[master] Merge branch 'trac3562'

Conflicts:
	src/lib/dhcpsrv/srv_config.cc
	src/lib/dhcpsrv/srv_config.h

src/lib/dhcpsrv/Makefile.am

@@ -44,7 +44,9 @@ lib_LTLIBRARIES = libkea-dhcpsrv.la
 libkea_dhcpsrv_la_SOURCES  =
 libkea_dhcpsrv_la_SOURCES += addr_utilities.cc addr_utilities.h
 libkea_dhcpsrv_la_SOURCES += alloc_engine.cc alloc_engine.h
-libkea_dhcpsrv_la_SOURCES += callout_handle_store.h
+libkea_dhcpsrv_la_SOURCES += base_host_data_source.h
+libkea_dhcpsrv_la_SOURCES += callout_handle_store.
+libkea_dhcpsrv_la_SOURCES += cfg_hosts.cc cfg_hosts.h
 libkea_dhcpsrv_la_SOURCES += cfg_iface.cc cfg_iface.h
 libkea_dhcpsrv_la_SOURCES += cfg_option.cc cfg_option.h
 libkea_dhcpsrv_la_SOURCES += cfg_option_def.cc cfg_option_def.h
@@ -61,6 +63,8 @@ libkea_dhcpsrv_la_SOURCES += dhcpsrv_log.cc dhcpsrv_log.h
 libkea_dhcpsrv_la_SOURCES += dhcp_config_parser.h
 libkea_dhcpsrv_la_SOURCES += dhcp_parsers.cc dhcp_parsers.h
 libkea_dhcpsrv_la_SOURCES += host.cc host.h
+libkea_dhcpsrv_la_SOURCES += host_container.h
+libkea_dhcpsrv_la_SOURCES += host_reservation_parser.cc host_reservation_parser.h
 libkea_dhcpsrv_la_SOURCES += key_from_key.h
 libkea_dhcpsrv_la_SOURCES += lease.cc lease.h
 libkea_dhcpsrv_la_SOURCES += lease_mgr.cc lease_mgr.h

src/lib/dhcpsrv/base_host_data_source.h

+// Copyright (C) 2014 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.
+
+#ifndef BASE_HOST_DATA_SOURCE_H
+#define BASE_HOST_DATA_SOURCE_H
+
+#include <asiolink/io_address.h>
+#include <dhcp/duid.h>
+#include <dhcp/hwaddr.h>
+#include <dhcpsrv/host.h>
+#include <exceptions/exceptions.h>
+
+namespace isc {
+namespace dhcp {
+
+/// @brief Exception thrown when the duplicate @c Host object is detected.
+class DuplicateHost : public Exception {
+public:
+    DuplicateHost(const char* file, size_t line, const char* what) :
+        isc::Exception(file, line, what) { };
+};
+
+/// @brief Base interface for the classes implementing simple data source
+/// for host reservations.
+///
+/// This abstract class defines an interface for the classes implementing
+/// basic data source for host reservations. This interface allows for
+/// adding new reservations (represented by @c Host objects) and retrieving
+/// these reservations using various parameters such as HW address or DUID,
+/// subnet identifier (either IPv4 or IPv6) or reserved IP address.
+///
+/// This interface DOES NOT specify the methods to manage existing
+/// host reservations such as to remove one IPv6 reservation but leave
+/// other reservations. It also lacks the methods used for preparing
+/// the data to be added to the SQL database: commit, rollback etc.
+/// Such methods are declared in other interfaces.
+class BaseHostDataSource {
+public:
+
+    /// @brief Default destructor implementation.
+    virtual ~BaseHostDataSource() {
+    }
+
+    /// @brief Return all hosts for the specified HW address or DUID.
+    ///
+    /// This method returns all @c Host objects which represent reservations
+    /// for the specified HW address or DUID. Note, that this method may
+    /// return multiple reservations because a particular client may have
+    /// reservations in multiple subnets and the same client may be identified
+    /// by HW address or DUID. The server is unable to verify that the specific
+    /// DUID and HW address belong to the same client, until the client sends
+    /// a DHCP message.
+    ///
+    /// Specifying both hardware address and DUID is allowed for this method
+    /// and results in returning all objects that are associated with hardware
+    /// address OR duid. For example: if one host is associated with the
+    /// specified hardware address and another host is associated with the
+    /// specified DUID, two hosts will be returned.
