Adding upstream version 2.4.1.upstream/2.4.1upstream

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

1 files changed, 4776 insertions, 0 deletions

diff --git a/src/bin/dhcp6/dhcp6_srv.cc b/src/bin/dhcp6/dhcp6_srv.cc
new file mode 100644
index 0000000..c47e17c
--- /dev/null
+++ b/src/bin/dhcp6/dhcp6_srv.cc
@@ -0,0 +1,4776 @@
+// 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 <asiolink/io_address.h>
+#include <dhcp_ddns/ncr_msg.h>
+#include <dhcp/dhcp6.h>
+#include <dhcp/docsis3_option_defs.h>
+#include <dhcp/duid.h>
+#include <dhcp/duid_factory.h>
+#include <dhcpsrv/fuzz.h>
+#include <dhcp/iface_mgr.h>
+#include <dhcp/libdhcp++.h>
+#include <dhcp/option6_addrlst.h>
+#include <dhcp/option6_client_fqdn.h>
+#include <dhcp/option6_ia.h>
+#include <dhcp/option6_iaaddr.h>
+#include <dhcp/option6_iaprefix.h>
+#include <dhcp/option6_status_code.h>
+#include <dhcp/option6_pdexclude.h>
+#include <dhcp/option_custom.h>
+#include <dhcp/option_vendor.h>
+#include <dhcp/option_vendor_class.h>
+#include <dhcp/option_int_array.h>
+#include <dhcp/pkt6.h>
+#include <dhcp6/client_handler.h>
+#include <dhcp6/dhcp6to4_ipc.h>
+#include <dhcp6/dhcp6_log.h>
+#include <dhcp6/dhcp6_srv.h>
+#include <dhcpsrv/cfg_host_operations.h>
+#include <dhcpsrv/cfgmgr.h>
+#include <dhcpsrv/lease_mgr.h>
+#include <dhcpsrv/lease_mgr_factory.h>
+#include <dhcpsrv/ncr_generator.h>
+#include <dhcpsrv/subnet.h>
+#include <dhcpsrv/subnet_selector.h>
+#include <dhcpsrv/utils.h>
+#include <eval/evaluate.h>
+#include <eval/eval_messages.h>
+#include <exceptions/exceptions.h>
+#include <hooks/callout_handle.h>
+#include <hooks/hooks_log.h>
+#include <hooks/hooks_manager.h>
+#include <stats/stats_mgr.h>
+#include <util/encode/hex.h>
+#include <util/io_utilities.h>
+#include <util/pointer_util.h>
+#include <util/range_utilities.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/foreach.hpp>
+#include <boost/tokenizer.hpp>
+#include <boost/algorithm/string/erase.hpp>
+#include <boost/algorithm/string/join.hpp>
+#include <boost/algorithm/string/split.hpp>
+
+#include <algorithm>
+#include <functional>
+#include <stdlib.h>
+#include <time.h>
+#include <iomanip>
+#include <fstream>
+#include <sstream>
+#include <map>
+#include <set>
+
+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 Dhcp6Hooks {
+    int hook_index_buffer6_receive_;  ///< index for "buffer6_receive" hook point
+    int hook_index_pkt6_receive_;     ///< index for "pkt6_receive" hook point
+    int hook_index_subnet6_select_;   ///< index for "subnet6_select" hook point
+    int hook_index_leases6_committed_;///< index for "leases6_committed" hook point
+    int hook_index_lease6_release_;   ///< index for "lease6_release" hook point
+    int hook_index_pkt6_send_;        ///< index for "pkt6_send" hook point
+    int hook_index_buffer6_send_;     ///< index for "buffer6_send" hook point
+    int hook_index_lease6_decline_;   ///< index for "lease6_decline" hook point
+    int hook_index_host6_identifier_; ///< index for "host6_identifier" hook point
+    int hook_index_ddns6_update_;     ///< index for "ddns6_update" hook point
+
+    /// Constructor that registers hook points for DHCPv6 engine
+    Dhcp6Hooks() {
+        hook_index_buffer6_receive_   = HooksManager::registerHook("buffer6_receive");
+        hook_index_pkt6_receive_      = HooksManager::registerHook("pkt6_receive");
+        hook_index_subnet6_select_    = HooksManager::registerHook("subnet6_select");
+        hook_index_leases6_committed_ = HooksManager::registerHook("leases6_committed");
+        hook_index_lease6_release_    = HooksManager::registerHook("lease6_release");
+        hook_index_pkt6_send_         = HooksManager::registerHook("pkt6_send");
+        hook_index_buffer6_send_      = HooksManager::registerHook("buffer6_send");
+        hook_index_lease6_decline_    = HooksManager::registerHook("lease6_decline");
+        hook_index_host6_identifier_  = HooksManager::registerHook("host6_identifier");
+        hook_index_ddns6_update_      = HooksManager::registerHook("ddns6_update");
+    }
+};
+
+// 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.
+Dhcp6Hooks Hooks;
+
+/// @brief Creates instance of the Status Code option.
+///
+/// This variant of the function is used when the Status Code option
+/// is added as a top-level option. It logs the debug message and
+/// includes the information about the client and transaction.
+///
+/// @param pkt Reference to the client's message.
+/// @param status_code Numeric status code.
+/// @param status_message Status message.
+///
+/// @return Pointer to the Status Code option.
+OptionPtr
+createStatusCode(const Pkt6& pkt, const uint16_t status_code,
+                 const std::string& status_message) {
+    Option6StatusCodePtr option_status(new Option6StatusCode(status_code,
+                                                             status_message));
+    LOG_DEBUG(options6_logger, DBG_DHCP6_DETAIL, DHCP6_ADD_GLOBAL_STATUS_CODE)
+        .arg(pkt.getLabel())
+        .arg(option_status->dataToText());
+    return (option_status);
+}
+
+/// @brief Creates instance of the Status Code option.
+///
+/// This variant of the function is used when the Status Code option
+/// is added to one of the IA options. It logs the debug message and
+/// includes the information about the client and transaction as well
+/// as IAID of the IA option.
+///
+/// @param pkt Reference to the client's message.
+/// param ia Reference to the IA option to which the Status Code is
+/// being added.
+/// @param status_code Numeric status code.
+/// @param status_message Status message.
+///
+/// @return Pointer to the Status Code option.
+OptionPtr
+createStatusCode(const Pkt6& pkt, const Option6IA& ia, const uint16_t status_code,
+                 const std::string& status_message) {
+    Option6StatusCodePtr option_status(new Option6StatusCode(status_code,
+                                                             status_message));
+    LOG_DEBUG(options6_logger, DBG_DHCP6_DETAIL, DHCP6_ADD_STATUS_CODE_FOR_IA)
+        .arg(pkt.getLabel())
+        .arg(ia.getIAID())
+        .arg(option_status->dataToText());
+    return (option_status);
+}
+
+/// List of statistics which is initialized to 0 during the DHCPv6
+/// server startup.
+std::set<std::string> dhcp6_statistics = {
+    "pkt6-received",
+    "pkt6-solicit-received",
+    "pkt6-advertise-received",
+    "pkt6-request-received",
+    "pkt6-reply-received",
+    "pkt6-renew-received",
+    "pkt6-rebind-received",
+    "pkt6-decline-received",
+    "pkt6-release-received",
+    "pkt6-infrequest-received",
+    "pkt6-dhcpv4-query-received",
+    "pkt6-dhcpv4-response-received",
+    "pkt6-unknown-received",
+    "pkt6-sent",
+    "pkt6-advertise-sent",
+    "pkt6-reply-sent",
+    "pkt6-dhcpv4-response-sent",
+    "pkt6-parse-failed",
+    "pkt6-receive-drop",
+    "v6-allocation-fail",
+    "v6-allocation-fail-shared-network",
+    "v6-allocation-fail-subnet",
+    "v6-allocation-fail-no-pools",
+    "v6-allocation-fail-classes",
+    "v6-ia-na-lease-reuses",
+    "v6-ia-pd-lease-reuses",
+};
+
+}  // namespace
+
+namespace isc {
+namespace dhcp {
+
+const std::string Dhcpv6Srv::VENDOR_CLASS_PREFIX("VENDOR_CLASS_");
+
+Dhcpv6Srv::Dhcpv6Srv(uint16_t server_port, uint16_t client_port)
+    : io_service_(new IOService()), server_port_(server_port),
+      client_port_(client_port), serverid_(), shutdown_(true),
+      alloc_engine_(), name_change_reqs_(),
+      network_state_(new NetworkState(NetworkState::DHCPv6)),
+      cb_control_(new CBControlDHCPv6()) {
+    LOG_DEBUG(dhcp6_logger, DBG_DHCP6_START, DHCP6_OPEN_SOCKET)
+        .arg(server_port);
+
+    Dhcp6to4Ipc::instance().client_port = client_port;
+
+    // Initialize objects required for DHCP server operation.
+    try {
+        // Port 0 is used for testing purposes where in most cases we don't
+        // rely on the physical interfaces. Therefore, it should be possible
+        // to create an object even when there are no usable interfaces.
+        if ((server_port > 0) && (IfaceMgr::instance().countIfaces() == 0)) {
+            LOG_ERROR(dhcp6_logger, DHCP6_NO_INTERFACES);
+            return;
+        }
+
+        // Create a DUID instance but do not store it into a file.
+        DUIDFactory duid_factory;
+        DuidPtr duid = duid_factory.get();
+        serverid_.reset(new Option(Option::V6, D6O_SERVERID, duid->getDuid()));
+
+        // 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(dhcp6_logger, DHCP6_SRV_CONSTRUCT_ERROR).arg(e.what());
+        return;
+    }
+    // Initializing all observations with default value
+    setPacketStatisticsDefaults();
+
+    // All done, so can proceed
+    shutdown_ = false;
+}
+
+void Dhcpv6Srv::setPacketStatisticsDefaults() {
+    isc::stats::StatsMgr& stats_mgr = isc::stats::StatsMgr::instance();
+
+    // Iterate over set of observed statistics
+    for (auto it = dhcp6_statistics.begin(); it != dhcp6_statistics.end(); ++it) {
+        // Initialize them with default value 0
+        stats_mgr.setValue((*it), static_cast<int64_t>(0));
+    }
+}
+
+Dhcpv6Srv::~Dhcpv6Srv() {
+    // Discard any parked packets
+    discardPackets();
+
+    try {
+        stopD2();
+    } catch (const std::exception& ex) {
+        // Highly unlikely, but lets Report it but go on
+        LOG_ERROR(dhcp6_logger, DHCP6_SRV_D2STOP_ERROR).arg(ex.what());
+    }
+
+    try {
+        Dhcp6to4Ipc::instance().close();
+    } catch (const std::exception& ex) {
+        // Highly unlikely, but lets Report it but go on
+        // LOG_ERROR(dhcp6_logger, DHCP6_SRV_DHCP4O6_ERROR).arg(ex.what());
+    }
+
+    IfaceMgr::instance().closeSockets();
+
+    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(dhcp6_logger, DHCP6_SRV_UNLOAD_LIBRARIES_ERROR).arg(msg);
+    }
+}
+
+void Dhcpv6Srv::shutdown() {
+    LOG_DEBUG(dhcp6_logger, DBG_DHCP6_BASIC, DHCP6_SHUTDOWN_REQUEST);
+    shutdown_ = true;
+}
+
+Pkt6Ptr Dhcpv6Srv::receivePacket(int timeout) {
+    return (IfaceMgr::instance().receive6(timeout));
+}
+
+void Dhcpv6Srv::sendPacket(const Pkt6Ptr& packet) {
+    IfaceMgr::instance().send(packet);
+}
+
+bool
+Dhcpv6Srv::testServerID(const Pkt6Ptr& pkt) {
+    /// @todo Currently we always check server identifier regardless if
+    /// it is allowed in the received message or not (per RFC 8415).
+    /// If the server identifier is not allowed in the message, the
+    /// sanityCheck function should deal with it.
+    OptionPtr server_id = pkt->getOption(D6O_SERVERID);
+    if (server_id){
+        // Let us test received ServerID if it is same as ServerID
+        // which is being used by server
+        if (getServerID()->getData() != server_id->getData()){
+            LOG_DEBUG(bad_packet6_logger, DBGLVL_PKT_HANDLING, DHCP6_PACKET_DROP_SERVERID_MISMATCH)
+                .arg(pkt->getLabel())
+                .arg(duidToString(server_id))
+                .arg(duidToString(getServerID()));
+            return (false);
+        }
+    }
+    // return True if: no serverid received or ServerIDs matching
+    return (true);
+}
+
+bool
+Dhcpv6Srv::testUnicast(const Pkt6Ptr& pkt) const {
+    switch (pkt->getType()) {
+    case DHCPV6_SOLICIT:
+    case DHCPV6_CONFIRM:
+    case DHCPV6_REBIND:
+    case DHCPV6_INFORMATION_REQUEST:
+        if (pkt->relay_info_.empty() && !pkt->getLocalAddr().isV6Multicast()) {
+            LOG_DEBUG(bad_packet6_logger, DBGLVL_PKT_HANDLING, DHCP6_PACKET_DROP_UNICAST)
+                .arg(pkt->getLabel())
+                .arg(pkt->getName());
+            return (false);
+        }
+        break;
+    default:
+        // do nothing
+        ;
+    }
+    return (true);
+}
+
+void
+Dhcpv6Srv::setHostIdentifiers(AllocEngine::ClientContext6& ctx) {
+    const ConstCfgHostOperationsPtr cfg =
+        CfgMgr::instance().getCurrentCfg()->getCfgHostOperations6();
+    BOOST_FOREACH(const Host::IdentifierType& id_type,
+                  cfg->getIdentifierTypes()) {
+        switch (id_type) {
+        case Host::IDENT_DUID:
+            if (ctx.duid_) {
+                ctx.addHostIdentifier(id_type, ctx.duid_->getDuid());
+            }
+            break;
+
+        case Host::IDENT_HWADDR:
+            if (ctx.hwaddr_) {
+                ctx.addHostIdentifier(id_type, ctx.hwaddr_->hwaddr_);
+            }
+            break;
+        case Host::IDENT_FLEX:
+            // At this point the information in the packet has been unpacked into
+            // the various packet fields and option objects has been created.
+            // Execute callouts registered for host6_identifier.
+            if (HooksManager::calloutsPresent(Hooks.hook_index_host6_identifier_)) {
+                CalloutHandlePtr callout_handle = getCalloutHandle(ctx.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("query6", ctx.query_);
+                callout_handle->setArgument("id_type", type);
+                callout_handle->setArgument("id_value", id);
+
+                // Call callouts
+                HooksManager::callCallouts(Hooks.hook_index_host6_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(packet6_logger, DBGLVL_TRACE_BASIC, DHCP6_FLEX_ID)
+                        .arg(Host::getIdentifierAsText(type, &id[0], id.size()));
+
+                    ctx.addHostIdentifier(type, id);
+                }
+            }
+            break;
+        default:
+            ;
+        }
+    }
+}
+
+bool
+Dhcpv6Srv::earlyGHRLookup(const Pkt6Ptr& query,
+                          AllocEngine::ClientContext6& ctx) {
+    // Pointer to client's query.
+    ctx.query_ = query;
+
+    // DUID.
+    ctx.duid_ = query->getClientId();
+
+    // Hardware address.
+    ctx.hwaddr_ = getMAC(query);
+
+    // 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_) {
+        // Get the host identifiers.
+        setHostIdentifiers(ctx);
+
+        // Check for global host reservations.
+        ConstHostPtr global_host = alloc_engine_->findGlobalReservation(ctx);
+
+        if (global_host && !global_host->getClientClasses6().empty()) {
+            // Remove dependent evaluated classes.
+            removeDependentEvaluatedClasses(query);
+
+            // Add classes from the global reservations.
+            const ClientClasses& classes = global_host->getClientClasses6();
+            for (ClientClasses::const_iterator cclass = classes.cbegin();
+                 cclass != classes.cend(); ++cclass) {
+                query->addClass(*cclass);
+            }
+
+            // Evaluate classes before KNOWN.
+            evaluateClasses(query, false);
+        }
+
+        if (global_host) {
+            // Add the KNOWN class;
+            query->addClass("KNOWN");
+            LOG_DEBUG(dhcp6_logger, DBG_DHCP6_BASIC, DHCP6_CLASS_ASSIGNED)
+                .arg(query->getLabel())
+                .arg("KNOWN");
+
+            // Evaluate classes after KNOWN.
+            evaluateClasses(query, true);
+
+            // Check the DROP special class.
+            if (query->inClass("DROP")) {
+                LOG_DEBUG(packet6_logger, DBGLVL_PKT_HANDLING,
+                          DHCP6_PACKET_DROP_DROP_CLASS_EARLY)
+                    .arg(query->makeLabel(query->getClientId(), nullptr))
+                    .arg(query->toText());
+                StatsMgr::instance().addValue("pkt6-receive-drop",
+                                              static_cast<int64_t>(1));
+                return (false);
+            }
+
+            // Store the reservation.
+            ctx.hosts_[SUBNET_ID_GLOBAL] = global_host;
+        }
+    }
+
+    return (true);
+}
+
+void
+Dhcpv6Srv::initContext(const Pkt6Ptr& pkt,
+                       AllocEngine::ClientContext6& ctx,
+                       bool& drop) {
+    ctx.subnet_ = selectSubnet(pkt, drop);
+    ctx.fwd_dns_update_ = false;
+    ctx.rev_dns_update_ = false;
+    ctx.hostname_ = "";
+    ctx.callout_handle_ = getCalloutHandle(pkt);
+
+    if (drop) {
+        // Caller will immediately drop the packet so simply return now.
+        return;
+    }
+
+    // Collect host identifiers if host reservations enabled. The identifiers
+    // are stored in order of preference. The server will use them in that
+    // order to search for host reservations.
+    SharedNetwork6Ptr sn;
+    if (ctx.subnet_) {
+        // Before we can check for static reservations, we need to prepare
+        // a set of identifiers to be used for this.
+        if (!ctx.early_global_reservations_lookup_) {
+            setHostIdentifiers(ctx);
+        }
+
+        // Find host reservations using specified identifiers.
+        alloc_engine_->findReservation(ctx);
+
+        // Get shared network to see if it is set for a subnet.
+        ctx.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 = ctx.globalHost();
+    auto current_host = ctx.currentHost();
+    if ((!ctx.early_global_reservations_lookup_ &&
+         global_host && !global_host->getClientClasses6().empty()) ||
+        (!sn && current_host && !current_host->getClientClasses6().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(pkt);
+        setReservedClientClasses(pkt, ctx);
+        evaluateClasses(pkt, false);
+    }
+
+    // Set KNOWN builtin class if something was found, UNKNOWN if not.
+    if (!ctx.hosts_.empty()) {
+        pkt->addClass("KNOWN");
+        LOG_DEBUG(dhcp6_logger, DBG_DHCP6_BASIC, DHCP6_CLASS_ASSIGNED)
+          .arg(pkt->getLabel())
+          .arg("KNOWN");
+    } else {
+        pkt->addClass("UNKNOWN");
+        LOG_DEBUG(dhcp6_logger, DBG_DHCP6_BASIC, DHCP6_CLASS_ASSIGNED)
+          .arg(pkt->getLabel())
+          .arg("UNKNOWN");
+    }
+
+    // Perform second pass of classification.
+    evaluateClasses(pkt, true);
+
+    const ClientClasses& classes = pkt->getClasses();
+    if (!classes.empty()) {
+        LOG_DEBUG(dhcp6_logger, DBG_DHCP6_BASIC, DHCP6_CLASS_ASSIGNED)
+            .arg(pkt->getLabel())
+            .arg(classes.toText());
+    }
+
+    // Check the DROP special class.
+    if (pkt->inClass("DROP")) {
+        LOG_DEBUG(packet6_logger, DBGLVL_PKT_HANDLING, DHCP6_PACKET_DROP_DROP_CLASS2)
+            .arg(pkt->makeLabel(pkt->getClientId(), nullptr))
+            .arg(pkt->toText());
+        StatsMgr::instance().addValue("pkt6-receive-drop",
+                                      static_cast<int64_t>(1));
+        drop = true;
+    }
+}
+
+int Dhcpv6Srv::run() {
+#ifdef ENABLE_AFL
+    // Set up structures needed for fuzzing.
+    Fuzz fuzzer(6, 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 standard exceptions that are not caught by more
+            // specific catches.
+            LOG_ERROR(packet6_logger, DHCP6_PACKET_PROCESS_STD_EXCEPTION)
+                .arg(e.what());
+
+        } catch (...) {
+            // General catch-all non-standard exception that are not caught
+            // by more specific catches.
