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// Copyright (C) 2012 Internet Systems Consortium, Inc. ("ISC")
//
// Permission to use, copy, modify, and/or distribute this software for any
// purpose with or without fee is hereby granted, provided that the above
// copyright notice and this permission notice appear in all copies.
//
// THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
// REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
// AND FITNESS.  IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT,
// INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
// LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
// OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
// PERFORMANCE OF THIS SOFTWARE.

#include <string>
#include <fstream>
#include <vector>
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#include <map>
#include <asiolink/io_address.h>
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#include <boost/noncopyable.hpp>
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#include <boost/shared_ptr.hpp>
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#include <dhcp/option.h>
#include <dhcp/duid.h>
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#include <dhcp/subnet.h>
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/// @file dhcp/lease_mgr.h
/// @brief An abstract API for lease database
///
/// This file contains declarations of Lease4, Lease6 and LeaseMgr classes.
/// They are essential components of the interface to any database backend.
/// Each concrete database backend (e.g. MySQL) will define a class derived
/// from LeaseMgr class.
///
/// Failover considerations:
/// There are no intermediate plans to implement DHCPv4 failover
/// (draft-ietf-dhc-failover-12.txt). Currently (Oct. 2012) the DHCPv6 failover
/// is being defined in DHC WG in IETF (draft-ietf-dhcpv6-failover-requirements,
/// draft-ietf-dhcpv6-dailover-design), but the work is not advanced enough
/// for implementation plans yet. v4 failover requires additional parameters
/// to be kept with a lease. It is likely that v6 failover will require similar
/// fields. Such implementation will require database schema extension.
/// We have designed a way to expand/upgrade schemas during upgrades: a database
/// schema is versioned and sanity checks about required version will be done
/// upon start and/or upgrade. With this mechanism in place, we can add new
/// fields to the database. In particular we can use that capability to
/// introduce failover related fields.
///
/// However, there is another approach that can be reliably used to provide
/// failover, even without the actual failover protocol implemented. As the
/// first backend will use MySQL, we will be able to use Multi-Master capability
/// offered by MySQL and use two separatate Kea instances connecting to the
/// same database.
///
/// Nevertheless, we hope to have failover protocol eventually implemented in
/// the Kea.

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namespace isc {
namespace dhcp {

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/// @brief Structure that holds a lease for IPv4 address
///
/// For performance reasons it is a simple structure, not a class. If we chose
/// make it a class, all fields would have to made private and getters/setters
/// would be required. As this is a critical part of the code that will be used
/// extensively, direct access is warranted.
struct Lease4 {
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    /// IPv4 address
    isc::asiolink::IOAddress addr_;
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    /// @brief Address extension
    ///
    /// It is envisaged that in some cases IPv4 address will be accompanied with some
    /// additional data. One example of such use are Address + Port solutions (or
    /// Port-restricted Addresses), where several clients may get the same address, but
    /// different port ranges. This feature is not expected to be widely used.
    /// Under normal circumstances, the value should be 0.
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    uint32_t ext_;
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    /// @brief hardware address
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    std::vector<uint8_t> hwaddr_;
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    /// @brief client identifier
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    boost::shared_ptr<ClientId> client_id_;
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    /// @brief renewal timer
    ///
    /// Specifies renewal time. Although technically it is a property of IA container,
    /// not the address itself, since our data model does not define separate IA
    /// entity, we are keeping it in the lease. In case of multiple addresses/prefixes
    /// for the same IA, each must have consistent T1 and T2 values. Specified in
    /// seconds since cltt.
    uint32_t t1_;

    /// @brief rebinding timer
    ///
    /// Specifies rebinding time. Although technically it is a property of IA container,
    /// not the address itself, since our data model does not define separate IA
    /// entity, we are keeping it in the lease. In case of multiple addresses/prefixes
    /// for the same IA, each must have consistent T1 and T2 values. Specified in
    /// seconds since cltt.
    uint32_t t2_;

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    /// @brief valid lifetime
    ///
    /// Expressed as number of seconds since cltt
    uint32_t valid_lft_;
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    /// @brief client last transmission time
    ///
    /// Specifies a timestamp, when last transmission from a client was received.
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    time_t cltt_;
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    /// @brief Subnet identifier
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    ///
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    /// Specifies subnet-id of the subnet that the lease belongs to
    SubnetID subnet_id_;
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    /// @brief Is this a fixed lease?
    ///
    /// Fixed leases are kept after they are released/expired.
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    bool fixed_;
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    /// @brief client hostname
    ///
    /// This field may be empty
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    std::string hostname_;
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    /// @brief did we update AAAA record for this lease?
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    bool fqdn_fwd_;
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    /// @brief did we update PTR record for this lease?
    bool fqdn_rev_;
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    /// @brief Lease comments.
    ///
    /// Currently not used. It may be used for keeping comments made by the
    /// system administrator.
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    std::string comments_;
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    /// @todo: Add DHCPv4 failover related fields here
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};

