text: # Copyright (C) 2012 Nippon Telegraph and Telephone Corporation.
  #
  # 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.
  
  import struct
  
  from . import packet_base
  from . import packet_utils
  from ryu.lib import stringify
  
  
  ICMP_ECHO_REPLY = 0
  ICMP_DEST_UNREACH = 3
  ICMP_SRC_QUENCH = 4
  ICMP_REDIRECT = 5
  ICMP_ECHO_REQUEST = 8
  ICMP_TIME_EXCEEDED = 11
  
  ICMP_ECHO_REPLY_CODE = 0
  ICMP_HOST_UNREACH_CODE = 1
  ICMP_PORT_UNREACH_CODE = 3
  ICMP_TTL_EXPIRED_CODE = 0
  
  
  class icmp(packet_base.PacketBase):
      """ICMP (RFC 792) header encoder/decoder class.
  
      An instance has the following attributes at least.
      Most of them are same to the on-wire counterparts but in host byte order.
      __init__ takes the corresponding args in this order.
  
      .. tabularcolumns:: |l|L|
  
      ============== ====================
      Attribute      Description
      ============== ====================
      type           Type
      code           Code
      csum           CheckSum \
                     (0 means automatically-calculate when encoding)
      data           Payload. \
                     Either a bytearray, or \
                     ryu.lib.packet.icmp.echo or \
                     ryu.lib.packet.icmp.dest_unreach or \
                     ryu.lib.packet.icmp.TimeExceeded object \
                     NOTE for icmp.echo: \
                     This includes "unused" 16 bits and the following \
                     "Internet Header + 64 bits of Original Data Datagram" of \
                     the ICMP header. \
                     NOTE for icmp.dest_unreach and icmp.TimeExceeded: \
                     This includes "unused" 8 or 24 bits and the following \
                     "Internet Header + leading octets of original datagram" \
                     of the original packet.
      ============== ====================
      """
  
      _PACK_STR = '!BBH'
      _MIN_LEN = struct.calcsize(_PACK_STR)
      _ICMP_TYPES = {}
  
      @staticmethod
      def register_icmp_type(*args):
          def _register_icmp_type(cls):
              for type_ in args:
                  icmp._ICMP_TYPES[type_] = cls
              return cls
          return _register_icmp_type
  
      def __init__(self, type_=ICMP_ECHO_REQUEST, code=0, csum=0, data=None):
          super(icmp, self).__init__()
          self.type = type_
          self.code = code
          self.csum = csum
          self.data = data
  
      @classmethod
      def parser(cls, buf):
          (type_, code, csum) = struct.unpack_from(cls._PACK_STR, buf)
          msg = cls(type_, code, csum)
          offset = cls._MIN_LEN
  
          if len(buf) > offset:
              cls_ = cls._ICMP_TYPES.get(type_, None)
              if cls_:
                  msg.data = cls_.parser(buf, offset)
              else:
                  msg.data = buf[offset:]
  
          return msg, None, None
  
      def serialize(self, payload, prev):
          hdr = bytearray(struct.pack(icmp._PACK_STR, self.type,
                                      self.code, self.csum))
  
          if self.data is not None:
              if self.type in icmp._ICMP_TYPES:
                  hdr += self.data.serialize()
              else:
                  hdr += self.data
          else:
              self.data = echo()
              hdr += self.data.serialize()
  
          if self.csum == 0:
              self.csum = packet_utils.checksum(hdr)
              struct.pack_into('!H', hdr, 2, self.csum)
  
          return hdr
  
      def __len__(self):
          return self._MIN_LEN + len(self.data)
  
  
  @icmp.register_icmp_type(ICMP_ECHO_REPLY, ICMP_ECHO_REQUEST)
  class echo(stringify.StringifyMixin):
      """ICMP sub encoder/decoder class for Echo and Echo Reply messages.
  
      This is used with ryu.lib.packet.icmp.icmp for
      ICMP Echo and Echo Reply messages.
  
      An instance has the following attributes at least.
      Most of them are same to the on-wire counterparts but in host byte order.
      __init__ takes the corresponding args in this order.
  