+    ///
+    /// @param hwaddr HW address of the client or NULL if no HW address
+    /// available.
+    /// @param duid client id or NULL if not available, e.g. DHCPv4 client case.
+    ///
+    /// @return Collection of const @c Host objects.
+    virtual ConstHostCollection
+    getAll(const HWAddrPtr& hwaddr, const DuidPtr& duid = DuidPtr()) const = 0;
+
+    /// @brief Non-const version of the @c getAll const method.
+    ///
+    /// Specifying both hardware address and DUID is allowed for this method
+    /// and results in returning all objects that are associated with hardware
+    /// address OR duid. For example: if one host is associated with the
+    /// specified hardware address and another host is associated with the
+    /// specified DUID, two hosts will be returned.
+    ///
+    /// @param hwaddr HW address of the client or NULL if no HW address
+    /// available.
+    /// @param duid client id or NULL if not available, e.g. DHCPv4 client case.
+    ///
+    /// @return Collection of non-const @c Host objects.
+    virtual HostCollection
+    getAll(const HWAddrPtr& hwaddr, const DuidPtr& duid = DuidPtr()) = 0;
+
+    /// @brief Returns a collection of hosts using the specified IPv4 address.
+    ///
+    /// This method may return multiple @c Host objects if they are connected
+    /// to different subnets.
+    ///
+    /// @param address IPv4 address for which the @c Host object is searched.
+    ///
+    /// @return Collection of const @c Host objects.
+    virtual ConstHostCollection
+    getAll4(const asiolink::IOAddress& address) const = 0;
+
+    /// @brief Returns a collection of hosts using the specified IPv4 address.
+    ///
+    /// This method may return multiple @c Host objects if they are connected
+    /// to different subnets.
+    ///
+    /// @param address IPv4 address for which the @c Host object is searched.
+    ///
+    /// @return Collection of @c Host objects.
+    virtual HostCollection
+    getAll4(const asiolink::IOAddress& address) = 0;
+
+    /// @brief Returns a host connected to the IPv4 subnet.
+    ///
+    /// Implementations of this method should guard against the case when
+    /// mutliple instances of the @c Host are present, e.g. when two
+    /// @c Host objects are found, one for the DUID, another one for the
+    /// HW address. In such case, an implementation of this method
+    /// should throw an exception.
+    ///
+    /// @param subnet_id Subnet identifier.
+    /// @param hwaddr HW address of the client or NULL if no HW address
+    /// available.
+    /// @param duid client id or NULL if not available.
+    ///
+    /// @return Const @c Host object using a specified HW address or DUID.
+    virtual ConstHostPtr
+    get4(const SubnetID& subnet_id, const HWAddrPtr& hwaddr,
+         const DuidPtr& duid = DuidPtr()) const = 0;
+
+    /// @brief Returns a host connected to the IPv4 subnet.
+    ///
+    /// Implementations of this method should guard against the case when
+    /// mutliple instances of the @c Host are present, e.g. when two
+    /// @c Host objects are found, one for the DUID, another one for the
+    /// HW address. In such case, an implementation of this method
+    /// should throw an exception.
+    ///
+    /// @param subnet_id Subnet identifier.
+    /// @param hwaddr HW address of the client or NULL if no HW address
+    /// available.
+    /// @param duid client id or NULL if not available.
+    ///
+    /// @return Non-const @c Host object using a specified HW address or DUID.
+    virtual HostPtr
+    get4(const SubnetID& subnet_id, const HWAddrPtr& hwaddr,
+         const DuidPtr& duid = DuidPtr()) = 0;
+
+    /// @brief Returns a host connected to the IPv6 subnet.
+    ///
+    /// Implementations of this method should guard against the case when
+    /// mutliple instances of the @c Host are present, e.g. when two
+    /// @c Host objects are found, one for the DUID, another one for the
+    /// HW address. In such case, an implementation of this method
+    /// should throw an exception.
+    ///
+    /// @param subnet_id Subnet identifier.
+    /// @param hwaddr HW address of the client or NULL if no HW address
+    /// available.
+    /// @param duid DUID or NULL if not available.
