Finally, finally got to the bottom of the 'simple topology' Forwarding bug.

src/main/java/net/floodlightcontroller/forwarding/Forwarding.java

@@ -20,6 +20,7 @@ package net.floodlightcontroller.forwarding;
 import java.io.IOException;
 import java.util.ArrayList;
 import java.util.Collection;
+import java.util.Collections;
 import java.util.List;
 import java.util.Map;
 import java.util.Set;
@@ -47,6 +48,7 @@ import net.floodlightcontroller.routing.IRoutingDecision;
 import net.floodlightcontroller.routing.IRoutingService;
 import net.floodlightcontroller.routing.Route;
 import net.floodlightcontroller.topology.ITopologyService;
+import net.floodlightcontroller.topology.NodePortTuple;
 
 import org.projectfloodlight.openflow.protocol.OFFlowMod;
 import org.projectfloodlight.openflow.protocol.OFFlowModCommand;
@@ -79,7 +81,7 @@ public class Forwarding extends ForwardingBase implements IFloodlightModule {
 		// We found a routing decision (i.e. Firewall is enabled... it's the only thing that makes RoutingDecisions)
 		if (decision != null) {
 			if (log.isTraceEnabled()) {
-				log.trace("Forwaring decision={} was made for PacketIn={}", decision.getRoutingAction().toString(), pi);
+				log.trace("Forwarding decision={} was made for PacketIn={}", decision.getRoutingAction().toString(), pi);
 			}
 
 			switch(decision.getRoutingAction()) {
@@ -223,6 +225,9 @@ public class Forwarding extends ForwardingBase implements IFloodlightModule {
 					dstDap.getSwitchDPID(),
 					dstDap.getPort(), U64.of(0)); //cookie = 0, i.e., default route
 
+			Match m = createMatchFromPacket(sw, inPort, cntx);
+			U64 cookie = AppCookie.makeCookie(FORWARDING_APP_ID, 0);
+			
 			if (route != null) {
 				log.debug("pushRoute inPort={} route={} " +
 						"destination={}:{}",
@@ -230,15 +235,24 @@ public class Forwarding extends ForwardingBase implements IFloodlightModule {
 						dstDap.getSwitchDPID(),
 						dstDap.getPort()});
 
-				U64 cookie = AppCookie.makeCookie(FORWARDING_APP_ID, 0);
 
-				Match m = createMatchFromPacket(sw, inPort, cntx);
 				log.debug("Cretaing flow rules on the route, match rule: {}", m);
 				pushRoute(route, m, pi, sw.getId(), cookie, 
 						cntx, requestFlowRemovedNotifn,
 						OFFlowModCommand.ADD);	
 			} else {
-				log.error("Could not compute route between {} and {}. Dropping packet", srcDevice, dstDevice);
+				/* Route traverses no links --> src/dst devices on same switch */
+				log.debug("Could not compute route. Devices should be on same switch src={} and dst={}", srcDevice, dstDevice);
+				Route r = new Route(srcDevice.getAttachmentPoints()[0].getSwitchDPID(), dstDevice.getAttachmentPoints()[0].getSwitchDPID());
+				List<NodePortTuple> path = new ArrayList<NodePortTuple>(2);
+				path.add(new NodePortTuple(srcDevice.getAttachmentPoints()[0].getSwitchDPID(),
+						srcDevice.getAttachmentPoints()[0].getPort()));
+				path.add(new NodePortTuple(dstDevice.getAttachmentPoints()[0].getSwitchDPID(),
+						dstDevice.getAttachmentPoints()[0].getPort()));
+				r.setPath(path);
+				pushRoute(r, m, pi, sw.getId(), cookie,
+						cntx, requestFlowRemovedNotifn,
+						OFFlowModCommand.ADD);
 			}
 		} else {
 			log.debug("Destination unknown. Flooding packet");
@@ -365,7 +379,9 @@ public class Forwarding extends ForwardingBase implements IFloodlightModule {
 		Set<OFPort> broadcastPorts = this.topologyService.getSwitchBroadcastPorts(sw.getId());
 
 		if (broadcastPorts == null) {
-			return;
+			log.debug("BroadcastPorts returned null. Assuming single switch w/no links.");
+			/* Must be a single-switch w/no links */
+			broadcastPorts = Collections.singleton(OFPort.FLOOD);
 		}
 		
 		for (OFPort p : broadcastPorts) {

src/main/java/net/floodlightcontroller/topology/TopologyManager.java

@@ -1148,7 +1148,12 @@ public class TopologyManager implements IFloodlightModule, ITopologyService, IRo
 	}
 
 	protected void addOrUpdateSwitch(DatapathId sw) {
-		// nothing to do here for the time being.
+		/*TODO react appropriately
+		addSwitch(sw);
+		for (OFPortDesc p : switchService.getSwitch(sw).getPorts()) {
+			addPortToSwitch(sw, p.getPortNo());
+		}
+		*/
 		return;
 	}