Initial base code for DHCP L2 Relay, integrated with Sadis

Change-Id: I2a7de8e2cfbff2c7e873ba1c0e473aac46466b90
diff --git a/pom.xml b/pom.xml
new file mode 100755
index 0000000..6ab1da6
--- /dev/null
+++ b/pom.xml
@@ -0,0 +1,148 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!--
+  ~ Copyright 2016-present Open Networking Laboratory
+  ~
+  ~ Licensed under the Apache License, Version 2.0 (the "License");
+  ~ you may not use this file except in compliance with the License.
+  ~ You may obtain a copy of the License at
+  ~
+  ~     http://www.apache.org/licenses/LICENSE-2.0
+  ~
+  ~ Unless required by applicable law or agreed to in writing, software
+  ~ distributed under the License is distributed on an "AS IS" BASIS,
+  ~ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+  ~ See the License for the specific language governing permissions and
+  ~ limitations under the License.
+  -->
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+
+    <parent>
+        <groupId>org.onosproject</groupId>
+        <artifactId>onos-dependencies</artifactId>
+        <version>1.10.0</version>
+        <relativePath></relativePath>
+    </parent>
+
+    <groupId>org.opencord</groupId>
+    <artifactId>dhcpl2relay</artifactId>
+    <version>1.2-SNAPSHOT</version>
+    <packaging>bundle</packaging>
+
+    <description>DHCP L2 Relay Agent</description>
+    <url>http://opencord.org</url>
+
+    <properties>
+        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
+        <onos.app.name>org.opencord.dhcpl2relay</onos.app.name>
+        <onos.app.title>DHCP Relay Agent App</onos.app.title>
+        <onos.app.origin>ON.Lab</onos.app.origin>
+        <onos.app.category>default</onos.app.category>
+        <onos.app.url>http://opencord.org</onos.app.url>
+        <onos.app.readme>DHCP L2 Relay Agent Application.</onos.app.readme>
+        <onos.version>1.10.0</onos.version>
+    </properties>
+
+    <dependencies>
+        <dependency>
+            <groupId>org.onosproject</groupId>
+            <artifactId>onos-api</artifactId>
+            <version>${onos.version}</version>
+        </dependency>
+
+        <dependency>
+            <groupId>org.opencord</groupId>
+            <artifactId>sadis</artifactId>
+            <version>1.0.0</version>
+        </dependency>
+
+        <dependency>
+            <groupId>org.onosproject</groupId>
+            <artifactId>onos-incubator-api</artifactId>
+            <version>${onos.version}</version>
+        </dependency>
+
+        <dependency>
+            <groupId>org.onosproject</groupId>
+            <artifactId>onlab-osgi</artifactId>
+            <version>${onos.version}</version>
+        </dependency>
+
+        <dependency>
+            <groupId>junit</groupId>
+            <artifactId>junit</artifactId>
+            <scope>test</scope>
+        </dependency>
+
+        <dependency>
+            <groupId>org.onosproject</groupId>
+            <artifactId>onlab-junit</artifactId>
+            <version>${onos.version}</version>
+            <scope>test</scope>
+        </dependency>
+
+        <dependency>
+            <groupId>org.onosproject</groupId>
+            <artifactId>onos-api</artifactId>
+            <version>${onos.version}</version>
+            <scope>test</scope>
+            <classifier>tests</classifier>
+        </dependency>
+
+        <dependency>
+            <groupId>org.apache.felix</groupId>
+            <artifactId>org.apache.felix.scr.annotations</artifactId>
+            <scope>provided</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.osgi</groupId>
+            <artifactId>org.osgi.compendium</artifactId>
+        </dependency>
+    </dependencies>
+
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.apache.felix</groupId>
+                <artifactId>maven-bundle-plugin</artifactId>
+            </plugin>
+
+            <plugin>
+                <groupId>org.apache.felix</groupId>
+                <artifactId>maven-scr-plugin</artifactId>
+            </plugin>
+
+            <plugin>