+            LOG_ERROR(packet6_logger, DHCP6_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 Dhcpv6Srv::run_one() {
+    // client's message and server's response
+    Pkt6Ptr 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(packet6_logger, DBG_DHCP6_BASIC, DHCP6_BUFFER_RECEIVED)
+                .arg(query->getRemoteAddr().toText())
+                .arg(query->getRemotePort())
+                .arg(query->getLocalAddr().toText())
+                .arg(query->getLocalPort())
+                .arg(query->getIface());
+
+            // 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 packets further down the road.
+            // See processStatsReceived().
+            StatsMgr::instance().addValue("pkt6-received", static_cast<int64_t>(1));
+        }
+
+        // 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(packet6_logger, DBG_DHCP6_DETAIL, DHCP6_BUFFER_WAIT_SIGNAL);
+    } catch (const std::exception& e) {
+        LOG_ERROR(packet6_logger, DHCP6_PACKET_RECEIVE_FAIL).arg(e.what());
+    }
+
+    // Timeout may be reached or signal received, which breaks select()
+    // with no packet received
+    if (!query) {
+        return;
+    }
+
+    // If the DHCP service has been globally disabled, drop the packet.
+    if (!network_state_->isServiceEnabled()) {
+        LOG_DEBUG(bad_packet6_logger, DBGLVL_PKT_HANDLING, DHCP6_PACKET_DROP_DHCP_DISABLED)
+            .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(&Dhcpv6Srv::processPacketAndSendResponseNoThrow,
+                                                       this, query));
+            if (!MultiThreadingMgr::instance().getThreadPool().add(call_back)) {
+                LOG_DEBUG(dhcp6_logger, DBG_DHCP6_BASIC, DHCP6_PACKET_QUEUE_FULL);
+            }
+        } else {
+            processPacketAndSendResponse(query);
+        }
+    }
+}
+
+void
+Dhcpv6Srv::processPacketAndSendResponseNoThrow(Pkt6Ptr& query) {
+    try {
+        processPacketAndSendResponse(query);
+    } catch (const std::exception& e) {
+        LOG_ERROR(packet6_logger, DHCP6_PACKET_PROCESS_STD_EXCEPTION)
+            .arg(e.what());
+    } catch (...) {
+        LOG_ERROR(packet6_logger, DHCP6_PACKET_PROCESS_EXCEPTION);
+    }
+}
+
+void
+Dhcpv6Srv::processPacketAndSendResponse(Pkt6Ptr& query) {
+    Pkt6Ptr rsp;
+    processPacket(query, rsp);
+    if (!rsp) {
+        return;
+    }
+
+    CalloutHandlePtr callout_handle = getCalloutHandle(query);
+    processPacketBufferSend(callout_handle, rsp);
+}
+
+void
+Dhcpv6Srv::processPacket(Pkt6Ptr& query, Pkt6Ptr& rsp) {
+    // All packets belong to ALL.
+    query->addClass("ALL");
+
+    bool skip_unpack = false;
+
+    // The packet has just been received so contains the uninterpreted wire
+    // data; execute callouts registered for buffer6_receive.
+    if (HooksManager::calloutsPresent(Hooks.hook_index_buffer6_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<Pkt6> query6_options_copy(query);
+
+        // Pass incoming packet as argument
+        callout_handle->setArgument("query6", query);
+
+        // Call callouts
+        HooksManager::callCallouts(Hooks.hook_index_buffer6_receive_, *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 that callouts did the parsing already, so server
+        // should skip parsing.
+        if (callout_handle->getStatus() == CalloutHandle::NEXT_STEP_SKIP) {
+            LOG_DEBUG(hooks_logger, DBG_DHCP6_DETAIL, DHCP6_HOOK_BUFFER_RCVD_SKIP)
+                .arg(query->getRemoteAddr().toText())
+                .arg(query->getLocalAddr().toText())
+                .arg(query->getIface());
+            skip_unpack = true;
+        }
+
+        // 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, DHCP6_HOOK_BUFFER_RCVD_DROP)
+                .arg(query->getRemoteAddr().toText())
+                .arg(query->getLocalAddr().toText())
+                .arg(query->getIface());
+
+            // Increase the statistic of dropped packets.
+            StatsMgr::instance().addValue("pkt6-receive-drop",
+                                          static_cast<int64_t>(1));
+            return;
+        }
+
+        callout_handle->getArgument("query6", query);
+    }
+
+    // Unpack the packet information unless the buffer6_receive callouts
+    // indicated they did it
+    if (!skip_unpack) {
+        try {
+            LOG_DEBUG(options6_logger, DBG_DHCP6_DETAIL, DHCP6_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(options6_logger, DBG_DHCP6_DETAIL,
+                      DHCP6_PACKET_OPTIONS_SKIPPED)
+                .arg(e.what());
+        } catch (const std::exception &e) {
+            // Failed to parse the packet.
+            LOG_DEBUG(bad_packet6_logger, DBGLVL_PKT_HANDLING, DHCP6_PACKET_DROP_PARSE_FAIL)
+                .arg(query->getRemoteAddr().toText())
+                .arg(query->getLocalAddr().toText())
+                .arg(query->getIface())
+                .arg(e.what())
+                .arg(query->makeLabel(query->getClientId(), nullptr));
+
+            // Increase the statistics of parse failures and dropped packets.
+            StatsMgr::instance().addValue("pkt6-parse-failed",
+                                          static_cast<int64_t>(1));
+            StatsMgr::instance().addValue("pkt6-receive-drop",
+                                          static_cast<int64_t>(1));
+            return;
+        }
+    }
+
+    // Update statistics accordingly for received packet.
+    processStatsReceived(query);
+
+    // Check if received query carries server identifier matching
+    // server identifier being used by the server.
+    if (!testServerID(query)) {
+
+        // Increase the statistic of dropped packets.
+        StatsMgr::instance().addValue("pkt6-receive-drop", static_cast<int64_t>(1));
+        return;
+    }
+
+    // Check if the received query has been sent to unicast or multicast.
+    // The Solicit, Confirm, Rebind and Information Request will be
+    // discarded if sent to unicast address.
+    if (!testUnicast(query)) {
+
+        // Increase the statistic of dropped packets.
+        StatsMgr::instance().addValue("pkt6-receive-drop", static_cast<int64_t>(1));
+        return;
+    }
+
+    // Assign this packet to a class, if possible
+    classifyPacket(query);
+
+    LOG_DEBUG(packet6_logger, DBG_DHCP6_BASIC_DATA, DHCP6_PACKET_RECEIVED)
+        .arg(query->getLabel())
+        .arg(query->getName())
+        .arg(static_cast<int>(query->getType()))
+        .arg(query->getRemoteAddr())
+        .arg(query->getLocalAddr())
+        .arg(query->getIface());
+    LOG_DEBUG(packet6_logger, DBG_DHCP6_DETAIL_DATA, DHCP6_QUERY_DATA)
+        .arg(query->getLabel())
+        .arg(query->toText());
+
+    // At this point the information in the packet has been unpacked into
+    // the various packet fields and option objects has been created.
+    // Execute callouts registered for packet6_receive.
+    if (HooksManager::calloutsPresent(Hooks.hook_index_pkt6_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<Pkt6> query6_options_copy(query);
+
+        // Pass incoming packet as argument
+        callout_handle->setArgument("query6", query);
+
+        // Call callouts
+        HooksManager::callCallouts(Hooks.hook_index_pkt6_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_DHCP6_HOOKS, DHCP6_HOOK_PACKET_RCVD_SKIP)
+                .arg(query->getLabel());
+            // Increase the statistic of dropped packets.
+            StatsMgr::instance().addValue("pkt6-receive-drop",
+                                          static_cast<int64_t>(1));
+            return;
+        }
+
+        callout_handle->getArgument("query6", query);
+    }
+
+    // Reject the message if it doesn't pass the sanity check.
+    if (!sanityCheck(query)) {
+        return;
+    }
+
+    // Check the DROP special class.
+    if (query->inClass("DROP")) {
+        LOG_DEBUG(packet6_logger, DBGLVL_PKT_HANDLING, DHCP6_PACKET_DROP_DROP_CLASS)
+            .arg(query->makeLabel(query->getClientId(), nullptr))
+            .arg(query->toText());
+        StatsMgr::instance().addValue("pkt6-receive-drop",
+                                      static_cast<int64_t>(1));
+        return;
+    }
+
+    processDhcp6Query(query, rsp);
+}
+
+void
+Dhcpv6Srv::processDhcp6QueryAndSendResponse(Pkt6Ptr& query, Pkt6Ptr& rsp) {
+    try {
+        processDhcp6Query(query, rsp);
+        if (!rsp) {
+            return;
+        }
+
+        CalloutHandlePtr callout_handle = getCalloutHandle(query);
+        processPacketBufferSend(callout_handle, rsp);
+    } catch (const std::exception& e) {
+        LOG_ERROR(packet6_logger, DHCP6_PACKET_PROCESS_STD_EXCEPTION)
+            .arg(e.what());
+    } catch (...) {
+        LOG_ERROR(packet6_logger, DHCP6_PACKET_PROCESS_EXCEPTION);
+    }
+}
+
+void
+Dhcpv6Srv::processDhcp6Query(Pkt6Ptr& query, Pkt6Ptr& rsp) {
+    // 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() == DHCPV6_SOLICIT) ||
+         (query->getType() == DHCPV6_REQUEST) ||
+         (query->getType() == DHCPV6_RENEW) ||
+         (query->getType() == DHCPV6_REBIND) ||
+         (query->getType() == DHCPV6_RELEASE) ||
+         (query->getType() == DHCPV6_DECLINE))) {
+        ContinuationPtr cont =
+            makeContinuation(std::bind(&Dhcpv6Srv::processDhcp6QueryAndSendResponse,
+                                       this, query, rsp));
+        if (!client_handler.tryLock(query, cont)) {
+            return;
+        }
+    }
+
+    // Let's create a simplified client context here.
+    AllocEngine::ClientContext6 ctx;
+    if (!earlyGHRLookup(query, ctx)) {
+        return;
+    }
+
+    if (query->getType() == DHCPV6_DHCPV4_QUERY) {
+        // This call never throws. Should this change, this section must be
+        // enclosed in try-catch.
+        processDhcp4Query(query);
+        return;
+    }
+
+    // Complete the client context initialization.
+    bool drop = false;
+    initContext(query, ctx, drop);
+
+    // Stop here if initContext decided to drop the packet.
+    if (drop) {
+        return;
+    }
+
+    // Park point here.
+
+    try {
+        switch (query->getType()) {
+        case DHCPV6_SOLICIT:
+            rsp = processSolicit(ctx);
+            break;
+
+        case DHCPV6_REQUEST:
+            rsp = processRequest(ctx);
+            break;
+
+        case DHCPV6_RENEW:
+            rsp = processRenew(ctx);
+            break;
+
+        case DHCPV6_REBIND:
+            rsp = processRebind(ctx);
+            break;
+
+        case DHCPV6_CONFIRM:
+            rsp = processConfirm(ctx);
+            break;
+
+        case DHCPV6_RELEASE:
+            rsp = processRelease(ctx);
+            break;
+
+        case DHCPV6_DECLINE:
+            rsp = processDecline(ctx);
+            break;
+
+        case DHCPV6_INFORMATION_REQUEST:
+            rsp = processInfRequest(ctx);
+            break;
+
+        default:
+            return;
+        }
+
+    } catch (const std::exception& e) {
+
+        // Catch-all exception (at least for ones based on the isc Exception
+        // class, which covers more or less all that are explicitly raised
+        // in the Kea code), but also the standard one, which may possibly be
+        // thrown from boost code.  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_packet6_logger, DBG_DHCP6_BASIC, DHCP6_PACKET_PROCESS_FAIL)
+            .arg(query->getName())
+            .arg(query->getRemoteAddr().toText())
+            .arg(e.what());
+
+        // Increase the statistic of dropped packets.
+        StatsMgr::instance().addValue("pkt6-receive-drop", static_cast<int64_t>(1));
+    }
+
+    if (!rsp) {
+        return;
+    }
+
+    // Process relay-supplied options. It is important to call this very
+    // late in the process, because we now have all the options the
+    // server wanted to send already set. This is important, because
+    // RFC6422, section 6 states:
+    //
+    //   The server SHOULD discard any options that appear in the RSOO
+    //   for which it already has one or more candidates.
+    //
+    // So we ignore any RSOO options if there's an option with the same
+    // code already present.
+    processRSOO(query, rsp);
+
+    rsp->setRemoteAddr(query->getRemoteAddr());
+    rsp->setLocalAddr(query->getLocalAddr());
+
+    if (client_port_) {
+        // A command line option enforces a specific client port
+        rsp->setRemotePort(client_port_);
+    } else if (rsp->relay_info_.empty()) {
+        // Direct traffic, send back to the client directly
+        rsp->setRemotePort(DHCP6_CLIENT_PORT);
+    } else {
+        // Relayed traffic, send back to the relay agent
+        uint16_t relay_port = checkRelaySourcePort(query);
+        rsp->setRemotePort(relay_port ? relay_port : DHCP6_SERVER_PORT);
+    }
+
+    if (server_port_) {
+        rsp->setLocalPort(server_port_);
+    } else {
+        rsp->setLocalPort(DHCP6_SERVER_PORT);
+    }
+    rsp->setIndex(query->getIndex());
+    rsp->setIface(query->getIface());
+
+    CalloutHandlePtr callout_handle = getCalloutHandle(query);
+    if (!ctx.fake_allocation_ && (ctx.query_->getType() != DHCPV6_CONFIRM) &&
+        (ctx.query_->getType() != DHCPV6_INFORMATION_REQUEST) &&
+        HooksManager::calloutsPresent(Hooks.hook_index_leases6_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<Pkt6> query6_options_copy(query);
+
+        // Also pass the corresponding query packet as argument
+        callout_handle->setArgument("query6", query);
+
+        Lease6CollectionPtr new_leases(new Lease6Collection());
+        if (!ctx.new_leases_.empty()) {
+            // Filter out reused leases as they were not committed.
+            for (auto new_lease : ctx.new_leases_) {
+                if (new_lease->reuseable_valid_lft_ == 0) {
+                    new_leases->push_back(new_lease);
+                }
+            }
+        }
+        callout_handle->setArgument("leases6", new_leases);
+
+        Lease6CollectionPtr deleted_leases(new Lease6Collection());
+
+        // Do per IA lists
+        for (auto const& iac : ctx.ias_) {
+            if (!iac.old_leases_.empty()) {
+                for (auto old_lease : iac.old_leases_) {
+                    if (ctx.new_leases_.empty()) {
+                        deleted_leases->push_back(old_lease);
+                        continue;
+                    }
+                    bool in_new = false;
+                    for (auto const& new_lease : ctx.new_leases_) {
+                        if ((new_lease->addr_ == old_lease->addr_) &&
+                            ((new_lease->type_ != Lease::TYPE_PD) ||
+                             (new_lease->prefixlen_ == old_lease->prefixlen_))) {
+                            in_new = true;
+                            break;
+                        }
+                    }
+                    if (!in_new) {
+                        deleted_leases->push_back(old_lease);
+                    }
+                }
+            }
+        }
+        callout_handle->setArgument("deleted_leases6", deleted_leases);
+
+        // 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("leases6_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(packet6_logger, DBGLVL_PKT_HANDLING,
+                          DHCP6_HOOK_LEASES6_PARKING_LOT_FULL)
+                          .arg(parked_packet_limit)
+                          .arg(query->getLabel());
+                isc::stats::StatsMgr::instance().addValue("pkt6-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("leases6_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(&Dhcpv6Srv::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_leases6_committed_,
+                                       *callout_handle);
+        } catch (...) {
+            // Make sure we don't orphan a parked packet.
+            HooksManager::drop("leases6_committed", query);
+            throw;
+        }
+
+        if (callout_handle->getStatus() == CalloutHandle::NEXT_STEP_PARK) {
+            LOG_DEBUG(hooks_logger, DBG_DHCP6_HOOKS, DHCP6_HOOK_LEASES6_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("leases6_committed", query);
+            if (callout_handle->getStatus() == CalloutHandle::NEXT_STEP_DROP) {
+                LOG_DEBUG(hooks_logger, DBGLVL_PKT_HANDLING, DHCP6_HOOK_LEASES6_COMMITTED_DROP)
+                          .arg(query->getLabel());
+                rsp.reset();
+            }
+        }
+    }
+
+    // If we have a response prep it for shipment.
+    if (rsp) {
+        processPacketPktSend(callout_handle, query, rsp);
+    }
+}
+
+void
+Dhcpv6Srv::sendResponseNoThrow(hooks::CalloutHandlePtr& callout_handle,
+                               Pkt6Ptr& query, Pkt6Ptr& rsp) {
+    try {
+            processPacketPktSend(callout_handle, query, rsp);
+            processPacketBufferSend(callout_handle, rsp);
+        } catch (const std::exception& e) {
+            LOG_ERROR(packet6_logger, DHCP6_PACKET_PROCESS_STD_EXCEPTION)
+                .arg(e.what());
+    } catch (...) {
+        LOG_ERROR(packet6_logger, DHCP6_PACKET_PROCESS_EXCEPTION);
+    }
+}
+
+void
+Dhcpv6Srv::processPacketPktSend(hooks::CalloutHandlePtr& callout_handle,
+                                Pkt6Ptr& query, Pkt6Ptr& rsp) {
+    if (!rsp) {
+        return;
+    }
+
+    // Specifies if server should do the packing
+    bool skip_pack = false;
+
+    // Server's reply packet now has all options and fields set.
+    // Options are represented by individual objects, but the
+    // output wire data has not been prepared yet.
+    // Execute all callouts registered for packet6_send
+    if (HooksManager::calloutsPresent(Hooks.hook_index_pkt6_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 packets within hook library.
+        ScopedEnableOptionsCopy<Pkt6> query_resp_options_copy(query, rsp);
+
+        // Pass incoming packet as argument
+        callout_handle->setArgument("query6", query);
+
+        // Set our response
+        callout_handle->setArgument("response6", rsp);
+
+        // Call all installed callouts
+        HooksManager::callCallouts(Hooks.hook_index_pkt6_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_DHCP6_HOOKS, DHCP6_HOOK_PACKET_SEND_SKIP)
+                .arg(rsp->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, DHCP6_HOOK_PACKET_SEND_DROP)
+                .arg(rsp->getLabel());
+            rsp.reset();
+            return;
+        }
+    }
+
+    if (!skip_pack) {
+        try {
+            rsp->pack();
+        } catch (const std::exception& e) {
+            LOG_ERROR(options6_logger, DHCP6_PACK_FAIL).arg(e.what());
+            return;
+        }
+
+    }
+}
+
+void
+Dhcpv6Srv::processPacketBufferSend(CalloutHandlePtr& callout_handle,
+                                   Pkt6Ptr& 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 buffer6_send
+        if (HooksManager::calloutsPresent(Hooks.hook_index_buffer6_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<Pkt6> response6_options_copy(rsp);
+
+            // Pass incoming packet as argument
+            callout_handle->setArgument("response6", rsp);
+
+            // Call callouts
+            HooksManager::callCallouts(Hooks.hook_index_buffer6_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_DHCP6_HOOKS,
+                          DHCP6_HOOK_BUFFER_SEND_SKIP)
+                    .arg(rsp->getLabel());
+                return;
+            }
+
+            callout_handle->getArgument("response6", rsp);
+        }
+
+        LOG_DEBUG(packet6_logger, DBG_DHCP6_BASIC, DHCP6_PACKET_SEND)
+            .arg(rsp->getLabel())
+            .arg(rsp->getName())
+            .arg(static_cast<int>(rsp->getType()))
+            .arg(rsp->getLocalAddr().isV6Zero() ? "*" : rsp->getLocalAddr().toText())
+            .arg(rsp->getLocalPort())
+            .arg(rsp->getRemoteAddr())
+            .arg(rsp->getRemotePort())
+            .arg(rsp->getIface());
+
+        LOG_DEBUG(packet6_logger, DBG_DHCP6_DETAIL_DATA, DHCP6_RESPONSE_DATA)
+            .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(packet6_logger, DHCP6_PACKET_SEND_FAIL).arg(e.what());
+    }
+}
+
+std::string
+Dhcpv6Srv::duidToString(const OptionPtr& opt) {
+    stringstream tmp;
+
+    OptionBuffer data = opt->getData();
+
+    bool colon = false;
+    for (OptionBufferConstIter it = data.begin(); it != data.end(); ++it) {
+        if (colon) {
+            tmp << ":";
+        }
+        tmp << hex << setw(2) << setfill('0') << static_cast<uint16_t>(*it);
+        if (!colon) {
+            colon = true;
+        }
+    }
+
+    return tmp.str();
+}
+
+void
+Dhcpv6Srv::copyClientOptions(const Pkt6Ptr& question, Pkt6Ptr& answer) {
+    // Add client-id.
