linux-kernel - [PATCH net-next] tcp: fix condition for increasing pingpong count

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Message-Id: <20220719130136.11907-1-hlm3280@163.com>
Date:   Tue, 19 Jul 2022 21:01:37 +0800
From:   LemmyHuang <hlm3280@....com>
To:     edumazet@...gle.com, davem@...emloft.net, dsahern@...nel.org,
        kuba@...nel.org, pabeni@...hat.com
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        LemmyHuang <hlm3280@....com>
Subject: [PATCH net-next] tcp: fix condition for increasing pingpong count

When CONFIG_HZ defaults to 1000Hz and the network transmission time is
less than 1ms, lsndtime and lrcvtime are likely to be equal, which will
lead to hundreds of interactions before entering pingpong mode.

Signed-off-by: LemmyHuang <hlm3280@....com>
---
 net/ipv4/tcp_output.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 858a15cc2..35ed65f80 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -172,7 +172,7 @@ static void tcp_event_data_sent(struct tcp_sock *tp,
 	 * and it is a reply for ato after last received packet,
 	 * increase pingpong count.
 	 */
-	if (before(tp->lsndtime, icsk->icsk_ack.lrcvtime) &&
+	if ((tp->lsndtime <= icsk->icsk_ack.lrcvtime) &&
 	    (u32)(now - icsk->icsk_ack.lrcvtime) < icsk->icsk_ack.ato)
 		inet_csk_inc_pingpong_cnt(sk);
 
-- 
2.27.0