1# Copyright (C) 2012 Nippon Telegraph and Telephone Corporation.
2#
3# Licensed under the Apache License, Version 2.0 (the "License");
4# you may not use this file except in compliance with the License.
5# You may obtain a copy of the License at
6#
7#    http://www.apache.org/licenses/LICENSE-2.0
8#
9# Unless required by applicable law or agreed to in writing, software
10# distributed under the License is distributed on an "AS IS" BASIS,
11# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
12# implied.
13# See the License for the specific language governing permissions and
14# limitations under the License.
15
16import struct
17from . import packet_base
18from . import vlan
19from . import mpls
20from . import ether_types as ether
21from ryu.lib import addrconv
22from ryu.lib.pack_utils import msg_pack_into
23
24
25class ethernet(packet_base.PacketBase):
26    """Ethernet header encoder/decoder class.
27
28    An instance has the following attributes at least.
29    MAC addresses are represented as a string like '08:60:6e:7f:74:e7'.
30    __init__ takes the corresponding args in this order.
31
32    ============== ==================== =====================
33    Attribute      Description          Example
34    ============== ==================== =====================
35    dst            destination address  'ff:ff:ff:ff:ff:ff'
36    src            source address       '08:60:6e:7f:74:e7'
37    ethertype      ether type           0x0800
38    ============== ==================== =====================
39    """
40
41    _PACK_STR = '!6s6sH'
42    _MIN_LEN = struct.calcsize(_PACK_STR)
43    _MIN_PAYLOAD_LEN = 46
44    _TYPE = {
45        'ascii': [
46            'src', 'dst'
47        ]
48    }
49
50    def __init__(self, dst='ff:ff:ff:ff:ff:ff', src='00:00:00:00:00:00',
51                 ethertype=ether.ETH_TYPE_IP):
52        super(ethernet, self).__init__()
53        self.dst = dst
54        self.src = src
55        self.ethertype = ethertype
56
57    @classmethod
58    def parser(cls, buf):
59        dst, src, ethertype = struct.unpack_from(cls._PACK_STR, buf)
60        return (cls(addrconv.mac.bin_to_text(dst),
61                    addrconv.mac.bin_to_text(src), ethertype),
62                ethernet.get_packet_type(ethertype),
63                buf[ethernet._MIN_LEN:])
64
65    def serialize(self, payload, prev):
66        # Append padding if the payload is less than 46 bytes long
67        pad_len = self._MIN_PAYLOAD_LEN - len(payload)
68        if pad_len > 0:
69            payload.extend(b'\x00' * pad_len)
70
71        return struct.pack(ethernet._PACK_STR,
72                           addrconv.mac.text_to_bin(self.dst),
73                           addrconv.mac.text_to_bin(self.src),
74                           self.ethertype)
75
76    @classmethod
77    def get_packet_type(cls, type_):
78        """Override method for the ethernet IEEE802.3 Length/Type
79        field (self.ethertype).
80
81        If the value of Length/Type field is less than or equal to
82        1500 decimal(05DC hexadecimal), it means Length interpretation
83        and be passed to the LLC sublayer."""
84        if type_ <= ether.ETH_TYPE_IEEE802_3:
85            type_ = ether.ETH_TYPE_IEEE802_3
86        return cls._TYPES.get(type_)
87
88
89# copy vlan _TYPES
90ethernet._TYPES = vlan.vlan._TYPES
91ethernet.register_packet_type(vlan.vlan, ether.ETH_TYPE_8021Q)
92ethernet.register_packet_type(vlan.svlan, ether.ETH_TYPE_8021AD)
93ethernet.register_packet_type(mpls.mpls, ether.ETH_TYPE_MPLS)
94