Merge branch 'tipc-make-link-protocol-more-resilient'

Jon Maloy says:

====================
tipc: make link protocol more resilient

These two commits make the link ptotocol more resilient to
infrastructures with frequent packet duplication and long delays.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 59 insertions, 17 deletions

diff --git a/net/tipc/link.c b/net/tipc/link.c
index ec4d28328652..df763be38541 100644
--- a/net/tipc/link.c
+++ b/net/tipc/link.c
@@ -128,14 +128,17 @@ struct tipc_link {
 	struct net *net;
 
 	/* Management and link supervision data */
-	u32 peer_session;
-	u32 session;
+	u16 peer_session;
+	u16 session;
+	u16 snd_nxt_state;
+	u16 rcv_nxt_state;
 	u32 peer_bearer_id;
 	u32 bearer_id;
 	u32 tolerance;
 	u32 abort_limit;
 	u32 state;
 	u16 peer_caps;
+	bool in_session;
 	bool active;
 	u32 silent_intv_cnt;
 	char if_name[TIPC_MAX_IF_NAME];
@@ -214,11 +217,6 @@ enum {
  */
 #define TIPC_NACK_INTV (TIPC_MIN_LINK_WIN * 2)
 
-/* Wildcard value for link session numbers. When it is known that
- * peer endpoint is down, any session number must be accepted.
- */
-#define ANY_SESSION 0x10000
-
 /* Link FSM states:
  */
 enum {
@@ -339,6 +337,11 @@ char tipc_link_plane(struct tipc_link *l)
 	return l->net_plane;
 }
 
+void tipc_link_update_caps(struct tipc_link *l, u16 capabilities)
+{
+	l->peer_caps = capabilities;
+}
+
 void tipc_link_add_bc_peer(struct tipc_link *snd_l,
 			   struct tipc_link *uc_l,
 			   struct sk_buff_head *xmitq)
@@ -471,7 +474,7 @@ bool tipc_link_create(struct net *net, char *if_name, int bearer_id,
 	l->addr = peer;
 	l->peer_caps = peer_caps;
 	l->net = net;
-	l->peer_session = ANY_SESSION;
+	l->in_session = false;
 	l->bearer_id = bearer_id;
 	l->tolerance = tolerance;
 	l->net_plane = net_plane;
@@ -840,7 +843,7 @@ void link_prepare_wakeup(struct tipc_link *l)
 
 void tipc_link_reset(struct tipc_link *l)
 {
-	l->peer_session = ANY_SESSION;
+	l->in_session = false;
 	l->session++;
 	l->mtu = l->advertised_mtu;
 	__skb_queue_purge(&l->transmq);
@@ -859,6 +862,8 @@ void tipc_link_reset(struct tipc_link *l)
 	l->rcv_unacked = 0;
 	l->snd_nxt = 1;
 	l->rcv_nxt = 1;
+	l->snd_nxt_state = 1;
+	l->rcv_nxt_state = 1;
 	l->acked = 0;
 	l->silent_intv_cnt = 0;
 	l->rst_cnt = 0;
@@ -1353,6 +1358,8 @@ static void tipc_link_build_proto_msg(struct tipc_link *l, int mtyp, bool probe,
 	msg_set_seqno(hdr, l->snd_nxt + U16_MAX / 2);
 
 	if (mtyp == STATE_MSG) {
+		if (l->peer_caps & TIPC_LINK_PROTO_SEQNO)
+			msg_set_seqno(hdr, l->snd_nxt_state++);
 		msg_set_seq_gap(hdr, rcvgap);
 		msg_set_bc_gap(hdr, link_bc_rcv_gap(bcl));
 		msg_set_probe(hdr, probe);
@@ -1444,6 +1451,44 @@ tnl:
 	}
 }
 
+/* tipc_link_validate_msg(): validate message against current link state
+ * Returns true if message should be accepted, otherwise false
+ */
+bool tipc_link_validate_msg(struct tipc_link *l, struct tipc_msg *hdr)
+{
+	u16 curr_session = l->peer_session;
+	u16 session = msg_session(hdr);
+	int mtyp = msg_type(hdr);
+
+	if (msg_user(hdr) != LINK_PROTOCOL)
+		return true;
+
+	switch (mtyp) {
+	case RESET_MSG:
+		if (!l->in_session)
+			return true;
+		/* Accept only RESET with new session number */
+		return more(session, curr_session);
+	case ACTIVATE_MSG:
+		if (!l->in_session)
+			return true;
+		/* Accept only ACTIVATE with new or current session number */
+		return !less(session, curr_session);
+	case STATE_MSG:
+		/* Accept only STATE with current session number */
+		if (!l->in_session)
+			return false;
+		if (session != curr_session)
+			return false;
+		if (!(l->peer_caps & TIPC_LINK_PROTO_SEQNO))
+			return true;
+		/* Accept only STATE with new sequence number */
+		return !less(msg_seqno(hdr), l->rcv_nxt_state);
+	default:
+		return false;
+	}
+}
+
 /* tipc_link_proto_rcv(): receive link level protocol message :
  * Note that network plane id propagates through the network, and may
  * change at any time. The node with lowest numerical id determines
@@ -1477,17 +1522,12 @@ static int tipc_link_proto_rcv(struct tipc_link *l, struct sk_buff *skb,
 	hdr = buf_msg(skb);
 	data = msg_data(hdr);
 
+	if (!tipc_link_validate_msg(l, hdr))
+		goto exit;
+
 	switch (mtyp) {
 	case RESET_MSG:
-
-		/* Ignore duplicate RESET with old session number */
-		if ((less_eq(msg_session(hdr), l->peer_session)) &&
-		    (l->peer_session != ANY_SESSION))
-			break;
-		/* fall thru' */
-
 	case ACTIVATE_MSG:
-
 		/* Complete own link name with peer's interface name */
 		if_name =  strrchr(l->name, ':') + 1;
 		if (sizeof(l->name) - (if_name - l->name) <= TIPC_MAX_IF_NAME)
@@ -1515,12 +1555,14 @@ static int tipc_link_proto_rcv(struct tipc_link *l, struct sk_buff *skb,
 			rc = TIPC_LINK_UP_EVT;
 
 		l->peer_session = msg_session(hdr);
+		l->in_session = true;
 		l->peer_bearer_id = msg_bearer_id(hdr);
 		if (l->mtu > msg_max_pkt(hdr))
 			l->mtu = msg_max_pkt(hdr);
 		break;
 
 	case STATE_MSG:
+		l->rcv_nxt_state = msg_seqno(hdr) + 1;
 
 		/* Update own tolerance if peer indicates a non-zero value */
 		if (in_range(peers_tol, TIPC_MIN_LINK_TOL, TIPC_MAX_LINK_TOL))