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Index: head/sys/netinet/tcp_input.c
===================================================================
--- head/sys/netinet/tcp_input.c
+++ head/sys/netinet/tcp_input.c
@@ -1481,7 +1481,7 @@
struct tcpcb *tp, int drop_hdrlen, int tlen, uint8_t iptos,
int ti_locked)
{
- int thflags, acked, ourfinisacked, needoutput = 0;
+ int thflags, acked, ourfinisacked, needoutput = 0, sack_changed;
int rstreason, todrop, win;
u_long tiwin;
char *s;
@@ -1501,6 +1501,7 @@
thflags = th->th_flags;
inc = &tp->t_inpcb->inp_inc;
tp->sackhint.last_sack_ack = 0;
+ sack_changed = 0;
/*
* If this is either a state-changing packet or current state isn't
@@ -2424,7 +2425,7 @@
if ((tp->t_flags & TF_SACK_PERMIT) &&
((to.to_flags & TOF_SACK) ||
!TAILQ_EMPTY(&tp->snd_holes)))
- tcp_sack_doack(tp, &to, th->th_ack);
+ sack_changed = tcp_sack_doack(tp, &to, th->th_ack);
else
/*
* Reset the value so that previous (valid) value
@@ -2436,7 +2437,9 @@
hhook_run_tcp_est_in(tp, th, &to);
if (SEQ_LEQ(th->th_ack, tp->snd_una)) {
- if (tlen == 0 && tiwin == tp->snd_wnd) {
+ if (tlen == 0 &&
+ (tiwin == tp->snd_wnd ||
+ (tp->t_flags & TF_SACK_PERMIT))) {
/*
* If this is the first time we've seen a
* FIN from the remote, this is not a
@@ -2478,8 +2481,20 @@
* When using TCP ECN, notify the peer that
* we reduced the cwnd.
*/
- if (!tcp_timer_active(tp, TT_REXMT) ||
- th->th_ack != tp->snd_una)
+ /*
+ * Following 2 kinds of acks should not affect
+ * dupack counting:
+ * 1) Old acks
+ * 2) Acks with SACK but without any new SACK
+ * information in them. These could result from
+ * any anomaly in the network like a switch
+ * duplicating packets or a possible DoS attack.
+ */
+ if (th->th_ack != tp->snd_una ||
+ ((tp->t_flags & TF_SACK_PERMIT) &&
+ !sack_changed))
+ break;
+ else if (!tcp_timer_active(tp, TT_REXMT))
tp->t_dupacks = 0;
else if (++tp->t_dupacks > tcprexmtthresh ||
IN_FASTRECOVERY(tp->t_flags)) {
@@ -2608,9 +2623,20 @@
tp->snd_cwnd = oldcwnd;
goto drop;
}
- } else
- tp->t_dupacks = 0;
+ }
break;
+ } else {
+ /*
+ * This ack is advancing the left edge, reset the
+ * counter.
+ */
+ tp->t_dupacks = 0;
+ /*
+ * If this ack also has new SACK info, increment the
+ * counter as per rfc6675.
+ */
+ if ((tp->t_flags & TF_SACK_PERMIT) && sack_changed)
+ tp->t_dupacks++;
}
KASSERT(SEQ_GT(th->th_ack, tp->snd_una),
@@ -2629,7 +2655,6 @@
} else
cc_post_recovery(tp, th);
}
- tp->t_dupacks = 0;
/*
* If we reach this point, ACK is not a duplicate,
* i.e., it ACKs something we sent.
Index: head/sys/netinet/tcp_sack.c
===================================================================
--- head/sys/netinet/tcp_sack.c
+++ head/sys/netinet/tcp_sack.c
@@ -345,17 +345,22 @@
* Process cumulative ACK and the TCP SACK option to update the scoreboard.
* tp->snd_holes is an ordered list of holes (oldest to newest, in terms of
* the sequence space).
+ * Returns 1 if incoming ACK has previously unknown SACK information,
+ * 0 otherwise. Note: We treat (snd_una, th_ack) as a sack block so any changes
+ * to that (i.e. left edge moving) would also be considered a change in SACK
+ * information which is slightly different than rfc6675.
*/
-void
+int
tcp_sack_doack(struct tcpcb *tp, struct tcpopt *to, tcp_seq th_ack)
{
struct sackhole *cur, *temp;
struct sackblk sack, sack_blocks[TCP_MAX_SACK + 1], *sblkp;
- int i, j, num_sack_blks;
+ int i, j, num_sack_blks, sack_changed;
INP_WLOCK_ASSERT(tp->t_inpcb);
num_sack_blks = 0;
+ sack_changed = 0;
/*
* If SND.UNA will be advanced by SEG.ACK, and if SACK holes exist,
* treat [SND.UNA, SEG.ACK) as if it is a SACK block.
@@ -392,7 +397,7 @@
* received.
*/
if (num_sack_blks == 0)
- return;
+ return (sack_changed);
/*
* Sort the SACK blocks so we can update the scoreboard with just one
@@ -443,6 +448,7 @@
tp->snd_fack = sblkp->end;
/* Go to the previous sack block. */
sblkp--;
+ sack_changed = 1;
} else {
/*
* We failed to add a new hole based on the current
@@ -459,9 +465,11 @@
SEQ_LT(tp->snd_fack, sblkp->end))
tp->snd_fack = sblkp->end;
}
- } else if (SEQ_LT(tp->snd_fack, sblkp->end))
+ } else if (SEQ_LT(tp->snd_fack, sblkp->end)) {
/* fack is advanced. */
tp->snd_fack = sblkp->end;
+ sack_changed = 1;
+ }
/* We must have at least one SACK hole in scoreboard. */
KASSERT(!TAILQ_EMPTY(&tp->snd_holes),
("SACK scoreboard must not be empty"));
@@ -490,6 +498,7 @@
tp->sackhint.sack_bytes_rexmit -= (cur->rxmit - cur->start);
KASSERT(tp->sackhint.sack_bytes_rexmit >= 0,
("sackhint bytes rtx >= 0"));
+ sack_changed = 1;
if (SEQ_LEQ(sblkp->start, cur->start)) {
/* Data acks at least the beginning of hole. */
if (SEQ_GEQ(sblkp->end, cur->end)) {
@@ -545,6 +554,7 @@
else
sblkp--;
}
+ return (sack_changed);
}
/*
Index: head/sys/netinet/tcp_var.h
===================================================================
--- head/sys/netinet/tcp_var.h
+++ head/sys/netinet/tcp_var.h
@@ -741,7 +741,7 @@
extern struct pr_usrreqs tcp_usrreqs;
tcp_seq tcp_new_isn(struct tcpcb *);
-void tcp_sack_doack(struct tcpcb *, struct tcpopt *, tcp_seq);
+int tcp_sack_doack(struct tcpcb *, struct tcpopt *, tcp_seq);
void tcp_update_sack_list(struct tcpcb *tp, tcp_seq rcv_laststart, tcp_seq rcv_lastend);
void tcp_clean_sackreport(struct tcpcb *tp);
void tcp_sack_adjust(struct tcpcb *tp);

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