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diff --git a/sys/netinet/tcp_input.c b/sys/netinet/tcp_input.c
--- a/sys/netinet/tcp_input.c
+++ b/sys/netinet/tcp_input.c
@@ -268,6 +268,20 @@
counter_u64_add(VNET(tcpstat)[statnum], val);
}
+/*
+ * Make sure that we only start a SACK loss recovery when
+ * receiving a duplicate ACK with a SACK block, and also
+ * complete SACK loss recovery in case the other end
+ * reneges.
+ */
+static bool inline
+tcp_is_sack_recovery(struct tcpcb *tp, struct tcpopt *to)
+{
+ return ((tp->t_flags & TF_SACK_PERMIT) &&
+ ((to->to_flags & TOF_SACK) ||
+ (!TAILQ_EMPTY(&tp->snd_holes))));
+}
+
#ifdef TCP_HHOOK
/*
* Wrapper for the TCP established input helper hook.
@@ -2491,9 +2505,7 @@
TCPSTAT_INC(tcps_rcvacktoomuch);
goto dropafterack;
}
- if ((tp->t_flags & TF_SACK_PERMIT) &&
- ((to.to_flags & TOF_SACK) ||
- !TAILQ_EMPTY(&tp->snd_holes))) {
+ if (tcp_is_sack_recovery(tp, &to)) {
if (((sack_changed = tcp_sack_doack(tp, &to, th->th_ack)) != 0) &&
(tp->t_flags & TF_LRD)) {
tcp_sack_lost_retransmission(tp, th);
@@ -2566,8 +2578,7 @@
* duplicating packets or a possible DoS attack.
*/
if (th->th_ack != tp->snd_una ||
- ((tp->t_flags & TF_SACK_PERMIT) &&
- (to.to_flags & TOF_SACK) &&
+ (tcp_is_sack_recovery(tp, &to) &&
!sack_changed))
break;
else if (!tcp_timer_active(tp, TT_REXMT))
@@ -2579,8 +2590,7 @@
if (V_tcp_do_prr &&
IN_FASTRECOVERY(tp->t_flags)) {
tcp_do_prr_ack(tp, th, &to);
- } else if ((tp->t_flags & TF_SACK_PERMIT) &&
- (to.to_flags & TOF_SACK) &&
+ } else if (tcp_is_sack_recovery(tp, &to) &&
IN_FASTRECOVERY(tp->t_flags)) {
int awnd;
@@ -2653,8 +2663,7 @@
* snd_ssthresh is already updated by
* cc_cong_signal.
*/
- if ((tp->t_flags & TF_SACK_PERMIT) &&
- (to.to_flags & TOF_SACK)) {
+ if (tcp_is_sack_recovery(tp, &to)) {
tp->sackhint.prr_delivered =
tp->sackhint.sacked_bytes;
} else {
@@ -2666,8 +2675,7 @@
tp->sackhint.recover_fs = max(1,
tp->snd_nxt - tp->snd_una);
}
- if ((tp->t_flags & TF_SACK_PERMIT) &&
- (to.to_flags & TOF_SACK)) {
+ if (tcp_is_sack_recovery(tp, &to)) {
TCPSTAT_INC(
tcps_sack_recovery_episode);
tp->snd_recover = tp->snd_nxt;
@@ -2759,8 +2767,7 @@
* from the left side. Such partial ACKs should not be
* counted as dupacks here.
*/
- if ((tp->t_flags & TF_SACK_PERMIT) &&
- (to.to_flags & TOF_SACK) &&
+ if (tcp_is_sack_recovery(tp, &to) &&
sack_changed) {
tp->t_dupacks++;
/* limit overhead by setting maxseg last */
@@ -3942,8 +3949,7 @@
* (del_data) and an estimate of how many bytes are in the
* network.
*/
- if (((tp->t_flags & TF_SACK_PERMIT) &&
- (to->to_flags & TOF_SACK)) ||
+ if (tcp_is_sack_recovery(tp, to) ||
(IN_CONGRECOVERY(tp->t_flags) &&
!IN_FASTRECOVERY(tp->t_flags))) {
del_data = tp->sackhint.delivered_data;
@@ -3987,8 +3993,7 @@
* accordingly.
*/
if (IN_FASTRECOVERY(tp->t_flags)) {
- if ((tp->t_flags & TF_SACK_PERMIT) &&
- (to->to_flags & TOF_SACK)) {
+ if (tcp_is_sack_recovery(tp, to)) {
tp->snd_cwnd = tp->snd_nxt - tp->snd_recover +
tp->sackhint.sack_bytes_rexmit +
(snd_cnt * maxseg);

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