NFD Face System design for LinkService http://redmine.named-data.net/issues/2222 and permanent face http://redmine.named-data.net/issues/2491

LAL-face.hpp

// TODO: decide which component is responsible for repairing a link failure in permanent face
// TODO: add details on internal structure of GenericLal

// -------- Face, Lal, Link --------

namespace nfd {
namespace face {

typedef uint64_t FaceId;

enum class FaceStatus {
  DOWN,
  UP
};

class Face
{
public:
  Face(Lal& lal, Link& link);

public: // upper interface connected to forwarding
  void
  sendInterest(const Interest& interest);

  void
  sendData(const Data& interest);

  void
  sendNack(const Nack& interest);

  Signal<Lal, Interest>& afterReceiveInterest;

  Signal<Lal, Data>& afterReceiveData;

  Signal<Lal, Nack>& afterReceiveNack;

public: // static properties
  FaceId
  getId() const; // from Face

  FaceUri
  getLocalUri() const; // from Link

  FaceUri
  getRemoteUri() const; // from Link

  FacePersistency
  getPersistency() const; // (undecided)

  LinkType // point-to-point|multi-access
  getLinkType() const; // from Link

public: // dynamic properties
  FaceState
  getState() const; // from Link

  Signal<Link, FaceState/*old*/, FaceState/*new*/>& afterStateChange;

  FaceCounters
  getCounters() const; // network layer packet counters from Lal, link layer packet and byte counters from Link
};

struct LinkPacket
{
  Block packet;
  NetworkAddress localAddr;
  NetworkAddress remoteAddr;
};

class Link
{
public: // upper interface
  void
  send(const LinkPacket& packet); // increment counter and call .doSend

  Signal<Link, LinkPacket> afterReceive;

private: // upper interface to be overridden by subclass
  virtual void
  doSend(const LinkPacket& packet) = 0;

protected: // upper interface to be invoked by subclass
  void
  receive(const LinkPacket& packet); // increment counter and signal afterReceive

public: // static properties
  FaceUri
  getLocalUri() const;

  FaceUri
  getRemoteUri() const;

  LinkType
  getLinkType() const;

public: // dynamic properties
  FaceState
  getState() const;

  Signal<Link, FaceState/*old*/, FaceState/*new*/> afterStateChange;

  LinkCounters
  getCounters() const; // link layer packet and byte counters

protected:
  void
  changeState(FaceState newState);
};

class Lal
{
public:
  void
  setLink(Link& link);

public: // upper interface connected to forwarding
  void
  sendInterest(const Interest& interest); // increment counter and call .doSendInterest

  void
  sendData(const Data& interest);

  void
  sendNack(const Nack& interest);

  Signal<Lal, Interest> afterReceiveInterest;

  Signal<Lal, Data> afterReceiveData;

  Signal<Lal, Nack> afterReceiveNack;

private: // upper interface to be overridden in subclass
  virtual void
  doSendInterest(const Interest& interest) = 0;

  virtual void
  doSendData(const Data& interest) = 0;

  virtual void
  doSendNack(const Nack& interest) = 0;

protected: // upper interface to be invoked in subclass
  void
  receiveInterest(const Interest& interest); // increment counter and signal afterReceiveInterest

  void
  receiveData(const Data& data);

  void
  receiveNack(const Nack& nack);

protected: // lower interface
  bool
  sendLinkPacket(const LinkPacket& packet);

private: // lower interface
  virtual void
  receiveLinkPacket(const LinkPacket& packet) = 0;

public: // dynamic properties
  NetCounters
  getCounters(); // network layer packet counters
};

} // namespace face
} // namespace nfd

// -------- generic LAL --------

namespace nfd {
namespace face {
namespace generic_lal {

class Options
{
  bool enableFragmentation;
  bool enableReassembly;
  // send path and receive path should have separate options if it makes sense
  time::nanoseconds reassemblyTimeout;

  // (omitted)
};

class GenericLal : public face::Lal
{
public:
  GenericLal(Options options);

  const Options&
  getOptions() const;

  void
  setOptions(const Options& options);

private: // send path entrypoint
  virtual void
  doSendInterest(const Interest& interest) override;

  virtual void
  doSendData(const Data& interest) override;

  virtual void
  doSendNack(const Nack& interest) override;

private: // receive path entrypoint
  virtual void
  receiveLinkPacket(const LinkPacket& packet) override;
};

} // namespace generic_lal
} // namespace face
} // namespace nfd