Package dpkt :: Module ethernet
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Source Code for Module dpkt.ethernet

  1  # $Id: ethernet.py 65 2010-03-26 02:53:51Z dugsong $ 
  2   
  3  """Ethernet II, LLC (802.3+802.2), LLC/SNAP, and Novell raw 802.3, 
  4  with automatic 802.1q, MPLS, PPPoE, and Cisco ISL decapsulation.""" 
  5   
  6  import struct 
  7  import dpkt, stp 
  8   
  9  ETH_CRC_LEN     = 4 
 10  ETH_HDR_LEN     = 14 
 11   
 12  ETH_LEN_MIN     = 64            # minimum frame length with CRC 
 13  ETH_LEN_MAX     = 1518          # maximum frame length with CRC 
 14   
 15  ETH_MTU         = (ETH_LEN_MAX - ETH_HDR_LEN - ETH_CRC_LEN) 
 16  ETH_MIN         = (ETH_LEN_MIN - ETH_HDR_LEN - ETH_CRC_LEN) 
 17   
 18  # Ethernet payload types - http://standards.ieee.org/regauth/ethertype 
 19  ETH_TYPE_PUP    = 0x0200                # PUP protocol 
 20  ETH_TYPE_IP         = 0x0800            # IP protocol 
 21  ETH_TYPE_ARP    = 0x0806                # address resolution protocol 
 22  ETH_TYPE_AOE    = 0x88a2                # AoE protocol 
 23  ETH_TYPE_CDP    = 0x2000                # Cisco Discovery Protocol 
 24  ETH_TYPE_DTP    = 0x2004                # Cisco Dynamic Trunking Protocol 
 25  ETH_TYPE_REVARP = 0x8035                # reverse addr resolution protocol 
 26  ETH_TYPE_8021Q  = 0x8100                # IEEE 802.1Q VLAN tagging 
 27  ETH_TYPE_IPX    = 0x8137                # Internetwork Packet Exchange 
 28  ETH_TYPE_IP6    = 0x86DD                # IPv6 protocol 
 29  ETH_TYPE_PPP    = 0x880B                # PPP 
 30  ETH_TYPE_MPLS   = 0x8847                # MPLS 
 31  ETH_TYPE_MPLS_MCAST     = 0x8848        # MPLS Multicast 
 32  ETH_TYPE_PPPoE_DISC     = 0x8863        # PPP Over Ethernet Discovery Stage 
 33  ETH_TYPE_PPPoE          = 0x8864        # PPP Over Ethernet Session Stage 
 34  ETH_TYPE_LLDP   = 0x88CC        #Link Layer Discovery Protocol 
 35   
 36  # MPLS label stack fields 
 37  MPLS_LABEL_MASK = 0xfffff000 
 38  MPLS_QOS_MASK   = 0x00000e00 
 39  MPLS_TTL_MASK   = 0x000000ff 
 40  MPLS_LABEL_SHIFT= 12 
 41  MPLS_QOS_SHIFT  = 9 
 42  MPLS_TTL_SHIFT  = 0 
 43  MPLS_STACK_BOTTOM=0x0100 
 44   
45 -class Ethernet(dpkt.Packet):
46 __hdr__ = ( 47 ('dst', '6s', ''), 48 ('src', '6s', ''), 49 ('type', 'H', ETH_TYPE_IP) 50 ) 51 _typesw = {} 52
53 - def _unpack_data(self, buf):
