mirror of
https://git.FreeBSD.org/src.git
synced 2024-10-18 02:19:39 +00:00
tcp: fix duplicate retransmissions when RTO happens during SACK loss recovery
When snd_nxt doesn't track snd_max, partial SACK ACKs may elicit unexpected duplicate retransmissions. This is usually masked by LRO not necessarily ACKing every individual segment, and prior to RFC6675 SACK loss recovery, harder to trigger even when an RTO happens while SACK loss recovery is ongoing. Address this by improving the logic when to start a SACK loss recovery and how to deal with a RTO, as well as improvements to the adjusted congestion window during transmission selection. Reviewed By: tuexen, cc, #transport Sponsored by: NetApp, Inc. MFC after: 1 week Differential Revision: https://reviews.freebsd.org/D43355
This commit is contained in:
parent
d9daa28c36
commit
440f4ba18e
@ -444,10 +444,7 @@ cc_cong_signal(struct tcpcb *tp, struct tcphdr *th, uint32_t type)
|
||||
case CC_RTO:
|
||||
tp->t_dupacks = 0;
|
||||
tp->t_bytes_acked = 0;
|
||||
if ((tp->t_rxtshift > 1) ||
|
||||
!((tp->t_flags & TF_SACK_PERMIT) &&
|
||||
(!TAILQ_EMPTY(&tp->snd_holes))))
|
||||
EXIT_RECOVERY(tp->t_flags);
|
||||
EXIT_RECOVERY(tp->t_flags);
|
||||
if (tp->t_flags2 & TF2_ECN_PERMIT)
|
||||
tp->t_flags2 |= TF2_ECN_SND_CWR;
|
||||
break;
|
||||
@ -2747,7 +2744,6 @@ tcp_do_segment(struct tcpcb *tp, struct mbuf *m, struct tcphdr *th,
|
||||
}
|
||||
if (tcp_is_sack_recovery(tp, &to)) {
|
||||
TCPSTAT_INC(tcps_sack_recovery_episode);
|
||||
tp->snd_recover = tp->snd_nxt;
|
||||
tp->snd_cwnd = maxseg;
|
||||
(void) tcp_output(tp);
|
||||
if (SEQ_GT(th->th_ack, tp->snd_una)) {
|
||||
@ -2790,8 +2786,12 @@ tcp_do_segment(struct tcpcb *tp, struct mbuf *m, struct tcphdr *th,
|
||||
__func__));
|
||||
if (tp->t_dupacks == 1)
|
||||
tp->snd_limited = 0;
|
||||
tp->snd_cwnd =
|
||||
(tp->snd_nxt - tp->snd_una) +
|
||||
if ((tp->snd_nxt == tp->snd_max) &&
|
||||
(tp->t_rxtshift == 0))
|
||||
tp->snd_cwnd =
|
||||
SEQ_SUB(tp->snd_nxt,
|
||||
tp->snd_una);
|
||||
tp->snd_cwnd +=
|
||||
(tp->t_dupacks - tp->snd_limited) *
|
||||
maxseg;
|
||||
/*
|
||||
@ -2840,7 +2840,9 @@ tcp_do_segment(struct tcpcb *tp, struct mbuf *m, struct tcphdr *th,
|
||||
* counted as dupacks here.
