src/detail/face-impl.hpp - ndn-cxx - Gitiles

 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /*
  * Copyright (c) 2013-2017 Regents of the University of California.
  *
  * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
  *
  * ndn-cxx library is free software: you can redistribute it and/or modify it under the
  * terms of the GNU Lesser General Public License as published by the Free Software
  * Foundation, either version 3 of the License, or (at your option) any later version.
  *
  * ndn-cxx library is distributed in the hope that it will be useful, but WITHOUT ANY
  * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A
  * PARTICULAR PURPOSE.  See the GNU Lesser General Public License for more details.
  *
  * You should have received copies of the GNU General Public License and GNU Lesser
  * General Public License along with ndn-cxx, e.g., in COPYING.md file.  If not, see
  * <http://www.gnu.org/licenses/>.
  *
  * See AUTHORS.md for complete list of ndn-cxx authors and contributors.
  */

 #ifndef NDN_DETAIL_FACE_IMPL_HPP
 #define NDN_DETAIL_FACE_IMPL_HPP

 #include "../face.hpp"
 #include "container-with-on-empty-signal.hpp"
 #include "lp-field-tag.hpp"
 #include "pending-interest.hpp"
 #include "registered-prefix.hpp"
 #include "../lp/packet.hpp"
 #include "../lp/tags.hpp"
 #include "../mgmt/nfd/command-options.hpp"
 #include "../mgmt/nfd/controller.hpp"
 #include "../transport/tcp-transport.hpp"
 #include "../transport/unix-transport.hpp"
 #include "../util/config-file.hpp"
 #include "../util/logger.hpp"
 #include "../util/scheduler.hpp"
 #include "../util/signal.hpp"

 NDN_LOG_INIT(ndn.Face);
 // INFO level: prefix registration, etc.
 //
 // DEBUG level: packet logging.
 // Each log entry starts with a direction symbol ('<' denotes an outgoing packet, '>' denotes an
 // incoming packet) and a packet type symbol ('I' denotes an Interest, 'D' denotes a Data, 'N'
 // denotes a Nack). Interest is printed as its string representation, Data is printed as name only,
 // Nack is printed as the Interest followed by the Nack reason and delimited by a '~' symbol. A
 // log line about an incoming packet may be followed by zero or more lines about Interest matching
 // InterestFilter, Data satisfying Interest, or Nack rejecting Interest, which are also written at
 // DEBUG level.
 //
 // TRACE level: more detailed unstructured messages.

 namespace ndn {

 /** @brief implementation detail of Face
  */
 class Face::Impl : noncopyable
 {
 public:
   using PendingInterestTable = ContainerWithOnEmptySignal<shared_ptr<PendingInterest>>;
   using InterestFilterTable = std::list<shared_ptr<InterestFilterRecord>>;
   using RegisteredPrefixTable = ContainerWithOnEmptySignal<shared_ptr<RegisteredPrefix>>;

   explicit
   Impl(Face& face)
     : m_face(face)
     , m_scheduler(m_face.getIoService())
     , m_processEventsTimeoutEvent(m_scheduler)
   {
     auto postOnEmptyPitOrNoRegisteredPrefixes = [this] {
       this->m_face.getIoService().post([this] { this->onEmptyPitOrNoRegisteredPrefixes(); });
       // without this extra "post", transport can get paused (-async_read) and then resumed
       // (+async_read) from within onInterest/onData callback.  After onInterest/onData
       // finishes, there is another +async_read with the same memory block.  A few of such
       // async_read duplications can cause various effects and result in segfault.
     };

     m_pendingInterestTable.onEmpty.connect(postOnEmptyPitOrNoRegisteredPrefixes);
     m_registeredPrefixTable.onEmpty.connect(postOnEmptyPitOrNoRegisteredPrefixes);
   }

 public: // consumer
   void
   asyncExpressInterest(shared_ptr<const Interest> interest,
                        const DataCallback& afterSatisfied,
                        const NackCallback& afterNacked,
                        const TimeoutCallback& afterTimeout)
   {
     this->ensureConnected(true);