/// @brief Pointer to a Lease4 structure.
typedef boost::shared_ptr<Lease4> Lease4Ptr;

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/// @brief A collection of IPv4 leases.
typedef std::vector< boost::shared_ptr<Lease4Ptr> > Lease4Collection;
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/// @brief Structure that holds a lease for IPv6 address and/or prefix
///
/// For performance reasons it is a simple structure, not a class. Had we chose to
/// make it a class, all fields would have to be made private and getters/setters
/// would be required. As this is a critical part of the code that will be used
/// extensively, direct access rather than through getters/setters is warranted.
struct Lease6 {
    typedef enum {
        LEASE_IA_NA, /// the lease contains non-temporary IPv6 address
        LEASE_IA_TA, /// the lease contains temporary IPv6 address
        LEASE_IA_PD  /// the lease contains IPv6 prefix (for prefix delegation)
    } LeaseType;

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    Lease6(LeaseType type, const isc::asiolink::IOAddress& addr, DuidPtr duid,
           uint32_t iaid, uint32_t preferred, uint32_t valid, uint32_t t1,
           uint32_t t2, SubnetID subnet_id);

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    /// @brief specifies lease type (normal addr, temporary addr, prefix)
    LeaseType type_;

    /// IPv6 address
    isc::asiolink::IOAddress addr_;

    /// IPv6 prefix length (used only for PD)
    uint8_t prefixlen_;

    /// @brief IAID
    ///
    /// Identity Association IDentifier. DHCPv6 stores all addresses and prefixes
    /// in IA containers (IA_NA, IA_TA, IA_PD). Most containers may appear more
    /// than once in a message. To differentiate between them, IAID field is present
    uint32_t iaid_;

    /// @brief hardware address
    ///
    /// This field is not really used and is optional at best. The concept of identifying
    /// clients by their hardware address was replaced in DHCPv6 by DUID concept. Each
    /// client has its own unique DUID (DHCP Unique IDentifier). Furthermore, client's
    /// HW address is not always available, because client may be behind a relay (relay
    /// stores only link-local address).
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    std::vector<uint8_t> hwaddr_;
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    /// @brief client identifier
    boost::shared_ptr<DUID> duid_;

    /// @brief preferred lifetime
    ///
    /// This parameter specifies preferred lifetime since the lease was assigned/renewed
    /// (cltt), expressed in seconds.
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    uint32_t preferred_lft_;
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    /// @brief valid lifetime
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    ///
    /// This parameter specified valid lifetime since the lease was assigned/renewed
    /// (cltt), expressed in seconds.
    uint32_t valid_lft_;
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    /// @brief T1 timer
    ///
    /// Specifies renewal time. Although technically it is a property of IA container,
    /// not the address itself, since our data model does not define separate IA
    /// entity, we are keeping it in the lease. In case of multiple addresses/prefixes
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    /// for the same IA, each must have consistent T1 and T2 values. Specified in
    /// seconds since cltt.
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    /// This value will also be useful for failover to calculate the next expected
    /// client transmission time.
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    uint32_t t1_;

    /// @brief T2 timer
    ///
    /// Specifies rebinding time. Although technically it is a property of IA container,
    /// not the address itself, since our data model does not define separate IA
    /// entity, we are keeping it in the lease. In case of multiple addresses/prefixes
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    /// for the same IA, each must have consistent T1 and T2 values. Specified in
    /// seconds since cltt.
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    uint32_t t2_;

    /// @brief client last transmission time
    ///
    /// Specifies a timestamp, when last transmission from a client was received.
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    time_t cltt_;
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    /// @brief Subnet identifier
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    ///
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    /// Specifies subnet-id of the subnet that the lease belongs to
    SubnetID subnet_id_;
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    /// @brief Is this a fixed lease?
    ///
    /// Fixed leases are kept after they are released/expired.
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    bool fixed_;
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    /// @brief client hostname
    ///
    /// This field may be empty
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    std::string hostname_;
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    /// @brief did we update AAAA record for this lease?
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    bool fqdn_fwd_;
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    /// @brief did we update PTR record for this lease?
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    bool fqdn_rev_;
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    /// @brief Lease comments
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    ///
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    /// This field is currently not used.
    std::string comments_;
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    /// @todo: Add DHCPv6 failover related fields here
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};

/// @brief Pointer to a Lease6 structure.
typedef boost::shared_ptr<Lease6> Lease6Ptr;

