Adding upstream version 2.4.1.upstream/2.4.1upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 4570 insertions, 0 deletions

diff --git a/src/bin/dhcp4/dhcp4_srv.cc b/src/bin/dhcp4/dhcp4_srv.cc
new file mode 100644
index 0000000..ec1f56f
--- /dev/null
+++ b/src/bin/dhcp4/dhcp4_srv.cc
@@ -0,0 +1,4570 @@
+// Copyright (C) 2011-2023 Internet Systems Consortium, Inc. ("ISC")
+//
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+#include <config.h>
+#include <kea_version.h>
+
+#include <dhcp/dhcp4.h>
+#include <dhcp/duid.h>
+#include <dhcp/hwaddr.h>
+#include <dhcp/iface_mgr.h>
+#include <dhcp/libdhcp++.h>
+#include <dhcp/option4_addrlst.h>
+#include <dhcp/option_custom.h>
+#include <dhcp/option_int.h>
+#include <dhcp/option_int_array.h>
+#include <dhcp/option_vendor.h>
+#include <dhcp/option_vendor_class.h>
+#include <dhcp/option_string.h>
+#include <dhcp/pkt4.h>
+#include <dhcp/pkt4o6.h>
+#include <dhcp/pkt6.h>
+#include <dhcp/docsis3_option_defs.h>
+#include <dhcp4/client_handler.h>
+#include <dhcp4/dhcp4to6_ipc.h>
+#include <dhcp4/dhcp4_log.h>
+#include <dhcp4/dhcp4_srv.h>
+#include <asiolink/addr_utilities.h>
+#include <dhcpsrv/cfgmgr.h>
+#include <dhcpsrv/cfg_host_operations.h>
+#include <dhcpsrv/cfg_iface.h>
+#include <dhcpsrv/cfg_shared_networks.h>
+#include <dhcpsrv/cfg_subnets4.h>
+#include <dhcpsrv/fuzz.h>
+#include <dhcpsrv/lease_mgr.h>
+#include <dhcpsrv/lease_mgr_factory.h>
+#include <dhcpsrv/ncr_generator.h>
+#include <dhcpsrv/shared_network.h>
+#include <dhcpsrv/subnet.h>
+#include <dhcpsrv/subnet_selector.h>
+#include <dhcpsrv/utils.h>
+#include <eval/evaluate.h>
+#include <eval/eval_messages.h>
+#include <hooks/callout_handle.h>
+#include <hooks/hooks_log.h>
+#include <hooks/hooks_manager.h>
+#include <stats/stats_mgr.h>
+#include <util/strutil.h>
+#include <log/logger.h>
+#include <cryptolink/cryptolink.h>
+#include <process/cfgrpt/config_report.h>
+
+#ifdef HAVE_MYSQL
+#include <dhcpsrv/mysql_lease_mgr.h>
+#endif
+#ifdef HAVE_PGSQL
+#include <dhcpsrv/pgsql_lease_mgr.h>
+#endif
+#include <dhcpsrv/memfile_lease_mgr.h>
+
+#include <boost/algorithm/string.hpp>
+#include <boost/foreach.hpp>
+#include <boost/pointer_cast.hpp>
+#include <boost/shared_ptr.hpp>
+
+#include <functional>
+#include <iomanip>
+#include <set>
+#include <cstdlib>
+
+using namespace isc;
+using namespace isc::asiolink;
+using namespace isc::cryptolink;
+using namespace isc::dhcp;
+using namespace isc::dhcp_ddns;
+using namespace isc::hooks;
+using namespace isc::log;
+using namespace isc::stats;
+using namespace isc::util;
+using namespace std;
+namespace ph = std::placeholders;
+
+namespace {
+
+/// Structure that holds registered hook indexes
+struct Dhcp4Hooks {
+    int hook_index_buffer4_receive_;   ///< index for "buffer4_receive" hook point
+    int hook_index_pkt4_receive_;      ///< index for "pkt4_receive" hook point
+    int hook_index_subnet4_select_;    ///< index for "subnet4_select" hook point
+    int hook_index_leases4_committed_; ///< index for "leases4_committed" hook point
+    int hook_index_lease4_release_;    ///< index for "lease4_release" hook point
+    int hook_index_pkt4_send_;         ///< index for "pkt4_send" hook point
+    int hook_index_buffer4_send_;      ///< index for "buffer4_send" hook point
+    int hook_index_lease4_decline_;    ///< index for "lease4_decline" hook point
+    int hook_index_host4_identifier_;  ///< index for "host4_identifier" hook point
+    int hook_index_ddns4_update_;      ///< index for "ddns4_update" hook point
+
+    /// Constructor that registers hook points for DHCPv4 engine
+    Dhcp4Hooks() {
+        hook_index_buffer4_receive_   = HooksManager::registerHook("buffer4_receive");
+        hook_index_pkt4_receive_      = HooksManager::registerHook("pkt4_receive");
+        hook_index_subnet4_select_    = HooksManager::registerHook("subnet4_select");
+        hook_index_leases4_committed_ = HooksManager::registerHook("leases4_committed");
+        hook_index_lease4_release_    = HooksManager::registerHook("lease4_release");
+        hook_index_pkt4_send_         = HooksManager::registerHook("pkt4_send");
+        hook_index_buffer4_send_      = HooksManager::registerHook("buffer4_send");
+        hook_index_lease4_decline_    = HooksManager::registerHook("lease4_decline");
+        hook_index_host4_identifier_  = HooksManager::registerHook("host4_identifier");
+        hook_index_ddns4_update_      = HooksManager::registerHook("ddns4_update");
+    }
+};
+
+/// List of statistics which is initialized to 0 during the DHCPv4
+/// server startup.
+std::set<std::string> dhcp4_statistics = {
+    "pkt4-received",
+    "pkt4-discover-received",
+    "pkt4-offer-received",
+    "pkt4-request-received",
+    "pkt4-ack-received",
+    "pkt4-nak-received",
+    "pkt4-release-received",
+    "pkt4-decline-received",
+    "pkt4-inform-received",
+    "pkt4-unknown-received",
+    "pkt4-sent",
+    "pkt4-offer-sent",
+    "pkt4-ack-sent",
+    "pkt4-nak-sent",
+    "pkt4-parse-failed",
+    "pkt4-receive-drop",
+    "v4-allocation-fail",
+    "v4-allocation-fail-shared-network",
+    "v4-allocation-fail-subnet",
+    "v4-allocation-fail-no-pools",
+    "v4-allocation-fail-classes",
+    "v4-reservation-conflicts",
+    "v4-lease-reuses",
+};
+
+} // end of anonymous namespace
+
+// Declare a Hooks object. As this is outside any function or method, it
+// will be instantiated (and the constructor run) when the module is loaded.
+// As a result, the hook indexes will be defined before any method in this
+// module is called.
+Dhcp4Hooks Hooks;
+
+namespace isc {
+namespace dhcp {
+
+Dhcpv4Exchange::Dhcpv4Exchange(const AllocEnginePtr& alloc_engine,
+                               const Pkt4Ptr& query,
+                               AllocEngine::ClientContext4Ptr& context,
+                               const Subnet4Ptr& subnet,
+                               bool& drop)
+    : alloc_engine_(alloc_engine), query_(query), resp_(),
+      context_(context) {
+
+    if (!alloc_engine_) {
+        isc_throw(BadValue, "alloc_engine value must not be NULL"
+                  " when creating an instance of the Dhcpv4Exchange");
+    }
+
+    if (!query_) {
+        isc_throw(BadValue, "query value must not be NULL when"
+                  " creating an instance of the Dhcpv4Exchange");
+    }
+
+    // Reset the given context argument.
+    context.reset();
+
+    // Create response message.
+    initResponse();
+    // Select subnet for the query message.
+    context_->subnet_ = subnet;
+
+    // If subnet found, retrieve client identifier which will be needed
+    // for allocations and search for reservations associated with a
+    // subnet/shared network.
+    SharedNetwork4Ptr sn;
+    if (subnet && !context_->early_global_reservations_lookup_) {
+        OptionPtr opt_clientid = query->getOption(DHO_DHCP_CLIENT_IDENTIFIER);
+        if (opt_clientid) {
+            context_->clientid_.reset(new ClientId(opt_clientid->getData()));
+        }
+    }
+
+    if (subnet) {
+        // Find static reservations if not disabled for our subnet.
+        if (subnet->getReservationsInSubnet() ||
+            subnet->getReservationsGlobal()) {
+            // Before we can check for static reservations, we need to prepare a set
+            // of identifiers to be used for this.
+            if (!context_->early_global_reservations_lookup_) {
+                setHostIdentifiers(context_);
+            }
+
+            // Check for static reservations.
+            alloc_engine->findReservation(*context_);
+
+            // Get shared network to see if it is set for a subnet.
+            subnet->getSharedNetwork(sn);
+        }
+    }
+
+    // Global host reservations are independent of a selected subnet. If the
+    // global reservations contain client classes we should use them in case
+    // they are meant to affect pool selection. Also, if the subnet does not
+    // belong to a shared network we can use the reserved client classes
+    // because there is no way our subnet could change. Such classes may
+    // affect selection of a pool within the selected subnet.
+    auto global_host = context_->globalHost();
+    auto current_host = context_->currentHost();
+    if ((!context_->early_global_reservations_lookup_ &&
+         global_host && !global_host->getClientClasses4().empty()) ||
+        (!sn && current_host && !current_host->getClientClasses4().empty())) {
+        // We have already evaluated client classes and some of them may
+        // be in conflict with the reserved classes. Suppose there are
+        // two classes defined in the server configuration: first_class
+        // and second_class and the test for the second_class it looks
+        // like this: "not member('first_class')". If the first_class
+        // initially evaluates to false, the second_class evaluates to
+        // true. If the first_class is now set within the hosts reservations
+        // and we don't remove the previously evaluated second_class we'd
+        // end up with both first_class and second_class evaluated to
+        // true. In order to avoid that, we have to remove the classes
+        // evaluated in the first pass and evaluate them again. As
+        // a result, the first_class set via the host reservation will
+        // replace the second_class because the second_class will this
+        // time evaluate to false as desired.
+        removeDependentEvaluatedClasses(query);
+        setReservedClientClasses(context_);
+        evaluateClasses(query, false);
+    }
+
+    // Set KNOWN builtin class if something was found, UNKNOWN if not.
+    if (!context_->hosts_.empty()) {
+        query->addClass("KNOWN");
+        LOG_DEBUG(dhcp4_logger, DBG_DHCP4_BASIC, DHCP4_CLASS_ASSIGNED)
+            .arg(query->getLabel())
+            .arg("KNOWN");
+    } else {
+        query->addClass("UNKNOWN");
+        LOG_DEBUG(dhcp4_logger, DBG_DHCP4_BASIC, DHCP4_CLASS_ASSIGNED)
+            .arg(query->getLabel())
+            .arg("UNKNOWN");
+    }
+
+    // Perform second pass of classification.
+    evaluateClasses(query, true);
+
+    const ClientClasses& classes = query_->getClasses();
+    if (!classes.empty()) {
+        LOG_DEBUG(dhcp4_logger, DBG_DHCP4_BASIC, DHCP4_CLASS_ASSIGNED)
+            .arg(query_->getLabel())
+            .arg(classes.toText());
+    }
+
+    // Check the DROP special class.
+    if (query_->inClass("DROP")) {
+        LOG_DEBUG(packet4_logger, DBGLVL_PKT_HANDLING, DHCP4_PACKET_DROP_0013)
+            .arg(query_->getHWAddrLabel())
+            .arg(query_->toText());
+        isc::stats::StatsMgr::instance().addValue("pkt4-receive-drop",
+                                                  static_cast<int64_t>(1));
+        drop = true;
+    }
+}
+
+void
+Dhcpv4Exchange::initResponse() {
+    uint8_t resp_type = 0;
+    switch (getQuery()->getType()) {
+    case DHCPDISCOVER:
+        resp_type = DHCPOFFER;
+        break;
+    case DHCPREQUEST:
+    case DHCPINFORM:
+        resp_type = DHCPACK;
+        break;
+    default:
+        ;
+    }
+    // Only create a response if one is required.
+    if (resp_type > 0) {
+        resp_.reset(new Pkt4(resp_type, getQuery()->getTransid()));
+        copyDefaultFields();
+        copyDefaultOptions();
+
+        if (getQuery()->isDhcp4o6()) {
+            initResponse4o6();
+        }
+    }
+}
+
+void
+Dhcpv4Exchange::initResponse4o6() {
+    Pkt4o6Ptr query = boost::dynamic_pointer_cast<Pkt4o6>(getQuery());
+    if (!query) {
+        return;
+    }
+    const Pkt6Ptr& query6 = query->getPkt6();
+    Pkt6Ptr resp6(new Pkt6(DHCPV6_DHCPV4_RESPONSE, query6->getTransid()));
+    // Don't add client-id or server-id
+    // But copy relay info
+    if (!query6->relay_info_.empty()) {
+        resp6->copyRelayInfo(query6);
+    }
+    // Copy interface, and remote address and port
+    resp6->setIface(query6->getIface());
+    resp6->setIndex(query6->getIndex());
+    resp6->setRemoteAddr(query6->getRemoteAddr());
+    resp6->setRemotePort(query6->getRemotePort());
+    resp_.reset(new Pkt4o6(resp_, resp6));
+}
+
+void
+Dhcpv4Exchange::copyDefaultFields() {
+    resp_->setIface(query_->getIface());
+    resp_->setIndex(query_->getIndex());
+
+    // explicitly set this to 0
+    resp_->setSiaddr(IOAddress::IPV4_ZERO_ADDRESS());
+    // ciaddr is always 0, except for the Renew/Rebind state and for
+    // Inform when it may be set to the ciaddr sent by the client.
+    if (query_->getType() == DHCPINFORM) {
+        resp_->setCiaddr(query_->getCiaddr());
+    } else {
+        resp_->setCiaddr(IOAddress::IPV4_ZERO_ADDRESS());
+    }
+    resp_->setHops(query_->getHops());
+
+    // copy MAC address
+    resp_->setHWAddr(query_->getHWAddr());
+
+    // relay address
+    resp_->setGiaddr(query_->getGiaddr());
+
+    // If src/dest HW addresses are used by the packet filtering class
+    // we need to copy them as well. There is a need to check that the
+    // address being set is not-NULL because an attempt to set the NULL
+    // HW would result in exception. If these values are not set, the
+    // the default HW addresses (zeroed) should be generated by the
+    // packet filtering class when creating Ethernet header for
+    // outgoing packet.
+    HWAddrPtr src_hw_addr = query_->getLocalHWAddr();
+    if (src_hw_addr) {
+        resp_->setLocalHWAddr(src_hw_addr);
+    }
+    HWAddrPtr dst_hw_addr = query_->getRemoteHWAddr();
+    if (dst_hw_addr) {
+        resp_->setRemoteHWAddr(dst_hw_addr);
+    }
+
+    // Copy flags from the request to the response per RFC 2131
+    resp_->setFlags(query_->getFlags());
+}
+
+void
+Dhcpv4Exchange::copyDefaultOptions() {
+    // Let's copy client-id to response. See RFC6842.
+    // It is possible to disable RFC6842 to keep backward compatibility
+    bool echo = CfgMgr::instance().getCurrentCfg()->getEchoClientId();
+    OptionPtr client_id = query_->getOption(DHO_DHCP_CLIENT_IDENTIFIER);
+    if (client_id && echo) {
+        resp_->addOption(client_id);
+    }
+
+    // If this packet is relayed, we want to copy Relay Agent Info option
+    // when it is not empty.
+    OptionPtr rai = query_->getOption(DHO_DHCP_AGENT_OPTIONS);
+    if (rai && (rai->len() > Option::OPTION4_HDR_LEN)) {
+        resp_->addOption(rai);
+    }
+
+    // RFC 3011 states about the Subnet Selection Option
+
+    // "Servers configured to support this option MUST return an
+    //  identical copy of the option to any client that sends it,
+    //  regardless of whether or not the client requests the option in
+    //  a parameter request list. Clients using this option MUST
+    //  discard DHCPOFFER or DHCPACK packets that do not contain this
+    //  option."
+    OptionPtr subnet_sel = query_->getOption(DHO_SUBNET_SELECTION);
+    if (subnet_sel) {
+        resp_->addOption(subnet_sel);
+    }
+}
+
+void
+Dhcpv4Exchange::setHostIdentifiers(AllocEngine::ClientContext4Ptr context) {
+    const ConstCfgHostOperationsPtr cfg =
+        CfgMgr::instance().getCurrentCfg()->getCfgHostOperations4();
+
+    // Collect host identifiers. The identifiers are stored in order of preference.
+    // The server will use them in that order to search for host reservations.
+    BOOST_FOREACH(const Host::IdentifierType& id_type,
+                  cfg->getIdentifierTypes()) {
+        switch (id_type) {
+        case Host::IDENT_HWADDR:
+            if (context->hwaddr_ && !context->hwaddr_->hwaddr_.empty()) {
+                context->addHostIdentifier(id_type, context->hwaddr_->hwaddr_);
+            }
+            break;
+
+        case Host::IDENT_DUID:
+            if (context->clientid_) {
+                const std::vector<uint8_t>& vec = context->clientid_->getClientId();
+                if (!vec.empty()) {
+                    // Client identifier type = DUID? Client identifier holding a DUID
+                    // comprises Type (1 byte), IAID (4 bytes), followed by the actual
+                    // DUID. Thus, the minimal length is 6.
+                    if ((vec[0] == CLIENT_ID_OPTION_TYPE_DUID) && (vec.size() > 5)) {
+                        // Extract DUID, skip IAID.
+                        context->addHostIdentifier(id_type,
+                                                   std::vector<uint8_t>(vec.begin() + 5,
+                                                                        vec.end()));
+                    }
+                }
+            }
+            break;
+
+        case Host::IDENT_CIRCUIT_ID:
+            {
+                OptionPtr rai = context->query_->getOption(DHO_DHCP_AGENT_OPTIONS);
+                if (rai) {
+                    OptionPtr circuit_id_opt = rai->getOption(RAI_OPTION_AGENT_CIRCUIT_ID);
+                    if (circuit_id_opt) {
+                        const OptionBuffer& circuit_id_vec = circuit_id_opt->getData();
+                        if (!circuit_id_vec.empty()) {
+                            context->addHostIdentifier(id_type, circuit_id_vec);
+                        }
+                    }
+                }
+            }
+            break;
+
+        case Host::IDENT_CLIENT_ID:
+            if (context->clientid_) {
+                const std::vector<uint8_t>& vec = context->clientid_->getClientId();
+                if (!vec.empty()) {
+                    context->addHostIdentifier(id_type, vec);
+                }
+            }
+            break;
+        case Host::IDENT_FLEX:
+            {
+                if (!HooksManager::calloutsPresent(Hooks.hook_index_host4_identifier_)) {
+                    break;
+                }
+
+                CalloutHandlePtr callout_handle = getCalloutHandle(context->query_);
+
+                Host::IdentifierType type = Host::IDENT_FLEX;
+                std::vector<uint8_t> id;
+
+                // Use the RAII wrapper to make sure that the callout handle state is
+                // reset when this object goes out of scope. All hook points must do
+                // it to prevent possible circular dependency between the callout
+                // handle and its arguments.
+                ScopedCalloutHandleState callout_handle_state(callout_handle);
+
+                // Pass incoming packet as argument
+                callout_handle->setArgument("query4", context->query_);
+                callout_handle->setArgument("id_type", type);
+                callout_handle->setArgument("id_value", id);
+
+                // Call callouts
+                HooksManager::callCallouts(Hooks.hook_index_host4_identifier_,
+                                           *callout_handle);
+
+                callout_handle->getArgument("id_type", type);
+                callout_handle->getArgument("id_value", id);
+
+                if ((callout_handle->getStatus() == CalloutHandle::NEXT_STEP_CONTINUE) &&
+                    !id.empty()) {
+
+                    LOG_DEBUG(packet4_logger, DBGLVL_TRACE_BASIC, DHCP4_FLEX_ID)
+                        .arg(Host::getIdentifierAsText(type, &id[0], id.size()));
+
+                    context->addHostIdentifier(type, id);
+                }
+                break;
+            }
+        default:
+            ;
+        }
+    }
+}
+
+void
+Dhcpv4Exchange::removeDependentEvaluatedClasses(const Pkt4Ptr& query) {
+    const ClientClassDictionaryPtr& dict =
+        CfgMgr::instance().getCurrentCfg()->getClientClassDictionary();
+    const ClientClassDefListPtr& defs_ptr = dict->getClasses();
+    for (auto def : *defs_ptr) {
+        // Only remove evaluated classes. Other classes can be
+        // assigned via hooks libraries and we should not remove
+        // them because there is no way they can be added back.
+        if (def->getMatchExpr()) {
+            query->classes_.erase(def->getName());
+        }
+    }
+}
+
+void
+Dhcpv4Exchange::setReservedClientClasses(AllocEngine::ClientContext4Ptr context) {
+    if (context->currentHost() && context->query_) {
+        const ClientClasses& classes = context->currentHost()->getClientClasses4();
+        for (ClientClasses::const_iterator cclass = classes.cbegin();
+             cclass != classes.cend(); ++cclass) {
+            context->query_->addClass(*cclass);
+        }
+    }
+}
+
+void
+Dhcpv4Exchange::conditionallySetReservedClientClasses() {
+    if (context_->subnet_) {
+        SharedNetwork4Ptr shared_network;
+        context_->subnet_->getSharedNetwork(shared_network);
+        if (shared_network) {
+            ConstHostPtr host = context_->currentHost();
+            if (host && (host->getIPv4SubnetID() != SUBNET_ID_GLOBAL)) {
+                setReservedClientClasses(context_);
+            }
+        }
+    }
+}
+
+void
+Dhcpv4Exchange::setReservedMessageFields() {
+    ConstHostPtr host = context_->currentHost();
+    // Nothing to do if host reservations not specified for this client.
+    if (host) {
+        if (!host->getNextServer().isV4Zero()) {
+            resp_->setSiaddr(host->getNextServer());
+        }
+
+        std::string sname = host->getServerHostname();
+        if (!sname.empty()) {
+            resp_->setSname(reinterpret_cast<const uint8_t*>(sname.c_str()),
+                            sname.size());
+        }
+
+        std::string bootfile = host->getBootFileName();
+        if (!bootfile.empty()) {
+            resp_->setFile(reinterpret_cast<const uint8_t*>(bootfile.c_str()),
+                           bootfile.size());
+        }
+    }
+}
+
+void Dhcpv4Exchange::classifyByVendor(const Pkt4Ptr& pkt) {
+    // Built-in vendor class processing
+    boost::shared_ptr<OptionString> vendor_class =
+        boost::dynamic_pointer_cast<OptionString>(pkt->getOption(DHO_VENDOR_CLASS_IDENTIFIER));
+
+    if (!vendor_class) {
+        return;
+    }
+
+    pkt->addClass(Dhcpv4Srv::VENDOR_CLASS_PREFIX + vendor_class->getValue());
+}
+
+void Dhcpv4Exchange::classifyPacket(const Pkt4Ptr& pkt) {
+    // All packets belong to ALL.
+    pkt->addClass("ALL");
+
+    // First: built-in vendor class processing.
+    classifyByVendor(pkt);
+
+    // Run match expressions on classes not depending on KNOWN/UNKNOWN.
