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>

5 files changed, 16 insertions, 1 deletions

diff --git a/include/net/sctp/command.h b/include/net/sctp/command.h
index 5e848884ff61..2058fabffbf6 100644
--- a/include/net/sctp/command.h
+++ b/include/net/sctp/command.h
@@ -59,6 +59,7 @@ enum sctp_verb {
 	SCTP_CMD_HB_TIMERS_START,    /* Start the heartbeat timers. */
 	SCTP_CMD_HB_TIMER_UPDATE,    /* Update a heartbeat timers.  */
 	SCTP_CMD_HB_TIMERS_STOP,     /* Stop the heartbeat timers.  */
+	SCTP_CMD_PROBE_TIMER_UPDATE, /* Update a probe timer.  */
 	SCTP_CMD_TRANSPORT_HB_SENT,  /* Reset the status of a transport. */
 	SCTP_CMD_TRANSPORT_IDLE,     /* Do manipulations on idle transport */
 	SCTP_CMD_TRANSPORT_ON,       /* Mark the transport as active. */
diff --git a/include/net/sctp/constants.h b/include/net/sctp/constants.h
index 85f6a105c59d..265fffa33dad 100644
--- a/include/net/sctp/constants.h
+++ b/include/net/sctp/constants.h
@@ -77,6 +77,7 @@ enum sctp_event_timeout {
 	SCTP_EVENT_TIMEOUT_T5_SHUTDOWN_GUARD,
 	SCTP_EVENT_TIMEOUT_HEARTBEAT,
 	SCTP_EVENT_TIMEOUT_RECONF,
+	SCTP_EVENT_TIMEOUT_PROBE,
 	SCTP_EVENT_TIMEOUT_SACK,
 	SCTP_EVENT_TIMEOUT_AUTOCLOSE,
 };
diff --git a/include/net/sctp/sctp.h b/include/net/sctp/sctp.h
index 08347d3f004f..f7e083602c10 100644
--- a/include/net/sctp/sctp.h
+++ b/include/net/sctp/sctp.h
@@ -635,10 +635,14 @@ static inline void sctp_transport_pl_reset(struct sctp_transport *t)
 			t->pl.state = SCTP_PL_BASE;
 			t->pl.pmtu = SCTP_BASE_PLPMTU;
 			t->pl.probe_size = SCTP_BASE_PLPMTU;
+			sctp_transport_reset_probe_timer(t);
 		}
 	} else {
-		if (t->pl.state != SCTP_PL_DISABLED)
+		if (t->pl.state != SCTP_PL_DISABLED) {
+			if (del_timer(&t->probe_timer))
+				sctp_transport_put(t);
 			t->pl.state = SCTP_PL_DISABLED;
+		}
 	}
 }
 
@@ -647,6 +651,9 @@ static inline void sctp_transport_pl_update(struct sctp_transport *t)
 	if (t->pl.state == SCTP_PL_DISABLED)
 		return;
 
+	if (del_timer(&t->probe_timer))
+		sctp_transport_put(t);
+
 	t->pl.state = SCTP_PL_BASE;
 	t->pl.pmtu = SCTP_BASE_PLPMTU;
 	t->pl.probe_size = SCTP_BASE_PLPMTU;
diff --git a/include/net/sctp/sm.h b/include/net/sctp/sm.h
index 09c59154634d..45542e2bac93 100644
--- a/include/net/sctp/sm.h
+++ b/include/net/sctp/sm.h
@@ -151,6 +151,7 @@ sctp_state_fn_t sctp_sf_cookie_wait_icmp_abort;
 /* Prototypes for timeout event state functions.  */
 sctp_state_fn_t sctp_sf_do_6_3_3_rtx;
 sctp_state_fn_t sctp_sf_send_reconf;
+sctp_state_fn_t sctp_sf_send_probe;
 sctp_state_fn_t sctp_sf_do_6_2_sack;
 sctp_state_fn_t sctp_sf_autoclose_timer_expire;
 
@@ -311,6 +312,7 @@ int sctp_do_sm(struct net *net, enum sctp_event_type event_type,
 void sctp_generate_t3_rtx_event(struct timer_list *t);
 void sctp_generate_heartbeat_event(struct timer_list *t);
 void sctp_generate_reconf_event(struct timer_list *t);
+void sctp_generate_probe_event(struct timer_list *t);
 void sctp_generate_proto_unreach_event(struct timer_list *t);
 
 void sctp_ootb_pkt_free(struct sctp_packet *packet);
diff --git a/include/net/sctp/structs.h b/include/net/sctp/structs.h
index 85d3566c2227..a3772f8ee7f6 100644
--- a/include/net/sctp/structs.h
+++ b/include/net/sctp/structs.h
@@ -936,6 +936,9 @@ struct sctp_transport {
 	/* Timer to handler reconf chunk rtx */
 	struct timer_list reconf_timer;
 
+	/* Timer to send a probe HB packet for PLPMTUD */
+	struct timer_list probe_timer;
+
 	/* Since we're using per-destination retransmission timers
 	 * (see above), we're also using per-destination "transmitted"
 	 * queues.  This probably ought to be a private struct
@@ -1003,6 +1006,7 @@ void sctp_transport_free(struct sctp_transport *);
 void sctp_transport_reset_t3_rtx(struct sctp_transport *);
 void sctp_transport_reset_hb_timer(struct sctp_transport *);
 void sctp_transport_reset_reconf_timer(struct sctp_transport *transport);
+void sctp_transport_reset_probe_timer(struct sctp_transport *transport);
 int sctp_transport_hold(struct sctp_transport *);
 void sctp_transport_put(struct sctp_transport *);
 void sctp_transport_update_rto(struct sctp_transport *, __u32);