ProxyArp: Reply directly when we know an external target host

Change-Id: I38773dcdcae05506c678c2006d1f63306af6b383

@@ -146,9 +146,9 @@ public class ProxyArpManager implements ProxyArpService {
 
         VlanId vlan = VlanId.vlanId(eth.getVlanID());
 
+        if (isOutsidePort(inPort)) {
             // If the request came from outside the network, only reply if it was
             // for one of our external addresses.
-        if (isOutsidePort(inPort)) {
             Set<PortAddresses> addressSet =
                     hostService.getAddressBindingsForPort(inPort);
 
@@ -162,10 +162,33 @@ public class ProxyArpManager implements ProxyArpService {
                 }
             }
             return;
-        } else {
+        }
+
+        // See if we have the target host in the host store
+
+        Set<Host> hosts = hostService.getHostsByIp(targetAddress);
+
+        Host dst = null;
+        Host src = hostService.getHost(HostId.hostId(eth.getSourceMAC(),
+                VlanId.vlanId(eth.getVlanID())));
+
+        for (Host host : hosts) {
+            if (host.vlan().equals(vlan)) {
+                dst = host;
+                break;
+            }
+        }
+
+        if (src != null && dst != null) {
+            // We know the target host so we can respond
+            Ethernet arpReply = buildArpReply(targetAddress, dst.mac(), eth);
+            sendTo(arpReply, inPort);
+            return;
+        }
+
         // If the source address matches one of our external addresses
         // it could be a request from an internal host to an external
-            // address. Forward it over to the correct ports.
+        // address. Forward it over to the correct port.
         Ip4Address source =
                 Ip4Address.valueOf(arp.getSenderProtocolAddress());
         Set<PortAddresses> sourceAddresses = findPortsInSubnet(source);
@@ -184,39 +207,15 @@ public class ProxyArpManager implements ProxyArpService {
         if (matched) {
             return;
         }
-        }
-
-        // Continue with normal proxy ARP case
 
-        Set<Host> hosts = hostService.getHostsByIp(targetAddress);
-
-        Host dst = null;
-        Host src = hostService.getHost(HostId.hostId(eth.getSourceMAC(),
-                VlanId.vlanId(eth.getVlanID())));
-
-        for (Host host : hosts) {
-            if (host.vlan().equals(vlan)) {
-                dst = host;
-                break;
-            }
-        }
-
-        if (src == null || dst == null) {
         //
         // The request couldn't be resolved.
-            // Flood the request on all ports except the incoming ports.
+        // Flood the request on all ports except the incoming port.
         //
         flood(eth, inPort);
         return;
     }
 
-        //
-        // Reply on the port the request was received on
-        //
-        Ethernet arpReply = buildArpReply(targetAddress, dst.mac(), eth);
-        sendTo(arpReply, inPort);
-    }
-
     private void replyNdp(Ethernet eth, ConnectPoint inPort) {
 
         IPv6 ipv6 = (IPv6) eth.getPayload();

@@ -242,8 +242,8 @@ public class ProxyArpManagerTest {
     }
 
     /**
-     * Tests {@link ProxyArpManager#isKnown(Ip4Address)} in the case where the
-     * IP address is not known.
+     * Tests {@link ProxyArpManager#isKnown(org.onlab.packet.IpAddress)} in the
+     * case where the IP address is not known.
      * Verifies the method returns false.
      */
     @Test
@@ -255,8 +255,8 @@ public class ProxyArpManagerTest {
     }
 
     /**
-     * Tests {@link ProxyArpManager#isKnown(Ip4Address)} in the case where the
-     * IP address is known.
+     * Tests {@link ProxyArpManager#isKnown(org.onlab.packet.IpAddress)} in the
+     * case where the IP address is known.
      * Verifies the method returns true.
      */
     @Test
@@ -403,12 +403,14 @@ public class ProxyArpManagerTest {
 
     @Test
     public void testReplyToRequestFromUs() {
-        replay(hostService); // no further host service expectations
-
         Ip4Address ourIp = Ip4Address.valueOf("10.0.1.1");
         MacAddress ourMac = MacAddress.valueOf(1L);
         Ip4Address theirIp = Ip4Address.valueOf("10.0.1.100");
 
+        expect(hostService.getHostsByIp(theirIp)).andReturn(Collections.emptySet());
+        expect(hostService.getHost(HostId.hostId(ourMac, VLAN1))).andReturn(null);
+        replay(hostService);
+
         // This is a request from something inside our network (like a BGP
         // daemon) to an external host.
         Ethernet arpRequest = buildArp(ARP.OP_REQUEST, ourMac, null, ourIp, theirIp);