linux-kernel - [PATCH v3 2/2] net: make tcp keepalive timer upper bound

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Date:   Wed, 30 Mar 2022 10:20:46 +0200
From:   Artem Savkov <asavkov@...hat.com>
To:     netdev@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
        asavkov@...hat.com, Josh Poimboeuf <jpoimboe@...hat.com>
Cc:     davem@...emloft.net, yoshfuji@...ux-ipv6.org,
        Anna-Maria Gleixner <anna-maria@...utronix.de>,
        dsahern@...nel.org, linux-kernel@...r.kernel.org
Subject: [PATCH v3 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 1e5b53c2bb267..bb2dbfb6f5b50 100644
--- a/net/ipv4/inet_connection_sock.c
+++ b/net/ipv4/inet_connection_sock.c
@@ -589,7 +589,7 @@ EXPORT_SYMBOL(inet_csk_delete_keepalive_timer);
 
 void inet_csk_reset_keepalive_timer(struct sock *sk, unsigned long len)
 {
-	sk_reset_timer(sk, &sk->sk_timer, jiffies + len);
+	sk_reset_timer(sk, &sk->sk_timer, jiffies + upper_bound_timeout(len));
 }
 EXPORT_SYMBOL(inet_csk_reset_keepalive_timer);
 
-- 
2.34.1