sctp: add the probe timer in transport for PLPMTUD

There are 3 timers described in rfc8899#section-5.1.1:

  PROBE_TIMER, PMTU_RAISE_TIMER, CONFIRMATION_TIMER

This patches adds a 'probe_timer' in transport, and it works as either
PROBE_TIMER or PMTU_RAISE_TIMER. At most time, it works as PROBE_TIMER
and expires every a 'probe_interval' time to send the HB probe packet.
When transport pl enters COMPLETE state, it works as PMTU_RAISE_TIMER
and expires in 'probe_interval * 30' time to go back to SEARCH state
and do searching again.

SCTP HB is an acknowledged packet, CONFIRMATION_TIMER is not needed.

The timer will start when transport pl enters BASE state and stop
when it enters DISABLED state.

Signed-off-by: Xin Long <lucien.xin@gmail.com>
Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 18 insertions, 0 deletions

diff --git a/net/sctp/transport.c b/net/sctp/transport.c
index bf0ac467e757..ca3343c2c80e 100644
--- a/net/sctp/transport.c
+++ b/net/sctp/transport.c
@@ -75,6 +75,7 @@ static struct sctp_transport *sctp_transport_init(struct net *net,
 	timer_setup(&peer->T3_rtx_timer, sctp_generate_t3_rtx_event, 0);
 	timer_setup(&peer->hb_timer, sctp_generate_heartbeat_event, 0);
 	timer_setup(&peer->reconf_timer, sctp_generate_reconf_event, 0);
+	timer_setup(&peer->probe_timer, sctp_generate_probe_event, 0);
 	timer_setup(&peer->proto_unreach_timer,
 		    sctp_generate_proto_unreach_event, 0);
 
@@ -131,6 +132,9 @@ void sctp_transport_free(struct sctp_transport *transport)
 	if (del_timer(&transport->reconf_timer))
 		sctp_transport_put(transport);
 
+	if (del_timer(&transport->probe_timer))
+		sctp_transport_put(transport);
+
 	/* Delete the ICMP proto unreachable timer if it's active. */
 	if (del_timer(&transport->proto_unreach_timer))
 		sctp_transport_put(transport);
@@ -207,6 +211,20 @@ void sctp_transport_reset_reconf_timer(struct sctp_transport *transport)
 			sctp_transport_hold(transport);
 }
 
+void sctp_transport_reset_probe_timer(struct sctp_transport *transport)
+{
+	int scale = 1;
+
+	if (timer_pending(&transport->probe_timer))
+		return;
+	if (transport->pl.state == SCTP_PL_COMPLETE &&
+	    transport->pl.probe_count == 1)
+		scale = 30; /* works as PMTU_RAISE_TIMER */
+	if (!mod_timer(&transport->probe_timer,
+		       jiffies + transport->probe_interval * scale))
+		sctp_transport_hold(transport);
+}
+
 /* This transport has been assigned to an association.
  * Initialize fields from the association or from the sock itself.
  * Register the reference count in the association.