+    OptionPtr clientid = question->getOption(D6O_CLIENTID);
+    if (clientid) {
+        answer->addOption(clientid);
+    }
+    /// @todo: Should throw if there is no client-id (except anonymous INF-REQUEST)
+
+    // If this is a relayed message, we need to copy relay information
+    if (!question->relay_info_.empty()) {
+        answer->copyRelayInfo(question);
+    }
+
+}
+
+void
+Dhcpv6Srv::appendDefaultOptions(const Pkt6Ptr&, Pkt6Ptr& answer,
+                                const CfgOptionList&) {
+    // add server-id
+    answer->addOption(getServerID());
+}
+
+void
+Dhcpv6Srv::buildCfgOptionList(const Pkt6Ptr& question,
+                              AllocEngine::ClientContext6& ctx,
+                              CfgOptionList& co_list) {
+    // Firstly, host specific options.
+    if (ctx.currentHost() && !ctx.currentHost()->getCfgOption6()->empty()) {
+        co_list.push_back(ctx.currentHost()->getCfgOption6());
+    }
+
+    // Secondly, pool specific options. Pools are defined within a subnet, so
+    // if there is no subnet, there is nothing to do.
+    if (ctx.subnet_) {
+        for (auto resource : ctx.allocated_resources_) {
+            PoolPtr pool =
+                ctx.subnet_->getPool(resource.getPrefixLength() == 128 ?
+                                     Lease::TYPE_NA : Lease::TYPE_PD,
+                                     resource.getAddress(),
+                                     false);
+            if (pool && !pool->getCfgOption()->empty()) {
+                co_list.push_back(pool->getCfgOption());
+            }
+        }
+
+        // Thirdly, subnet configured options.
+        if (!ctx.subnet_->getCfgOption()->empty()) {
+            co_list.push_back(ctx.subnet_->getCfgOption());
+        }
+
+        // Fourthly, shared network specific options.
+        SharedNetwork6Ptr network;
+        ctx.subnet_->getSharedNetwork(network);
+        if (network && !network->getCfgOption()->empty()) {
+            co_list.push_back(network->getCfgOption());
+        }
+    }
+
+    // Each class in the incoming packet
+    const ClientClasses& classes = question->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(dhcp6_logger, DBG_DHCP6_BASIC, DHCP6_CLASS_UNCONFIGURED)
+                    .arg(question->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
+Dhcpv6Srv::appendRequestedOptions(const Pkt6Ptr& question, Pkt6Ptr& answer,
+                                  const CfgOptionList& co_list) {
+    // Unlikely short cut
+    if (co_list.empty()) {
+        return;
+    }
+
+    set<uint16_t> requested_opts;
+
+    // Client requests some options using ORO option. Try to
+    // get this option from client's message.
+    OptionUint16ArrayPtr option_oro = boost::dynamic_pointer_cast<
+        OptionUint16Array>(question->getOption(D6O_ORO));
+
+    // Get the list of options that client requested.
+    if (option_oro) {
+        for (uint16_t code : option_oro->getValues()) {
+            static_cast<void>(requested_opts.insert(code));
+        }
+    }
+
+    set<uint16_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(DHCP6_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_) {
+                uint16_t code = 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 the cancelled options.
+            if (desc->option_) {
+                uint16_t code = 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 (uint16_t opt : requested_opts) {
+        // Skip if cancelled.
+        if (cancelled_opts.count(opt) > 0) {
+            continue;
+        }
+        // Add nothing when it is already there.
+        // Skip special cases: D6O_VENDOR_OPTS
+        if (opt == D6O_VENDOR_OPTS) {
+            continue;
+        }
+        if (!answer->getOption(opt)) {
+            // Iterate on the configured option list
+            for (auto const& copts : co_list) {
+                OptionDescriptor desc = copts->get(DHCP6_OPTION_SPACE, opt);
+                // Got it: add it and jump to the outer loop
+                if (desc.option_) {
+                    answer->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(D6O_VENDOR_CLASS) > 0) &&
+        (cancelled_opts.count(D6O_VENDOR_CLASS) == 0)) {
+        // Keep vendor ids which are already in the response to insert
+        // D6O_VENDOR_CLASS options at most once per vendor.
+        set<uint32_t> vendor_ids;
+        // Get what already exists in the response.
+        for (auto opt : answer->getOptions(D6O_VENDOR_CLASS)) {
+            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));
+            }
+        }
+        // Iterate on the configured option list.
+        for (auto const& copts : co_list) {
+            for (OptionDescriptor desc : copts->getList(DHCP6_OPTION_SPACE,
+                                                        D6O_VENDOR_CLASS)) {
+                if (!desc.option_) {
+                    continue;
+                }
+                OptionVendorClassPtr vendor_class =
+                    boost::dynamic_pointer_cast<OptionVendorClass>(desc.option_);
+                if (!vendor_class) {
+                    continue;
+                }
+                // Is the vendor id already in the response?
+                uint32_t vendor_id = vendor_class->getVendorId();
+                if (vendor_ids.count(vendor_id) > 0) {
+                    continue;
+                }
+                // Got it: add it.
+                answer->addOption(desc.option_);
+                static_cast<void>(vendor_ids.insert(vendor_id));
+            }
+        }
+    }
+
+    if ((requested_opts.count(D6O_VENDOR_OPTS) > 0) &&
+        (cancelled_opts.count(D6O_VENDOR_OPTS) == 0)) {
+        // Keep vendor ids which are already in the response to insert
+        // D6O_VENDOR_OPTS options at most once per vendor.
+        set<uint32_t> vendor_ids;
+        // Get what already exists in the response.
+        for (auto opt : answer->getOptions(D6O_VENDOR_OPTS)) {
+            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(DHCP6_OPTION_SPACE,
+                                                        D6O_VENDOR_OPTS)) {
+                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::V6, vendor_id));
+                answer->addOption(vendor_opts);
+                static_cast<void>(vendor_ids.insert(vendor_id));
+            }
+        }
+    }
+}
+
+void
+Dhcpv6Srv::appendRequestedVendorOptions(const Pkt6Ptr& question,
+                                        Pkt6Ptr& answer,
+                                        AllocEngine::ClientContext6& ctx,
+                                        const CfgOptionList& co_list) {
+
+    // 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 (!ctx.subnet_ || co_list.empty()) {
+        return;
+    }
+
+    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 : answer->getOptions(D6O_VENDOR_OPTS)) {
+        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 (17).
+    map<uint32_t, OptionVendorPtr> vendor_reqs;
+    for (auto opt : question->getOptions(D6O_VENDOR_OPTS)) {
+        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-class
+    // option (16).
+    for (auto opt : question->getOptions(D6O_VENDOR_CLASS)) {
+        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<uint16_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.
+    OptionUint16ArrayPtr 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_V6_ORO);
+        if (oro_generic) {
+            // Vendor ID 4491 makes Kea look at DOCSIS3_V6_OPTION_DEFINITIONS
+            // when parsing options. Based on that, oro_generic will have been
+            // created as an OptionUint16Array, but might not be for other
+            // vendor IDs.
+            oro = boost::dynamic_pointer_cast<OptionUint16Array>(oro_generic);
+        }
+        if (oro) {
+            set<uint16_t> oro_req_opts;
+            for (uint16_t code : oro->getValues()) {
+                static_cast<void>(oro_req_opts.insert(code));
+            }
+            requested_opts[VENDOR_ID_CABLE_LABS] = oro_req_opts;
+        }
+    }
+
+    map<uint32_t, set<uint16_t> > cancelled_opts;
+
+    // Iterate on the configured option list to add persistent and
+    // cancelled options.
+    for (uint32_t vendor_id : vendor_ids) {
+        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) {
+                if (!desc->option_) {
+                    continue;
+                }
+                // Add the persistent option code to requested options
+                uint16_t code = 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) {
+                if (!desc->option_) {
+                    continue;
+                }
+                // Add the cancelled option code to cancelled options
+                uint16_t code = desc->option_->getType();
+                static_cast<void>(cancelled_opts[vendor_id].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 the vendor opts option 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::V6, vendor_id));
+        }
+
+        // Get the list of options that client requested.
+        bool added = false;
+
+        for (uint16_t opt : requested_opts[vendor_id]) {
+            if (cancelled_opts[vendor_id].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)) {
+            answer->addOption(vendor_rsp);
+        }
+    }
+}
+
+bool
+Dhcpv6Srv::sanityCheck(const Pkt6Ptr& pkt) {
+    try {
+        switch (pkt->getType()) {
+        case DHCPV6_SOLICIT:
+        case DHCPV6_REBIND:
+        case DHCPV6_CONFIRM:
+            sanityCheck(pkt, MANDATORY, FORBIDDEN);
+            return (true);
+
+        case DHCPV6_REQUEST:
+        case DHCPV6_RENEW:
+        case DHCPV6_RELEASE:
+        case DHCPV6_DECLINE:
+            sanityCheck(pkt, MANDATORY, MANDATORY);
+            return (true);
+
+        case DHCPV6_INFORMATION_REQUEST:
+        case DHCPV6_DHCPV4_QUERY:
+            sanityCheck(pkt, OPTIONAL, OPTIONAL);
+            return (true);
+
+        default:
+            LOG_DEBUG(bad_packet6_logger, DBG_DHCP6_BASIC,
+                      DHCP6_UNKNOWN_MSG_RECEIVED)
+                .arg(static_cast<int>(pkt->getType()))
+                .arg(pkt->getIface());
+        }
+
+    } catch (const RFCViolation& e) {
+        LOG_DEBUG(bad_packet6_logger, DBG_DHCP6_BASIC, DHCP6_REQUIRED_OPTIONS_CHECK_FAIL)
+            .arg(pkt->getName())
+            .arg(pkt->getRemoteAddr().toText())
+            .arg(e.what());
+
+    }
+
+    // Increase the statistic of dropped packets.
+    StatsMgr::instance().addValue("pkt6-receive-drop", static_cast<int64_t>(1));
+    return (false);
+}
+
+void
+Dhcpv6Srv::sanityCheck(const Pkt6Ptr& pkt, RequirementLevel clientid,
+                       RequirementLevel serverid) {
+    OptionCollection client_ids = pkt->getOptions(D6O_CLIENTID);
+    switch (clientid) {
+    case MANDATORY: {
+        if (client_ids.size() != 1) {
+            isc_throw(RFCViolation, "Exactly 1 client-id option expected in "
+                      << pkt->getName() << ", but " << client_ids.size()
+                      << " received");
+        }
+        sanityCheckDUID(client_ids.begin()->second, "client-id");
+        break;
+    }
+    case OPTIONAL:
+        if (client_ids.size() > 1) {
+            isc_throw(RFCViolation, "Too many (" << client_ids.size()
+                      << ") client-id options received in " << pkt->getName());
+        }
+        if (!client_ids.empty()) {
+            sanityCheckDUID(client_ids.begin()->second, "client-id");
+        }
+        break;
+
+    case FORBIDDEN:
+        // doesn't make sense - client-id is always allowed
+        break;
+    }
+
+    OptionCollection server_ids = pkt->getOptions(D6O_SERVERID);
+    switch (serverid) {
+    case FORBIDDEN:
+        if (!server_ids.empty()) {
+            isc_throw(RFCViolation, "Server-id option was not expected, but "
+                      << server_ids.size() << " received in " << pkt->getName());
+        }
+        break;
+
+    case MANDATORY:
+        if (server_ids.size() != 1) {
+            isc_throw(RFCViolation, "Invalid number of server-id options received ("
+                      << server_ids.size() << "), exactly 1 expected in message "
+                      << pkt->getName());
+        }
+        sanityCheckDUID(server_ids.begin()->second, "server-id");
+        break;
+
+    case OPTIONAL:
+        if (server_ids.size() > 1) {
+            isc_throw(RFCViolation, "Too many (" << server_ids.size()
+                      << ") server-id options received in " << pkt->getName());
+        }
+        if (!server_ids.empty()) {
+            sanityCheckDUID(server_ids.begin()->second, "server-id");
+        }
+    }
+}
+
+void Dhcpv6Srv::sanityCheckDUID(const OptionPtr& opt, const std::string& opt_name) {
+    if (!opt) {
+        isc_throw(RFCViolation, "Unable to find expected option " << opt_name);
+    }
+
+    // The client-id or server-id has to have at least 3 bytes of useful data:
+    // two for duid type and one more for actual duid value.
+    uint16_t len = opt->len() - opt->getHeaderLen();
+    if (len < DUID::MIN_DUID_LEN || len > DUID::MAX_DUID_LEN) {
+        isc_throw(RFCViolation, "Received invalid DUID for " << opt_name << ", received "
+                  << len << " byte(s). It must be at least " << DUID::MIN_DUID_LEN
+                  << " and no more than " << DUID::MAX_DUID_LEN);
+    }
+}
+
+Subnet6Ptr
+Dhcpv6Srv::selectSubnet(const Pkt6Ptr& question, bool& drop) {
+    const SubnetSelector& selector = CfgSubnets6::initSelector(question);
+
+    Subnet6Ptr subnet = CfgMgr::instance().getCurrentCfg()->
+        getCfgSubnets6()->selectSubnet(selector);
+
+    // Let's execute all callouts registered for subnet6_receive
+    if (HooksManager::calloutsPresent(Hooks.hook_index_subnet6_select_)) {
+        CalloutHandlePtr callout_handle = getCalloutHandle(question);
+
+        // 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<Pkt6> query6_options_copy(question);
+
+        // Set new arguments
+        callout_handle->setArgument("query6", question);
+        callout_handle->setArgument("subnet6", subnet);
+
+        // We pass pointer to const collection for performance reasons.
+        // Otherwise we would get a non-trivial performance penalty each
+        // time subnet6_select is called.
+        callout_handle->setArgument("subnet6collection",
+                                    CfgMgr::instance().getCurrentCfg()->
+                                    getCfgSubnets6()->getAll());
+
+        // Call user (and server-side) callouts
+        HooksManager::callCallouts(Hooks.hook_index_subnet6_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_DHCP6_HOOKS, DHCP6_HOOK_SUBNET6_SELECT_SKIP)
+                .arg(question->getLabel());
+            return (Subnet6Ptr());
+        }
+
+        // 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_DHCP6_HOOKS, DHCP6_HOOK_SUBNET6_SELECT_DROP)
+                .arg(question->getLabel());
+            drop = true;
+            return (Subnet6Ptr());
+        }
+
+        // Use whatever subnet was specified by the callout
+        callout_handle->getArgument("subnet6", subnet);
+    }
+
+    if (subnet) {
+        // Log at higher debug level that subnet has been found.
+        LOG_DEBUG(packet6_logger, DBG_DHCP6_BASIC_DATA, DHCP6_SUBNET_SELECTED)
+            .arg(question->getLabel())
+            .arg(subnet->getID());
+        // Log detailed information about the selected subnet at the
+        // lower debug level.
+        LOG_DEBUG(packet6_logger, DBG_DHCP6_DETAIL_DATA, DHCP6_SUBNET_DATA)
+            .arg(question->getLabel())
+            .arg(subnet->toText());
+
+    } else {
+        LOG_DEBUG(packet6_logger, DBG_DHCP6_DETAIL, DHCP6_SUBNET_SELECTION_FAILED)
+            .arg(question->getLabel());
+    }
+
+    return (subnet);
+}
+
+void
+Dhcpv6Srv::assignLeases(const Pkt6Ptr& question, Pkt6Ptr& answer,
+                        AllocEngine::ClientContext6& ctx) {
+    // Save the originally selected subnet.
+    Subnet6Ptr orig_subnet = ctx.subnet_;
+
+    // We need to allocate addresses for all IA_NA options in the client's
+    // question (i.e. SOLICIT or REQUEST) message.
+    // @todo add support for IA_TA
+
+    // For the lease allocation it is critical that the client has sent
+    // DUID. There is no need to check for the presence of the DUID here
+    // because we have already checked it in the sanityCheck().
+
+    // Now that we have all information about the client, let's iterate over all
+    // received options and handle IA_NA options one by one and store our
+    // responses in answer message (ADVERTISE or REPLY).
+    //
+    // @todo: IA_TA once we implement support for temporary addresses.
+    for (const auto& opt : question->options_) {
+        switch (opt.second->getType()) {
+        case D6O_IA_NA: {
+            OptionPtr answer_opt = assignIA_NA(question, ctx,
+                                               boost::dynamic_pointer_cast<
+                                               Option6IA>(opt.second));
+            if (answer_opt) {
+                answer->addOption(answer_opt);
+            }
+            break;
+        }
+        case D6O_IA_PD: {
+            OptionPtr answer_opt = assignIA_PD(question, ctx,
+                                               boost::dynamic_pointer_cast<
+                                               Option6IA>(opt.second));
+            if (answer_opt) {
+                answer->addOption(answer_opt);
+            }
+            break;
+        }
+        default:
+            break;
+        }
+    }
+
+    // Subnet may be modified by the allocation engine, there are things
+    // we need to do when that happens.
+    checkDynamicSubnetChange(question, answer, ctx, orig_subnet);
+}
+
+void
+Dhcpv6Srv::processClientFqdn(const Pkt6Ptr& question, const Pkt6Ptr& answer,
+                             AllocEngine::ClientContext6& ctx) {
+    D2ClientMgr& d2_mgr = CfgMgr::instance().getD2ClientMgr();
+    DdnsParamsPtr ddns_params = ctx.getDdnsParams();
+
+    // Get Client FQDN Option from the client's message. If this option hasn't
+    // been included, do nothing.
+    Option6ClientFqdnPtr fqdn = boost::dynamic_pointer_cast<
+        Option6ClientFqdn>(question->getOption(D6O_CLIENT_FQDN));
+    if (!fqdn) {
+        if (ddns_params->getEnableUpdates() &&
+            (ddns_params->getReplaceClientNameMode() == D2ClientConfig::RCM_ALWAYS ||
+             ddns_params->getReplaceClientNameMode() == D2ClientConfig::RCM_WHEN_NOT_PRESENT)) {
+            // Fabricate an empty "client" FQDN with flags requesting
+            // the server do all the updates.  The flags will get modified
+            // below according the configuration options, the name will
+            // be supplied later on.
+            fqdn.reset(new Option6ClientFqdn(Option6ClientFqdn::FLAG_S, "",
+                                             Option6ClientFqdn::PARTIAL));
+            LOG_DEBUG(ddns6_logger, DBG_DHCP6_DETAIL, DHCP6_DDNS_GENERATE_FQDN)
+                .arg(question->getLabel());
+        } else {
+            // No FQDN so get the lease hostname from the host reservation if
+            // there is one.
+            if (ctx.currentHost()) {
+                ctx.hostname_ = ctx.currentHost()->getHostname();
+            }
+
+            return;
+        }
+    }
+
+    LOG_DEBUG(ddns6_logger, DBG_DHCP6_DETAIL, DHCP6_DDNS_RECEIVE_FQDN)
+        .arg(question->getLabel())
+        .arg(fqdn->toText());
+
+    // Create the DHCPv6 Client FQDN Option to be included in the server's
+    // response to a client.
+    Option6ClientFqdnPtr fqdn_resp(new Option6ClientFqdn(*fqdn));
+
+    // Set the server S, N, and O flags based on client's flags and
+    // current configuration.
+    d2_mgr.adjustFqdnFlags<Option6ClientFqdn>(*fqdn, *fqdn_resp, *ddns_params);
+
+    // Get DDNS update direction flags
+    CfgMgr::instance().getD2ClientMgr().getUpdateDirections(*fqdn_resp, ctx.fwd_dns_update_,
+                                                            ctx.rev_dns_update_);
+
+    // If there's a reservation and it has a hostname specified, use it!
+    if (ctx.currentHost() && !ctx.currentHost()->getHostname().empty()) {
+        // Add the qualifying suffix.
+        // After #3765, this will only occur if the suffix is not empty.
+        fqdn_resp->setDomainName(d2_mgr.qualifyName(ctx.currentHost()->getHostname(),
+                                                    *ddns_params, true),
+                                                    Option6ClientFqdn::FULL);
+    } else {
+        // Adjust the domain name based on domain name value and type sent by
+        // the client and current configuration.