+                <groupId>org.onosproject</groupId>
+                <artifactId>onos-maven-plugin</artifactId>
+            </plugin>
+        </plugins>
+    </build>
+
+    <repositories>
+        <repository>
+            <id>central</id>
+            <name>Central Repository</name>
+            <url>http://repo.maven.apache.org/maven2</url>
+            <layout>default</layout>
+            <snapshots>
+                <enabled>false</enabled>
+            </snapshots>
+            <releases>
+                <enabled>true</enabled>
+                <updatePolicy>always</updatePolicy>
+                <checksumPolicy>fail</checksumPolicy>
+            </releases>
+        </repository>
+
+        <repository>
+            <id>snapshots</id>
+            <url>https://oss.sonatype.org/content/repositories/snapshots</url>
+            <snapshots>
+                <enabled>true</enabled>
+                <updatePolicy>always</updatePolicy>
+                <checksumPolicy>fail</checksumPolicy>
+            </snapshots>
+        </repository>
+    </repositories>
+</project>
diff --git a/src/main/java/org/opencord/dhcpl2relay/DhcpL2Relay.java b/src/main/java/org/opencord/dhcpl2relay/DhcpL2Relay.java
new file mode 100755
index 0000000..a224b6d
--- /dev/null
+++ b/src/main/java/org/opencord/dhcpl2relay/DhcpL2Relay.java
@@ -0,0 +1,532 @@
+/*
+ * Copyright 2017-present Open Networking Laboratory
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.opencord.dhcpl2relay;
+
+import com.google.common.collect.ImmutableSet;
+import org.apache.felix.scr.annotations.Activate;
+import org.apache.felix.scr.annotations.Component;
+import org.apache.felix.scr.annotations.Deactivate;
+import org.apache.felix.scr.annotations.Modified;
+import org.apache.felix.scr.annotations.Property;
+import org.apache.felix.scr.annotations.Reference;
+import org.apache.felix.scr.annotations.ReferenceCardinality;
+import org.onlab.packet.Ethernet;
+import org.onlab.packet.MacAddress;
+import org.onlab.packet.DHCP;
+import org.onlab.packet.DHCPOption;
+import org.onlab.packet.DHCPPacketType;
+import org.onlab.packet.Ip4Address;
+import org.onlab.packet.IPv4;
+import org.onlab.packet.TpPort;
+import org.onlab.packet.UDP;
+import org.onlab.packet.VlanId;
+
+import org.onlab.util.Tools;
+import org.onosproject.cfg.ComponentConfigService;
+import org.onosproject.core.ApplicationId;
+import org.onosproject.core.CoreService;
+import org.onosproject.net.AnnotationKeys;
+import org.onosproject.net.ConnectPoint;
+import org.onosproject.net.Host;
+import org.onosproject.net.Port;
+import org.onosproject.net.config.ConfigFactory;
+import org.onosproject.net.config.NetworkConfigEvent;
+import org.onosproject.net.config.NetworkConfigListener;
+import org.onosproject.net.config.NetworkConfigRegistry;
+import org.onosproject.net.device.DeviceService;
+import org.onosproject.net.flow.DefaultTrafficSelector;
+import org.onosproject.net.flow.DefaultTrafficTreatment;
+import org.onosproject.net.flow.TrafficSelector;
+import org.onosproject.net.flow.TrafficTreatment;
+import org.onosproject.net.host.HostService;
+import org.onosproject.net.packet.DefaultOutboundPacket;
+import org.onosproject.net.packet.OutboundPacket;
+import org.onosproject.net.packet.PacketContext;
+import org.onosproject.net.packet.PacketPriority;
+import org.onosproject.net.packet.PacketProcessor;
+import org.onosproject.net.packet.PacketService;
+
+import org.opencord.sadis.SubscriberAndDeviceInformation;
+import org.opencord.sadis.SubscriberAndDeviceInformationService;
+
+import org.osgi.service.component.ComponentContext;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.nio.ByteBuffer;
+import java.util.Dictionary;
+import java.util.Set;
+import java.util.Optional;
+
+import static org.onlab.packet.DHCP.DHCPOptionCode.OptionCode_MessageType;
+import static org.onlab.packet.MacAddress.valueOf;
+import static org.onosproject.net.config.basics.SubjectFactories.APP_SUBJECT_FACTORY;
+
+/**
+ * DHCP Relay Agent Application Component.
