src/lib/address_resolve/AddressResolve_DefaultImpl.cpp - third_party/github/project-chip/connectedhomeip - Git at Google

 /*
  *
  *    Copyright (c) 2022 Project CHIP Authors
  *
  *    Licensed under the Apache License, Version 2.0 (the "License");
  *    you may not use this file except in compliance with the License.
  *    You may obtain a copy of the License at
  *
  *        http://www.apache.org/licenses/LICENSE-2.0
  *
  *    Unless required by applicable law or agreed to in writing, software
  *    distributed under the License is distributed on an "AS IS" BASIS,
  *    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  *    See the License for the specific language governing permissions and
  *    limitations under the License.
  */

 #include <lib/address_resolve/AddressResolve_DefaultImpl.h>

 namespace chip {
 namespace AddressResolve {
 namespace Impl {
 namespace {

 static constexpr System::Clock::Timeout kInvalidTimeout{ System::Clock::Timeout::max() };

 } // namespace

 void NodeLookupHandle::ResetForLookup(System::Clock::Timestamp now, const NodeLookupRequest & request)
 {
     mRequestStartTime = now;
     mRequest          = request;
     mResults          = NodeLookupResults();
 }

 void NodeLookupHandle::LookupResult(const ResolveResult & result)
 {
     auto score = Dnssd::IPAddressSorter::ScoreIpAddress(result.address.GetIPAddress(), result.address.GetInterface());
     [[maybe_unused]] bool success = mResults.UpdateResults(result, score);

 #if CHIP_PROGRESS_LOGGING
     char addr_string[Transport::PeerAddress::kMaxToStringSize];
     result.address.ToString(addr_string);

     if (success)
     {
         ChipLogProgress(Discovery, "%s: new best score: %u", addr_string, to_underlying(score));
     }
     else
     {
         ChipLogProgress(Discovery, "%s: score has not improved: %u", addr_string, to_underlying(score));
     }
 #endif
 }

 System::Clock::Timeout NodeLookupHandle::NextEventTimeout(System::Clock::Timestamp now)
 {
     const System::Clock::Timestamp elapsed = now - mRequestStartTime;

     if (elapsed < mRequest.GetMinLookupTime())
     {
         return mRequest.GetMinLookupTime() - elapsed;
     }

     if (HasLookupResult())
     {
         // We can get here if we got our result before our min lookup time had
         // elapsed, but time has passed between then and this attempt to re-arm
         // the timer, such that now we are past our min lookup time.  For
         // example, this can happen because the timer is a bit delayed in firing
         // but is now being re-scheduled due to a cancellation of a lookup or
         // start of a new lookup.  Or it could happen because
         // OnOperationalNodeResolved got called close to our min lookup time,
         // and we crossed that line while going through mActiveLookups and
         // before we got to calling ReArmTimer.
         //
         // In this case, we should just fire the timer ASAP, since our min
         // lookup time has elapsed and we have results.
         return System::Clock::Timeout::zero();
     }

     if (elapsed < mRequest.GetMaxLookupTime())
     {
         return mRequest.GetMaxLookupTime() - elapsed;
     }

     ChipLogError(Discovery, "Unexpected timeout: lookup should have been cleaned already.");
     return System::Clock::Timeout::zero();
 }

 NodeLookupAction NodeLookupHandle::NextAction(System::Clock::Timestamp now)
 {
     const System::Clock::Timestamp elapsed = now - mRequestStartTime;

     ChipLogProgress(Discovery, "Checking node lookup status after %lu ms", static_cast<unsigned long>(elapsed.count()));

     // We are still within the minimal search time. Wait for more results.
     if (elapsed < mRequest.GetMinLookupTime())
     {
         ChipLogProgress(Discovery, "Keeping DNSSD lookup active");
         return NodeLookupAction::KeepSearching();
     }

     // Minimal time to search reached. If any IP available, ready to return it.
     if (HasLookupResult())
     {
         auto result = TakeLookupResult();
         return NodeLookupAction::Success(result);
     }