+        d2_mgr.adjustDomainName<Option6ClientFqdn>(*fqdn, *fqdn_resp, *ddns_params);
+    }
+
+    // Once we have the FQDN setup to use it for the lease hostname.  This
+    // only gets replaced later if the FQDN is to be generated from the address.
+    ctx.hostname_ = fqdn_resp->getDomainName();
+
+    // The FQDN has been processed successfully. Let's append it to the
+    // response to be sent to a client. Note that the Client FQDN option is
+    // always sent back to the client if Client FQDN was included in the
+    // client's message.
+    LOG_DEBUG(ddns6_logger, DBG_DHCP6_DETAIL, DHCP6_DDNS_RESPONSE_FQDN_DATA)
+        .arg(question->getLabel())
+        .arg(fqdn_resp->toText());
+    answer->addOption(fqdn_resp);
+
+    // Optionally, call a hook that may override the decisions made
+    // earlier.
+    if (HooksManager::calloutsPresent(Hooks.hook_index_ddns6_update_)) {
+        CalloutHandlePtr callout_handle = getCalloutHandle(question);
+
+        // 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.
+        Subnet6Ptr subnet = ctx.subnet_;
+        callout_handle->setArgument("query6", question);
+        callout_handle->setArgument("response6", answer);
+        callout_handle->setArgument("subnet6", subnet);
+        callout_handle->setArgument("hostname", ctx.hostname_);
+        callout_handle->setArgument("fwd-update", ctx.fwd_dns_update_);
+        callout_handle->setArgument("rev-update", ctx.rev_dns_update_);
+        callout_handle->setArgument("ddns-params", ddns_params);
+
+        // Call callouts
+        HooksManager::callCallouts(Hooks.hook_index_ddns6_update_, *callout_handle);
+
+        // Let's get the parameters returned by hook.
+        string hook_hostname;
+        bool hook_fwd_dns_update;
+        bool hook_rev_dns_update;
+        callout_handle->getArgument("hostname", hook_hostname);
+        callout_handle->getArgument("fwd-update", hook_fwd_dns_update);
+        callout_handle->getArgument("rev-update", hook_rev_dns_update);
+
+        // If there's anything changed by the hook, log it and then update the parameters
+        if ((ctx.hostname_ != hook_hostname) || (ctx.fwd_dns_update_!= hook_fwd_dns_update) ||
+            (ctx.rev_dns_update_ != hook_rev_dns_update)) {
+            LOG_DEBUG(hooks_logger, DBGLVL_PKT_HANDLING, DHCP6_HOOK_DDNS_UPDATE)
+                      .arg(ctx.hostname_).arg(hook_hostname)
+                      .arg(ctx.fwd_dns_update_).arg(hook_fwd_dns_update)
+                      .arg(ctx.rev_dns_update_).arg(hook_rev_dns_update);
+
+            // Update the FQDN option in the response.
+            fqdn_resp = boost::dynamic_pointer_cast<Option6ClientFqdn>(answer->getOption(D6O_CLIENT_FQDN));
+            if (fqdn) {
+                fqdn_resp->setDomainName(hook_hostname, Option6ClientFqdn::FULL);
+                if (!(hook_fwd_dns_update || hook_rev_dns_update)) {
+                    // Hook disabled updates, Set flags back to client accordingly.
+                    fqdn_resp->setFlag(Option6ClientFqdn::FLAG_S, 0);
+                    fqdn_resp->setFlag(Option6ClientFqdn::FLAG_N, 1);
+                }
+            }
+
+            ctx.hostname_ = hook_hostname;
+            ctx.fwd_dns_update_ = hook_fwd_dns_update;
+            ctx.rev_dns_update_ = hook_rev_dns_update;
+        }
+    }
+}
+
+void
+Dhcpv6Srv::createNameChangeRequests(const Pkt6Ptr& answer,
+                                    AllocEngine::ClientContext6& ctx) {
+    // Don't create NameChangeRequests if DNS updates are disabled.
+    if (!(ctx.getDdnsParams()->getEnableUpdates())) {
+        return;
+    }
+
+    // The response message instance is always required. For instance it
+    // holds the Client Identifier. It is a programming error if supplied
+    // message is NULL.
+    if (!answer) {
+        isc_throw(isc::Unexpected, "an instance of the object"
+                  << " encapsulating server's message must not be"
+                  << " NULL when creating DNS NameChangeRequest");
+    }
+
+    // It is likely that client haven't included the FQDN option. In such case,
+    // FQDN option will be NULL. This is valid state, so we simply return.
+    Option6ClientFqdnPtr opt_fqdn = boost::dynamic_pointer_cast<
+        Option6ClientFqdn>(answer->getOption(D6O_CLIENT_FQDN));
+    if (!opt_fqdn) {
+        return;
+    }
+
+    // Get the update directions that should be performed based on our
+    // response FQDN flags.
+    bool do_fwd = false;
+    bool do_rev = false;
+    CfgMgr::instance().getD2ClientMgr().getUpdateDirections(*opt_fqdn,
+                                                             do_fwd, do_rev);
+
+    // Get the Client Id. It is mandatory and a function creating a response
+    // would have thrown an exception if it was missing. Thus throwing
+    // Unexpected if it is missing as it is a programming error.
+    OptionPtr opt_duid = answer->getOption(D6O_CLIENTID);
+    if (!opt_duid) {
+        isc_throw(isc::Unexpected,
+                  "client identifier is required when creating a new"
+                  " DNS NameChangeRequest");
+    }
+    DuidPtr duid = DuidPtr(new DUID(opt_duid->getData()));
+
+    // Get the FQDN in the on-wire format. It will be needed to compute
+    // DHCID.
+    OutputBuffer name_buf(1);
+    opt_fqdn->packDomainName(name_buf);
+    const uint8_t* name_data = static_cast<const uint8_t*>(name_buf.getData());
+    // @todo currently D2Dhcid accepts a vector holding FQDN.
+    // However, it will be faster if we used a pointer name_data.
+    std::vector<uint8_t> buf_vec(name_data, name_data + name_buf.getLength());
+    // Compute DHCID from Client Identifier and FQDN.
+    isc::dhcp_ddns::D2Dhcid dhcid(*duid, buf_vec);
+
+    // Get all IAs from the answer. For each IA, holding an address we will
+    // create a corresponding NameChangeRequest.
+    for (auto answer_ia : answer->getOptions(D6O_IA_NA)) {
+        /// @todo IA_NA may contain multiple addresses. We should process
+        /// each address individually. Currently we get only one.
+        Option6IAAddrPtr iaaddr = boost::static_pointer_cast<
+            Option6IAAddr>(answer_ia.second->getOption(D6O_IAADDR));
+
+        // We need an address to create a name-to-address mapping.
+        // If address is missing for any reason, go to the next IA.
+        if (!iaaddr) {
+            continue;
+        }
+
+        // If the lease for iaaddr is in the list of changed leases, we need
+        // to determine if the changes included changes to the FQDN. If so
+        // then we may need to do a CHG_REMOVE.
+        bool extended_only = false;
+        for (Lease6Collection::const_iterator l = ctx.currentIA().changed_leases_.begin();
+             l != ctx.currentIA().changed_leases_.end(); ++l) {
+
+            if ((*l)->addr_ == iaaddr->getAddress()) {
+                // The address is the same so this must be renewal. If we're not
+                // always updating on renew, then we only renew if DNS info has
+                // changed.
+                if (!ctx.getDdnsParams()->getUpdateOnRenew() &&
+                    ((*l)->hostname_ == opt_fqdn->getDomainName() &&
+                     (*l)->fqdn_fwd_ == do_fwd && (*l)->fqdn_rev_ == do_rev)) {
+                    extended_only = true;
+                } else {
+                    // Queue a CHG_REMOVE of the old data.
+                    // NCR will only be created if the lease hostname is not
+                    // empty and at least one of the direction flags is true
+                    queueNCR(CHG_REMOVE, *l);
+                }
+
+                break;
+            }
+        }
+
+        if (!(do_fwd || do_rev) || (extended_only)) {
+            // Flags indicate no updates needed  or it was an extension of
+            // an existing lease with no FQDN changes.  In the case of the
+            // former, the most likely scenario is that we are honoring the
+            // client's request that no updates be done.
+            continue;
+        }
+
+        // Create new NameChangeRequest. Use the domain name from the FQDN.
+        // This is an FQDN included in the response to the client, so it
+        // holds a fully qualified domain-name already (not partial).
+        // Get the IP address from the lease.
+        NameChangeRequestPtr ncr;
+        ncr.reset(new NameChangeRequest(isc::dhcp_ddns::CHG_ADD,
+                                        do_fwd, do_rev,
+                                        opt_fqdn->getDomainName(),
+                                        iaaddr->getAddress().toText(),
+                                        dhcid, 0,
+                                        calculateDdnsTtl(iaaddr->getValid(),
+                                                         ctx.getDdnsParams()->getTtlPercent()),
+                                        ctx.getDdnsParams()->getUseConflictResolution()));
+        LOG_DEBUG(ddns6_logger, DBG_DHCP6_DETAIL,
+                  DHCP6_DDNS_CREATE_ADD_NAME_CHANGE_REQUEST).arg(ncr->toText());
+
+        // Post the NCR to the D2ClientMgr.
+        CfgMgr::instance().getD2ClientMgr().sendRequest(ncr);
+
+        /// @todo Currently we create NCR with the first IPv6 address that
+        /// is carried in one of the IA_NAs. In the future, the NCR API should
+        /// be extended to map multiple IPv6 addresses to a single FQDN.
+        /// In such case, this return statement will be removed.
+        return;
+    }
+}
+
+HWAddrPtr
+Dhcpv6Srv::getMAC(const Pkt6Ptr& pkt) {
+    CfgMACSources mac_sources = CfgMgr::instance().getCurrentCfg()->
+        getMACSources().get();
+    HWAddrPtr hwaddr;
+    for (CfgMACSources::const_iterator it = mac_sources.begin();
+         it != mac_sources.end(); ++it) {
+        hwaddr = pkt->getMAC(*it);
+        if (hwaddr) {
+            return (hwaddr);
+        }
+    }
+    return (hwaddr);
+}
+
+OptionPtr
+Dhcpv6Srv::assignIA_NA(const Pkt6Ptr& query,
+                       AllocEngine::ClientContext6& ctx,
+                       boost::shared_ptr<Option6IA> ia) {
+
+    // Check if the client sent us a hint in his IA_NA. Clients may send an
+    // address in their IA_NA options as a suggestion (e.g. the last address
+    // they used before).
+    Option6IAAddrPtr hint_opt =
+        boost::dynamic_pointer_cast<Option6IAAddr>(ia->getOption(D6O_IAADDR));
+    IOAddress hint = IOAddress::IPV6_ZERO_ADDRESS();
+    if (hint_opt) {
+        hint = hint_opt->getAddress();
+    }
+
+    LOG_DEBUG(lease6_logger, DBG_DHCP6_DETAIL, DHCP6_PROCESS_IA_NA_REQUEST)
+        .arg(query->getLabel())
+        .arg(ia->getIAID())
+        .arg(hint_opt ? hint.toText() : "(no hint)");
+
+    // convenience values
+    const Subnet6Ptr& subnet = ctx.subnet_;
+
+    // If there is no subnet selected for handling this IA_NA, the only thing left to do is
+    // to say that we are sorry, but the user won't get an address. As a convenience, we
+    // use a different status text to indicate that (compare to the same status code,
+    // but different wording below)
+    if (!subnet) {
+        // Create an empty IA_NA option with IAID matching the request.
+        // Note that we don't use OptionDefinition class to create this option.
+        // This is because we prefer using a constructor of Option6IA that
+        // initializes IAID. Otherwise we would have to use setIAID() after
+        // creation of the option which has some performance implications.
+        boost::shared_ptr<Option6IA> ia_rsp(new Option6IA(D6O_IA_NA, ia->getIAID()));
+
+        // Insert status code NoAddrsAvail.
+        ia_rsp->addOption(createStatusCode(*query, *ia_rsp, STATUS_NoAddrsAvail,
+                                           "Server could not select subnet for"
+                                           " this client"));
+        return (ia_rsp);
+    }
+
+    // Set per-IA context values.
+    ctx.createIAContext();
+    ctx.currentIA().iaid_ = ia->getIAID();
+    if (hint_opt) {
+        ctx.currentIA().addHint(hint_opt);
+    } else {
+        ctx.currentIA().addHint(hint);
+    }
+    ctx.currentIA().type_ = Lease::TYPE_NA;
+
+    // Use allocation engine to pick a lease for this client. Allocation engine
+    // will try to honor the hint, but it is just a hint - some other address
+    // may be used instead. If fake_allocation is set to false, the lease will
+    // be inserted into the LeaseMgr as well.
+    Lease6Collection leases = alloc_engine_->allocateLeases6(ctx);
+
+    /// @todo: Handle more than one lease
+    Lease6Ptr lease;
+    if (!leases.empty()) {
+        lease = *leases.begin();
+    }
+
+    // Create IA_NA that we will put in the response.
+    // Do not use OptionDefinition to create option's instance so
+    // as we can initialize IAID using a constructor.
+    Option6IAPtr ia_rsp(new Option6IA(D6O_IA_NA, ia->getIAID()));
+
+    if (lease) {
+        // We have a lease! Let's wrap its content into IA_NA option
+        // with IAADDR suboption.
+        if (ctx.fake_allocation_) {
+            LOG_INFO(lease6_logger, DHCP6_LEASE_ADVERT)
+                .arg(query->getLabel())
+                .arg(lease->addr_.toText())
+                .arg(ia->getIAID());
+        } else if (lease->reuseable_valid_lft_ == 0) {
+            LOG_INFO(lease6_logger, DHCP6_LEASE_ALLOC)
+                .arg(query->getLabel())
+                .arg(lease->addr_.toText())
+                .arg(ia->getIAID())
+                .arg(Lease::lifetimeToText(lease->valid_lft_));
+        } else {
+            lease->valid_lft_ = lease->reuseable_valid_lft_;
+            lease->preferred_lft_ = lease->reuseable_preferred_lft_;
+            LOG_INFO(lease6_logger, DHCP6_LEASE_REUSE)
+                .arg(query->getLabel())
+                .arg(lease->addr_.toText())
+                .arg(ia->getIAID())
+                .arg(Lease::lifetimeToText(lease->valid_lft_));
+
+            // Increment the reuse statistics.
+            StatsMgr::instance().addValue("v6-ia-na-lease-reuses", int64_t(1));
+            StatsMgr::instance().addValue(StatsMgr::generateName("subnet", lease->subnet_id_,
+                                                                 "v6-ia-na-lease-reuses"),
+                                          int64_t(1));
+        }
+        LOG_DEBUG(lease6_logger, DBG_DHCP6_DETAIL_DATA, DHCP6_LEASE_DATA)
+            .arg(query->getLabel())
+            .arg(ia->getIAID())
+            .arg(lease->toText());
+
+        // Set the values for T1 and T2.
+        setTeeTimes(lease->preferred_lft_, subnet, ia_rsp);
+
+        Option6IAAddrPtr addr(new Option6IAAddr(D6O_IAADDR, lease->addr_,
+                                                lease->preferred_lft_,
+                                                lease->valid_lft_));
+        ia_rsp->addOption(addr);
+
+        // It would be possible to insert status code=0(success) as well,
+        // but this is considered waste of bandwidth as absence of status
+        // code is considered a success.
+
+    } else {
+        // Allocation engine did not allocate a lease. The engine logged
+        // cause of that failure. The only thing left is to insert
+        // status code to pass the sad news to the client.
+
+        LOG_DEBUG(lease6_logger, DBG_DHCP6_DETAIL, ctx.fake_allocation_ ?
+                  DHCP6_LEASE_ADVERT_FAIL : DHCP6_LEASE_ALLOC_FAIL)
+            .arg(query->getLabel())
+            .arg(ia->getIAID());
+
+        ia_rsp->addOption(createStatusCode(*query, *ia_rsp,
+                                           STATUS_NoAddrsAvail,
+                                           "Sorry, no address could be"
+                                           " allocated."));
+    }
+    return (ia_rsp);
+}
+
+OptionPtr
+Dhcpv6Srv::assignIA_PD(const Pkt6Ptr& query,
+                       AllocEngine::ClientContext6& ctx,
+                       boost::shared_ptr<Option6IA> ia) {
+
+    // Check if the client sent us a hint in his IA_PD. Clients may send an
+    // address in their IA_PD options as a suggestion (e.g. the last address
+    // they used before). While the hint consists of a full prefix (prefix +
+    // length), getting just the prefix is sufficient to identify a lease.
+    Option6IAPrefixPtr hint_opt =
+        boost::dynamic_pointer_cast<Option6IAPrefix>(ia->getOption(D6O_IAPREFIX));
+    IOAddress hint = IOAddress::IPV6_ZERO_ADDRESS();
+    if (hint_opt) {
+        hint = hint_opt->getAddress();
+    }
+
+    LOG_DEBUG(lease6_logger, DBG_DHCP6_DETAIL, DHCP6_PROCESS_IA_PD_REQUEST)
+        .arg(query->getLabel())
+        .arg(ia->getIAID())
+        .arg(hint_opt ? hint.toText() : "(no hint)");
+
+    const Subnet6Ptr& subnet = ctx.subnet_;
+
+    // Create IA_PD that we will put in the response.
+    // Do not use OptionDefinition to create option's instance so
+    // as we can initialize IAID using a constructor.
+    boost::shared_ptr<Option6IA> ia_rsp(new Option6IA(D6O_IA_PD, ia->getIAID()));
+
+    // If there is no subnet selected for handling this IA_PD, the only thing
+    // left to do is to say that we are sorry, but the user won't get an address.
+    // As a convenience, we use a different status text to indicate that
+    // (compare to the same status code, but different wording below)
+    if (!subnet) {
+
+        // Insert status code NoAddrsAvail.
+        ia_rsp->addOption(createStatusCode(*query, *ia_rsp, STATUS_NoPrefixAvail,
+                                           "Sorry, no subnet available."));
+        return (ia_rsp);
+    }
+
+    // Set per-IA context values.
+    ctx.createIAContext();
+    ctx.currentIA().iaid_ = ia->getIAID();
+    if (hint_opt) {
+        ctx.currentIA().addHint(hint_opt);
+    } else {
+        ctx.currentIA().addHint(hint, 0);
+    }
+    ctx.currentIA().type_ = Lease::TYPE_PD;
+
+    // Use allocation engine to pick a lease for this client. Allocation engine
+    // will try to honor the hint, but it is just a hint - some other address
+    // may be used instead. If fake_allocation is set to false, the lease will
+    // be inserted into the LeaseMgr as well.
+    Lease6Collection leases = alloc_engine_->allocateLeases6(ctx);
+
+    if (!leases.empty()) {
+
+        // Need to retain the shortest preferred lease time to use
+        // for calculating T1 and T2.
+        uint32_t min_preferred_lft = (*leases.begin())->preferred_lft_;
+
+        const bool pd_exclude_requested = requestedInORO(query, D6O_PD_EXCLUDE);
+        for (Lease6Collection::iterator l = leases.begin();
+             l != leases.end(); ++l) {
+
+            // We have a lease! Let's wrap its content into IA_PD option
+            // with IAADDR suboption.
+            if (ctx.fake_allocation_) {
+                LOG_INFO(lease6_logger, DHCP6_PD_LEASE_ADVERT)
+                    .arg(query->getLabel())
+                    .arg((*l)->addr_.toText())
+                    .arg(static_cast<int>((*l)->prefixlen_))
+                    .arg(ia->getIAID());
+            } else if ((*l)->reuseable_valid_lft_ == 0) {
+                LOG_INFO(lease6_logger, DHCP6_PD_LEASE_ALLOC)
+                    .arg(query->getLabel())
+                    .arg((*l)->addr_.toText())
+                    .arg(static_cast<int>((*l)->prefixlen_))
+                    .arg(ia->getIAID())
+                    .arg(Lease::lifetimeToText((*l)->valid_lft_));
+            } else {
+                (*l)->valid_lft_ = (*l)->reuseable_valid_lft_;
+                (*l)->preferred_lft_ = (*l)->reuseable_preferred_lft_;
+                LOG_INFO(lease6_logger, DHCP6_PD_LEASE_REUSE)
+                    .arg(query->getLabel())
+                    .arg((*l)->addr_.toText())
+                    .arg(static_cast<int>((*l)->prefixlen_))
+                    .arg(ia->getIAID())
+                    .arg(Lease::lifetimeToText((*l)->valid_lft_));
+
+                // Increment the reuse statistics.
