/*
 * Copyright 2017-present Open Networking Foundation
 *
 * 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.onosproject.dhcprelay;

import org.apache.felix.scr.annotations.Activate;
import org.apache.felix.scr.annotations.Deactivate;
import com.google.common.base.MoreObjects;
import com.google.common.collect.Sets;
import com.google.common.collect.ImmutableSet;
import org.apache.felix.scr.annotations.Component;
import org.apache.felix.scr.annotations.Property;
import org.apache.felix.scr.annotations.Reference;
import org.apache.felix.scr.annotations.ReferenceCardinality;
import org.apache.felix.scr.annotations.Service;
import org.onlab.packet.BasePacket;
import org.onlab.packet.DHCP6;
import org.onlab.packet.IPv6;
import org.onlab.packet.Ethernet;
import org.onlab.packet.Ip6Address;
import org.onlab.packet.IpAddress;
import org.onlab.packet.IpPrefix;
import org.onlab.packet.MacAddress;
import org.onlab.packet.UDP;
import org.onlab.packet.VlanId;
import org.onlab.packet.dhcp.Dhcp6RelayOption;
import org.onlab.packet.dhcp.Dhcp6InterfaceIdOption;
import org.onlab.packet.dhcp.Dhcp6Option;
import org.onlab.packet.dhcp.Dhcp6IaNaOption;
import org.onlab.packet.dhcp.Dhcp6IaTaOption;
import org.onlab.packet.dhcp.Dhcp6IaPdOption;
import org.onlab.packet.dhcp.Dhcp6IaAddressOption;
import org.onlab.packet.dhcp.Dhcp6IaPrefixOption;
import org.onlab.util.HexString;
import org.onosproject.dhcprelay.api.DhcpHandler;
import org.onosproject.dhcprelay.store.DhcpRelayStore;
import org.onosproject.net.host.HostStore;
import org.onosproject.net.host.HostService;
import org.onosproject.net.host.DefaultHostDescription;
import org.onosproject.net.host.HostDescription;
import org.onosproject.net.host.InterfaceIpAddress;
import org.onosproject.net.host.HostListener;
import org.onosproject.net.host.HostEvent;
import org.onosproject.net.intf.Interface;
import org.onosproject.net.intf.InterfaceService;
import org.onosproject.routeservice.Route;
import org.onosproject.routeservice.RouteStore;
import org.onosproject.dhcprelay.config.DhcpServerConfig;
import org.onosproject.net.ConnectPoint;
import org.onosproject.net.Host;
import org.onosproject.net.HostId;
import org.onosproject.net.HostLocation;
import org.onosproject.net.packet.DefaultOutboundPacket;
import org.onosproject.net.packet.OutboundPacket;
import org.onosproject.net.packet.PacketContext;
import org.onosproject.net.packet.PacketService;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.onosproject.net.flow.DefaultTrafficTreatment;
import org.onosproject.net.flow.TrafficTreatment;


import java.nio.ByteBuffer;
import java.util.List;
import java.util.Collection;
import java.util.Optional;
import java.util.Set;
import java.util.ArrayList;


import static com.google.common.base.Preconditions.checkNotNull;
import static com.google.common.base.Preconditions.checkState;

@Component
@Service
@Property(name = "version", value = "6")
public class Dhcp6HandlerImpl implements DhcpHandler {
    private static Logger log = LoggerFactory.getLogger(Dhcp6HandlerImpl.class);

    @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
    protected DhcpRelayStore dhcpRelayStore;

    @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
    protected PacketService packetService;

    @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
    protected HostStore hostStore;

    @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
    protected RouteStore routeStore;

    @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
    protected InterfaceService interfaceService;

    @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
    protected HostService hostService;

    private InternalHostListener hostListener = new InternalHostListener();

    private Ip6Address dhcpServerIp = null;
    // dhcp server may be connected directly to the SDN network or
    // via an external gateway. When connected directly, the dhcpConnectPoint, dhcpConnectMac,
    // and dhcpConnectVlan refer to the server. When connected via the gateway, they refer
    // to the gateway.
    private ConnectPoint dhcpServerConnectPoint = null;
    private MacAddress dhcpConnectMac = null;
    private VlanId dhcpConnectVlan = null;
    private Ip6Address dhcpGatewayIp = null;
    private Ip6Address relayAgentIpFromCfg = null;

    private Ip6Address indirectDhcpServerIp = null;
    private ConnectPoint indirectDhcpServerConnectPoint = null;
    private MacAddress indirectDhcpConnectMac = null;
    private VlanId indirectDhcpConnectVlan = null;
    private Ip6Address indirectDhcpGatewayIp = null;
    private Ip6Address indirectRelayAgentIpFromCfg = null;


    // CLIENT message types
    public static final Set<Byte> MSG_TYPE_FROM_CLIENT =
            ImmutableSet.of(DHCP6.MsgType.SOLICIT.value(),
                            DHCP6.MsgType.REQUEST.value(),
                            DHCP6.MsgType.REBIND.value(),
                            DHCP6.MsgType.RENEW.value(),
                            DHCP6.MsgType.RELEASE.value(),
                            DHCP6.MsgType.DECLINE.value(),
                            DHCP6.MsgType.CONFIRM.value(),
                            DHCP6.MsgType.RELAY_FORW.value());
    // SERVER message types
    public static final Set<Byte> MSG_TYPE_FROM_SERVER =
            ImmutableSet.of(DHCP6.MsgType.RELAY_REPL.value());

    @Activate
    protected void activate() {
        hostService.addListener(hostListener);
    }

    @Deactivate
    protected void deactivate() {
        hostService.removeListener(hostListener);
        this.dhcpConnectMac = null;
        this.dhcpConnectVlan = null;

        if (dhcpGatewayIp != null) {
            hostService.stopMonitoringIp(dhcpGatewayIp);
        } else if (dhcpServerIp != null) {
            hostService.stopMonitoringIp(dhcpServerIp);
        }
    }


    @Override
    public void setDhcpServerIp(IpAddress dhcpServerIp) {
        checkNotNull(dhcpServerIp, "DHCP server IP can't be null");
        checkState(dhcpServerIp.isIp6(), "Invalid server IP for DHCPv6 relay handler");
        this.dhcpServerIp = dhcpServerIp.getIp6Address();
    }

