[4.2.y-ckt stable] Patch "tcp: apply Kern's check on RTTs used for congestion control" has been added to staging queue
Kamal Mostafa
kamal at canonical.com
Mon Jan 4 23:23:35 UTC 2016
This is a note to let you know that I have just added a patch titled
tcp: apply Kern's check on RTTs used for congestion control
to the linux-4.2.y-queue branch of the 4.2.y-ckt extended stable tree
which can be found at:
http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-4.2.y-queue
This patch is scheduled to be released in version 4.2.8-ckt1.
If you, or anyone else, feels it should not be added to this tree, please
reply to this email.
For more information about the 4.2.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable
Thanks.
-Kamal
------
>From fa2b5fb661dd7807ada8e19ad146f0474feea5dc Mon Sep 17 00:00:00 2001
From: Yuchung Cheng <ycheng at google.com>
Date: Fri, 16 Oct 2015 21:57:41 -0700
Subject: tcp: apply Kern's check on RTTs used for congestion control
commit 9e45a3e36b363cc4c79c70f2b4f994e66543a219 upstream.
Currently ca_seq_rtt_us does not use Kern's check. Fix that by
checking if any packet acked is a retransmit, for both RTT used
for RTT estimation and congestion control.
Fixes: 5b08e47ca ("tcp: prefer packet timing to TS-ECR for RTT")
Signed-off-by: Yuchung Cheng <ycheng at google.com>
Signed-off-by: Neal Cardwell <ncardwell at google.com>
Signed-off-by: Eric Dumazet <edumazet at google.com>
Signed-off-by: David S. Miller <davem at davemloft.net>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
net/ipv4/tcp_input.c | 5 +----
1 file changed, 1 insertion(+), 4 deletions(-)
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 77730b4..297b358 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -2902,9 +2902,6 @@ static inline bool tcp_ack_update_rtt(struct sock *sk, const int flag,
* Karn's algorithm forbids taking RTT if some retransmitted data
* is acked (RFC6298).
*/
- if (flag & FLAG_RETRANS_DATA_ACKED)
- seq_rtt_us = -1L;
-
if (seq_rtt_us < 0)
seq_rtt_us = sack_rtt_us;
@@ -3146,7 +3143,7 @@ static int tcp_clean_rtx_queue(struct sock *sk, int prior_fackets,
flag |= FLAG_SACK_RENEGING;
skb_mstamp_get(&now);
- if (likely(first_ackt.v64)) {
+ if (likely(first_ackt.v64) && !(flag & FLAG_RETRANS_DATA_ACKED)) {
seq_rtt_us = skb_mstamp_us_delta(&now, &first_ackt);
ca_rtt_us = skb_mstamp_us_delta(&now, &last_ackt);
}
--
1.9.1
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