+    ///
+    /// @return Const @c Host object using a specified HW address or DUID.
+    virtual ConstHostPtr
+    get6(const SubnetID& subnet_id, const DuidPtr& duid,
+         const HWAddrPtr& hwaddr = HWAddrPtr()) const = 0;
+
+    /// @brief Returns a host connected to the IPv6 subnet.
+    ///
+    /// Implementations of this method should guard against the case when
+    /// mutliple instances of the @c Host are present, e.g. when two
+    /// @c Host objects are found, one for the DUID, another one for the
+    /// HW address. In such case, an implementation of this method
+    /// should throw an exception.
+    ///
+    /// @param subnet_id Subnet identifier.
+    /// @param hwaddr HW address of the client or NULL if no HW address
+    /// available.
+    /// @param duid DUID or NULL if not available.
+    ///
+    /// @return Non-const @c Host object using a specified HW address or DUID.
+    virtual HostPtr
+    get6(const SubnetID& subnet_id, const DuidPtr& duid,
+         const HWAddrPtr& hwaddr = HWAddrPtr()) = 0;
+
+    /// @brief Returns a host using the specified IPv6 prefix.
+    ///
+    /// @param prefix IPv6 prefix for which the @c Host object is searched.
+    /// @param prefix_len IPv6 prefix length.
+    ///
+    /// @return Const @c Host object using a specified HW address or DUID.
+    virtual ConstHostPtr
+    get6(const asiolink::IOAddress& prefix, const uint8_t prefix_len) const = 0;
+
+    /// @brief Returns a host using the specified IPv6 prefix.
+    ///
+    /// @param prefix IPv6 prefix for which the @c Host object is searched.
+    /// @param prefix_len IPv6 prefix length.
+    ///
+    /// @return Non-const @c Host object using a specified HW address or DUID.
+    virtual HostPtr
+    get6(const asiolink::IOAddress& prefix, const uint8_t prefix_len) = 0;
+
+    /// @brief Adds a new host to the collection.
+    ///
+    /// The implementations of this method should guard against duplicate
+    /// reservations for the same host, where possible. For example, when the
+    /// reservation for the same HW address and subnet id is added twice, the
+    /// implementation should throw an exception. Note, that usually it is
+    /// impossible to guard against adding duplicated host, where one instance
+    /// is identified by HW address, another one by DUID.
+    ///
+    /// @param host Pointer to the new @c Host object being added.
+    virtual void add(const HostPtr& host) = 0;
+
+};
+
+}
+}
+
+#endif // BASE_HOST_DATA_SOURCE_H

src/lib/dhcpsrv/cfg_hosts.cc

+// Copyright (C) 2014 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 <dhcpsrv/cfg_hosts.h>
+#include <exceptions/exceptions.h>
+
+using namespace isc::asiolink;
+
+namespace isc {
+namespace dhcp {
+
+ConstHostCollection
+CfgHosts::getAll(const HWAddrPtr& hwaddr, const DuidPtr& duid) const {
+    ConstHostCollection collection;
+    getAllInternal<ConstHostCollection>(hwaddr, duid, collection);
+    return (collection);
+}
+
+HostCollection
+CfgHosts::getAll(const HWAddrPtr& hwaddr, const DuidPtr& duid) {
+    HostCollection collection;
+    getAllInternal<HostCollection>(hwaddr, duid, collection);
+    return (collection);
+}
+
+ConstHostCollection
+CfgHosts::getAll4(const IOAddress&) const {
+    isc_throw(isc::NotImplemented, "getAll4(address) const is not implemented");
+}
+
+HostCollection
+CfgHosts::getAll4(const IOAddress&) {
+    isc_throw(isc::NotImplemented, "getAll4(address) is not implemented");
+}
+
+template<typename Storage>
+void
+CfgHosts::getAllInternal(const std::vector<uint8_t>& identifier,
+                         const Host::IdentifierType& identifier_type,
+                         Storage& storage) const {
+    // Search for the Host using the identifier and identifier type as a
+    // composite key.
+    const HostContainerIndex0& idx = hosts_.get<0>();
+    std::pair<HostContainerIndex0::iterator, HostContainerIndex0::iterator> r =
+        idx.equal_range(boost::make_tuple(identifier, identifier_type));
+    // Append each Host object to the storage.
