[PATCH v5 2/2] net: make tcp keepalive timer upper bound

[Artem Savkov]

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.
This adds minimal overhead as keepalive timers are never re-armed and
are usually quite long.

Signed-off-by: Artem Savkov <asavkov@xxxxxxxxxx>
---
 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 1e5b53c2bb26..bb2dbfb6f5b5 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