54 if self.type == ETH_TYPE_8021Q: 55 self.tag, self.type = struct.unpack('>HH', buf[:4]) 56 buf = buf[4:] 57 elif self.type == ETH_TYPE_MPLS or \ 58 self.type == ETH_TYPE_MPLS_MCAST: 59 # XXX - skip labels (max # of labels is undefined, just use 24) 60 self.labels = [] 61 for i in range(24): 62 entry = struct.unpack('>I', buf[i*4:i*4+4])[0] 63 label = ((entry & MPLS_LABEL_MASK) >> MPLS_LABEL_SHIFT, \ 64 (entry & MPLS_QOS_MASK) >> MPLS_QOS_SHIFT, \ 65 (entry & MPLS_TTL_MASK) >> MPLS_TTL_SHIFT) 66 self.labels.append(label) 67 if entry & MPLS_STACK_BOTTOM: 68 break 69 self.type = ETH_TYPE_IP 70 buf = buf[(i + 1) * 4:] 71 try: 72 self.data = self._typesw[self.type](buf) 73 setattr(self, self.data.__class__.__name__.lower(), self.data) 74 except (KeyError, dpkt.UnpackError): 75 self.data = buf
76
77 - def unpack(self, buf):
78 dpkt.Packet.unpack(self, buf) 79 if self.type > 1500: 80 # Ethernet II 81 self._unpack_data(self.data) 82 elif self.dst.startswith('\x01\x00\x0c\x00\x00') or \ 83 self.dst.startswith('\x03\x00\x0c\x00\x00'): 84 # Cisco ISL 85 self.vlan = struct.unpack('>H', self.data[6:8])[0] 86 self.unpack(self.data[12:]) 87 elif self.data.startswith('\xff\xff'): 88 # Novell "raw" 802.3 89 self.type = ETH_TYPE_IPX 90 self.data = self.ipx = self._typesw[ETH_TYPE_IPX](self.data[2:]) 91 else: 92 # 802.2 LLC 93 self.dsap, self.ssap, self.ctl = struct.unpack('BBB', self.data[:3]) 94 if self.data.startswith('\xaa\xaa'): 95 # SNAP 96 self.type = struct.unpack('>H', self.data[6:8])[0] 97 self._unpack_data(self.data[8:]) 98 else: 99 # non-SNAP 100 dsap = ord(self.data[0]) 101 if dsap == 0x06: # SAP_IP 102 self.data = self.ip = self._typesw[ETH_TYPE_IP](self.data[3:]) 103 elif dsap == 0x10 or dsap == 0xe0: # SAP_NETWARE{1,2} 104 self.data = self.ipx = self._typesw[ETH_TYPE_IPX](self.data[3:]) 105 elif dsap == 0x42: # SAP_STP 106 self.data = self.stp = stp.STP(self.data[3:])
107
108 - def set_type(cls, t, pktclass):
109 cls._typesw[t] = pktclass
110 set_type = classmethod(set_type) 111
112 - def get_type(cls, t):
113 return cls._typesw[t]
114 get_type = classmethod(get_type)
115 116 # XXX - auto-load Ethernet dispatch table from ETH_TYPE_* definitions
117 -def __load_types():
118 g = globals() 119 for k, v in g.iteritems(): 120 if k.startswith('ETH_TYPE_'): 121 name = k[9:] 122 modname = name.lower() 123 try: 124 mod = __import__(modname, g) 125 except ImportError: 126 continue 127 Ethernet.set_type(v, getattr(mod, name))
128 129 if not Ethernet._typesw: 130 __load_types() 131 132 if __name__ == '__main__': 133 import unittest 134
135 - class EthTestCase(unittest.TestCase):
136 - def test_eth(self):
137 s = '\x00\xb0\xd0\xe1\x80r\x00\x11$\x8c\x11\xde\x86\xdd`\x00\x00\x00\x00(\x06@\xfe\x80\x00\x00\x00\x00\x00\x00\x02\x11$\xff\xfe\x8c\x11\xde\xfe\x80\x00\x00\x00\x00\x00\x00\x02\xb0\xd0\xff\xfe\xe1\x80r\xcd\xd3\x00\x16\xffP\xd7\x13\x00\x00\x00\x00\xa0\x02\xff\xffg\xd3\x00\x00\x02\x04\x05\xa0\x01\x03\x03\x00\x01\x01\x08\n}\x18:a\x00\x00\x00\x00' 138 eth = Ethernet(s)
139 140 unittest.main() 141