    @Override
    public void setDhcpServerConnectPoint(ConnectPoint dhcpServerConnectPoint) {
        checkNotNull(dhcpServerConnectPoint, "Server connect point can't null");
        this.dhcpServerConnectPoint = dhcpServerConnectPoint;
    }

    @Override
    public void setDhcpConnectMac(MacAddress dhcpConnectMac) {
        this.dhcpConnectMac = dhcpConnectMac;
    }

    @Override
    public void setDhcpConnectVlan(VlanId dhcpConnectVlan) {
        this.dhcpConnectVlan = dhcpConnectVlan;
    }

    @Override
    public void setDhcpGatewayIp(IpAddress dhcpGatewayIp) {
        if (dhcpGatewayIp != null) {
            checkState(dhcpGatewayIp.isIp6(), "Invalid gateway IP for DHCPv6 relay handler");
            this.dhcpGatewayIp = dhcpGatewayIp.getIp6Address();
        } else {
            // removes gateway config
            this.dhcpGatewayIp = null;
        }
    }
    @Override
    public Optional<IpAddress> getDhcpServerIp() {
        return Optional.ofNullable(dhcpServerIp);
    }

    @Override
    public Optional<IpAddress> getDhcpGatewayIp() {
        return Optional.ofNullable(dhcpGatewayIp);
    }

    @Override
    public Optional<MacAddress> getDhcpConnectMac() {
        return Optional.ofNullable(dhcpConnectMac);
    }

    // Indirect DHCP server

    public void setIndirectDhcpServerIp(IpAddress dhcpServerIp) {
        checkNotNull(dhcpServerIp, "DHCP indirect server IP can't be null");
        checkState(dhcpServerIp.isIp6(), "Invalid indirect server IP for DHCPv6 relay handler");
        this.indirectDhcpServerIp = dhcpServerIp.getIp6Address();
    }


    public void setIndirectDhcpServerConnectPoint(ConnectPoint dhcpServerConnectPoint) {
        checkNotNull(dhcpServerConnectPoint, "Indirect Server connect point can't null");
        this.indirectDhcpServerConnectPoint = dhcpServerConnectPoint;
    }


    public void setIndirectDhcpConnectMac(MacAddress dhcpConnectMac) {
        this.indirectDhcpConnectMac = dhcpConnectMac;
    }


    public void setIndirectDhcpConnectVlan(VlanId dhcpConnectVlan) {
        this.indirectDhcpConnectVlan = dhcpConnectVlan;
    }


    public void setIndirectDhcpGatewayIp(IpAddress dhcpGatewayIp) {
        if (dhcpGatewayIp != null) {
            checkState(dhcpGatewayIp.isIp6(), "Invalid indirect gateway IP for DHCPv6 relay handler");
            this.indirectDhcpGatewayIp = dhcpGatewayIp.getIp6Address();
        } else {
            // removes gateway config
            this.indirectDhcpGatewayIp = null;
        }
    }

    public Optional<IpAddress> getIndirectDhcpServerIp() {
        return Optional.ofNullable(indirectDhcpServerIp);
    }


    public Optional<IpAddress> getIndirectDhcpGatewayIp() {
        return Optional.ofNullable(indirectDhcpGatewayIp);
    }


    public Optional<MacAddress> getIndirectDhcpConnectMac() {
        return Optional.ofNullable(indirectDhcpConnectMac);
    }


    @Override
    public void processDhcpPacket(PacketContext context, BasePacket payload) {
        checkNotNull(payload, "DHCP6 payload can't be null");
        checkState(payload instanceof DHCP6, "Payload is not a DHCP6");
        DHCP6 dhcp6Payload = (DHCP6) payload;
        Ethernet receivedPacket = context.inPacket().parsed();

        if (!configured()) {
            log.warn("Missing DHCP6 relay server config. Abort packet processing");
            log.warn("dhcp6 payload {}", dhcp6Payload);

            return;
        }

        byte msgType = dhcp6Payload.getMsgType();
        log.warn("msgType is {}", msgType);

        ConnectPoint inPort = context.inPacket().receivedFrom();
        if (inPort == null) {
            log.warn("incommin ConnectPoint is null");
        }
        Set<Interface> receivingInterfaces = interfaceService.getInterfacesByPort(inPort);
        //ignore the packets if dhcp client interface is not configured on onos.
        if (receivingInterfaces.isEmpty()) {
            log.warn("Virtual interface is not configured on {}", inPort);
            return;
        }


        if (MSG_TYPE_FROM_CLIENT.contains(msgType)) {

            InternalPacket ethernetClientPacket =
                    processDhcp6PacketFromClient(context, receivedPacket, receivingInterfaces);
            if (ethernetClientPacket != null) {
                forwardPacket(ethernetClientPacket);
            }

        } else if (MSG_TYPE_FROM_SERVER.contains(msgType)) {
            log.warn("calling processDhcp6PacketFromServer with RELAY_REPL", msgType);
            InternalPacket ethernetPacketReply =
                    processDhcp6PacketFromServer(context, receivedPacket, receivingInterfaces);
            if (ethernetPacketReply != null) {
                forwardPacket(ethernetPacketReply);
            }
        } else {
            log.warn("Not so fast, packet type {} not supported yet", msgType);
        }
    }


    /**
     * Checks if this app has been configured.
     *
     * @return true if all information we need have been initialized
     */
    public boolean configured() {
        log.warn("dhcpServerConnectPoint {} dhcpServerIp {}",
                this.dhcpServerConnectPoint, this.dhcpServerIp);
        return this.dhcpServerConnectPoint != null && this.dhcpServerIp != null;
    }

    // the new class the contains Ethernet packet and destination port, kind of like adding
    // internal header to the packet
    private class InternalPacket {
        Ethernet packet;
        ConnectPoint destLocation;
        public InternalPacket(Ethernet newPacket, ConnectPoint newLocation) {
            packet = newPacket;
            destLocation = newLocation;
        }
        void setLocation(ConnectPoint newLocation) {
            destLocation = newLocation;
        }
    }