|
||||
*/
|
||||
if (tcp_is_sack_recovery(tp, &to) &&
|
||||
(sack_changed != SACK_NOCHANGE)) {
|
||||
(((tp->t_rxtshift == 0) && (sack_changed != SACK_NOCHANGE)) ||
|
||||
((tp->t_rxtshift > 0) && (sack_changed == SACK_NEWLOSS))) &&
|
||||
(tp->snd_nxt == tp->snd_max)) {
|
||||
tp->t_dupacks++;
|
||||
/* limit overhead by setting maxseg last */
|
||||
if (!IN_FASTRECOVERY(tp->t_flags) &&
|
||||
|
@ -259,6 +259,7 @@ tcp_default_output(struct tcpcb *tp)
|
||||
}
|
||||
}
|
||||
again:
|
||||
sendwin = 0;
|
||||
/*
|
||||
* If we've recently taken a timeout, snd_max will be greater than
|
||||
* snd_nxt. There may be SACK information that allows us to avoid
|
||||
@ -266,12 +267,12 @@ tcp_default_output(struct tcpcb *tp)
|
||||
*/
|
||||
if ((tp->t_flags & TF_SACK_PERMIT) &&
|
||||
SEQ_LT(tp->snd_nxt, tp->snd_max))
|
||||
tcp_sack_adjust(tp);
|
||||
sendwin = tcp_sack_adjust(tp);
|
||||
sendalot = 0;
|
||||
tso = 0;
|
||||
mtu = 0;
|
||||
off = tp->snd_nxt - tp->snd_una;
|
||||
sendwin = min(tp->snd_wnd, tp->snd_cwnd);
|
||||
sendwin = min(tp->snd_wnd, tp->snd_cwnd + sendwin);
|
||||
|
||||
flags = tcp_outflags[tp->t_state];
|
||||
/*
|
||||
@ -288,7 +289,8 @@ tcp_default_output(struct tcpcb *tp)
|
||||
sack_bytes_rxmt = 0;
|
||||
len = 0;
|
||||
p = NULL;
|
||||
if ((tp->t_flags & TF_SACK_PERMIT) && IN_FASTRECOVERY(tp->t_flags) &&
|
||||
if ((tp->t_flags & TF_SACK_PERMIT) &&
|
||||
(IN_FASTRECOVERY(tp->t_flags) || SEQ_LT(tp->snd_nxt, tp->snd_max)) &&
|
||||
(p = tcp_sack_output(tp, &sack_bytes_rxmt))) {
|
||||
uint32_t cwin;
|
||||
|
||||
@ -387,7 +389,7 @@ tcp_default_output(struct tcpcb *tp)
|
||||
* in which case len is already set.
|
||||
*/
|
||||
if (sack_rxmit == 0) {
|
||||
if (sack_bytes_rxmt == 0) {
|
||||
if ((sack_bytes_rxmt == 0) || SEQ_LT(tp->snd_nxt, tp->snd_max)) {
|
||||
len = ((int32_t)min(sbavail(&so->so_snd), sendwin) -
|
||||
off);
|
||||
} else {
|
||||
@ -1636,11 +1638,16 @@ tcp_default_output(struct tcpcb *tp)
|
||||
tp->snd_max = tp->snd_nxt + xlen;
|
||||
}
|
||||
if ((error == 0) &&
|
||||
(TCPS_HAVEESTABLISHED(tp->t_state) &&
|
||||
(tp->t_flags & TF_SACK_PERMIT) &&
|
||||
tp->rcv_numsacks > 0)) {
|
||||
/* Clean up any DSACK's sent */
|
||||
tcp_clean_dsack_blocks(tp);
|
||||
(tp->rcv_numsacks > 0) &&
|
||||
TCPS_HAVEESTABLISHED(tp->t_state) &&
|
||||
(tp->t_flags & TF_SACK_PERMIT)) {
|
||||
/* Clean up any DSACK's sent */
|
||||
tcp_clean_dsack_blocks(tp);
|
||||
}
|
||||
if ((error == 0) &&
|
||||
sack_rxmit &&
|
||||
SEQ_LT(tp->snd_nxt, SEQ_MIN(p->rxmit, p->end))) {
|
||||
tp->snd_nxt = SEQ_MIN(p->rxmit, p->end);
|
||||
}
|
||||
if (error) {
|
||||
/*
|
||||
|
@ -1006,7 +1006,7 @@ tcp_sack_partialack(struct tcpcb *tp, struct tcphdr *th, u_int *maxsegp)
|
||||
highdata--;
|
||||
highdata = SEQ_MIN(highdata, tp->snd_recover);
|
||||
if (SEQ_LT(th->th_ack, highdata)) {
|
||||
tp->snd_fack = th->th_ack;
|
||||
tp->snd_fack = SEQ_MAX(th->th_ack, tp->snd_fack);
|
||||
if ((temp = tcp_sackhole_insert(tp, SEQ_MAX(th->th_ack,
|
||||
highdata - maxseg), highdata, NULL)) != NULL) {
|
||||
tp->sackhint.hole_bytes +=
|
||||
@ -1076,41 +1076,47 @@ tcp_sack_output(struct tcpcb *tp, int *sack_bytes_rexmt)
|
||||
* After a timeout, the SACK list may be rebuilt. This SACK information
|
||||
* should be used to avoid retransmitting SACKed data. This function
|
||||
* traverses the SACK list to see if snd_nxt should be moved forward.
