Refactoring ICMP handler in Segment Routing

- No longer handle ICMPv6 packets except those target routerIP and gatewayIP
- Remove source IP validation for ICMPv6 since IPv6 hosts often speak with their link local address

Change-Id: If92826c080a4643bad71b0d39fc89b7123dc11d5
diff --git a/apps/segmentrouting/src/main/java/org/onosproject/segmentrouting/IcmpHandler.java b/apps/segmentrouting/src/main/java/org/onosproject/segmentrouting/IcmpHandler.java
index a42a806..38293d0 100644
--- a/apps/segmentrouting/src/main/java/org/onosproject/segmentrouting/IcmpHandler.java
+++ b/apps/segmentrouting/src/main/java/org/onosproject/segmentrouting/IcmpHandler.java
@@ -23,7 +23,6 @@
 import org.onlab.packet.Ip4Address;
 import org.onlab.packet.Ip6Address;
 import org.onlab.packet.IpAddress;
-import org.onlab.packet.IpPrefix;
 import org.onlab.packet.MPLS;
 import org.onlab.packet.MacAddress;
 import org.onlab.packet.VlanId;
@@ -117,10 +116,8 @@
 
     /**
      * Process incoming ICMP packet.
-     * If it is an ICMP request to router or known host, then sends an ICMP response.
-     * If it is an ICMP packet to known host and forward the packet to the host.
-     * If it is an ICMP packet to unknown host in a subnet, then sends an ARP request
-     * to the subnet.
+     * If it is an ICMP request to router, then sends an ICMP response.
+     * Otherwise ignore the packet.
      *
      * @param eth inbound ICMP packet
      * @param inPort the input port
@@ -142,24 +139,11 @@
                 (destinationAddress.equals(routerIp.getIp4Address()) ||
                         gatewayIpAddresses.contains(destinationAddress))) {
             sendIcmpResponse(eth, inPort);
-            // We remove the packet from the queue
-            srManager.ipHandler.dequeuePacket(ipv4Packet, destinationAddress);
-
-        // ICMP for any known host
-        } else if (!srManager.hostService.getHostsByIp(destinationAddress).isEmpty()) {
-            // TODO: known host packet should not be coming to controller - resend flows?
-            srManager.ipHandler.forwardPackets(deviceId, destinationAddress);
-
-        // ICMP for an unknown host in the subnet of the router
-        } else if (config.inSameSubnet(deviceId, destinationAddress)) {
-            srManager.arpHandler.sendArpRequest(deviceId, destinationAddress, inPort);
-
-        // ICMP for an unknown host
         } else {
-            log.debug("ICMP request for unknown host {} ", destinationAddress);
-            // We remove the packet from the queue
-            srManager.ipHandler.dequeuePacket(ipv4Packet, destinationAddress);
+            log.trace("Ignore ICMP that targets for {}", destinationAddress);
         }
+        // We remove the packet from the queue
+        srManager.ipHandler.dequeuePacket(ipv4Packet, destinationAddress);
     }
 
     /**
@@ -192,10 +176,8 @@
 
     /**
      * Process incoming ICMPv6 packet.
-     * If it is an ICMP request to router or known host, then sends an ICMP response.
-     * If it is an ICMP packet to known host and forward the packet to the host.
-     * If it is an ICMP packet to unknown host in a subnet, then sends an ARP request
-     * to the subnet.
+     * If it is an ICMPv6 request to router, then sends an ICMPv6 response.
+     * Otherwise ignore the packet.
      *
      * @param eth the incoming ICMPv6 packet
      * @param inPort the input port
@@ -218,20 +200,8 @@
                 (destinationAddress.equals(routerIp.getIp6Address()) ||
                         gatewayIpAddresses.contains(destinationAddress))) {
             sendIcmpv6Response(eth, inPort);
-            // We remove the packet from the queue
-            srManager.ipHandler.dequeuePacket(ipv6Packet, destinationAddress);
-            // ICMP for any known host
-        } else if (!srManager.hostService.getHostsByIp(destinationAddress).isEmpty()) {
-            // TODO: known host packet should not be coming to controller - resend flows?
-            srManager.ipHandler.forwardPackets(deviceId, destinationAddress);
-            // ICMP for an unknown host in the subnet of the router
-        } else if (config.inSameSubnet(deviceId, destinationAddress)) {
-            sendNdpRequest(deviceId, destinationAddress, inPort);
-            // ICMP for an unknown host or not configured host
         } else {
-            log.debug("ICMPv6 request for unknown host or not configured host {} ", destinationAddress);
-            // We remove the packet from the queue
-            srManager.ipHandler.dequeuePacket(ipv6Packet, destinationAddress);
+            log.trace("Ignore ICMPv6 that targets for {}", destinationAddress);
         }
     }
 
@@ -276,9 +246,7 @@
      * @param hostService the host service
      */
     public void processPacketIn(NeighbourMessageContext pkt, HostService hostService) {
-        /*
-         * First we validate the ndp packet
-         */
+        // First we validate the ndp packet
         SegmentRoutingAppConfig appConfig = srManager.cfgService
                 .getConfig(srManager.appId, SegmentRoutingAppConfig.class);
         if (appConfig != null && appConfig.suppressSubnet().contains(pkt.inPort())) {
@@ -286,12 +254,6 @@
             pkt.drop();
             return;
         }
-        if (!validateSrcIp(pkt)) {
-            log.debug("Ignore NDP packet discovered on {} with unexpected src ip address {}.",
-                      pkt.inPort(), pkt.sender());
-            pkt.drop();
-            return;
-        }
 
         if (pkt.type() == NeighbourMessageType.REQUEST) {
             handleNdpRequest(pkt, hostService);
@@ -302,23 +264,6 @@
     }
 
     /**
-     * Utility function to verify if the src ip belongs to the same
-     * subnet configured on the port it is seen.
-     *
-     * @param pkt the ndp packet and context information
-     * @return true if the src ip is a valid address for the subnet configured
-     * for the connect point
-     */
-    private boolean validateSrcIp(NeighbourMessageContext pkt) {
-        ConnectPoint connectPoint = pkt.inPort();
-        IpPrefix subnet = config.getPortIPv6Subnet(
-                connectPoint.deviceId(),
-                connectPoint.port()
-        );
-        return subnet != null && subnet.contains(pkt.sender());
-    }
-
-    /**
      * Helper method to handle the ndp requests.
      *
      * @param pkt the ndp packet request and context information
@@ -422,22 +367,15 @@
     public void sendNdpRequest(DeviceId deviceId, IpAddress targetAddress, ConnectPoint inPort) {
         byte[] senderMacAddress = new byte[MacAddress.MAC_ADDRESS_LENGTH];
         byte[] senderIpAddress = new byte[Ip6Address.BYTE_LENGTH];
-        /*
-         * Retrieves device info.
-         */
+        // Retrieves device info.
         if (!getSenderInfo(senderMacAddress, senderIpAddress, deviceId, targetAddress)) {
             log.warn("Aborting sendNdpRequest, we cannot get all the information needed");
             return;
         }
-        /*
-         * We have to compute the dst mac address and dst
-         * ip address.
-         */
+        // We have to compute the dst mac address and dst ip address.
         byte[] dstIp = IPv6.getSolicitNodeAddress(targetAddress.toOctets());
         byte[] dstMac = IPv6.getMCastMacAddress(dstIp);
-        /*
-         * Creates the request.
-         */
+        // Creates the request.
         Ethernet ndpRequest = NeighborSolicitation.buildNdpSolicit(
                 targetAddress.toOctets(),
                 senderIpAddress,