This is a note to let you know that I've just added the patch titled
Revert "tcp: change pingpong threshold to 3"
to the 5.15-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:
revert-tcp-change-pingpong-threshold-to-3.patch
and it can be found in the queue-5.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 8f85722e7d52d3f218ef18d54b8a84fb170f4f22
Author: Wei Wang <weiwan@xxxxxxxxxx>
Date: Thu Jul 21 20:44:04 2022 +0000
Revert "tcp: change pingpong threshold to 3"
[ Upstream commit 4d8f24eeedc58d5f87b650ddda73c16e8ba56559 ]
This reverts commit 4a41f453bedfd5e9cd040bad509d9da49feb3e2c.
This to-be-reverted commit was meant to apply a stricter rule for the
stack to enter pingpong mode. However, the condition used to check for
interactive session "before(tp->lsndtime, icsk->icsk_ack.lrcvtime)" is
jiffy based and might be too coarse, which delays the stack entering
pingpong mode.
We revert this patch so that we no longer use the above condition to
determine interactive session, and also reduce pingpong threshold to 1.
Fixes: 4a41f453bedf ("tcp: change pingpong threshold to 3")
Reported-by: LemmyHuang <hlm3280@xxxxxxx>
Suggested-by: Neal Cardwell <ncardwell@xxxxxxxxxx>
Signed-off-by: Wei Wang <weiwan@xxxxxxxxxx>
Acked-by: Neal Cardwell <ncardwell@xxxxxxxxxx>
Reviewed-by: Eric Dumazet <edumazet@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20220721204404.388396-1-weiwan@xxxxxxxxxx
Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/include/net/inet_connection_sock.h b/include/net/inet_connection_sock.h
index fa6a87246a7b..695ed45841f0 100644
--- a/include/net/inet_connection_sock.h
+++ b/include/net/inet_connection_sock.h
@@ -315,7 +315,7 @@ void inet_csk_update_fastreuse(struct inet_bind_bucket *tb,
struct dst_entry *inet_csk_update_pmtu(struct sock *sk, u32 mtu);
-#define TCP_PINGPONG_THRESH 3
+#define TCP_PINGPONG_THRESH 1
static inline void inet_csk_enter_pingpong_mode(struct sock *sk)
{
@@ -332,14 +332,6 @@ static inline bool inet_csk_in_pingpong_mode(struct sock *sk)
return inet_csk(sk)->icsk_ack.pingpong >= TCP_PINGPONG_THRESH;
}
-static inline void inet_csk_inc_pingpong_cnt(struct sock *sk)
-{
- struct inet_connection_sock *icsk = inet_csk(sk);
-
- if (icsk->icsk_ack.pingpong < U8_MAX)
- icsk->icsk_ack.pingpong++;
-}
-
static inline bool inet_csk_has_ulp(struct sock *sk)
{
return inet_sk(sk)->is_icsk && !!inet_csk(sk)->icsk_ulp_ops;
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 3a84553fb4ed..51f31311fdb6 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -167,16 +167,13 @@ static void tcp_event_data_sent(struct tcp_sock *tp,
if (tcp_packets_in_flight(tp) == 0)
tcp_ca_event(sk, CA_EVENT_TX_START);
- /* If this is the first data packet sent in response to the
- * previous received data,
- * and it is a reply for ato after last received packet,
- * increase pingpong count.
- */
- if (before(tp->lsndtime, icsk->icsk_ack.lrcvtime) &&
- (u32)(now - icsk->icsk_ack.lrcvtime) < icsk->icsk_ack.ato)
- inet_csk_inc_pingpong_cnt(sk);
-
tp->lsndtime = now;
+
+ /* If it is a reply for ato after last received
+ * packet, enter pingpong mode.
+ */
+ if ((u32)(now - icsk->icsk_ack.lrcvtime) < icsk->icsk_ack.ato)
+ inet_csk_enter_pingpong_mode(sk);
}
/* Account for an ACK we sent. */