     // Give up if the maximum search time has been reached
     if (elapsed >= mRequest.GetMaxLookupTime())
     {
         return NodeLookupAction::Error(CHIP_ERROR_TIMEOUT);
     }

     return NodeLookupAction::KeepSearching();
 }

 bool NodeLookupResults::UpdateResults(const ResolveResult & result, const Dnssd::IPAddressSorter::IpScore newScore)
 {
     uint8_t insertAtIndex = 0;
     for (; insertAtIndex < kNodeLookupResultsLen; insertAtIndex++)
     {
         if (insertAtIndex >= count)
         {
             // This is a new entry.
             break;
         }

         auto & oldAddress = results[insertAtIndex].address;
         auto oldScore     = Dnssd::IPAddressSorter::ScoreIpAddress(oldAddress.GetIPAddress(), oldAddress.GetInterface());
         if (newScore > oldScore)
         {
             // This is a score update, it will replace a previous entry.
             break;
         }
     }

     if (insertAtIndex == kNodeLookupResultsLen)
     {
         return false;
     }

     // Move the following valid entries one level down.
     for (auto i = count; i > insertAtIndex; i--)
     {
         if (i >= kNodeLookupResultsLen)
         {
             continue;
         }

         results[i] = results[i - 1];
     }

     // If the number of valid entries is less than the size of the array there is an additional entry.
     if (count < kNodeLookupResultsLen)
     {
         count++;
     }

     auto & updatedResult = results[insertAtIndex];
     updatedResult        = result;
     if (!updatedResult.address.GetIPAddress().IsIPv6LinkLocal())
     {
         // Only use the DNS-SD resolution's InterfaceID for addresses that are IPv6 LLA.
         // For all other addresses, we should rely on the device's routing table to route messages sent.
         // Forcing messages down an InterfaceId might fail. For example, in bridged networks like Thread,
         // mDNS advertisements are not usually received on the same interface the peer is reachable on.
         updatedResult.address.SetInterface(Inet::InterfaceId::Null());
         ChipLogDetail(Discovery, "Lookup clearing interface for non LL address");
     }

     return true;
 }

 CHIP_ERROR Resolver::LookupNode(const NodeLookupRequest & request, Impl::NodeLookupHandle & handle)
 {
     VerifyOrReturnError(mSystemLayer != nullptr, CHIP_ERROR_INCORRECT_STATE);

     handle.ResetForLookup(mTimeSource.GetMonotonicTimestamp(), request);
     ReturnErrorOnFailure(Dnssd::Resolver::Instance().ResolveNodeId(request.GetPeerId()));
     mActiveLookups.PushBack(&handle);
     ReArmTimer();
     return CHIP_NO_ERROR;
 }

 CHIP_ERROR Resolver::TryNextResult(Impl::NodeLookupHandle & handle)
 {
     VerifyOrReturnError(!mActiveLookups.Contains(&handle), CHIP_ERROR_INCORRECT_STATE);
     VerifyOrReturnError(handle.HasLookupResult(), CHIP_ERROR_WELL_EMPTY);

     auto listener = handle.GetListener();
     auto peerId   = handle.GetRequest().GetPeerId();
     auto result   = handle.TakeLookupResult();
     listener->OnNodeAddressResolved(peerId, result);
     return CHIP_NO_ERROR;
 }

 CHIP_ERROR Resolver::CancelLookup(Impl::NodeLookupHandle & handle, FailureCallback cancel_method)
 {
     VerifyOrReturnError(handle.IsActive(), CHIP_ERROR_INVALID_ARGUMENT);
     mActiveLookups.Remove(&handle);
     Dnssd::Resolver::Instance().NodeIdResolutionNoLongerNeeded(handle.GetRequest().GetPeerId());

     // Adjust any timing updates.
     ReArmTimer();

     if (cancel_method == FailureCallback::Call)
     {
         handle.GetListener()->OnNodeAddressResolutionFailed(handle.GetRequest().GetPeerId(), CHIP_ERROR_CANCELLED);
     }

     // TODO: There should be some form of cancel into Dnssd::Resolver::Instance()
     //       to stop any resolution mechanism if applicable.
     //
     // Current code just removes the internal list and any callbacks of resolution will
     // be ignored. This works from the perspective of the caller of this method,
     // but may be wasteful by letting dnssd still work in the background.

