Patch "tcp: when rearming RTO, if RTO time is in past then fire RTO ASAP" has been added to the 3.18-stable tree

This is a note to let you know that I've just added the patch titled

tcp: when rearming RTO, if RTO time is in past then fire RTO ASAP

to the 3.18-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
tcp-when-rearming-rto-if-rto-time-is-in-past-then-fire-rto-asap.patch
and it can be found in the queue-3.18 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Neal Cardwell <[email protected]>
Date: Wed, 16 Aug 2017 17:53:36 -0400
Subject: tcp: when rearming RTO, if RTO time is in past then fire RTO ASAP

From: Neal Cardwell <[email protected]>

[ Upstream commit cdbeb633ca71a02b7b63bfeb94994bf4e1a0b894 ]

In some situations tcp_send_loss_probe() can realize that it's unable to send a loss probe (TLP), and falls back to calling tcp_rearm_rto() to schedule an RTO timer. In such cases, sometimes tcp_rearm_rto() realizes that the RTO was eligible to fire immediately or at some point in the past (delta_us <= 0). Previously in such cases tcp_rearm_rto() was scheduling such "overdue" RTOs to happen at now + icsk_rto, which caused needless delays of hundreds of milliseconds (and non-linear behavior that made reproducible testing difficult). This commit changes the logic to schedule "overdue" RTOs ASAP, rather than at now + icsk_rto.

---
 net/ipv4/tcp_input.c |    3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

@@ -2985,8 +2985,7 @@ void tcp_rearm_rto(struct sock *sk)
 			/* delta may not be positive if the socket is locked
 			 * when the retrans timer fires and is rescheduled.
 			 */
-			if (delta > 0)
-				rto = delta;
+			delta = max(delta, 1);
 		}
 		inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, rto,
 					  TCP_RTO_MAX);

Patches currently in stable-queue which might be from [email protected] are

queue-3.18/tcp-when-rearming-rto-if-rto-time-is-in-past-then-fire-rto-asap.patch