sctp: make the raise timer more simple and accurate

Currently, the probe timer is reused as the raise timer when PLPMTUD is in
the Search Complete state. raise_count was introduced to count how many
times the probe timer has timed out. When raise_count reaches to 30, the
raise timer handler will be triggered.

During the whole processing above, the timer keeps timing out every probe_
interval. It is a waste for the Search Complete state, as the raise timer
only needs to time out after 30 * probe_interval.

Since the raise timer and probe timer are never used at the same time, it
is no need to keep probe timer 'alive' in the Search Complete state. This
patch to introduce sctp_transport_reset_raise_timer() to start the timer
as the raise timer when entering the Search Complete state. When entering
the other states, sctp_transport_reset_probe_timer() will still be called
to reset the timer to the probe timer.

raise_count can be removed from sctp_transport as no need to count probe
timer timeout for raise timer timeout. last_rtx_chunks can be removed as
sctp_transport_reset_probe_timer() can be called in the place where asoc
rtx_data_chunks is changed.

Signed-off-by: Xin Long <lucien.xin@gmail.com>
Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Link: https://lore.kernel.org/r/edb0e48988ea85997488478b705b11ddc1ba724a.1637781974.git.lucien.xin@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

3 files changed, 19 insertions, 21 deletions

diff --git a/net/sctp/outqueue.c b/net/sctp/outqueue.c
index ff47091c385e..a18609f608fb 100644
--- a/net/sctp/outqueue.c
+++ b/net/sctp/outqueue.c
@@ -547,6 +547,9 @@ void sctp_retransmit(struct sctp_outq *q, struct sctp_transport *transport,
 			sctp_assoc_update_retran_path(transport->asoc);
 		transport->asoc->rtx_data_chunks +=
 			transport->asoc->unack_data;
+		if (transport->pl.state == SCTP_PL_COMPLETE &&
+		    transport->asoc->unack_data)
+			sctp_transport_reset_probe_timer(transport);
 		break;
 	case SCTP_RTXR_FAST_RTX:
 		SCTP_INC_STATS(net, SCTP_MIB_FAST_RETRANSMITS);
diff --git a/net/sctp/sm_statefuns.c b/net/sctp/sm_statefuns.c
index 354c1c4de19b..cc544a97c4af 100644
--- a/net/sctp/sm_statefuns.c
+++ b/net/sctp/sm_statefuns.c
@@ -1124,12 +1124,11 @@ enum sctp_disposition sctp_sf_send_probe(struct net *net,
 	if (!sctp_transport_pl_enabled(transport))
 		return SCTP_DISPOSITION_CONSUME;
 
-	if (sctp_transport_pl_send(transport)) {
-		reply = sctp_make_heartbeat(asoc, transport, transport->pl.probe_size);
-		if (!reply)
-			return SCTP_DISPOSITION_NOMEM;
-		sctp_add_cmd_sf(commands, SCTP_CMD_REPLY, SCTP_CHUNK(reply));
-	}
+	sctp_transport_pl_send(transport);
+	reply = sctp_make_heartbeat(asoc, transport, transport->pl.probe_size);
+	if (!reply)
+		return SCTP_DISPOSITION_NOMEM;
+	sctp_add_cmd_sf(commands, SCTP_CMD_REPLY, SCTP_CHUNK(reply));
 	sctp_add_cmd_sf(commands, SCTP_CMD_PROBE_TIMER_UPDATE,
 			SCTP_TRANSPORT(transport));
 
diff --git a/net/sctp/transport.c b/net/sctp/transport.c
index 133f1719bf1b..f8fd98784977 100644
--- a/net/sctp/transport.c
+++ b/net/sctp/transport.c
@@ -213,13 +213,18 @@ void sctp_transport_reset_reconf_timer(struct sctp_transport *transport)
 
 void sctp_transport_reset_probe_timer(struct sctp_transport *transport)
 {
-	if (timer_pending(&transport->probe_timer))
-		return;
 	if (!mod_timer(&transport->probe_timer,
 		       jiffies + transport->probe_interval))
 		sctp_transport_hold(transport);
 }
 