     return CHIP_NO_ERROR;
 }

 CHIP_ERROR Resolver::Init(System::Layer * systemLayer)
 {
     mSystemLayer = systemLayer;
     Dnssd::Resolver::Instance().SetOperationalDelegate(this);
     return CHIP_NO_ERROR;
 }

 void Resolver::Shutdown()
 {
     while (mActiveLookups.begin() != mActiveLookups.end())
     {
         auto current = mActiveLookups.begin();

         const PeerId peerId     = current->GetRequest().GetPeerId();
         NodeListener * listener = current->GetListener();

         mActiveLookups.Erase(current);

         Dnssd::Resolver::Instance().NodeIdResolutionNoLongerNeeded(peerId);
         // Failure callback only called after iterator was cleared:
         // This allows failure handlers to deallocate structures that may
         // contain the active lookup data as a member (intrusive lists members)
         listener->OnNodeAddressResolutionFailed(peerId, CHIP_ERROR_SHUT_DOWN);
     }

     // Re-arm of timer is expected to cancel any active timer as the
     // internal list of active lookups is empty at this point.
     ReArmTimer();

     mSystemLayer = nullptr;
     Dnssd::Resolver::Instance().SetOperationalDelegate(nullptr);
 }

 void Resolver::OnOperationalNodeResolved(const Dnssd::ResolvedNodeData & nodeData)
 {
     auto it = mActiveLookups.begin();
     while (it != mActiveLookups.end())
     {
         auto current = it;
         it++;
         if (current->GetRequest().GetPeerId() != nodeData.operationalData.peerId)
         {
             continue;
         }

         ResolveResult result;

         result.address.SetPort(nodeData.resolutionData.port);
         result.address.SetInterface(nodeData.resolutionData.interfaceId);
         result.mrpRemoteConfig = nodeData.resolutionData.GetRemoteMRPConfig();
         result.supportsTcp     = nodeData.resolutionData.supportsTcp;

         for (size_t i = 0; i < nodeData.resolutionData.numIPs; i++)
         {
 #if !INET_CONFIG_ENABLE_IPV4
             if (!nodeData.resolutionData.ipAddress[i].IsIPv6())
             {
                 ChipLogError(Discovery, "Skipping IPv4 address during operational resolve.");
                 continue;
             }
 #endif
             result.address.SetIPAddress(nodeData.resolutionData.ipAddress[i]);
             current->LookupResult(result);
         }

         HandleAction(current);
     }

     ReArmTimer();
 }

 void Resolver::HandleAction(IntrusiveList<NodeLookupHandle>::Iterator & current)
 {
     const NodeLookupAction action = current->NextAction(mTimeSource.GetMonotonicTimestamp());

     if (action.Type() == NodeLookupResult::kKeepSearching)
     {
         // No change in iterator
         return;
     }

     // final result, handle either success or failure
     const PeerId peerId     = current->GetRequest().GetPeerId();
     NodeListener * listener = current->GetListener();
     mActiveLookups.Erase(current);

     Dnssd::Resolver::Instance().NodeIdResolutionNoLongerNeeded(peerId);

     // ensure action is taken AFTER the current current lookup is marked complete
     // This allows failure handlers to deallocate structures that may
     // contain the active lookup data as a member (intrusive lists members)
     switch (action.Type())
     {
     case NodeLookupResult::kLookupError:
         listener->OnNodeAddressResolutionFailed(peerId, action.ErrorResult());
         break;
     case NodeLookupResult::kLookupSuccess:
         listener->OnNodeAddressResolved(peerId, action.ResolveResult());
         break;
     default:
         ChipLogError(Discovery, "Unexpected lookup state (not success or fail).");
         break;
     }
 }

 void Resolver::HandleTimer()
 {
     auto it = mActiveLookups.begin();
     while (it != mActiveLookups.end())
     {
         auto current = it;
         it++;

         HandleAction(current);
     }

     ReArmTimer();
 }

 void Resolver::OnOperationalNodeResolutionFailed(const PeerId & peerId, CHIP_ERROR error)
 {
     auto it = mActiveLookups.begin();
     while (it != mActiveLookups.end())
     {
         auto current = it;
         it++;
         if (current->GetRequest().GetPeerId() != peerId)
         {
             continue;
         }

         NodeListener * listener = current->GetListener();
         mActiveLookups.Erase(current);

         Dnssd::Resolver::Instance().NodeIdResolutionNoLongerNeeded(peerId);

