Detection for loops with leafnodes.

We need to send the unique LDS subject to all leafnodes to properly detect setups like triangles.
This will have the server who completes the loop be the one that detects the error soley based on
its own loop detection subject.

Otehr changes are just to fix tests that were not waiting for the new LDS sub.

Signed-off-by: Derek Collison <derek@nats.io>

server/leafnode.go

@@ -45,8 +45,7 @@ const leafnodeTLSInsecureWarning = "TLS certificate chain and hostname of solici
 const leafNodeReconnectDelayAfterLoopDetected = 30 * time.Second
 
 // Prefix for loop detection subject
-const leafNodeLoopDetectionSubjectPrefixOld = "lds."
-const leafNodeLoopDetectionSubjectPrefix = "$" + leafNodeLoopDetectionSubjectPrefixOld
+const leafNodeLoopDetectionSubjectPrefix = "$LDS."
 
 type leaf struct {
 	// Used to suppress sub and unsub interest. Same as routes but our audience
@@ -1088,9 +1087,8 @@ func (s *Server) initLeafNodeSmap(c *client) int {
 	}
 	// Detect loop by subscribing to a specific subject and checking
 	// if this is coming back to us.
-	if c.leaf.remote == nil {
-		c.leaf.smap[lds]++
-	}
+	c.leaf.smap[lds]++
+
 	lenMap := len(c.leaf.smap)
 	c.mu.Unlock()
 	return lenMap
@@ -1271,6 +1269,14 @@ func (c *client) processLeafSub(argo []byte) (err error) {
 		return nil
 	}
 
+	acc := c.acc
+	// Check if we have a loop.
+	if string(sub.subject) == acc.getLDSubject() {
+		c.mu.Unlock()
+		srv.reportLeafNodeLoop(c)
+		return nil
+	}
+
 	// Check permissions if applicable.
 	if !c.canExport(string(sub.subject)) {
 		c.mu.Unlock()
@@ -1295,44 +1301,10 @@ func (c *client) processLeafSub(argo []byte) (err error) {
 	key := string(sub.sid)
 	osub := c.subs[key]
 	updateGWs := false
-	acc := c.acc
 	if osub == nil {
-		subj := string(sub.subject)
-		accUnlock := false
-		// Check if we have a loop.
-		if len(subj) >= len(leafNodeLoopDetectionSubjectPrefixOld) {
-			subStripped := subj
-			if subStripped[0] == '$' {
-				subStripped = subStripped[1:]
-			}
-			if strings.HasPrefix(subStripped, leafNodeLoopDetectionSubjectPrefixOld) {
-				// The following check (involving acc.sl) and the later insert need to be tied together
-				// using the account lock, such that checking and modifying the sublist appear as one operation.
-				acc.mu.Lock()
-				accUnlock = true
-				// There is a loop if we receive our own subscription back.
-				loopFound := subj == acc.lds
-				if !loopFound {
-					// Or if a subscription from a different client already exists.
-					if res := acc.sl.Match(subj); res != nil && len(res.psubs)+len(res.qsubs) != 0 {
-						loopFound = true
-					}
-				}
-				if loopFound {
-					acc.mu.Unlock()
-					c.mu.Unlock()
-					srv.reportLeafNodeLoop(c)
-					return nil
-				}
-			}
-		}
 		c.subs[key] = sub
 		// Now place into the account sl.
-		err := acc.sl.Insert(sub)
-		if accUnlock {
-			acc.mu.Unlock()
-		}
-		if err != nil {
+		if err := acc.sl.Insert(sub); err != nil {
 			delete(c.subs, key)
 			c.mu.Unlock()
 			c.Errorf("Could not insert subscription: %v", err)