[5305] Introduced shared networks holding subnets.

src/lib/dhcpsrv/Makefile.am

@@ -88,6 +88,7 @@ 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 += alloc_engine_log.cc alloc_engine_log.h
+libkea_dhcpsrv_la_SOURCES += assignable_network.h
 libkea_dhcpsrv_la_SOURCES += base_host_data_source.h
 libkea_dhcpsrv_la_SOURCES += callout_handle_store.h
 libkea_dhcpsrv_la_SOURCES += cfg_4o6.cc cfg_4o6.h
@@ -101,6 +102,8 @@ libkea_dhcpsrv_la_SOURCES += cfg_host_operations.cc cfg_host_operations.h
 libkea_dhcpsrv_la_SOURCES += cfg_option.cc cfg_option.h
 libkea_dhcpsrv_la_SOURCES += cfg_option_def.cc cfg_option_def.h
 libkea_dhcpsrv_la_SOURCES += cfg_rsoo.cc cfg_rsoo.h
+libkea_dhcpsrv_la_SOURCES += cfg_shared_networks4.cc cfg_shared_networks4.h
+libkea_dhcpsrv_la_SOURCES += cfg_shared_networks6.h
 libkea_dhcpsrv_la_SOURCES += cfg_subnets4.cc cfg_subnets4.h
 libkea_dhcpsrv_la_SOURCES += cfg_subnets6.cc cfg_subnets6.h
 libkea_dhcpsrv_la_SOURCES += cfg_mac_source.cc cfg_mac_source.h
@@ -138,6 +141,7 @@ libkea_dhcpsrv_la_SOURCES += mysql_host_data_source.cc mysql_host_data_source.h
 endif
 
 libkea_dhcpsrv_la_SOURCES += ncr_generator.cc ncr_generator.h
+libkea_dhcpsrv_la_SOURCES += network.h
 
 if HAVE_PGSQL
 libkea_dhcpsrv_la_SOURCES += pgsql_connection.cc pgsql_connection.h
@@ -150,6 +154,7 @@ libkea_dhcpsrv_la_SOURCES += cql_lease_mgr.cc cql_lease_mgr.h
 libkea_dhcpsrv_la_SOURCES += cql_connection.cc cql_connection.h
 endif
 libkea_dhcpsrv_la_SOURCES += pool.cc pool.h
+libkea_dhcpsrv_la_SOURCES += shared_network.cc shared_network.h
 libkea_dhcpsrv_la_SOURCES += srv_config.cc srv_config.h
 libkea_dhcpsrv_la_SOURCES += subnet.cc subnet.h
 libkea_dhcpsrv_la_SOURCES += subnet_id.h
@@ -178,6 +183,9 @@ libkea_dhcpsrv_la_SOURCES += parsers/ifaces_config_parser.cc
 libkea_dhcpsrv_la_SOURCES += parsers/ifaces_config_parser.h
 libkea_dhcpsrv_la_SOURCES += parsers/option_data_parser.cc
 libkea_dhcpsrv_la_SOURCES += parsers/option_data_parser.h
+libkea_dhcpsrv_la_SOURCES += parsers/shared_network_parser.cc
+libkea_dhcpsrv_la_SOURCES += parsers/shared_network_parser.h
+libkea_dhcpsrv_la_SOURCES += parsers/shared_networks_list_parser.h
 libkea_dhcpsrv_la_SOURCES += parsers/simple_parser4.cc
 libkea_dhcpsrv_la_SOURCES += parsers/simple_parser4.h
 libkea_dhcpsrv_la_SOURCES += parsers/simple_parser6.cc

src/lib/dhcpsrv/assignable_network.h

@@ -0,0 +1,59 @@
+// Copyright (C) 2017 Internet Systems Consortium, Inc. ("ISC")
+//
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+#ifndef ASSIGNABLE_NETWORK_H
+#define ASSIGNABLE_NETWORK_H
+
+#include <dhcpsrv/network.h>
+
+namespace isc {
+namespace dhcp {
+
+/// @brief Represents a network that can be associated with a subnet.
+///
+/// This class represents a network that can be associated with a subnet
+/// using @c Subnet::setSharedNetwork method. This class is a friend
+/// of a @ref Subnet class, so it can call its @c Subnet::setSharedNetwork
+/// private method. Association of a network with a subnet must be always
+/// conducted using this class. This prevents unwanted replacements of
+/// shared networks within subnets.
+class AssignableNetwork : public Network {
+protected:
+
+    /// @brief Returns shared pointer to this object.
+    ///
+    /// This abstract method must be implemented by derived classes to
+    /// return shared pointers the derivation.
+    ///
+    /// @return Pointer to this network.
+    virtual NetworkPtr sharedFromThis() = 0;
+
+    /// @brief Associates a subnet with this network.
+    ///
+    /// @param subnet Pointer to a subnet to be associated with the network.
+    ///
+    /// @tparam SubnetPtr Type of the subnet pointer.
+    template<typename SubnetPtr>
+    void setSharedNetwork(const SubnetPtr& subnet) {
+        subnet->setSharedNetwork(sharedFromThis());
+    }
+
+    /// @brief Removes association of a subnet with a network.
+    ///
+    /// @param subnet Pointer to a subnet for which association should be
+    /// removed.
+    ///
+    /// @tparam SubnetPtr Type of the subnet pointer.
+    template<typename SubnetPtr>
+    void clearSharedNetwork(const SubnetPtr& subnet) {
+        subnet->setSharedNetwork(NetworkPtr());
+    }
+};
+
+} // end of namespace isc::dhcp
+} // end of namespace isc
+
+#endif // ASSIGNABLE_NETWORK_H