         // Failure callback only called after iterator was cleared:
         // This allows failure handlers to deallocate structures that may
         // contain the active lookup data as a member (intrusive lists members)
         listener->OnNodeAddressResolutionFailed(peerId, error);
     }
     ReArmTimer();
 }

 void Resolver::ReArmTimer()
 {
     mSystemLayer->CancelTimer(&OnResolveTimer, static_cast<void *>(this));

     System::Clock::Timestamp now = mTimeSource.GetMonotonicTimestamp();

     System::Clock::Timeout nextTimeout = kInvalidTimeout;
     for (auto & activeLookup : mActiveLookups)
     {
         System::Clock::Timeout timeout = activeLookup.NextEventTimeout(now);

         if (timeout < nextTimeout)
         {
             nextTimeout = timeout;
         }
     }

     if (nextTimeout == kInvalidTimeout)
     {
 #if CHIP_MINMDNS_HIGH_VERBOSITY
         // Generally this is only expected when no active lookups exist
         ChipLogProgress(Discovery, "Discovery does not require any more timeouts");
 #endif
         return;
     }

     CHIP_ERROR err = mSystemLayer->StartTimer(nextTimeout, &OnResolveTimer, static_cast<void *>(this));
     if (err != CHIP_NO_ERROR)
     {
         ChipLogError(Discovery, "Timer schedule error %s assumed permanent", err.AsString());

         // Clear out all active lookups: without timers there is no guarantee of success
         auto it = mActiveLookups.begin();
         while (it != mActiveLookups.end())
         {
             const PeerId peerId     = it->GetRequest().GetPeerId();
             NodeListener * listener = it->GetListener();

             mActiveLookups.Erase(it);
             it = mActiveLookups.begin();

             Dnssd::Resolver::Instance().NodeIdResolutionNoLongerNeeded(peerId);
             // Callback only called after active lookup is cleared
             // This allows failure handlers to deallocate structures that may
             // contain the active lookup data as a member (intrusive lists members)
             listener->OnNodeAddressResolutionFailed(peerId, err);
         }
     }
 }

 } // namespace Impl

 Resolver & Resolver::Instance()
 {
     static Impl::Resolver gResolver;
     return gResolver;
 }

 } // namespace AddressResolve
 } // namespace chip
	/*
	*
	* Copyright (c) 2022 Project CHIP Authors
	*
	* Licensed under the Apache License, Version 2.0 (the "License");
	* you may not use this file except in compliance with the License.
	* You may obtain a copy of the License at
	*
	* http://www.apache.org/licenses/LICENSE-2.0
	*
	* Unless required by applicable law or agreed to in writing, software
	* distributed under the License is distributed on an "AS IS" BASIS,
	* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	* See the License for the specific language governing permissions and
	* limitations under the License.
	*/

	#include <lib/address_resolve/AddressResolve_DefaultImpl.h>

	namespace chip {
	namespace AddressResolve {
	namespace Impl {
	namespace {

	static constexpr System::Clock::Timeout kInvalidTimeout{ System::Clock::Timeout::max() };

	} // namespace

	void NodeLookupHandle::ResetForLookup(System::Clock::Timestamp now, const NodeLookupRequest & request)
	{
	mRequestStartTime = now;
	mRequest = request;
	mResults = NodeLookupResults();
	}

	void NodeLookupHandle::LookupResult(const ResolveResult & result)
	{
	auto score = Dnssd::IPAddressSorter::ScoreIpAddress(result.address.GetIPAddress(), result.address.GetInterface());
	[[maybe_unused]] bool success = mResults.UpdateResults(result, score);

	#if CHIP_PROGRESS_LOGGING
	char addr_string[Transport::PeerAddress::kMaxToStringSize];
	result.address.ToString(addr_string);

	if (success)
	{
	ChipLogProgress(Discovery, "%s: new best score: %u", addr_string, to_underlying(score));
	}
	else
	{
	ChipLogProgress(Discovery, "%s: score has not improved: %u", addr_string, to_underlying(score));
	}
	#endif
	}

