dhcp4_srv.cc 112 KB
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// Copyright (C) 2011-2017 Internet Systems Consortium, Inc. ("ISC")
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//
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// 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/.
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#include <config.h>
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#include <asiolink/io_address.h>
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#include <dhcp/dhcp4.h>
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#include <dhcp/duid.h>
#include <dhcp/hwaddr.h>
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#include <dhcp/iface_mgr.h>
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#include <dhcp/option4_addrlst.h>
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#include <dhcp/option_int.h>
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#include <dhcp/option_int_array.h>
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#include <dhcp/option_vendor.h>
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#include <dhcp/option_string.h>
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#include <dhcp/pkt4.h>
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#include <dhcp/pkt4o6.h>
#include <dhcp/pkt6.h>
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#include <dhcp/docsis3_option_defs.h>
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#include <dhcp4/dhcp4to6_ipc.h>
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#include <dhcp4/dhcp4_log.h>
#include <dhcp4/dhcp4_srv.h>
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#include <dhcpsrv/addr_utilities.h>
#include <dhcpsrv/callout_handle_store.h>
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#include <dhcpsrv/cfgmgr.h>
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#include <dhcpsrv/cfg_host_operations.h>
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#include <dhcpsrv/cfg_subnets4.h>
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#include <dhcpsrv/lease_mgr.h>
#include <dhcpsrv/lease_mgr_factory.h>
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#include <dhcpsrv/ncr_generator.h>
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#include <dhcpsrv/subnet.h>
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#include <dhcpsrv/subnet_selector.h>
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#include <dhcpsrv/utils.h>
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#include <dhcpsrv/utils.h>
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#include <eval/evaluate.h>
#include <eval/eval_messages.h>
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#include <hooks/callout_handle.h>
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#include <hooks/hooks_log.h>
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#include <hooks/hooks_manager.h>
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#include <stats/stats_mgr.h>
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#include <util/strutil.h>
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#include <stats/stats_mgr.h>
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#include <log/logger.h>
#include <cryptolink/cryptolink.h>
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#include <cfgrpt/config_report.h>
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#ifdef HAVE_MYSQL
#include <dhcpsrv/mysql_lease_mgr.h>
#endif
#ifdef HAVE_PGSQL
#include <dhcpsrv/pgsql_lease_mgr.h>
#endif
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#ifdef HAVE_CQL
#include <dhcpsrv/cql_lease_mgr.h>
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#endif
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#include <dhcpsrv/memfile_lease_mgr.h>

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#include <boost/algorithm/string/join.hpp>
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#include <boost/bind.hpp>
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#include <boost/foreach.hpp>
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#include <boost/shared_ptr.hpp>
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#include <iomanip>

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using namespace isc;
using namespace isc::asiolink;
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using namespace isc::cryptolink;
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using namespace isc::dhcp;
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using namespace isc::dhcp_ddns;
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using namespace isc::hooks;
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using namespace isc::log;
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using namespace isc::stats;
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using namespace std;
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/// Structure that holds registered hook indexes
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struct Dhcp4Hooks {
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    int hook_index_buffer4_receive_; ///< index for "buffer4_receive" hook point
    int hook_index_pkt4_receive_;    ///< index for "pkt4_receive" hook point
    int hook_index_subnet4_select_;  ///< index for "subnet4_select" hook point
    int hook_index_lease4_release_;  ///< index for "lease4_release" hook point
    int hook_index_pkt4_send_;       ///< index for "pkt4_send" hook point
    int hook_index_buffer4_send_;    ///< index for "buffer4_send" hook point
    int hook_index_lease4_decline_;  ///< index for "lease4_decline" hook point
    int hook_index_host4_identifier_;///< index for "host4_identifier" hook point
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    /// Constructor that registers hook points for DHCPv4 engine
    Dhcp4Hooks() {
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        hook_index_buffer4_receive_  = HooksManager::registerHook("buffer4_receive");
        hook_index_pkt4_receive_     = HooksManager::registerHook("pkt4_receive");
        hook_index_subnet4_select_   = HooksManager::registerHook("subnet4_select");
        hook_index_pkt4_send_        = HooksManager::registerHook("pkt4_send");
        hook_index_lease4_release_   = HooksManager::registerHook("lease4_release");
        hook_index_buffer4_send_     = HooksManager::registerHook("buffer4_send");
        hook_index_lease4_decline_   = HooksManager::registerHook("lease4_decline");
        hook_index_host4_identifier_ = HooksManager::registerHook("host4_identifier");
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    }
};

// 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.
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Dhcp4Hooks Hooks;
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namespace isc {
namespace dhcp {