+    evaluateClasses(pkt, false);
+}
+
+void Dhcpv4Exchange::evaluateClasses(const Pkt4Ptr& pkt, bool depend_on_known) {
+    // Note getClientClassDictionary() cannot be null
+    const ClientClassDictionaryPtr& dict =
+        CfgMgr::instance().getCurrentCfg()->getClientClassDictionary();
+    const ClientClassDefListPtr& defs_ptr = dict->getClasses();
+    for (ClientClassDefList::const_iterator it = defs_ptr->cbegin();
+         it != defs_ptr->cend(); ++it) {
+        // Note second cannot be null
+        const ExpressionPtr& expr_ptr = (*it)->getMatchExpr();
+        // Nothing to do without an expression to evaluate
+        if (!expr_ptr) {
+            continue;
+        }
+        // Not the right time if only when required
+        if ((*it)->getRequired()) {
+            continue;
+        }
+        // Not the right pass.
+        if ((*it)->getDependOnKnown() != depend_on_known) {
+            continue;
+        }
+        (*it)->test(pkt, expr_ptr);
+    }
+}
+
+const std::string Dhcpv4Srv::VENDOR_CLASS_PREFIX("VENDOR_CLASS_");
+
+Dhcpv4Srv::Dhcpv4Srv(uint16_t server_port, uint16_t client_port,
+                     const bool use_bcast, const bool direct_response_desired)
+    : io_service_(new IOService()), server_port_(server_port),
+      client_port_(client_port), shutdown_(true),
+      alloc_engine_(), use_bcast_(use_bcast),
+      network_state_(new NetworkState(NetworkState::DHCPv4)),
+      cb_control_(new CBControlDHCPv4()),
+      test_send_responses_to_source_(false) {
+
+    const char* env = std::getenv("KEA_TEST_SEND_RESPONSES_TO_SOURCE");
+    if (env) {
+        LOG_WARN(dhcp4_logger, DHCP4_TESTING_MODE_SEND_TO_SOURCE_ENABLED);
+        test_send_responses_to_source_ = true;
+    }
+
+    LOG_DEBUG(dhcp4_logger, DBG_DHCP4_START, DHCP4_OPEN_SOCKET)
+        .arg(server_port);
+
+    try {
+        // Port 0 is used for testing purposes where we don't open broadcast
+        // capable sockets. So, set the packet filter handling direct traffic
+        // only if we are in non-test mode.
+        if (server_port) {
+            // First call to instance() will create IfaceMgr (it's a singleton)
+            // it may throw something if things go wrong.
+            // The 'true' value of the call to setMatchingPacketFilter imposes
+            // that IfaceMgr will try to use the mechanism to respond directly
+            // to the client which doesn't have address assigned. This capability
+            // may be lacking on some OSes, so there is no guarantee that server
+            // will be able to respond directly.
+            IfaceMgr::instance().setMatchingPacketFilter(direct_response_desired);
+        }
+
+        // Instantiate allocation engine. The number of allocation attempts equal
+        // to zero indicates that the allocation engine will use the number of
+        // attempts depending on the pool size.
+        alloc_engine_.reset(new AllocEngine(0));
+
+        /// @todo call loadLibraries() when handling configuration changes
+
+    } catch (const std::exception &e) {
+        LOG_ERROR(dhcp4_logger, DHCP4_SRV_CONSTRUCT_ERROR).arg(e.what());
+        shutdown_ = true;
+        return;
+    }
+
+    // Initializing all observations with default value
+    setPacketStatisticsDefaults();
+    shutdown_ = false;
+}
+
+void Dhcpv4Srv::setPacketStatisticsDefaults() {
+    isc::stats::StatsMgr& stats_mgr = isc::stats::StatsMgr::instance();
+
+    // Iterate over set of observed statistics
+    for (auto it = dhcp4_statistics.begin(); it != dhcp4_statistics.end(); ++it) {
+        // Initialize them with default value 0
+        stats_mgr.setValue((*it), static_cast<int64_t>(0));
+    }
+}
+
+Dhcpv4Srv::~Dhcpv4Srv() {
+    // Discard any parked packets
+    discardPackets();
+
+    try {
+        stopD2();
+    } catch (const std::exception& ex) {
+        // Highly unlikely, but lets Report it but go on
+        LOG_ERROR(dhcp4_logger, DHCP4_SRV_D2STOP_ERROR).arg(ex.what());
+    }
+
+    try {
+        Dhcp4to6Ipc::instance().close();
+    } catch (const std::exception& ex) {
+        // Highly unlikely, but lets Report it but go on
+        LOG_ERROR(dhcp4_logger, DHCP4_SRV_DHCP4O6_ERROR).arg(ex.what());
+    }
+
+    IfaceMgr::instance().closeSockets();
+
+    // The lease manager was instantiated during DHCPv4Srv configuration,
+    // so we should clean up after ourselves.
+    LeaseMgrFactory::destroy();
+
+    // Explicitly unload hooks
+    HooksManager::prepareUnloadLibraries();
+    if (!HooksManager::unloadLibraries()) {
+        auto names = HooksManager::getLibraryNames();
+        std::string msg;
+        if (!names.empty()) {
+            msg = names[0];
+            for (size_t i = 1; i < names.size(); ++i) {
+                msg += std::string(", ") + names[i];
+            }
+        }
+        LOG_ERROR(dhcp4_logger, DHCP4_SRV_UNLOAD_LIBRARIES_ERROR).arg(msg);
+    }
+}
+
+void
+Dhcpv4Srv::shutdown() {
+    LOG_DEBUG(dhcp4_logger, DBG_DHCP4_BASIC, DHCP4_SHUTDOWN_REQUEST);
+    shutdown_ = true;
+}
+
+isc::dhcp::Subnet4Ptr
+Dhcpv4Srv::selectSubnet(const Pkt4Ptr& query, bool& drop,
+                        bool sanity_only) const {
+
+    // DHCPv4-over-DHCPv6 is a special (and complex) case
+    if (query->isDhcp4o6()) {
+        return (selectSubnet4o6(query, drop, sanity_only));
+    }
+
+    Subnet4Ptr subnet;
+
+    const SubnetSelector& selector = CfgSubnets4::initSelector(query);
+
+    CfgMgr& cfgmgr = CfgMgr::instance();
+    subnet = cfgmgr.getCurrentCfg()->getCfgSubnets4()->selectSubnet(selector);
+
+    // Let's execute all callouts registered for subnet4_select
+    // (skip callouts if the selectSubnet was called to do sanity checks only)
+    if (!sanity_only &&
+        HooksManager::calloutsPresent(Hooks.hook_index_subnet4_select_)) {
+        CalloutHandlePtr callout_handle = getCalloutHandle(query);
+
+        // Use the RAII wrapper to make sure that the callout handle state is
+        // reset when this object goes out of scope. All hook points must do
+        // it to prevent possible circular dependency between the callout
+        // handle and its arguments.
+        ScopedCalloutHandleState callout_handle_state(callout_handle);
+
+        // Enable copying options from the packet within hook library.
+        ScopedEnableOptionsCopy<Pkt4> query4_options_copy(query);
+
+        // Set new arguments
+        callout_handle->setArgument("query4", query);
+        callout_handle->setArgument("subnet4", subnet);
+        callout_handle->setArgument("subnet4collection",
+                                    cfgmgr.getCurrentCfg()->
+                                    getCfgSubnets4()->getAll());
+
+        // Call user (and server-side) callouts
+        HooksManager::callCallouts(Hooks.hook_index_subnet4_select_,
+                                   *callout_handle);
+
+        // Callouts decided to skip this step. This means that no subnet
+        // will be selected. Packet processing will continue, but it will
+        // be severely limited (i.e. only global options will be assigned)
+        if (callout_handle->getStatus() == CalloutHandle::NEXT_STEP_SKIP) {
+            LOG_DEBUG(hooks_logger, DBG_DHCP4_HOOKS,
+                      DHCP4_HOOK_SUBNET4_SELECT_SKIP)
+                .arg(query->getLabel());
+            return (Subnet4Ptr());
+        }
+
+        // Callouts decided to drop the packet. It is a superset of the
+        // skip case so no subnet will be selected.
+        if (callout_handle->getStatus() == CalloutHandle::NEXT_STEP_DROP) {
+            LOG_DEBUG(hooks_logger, DBG_DHCP4_HOOKS,
+                      DHCP4_HOOK_SUBNET4_SELECT_DROP)
+                .arg(query->getLabel());
+            drop = true;
+            return (Subnet4Ptr());
+        }
+
+        // Use whatever subnet was specified by the callout
+        callout_handle->getArgument("subnet4", subnet);
+    }
+
+    if (subnet) {
+        // Log at higher debug level that subnet has been found.
+        LOG_DEBUG(packet4_logger, DBG_DHCP4_BASIC_DATA, DHCP4_SUBNET_SELECTED)
+            .arg(query->getLabel())
+            .arg(subnet->getID());
+        // Log detailed information about the selected subnet at the
+        // lower debug level.
+        LOG_DEBUG(packet4_logger, DBG_DHCP4_DETAIL_DATA, DHCP4_SUBNET_DATA)
+            .arg(query->getLabel())
+            .arg(subnet->toText());
+
+    } else {
+        LOG_DEBUG(packet4_logger, DBG_DHCP4_DETAIL,
+                  DHCP4_SUBNET_SELECTION_FAILED)
+            .arg(query->getLabel());
+    }
+
+    return (subnet);
+}
+
+isc::dhcp::Subnet4Ptr
+Dhcpv4Srv::selectSubnet4o6(const Pkt4Ptr& query, bool& drop,
+                           bool sanity_only) const {
+    Subnet4Ptr subnet;
+
+    SubnetSelector selector;
+    selector.ciaddr_ = query->getCiaddr();
+    selector.giaddr_ = query->getGiaddr();
+    selector.local_address_ = query->getLocalAddr();
+    selector.client_classes_ = query->classes_;
+    selector.iface_name_ = query->getIface();
+    // Mark it as DHCPv4-over-DHCPv6
+    selector.dhcp4o6_ = true;
+    // Now the DHCPv6 part
+    selector.remote_address_ = query->getRemoteAddr();
+    selector.first_relay_linkaddr_ = IOAddress("::");
+
+    // Handle a DHCPv6 relayed query
+    Pkt4o6Ptr query4o6 = boost::dynamic_pointer_cast<Pkt4o6>(query);
+    if (!query4o6) {
+        isc_throw(Unexpected, "Can't get DHCP4o6 message");
+    }
+    const Pkt6Ptr& query6 = query4o6->getPkt6();
+
+    // Initialize fields specific to relayed messages.
+    if (query6 && !query6->relay_info_.empty()) {
+        BOOST_REVERSE_FOREACH(Pkt6::RelayInfo relay, query6->relay_info_) {
+            if (!relay.linkaddr_.isV6Zero() &&
+                !relay.linkaddr_.isV6LinkLocal()) {
+                selector.first_relay_linkaddr_ = relay.linkaddr_;
+                break;
+            }
+        }
+        selector.interface_id_ =
+            query6->getAnyRelayOption(D6O_INTERFACE_ID,
+                                      Pkt6::RELAY_GET_FIRST);
+    }
+
+    // If the Subnet Selection option is present, extract its value.
+    OptionPtr sbnsel = query->getOption(DHO_SUBNET_SELECTION);
+    if (sbnsel) {
+        OptionCustomPtr oc = boost::dynamic_pointer_cast<OptionCustom>(sbnsel);
+        if (oc) {
+            selector.option_select_ = oc->readAddress();
+        }
+    }
+
+    CfgMgr& cfgmgr = CfgMgr::instance();
+    subnet = cfgmgr.getCurrentCfg()->getCfgSubnets4()->selectSubnet4o6(selector);
+
+    // Let's execute all callouts registered for subnet4_select.
+    // (skip callouts if the selectSubnet was called to do sanity checks only)
+    if (!sanity_only &&
+        HooksManager::calloutsPresent(Hooks.hook_index_subnet4_select_)) {
+        CalloutHandlePtr callout_handle = getCalloutHandle(query);
+
+        // Use the RAII wrapper to make sure that the callout handle state is
+        // reset when this object goes out of scope. All hook points must do
+        // it to prevent possible circular dependency between the callout
+        // handle and its arguments.
+        ScopedCalloutHandleState callout_handle_state(callout_handle);
+
+        // Set new arguments
+        callout_handle->setArgument("query4", query);
+        callout_handle->setArgument("subnet4", subnet);
+        callout_handle->setArgument("subnet4collection",
+                                    cfgmgr.getCurrentCfg()->
+                                    getCfgSubnets4()->getAll());
+
+        // Call user (and server-side) callouts
+        HooksManager::callCallouts(Hooks.hook_index_subnet4_select_,
+                                   *callout_handle);
+
+        // Callouts decided to skip this step. This means that no subnet
+        // will be selected. Packet processing will continue, but it will
+        // be severely limited (i.e. only global options will be assigned)
+        if (callout_handle->getStatus() == CalloutHandle::NEXT_STEP_SKIP) {
+            LOG_DEBUG(hooks_logger, DBG_DHCP4_HOOKS,
+                      DHCP4_DHCP4O6_HOOK_SUBNET4_SELECT_SKIP)
+                .arg(query->getLabel());
+            return (Subnet4Ptr());
+        }
+
+        // Callouts decided to drop the packet. It is a superset of the
+        // skip case so no subnet will be selected.
+        if (callout_handle->getStatus() == CalloutHandle::NEXT_STEP_DROP) {
+            LOG_DEBUG(hooks_logger, DBG_DHCP4_HOOKS,
+                      DHCP4_DHCP4O6_HOOK_SUBNET4_SELECT_DROP)
+                .arg(query->getLabel());
+            drop = true;
+            return (Subnet4Ptr());
+        }
+
+        // Use whatever subnet was specified by the callout
+        callout_handle->getArgument("subnet4", subnet);
+    }
+
+    if (subnet) {
+        // Log at higher debug level that subnet has been found.
+        LOG_DEBUG(packet4_logger, DBG_DHCP4_BASIC_DATA,
+                  DHCP4_DHCP4O6_SUBNET_SELECTED)
+            .arg(query->getLabel())
+            .arg(subnet->getID());
+        // Log detailed information about the selected subnet at the
+        // lower debug level.
+        LOG_DEBUG(packet4_logger, DBG_DHCP4_DETAIL_DATA,
+                  DHCP4_DHCP4O6_SUBNET_DATA)
+            .arg(query->getLabel())
+            .arg(subnet->toText());
+
+    } else {
+        LOG_DEBUG(packet4_logger, DBG_DHCP4_DETAIL,
+                  DHCP4_DHCP4O6_SUBNET_SELECTION_FAILED)
+            .arg(query->getLabel());
+    }
+
+    return (subnet);
+}
+
+Pkt4Ptr
+Dhcpv4Srv::receivePacket(int timeout) {
+    return (IfaceMgr::instance().receive4(timeout));
+}
+
+void
+Dhcpv4Srv::sendPacket(const Pkt4Ptr& packet) {
+    IfaceMgr::instance().send(packet);
+}
+
+bool
+Dhcpv4Srv::earlyGHRLookup(const Pkt4Ptr& query,
+                          AllocEngine::ClientContext4Ptr ctx) {
+    // Pointer to client's query.
+    ctx->query_ = query;
+
+    // Hardware address.
+    ctx->hwaddr_ = query->getHWAddr();
+
+    // Get the early-global-reservations-lookup flag value.
+    data::ConstElementPtr egrl = CfgMgr::instance().getCurrentCfg()->
+        getConfiguredGlobal(CfgGlobals::EARLY_GLOBAL_RESERVATIONS_LOOKUP);
+    if (egrl) {
+        ctx->early_global_reservations_lookup_ = egrl->boolValue();
+    }
+
+    // Perform early global reservations lookup when wanted.
+    if (ctx->early_global_reservations_lookup_) {
+        // Retrieve retrieve client identifier.
+        OptionPtr opt_clientid = query->getOption(DHO_DHCP_CLIENT_IDENTIFIER);
+        if (opt_clientid) {
+            ctx->clientid_.reset(new ClientId(opt_clientid->getData()));
+        }
+
+        // Get the host identifiers.
+        Dhcpv4Exchange::setHostIdentifiers(ctx);
+
+        // Check for global host reservations.
+        ConstHostPtr global_host = alloc_engine_->findGlobalReservation(*ctx);
+
+        if (global_host && !global_host->getClientClasses4().empty()) {
+            // Remove dependent evaluated classes.
+            Dhcpv4Exchange::removeDependentEvaluatedClasses(query);
+
+            // Add classes from the global reservations.
+            const ClientClasses& classes = global_host->getClientClasses4();
+            for (ClientClasses::const_iterator cclass = classes.cbegin();
+                 cclass != classes.cend(); ++cclass) {
+                query->addClass(*cclass);
+            }
+
+            // Evaluate classes before KNOWN.
+            Dhcpv4Exchange::evaluateClasses(query, false);
+        }
+
+        if (global_host) {
+            // Add the KNOWN class;
+            query->addClass("KNOWN");
+            LOG_DEBUG(dhcp4_logger, DBG_DHCP4_BASIC, DHCP4_CLASS_ASSIGNED)
+                .arg(query->getLabel())
+                .arg("KNOWN");
+
+            // Evaluate classes after KNOWN.
+            Dhcpv4Exchange::evaluateClasses(query, true);
+
+            // Check the DROP special class.
+            if (query->inClass("DROP")) {
+                LOG_DEBUG(packet4_logger, DBGLVL_PKT_HANDLING,
+                          DHCP4_PACKET_DROP_0014)
+                    .arg(query->getHWAddrLabel())
+                    .arg(query->toText());
+                isc::stats::StatsMgr::instance().addValue("pkt4-receive-drop",
+                                                          static_cast<int64_t>(1));
+                return (false);
+            }
+
+            // Store the reservation.
+            ctx->hosts_[SUBNET_ID_GLOBAL] = global_host;
+        }
+    }
+
+    return (true);
+}
+
+int
+Dhcpv4Srv::run() {
+#ifdef ENABLE_AFL
+    // Set up structures needed for fuzzing.
+    Fuzz fuzzer(4, server_port_);
+    //
+    // The next line is needed as a signature for AFL to recognize that we are
+    // running persistent fuzzing.  This has to be in the main image file.
+    while (__AFL_LOOP(fuzzer.maxLoopCount())) {
+        // Read from stdin and put the data read into an address/port on which
+        // Kea is listening, read for Kea to read it via asynchronous I/O.
+        fuzzer.transfer();
+#else
+    while (!shutdown_) {
+#endif // ENABLE_AFL
+        try {
+            run_one();
+            getIOService()->poll();
+        } catch (const std::exception& e) {
+            // General catch-all exception that are not caught by more specific
+            // catches. This one is for exceptions derived from std::exception.
+            LOG_ERROR(packet4_logger, DHCP4_PACKET_PROCESS_STD_EXCEPTION)
+                .arg(e.what());
+        } catch (...) {
+            // General catch-all exception that are not caught by more specific
+            // catches. This one is for other exceptions, not derived from
+            // std::exception.
+            LOG_ERROR(packet4_logger, DHCP4_PACKET_PROCESS_EXCEPTION);
+        }
+    }
+
+    // Stop everything before we change into single-threaded mode.
+    MultiThreadingCriticalSection cs;
+
+    // destroying the thread pool
+    MultiThreadingMgr::instance().apply(false, 0, 0);
+
+    return (getExitValue());
+}
+
+void
+Dhcpv4Srv::run_one() {
+    // client's message and server's response
+    Pkt4Ptr query;
+
+    try {
+        // Set select() timeout to 1s. This value should not be modified
+        // because it is important that the select() returns control
+        // frequently so as the IOService can be polled for ready handlers.
+        uint32_t timeout = 1;
+        query = receivePacket(timeout);
+
+        // Log if packet has arrived. We can't log the detailed information
+        // about the DHCP message because it hasn't been unpacked/parsed
+        // yet, and it can't be parsed at this point because hooks will
+        // have to process it first. The only information available at this
+        // point are: the interface, source address and destination addresses
+        // and ports.
+        if (query) {
+            LOG_DEBUG(packet4_logger, DBG_DHCP4_BASIC, DHCP4_BUFFER_RECEIVED)
+                .arg(query->getRemoteAddr().toText())
+                .arg(query->getRemotePort())
+                .arg(query->getLocalAddr().toText())
+                .arg(query->getLocalPort())
+                .arg(query->getIface());
+        }
+
+        // We used to log that the wait was interrupted, but this is no longer
+        // the case. Our wait time is 1s now, so the lack of query packet more
+        // likely means that nothing new appeared within a second, rather than
+        // we were interrupted. And we don't want to print a message every
+        // second.
+
+    } catch (const SignalInterruptOnSelect&) {
+        // Packet reception interrupted because a signal has been received.
+        // This is not an error because we might have received a SIGTERM,
+        // SIGINT, SIGHUP or SIGCHLD which are handled by the server. For
+        // signals that are not handled by the server we rely on the default
+        // behavior of the system.
+        LOG_DEBUG(packet4_logger, DBG_DHCP4_DETAIL, DHCP4_BUFFER_WAIT_SIGNAL);
+    } catch (const std::exception& e) {
+        // Log all other errors.
+        LOG_ERROR(packet4_logger, DHCP4_BUFFER_RECEIVE_FAIL).arg(e.what());
+    }
+
+    // Timeout may be reached or signal received, which breaks select()
+    // with no reception occurred. No need to log anything here because
+    // we have logged right after the call to receivePacket().
+    if (!query) {
+        return;
+    }
+
+    // If the DHCP service has been globally disabled, drop the packet.
+    if (!network_state_->isServiceEnabled()) {
+        LOG_DEBUG(bad_packet4_logger, DBGLVL_PKT_HANDLING, DHCP4_PACKET_DROP_0008)
+            .arg(query->getLabel());
+        return;
+    } else {
+        if (MultiThreadingMgr::instance().getMode()) {
+            typedef function<void()> CallBack;
+            boost::shared_ptr<CallBack> call_back =
+                boost::make_shared<CallBack>(std::bind(&Dhcpv4Srv::processPacketAndSendResponseNoThrow,
+                                                       this, query));
+            if (!MultiThreadingMgr::instance().getThreadPool().add(call_back)) {
+                LOG_DEBUG(dhcp4_logger, DBG_DHCP4_BASIC, DHCP4_PACKET_QUEUE_FULL);
+            }
+        } else {
+            processPacketAndSendResponse(query);
+        }
+    }
+}
+
+void
+Dhcpv4Srv::processPacketAndSendResponseNoThrow(Pkt4Ptr& query) {
+    try {
+        processPacketAndSendResponse(query);
+    } catch (const std::exception& e) {
+        LOG_ERROR(packet4_logger, DHCP4_PACKET_PROCESS_STD_EXCEPTION)
+            .arg(e.what());
+    } catch (...) {
+        LOG_ERROR(packet4_logger, DHCP4_PACKET_PROCESS_EXCEPTION);
+    }
+}
+
+void
+Dhcpv4Srv::processPacketAndSendResponse(Pkt4Ptr& query) {
+    Pkt4Ptr rsp;
+    processPacket(query, rsp);
+    if (!rsp) {
+        return;
+    }
+
+    CalloutHandlePtr callout_handle = getCalloutHandle(query);
+    processPacketBufferSend(callout_handle, rsp);
+}
+
+void
+Dhcpv4Srv::processPacket(Pkt4Ptr& query, Pkt4Ptr& rsp, bool allow_packet_park) {
+    // All packets belong to ALL.