+                StatsMgr::instance().addValue("v6-ia-pd-lease-reuses", int64_t(1));
+                StatsMgr::instance().addValue(StatsMgr::generateName("subnet", (*l)->subnet_id_,
+                                                                    "v6-ia-pd-lease-reuses"),
+                                            int64_t(1));
+            }
+
+            // Check for new minimum lease time
+            if (((*l)->preferred_lft_ > 0) && (min_preferred_lft > (*l)->preferred_lft_)) {
+                min_preferred_lft = (*l)->preferred_lft_;
+            }
+
+            boost::shared_ptr<Option6IAPrefix>
+                addr(new Option6IAPrefix(D6O_IAPREFIX, (*l)->addr_,
+                                         (*l)->prefixlen_, (*l)->preferred_lft_,
+                                         (*l)->valid_lft_));
+            ia_rsp->addOption(addr);
+
+            if (pd_exclude_requested) {
+                // PD exclude option has been requested via ORO, thus we need to
+                // include it if the pool configuration specifies this option.
+                Pool6Ptr pool = boost::dynamic_pointer_cast<
+                    Pool6>(subnet->getPool(Lease::TYPE_PD, (*l)->addr_));
+                if (pool) {
+                    Option6PDExcludePtr pd_exclude_option = pool->getPrefixExcludeOption();
+                    if (pd_exclude_option) {
+                        addr->addOption(pd_exclude_option);
+                    }
+                }
+            }
+        }
+
+        // Set T1 and T2, using the shortest preferred lifetime among the leases.
+        setTeeTimes(min_preferred_lft, subnet, ia_rsp);
+
+        // It would be possible to insert status code=0(success) as well,
+        // but this is considered waste of bandwidth as absence of status
+        // code is considered a success.
+
+    } else {
+        // Allocation engine did not allocate a lease. The engine logged
+        // cause of that failure. The only thing left is to insert
+        // status code to pass the sad news to the client.
+
+        LOG_DEBUG(lease6_logger, DBG_DHCP6_DETAIL, ctx.fake_allocation_ ?
+                  DHCP6_PD_LEASE_ADVERT_FAIL : DHCP6_PD_LEASE_ALLOC_FAIL)
+            .arg(query->getLabel())
+            .arg(ia->getIAID());
+
+        ia_rsp->addOption(createStatusCode(*query, *ia_rsp,
+                                           STATUS_NoPrefixAvail,
+                                           "Sorry, no prefixes could"
+                                           " be allocated."));
+    }
+    return (ia_rsp);
+}
+
+OptionPtr
+Dhcpv6Srv::extendIA_NA(const Pkt6Ptr& query,
+                       AllocEngine::ClientContext6& ctx,
+                       boost::shared_ptr<Option6IA> ia) {
+
+    LOG_DEBUG(lease6_logger, DBG_DHCP6_DETAIL, DHCP6_PROCESS_IA_NA_EXTEND)
+        .arg(query->getLabel())
+        .arg(ia->getIAID());
+
+    // convenience values
+    const Subnet6Ptr& subnet = ctx.subnet_;
+
+    // Create empty IA_NA option with IAID matching the request.
+    Option6IAPtr ia_rsp(new Option6IA(D6O_IA_NA, ia->getIAID()));
+
+    if (!subnet) {
+        /// @todo For simplicity and due to limitations of LeaseMgr we don't
+        /// get the binding for the client for which we don't get subnet id.
+        /// Subnet id is a required value when searching for the bindings.
+        /// The fact that we can't identify the subnet for the returning client
+        /// doesn't really mean that the client has no binding. It is possible
+        /// that due to server's reconfiguration the subnet has been removed
+        /// or modified since the client has got his lease. We may need to
+        /// rethink whether it is appropriate to send no binding if the subnet
+        /// hasn't been found for the client.
+        ia_rsp->addOption(createStatusCode(*query, *ia_rsp, STATUS_NoBinding,
+                          "Sorry, no known leases for this duid/iaid."));
+        return (ia_rsp);
+    }
+
+    // Set per-IA context values.
+    ctx.createIAContext();
+    ctx.currentIA().iaid_ = ia->getIAID();
+    ctx.currentIA().type_ = Lease::TYPE_NA;
+    ctx.currentIA().ia_rsp_ = ia_rsp;
+
+    // Extract the addresses that the client is trying to obtain.
+    OptionCollection addrs = ia->getOptions();
+    for (OptionCollection::const_iterator it = addrs.begin();
+         it != addrs.end(); ++it) {
+        if (it->second->getType() != D6O_IAADDR) {
+            continue;
+        }
+        Option6IAAddrPtr iaaddr = boost::dynamic_pointer_cast<Option6IAAddr>(it->second);
+        if (!iaaddr) {
+            // That's weird. Option code was ok, but the object type was not.
+            // This should never happen. The only case would be with badly
+            // mis-implemented hook libraries that insert invalid option objects.
+            // There's no way to protect against this.
+            continue;
+        }
+        ctx.currentIA().addHint(iaaddr);
+    }
+
+    Lease6Collection leases = alloc_engine_->renewLeases6(ctx);
+
+    // Ok, now we have the leases extended. We have:
+    // - what the client tried to renew in ctx.hints_
+    // - what we actually assigned in leases
+    // - old leases that are no longer valid in ctx.old_leases_
+
+    // For each IA inserted by the client we have to determine what to do
+    // about included addresses and notify the client. We will iterate over
+    // those prefixes and remove those that we have already processed. We
+    // don't want to remove them from the context, so we need to copy them
+    // into temporary container.
+    AllocEngine::HintContainer hints = ctx.currentIA().hints_;
+
+    // Retains the shortest valid lease time to use
+    // for calculating T1 and T2.
+    uint32_t min_preferred_lft = std::numeric_limits<uint32_t>::max();
+
+    // For all leases we have now, add the IAADDR with non-zero lifetimes.
+    for (Lease6Collection::iterator l = leases.begin(); l != leases.end(); ++l) {
+        if ((*l)->reuseable_valid_lft_ == 0) {
+            LOG_INFO(lease6_logger, DHCP6_LEASE_RENEW)
+                .arg(query->getLabel())
+                .arg((*l)->addr_.toText())
+                .arg(ia->getIAID());
+        } else {
+            (*l)->valid_lft_ = (*l)->reuseable_valid_lft_;
+            (*l)->preferred_lft_ = (*l)->reuseable_preferred_lft_;
+            LOG_INFO(lease6_logger, DHCP6_LEASE_REUSE)
+                .arg(query->getLabel())
+                .arg((*l)->addr_.toText())
+                .arg(ia->getIAID())
+                .arg(Lease::lifetimeToText((*l)->valid_lft_));
+
+            // Increment the reuse statistics.
+            StatsMgr::instance().addValue("v6-ia-na-lease-reuses", int64_t(1));
+            StatsMgr::instance().addValue(StatsMgr::generateName("subnet", (*l)->subnet_id_,
+                                                                 "v6-ia-na-lease-reuses"),
+                                          int64_t(1));
+        }
+
+        Option6IAAddrPtr iaaddr(new Option6IAAddr(D6O_IAADDR,
+                                (*l)->addr_, (*l)->preferred_lft_, (*l)->valid_lft_));
+        ia_rsp->addOption(iaaddr);
+
+        // Check for new minimum lease time
+        if (((*l)->preferred_lft_ > 0) && (min_preferred_lft > (*l)->preferred_lft_)) {
+            min_preferred_lft = (*l)->preferred_lft_;
+        }
+
+        // Now remove this address from the hints list.
+        AllocEngine::Resource hint_type((*l)->addr_);
+        hints.erase(std::remove(hints.begin(), hints.end(), hint_type),
+                    hints.end());
+    }
+
+    // For the leases that we just retired, send the addresses with 0 lifetimes.
+    for (Lease6Collection::iterator l = ctx.currentIA().old_leases_.begin();
+         l != ctx.currentIA().old_leases_.end(); ++l) {
+
+        // Send an address with zero lifetimes only when this lease belonged to
+        // this client. Do not send it when we're reusing an old lease that belonged
+        // to someone else.
+        if (equalValues(query->getClientId(), (*l)->duid_)) {
+            Option6IAAddrPtr iaaddr(new Option6IAAddr(D6O_IAADDR,
+                                                      (*l)->addr_, 0, 0));
+            ia_rsp->addOption(iaaddr);
+        }
+
+        // Now remove this address from the hints list.
+        AllocEngine::Resource hint_type((*l)->addr_);
+        hints.erase(std::remove(hints.begin(), hints.end(), hint_type), hints.end());
+
+        // If the new FQDN settings have changed for the lease, we need to
+        // delete any existing FQDN records for this lease.
+        if (((*l)->hostname_ != ctx.hostname_) || ((*l)->fqdn_fwd_ != ctx.fwd_dns_update_) ||
+            ((*l)->fqdn_rev_ != ctx.rev_dns_update_)) {
+            LOG_DEBUG(ddns6_logger, DBG_DHCP6_DETAIL,
+                      DHCP6_DDNS_REMOVE_OLD_LEASE_FQDN)
+                .arg(query->getLabel())
+                .arg((*l)->toText())
+                .arg(ctx.hostname_)
+                .arg(ctx.rev_dns_update_ ? "true" : "false")
+                .arg(ctx.fwd_dns_update_ ? "true" : "false");
+
+            queueNCR(CHG_REMOVE, *l);
+        }
+    }
+
+    // Finally, if there are any addresses requested that we haven't dealt with
+    // already, inform the client that he can't have them.
+    for (AllocEngine::HintContainer::const_iterator hint = hints.begin();
+         hint != hints.end(); ++hint) {
+        Option6IAAddrPtr iaaddr(new Option6IAAddr(D6O_IAADDR,
+                                                  hint->getAddress(), 0, 0));
+        ia_rsp->addOption(iaaddr);
+    }
+
+    if (!leases.empty()) {
+        // We allocated leases so we need to update T1 and T2.
+        setTeeTimes(min_preferred_lft, subnet, ia_rsp);
+    } else {
+        // The server wasn't able allocate new lease and renew an existing
+        // lease. In that case, the server sends NoAddrsAvail per RFC 8415.
+        ia_rsp->addOption(createStatusCode(*query, *ia_rsp,
+                                           STATUS_NoAddrsAvail,
+                                           "Sorry, no addresses could be"
+                                           " assigned at this time."));
+    }
+
+    return (ia_rsp);
+}
+
+OptionPtr
+Dhcpv6Srv::extendIA_PD(const Pkt6Ptr& query,
+                       AllocEngine::ClientContext6& ctx,
+                       boost::shared_ptr<Option6IA> ia) {
+
+    LOG_DEBUG(lease6_logger, DBG_DHCP6_DETAIL, DHCP6_PROCESS_IA_PD_EXTEND)
+        .arg(query->getLabel())
+        .arg(ia->getIAID());
+
+    const Subnet6Ptr& subnet = ctx.subnet_;
+    const DuidPtr& duid = ctx.duid_;
+
+    // Let's create a IA_PD response and fill it in later
+    Option6IAPtr ia_rsp(new Option6IA(D6O_IA_PD, ia->getIAID()));
+
+    // If there is no subnet for the particular client, we can't retrieve
+    // information about client's leases from lease database. We treat this
+    // as no binding for the client.
+    if (!subnet) {
+        // Per RFC 8415, section 18.3.4, if there is no binding and we are
+        // processing a Renew, the NoBinding status code should be returned.
+        if (query->getType() == DHCPV6_RENEW) {
+            // Insert status code NoBinding
+            ia_rsp->addOption(createStatusCode(*query, *ia_rsp, STATUS_NoBinding,
+                                               "Sorry, no known PD leases"
+                                               " for this duid/iaid."));
+            return (ia_rsp);
+
+        // Per RFC 8415, section 18.3.5, if there is no binding and we are
+        // processing Rebind, the message has to be discarded (assuming that
+        // the server doesn't know if the prefix in the IA_PD option is
+        // appropriate for the client's link). The exception being thrown
+        // here should propagate to the main loop and cause the message to
+        // be discarded.
+        } else {
+
+            /// @todo: We may consider in which cases we could determine
+            /// whether the delegated prefixes are appropriate for the
+            /// link to which the client's interface is attached. Just not
+            /// being able to select the subnet may not be enough, because
+            /// there might be other DHCP servers around that are configured
+            /// to handle that subnet. Therefore we don't fully follow all
+            /// the paths in section 18.3.5 of RFC 8415 to respond with
+            /// zero lifetimes for the prefixes being rebound.
+            isc_throw(DHCPv6DiscardMessageError, "no subnet found for the"
+                      " client sending Rebind to extend lifetime of the"
+                      " prefix (DUID=" << duid->toText() << ", IAID="
+                      << ia->getIAID() << ")");
+        }
+    }
+
+    // Set per-IA context values.
+    ctx.createIAContext();
+    ctx.currentIA().iaid_ = ia->getIAID();
+    ctx.currentIA().type_ = Lease::TYPE_PD;
+    ctx.currentIA().ia_rsp_ = ia_rsp;
+
+    // Extract prefixes that the client is trying to renew.
+    OptionCollection addrs = ia->getOptions();
+    for (OptionCollection::const_iterator it = addrs.begin();
+         it != addrs.end(); ++it) {
+        if (it->second->getType() != D6O_IAPREFIX) {
+            continue;
+        }
+        Option6IAPrefixPtr prf = boost::dynamic_pointer_cast<Option6IAPrefix>(it->second);
+        if (!prf) {
+            // That's weird. Option code was ok, but the object type was not.
+            // This should never happen. The only case would be with badly
+            // mis-implemented hook libraries that insert invalid option objects.
+            // There's no way to protect against this.
+            continue;
+        }
+
+        // Put the client's prefix into the hints list.
+        ctx.currentIA().addHint(prf);
+    }
+
+    // Call Allocation Engine and attempt to renew leases. Number of things
+    // may happen. Leases may be extended, revoked (if the lease is no longer
+    // valid or reserved for someone else), or new leases may be added.
+    // Important parameters are:
+    // - returned container - current valid leases
+    // - old_leases - leases that used to be, but are no longer valid
+    // - changed_leases - leases that have FQDN changed (not really important
+    //                    in PD context)
+    Lease6Collection leases = alloc_engine_->renewLeases6(ctx);
+
+    // For each IA inserted by the client we have to determine what to do
+    // about included prefixes and notify the client. We will iterate over
+    // those prefixes and remove those that we have already processed. We
+    // don't want to remove them from the context, so we need to copy them
+    // into temporary container.
+    AllocEngine::HintContainer hints = ctx.currentIA().hints_;
+
+    const bool pd_exclude_requested = requestedInORO(query, D6O_PD_EXCLUDE);
+
+    // Retains the shortest valid lease time to use
+    // for calculating T1 and T2.
+    uint32_t min_preferred_lft = std::numeric_limits<uint32_t>::max();
+
+    for (Lease6Collection::iterator l = leases.begin(); l != leases.end(); ++l) {
+        if ((*l)->reuseable_valid_lft_ == 0) {
+            LOG_INFO(lease6_logger, DHCP6_PD_LEASE_RENEW)
+                .arg(query->getLabel())
+                .arg((*l)->addr_.toText())
+                .arg(static_cast<int>((*l)->prefixlen_))
+                .arg(ia->getIAID());
+        } else {
+            (*l)->valid_lft_ = (*l)->reuseable_valid_lft_;
+            (*l)->preferred_lft_ = (*l)->reuseable_preferred_lft_;
+            LOG_INFO(lease6_logger, DHCP6_PD_LEASE_REUSE)
+                .arg(query->getLabel())
+                .arg((*l)->addr_.toText())
+                .arg(static_cast<int>((*l)->prefixlen_))
+                .arg(ia->getIAID())
+                .arg(Lease::lifetimeToText((*l)->valid_lft_));
+
+            // Increment the reuse statistics.
+            StatsMgr::instance().addValue("v6-ia-pd-lease-reuses", int64_t(1));
+            StatsMgr::instance().addValue(StatsMgr::generateName("subnet", (*l)->subnet_id_,
+                                                                 "v6-ia-pd-lease-reuses"),
+                                          int64_t(1));
+        }
+
+        Option6IAPrefixPtr prf(new Option6IAPrefix(D6O_IAPREFIX,
+                               (*l)->addr_, (*l)->prefixlen_,
+                               (*l)->preferred_lft_, (*l)->valid_lft_));
+        ia_rsp->addOption(prf);
+
+        if (pd_exclude_requested) {
+            // PD exclude option has been requested via ORO, thus we need to
+            // include it if the pool configuration specifies this option.
+            Pool6Ptr pool = boost::dynamic_pointer_cast<
+                Pool6>(subnet->getPool(Lease::TYPE_PD, (*l)->addr_));
+
+            if (pool) {
+                Option6PDExcludePtr pd_exclude_option = pool->getPrefixExcludeOption();
+                if (pd_exclude_option) {
+                    prf->addOption(pd_exclude_option);
+                }
+            }
+        }
+
+        // Check for new minimum lease time
+        if (((*l)->preferred_lft_ > 0) && ((*l)->preferred_lft_ < min_preferred_lft)) {
+            min_preferred_lft = (*l)->preferred_lft_;
+        }
+
+        // Now remove this prefix from the hints list.
+        AllocEngine::Resource hint_type((*l)->addr_, (*l)->prefixlen_);
+        hints.erase(std::remove(hints.begin(), hints.end(), hint_type),
+                    hints.end());
+    }
+
+    /// For the leases that we just retired, send the prefixes with 0 lifetimes.
+    for (Lease6Collection::iterator l = ctx.currentIA().old_leases_.begin();
+         l != ctx.currentIA().old_leases_.end(); ++l) {
+
+        // Send a prefix with zero lifetimes only when this lease belonged to
+        // this client. Do not send it when we're reusing an old lease that belonged
+        // to someone else.
+        if (equalValues(query->getClientId(), (*l)->duid_)) {
+            Option6IAPrefixPtr prefix(new Option6IAPrefix(D6O_IAPREFIX, (*l)->addr_,
+                                                          (*l)->prefixlen_, 0, 0));
+            ia_rsp->addOption(prefix);
+        }
+
+        // Now remove this prefix from the hints list.
+        AllocEngine::Resource hint_type((*l)->addr_, (*l)->prefixlen_);
+        hints.erase(std::remove(hints.begin(), hints.end(), hint_type), hints.end());
+    }
+
+    // Finally, if there are any prefixes requested that we haven't dealt with
+    // already, inform the client that he can't have them.
+    for (AllocEngine::HintContainer::const_iterator prefix = hints.begin();
+         prefix != hints.end(); ++prefix) {
+
+        // Send the prefix with the zero lifetimes only if the prefix
+        // contains non-zero value. A zero value indicates that the hint was
+        // for the prefix length.
+        if (!prefix->getAddress().isV6Zero()) {
+            OptionPtr prefix_opt(new Option6IAPrefix(D6O_IAPREFIX,
+                                                     prefix->getAddress(),
+                                                     prefix->getPrefixLength(),
+                                                     0, 0));
+            ia_rsp->addOption(prefix_opt);
+        }
+    }
+
+    if (!leases.empty()) {
+        // We allocated leases so we need to update T1 and T2.
+        setTeeTimes(min_preferred_lft, subnet, ia_rsp);
+    } else {
+        // All is left is to insert the status code.
+        // The server wasn't able allocate new lease and renew an existing
+        // lease. In that case, the server sends NoPrefixAvail per RFC 8415.
+        ia_rsp->addOption(createStatusCode(*query, *ia_rsp,
+                                           STATUS_NoPrefixAvail,
+                                           "Sorry, no prefixes could be"
+                                           " assigned at this time."));
+    }
+
+    return (ia_rsp);
+}
+
+void
+Dhcpv6Srv::extendLeases(const Pkt6Ptr& query, Pkt6Ptr& reply,
+                       AllocEngine::ClientContext6& ctx) {
+
+    // We will try to extend lease lifetime for all IA options in the client's
+    // Renew or Rebind message.
+    /// @todo add support for IA_TA
+
+    // For the lease extension it is critical that the client has sent
+    // DUID. There is no need to check for the presence of the DUID here
+    // because we have already checked it in the sanityCheck().
+
+    // Save the originally selected subnet.