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Dhcpv4Exchange::Dhcpv4Exchange(const AllocEnginePtr& alloc_engine,
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                               const Pkt4Ptr& query,
                               const Subnet4Ptr& subnet)
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    : alloc_engine_(alloc_engine), query_(query), resp_(),
      context_(new AllocEngine::ClientContext4()) {
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    if (!alloc_engine_) {
        isc_throw(BadValue, "alloc_engine value must not be NULL"
                  " when creating an instance of the Dhcpv4Exchange");
    }

    if (!query_) {
        isc_throw(BadValue, "query value must not be NULL when"
                  " creating an instance of the Dhcpv4Exchange");
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    }

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    // Create response message.
    initResponse();
    // Select subnet for the query message.
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    context_->subnet_ = subnet;
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    // Hardware address.
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    context_->hwaddr_ = query->getHWAddr();
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    // Pointer to client's query.
    context_->query_ = query;
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    // Set client identifier if the match-client-id flag is enabled (default).
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    // If the subnet wasn't found it doesn't matter because we will not be
    // able to allocate a lease anyway so this context will not be used.
    if (subnet) {
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        if (subnet->getMatchClientId()) {
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            OptionPtr opt_clientid = query->getOption(DHO_DHCP_CLIENT_IDENTIFIER);
            if (opt_clientid) {
                context_->clientid_.reset(new ClientId(opt_clientid->getData()));
            }
        } else {
            /// @todo When merging with #3806 use different logger.
            LOG_DEBUG(dhcp4_logger, DBG_DHCP4_DETAIL, DHCP4_CLIENTID_IGNORED_FOR_LEASES)
                .arg(query->getLabel())
                .arg(subnet->getID());
        }
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        // Find static reservations if not disabled for our subnet.
        if (subnet->getHostReservationMode() != Subnet::HR_DISABLED) {
            // Before we can check for static reservations, we need to prepare a set
            // of identifiers to be used for this.
            setHostIdentifiers();
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            // Check for static reservations.
            alloc_engine->findReservation(*context_);
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            // Assign classes.
            setReservedClientClasses();
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        }
    }
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    const ClientClasses& classes = query_->getClasses();
    if (!classes.empty()) {
        std::string joined_classes = boost::algorithm::join(classes, ", ");
        LOG_DEBUG(dhcp4_logger, DBG_DHCP4_BASIC, DHCP4_CLASS_ASSIGNED)
            .arg(query_->getLabel())
            .arg(joined_classes);
    }
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};

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void
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Dhcpv4Exchange::initResponse() {
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    uint8_t resp_type = 0;
    switch (getQuery()->getType()) {
    case DHCPDISCOVER:
        resp_type = DHCPOFFER;
        break;
    case DHCPREQUEST:
    case DHCPINFORM:
        resp_type = DHCPACK;
        break;
    default:
        ;
    }
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    // Only create a response if one is required.
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    if (resp_type > 0) {
        resp_.reset(new Pkt4(resp_type, getQuery()->getTransid()));
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        copyDefaultFields();
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        copyDefaultOptions();
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        if (getQuery()->isDhcp4o6()) {
            initResponse4o6();
        }
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    }
}

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void
Dhcpv4Exchange::initResponse4o6() {
    Pkt4o6Ptr query = boost::dynamic_pointer_cast<Pkt4o6>(getQuery());
    if (!query) {
        return;
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    }
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    const Pkt6Ptr& query6 = query->getPkt6();
    Pkt6Ptr resp6(new Pkt6(DHCPV6_DHCPV4_RESPONSE, query6->getTransid()));
    // Don't add client-id or server-id
    // But copy relay info
    if (!query6->relay_info_.empty()) {
        resp6->copyRelayInfo(query6);
    }
    // Copy interface and remote address
    resp6->setIface(query6->getIface());
    resp6->setIndex(query6->getIndex());
    resp6->setRemoteAddr(query6->getRemoteAddr());
    resp_.reset(new Pkt4o6(resp_, resp6));
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}

void
Dhcpv4Exchange::copyDefaultFields() {
    resp_->setIface(query_->getIface());
    resp_->setIndex(query_->getIndex());

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    // explicitly set this to 0
    resp_->setSiaddr(IOAddress::IPV4_ZERO_ADDRESS());
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    // ciaddr is always 0, except for the Renew/Rebind state when it may
    // be set to the ciaddr sent by the client.
    resp_->setCiaddr(IOAddress::IPV4_ZERO_ADDRESS());
    resp_->setHops(query_->getHops());

    // copy MAC address
    resp_->setHWAddr(query_->getHWAddr());

    // relay address
    resp_->setGiaddr(query_->getGiaddr());