+    query->addClass("ALL");
+
+    // Log reception of the packet. We need to increase it early, as any
+    // failures in unpacking will cause the packet to be dropped. We
+    // will increase type specific statistic further down the road.
+    // See processStatsReceived().
+    isc::stats::StatsMgr::instance().addValue("pkt4-received",
+                                              static_cast<int64_t>(1));
+
+    bool skip_unpack = false;
+
+    // The packet has just been received so contains the uninterpreted wire
+    // data; execute callouts registered for buffer4_receive.
+    if (HooksManager::calloutsPresent(Hooks.hook_index_buffer4_receive_)) {
+        CalloutHandlePtr callout_handle = getCalloutHandle(query);
+
+        // Use the RAII wrapper to make sure that the callout handle state is
+        // reset when this object goes out of scope. All hook points must do
+        // it to prevent possible circular dependency between the callout
+        // handle and its arguments.
+        ScopedCalloutHandleState callout_handle_state(callout_handle);
+
+        // Enable copying options from the packet within hook library.
+        ScopedEnableOptionsCopy<Pkt4> query4_options_copy(query);
+
+        // Pass incoming packet as argument
+        callout_handle->setArgument("query4", query);
+
+        // Call callouts
+        HooksManager::callCallouts(Hooks.hook_index_buffer4_receive_,
+                                   *callout_handle);
+
+        // Callouts decided to drop the received packet.
+        // The response (rsp) is null so the caller (run_one) will
+        // immediately return too.
+        if (callout_handle->getStatus() == CalloutHandle::NEXT_STEP_DROP) {
+            LOG_DEBUG(hooks_logger, DBGLVL_PKT_HANDLING,
+                      DHCP4_HOOK_BUFFER_RCVD_DROP)
+                .arg(query->getRemoteAddr().toText())
+                .arg(query->getLocalAddr().toText())
+                .arg(query->getIface());
+            return;
+        }
+
+        // Callouts decided to skip the next processing step. The next
+        // processing step would be to parse the packet, so skip at this
+        // stage means that callouts did the parsing already, so server
+        // should skip parsing.
+        if (callout_handle->getStatus() == CalloutHandle::NEXT_STEP_SKIP) {
+            LOG_DEBUG(hooks_logger, DBG_DHCP4_DETAIL,
+                      DHCP4_HOOK_BUFFER_RCVD_SKIP)
+                .arg(query->getRemoteAddr().toText())
+                .arg(query->getLocalAddr().toText())
+                .arg(query->getIface());
+            skip_unpack = true;
+        }
+
+        callout_handle->getArgument("query4", query);
+    }
+
+    // Unpack the packet information unless the buffer4_receive callouts
+    // indicated they did it
+    if (!skip_unpack) {
+        try {
+            LOG_DEBUG(options4_logger, DBG_DHCP4_DETAIL, DHCP4_BUFFER_UNPACK)
+                .arg(query->getRemoteAddr().toText())
+                .arg(query->getLocalAddr().toText())
+                .arg(query->getIface());
+            query->unpack();
+        } catch (const SkipRemainingOptionsError& e) {
+            // An option failed to unpack but we are to attempt to process it
+            // anyway.  Log it and let's hope for the best.
+            LOG_DEBUG(options4_logger, DBG_DHCP4_DETAIL,
+                      DHCP4_PACKET_OPTIONS_SKIPPED)
+                .arg(e.what());
+        } catch (const std::exception& e) {
+            // Failed to parse the packet.
+            LOG_DEBUG(bad_packet4_logger, DBGLVL_PKT_HANDLING, DHCP4_PACKET_DROP_0001)
+                .arg(query->getRemoteAddr().toText())
+                .arg(query->getLocalAddr().toText())
+                .arg(query->getIface())
+                .arg(e.what())
+                .arg(query->getHWAddrLabel());
+
+            // Increase the statistics of parse failures and dropped packets.
+            isc::stats::StatsMgr::instance().addValue("pkt4-parse-failed",
+                                                      static_cast<int64_t>(1));
+            isc::stats::StatsMgr::instance().addValue("pkt4-receive-drop",
+                                                      static_cast<int64_t>(1));
+            return;
+        }
+    }
+
+    // Update statistics accordingly for received packet.
+    processStatsReceived(query);
+
+    // Assign this packet to one or more classes if needed. We need to do
+    // this before calling accept(), because getSubnet4() may need client
+    // class information.
+    classifyPacket(query);
+
+    // Now it is classified the deferred unpacking can be done.
+    deferredUnpack(query);
+
+    // Check whether the message should be further processed or discarded.
+    // There is no need to log anything here. This function logs by itself.
+    if (!accept(query)) {
+        // Increase the statistic of dropped packets.
+        isc::stats::StatsMgr::instance().addValue("pkt4-receive-drop",
+                                                  static_cast<int64_t>(1));
+        return;
+    }
+
+    // We have sanity checked (in accept() that the Message Type option
+    // exists, so we can safely get it here.
+    int type = query->getType();
+    LOG_DEBUG(packet4_logger, DBG_DHCP4_BASIC_DATA, DHCP4_PACKET_RECEIVED)
+        .arg(query->getLabel())
+        .arg(query->getName())
+        .arg(type)
+        .arg(query->getRemoteAddr())
+        .arg(query->getLocalAddr())
+        .arg(query->getIface());
+    LOG_DEBUG(packet4_logger, DBG_DHCP4_DETAIL_DATA, DHCP4_QUERY_DATA)
+        .arg(query->getLabel())
+        .arg(query->toText());
+
+    // Let's execute all callouts registered for pkt4_receive
+    if (HooksManager::calloutsPresent(Hooks.hook_index_pkt4_receive_)) {
+        CalloutHandlePtr callout_handle = getCalloutHandle(query);
+
+        // Use the RAII wrapper to make sure that the callout handle state is
+        // reset when this object goes out of scope. All hook points must do
+        // it to prevent possible circular dependency between the callout
+        // handle and its arguments.
+        ScopedCalloutHandleState callout_handle_state(callout_handle);
+
+        // Enable copying options from the packet within hook library.
+        ScopedEnableOptionsCopy<Pkt4> query4_options_copy(query);
+
+        // Pass incoming packet as argument
+        callout_handle->setArgument("query4", query);
+
+        // Call callouts
+        HooksManager::callCallouts(Hooks.hook_index_pkt4_receive_,
+                                   *callout_handle);
+
+        // Callouts decided to skip the next processing step. The next
+        // processing step would be to process the packet, so skip at this
+        // stage means drop.
+        if ((callout_handle->getStatus() == CalloutHandle::NEXT_STEP_SKIP) ||
+            (callout_handle->getStatus() == CalloutHandle::NEXT_STEP_DROP)) {
+            LOG_DEBUG(hooks_logger, DBG_DHCP4_HOOKS,
+                      DHCP4_HOOK_PACKET_RCVD_SKIP)
+                .arg(query->getLabel());
+            return;
+        }
+
+        callout_handle->getArgument("query4", query);
+    }
+
+    // Check the DROP special class.
+    if (query->inClass("DROP")) {
+        LOG_DEBUG(packet4_logger, DBGLVL_PKT_HANDLING, DHCP4_PACKET_DROP_0010)
+            .arg(query->getHWAddrLabel())
+            .arg(query->toText());
+        isc::stats::StatsMgr::instance().addValue("pkt4-receive-drop",
+                                                  static_cast<int64_t>(1));
+        return;
+    }
+
+    processDhcp4Query(query, rsp, allow_packet_park);
+}
+
+void
+Dhcpv4Srv::processDhcp4QueryAndSendResponse(Pkt4Ptr& query, Pkt4Ptr& rsp,
+                                            bool allow_packet_park) {
+    try {
+        processDhcp4Query(query, rsp, allow_packet_park);
+        if (!rsp) {
+            return;
+        }
+
+        CalloutHandlePtr callout_handle = getCalloutHandle(query);
+        processPacketBufferSend(callout_handle, rsp);
+    } catch (const std::exception& e) {
+        LOG_ERROR(packet4_logger, DHCP4_PACKET_PROCESS_STD_EXCEPTION)
+            .arg(e.what());
+    } catch (...) {
+        LOG_ERROR(packet4_logger, DHCP4_PACKET_PROCESS_EXCEPTION);
+    }
+}
+
+void
+Dhcpv4Srv::processDhcp4Query(Pkt4Ptr& query, Pkt4Ptr& rsp,
+                             bool allow_packet_park) {
+    // Create a client race avoidance RAII handler.
+    ClientHandler client_handler;
+
+    // Check for lease modifier queries from the same client being processed.
+    if (MultiThreadingMgr::instance().getMode() &&
+        ((query->getType() == DHCPDISCOVER) ||
+         (query->getType() == DHCPREQUEST) ||
+         (query->getType() == DHCPRELEASE) ||
+         (query->getType() == DHCPDECLINE))) {
+        ContinuationPtr cont =
+            makeContinuation(std::bind(&Dhcpv4Srv::processDhcp4QueryAndSendResponse,
+                                       this, query, rsp, allow_packet_park));
+        if (!client_handler.tryLock(query, cont)) {
+            return;
+        }
+    }
+
+    AllocEngine::ClientContext4Ptr ctx(new AllocEngine::ClientContext4());
+    if (!earlyGHRLookup(query, ctx)) {
+        return;
+    }
+
+    try {
+        switch (query->getType()) {
+        case DHCPDISCOVER:
+            rsp = processDiscover(query, ctx);
+            break;
+
+        case DHCPREQUEST:
+            // Note that REQUEST is used for many things in DHCPv4: for
+            // requesting new leases, renewing existing ones and even
+            // for rebinding.
+            rsp = processRequest(query, ctx);
+            break;
+
+        case DHCPRELEASE:
+            processRelease(query, ctx);
+            break;
+
+        case DHCPDECLINE:
+            processDecline(query, ctx);
+            break;
+
+        case DHCPINFORM:
+            rsp = processInform(query, ctx);
+            break;
+
+        default:
+            // Only action is to output a message if debug is enabled,
+            // and that is covered by the debug statement before the
+            // "switch" statement.
+            ;
+        }
+    } catch (const std::exception& e) {
+
+        // Catch-all exception (we used to call only isc::Exception, but
+        // std::exception could potentially be raised and if we don't catch
+        // it here, it would be caught in main() and the process would
+        // terminate).  Just log the problem and ignore the packet.
+        // (The problem is logged as a debug message because debug is
+        // disabled by default - it prevents a DDOS attack based on the
+        // sending of problem packets.)
+        LOG_DEBUG(bad_packet4_logger, DBGLVL_PKT_HANDLING, DHCP4_PACKET_DROP_0007)
+            .arg(query->getLabel())
+            .arg(e.what());
+
+        // Increase the statistic of dropped packets.
+        isc::stats::StatsMgr::instance().addValue("pkt4-receive-drop",
+                                                  static_cast<int64_t>(1));
+    }
+
+    CalloutHandlePtr callout_handle = getCalloutHandle(query);
+    if (ctx && HooksManager::calloutsPresent(Hooks.hook_index_leases4_committed_)) {
+        // The ScopedCalloutHandleState class which guarantees that the task
+        // is added to the thread pool after the response is reset (if needed)
+        // and CalloutHandle state is reset. In ST it does nothing.
+        // A smart pointer is used to store the ScopedCalloutHandleState so that
+        // a copy of the pointer is created by the lambda and only on the
+        // destruction of the last reference the task is added.
+        // In MT there are 2 cases:
+        // 1. packet is unparked before current thread smart pointer to
+        //    ScopedCalloutHandleState is destroyed:
+        //  - the lambda uses the smart pointer to set the callout which adds the
+        //    task, but the task is added after ScopedCalloutHandleState is
+        //    destroyed, on the destruction of the last reference which is held
+        //    by the current thread.
+        // 2. packet is unparked after the current thread smart pointer to
+        //    ScopedCalloutHandleState is destroyed:
+        //  - the current thread reference to ScopedCalloutHandleState is
+        //    destroyed, but the reference in the lambda keeps it alive until
+        //    the lambda is called and the last reference is released, at which
+        //    time the task is actually added.
+        // Use the RAII wrapper to make sure that the callout handle state is
+        // reset when this object goes out of scope. All hook points must do
+        // it to prevent possible circular dependency between the callout
+        // handle and its arguments.
+        std::shared_ptr<ScopedCalloutHandleState> callout_handle_state =
+                std::make_shared<ScopedCalloutHandleState>(callout_handle);
+
+        ScopedEnableOptionsCopy<Pkt4> query4_options_copy(query);
+
+        // Also pass the corresponding query packet as argument
+        callout_handle->setArgument("query4", query);
+
+        Lease4CollectionPtr new_leases(new Lease4Collection());
+        // Filter out the new lease if it was reused so not committed.
+        if (ctx->new_lease_ && (ctx->new_lease_->reuseable_valid_lft_ == 0)) {
+            new_leases->push_back(ctx->new_lease_);
+        }
+        callout_handle->setArgument("leases4", new_leases);
+
+        Lease4CollectionPtr deleted_leases(new Lease4Collection());
+        if (ctx->old_lease_) {
+            if ((!ctx->new_lease_) || (ctx->new_lease_->addr_ != ctx->old_lease_->addr_)) {
+                deleted_leases->push_back(ctx->old_lease_);
+            }
+        }
+        callout_handle->setArgument("deleted_leases4", deleted_leases);
+
+        if (allow_packet_park) {
+            // Get the parking limit. Parsing should ensure the value is present.
+            uint32_t parked_packet_limit = 0;
+            data::ConstElementPtr ppl = CfgMgr::instance().getCurrentCfg()->
+                getConfiguredGlobal(CfgGlobals::PARKED_PACKET_LIMIT);
+            if (ppl) {
+                parked_packet_limit = ppl->intValue();
+            }
+
+            if (parked_packet_limit) {
+                const auto& parking_lot = ServerHooks::getServerHooks().
+                    getParkingLotPtr("leases4_committed");
+
+                if (parking_lot && (parking_lot->size() >= parked_packet_limit)) {
+                    // We can't park it so we're going to throw it on the floor.
+                    LOG_DEBUG(packet4_logger, DBGLVL_PKT_HANDLING,
+                              DHCP4_HOOK_LEASES4_PARKING_LOT_FULL)
+                              .arg(parked_packet_limit)
+                              .arg(query->getLabel());
+                    isc::stats::StatsMgr::instance().addValue("pkt4-receive-drop",
+                                                              static_cast<int64_t>(1));
+                    rsp.reset();
+                    return;
+                }
+            }
+
+            // We proactively park the packet. We'll unpark it without invoking
+            // the callback (i.e. drop) unless the callout status is set to
+            // NEXT_STEP_PARK.  Otherwise the callback we bind here will be
+            // executed when the hook library unparks the packet.
+            HooksManager::park("leases4_committed", query,
+            [this, callout_handle, query, rsp, callout_handle_state]() mutable {
+                if (MultiThreadingMgr::instance().getMode()) {
+                    typedef function<void()> CallBack;
+                    boost::shared_ptr<CallBack> call_back =
+                        boost::make_shared<CallBack>(std::bind(&Dhcpv4Srv::sendResponseNoThrow,
+                                                               this, callout_handle, query, rsp));
+                    callout_handle_state->on_completion_ = [call_back]() {
+                        MultiThreadingMgr::instance().getThreadPool().add(call_back);
+                    };
+                } else {
+                    processPacketPktSend(callout_handle, query, rsp);
+                    processPacketBufferSend(callout_handle, rsp);
+                }
+            });
+        }
+
+        try {
+            // Call all installed callouts
+            HooksManager::callCallouts(Hooks.hook_index_leases4_committed_,
+                                       *callout_handle);
+        } catch (...) {
+            // Make sure we don't orphan a parked packet.
+            if (allow_packet_park) {
+                HooksManager::drop("leases4_committed", query);
+            }
+
+            throw;
+        }
+
+        if ((callout_handle->getStatus() == CalloutHandle::NEXT_STEP_PARK)
+            && allow_packet_park) {
+            LOG_DEBUG(hooks_logger, DBG_DHCP4_HOOKS, DHCP4_HOOK_LEASES4_COMMITTED_PARK)
+                      .arg(query->getLabel());
+            // Since the hook library(ies) are going to do the unparking, then
+            // reset the pointer to the response to indicate to the caller that
+            // it should return, as the packet processing will continue via
+            // the callback.
+            rsp.reset();
+        } else {
+            // Drop the park job on the packet, it isn't needed.
+            HooksManager::drop("leases4_committed", query);
+            if (callout_handle->getStatus() == CalloutHandle::NEXT_STEP_DROP) {
+                LOG_DEBUG(hooks_logger, DBGLVL_PKT_HANDLING, DHCP4_HOOK_LEASES4_COMMITTED_DROP)
+                          .arg(query->getLabel());
+                rsp.reset();
+            }
+        }
+    }
+
+    // If we have a response prep it for shipment.
+    if (rsp) {
+        processPacketPktSend(callout_handle, query, rsp);
+    }
+}
+
+void
+Dhcpv4Srv::sendResponseNoThrow(hooks::CalloutHandlePtr& callout_handle,
+                               Pkt4Ptr& query, Pkt4Ptr& rsp) {
+    try {
+            processPacketPktSend(callout_handle, query, rsp);
+            processPacketBufferSend(callout_handle, rsp);
+        } catch (const std::exception& e) {
+            LOG_ERROR(packet4_logger, DHCP4_PACKET_PROCESS_STD_EXCEPTION)
+                .arg(e.what());
+    } catch (...) {
+        LOG_ERROR(packet4_logger, DHCP4_PACKET_PROCESS_EXCEPTION);
+    }
+}
+
+void
+Dhcpv4Srv::processPacketPktSend(hooks::CalloutHandlePtr& callout_handle,
+                                Pkt4Ptr& query, Pkt4Ptr& rsp) {
+    if (!rsp) {
+        return;
+    }
+
+    // Specifies if server should do the packing
+    bool skip_pack = false;
+
+    // Execute all callouts registered for pkt4_send
+    if (HooksManager::calloutsPresent(Hooks.hook_index_pkt4_send_)) {
+
+        // Use the RAII wrapper to make sure that the callout handle state is
+        // reset when this object goes out of scope. All hook points must do
+        // it to prevent possible circular dependency between the callout
+        // handle and its arguments.
+        ScopedCalloutHandleState callout_handle_state(callout_handle);
+
+        // Enable copying options from the query and response packets within
+        // hook library.
+        ScopedEnableOptionsCopy<Pkt4> query_resp_options_copy(query, rsp);
+
+        // Pass incoming packet as argument
+        callout_handle->setArgument("query4", query);
+
+        // Set our response
+        callout_handle->setArgument("response4", rsp);
+
+        // Call all installed callouts
+        HooksManager::callCallouts(Hooks.hook_index_pkt4_send_,
+                                   *callout_handle);
+
+        // Callouts decided to skip the next processing step. The next
+        // processing step would be to pack the packet (create wire data).
+        // That step will be skipped if any callout sets skip flag.
+        // It essentially means that the callout already did packing,
+        // so the server does not have to do it again.
+        if (callout_handle->getStatus() == CalloutHandle::NEXT_STEP_SKIP) {
+            LOG_DEBUG(hooks_logger, DBG_DHCP4_HOOKS, DHCP4_HOOK_PACKET_SEND_SKIP)
+                .arg(query->getLabel());
+            skip_pack = true;
+        }
+
+        /// Callouts decided to drop the packet.
+        if (callout_handle->getStatus() == CalloutHandle::NEXT_STEP_DROP) {
+            LOG_DEBUG(hooks_logger, DBGLVL_PKT_HANDLING, DHCP4_HOOK_PACKET_SEND_DROP)
+                .arg(rsp->getLabel());
+            rsp.reset();
+            return;
+        }
+    }
+
+    if (!skip_pack) {
+        try {
+            LOG_DEBUG(options4_logger, DBG_DHCP4_DETAIL, DHCP4_PACKET_PACK)
+                .arg(rsp->getLabel());
+            rsp->pack();
+        } catch (const std::exception& e) {
+            LOG_ERROR(options4_logger, DHCP4_PACKET_PACK_FAIL)
+                .arg(rsp->getLabel())
+                .arg(e.what());
+        }
+    }
+}
+
+void
+Dhcpv4Srv::processPacketBufferSend(CalloutHandlePtr& callout_handle,
+                                   Pkt4Ptr& rsp) {
+    if (!rsp) {
+        return;
+    }
+
+    try {
+        // Now all fields and options are constructed into output wire buffer.
+        // Option objects modification does not make sense anymore. Hooks
+        // can only manipulate wire buffer at this stage.
+        // Let's execute all callouts registered for buffer4_send
+        if (HooksManager::calloutsPresent(Hooks.hook_index_buffer4_send_)) {
+
+            // Use the RAII wrapper to make sure that the callout handle state is
+            // reset when this object goes out of scope. All hook points must do
+            // it to prevent possible circular dependency between the callout
+            // handle and its arguments.
+            ScopedCalloutHandleState callout_handle_state(callout_handle);
+
+            // Enable copying options from the packet within hook library.
+            ScopedEnableOptionsCopy<Pkt4> resp4_options_copy(rsp);
+
+            // Pass incoming packet as argument
+            callout_handle->setArgument("response4", rsp);
+
+            // Call callouts
+            HooksManager::callCallouts(Hooks.hook_index_buffer4_send_,
+                                       *callout_handle);
+
+            // Callouts decided to skip the next processing step. The next
+            // processing step would be to parse the packet, so skip at this
+            // stage means drop.
+            if ((callout_handle->getStatus() == CalloutHandle::NEXT_STEP_SKIP) ||
+                (callout_handle->getStatus() == CalloutHandle::NEXT_STEP_DROP)) {
+                LOG_DEBUG(hooks_logger, DBG_DHCP4_HOOKS,
+                          DHCP4_HOOK_BUFFER_SEND_SKIP)
+                    .arg(rsp->getLabel());
+                return;
+            }
+
+            callout_handle->getArgument("response4", rsp);
+        }
+
+        LOG_DEBUG(packet4_logger, DBG_DHCP4_BASIC, DHCP4_PACKET_SEND)
+            .arg(rsp->getLabel())
+            .arg(rsp->getName())
+            .arg(static_cast<int>(rsp->getType()))
+            .arg(rsp->getLocalAddr().isV4Zero() ? "*" : rsp->getLocalAddr().toText())
+            .arg(rsp->getLocalPort())
+            .arg(rsp->getRemoteAddr())
+            .arg(rsp->getRemotePort())
+            .arg(rsp->getIface().empty() ? "to be determined from routing" :
+                 rsp->getIface());
+
+        LOG_DEBUG(packet4_logger, DBG_DHCP4_DETAIL_DATA,
+                  DHCP4_RESPONSE_DATA)
+            .arg(rsp->getLabel())
+            .arg(rsp->getName())
+            .arg(static_cast<int>(rsp->getType()))
+            .arg(rsp->toText());
+        sendPacket(rsp);
+
+        // Update statistics accordingly for sent packet.
