To avoid control data losses do not acknowledge recieving of control packet

if netgraph reported error while delivering to destination.
Reset 'next send' counter to the last requested by peer on ack timeout
to resend all subsequest packets after lost one again without additional hints.

1 files changed, 44 insertions, 54 deletions

diff --git a/sys/netgraph/ng_l2tp.c b/sys/netgraph/ng_l2tp.c
index accf48d..5368b82 100644
--- a/sys/netgraph/ng_l2tp.c
+++ b/sys/netgraph/ng_l2tp.c
@@ -118,6 +118,7 @@ MALLOC_DEFINE(M_NETGRAPH_L2TP, "netgraph_l2tp", "netgraph l2tp node");
 struct l2tp_seq {
 	u_int16_t		ns;		/* next xmit seq we send */
 	u_int16_t		nr;		/* next recv seq we expect */
+	u_int16_t		inproc;		/* packet is in processing */
 	u_int16_t		rack;		/* last 'nr' we rec'd */
 	u_int16_t		xack;		/* last 'nr' we sent */
 	u_int16_t		wmax;		/* peer's max recv window */
@@ -173,7 +174,6 @@ static int	ng_l2tp_seq_adjust(priv_p priv,
 static void	ng_l2tp_seq_reset(priv_p priv);
 static void	ng_l2tp_seq_failure(priv_p priv);
 static void	ng_l2tp_seq_recv_nr(priv_p priv, u_int16_t nr);
-static int	ng_l2tp_seq_recv_ns(priv_p priv, u_int16_t ns);
 static void	ng_l2tp_seq_xack_timeout(node_p node, hook_p hook,
 		    void *arg1, int arg2);
 static void	ng_l2tp_seq_rack_timeout(node_p node, hook_p hook,
@@ -911,6 +911,7 @@ ng_l2tp_rcvdata_lower(hook_p h, item_p item)
 
 	/* Handle control packets */
 	if ((hdr & L2TP_HDR_CTRL) != 0) {
+		struct l2tp_seq *const seq = &priv->seq;
 
 		/* Handle receive ack sequence number Nr */
 		ng_l2tp_seq_recv_nr(priv, nr);
@@ -923,12 +924,30 @@ ng_l2tp_rcvdata_lower(hook_p h, item_p item)
 			ERROUT(0);
 		}
 
+		mtx_lock(&seq->mtx);
 		/*
-		 * Prepend session ID to packet here: we don't want to accept
-		 * the send sequence number Ns if we have to drop the packet
-		 * later because of a memory error, because then the upper
-		 * layer would never get the packet.
+		 * If not what we expect or we are busy, drop packet and
+		 * send an immediate ZLB ack.
 		 */
+		if (ns != seq->nr || seq->inproc) {
+			if (L2TP_SEQ_DIFF(ns, seq->nr) <= 0)
+				priv->stats.recvDuplicates++;
+			else
+				priv->stats.recvOutOfOrder++;
+			mtx_unlock(&seq->mtx);
+			ng_l2tp_xmit_ctrl(priv, NULL, seq->ns);
+			NG_FREE_ITEM(item);
+			NG_FREE_M(m);
+			ERROUT(0);
+		}
+		/*
+		 * Until we deliver this packet we can't receive next one as
+		 * we have no information for sending ack.
+		 */
+		seq->inproc = 1;
+		mtx_unlock(&seq->mtx);
+
+		/* Prepend session ID to packet. */
 		M_PREPEND(m, 2, M_DONTWAIT);
 		if (m == NULL) {
 			priv->stats.memoryFailures++;
@@ -937,15 +956,26 @@ ng_l2tp_rcvdata_lower(hook_p h, item_p item)
 		}
 		memcpy(mtod(m, u_int16_t *), &ids[1], 2);
 
-		/* Now handle send sequence number */
-		if (ng_l2tp_seq_recv_ns(priv, ns) == -1) {
-			NG_FREE_ITEM(item);
-			NG_FREE_M(m);
-			ERROUT(0);
-		}
-
 		/* Deliver packet to upper layers */
 		NG_FWD_NEW_DATA(error, item, priv->ctrl, m);
+		
+		mtx_lock(&seq->mtx);
+		/* Ready to process next packet. */
+		seq->inproc = 0;
+
+		/* If packet was successfully delivered send ack. */
+		if (error == 0) {
+			/* Update recv sequence number */
+			seq->nr++;
+			/* Start receive ack timer, if not already running */
+			if (!callout_active(&seq->xack_timer)) {
+				ng_callout(&seq->xack_timer, priv->node, NULL,
+				    L2TP_DELAYED_ACK, ng_l2tp_seq_xack_timeout,
+				    NULL, 0);
+			}
+		}
+		mtx_unlock(&seq->mtx);
+
 		ERROUT(error);
 	}
 
@@ -1389,47 +1419,6 @@ ng_l2tp_seq_recv_nr(priv_p priv, u_int16_t nr)
 }
 
 /*
- * Handle receipt of a sequence number value (Ns) from peer.
- * We make no attempt to re-order out of order packets.
- *
- * This function should only be called for non-ZLB packets.
- *
- * Returns:
- *	 0	Accept packet
- *	-1	Drop packet
- */
-static int
-ng_l2tp_seq_recv_ns(priv_p priv, u_int16_t ns)
-{
-	struct l2tp_seq *const seq = &priv->seq;
-
-	/* If not what we expect, drop packet and send an immediate ZLB ack */
-	if (ns != seq->nr) {
-		if (L2TP_SEQ_DIFF(ns, seq->nr) < 0)
-			priv->stats.recvDuplicates++;
-		else
-			priv->stats.recvOutOfOrder++;
-		ng_l2tp_xmit_ctrl(priv, NULL, seq->ns);
-		return (-1);
-	}
-
-	mtx_lock(&seq->mtx);
-
-	/* Update recv sequence number */
-	seq->nr++;
-
-	/* Start receive ack timer, if not already running */
-	if (!callout_active(&seq->xack_timer))
-		ng_callout(&seq->xack_timer, priv->node, NULL,
-		    L2TP_DELAYED_ACK, ng_l2tp_seq_xack_timeout, NULL, 0);
-
-	mtx_unlock(&seq->mtx);
-
-	/* Accept packet */
-	return (0);
-}
-
-/*
  * Handle an ack timeout. We have an outstanding ack that we
  * were hoping to piggy-back, but haven't, so send a ZLB.
  */
@@ -1491,6 +1480,7 @@ ng_l2tp_seq_rack_timeout(node_p node, hook_p hook, void *arg1, int arg2)
 	    hz * delay, ng_l2tp_seq_rack_timeout, NULL, 0);
 
 	/* Do slow-start/congestion algorithm windowing algorithm */
+	seq->ns = seq->rack;
 	seq->ssth = (seq->cwnd + 1) / 2;
 	seq->cwnd = 1;
 	seq->acks = 0;
@@ -1499,7 +1489,7 @@ ng_l2tp_seq_rack_timeout(node_p node, hook_p hook, void *arg1, int arg2)
 	if ((m = L2TP_COPY_MBUF(seq->xwin[0], M_DONTWAIT)) == NULL)
 		priv->stats.memoryFailures++;
 	else
-		ng_l2tp_xmit_ctrl(priv, m, seq->rack);
+		ng_l2tp_xmit_ctrl(priv, m, seq->ns++);
 
 	/* callout_deactivate() is not needed here 
 	    as ng_callout() is getting called each time */