    // If src/dest HW addresses are used by the packet filtering class
    // we need to copy them as well. There is a need to check that the
    // address being set is not-NULL because an attempt to set the NULL
    // HW would result in exception. If these values are not set, the
    // the default HW addresses (zeroed) should be generated by the
    // packet filtering class when creating Ethernet header for
    // outgoing packet.
    HWAddrPtr src_hw_addr = query_->getLocalHWAddr();
    if (src_hw_addr) {
        resp_->setLocalHWAddr(src_hw_addr);
    }
    HWAddrPtr dst_hw_addr = query_->getRemoteHWAddr();
    if (dst_hw_addr) {
        resp_->setRemoteHWAddr(dst_hw_addr);
    }
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    // Copy flags from the request to the response per RFC 2131
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    resp_->setFlags(query_->getFlags());
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}
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void
Dhcpv4Exchange::copyDefaultOptions() {
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    // Let's copy client-id to response. See RFC6842.
    // It is possible to disable RFC6842 to keep backward compatibility
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    bool echo = CfgMgr::instance().getCurrentCfg()->getEchoClientId();
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    OptionPtr client_id = query_->getOption(DHO_DHCP_CLIENT_IDENTIFIER);
    if (client_id && echo) {
        resp_->addOption(client_id);
    }
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    // If this packet is relayed, we want to copy Relay Agent Info option
    OptionPtr rai = query_->getOption(DHO_DHCP_AGENT_OPTIONS);
    if (rai) {
        resp_->addOption(rai);
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    }
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    // RFC 3011 states about the Subnet Selection Option

    // "Servers configured to support this option MUST return an
    //  identical copy of the option to any client that sends it,
    //  regardless of whether or not the client requests the option in
    //  a parameter request list. Clients using this option MUST
    //  discard DHCPOFFER or DHCPACK packets that do not contain this
    //  option."
    OptionPtr subnet_sel = query_->getOption(DHO_SUBNET_SELECTION);
    if (subnet_sel) {
        resp_->addOption(subnet_sel);
    }
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}

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void
Dhcpv4Exchange::setHostIdentifiers() {
    const ConstCfgHostOperationsPtr cfg =
        CfgMgr::instance().getCurrentCfg()->getCfgHostOperations4();
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    // Collect host identifiers. The identifiers are stored in order of preference.
    // The server will use them in that order to search for host reservations.
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    BOOST_FOREACH(const Host::IdentifierType& id_type,
                  cfg->getIdentifierTypes()) {
        switch (id_type) {
        case Host::IDENT_HWADDR:
            if (context_->hwaddr_ && !context_->hwaddr_->hwaddr_.empty()) {
                context_->addHostIdentifier(id_type, context_->hwaddr_->hwaddr_);
            }
            break;

        case Host::IDENT_DUID:
            if (context_->clientid_) {
                const std::vector<uint8_t>& vec = context_->clientid_->getDuid();
                if (!vec.empty()) {
                    // Client identifier type = DUID? Client identifier holding a DUID
                    // comprises Type (1 byte), IAID (4 bytes), followed by the actual
                    // DUID. Thus, the minimal length is 6.
                    if ((vec[0] == CLIENT_ID_OPTION_TYPE_DUID) && (vec.size() > 5)) {
                        // Extract DUID, skip IAID.
                        context_->addHostIdentifier(id_type,
                                                    std::vector<uint8_t>(vec.begin() + 5,
                                                                         vec.end()));
                    }
                }
            }
            break;

        case Host::IDENT_CIRCUIT_ID:
            {
                OptionPtr rai = query_->getOption(DHO_DHCP_AGENT_OPTIONS);
                if (rai) {
                    OptionPtr circuit_id_opt = rai->getOption(RAI_OPTION_AGENT_CIRCUIT_ID);
                    if (circuit_id_opt) {
                        const OptionBuffer& circuit_id_vec = circuit_id_opt->getData();
                        if (!circuit_id_vec.empty()) {
                            context_->addHostIdentifier(id_type, circuit_id_vec);
                        }
                    }
                }
            }
            break;

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        case Host::IDENT_CLIENT_ID:
            if (context_->clientid_) {
                const std::vector<uint8_t>& vec = context_->clientid_->getDuid();
                if (!vec.empty()) {
                    context_->addHostIdentifier(id_type, vec);
                }
            }
            break;
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        case Host::IDENT_FLEX:
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            {
                if (!HooksManager::calloutsPresent(Hooks.hook_index_host4_identifier_)) {
                    break;
                }

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                CalloutHandlePtr callout_handle = getCalloutHandle(context_->query_);
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                Host::IdentifierType type = Host::IDENT_FLEX;
                std::vector<uint8_t> id;

                // Delete previously set arguments
                callout_handle->deleteAllArguments();

                // Pass incoming packet as argument
                callout_handle->setArgument("query4", context_->query_);
                callout_handle->setArgument("id_type", type);
                callout_handle->setArgument("id_value", id);

