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diff --git a/src/lib/dhcpsrv/iterative_allocator.h b/src/lib/dhcpsrv/iterative_allocator.h
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+// Copyright (C) 2022-2023 Internet Systems Consortium, Inc. ("ISC")
+//
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+#ifndef ITERATIVE_ALLOCATOR_H
+#define ITERATIVE_ALLOCATOR_H
+
+#include <dhcpsrv/allocator.h>
+#include <dhcpsrv/iterative_allocation_state.h>
+#include <dhcpsrv/lease.h>
+
+#include <cstdint>
+
+namespace isc {
+namespace dhcp {
+
+/// @brief Address/prefix allocator that iterates over all addresses.
+///
+/// This class implements an iterative algorithm that returns all addresses in
+/// a pool iteratively, one after another. Once the last address is reached,
+/// it starts allocating from the beginning of the first pool (i.e. it loops
+/// over).
+class IterativeAllocator : public Allocator {
+public:
+
+    /// @brief Constructor.
+    ///
+    /// @param type specifies the type of allocated leases.
+    /// @param subnet weak pointer to the subnet owning the allocator.
+    IterativeAllocator(Lease::Type type, const WeakSubnetPtr& subnet);
+
+    /// @brief Returns the allocator type string.
+    ///
+    /// @return iterative string.
+    virtual std::string getType() const {
+        return ("iterative");
+    }
+
+private:
+
+    /// @brief Returns the next address from the pools in the subnet.
+    ///
+    /// Internal thread-unsafe implementation of the @c pickAddress.
+    ///
+    /// @param client_classes list of classes client belongs to.
+    /// @param duid client DUID (ignored).
+    /// @param hint client hint (ignored).
+    ///
+    /// @return next offered address.
+    virtual asiolink::IOAddress pickAddressInternal(const ClientClasses& client_classes,
+                                                    const IdentifierBaseTypePtr& duid,
+                                                    const asiolink::IOAddress& hint);
+
+    /// @brief Picks a delegated prefix.
+    ///
+    /// Internal thread-unsafe implementation of the @c pickPrefix.
+    ///
+    /// @param client_classes list of classes client belongs to.
+    /// @param pool the selected pool satisfying all required conditions.
+    /// @param duid Client's DUID.
+    /// @param prefix_length_match type which indicates the selection criteria
+    ///        for the pools relative to the provided hint prefix length.
+    /// @param hint Client's hint.
+    /// @param hint_prefix_length the hint prefix length that the client
+    ///        provided. The 0 value means that there is no hint and that any
+    ///        pool will suffice.
+    ///
+    /// @return the next prefix.
+    virtual asiolink::IOAddress pickPrefixInternal(const ClientClasses& client_classes,
+                                                   Pool6Ptr& pool,
+                                                   const IdentifierBaseTypePtr& duid,
+                                                   PrefixLenMatchType prefix_length_match,
+                                                   const asiolink::IOAddress& hint,
+                                                   uint8_t hint_prefix_length);
+
+    /// @brief Convenience function returning subnet allocation state instance.
+    ///
+    /// It creates a new subnet state instance and assigns it to the subnet
+    /// if it hasn't been initialized.
+    ///
+    /// @return allocation state instance for the subnet.
+    SubnetIterativeAllocationStatePtr getSubnetState() const;
+
+    /// @brief Convenience function returning pool allocation state instance.
+    ///
+    /// It creates a new pool state instance and assigns it to the pool
+    /// if it hasn't been initialized.
+    ///
+    /// @param pool pool instance.
+    /// @return allocation state instance for the pool.
+    PoolIterativeAllocationStatePtr getPoolState(const PoolPtr& pool) const;
+
+protected:
+
+    /// @brief Returns the next prefix.
+    ///
+    /// This method works for IPv6 addresses only. It increases the
+    /// specified prefix by a given prefix_len. For example, 2001:db8::
+    /// increased by prefix length /32 will become 2001:db9::. This method
+    /// is used to iterate over IPv6 prefix pools
+    ///
+    /// @param prefix prefix to be increased.
+    /// @param prefix_len length of the prefix to be increased.
+    ///
+    /// @return next prefix.
+    static asiolink::IOAddress increasePrefix(const asiolink::IOAddress& prefix,
+                                              const uint8_t prefix_len);
+
+    /// @brief Returns the next address or prefix.
+    ///
+    /// This method works for IPv4 addresses, IPv6 addresses and
+    /// IPv6 prefixes.
+    ///
+    /// @param address address or prefix to be increased
+    /// @param prefix true when the previous argument is a prefix.
+    /// @param prefix_len length of the prefix.
+    ///
+    /// @return result address or prefix
+    static asiolink::IOAddress increaseAddress(const asiolink::IOAddress& address,
+                                               bool prefix,
+                                               const uint8_t prefix_len);
+};
+
+}  // namespace dhcp
+}  // end of namespace isc
+
+#endif  // ITERATIVE_ALLOCATOR_H