+    Subnet6Ptr orig_subnet = ctx.subnet_;
+
+    for (const auto& opt : query->options_) {
+        switch (opt.second->getType()) {
+        case D6O_IA_NA: {
+            OptionPtr answer_opt = extendIA_NA(query, ctx,
+                                               boost::dynamic_pointer_cast<
+                                                   Option6IA>(opt.second));
+            if (answer_opt) {
+                reply->addOption(answer_opt);
+            }
+            break;
+        }
+
+        case D6O_IA_PD: {
+            OptionPtr answer_opt = extendIA_PD(query, ctx,
+                                               boost::dynamic_pointer_cast<
+                                                   Option6IA>(opt.second));
+            if (answer_opt) {
+                reply->addOption(answer_opt);
+            }
+            break;
+        }
+
+        default:
+            break;
+        }
+    }
+
+    // Subnet may be modified by the allocation engine, there are things
+    // we need to do when that happens.
+    checkDynamicSubnetChange(query, reply, ctx, orig_subnet);
+}
+
+void
+Dhcpv6Srv::releaseLeases(const Pkt6Ptr& release, Pkt6Ptr& reply,
+                         AllocEngine::ClientContext6& ctx) {
+
+    // We need to release addresses for all IA options in the client's
+    // RELEASE message.
+
+    /// @todo Add support for IA_TA
+    /// @todo Consider supporting more than one address in a single IA.
+    /// It is allowed by RFC 8415, but it is not widely implemented. The only
+    /// software that supports that is Dibbler, but its author seriously doubts
+    /// if anyone is really using it. Clients that want more than one address
+    /// or prefix just include more instances of IA options.
+
+    // Let's set the status to be success by default. We can override it with
+    // error status if needed. The important thing to understand here is that
+    // the global status code may be set to success only if all IA options were
+    // handled properly. Therefore the releaseIA_NA and releaseIA_PD options
+    // may turn the status code to some error, but can't turn it back to success.
+    int general_status = STATUS_Success;
+    for (const auto& opt : release->options_) {
+        Lease6Ptr old_lease;
+        switch (opt.second->getType()) {
+        case D6O_IA_NA: {
+            OptionPtr answer_opt = releaseIA_NA(ctx.duid_, release, general_status,
+                                                boost::dynamic_pointer_cast<Option6IA>(opt.second),
+                                                old_lease);
+            if (answer_opt) {
+                reply->addOption(answer_opt);
+            }
+            break;
+        }
+        case D6O_IA_PD: {
+            OptionPtr answer_opt = releaseIA_PD(ctx.duid_, release, general_status,
+                                                boost::dynamic_pointer_cast<Option6IA>(opt.second),
+                                                old_lease);
+            if (answer_opt) {
+                reply->addOption(answer_opt);
+            }
+            break;
+        }
+        // @todo: add support for IA_TA
+        default:
+            // remaining options are stateless and thus ignored in this context
+            ;
+        }
+
+        // Store the old lease.
+        if (old_lease) {
+            ctx.currentIA().old_leases_.push_back(old_lease);
+        }
+    }
+
+    // Include top-level status code as well.
+    reply->addOption(createStatusCode(*release, general_status,
+                     "Summary status for all processed IA_NAs"));
+}
+
+OptionPtr
+Dhcpv6Srv::releaseIA_NA(const DuidPtr& duid, const Pkt6Ptr& query,
+                        int& general_status, boost::shared_ptr<Option6IA> ia,
+                        Lease6Ptr& old_lease) {
+
+    LOG_DEBUG(lease6_logger, DBG_DHCP6_DETAIL, DHCP6_PROCESS_IA_NA_RELEASE)
+        .arg(query->getLabel())
+        .arg(ia->getIAID());
+
+    // Release can be done in one of two ways:
+    // Approach 1: extract address from client's IA_NA and see if it belongs
+    // to this particular client.
+    // Approach 2: find a subnet for this client, get a lease for
+    // this subnet/duid/iaid and check if its content matches to what the
+    // client is asking us to release.
+    //
+    // This method implements approach 1.
+
+    // That's our response
+    boost::shared_ptr<Option6IA> ia_rsp(new Option6IA(D6O_IA_NA, ia->getIAID()));
+
+    Option6IAAddrPtr release_addr = boost::dynamic_pointer_cast<Option6IAAddr>
+        (ia->getOption(D6O_IAADDR));
+    if (!release_addr) {
+        ia_rsp->addOption(createStatusCode(*query, STATUS_NoBinding,
+                                           "You did not include an address in your RELEASE"));
+        general_status = STATUS_NoBinding;
+        return (ia_rsp);
+    }
+
+    Lease6Ptr lease = LeaseMgrFactory::instance().getLease6(Lease::TYPE_NA,
+                                                            release_addr->getAddress());
+
+    if (!lease) {
+        // client releasing a lease that we don't know about.
+
+        // Insert status code NoBinding.
+        ia_rsp->addOption(createStatusCode(*query, *ia_rsp, STATUS_NoBinding,
+                          "Sorry, no known leases for this duid/iaid, can't release."));
+        general_status = STATUS_NoBinding;
+
+        return (ia_rsp);
+    }
+
+    if (!lease->duid_) {
+        // Something is gravely wrong here. We do have a lease, but it does not
+        // have mandatory DUID information attached. Someone was messing with our
+        // database.
+
+        LOG_ERROR(lease6_logger, DHCP6_LEASE_NA_WITHOUT_DUID)
+            .arg(query->getLabel())
+            .arg(release_addr->getAddress().toText());
+
+        general_status = STATUS_UnspecFail;
+        ia_rsp->addOption(createStatusCode(*query, *ia_rsp, STATUS_UnspecFail,
+                          "Database consistency check failed when trying to RELEASE"));
+        return (ia_rsp);
+    }
+
+    if (*duid != *(lease->duid_)) {
+
+        // Sorry, it's not your address. You can't release it.
+        LOG_INFO(lease6_logger, DHCP6_RELEASE_NA_FAIL_WRONG_DUID)
+            .arg(query->getLabel())
+            .arg(release_addr->getAddress().toText())
+            .arg(lease->duid_->toText());
+
+        general_status = STATUS_NoBinding;
+        ia_rsp->addOption(createStatusCode(*query, *ia_rsp, STATUS_NoBinding,
+                          "This address does not belong to you, you can't release it"));
+        return (ia_rsp);
+    }
+
+    if (ia->getIAID() != lease->iaid_) {
+        // This address belongs to this client, but to a different IA
+        LOG_WARN(lease6_logger, DHCP6_RELEASE_NA_FAIL_WRONG_IAID)
+            .arg(query->getLabel())
+            .arg(release_addr->getAddress().toText())
+            .arg(lease->iaid_)
+            .arg(ia->getIAID());
+        ia_rsp->addOption(createStatusCode(*query, *ia_rsp, STATUS_NoBinding,
+                          "This is your address, but you used wrong IAID"));
+        general_status = STATUS_NoBinding;
+        return (ia_rsp);
+    }
+
+    // It is not necessary to check if the address matches as we used
+    // getLease6(addr) method that is supposed to return a proper lease.
+
+    bool skip = false;
+    // Execute all callouts registered for packet6_send
+    if (HooksManager::calloutsPresent(Hooks.hook_index_lease6_release_)) {
+        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<Pkt6> query6_options_copy(query);
+
+        // Delete all previous arguments
+        callout_handle->deleteAllArguments();
+
+        // Pass the original packet
+        callout_handle->setArgument("query6", query);
+
+        // Pass the lease to be updated
+        callout_handle->setArgument("lease6", lease);
+
+        // Call all installed callouts
+        HooksManager::callCallouts(Hooks.hook_index_lease6_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, DBG_DHCP6_HOOKS, DHCP6_HOOK_LEASE6_RELEASE_NA_SKIP)
+                .arg(query->getLabel());
+        }
+    }
+
+    // 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();
+
+    // Callout didn't indicate to skip the release process. Let's release
+    // the lease.
+    if (!skip) {
+        // 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;
+            lease->preferred_lft_ = 0;
+            LeaseMgrFactory::instance().updateLease6(lease);
+            expired = true;
+            success = true;
+        } else {
+            success = LeaseMgrFactory::instance().deleteLease(lease);
+        }
+    }
+
+    // Here the success should be true if we removed lease successfully
+    // and false if skip flag was set or the removal failed for whatever reason
+
+    if (!success) {
+        ia_rsp->addOption(createStatusCode(*query, *ia_rsp, STATUS_UnspecFail,
+                          "Server failed to release a lease"));
+
+        LOG_ERROR(lease6_logger, DHCP6_RELEASE_NA_FAIL)
+            .arg(query->getLabel())
+            .arg(lease->addr_.toText())
+            .arg(lease->iaid_);
+        general_status = STATUS_UnspecFail;
+
+        return (ia_rsp);
+    } else {
+        old_lease = lease;
+
+        LOG_INFO(lease6_logger, DHCP6_RELEASE_NA)
+            .arg(query->getLabel())
+            .arg(lease->addr_.toText())
+            .arg(lease->iaid_);
+
+        ia_rsp->addOption(createStatusCode(*query, *ia_rsp, STATUS_Success,
+                          "Lease released. Thank you, please come again."));
+
+        if (expired) {
+            LOG_INFO(lease6_logger, DHCP6_RELEASE_NA_EXPIRED)
+                .arg(query->getLabel())
+                .arg(lease->addr_.toText())
+                .arg(lease->iaid_);
+        } else {
+            LOG_INFO(lease6_logger, DHCP6_RELEASE_NA_DELETED)
+                .arg(query->getLabel())
+                .arg(lease->addr_.toText())
+                .arg(lease->iaid_);
+
+            // Need to decrease statistic for assigned addresses.
+            StatsMgr::instance().addValue(
+                StatsMgr::generateName("subnet", lease->subnet_id_, "assigned-nas"),
+                static_cast<int64_t>(-1));
+
+            const auto& subnet = CfgMgr::instance().getCurrentCfg()->getCfgSubnets6()->getBySubnetId(lease->subnet_id_);
+            if (subnet) {
+                const auto& pool = subnet->getPool(Lease::TYPE_NA, lease->addr_, false);
+                if (pool) {
+                    StatsMgr::instance().addValue(
+                        StatsMgr::generateName("subnet", subnet->getID(),
+                                               StatsMgr::generateName("pool", pool->getID(), "assigned-nas")),
+                        static_cast<int64_t>(-1));
+                }
+            }
+
+            // Check if a lease has flags indicating that the FQDN update has
+            // been performed. If so, create NameChangeRequest which removes
+            // the entries.
+            queueNCR(CHG_REMOVE, lease);
+        }
+
+        return (ia_rsp);
+    }
+}
+
+OptionPtr
+Dhcpv6Srv::releaseIA_PD(const DuidPtr& duid, const Pkt6Ptr& query,
+                        int& general_status, boost::shared_ptr<Option6IA> ia,
+                        Lease6Ptr& old_lease) {
+    // Release can be done in one of two ways:
+    // Approach 1: extract address from client's IA_NA and see if it belongs
+    // to this particular client.
+    // Approach 2: find a subnet for this client, get a lease for
+    // this subnet/duid/iaid and check if its content matches to what the
+    // client is asking us to release.
+    //
+    // This method implements approach 1.
+
+    // That's our response. We will fill it in as we check the lease to be
+    // released.
+    boost::shared_ptr<Option6IA> ia_rsp(new Option6IA(D6O_IA_PD, ia->getIAID()));
+
+    boost::shared_ptr<Option6IAPrefix> release_prefix =
+        boost::dynamic_pointer_cast<Option6IAPrefix>(ia->getOption(D6O_IAPREFIX));
+    if (!release_prefix) {
+        ia_rsp->addOption(createStatusCode(*query, *ia_rsp, STATUS_NoBinding,
+                          "You did not include a prefix in your RELEASE"));
+        general_status = STATUS_NoBinding;
+        return (ia_rsp);
+    }
+
+    Lease6Ptr lease = LeaseMgrFactory::instance().getLease6(Lease::TYPE_PD,
+                                                            release_prefix->getAddress());
+
+    if (!lease) {
+        // Client releasing a lease that we don't know about.
+
+        // Insert status code NoBinding.
+        ia_rsp->addOption(createStatusCode(*query, *ia_rsp, STATUS_NoBinding,
+                          "Sorry, no known leases for this duid/iaid, can't release."));
+        general_status = STATUS_NoBinding;
+
+        return (ia_rsp);
+    }
+
+    if (!lease->duid_) {
+        // Something is gravely wrong here. We do have a lease, but it does not
+        // have mandatory DUID information attached. Someone was messing with our
+        // database.
+        LOG_ERROR(lease6_logger, DHCP6_LEASE_PD_WITHOUT_DUID)
+            .arg(query->getLabel())
+            .arg(release_prefix->getAddress().toText())
+            .arg(static_cast<int>(release_prefix->getLength()));
+
+        general_status = STATUS_UnspecFail;
+        ia_rsp->addOption(createStatusCode(*query, *ia_rsp, STATUS_UnspecFail,
+                          "Database consistency check failed when trying to RELEASE"));
+        return (ia_rsp);
+    }
+
+    if (*duid != *(lease->duid_)) {
+        // Sorry, it's not your address. You can't release it.
+        LOG_INFO(lease6_logger, DHCP6_RELEASE_PD_FAIL_WRONG_DUID)
+            .arg(query->getLabel())
+            .arg(release_prefix->getAddress().toText())
+            .arg(static_cast<int>(release_prefix->getLength()))
+            .arg(lease->duid_->toText());
+
+        general_status = STATUS_NoBinding;
+        ia_rsp->addOption(createStatusCode(*query, *ia_rsp, STATUS_NoBinding,
+                          "This address does not belong to you, you can't release it"));
+        return (ia_rsp);
+    }
+
+    if (ia->getIAID() != lease->iaid_) {
+        // This address belongs to this client, but to a different IA
+        LOG_WARN(lease6_logger, DHCP6_RELEASE_PD_FAIL_WRONG_IAID)
+            .arg(query->getLabel())
+            .arg(release_prefix->getAddress().toText())
+            .arg(static_cast<int>(release_prefix->getLength()))
+            .arg(lease->iaid_)
+            .arg(ia->getIAID());
+        ia_rsp->addOption(createStatusCode(*query, *ia_rsp, STATUS_NoBinding,
+                          "This is your address, but you used wrong IAID"));
+        general_status = STATUS_NoBinding;
+        return (ia_rsp);
+    }
+
+    // It is not necessary to check if the address matches as we used
+    // getLease6(addr) method that is supposed to return a proper lease.
+
+    bool skip = false;
+    // Execute all callouts registered for packet6_send
+    if (HooksManager::calloutsPresent(Hooks.hook_index_lease6_release_)) {
+        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<Pkt6> query6_options_copy(query);
+
+        // Pass the original packet
+        callout_handle->setArgument("query6", query);
+
+        // Pass the lease to be updated
+        callout_handle->setArgument("lease6", lease);
+
+        // Call all installed callouts
+        HooksManager::callCallouts(Hooks.hook_index_lease6_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, DBG_DHCP6_HOOKS, DHCP6_HOOK_LEASE6_RELEASE_PD_SKIP)
+                .arg(query->getLabel());
+        }
+    }
+
+    // Ok, we've passed all checks. Let's release this prefix.
+    bool success = false; // was the removal operation successful?
+    bool expired = false; // explicitly expired instead of removed?
+    auto expiration_cfg = CfgMgr::instance().getCurrentCfg()->getCfgExpiration();
+
+    // Callout didn't indicate to skip the release process. Let's release
+    // the lease.
+    if (!skip) {
+        // 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;
+            lease->preferred_lft_ = 0;
+            LeaseMgrFactory::instance().updateLease6(lease);
+            expired = true;
+            success = true;
+        } else {
+            success = LeaseMgrFactory::instance().deleteLease(lease);
+        }
+    }
+
+    // Here the success should be true if we removed lease successfully
+    // and false if skip flag was set or the removal failed for whatever reason
+
+    if (!success) {
+        ia_rsp->addOption(createStatusCode(*query, *ia_rsp, STATUS_UnspecFail,
+                          "Server failed to release a lease"));
+
+        LOG_ERROR(lease6_logger, DHCP6_RELEASE_PD_FAIL)
+            .arg(query->getLabel())
+            .arg(lease->addr_.toText())
+            .arg(static_cast<int>(lease->prefixlen_))
+            .arg(lease->iaid_);
+        general_status = STATUS_UnspecFail;
+
+    } else {
+        old_lease = lease;
+
+        LOG_INFO(lease6_logger, DHCP6_RELEASE_PD)
+            .arg(query->getLabel())
+            .arg(lease->addr_.toText())
+            .arg(static_cast<int>(lease->prefixlen_))
+            .arg(lease->iaid_);
+
+        ia_rsp->addOption(createStatusCode(*query, *ia_rsp, STATUS_Success,
+                          "Lease released. Thank you, please come again."));
+
+        if (expired) {
+            LOG_INFO(lease6_logger, DHCP6_RELEASE_PD_EXPIRED)
+                .arg(query->getLabel())
+                .arg(lease->addr_.toText())
+                .arg(static_cast<int>(lease->prefixlen_))
+                .arg(lease->iaid_);
+        } else {
+            LOG_INFO(lease6_logger, DHCP6_RELEASE_PD_DELETED)
+                .arg(query->getLabel())
+                .arg(lease->addr_.toText())
+                .arg(static_cast<int>(lease->prefixlen_))
+                .arg(lease->iaid_);
+
+            // Need to decrease statistic for assigned prefixes.
+            StatsMgr::instance().addValue(
+                StatsMgr::generateName("subnet", lease->subnet_id_, "assigned-pds"),
+                static_cast<int64_t>(-1));
+
+            const auto& subnet = CfgMgr::instance().getCurrentCfg()->getCfgSubnets6()->getBySubnetId(lease->subnet_id_);
+            if (subnet) {
+                const auto& pool = subnet->getPool(Lease::TYPE_PD, lease->addr_, false);
+                if (pool) {
+                    StatsMgr::instance().addValue(
+                        StatsMgr::generateName("subnet", subnet->getID(),
+                                               StatsMgr::generateName("pd-pool", pool->getID(), "assigned-pds")),
+                        static_cast<int64_t>(-1));
+                }
+            }
+        }
+    }
+
+    return (ia_rsp);
+}
+
+Pkt6Ptr
+Dhcpv6Srv::processSolicit(AllocEngine::ClientContext6& ctx) {
+
+    Pkt6Ptr solicit = ctx.query_;
+    Pkt6Ptr response(new Pkt6(DHCPV6_ADVERTISE, solicit->getTransid()));
+
+    // Handle Rapid Commit option, if present.
+    if (ctx.subnet_ && ctx.subnet_->getRapidCommit()) {
+        OptionPtr opt_rapid_commit = solicit->getOption(D6O_RAPID_COMMIT);
+        if (opt_rapid_commit) {
+
+            LOG_DEBUG(options6_logger, DBG_DHCP6_DETAIL, DHCP6_RAPID_COMMIT)
+                .arg(solicit->getLabel());
+
+            // If Rapid Commit has been sent by the client, change the
+            // response type to Reply and include Rapid Commit option.
+            response->setType(DHCPV6_REPLY);
+            response->addOption(opt_rapid_commit);
+        }
+    }
+
+    // "Fake" allocation is the case when the server is processing the Solicit
+    // message without the Rapid Commit option and advertises a lease to
+    // the client, but doesn't commit this lease to the lease database. If
+    // the Solicit contains the Rapid Commit option and the server is
+    // configured to honor the Rapid Commit option, or the client has sent
+    // the Request message, the lease will be committed to the lease
+    // database. The type of the server's response may be used to determine
+    // if this is the fake allocation case or not. When the server sends
+    // Reply message it means that it is committing leases. Other message
+    // type (Advertise) means that server is not committing leases (fake
+    // allocation).
+    ctx.fake_allocation_ = (response->getType() != DHCPV6_REPLY);
+
+    processClientFqdn(solicit, response, ctx);
+
+    if (MultiThreadingMgr::instance().getMode()) {
+        // The lease reclamation cannot run at the same time.
+        ReadLockGuard share(alloc_engine_->getReadWriteMutex());
+
+        assignLeases(solicit, response, ctx);
+    } else {
+        assignLeases(solicit, response, ctx);
+    }
+
+    conditionallySetReservedClientClasses(solicit, ctx);
+    requiredClassify(solicit, ctx);
+
+    copyClientOptions(solicit, response);
+    CfgOptionList co_list;
+    buildCfgOptionList(solicit, ctx, co_list);
+    appendDefaultOptions(solicit, response, co_list);
+    appendRequestedOptions(solicit, response, co_list);
+    appendRequestedVendorOptions(solicit, response, ctx, co_list);
+
+    updateReservedFqdn(ctx, response);
+
+    // Only generate name change requests if sending a Reply as a result
+    // of receiving Rapid Commit option.