+    for (HostContainerIndex0::iterator host = r.first; host != r.second;
+         ++host) {
+        storage.push_back(*host);
+    }
+}
+
+template<typename Storage>
+void
+CfgHosts::getAllInternal(const HWAddrPtr& hwaddr, const DuidPtr& duid,
+                         Storage& storage) const {
+    // Get hosts using HW address.
+    if (hwaddr) {
+        getAllInternal<Storage>(hwaddr->hwaddr_, Host::IDENT_HWADDR, storage);
+    }
+    // Get hosts using DUID.
+    if (duid) {
+        getAllInternal<Storage>(duid->getDuid(), Host::IDENT_DUID, storage);
+    }
+}
+
+ConstHostPtr
+CfgHosts::get4(const SubnetID& subnet_id, const HWAddrPtr& hwaddr,
+               const DuidPtr& duid) const {
+    // The false value indicates that it is an IPv4 subnet.
+    return (getHostInternal(subnet_id, false, hwaddr, duid));
+}
+
+HostPtr
+CfgHosts::get4(const SubnetID& subnet_id, const HWAddrPtr& hwaddr,
+               const DuidPtr& duid) {
+    // The false value indicates that it is an IPv4 subnet.
+    return (getHostInternal(subnet_id, false, hwaddr, duid));
+}
+
+ConstHostPtr
+CfgHosts::get6(const SubnetID& subnet_id, const DuidPtr& duid,
+               const HWAddrPtr& hwaddr) const {
+    // The true value indicates that it is an IPv6 subnet.
+    return (getHostInternal(subnet_id, true, hwaddr, duid));
+}
+
+HostPtr
+CfgHosts::get6(const SubnetID& subnet_id, const DuidPtr& duid,
+               const HWAddrPtr& hwaddr) {
+    // The true value indicates that it is an IPv6 subnet.
+    return (getHostInternal(subnet_id, true, hwaddr, duid));
+}
+
+ConstHostPtr
+CfgHosts::get6(const IOAddress&, const uint8_t) const {
+    isc_throw(isc::NotImplemented,
+              "get6(prefix, len) const is not implemented");
+}
+
+HostPtr
+CfgHosts::get6(const IOAddress&, const uint8_t) {
+    isc_throw(isc::NotImplemented, "get6(prefix, len) is not implemented");
+}
+
+HostPtr
+CfgHosts::getHostInternal(const SubnetID& subnet_id, const bool subnet6,
+                          const HWAddrPtr& hwaddr, const DuidPtr& duid) const {
+    // Get all hosts for the HW address and DUID. This may return multiple hosts
+    // for different subnets, but the number of hosts returned should be low
+    // because one host presumably doesn't show up in many subnets.
+    HostCollection hosts;
+    getAllInternal<HostCollection>(hwaddr, duid, hosts);
+
+    HostPtr host;
+    // Iterate over the returned hosts and select those for which the
+    // subnet id matches.
+    for (HostCollection::const_iterator host_it = hosts.begin();
+         host_it != hosts.end(); ++host_it) {
+        // Check if this is IPv4 subnet or IPv6 subnet.
+        SubnetID host_subnet_id = subnet6 ? (*host_it)->getIPv6SubnetID() :
+            (*host_it)->getIPv4SubnetID();
+
+        if (subnet_id == host_subnet_id) {
+            // If this is the first occurrence of the host for this subnet,
+            // remember it. But, if we find that this is second @c Host object
+            // for the same client, it is a misconfiguration. Most likely,
+            // the administrator has specified one reservation for a HW
+            // address and another one for the DUID, which gives an ambiguous
+            // result, and we don't know which reservation we should choose.
+            // Therefore, throw an exception.
+            if (!host) {
+                host = *host_it;
+
+            } else {
+                isc_throw(DuplicateHost,  "more than one reservation found"
+                          " for the host belonging to the subnet with id '"
+                          << subnet_id << "' and using the HW address '"
+                          << (hwaddr ? hwaddr->toText(false) : "(null)")
+                          << "' and DUID '"
+                          << (duid ? duid->toText() : "(null)")
+                          << "'");
+            }
+        }
+    }
+    return (host);
+}
+
+
+void
+CfgHosts::add(const HostPtr& host) {
+    // Sanity check that the host is non-null.