+        processStatsSent(rsp);
+
+    } catch (const std::exception& e) {
+        LOG_ERROR(packet4_logger, DHCP4_PACKET_SEND_FAIL)
+            .arg(rsp->getLabel())
+            .arg(e.what());
+    }
+}
+
+string
+Dhcpv4Srv::srvidToString(const OptionPtr& srvid) {
+    if (!srvid) {
+        isc_throw(BadValue, "NULL pointer passed to srvidToString()");
+    }
+    boost::shared_ptr<Option4AddrLst> generated =
+        boost::dynamic_pointer_cast<Option4AddrLst>(srvid);
+    if (!srvid) {
+        isc_throw(BadValue, "Pointer to invalid option passed to srvidToString()");
+    }
+
+    Option4AddrLst::AddressContainer addrs = generated->getAddresses();
+    if (addrs.size() != 1) {
+        isc_throw(BadValue, "Malformed option passed to srvidToString(). "
+                  << "Expected to contain a single IPv4 address.");
+    }
+
+    return (addrs[0].toText());
+}
+
+void
+Dhcpv4Srv::appendServerID(Dhcpv4Exchange& ex) {
+
+    // Do not append generated server identifier if there is one appended already.
+    // This is when explicitly configured server identifier option is present.
+    if (ex.getResponse()->getOption(DHO_DHCP_SERVER_IDENTIFIER)) {
+        return;
+    }
+
+    // Use local address on which the packet has been received as a
+    // server identifier. In some cases it may be a different address,
+    // e.g. broadcast packet or DHCPv4o6 packet.
+    IOAddress local_addr = ex.getQuery()->getLocalAddr();
+    Pkt4Ptr query = ex.getQuery();
+
+    if (local_addr.isV4Bcast() || query->isDhcp4o6()) {
+        local_addr = IfaceMgr::instance().getSocket(query).addr_;
+    }
+
+    OptionPtr opt_srvid(new Option4AddrLst(DHO_DHCP_SERVER_IDENTIFIER,
+                                           local_addr));
+    ex.getResponse()->addOption(opt_srvid);
+}
+
+void
+Dhcpv4Srv::buildCfgOptionList(Dhcpv4Exchange& ex) {
+    CfgOptionList& co_list = ex.getCfgOptionList();
+
+    // Retrieve subnet.
+    Subnet4Ptr subnet = ex.getContext()->subnet_;
+    if (!subnet) {
+        // All methods using the CfgOptionList object return soon when
+        // there is no subnet so do the same
+        return;
+    }
+
+    // Firstly, host specific options.
+    const ConstHostPtr& host = ex.getContext()->currentHost();
+    if (host && !host->getCfgOption4()->empty()) {
+        co_list.push_back(host->getCfgOption4());
+    }
+
+    // Secondly, pool specific options.
+    Pkt4Ptr resp = ex.getResponse();
+    IOAddress addr = IOAddress::IPV4_ZERO_ADDRESS();
+    if (resp) {
+        addr = resp->getYiaddr();
+    }
+    if (!addr.isV4Zero()) {
+        PoolPtr pool = subnet->getPool(Lease::TYPE_V4, addr, false);
+        if (pool && !pool->getCfgOption()->empty()) {
+            co_list.push_back(pool->getCfgOption());
+        }
+    }
+
+    // Thirdly, subnet configured options.
+    if (!subnet->getCfgOption()->empty()) {
+        co_list.push_back(subnet->getCfgOption());
+    }
+
+    // Fourthly, shared network specific options.
+    SharedNetwork4Ptr network;
+    subnet->getSharedNetwork(network);
+    if (network && !network->getCfgOption()->empty()) {
+        co_list.push_back(network->getCfgOption());
+    }
+
+    // Each class in the incoming packet
+    const ClientClasses& classes = ex.getQuery()->getClasses();
+    for (ClientClasses::const_iterator cclass = classes.cbegin();
+         cclass != classes.cend(); ++cclass) {
+        // Find the client class definition for this class
+        const ClientClassDefPtr& ccdef = CfgMgr::instance().getCurrentCfg()->
+            getClientClassDictionary()->findClass(*cclass);
+        if (!ccdef) {
+            // Not found: the class is built-in or not configured
+            if (!isClientClassBuiltIn(*cclass)) {
+                LOG_DEBUG(dhcp4_logger, DBG_DHCP4_BASIC, DHCP4_CLASS_UNCONFIGURED)
+                    .arg(ex.getQuery()->getLabel())
+                    .arg(*cclass);
+            }
+            // Skip it
+            continue;
+        }
+
+        if (ccdef->getCfgOption()->empty()) {
+            // Skip classes which don't configure options
+            continue;
+        }
+
+        co_list.push_back(ccdef->getCfgOption());
+    }
+
+    // Last global options
+    if (!CfgMgr::instance().getCurrentCfg()->getCfgOption()->empty()) {
+        co_list.push_back(CfgMgr::instance().getCurrentCfg()->getCfgOption());
+    }
+}
+
+void
+Dhcpv4Srv::appendRequestedOptions(Dhcpv4Exchange& ex) {
+    // Get the subnet relevant for the client. We will need it
+    // to get the options associated with it.
+    Subnet4Ptr subnet = ex.getContext()->subnet_;
+    // If we can't find the subnet for the client there is no way
+    // to get the options to be sent to a client. We don't log an
+    // error because it will be logged by the assignLease method
+    // anyway.
+    if (!subnet) {
+        return;
+    }
+
+    // Unlikely short cut
+    const CfgOptionList& co_list = ex.getCfgOptionList();
+    if (co_list.empty()) {
+        return;
+    }
+
+    Pkt4Ptr query = ex.getQuery();
+    Pkt4Ptr resp = ex.getResponse();
+    set<uint8_t> requested_opts;
+
+    // try to get the 'Parameter Request List' option which holds the
+    // codes of requested options.
+    OptionUint8ArrayPtr option_prl = boost::dynamic_pointer_cast<
+        OptionUint8Array>(query->getOption(DHO_DHCP_PARAMETER_REQUEST_LIST));
+
+    // Get the list of options that client requested.
+    if (option_prl) {
+        for (uint16_t code : option_prl->getValues()) {
+            static_cast<void>(requested_opts.insert(code));
+        }
+    }
+
+    std::set<uint8_t> cancelled_opts;
+
+    // Iterate on the configured option list to add persistent and
+    // cancelled options.
+    for (auto const& copts : co_list) {
+        const OptionContainerPtr& opts = copts->getAll(DHCP4_OPTION_SPACE);
+        if (!opts) {
+            continue;
+        }
+        // Get persistent options.
+        const OptionContainerPersistIndex& pidx = opts->get<2>();
+        const OptionContainerPersistRange& prange = pidx.equal_range(true);
+        for (OptionContainerPersistIndex::const_iterator desc = prange.first;
+             desc != prange.second; ++desc) {
+            // Add the persistent option code to requested options.
+            if (desc->option_) {
+                uint8_t code = static_cast<uint8_t>(desc->option_->getType());
+                static_cast<void>(requested_opts.insert(code));
+            }
+        }
+        // Get cancelled options.
+        const OptionContainerCancelIndex& cidx = opts->get<5>();
+        const OptionContainerCancelRange& crange = cidx.equal_range(true);
+        for (OptionContainerCancelIndex::const_iterator desc = crange.first;
+             desc != crange.second; ++desc) {
+            // Add the cancelled option code to cancelled options.
+            if (desc->option_) {
+                uint8_t code = static_cast<uint8_t>(desc->option_->getType());
+                static_cast<void>(cancelled_opts.insert(code));
+            }
+        }
+    }
+
+    // For each requested option code get the first instance of the option
+    // to be returned to the client.
+    for (uint8_t opt : requested_opts) {
+        if (cancelled_opts.count(opt) > 0) {
+            continue;
+        }
+        // Skip special cases: DHO_VIVSO_SUBOPTIONS.
+        if (opt == DHO_VIVSO_SUBOPTIONS) {
+            continue;
+        }
+        // Add nothing when it is already there.
+        if (!resp->getOption(opt)) {
+            // Iterate on the configured option list
+            for (auto const& copts : co_list) {
+                OptionDescriptor desc = copts->get(DHCP4_OPTION_SPACE, opt);
+                // Got it: add it and jump to the outer loop
+                if (desc.option_) {
+                    resp->addOption(desc.option_);
+                    break;
+                }
+            }
+        }
+    }
+
+    // Special cases for vendor class and options which are identified
+    // by the code/type and the vendor/enterprise id vs. the code/type only.
+    if ((requested_opts.count(DHO_VIVCO_SUBOPTIONS) > 0) &&
+        (cancelled_opts.count(DHO_VIVCO_SUBOPTIONS) == 0)) {
+        // Keep vendor ids which are already in the response to insert
+        // VIVCO options at most once per vendor.
+        set<uint32_t> vendor_ids;
+        // Get what already exists in the response.
+        for (auto opt : resp->getOptions(DHO_VIVCO_SUBOPTIONS)) {
+            OptionVendorClassPtr vendor_opts;
+            vendor_opts = boost::dynamic_pointer_cast<OptionVendorClass>(opt.second);
+            if (vendor_opts) {
+                uint32_t vendor_id = vendor_opts->getVendorId();
+                static_cast<void>(vendor_ids.insert(vendor_id));
+            }
+        }
+        // Iterate on the configured option list.
+        for (auto const& copts : co_list) {
+            for (OptionDescriptor desc : copts->getList(DHCP4_OPTION_SPACE,
+                                                        DHO_VIVCO_SUBOPTIONS)) {
+                if (!desc.option_) {
+                    continue;
+                }
+                OptionVendorClassPtr vendor_opts =
+                    boost::dynamic_pointer_cast<OptionVendorClass>(desc.option_);
+                if (!vendor_opts) {
+                    continue;
+                }
+                // Is the vendor id already in the response?
+                uint32_t vendor_id = vendor_opts->getVendorId();
+                if (vendor_ids.count(vendor_id) > 0) {
+                    continue;
+                }
+                // Got it: add it.
+                resp->Pkt::addOption(desc.option_);
+                static_cast<void>(vendor_ids.insert(vendor_id));
+            }
+        }
+    }
+
+    if ((requested_opts.count(DHO_VIVSO_SUBOPTIONS) > 0) &&
+        (cancelled_opts.count(DHO_VIVSO_SUBOPTIONS) == 0)) {
+        // Keep vendor ids which are already in the response to insert
+        // VIVSO options at most once per vendor.
+        set<uint32_t> vendor_ids;
+        // Get what already exists in the response.
+        for (auto opt : resp->getOptions(DHO_VIVSO_SUBOPTIONS)) {
+            OptionVendorPtr vendor_opts;
+            vendor_opts = boost::dynamic_pointer_cast<OptionVendor>(opt.second);
+            if (vendor_opts) {
+                uint32_t vendor_id = vendor_opts->getVendorId();
+                static_cast<void>(vendor_ids.insert(vendor_id));
+            }
+        }
+        // Iterate on the configured option list
+        for (auto const& copts : co_list) {
+            for (OptionDescriptor desc : copts->getList(DHCP4_OPTION_SPACE,
+                                                        DHO_VIVSO_SUBOPTIONS)) {
+                if (!desc.option_) {
+                    continue;
+                }
+                OptionVendorPtr vendor_opts =
+                    boost::dynamic_pointer_cast<OptionVendor>(desc.option_);
+                if (!vendor_opts) {
+                    continue;
+                }
+                // Is the vendor id already in the response?
+                uint32_t vendor_id = vendor_opts->getVendorId();
+                if (vendor_ids.count(vendor_id) > 0) {
+                    continue;
+                }
+                // Append a fresh vendor option as the next method should
+                // add suboptions to it.
+                vendor_opts.reset(new OptionVendor(Option::V4, vendor_id));
+                resp->Pkt::addOption(vendor_opts);
+                static_cast<void>(vendor_ids.insert(vendor_id));
+            }
+        }
+    }
+}
+
+void
+Dhcpv4Srv::appendRequestedVendorOptions(Dhcpv4Exchange& ex) {
+    // Get the configured subnet suitable for the incoming packet.
+    Subnet4Ptr subnet = ex.getContext()->subnet_;
+
+    const CfgOptionList& co_list = ex.getCfgOptionList();
+
+    // Leave if there is no subnet matching the incoming packet.
+    // There is no need to log the error message here because
+    // it will be logged in the assignLease() when it fails to
+    // pick the suitable subnet. We don't want to duplicate
+    // error messages in such case.
+    //
+    // Also, if there's no options to possibly assign, give up.
+    if (!subnet || co_list.empty()) {
+        return;
+    }
+
+    Pkt4Ptr query = ex.getQuery();
+    Pkt4Ptr resp = ex.getResponse();
+    set<uint32_t> vendor_ids;
+
+    // The server could have provided the option using client classification or
+    // hooks. If there're vendor info options in the response already, use them.
+    map<uint32_t, OptionVendorPtr> vendor_rsps;
+    for (auto opt : resp->getOptions(DHO_VIVSO_SUBOPTIONS)) {
+        OptionVendorPtr vendor_rsp;
+        vendor_rsp = boost::dynamic_pointer_cast<OptionVendor>(opt.second);
+        if (vendor_rsp) {
+            uint32_t vendor_id = vendor_rsp->getVendorId();
+            vendor_rsps[vendor_id] = vendor_rsp;
+            static_cast<void>(vendor_ids.insert(vendor_id));
+        }
+    }
+
+    // Next, try to get the vendor-id from the client packet's
+    // vendor-specific information option (125).
+    map<uint32_t, OptionVendorPtr> vendor_reqs;
+    for (auto opt : query->getOptions(DHO_VIVSO_SUBOPTIONS)) {
+        OptionVendorPtr vendor_req;
+        vendor_req = boost::dynamic_pointer_cast<OptionVendor>(opt.second);
+        if (vendor_req) {
+            uint32_t vendor_id = vendor_req->getVendorId();
+            vendor_reqs[vendor_id] = vendor_req;
+            static_cast<void>(vendor_ids.insert(vendor_id));
+        }
+    }
+
+    // Finally, try to get the vendor-id from the client packet's
+    // vendor-specific class option (124).
+    for (auto opt : query->getOptions(DHO_VIVCO_SUBOPTIONS)) {
+        OptionVendorClassPtr vendor_class;
+        vendor_class = boost::dynamic_pointer_cast<OptionVendorClass>(opt.second);
+        if (vendor_class) {
+            uint32_t vendor_id = vendor_class->getVendorId();
+            static_cast<void>(vendor_ids.insert(vendor_id));
+        }
+    }
+
+    // If there's no vendor option in either request or response, then there's no way
+    // to figure out what the vendor-id values are and we give up.
+    if (vendor_ids.empty()) {
+        return;
+    }
+
+    map<uint32_t, set<uint8_t> > requested_opts;
+
+    // Let's try to get ORO within that vendor-option.
+    // This is specific to vendor-id=4491 (Cable Labs). Other vendors may have
+    // different policies.
+    OptionUint8ArrayPtr oro;
+    if (vendor_reqs.count(VENDOR_ID_CABLE_LABS) > 0) {
+        OptionVendorPtr vendor_req = vendor_reqs[VENDOR_ID_CABLE_LABS];
+        OptionPtr oro_generic = vendor_req->getOption(DOCSIS3_V4_ORO);
+        if (oro_generic) {
+            // Vendor ID 4491 makes Kea look at DOCSIS3_V4_OPTION_DEFINITIONS
+            // when parsing options. Based on that, oro_generic will have been
+            // created as an OptionUint8Array, but might not be for other
+            // vendor IDs.
+            oro = boost::dynamic_pointer_cast<OptionUint8Array>(oro_generic);
+        }
+        if (oro) {
+            set<uint8_t> oro_req_opts;
+            for (uint8_t code : oro->getValues()) {
+                static_cast<void>(oro_req_opts.insert(code));
+            }
+            requested_opts[VENDOR_ID_CABLE_LABS] = oro_req_opts;
+        }
+    }
+
+    for (uint32_t vendor_id : vendor_ids) {
+
+        std::set<uint8_t> cancelled_opts;
+
+        // Iterate on the configured option list to add persistent and
+        // cancelled options,
+        for (auto const& copts : co_list) {
+            const OptionContainerPtr& opts = copts->getAll(vendor_id);
+            if (!opts) {
+                continue;
+            }
+
+            // Get persistent options.
+            const OptionContainerPersistIndex& pidx = opts->get<2>();
+            const OptionContainerPersistRange& prange = pidx.equal_range(true);
+            for (OptionContainerPersistIndex::const_iterator desc = prange.first;
+                 desc != prange.second; ++desc) {
+                // Add the persistent option code to requested options.
+                if (desc->option_) {
+                    uint8_t code = static_cast<uint8_t>(desc->option_->getType());
+                    static_cast<void>(requested_opts[vendor_id].insert(code));
+                }
+            }
+
+            // Get cancelled options.
+            const OptionContainerCancelIndex& cidx = opts->get<5>();
+            const OptionContainerCancelRange& crange = cidx.equal_range(true);
+            for (OptionContainerCancelIndex::const_iterator desc = crange.first;
+                 desc != crange.second; ++desc) {
+                // Add the cancelled option code to cancelled options.
+                if (desc->option_) {
+                    uint8_t code = static_cast<uint8_t>(desc->option_->getType());
+                    static_cast<void>(cancelled_opts.insert(code));
+                }
+            }
+        }
+
+        // If there is nothing to add don't do anything with this vendor.
+        // This will explicitly not echo back vendor options from the request
+        // that either correspond to a vendor not known to Kea even if the
+        // option encapsulates data or there are no persistent options
+        // configured for this vendor so Kea does not send any option back.
+        if (requested_opts[vendor_id].empty()) {
+            continue;
+        }
+
+
+        // It's possible that vivso was inserted already by client class or
+        // a hook. If that is so, let's use it.
+        OptionVendorPtr vendor_rsp;
+        if (vendor_rsps.count(vendor_id) > 0) {
+            vendor_rsp = vendor_rsps[vendor_id];
+        } else {
+            vendor_rsp.reset(new OptionVendor(Option::V4, vendor_id));
+        }
+
+        // Get the list of options that client requested.
+        bool added = false;
+
+        for (uint8_t opt : requested_opts[vendor_id]) {
+            if (cancelled_opts.count(opt) > 0) {
+                continue;
+            }
+            if (!vendor_rsp->getOption(opt)) {
+                for (auto const& copts : co_list) {
+                    OptionDescriptor desc = copts->get(vendor_id, opt);
+                    if (desc.option_) {
+                        vendor_rsp->addOption(desc.option_);
+                        added = true;
+                        break;
+                    }
+                }
+            }
+        }
+
+        // If we added some sub-options and the vendor opts option is not in
+        // the response already, then add it.
+        if (added && (vendor_rsps.count(vendor_id) == 0)) {
+            resp->Pkt::addOption(vendor_rsp);
+        }
+    }
+}
+
+void
+Dhcpv4Srv::appendBasicOptions(Dhcpv4Exchange& ex) {
+    // Identify options that we always want to send to the
+    // client (if they are configured).
+    static const std::vector<uint16_t> required_options = {
+        DHO_ROUTERS,
+        DHO_DOMAIN_NAME_SERVERS,
+        DHO_DOMAIN_NAME,
+        DHO_DHCP_SERVER_IDENTIFIER };
+
+    // Get the subnet.
+    Subnet4Ptr subnet = ex.getContext()->subnet_;
+    if (!subnet) {
+        return;
+    }
+
+    // Unlikely short cut
+    const CfgOptionList& co_list = ex.getCfgOptionList();
+    if (co_list.empty()) {
+        return;
+    }
+
+    Pkt4Ptr resp = ex.getResponse();
+
+    // Try to find all 'required' options in the outgoing
+    // message. Those that are not present will be added.
+    for (auto const& required : required_options) {
+        OptionPtr opt = resp->getOption(required);
+        if (!opt) {
+            // Check whether option has been configured.
+            for (auto const& copts : co_list) {
+                OptionDescriptor desc = copts->get(DHCP4_OPTION_SPACE, required);
+                if (desc.option_) {
+                    resp->addOption(desc.option_);
+                    break;
+                }
+            }
+        }
+    }
+}
+
+void
+Dhcpv4Srv::processClientName(Dhcpv4Exchange& ex) {
+    // It is possible that client has sent both Client FQDN and Hostname
+    // option. In that the server should prefer Client FQDN option and
+    // ignore the Hostname option.
+    try {
+        Pkt4Ptr query = ex.getQuery();
+        Pkt4Ptr resp = ex.getResponse();
+        Option4ClientFqdnPtr fqdn = boost::dynamic_pointer_cast<Option4ClientFqdn>
+            (query->getOption(DHO_FQDN));
+        if (fqdn) {
+            LOG_DEBUG(ddns4_logger, DBG_DHCP4_DETAIL, DHCP4_CLIENT_FQDN_PROCESS)
+                .arg(query->getLabel());
+            processClientFqdnOption(ex);
+
+        } else {
+            LOG_DEBUG(ddns4_logger, DBG_DHCP4_DETAIL,
+                      DHCP4_CLIENT_HOSTNAME_PROCESS)
+                    .arg(query->getLabel());
+            processHostnameOption(ex);
+        }
+
+        // Based on the output option added to the response above, we figure out
+        // the values for the hostname and dns flags to set in the context.  These
+        // will be used to populate the lease.
+        std::string hostname;
+        bool fqdn_fwd = false;
+        bool fqdn_rev = false;
+
+
+        OptionStringPtr opt_hostname;
+        fqdn = boost::dynamic_pointer_cast<Option4ClientFqdn>(resp->getOption(DHO_FQDN));
+        if (fqdn) {
+            hostname = fqdn->getDomainName();
+            CfgMgr::instance().getD2ClientMgr().getUpdateDirections(*fqdn, fqdn_fwd, fqdn_rev);
+        } else {
+            opt_hostname = boost::dynamic_pointer_cast<OptionString>
+                           (resp->getOption(DHO_HOST_NAME));
+
+            if (opt_hostname) {
+                hostname = opt_hostname->getValue();
+                // DHO_HOST_NAME is string option which cannot be blank,
+                // we use "." to know we should replace it with a fully
+                // generated name. The local string variable needs to be
+                // blank in logic below.
+                if (hostname == ".") {
+                    hostname = "";
+                }
+
+                /// @todo It could be configurable what sort of updates the
+                /// server is doing when Hostname option was sent.
+                if (ex.getContext()->getDdnsParams()->getEnableUpdates()) {
+                    fqdn_fwd = true;
+                    fqdn_rev = true;
+                }
+            }
+        }
+
+        // Optionally, call a hook that may possibly override the decisions made
+        // earlier.
+        if (HooksManager::calloutsPresent(Hooks.hook_index_ddns4_update_)) {
+            CalloutHandlePtr callout_handle = getCalloutHandle(query);
+
+            // Use the RAII wrapper to make sure that the callout handle state is
+            // reset when this object goes out of scope. All hook points must do
+            // it to prevent possible circular dependency between the callout
+            // handle and its arguments.
+            ScopedCalloutHandleState callout_handle_state(callout_handle);
+
+            // Setup the callout arguments.
+            Subnet4Ptr subnet = ex.getContext()->subnet_;
+            callout_handle->setArgument("query4", query);
+            callout_handle->setArgument("response4", resp);
+            callout_handle->setArgument("subnet4", subnet);
+            callout_handle->setArgument("hostname", hostname);
+            callout_handle->setArgument("fwd-update", fqdn_fwd);
+            callout_handle->setArgument("rev-update", fqdn_rev);
+            callout_handle->setArgument("ddns-params", ex.getContext()->getDdnsParams());
+
+            // Call callouts
+            HooksManager::callCallouts(Hooks.hook_index_ddns4_update_, *callout_handle);
+
+            // Let's get the parameters returned by hook.