src/lib/dhcpsrv/cfg_shared_networks4.cc

@@ -0,0 +1,17 @@
+// Copyright (C) 2017 Internet Systems Consortium, Inc. ("ISC")
+//
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+#include <dhcpsrv/cfg_shared_networks4.h>
+
+namespace isc {
+namespace dhcp {
+
+void
+CfgSharedNetworks4::add(const SharedNetwork4Ptr& network) {
+}
+
+} // end of namespace isc::dhcp
+} // end of namespace isc

src/lib/dhcpsrv/cfg_shared_networks4.h

@@ -0,0 +1,29 @@
+// Copyright (C) 2017 Internet Systems Consortium, Inc. ("ISC")
+//
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+#ifndef CFG_SHARED_NETWORKS4_H
+#define CFG_SHARED_NETWORKS4_H
+
+#include <cc/cfg_to_element.h>
+#include <dhcpsrv/shared_network.h>
+#include <boost/shared_ptr.hpp>
+
+namespace isc {
+namespace dhcp {
+
+class CfgSharedNetworks4 : public data::CfgToElement {
+public:
+
+    void add(const SharedNetwork4Ptr& shared_network);
+
+};
+
+typedef boost::shared_ptr<CfgSharedNetworks4> CfgSharedNetworks4Ptr;
+
+} // end of namespace isc::dhcp
+} // end of namespace isc
+
+#endif // CFG_SHARED_NETWORKS4_H

src/lib/dhcpsrv/cfg_shared_networks6.h

@@ -0,0 +1,26 @@
+// Copyright (C) 2017 Internet Systems Consortium, Inc. ("ISC")
+//
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+#ifndef CFG_SHARED_NETWORKS6_H
+#define CFG_SHARED_NETWORKS6_H
+
+#include <cc/cfg_to_element.h>
+#include <boost/shared_ptr.hpp>
+
+namespace isc {
+namespace dhcp {
+
+class CfgSharedNetworks6 : public data::CfgToElement {
+public:
+
+};
+
+typedef boost::shared_ptr<CfgSharedNetworks6> CfgSharedNetworks6Ptr;
+
+} // end of namespace isc::dhcp
+} // end of namespace isc
+
+#endif // CFG_SHARED_NETWORKS6_H

src/lib/dhcpsrv/network.h

@@ -0,0 +1,74 @@
+// Copyright (C) 2017 Internet Systems Consortium, Inc. ("ISC")
+//
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+#ifndef NETWORK_H
+#define NETWORK_H
+
+#include <boost/shared_ptr.hpp>
+#include <string>
+
+namespace isc {
+namespace dhcp {
+
+/// @brief Common interface representing a network to which the DHCP clients
+/// are connected.
+///
+/// The most common type of network, in Kea's terminology, is a subnet. The
+/// @ref Subnet implements this interface. Another types of objects implementing
+/// this interface are @ref SharedNetwork objects. They group multiple subnets
+/// together to provide means for extending available address pools (a single
+/// client may obtain IP address from any of the pools belonging to subnets in
+/// the shared network), or for selecting a subnet on a given link, depending
+/// on the class of the client (e.g. cable network case: different subnet is
+/// selected for cable modems, different one for routers).
+///
+/// The subnets and shared networks share many data structures, e.g. DHCP
+/// options, local interface name, address manipulation methods, thus this
+/// class provides an abstract interface that must be implemented by derived
+/// classes and, where appropriate, implements common methods used by the
+/// derived classes.
+class Network {
+public:
+
+    /// @brief Virtual destructor.
+    ///
+    /// Does nothing at the moment.
+    virtual ~Network() { };
+
+    /// @brief Sets local name of the interface for which this network is
+    /// selected.
+    ///
+    /// If the interface is specified, the server will use the network
+    /// associated with this local interface to allocate IP addresses and
+    /// other resources to a client.
+    ///
+    /// @param iface_name Interface name.
+    void setIface(const std::string& iface_name) {
+        iface_name_ = iface_name;
+    }
+
+    /// @brief Returns name of the local interface for which this network is
+    /// selected.
+    ///
+    /// @return Interface name as text.
+    std::string getIface() const {
+        return (iface_name_);
+    };
+
+protected:
+
+    /// @brief Holds interface name for which this network is selected.
+    std::string iface_name_;
+
+};
+
+/// @brief Pointer to the @ref Network object.
+typedef boost::shared_ptr<Network> NetworkPtr;
+
+} // end of namespace isc::dhcp
+} // end of namespace isc
+
+#endif // NETWORK_H

src/lib/dhcpsrv/parsers/shared_network_parser.cc

@@ -0,0 +1,30 @@
+// Copyright (C) 2017 Internet Systems Consortium, Inc. ("ISC")
+//
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+#ifndef SHARED_NETWORK_PARSER_H
+#define SHARED_NETWORK_PARSER_H
+
+#include <cc/data.h>
+#include <dhcpsrv/parsers/shared_network_parser.h>
+#include <dhcpsrv/shared_network.h>
+
+using namespace isc::data;
+
+namespace isc {
+namespace dhcp {
+
+SharedNetworkParser::~SharedNetworkParser() {
+}
+
+SharedNetworkPtr
+SharedNetworkParser::parse(const ConstElementPtr& shared_network_data) {
+    return (SharedNetworkPtr());
+}
+
+} // end of namespace isc::dhcp
+} // end of namespace isc
+
+#endif // SHARED_NETWORK_PARSER_H