     const Interest& interest2 = *interest;
     auto i = m_pendingInterestTable.insert(make_shared<PendingInterest>(
       std::move(interest), afterSatisfied, afterNacked, afterTimeout, ref(m_scheduler))).first;
     PendingInterest& entry = **i;
     entry.setDeleter([this, i] { m_pendingInterestTable.erase(i); });

     lp::Packet lpPacket;
     addFieldFromTag<lp::NextHopFaceIdField, lp::NextHopFaceIdTag>(lpPacket, interest2);
     addFieldFromTag<lp::CongestionMarkField, lp::CongestionMarkTag>(lpPacket, interest2);

     m_face.m_transport->send(finishEncoding(std::move(lpPacket), interest2.wireEncode(),
                                             'I', interest2.getName()));
     entry.recordForwarding();
   }

   void
   asyncRemovePendingInterest(const PendingInterestId* pendingInterestId)
   {
     m_pendingInterestTable.remove_if(MatchPendingInterestId(pendingInterestId));
   }

   void
   asyncRemoveAllPendingInterests()
   {
     m_pendingInterestTable.clear();
   }

   /** @return whether the Data should be sent to the forwarder, if it does not come from the forwarder
    */
   bool
   satisfyPendingInterests(const Data& data)
   {
     bool hasAppMatch = false, hasForwarderMatch = false;
     for (auto i = m_pendingInterestTable.begin(); i != m_pendingInterestTable.end(); ) {
       shared_ptr<PendingInterest> entry = *i;
       if (!entry->getInterest()->matchesData(data)) {
         ++i;
         continue;
       }

       NDN_LOG_DEBUG("   satisfying " << *entry->getInterest() << " from " << entry->getOrigin());
       i = m_pendingInterestTable.erase(i);

       if (entry->getOrigin() == PendingInterestOrigin::APP) {
         hasAppMatch = true;
         entry->invokeDataCallback(data);
       }
       else {
         hasForwarderMatch = true;
       }
     }
     // if Data matches no pending Interest record, it is sent to the forwarder as unsolicited Data
     return hasForwarderMatch || !hasAppMatch;
   }

   /** @return a Nack to be sent to the forwarder, or nullopt if no Nack should be sent
    */
   optional<lp::Nack>
   nackPendingInterests(const lp::Nack& nack)
   {
     optional<lp::Nack> outNack;
     for (auto i = m_pendingInterestTable.begin(); i != m_pendingInterestTable.end(); ) {
       shared_ptr<PendingInterest> entry = *i;
       if (!nack.getInterest().matchesInterest(*entry->getInterest())) {
         ++i;
         continue;
       }

       NDN_LOG_DEBUG("   nacking " << *entry->getInterest() << " from " << entry->getOrigin());

       optional<lp::Nack> outNack1 = entry->recordNack(nack);
       if (!outNack1) {
         ++i;
         continue;
       }

       if (entry->getOrigin() == PendingInterestOrigin::APP) {
         entry->invokeNackCallback(*outNack1);
       }
       else {
         outNack = outNack1;
       }
       i = m_pendingInterestTable.erase(i);
     }
     // send "least severe" Nack from any PendingInterest record originated from forwarder, because
     // it is unimportant to consider Nack reason for the unlikely case when forwarder sends multiple
     // Interests to an app in a short while
     return outNack;
   }

 public: // producer
   void
   asyncSetInterestFilter(shared_ptr<InterestFilterRecord> interestFilterRecord)
   {
     NDN_LOG_INFO("setting InterestFilter: " << interestFilterRecord->getFilter());
     m_interestFilterTable.push_back(std::move(interestFilterRecord));
   }