+ */
+@Component(immediate = true)
+public class DhcpL2Relay {
+
+    public static final String DHCP_L2RELAY_APP = "org.opencord.dhcpl2relay";
+    private final Logger log = LoggerFactory.getLogger(getClass());
+    private final InternalConfigListener cfgListener =
+            new InternalConfigListener();
+
+    private final Set<ConfigFactory> factories = ImmutableSet.of(
+            new ConfigFactory<ApplicationId, DhcpL2RelayConfig>(APP_SUBJECT_FACTORY,
+                    DhcpL2RelayConfig.class,
+                    "dhcpl2relay") {
+                @Override
+                public DhcpL2RelayConfig createConfig() {
+                    return new DhcpL2RelayConfig();
+                }
+            }
+    );
+
+    @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
+    protected NetworkConfigRegistry cfgService;
+
+    @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
+    protected CoreService coreService;
+
+    @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
+    protected PacketService packetService;
+
+    @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
+    protected HostService hostService;
+
+    @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
+    protected ComponentConfigService componentConfigService;
+
+    @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
+    protected SubscriberAndDeviceInformationService subsService;
+
+    @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
+    protected DeviceService deviceService;
+
+    @Property(name = "option82", boolValue = true,
+            label = "Add option 82 to relayed packets")
+    protected boolean option82 = true;
+
+    private DhcpRelayPacketProcessor dhcpRelayPacketProcessor =
+            new DhcpRelayPacketProcessor();
+
+
+    private ConnectPoint dhcpServerConnectPoint = null;
+    private MacAddress dhcpConnectMac = MacAddress.BROADCAST;
+    private ApplicationId appId;
+
+    @Activate
+    protected void activate(ComponentContext context) {
+        //start the dhcp relay agent
+        appId = coreService.registerApplication(DHCP_L2RELAY_APP);
+        componentConfigService.registerProperties(getClass());
+
+        cfgService.addListener(cfgListener);
+        factories.forEach(cfgService::registerConfigFactory);
+        //update the dhcp server configuration.
+        updateConfig();
+        //add the packet services.
+        packetService.addProcessor(dhcpRelayPacketProcessor,
+                PacketProcessor.director(0));
+        requestDhcpPackets();
+        modified(context);
+
+        log.info("DHCP-L2-RELAY Started");
+    }
+
+    @Deactivate
+    protected void deactivate() {
+        cfgService.removeListener(cfgListener);
+        factories.forEach(cfgService::unregisterConfigFactory);
+        packetService.removeProcessor(dhcpRelayPacketProcessor);
+        cancelDhcpPackets();
+
+        componentConfigService.unregisterProperties(getClass(), false);
+
+        log.info("DHCP-L2-RELAY Stopped");
+    }
+
+    @Modified
+    protected void modified(ComponentContext context) {
+        Dictionary<?, ?> properties = context.getProperties();
+
+        Boolean o = Tools.isPropertyEnabled(properties, "option82");
+        if (o != null) {
+            option82 = o;
+        }
+    }
+
+    /**
+     * Checks if this app has been configured.
+     *
+     * @return true if all information we need have been initialized
+     */
+    private boolean configured() {
+        return dhcpServerConnectPoint != null;
+    }
+
+    private void updateConfig() {
+        DhcpL2RelayConfig cfg = cfgService.getConfig(appId, DhcpL2RelayConfig.class);
+        if (cfg == null) {
+            log.warn("Dhcp Server info not available");
+            return;
+        }
+
+        dhcpServerConnectPoint = cfg.getDhcpServerConnectPoint();
+        log.info("dhcp server connect point: " + dhcpServerConnectPoint);
+    }
+
+    /**
+     * Request DHCP packet in via PacketService.