	System::Clock::Timeout NodeLookupHandle::NextEventTimeout(System::Clock::Timestamp now)
	{
	const System::Clock::Timestamp elapsed = now - mRequestStartTime;

	if (elapsed < mRequest.GetMinLookupTime())
	{
	return mRequest.GetMinLookupTime() - elapsed;
	}

	if (HasLookupResult())
	{
	// We can get here if we got our result before our min lookup time had
	// elapsed, but time has passed between then and this attempt to re-arm
	// the timer, such that now we are past our min lookup time. For
	// example, this can happen because the timer is a bit delayed in firing
	// but is now being re-scheduled due to a cancellation of a lookup or
	// start of a new lookup. Or it could happen because
	// OnOperationalNodeResolved got called close to our min lookup time,
	// and we crossed that line while going through mActiveLookups and
	// before we got to calling ReArmTimer.
	//
	// In this case, we should just fire the timer ASAP, since our min
	// lookup time has elapsed and we have results.
	return System::Clock::Timeout::zero();
	}

	if (elapsed < mRequest.GetMaxLookupTime())
	{
	return mRequest.GetMaxLookupTime() - elapsed;
	}

	ChipLogError(Discovery, "Unexpected timeout: lookup should have been cleaned already.");
	return System::Clock::Timeout::zero();
	}

	NodeLookupAction NodeLookupHandle::NextAction(System::Clock::Timestamp now)
	{
	const System::Clock::Timestamp elapsed = now - mRequestStartTime;

	ChipLogProgress(Discovery, "Checking node lookup status after %lu ms", static_cast<unsigned long>(elapsed.count()));

	// We are still within the minimal search time. Wait for more results.
	if (elapsed < mRequest.GetMinLookupTime())
	{
	ChipLogProgress(Discovery, "Keeping DNSSD lookup active");
	return NodeLookupAction::KeepSearching();
	}

	// Minimal time to search reached. If any IP available, ready to return it.
	if (HasLookupResult())
	{
	auto result = TakeLookupResult();
	return NodeLookupAction::Success(result);
	}

	// Give up if the maximum search time has been reached
	if (elapsed >= mRequest.GetMaxLookupTime())
	{
	return NodeLookupAction::Error(CHIP_ERROR_TIMEOUT);
	}

	return NodeLookupAction::KeepSearching();
	}

	bool NodeLookupResults::UpdateResults(const ResolveResult & result, const Dnssd::IPAddressSorter::IpScore newScore)
	{
	uint8_t insertAtIndex = 0;
	for (; insertAtIndex < kNodeLookupResultsLen; insertAtIndex++)
	{
	if (insertAtIndex >= count)
	{
	// This is a new entry.
	break;
	}

	auto & oldAddress = results[insertAtIndex].address;
	auto oldScore = Dnssd::IPAddressSorter::ScoreIpAddress(oldAddress.GetIPAddress(), oldAddress.GetInterface());
	if (newScore > oldScore)
	{
	// This is a score update, it will replace a previous entry.
	break;
	}
	}

	if (insertAtIndex == kNodeLookupResultsLen)
	{
	return false;
	}

	// Move the following valid entries one level down.
	for (auto i = count; i > insertAtIndex; i--)
	{
	if (i >= kNodeLookupResultsLen)
	{
	continue;
	}

	results[i] = results[i - 1];
	}

	// If the number of valid entries is less than the size of the array there is an additional entry.
	if (count < kNodeLookupResultsLen)
	{
	count++;
	}

	auto & updatedResult = results[insertAtIndex];
	updatedResult = result;
	if (!updatedResult.address.GetIPAddress().IsIPv6LinkLocal())
	{
	// Only use the DNS-SD resolution's InterfaceID for addresses that are IPv6 LLA.
	// For all other addresses, we should rely on the device's routing table to route messages sent.
	// Forcing messages down an InterfaceId might fail. For example, in bridged networks like Thread,
	// mDNS advertisements are not usually received on the same interface the peer is reachable on.
	updatedResult.address.SetInterface(Inet::InterfaceId::Null());
	ChipLogDetail(Discovery, "Lookup clearing interface for non LL address");
	}

	return true;
	}

	CHIP_ERROR Resolver::LookupNode(const NodeLookupRequest & request, Impl::NodeLookupHandle & handle)
	{
	VerifyOrReturnError(mSystemLayer != nullptr, CHIP_ERROR_INCORRECT_STATE);

	handle.ResetForLookup(mTimeSource.GetMonotonicTimestamp(), request);
	ReturnErrorOnFailure(Dnssd::Resolver::Instance().ResolveNodeId(request.GetPeerId()));
	mActiveLookups.PushBack(&handle);
	ReArmTimer();
	return CHIP_NO_ERROR;
	}