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                // Call callouts
                HooksManager::callCallouts(Hooks.hook_index_host4_identifier_,
                                           *callout_handle);
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                callout_handle->getArgument("id_type", type);
                callout_handle->getArgument("id_value", id);
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                if ((callout_handle->getStatus() == CalloutHandle::NEXT_STEP_CONTINUE) &&
                    !id.empty()) {
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                    LOG_DEBUG(packet4_logger, DBGLVL_TRACE_BASIC, DHCP4_FLEX_ID)
                        .arg(Host::getIdentifierAsText(type, &id[0], id.size()));
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                    context_->addHostIdentifier(type, id);
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                }
                break;
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            }
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        default:
            ;
        }
    }
}

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void
Dhcpv4Exchange::setReservedClientClasses() {
    if (context_->host_ && query_) {
        BOOST_FOREACH(const std::string& client_class,
                      context_->host_->getClientClasses4()) {
            query_->addClass(client_class);
        }
    }
}

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void
Dhcpv4Exchange::setReservedMessageFields() {
    ConstHostPtr host = context_->host_;
    // Nothing to do if host reservations not specified for this client.
    if (host) {
        if (!host->getNextServer().isV4Zero()) {
            resp_->setSiaddr(host->getNextServer());
        }

        if (!host->getServerHostname().empty()) {
            resp_->setSname(reinterpret_cast<
                            const uint8_t*>(host->getServerHostname().c_str()));
        }

        if (!host->getBootFileName().empty()) {
            resp_->setFile(reinterpret_cast<
                           const uint8_t*>(host->getBootFileName().c_str()));
        }
    }
}

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const std::string Dhcpv4Srv::VENDOR_CLASS_PREFIX("VENDOR_CLASS_");

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Dhcpv4Srv::Dhcpv4Srv(uint16_t port, const bool use_bcast,
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                     const bool direct_response_desired)
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    : shutdown_(true), alloc_engine_(), port_(port),
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      use_bcast_(use_bcast) {
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    LOG_DEBUG(dhcp4_logger, DBG_DHCP4_START, DHCP4_OPEN_SOCKET).arg(port);
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    try {
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        // Port 0 is used for testing purposes where we don't open broadcast
        // capable sockets. So, set the packet filter handling direct traffic
        // only if we are in non-test mode.
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        if (port) {
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            // First call to instance() will create IfaceMgr (it's a singleton)
            // it may throw something if things go wrong.
            // The 'true' value of the call to setMatchingPacketFilter imposes
            // that IfaceMgr will try to use the mechanism to respond directly
            // to the client which doesn't have address assigned. This capability
            // may be lacking on some OSes, so there is no guarantee that server
            // will be able to respond directly.
            IfaceMgr::instance().setMatchingPacketFilter(direct_response_desired);
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        }
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        // 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(AllocEngine::ALLOC_ITERATIVE, 0,
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                                            false /* false = IPv4 */));
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        /// @todo call loadLibraries() when handling configuration changes

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    } catch (const std::exception &e) {
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        LOG_ERROR(dhcp4_logger, DHCP4_SRV_CONSTRUCT_ERROR).arg(e.what());
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        shutdown_ = true;
        return;
    }
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    shutdown_ = false;
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}

Dhcpv4Srv::~Dhcpv4Srv() {
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    try {
        stopD2();
    } catch(const std::exception& ex) {
        // Highly unlikely, but lets Report it but go on
        LOG_ERROR(dhcp4_logger, DHCP4_SRV_D2STOP_ERROR).arg(ex.what());
    }
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    try {
        Dhcp4to6Ipc::instance().close();
    } catch(const std::exception& ex) {
        // Highly unlikely, but lets Report it but go on
        LOG_ERROR(dhcp4_logger, DHCP4_SRV_DHCP4O6_ERROR).arg(ex.what());
    }

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    IfaceMgr::instance().closeSockets();
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    // The lease manager was instantiated during DHCPv4Srv configuration,
    // so we should clean up after ourselves.
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    LeaseMgrFactory::destroy();
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    // Explicitly unload hooks
    HooksManager::getHooksManager().unloadLibraries();
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}

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void
Dhcpv4Srv::shutdown() {
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    LOG_DEBUG(dhcp4_logger, DBG_DHCP4_BASIC, DHCP4_SHUTDOWN_REQUEST);
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    shutdown_ = true;
}

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isc::dhcp::Subnet4Ptr
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Dhcpv4Srv::selectSubnet(const Pkt4Ptr& query) const {
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    // DHCPv4-over-DHCPv6 is a special (and complex) case
    if (query->isDhcp4o6()) {
        return (selectSubnet4o6(query));
    }

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    Subnet4Ptr subnet;

    SubnetSelector selector;
    selector.ciaddr_ = query->getCiaddr();
    selector.giaddr_ = query->getGiaddr();
    selector.local_address_ = query->getLocalAddr();
    selector.remote_address_ = query->getRemoteAddr();
    selector.client_classes_ = query->classes_;
    selector.iface_name_ = query->getIface();