+            string hook_hostname;
+            bool hook_fqdn_fwd = false;
+            bool hook_fqdn_rev = false;
+            callout_handle->getArgument("hostname", hook_hostname);
+            callout_handle->getArgument("fwd-update", hook_fqdn_fwd);
+            callout_handle->getArgument("rev-update", hook_fqdn_rev);
+
+            // If there's anything changed by the hook, log it and then update
+            // the parameters.
+            if ((hostname != hook_hostname) || (fqdn_fwd != hook_fqdn_fwd) ||
+                (fqdn_rev != hook_fqdn_rev)) {
+                LOG_DEBUG(hooks_logger, DBGLVL_PKT_HANDLING, DHCP4_HOOK_DDNS_UPDATE)
+                    .arg(hostname).arg(hook_hostname).arg(fqdn_fwd).arg(hook_fqdn_fwd)
+                    .arg(fqdn_rev).arg(hook_fqdn_rev);
+                hostname = hook_hostname;
+                fqdn_fwd = hook_fqdn_fwd;
+                fqdn_rev = hook_fqdn_rev;
+
+                // If there's an outbound host-name option in the response we
+                // need to updated it with the new host name.
+                OptionStringPtr hostname_opt = boost::dynamic_pointer_cast<OptionString>
+                                              (resp->getOption(DHO_HOST_NAME));
+                if (hostname_opt) {
+                    hostname_opt->setValue(hook_hostname);
+                }
+
+                // If there's an outbound FQDN option in the response we need
+                // to update it with the new host name.
+                Option4ClientFqdnPtr fqdn = boost::dynamic_pointer_cast<Option4ClientFqdn>
+                                            (resp->getOption(DHO_FQDN));
+                if (fqdn) {
+                    fqdn->setDomainName(hook_hostname, Option4ClientFqdn::FULL);
+                    // Hook disabled updates, Set flags back to client accordingly.
+                    fqdn->setFlag(Option4ClientFqdn::FLAG_S, 0);
+                    fqdn->setFlag(Option4ClientFqdn::FLAG_N, 1);
+                }
+            }
+        }
+
+        // Update the context
+        auto ctx = ex.getContext();
+        ctx->fwd_dns_update_ = fqdn_fwd;
+        ctx->rev_dns_update_ = fqdn_rev;
+        ctx->hostname_ = hostname;
+
+    } catch (const Exception& e) {
+        // In some rare cases it is possible that the client's name processing
+        // fails. For example, the Hostname option may be malformed, or there
+        // may be an error in the server's logic which would cause multiple
+        // attempts to add the same option to the response message. This
+        // error message aggregates all these errors so they can be diagnosed
+        // from the log. We don't want to throw an exception here because,
+        // it will impact the processing of the whole packet. We rather want
+        // the processing to continue, even if the client's name is wrong.
+        LOG_DEBUG(ddns4_logger, DBG_DHCP4_DETAIL_DATA, DHCP4_CLIENT_NAME_PROC_FAIL)
+            .arg(ex.getQuery()->getLabel())
+            .arg(e.what());
+    }
+}
+
+void
+Dhcpv4Srv::processClientFqdnOption(Dhcpv4Exchange& ex) {
+    // Obtain the FQDN option from the client's message.
+    Option4ClientFqdnPtr fqdn = boost::dynamic_pointer_cast<
+        Option4ClientFqdn>(ex.getQuery()->getOption(DHO_FQDN));
+
+    LOG_DEBUG(ddns4_logger, DBG_DHCP4_DETAIL_DATA, DHCP4_CLIENT_FQDN_DATA)
+        .arg(ex.getQuery()->getLabel())
+        .arg(fqdn->toText());
+
+    // Create the DHCPv4 Client FQDN Option to be included in the server's
+    // response to a client.
+    Option4ClientFqdnPtr fqdn_resp(new Option4ClientFqdn(*fqdn));
+
+    // Set the server S, N, and O flags based on client's flags and
+    // current configuration.
+    D2ClientMgr& d2_mgr = CfgMgr::instance().getD2ClientMgr();
+    d2_mgr.adjustFqdnFlags<Option4ClientFqdn>(*fqdn, *fqdn_resp,
+                                              *(ex.getContext()->getDdnsParams()));
+    // Carry over the client's E flag.
+    fqdn_resp->setFlag(Option4ClientFqdn::FLAG_E,
+                       fqdn->getFlag(Option4ClientFqdn::FLAG_E));
+
+    if (ex.getContext()->currentHost() &&
+        !ex.getContext()->currentHost()->getHostname().empty()) {
+        D2ClientMgr& d2_mgr = CfgMgr::instance().getD2ClientMgr();
+        fqdn_resp->setDomainName(d2_mgr.qualifyName(ex.getContext()->currentHost()->getHostname(),
+                                                    *(ex.getContext()->getDdnsParams()), true),
+                                 Option4ClientFqdn::FULL);
+
+    } else {
+        // Adjust the domain name based on domain name value and type sent by the
+        // client and current configuration.
+        d2_mgr.adjustDomainName<Option4ClientFqdn>(*fqdn, *fqdn_resp,
+                                                   *(ex.getContext()->getDdnsParams()));
+    }
+
+    // Add FQDN option to the response message. Note that, there may be some
+    // cases when server may choose not to include the FQDN option in a
+    // response to a client. In such cases, the FQDN should be removed from the
+    // outgoing message. In theory we could cease to include the FQDN option
+    // in this function until it is confirmed that it should be included.
+    // However, we include it here for simplicity. Functions used to acquire
+    // lease for a client will scan the response message for FQDN and if it
+    // is found they will take necessary actions to store the FQDN information
+    // in the lease database as well as to generate NameChangeRequests to DNS.
+    // If we don't store the option in the response message, we will have to
+    // propagate it in the different way to the functions which acquire the
+    // lease. This would require modifications to the API of this class.
+    LOG_DEBUG(ddns4_logger, DBG_DHCP4_DETAIL_DATA, DHCP4_RESPONSE_FQDN_DATA)
+        .arg(ex.getQuery()->getLabel())
+        .arg(fqdn_resp->toText());
+    ex.getResponse()->addOption(fqdn_resp);
+}
+
+void
+Dhcpv4Srv::processHostnameOption(Dhcpv4Exchange& ex) {
+    // Fetch D2 configuration.
+    D2ClientMgr& d2_mgr = CfgMgr::instance().getD2ClientMgr();
+
+    // Obtain the Hostname option from the client's message.
+    OptionStringPtr opt_hostname = boost::dynamic_pointer_cast<OptionString>
+        (ex.getQuery()->getOption(DHO_HOST_NAME));
+
+    if (opt_hostname) {
+        LOG_DEBUG(ddns4_logger, DBG_DHCP4_DETAIL_DATA, DHCP4_CLIENT_HOSTNAME_DATA)
+            .arg(ex.getQuery()->getLabel())
+            .arg(opt_hostname->getValue());
+    }
+
+    AllocEngine::ClientContext4Ptr ctx = ex.getContext();
+
+    // Hostname reservations take precedence over any other configuration,
+    // i.e. DDNS configuration.  If we have a reserved hostname we should
+    // use it and send it back.
+    if (ctx->currentHost() && !ctx->currentHost()->getHostname().empty()) {
+        // Qualify if there is a suffix configured.
+        std::string hostname = d2_mgr.qualifyName(ctx->currentHost()->getHostname(),
+                                                  *(ex.getContext()->getDdnsParams()), false);
+        // Convert it to lower case.
+        boost::algorithm::to_lower(hostname);
+        LOG_DEBUG(ddns4_logger, DBG_DHCP4_DETAIL_DATA, DHCP4_RESERVED_HOSTNAME_ASSIGNED)
+                .arg(ex.getQuery()->getLabel())
+                .arg(hostname);
+
+        // Add it to the response
+        OptionStringPtr opt_hostname_resp(new OptionString(Option::V4, DHO_HOST_NAME, hostname));
+        ex.getResponse()->addOption(opt_hostname_resp);
+
+        // We're done here.
+        return;
+    }
+
+    // There is no reservation for this client however there is still a
+    // possibility that we'll have to send hostname option to this client
+    // if the client has included hostname option or the configuration of
+    // the server requires that we send the option regardless.
+    D2ClientConfig::ReplaceClientNameMode replace_name_mode =
+        ex.getContext()->getDdnsParams()->getReplaceClientNameMode();
+
+    // If we don't have a hostname then either we'll supply it or do nothing.
+    if (!opt_hostname) {
+        // If we're configured to supply it then add it to the response.
+        // Use the root domain to signal later on that we should replace it.
+        if (replace_name_mode == D2ClientConfig::RCM_ALWAYS ||
+            replace_name_mode == D2ClientConfig::RCM_WHEN_NOT_PRESENT) {
+            LOG_DEBUG(ddns4_logger, DBG_DHCP4_DETAIL_DATA,
+                      DHCP4_GENERATE_FQDN)
+                .arg(ex.getQuery()->getLabel());
+            OptionStringPtr opt_hostname_resp(new OptionString(Option::V4,
+                                                               DHO_HOST_NAME,
+                                                               "."));
+            ex.getResponse()->addOption(opt_hostname_resp);
+        }
+
+        return;
+    }
+
+    // Client sent us a hostname option so figure out what to do with it.
+    LOG_DEBUG(ddns4_logger, DBG_DHCP4_DETAIL_DATA, DHCP4_CLIENT_HOSTNAME_DATA)
+        .arg(ex.getQuery()->getLabel())
+        .arg(opt_hostname->getValue());
+
+    std::string hostname = isc::util::str::trim(opt_hostname->getValue());
+    unsigned int label_count;
+
+    try  {
+        // Parsing into labels can throw on malformed content so we're
+        // going to explicitly catch that here.
+        label_count = OptionDataTypeUtil::getLabelCount(hostname);
+    } catch (const std::exception& exc) {
+        LOG_DEBUG(ddns4_logger, DBG_DHCP4_DETAIL, DHCP4_CLIENT_HOSTNAME_MALFORMED)
+            .arg(ex.getQuery()->getLabel())
+            .arg(exc.what());
+        return;
+    }
+
+    // The hostname option sent by the client should be at least 1 octet long.
+    // If it isn't we ignore this option. (Per RFC 2131, section 3.14)
+    /// @todo It would be more liberal to accept this and let it fall into
+    /// the case  of replace or less than two below.
+    if (label_count == 0) {
+        LOG_DEBUG(ddns4_logger, DBG_DHCP4_DETAIL, DHCP4_EMPTY_HOSTNAME)
+            .arg(ex.getQuery()->getLabel());
+        return;
+    }
+
+    // Stores the value we eventually use, so we can send it back.
+    OptionStringPtr opt_hostname_resp;
+
+    // The hostname option may be unqualified or fully qualified. The lab_count
+    // holds the number of labels for the name. The number of 1 means that
+    // there is only root label "." (even for unqualified names, as the
+    // getLabelCount function treats each name as a fully qualified one).
+    // By checking the number of labels present in the hostname we may infer
+    // whether client has sent the fully qualified or unqualified hostname.
+
+    if ((replace_name_mode == D2ClientConfig::RCM_ALWAYS ||
+         replace_name_mode == D2ClientConfig::RCM_WHEN_PRESENT)
+        || label_count < 2) {
+        // Set to root domain to signal later on that we should replace it.
+        // DHO_HOST_NAME is a string option which cannot be empty.
+        /// @todo We may want to reconsider whether it is appropriate for the
+        /// client to send a root domain name as a Hostname. There are
+        /// also extensions to the auto generation of the client's name,
+        /// e.g. conversion to the puny code which may be considered at some
+        /// point.
+        /// For now, we just remain liberal and expect that the DNS will handle
+        /// conversion if needed and possible.
+        opt_hostname_resp.reset(new OptionString(Option::V4, DHO_HOST_NAME, "."));
+    } else {
+        // Sanitize the name the client sent us, if we're configured to do so.
+        isc::util::str::StringSanitizerPtr sanitizer =
+            ex.getContext()->getDdnsParams()->getHostnameSanitizer();
+
+        if (sanitizer) {
+            hostname = sanitizer->scrub(hostname);
+        }
+
+        // Convert hostname to lower case.
+        boost::algorithm::to_lower(hostname);
+
+        if (label_count == 2) {
+            // If there are two labels, it means that the client has specified
+            // the unqualified name. We have to concatenate the unqualified name
+            // with the domain name. The false value passed as a second argument
+            // indicates that the trailing dot should not be appended to the
+            // hostname. We don't want to append the trailing dot because
+            // we don't know whether the hostname is partial or not and some
+            // clients do not handle the hostnames with the trailing dot.
+            opt_hostname_resp.reset(
+                new OptionString(Option::V4, DHO_HOST_NAME,
+                                 d2_mgr.qualifyName(hostname, *(ex.getContext()->getDdnsParams()),
+                                                    false)));
+        } else {
+            opt_hostname_resp.reset(new OptionString(Option::V4, DHO_HOST_NAME, hostname));
+        }
+    }
+
+    LOG_DEBUG(ddns4_logger, DBG_DHCP4_DETAIL_DATA, DHCP4_RESPONSE_HOSTNAME_DATA)
+        .arg(ex.getQuery()->getLabel())
+        .arg(opt_hostname_resp->getValue());
+    ex.getResponse()->addOption(opt_hostname_resp);
+}
+
+void
+Dhcpv4Srv::createNameChangeRequests(const Lease4Ptr& lease,
+                                    const Lease4Ptr& old_lease,
+                                    const DdnsParams& ddns_params) {
+    if (!lease) {
+        isc_throw(isc::Unexpected,
+                  "NULL lease specified when creating NameChangeRequest");
+    }
+
+    // Nothing to do if updates are not enabled.
+    if (!ddns_params.getEnableUpdates()) {
+        return;
+    }
+
+    if (!old_lease || ddns_params.getUpdateOnRenew() || !lease->hasIdenticalFqdn(*old_lease)) {
+        if (old_lease) {
+            // Queue's up a remove of the old lease's DNS (if needed)
+            queueNCR(CHG_REMOVE, old_lease);
+        }
+
+        // We may need to generate the NameChangeRequest for the new lease. It
+        // will be generated only if hostname is set and if forward or reverse
+        // update has been requested.
+        queueNCR(CHG_ADD, lease);
+    }
+}
+
+void
+Dhcpv4Srv::assignLease(Dhcpv4Exchange& ex) {
+    // Get the pointers to the query and the response messages.
+    Pkt4Ptr query = ex.getQuery();
+    Pkt4Ptr resp = ex.getResponse();
+
+    // Get the context.
+    AllocEngine::ClientContext4Ptr ctx = ex.getContext();
+
+    // Get the server identifier. It will be used to determine the state
+    // of the client.
+    OptionCustomPtr opt_serverid = boost::dynamic_pointer_cast<
+        OptionCustom>(query->getOption(DHO_DHCP_SERVER_IDENTIFIER));
+
+    // Check if the client has sent a requested IP address option or
+    // ciaddr.
+    OptionCustomPtr opt_requested_address = boost::dynamic_pointer_cast<
+        OptionCustom>(query->getOption(DHO_DHCP_REQUESTED_ADDRESS));
+    IOAddress hint(IOAddress::IPV4_ZERO_ADDRESS());
+    if (opt_requested_address) {
+        hint = opt_requested_address->readAddress();
+
+    } else if (!query->getCiaddr().isV4Zero()) {
+        hint = query->getCiaddr();
+
+    }
+
+    // "Fake" allocation is processing of DISCOVER message. We pretend to do an
+    // allocation, but we do not put the lease in the database. That is ok,
+    // because we do not guarantee that the user will get that exact lease. If
+    // the user selects this server to do actual allocation (i.e. sends REQUEST)
+    // it should include this hint. That will help us during the actual lease
+    // allocation.
+    bool fake_allocation = (query->getType() == DHCPDISCOVER);
+
+    // Subnet should have been already selected when the context was created.
+    Subnet4Ptr subnet = ctx->subnet_;
+
+    // This flag controls whether or not the server should respond to the clients
+    // in the INIT-REBOOT state. We will initialize it to a configured value only
+    // when the client is in that state.
+    auto authoritative = false;
+
+    // If there is no server id and there is a Requested IP Address option
+    // the client is in the INIT-REBOOT state in which the server has to
+    // determine whether the client's notion of the address is correct
+    // and whether the client is known, i.e., has a lease.
+    auto init_reboot = (!fake_allocation && !opt_serverid && opt_requested_address);
+    if (init_reboot) {
+        LOG_INFO(lease4_logger, DHCP4_INIT_REBOOT)
+            .arg(query->getLabel())
+            .arg(hint.toText());
+
+        // Find the authoritative flag configuration.
+        if (subnet) {
+            authoritative = subnet->getAuthoritative();
+        } else {
+            // If there is no subnet, use the global value.
+            auto flag = CfgMgr::instance().getCurrentCfg()->getConfiguredGlobals()->
+                get(CfgGlobals::AUTHORITATIVE);
+            if (flag && (flag->getType() == data::Element::boolean)) {
+                authoritative = flag->boolValue();
+            }
+        }
+    }
+
+    // If there is no subnet configuration for that client we ignore the
+    // request from the INIT-REBOOT client if we're not authoritative, because
+    // we don't know whether the network configuration is correct for this
+    // client. We return DHCPNAK if we're authoritative, though.
+    if (!subnet && (!init_reboot || authoritative)) {
+        // This particular client is out of luck today. We do not have
+        // information about the subnet he is connected to. This likely means
+        // misconfiguration of the server (or some relays).
+
+        // Perhaps this should be logged on some higher level?
+        LOG_ERROR(bad_packet4_logger, DHCP4_PACKET_NAK_0001)
+            .arg(query->getLabel())
+            .arg(query->getRemoteAddr().toText())
+            .arg(query->getName());
+        resp->setType(DHCPNAK);
+        resp->setYiaddr(IOAddress::IPV4_ZERO_ADDRESS());
+        return;
+    }
+
+    HWAddrPtr hwaddr = query->getHWAddr();
+
+    Subnet4Ptr original_subnet = subnet;
+
+    // Get client-id. It is not mandatory in DHCPv4.
+    ClientIdPtr client_id = ex.getContext()->clientid_;
+
+    // In the INIT-REBOOT state, a client remembering its previously assigned
+    // address is trying to confirm whether or not this address is still usable.
+    if (init_reboot) {
+        Lease4Ptr lease;
+
+        auto const& classes = query->getClasses();
+
+        // We used to issue a separate query (two actually: one for client-id
+        // and another one for hw-addr for) each subnet in the shared network.
+        // That was horribly inefficient if the client didn't have any lease
+        // (or there were many subnets and the client happened to be in one
+        // of the last subnets).
+        //
+        // We now issue at most two queries: get all the leases for specific
+        // client-id and then get all leases for specific hw-address.
+        if (original_subnet && client_id) {
+
+            // Get all the leases for this client-id
+            Lease4Collection leases_client_id = LeaseMgrFactory::instance().getLease4(*client_id);
+            if (!leases_client_id.empty()) {
+                Subnet4Ptr s = original_subnet;
+
+                // Among those returned try to find a lease that belongs to
+                // current shared network.
+                while (s) {
+                    for (auto l = leases_client_id.begin(); l != leases_client_id.end(); ++l) {
+                        if ((*l)->subnet_id_ == s->getID()) {
+                            lease = *l;
+                            break;
+                        }
+                    }
+
+                    if (lease) {
+                        break;
+
+                    } else {
+                        s = s->getNextSubnet(original_subnet, classes);
+                    }
+                }
+            }
+        }
+
+        // If we haven't found a lease yet, try again by hardware-address.
+        // The logic is the same.
+        if (original_subnet && !lease && hwaddr) {
+
+            // Get all leases for this particular hw-address.
+            Lease4Collection leases_hwaddr = LeaseMgrFactory::instance().getLease4(*hwaddr);
+            if (!leases_hwaddr.empty()) {
+                Subnet4Ptr s = original_subnet;
+
+                // Pick one that belongs to a subnet in this shared network.
+                while (s) {
+                    for (auto l = leases_hwaddr.begin(); l != leases_hwaddr.end(); ++l) {
+                        if ((*l)->subnet_id_ == s->getID()) {
+                            lease = *l;
+                            break;
+                        }
+                    }
+
+                    if (lease) {
+                        break;
+
+                    } else {
+                        s = s->getNextSubnet(original_subnet, classes);
+                    }
+                }
+            }
+        }
+
+        // Check the first error case: unknown client. We check this before
+        // validating the address sent because we don't want to respond if
+        // we don't know this client, except if we're authoritative.
+        bool known_client = lease && lease->belongsToClient(hwaddr, client_id);
+        if (!authoritative && !known_client) {
+            LOG_DEBUG(bad_packet4_logger, DBG_DHCP4_DETAIL,
+                      DHCP4_NO_LEASE_INIT_REBOOT)
+                .arg(query->getLabel())
+                .arg(hint.toText());
+
+            ex.deleteResponse();
+            return;
+        }
+
+        // If we know this client, check if his notion of the IP address is
+        // correct, if we don't know him, check if we are authoritative.
+        if ((known_client && (lease->addr_ != hint)) ||
+            (!known_client && authoritative) ||
+            (!original_subnet)) {
+            LOG_DEBUG(bad_packet4_logger, DBG_DHCP4_DETAIL,
+                      DHCP4_PACKET_NAK_0002)
+                .arg(query->getLabel())
+                .arg(hint.toText());
+
+            resp->setType(DHCPNAK);
+            resp->setYiaddr(IOAddress::IPV4_ZERO_ADDRESS());
+            return;
+        }
+    }
+
+    CalloutHandlePtr callout_handle = getCalloutHandle(query);
+
+    // We need to set these values in the context as they haven't been set yet.
+    ctx->requested_address_ = hint;
+    ctx->fake_allocation_ = fake_allocation;
+    ctx->callout_handle_ = callout_handle;
+
+    // If client query contains an FQDN or Hostname option, server
+    // should respond to the client with the appropriate FQDN or Hostname
+    // option to indicate if it takes responsibility for the DNS updates.
+    // This is also the source for the hostname and dns flags that are
+    // initially added to the lease.  In most cases, this information is
+    // good now.  If we end up changing subnets in allocation we'll have to
+    // do it again and then update the lease.
+    processClientName(ex);
+
+    // Get a lease.
+    Lease4Ptr lease = alloc_engine_->allocateLease4(*ctx);
+
+    // Tracks whether or not the client name (FQDN or host) has changed since
+    // the lease was allocated.
+    bool client_name_changed = false;
+
+    // Subnet may be modified by the allocation engine, if the initial subnet
+    // belongs to a shared network.
+    if (subnet && ctx->subnet_ && subnet->getID() != ctx->subnet_->getID()) {
+        SharedNetwork4Ptr network;
+        subnet->getSharedNetwork(network);
+        LOG_DEBUG(packet4_logger, DBG_DHCP4_BASIC_DATA, DHCP4_SUBNET_DYNAMICALLY_CHANGED)
+                .arg(query->getLabel())
+                .arg(subnet->toText())
+                .arg(ctx->subnet_->toText())
+                .arg(network ? network->getName() : "<no network?>");
+
+        subnet = ctx->subnet_;
+
+        if (lease) {
+            // We changed subnets and that means DDNS parameters might be different
+            // so we need to rerun client name processing logic.  Arguably we could
+            // compare DDNS parameters for both subnets and then decide if we need
+            // to rerun the name logic, but that's not likely to be any faster than
+            // just re-running the name logic.  @todo When inherited parameter
+            // performance is improved this argument could be revisited.