    //forward the packet to ConnectPoint where the DHCP server is attached.
    private void forwardPacket(InternalPacket packet) {
        //send Packetout to dhcp server connectpoint.
        if (packet.destLocation != null) {
            TrafficTreatment t = DefaultTrafficTreatment.builder()
                    .setOutput(packet.destLocation.port()).build();
            OutboundPacket o = new DefaultOutboundPacket(
                    packet.destLocation.deviceId(), t, ByteBuffer.wrap(packet.packet.serialize()));
            if (log.isTraceEnabled()) {
                log.trace("Relaying packet to destination {}", packet.destLocation);
            }
            packetService.emit(o);
        } // if
    }

    /**
     * Check if the host is directly connected to the network or not.
     *
     * @param dhcp6Payload the dhcp6 payload
     * @return true if the host is directly connected to the network; false otherwise
     */
    private boolean directlyConnected(DHCP6 dhcp6Payload) {
        log.debug("directlyConnected enters");

        if (dhcp6Payload.getMsgType() != DHCP6.MsgType.RELAY_FORW.value() &&
                dhcp6Payload.getMsgType() != DHCP6.MsgType.RELAY_REPL.value()) {
            log.debug("directlyConnected true. MsgType {}", dhcp6Payload.getMsgType());

            return true;
        }

        // Regardless of relay-forward or relay-replay, check if we see another relay message
        DHCP6 dhcp6Payload2 = dhcp6PacketFromRelayPacket(dhcp6Payload);
        if (dhcp6Payload2 != null) {
            if (dhcp6Payload.getMsgType() == DHCP6.MsgType.RELAY_FORW.value()) {
                log.debug("directlyConnected  false. 1st realy-foward, 2nd MsgType {}", dhcp6Payload2.getMsgType());
                return false;
            } else {
                // relay-reply
                if (dhcp6Payload2.getMsgType() != DHCP6.MsgType.RELAY_REPL.value()) {
                    log.debug("directlyConnected  true. 2nd MsgType {}", dhcp6Payload2.getMsgType());
                    return true;  // must be directly connected
                } else {
                    log.debug("directlyConnected  false. 1st relay-reply, 2nd relay-reply MsgType {}",
                               dhcp6Payload2.getMsgType());
                    return false;  // must be indirectly connected
                }
            }
        } else {
            log.warn("directlyConnected  true.");
            return true;
        }
    }

    /**
     * extract DHCP6 payload from dhcp6 relay message within relay-forwrd/reply.
     *
     * @param dhcp6 dhcp6 relay-reply or relay-foward
     * @return dhcp6Packet dhcp6 packet extracted from relay-message
     */
    private DHCP6 dhcp6PacketFromRelayPacket(DHCP6 dhcp6) {
        log.debug("dhcp6PacketFromRelayPacket  enters. dhcp6 {}", dhcp6);

        // extract the relay message if exist
        DHCP6 dhcp6Payload = dhcp6.getOptions().stream()
                    .filter(opt -> opt instanceof Dhcp6RelayOption)
                    .map(BasePacket::getPayload)
                    .map(pld -> (DHCP6) pld)
                    .findFirst()
                    .orElse(null);


        if (dhcp6Payload == null) {
            // Can't find dhcp payload
            log.debug("Can't find dhcp6 payload from relay message");
        } else {
            log.debug("dhcp6 payload found from relay message {}", dhcp6Payload);
        }

        return dhcp6Payload;
    }

    /**
     * find the leaf DHCP6 packet from multi-level relay packet.
     *
     * @param relayPacket dhcp6 relay packet
     * @return leafPacket non-relay dhcp6 packet
     */
    private DHCP6 getDhcp6Leaf(DHCP6 relayPacket) {
        DHCP6 dhcp6Parent = relayPacket;
        DHCP6 dhcp6Child = null;

        log.debug("getDhcp6Leaf entered.");
        while (dhcp6Parent != null) {
            dhcp6Child = dhcp6PacketFromRelayPacket(dhcp6Parent);

            if (dhcp6Child != null) {
                if (dhcp6Child.getMsgType() != DHCP6.MsgType.RELAY_FORW.value() &&
                        dhcp6Child.getMsgType() != DHCP6.MsgType.RELAY_REPL.value()) {
                    log.debug("leaf dhcp6 packet found.");
                    break;
                } else {
                    // found another relay
                    // go for another loop
                    dhcp6Parent = dhcp6Child;
                }
            } else {
                log.warn("malformed pkt! Expected dhcp6 within relay pkt, but no dhcp6 leaf found.");
                break;
            }
        }
        return dhcp6Child;
    }

    /**
     * check if DHCP6 relay-reply is reply.
     *
     * @param relayPacket dhcp6 relay-reply
     * @return boolean relay-reply contains ack
     */
    private boolean isDhcp6Reply(DHCP6 relayPacket) {
        log.debug("isDhcp6Reply  entered.");

        DHCP6 leafDhcp6 = getDhcp6Leaf(relayPacket);

        if (leafDhcp6 != null) {
            if (leafDhcp6.getMsgType() == DHCP6.MsgType.REPLY.value()) {
                log.debug("isDhcp6Reply  true.");
                return true;  // must be directly connected
            } else {
                log.debug("isDhcp6Reply false. leaf dhcp6 is not replay. MsgType {}", leafDhcp6.getMsgType());
            }
        } else {
            log.debug("isDhcp6Reply false. Expected dhcp6 within relay pkt but not found.");
        }
        log.debug("isDhcp6Reply  false.");
        return false;
    }

    /**
     * check if DHCP6 is release or relay-forward contains release.
     *
     * @param dhcp6Payload dhcp6 packet
     * @return boolean dhcp6 contains release
     */
    private boolean isDhcp6Release(DHCP6 dhcp6Payload) {

        log.debug("isDhcp6Release  entered.");

        if (dhcp6Payload.getMsgType() ==  DHCP6.MsgType.RELEASE.value()) {
            log.debug("isDhcp6Release  true.");
            return true;  // must be directly connected
        } else {
            DHCP6 dhcp6Leaf = getDhcp6Leaf(dhcp6Payload);
            if (dhcp6Leaf != null) {
                if (dhcp6Leaf.getMsgType() ==  DHCP6.MsgType.RELEASE.value()) {
                    log.debug("isDhcp6Release  true. indirectlry connected");
                    return true;
                } else {
                    log.debug("leaf dhcp6 is not release. MsgType {}",  dhcp6Leaf.getMsgType());
                    return false;
                }
            } else {
                log.debug("isDhcp6Release  false. dhcp6 is niether relay nor release.");
                return false;
            }
        }
    }

