def encode_nack_reason(self, reason: NackReason) -> bytearray:
"""
Encode a NackReason
:param reason: NackReason
:return: Nack reason in wire format
"""
encoder = TlvEncoder()
encoder.writeVarNumber(self.__nack_reason_values[reason])
return encoder.getOutput().tobytes()
def encode_name(self, name: Name) -> bytearray:
"""
Assembly a name-TLV
:param name: Name
:return: Name-TLV
"""
encoder = TlvEncoder()
# name = name[1:].split('/')
# for component in name[::-1]:
# encoder.writeBlobTlv(Tlv.NameComponent, [ord(c) for c in component])
# fill backwards
if name.digest:
encoder.writeBlobTlv(Tlv.ImplicitSha256DigestComponent, name.digest)
for c in name._components[::-1]:
encoder.writeBlobTlv(Tlv.NameComponent, c)
encoder.writeTypeAndLength(Tlv.Name, len(encoder))
return encoder.getOutput() #.tobytes()
def encode_interest(self, name: Name) -> bytearray:
"""
Assembly an interest packet
:param name: Name
:return: Interest-TLV
"""
encoder = TlvEncoder()
# Add nonce
nonce = bytearray(4)
for i in range(4):
nonce[i] = SystemRandom().randint(0, 0xff)
encoder.writeBlobTlv(Tlv.Nonce, nonce)
# TODO: add implicitDigest flag here ?
# Add name
encoder.writeBuffer(self.encode_name(name))
# Add interest type and len
encoder.writeTypeAndLength(Tlv.Interest, len(encoder))
return encoder.getOutput().tobytes()
def encode_heartbeat(self, name: Name) -> bytearray:
"""
Assembly an heartbeat packet
:param name: Name
:return: Heartbeat-TLV
"""
encoder = TlvEncoder()
# Add name
encoder.writeBuffer(self.encode_name(name))
# Add heartbeat type and len
encoder.writeTypeAndLength(self.heartbeatTV, len(encoder))
return encoder.getOutput().tobytes()
def encode_nack(self, name: Name, reason: NackReason, interest: Interest) -> bytearray:
"""
Assembly a negative acknowledgement packet
:param name: Name carried by interest for which this NACK is generated
:param reason: Nack reason
:param interest: Interest for which this NACk is generated
:return: NACK-TLV
"""
encoder = TlvEncoder()
# write fragment (interest packet)
if interest.wire_format is None:
interest._wire_format = self.encode(interest)
encoder.writeBuffer(interest.wire_format)
encoder.writeTypeAndLength(Tlv.LpPacket_Fragment, len(encoder))
fragment_len = len(encoder)
# write nack reason if needed
if reason is not NackReason.NOT_SET:
wire_reason = self.encode_nack_reason(reason)
encoder.writeBuffer(wire_reason)
encoder.writeTypeAndLength(Tlv.LpPacket_NackReason, len(wire_reason))
# write nack header
encoder.writeTypeAndLength(Tlv.LpPacket_Nack, len(encoder) - fragment_len)
# write link packet header
encoder.writeTypeAndLength(Tlv.LpPacket_LpPacket, len(encoder))
return encoder.getOutput().tobytes()
def encode_data(self, name: Name, payload: bytearray) -> bytearray:
"""
Assembly a data packet including a signature according to NDN packet format specification 0.3 (DigestSha256).
:param name: Name
:param payload: Payload
:return: Data-TLV
"""
encoder = TlvEncoder()
# Add signature (DigestSha256, zeroed)
encoder.writeBlobTlv(Tlv.SignatureValue, bytearray(32)) # signature value to set later
encoder.writeBlobTlv(Tlv.SignatureInfo, bytearray([Tlv.SignatureType, 1, 0]))
# Add content
encoder.writeBlobTlv(Tlv.Content, payload)
# Add meta info (empty)
encoder.writeTypeAndLength(Tlv.MetaInfo, 0)
# Add name
encoder.writeBuffer(self.encode_name(name))
# Add data type and len
encoder.writeTypeAndLength(Tlv.Data, len(encoder))
# Add signature value
packet_without_sig = encoder.getOutput().tobytes()
m = hashlib.sha256()
m.update(packet_without_sig[:-32])
sig = m.digest()
packet_with_sig = packet_without_sig[:-32] + sig
return packet_with_sig
def encode_data(self, name: Name, payload: bytearray) -> bytearray:
"""
Assembly a data packet
:param name: Name
:param payload: Payload
:return: Data-TLV
"""
encoder = TlvEncoder()
# Add content
encoder.writeBlobTlv(Tlv.Content, payload)
# Add meta info (empty)
encoder.writeTypeAndLength(Tlv.MetaInfo, 0)
# Add name
encoder.writeBuffer(self.encode_name(name))
# Add data type and len
encoder.writeTypeAndLength(Tlv.Data, len(encoder))
return encoder.getOutput().tobytes()