	CHIP_ERROR Resolver::TryNextResult(Impl::NodeLookupHandle & handle)
	{
	VerifyOrReturnError(!mActiveLookups.Contains(&handle), CHIP_ERROR_INCORRECT_STATE);
	VerifyOrReturnError(handle.HasLookupResult(), CHIP_ERROR_WELL_EMPTY);

	auto listener = handle.GetListener();
	auto peerId = handle.GetRequest().GetPeerId();
	auto result = handle.TakeLookupResult();
	listener->OnNodeAddressResolved(peerId, result);
	return CHIP_NO_ERROR;
	}

	CHIP_ERROR Resolver::CancelLookup(Impl::NodeLookupHandle & handle, FailureCallback cancel_method)
	{
	VerifyOrReturnError(handle.IsActive(), CHIP_ERROR_INVALID_ARGUMENT);
	mActiveLookups.Remove(&handle);
	Dnssd::Resolver::Instance().NodeIdResolutionNoLongerNeeded(handle.GetRequest().GetPeerId());

	// Adjust any timing updates.
	ReArmTimer();

	if (cancel_method == FailureCallback::Call)
	{
	handle.GetListener()->OnNodeAddressResolutionFailed(handle.GetRequest().GetPeerId(), CHIP_ERROR_CANCELLED);
	}

	// TODO: There should be some form of cancel into Dnssd::Resolver::Instance()
	// to stop any resolution mechanism if applicable.
	//
	// Current code just removes the internal list and any callbacks of resolution will
	// be ignored. This works from the perspective of the caller of this method,
	// but may be wasteful by letting dnssd still work in the background.

	return CHIP_NO_ERROR;
	}

	CHIP_ERROR Resolver::Init(System::Layer * systemLayer)
	{
	mSystemLayer = systemLayer;
	Dnssd::Resolver::Instance().SetOperationalDelegate(this);
	return CHIP_NO_ERROR;
	}

	void Resolver::Shutdown()
	{
	while (mActiveLookups.begin() != mActiveLookups.end())
	{
	auto current = mActiveLookups.begin();

	const PeerId peerId = current->GetRequest().GetPeerId();
	NodeListener * listener = current->GetListener();

	mActiveLookups.Erase(current);

	Dnssd::Resolver::Instance().NodeIdResolutionNoLongerNeeded(peerId);
	// Failure callback only called after iterator was cleared:
	// This allows failure handlers to deallocate structures that may
	// contain the active lookup data as a member (intrusive lists members)
	listener->OnNodeAddressResolutionFailed(peerId, CHIP_ERROR_SHUT_DOWN);
	}

	// Re-arm of timer is expected to cancel any active timer as the
	// internal list of active lookups is empty at this point.
	ReArmTimer();

	mSystemLayer = nullptr;
	Dnssd::Resolver::Instance().SetOperationalDelegate(nullptr);
	}

	void Resolver::OnOperationalNodeResolved(const Dnssd::ResolvedNodeData & nodeData)
	{
	auto it = mActiveLookups.begin();
	while (it != mActiveLookups.end())
	{
	auto current = it;
	it++;
	if (current->GetRequest().GetPeerId() != nodeData.operationalData.peerId)
	{
	continue;
	}

	ResolveResult result;

	result.address.SetPort(nodeData.resolutionData.port);
	result.address.SetInterface(nodeData.resolutionData.interfaceId);
	result.mrpRemoteConfig = nodeData.resolutionData.GetRemoteMRPConfig();
	result.supportsTcp = nodeData.resolutionData.supportsTcp;

	for (size_t i = 0; i < nodeData.resolutionData.numIPs; i++)
	{
	#if !INET_CONFIG_ENABLE_IPV4
	if (!nodeData.resolutionData.ipAddress[i].IsIPv6())
	{
	ChipLogError(Discovery, "Skipping IPv4 address during operational resolve.");
	continue;
	}
	#endif
	result.address.SetIPAddress(nodeData.resolutionData.ipAddress[i]);
	current->LookupResult(result);
	}