   void
   asyncUnsetInterestFilter(const InterestFilterId* interestFilterId)
   {
     InterestFilterTable::iterator i = std::find_if(m_interestFilterTable.begin(),
                                                    m_interestFilterTable.end(),
                                                    MatchInterestFilterId(interestFilterId));
     if (i != m_interestFilterTable.end()) {
       NDN_LOG_INFO("unsetting InterestFilter: " << (*i)->getFilter());
       m_interestFilterTable.erase(i);
     }
   }

   void
   processIncomingInterest(shared_ptr<const Interest> interest)
   {
     const Interest& interest2 = *interest;
     auto i = m_pendingInterestTable.insert(make_shared<PendingInterest>(
       std::move(interest), ref(m_scheduler))).first;
     PendingInterest& entry = **i;
     entry.setDeleter([this, i] { m_pendingInterestTable.erase(i); });

     for (const auto& filter : m_interestFilterTable) {
       if (filter->doesMatch(interest2.getName())) {
         NDN_LOG_DEBUG("   matches " << filter->getFilter());
         filter->invokeInterestCallback(interest2);
         entry.recordForwarding();
       }
     }
   }

   void
   asyncPutData(const Data& data)
   {
     bool shouldSendToForwarder = satisfyPendingInterests(data);
     if (!shouldSendToForwarder) {
       return;
     }

     this->ensureConnected(true);

     lp::Packet lpPacket;
     addFieldFromTag<lp::CachePolicyField, lp::CachePolicyTag>(lpPacket, data);
     addFieldFromTag<lp::CongestionMarkField, lp::CongestionMarkTag>(lpPacket, data);

     m_face.m_transport->send(finishEncoding(std::move(lpPacket), data.wireEncode(),
                                             'D', data.getName()));
   }

   void
   asyncPutNack(const lp::Nack& nack)
   {
     optional<lp::Nack> outNack = nackPendingInterests(nack);
     if (!outNack) {
       return;
     }

     this->ensureConnected(true);

     lp::Packet lpPacket;
     lpPacket.add<lp::NackField>(outNack->getHeader());
     addFieldFromTag<lp::CongestionMarkField, lp::CongestionMarkTag>(lpPacket, *outNack);

     const Interest& interest = outNack->getInterest();
     m_face.m_transport->send(finishEncoding(std::move(lpPacket), interest.wireEncode(),
                                             'N', interest.getName()));
   }

 public: // prefix registration
   const RegisteredPrefixId*
   registerPrefix(const Name& prefix,
                  shared_ptr<InterestFilterRecord> filter,
                  const RegisterPrefixSuccessCallback& onSuccess,
                  const RegisterPrefixFailureCallback& onFailure,
                  uint64_t flags,
                  const nfd::CommandOptions& options)
   {
     NDN_LOG_INFO("registering prefix: " << prefix);
     auto record = make_shared<RegisteredPrefix>(prefix, filter, options);

     nfd::ControlParameters params;
     params.setName(prefix);
     params.setFlags(flags);
     m_face.m_nfdController->start<nfd::RibRegisterCommand>(
       params,
       [=] (const nfd::ControlParameters&) { this->afterPrefixRegistered(record, onSuccess); },
       [=] (const nfd::ControlResponse& resp) {
         NDN_LOG_INFO("register prefix failed: " << record->getPrefix());
         onFailure(record->getPrefix(), resp.getText());
       },
       options);

     return reinterpret_cast<const RegisteredPrefixId*>(record.get());
   }

   void
   afterPrefixRegistered(shared_ptr<RegisteredPrefix> registeredPrefix,
                         const RegisterPrefixSuccessCallback& onSuccess)
   {
     NDN_LOG_INFO("registered prefix: " << registeredPrefix->getPrefix());
     m_registeredPrefixTable.insert(registeredPrefix);

     if (registeredPrefix->getFilter() != nullptr) {
       // it was a combined operation
       m_interestFilterTable.push_back(registeredPrefix->getFilter());
     }

     if (onSuccess != nullptr) {
       onSuccess(registeredPrefix->getPrefix());
     }
   }