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    // If the link-selection sub-option is present, extract its value.
    // "The link-selection sub-option is used by any DHCP relay agent
    // that desires to specify a subnet/link for a DHCP client request
    // that it is relaying but needs the subnet/link specification to
    // be different from the IP address the DHCP server should use
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    // when communicating with the relay agent." (RFC 3527)
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    //
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    // Try first Relay Agent Link Selection sub-option
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    OptionPtr rai = query->getOption(DHO_DHCP_AGENT_OPTIONS);
    if (rai) {
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        OptionCustomPtr rai_custom =
            boost::dynamic_pointer_cast<OptionCustom>(rai);
        if (rai_custom) {
            OptionPtr link_select =
                rai_custom->getOption(RAI_OPTION_LINK_SELECTION);
            if (link_select) {
                OptionBuffer link_select_buf = link_select->getData();
                if (link_select_buf.size() == sizeof(uint32_t)) {
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                    selector.option_select_ =
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                        IOAddress::fromBytes(AF_INET, &link_select_buf[0]);
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                }
            }
        }
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    } else {
        // Or Subnet Selection option
        OptionPtr sbnsel = query->getOption(DHO_SUBNET_SELECTION);
        if (sbnsel) {
            OptionCustomPtr oc =
                boost::dynamic_pointer_cast<OptionCustom>(sbnsel);
            if (oc) {
                selector.option_select_ = oc->readAddress();
            }
        }
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    }

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    CfgMgr& cfgmgr = CfgMgr::instance();
    subnet = cfgmgr.getCurrentCfg()->getCfgSubnets4()->selectSubnet(selector);

    // Let's execute all callouts registered for subnet4_select
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    if (HooksManager::calloutsPresent(Hooks.hook_index_subnet4_select_)) {
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        CalloutHandlePtr callout_handle = getCalloutHandle(query);

        // We're reusing callout_handle from previous calls
        callout_handle->deleteAllArguments();

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        // Enable copying options from the packet within hook library.
        ScopedEnableOptionsCopy<Pkt4> query4_options_copy(query);

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        // Set new arguments
        callout_handle->setArgument("query4", query);
        callout_handle->setArgument("subnet4", subnet);
        callout_handle->setArgument("subnet4collection",
                                    cfgmgr.getCurrentCfg()->
                                    getCfgSubnets4()->getAll());

        // Call user (and server-side) callouts
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        HooksManager::callCallouts(Hooks.hook_index_subnet4_select_,
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                                   *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)
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        if (callout_handle->getStatus() == CalloutHandle::NEXT_STEP_SKIP) {
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            LOG_DEBUG(hooks_logger, DBG_DHCP4_HOOKS,
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                      DHCP4_HOOK_SUBNET4_SELECT_SKIP)
                .arg(query->getLabel());
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            return (Subnet4Ptr());
        }

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        /// @todo: Add support for DROP status

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        // Use whatever subnet was specified by the callout
        callout_handle->getArgument("subnet4", subnet);
    }

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    if (subnet) {
        // Log at higher debug level that subnet has been found.
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        LOG_DEBUG(packet4_logger, DBG_DHCP4_BASIC_DATA, DHCP4_SUBNET_SELECTED)
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            .arg(query->getLabel())
            .arg(subnet->getID());
        // Log detailed information about the selected subnet at the
        // lower debug level.
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        LOG_DEBUG(packet4_logger, DBG_DHCP4_DETAIL_DATA, DHCP4_SUBNET_DATA)
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            .arg(query->getLabel())
            .arg(subnet->toText());

    } else {
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        LOG_DEBUG(packet4_logger, DBG_DHCP4_DETAIL,
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                  DHCP4_SUBNET_SELECTION_FAILED)
            .arg(query->getLabel());
    }

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    return (subnet);
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}

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isc::dhcp::Subnet4Ptr
Dhcpv4Srv::selectSubnet4o6(const Pkt4Ptr& query) const {

    Subnet4Ptr subnet;

    SubnetSelector selector;
    selector.ciaddr_ = query->getCiaddr();
    selector.giaddr_ = query->getGiaddr();
    selector.local_address_ = query->getLocalAddr();
    selector.client_classes_ = query->classes_;
    selector.iface_name_ = query->getIface();
    // Mark it as DHCPv4-over-DHCPv6
    selector.dhcp4o6_ = true;
    // Now the DHCPv6 part
    selector.remote_address_ = query->getRemoteAddr();
    selector.first_relay_linkaddr_ = IOAddress("::");

    // Handle a DHCPv6 relayed query
    Pkt4o6Ptr query4o6 = boost::dynamic_pointer_cast<Pkt4o6>(query);
    if (!query4o6) {
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        isc_throw(Unexpected, "Can't get DHCP4o6 message");
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    }
    const Pkt6Ptr& query6 = query4o6->getPkt6();