+     */
+    private void requestDhcpPackets() {
+        if (dhcpServerConnectPoint != null) {
+            TrafficSelector.Builder selectorServer = DefaultTrafficSelector.builder()
+                    .matchEthType(Ethernet.TYPE_IPV4)
+                    .matchIPProtocol(IPv4.PROTOCOL_UDP)
+                    .matchUdpSrc(TpPort.tpPort(UDP.DHCP_SERVER_PORT));
+            packetService.requestPackets(selectorServer.build(),
+                    PacketPriority.CONTROL, appId,
+                    Optional.of(dhcpServerConnectPoint.deviceId()));
+
+            TrafficSelector.Builder selectorClient = DefaultTrafficSelector.builder()
+                    .matchEthType(Ethernet.TYPE_IPV4)
+                    .matchIPProtocol(IPv4.PROTOCOL_UDP)
+                    .matchUdpSrc(TpPort.tpPort(UDP.DHCP_CLIENT_PORT));
+            packetService.requestPackets(selectorClient.build(),
+                    PacketPriority.CONTROL, appId,
+                    Optional.of(dhcpServerConnectPoint.deviceId()));
+        }
+    }
+
+    /**
+     * Cancel requested DHCP packets in via packet service.
+     */
+    private void cancelDhcpPackets() {
+        if (dhcpServerConnectPoint != null) {
+            TrafficSelector.Builder selectorServer = DefaultTrafficSelector.builder()
+                    .matchEthType(Ethernet.TYPE_IPV4)
+                    .matchIPProtocol(IPv4.PROTOCOL_UDP)
+                    .matchUdpSrc(TpPort.tpPort(UDP.DHCP_SERVER_PORT));
+            packetService.cancelPackets(selectorServer.build(),
+                    PacketPriority.CONTROL, appId,
+                    Optional.of(dhcpServerConnectPoint.deviceId()));
+
+            TrafficSelector.Builder selectorClient = DefaultTrafficSelector.builder()
+                    .matchEthType(Ethernet.TYPE_IPV4)
+                    .matchIPProtocol(IPv4.PROTOCOL_UDP)
+                    .matchUdpSrc(TpPort.tpPort(UDP.DHCP_CLIENT_PORT));
+            packetService.cancelPackets(selectorClient.build(),
+                    PacketPriority.CONTROL, appId,
+                    Optional.of(dhcpServerConnectPoint.deviceId()));
+        }
+    }
+
+    private SubscriberAndDeviceInformation getDevice(PacketContext context) {
+        String serialNo = deviceService.getDevice(context.inPacket().
+                receivedFrom().deviceId()).serialNumber();
+
+        return subsService.get(serialNo);
+    }
+
+    private SubscriberAndDeviceInformation getDevice(ConnectPoint cp) {
+        String serialNo = deviceService.getDevice(cp.deviceId()).
+                serialNumber();
+
+        return subsService.get(serialNo);
+    }
+    private Ip4Address relayAgentIPv4Address(ConnectPoint cp) {
+
+        SubscriberAndDeviceInformation device = getDevice(cp);
+        if (device == null) {
+            log.warn("Device not found for {}", cp);
+            return null;
+        }
+
+        return device.ipAddress();
+    }
+
+    private MacAddress relayAgentMacAddress(PacketContext context) {
+
+        SubscriberAndDeviceInformation device = getDevice(context);
+        if (device == null) {
+            log.warn("Device not found for {}", context.inPacket().
+                    receivedFrom());
+            return null;
+        }
+
+        return device.hardwareIdentifier();
+    }
+
+    private String nasPortId(PacketContext context) {
+        Port p = deviceService.getPort(context.inPacket().receivedFrom());
+
+        return p.annotations().value(AnnotationKeys.PORT_NAME);
+    }
+
+    private SubscriberAndDeviceInformation getSubscriber(PacketContext context) {
+
+        return subsService.get(nasPortId(context));
+    }
+
+    private VlanId cTag(PacketContext context) {
+        SubscriberAndDeviceInformation sub = getSubscriber(context);
+        if (sub == null) {
+            log.warn("Subscriber info not found for {}", context.inPacket().