   void
   asyncUnregisterPrefix(const RegisteredPrefixId* registeredPrefixId,
                         const UnregisterPrefixSuccessCallback& onSuccess,
                         const UnregisterPrefixFailureCallback& onFailure)
   {
     auto i = std::find_if(m_registeredPrefixTable.begin(),
                           m_registeredPrefixTable.end(),
                           MatchRegisteredPrefixId(registeredPrefixId));
     if (i != m_registeredPrefixTable.end()) {
       RegisteredPrefix& record = **i;
       const shared_ptr<InterestFilterRecord>& filter = record.getFilter();

       if (filter != nullptr) {
         // it was a combined operation
         m_interestFilterTable.remove(filter);
       }

       NDN_LOG_INFO("unregistering prefix: " << record.getPrefix());

       nfd::ControlParameters params;
       params.setName(record.getPrefix());
       m_face.m_nfdController->start<nfd::RibUnregisterCommand>(
         params,
         [=] (const nfd::ControlParameters&) { this->finalizeUnregisterPrefix(i, onSuccess); },
         [=] (const nfd::ControlResponse& resp) {
           NDN_LOG_INFO("unregister prefix failed: " << params.getName());
           onFailure(resp.getText());
         },
         record.getCommandOptions());
     }
     else {
       if (onFailure != nullptr) {
         onFailure("Unrecognized PrefixId");
       }
     }

     // there cannot be two registered prefixes with the same id
   }

   void
   finalizeUnregisterPrefix(RegisteredPrefixTable::iterator item,
                            const UnregisterPrefixSuccessCallback& onSuccess)
   {
     NDN_LOG_INFO("unregistered prefix: " << (*item)->getPrefix());
     m_registeredPrefixTable.erase(item);

     if (onSuccess != nullptr) {
       onSuccess();
     }
   }

 public: // IO routine
   void
   ensureConnected(bool wantResume)
   {
     if (!m_face.m_transport->isConnected())
       m_face.m_transport->connect(m_face.m_ioService,
                                   [=] (const Block& wire) { m_face.onReceiveElement(wire); });

     if (wantResume && !m_face.m_transport->isReceiving()) {
       m_face.m_transport->resume();
     }
   }

   void
   onEmptyPitOrNoRegisteredPrefixes()
   {
     if (m_pendingInterestTable.empty() && m_registeredPrefixTable.empty()) {
       m_face.m_transport->pause();
       if (!m_ioServiceWork) {
         m_processEventsTimeoutEvent.cancel();
       }
     }
   }

 private:
   /** @brief Finish packet encoding
    *  @param lpPacket NDNLP packet without FragmentField
    *  @param wire wire encoding of Interest or Data
    *  @param pktType packet type, 'I' for Interest, 'D' for Data, 'N' for Nack
    *  @param name packet name
    *  @return wire encoding of either NDNLP or bare network packet
    *  @throw Face::OversizedPacketError wire encoding exceeds limit
    */
   Block
   finishEncoding(lp::Packet&& lpPacket, Block wire, char pktType, const Name& name)
   {
     if (!lpPacket.empty()) {
       lpPacket.add<lp::FragmentField>(std::make_pair(wire.begin(), wire.end()));
       wire = lpPacket.wireEncode();
     }

     if (wire.size() > MAX_NDN_PACKET_SIZE) {
       BOOST_THROW_EXCEPTION(Face::OversizedPacketError(pktType, name, wire.size()));
     }

     return wire;
   }

 private:
   Face& m_face;
   util::Scheduler m_scheduler;
   util::scheduler::ScopedEventId m_processEventsTimeoutEvent;

   PendingInterestTable m_pendingInterestTable;
   InterestFilterTable m_interestFilterTable;
   RegisteredPrefixTable m_registeredPrefixTable;

   unique_ptr<boost::asio::io_service::work> m_ioServiceWork; // if thread needs to be preserved

   friend class Face;
 };