    // Initialize fields specific to relayed messages.
    if (query6 && !query6->relay_info_.empty()) {
        BOOST_REVERSE_FOREACH(Pkt6::RelayInfo relay, query6->relay_info_) {
            if (!relay.linkaddr_.isV6Zero() &&
                !relay.linkaddr_.isV6LinkLocal()) {
                selector.first_relay_linkaddr_ = relay.linkaddr_;
                break;
            }
        }
        selector.interface_id_ =
            query6->getAnyRelayOption(D6O_INTERFACE_ID,
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                                      Pkt6::RELAY_GET_FIRST);
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    }

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    // If the Subnet Selection option is present, extract its value.
    OptionPtr sbnsel = query->getOption(DHO_SUBNET_SELECTION);
    if (sbnsel) {
        OptionCustomPtr oc = boost::dynamic_pointer_cast<OptionCustom>(sbnsel);
        if (oc) {
            selector.option_select_ = oc->readAddress();
        }
    }

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    CfgMgr& cfgmgr = CfgMgr::instance();
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    subnet = cfgmgr.getCurrentCfg()->getCfgSubnets4()->selectSubnet4o6(selector);
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    // Let's execute all callouts registered for subnet4_select
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    if (HooksManager::calloutsPresent(Hooks.hook_index_subnet4_select_)) {
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        CalloutHandlePtr callout_handle = getCalloutHandle(query);

        // We're reusing callout_handle from previous calls
        callout_handle->deleteAllArguments();

        // Set new arguments
        callout_handle->setArgument("query4", query);
        callout_handle->setArgument("subnet4", subnet);
        callout_handle->setArgument("subnet4collection",
                                    cfgmgr.getCurrentCfg()->
                                    getCfgSubnets4()->getAll());

        // Call user (and server-side) callouts
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        HooksManager::callCallouts(Hooks.hook_index_subnet4_select_,
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                                   *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)
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        if (callout_handle->getStatus() == CalloutHandle::NEXT_STEP_SKIP) {
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            LOG_DEBUG(hooks_logger, DBG_DHCP4_HOOKS,
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                      DHCP4_HOOK_SUBNET4_SELECT_SKIP)
                .arg(query->getLabel());
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            return (Subnet4Ptr());
        }

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        /// @todo: Add support for DROP status

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        // Use whatever subnet was specified by the callout
        callout_handle->getArgument("subnet4", subnet);
    }

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    if (subnet) {
        // Log at higher debug level that subnet has been found.
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        LOG_DEBUG(packet4_logger, DBG_DHCP4_BASIC_DATA, DHCP4_SUBNET_SELECTED)
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            .arg(query->getLabel())
            .arg(subnet->getID());
        // Log detailed information about the selected subnet at the
        // lower debug level.
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        LOG_DEBUG(packet4_logger, DBG_DHCP4_DETAIL_DATA, DHCP4_SUBNET_DATA)
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            .arg(query->getLabel())
            .arg(subnet->toText());

    } else {
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        LOG_DEBUG(packet4_logger, DBG_DHCP4_DETAIL,
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                  DHCP4_SUBNET_SELECTION_FAILED)
            .arg(query->getLabel());
    }

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    return (subnet);
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}

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Pkt4Ptr
Dhcpv4Srv::receivePacket(int timeout) {
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    return (IfaceMgr::instance().receive4(timeout));
}

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void
Dhcpv4Srv::sendPacket(const Pkt4Ptr& packet) {
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    IfaceMgr::instance().send(packet);
}

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bool
Dhcpv4Srv::run() {
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    while (!shutdown_) {
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        try {
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            run_one();
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        } catch (const std::exception& e) {
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            // General catch-all exception that are not caught by more specific
            // catches. This one is for exceptions derived from std::exception.
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            LOG_ERROR(packet4_logger, DHCP4_PACKET_PROCESS_STD_EXCEPTION)
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                .arg(e.what());
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        } catch (...) {
            // General catch-all exception that are not caught by more specific
            // catches. This one is for other exceptions, not derived from
            // std::exception.
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            LOG_ERROR(packet4_logger, DHCP4_PACKET_PROCESS_EXCEPTION);
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        }
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    }

    return (true);
}
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void
Dhcpv4Srv::run_one() {
    // client's message and server's response
    Pkt4Ptr query;
    Pkt4Ptr rsp;
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    try {
        uint32_t timeout = 1000;
        LOG_DEBUG(packet4_logger, DBG_DHCP4_DETAIL, DHCP4_BUFFER_WAIT).arg(timeout);
        query = receivePacket(timeout);

        // Log if packet has arrived. We can't log the detailed information
        // about the DHCP message because it hasn't been unpacked/parsed
        // yet, and it can't be parsed at this point because hooks will
        // have to process it first. The only information available at this
        // point are: the interface, source address and destination addresses
        // and ports.
        if (query) {
            LOG_DEBUG(packet4_logger, DBG_DHCP4_BASIC, DHCP4_BUFFER_RECEIVED)
                .arg(query->getRemoteAddr().toText())
                .arg(query->getRemotePort())
                .arg(query->getLocalAddr().toText())
                .arg(query->getLocalPort())
                .arg(query->getIface());
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        } else {
            LOG_DEBUG(packet4_logger, DBG_DHCP4_DETAIL, DHCP4_BUFFER_WAIT_INTERRUPTED)
                .arg(timeout);
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        }