src/lib/dhcpsrv/parsers/shared_network_parser.h

@@ -0,0 +1,30 @@
+// Copyright (C) 2017 Internet Systems Consortium, Inc. ("ISC")
+//
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+#ifndef SHARED_SUBNET_PARSER_H
+#define SHARED_SUBNET_PARSER_H
+
+#include <cc/data.h>
+#include <cc/simple_parser.h>
+#include <dhcpsrv/shared_network.h>
+
+namespace isc {
+namespace dhcp {
+
+class SharedNetworkParser : public isc::data::SimpleParser {
+public:
+
+    virtual ~SharedNetworkParser();
+
+    virtual SharedNetworkPtr
+    parse(const data::ConstElementPtr& shared_network_data);
+
+};
+
+} // enf of namespace isc::dhcp
+} // end of namespace isc
+
+#endif // SHARED_SUBNET_PARSER_H

src/lib/dhcpsrv/parsers/shared_networks_list_parser.h

@@ -0,0 +1,37 @@
+// Copyright (C) 2017 Internet Systems Consortium, Inc. ("ISC")
+//
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+#ifndef SHARED_NETWORKS_LIST_PARSER_H
+#define SHARED_NETWORKS_LIST_PARSER_H
+
+#include <cc/data.h>
+#include <cc/dhcp_config_error.h>
+#include <cc/simple_parser.h>
+#include <exceptions/exceptions.h>
+#include <dhcpsrv/subnet.h>
+#include <dhcpsrv/parsers/shared_network_parser.h>
+
+namespace isc {
+namespace dhcp {
+
+template<typename SharedNetworkParserType>
+class SharedNetworksListParser : public data::SimpleParser {
+protected:
+
+    template<typename CfgSharedNetworksTypePtr>
+    void parse(const data::ConstElementPtr& shared_networks_list_data,
+               CfgSharedNetworksTypePtr& cfg) {
+        if (shared_networks_list_data->getType() != Element::list) {
+            isc_throw(data::DhcpConfigError, "shared-networks value must be a list");
+        }
+    }
+               
+};
+
+} // end of namespace isc::dhcp
+} // end of namespace isc
+
+#endif // SHARED_NETWORKS_LIST_PARSER_H

src/lib/dhcpsrv/shared_network.cc

@@ -0,0 +1,69 @@
+// Copyright (C) 2017 Internet Systems Consortium, Inc. ("ISC")
+//
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+#include <dhcpsrv/shared_network.h>
+
+using namespace isc::dhcp;
+
+namespace isc {
+namespace dhcp {
+
+NetworkPtr
+SharedNetwork4::sharedFromThis() {
+    return (shared_from_this());
+}
+
+void
+SharedNetwork4::add(const Subnet4Ptr& subnet) {
+    SharedNetwork::add(subnets_, subnet);
+}
+
+void
+SharedNetwork4::del(const SubnetID& subnet_id) {
+    SharedNetwork::del(subnets_, subnet_id);
+}
+
+Subnet4Ptr
+SharedNetwork4::getSubnet(const SubnetID& subnet_id) const {
+    return (SharedNetwork::getSubnet<Subnet4Ptr>(subnets_, subnet_id));
+}
+
+Subnet4Ptr
+SharedNetwork4::getNextSubnet(const Subnet4Ptr& first_subnet,
+                              const Subnet4Ptr& current_subnet) const {
+    return (SharedNetwork::getNextSubnet(subnets_, first_subnet,
+                                         current_subnet));
+}
+
+NetworkPtr
+SharedNetwork6::sharedFromThis() {
+    return (shared_from_this());
+}
+
+void
+SharedNetwork6::add(const Subnet6Ptr& subnet) {
+    SharedNetwork::add(subnets_, subnet);
+}
+
+void
+SharedNetwork6::del(const SubnetID& subnet_id) {
+    SharedNetwork::del(subnets_, subnet_id);
+}
+
+Subnet6Ptr
+SharedNetwork6::getSubnet(const SubnetID& subnet_id) const {
+    return (SharedNetwork::getSubnet<Subnet6Ptr>(subnets_, subnet_id));
+}
+
+Subnet6Ptr
+SharedNetwork6::getNextSubnet(const Subnet6Ptr& first_subnet,
+                              const Subnet6Ptr& current_subnet) const {
+    return (SharedNetwork::getNextSubnet(subnets_, first_subnet,
+                                         current_subnet));
+}
+
+} // end of namespace isc::dhcp
+} // end of namespace isc