 } // namespace ndn

 #endif // NDN_DETAIL_FACE_IMPL_HPP
	/* -- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -- */
	/*
	* Copyright (c) 2013-2017 Regents of the University of California.
	*
	* This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
	*
	* ndn-cxx library is free software: you can redistribute it and/or modify it under the
	* terms of the GNU Lesser General Public License as published by the Free Software
	* Foundation, either version 3 of the License, or (at your option) any later version.
	*
	* ndn-cxx library is distributed in the hope that it will be useful, but WITHOUT ANY
	* WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A
	* PARTICULAR PURPOSE. See the GNU Lesser General Public License for more details.
	*
	* You should have received copies of the GNU General Public License and GNU Lesser
	* General Public License along with ndn-cxx, e.g., in COPYING.md file. If not, see
	* <http://www.gnu.org/licenses/>.
	*
	* See AUTHORS.md for complete list of ndn-cxx authors and contributors.
	*/

	#ifndef NDN_DETAIL_FACE_IMPL_HPP
	#define NDN_DETAIL_FACE_IMPL_HPP

	#include "../face.hpp"
	#include "container-with-on-empty-signal.hpp"
	#include "lp-field-tag.hpp"
	#include "pending-interest.hpp"
	#include "registered-prefix.hpp"
	#include "../lp/packet.hpp"
	#include "../lp/tags.hpp"
	#include "../mgmt/nfd/command-options.hpp"
	#include "../mgmt/nfd/controller.hpp"
	#include "../transport/tcp-transport.hpp"
	#include "../transport/unix-transport.hpp"
	#include "../util/config-file.hpp"
	#include "../util/logger.hpp"
	#include "../util/scheduler.hpp"
	#include "../util/signal.hpp"

	NDN_LOG_INIT(ndn.Face);
	// INFO level: prefix registration, etc.
	//
	// DEBUG level: packet logging.
	// Each log entry starts with a direction symbol ('<' denotes an outgoing packet, '>' denotes an
	// incoming packet) and a packet type symbol ('I' denotes an Interest, 'D' denotes a Data, 'N'
	// denotes a Nack). Interest is printed as its string representation, Data is printed as name only,
	// Nack is printed as the Interest followed by the Nack reason and delimited by a '~' symbol. A
	// log line about an incoming packet may be followed by zero or more lines about Interest matching
	// InterestFilter, Data satisfying Interest, or Nack rejecting Interest, which are also written at
	// DEBUG level.
	//
	// TRACE level: more detailed unstructured messages.

	namespace ndn {

	/** @brief implementation detail of Face
	*/
	class Face::Impl : noncopyable
	{
	public:
	using PendingInterestTable = ContainerWithOnEmptySignal<shared_ptr<PendingInterest>>;
	using InterestFilterTable = std::list<shared_ptr<InterestFilterRecord>>;
	using RegisteredPrefixTable = ContainerWithOnEmptySignal<shared_ptr<RegisteredPrefix>>;

	explicit
	Impl(Face& face)
	: m_face(face)
	, m_scheduler(m_face.getIoService())
	, m_processEventsTimeoutEvent(m_scheduler)
	{
	auto postOnEmptyPitOrNoRegisteredPrefixes = [this] {
	this->m_face.getIoService().post([this] { this->onEmptyPitOrNoRegisteredPrefixes(); });
	// without this extra "post", transport can get paused (-async_read) and then resumed
	// (+async_read) from within onInterest/onData callback. After onInterest/onData
	// finishes, there is another +async_read with the same memory block. A few of such
	// async_read duplications can cause various effects and result in segfault.
	};

	m_pendingInterestTable.onEmpty.connect(postOnEmptyPitOrNoRegisteredPrefixes);
	m_registeredPrefixTable.onEmpty.connect(postOnEmptyPitOrNoRegisteredPrefixes);
	}