+void sctp_transport_reset_raise_timer(struct sctp_transport *transport)
+{
+	if (!mod_timer(&transport->probe_timer,
+		       jiffies + transport->probe_interval * 30))
+		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.
@@ -258,12 +263,11 @@ void sctp_transport_pmtu(struct sctp_transport *transport, struct sock *sk)
 	sctp_transport_pl_update(transport);
 }
 
-bool sctp_transport_pl_send(struct sctp_transport *t)
+void sctp_transport_pl_send(struct sctp_transport *t)
 {
 	if (t->pl.probe_count < SCTP_MAX_PROBES)
 		goto out;
 
-	t->pl.last_rtx_chunks = t->asoc->rtx_data_chunks;
 	t->pl.probe_count = 0;
 	if (t->pl.state == SCTP_PL_BASE) {
 		if (t->pl.probe_size == SCTP_BASE_PLPMTU) { /* BASE_PLPMTU Confirmation Failed */
@@ -298,17 +302,9 @@ bool sctp_transport_pl_send(struct sctp_transport *t)
 	}
 
 out:
-	if (t->pl.state == SCTP_PL_COMPLETE && t->pl.raise_count < 30 &&
-	    !t->pl.probe_count && t->pl.last_rtx_chunks == t->asoc->rtx_data_chunks) {
-		t->pl.raise_count++;
-		return false;
-	}
-
 	pr_debug("%s: PLPMTUD: transport: %p, state: %d, pmtu: %d, size: %d, high: %d\n",
 		 __func__, t, t->pl.state, t->pl.pmtu, t->pl.probe_size, t->pl.probe_high);
-
 	t->pl.probe_count++;
-	return true;
 }
 
 bool sctp_transport_pl_recv(struct sctp_transport *t)
@@ -316,7 +312,6 @@ bool sctp_transport_pl_recv(struct sctp_transport *t)
 	pr_debug("%s: PLPMTUD: transport: %p, state: %d, pmtu: %d, size: %d, high: %d\n",
 		 __func__, t, t->pl.state, t->pl.pmtu, t->pl.probe_size, t->pl.probe_high);
 
-	t->pl.last_rtx_chunks = t->asoc->rtx_data_chunks;
 	t->pl.pmtu = t->pl.probe_size;
 	t->pl.probe_count = 0;
 	if (t->pl.state == SCTP_PL_BASE) {
@@ -338,14 +333,14 @@ bool sctp_transport_pl_recv(struct sctp_transport *t)
 		t->pl.probe_size += SCTP_PL_MIN_STEP;
 		if (t->pl.probe_size >= t->pl.probe_high) {
 			t->pl.probe_high = 0;
-			t->pl.raise_count = 0;
 			t->pl.state = SCTP_PL_COMPLETE; /* Search -> Search Complete */
 
 			t->pl.probe_size = t->pl.pmtu;
 			t->pathmtu = t->pl.pmtu + sctp_transport_pl_hlen(t);
 			sctp_assoc_sync_pmtu(t->asoc);
+			sctp_transport_reset_raise_timer(t);
 		}
-	} else if (t->pl.state == SCTP_PL_COMPLETE && t->pl.raise_count == 30) {
+	} else if (t->pl.state == SCTP_PL_COMPLETE) {
 		/* Raise probe_size again after 30 * interval in Search Complete */
 		t->pl.state = SCTP_PL_SEARCH; /* Search Complete -> Search */
 		t->pl.probe_size += SCTP_PL_MIN_STEP;
@@ -393,6 +388,7 @@ static bool sctp_transport_pl_toobig(struct sctp_transport *t, u32 pmtu)
 			t->pl.probe_high = 0;
 			t->pl.pmtu = SCTP_BASE_PLPMTU;
 			t->pathmtu = t->pl.pmtu + sctp_transport_pl_hlen(t);
+			sctp_transport_reset_probe_timer(t);
 			return true;
 		}
 	}