From: Neal Cardwell <ncardwell@xxxxxxxxxx>
3.12-stable review patch. If anyone has any objections, please let me know.
===============
[ Upstream commit 666b805150efd62f05810ff0db08f44a2370c937 ]
On processing cumulative ACKs, the FRTO code was not checking the
SACKed bit, meaning that there could be a spurious FRTO undo on a
cumulative ACK of a previously SACKed skb.
The FRTO code should only consider a cumulative ACK to indicate that
an original/unretransmitted skb is newly ACKed if the skb was not yet
SACKed.
The effect of the spurious FRTO undo would typically be to make the
connection think that all previously-sent packets were in flight when
they really weren't, leading to a stall and an RTO.
Signed-off-by: Neal Cardwell <ncardwell@xxxxxxxxxx>
Signed-off-by: Yuchung Cheng <ycheng@xxxxxxxxxx>
Fixes: e33099f96d99c ("tcp: implement RFC5682 F-RTO")
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Jiri Slaby <jslaby@xxxxxxx>
---
net/ipv4/tcp_input.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 172cd999290c..49c87a39948f 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -3014,10 +3014,11 @@ static int tcp_clean_rtx_queue(struct sock *sk, int prior_fackets,
if (seq_rtt < 0) {
seq_rtt = ca_seq_rtt;
}
- if (!(sacked & TCPCB_SACKED_ACKED))
+ if (!(sacked & TCPCB_SACKED_ACKED)) {
reord = min(pkts_acked, reord);
- if (!after(scb->end_seq, tp->high_seq))
- flag |= FLAG_ORIG_SACK_ACKED;
+ if (!after(scb->end_seq, tp->high_seq))
+ flag |= FLAG_ORIG_SACK_ACKED;
+ }
}
if (sacked & TCPCB_SACKED_ACKED)
--
2.3.5
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