	public: // consumer
	void
	asyncExpressInterest(shared_ptr<const Interest> interest,
	const DataCallback& afterSatisfied,
	const NackCallback& afterNacked,
	const TimeoutCallback& afterTimeout)
	{
	this->ensureConnected(true);

	const Interest& interest2 = *interest;
	auto i = m_pendingInterestTable.insert(make_shared<PendingInterest>(
	std::move(interest), afterSatisfied, afterNacked, afterTimeout, ref(m_scheduler))).first;
	PendingInterest& entry = **i;
	entry.setDeleter([this, i] { m_pendingInterestTable.erase(i); });

	lp::Packet lpPacket;
	addFieldFromTag<lp::NextHopFaceIdField, lp::NextHopFaceIdTag>(lpPacket, interest2);
	addFieldFromTag<lp::CongestionMarkField, lp::CongestionMarkTag>(lpPacket, interest2);

	m_face.m_transport->send(finishEncoding(std::move(lpPacket), interest2.wireEncode(),
	'I', interest2.getName()));
	entry.recordForwarding();
	}

	void
	asyncRemovePendingInterest(const PendingInterestId* pendingInterestId)
	{
	m_pendingInterestTable.remove_if(MatchPendingInterestId(pendingInterestId));
	}

	void
	asyncRemoveAllPendingInterests()
	{
	m_pendingInterestTable.clear();
	}

	/** @return whether the Data should be sent to the forwarder, if it does not come from the forwarder
	*/
	bool
	satisfyPendingInterests(const Data& data)
	{
	bool hasAppMatch = false, hasForwarderMatch = false;
	for (auto i = m_pendingInterestTable.begin(); i != m_pendingInterestTable.end(); ) {
	shared_ptr<PendingInterest> entry = *i;
	if (!entry->getInterest()->matchesData(data)) {
	++i;
	continue;
	}

	NDN_LOG_DEBUG(" satisfying " << *entry->getInterest() << " from " << entry->getOrigin());
	i = m_pendingInterestTable.erase(i);

	if (entry->getOrigin() == PendingInterestOrigin::APP) {
	hasAppMatch = true;
	entry->invokeDataCallback(data);
	}
	else {
	hasForwarderMatch = true;
	}
	}
	// if Data matches no pending Interest record, it is sent to the forwarder as unsolicited Data
	return hasForwarderMatch \|\| !hasAppMatch;
	}

	/** @return a Nack to be sent to the forwarder, or nullopt if no Nack should be sent
	*/
	optional<lp::Nack>
	nackPendingInterests(const lp::Nack& nack)
	{
	optional<lp::Nack> outNack;
	for (auto i = m_pendingInterestTable.begin(); i != m_pendingInterestTable.end(); ) {
	shared_ptr<PendingInterest> entry = *i;
	if (!nack.getInterest().matchesInterest(*entry->getInterest())) {
	++i;
	continue;
	}

	NDN_LOG_DEBUG(" nacking " << *entry->getInterest() << " from " << entry->getOrigin());

	optional<lp::Nack> outNack1 = entry->recordNack(nack);
	if (!outNack1) {
	++i;
	continue;
	}

	if (entry->getOrigin() == PendingInterestOrigin::APP) {
	entry->invokeNackCallback(*outNack1);
	}
	else {
	outNack = outNack1;
	}
	i = m_pendingInterestTable.erase(i);
	}
	// send "least severe" Nack from any PendingInterest record originated from forwarder, because
	// it is unimportant to consider Nack reason for the unlikely case when forwarder sends multiple
	// Interests to an app in a short while
	return outNack;
	}

	public: // producer
	void
	asyncSetInterestFilter(shared_ptr<InterestFilterRecord> interestFilterRecord)
	{
	NDN_LOG_INFO("setting InterestFilter: " << interestFilterRecord->getFilter());
	m_interestFilterTable.push_back(std::move(interestFilterRecord));
	}

