp, th);
}
tp->snd_una = th->th_ack;
if (tp->t_flags & TF_SACK_PERMIT) {
if (SEQ_GT(tp->snd_una, tp->snd_recover))
tp->snd_recover = tp->snd_una;