src/lib/dhcpsrv/shared_network.h

@@ -0,0 +1,374 @@
+// Copyright (C) 2017 Internet Systems Consortium, Inc. ("ISC")
+//
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+#ifndef SHARED_NETWORK_H
+#define SHARED_NETWORK_H
+
+#include <exceptions/exceptions.h>
+#include <dhcpsrv/assignable_network.h>
+#include <dhcpsrv/subnet.h>
+#include <dhcpsrv/subnet_id.h>
+#include <boost/enable_shared_from_this.hpp>
+#include <boost/shared_ptr.hpp>
+
+namespace isc {
+namespace dhcp {
+
+class SharedNetwork;
+
+/// @brief Pointer to the @ref SharedNetwork object.
+typedef boost::shared_ptr<SharedNetwork> SharedNetworkPtr;
+
+/// @brief Represents shared network, which groups multiple subnets.
+///
+/// Shared networks provide means for grouping multiple subnets together.
+/// There are two major use cases for such grouping:
+///
+/// - Extending available address pools to be allocated for clients on
+/// a particular link without a need to renumber.
+/// - Fulfill requirement in cable networks whereby two classes of devices
+/// are connected on the same link: cable modems and routers. Such devices
+/// must be assign addresses/prefixes from different pools based on client
+/// classification.
+///
+/// Shared networks provide similar interface like subnets, thus they both
+/// derive from the @ref Network class.
+class SharedNetwork : public AssignableNetwork {
+protected:
+
+    /// @brief Adds a subnet to a shared network.
+    ///
+    /// This is a generic method for adding a new subnet to a shared network.
+    ///
+    /// @param [out] subnets Container holding subnets for this shared network.
+    /// @param subnet Pointer to a subnet being added to this shared network.
+    ///
+    /// @tparam SubnetPtrType Type of a pointer to a subnet, i.e. Subnet4Ptr
+    /// or @ref Subnet6Ptr.
+    /// @tparam SubnetCollectionType Type of a container holding subnets, i.e.
+    /// @ref Subnet4Collection or @ref Subnet6Collection.
+    ///
+    /// @throw isc::BadValue if subnet is null.
+    /// @throw isc::DuplicateSubnetID if a subnet with the given subnet id
+    /// already exists in this shared network.
+    /// @throw InvalidOperation if a subnet is already associated with some
+    /// shared network.
+    template<typename SubnetPtrType, typename SubnetCollectionType>
+    void add(SubnetCollectionType& subnets, const SubnetPtrType& subnet) {
+        //  Subnet must be non-null.
+        if (!subnet) {
+            isc_throw(BadValue, "null pointer specified when adding a subnet"
+                      " to a shared network");
+        }
+
+        // Check if a subnet with this id already exists.
+        if (getSubnet<SubnetPtrType>(subnets, subnet->getID())) {
+            isc_throw(DuplicateSubnetID, "attempted to add subnet with a"
+                      " duplicated subnet identifier " << subnet->getID());
+        }
+
+        // Check if the subnet is already associated with some network.
+        SharedNetworkPtr network;
+        subnet->getSharedNetwork(network);
+        if (network) {
+            isc_throw(InvalidOperation, "subnet " << subnet->getID()
+                      << " being added to a shared network"
+                      " already belongs to a shared network");
+        }
+
+        // Add a subnet to the collection of subnets for this shared network.
+        subnets.push_back(subnet);
+        // Associate the subnet with this network.
+        setSharedNetwork(subnet);
+    }
+
+    /// @brief Removes a subnet from the shared network.
+    ///
+    /// @param [out] subnets Container holding subnets for this shared network.
+    /// @param subnet_id Identifier of a subnet to be removed.
+    ///
+    /// @tparam SubnetCollectionType Type of a container holding subnets, i.e.
+    /// @ref Subnet4Collection or @ref Subnet6Collection.
+    ///
+    /// @throw BadValue if a subnet with specified identifier doesn't exist.
+    template<typename SubnetCollectionType>
+    void del(SubnetCollectionType& subnets, const SubnetID& subnet_id) {
+        auto& index = subnets.template get<SubnetSubnetIdIndexTag>();
+        auto subnet_it = index.find(subnet_id);
+        if (subnet_it == index.end()) {
+            isc_throw(BadValue, "unable to delete subnet " << subnet_id
+                      << " from shared network. Subnet doesn't belong"
+                      " to this shared network");
+        }
+        auto subnet = *subnet_it;
+        index.erase(subnet_it);
+        clearSharedNetwork(subnet);
+    }
+
+    /// @brief Returns a subnet belonging to this network for a given subnet id.
+    ///
+    /// @param subnets Container holding subnets for this shared network.
+    /// @param subnet_id Identifier of a subnet being retrieved.
+    ///
+    /// @tparam SubnetPtrType Type of a pointer to a subnet, i.e. Subnet4Ptr
+    /// or @ref Subnet6Ptr.
+    /// @tparam SubnetCollectionType Type of a container holding subnets, i.e.
+    /// @ref Subnet4Collection or @ref Subnet6Collection.
+    ///
+    /// @return Pointer to the subnet or null if the subnet doesn't exist.
+    template<typename SubnetPtrType, typename SubnetCollectionType>
+    SubnetPtrType getSubnet(const SubnetCollectionType& subnets,
+                            const SubnetID& subnet_id) const {
+        const auto& index = subnets.template get<SubnetSubnetIdIndexTag>();
+        auto subnet_it = index.find(subnet_id);
+        if (subnet_it != index.cend()) {
+            return (*subnet_it);
+        }
+
+        // Subnet not found.
+        return (SubnetPtrType());
+    }
+
+    /// @brief Retrieves next available subnet within shared network.
+    ///
+    /// This method returns next available subnet within a shared network.
+    /// The subnets are ordered and retrieved using random access index
+    /// (first in/first out). The next subnet means next in turn after
+    /// the current subnet, which is specified as an argument. A caller
+    /// can iterate over all subnets starting from any of the subnets
+    /// belonging to a shared network. This subnet is called here as
+    /// a first subnet and is also specified as a method argument. When the
+    /// method detects that the next available subnet is a first subnet, it
+    /// returns a null pointer to indicate that there are no more subnets
+    /// available.
+    ///
+    /// The typical use case for this method is to allow DHCP server's
+    /// allocation engine to walk over the available subnets within a shared
+    /// network, starting from a subnet that has been selected during the
+    /// "subnet selection" processing step. In some cases the allocation
+    /// engine is unable to allocate resources from a selected subnet due
+    /// to client classification restrictions or address shortage within
+    /// its pools. It then uses this mechanism to move to another subnet
+    /// belonging to the same shared network.
+    ///
+    /// @param subnets Container holding subnets belonging to this shared
+    /// network.
+    /// @param first_subnet Pointer to a subnet from which the caller is
+    /// iterating over subnets within shared network. This is typically a
+    /// subnet selected during "subnet selection" step.
+    /// @param current_subnet Pointer to a subnet for which next subnet is
+    /// to be found.
+    ///
+    /// @tparam SubnetPtrType Type of the pointer to a subnet, i.e.
+    /// @ref Subnet4Ptr or @ref Subnet6Ptr.
+    /// @tparam SubnetCollectionType Type of the container holding subnets, i.e.
+    /// @ref Subnet4Collection or @ref Subnet6Collection.
+    ///
+    /// @return Pointer to next subnet or null pointer if no more subnets found.
+    ///
+    /// @throw isc::BadValue if invalid arguments specified, e.g. unable to
+    /// find first or current subnet within the container.
+    template<typename SubnetPtrType, typename SubnetCollectionType>