+                    receivedFrom());
+            return VlanId.NONE;
+        }
+        return sub.cTag();
+    }
+
+    private VlanId sTag(PacketContext context) {
+        SubscriberAndDeviceInformation sub = getSubscriber(context);
+        if (sub == null) {
+            log.warn("Subscriber info not found for {}", context.inPacket().
+                    receivedFrom());
+            return VlanId.NONE;
+        }
+        return sub.sTag();
+    }
+
+    private class DhcpRelayPacketProcessor implements PacketProcessor {
+
+        @Override
+        public void process(PacketContext context) {
+            if (!configured()) {
+                log.warn("Missing DHCP relay config. Abort packet processing");
+                return;
+            }
+
+            // process the packet and get the payload
+            Ethernet packet = context.inPacket().parsed();
+            if (packet == null) {
+                log.warn("Packet is null");
+                return;
+            }
+
+            //log.info("Got a packet of type {}", packet.getEtherType());
+
+            if (packet.getEtherType() == Ethernet.TYPE_IPV4) {
+                IPv4 ipv4Packet = (IPv4) packet.getPayload();
+
+                if (ipv4Packet.getProtocol() == IPv4.PROTOCOL_UDP) {
+                    UDP udpPacket = (UDP) ipv4Packet.getPayload();
+                    if (udpPacket.getSourcePort() == UDP.DHCP_CLIENT_PORT ||
+                        udpPacket.getSourcePort() == UDP.DHCP_SERVER_PORT) {
+                        DHCP dhcpPayload = (DHCP) udpPacket.getPayload();
+                        //This packet is dhcp.
+                        processDhcpPacket(context, packet, dhcpPayload);
+                    }
+                }
+            }
+        }
+
+        //forward the packet to ConnectPoint where the DHCP server is attached.
+        private void forwardPacket(Ethernet packet) {
+
+            if (dhcpServerConnectPoint != null) {
+                TrafficTreatment t = DefaultTrafficTreatment.builder()
+                        .setOutput(dhcpServerConnectPoint.port()).build();
+                OutboundPacket o = new DefaultOutboundPacket(
+                        dhcpServerConnectPoint.deviceId(), t,
+                        ByteBuffer.wrap(packet.serialize()));
+                if (log.isTraceEnabled()) {
+                    log.trace("Relaying packet to dhcp server {} at {}",
+                            packet, dhcpServerConnectPoint);
+                }
+                packetService.emit(o);
+            } else {
+                log.warn("No dhcp server connect point");
+            }
+        }
+
+        //process the dhcp packet before sending to server
+        private void processDhcpPacket(PacketContext context, Ethernet packet,
+                                       DHCP dhcpPayload) {
+            if (dhcpPayload == null) {
+                log.warn("DHCP payload is null");
+                return;
+            }
+
+            DHCPPacketType incomingPacketType = null;
+            for (DHCPOption option : dhcpPayload.getOptions()) {
+                if (option.getCode() == OptionCode_MessageType.getValue()) {
+                    byte[] data = option.getData();
+                    incomingPacketType = DHCPPacketType.getType(data[0]);
+                }
+            }
+            log.info("Received DHCP Packet of type {}", incomingPacketType);
+            log.trace("Processing Packet {}", packet);
+
+            switch (incomingPacketType) {
+            case DHCPDISCOVER:
+                Ethernet ethernetPacketDiscover =
+                    processDhcpPacketFromClient(context, packet);
+                if (ethernetPacketDiscover != null) {
+                    forwardPacket(ethernetPacketDiscover);
+                }
+                break;
+            case DHCPOFFER:
+                //reply to dhcp client.
+                Ethernet ethernetPacketOffer = processDhcpPacketFromServer(packet);
+                if (ethernetPacketOffer != null) {
+                    sendReply(ethernetPacketOffer, dhcpPayload);
+                }
+                break;
+            case DHCPREQUEST:
+                Ethernet ethernetPacketRequest =
+                    processDhcpPacketFromClient(context, packet);
+                if (ethernetPacketRequest != null) {
+                    forwardPacket(ethernetPacketRequest);
+                }
+                break;
+            case DHCPACK:
+                //reply to dhcp client.
