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// Copyright (C) 2020-2021 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 RESOURCE_HANDLER_H
#define RESOURCE_HANDLER_H
#include <asiolink/io_address.h>
#include <dhcpsrv/lease.h>
#include <boost/noncopyable.hpp>
#include <boost/multi_index_container.hpp>
#include <boost/multi_index/composite_key.hpp>
#include <boost/multi_index/hashed_index.hpp>
#include <boost/multi_index/member.hpp>
#include <boost/multi_index/mem_fun.hpp>
#include <boost/shared_ptr.hpp>
#include <mutex>
namespace isc {
namespace dhcp {
/// @brief Thrown by lock users when a resource lock cannot be obtained.
class ResourceBusy : public Exception {
public:
ResourceBusy(const char* file, size_t line, const char* what) :
isc::Exception(file, line, what) {}
};
/// @brief Resource race avoidance RAII handler.
class ResourceHandler : public boost::noncopyable {
public:
/// @brief Constructor.
ResourceHandler();
/// @brief Destructor.
///
/// Releases owned resources.
virtual ~ResourceHandler();
/// @brief Tries to acquires a resource.
///
/// Lookup the resource, if not found insert the resource
/// in the resource container and return true, if found return false
///
/// @param type Type of the resource, member of @c Lease::Type enum.
/// @param addr The address or prefix aka the resource.
/// @return true if the resource was acquired, false if the resource is
/// busy i.e. owned by a handler.
bool tryLock(Lease::Type type, const asiolink::IOAddress& addr);
/// @brief Checks if a resource is owned by this handler.
///
/// @param type Type of the resource, member of @c Lease::Type enum.
/// @param addr The address or prefix aka the resource.
/// @return true if this handler owns the resource, false otherwise.
bool isLocked(Lease::Type type, const asiolink::IOAddress& addr);
/// @brief Releases a resource.
///
/// Remove the resource from the resource container.
///
/// @param type Type of the resource, member of @c Lease::Type enum.
/// @param addr The address or prefix aka the resource.
/// @throw when we do not own the resource.
void unLock(Lease::Type type, const asiolink::IOAddress& addr);
private:
/// Type definitions.
//@{
/// @brief Structure representing a resource.
struct Resource {
/// @brief Constructor.
///
/// @param addr The address or prefix aka the resource..
Resource(Lease::Type type, const asiolink::IOAddress& addr)
: type_(type), addr_(addr) {
}
/// @brief The type.
Lease::Type type_;
/// @brief The resource.
asiolink::IOAddress addr_;
/// @brief The key extractor.
std::vector<uint8_t> toBytes() const {
return (addr_.toBytes());
}
};
/// @brief The type of shared pointers to resources.
typedef boost::shared_ptr<Resource> ResourcePtr;
/// @brief The type of the resource container.
typedef boost::multi_index_container<
// This container stores pointers to resource objects.
ResourcePtr,
// Start specification of indexes here.
boost::multi_index::indexed_by<
// First index is used to search by type and address.
boost::multi_index::hashed_unique<
boost::multi_index::composite_key<
Resource,
// Lease type.
boost::multi_index::member<
Resource, Lease::Type, &Resource::type_
>,
// Address bytes.
boost::multi_index::const_mem_fun<
Resource, std::vector<uint8_t>, &Resource::toBytes
>
>
>
>
> ResourceContainer;
//@}
/// Class members.
//@{
/// @brief The resource container.
static ResourceContainer resources_;
/// @brief Mutex to protect the resource container.
static std::mutex mutex_;
/// @brief Lookup a resource.
///
/// The mutex must be held by the caller.
///
/// @param type Type of the resource, member of @c Lease::Type enum.
/// @param addr The address or prefix aka the resource.
/// @return The busy resource or null.
static ResourcePtr
lookup(Lease::Type type, const asiolink::IOAddress& addr);
//@}
/// Instance members.
//@{
/// @brief Acquire a resource.
///
/// The mutex must be held by the caller.
///
/// @param type Type of the resource, member of @c Lease::Type enum.
/// @param addr The address or prefix aka the resource.
void lock(Lease::Type type, const asiolink::IOAddress& addr);
/// @brief Release a resource.
///
/// The mutex must be held by the caller.
///
/// Remove the resource from the resource container.
///
/// @param type Type of the resource, member of @c Lease::Type enum.
/// @param addr The address or prefix aka the resource.
void unLockInternal(Lease::Type type, const asiolink::IOAddress& addr);
/// @brief List of resources this handler owns.
ResourceContainer owned_;
//@}
};
/// @brief Resource race avoidance RAII handler for DHCPv4.
class ResourceHandler4 : public ResourceHandler {
public:
/// @brief Destructor.
///
/// Releases owned resources.
virtual ~ResourceHandler4() { }
/// @brief Tries to acquires a resource.
///
/// Lookup the resource, if not found insert the resource
/// in the resource container and return true, if found return false
///
/// @param addr The address aka the resource.
/// @return true if the resource was acquired, false if the resource is
/// busy i.e. owned by a handler.
bool tryLock4(const asiolink::IOAddress& addr) {
return (tryLock(Lease::TYPE_V4, addr));
}
/// @brief Checks if a resource is owned by this handler.
///
/// @param addr The address aka the resource.
/// @return true if this handler owns the resource, false otherwise.
bool isLocked4(const asiolink::IOAddress& addr) {
return (isLocked(Lease::TYPE_V4, addr));
}
/// @brief Releases a resource.
///
/// Remove the resource from the resource container.
///
/// @param addr The address aka the resource.
/// @throw when we do not own the resource.
void unLock4(const asiolink::IOAddress& addr) {
unLock(Lease::TYPE_V4, addr);
}
};
} // namespace isc
} // namespace dhcp
#endif // RESOURCE_HANDLER_H
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