+    SubnetPtrType getNextSubnet(const SubnetCollectionType& subnets,
+                                const SubnetPtrType& first_subnet,
+                                const SubnetPtrType& current_subnet) const {
+        // Current subnet must not be null. The caller must explicitly set it
+        // to one of the pointers that belong to this shared network, typically
+        // to a selected subnet.
+        if (!current_subnet) {
+            isc_throw(BadValue, "null subnet specified for a shared"
+                      " network while searching for next subnet is this"
+                      " network");
+        }
+
+        // It is ok to have a shared network without any subnets, but in this
+        // case there is nothing else we can return but null pointer.
+        if (subnets.empty()) {
+            return (SubnetPtrType());
+        }
+
+        // Need to retrieve an iterator to the current subnet first. The
+        // subnet must exist in this container, thus we throw if the iterator
+        // is not found.
+        const auto& index = subnets.template get<SubnetSubnetIdIndexTag>();
+        auto subnet_id_it = index.find(current_subnet->getID());
+        if (subnet_id_it == index.cend()) {
+            isc_throw(BadValue, "no such subnet " << current_subnet->getID()
+                      << " within shared network");
+        }
+
+        // We need to transform this iterator (by subnet id) to a random access
+        // index iterator. Multi index container has a nice way of doing it.
+        auto subnet_it = subnets.template project<SubnetRandomAccessIndexTag>(subnet_id_it);
+
+        // Step to a next subnet within random access index.
+        if (++subnet_it == subnets.cend()) {
+            // If we reached the end of the container, start over from the
+            // beginning.
+            subnet_it = subnets.cbegin();
+        }
+
+        // Check if we have made a full circle. If we did, return a null pointer
+        // to indicate that there are no more subnets.
+        if ((*subnet_it)->getID() == first_subnet->getID()) {
+            return (SubnetPtrType());
+        }
+
+        // Got the next subnet, so return it.
+        return (*subnet_it);
+    }
+
+};
+
+/// @brief Shared network holding IPv4 subnets.
+///
+/// Specialization of the @ref SharedNetwork class for IPv4 subnets.
+class SharedNetwork4 : public SharedNetwork,
+                       public boost::enable_shared_from_this<SharedNetwork4> {
+public:
+
+    /// @brief Returns shared pointer to this network.
+    ///
+    /// This method is required by the parent @ref AssignableNetwork class.
+    ///
+    /// @return Shared pointer to this object.
+    virtual NetworkPtr sharedFromThis();
+
+    /// @brief Adds IPv4 subnet to a shared network.
+    ///
+    /// @param subnet Pointer to a subnet being added to this shared network.
+    ///
+    /// @throw isc::BadValue if subnet is null.
+    /// @throw isc::DuplicateSubnetID if a subnet with the given subnet id
+    /// already exists in this shared network.
+    /// @throw InvalidOperation if a subnet is already associated with some
+    /// shared network.
+    void add(const Subnet4Ptr& subnet);
+
+    /// @brief Removes subnet from a shared network.
+    ///
+    /// @param subnet_id Identifier of a subnet to be removed.
+    ///
+    /// @throw BadValue When specified subnet doesn't exist.
+    void del(const SubnetID& subnet_id);
+
+    /// @brief Returns a pointer to the collection of subnets within this
+    /// shared network.
+    const Subnet4Collection* getAllSubnets() const {
+        return (&subnets_);
+    }
+
+    /// @brief Returns a subnet for a specified subnet id.
+    ///
+    /// @param subnet_id Subnet identifier.
+    ///
+    /// @return Shared pointer to a subnet using this id or null pointer
+    /// if such subnet doesn't exist within shared network.
+    Subnet4Ptr getSubnet(const SubnetID& subnet_id) const;
+
+    /// @brief Retrieves next available IPv4 subnet within shared network.
+    ///
+    /// See documentation for @ref SharedNetwork::getNextSubnet.
+    ///
+    /// @param first_subnet Pointer to a subnet from which the caller is
+    /// iterating over subnets within shared network. This is typically a
+    /// subnet selected during "subnet selection" step.
+    /// @param current_subnet Pointer to a subnet for which next subnet is
+    /// to be found.
+    ///
+    /// @return Pointer to next subnet or null pointer if no more subnets found.
+    ///
+    /// @throw isc::BadValue if invalid arguments specified, e.g. unable to
+    /// find first or current subnet within shared network.
+    Subnet4Ptr getNextSubnet(const Subnet4Ptr& first_subnet,
+                             const Subnet4Ptr& current_subnet) const;
+
+private:
+
+    /// @brief Collection of IPv4 subnets within shared network.
+    Subnet4Collection subnets_;
+
+};
+
+/// @brief Pointer to @ref SharedNetwork4 object.
+typedef boost::shared_ptr<SharedNetwork4> SharedNetwork4Ptr;
+
+/// @brief Shared network holding IPv6 subnets.
+///
+/// Specialization of the @ref SharedNetwork class for IPv6 subnets.
+class SharedNetwork6 : public SharedNetwork,
+                       public boost::enable_shared_from_this<SharedNetwork6> {
+public:
+
+    /// @brief Returns shared pointer to this network.
+    ///
+    /// This method is required by the parent @ref AssignableNetwork class.
+    ///
+    /// @return Shared pointer to this object.
+    virtual NetworkPtr sharedFromThis();
+
+    /// @brief Adds IPv6 subnet to a shared network.
+    ///
+    /// @param subnet Pointer to a subnet being added to this shared network.
+    ///
+    /// @throw isc::BadValue if subnet is null.
+    /// @throw isc::DuplicateSubnetID if a subnet with the given subnet id
+    /// already exists in this shared network.
+    /// @throw InvalidOperation if a subnet is already associated with some
+    /// shared network.
+    void add(const Subnet6Ptr& subnet);
+
+    /// @brief Removes subnet from a shared network.
+    ///
+    /// @param subnet_id Identifier of a subnet to be removed.
+    ///
+    /// @throw BadValue When specified subnet doesn't exist.
+    void del(const SubnetID& subnet_id);
+
+    /// @brief Returns a pointer to the collection of subnets within this
+    /// shared network.
+    const Subnet6Collection* getAllSubnets() const {
+        return (&subnets_);
+    }
+
+    /// @brief Returns a subnet for a specified subnet id.
+    ///
+    /// @param subnet_id Subnet identifier.
+    ///
+    /// @return Shared pointer to a subnet using this id or null pointer
+    /// if such subnet doesn't exist within shared network.
+    Subnet6Ptr getSubnet(const SubnetID& subnet_id) const;
+
+    /// @brief Retrieves next available IPv6 subnet within shared network.
+    ///
+    /// See documentation for @ref SharedNetwork::getNextSubnet.
+    ///
+    /// @param first_subnet Pointer to a subnet from which the caller is
+    /// iterating over subnets within shared network. This is typically a
+    /// subnet selected during "subnet selection" step.
+    /// @param current_subnet Pointer to a subnet for which next subnet is
+    /// to be found.
+    ///
+    /// @return Pointer to next subnet or null pointer if no more subnets found.
+    ///
+    /// @throw isc::BadValue if invalid arguments specified, e.g. unable to
+    /// find first or current subnet within shared network.
+    Subnet6Ptr getNextSubnet(const Subnet6Ptr& first_subnet,
+                             const Subnet6Ptr& current_subnet) const;
+
+private:
+
+    /// @brief Collection of IPv6 subnets within shared network.
+    Subnet6Collection subnets_;
+};
+
+/// @brief Pointer to @ref SharedNetwork6 object.
+typedef boost::shared_ptr<SharedNetwork6> SharedNetwork6Ptr;
+
+} // end of namespace isc::dhcp
+} // end of namespace isc
+
+#endif // SHARED_NETWORK_H