      .. tabularcolumns:: |l|L|
  
      ============== ====================
      Attribute      Description
      ============== ====================
      id             Identifier
      seq            Sequence Number
      data           Internet Header + 64 bits of Original Data Datagram
      ============== ====================
      """
  
      _PACK_STR = '!HH'
      _MIN_LEN = struct.calcsize(_PACK_STR)
  
      def __init__(self, id_=0, seq=0, data=None):
          super(echo, self).__init__()
          self.id = id_
          self.seq = seq
          self.data = data
  
      @classmethod
      def parser(cls, buf, offset):
          (id_, seq) = struct.unpack_from(cls._PACK_STR, buf, offset)
          msg = cls(id_, seq)
          offset += cls._MIN_LEN
  
          if len(buf) > offset:
              msg.data = buf[offset:]
  
          return msg
  
      def serialize(self):
          hdr = bytearray(struct.pack(echo._PACK_STR, self.id,
                                      self.seq))
  
          if self.data is not None:
              hdr += self.data
  
          return hdr
  
      def __len__(self):
          length = self._MIN_LEN
          if self.data is not None:
              length += len(self.data)
          return length
  
  
  @icmp.register_icmp_type(ICMP_DEST_UNREACH)
  class dest_unreach(stringify.StringifyMixin):
      """ICMP sub encoder/decoder class for Destination Unreachable Message.
  
      This is used with ryu.lib.packet.icmp.icmp for
      ICMP Destination Unreachable Message.
  
      An instance has the following attributes at least.
      Most of them are same to the on-wire counterparts but in host byte order.
      __init__ takes the corresponding args in this order.
  
      [RFC1191] reserves bits for the "Next-Hop MTU" field.
      [RFC4884] introduced 8-bit data length attribute.
  
      .. tabularcolumns:: |l|p{35em}|
  
      ============== =====================================================
      Attribute      Description
      ============== =====================================================
      data_len       data length
      mtu            Next-Hop MTU
  
                     NOTE: This field is required when icmp code is 4
  
                     code 4 = fragmentation needed and DF set
      data           Internet Header + leading octets of original datagram
      ============== =====================================================
      """
  
      _PACK_STR = '!xBH'
      _MIN_LEN = struct.calcsize(_PACK_STR)
  
      def __init__(self, data_len=0, mtu=0, data=None):
          super(dest_unreach, self).__init__()
          self.data_len = data_len
          self.mtu = mtu
          self.data = data
  
      @classmethod
      def parser(cls, buf, offset):
          (data_len, mtu) = struct.unpack_from(cls._PACK_STR,
                                               buf, offset)
          msg = cls(data_len, mtu)
          offset += cls._MIN_LEN
  
          if len(buf) > offset:
              msg.data = buf[offset:]
  
          return msg
  
      def serialize(self):
          hdr = bytearray(struct.pack(dest_unreach._PACK_STR,
                          self.data_len, self.mtu))
  
          if self.data is not None:
              hdr += self.data
  
          return hdr
  
      def __len__(self):
          length = self._MIN_LEN
          if self.data is not None:
              length += len(self.data)
          return length
  
  
  @icmp.register_icmp_type(ICMP_TIME_EXCEEDED)
  class TimeExceeded(stringify.StringifyMixin):
      """ICMP sub encoder/decoder class for Time Exceeded Message.
  
      This is used with ryu.lib.packet.icmp.icmp for
      ICMP Time Exceeded Message.
  
      An instance has the following attributes at least.
      Most of them are same to the on-wire counterparts but in host byte order.
      __init__ takes the corresponding args in this order.
  
      [RFC4884] introduced 8-bit data length attribute.
  
      .. tabularcolumns:: |l|L|
  
      ============== ====================
      Attribute      Description
      ============== ====================
      data_len       data length
      data           Internet Header + leading octets of original datagram
      ============== ====================
      """
  
      _PACK_STR = '!xBxx'
      _MIN_LEN = struct.calcsize(_PACK_STR)
  
      def __init__(self, data_len=0, data=None):
          self.data_len = data_len
          self.data = data
  
      @classmethod
      def parser(cls, buf, offset):
          (data_len, ) = struct.unpack_from(cls._PACK_STR, buf, offset)
          msg = cls(data_len)
          offset += cls._MIN_LEN
  
          if len(buf) > offset:
              msg.data = buf[offset:]
  
          return msg
  
      def serialize(self):
          hdr = bytearray(struct.pack(TimeExceeded._PACK_STR, self.data_len))
  
          if self.data is not None:
              hdr += self.data
  
          return hdr
  
      def __len__(self):
          length = self._MIN_LEN
          if self.data is not None:
              length += len(self.data)
          return length
  
  
  icmp.set_classes(icmp._ICMP_TYPES)
  