v0.6.0

• Makes compatible with Cefore v0.8.3a
• Makes cefapp available.
• Supports to receive a InterestReturn packet (for cefore's future update).
  • is_interest_return (or is_return) property of CcnPacketInfo enables to determine whether the packet is InterestReturn or not.
  • The InterestReturn packet is returned by a forwarder (cefnetd) when an Interest packet cannot be forwarded because of some errors, e.g., missing an upward FIB entry (No Route).
  • The forwarding process of InterestReturn is conducted as like that of Data packet (NOTE: a PIT entry is deleted when an InterestReturn is replied).
  • ReturnCodes: https://datatracker.ietf.org/doc/html/rfc8609#section-4.2
  • Description: https://datatracker.ietf.org/doc/html/rfc8569#section-10