src/lib/dhcpsrv/subnet.cc

@@ -354,16 +354,6 @@ Subnet::delPools(Lease::Type type) {
     getPoolsWritable(type).clear();
 }
 
-void
-Subnet::setIface(const std::string& iface_name) {
-    iface_ = iface_name;
-}
-
-std::string
-Subnet::getIface() const {
-    return (iface_);
-}
-
 bool
 Subnet::inPool(Lease::Type type, const isc::asiolink::IOAddress& addr) const {
 

src/lib/dhcpsrv/subnet.h

@@ -12,6 +12,7 @@
 #include <dhcp/option.h>
 #include <dhcp/classify.h>
 #include <dhcp/option_space_container.h>
+#include <dhcpsrv/assignable_network.h>
 #include <dhcpsrv/cfg_option.h>
 #include <dhcpsrv/cfg_4o6.h>
 #include <dhcpsrv/lease.h>
@@ -24,12 +25,18 @@
 #include <boost/multi_index/ordered_index.hpp>
 #include <boost/multi_index/random_access_index.hpp>
 #include <boost/multi_index_container.hpp>
+#include <boost/pointer_cast.hpp>
 #include <boost/shared_ptr.hpp>
 
 namespace isc {
 namespace dhcp {
 
-class Subnet {
+class Subnet : public Network {
+
+    // Assignable network is our friend to allow it to call
+    // @ref Subnet::setSharedNetwork private function.
+    friend class AssignableNetwork;
+
 public:
 
     /// @brief Holds optional information about relay.
@@ -233,16 +240,6 @@ public:
     /// @param type type of the lease
     uint64_t getPoolCapacity(Lease::Type type) const;
 