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    } 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 SIGCHILD which are handled by the server. For
        // signals that are not handled by the server we rely on the default
        // behavior of the system.
        LOG_DEBUG(packet4_logger, DBG_DHCP4_DETAIL, DHCP4_BUFFER_WAIT_SIGNAL)
            .arg(signal_set_->getNext());
    } catch (const std::exception& e) {
        // Log all other errors.
        LOG_ERROR(packet4_logger, DHCP4_BUFFER_RECEIVE_FAIL).arg(e.what());
    }
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    // Handle next signal received by the process. It must be called after
    // an attempt to receive a packet to properly handle server shut down.
    // The SIGTERM or SIGINT will be received prior to, or during execution
    // of select() (select is invoked by receivePacket()). When that
    // happens, select will be interrupted. The signal handler will be
    // invoked immediately after select(). The handler will set the
    // shutdown flag and cause the process to terminate before the next
    // select() function is called. If the function was called before
    // receivePacket the process could wait up to the duration of timeout
    // of select() to terminate.
    try {
        handleSignal();
    } catch (const std::exception& e) {
        // Standard exception occurred. Let's be on the safe side to
        // catch std::exception.
        LOG_ERROR(dhcp4_logger, DHCP4_HANDLE_SIGNAL_EXCEPTION)
            .arg(e.what());
    }
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    // Timeout may be reached or signal received, which breaks select()
    // with no reception occurred. No need to log anything here because
    // we have logged right after the call to receivePacket().
    if (!query) {
        return;
    }
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    processPacket(query, rsp);
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    if (!rsp) {
        return;
    }
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    try {
        // Now all fields and options are constructed into output wire buffer.
        // Option objects modification does not make sense anymore. Hooks
        // can only manipulate wire buffer at this stage.
        // Let's execute all callouts registered for buffer4_send
        if (HooksManager::calloutsPresent(Hooks.hook_index_buffer4_send_)) {
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            CalloutHandlePtr callout_handle = getCalloutHandle(query);

            // Delete previously set arguments
            callout_handle->deleteAllArguments();

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            // Enable copying options from the packet within hook library.
            ScopedEnableOptionsCopy<Pkt4> resp4_options_copy(rsp);

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            // Pass incoming packet as argument
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            callout_handle->setArgument("response4", rsp);
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            // Call callouts
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            HooksManager::callCallouts(Hooks.hook_index_buffer4_send_,
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                                       *callout_handle);
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            // Callouts decided to skip the next processing step. The next
            // processing step would to parse the packet, so skip at this
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            // stage means drop.
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            if (callout_handle->getStatus() == CalloutHandle::NEXT_STEP_SKIP) {
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                LOG_DEBUG(hooks_logger, DBG_DHCP4_HOOKS,
                          DHCP4_HOOK_BUFFER_SEND_SKIP)
                    .arg(rsp->getLabel());
                return;
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            }

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            /// @todo: Add support for DROP status.
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            callout_handle->getArgument("response4", rsp);
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        }

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        LOG_DEBUG(packet4_logger, DBG_DHCP4_BASIC, DHCP4_PACKET_SEND)
            .arg(rsp->getLabel())
            .arg(rsp->getName())
            .arg(static_cast<int>(rsp->getType()))
            .arg(rsp->getLocalAddr())
            .arg(rsp->getLocalPort())
            .arg(rsp->getRemoteAddr())
            .arg(rsp->getRemotePort())
            .arg(rsp->getIface());

        LOG_DEBUG(packet4_logger, DBG_DHCP4_DETAIL_DATA,
                  DHCP4_RESPONSE_DATA)
            .arg(rsp->getLabel())
            .arg(rsp->getName())
            .arg(static_cast<int>(rsp->getType()))
            .arg(rsp->toText());
        sendPacket(rsp);

        // Update statistics accordingly for sent packet.
        processStatsSent(rsp);

    } catch (const std::exception& e) {
        LOG_ERROR(packet4_logger, DHCP4_PACKET_SEND_FAIL)
            .arg(rsp->getLabel())
            .arg(e.what());
    }
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}
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void
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Dhcpv4Srv::processPacket(Pkt4Ptr& query, Pkt4Ptr& rsp) {
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    // Log reception of the packet. We need to increase it early, as any
    // failures in unpacking will cause the packet to be dropped. We
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    // will increase type specific statistic further down the road.
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    // See processStatsReceived().
    isc::stats::StatsMgr::instance().addValue("pkt4-received",
                                              static_cast<int64_t>(1));

    bool skip_unpack = false;