+    if (response->getType() == DHCPV6_REPLY) {
+        createNameChangeRequests(response, ctx);
+    }
+
+    return (response);
+}
+
+Pkt6Ptr
+Dhcpv6Srv::processRequest(AllocEngine::ClientContext6& ctx) {
+
+    Pkt6Ptr request = ctx.query_;
+    Pkt6Ptr reply(new Pkt6(DHCPV6_REPLY, request->getTransid()));
+
+    processClientFqdn(request, reply, ctx);
+
+    if (MultiThreadingMgr::instance().getMode()) {
+        // The lease reclamation cannot run at the same time.
+        ReadLockGuard share(alloc_engine_->getReadWriteMutex());
+
+        assignLeases(request, reply, ctx);
+    } else {
+        assignLeases(request, reply, ctx);
+    }
+
+    conditionallySetReservedClientClasses(request, ctx);
+    requiredClassify(request, ctx);
+
+    copyClientOptions(request, reply);
+    CfgOptionList co_list;
+    buildCfgOptionList(request, ctx, co_list);
+    appendDefaultOptions(request, reply, co_list);
+    appendRequestedOptions(request, reply, co_list);
+    appendRequestedVendorOptions(request, reply, ctx, co_list);
+
+    updateReservedFqdn(ctx, reply);
+    generateFqdn(reply, ctx);
+    createNameChangeRequests(reply, ctx);
+
+    return (reply);
+}
+
+Pkt6Ptr
+Dhcpv6Srv::processRenew(AllocEngine::ClientContext6& ctx) {
+
+    Pkt6Ptr renew = ctx.query_;
+    Pkt6Ptr reply(new Pkt6(DHCPV6_REPLY, renew->getTransid()));
+
+    processClientFqdn(renew, reply, ctx);
+
+    if (MultiThreadingMgr::instance().getMode()) {
+        // The lease reclamation cannot run at the same time.
+        ReadLockGuard share(alloc_engine_->getReadWriteMutex());
+
+        extendLeases(renew, reply, ctx);
+    } else {
+        extendLeases(renew, reply, ctx);
+    }
+
+    conditionallySetReservedClientClasses(renew, ctx);
+    requiredClassify(renew, ctx);
+
+    copyClientOptions(renew, reply);
+    CfgOptionList co_list;
+    buildCfgOptionList(renew, ctx, co_list);
+    appendDefaultOptions(renew, reply, co_list);
+    appendRequestedOptions(renew, reply, co_list);
+    appendRequestedVendorOptions(renew, reply, ctx, co_list);
+
+    updateReservedFqdn(ctx, reply);
+    generateFqdn(reply, ctx);
+    createNameChangeRequests(reply, ctx);
+
+    return (reply);
+}
+
+Pkt6Ptr
+Dhcpv6Srv::processRebind(AllocEngine::ClientContext6& ctx) {
+
+    Pkt6Ptr rebind = ctx.query_;
+    Pkt6Ptr reply(new Pkt6(DHCPV6_REPLY, rebind->getTransid()));
+
+    processClientFqdn(rebind, reply, ctx);
+
+    if (MultiThreadingMgr::instance().getMode()) {
+        // The lease reclamation cannot run at the same time.
+        ReadLockGuard share(alloc_engine_->getReadWriteMutex());
+
+        extendLeases(rebind, reply, ctx);
+    } else {
+        extendLeases(rebind, reply, ctx);
+    }
+
+    conditionallySetReservedClientClasses(rebind, ctx);
+    requiredClassify(rebind, ctx);
+
+    copyClientOptions(rebind, reply);
+    CfgOptionList co_list;
+    buildCfgOptionList(rebind, ctx, co_list);
+    appendDefaultOptions(rebind, reply, co_list);
+    appendRequestedOptions(rebind, reply, co_list);
+    appendRequestedVendorOptions(rebind, reply, ctx, co_list);
+
+    updateReservedFqdn(ctx, reply);
+    generateFqdn(reply, ctx);
+    createNameChangeRequests(reply, ctx);
+
+    return (reply);
+}
+
+Pkt6Ptr
+Dhcpv6Srv::processConfirm(AllocEngine::ClientContext6& ctx) {
+
+    Pkt6Ptr confirm = ctx.query_;
+    conditionallySetReservedClientClasses(confirm, ctx);
+    requiredClassify(confirm, ctx);
+
+    // Get IA_NAs from the Confirm. If there are none, the message is
+    // invalid and must be discarded. There is nothing more to do.
+    OptionCollection ias = confirm->getOptions(D6O_IA_NA);
+    if (ias.empty()) {
+        return (Pkt6Ptr());
+    }
+
+    // The server sends Reply message in response to Confirm.
+    Pkt6Ptr reply(new Pkt6(DHCPV6_REPLY, confirm->getTransid()));
+    // Make sure that the necessary options are included.
+    copyClientOptions(confirm, reply);
+    CfgOptionList co_list;
+    buildCfgOptionList(confirm, ctx, co_list);
+    appendDefaultOptions(confirm, reply, co_list);
+    appendRequestedOptions(confirm, reply, co_list);
+    appendRequestedVendorOptions(confirm, reply, ctx, co_list);
+    // Indicates if at least one address has been verified. If no addresses
+    // are verified it means that the client has sent no IA_NA options
+    // or no IAAddr options and that client's message has to be discarded.
+    bool verified = false;
+    // Check if subnet was selected for the message. If no subnet
+    // has been selected, the client is not on link.
+    SubnetPtr subnet = ctx.subnet_;
+
+    // Regardless if the subnet has been selected or not, we will iterate
+    // over the IA_NA options to check if they hold any addresses. If there
+    // are no, the Confirm is discarded.
+    // Check addresses in IA_NA options and make sure they are appropriate.
+    for (OptionCollection::const_iterator ia = ias.begin();
+         ia != ias.end(); ++ia) {
+        const OptionCollection& opts = ia->second->getOptions();
+        for (OptionCollection::const_iterator opt = opts.begin();
+             opt != opts.end(); ++opt) {
+            // Ignore options other than IAAddr.
+            if (opt->second->getType() == D6O_IAADDR) {
+                // Check that the address is in range in the subnet selected.
+                Option6IAAddrPtr iaaddr = boost::dynamic_pointer_cast<
+                    Option6IAAddr>(opt->second);
+                // If there is subnet selected and the address has been included
+                // in IA_NA, mark it verified and verify that it belongs to the
+                // subnet.
+                if (iaaddr) {
+                    // If at least one address is not in range, then return
+                    // the NotOnLink status code.
+                    if (subnet && !subnet->inRange(iaaddr->getAddress())) {
+                        std::ostringstream status_msg;
+                        status_msg << "Address " << iaaddr->getAddress()
+                                   << " is not on link.";
+                        reply->addOption(createStatusCode(*confirm,
+                                                          STATUS_NotOnLink,
+                                                          status_msg.str()));
+                        return (reply);
+                    }
+                    verified = true;
+                } else {
+                    isc_throw(Unexpected, "failed to cast the IA Address option"
+                              " to the Option6IAAddrPtr. This is programming"
+                              " error and should be reported");
+                }
+            }
+        }
+    }
+
+    // It seems that the client hasn't included any addresses in which case
+    // the Confirm must be discarded.
+    if (!verified) {
+        return (Pkt6Ptr());
+    }
+
+    // If there is a subnet, there were addresses in IA_NA options and the
+    // addresses where consistent with the subnet then the client is on link.
+    if (subnet) {
+        // All addresses in range, so return success.
+        reply->addOption(createStatusCode(*confirm, STATUS_Success,
+                                          "All addresses are on-link"));
+    } else {
+        reply->addOption(createStatusCode(*confirm, STATUS_NotOnLink,
+                                          "No subnet selected"));
+    }
+
+    return (reply);
+}
+
+Pkt6Ptr
+Dhcpv6Srv::processRelease(AllocEngine::ClientContext6& ctx) {
+
+    Pkt6Ptr release = ctx.query_;
+    conditionallySetReservedClientClasses(release, ctx);
+    requiredClassify(release, ctx);
+
+    // Create an empty Reply message.
+    Pkt6Ptr reply(new Pkt6(DHCPV6_REPLY, release->getTransid()));
+
+    // Copy client options (client-id, also relay information if present)
+    copyClientOptions(release, reply);
+
+    // Get the configured option list
+    CfgOptionList co_list;
+    // buildCfgOptionList(release, ctx, co_list);
+    appendDefaultOptions(release, reply, co_list);
+
+    releaseLeases(release, reply, ctx);
+
+    /// @todo If client sent a release and we should remove outstanding
+    /// DNS records.
+
+    return (reply);
+}
+
+Pkt6Ptr
+Dhcpv6Srv::processDecline(AllocEngine::ClientContext6& ctx) {
+
+    Pkt6Ptr decline = ctx.query_;
+    conditionallySetReservedClientClasses(decline, ctx);
+    requiredClassify(decline, ctx);
+
+    // Create an empty Reply message.
+    Pkt6Ptr reply(new Pkt6(DHCPV6_REPLY, decline->getTransid()));
+
+    // Copy client options (client-id, also relay information if present)
+    copyClientOptions(decline, reply);
+
+    // Get the configured option list
+    CfgOptionList co_list;
+    buildCfgOptionList(decline, ctx, co_list);
+
+    // Include server-id
+    appendDefaultOptions(decline, reply, co_list);
+
+    if (declineLeases(decline, reply, ctx)) {
+        return (reply);
+    } else {
+
+        // declineLeases returns false only if the hooks set the next step
+        // status to DROP. We'll just doing as requested.
+        return (Pkt6Ptr());
+    }
+}
+
+bool
+Dhcpv6Srv::declineLeases(const Pkt6Ptr& decline, Pkt6Ptr& reply,
+                         AllocEngine::ClientContext6& ctx) {
+
+    // We need to decline addresses for all IA_NA options in the client's
+    // DECLINE message.
+
+    // Let's set the status to be success by default. We can override it with
+    // error status if needed. The important thing to understand here is that
+    // the global status code may be set to success only if all IA options were
+    // handled properly. Therefore the declineIA  options
+    // may turn the status code to some error, but can't turn it back to success.
+    int general_status = STATUS_Success;
+
+    for (const auto& opt : decline->options_) {
+        switch (opt.second->getType()) {
+        case D6O_IA_NA: {
+            OptionPtr answer_opt = declineIA(decline, ctx.duid_, general_status,
+                                             boost::dynamic_pointer_cast<Option6IA>(opt.second),
+                                             ctx.new_leases_);
+            if (answer_opt) {
+
+                // We have an answer, let's use it.
+                reply->addOption(answer_opt);
+            } else {
+
+                // The only case when declineIA could return NULL is if one of the
+                // hook callouts set next step status to DROP. We just need to drop
+                // this packet.
+                return (false);
+            }
+            break;
+        }
+        default:
+            // We don't care for the remaining options
+            ;
+        }
+    }
+
+    return (true);
+}
+
+OptionPtr
+Dhcpv6Srv::declineIA(const Pkt6Ptr& decline, const DuidPtr& duid,
+                     int& general_status, boost::shared_ptr<Option6IA> ia,
+                     Lease6Collection& new_leases) {
+
+    LOG_DEBUG(lease6_logger, DBG_DHCP6_DETAIL, DHCP6_DECLINE_PROCESS_IA)
+        .arg(decline->getLabel())
+        .arg(ia->getIAID());
+
+    // Decline can be done in one of two ways:
+    // Approach 1: extract address from client's IA_NA and see if it belongs
+    // to this particular client.
+    // Approach 2: find a subnet for this client, get a lease for
+    // this subnet/duid/iaid and check if its content matches to what the
+    // client is asking us to decline.
+    //
+    // This method implements approach 1.
+
+    // That's our response
+    boost::shared_ptr<Option6IA> ia_rsp(new Option6IA(D6O_IA_NA, ia->getIAID()));
+
+    const OptionCollection& opts = ia->getOptions();
+    int total_addrs = 0; // Let's count the total number of addresses.
+    for (OptionCollection::const_iterator opt = opts.begin(); opt != opts.end();
+         ++opt) {
+
+        // Let's ignore nested options other than IAADDR (there shouldn't be anything
+        // else in IA_NA in Decline message, but let's be on the safe side).
+        if (opt->second->getType() != D6O_IAADDR) {
+            continue;
+        }
+        Option6IAAddrPtr decline_addr = boost::dynamic_pointer_cast<Option6IAAddr>
+            (opt->second);
+        if (!decline_addr) {
+            continue;
+        }
+
+        total_addrs++;
+
+        Lease6Ptr lease = LeaseMgrFactory::instance().getLease6(Lease::TYPE_NA,
+                                                                decline_addr->getAddress());
+
+        if (!lease) {
+            // Client trying to decline a lease that we don't know about.
+            LOG_INFO(lease6_logger, DHCP6_DECLINE_FAIL_NO_LEASE)
+                .arg(decline->getLabel()).arg(decline_addr->getAddress().toText());
+
+            // According to RFC 8415, section 18.3.8:
+            // "For each IA in the Decline message for which the server has no
+            // binding information, the server adds an IA option using the IAID
+            // from the Decline message and includes a Status Code option with
+            // the value NoBinding in the IA option".
+            setStatusCode(ia_rsp, createStatusCode(*decline, *ia_rsp, STATUS_NoBinding,
+                                  "Server does not know about such an address."));
+
+            // In the same section of RFC 8415:
+            // "The server ignores addresses not assigned to the IAs (though it may"
+            // choose to log an error if it finds such addresses)."
+            continue; // There may be other addresses.
+        }
+
+        if (!lease->duid_) {
+            // Something is gravely wrong here. We do have a lease, but it does not
+            // have mandatory DUID information attached. Someone was messing with our
+            // database.
+
+            LOG_ERROR(lease6_logger, DHCP6_DECLINE_FAIL_LEASE_WITHOUT_DUID)
+                .arg(decline->getLabel())
+                .arg(decline_addr->getAddress().toText());
+
+            ia_rsp->addOption(createStatusCode(*decline, *ia_rsp, STATUS_UnspecFail,
+                    "Database consistency check failed when attempting Decline."));
+
+            continue;
+        }
+
+        // Ok, there's a sane lease with an address. Let's check if DUID matches first.
+        if (*duid != *(lease->duid_)) {
+
+            // Sorry, it's not your address. You can't release it.
+            LOG_INFO(lease6_logger, DHCP6_DECLINE_FAIL_DUID_MISMATCH)
+                .arg(decline->getLabel())
+                .arg(decline_addr->getAddress().toText())
+                .arg(lease->duid_->toText());
+
+            ia_rsp->addOption(createStatusCode(*decline, *ia_rsp, STATUS_NoBinding,
+                     "This address does not belong to you, you can't decline it"));
+
+            continue;
+        }
+
+        // Let's check if IAID matches.
+        if (ia->getIAID() != lease->iaid_) {
+            // This address belongs to this client, but to a different IA
+            LOG_INFO(lease6_logger, DHCP6_DECLINE_FAIL_IAID_MISMATCH)
+                .arg(decline->getLabel())
+                .arg(lease->addr_.toText())
+                .arg(ia->getIAID())
+                .arg(lease->iaid_);
+            setStatusCode(ia_rsp, createStatusCode(*decline, *ia_rsp, STATUS_NoBinding,
+                              "This is your address, but you used wrong IAID"));
+
+            continue;
+        }
+
+        // Ok, all is good. Decline this lease.
+        if (!declineLease(decline, lease, ia_rsp)) {
+            // declineLease returns false only when hook callouts set the next
+            // step status to drop. We just propagate the bad news here.
+            return (OptionPtr());
+
+        } else {
+            new_leases.push_back(lease);
+        }
+    }
+
+    if (total_addrs == 0) {
+        setStatusCode(ia_rsp, createStatusCode(*decline, *ia_rsp, STATUS_NoBinding,
+                                               "No addresses sent in IA_NA"));
+        general_status = STATUS_NoBinding;
+    }
+
+    return (ia_rsp);
+}
+
+void
+Dhcpv6Srv::setStatusCode(boost::shared_ptr<isc::dhcp::Option6IA>& container,
+                         const OptionPtr& status) {
+    // Let's delete any old status code we may have.
+    container->delOption(D6O_STATUS_CODE);
+
+    container->addOption(status);
+}
+
+bool
+Dhcpv6Srv::declineLease(const Pkt6Ptr& decline, const Lease6Ptr lease,
+                        boost::shared_ptr<Option6IA> ia_rsp) {
+    // We do not want to decrease the assigned-nas at this time. While
+    // technically a declined address is no longer allocated, the
+    // primary usage of the assigned-nas statistic is to monitor pool
+    // utilization. Most people would forget to include declined-addresses
+    // in the calculation, and simply do assigned-nas/total-nas. 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.
+
+    // Let's call lease6_decline hooks if necessary.
+    if (HooksManager::calloutsPresent(Hooks.hook_index_lease6_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<Pkt6> query6_options_copy(decline);
+
+        // Pass the original packet
+        callout_handle->setArgument("query6", decline);
+
+        // Pass the lease to be updated
+        callout_handle->setArgument("lease6", lease);
+
+        // Call callouts
+        HooksManager::callCallouts(Hooks.hook_index_lease6_decline_,
+                                   *callout_handle);
+
+        // Callouts decided to SKIP the next processing step. The next
+        // processing step would be to actually decline the lease, so we'll
+        // keep the lease as is.
+        if (callout_handle->getStatus() == CalloutHandle::NEXT_STEP_SKIP) {
+            LOG_DEBUG(hooks_logger, DBG_DHCP6_DETAIL, DHCP6_HOOK_DECLINE_SKIP)
+                .arg(decline->getLabel())
+                .arg(decline->getIface())
+                .arg(lease->addr_.toText());
+            return (true);
+        }
+
+        // Callouts decided to DROP the packet. Let's simply log it and
+        // return false, so callers will act accordingly.
+        if (callout_handle->getStatus() == CalloutHandle::NEXT_STEP_DROP) {
+            LOG_DEBUG(hooks_logger, DBGLVL_PKT_HANDLING, DHCP6_HOOK_DECLINE_DROP)
+                .arg(decline->getLabel())
+                .arg(decline->getIface())
+                .arg(lease->addr_.toText());
+            return (false);
+        }
+    }
+
+    Lease6Ptr old_values = boost::make_shared<Lease6>(*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().updateLease6(lease);
+    } catch (const Exception& ex) {
+        // Update failed.
+        LOG_ERROR(lease6_logger, DHCP6_DECLINE_FAIL)
+            .arg(decline->getLabel())
+            .arg(lease->addr_.toText())
+            .arg(ex.what());
+        return (false);
+    }
+
+    // Check if a lease has flags indicating that the FQDN update has
+    // been performed. If so, create NameChangeRequest which removes
+    // the entries. This method does all necessary checks.
+    queueNCR(CHG_REMOVE, old_values);
+
+    // Bump up the subnet-specific statistic.
+    StatsMgr::instance().addValue(
+        StatsMgr::generateName("subnet", lease->subnet_id_, "declined-addresses"),
+        static_cast<int64_t>(1));
+
+    const auto& subnet = CfgMgr::instance().getCurrentCfg()->getCfgSubnets6()->getBySubnetId(lease->subnet_id_);
+    if (subnet) {
+        const auto& pool = subnet->getPool(Lease::TYPE_NA, 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));
+
+    LOG_INFO(lease6_logger, DHCP6_DECLINE_LEASE).arg(decline->getLabel())
+        .arg(lease->addr_.toText()).arg(lease->valid_lft_);
+
+    ia_rsp->addOption(createStatusCode(*decline, *ia_rsp, STATUS_Success,
+                      "Lease declined. Hopefully the next one will be better."));
+
+    return (true);
+}
+
+Pkt6Ptr
+Dhcpv6Srv::processInfRequest(AllocEngine::ClientContext6& ctx) {
+
+    Pkt6Ptr inf_request = ctx.query_;
+    conditionallySetReservedClientClasses(inf_request, ctx);
+    requiredClassify(inf_request, ctx);
+
+    // Create a Reply packet, with the same trans-id as the client's.
+    Pkt6Ptr reply(new Pkt6(DHCPV6_REPLY, inf_request->getTransid()));
+
+    // Copy client options (client-id, also relay information if present)
+    copyClientOptions(inf_request, reply);
+
+    // Build the configured option list for append methods
+    CfgOptionList co_list;
+    buildCfgOptionList(inf_request, ctx, co_list);
+
+    // Append default options, i.e. options that the server is supposed
+    // to put in all messages it sends (server-id for now, but possibly other
+    // options once we start supporting authentication)
+    appendDefaultOptions(inf_request, reply, co_list);
+
+    // Try to assign options that were requested by the client.