-    /// @brief Sets name of the network interface for directly attached networks
-    ///
-    /// @param iface_name name of the interface
-    void setIface(const std::string& iface_name);
-
-    /// @brief Network interface name used to reach subnet (or "" for remote
-    /// subnets)
-    /// @return network interface name for directly attached subnets or ""
-    std::string getIface() const;
-
     /// @brief Returns textual representation of the subnet (e.g.
     /// "2001:db8::/64")
     ///
@@ -349,6 +346,41 @@ public:
         host_reservation_mode_ = mode;
     }
 
+    /// @brief Retrieves pointer to a shared network associated with a subnet.
+    ///
+    /// By implementing it as a template function we overcome a need to
+    /// include shared_network.h header file to specify return type explicitly.
+    /// The header can't be included because it would cause circular dependency
+    /// between subnet.h and shared_network.h.
+    ///
+    /// This method uses an argument to hold a return value to allow the compiler
+    /// to infer the return type without a need to call this function with an
+    /// explicit return type as template argument.
+    ///
+    /// @param [out] shared_network Pointer to the shared network where returned
+    /// value should be assigned.
+    ///
+    /// @tparam Type of the shared network, i.e. @ref SharedNetwork4 or a
+    /// @ref SharedNetwork6.
+    template<typename SharedNetworkPtrType>
+    void getSharedNetwork(SharedNetworkPtrType& shared_network) const {
+        shared_network = boost::dynamic_pointer_cast<
+            typename SharedNetworkPtrType::element_type>(shared_network_);
+    }
+
+private:
+
+    /// @brief Assigns shared network to a subnet.
+    ///
+    /// This method replaces any shared network associated with a subnet with
+    /// a new shared network.
+    ///
+    /// @param shared_network Pointer to a new shared network to be associated
+    /// with the subnet.
+    void setSharedNetwork(const NetworkPtr& shared_network) {
+        shared_network_ = shared_network;
+    }
+
 protected:
     /// @brief Returns all pools (non-const variant)
     ///
@@ -518,10 +550,11 @@ protected:
     ///
     /// See @ref HRMode type for details.
     HRMode host_reservation_mode_;
-private:
 
     /// @brief Pointer to the option data configuration for this subnet.
     CfgOptionPtr cfg_option_;
+
+    NetworkPtr shared_network_;
 };
 
 /// @brief A generic pointer to either Subnet4 or Subnet6 object

src/lib/dhcpsrv/tests/Makefile.am

@@ -121,6 +121,7 @@ if HAVE_CQL
 libdhcpsrv_unittests_SOURCES += cql_lease_mgr_unittest.cc
 endif
 libdhcpsrv_unittests_SOURCES += pool_unittest.cc
+libdhcpsrv_unittests_SOURCES += shared_network_unittest.cc
 libdhcpsrv_unittests_SOURCES += srv_config_unittest.cc
 libdhcpsrv_unittests_SOURCES += subnet_unittest.cc
 libdhcpsrv_unittests_SOURCES += test_get_callout_handle.cc test_get_callout_handle.h