    /**
     * extract from dhcp6 packet client ipv6 address of given by dhcp server.
     *
     * @param dhcp6 the dhcp6 packet
     * @return Ip6Address  Ip6Address given by dhcp server, or null if not exists
     */
    private Ip6Address extractIpAddress(DHCP6 dhcp6) {
        Ip6Address ip = null;

        log.debug("extractIpAddress  enters dhcp6 {}.", dhcp6);
        // Extract IPv6 address from IA NA ot IA TA option
        Optional<Dhcp6IaNaOption> iaNaOption = dhcp6.getOptions()
                .stream()
                .filter(opt -> opt instanceof Dhcp6IaNaOption)
                .map(opt -> (Dhcp6IaNaOption) opt)
                .findFirst();
        Optional<Dhcp6IaTaOption> iaTaOption = dhcp6.getOptions()
                .stream()
                .filter(opt -> opt instanceof Dhcp6IaTaOption)
                .map(opt -> (Dhcp6IaTaOption) opt)
                .findFirst();
        Optional<Dhcp6IaAddressOption> iaAddressOption;
        if (iaNaOption.isPresent()) {
            log.debug("Found IPv6 address from iaNaOption {}", iaNaOption);

            iaAddressOption = iaNaOption.get().getOptions().stream()
                    .filter(opt -> opt instanceof Dhcp6IaAddressOption)
                    .map(opt -> (Dhcp6IaAddressOption) opt)
                    .findFirst();
        } else if (iaTaOption.isPresent()) {
            log.debug("Found IPv6 address from iaTaOption {}", iaTaOption);

            iaAddressOption = iaTaOption.get().getOptions().stream()
                    .filter(opt -> opt instanceof Dhcp6IaAddressOption)
                    .map(opt -> (Dhcp6IaAddressOption) opt)
                    .findFirst();
        } else {
            iaAddressOption = Optional.empty();
        }
        if (iaAddressOption.isPresent()) {
            ip = iaAddressOption.get().getIp6Address();
            log.debug("Found IPv6 address from iaAddressOption {}", iaAddressOption);


        } else {
            log.debug("Can't find IPv6 address from DHCPv6 {}", dhcp6);
        }

        return ip;
    }
    /**
     * extract from dhcp6 packet Prefix prefix provided by dhcp server.
     *
     * @param dhcp6 the dhcp6 payload
     * @return IpPrefix Prefix Delegation prefix, or null if not exists.
     */
    private IpPrefix extractPrefix(DHCP6 dhcp6) {
        log.warn("extractPrefix  enters {}", dhcp6);

        // extract prefix
        IpPrefix  prefixPrefix = null;

        Ip6Address prefixAddress = null;

        // Extract IPv6 prefix from IA PD option
        Optional<Dhcp6IaPdOption> iaPdOption = dhcp6.getOptions()
                .stream()
                .filter(opt -> opt instanceof Dhcp6IaPdOption)
                .map(opt -> (Dhcp6IaPdOption) opt)
                .findFirst();

        Optional<Dhcp6IaPrefixOption> iaPrefixOption;
        if (iaPdOption.isPresent()) {
            log.warn("IA_PD option found {}", iaPdOption);

            iaPrefixOption = iaPdOption.get().getOptions().stream()
                    .filter(opt -> opt instanceof Dhcp6IaPrefixOption)
                    .map(opt -> (Dhcp6IaPrefixOption) opt)
                    .findFirst();
        } else {
            log.warn("IA_PD option NOT found");

            iaPrefixOption = Optional.empty();
        }
        if (iaPrefixOption.isPresent()) {
            log.warn("IAPrefix Option within IA_PD option found {}", iaPrefixOption);

            prefixAddress = iaPrefixOption.get().getIp6Prefix();
            int prefixLen = (int) iaPrefixOption.get().getPrefixLength();
            log.warn("Prefix length is  {} bits", prefixLen);
            prefixPrefix = IpPrefix.valueOf(prefixAddress, prefixLen);

        } else {
            log.warn("Can't find IPv6 prefix from DHCPv6 {}", dhcp6);
        }

        return prefixPrefix;
    }

    /**
     * remove host or route.
     *
     * @param directConnFlag  flag to show that packet is from directly connected client
     * @param dhcp6Packet the dhcp6 payload
     * @param clientPacket client's ethernet packet
     * @param clientIpv6 client's Ipv6 packet
     * @param clientInterfaces set of client interfaces
     */
    private void removeHostOrRoute(boolean directConnFlag, DHCP6 dhcp6Packet,
                                   Ethernet clientPacket, IPv6 clientIpv6,
                                   Set<Interface> clientInterfaces) {
        log.debug("extractPrefix  enters {}", dhcp6Packet);
        // add host or route
        if (isDhcp6Release(dhcp6Packet)) {
            IpAddress ip = null;
            if (directConnFlag) {
                // Add to host store if it is connected to network directly
                ip = extractIpAddress(dhcp6Packet);
                if (ip != null) {
                    VlanId vlanId = clientInterfaces.iterator().next().vlan();
                    MacAddress clientMac = clientPacket.getSourceMAC();
                    HostId hostId = HostId.hostId(clientMac, vlanId);
                    log.debug("remove Host {} ip for directly connected.", hostId.toString());

                    log.debug("client mac {} client vlan {}", HexString.toHexString(clientMac.toBytes(), ":"), vlanId);


                    // Remove host's ip of  when dhcp release msg is received
                    hostStore.removeIp(hostId, ip);
                } else {
                    log.debug("ipAddress not found. Do not add Host for directly connected.");
                }
            } else {
                // Remove from route store if it is not connected to network directly
                IpAddress nextHopIp = IpAddress.valueOf(IpAddress.Version.INET6, clientIpv6.getSourceAddress());