+    appendRequestedOptions(inf_request, reply, co_list);
+
+    // Try to assign vendor options that were requested by the client.
+    appendRequestedVendorOptions(inf_request, reply, ctx, co_list);
+
+    return (reply);
+}
+
+void
+Dhcpv6Srv::processDhcp4Query(const Pkt6Ptr& dhcp4_query) {
+
+    // flags are in transid
+    // uint32_t flags = dhcp4_query->getTransid();
+    // do nothing with DHCPV4_QUERY_FLAGS_UNICAST
+
+    // Get the DHCPv4 message option
+    OptionPtr dhcp4_msg = dhcp4_query->getOption(D6O_DHCPV4_MSG);
+    if (dhcp4_msg) {
+        try {
+            // Forward the whole message to the DHCPv4 server via IPC
+            Dhcp6to4Ipc::instance().send(dhcp4_query);
+        } catch (...) {
+            // Assume the error was already logged
+            return;
+        }
+    }
+
+    // This method does not return anything as we always sent back
+    // the response via Dhcp6To4Ipc.
+}
+
+void Dhcpv6Srv::classifyByVendor(const Pkt6Ptr& pkt) {
+    OptionVendorClassPtr vclass;
+    for (auto opt : pkt->getOptions(D6O_VENDOR_CLASS)) {
+        vclass = boost::dynamic_pointer_cast<OptionVendorClass>(opt.second);
+        if (!vclass || vclass->getTuplesNum() == 0) {
+            continue;
+        }
+
+        if (vclass->hasTuple(DOCSIS3_CLASS_MODEM)) {
+            pkt->addClass(VENDOR_CLASS_PREFIX + DOCSIS3_CLASS_MODEM);
+
+        } else if (vclass->hasTuple(DOCSIS3_CLASS_EROUTER)) {
+            pkt->addClass(VENDOR_CLASS_PREFIX + DOCSIS3_CLASS_EROUTER);
+
+        } else {
+            pkt->addClass(VENDOR_CLASS_PREFIX + vclass->getTuple(0).getText());
+        }
+    }
+}
+
+void Dhcpv6Srv::classifyPacket(const Pkt6Ptr& 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 Dhcpv6Srv::evaluateClasses(const Pkt6Ptr& 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);
+    }
+}
+
+void
+Dhcpv6Srv::removeDependentEvaluatedClasses(const Pkt6Ptr& pkt) {
+    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()) {
+            pkt->classes_.erase(def->getName());
+        }
+    }
+}
+
+void
+Dhcpv6Srv::setReservedClientClasses(const Pkt6Ptr& pkt,
+                                    const AllocEngine::ClientContext6& ctx) {
+    if (ctx.currentHost() && pkt) {
+        const ClientClasses& classes = ctx.currentHost()->getClientClasses6();
+        for (ClientClasses::const_iterator cclass = classes.cbegin();
+             cclass != classes.cend(); ++cclass) {
+            pkt->addClass(*cclass);
+        }
+    }
+
+    const ClientClasses& classes = pkt->getClasses();
+    if (!classes.empty()) {
+        LOG_DEBUG(dhcp6_logger, DBG_DHCP6_BASIC, DHCP6_CLASS_ASSIGNED)
+            .arg(pkt->getLabel())
+            .arg(classes.toText());
+    }
+}
+
+void
+Dhcpv6Srv::conditionallySetReservedClientClasses(const Pkt6Ptr& pkt,
+                                                 const AllocEngine::ClientContext6& ctx) {
+    if (ctx.subnet_) {
+        SharedNetwork6Ptr shared_network;
+        ctx.subnet_->getSharedNetwork(shared_network);
+        if (shared_network) {
+            ConstHostPtr host = ctx.currentHost();
+            if (host && (host->getIPv6SubnetID() != SUBNET_ID_GLOBAL)) {
+                setReservedClientClasses(pkt, ctx);
+            }
+        }
+    }
+}
+
+void
+Dhcpv6Srv::requiredClassify(const Pkt6Ptr& pkt, AllocEngine::ClientContext6& ctx) {
+    // First collect required classes
+    ClientClasses classes = pkt->getClasses(true);
+    Subnet6Ptr subnet = ctx.subnet_;
+
+    if (subnet) {
+        // Begin by the shared-network
+        SharedNetwork6Ptr 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 pools
+        for (auto resource : ctx.allocated_resources_) {
+            PoolPtr pool =
+                ctx.subnet_->getPool(resource.getPrefixLength() == 128 ?
+                                     Lease::TYPE_NA : Lease::TYPE_PD,
+                                     resource.getAddress(),
+                                     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(dhcp6_logger, DBG_DHCP6_BASIC, DHCP6_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(dhcp6_logger, DBG_DHCP6_BASIC, DHCP6_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, *pkt);
+            if (status) {
+                LOG_INFO(dhcp6_logger, EVAL_RESULT)
+                    .arg(*cclass)
+                    .arg(status);
+                // Matching: add the class
+                pkt->addClass(*cclass);
+            } else {
+                LOG_DEBUG(dhcp6_logger, DBG_DHCP6_DETAIL, EVAL_RESULT)
+                    .arg(*cclass)
+                    .arg(status);
+            }
+        } catch (const Exception& ex) {
+            LOG_ERROR(dhcp6_logger, EVAL_RESULT)
+                .arg(*cclass)
+                .arg(ex.what());
+        } catch (...) {
+            LOG_ERROR(dhcp6_logger, EVAL_RESULT)
+                .arg(*cclass)
+                .arg("get exception?");
+        }
+    }
+}
+
+void
+Dhcpv6Srv::updateReservedFqdn(AllocEngine::ClientContext6& ctx,
+                              const Pkt6Ptr& answer) {
+    if (!answer) {
+        isc_throw(isc::Unexpected, "an instance of the object encapsulating"
+                  " a message must not be NULL when updating reserved FQDN");
+    }
+
+    Option6ClientFqdnPtr fqdn = boost::dynamic_pointer_cast<Option6ClientFqdn>
+        (answer->getOption(D6O_CLIENT_FQDN));
+
+   // If Client FQDN option is not included, there is nothing to do.
+   if (!fqdn) {
+       return;
+   }
+
+   std::string name = fqdn->getDomainName();
+
+   // If there is a host reservation for this client we have to check whether
+   // this reservation has the same hostname as the hostname currently
+   // present in the FQDN option. If not, it indicates that the allocation
+   // engine picked a different subnet (from within a shared network) for
+   // reservations and we have to send this new value to the client.
+   if (ctx.currentHost() &&
+       !ctx.currentHost()->getHostname().empty()) {
+       std::string new_name = CfgMgr::instance().getD2ClientMgr().
+           qualifyName(ctx.currentHost()->getHostname(), *ctx.getDdnsParams(), true);
+
+       if (new_name != name) {
+           fqdn->setDomainName(new_name, Option6ClientFqdn::FULL);
+
+           // Replace previous instance of Client FQDN option.
+           answer->delOption(D6O_CLIENT_FQDN);
+           answer->addOption(fqdn);
+       }
+   }
+}
+
+void
+Dhcpv6Srv::generateFqdn(const Pkt6Ptr& answer,
+                        AllocEngine::ClientContext6& ctx) {
+    if (!answer) {
+        isc_throw(isc::Unexpected, "an instance of the object encapsulating"
+                  " a message must not be NULL when generating FQDN");
+    }
+
+    /// @todo Add proper logging for cases when we can't generate FQDN.
+    /// See #3885 for details.
+
+    // It is likely that client hasn't included the FQDN option. In such case,
+    // FQDN option will be NULL. Also, there is nothing to do if the option
+    // is present and conveys the non-empty FQDN.
+    Option6ClientFqdnPtr fqdn = boost::dynamic_pointer_cast<
+        Option6ClientFqdn>(answer->getOption(D6O_CLIENT_FQDN));
+    if (!fqdn || !fqdn->getDomainName().empty()) {
+        return;
+    }
+
+    // Get the first IA_NA acquired for the client.
+    OptionPtr ia = answer->getOption(D6O_IA_NA);
+    if (!ia) {
+        return;
+    }
+
+    // If it has any IAAddr, use the first one to generate unique FQDN.
+    Option6IAAddrPtr iaaddr = boost::dynamic_pointer_cast<
+        Option6IAAddr>(ia->getOption(D6O_IAADDR));
+    if (!iaaddr) {
+        return;
+    }
+    // Get the IPv6 address acquired by the client.
+    IOAddress addr = iaaddr->getAddress();
+    std::string generated_name =
+        CfgMgr::instance().getD2ClientMgr().generateFqdn(addr, *ctx.getDdnsParams());
+
+    LOG_DEBUG(ddns6_logger, DBG_DHCP6_DETAIL_DATA, DHCP6_DDNS_FQDN_GENERATED)
+        .arg(answer->getLabel())
+        .arg(generated_name);
+
+    try {
+        // The lease has been acquired but the FQDN for this lease hasn't
+        // been updated in the lease database. We now have new FQDN
+        // generated, so the lease database has to be updated here.
+        // However, never update lease database for Advertise, just send
+        // our notion of client's FQDN in the Client FQDN option.
+        if (answer->getType() != DHCPV6_ADVERTISE) {
+            Lease6Ptr lease;
+            for (auto l : ctx.new_leases_) {
+                if ((l->type_ == Lease::TYPE_NA) && (l->addr_ == addr)) {
+                    lease = l;
+                    break;
+                }
+            }
+            if (lease) {
+                lease->hostname_ = generated_name;
+                lease->reuseable_valid_lft_ = 0;
+                LeaseMgrFactory::instance().updateLease6(lease);
+
+            } else {
+                isc_throw(isc::Unexpected, "there is no lease in the database "
+                          " for address " << addr << ", so as it is impossible"
+                          " to update FQDN data. This is a programmatic error"
+                          " as the given address is now being handed to the"
+                          " client");
+            }
+        }
+        // Set the generated FQDN in the Client FQDN option.
+        fqdn->setDomainName(generated_name, Option6ClientFqdn::FULL);
+
+        answer->delOption(D6O_CLIENT_FQDN);
+        answer->addOption(fqdn);
+        ctx.hostname_ = generated_name;
+    } catch (const Exception& ex) {
+        LOG_ERROR(ddns6_logger, DHCP6_DDNS_GENERATED_FQDN_UPDATE_FAIL)
+            .arg(answer->getLabel())
+            .arg(addr.toText())
+            .arg(ex.what());
+    }
+}
+
+void
+Dhcpv6Srv::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(&Dhcpv6Srv::d2ClientErrorHandler,
+                                     this, ph::_1, ph::_2));
+    }
+}
+
+void
+Dhcpv6Srv::stopD2() {
+    D2ClientMgr& d2_mgr = CfgMgr::instance().getD2ClientMgr();
+    if (d2_mgr.ddnsEnabled()) {
+        // Updates are enabled, so lets stop the sender
+        d2_mgr.stopSender();
+    }
+}
+
+void
+Dhcpv6Srv::d2ClientErrorHandler(const
+                                dhcp_ddns::NameChangeSender::Result result,
+                                dhcp_ddns::NameChangeRequestPtr& ncr) {
+    LOG_ERROR(ddns6_logger, DHCP6_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
+Dhcpv6Srv::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::V6);
+
+        // @todo: more details about database runtime
+    }
+
+    return (tmp.str());
+}
+
+void Dhcpv6Srv::processRSOO(const Pkt6Ptr& query, const Pkt6Ptr& rsp) {
+
+    if (query->relay_info_.empty()) {
+        // RSOO is inserted by relay agents, nothing to do here if it's
+        // a direct message.
+        return;
+    }
+
+    // Get RSOO configuration.
+    ConstCfgRSOOPtr cfg_rsoo  = CfgMgr::instance().getCurrentCfg()->getCfgRSOO();
+
+    // Let's get over all relays (encapsulation levels). We need to do
+    // it in the same order as the client packet traversed the relays.
+    for (int i = query->relay_info_.size(); i > 0 ; --i) {
+        OptionPtr rsoo_container = query->getRelayOption(D6O_RSOO, i - 1);
+        if (rsoo_container) {
+            // There are RSOO options. Let's get through them one by one
+            // and if it's RSOO-enabled and there's no such option provided yet,
+            // copy it to the server's response
+            const OptionCollection& rsoo = rsoo_container->getOptions();
+            for (OptionCollection::const_iterator opt = rsoo.begin();
+                 opt != rsoo.end(); ++opt) {
+
+                // Echo option if it is RSOO enabled option and there is no such
+                // option added yet.
+                if (cfg_rsoo->enabled(opt->second->getType()) &&
+                    !rsp->getOption(opt->second->getType())) {
+                    rsp->addOption(opt->second);
+                }
+            }
+        }
+    }
+}
+
+uint16_t Dhcpv6Srv::checkRelaySourcePort(const Pkt6Ptr& query) {
+
+    if (query->relay_info_.empty()) {
+        // No relay agent
+        return (0);
+    }
+
+    // Did the last relay agent add a relay-source-port?
+    if (query->getRelayOption(D6O_RELAY_SOURCE_PORT, 0)) {
+        // RFC 8357 section 5.2
+        return (query->getRemotePort());
+    }
+
+    return (0);
+}
+
+void Dhcpv6Srv::processStatsReceived(const Pkt6Ptr& query) {
+    // Note that we're not bumping pkt6-received statistic as it was
+    // increased early in the packet reception code.
+
+    string stat_name = "pkt6-unknown-received";
+    switch (query->getType()) {
+    case DHCPV6_SOLICIT:
+        stat_name = "pkt6-solicit-received";
+        break;
+    case DHCPV6_ADVERTISE:
+        // Should not happen, but let's keep a counter for it
+        stat_name = "pkt6-advertise-received";
+        break;
+    case DHCPV6_REQUEST:
+        stat_name = "pkt6-request-received";
+        break;
+    case DHCPV6_CONFIRM:
+        stat_name = "pkt6-confirm-received";
+        break;
+    case DHCPV6_RENEW:
+        stat_name = "pkt6-renew-received";
+        break;
+    case DHCPV6_REBIND:
+        stat_name = "pkt6-rebind-received";
+        break;
+    case DHCPV6_REPLY:
+        // Should not happen, but let's keep a counter for it
+        stat_name = "pkt6-reply-received";
+        break;
+    case DHCPV6_RELEASE:
+        stat_name = "pkt6-release-received";
+        break;
+    case DHCPV6_DECLINE:
+        stat_name = "pkt6-decline-received";
+        break;
+    case DHCPV6_RECONFIGURE:
+        stat_name = "pkt6-reconfigure-received";
+        break;
+    case DHCPV6_INFORMATION_REQUEST:
+        stat_name = "pkt6-infrequest-received";
+        break;
+    case DHCPV6_DHCPV4_QUERY:
+        stat_name = "pkt6-dhcpv4-query-received";
+        break;
+    case DHCPV6_DHCPV4_RESPONSE:
+        // Should not happen, but let's keep a counter for it
+        stat_name = "pkt6-dhcpv4-response-received";
+        break;
+    default:
+            ; // do nothing
+    }
+
+    StatsMgr::instance().addValue(stat_name, static_cast<int64_t>(1));
+}
+
+void Dhcpv6Srv::processStatsSent(const Pkt6Ptr& response) {
+    // Increase generic counter for sent packets.
+    StatsMgr::instance().addValue("pkt6-sent", static_cast<int64_t>(1));
+
+    // Increase packet type specific counter for packets sent.
+    string stat_name;
+    switch (response->getType()) {
+    case DHCPV6_ADVERTISE:
+        stat_name = "pkt6-advertise-sent";
+        break;
+    case DHCPV6_REPLY:
+        stat_name = "pkt6-reply-sent";
+        break;
+    case DHCPV6_DHCPV4_RESPONSE:
+        stat_name = "pkt6-dhcpv4-response-sent";
+        break;
+    default:
+        // That should never happen
+        return;
+    }
+
+    StatsMgr::instance().addValue(stat_name, static_cast<int64_t>(1));
+}
+
+int Dhcpv6Srv::getHookIndexBuffer6Send() {
+    return (Hooks.hook_index_buffer6_send_);
+}
+
+bool
+Dhcpv6Srv::requestedInORO(const Pkt6Ptr& query, const uint16_t code) const {
+    OptionUint16ArrayPtr oro =
+        boost::dynamic_pointer_cast<OptionUint16Array>(query->getOption(D6O_ORO));
+
+    if (oro) {
+        const std::vector<uint16_t>& codes = oro->getValues();
+        return (std::find(codes.begin(), codes.end(), code) != codes.end());
+    }
+
+    return (false);
+}
+
+void Dhcpv6Srv::discardPackets() {
+    // Dump all of our current packets, anything that is mid-stream
+    HooksManager::clearParkingLots();
+}
+
+/// @todo This logic to be modified if we decide to support infinite lease times.
+void
+Dhcpv6Srv::setTeeTimes(uint32_t preferred_lft, const Subnet6Ptr& subnet, Option6IAPtr& resp) {
+    // Default T2 time to zero.
+    uint32_t t2_time = 0;
+
+    // If T2 is explicitly configured we'll use that value.
+    if (!subnet->getT2().unspecified()) {
+        t2_time = subnet->getT2();
+    } else if (subnet->getCalculateTeeTimes()) {
+        // Calculating tee times is enabled, so calculate it.
+        t2_time = static_cast<uint32_t>(round(subnet->getT2Percent() * preferred_lft));
+    }
+
+    // We allow T2 to be any value.
+    resp->setT2(t2_time);
+
+    // Default T1 time to zero.
+    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() * preferred_lft));
+    }
+
+    // T1 is sane if it is less than or equal to T2.
+    if (t1_time < t2_time) {
+        resp->setT1(t1_time);
+    } else {
+        // It's either explicitly 0 or insane, leave it to the client
+        resp->setT1(0);
+    }
+}
+
+void
+Dhcpv6Srv::checkDynamicSubnetChange(const Pkt6Ptr& question, Pkt6Ptr& answer,
+                                    AllocEngine::ClientContext6& ctx,
+                                    const Subnet6Ptr orig_subnet) {
+    // If the subnet's are the same there's nothing to do.
+    if ((!ctx.subnet_) || (!orig_subnet) || (orig_subnet->getID() == ctx.subnet_->getID())) {
+        return;
+    }
+
+    // We get the network for logging only. It should always be set as this a dynamic
+    // change should only happen within shared-networks.  Not having one might not be
+    // an error if a hook changed the subnet?
+    SharedNetwork6Ptr network;
+    orig_subnet->getSharedNetwork(network);
+    LOG_DEBUG(packet6_logger, DBG_DHCP6_BASIC_DATA, DHCP6_SUBNET_DYNAMICALLY_CHANGED)
+             .arg(question->getLabel())
+             .arg(orig_subnet->toText())
+             .arg(ctx.subnet_->toText())
+             .arg(network ? network->getName() : "<no network?>");
+
+    // The DDNS parameters may have changed with the subnet, so we need to
+    // recalculate the client name.
+
+    // Save the current DNS values on the context.
+    std::string prev_hostname = ctx.hostname_;
+    bool prev_fwd_dns_update = ctx.fwd_dns_update_;
+    bool prev_rev_dns_update = ctx.rev_dns_update_;
+
+    // Remove the current FQDN option from the answer.
+    answer->delOption(D6O_CLIENT_FQDN);
+
+    // Recalculate the client's FQDN.  This will replace the FQDN option and
+    // update the context values for hostname_ and DNS directions.
+    processClientFqdn(question, answer, ctx);
+
+    // If this is a real allocation and the DNS values changed we need to
+    // update the leases.
+    if (!ctx.fake_allocation_ &&
+        ((prev_hostname != ctx.hostname_) ||
+        (prev_fwd_dns_update != ctx.fwd_dns_update_) ||
+        (prev_rev_dns_update != ctx.rev_dns_update_))) {
+        for (Lease6Collection::const_iterator l = ctx.new_leases_.begin();
+            l != ctx.new_leases_.end(); ++l) {
+            (*l)->hostname_ = ctx.hostname_;
+            (*l)->fqdn_fwd_ = ctx.fwd_dns_update_;
+            (*l)->fqdn_rev_ = ctx.rev_dns_update_;
+            (*l)->reuseable_valid_lft_ = 0;
+            LeaseMgrFactory::instance().updateLease6(*l);
+        }
+    }
+}
+
+std::list<std::list<std::string>> Dhcpv6Srv::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