src/lib/dhcpsrv/tests/shared_network_unittest.cc

@@ -0,0 +1,172 @@
+// Copyright (C) 2017 Internet Systems Consortium, Inc. ("ISC")
+//
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+#include <asiolink/io_address.h>
+#include <dhcpsrv/shared_network.h>
+#include <dhcpsrv/subnet.h>
+#include <dhcpsrv/subnet_id.h>
+#include <dhcpsrv/triplet.h>
+#include <exceptions/exceptions.h>
+#include <gtest/gtest.h>
+#include <cstdint>
+#include <vector>
+
+using namespace isc;
+using namespace isc::asiolink;
+using namespace isc::dhcp;
+
+namespace {
+
+// This test verifies that an IPv4 subnet can be added to a shared network.
+// It also verifies that two subnets with the same ID can't be added to
+// a shared network and that a single subnet can't be added to two different
+// shared subnets.
+TEST(SharedNetwork4Test, addSubnet4) {
+    // First, create a network.
+    SharedNetwork4Ptr network(new SharedNetwork4());
+
+    // Try to add null pointer. It should throw.
+    Subnet4Ptr subnet;
+    ASSERT_THROW(network->add(subnet), BadValue);
+
+    // Create a valid subnet. It should now be added successfully.
+    subnet.reset(new Subnet4(IOAddress("10.0.0.0"), 8, 10, 20, 30,
+                             SubnetID(15)));
+    ASSERT_NO_THROW(network->add(subnet));
+    ASSERT_EQ(1, network->getAllSubnets()->size());
+
+    // Retrieve the subnet from the network and make sure it is returned
+    // as expected.
+    Subnet4Ptr returned_subnet = network->getAllSubnets()->front();
+    ASSERT_TRUE(returned_subnet);
+    EXPECT_EQ(subnet->getID(), returned_subnet->getID());
+    SharedNetwork4Ptr network1;
+    subnet->getSharedNetwork(network1);
+    ASSERT_TRUE(network1);
+    EXPECT_TRUE(network1 == network);
+
+    // Create another subnet with the same ID. Adding a network with the
+    // same ID should cause an error.
+    Subnet4Ptr subnet2(new Subnet4(IOAddress("192.0.2.0"), 24, 10, 20, 30,
+                                   SubnetID(15)));
+    ASSERT_THROW(network->add(subnet), DuplicateSubnetID);
+
+    // Create another network and try to add a subnet to it. It should fail
+    // because the subnet is already associated with the first network.
+    SharedNetwork4Ptr network2(new SharedNetwork4());
+    ASSERT_THROW(network2->add(subnet), InvalidOperation);
+}
+
+// This test verifies that it is possible to remove a specified subnet.
+TEST(SharedNetwork4Test, delSubnet4) {
+    // Create two subnets and add them to the shared network.
+    Subnet4Ptr subnet1(new Subnet4(IOAddress("10.0.0.0"), 8, 10, 20, 30,
+                                   SubnetID(1)));
+    Subnet4Ptr subnet2(new Subnet4(IOAddress("192.0.2.0"), 24, 10, 20, 30,
+                                   SubnetID(2)));
+
+    SharedNetwork4Ptr network(new SharedNetwork4());
+    ASSERT_NO_THROW(network->add(subnet1));
+    ASSERT_NO_THROW(network->add(subnet2));
+
+    // Make sure they have been added successfully.
+    ASSERT_EQ(2, network->getAllSubnets()->size());
+
+    // Try to remove a subnet that doesn't exist in this shared network.
+    // It should cause an error.
+    ASSERT_THROW(network->del(SubnetID(5)), BadValue);
+
+    // Now delete the subnet that exists.
+    ASSERT_NO_THROW(network->del(subnet1->getID()));
+    // We should be left with only one subnet.
+    ASSERT_EQ(1, network->getAllSubnets()->size());
+    Subnet4Ptr subnet_returned = network->getAllSubnets()->front();
+    ASSERT_TRUE(subnet_returned);
+    EXPECT_EQ(subnet2->getID(), subnet_returned->getID());
+
+    // Check that shared network has been cleared for the removed subnet.
+    SharedNetwork4Ptr network1;
+    subnet1->getSharedNetwork(network1);
+    EXPECT_FALSE(network1);
+
+    // Remove another subnet and make sure there are no subnets left.
+    ASSERT_NO_THROW(network->del(subnet2->getID()));
+    EXPECT_EQ(0, network->getAllSubnets()->size());
+
+    // The network pointer should be cleared for this second subnet too.
+    SharedNetwork4Ptr network2;
+    subnet1->getSharedNetwork(network2);
+    EXPECT_FALSE(network2);
+}
+
+// This test verifies that it is possible to iterate over the subnets
+// associated with a particular shared network.
+TEST(SharedNetwork4Test, getNextSubnet) {
+    SharedNetwork4Ptr network(new SharedNetwork4());
+
+    // Create three subnets.
+    Subnet4Ptr subnet1(new Subnet4(IOAddress("10.0.0.0"), 8, 10, 20, 30,
+                                   SubnetID(1)));
+    Subnet4Ptr subnet2(new Subnet4(IOAddress("192.0.2.0"), 24, 10, 20, 30,
+                                   SubnetID(2)));
+    Subnet4Ptr subnet3(new Subnet4(IOAddress("172.16.25.0"), 24, 10, 20, 30,
+                                   SubnetID(3)));
+    std::vector<Subnet4Ptr> subnets;
+    subnets.push_back(subnet1);
+    subnets.push_back(subnet2);
+    subnets.push_back(subnet3);
+
+    // Subnets have unique IDs so they should successfully be added to the
+    // network.
+    for (auto i = 0; i < subnets.size(); ++i) {
+        ASSERT_NO_THROW(network->add(subnets[i]))
+            << "failed to add subnet with id " << subnets[i]->getID()
+            << " to shared network";
+    }
+
+    // Collect networks associated with our subnets in the vector.
+    std::vector<SharedNetwork4Ptr> networks;
+    for (auto i = 0; i < subnets.size(); ++i) {
+        SharedNetwork4Ptr network;
+        subnets[i]->getSharedNetwork(network);
+        ASSERT_TRUE(network) << "failed to retrieve shared network for a"
+            << " subnet id " << subnets[i]->getID();
+        networks.push_back(network);
+    }
+
+    // All subnets should be associated with the same network.
+    for (auto i = 1; i < networks.size(); ++i) {
+        EXPECT_TRUE(networks[0] == networks[i]);
+    }
+
+    // Perform the test 3 times where each subnet belonging to the shared
+    // network is treated as a "first" subnet in the call to getNextSubnet.
+    for (auto i = 0; i < subnets.size(); ++i) {
+        Subnet4Ptr s = subnets[i];
+
+        // Iterate over the subnets starting from the subnet with index i.
+        for (auto j = 0; j < subnets.size(); ++j) {
+            // Get next subnet (following the one currently in s).
+            s = networks[0]->getNextSubnet(subnets[i], s);
+            // The last iteration should return empty pointer to indicate end of
+            // the subnets within shared network. If we're not at last iteration
+            // check that the subnet identifier of the returned subnet is valid.
+            if (j < subnets.size() - 1) {
+                ASSERT_TRUE(s) << "retrieving next subnet failed for pair of"
+                    " indexes (i, j) = (" << i << ", " << j << ")";
+                const auto expected_subnet_id = (i + j + 1) % subnets.size() + 1;
+                EXPECT_EQ(expected_subnet_id, s->getID());
+            } else {
+                // Null subnet returned for a last iteration.
+                ASSERT_FALSE(s) << "expected null pointer to be returned as"
+                    " next subnet for pair of indexes (i, j) = ("
+                                << i << ", " << j << ")";
+            }
+        }
+    }
+}
+
+} // end of anonymous namespace