	HandleAction(current);
	}

	ReArmTimer();
	}

	void Resolver::HandleAction(IntrusiveList<NodeLookupHandle>::Iterator & current)
	{
	const NodeLookupAction action = current->NextAction(mTimeSource.GetMonotonicTimestamp());

	if (action.Type() == NodeLookupResult::kKeepSearching)
	{
	// No change in iterator
	return;
	}

	// final result, handle either success or failure
	const PeerId peerId = current->GetRequest().GetPeerId();
	NodeListener * listener = current->GetListener();
	mActiveLookups.Erase(current);

	Dnssd::Resolver::Instance().NodeIdResolutionNoLongerNeeded(peerId);

	// ensure action is taken AFTER the current current lookup is marked complete
	// This allows failure handlers to deallocate structures that may
	// contain the active lookup data as a member (intrusive lists members)
	switch (action.Type())
	{
	case NodeLookupResult::kLookupError:
	listener->OnNodeAddressResolutionFailed(peerId, action.ErrorResult());
	break;
	case NodeLookupResult::kLookupSuccess:
	listener->OnNodeAddressResolved(peerId, action.ResolveResult());
	break;
	default:
	ChipLogError(Discovery, "Unexpected lookup state (not success or fail).");
	break;
	}
	}

	void Resolver::HandleTimer()
	{
	auto it = mActiveLookups.begin();
	while (it != mActiveLookups.end())
	{
	auto current = it;
	it++;

	HandleAction(current);
	}

	ReArmTimer();
	}

	void Resolver::OnOperationalNodeResolutionFailed(const PeerId & peerId, CHIP_ERROR error)
	{
	auto it = mActiveLookups.begin();
	while (it != mActiveLookups.end())
	{
	auto current = it;
	it++;
	if (current->GetRequest().GetPeerId() != peerId)
	{
	continue;
	}

	NodeListener * listener = current->GetListener();
	mActiveLookups.Erase(current);

	Dnssd::Resolver::Instance().NodeIdResolutionNoLongerNeeded(peerId);

	// Failure callback only called after iterator was cleared:
	// This allows failure handlers to deallocate structures that may
	// contain the active lookup data as a member (intrusive lists members)
	listener->OnNodeAddressResolutionFailed(peerId, error);
	}
	ReArmTimer();
	}

	void Resolver::ReArmTimer()
	{
	mSystemLayer->CancelTimer(&OnResolveTimer, static_cast<void *>(this));

	System::Clock::Timestamp now = mTimeSource.GetMonotonicTimestamp();

	System::Clock::Timeout nextTimeout = kInvalidTimeout;
	for (auto & activeLookup : mActiveLookups)
	{
	System::Clock::Timeout timeout = activeLookup.NextEventTimeout(now);

	if (timeout < nextTimeout)
	{
	nextTimeout = timeout;
	}
	}

	if (nextTimeout == kInvalidTimeout)
	{
	#if CHIP_MINMDNS_HIGH_VERBOSITY
	// Generally this is only expected when no active lookups exist
	ChipLogProgress(Discovery, "Discovery does not require any more timeouts");
	#endif
	return;
	}

	CHIP_ERROR err = mSystemLayer->StartTimer(nextTimeout, &OnResolveTimer, static_cast<void *>(this));
	if (err != CHIP_NO_ERROR)
	{
	ChipLogError(Discovery, "Timer schedule error %s assumed permanent", err.AsString());

	// Clear out all active lookups: without timers there is no guarantee of success
	auto it = mActiveLookups.begin();
	while (it != mActiveLookups.end())
	{
	const PeerId peerId = it->GetRequest().GetPeerId();
	NodeListener * listener = it->GetListener();

	mActiveLookups.Erase(it);
	it = mActiveLookups.begin();

	Dnssd::Resolver::Instance().NodeIdResolutionNoLongerNeeded(peerId);
	// Callback only called after active lookup is cleared
	// This allows failure handlers to deallocate structures that may
	// contain the active lookup data as a member (intrusive lists members)
	listener->OnNodeAddressResolutionFailed(peerId, err);
	}
	}
	}

	} // namespace Impl

	Resolver & Resolver::Instance()
	{
	static Impl::Resolver gResolver;
	return gResolver;
	}

	} // namespace AddressResolve
	} // namespace chip