+                Ethernet ethernetPacketAck = processDhcpPacketFromServer(packet);
+                if (ethernetPacketAck != null) {
+                    sendReply(ethernetPacketAck, dhcpPayload);
+                }
+                break;
+            default:
+                break;
+            }
+        }
+
+        private Ethernet processDhcpPacketFromClient(PacketContext context,
+                                                     Ethernet ethernetPacket) {
+            log.info("Processing packet from client");
+
+            MacAddress relayAgentMac = relayAgentMacAddress(context);
+            if (relayAgentMac == null) {
+                log.warn("RelayAgent MAC not found ");
+
+                return null;
+            }
+
+            Ethernet etherReply = ethernetPacket;
+
+            IPv4 ipv4Packet = (IPv4) etherReply.getPayload();
+            UDP udpPacket = (UDP) ipv4Packet.getPayload();
+            DHCP dhcpPacket = (DHCP) udpPacket.getPayload();
+
+            etherReply.setSourceMACAddress(relayAgentMac);
+            etherReply.setDestinationMACAddress(dhcpConnectMac);
+
+            etherReply.setVlanID(cTag(context).toShort());
+            etherReply.setQinQTPID(Ethernet.TYPE_VLAN);
+            etherReply.setQinQVID(sTag(context).toShort());
+
+            log.info("Finished processing");
+            return etherReply;
+        }
+
+        //build the DHCP offer/ack with proper client port.
+        private Ethernet processDhcpPacketFromServer(Ethernet ethernetPacket) {
+            log.warn("Processing DHCP packet from server");
+            // get dhcp header.
+            Ethernet etherReply = (Ethernet) ethernetPacket.clone();
+            IPv4 ipv4Packet = (IPv4) etherReply.getPayload();
+            UDP udpPacket = (UDP) ipv4Packet.getPayload();
+            DHCP dhcpPayload = (DHCP) udpPacket.getPayload();
+
+
+            MacAddress dstMac = valueOf(dhcpPayload.getClientHardwareAddress());
+            Set<Host> hosts = hostService.getHostsByMac(dstMac);
+            if (hosts == null || hosts.isEmpty()) {
+                log.warn("Cannot determine host for DHCP client: {}. Aborting "
+                        + "relay for dhcp packet from server {}",
+                         dstMac, ethernetPacket);
+                return null;
+            } else if (hosts.size() > 1) {
+                // XXX  redo to send reply to all hosts found
+                log.warn("Multiple hosts found for mac:{}. Picking one "
+                        + "host out of {}", dstMac, hosts);
+            }
+            Host host = hosts.iterator().next();
+
+            etherReply.setDestinationMACAddress(dstMac);
+            etherReply.setQinQVID(Ethernet.VLAN_UNTAGGED);
+            etherReply.setPriorityCode(ethernetPacket.getPriorityCode());
+            etherReply.setVlanID((short) 0);
+
+            // we leave the srcMac from the original packet
+
+            // figure out the relay agent IP corresponding to the original request
+            Ip4Address relayAgentIP = relayAgentIPv4Address(
+                    new ConnectPoint(host.location().deviceId(),
+                            host.location().port()));
+            if (relayAgentIP == null) {
+                log.warn("Cannot determine relay agent Ipv4 addr for host {}. "
+                        + "Aborting relay for dhcp packet from server {}",
+                        host, ethernetPacket);
+                return null;
+            }
+
+            ipv4Packet.setSourceAddress(relayAgentIP.toInt());
+            ipv4Packet.setDestinationAddress(dhcpPayload.getYourIPAddress());
+
+            udpPacket.setDestinationPort(UDP.DHCP_CLIENT_PORT);
+            udpPacket.setPayload(dhcpPayload);
+            ipv4Packet.setPayload(udpPacket);
+            etherReply.setPayload(ipv4Packet);
+
+            log.info("Finished processing packet");
+            return etherReply;
+        }
+
+        //send the response to the requester host.
