netdev - [PATCH 2/2] net: make tcp keepalive timer upper bound

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Date:   Wed, 23 Mar 2022 12:16:42 +0100
From:   Artem Savkov <asavkov@...hat.com>
To:     tglx@...utronix.de, jpoimboe@...hat.com, netdev@...r.kernel.org
Cc:     davem@...emloft.net, yoshfuji@...ux-ipv6.org, dsahern@...nel.org,
        linux-kernel@...r.kernel.org, Artem Savkov <asavkov@...hat.com>
Subject: [PATCH 2/2] net: make tcp keepalive timer upper bound

Make sure TCP keepalive timer does not expire late. Switching to upper
bound timers means it can fire off early but in case of keepalive
tcp_keepalive_timer() handler checks elapsed time and resets the timer
if it was triggered early. This results in timer "cascading" to a
higher precision and being just a couple of milliseconds off it's
original mark.

Signed-off-by: Artem Savkov <asavkov@...hat.com>
---
 net/ipv4/inet_connection_sock.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/ipv4/inet_connection_sock.c b/net/ipv4/inet_connection_sock.c
index fc2a985f6064..a8fea958960b 100644
--- a/net/ipv4/inet_connection_sock.c
+++ b/net/ipv4/inet_connection_sock.c
@@ -564,7 +564,7 @@ void inet_csk_init_xmit_timers(struct sock *sk,
 
 	timer_setup(&icsk->icsk_retransmit_timer, retransmit_handler, 0);
 	timer_setup(&icsk->icsk_delack_timer, delack_handler, 0);
-	timer_setup(&sk->sk_timer, keepalive_handler, 0);
+	timer_setup(&sk->sk_timer, keepalive_handler, TIMER_UPPER_BOUND);
 	icsk->icsk_pending = icsk->icsk_ack.pending = 0;
 }
 EXPORT_SYMBOL(inet_csk_init_xmit_timers);
-- 
2.34.1