    // The packet has just been received so contains the uninterpreted wire
    // data; execute callouts registered for buffer4_receive.
    if (HooksManager::calloutsPresent(Hooks.hook_index_buffer4_receive_)) {
        CalloutHandlePtr callout_handle = getCalloutHandle(query);
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        // Delete previously set arguments
        callout_handle->deleteAllArguments();
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        // Enable copying options from the packet within hook library.
        ScopedEnableOptionsCopy<Pkt4> query4_options_copy(query);

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        // Pass incoming packet as argument
        callout_handle->setArgument("query4", query);
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        // Call callouts
        HooksManager::callCallouts(Hooks.hook_index_buffer4_receive_,
                                   *callout_handle);
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        // Callouts decided to skip the next processing step. The next
        // processing step would to parse the packet, so skip at this
        // stage means that callouts did the parsing already, so server
        // should skip parsing.
        if (callout_handle->getStatus() == CalloutHandle::NEXT_STEP_SKIP) {
            LOG_DEBUG(hooks_logger, DBG_DHCP4_DETAIL,
                      DHCP4_HOOK_BUFFER_RCVD_SKIP)
                .arg(query->getRemoteAddr().toText())
                .arg(query->getLocalAddr().toText())
                .arg(query->getIface());
            skip_unpack = true;
        }
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        callout_handle->getArgument("query4", query);
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        /// @todo: add support for DROP status
    }
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    // Unpack the packet information unless the buffer4_receive callouts
    // indicated they did it
    if (!skip_unpack) {
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        try {
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            LOG_DEBUG(options4_logger, DBG_DHCP4_DETAIL, DHCP4_BUFFER_UNPACK)
                .arg(query->getRemoteAddr().toText())
                .arg(query->getLocalAddr().toText())
                .arg(query->getIface());
            query->unpack();
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        } catch (const std::exception& e) {
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            // Failed to parse the packet.
            LOG_DEBUG(bad_packet4_logger, DBG_DHCP4_DETAIL,
                      DHCP4_PACKET_DROP_0001)
                .arg(query->getRemoteAddr().toText())
                .arg(query->getLocalAddr().toText())
                .arg(query->getIface())
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                .arg(e.what());
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            // Increase the statistics of parse failures and dropped packets.
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            isc::stats::StatsMgr::instance().addValue("pkt4-parse-failed",
                                                      static_cast<int64_t>(1));
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            isc::stats::StatsMgr::instance().addValue("pkt4-receive-drop",
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                                                      static_cast<int64_t>(1));
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            return;
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        }
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    }
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    // Update statistics accordingly for received packet.
    processStatsReceived(query);
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    // Assign this packet to one or more classes if needed. We need to do
    // this before calling accept(), because getSubnet4() may need client
    // class information.
    classifyPacket(query);
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    // Check whether the message should be further processed or discarded.
    // There is no need to log anything here. This function logs by itself.
    if (!accept(query)) {
        // Increase the statistic of dropped packets.
        isc::stats::StatsMgr::instance().addValue("pkt4-receive-drop",
                                                  static_cast<int64_t>(1));
        return;
    }
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    // We have sanity checked (in accept() that the Message Type option
    // exists, so we can safely get it here.
    int type = query->getType();
    LOG_DEBUG(packet4_logger, DBG_DHCP4_BASIC_DATA, DHCP4_PACKET_RECEIVED)
        .arg(query->getLabel())
        .arg(query->getName())
        .arg(type)
        .arg(query->getRemoteAddr())
        .arg(query->getLocalAddr())
        .arg(query->getIface());
    LOG_DEBUG(packet4_logger, DBG_DHCP4_DETAIL_DATA, DHCP4_QUERY_DATA)
        .arg(query->getLabel())
        .arg(query->toText());

    // Let's execute all callouts registered for pkt4_receive
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    if (HooksManager::calloutsPresent(Hooks.hook_index_pkt4_receive_)) {
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        CalloutHandlePtr callout_handle = getCalloutHandle(query);
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        // Delete previously set arguments
        callout_handle->deleteAllArguments();
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        // Enable copying options from the packet within hook library.
        ScopedEnableOptionsCopy<Pkt4> query4_options_copy(query);

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        // Pass incoming packet as argument
        callout_handle->setArgument("query4", query);
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        // Call callouts
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        HooksManager::callCallouts(Hooks.hook_index_pkt4_receive_,
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                                   *callout_handle);
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        // Callouts decided to skip the next processing step. The next
        // processing step would to process the packet, so skip at this
        // stage means drop.
        if (callout_handle->getStatus() == CalloutHandle::NEXT_STEP_SKIP) {
            LOG_DEBUG(hooks_logger, DBG_DHCP4_HOOKS,
                      DHCP4_HOOK_PACKET_RCVD_SKIP)
                .arg(query->getLabel());
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