                DHCP6 leafDhcp = getDhcp6Leaf(dhcp6Packet);
                ip = extractIpAddress(leafDhcp);
                if (ip == null) {
                    log.debug("ip is null");
                } else {
                    Route routeForIP = new Route(Route.Source.STATIC, ip.toIpPrefix(), nextHopIp);
                    log.debug("removing route of 128 address for indirectly connected.");
                    log.debug("128 ip {}, nexthop {}", HexString.toHexString(ip.toOctets(), ":"),
                            HexString.toHexString(nextHopIp.toOctets(), ":"));
                    routeStore.removeRoute(routeForIP);
                }

                IpPrefix ipPrefix = extractPrefix(leafDhcp);
                if (ipPrefix == null) {
                    log.debug("ipPrefix is null ");
                } else {
                    Route routeForPrefix = new Route(Route.Source.STATIC, ipPrefix, nextHopIp);
                    log.debug("removing route of PD for indirectly connected.");
                    log.debug("pd ip {}, nexthop {}", HexString.toHexString(ipPrefix.address().toOctets(), ":"),
                            HexString.toHexString(nextHopIp.toOctets(), ":"));

                    routeStore.removeRoute(routeForPrefix);
                }
            }
        }
    }

    /**
     * add host or route.
     *
     * @param directConnFlag  flag to show that packet is from directly connected client
     * @param dhcp6Relay the dhcp6 payload
     * @param embeddedDhcp6 client's ethernet packetthe dhcp6 payload within relay
     * @param clientMac client macAddress
     * @param clientInterfaces set of client interfaces
     */
    private void addHostOrRoute(boolean directConnFlag, DHCP6 dhcp6Relay,
                                   DHCP6 embeddedDhcp6,
                                   MacAddress clientMac,
                                   Set<Interface> clientInterfaces) {
        log.debug("addHostOrRoute entered.");
        // add host or route
        if (isDhcp6Reply(dhcp6Relay)) {
            IpAddress ip = null;
            if (directConnFlag) {
                // Add to host store if it connect to network directly
                ip = extractIpAddress(embeddedDhcp6);
                if (ip != null) {
                    Set<IpAddress> ips = Sets.newHashSet(ip);
                    VlanId vlanId = clientInterfaces.iterator().next().vlan();
                    HostId hostId = HostId.hostId(clientMac, vlanId);
                    HostLocation hostLocation = new HostLocation(clientInterfaces.iterator().next().connectPoint(),
                            System.currentTimeMillis());
                    HostDescription desc = new DefaultHostDescription(clientMac, vlanId,
                            hostLocation, ips);
                    log.debug("adding Host for directly connected.");
                    log.debug("client mac {} client vlan {} hostlocation {}",
                            HexString.toHexString(clientMac.toBytes(), ":"),
                            vlanId, hostLocation.toString());

                    // Replace the ip when dhcp server give the host new ip address
                    hostStore.createOrUpdateHost(DhcpRelayManager.PROVIDER_ID, hostId, desc, true);
                } else {
                    log.warn("ipAddress not found. Do not add Host for directly connected.");
                }
            } else {
                // Add to route store if it does not connect to network directly
                IpAddress nextHopIp = IpAddress.valueOf(IpAddress.Version.INET6, dhcp6Relay.getPeerAddress());

                DHCP6 leafDhcp = getDhcp6Leaf(embeddedDhcp6);
                ip = extractIpAddress(leafDhcp);
                if (ip == null) {
                    log.warn("ip is null");
                } else {
                    Route routeForIP = new Route(Route.Source.STATIC, ip.toIpPrefix(), nextHopIp);
                    log.warn("adding Route of 128 address for indirectly connected.");
                    routeStore.updateRoute(routeForIP);
                }

                IpPrefix ipPrefix = extractPrefix(leafDhcp);
                if (ipPrefix == null) {
                    log.warn("ipPrefix is null ");
                } else {
                    Route routeForPrefix = new Route(Route.Source.STATIC, ipPrefix, nextHopIp);
                    log.warn("adding Route of PD for indirectly connected.");
                    routeStore.updateRoute(routeForPrefix);
                }
            }
        }
    }

    /**
     *
     * build the DHCP6 solicit/request packet with gatewayip.
     *
     * @param context packet context
     * @param clientPacket client ethernet packet
     * @param clientInterfaces set of client side interfaces
     */
     private InternalPacket processDhcp6PacketFromClient(PacketContext context,
                                                        Ethernet clientPacket, Set<Interface> clientInterfaces) {
        Ip6Address relayAgentIp = getRelayAgentIPv6Address(clientInterfaces);
        MacAddress relayAgentMac = clientInterfaces.iterator().next().mac();
        if (relayAgentIp == null || relayAgentMac == null) {
            log.warn("Missing DHCP relay agent interface Ipv6 addr config for "
                            + "packet from client on port: {}. Aborting packet processing",
                    clientInterfaces.iterator().next().connectPoint());
            return null;
        }

        // get dhcp6 header.

        IPv6 clientIpv6 = (IPv6) clientPacket.getPayload();
        UDP clientUdp = (UDP) clientIpv6.getPayload();
        DHCP6 clientDhcp6 = (DHCP6) clientUdp.getPayload();

        boolean directConnFlag = directlyConnected(clientDhcp6);

        Ethernet etherReply = (Ethernet) clientPacket.clone();
        etherReply.setSourceMACAddress(relayAgentMac);

        if (directConnFlag && this.dhcpConnectMac == null) {
            log.warn("DHCP6 {} not yet resolved .. Aborting DHCP "
                            + "packet processing from client on port: {}",
                    (this.dhcpGatewayIp == null) ? "server IP " + this.dhcpServerIp
                            : "gateway IP " + this.dhcpGatewayIp,
                    clientInterfaces.iterator().next().connectPoint());

            return null;
        }

        if (!directConnFlag && this.indirectDhcpConnectMac == null) {
            log.warn("DHCP6 {} not yet resolved .. Aborting DHCP "
                            + "packet processing from client on port: {}",
                    (this.indirectDhcpGatewayIp == null) ? "server IP " + this.indirectDhcpServerIp
                            : "gateway IP " + this.indirectDhcpGatewayIp,
                    clientInterfaces.iterator().next().connectPoint());

            return null;

        }

        if (this.dhcpServerConnectPoint == null) {
            log.warn("DHCP6 server connection point is not set up yet");
            return null;
        }

        etherReply.setDestinationMACAddress(directConnFlag ? this.dhcpConnectMac : this.indirectDhcpConnectMac);
        etherReply.setVlanID(directConnFlag ? this.dhcpConnectVlan.toShort() : this.indirectDhcpConnectVlan.toShort());