+    if (!host) {
+        isc_throw(BadValue, "specified host object must not be NULL when it"
+                  " is added to the configuration");
+    }
+    /// @todo This may need further sanity checks. For example, a duplicate
+    /// should be rejected.
+    HWAddrPtr hwaddr = host->getHWAddress();
+    DuidPtr duid = host->getDuid();
+    // Check for duplicates for the specified IPv4 subnet.
+    if (get4(host->getIPv4SubnetID(), hwaddr, duid)) {
+        isc_throw(DuplicateHost, "failed to add new host using the HW"
+                  " address '" << (hwaddr ? hwaddr->toText(false) : "(null)")
+                  << " and DUID '" << (duid ? duid->toText() : "(null)")
+                  << "' to the IPv4 subnet id '" << host->getIPv4SubnetID()
+                  << "' as this host has already been added");
+
+    // Checek for duplicates for the specified IPv6 subnet.
+    } else if (get6(host->getIPv6SubnetID(), duid, hwaddr)) {
+        isc_throw(DuplicateHost, "failed to add new host using the HW"
+                  " address '" << (hwaddr ? hwaddr->toText(false) : "(null)")
+                  << " and DUID '" << (duid ? duid->toText() : "(null)")
+                  << "' to the IPv6 subnet id '" << host->getIPv6SubnetID()
+                  << "' as this host has already been added");
+    }
+
+    // This is a new instance - add it.
+    hosts_.insert(host);
+}
+
+} // end of namespace isc::dhcp
+} // end of namespace isc

src/lib/dhcpsrv/cfg_hosts.h

+// Copyright (C) 2014 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.
+
+#ifndef CFG_HOSTS_H
+#define CFG_HOSTS_H
+
+#include <asiolink/io_address.h>
+#include <dhcp/duid.h>
+#include <dhcp/hwaddr.h>
+#include <dhcpsrv/base_host_data_source.h>
+#include <dhcpsrv/host.h>
+#include <dhcpsrv/host_container.h>
+#include <dhcpsrv/subnet_id.h>
+#include <boost/shared_ptr.hpp>
+#include <vector>
+
+namespace isc {
+namespace dhcp {
+
+/// @brief Represents the host reservations specified in the configuration file.
+///
+/// This class holds a collection of the host reservations (@c Host objects)
+/// which can be retrieved using different search criteria.
+///
+/// In the typical case the reservations are searched using the client's MAC
+/// address of DUID and a subnet that the client is connected to. The
+/// reservations can be also retrieved using other parameters, such as reserved
+/// IP address.
+///
+/// The reservations are added to this object by the configuration parsers,
+/// when the new configuration is applied for the server. The reservations
+/// are retrieved by the @c HostMgr class when the server is allocating or
+/// renewing an address or prefix for the particular client.
+class CfgHosts : public BaseHostDataSource {
+public:
+
+    /// @brief Return all hosts for the specified HW address or DUID.
+    ///
+    /// This method returns all @c Host objects which represent reservations
+    /// for the specified HW address or DUID. Note, that this method may
+    /// return multiple reservations because a particular client may have
+    /// reservations in multiple subnets and the same client may be identified
+    /// by HW address or DUID. The server is unable to verify that the specific
+    /// DUID and HW address belong to the same client, until the client sends
+    /// a DHCP message.
+    ///
+    /// @param hwaddr HW address of the client or NULL if no HW address
+    /// available.
+    /// @param duid client id or NULL if not available, e.g. DHCPv4 client case.
+    ///
+    /// @return Collection of const @c Host objects.
+    virtual ConstHostCollection
+    getAll(const HWAddrPtr& hwaddr, const DuidPtr& duid = DuidPtr()) const;
+
+    /// @brief Non-const version of the @c getAll const method.
+    ///
+    /// @param hwaddr HW address of the client or NULL if no HW address
+    /// available.
+    /// @param duid client id or NULL if not available, e.g. DHCPv4 client case.
+    ///
+    /// @return Collection of non-const @c Host objects.
+    virtual HostCollection
+    getAll(const HWAddrPtr& hwaddr, const DuidPtr& duid = DuidPtr());
+
+    /// @brief Returns a collection of hosts using the specified IPv4 address.