+            // Another case is the new subnet has a reserved hostname.
+
+            // First, we need to remove the prior values from the response and reset
+            // those in context, to give processClientName a clean slate.
+            resp->delOption(DHO_FQDN);
+            resp->delOption(DHO_HOST_NAME);
+            ctx->hostname_ = "";
+            ctx->fwd_dns_update_  = false;
+            ctx->rev_dns_update_ = false;
+
+            // Regenerate the name and dns flags.
+            processClientName(ex);
+
+            // If the results are different from the values already on the
+            // lease, flag it so the lease gets updated down below.
+            if ((lease->hostname_ != ctx->hostname_) ||
+                (lease->fqdn_fwd_ != ctx->fwd_dns_update_) ||
+                (lease->fqdn_rev_ != ctx->rev_dns_update_)) {
+                lease->hostname_ = ctx->hostname_;
+                lease->fqdn_fwd_ = ctx->fwd_dns_update_;
+                lease->fqdn_rev_ = ctx->rev_dns_update_;
+                client_name_changed = true;
+            }
+        }
+    }
+
+    if (lease) {
+        // We have a lease! Let's set it in the packet and send it back to
+        // the client.
+        if (fake_allocation) {
+            LOG_INFO(lease4_logger, DHCP4_LEASE_ADVERT)
+                .arg(query->getLabel())
+                .arg(lease->addr_.toText());
+        } else {
+            LOG_INFO(lease4_logger, DHCP4_LEASE_ALLOC)
+                .arg(query->getLabel())
+                .arg(lease->addr_.toText())
+                .arg(Lease::lifetimeToText(lease->valid_lft_));
+        }
+
+        // We're logging this here, because this is the place where we know
+        // which subnet has been actually used for allocation. If the
+        // client identifier matching is disabled, we want to make sure that
+        // the user is notified.
+        if (!ctx->subnet_->getMatchClientId()) {
+            LOG_DEBUG(dhcp4_logger, DBG_DHCP4_DETAIL, DHCP4_CLIENTID_IGNORED_FOR_LEASES)
+                .arg(ctx->query_->getLabel())
+                .arg(ctx->subnet_->getID());
+        }
+
+        resp->setYiaddr(lease->addr_);
+
+        /// @todo The server should check what ciaddr the client has supplied
+        /// in ciaddr. Currently the ciaddr is ignored except for the subnet
+        /// selection. If the client supplied an invalid address, the server
+        /// will also return an invalid address here.
+        if (!fake_allocation) {
+            // If this is a renewing client it will set a ciaddr which the
+            // server may include in the response. If this is a new allocation
+            // the client will set ciaddr to 0 and this will also be propagated
+            // to the server's resp.
+            resp->setCiaddr(query->getCiaddr());
+        }
+
+        // We may need to update FQDN or hostname if the server is to generate
+        // a new name from the allocated IP address or if the allocation engine
+        // switched to a different subnet within a shared network.
+        postAllocateNameUpdate(ctx, lease, query, resp, client_name_changed);
+
+        // Reuse the lease if possible.
+        if (lease->reuseable_valid_lft_ > 0) {
+            lease->valid_lft_ = lease->reuseable_valid_lft_;
+            LOG_INFO(lease4_logger, DHCP4_LEASE_REUSE)
+                .arg(query->getLabel())
+                .arg(lease->addr_.toText())
+                .arg(Lease::lifetimeToText(lease->valid_lft_));
+
+            // Increment the reuse statistics.
+            StatsMgr::instance().addValue("v4-lease-reuses", int64_t(1));
+            StatsMgr::instance().addValue(StatsMgr::generateName("subnet", lease->subnet_id_,
+                                                                 "v4-lease-reuses"),
+                                          int64_t(1));
+        }
+
+        // IP Address Lease time (type 51)
+        // If we're not allocating on discover  then we just sent the lifetime on the lease.
+        // Otherwise (i.e. offer_lft > 0), the lease's lifetime has been set to offer_lft but
+        // we want to send the client the proper valid lifetime so we have to fetch it.
+        auto send_lft = (ctx->offer_lft_ ? AllocEngine::getValidLft(*ctx) : lease->valid_lft_);
+        OptionPtr opt(new OptionUint32(Option::V4, DHO_DHCP_LEASE_TIME, send_lft));
+
+        resp->addOption(opt);
+
+        // Subnet mask (type 1)
+        resp->addOption(getNetmaskOption(subnet));
+
+        // Set T1 and T2 per configuration.
+        setTeeTimes(lease, subnet, resp);
+
+        // Create NameChangeRequests if this is a real allocation.
+        if (!fake_allocation) {
+            try {
+                createNameChangeRequests(lease, ctx->old_lease_,
+                                         *ex.getContext()->getDdnsParams());
+            } catch (const Exception& ex) {
+                LOG_ERROR(ddns4_logger, DHCP4_NCR_CREATION_FAILED)
+                    .arg(query->getLabel())
+                    .arg(ex.what());
+            }
+        }
+
+    } else {
+        // Allocation engine did not allocate a lease. The engine logged
+        // cause of that failure.
+        if (ctx->unknown_requested_addr_) {
+            Subnet4Ptr s = original_subnet;
+            // Address might have been rejected via class guard (i.e. not
+            // allowed for this client). We need to determine if we truly
+            // do not know about the address or whether this client just
+            // isn't allowed to have that address. We should only DHCPNAK
+            // For the latter.
+            while (s) {
+                if (s->inPool(Lease::TYPE_V4, hint)) {
+                    break;
+                }
+
+                s = s->getNextSubnet(original_subnet);
+            }
+
+            // If we didn't find a subnet, it's not an address we know about
+            // so we drop the DHCPNAK.
+            if (!s) {
+                LOG_DEBUG(bad_packet4_logger, DBG_DHCP4_DETAIL,
+                          DHCP4_UNKNOWN_ADDRESS_REQUESTED)
+                          .arg(query->getLabel())
+                          .arg(query->getCiaddr().toText())
+                          .arg(opt_requested_address ?
+                          opt_requested_address->readAddress().toText() : "(no address)");
+                ex.deleteResponse();
+                return;
+            }
+        }
+
+        LOG_DEBUG(bad_packet4_logger, DBG_DHCP4_DETAIL, fake_allocation ?
+                  DHCP4_PACKET_NAK_0003 : DHCP4_PACKET_NAK_0004)
+            .arg(query->getLabel())
+            .arg(query->getCiaddr().toText())
+            .arg(opt_requested_address ?
+                 opt_requested_address->readAddress().toText() : "(no address)");
+
+        resp->setType(DHCPNAK);
+        resp->setYiaddr(IOAddress::IPV4_ZERO_ADDRESS());
+
+        resp->delOption(DHO_FQDN);
+        resp->delOption(DHO_HOST_NAME);
+    }
+}
+
+void
+Dhcpv4Srv::postAllocateNameUpdate(const AllocEngine::ClientContext4Ptr& ctx, const Lease4Ptr& lease,
+                                 const Pkt4Ptr& query, const Pkt4Ptr& resp, bool client_name_changed) {
+    // We may need to update FQDN or hostname if the server is to generate
+    // new name from the allocated IP address or if the allocation engine
+    // has switched to a different subnet within a shared network.  Get
+    // FQDN and hostname options from the response.
+    OptionStringPtr opt_hostname;
+    Option4ClientFqdnPtr fqdn = boost::dynamic_pointer_cast<
+                Option4ClientFqdn>(resp->getOption(DHO_FQDN));
+    if (!fqdn) {
+        opt_hostname = boost::dynamic_pointer_cast<OptionString>(resp->getOption(DHO_HOST_NAME));
+        if (!opt_hostname) {
+            // We don't have either one, nothing to do.
+            return;
+        }
+    }
+
+    // Empty hostname on the lease means we need to generate it.
+    if (lease->hostname_.empty()) {
+        // Note that if we have received the hostname option, rather than
+        // Client FQDN the trailing dot is not appended to the generated
+        // hostname because some clients don't handle the trailing dot in
+        // the hostname. Whether the trailing dot is appended or not is
+        // controlled by the second argument to the generateFqdn().
+        lease->hostname_ = CfgMgr::instance().getD2ClientMgr()
+                    .generateFqdn(lease->addr_, *(ctx->getDdnsParams()), static_cast<bool>(fqdn));
+
+        LOG_DEBUG(ddns4_logger, DBG_DHCP4_DETAIL, DHCP4_RESPONSE_HOSTNAME_GENERATE)
+            .arg(query->getLabel())
+            .arg(lease->hostname_);
+
+        client_name_changed = true;
+    }
+
+    if (client_name_changed) {
+        // The operations below are rather safe, but we want to catch
+        // any potential exceptions (e.g. invalid lease database backend
+        // implementation) and log an error.
+        try {
+            /// TKM - do this on committed-discover
+            if (!ctx->fake_allocation_ || (ctx->offer_lft_ > 0)) {
+                // The lease can't be reused.
+                lease->reuseable_valid_lft_ = 0;
+
+                // The lease update should be safe, because the lease should
+                // be already in the database. In most cases the exception
+                // would be thrown if the lease was missing.
+                LeaseMgrFactory::instance().updateLease4(lease);
+            }
+
+            // The name update in the outbound option should be also safe,
+            // because the generated name is well formed.
+            if (fqdn) {
+                fqdn->setDomainName(lease->hostname_, Option4ClientFqdn::FULL);
+            } else {
+                opt_hostname->setValue(lease->hostname_);
+            }
+        } catch (const Exception& ex) {
+            LOG_ERROR(ddns4_logger, DHCP4_POST_ALLOCATION_NAME_UPDATE_FAIL)
+                .arg(query->getLabel())
+                .arg(lease->hostname_)
+                .arg(ex.what());
+        }
+    }
+}
+
+/// @todo This logic to be modified if we decide to support infinite lease times.
+void
+Dhcpv4Srv::setTeeTimes(const Lease4Ptr& lease, const Subnet4Ptr& subnet, Pkt4Ptr resp) {
+
+    uint32_t t2_time = 0;
+    // If T2 is explicitly configured we'll use try value.
+    if (!subnet->getT2().unspecified()) {
+        t2_time = subnet->getT2();
+    } else if (subnet->getCalculateTeeTimes()) {
+        // Calculating tee times is enabled, so calculated it.
+        t2_time = static_cast<uint32_t>(round(subnet->getT2Percent() * (lease->valid_lft_)));
+    }
+
+    // Send the T2 candidate value only if it's sane: to be sane it must be less than
+    // the valid life time.
+    uint32_t timer_ceiling = lease->valid_lft_;
+    if (t2_time > 0 && t2_time < timer_ceiling) {
+        OptionUint32Ptr t2(new OptionUint32(Option::V4, DHO_DHCP_REBINDING_TIME, t2_time));
+        resp->addOption(t2);
+        // When we send T2, timer ceiling for T1 becomes T2.
+        timer_ceiling = t2_time;
+    }
+
+    uint32_t t1_time = 0;
+    // If T1 is explicitly configured we'll use try value.
+    if (!subnet->getT1().unspecified()) {
+        t1_time = subnet->getT1();
+    } else if (subnet->getCalculateTeeTimes()) {
+        // Calculating tee times is enabled, so calculate it.
+        t1_time = static_cast<uint32_t>(round(subnet->getT1Percent() * (lease->valid_lft_)));
+    }
+
+    // Send T1 if it's sane: If we sent T2, T1 must be less than that.  If not it must be
+    // less than the valid life time.
+    if (t1_time > 0 && t1_time < timer_ceiling) {
+        OptionUint32Ptr t1(new OptionUint32(Option::V4, DHO_DHCP_RENEWAL_TIME, t1_time));
+        resp->addOption(t1);
+    }
+}
+
+uint16_t
+Dhcpv4Srv::checkRelayPort(const Dhcpv4Exchange& ex) {
+
+    // Look for a relay-port RAI sub-option in the query.
+    const Pkt4Ptr& query = ex.getQuery();
+    const OptionPtr& rai = query->getOption(DHO_DHCP_AGENT_OPTIONS);
+    if (rai && rai->getOption(RAI_OPTION_RELAY_PORT)) {
+        // Got the sub-option so use the remote port set by the relay.
+        return (query->getRemotePort());
+    }
+    return (0);
+}
+
+void
+Dhcpv4Srv::adjustIfaceData(Dhcpv4Exchange& ex) {
+    adjustRemoteAddr(ex);
+
+    // Initialize the pointers to the client's message and the server's
+    // response.
+    Pkt4Ptr query = ex.getQuery();
+    Pkt4Ptr response = ex.getResponse();
+
+    // The DHCPINFORM is generally unicast to the client. The only situation
+    // when the server is unable to unicast to the client is when the client
+    // doesn't include ciaddr and the message is relayed. In this case the
+    // server has to reply via relay agent. For other messages we send back
+    // through relay if message is relayed, and unicast to the client if the
+    // message is not relayed.
+    // If client port was set from the command line enforce all responses
+    // to it. Of course it is only for testing purposes.
+    // Note that the call to this function may throw if invalid combination
+    // of hops and giaddr is found (hops = 0 if giaddr = 0 and hops != 0 if
+    // giaddr != 0). The exception will propagate down and eventually cause the
+    // packet to be discarded.
+    if (client_port_) {
+        response->setRemotePort(client_port_);
+    } else if (((query->getType() == DHCPINFORM) &&
+         ((!query->getCiaddr().isV4Zero()) ||
+          (!query->isRelayed() && !query->getRemoteAddr().isV4Zero()))) ||
+        ((query->getType() != DHCPINFORM) && !query->isRelayed())) {
+        response->setRemotePort(DHCP4_CLIENT_PORT);
+
+    } else {
+        // RFC 8357 section 5.1
+        uint16_t relay_port = checkRelayPort(ex);
+        response->setRemotePort(relay_port ? relay_port : DHCP4_SERVER_PORT);
+    }
+
+    CfgIfacePtr cfg_iface = CfgMgr::instance().getCurrentCfg()->getCfgIface();
+    if (query->isRelayed() &&
+        (cfg_iface->getSocketType() == CfgIface::SOCKET_UDP) &&
+        (cfg_iface->getOutboundIface() == CfgIface::USE_ROUTING)) {
+
+        // Mark the response to follow routing
+        response->setLocalAddr(IOAddress::IPV4_ZERO_ADDRESS());
+        response->resetIndex();
+        // But keep the interface name
+        response->setIface(query->getIface());
+
+    } else {
+
+        IOAddress local_addr = query->getLocalAddr();
+
+        // In many cases the query is sent to a broadcast address. This address
+        // appears as a local address in the query message. We can't simply copy
+        // this address to a response message and use it as a source address.
+        // Instead we will need to use the address assigned to the interface
+        // on which the query has been received. In other cases, we will just
+        // use this address as a source address for the response.
+        // Do the same for DHCPv4-over-DHCPv6 exchanges.
+        if (local_addr.isV4Bcast() || query->isDhcp4o6()) {
+            local_addr = IfaceMgr::instance().getSocket(query).addr_;
+        }
+
+        // We assume that there is an appropriate socket bound to this address
+        // and that the address is correct. This is safe assumption because
+        // the local address of the query is set when the query is received.
+        // The query sent to an incorrect address wouldn't have been received.
+        // However, if socket is closed for this address between the reception
+        // of the query and sending a response, the IfaceMgr should detect it
+        // and return an error.
+        response->setLocalAddr(local_addr);
+        // In many cases the query is sent to a broadcast address. This address
+        // appears as a local address in the query message. Therefore we can't
+        // simply copy local address from the query and use it as a source
+        // address for the response. Instead, we have to check what address our
+        // socket is bound to and use it as a source address. This operation
+        // may throw if for some reason the socket is closed.
+        /// @todo Consider an optimization that we use local address from
+        /// the query if this address is not broadcast.
+        response->setIndex(query->getIndex());
+        response->setIface(query->getIface());
+    }
+
+    if (server_port_) {
+        response->setLocalPort(server_port_);
+    } else {
+        response->setLocalPort(DHCP4_SERVER_PORT);
+    }
+}
+
+void
+Dhcpv4Srv::adjustRemoteAddr(Dhcpv4Exchange& ex) {
+    // Initialize the pointers to the client's message and the server's
+    // response.
+    Pkt4Ptr query = ex.getQuery();
+    Pkt4Ptr response = ex.getResponse();
+
+    // DHCPv4-over-DHCPv6 is simple
+    if (query->isDhcp4o6()) {
+        response->setRemoteAddr(query->getRemoteAddr());
+        return;
+    }
+
+    // The DHCPINFORM is slightly different than other messages in a sense
+    // that the server should always unicast the response to the ciaddr.
+    // It appears however that some clients don't set the ciaddr. We still
+    // want to provision these clients and we do what we can't to send the
+    // packet to the address where client can receive it.
+    if (query->getType() == DHCPINFORM) {
+        // If client adheres to RFC2131 it will set the ciaddr and in this
+        // case we always unicast our response to this address.
+        if (!query->getCiaddr().isV4Zero()) {
+            response->setRemoteAddr(query->getCiaddr());
+
+        // If we received DHCPINFORM via relay and the ciaddr is not set we
+        // will try to send the response via relay. The caveat is that the
+        // relay will not have any idea where to forward the packet because
+        // the yiaddr is likely not set. So, the broadcast flag is set so
+        // as the response may be broadcast.
+        } else if (query->isRelayed()) {
+            response->setRemoteAddr(query->getGiaddr());
+            response->setFlags(response->getFlags() | BOOTP_BROADCAST);
+
+        // If there is no ciaddr and no giaddr the only thing we can do is
+        // to use the source address of the packet.
+        } else {
+            response->setRemoteAddr(query->getRemoteAddr());
+        }
+        // Remote address is now set so return.
+        return;
+    }
+
+    // If received relayed message, server responds to the relay address.
+    if (query->isRelayed()) {
+        // The client should set the ciaddr when sending the DHCPINFORM
+        // but in case he didn't, the relay may not be able to determine the
+        // address of the client, because yiaddr is not set when responding
+        // to Confirm and the only address available was the source address
+        // of the client. The source address is however not used here because
+        // the message is relayed. Therefore, we set the BROADCAST flag so
+        // as the relay can broadcast the packet.
+        if ((query->getType() == DHCPINFORM) &&
+            query->getCiaddr().isV4Zero()) {
+            response->setFlags(BOOTP_BROADCAST);
+        }
+        response->setRemoteAddr(query->getGiaddr());
+
+    // If giaddr is 0 but client set ciaddr, server should unicast the
+    // response to ciaddr.
+    } else if (!query->getCiaddr().isV4Zero()) {
+        response->setRemoteAddr(query->getCiaddr());
+
+    // We can't unicast the response to the client when sending DHCPNAK,
+    // because we haven't allocated address for him. Therefore,
+    // DHCPNAK is broadcast.
+    } else if (response->getType() == DHCPNAK) {
+        response->setRemoteAddr(IOAddress::IPV4_BCAST_ADDRESS());
+
+    // If yiaddr is set it means that we have created a lease for a client.
+    } else if (!response->getYiaddr().isV4Zero()) {
+        // If the broadcast bit is set in the flags field, we have to
+        // send the response to broadcast address. Client may have requested it
+        // because it doesn't support reception of messages on the interface
+        // which doesn't have an address assigned. The other case when response
+        // must be broadcasted is when our server does not support responding
+        // directly to a client without address assigned.
+        const bool bcast_flag = ((query->getFlags() & Pkt4::FLAG_BROADCAST_MASK) != 0);
+        if (!IfaceMgr::instance().isDirectResponseSupported() || bcast_flag) {
+            response->setRemoteAddr(IOAddress::IPV4_BCAST_ADDRESS());
+
+        // Client cleared the broadcast bit and we support direct responses
+        // so we should unicast the response to a newly allocated address -
+        // yiaddr.
+        } else {
+            response->setRemoteAddr(response ->getYiaddr());
+
+        }
+
+    // In most cases, we should have the remote address found already. If we
+    // found ourselves at this point, the rational thing to do is to respond
+    // to the address we got the query from.
+    } else {
+        response->setRemoteAddr(query->getRemoteAddr());
+    }
+
+    // For testing *only*.
+    if (getSendResponsesToSource()) {
+        response->setRemoteAddr(query->getRemoteAddr());
+    }
+}
+
+void
+Dhcpv4Srv::setFixedFields(Dhcpv4Exchange& ex) {
+    Pkt4Ptr query = ex.getQuery();
+    Pkt4Ptr response = ex.getResponse();
+
+    // Step 1: Start with fixed fields defined on subnet level.
+    Subnet4Ptr subnet = ex.getContext()->subnet_;
+    if (subnet) {
+        IOAddress subnet_next_server = subnet->getSiaddr();
+        if (!subnet_next_server.isV4Zero()) {
+            response->setSiaddr(subnet_next_server);
+        }
+
+        const string& sname = subnet->getSname();
+        if (!sname.empty()) {
+            // Converting string to (const uint8_t*, size_t len) format is
+            // tricky. reinterpret_cast is not the most elegant solution,
+            // but it does avoid us making unnecessary copy. We will convert
+            // sname and file fields in Pkt4 to string one day and life
+            // will be easier.
+            response->setSname(reinterpret_cast<const uint8_t*>(sname.c_str()),
+                               sname.size());
+        }
+
+        const string& filename = subnet->getFilename();
+        if (!filename.empty()) {
+            // Converting string to (const uint8_t*, size_t len) format is
+            // tricky. reinterpret_cast is not the most elegant solution,
+            // but it does avoid us making unnecessary copy. We will convert
+            // sname and file fields in Pkt4 to string one day and life
+            // will be easier.
+            response->setFile(reinterpret_cast<const uint8_t*>(filename.c_str()),
+                              filename.size());
+        }
+    }
+
+    // Step 2: Try to set the values based on classes.
+    // Any values defined in classes will override those from subnet level.
+    const ClientClasses classes = query->getClasses();
+    if (!classes.empty()) {
+
+        // Let's get class definitions
+        const ClientClassDictionaryPtr& dict =
+            CfgMgr::instance().getCurrentCfg()->getClientClassDictionary();
+
+        // Now we need to iterate over the classes assigned to the
+        // query packet and find corresponding class definitions for it.
+        // We want the first value found for each field.  We track how
+        // many we've found so we can stop if we have all three.
+        IOAddress next_server = IOAddress::IPV4_ZERO_ADDRESS();
+        string sname;
+        string filename;
+        size_t found_cnt = 0;  // How many fields we have found.
+        for (ClientClasses::const_iterator name = classes.cbegin();
+             name != classes.cend() && found_cnt < 3; ++name) {
+
+            ClientClassDefPtr cl = dict->findClass(*name);
+            if (!cl) {
+                // Let's skip classes that don't have definitions. Currently
+                // these are automatic classes VENDOR_CLASS_something, but there
+                // may be other classes assigned under other circumstances, e.g.
+                // by hooks.