/// @brief Const pointer to a Lease6 structure.
typedef boost::shared_ptr<const Lease6> ConstLease6Ptr;

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/// @brief A collection of IPv6 leases.
typedef std::vector< boost::shared_ptr<Lease6Ptr> > Lease6Collection;
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/// @brief Abstract Lease Manager
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///
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/// This is an abstract API for lease database backends. It provides unified
/// interface to all backends. As this is an abstract class, it should not
/// be used directly, but rather specialized derived class should be used
/// instead.
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///
/// This class is a meta-singleton. At any given time, there is only one
/// instance of any classes derived from that class. That is achieved with
/// defining only a single protected constructor, so every derived class has
/// to use it. Furthermore, this sole constructor registers the first instance
/// (and throws InvalidOperation if there is an attempt to create a second one).
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class LeaseMgr : public boost::noncopyable {
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public:
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    /// Client Hardware address
    typedef std::vector<uint8_t> HWAddr;

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    /// @brief returns a single instance of LeaseMgr
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    ///
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    /// LeaseMgr is a singleton and this method is the only way of
    /// accessing it. LeaseMgr must be create first using
    /// instantiate() method, otherwise instance() will throw
    /// InvalidOperation exception.
    /// @throw InvalidOperation if LeaseMgr not instantiated
    static LeaseMgr& instance();

    /// @brief Destructor
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    virtual ~LeaseMgr();
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    /// @brief Adds an IPv4 lease.
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    ///
    /// @param lease lease to be added
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    virtual bool addLease(Lease4Ptr lease) = 0;
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    /// @brief Adds an IPv6 lease.
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    ///
    /// @param lease lease to be added
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    virtual bool addLease(Lease6Ptr lease) = 0;
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    /// @brief Returns existing IPv4 lease for specified IPv4 address and subnet_id
    ///
    /// This method is used to get a lease for specific subnet_id. There can be
    /// at most one lease for any given subnet, so this method returns a single
    /// pointer.
    ///
    /// @param addr address of the searched lease
    /// @param subnet_id ID of the subnet the lease must belong to
    ///
    /// @return smart pointer to the lease (or NULL if a lease is not found)
    virtual Lease4Ptr getLease4(isc::asiolink::IOAddress addr,
                                SubnetID subnet_id) const = 0;

    /// @brief Returns an IPv4 lease for specified IPv4 address
    ///
    /// This method return a lease that is associated with a given address.
    /// For other query types (by hardware addr, by client-id) there can be
    /// several leases in different subnets (e.g. for mobile clients that
    /// got address in different subnets). However, for a single address
    /// there can be only one lease, so this method returns a pointer to
    /// a single lease, not a container of leases.
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    ///
    /// @param addr address of the searched lease
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    /// @param subnet_id ID of the subnet the lease must belong to
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    ///
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    /// @return smart pointer to the lease (or NULL if a lease is not found)
    virtual Lease4Ptr getLease4(isc::asiolink::IOAddress addr) const = 0;
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    /// @brief Returns existing IPv4 leases for specified hardware address.
    ///
    /// Although in the usual case there will be only one lease, for mobile
    /// clients or clients with multiple static/fixed/reserved leases there
    /// can be more than one. Thus return type is a container, not a single
    /// pointer.
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    ///
    /// @param hwaddr hardware address of the client
    ///
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    /// @return lease collection
    virtual Lease4Collection getLease4(const HWAddr& hwaddr) const = 0;

    /// @brief Returns existing IPv4 leases for specified hardware address
    ///        and a subnet
    ///
    /// There can be at most one lease for a given HW address in a single
    /// pool, so this method with either return a single lease or NULL.
    ///
    /// @param hwaddr hardware address of the client
    /// @param subnet_id identifier of the subnet that lease must belong to
    ///
    /// @return a pointer to the lease (or NULL if a lease is not found)
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    virtual Lease4Ptr getLease4(const HWAddr& hwaddr,
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                                SubnetID subnet_id) const = 0;
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    /// @brief Returns existing IPv4 lease for specified client-id
    ///
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    /// Although in the usual case there will be only one lease, for mobile
    /// clients or clients with multiple static/fixed/reserved leases there
    /// can be more than one. Thus return type is a container, not a single
    /// pointer.
    ///
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    /// @param clientid client identifier
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    ///
    /// @return lease collection
    virtual Lease4Collection getLease4(const ClientId& clientid) const = 0;