+        private void sendReply(Ethernet ethPacket, DHCP dhcpPayload) {
+            MacAddress descMac = valueOf(dhcpPayload.getClientHardwareAddress());
+            Host host = hostService.getHostsByMac(descMac).stream().findFirst().orElse(null);
+
+            // Send packet out to requester if the host information is available
+            if (host != null) {
+                log.info("Sending DHCP packet to host: {}", host);
+                TrafficTreatment t = DefaultTrafficTreatment.builder()
+                        .setOutput(host.location().port()).build();
+                OutboundPacket o = new DefaultOutboundPacket(
+                        host.location().deviceId(), t, ByteBuffer.wrap(ethPacket.serialize()));
+                if (log.isTraceEnabled()) {
+                    log.trace("Relaying packet to dhcp client {}", ethPacket);
+                }
+                packetService.emit(o);
+                log.error("DHCP Packet sent to {}", host.location());
+            } else {
+                log.info("Dropping DHCP packet because can't find host for {}", descMac);
+            }
+        }
+    }
+
+    /**
+     * Listener for network config events.
+     */
+    private class InternalConfigListener implements NetworkConfigListener {
+
+        @Override
+        public void event(NetworkConfigEvent event) {
+
+            if ((event.type() == NetworkConfigEvent.Type.CONFIG_ADDED ||
+                    event.type() == NetworkConfigEvent.Type.CONFIG_UPDATED) &&
+                    event.configClass().equals(DhcpL2RelayConfig.class)) {
+                updateConfig();
+                log.info("Reconfigured");
+            }
+        }
+    }
+}
diff --git a/src/main/java/org/opencord/dhcpl2relay/DhcpL2RelayConfig.java b/src/main/java/org/opencord/dhcpl2relay/DhcpL2RelayConfig.java
new file mode 100755
index 0000000..4816285
--- /dev/null
+++ b/src/main/java/org/opencord/dhcpl2relay/DhcpL2RelayConfig.java
@@ -0,0 +1,46 @@
+/*
+ * Copyright 2017-present Open Networking Laboratory
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.opencord.dhcpl2relay;
+
+import org.onosproject.core.ApplicationId;
+import org.onosproject.net.ConnectPoint;
+import org.onosproject.net.config.Config;
+
+import static org.onosproject.net.config.Config.FieldPresence.MANDATORY;
+
+/**
+ * DHCP Relay Config class.
+ */
+public class DhcpL2RelayConfig extends Config<ApplicationId> {
+
+    private static final String DHCP_CONNECT_POINT = "dhcpserverConnectPoint";
+
+    @Override
+    public boolean isValid() {
+
+        return hasOnlyFields(DHCP_CONNECT_POINT) &&
+                isConnectPoint(DHCP_CONNECT_POINT, MANDATORY);
+    }
+
+    /**
+     * Returns the dhcp server connect point.
+     *
+     * @return dhcp server connect point
+     */
+    public ConnectPoint getDhcpServerConnectPoint() {
+        return ConnectPoint.deviceConnectPoint(object.path(DHCP_CONNECT_POINT).asText());
+    }
+}
diff --git a/src/main/java/org/opencord/dhcpl2relay/package-info.java b/src/main/java/org/opencord/dhcpl2relay/package-info.java
new file mode 100755
index 0000000..9774697
--- /dev/null
+++ b/src/main/java/org/opencord/dhcpl2relay/package-info.java
@@ -0,0 +1,20 @@
+/*
+ * Copyright 2017-present Open Networking Laboratory
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+/**
+ *  DHCP-L2RELAY application.
+ */
+package org.opencord.dhcpl2relay;
diff --git a/src/test/resources/dhcp-l2relay.json b/src/test/resources/dhcp-l2relay.json
new file mode 100755
index 0000000..2aae8bf
--- /dev/null
+++ b/src/test/resources/dhcp-l2relay.json
@@ -0,0 +1,9 @@
+{
+  "apps": {
+    "org.opencord.dhcpl2relay" : {
+      "dhcpl2relay" : {
+        "dhcpserverConnectPoint": "of:0000000000000002/2"
+      }
+    }
+  }
+}