+                continue;
+            }
+
+            if (next_server == IOAddress::IPV4_ZERO_ADDRESS()) {
+                next_server = cl->getNextServer();
+                if (!next_server.isV4Zero()) {
+                    response->setSiaddr(next_server);
+                    found_cnt++;
+                }
+            }
+
+            if (sname.empty()) {
+                sname = cl->getSname();
+                if (!sname.empty()) {
+                    // Converting string to (const uint8_t*, size_t len) format is
+                    // tricky. reinterpret_cast is not the most elegant solution,
+                    // but it does avoid us making unnecessary copy. We will convert
+                    // sname and file fields in Pkt4 to string one day and life
+                    // will be easier.
+                    response->setSname(reinterpret_cast<const uint8_t*>(sname.c_str()),
+                                       sname.size());
+                    found_cnt++;
+                }
+            }
+
+            if (filename.empty()) {
+                filename = cl->getFilename();
+                if (!filename.empty()) {
+                    // Converting string to (const uint8_t*, size_t len) format is
+                    // tricky. reinterpret_cast is not the most elegant solution,
+                    // but it does avoid us making unnecessary copy. We will convert
+                    // sname and file fields in Pkt4 to string one day and life
+                    // will be easier.
+                    response->setFile(reinterpret_cast<const uint8_t*>(filename.c_str()),
+                                     filename.size());
+                    found_cnt++;
+                }
+            }
+        }
+    }
+
+    // Step 3: try to set values using HR. Any values coming from there will override
+    // the subnet or class values.
+    ex.setReservedMessageFields();
+}
+
+OptionPtr
+Dhcpv4Srv::getNetmaskOption(const Subnet4Ptr& subnet) {
+    uint32_t netmask = getNetmask4(subnet->get().second).toUint32();
+
+    OptionPtr opt(new OptionInt<uint32_t>(Option::V4,
+                  DHO_SUBNET_MASK, netmask));
+
+    return (opt);
+}
+
+Pkt4Ptr
+Dhcpv4Srv::processDiscover(Pkt4Ptr& discover, AllocEngine::ClientContext4Ptr& context) {
+    // server-id is forbidden.
+    sanityCheck(discover, FORBIDDEN);
+
+    bool drop = false;
+    Subnet4Ptr subnet = selectSubnet(discover, drop);
+
+    // Stop here if selectSubnet decided to drop the packet
+    if (drop) {
+        return (Pkt4Ptr());
+    }
+
+    Dhcpv4Exchange ex(alloc_engine_, discover, context, subnet, drop);
+
+    // Stop here if Dhcpv4Exchange constructor decided to drop the packet
+    if (drop) {
+        return (Pkt4Ptr());
+    }
+
+    if (MultiThreadingMgr::instance().getMode()) {
+        // The lease reclamation cannot run at the same time.
+        ReadLockGuard share(alloc_engine_->getReadWriteMutex());
+
+        assignLease(ex);
+    } else {
+        assignLease(ex);
+    }
+
+    if (!ex.getResponse()) {
+        // The offer is empty so return it *now*!
+        return (Pkt4Ptr());
+    }
+
+    // Adding any other options makes sense only when we got the lease.
+    if (!ex.getResponse()->getYiaddr().isV4Zero()) {
+        // If this is global reservation or the subnet doesn't belong to a shared
+        // network we have already fetched it and evaluated the classes.
+        ex.conditionallySetReservedClientClasses();
+
+        // Required classification
+        requiredClassify(ex);
+
+        buildCfgOptionList(ex);
+        appendRequestedOptions(ex);
+        appendRequestedVendorOptions(ex);
+        // There are a few basic options that we always want to
+        // include in the response. If client did not request
+        // them we append them for him.
+        appendBasicOptions(ex);
+
+        // Set fixed fields (siaddr, sname, filename) if defined in
+        // the reservation, class or subnet specific configuration.
+        setFixedFields(ex);
+
+    } else {
+        // If the server can't offer an address, it drops the packet.
+        return (Pkt4Ptr());
+
+    }
+
+    // Set the src/dest IP address, port and interface for the outgoing
+    // packet.
+    adjustIfaceData(ex);
+
+    appendServerID(ex);
+
+    return (ex.getResponse());
+}
+
+Pkt4Ptr
+Dhcpv4Srv::processRequest(Pkt4Ptr& request, AllocEngine::ClientContext4Ptr& context) {
+    // Since we cannot distinguish  between client states
+    // we'll make server-id is optional for REQUESTs.
+    sanityCheck(request, OPTIONAL);
+
+    bool drop = false;
+    Subnet4Ptr subnet = selectSubnet(request, drop);
+
+    // Stop here if selectSubnet decided to drop the packet
+    if (drop) {
+        return (Pkt4Ptr());
+    }
+
+    Dhcpv4Exchange ex(alloc_engine_, request, context, subnet, drop);
+
+    // Stop here if Dhcpv4Exchange constructor decided to drop the packet
+    if (drop) {
+        return (Pkt4Ptr());
+    }
+
+    // Note that we treat REQUEST message uniformly, regardless if this is a
+    // first request (requesting for new address), renewing existing address
+    // or even rebinding.
+    if (MultiThreadingMgr::instance().getMode()) {
+        // The lease reclamation cannot run at the same time.
+        ReadLockGuard share(alloc_engine_->getReadWriteMutex());
+
+        assignLease(ex);
+    } else {
+        assignLease(ex);
+    }
+
+    Pkt4Ptr response = ex.getResponse();
+    if (!response) {
+        // The ack is empty so return it *now*!
+        return (Pkt4Ptr());
+    } else if (request->inClass("BOOTP")) {
+        // Put BOOTP responses in the BOOTP class.
+        response->addClass("BOOTP");
+    }
+
+    // Adding any other options makes sense only when we got the lease.
+    if (!response->getYiaddr().isV4Zero()) {
+        // If this is global reservation or the subnet doesn't belong to a shared
+        // network we have already fetched it and evaluated the classes.
+        ex.conditionallySetReservedClientClasses();
+
+        // Required classification
+        requiredClassify(ex);
+
+        buildCfgOptionList(ex);
+        appendRequestedOptions(ex);
+        appendRequestedVendorOptions(ex);
+        // There are a few basic options that we always want to
+        // include in the response. If client did not request
+        // them we append them for him.
+        appendBasicOptions(ex);
+
+        // Set fixed fields (siaddr, sname, filename) if defined in
+        // the reservation, class or subnet specific configuration.
+        setFixedFields(ex);
+    }
+
+    // Set the src/dest IP address, port and interface for the outgoing
+    // packet.
+    adjustIfaceData(ex);
+
+    appendServerID(ex);
+
+    // Return the pointer to the context, which will be required by the
+    // leases4_committed callouts.
+    context = ex.getContext();
+
+    return (ex.getResponse());
+}
+
+void
+Dhcpv4Srv::processRelease(Pkt4Ptr& release, AllocEngine::ClientContext4Ptr& context) {
+    // Server-id is mandatory in DHCPRELEASE (see table 5, RFC2131)
+    // but ISC DHCP does not enforce this, so we'll follow suit.
+    sanityCheck(release, OPTIONAL);
+
+    // Try to find client-id. Note that for the DHCPRELEASE we don't check if the
+    // match-client-id configuration parameter is disabled because this parameter
+    // is configured for subnets and we don't select subnet for the DHCPRELEASE.
+    // Bogus clients usually generate new client identifiers when they first
+    // connect to the network, so whatever client identifier has been used to
+    // acquire the lease, the client identifier carried in the DHCPRELEASE is
+    // likely to be the same and the lease will be correctly identified in the
+    // lease database. If supplied client identifier differs from the one used
+    // to acquire the lease then the lease will remain in the database and
+    // simply expire.
+    ClientIdPtr client_id;
+    OptionPtr opt = release->getOption(DHO_DHCP_CLIENT_IDENTIFIER);
+    if (opt) {
+        client_id = ClientIdPtr(new ClientId(opt->getData()));
+    }
+
+    try {
+        // Do we have a lease for that particular address?
+        Lease4Ptr lease = LeaseMgrFactory::instance().getLease4(release->getCiaddr());
+
+        if (!lease) {
+            // No such lease - bogus release
+            LOG_DEBUG(lease4_logger, DBG_DHCP4_DETAIL, DHCP4_RELEASE_FAIL_NO_LEASE)
+                .arg(release->getLabel())
+                .arg(release->getCiaddr().toText());
+            return;
+        }
+
+        if (!lease->belongsToClient(release->getHWAddr(), client_id)) {
+            LOG_DEBUG(lease4_logger, DBG_DHCP4_DETAIL, DHCP4_RELEASE_FAIL_WRONG_CLIENT)
+                .arg(release->getLabel())
+                .arg(release->getCiaddr().toText());
+            return;
+        }
+
+        bool skip = false;
+
+        // Execute all callouts registered for lease4_release
+        if (HooksManager::calloutsPresent(Hooks.hook_index_lease4_release_)) {
+            CalloutHandlePtr callout_handle = getCalloutHandle(release);
+
+            // Use the RAII wrapper to make sure that the callout handle state is
+            // reset when this object goes out of scope. All hook points must do
+            // it to prevent possible circular dependency between the callout
+            // handle and its arguments.
+            ScopedCalloutHandleState callout_handle_state(callout_handle);
+
+            // Enable copying options from the packet within hook library.
+            ScopedEnableOptionsCopy<Pkt4> query4_options_copy(release);
+
+            // Pass the original packet
+            callout_handle->setArgument("query4", release);
+
+            // Pass the lease to be updated
+            callout_handle->setArgument("lease4", lease);
+
+            // Call all installed callouts
+            HooksManager::callCallouts(Hooks.hook_index_lease4_release_,
+                                       *callout_handle);
+
+            // Callouts decided to skip the next processing step. The next
+            // processing step would be to send the packet, so skip at this
+            // stage means "drop response".
+            if ((callout_handle->getStatus() == CalloutHandle::NEXT_STEP_SKIP) ||
+                (callout_handle->getStatus() == CalloutHandle::NEXT_STEP_DROP)) {
+                skip = true;
+                LOG_DEBUG(hooks_logger, DBGLVL_PKT_HANDLING,
+                          DHCP4_HOOK_LEASE4_RELEASE_SKIP)
+                    .arg(release->getLabel());
+            }
+        }
+
+        // Callout didn't indicate to skip the release process. Let's release
+        // the lease.
+        if (!skip) {
+            // Ok, we've passed all checks. Let's release this address.
+            bool success = false; // was the removal operation successful?
+            bool expired = false; // explicitly expired instead of removed?
+            auto expiration_cfg = CfgMgr::instance().getCurrentCfg()->getCfgExpiration();
+
+            // Delete lease only if affinity is disabled.
+            if (expiration_cfg->getFlushReclaimedTimerWaitTime() &&
+                expiration_cfg->getHoldReclaimedTime() &&
+                lease->valid_lft_ != Lease::INFINITY_LFT) {
+                // Expire the lease.
+                lease->valid_lft_ = 0;
+                LeaseMgrFactory::instance().updateLease4(lease);
+                expired = true;
+                success = true;
+            } else {
+                success = LeaseMgrFactory::instance().deleteLease(lease);
+            }
+
+            if (success) {
+                context.reset(new AllocEngine::ClientContext4());
+                context->old_lease_ = lease;
+
+                // Release successful
+                LOG_INFO(lease4_logger, DHCP4_RELEASE)
+                    .arg(release->getLabel())
+                    .arg(lease->addr_.toText());
+
+                if (expired) {
+                    LOG_INFO(lease4_logger, DHCP4_RELEASE_EXPIRED)
+                                            .arg(release->getLabel())
+                                            .arg(lease->addr_.toText());
+                } else {
+                    LOG_INFO(lease4_logger, DHCP4_RELEASE_DELETED)
+                        .arg(release->getLabel())
+                        .arg(lease->addr_.toText());
+
+                    // Need to decrease statistic for assigned addresses.
+                    StatsMgr::instance().addValue(
+                        StatsMgr::generateName("subnet", lease->subnet_id_, "assigned-addresses"),
+                        static_cast<int64_t>(-1));
+
+                    const auto& subnet = CfgMgr::instance().getCurrentCfg()->getCfgSubnets4()->getBySubnetId(lease->subnet_id_);
+                    if (subnet) {
+                        const auto& pool = subnet->getPool(Lease::TYPE_V4, lease->addr_, false);
+                        if (pool) {
+                            StatsMgr::instance().addValue(
+                                StatsMgr::generateName("subnet", subnet->getID(),
+                                                       StatsMgr::generateName("pool", pool->getID(), "assigned-addresses")),
+                                static_cast<int64_t>(-1));
+                        }
+                    }
+
+                    // Remove existing DNS entries for the lease, if any.
+                    queueNCR(CHG_REMOVE, lease);
+                }
+            } else {
+                // Release failed
+                LOG_ERROR(lease4_logger, DHCP4_RELEASE_FAIL)
+                    .arg(release->getLabel())
+                    .arg(lease->addr_.toText());
+            }
+        }
+    } catch (const isc::Exception& ex) {
+        LOG_ERROR(lease4_logger, DHCP4_RELEASE_EXCEPTION)
+            .arg(release->getLabel())
+            .arg(release->getCiaddr())
+            .arg(ex.what());
+    }
+}
+
+void
+Dhcpv4Srv::processDecline(Pkt4Ptr& decline, AllocEngine::ClientContext4Ptr& context) {
+    // Server-id is mandatory in DHCPDECLINE (see table 5, RFC2131)
+    // but ISC DHCP does not enforce this, so we'll follow suit.
+    sanityCheck(decline, OPTIONAL);
+
+    // Client is supposed to specify the address being declined in
+    // Requested IP address option, but must not set its ciaddr.
+    // (again, see table 5 in RFC2131).
+
+    OptionCustomPtr opt_requested_address = boost::dynamic_pointer_cast<
+        OptionCustom>(decline->getOption(DHO_DHCP_REQUESTED_ADDRESS));
+    if (!opt_requested_address) {
+
+        isc_throw(RFCViolation, "Mandatory 'Requested IP address' option missing"
+                  " in DHCPDECLINE sent from " << decline->getLabel());
+    }
+    IOAddress addr(opt_requested_address->readAddress());
+
+    // We could also extract client's address from ciaddr, but that's clearly
+    // against RFC2131.
+
+    // Now we need to check whether this address really belongs to the client
+    // that attempts to decline it.
+    const Lease4Ptr lease = LeaseMgrFactory::instance().getLease4(addr);
+
+    if (!lease) {
+        // Client tried to decline an address, but we don't have a lease for
+        // that address. Let's ignore it.
+        //
+        // We could assume that we're recovering from a mishandled migration
+        // to a new server and mark the address as declined, but the window of
+        // opportunity for that to be useful is small and the attack vector
+        // would be pretty severe.
+        LOG_WARN(dhcp4_logger, DHCP4_DECLINE_LEASE_NOT_FOUND)
+            .arg(addr.toText()).arg(decline->getLabel());
+        return;
+    }
+
+    // Get client-id, if available.
+    OptionPtr opt_clientid = decline->getOption(DHO_DHCP_CLIENT_IDENTIFIER);
+    ClientIdPtr client_id;
+    if (opt_clientid) {
+        client_id.reset(new ClientId(opt_clientid->getData()));
+    }
+
+    // Check if the client attempted to decline a lease it doesn't own.
+    if (!lease->belongsToClient(decline->getHWAddr(), client_id)) {
+
+        // Get printable hardware addresses
+        string client_hw = decline->getHWAddr() ?
+            decline->getHWAddr()->toText(false) : "(none)";
+        string lease_hw = lease->hwaddr_ ?
+            lease->hwaddr_->toText(false) : "(none)";
+
+        // Get printable client-ids
+        string client_id_txt = client_id ? client_id->toText() : "(none)";
+        string lease_id_txt = lease->client_id_ ?
+            lease->client_id_->toText() : "(none)";
+
+        // Print the warning and we're done here.
+        LOG_WARN(dhcp4_logger, DHCP4_DECLINE_LEASE_MISMATCH)
+            .arg(addr.toText()).arg(decline->getLabel())
+            .arg(client_hw).arg(lease_hw).arg(client_id_txt).arg(lease_id_txt);
+
+        return;
+    }
+
+    // Ok, all is good. The client is reporting its own address. Let's
+    // process it.
+    declineLease(lease, decline, context);
+}
+
+void
+Dhcpv4Srv::declineLease(const Lease4Ptr& lease, const Pkt4Ptr& decline,
+                        AllocEngine::ClientContext4Ptr& context) {
+
+    // Let's check if there are hooks installed for decline4 hook point.
+    // If they are, let's pass the lease and client's packet. If the hook
+    // sets status to drop, we reject this Decline.
+    if (HooksManager::calloutsPresent(Hooks.hook_index_lease4_decline_)) {
+        CalloutHandlePtr callout_handle = getCalloutHandle(decline);
+
+        // Use the RAII wrapper to make sure that the callout handle state is
+        // reset when this object goes out of scope. All hook points must do
+        // it to prevent possible circular dependency between the callout
+        // handle and its arguments.
+        ScopedCalloutHandleState callout_handle_state(callout_handle);
+
+        // Enable copying options from the packet within hook library.
+        ScopedEnableOptionsCopy<Pkt4> query4_options_copy(decline);
+
+        // Pass the original packet
+        callout_handle->setArgument("query4", decline);
+
+        // Pass the lease to be updated
+        callout_handle->setArgument("lease4", lease);
+
+        // Call callouts
+        HooksManager::callCallouts(Hooks.hook_index_lease4_decline_,
+                                   *callout_handle);
+
+        // Check if callouts decided to skip the next processing step.
+        // If any of them did, we will drop the packet.
+        if ((callout_handle->getStatus() == CalloutHandle::NEXT_STEP_SKIP) ||
+            (callout_handle->getStatus() == CalloutHandle::NEXT_STEP_DROP)) {
+            LOG_DEBUG(hooks_logger, DBGLVL_PKT_HANDLING, DHCP4_HOOK_DECLINE_SKIP)
+                .arg(decline->getLabel()).arg(lease->addr_.toText());
+            return;
+        }
+    }
+
+    Lease4Ptr old_values = boost::make_shared<Lease4>(*lease);
+
+    // @todo: Call hooks.
+
+    // We need to disassociate the lease from the client. Once we move a lease
+    // to declined state, it is no longer associated with the client in any
+    // way.
+    lease->decline(CfgMgr::instance().getCurrentCfg()->getDeclinePeriod());
+
+    try {
+        LeaseMgrFactory::instance().updateLease4(lease);
+    } catch (const Exception& ex) {
+        // Update failed.
+        LOG_ERROR(lease4_logger, DHCP4_DECLINE_FAIL)
+            .arg(decline->getLabel())
+            .arg(lease->addr_.toText())
+            .arg(ex.what());
+        return;
+    }
+
+    // Remove existing DNS entries for the lease, if any.
+    // queueNCR will do the necessary checks and will skip the update, if not needed.
+    queueNCR(CHG_REMOVE, old_values);
+
+    // Bump up the statistics.
+
+    // Per subnet declined addresses counter.
+    StatsMgr::instance().addValue(
+        StatsMgr::generateName("subnet", lease->subnet_id_, "declined-addresses"),
+        static_cast<int64_t>(1));
+
+    const auto& subnet = CfgMgr::instance().getCurrentCfg()->getCfgSubnets4()->getBySubnetId(lease->subnet_id_);
+    if (subnet) {
+        const auto& pool = subnet->getPool(Lease::TYPE_V4, lease->addr_, false);
+        if (pool) {
+            StatsMgr::instance().addValue(
+                StatsMgr::generateName("subnet", subnet->getID(),
+                                       StatsMgr::generateName("pool", pool->getID(), "declined-addresses")),
+                static_cast<int64_t>(1));
+        }
+    }
+
+    // Global declined addresses counter.
+    StatsMgr::instance().addValue("declined-addresses", static_cast<int64_t>(1));
+
+    // We do not want to decrease the assigned-addresses at this time. While
+    // technically a declined address is no longer allocated, the primary usage
+    // of the assigned-addresses statistic is to monitor pool utilization. Most
+    // people would forget to include declined-addresses in the calculation,
+    // and simply do assigned-addresses/total-addresses. This would have a bias
+    // towards under-representing pool utilization, if we decreased allocated
+    // immediately after receiving DHCPDECLINE, rather than later when we recover
+    // the address.
+
+    context.reset(new AllocEngine::ClientContext4());
+    context->new_lease_ = lease;
+
+    LOG_INFO(lease4_logger, DHCP4_DECLINE_LEASE).arg(lease->addr_.toText())
+        .arg(decline->getLabel()).arg(lease->valid_lft_);
+}
+
+Pkt4Ptr
+Dhcpv4Srv::processInform(Pkt4Ptr& inform, AllocEngine::ClientContext4Ptr& context) {
+    // server-id is supposed to be forbidden (as is requested address)
+    // but ISC DHCP does not enforce either. So neither will we.
+    sanityCheck(inform, OPTIONAL);
+
+    bool drop = false;
+    Subnet4Ptr subnet = selectSubnet(inform, drop);
+
+    // Stop here if selectSubnet decided to drop the packet
+    if (drop) {
+        return (Pkt4Ptr());
+    }
+
+    Dhcpv4Exchange ex(alloc_engine_, inform, context, subnet, drop);
+
+    // Stop here if Dhcpv4Exchange constructor decided to drop the packet
+    if (drop) {
+        return (Pkt4Ptr());
+    }
+
+    Pkt4Ptr ack = ex.getResponse();
+
+    // If this is global reservation or the subnet doesn't belong to a shared
+    // network we have already fetched it and evaluated the classes.
+    ex.conditionallySetReservedClientClasses();
+
+    requiredClassify(ex);
+
+    buildCfgOptionList(ex);
+    appendRequestedOptions(ex);
+    appendRequestedVendorOptions(ex);
+    appendBasicOptions(ex);
+    adjustIfaceData(ex);
+
+    // Set fixed fields (siaddr, sname, filename) if defined in
+    // the reservation, class or subnet specific configuration.
+    setFixedFields(ex);
+
+    // There are cases for the DHCPINFORM that the server receives it via
+    // relay but will send the response to the client's unicast address
+    // carried in the ciaddr. In this case, the giaddr and hops field should
+    // be cleared (these fields were copied by the copyDefaultFields function).
+    // Also Relay Agent Options should be removed if present.
+    if (ack->getRemoteAddr() != inform->getGiaddr()) {
+        LOG_DEBUG(packet4_logger, DBG_DHCP4_DETAIL, DHCP4_INFORM_DIRECT_REPLY)
+            .arg(inform->getLabel())
+            .arg(ack->getRemoteAddr())
+            .arg(ack->getIface());
+        ack->setHops(0);
+        ack->setGiaddr(IOAddress::IPV4_ZERO_ADDRESS());
+        ack->delOption(DHO_DHCP_AGENT_OPTIONS);
+    }
+
+    // The DHCPACK must contain server id.
+    appendServerID(ex);
+
+    return (ex.getResponse());
+}
+
+bool
+Dhcpv4Srv::accept(const Pkt4Ptr& query) const {
+    // Check that the message type is accepted by the server. We rely on the
+    // function called to log a message if needed.
+    if (!acceptMessageType(query)) {
+        return (false);
+    }
+    // Check if the message from directly connected client (if directly
+    // connected) should be dropped or processed.
+    if (!acceptDirectRequest(query)) {
+        LOG_DEBUG(bad_packet4_logger, DBGLVL_PKT_HANDLING, DHCP4_PACKET_DROP_0002)
+            .arg(query->getLabel())
+            .arg(query->getIface());
+        return (false);
+    }
+
+    // Check if the DHCPv4 packet has been sent to us or to someone else.