        IPv6 ipv6Packet = (IPv6) etherReply.getPayload();
        byte[] peerAddress = clientIpv6.getSourceAddress();
        ipv6Packet.setSourceAddress(relayAgentIp.toOctets());
        ipv6Packet.setDestinationAddress(directConnFlag ? this.dhcpServerIp.toOctets() :
                                                          this.indirectDhcpServerIp.toOctets());

        UDP udpPacket = (UDP) ipv6Packet.getPayload();
        udpPacket.setSourcePort(UDP.DHCP_V6_SERVER_PORT);
        DHCP6 dhcp6Packet = (DHCP6) udpPacket.getPayload();
        byte[] dhcp6PacketByte = dhcp6Packet.serialize();

        // notify onos and quagga to release PD
        //releasePD(dhcp6Packet);

        removeHostOrRoute(directConnFlag, dhcp6Packet, clientPacket, clientIpv6, clientInterfaces);

        DHCP6 dhcp6Relay = new DHCP6();
        dhcp6Relay.setMsgType(DHCP6.MsgType.RELAY_FORW.value());
        // link address: server uses the address to identify the link on which the client
        // is located.
         if (directConnFlag) {
             dhcp6Relay.setLinkAddress(relayAgentIp.toOctets());
             log.debug("direct connection: relayAgentIp obtained dynamically {}",
                     HexString.toHexString(relayAgentIp.toOctets(), ":"));

         } else {
             if (this.indirectRelayAgentIpFromCfg == null) {
                 dhcp6Relay.setLinkAddress(relayAgentIp.toOctets());
                 log.warn("indirect connection: relayAgentIp NOT availale from config file! {}",
                         HexString.toHexString(relayAgentIp.toOctets(), ":"));

             } else {
                 dhcp6Relay.setLinkAddress(this.indirectRelayAgentIpFromCfg.toOctets());
                 log.debug("indirect connection: relayAgentIp from config file is available! {}",
                         HexString.toHexString(this.indirectRelayAgentIpFromCfg.toOctets(), ":"));
             }
         }

        // peer address:  address of the client or relay agent from which
        // the message to be relayed was received.
        dhcp6Relay.setPeerAddress(peerAddress);
        List<Dhcp6Option> options = new ArrayList<Dhcp6Option>();

        // directly connected case, hop count is zero
        // otherwise, hop count + 1
        if (directConnFlag) {
            dhcp6Relay.setHopCount((byte) 0);
        } else {
            dhcp6Relay.setHopCount((byte) (dhcp6Packet.getHopCount() + 1));
        }

        // create relay message option
        Dhcp6Option relayMessage = new Dhcp6Option();
        relayMessage.setCode(DHCP6.OptionCode.RELAY_MSG.value());
        relayMessage.setLength((short) dhcp6PacketByte.length);
        relayMessage.setData(dhcp6PacketByte);
        options.add(relayMessage);

        // create interfaceId option
        String inPortString = "-" + context.inPacket().receivedFrom().toString();
        Dhcp6Option interfaceId = new Dhcp6Option();
        interfaceId.setCode(DHCP6.OptionCode.INTERFACE_ID.value());
        byte[] clientSoureMacBytes = clientPacket.getSourceMACAddress();
        byte[] inPortStringBytes = inPortString.getBytes();
        byte[] interfaceIdBytes = new byte[clientSoureMacBytes.length +  inPortStringBytes.length];
        log.debug("Length: interfaceIdBytes  {} clientSoureMacBytes {} inPortStringBytes {} ",
                interfaceIdBytes.length, clientSoureMacBytes.length, inPortStringBytes.length);

        System.arraycopy(clientSoureMacBytes, 0, interfaceIdBytes, 0, clientSoureMacBytes.length);
        System.arraycopy(inPortStringBytes, 0, interfaceIdBytes, clientSoureMacBytes.length, inPortStringBytes.length);

        interfaceId.setData(interfaceIdBytes);
        interfaceId.setLength((short) interfaceIdBytes.length);

        options.add(interfaceId);

        log.debug("interfaceId write srcMac {} portString {}",
                  HexString.toHexString(clientSoureMacBytes, ":"), inPortString);
        dhcp6Relay.setOptions(options);
        //dhcp6Packet.setPayload(dhcp6Relay);
        //udpPacket.setPayload(dhcp6Packet);
        udpPacket.setPayload(dhcp6Relay);
        udpPacket.resetChecksum();
        ipv6Packet.setPayload(udpPacket);
        etherReply.setPayload(ipv6Packet);


        return new InternalPacket(etherReply, this.dhcpServerConnectPoint);
    }

    /**
     *
     * process the DHCP6 relay-reply packet from dhcp server.
     *
     * @param context packet context
     * @param receivedPacket server ethernet packet
     * @param recevingInterfaces set of server side interfaces
     */
    private InternalPacket processDhcp6PacketFromServer(PacketContext context,
                                                        Ethernet receivedPacket, Set<Interface> recevingInterfaces) {
        ConnectPoint inPort = context.inPacket().receivedFrom();
        if (!inPort.equals(this.dhcpServerConnectPoint)) {
            log.warn("Receiving port {} is not the same as server port {}",
                    inPort, this.dhcpServerConnectPoint);
            return null;
        }
        // get dhcp6 header.
        Ethernet etherReply = (Ethernet) receivedPacket.clone();
        IPv6 ipv6Packet = (IPv6) etherReply.getPayload();
        UDP udpPacket = (UDP) ipv6Packet.getPayload();
        DHCP6 dhcp6Relay = (DHCP6) udpPacket.getPayload();

        Boolean directConnFlag = directlyConnected(dhcp6Relay);

        Dhcp6InterfaceIdOption interfaceIdOption = dhcp6Relay.getOptions().stream()
                .filter(opt -> opt instanceof Dhcp6InterfaceIdOption)
                .map(opt -> (Dhcp6InterfaceIdOption) opt)
                .findFirst()
                .orElse(null);

        if (interfaceIdOption == null) {
            log.warn("Interface Id option is not present, abort packet...");
            return null;
        }