	void
	asyncUnsetInterestFilter(const InterestFilterId* interestFilterId)
	{
	InterestFilterTable::iterator i = std::find_if(m_interestFilterTable.begin(),
	m_interestFilterTable.end(),
	MatchInterestFilterId(interestFilterId));
	if (i != m_interestFilterTable.end()) {
	NDN_LOG_INFO("unsetting InterestFilter: " << (*i)->getFilter());
	m_interestFilterTable.erase(i);
	}
	}

	void
	processIncomingInterest(shared_ptr<const Interest> interest)
	{
	const Interest& interest2 = *interest;
	auto i = m_pendingInterestTable.insert(make_shared<PendingInterest>(
	std::move(interest), ref(m_scheduler))).first;
	PendingInterest& entry = **i;
	entry.setDeleter([this, i] { m_pendingInterestTable.erase(i); });

	for (const auto& filter : m_interestFilterTable) {
	if (filter->doesMatch(interest2.getName())) {
	NDN_LOG_DEBUG(" matches " << filter->getFilter());
	filter->invokeInterestCallback(interest2);
	entry.recordForwarding();
	}
	}
	}

	void
	asyncPutData(const Data& data)
	{
	bool shouldSendToForwarder = satisfyPendingInterests(data);
	if (!shouldSendToForwarder) {
	return;
	}

	this->ensureConnected(true);

	lp::Packet lpPacket;
	addFieldFromTag<lp::CachePolicyField, lp::CachePolicyTag>(lpPacket, data);
	addFieldFromTag<lp::CongestionMarkField, lp::CongestionMarkTag>(lpPacket, data);

	m_face.m_transport->send(finishEncoding(std::move(lpPacket), data.wireEncode(),
	'D', data.getName()));
	}

	void
	asyncPutNack(const lp::Nack& nack)
	{
	optional<lp::Nack> outNack = nackPendingInterests(nack);
	if (!outNack) {
	return;
	}

	this->ensureConnected(true);

	lp::Packet lpPacket;
	lpPacket.add<lp::NackField>(outNack->getHeader());
	addFieldFromTag<lp::CongestionMarkField, lp::CongestionMarkTag>(lpPacket, *outNack);

	const Interest& interest = outNack->getInterest();
	m_face.m_transport->send(finishEncoding(std::move(lpPacket), interest.wireEncode(),
	'N', interest.getName()));
	}

	public: // prefix registration
	const RegisteredPrefixId*
	registerPrefix(const Name& prefix,
	shared_ptr<InterestFilterRecord> filter,
	const RegisterPrefixSuccessCallback& onSuccess,
	const RegisterPrefixFailureCallback& onFailure,
	uint64_t flags,
	const nfd::CommandOptions& options)
	{
	NDN_LOG_INFO("registering prefix: " << prefix);
	auto record = make_shared<RegisteredPrefix>(prefix, filter, options);

	nfd::ControlParameters params;
	params.setName(prefix);
	params.setFlags(flags);
	m_face.m_nfdController->start<nfd::RibRegisterCommand>(
	params,
	[=] (const nfd::ControlParameters&) { this->afterPrefixRegistered(record, onSuccess); },
	[=] (const nfd::ControlResponse& resp) {
	NDN_LOG_INFO("register prefix failed: " << record->getPrefix());
	onFailure(record->getPrefix(), resp.getText());
	},
	options);

	return reinterpret_cast<const RegisteredPrefixId*>(record.get());
	}

	void
	afterPrefixRegistered(shared_ptr<RegisteredPrefix> registeredPrefix,
	const RegisterPrefixSuccessCallback& onSuccess)
	{
	NDN_LOG_INFO("registered prefix: " << registeredPrefix->getPrefix());
	m_registeredPrefixTable.insert(registeredPrefix);

	if (registeredPrefix->getFilter() != nullptr) {
	// it was a combined operation
	m_interestFilterTable.push_back(registeredPrefix->getFilter());
	}