+    // If it hasn't been sent to us, drop it!
+    if (!acceptServerId(query)) {
+        LOG_DEBUG(bad_packet4_logger, DBGLVL_PKT_HANDLING, DHCP4_PACKET_DROP_0003)
+            .arg(query->getLabel())
+            .arg(query->getIface());
+        return (false);
+    }
+
+    return (true);
+}
+
+bool
+Dhcpv4Srv::acceptDirectRequest(const Pkt4Ptr& pkt) const {
+    // Accept all relayed messages.
+    if (pkt->isRelayed()) {
+        return (true);
+    }
+
+    // Accept all DHCPv4-over-DHCPv6 messages.
+    if (pkt->isDhcp4o6()) {
+        return (true);
+    }
+
+    // The source address must not be zero for the DHCPINFORM message from
+    // the directly connected client because the server will not know where
+    // to respond if the ciaddr was not present.
+    try {
+        if (pkt->getType() == DHCPINFORM) {
+            if (pkt->getRemoteAddr().isV4Zero() &&
+                pkt->getCiaddr().isV4Zero()) {
+                return (false);
+            }
+        }
+    } catch (...) {
+        // If we got here, it is probably because the message type hasn't
+        // been set. But, this should not really happen assuming that
+        // we validate the message type prior to calling this function.
+        return (false);
+    }
+    bool drop = false;
+    bool result = (!pkt->getLocalAddr().isV4Bcast() ||
+                   selectSubnet(pkt, drop, true));
+    if (drop) {
+        // The packet must be dropped but as sanity_only is true it is dead code.
+        return (false);
+    }
+    return (result);
+}
+
+bool
+Dhcpv4Srv::acceptMessageType(const Pkt4Ptr& query) const {
+    // When receiving a packet without message type option, getType() will
+    // throw.
+    int type;
+    try {
+        type = query->getType();
+
+    } catch (...) {
+        LOG_DEBUG(bad_packet4_logger, DBGLVL_PKT_HANDLING, DHCP4_PACKET_DROP_0004)
+            .arg(query->getLabel())
+            .arg(query->getIface());
+        return (false);
+    }
+
+    // Once we know that the message type is within a range of defined DHCPv4
+    // messages, we do a detailed check to make sure that the received message
+    // is targeted at server. Note that we could have received some Offer
+    // message broadcasted by the other server to a relay. Even though, the
+    // server would rather unicast its response to a relay, let's be on the
+    // safe side. Also, we want to drop other messages which we don't support.
+    // All these valid messages that we are not going to process are dropped
+    // silently.
+
+    switch(type) {
+        case DHCPDISCOVER:
+        case DHCPREQUEST:
+        case DHCPRELEASE:
+        case DHCPDECLINE:
+        case DHCPINFORM:
+            return (true);
+            break;
+
+        case DHCP_NOTYPE:
+            LOG_DEBUG(bad_packet4_logger, DBGLVL_PKT_HANDLING, DHCP4_PACKET_DROP_0009)
+                     .arg(query->getLabel());
+            break;
+
+        default:
+            // If we receive a message with a non-existing type, we are logging it.
+            if (type >= DHCP_TYPES_EOF) {
+                LOG_DEBUG(bad_packet4_logger, DBGLVL_PKT_HANDLING, DHCP4_PACKET_DROP_0005)
+                          .arg(query->getLabel())
+                          .arg(type);
+            } else {
+                // Exists but we don't support it.
+                LOG_DEBUG(bad_packet4_logger, DBGLVL_PKT_HANDLING, DHCP4_PACKET_DROP_0006)
+                      .arg(query->getLabel())
+                      .arg(type);
+            }
+            break;
+    }
+
+    return (false);
+}
+
+bool
+Dhcpv4Srv::acceptServerId(const Pkt4Ptr& query) const {
+    // This function is meant to be called internally by the server class, so
+    // we rely on the caller to sanity check the pointer and we don't check
+    // it here.
+
+    // Check if server identifier option is present. If it is not present
+    // we accept the message because it is targeted to all servers.
+    // Note that we don't check cases that server identifier is mandatory
+    // but not present. This is meant to be sanity checked in other
+    // functions.
+    OptionPtr option = query->getOption(DHO_DHCP_SERVER_IDENTIFIER);
+    if (!option) {
+        return (true);
+    }
+    // Server identifier is present. Let's convert it to 4-byte address
+    // and try to match with server identifiers used by the server.
+    OptionCustomPtr option_custom =
+        boost::dynamic_pointer_cast<OptionCustom>(option);
+    // Unable to convert the option to the option type which encapsulates it.
+    // We treat this as non-matching server id.
+    if (!option_custom) {
+        return (false);
+    }
+    // The server identifier option should carry exactly one IPv4 address.
+    // If the option definition for the server identifier doesn't change,
+    // the OptionCustom object should have exactly one IPv4 address and
+    // this check is somewhat redundant. On the other hand, if someone
+    // breaks option it may be better to check that here.
+    if (option_custom->getDataFieldsNum() != 1) {
+        return (false);
+    }
+
+    // The server identifier MUST be an IPv4 address. If given address is
+    // v6, it is wrong.
+    IOAddress server_id = option_custom->readAddress();
+    if (!server_id.isV4()) {
+        return (false);
+    }
+
+    // According to RFC5107, the RAI_OPTION_SERVER_ID_OVERRIDE option if
+    // present, should match DHO_DHCP_SERVER_IDENTIFIER option.
+    OptionPtr rai_option = query->getOption(DHO_DHCP_AGENT_OPTIONS);
+    if (rai_option) {
+        OptionPtr rai_suboption = rai_option->getOption(RAI_OPTION_SERVER_ID_OVERRIDE);
+        if (rai_suboption && (server_id.toBytes() == rai_suboption->toBinary())) {
+            return (true);
+        }
+    }
+
+    // Skip address check if configured to ignore the server id.
+    SrvConfigPtr cfg = CfgMgr::instance().getCurrentCfg();
+    if (cfg->getIgnoreServerIdentifier()) {
+        return (true);
+    }
+
+    // This function iterates over all interfaces on which the
+    // server is listening to find the one which has a socket bound
+    // to the address carried in the server identifier option.
+    // This has some performance implications. However, given that
+    // typically there will be just a few active interfaces the
+    // performance hit should be acceptable. If it turns out to
+    // be significant, we will have to cache server identifiers
+    // when sockets are opened.
+    if (IfaceMgr::instance().hasOpenSocket(server_id)) {
+        return (true);
+    }
+
+    // There are some cases when an administrator explicitly sets server
+    // identifier (option 54) that should be used for a given, subnet,
+    // network etc. It doesn't have to be an address assigned to any of
+    // the server interfaces. Thus, we have to check if the server
+    // identifier received is the one that we explicitly set in the
+    // server configuration. At this point, we don't know which subnet
+    // the client belongs to so we can't match the server id with any
+    // subnet. We simply check if this server identifier is configured
+    // anywhere. This should be good enough to eliminate exchanges
+    // with other servers in the same network.
+
+    /// @todo Currently we only check server identifiers configured at the
+    /// subnet, shared network, client class and global levels.
+    /// This should be sufficient for most of cases. At this point, trying to
+    /// support server identifiers on the host reservations level seems to be an
+    /// overkill and is probably not needed. In fact, at this point we don't
+    /// know the reservations for the client communicating with the server.
+    /// We may revise some of these choices in the future.
+
+    // Check if there is at least one subnet configured with this server
+    // identifier.
+    ConstCfgSubnets4Ptr cfg_subnets = cfg->getCfgSubnets4();
+    if (cfg_subnets->hasSubnetWithServerId(server_id)) {
+        return (true);
+    }
+
+    // This server identifier is not configured for any of the subnets, so
+    // check on the shared network level.
+    CfgSharedNetworks4Ptr cfg_networks = cfg->getCfgSharedNetworks4();
+    if (cfg_networks->hasNetworkWithServerId(server_id)) {
+        return (true);
+    }
+
+    // Check if the server identifier is configured at client class level.
+    const ClientClasses& classes = query->getClasses();
+    for (ClientClasses::const_iterator cclass = classes.cbegin();
+         cclass != classes.cend(); ++cclass) {
+        // Find the client class definition for this class
+        const ClientClassDefPtr& ccdef = CfgMgr::instance().getCurrentCfg()->
+            getClientClassDictionary()->findClass(*cclass);
+        if (!ccdef) {
+            continue;
+        }
+
+        if (ccdef->getCfgOption()->empty()) {
+            // Skip classes which don't configure options
+            continue;
+        }
+
+        OptionCustomPtr context_opt_server_id = boost::dynamic_pointer_cast<OptionCustom>
+                (ccdef->getCfgOption()->get(DHCP4_OPTION_SPACE, DHO_DHCP_SERVER_IDENTIFIER).option_);
+        if (context_opt_server_id && (context_opt_server_id->readAddress() == server_id)) {
+            return (true);
+        }
+    }
+
+    // Finally, it is possible that the server identifier is specified
+    // on the global level.
+    ConstCfgOptionPtr cfg_global_options = cfg->getCfgOption();
+    OptionCustomPtr opt_server_id = boost::dynamic_pointer_cast<OptionCustom>
+        (cfg_global_options->get(DHCP4_OPTION_SPACE, DHO_DHCP_SERVER_IDENTIFIER).option_);
+
+    return (opt_server_id && (opt_server_id->readAddress() == server_id));
+}
+
+void
+Dhcpv4Srv::sanityCheck(const Pkt4Ptr& query, RequirementLevel serverid) {
+    OptionPtr server_id = query->getOption(DHO_DHCP_SERVER_IDENTIFIER);
+    switch (serverid) {
+    case FORBIDDEN:
+        if (server_id) {
+            isc_throw(RFCViolation, "Server-id option was not expected, but"
+                      << " received in message "
+                      << query->getName());
+        }
+        break;
+
+    case MANDATORY:
+        if (!server_id) {
+            isc_throw(RFCViolation, "Server-id option was expected, but not"
+                      " received in message "
+                      << query->getName());
+        }
+        break;
+
+    case OPTIONAL:
+        // do nothing here
+        ;
+    }
+
+    // If there is HWAddress set and it is non-empty, then we're good
+    if (query->getHWAddr() && !query->getHWAddr()->hwaddr_.empty()) {
+        return;
+    }
+
+    // There has to be something to uniquely identify the client:
+    // either non-zero MAC address or client-id option present (or both)
+    OptionPtr client_id = query->getOption(DHO_DHCP_CLIENT_IDENTIFIER);
+
+    // If there's no client-id (or a useless one is provided, i.e. 0 length)
+    if (!client_id || client_id->len() == client_id->getHeaderLen()) {
+        isc_throw(RFCViolation, "Missing or useless client-id and no HW address"
+                  " provided in message "
+                  << query->getName());
+    }
+}
+
+void Dhcpv4Srv::classifyPacket(const Pkt4Ptr& pkt) {
+    Dhcpv4Exchange::classifyPacket(pkt);
+}
+
+void Dhcpv4Srv::requiredClassify(Dhcpv4Exchange& ex) {
+    // First collect required classes
+    Pkt4Ptr query = ex.getQuery();
+    ClientClasses classes = query->getClasses(true);
+    Subnet4Ptr subnet = ex.getContext()->subnet_;
+
+    if (subnet) {
+        // Begin by the shared-network
+        SharedNetwork4Ptr network;
+        subnet->getSharedNetwork(network);
+        if (network) {
+            const ClientClasses& to_add = network->getRequiredClasses();
+            for (ClientClasses::const_iterator cclass = to_add.cbegin();
+                 cclass != to_add.cend(); ++cclass) {
+                classes.insert(*cclass);
+            }
+        }
+
+        // Followed by the subnet
+        const ClientClasses& to_add = subnet->getRequiredClasses();
+        for(ClientClasses::const_iterator cclass = to_add.cbegin();
+            cclass != to_add.cend(); ++cclass) {
+            classes.insert(*cclass);
+        }
+
+        // And finish by the pool
+        Pkt4Ptr resp = ex.getResponse();
+        IOAddress addr = IOAddress::IPV4_ZERO_ADDRESS();
+        if (resp) {
+            addr = resp->getYiaddr();
+        }
+        if (!addr.isV4Zero()) {
+            PoolPtr pool = subnet->getPool(Lease::TYPE_V4, addr, false);
+            if (pool) {
+                const ClientClasses& to_add = pool->getRequiredClasses();
+                for (ClientClasses::const_iterator cclass = to_add.cbegin();
+                     cclass != to_add.cend(); ++cclass) {
+                    classes.insert(*cclass);
+                }
+            }
+        }
+
+        // host reservation???
+    }
+
+    // Run match expressions
+    // Note getClientClassDictionary() cannot be null
+    const ClientClassDictionaryPtr& dict =
+        CfgMgr::instance().getCurrentCfg()->getClientClassDictionary();
+    for (ClientClasses::const_iterator cclass = classes.cbegin();
+         cclass != classes.cend(); ++cclass) {
+        const ClientClassDefPtr class_def = dict->findClass(*cclass);
+        if (!class_def) {
+            LOG_DEBUG(dhcp4_logger, DBG_DHCP4_BASIC, DHCP4_CLASS_UNDEFINED)
+                .arg(*cclass);
+            continue;
+        }
+        const ExpressionPtr& expr_ptr = class_def->getMatchExpr();
+        // Nothing to do without an expression to evaluate
+        if (!expr_ptr) {
+            LOG_DEBUG(dhcp4_logger, DBG_DHCP4_BASIC, DHCP4_CLASS_UNTESTABLE)
+                .arg(*cclass);
+            continue;
+        }
+        // Evaluate the expression which can return false (no match),
+        // true (match) or raise an exception (error)
+        try {
+            bool status = evaluateBool(*expr_ptr, *query);
+            if (status) {
+                LOG_INFO(dhcp4_logger, EVAL_RESULT)
+                    .arg(*cclass)
+                    .arg(status);
+                // Matching: add the class
+                query->addClass(*cclass);
+            } else {
+                LOG_DEBUG(dhcp4_logger, DBG_DHCP4_DETAIL, EVAL_RESULT)
+                    .arg(*cclass)
+                    .arg(status);
+            }
+        } catch (const Exception& ex) {
+            LOG_ERROR(dhcp4_logger, EVAL_RESULT)
+                .arg(*cclass)
+                .arg(ex.what());
+        } catch (...) {
+            LOG_ERROR(dhcp4_logger, EVAL_RESULT)
+                .arg(*cclass)
+                .arg("get exception?");
+        }
+    }
+}
+
+void
+Dhcpv4Srv::deferredUnpack(Pkt4Ptr& query) {
+    // Iterate on the list of deferred option codes
+    BOOST_FOREACH(const uint16_t& code, query->getDeferredOptions()) {
+        OptionDefinitionPtr def;
+        // Iterate on client classes
+        const ClientClasses& classes = query->getClasses();
+        for (ClientClasses::const_iterator cclass = classes.cbegin();
+             cclass != classes.cend(); ++cclass) {
+            // Get the client class definition for this class
+            const ClientClassDefPtr& ccdef =
+                CfgMgr::instance().getCurrentCfg()->
+                getClientClassDictionary()->findClass(*cclass);
+            // If not found skip it
+            if (!ccdef) {
+                continue;
+            }
+            // If there is no option definition skip it
+            if (!ccdef->getCfgOptionDef()) {
+                continue;
+            }
+            def = ccdef->getCfgOptionDef()->get(DHCP4_OPTION_SPACE, code);
+            // Stop at the first client class with a definition
+            if (def) {
+                break;
+            }
+        }
+        // If not found try the global definition
+        if (!def) {
+            def = LibDHCP::getOptionDef(DHCP4_OPTION_SPACE, code);
+        }
+        if (!def) {
+            def = LibDHCP::getRuntimeOptionDef(DHCP4_OPTION_SPACE, code);
+        }
+        // Finish by last resort definition
+        if (!def) {
+            def = LibDHCP::getLastResortOptionDef(DHCP4_OPTION_SPACE, code);
+        }
+        // If not defined go to the next option
+        if (!def) {
+            continue;
+        }
+        // Get the existing option for its content and remove all
+        OptionPtr opt = query->getOption(code);
+        if (!opt) {
+            // should not happen but do not crash anyway
+            LOG_DEBUG(bad_packet4_logger, DBG_DHCP4_DETAIL,
+                      DHCP4_DEFERRED_OPTION_MISSING)
+                .arg(code);
+            continue;
+        }
+        // Because options have already been fused, the buffer contains entire
+        // data.
+        const OptionBuffer buf = opt->getData();
+        try {
+            // Unpack the option
+            opt = def->optionFactory(Option::V4, code, buf);
+        } catch (const std::exception& e) {
+            // Failed to parse the option.
+            LOG_DEBUG(bad_packet4_logger, DBG_DHCP4_DETAIL,
+                      DHCP4_DEFERRED_OPTION_UNPACK_FAIL)
+                .arg(code)
+                .arg(e.what());
+            continue;
+        }
+        while (query->delOption(code)) {
+            // continue
+        }
+        // Add the unpacked option.
+        query->addOption(opt);
+    }
+}
+
+void
+Dhcpv4Srv::startD2() {
+    D2ClientMgr& d2_mgr = CfgMgr::instance().getD2ClientMgr();
+    if (d2_mgr.ddnsEnabled()) {
+        // Updates are enabled, so lets start the sender, passing in
+        // our error handler.
+        // This may throw so wherever this is called needs to ready.
+        d2_mgr.startSender(std::bind(&Dhcpv4Srv::d2ClientErrorHandler,
+                                     this, ph::_1, ph::_2));
+    }
+}
+
+void
+Dhcpv4Srv::stopD2() {
+    D2ClientMgr& d2_mgr = CfgMgr::instance().getD2ClientMgr();
+    if (d2_mgr.ddnsEnabled()) {
+        // Updates are enabled, so lets stop the sender
+        d2_mgr.stopSender();
+    }
+}
+
+void
+Dhcpv4Srv::d2ClientErrorHandler(const
+                                dhcp_ddns::NameChangeSender::Result result,
+                                dhcp_ddns::NameChangeRequestPtr& ncr) {
+    LOG_ERROR(ddns4_logger, DHCP4_DDNS_REQUEST_SEND_FAILED).
+              arg(result).arg((ncr ? ncr->toText() : " NULL "));
+    // We cannot communicate with kea-dhcp-ddns, suspend further updates.
+    /// @todo We may wish to revisit this, but for now we will simply turn
+    /// them off.
+    CfgMgr::instance().getD2ClientMgr().suspendUpdates();
+}
+
+std::string
+Dhcpv4Srv::getVersion(bool extended) {
+    std::stringstream tmp;
+
+    tmp << VERSION;
+    if (extended) {
+        tmp << endl << EXTENDED_VERSION << endl;
+        tmp << "linked with:" << endl;
+        tmp << Logger::getVersion() << endl;
+        tmp << CryptoLink::getVersion() << endl;
+        tmp << "database:" << endl;
+#ifdef HAVE_MYSQL
+        tmp << MySqlLeaseMgr::getDBVersion() << endl;
+#endif
+#ifdef HAVE_PGSQL
+        tmp << PgSqlLeaseMgr::getDBVersion() << endl;
+#endif
+        tmp << Memfile_LeaseMgr::getDBVersion(Memfile_LeaseMgr::V4);
+
+        // @todo: more details about database runtime
+    }
+
+    return (tmp.str());
+}
+
+void Dhcpv4Srv::processStatsReceived(const Pkt4Ptr& query) {
+    // Note that we're not bumping pkt4-received statistic as it was
+    // increased early in the packet reception code.
+
+    string stat_name = "pkt4-unknown-received";
+    try {
+        switch (query->getType()) {
+        case DHCPDISCOVER:
+            stat_name = "pkt4-discover-received";
+            break;
+        case DHCPOFFER:
+            // Should not happen, but let's keep a counter for it
+            stat_name = "pkt4-offer-received";
+            break;
+        case DHCPREQUEST:
+            stat_name = "pkt4-request-received";
+            break;
+        case DHCPACK:
+            // Should not happen, but let's keep a counter for it
+            stat_name = "pkt4-ack-received";
+            break;
+        case DHCPNAK:
+            // Should not happen, but let's keep a counter for it
+            stat_name = "pkt4-nak-received";
+            break;
+        case DHCPRELEASE:
+            stat_name = "pkt4-release-received";
+        break;
+        case DHCPDECLINE:
+            stat_name = "pkt4-decline-received";
+            break;
+        case DHCPINFORM:
+            stat_name = "pkt4-inform-received";
+            break;
+        default:
+            ; // do nothing
+        }
+    }
+    catch (...) {
+        // If the incoming packet doesn't have option 53 (message type)
+        // or a hook set pkt4_receive_skip, then Pkt4::getType() may
+        // throw an exception. That's ok, we'll then use the default
+        // name of pkt4-unknown-received.
+    }
+
+    isc::stats::StatsMgr::instance().addValue(stat_name,
+                                              static_cast<int64_t>(1));
+}
+
+void Dhcpv4Srv::processStatsSent(const Pkt4Ptr& response) {
+    // Increase generic counter for sent packets.
+    isc::stats::StatsMgr::instance().addValue("pkt4-sent",
+                                              static_cast<int64_t>(1));
+
+    // Increase packet type specific counter for packets sent.
+    string stat_name;
+    switch (response->getType()) {
+    case DHCPOFFER:
+        stat_name = "pkt4-offer-sent";
+        break;
+    case DHCPACK:
+        stat_name = "pkt4-ack-sent";
+        break;
+    case DHCPNAK:
+        stat_name = "pkt4-nak-sent";
+        break;
+    default:
+        // That should never happen
+        return;
+    }
+
+    isc::stats::StatsMgr::instance().addValue(stat_name,
+                                              static_cast<int64_t>(1));
+}
+
+int Dhcpv4Srv::getHookIndexBuffer4Receive() {
+    return (Hooks.hook_index_buffer4_receive_);
+}
+
+int Dhcpv4Srv::getHookIndexPkt4Receive() {
+    return (Hooks.hook_index_pkt4_receive_);
+}
+
+int Dhcpv4Srv::getHookIndexSubnet4Select() {
+    return (Hooks.hook_index_subnet4_select_);
+}
+
+int Dhcpv4Srv::getHookIndexLease4Release() {
+    return (Hooks.hook_index_lease4_release_);
+}
+
+int Dhcpv4Srv::getHookIndexPkt4Send() {
+    return (Hooks.hook_index_pkt4_send_);
+}
+
+int Dhcpv4Srv::getHookIndexBuffer4Send() {
+    return (Hooks.hook_index_buffer4_send_);
+}
+
+int Dhcpv4Srv::getHookIndexLease4Decline() {
+    return (Hooks.hook_index_lease4_decline_);
+}
+
+void Dhcpv4Srv::discardPackets() {
+    // Dump all of our current packets, anything that is mid-stream
+    HooksManager::clearParkingLots();
+}
+
+std::list<std::list<std::string>> Dhcpv4Srv::jsonPathsToRedact() const {
+    static std::list<std::list<std::string>> const list({
+        {"config-control", "config-databases", "[]"},
+        {"hooks-libraries", "[]", "parameters", "*"},
+        {"hosts-database"},
+        {"hosts-databases", "[]"},
+        {"lease-database"},
+    });
+    return list;
+}
+
+}  // namespace dhcp
+}  // namespace isc