        MacAddress peerMac = interfaceIdOption.getMacAddress();
        String clientConnectionPointStr = new String(interfaceIdOption.getInPort());

        ConnectPoint clientConnectionPoint = ConnectPoint.deviceConnectPoint(clientConnectionPointStr);

        Set<Interface> clientInterfaces = interfaceService.getInterfacesByPort(clientConnectionPoint);
        if (clientInterfaces.isEmpty()) {
            log.warn("Can not get client interface from packet, abort..");
            return null;
        }
        MacAddress relayAgentMac = clientInterfaces.iterator().next().mac();
        if (relayAgentMac == null) {
            log.warn("Can not get interface mac, abort packet..");
            return null;
        }
        etherReply.setSourceMACAddress(relayAgentMac);

        // find destMac
        MacAddress clientMac = null;
        Set<Host> clients = hostService.getHostsByIp(Ip6Address.valueOf(dhcp6Relay.getPeerAddress()));
        if (clients.isEmpty()) {
            log.warn("There's no host found for this address {}",
                    HexString.toHexString(dhcp6Relay.getPeerAddress(), ":"));
            log.warn("Let's look up interfaceId {}", HexString.toHexString(peerMac.toBytes(), ":"));
            clientMac = peerMac;
        } else {
            clientMac = clients.iterator().next().mac();
            if (clientMac == null) {
                log.warn("No client mac address found, abort packet...");
                return null;
            }
            log.warn("Client mac address found from getHostByIp");

        }
        etherReply.setDestinationMACAddress(clientMac);

        // ip header
        ipv6Packet.setSourceAddress(dhcp6Relay.getLinkAddress());
        ipv6Packet.setDestinationAddress(dhcp6Relay.getPeerAddress());
        // udp header
        udpPacket.setSourcePort(UDP.DHCP_V6_SERVER_PORT);
        if (directConnFlag) {
            udpPacket.setDestinationPort(UDP.DHCP_V6_CLIENT_PORT);
        } else {
            udpPacket.setDestinationPort(UDP.DHCP_V6_SERVER_PORT);
        }

        DHCP6 embeddedDhcp6 = dhcp6Relay.getOptions().stream()
                    .filter(opt -> opt instanceof Dhcp6RelayOption)
                    .map(BasePacket::getPayload)
                    .map(pld -> (DHCP6) pld)
                    .findFirst()
                    .orElse(null);


        // add host or route
        addHostOrRoute(directConnFlag, dhcp6Relay, embeddedDhcp6, clientMac, clientInterfaces);

        udpPacket.setPayload(embeddedDhcp6);
        udpPacket.resetChecksum();
        ipv6Packet.setPayload(udpPacket);
        etherReply.setPayload(ipv6Packet);

        return new InternalPacket(etherReply, clientConnectionPoint);
    }

    // Returns the first v4 interface ip out of a set of interfaces or null.
    // Checks all interfaces, and ignores v6 interface ips
    private Ip6Address getRelayAgentIPv6Address(Set<Interface> intfs) {
        for (Interface intf : intfs) {
            for (InterfaceIpAddress ip : intf.ipAddressesList()) {
                Ip6Address relayAgentIp = ip.ipAddress().getIp6Address();
                if (relayAgentIp != null) {
                    return relayAgentIp;
                }
            }
        }
        return null;
    }

    @Override
    public void setDefaultDhcpServerConfigs(Collection<DhcpServerConfig> configs) {
        if (configs.size() == 0) {
            // no config to update
            return;
        }

        // TODO: currently we pick up first DHCP server config.
        // Will use other server configs in the future for HA.
        DhcpServerConfig serverConfig = configs.iterator().next();
        if (!serverConfig.getDhcpServerConnectPoint().isPresent()) {
            log.warn("Connect point not exists");
            return;
        }
        if (!serverConfig.getDhcpServerIp6().isPresent()) {
            log.warn("IP of DHCP6 server not exists");
            return;
        }
        Ip6Address oldServerIp = this.dhcpServerIp;
        Ip6Address oldGatewayIp = this.dhcpGatewayIp;

        // stop monitoring gateway or server
        if (oldGatewayIp != null) {
            hostService.stopMonitoringIp(oldGatewayIp);
        } else if (oldServerIp != null) {
            hostService.stopMonitoringIp(oldServerIp);
        }

        this.dhcpServerConnectPoint = serverConfig.getDhcpServerConnectPoint().get();
        this.dhcpServerIp = serverConfig.getDhcpServerIp6().get();
        this.dhcpGatewayIp = serverConfig.getDhcpGatewayIp6().orElse(null);
        this.relayAgentIpFromCfg = serverConfig.getRelayAgentIp6().orElse(null);


        // reset server mac and vlan
        this.dhcpConnectMac = null;
        this.dhcpConnectVlan = null;

        log.info("DHCP6 server connect point: " + this.dhcpServerConnectPoint);
        log.info("DHCP6 server IP: " + this.dhcpServerIp);

        IpAddress ipToProbe = MoreObjects.firstNonNull(this.dhcpGatewayIp, this.dhcpServerIp);
        String hostToProbe = this.dhcpGatewayIp != null ? "gateway" : "DHCP6 server";

        if (ipToProbe == null) {
            log.warn("Server IP6 not set, can't probe it");
            return;
        }

        log.info("Probing to resolve {} IP6 {}", hostToProbe, ipToProbe);
        hostService.startMonitoringIp(ipToProbe);

        Set<Host> hosts = hostService.getHostsByIp(ipToProbe);
        if (!hosts.isEmpty()) {
            Host host = hosts.iterator().next();
            this.dhcpConnectVlan = host.vlan();
            this.dhcpConnectMac = host.mac();
        }

    }

    @Override
    public void setIndirectDhcpServerConfigs(Collection<DhcpServerConfig> configs) {
        if (configs.size() == 0) {
            // no config to update
            return;
        }

        // TODO: currently we pick up Second DHCP server config for indirect.
        // Will use other server configs in the future for HA.
        DhcpServerConfig serverConfig = configs.iterator().next();
        checkState(serverConfig.getDhcpServerConnectPoint().isPresent(),
                "Connect point not exists");
        checkState(serverConfig.getDhcpServerIp6().isPresent(),
                "IP of DHCP6 server not exists");
        Ip6Address oldServerIp = this.indirectDhcpServerIp;
        Ip6Address oldGatewayIp = this.indirectDhcpGatewayIp;

