sctp: do not check hb_timer.expires when resetting hb_timer

Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2167094
Tested: bug reproducer

Conflicts:
  - Context difference due to missing 8032bf1 in RHEL-9.

commit 8f35ae1
Author: Xin Long <lucien.xin@gmail.com>
Date:   Mon Jan 30 11:25:33 2023 -0500

    sctp: do not check hb_timer.expires when resetting hb_timer

    It tries to avoid the frequently hb_timer refresh in commit ba6f5e3
    ("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: ba6f5e3 ("sctp: avoid refreshing heartbeat timer too often")
    Signed-off-by: Xin Long <lucien.xin@gmail.com>
    Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
    Link: https://lore.kernel.org/r/d958c06985713ec84049a2d5664879802710179a.1675095933.git.lucien.xin@gmail.com
    Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Signed-off-by: Xin Long <lxin@redhat.com>

Author: Xin Long

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 + prandom_u32_max(transport->rto)))
 		sctp_transport_hold(transport);
 }