	if (onSuccess != nullptr) {
	onSuccess(registeredPrefix->getPrefix());
	}
	}

	void
	asyncUnregisterPrefix(const RegisteredPrefixId* registeredPrefixId,
	const UnregisterPrefixSuccessCallback& onSuccess,
	const UnregisterPrefixFailureCallback& onFailure)
	{
	auto i = std::find_if(m_registeredPrefixTable.begin(),
	m_registeredPrefixTable.end(),
	MatchRegisteredPrefixId(registeredPrefixId));
	if (i != m_registeredPrefixTable.end()) {
	RegisteredPrefix& record = **i;
	const shared_ptr<InterestFilterRecord>& filter = record.getFilter();

	if (filter != nullptr) {
	// it was a combined operation
	m_interestFilterTable.remove(filter);
	}

	NDN_LOG_INFO("unregistering prefix: " << record.getPrefix());

	nfd::ControlParameters params;
	params.setName(record.getPrefix());
	m_face.m_nfdController->start<nfd::RibUnregisterCommand>(
	params,
	[=] (const nfd::ControlParameters&) { this->finalizeUnregisterPrefix(i, onSuccess); },
	[=] (const nfd::ControlResponse& resp) {
	NDN_LOG_INFO("unregister prefix failed: " << params.getName());
	onFailure(resp.getText());
	},
	record.getCommandOptions());
	}
	else {
	if (onFailure != nullptr) {
	onFailure("Unrecognized PrefixId");
	}
	}

	// there cannot be two registered prefixes with the same id
	}

	void
	finalizeUnregisterPrefix(RegisteredPrefixTable::iterator item,
	const UnregisterPrefixSuccessCallback& onSuccess)
	{
	NDN_LOG_INFO("unregistered prefix: " << (*item)->getPrefix());
	m_registeredPrefixTable.erase(item);

	if (onSuccess != nullptr) {
	onSuccess();
	}
	}

	public: // IO routine
	void
	ensureConnected(bool wantResume)
	{
	if (!m_face.m_transport->isConnected())
	m_face.m_transport->connect(m_face.m_ioService,
	[=] (const Block& wire) { m_face.onReceiveElement(wire); });

	if (wantResume && !m_face.m_transport->isReceiving()) {
	m_face.m_transport->resume();
	}
	}

	void
	onEmptyPitOrNoRegisteredPrefixes()
	{
	if (m_pendingInterestTable.empty() && m_registeredPrefixTable.empty()) {
	m_face.m_transport->pause();
	if (!m_ioServiceWork) {
	m_processEventsTimeoutEvent.cancel();
	}
	}
	}

	private:
	/** @brief Finish packet encoding
	* @param lpPacket NDNLP packet without FragmentField
	* @param wire wire encoding of Interest or Data
	* @param pktType packet type, 'I' for Interest, 'D' for Data, 'N' for Nack
	* @param name packet name
	* @return wire encoding of either NDNLP or bare network packet
	* @throw Face::OversizedPacketError wire encoding exceeds limit
	*/
	Block
	finishEncoding(lp::Packet&& lpPacket, Block wire, char pktType, const Name& name)
	{
	if (!lpPacket.empty()) {
	lpPacket.add<lp::FragmentField>(std::make_pair(wire.begin(), wire.end()));
	wire = lpPacket.wireEncode();
	}

	if (wire.size() > MAX_NDN_PACKET_SIZE) {
	BOOST_THROW_EXCEPTION(Face::OversizedPacketError(pktType, name, wire.size()));
	}

	return wire;
	}

	private:
	Face& m_face;
	util::Scheduler m_scheduler;
	util::scheduler::ScopedEventId m_processEventsTimeoutEvent;

	PendingInterestTable m_pendingInterestTable;
	InterestFilterTable m_interestFilterTable;
	RegisteredPrefixTable m_registeredPrefixTable;

	unique_ptr<boost::asio::io_service::work> m_ioServiceWork; // if thread needs to be preserved

	friend class Face;
	};

	} // namespace ndn

	#endif // NDN_DETAIL_FACE_IMPL_HPP