[PATCHv2 net 1/2] sctp: improve the code for pmtu probe send and recv update

[Xin Long <lucien.xin@gmail.com>]

This patch does 3 things:

  - make sctp_transport_pl_send() and sctp_transport_pl_recv()
    return bool type to decide if more probe is needed to send.

  - pr_debug() only when probe is really needed to send.

  - count pl.raise_count in sctp_transport_pl_send() instead of
    sctp_transport_pl_recv(), and it's only incremented for the
    1st probe for the same size.

These are preparations for the next patch to make probes happen
only when there's packet loss in Search Complete state.

Signed-off-by: Xin Long <lucien.xin@gmail.com>
---
 include/net/sctp/structs.h |  4 ++--
 net/sctp/sm_statefuns.c    | 15 +++++++-------
 net/sctp/transport.c       | 41 +++++++++++++++++++++-----------------
 3 files changed, 32 insertions(+), 28 deletions(-)

diff --git a/include/net/sctp/structs.h b/include/net/sctp/structs.h
index 32fc4a309df5..f3d414ed208e 100644
--- a/include/net/sctp/structs.h
+++ b/include/net/sctp/structs.h
@@ -1024,8 +1024,8 @@ bool sctp_transport_update_pmtu(struct sctp_transport *t, u32 pmtu);
 void sctp_transport_immediate_rtx(struct sctp_transport *);
 void sctp_transport_dst_release(struct sctp_transport *t);
 void sctp_transport_dst_confirm(struct sctp_transport *t);
-void sctp_transport_pl_send(struct sctp_transport *t);
-void sctp_transport_pl_recv(struct sctp_transport *t);
+bool sctp_transport_pl_send(struct sctp_transport *t);
+bool sctp_transport_pl_recv(struct sctp_transport *t);
 
 
 /* This is the structure we use to queue packets as they come into
diff --git a/net/sctp/sm_statefuns.c b/net/sctp/sm_statefuns.c
index 09a8f23ec709..32df65f68c12 100644
--- a/net/sctp/sm_statefuns.c
+++ b/net/sctp/sm_statefuns.c
@@ -1109,12 +1109,12 @@ enum sctp_disposition sctp_sf_send_probe(struct net *net,
 	if (!sctp_transport_pl_enabled(transport))
 		return SCTP_DISPOSITION_CONSUME;
 
-	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));
+	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_add_cmd_sf(commands, SCTP_CMD_PROBE_TIMER_UPDATE,
 			SCTP_TRANSPORT(transport));
 
@@ -1274,8 +1274,7 @@ enum sctp_disposition sctp_sf_backbeat_8_3(struct net *net,
 		    !sctp_transport_pl_enabled(link))
 			return SCTP_DISPOSITION_DISCARD;
 
-		sctp_transport_pl_recv(link);
-		if (link->pl.state == SCTP_PL_COMPLETE)
+		if (sctp_transport_pl_recv(link))
 			return SCTP_DISPOSITION_CONSUME;
 
 		return sctp_sf_send_probe(net, ep, asoc, type, link, commands);
diff --git a/net/sctp/transport.c b/net/sctp/transport.c
index 397a6244dd97..23e7bd3e3bd4 100644
--- a/net/sctp/transport.c
+++ b/net/sctp/transport.c
@@ -258,16 +258,12 @@ void sctp_transport_pmtu(struct sctp_transport *transport, struct sock *sk)
 	sctp_transport_pl_update(transport);
 }
 
-void sctp_transport_pl_send(struct sctp_transport *t)
+bool sctp_transport_pl_send(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);
-
-	if (t->pl.probe_count < SCTP_MAX_PROBES) {
-		t->pl.probe_count++;
-		return;
-	}
+	if (t->pl.probe_count < SCTP_MAX_PROBES)
+		goto out;
 
+	t->pl.probe_count = 0;
 	if (t->pl.state == SCTP_PL_BASE) {
 		if (t->pl.probe_size == SCTP_BASE_PLPMTU) { /* BASE_PLPMTU Confirmation Failed */
 			t->pl.state = SCTP_PL_ERROR; /* Base -> Error */
@@ -299,10 +295,20 @@ void sctp_transport_pl_send(struct sctp_transport *t)
 			sctp_assoc_sync_pmtu(t->asoc);
 		}
 	}
-	t->pl.probe_count = 1;
+
+out:
+	if (t->pl.state == SCTP_PL_COMPLETE && t->pl.raise_count < 30 &&
+	    !t->pl.probe_count)
+		t->pl.raise_count++;
+
+	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;
 }
 
-void sctp_transport_pl_recv(struct sctp_transport *t)
+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);
@@ -323,7 +329,7 @@ void sctp_transport_pl_recv(struct sctp_transport *t)
 		if (!t->pl.probe_high) {
 			t->pl.probe_size = min(t->pl.probe_size + SCTP_PL_BIG_STEP,
 					       SCTP_MAX_PLPMTU);
-			return;
+			return false;
 		}
 		t->pl.probe_size += SCTP_PL_MIN_STEP;
 		if (t->pl.probe_size >= t->pl.probe_high) {
@@ -335,14 +341,13 @@ void sctp_transport_pl_recv(struct sctp_transport *t)
 			t->pathmtu = t->pl.pmtu + sctp_transport_pl_hlen(t);
 			sctp_assoc_sync_pmtu(t->asoc);
 		}
-	} else if (t->pl.state == SCTP_PL_COMPLETE) {
-		t->pl.raise_count++;
-		if (t->pl.raise_count == 30) {
-			/* 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;
-		}
+	} else if (t->pl.state == SCTP_PL_COMPLETE && t->pl.raise_count == 30) {
+		/* 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;
 	}
+
+	return t->pl.state == SCTP_PL_COMPLETE;
 }
 
 static bool sctp_transport_pl_toobig(struct sctp_transport *t, u32 pmtu)
-- 
2.27.0