|
||||
* In addition, cwnd will be inflated by the sacked bytes traversed when
|
||||
* moving snd_nxt forward. This prevents a traffic burst after the final
|
||||
* full ACK, and also keeps ACKs coming back.
|
||||
*/
|
||||
void
|
||||
int
|
||||
tcp_sack_adjust(struct tcpcb *tp)
|
||||
{
|
||||
int sacked = 0;
|
||||
struct sackhole *p, *cur = TAILQ_FIRST(&tp->snd_holes);
|
||||
|
||||
INP_WLOCK_ASSERT(tptoinpcb(tp));
|
||||
if (cur == NULL) {
|
||||
/* No holes */
|
||||
return;
|
||||
return (0);
|
||||
}
|
||||
if (SEQ_GEQ(tp->snd_nxt, tp->snd_fack)) {
|
||||
/* We're already beyond any SACKed blocks */
|
||||
return;
|
||||
return (tp->sackhint.sacked_bytes);
|
||||
}
|
||||
/*-
|
||||
/*
|
||||
* Two cases for which we want to advance snd_nxt:
|
||||
* i) snd_nxt lies between end of one hole and beginning of another
|
||||
* ii) snd_nxt lies between end of last hole and snd_fack
|
||||
*/
|
||||
while ((p = TAILQ_NEXT(cur, scblink)) != NULL) {
|
||||
if (SEQ_LT(tp->snd_nxt, cur->end)) {
|
||||
return;
|
||||
return (sacked);
|
||||
}
|
||||
sacked += p->start - cur->end;
|
||||
if (SEQ_GEQ(tp->snd_nxt, p->start)) {
|
||||
cur = p;
|
||||
} else {
|
||||
tp->snd_nxt = p->start;
|
||||
return;
|
||||
return (sacked);
|
||||
}
|
||||
}
|
||||
if (SEQ_LT(tp->snd_nxt, cur->end)) {
|
||||
return;
|
||||
return (sacked);
|
||||
}
|
||||
tp->snd_nxt = tp->snd_fack;
|
||||
return (tp->sackhint.sacked_bytes);
|
||||
}
|
||||
|
||||
/*
|
||||
|
@ -1508,7 +1508,7 @@ void tcp_update_sack_list(struct tcpcb *tp, tcp_seq rcv_laststart,
|
||||
tcp_seq rcv_lastend);
|
||||
void tcp_clean_dsack_blocks(struct tcpcb *tp);
|
||||
void tcp_clean_sackreport(struct tcpcb *tp);
|
||||
void tcp_sack_adjust(struct tcpcb *tp);
|
||||
int tcp_sack_adjust(struct tcpcb *tp);
|
||||
struct sackhole *tcp_sack_output(struct tcpcb *tp, int *sack_bytes_rexmt);
|
||||
void tcp_do_prr_ack(struct tcpcb *, struct tcphdr *, struct tcpopt *,
|
||||
sackstatus_t, u_int *);
|
||||
|
Loading…
Reference in New Issue
Block a user