    /// @brief Returns existing IPv4 lease for specified client-id
    ///
    /// There can be at most one lease for a given HW address in a single
    /// pool, so this method with either return a single lease or NULL.
    ///
    /// @param clientid client identifier
    /// @param subnet_id identifier of the subnet that lease must belong to
    ///
    /// @return a pointer to the lease (or NULL if a lease is not found)
    virtual Lease4Ptr getLease4(const ClientId& clientid,
                                SubnetID subnet_id) const = 0;
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    /// @brief Returns existing IPv6 lease for a given IPv6 address.
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    ///
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    /// For a given address, we assume that there will be only one lease.
    /// The assumtion here is that there will not be site or link-local
    /// addresses used, so there is no way of having address duplication.
    ///
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    /// @param addr address of the searched lease
    ///
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    /// @return smart pointer to the lease (or NULL if a lease is not found)
    virtual Lease6Ptr getLease6(isc::asiolink::IOAddress addr) const = 0;
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    /// @brief Returns existing IPv6 leases for a given DUID+IA combination
    ///
    /// Although in the usual case there will be only one lease, for mobile
    /// clients or clients with multiple static/fixed/reserved leases there
    /// can be more than one. Thus return type is a container, not a single
    /// pointer.
    ///
    /// @param duid client DUID
    /// @param iaid IA identifier
    ///
    /// @return smart pointer to the lease (or NULL if a lease is not found)
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    virtual Lease6Collection getLease6(const DUID& duid,
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                                       uint32_t iaid) const = 0;

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    /// @brief Returns existing IPv6 lease for a given DUID+IA combination
    ///
    /// @param duid client DUID
    /// @param iaid IA identifier
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    /// @param subnet_id subnet id of the subnet the lease belongs to
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    ///
    /// @return smart pointer to the lease (or NULL if a lease is not found)
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    virtual Lease6Ptr getLease6(const DUID& duid, uint32_t iaid,
                                SubnetID subnet_id) const = 0;
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    /// @brief Updates IPv4 lease.
    ///
    /// @param lease4 The lease to be updated.
    ///
    /// If no such lease is present, an exception will be thrown.
    virtual void updateLease4(Lease4Ptr lease4) = 0;
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    /// @brief Updates IPv4 lease.
    ///
    /// @param lease4 The lease to be updated.
    ///
    /// If no such lease is present, an exception will be thrown.
    virtual void updateLease6(Lease6Ptr lease6) = 0;
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    /// @brief Deletes a lease.
    ///
    /// @param addr IPv4 address of the lease to be deleted.
    ///
    /// @return true if deletion was successful, false if no such lease exists
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    virtual bool deleteLease4(uint32_t addr) = 0;
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    /// @brief Deletes a lease.
    ///
    /// @param addr IPv4 address of the lease to be deleted.
    ///
    /// @return true if deletion was successful, false if no such lease exists
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    virtual bool deleteLease6(isc::asiolink::IOAddress addr) = 0;
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    /// @brief Returns backend name.
    ///
    /// Each backend have specific name, e.g. "mysql" or "sqlite".
    virtual std::string getName() const = 0;
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    /// @brief Returns description of the backend.
    ///
    /// This description may be multiline text that describes the backend.
    virtual std::string getDescription() const = 0;
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    /// @brief Returns backend version.
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    ///
    /// @todo: We will need to implement 3 version functions eventually:
    /// A. abstract API version
    /// B. backend version
    /// C. database version (stored in the database scheme)
    ///
    /// and then check that:
    /// B>=A and B=C (it is ok to have newer backend, as it should be backward
    /// compatible)
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    /// Also if B>C, some database upgrade procedure may be triggered
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    virtual std::string getVersion() const = 0;
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    /// @todo: Add host management here
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    /// As host reservation is outside of scope for 2012, support for hosts
    /// is currently postponed.

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protected:
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    /// @brief The sole lease manager constructor
    ///
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    /// dbconfig is a generic way of passing parameters. Parameters are passed
    /// in the "name=value" format, separated by spaces. Values may be enclosed
    /// in double quotes, if needed. This ctor guarantees that there will be
    /// only one instance of any derived classes. If there is a second instance
    /// being created with the first one still around, it will throw
    /// InvalidOperation.
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    ///
    /// @param dbconfig database configuration
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    /// @throw InvalidOperation when trying to create second LeaseMgr
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    LeaseMgr(const std::string& dbconfig);

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    /// @brief returns value of the parameter
    std::string getParameter(const std::string& name) const;
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    /// @brief list of parameters passed in dbconfig
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    ///
    /// That will be mostly used for storing database name, username,
    /// password and other parameters required for DB access. It is not
    /// intended to keep any DHCP-related parameters.
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    std::map<std::string, std::string> parameters_;
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    static LeaseMgr* instance_;
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};
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}; // end of isc::dhcp namespace

}; // end of isc namespace