        // stop monitoring gateway or server
        if (oldGatewayIp != null) {
            hostService.stopMonitoringIp(oldGatewayIp);
        } else if (oldServerIp != null) {
            hostService.stopMonitoringIp(oldServerIp);
        }

        this.indirectDhcpServerConnectPoint = serverConfig.getDhcpServerConnectPoint().get();
        this.indirectDhcpServerIp = serverConfig.getDhcpServerIp6().get();
        this.indirectDhcpGatewayIp = serverConfig.getDhcpGatewayIp6().orElse(null);
        this.indirectRelayAgentIpFromCfg = serverConfig.getRelayAgentIp6().orElse(null);


        // reset server mac and vlan
        this.indirectDhcpConnectMac = null;
        this.indirectDhcpConnectVlan = null;

        log.info("DHCP6 server connect point: " + this.indirectDhcpServerConnectPoint);
        log.info("DHCP6 server IP: " + this.indirectDhcpServerIp);

        IpAddress ipToProbe = MoreObjects.firstNonNull(this.indirectDhcpGatewayIp, this.indirectDhcpServerIp);
        String hostToProbe = this.indirectDhcpGatewayIp != null ? "gateway" : "DHCP6 server";

        if (ipToProbe == null) {
            log.warn("Server IP6 not set, can't probe it");
            return;
        }

        log.info("Probing to resolve {} IP6 {}", hostToProbe, ipToProbe);
        hostService.startMonitoringIp(ipToProbe);

        Set<Host> hosts = hostService.getHostsByIp(ipToProbe);
        if (!hosts.isEmpty()) {
            Host host = hosts.iterator().next();
            this.indirectDhcpConnectVlan = host.vlan();
            this.indirectDhcpConnectMac = host.mac();
        }
    }

    class InternalHostListener implements HostListener {
        @Override
        public void event(HostEvent event) {
            switch (event.type()) {
                case HOST_ADDED:
                case HOST_UPDATED:
                    hostUpdated(event.subject());
                    break;
                case HOST_REMOVED:
                    hostRemoved(event.subject());
                    break;
                case HOST_MOVED:
                    hostMoved(event.subject());
                    break;
                default:
                    break;
            }
        }
    }

    /**
     * Handle host move.
     * If the host DHCP server or gateway and it moved to the location different
     * to user configured, unsets the connect mac and vlan
     *
     * @param host the host
     */
    private void hostMoved(Host host) {
        if (this.dhcpServerConnectPoint == null && this.indirectDhcpServerConnectPoint == null) {
            return;
        }
        if (this.dhcpGatewayIp != null) {
            if (host.ipAddresses().contains(this.dhcpGatewayIp) &&
                    !host.locations().contains(this.dhcpServerConnectPoint)) {
                this.dhcpConnectMac = null;
                this.dhcpConnectVlan = null;
            }
        }
        if (this.dhcpServerIp != null) {
            if (host.ipAddresses().contains(this.dhcpServerIp) &&
                    !host.locations().contains(this.dhcpServerConnectPoint)) {
                this.dhcpConnectMac = null;
                this.dhcpConnectVlan = null;
            }
        }
        if (this.indirectDhcpGatewayIp != null) {
            if (host.ipAddresses().contains(this.indirectDhcpGatewayIp) &&
                    !host.locations().contains(this.indirectDhcpServerConnectPoint)) {
                this.indirectDhcpConnectMac = null;
                this.indirectDhcpConnectVlan = null;
            }
        }
        if (this.indirectDhcpServerIp != null) {
            if (host.ipAddresses().contains(this.indirectDhcpServerIp) &&
                    !host.locations().contains(this.indirectDhcpServerConnectPoint)) {
                this.indirectDhcpConnectMac = null;
                this.indirectDhcpConnectVlan = null;
            }
        }
    }

    /**
     * Handle host updated.
     * If the host is DHCP server or gateway, update connect mac and vlan.
     *
     * @param host the host
     */
    private void hostUpdated(Host host) {
        if (this.dhcpGatewayIp != null) {
            if (host.ipAddresses().contains(this.dhcpGatewayIp)) {
                this.dhcpConnectMac = host.mac();
                this.dhcpConnectVlan = host.vlan();
            }
        }
        if (this.dhcpServerIp != null) {
            if (host.ipAddresses().contains(this.dhcpServerIp)) {
                this.dhcpConnectMac = host.mac();
                this.dhcpConnectVlan = host.vlan();
            }
        }
        if (this.indirectDhcpGatewayIp != null) {
            if (host.ipAddresses().contains(this.indirectDhcpGatewayIp)) {
                this.indirectDhcpConnectMac = host.mac();
                this.indirectDhcpConnectVlan = host.vlan();
            }
        }
        if (this.indirectDhcpServerIp != null) {
            if (host.ipAddresses().contains(this.indirectDhcpServerIp)) {
                this.indirectDhcpConnectMac = host.mac();
                this.indirectDhcpConnectVlan = host.vlan();
            }
        }
    }

    /**
     * Handle host removed.
     * If the host is DHCP server or gateway, unset connect mac and vlan.
     *
     * @param host the host
     */
    private void hostRemoved(Host host) {
        if (this.dhcpGatewayIp != null) {
            if (host.ipAddresses().contains(this.dhcpGatewayIp)) {
                this.dhcpConnectMac = null;
                this.dhcpConnectVlan = null;
            }
            //return;
        }
        if (this.dhcpServerIp != null) {
            if (host.ipAddresses().contains(this.dhcpServerIp)) {
                this.dhcpConnectMac = null;
                this.dhcpConnectVlan = null;
            }
        }
        if (this.indirectDhcpGatewayIp != null) {
            if (host.ipAddresses().contains(this.indirectDhcpGatewayIp)) {
                this.indirectDhcpConnectMac = null;
                this.indirectDhcpConnectVlan = null;
            }
            //return;
        }
        if (this.indirectDhcpServerIp != null) {
            if (host.ipAddresses().contains(this.indirectDhcpServerIp)) {
                this.indirectDhcpConnectMac = null;
                this.indirectDhcpConnectVlan = null;
            }
        }
    }
}