+    ///
+    /// This method may return multiple @c Host objects if they are connected
+    /// to different subnets.
+    ///
+    /// @param address IPv4 address for which the @c Host object is searched.
+    ///
+    /// @throw isc::NotImplemented.
+    virtual ConstHostCollection
+    getAll4(const asiolink::IOAddress& address) const;
+
+    /// @brief Returns a collection of hosts using the specified IPv4 address.
+    ///
+    /// This method may return multiple @c Host objects if they are connected
+    /// to different subnets.
+    ///
+    /// @param address IPv4 address for which the @c Host object is searched.
+    ///
+    /// @throw isc::NotImplemented
+    virtual HostCollection
+    getAll4(const asiolink::IOAddress& address);
+
+    /// @brief Returns a host connected to the IPv4 subnet and matching
+    /// specified identifiers.
+    ///
+    /// @param subnet_id Subnet identifier.
+    /// @param hwaddr HW address of the client or NULL if no HW address
+    /// available.
+    /// @param duid client id or NULL if not available.
+    ///
+    /// @return Const @c Host object using a specified HW address or DUID.
+    /// @throw isc::dhcp::DuplicateHost if more than one candidate host has
+    /// been found.
+    virtual ConstHostPtr
+    get4(const SubnetID& subnet_id, const HWAddrPtr& hwaddr,
+         const DuidPtr& duid = DuidPtr()) const;
+
+    /// @brief Returns a host connected to the IPv4 subnet and matching
+    /// specified identifiers.
+    ///
+    /// @param subnet_id Subnet identifier.
+    /// @param hwaddr HW address of the client or NULL if no HW address
+    /// available.
+    /// @param duid client id or NULL if not available.
+    ///
+    /// @return Non-const @c Host object using a specified HW address or DUID.
+    /// @throw isc::dhcp::DuplicateHost if more than one candidate host has
+    /// been found.
+    virtual HostPtr
+    get4(const SubnetID& subnet_id, const HWAddrPtr& hwaddr,
+         const DuidPtr& duid = DuidPtr());
+
+    /// @brief Returns a host connected to the IPv6 subnet and matching
+    /// the specified identifiers.
+    ///
+    /// @param subnet_id Subnet identifier.
+    /// @param hwaddr HW address of the client or NULL if no HW address
+    /// available.
+    /// @param duid DUID or NULL if not available.
+    ///
+    /// @return Const @c Host object using a specified HW address or DUID.
+    /// @throw isc::dhcp::DuplicateHost if more than one candidate host has
+    /// been found.
+    virtual ConstHostPtr
+    get6(const SubnetID& subnet_id, const DuidPtr& duid,
+         const HWAddrPtr& hwaddr = HWAddrPtr()) const;
+
+    /// @brief Returns a host connected to the IPv6 subnet and matching the
+    /// specified identifiers.
+    ///
+    /// @param subnet_id Subnet identifier.
+    /// @param hwaddr HW address of the client or NULL if no HW address
+    /// available.
+    /// @param duid DUID or NULL if not available.
+    ///
+    /// @return Non-const @c Host object using a specified HW address or DUID.
+    /// @throw isc::dhcp::DuplicateHost if more than one candidate host has
+    /// been found.
+    virtual HostPtr
+    get6(const SubnetID& subnet_id, const DuidPtr& duid,
+         const HWAddrPtr& hwaddr = HWAddrPtr());
+
+    /// @brief Returns a host using the specified IPv6 prefix.
+    ///
+    /// @param prefix IPv6 prefix for which the @c Host object is searched.
+    /// @param prefix_len IPv6 prefix length.
+    ///
+    /// @throw isc::NotImplemented
+    virtual ConstHostPtr
+    get6(const asiolink::IOAddress& prefix, const uint8_t prefix_len) const;
+
+    /// @brief Returns a host using the specified IPv6 prefix.
+    ///
+    /// @param prefix IPv6 prefix for which the @c Host object is searched.
+    /// @param prefix_len IPv6 prefix length.
+    ///
+    /// @throw isc::NotImplemented
+    virtual HostPtr
+    get6(const asiolink::IOAddress& prefix, const uint8_t prefix_len);
+
+
+    /// @brief Adds a new host to the collection.
+    ///
+    /// @param host Pointer to the new @c Host object being added.
+    ///