netdev - [PATCH net] sctp: do not check hb_timer.expires when resetting hb

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Message-Id: <d958c06985713ec84049a2d5664879802710179a.1675095933.git.lucien.xin@gmail.com>
Date:   Mon, 30 Jan 2023 11:25:33 -0500
From:   Xin Long <lucien.xin@...il.com>
To:     network dev <netdev@...r.kernel.org>, linux-sctp@...r.kernel.org
Cc:     davem@...emloft.net, kuba@...nel.org,
        Eric Dumazet <edumazet@...gle.com>,
        Paolo Abeni <pabeni@...hat.com>,
        Marcelo Ricardo Leitner <marcelo.leitner@...il.com>,
        Neil Horman <nhorman@...driver.com>
Subject: [PATCH net] sctp: do not check hb_timer.expires when resetting hb_timer

It tries to avoid the frequently hb_timer refresh in commit ba6f5e33bdbb
("sctp: avoid refreshing heartbeat timer too often"), and it only allows
mod_timer when the new expires is after hb_timer.expires. It means even
a much shorter interval for hb timer gets applied, it will have to wait
until the current hb timer to time out.

In sctp_do_8_2_transport_strike(), when a transport enters PF state, it
expects to update the hb timer to resend a heartbeat every rto after
calling sctp_transport_reset_hb_timer(), which will not work as the
change mentioned above.

The frequently hb_timer refresh was caused by sctp_transport_reset_timers()
called in sctp_outq_flush() and it was already removed in the commit above.
So we don't have to check hb_timer.expires when resetting hb_timer as it is
now not called very often.

Fixes: ba6f5e33bdbb ("sctp: avoid refreshing heartbeat timer too often")
Signed-off-by: Xin Long <lucien.xin@...il.com>
---
 net/sctp/transport.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/net/sctp/transport.c b/net/sctp/transport.c
index ca1eba95c293..2f66a2006517 100644
--- a/net/sctp/transport.c
+++ b/net/sctp/transport.c
@@ -196,9 +196,7 @@ void sctp_transport_reset_hb_timer(struct sctp_transport *transport)

 	/* When a data chunk is sent, reset the heartbeat interval.  */
 	expires = jiffies + sctp_transport_timeout(transport);
-	if ((time_before(transport->hb_timer.expires, expires) ||
-	     !timer_pending(&transport->hb_timer)) &&
-	    !mod_timer(&transport->hb_timer,
+	if (!mod_timer(&transport->hb_timer,
 		       expires + get_random_u32_below(transport->rto)))
 		sctp_transport_hold(transport);
 }
-- 
2.31.1