我正在尝试确定 802.11 协议变体 - 从由 wireshark 创建的 PcapNG 跟踪文件（参见StackOverflow 上的相关问题和 StackOverflow上的另一个相关问题）。
捕获数据包的接口的链路层标头类型是 LINKTYPE_IEEE802_11_RADIOTAP (127)，因此我可以使用radiotap.py提取Channel 字段，从而检查 802.11 协议变体是 a、b 还是 g。
但是，要检查我是否有 802.11n 或 802.11ac，我需要访问XChannel / MCS或VHT字段。
这些字段在radiotap.py中没有定义，这意味着我需要扩展radiotap.py的功能。parse
我尝试过但失败了：我怀疑我将对齐/结构设置错误（或其他一些晦涩的错误）并且现有的radiotap.py代码对我没有多大帮助。
谁能建议我应该在radiotap.py中进行哪些更改，以便它能够识别XChannel、MCS和VHT字段？
示例 PcapNG 跟踪文件在此处。
我的 Python 代码是：
#!/usr/bin/env python
from pcapng import FileScanner
import radiotap
def hex_str_to_num(hex_str,out_format='X'):
if out_format.upper() == 'B':
return ' '.join(format(ord(x), out_format).zfill(8) for x in hex_str)
else:
return ' '.join(format(ord(x), out_format).zfill(2) for x in hex_str)
def get_protocol_variant(channel):
"""
0x0010 Turbo Channel
0x0020 CCK channel
0x0040 OFDM channel
0x0080 2 GHz spectrum channel
0x0100 5 GHz spectrum channel
0x0200 Only passive scan allowed
0x0400 Dynamic CCK-OFDM channel
0x0800 GFSK channel (FHSS PHY)
If link-layer header type for the interface is LINKTYPE_IEEE802_11, protocol variant
cannot be ascertained.
If link-layer header type for the interface is LINKTYPE_IEEE802_11_RADIOTAP, then
the packet begins with a radiotap header giving various meta-data about the packet.
If the radiotap header includes the Channel field, then, from the information there,
the protocol variant may be ascertained as following:
"5 GHz spectrum channel" + "OFDM channel" = 802.11a;
"2 GHz spectrum channel" + "CCK channel" = 802.11b;
"2 GHz spectrum channel" + "OFDM channel" = 802.11g;
"2 GHz spectrum channel" + "Dynamic CCK-OFDM channel" = 802.11g;
(the difference between the two flavors of 802.11g indicates whether there
might also be 802.11b traffic on the same channel - that's what the
"Dynamic CCK-OFDM channel" indicates).
However, if the MCS field is present, it's 802.11n, not any of those other types,
and if the VHT field is present, it's 802.11ac.
There might also be an XChannel field, which can be interpreted similarly to the
Channel field, although it also contains some information for 802.11n.
"""
def check(_name, _const):
_bit = None
if (channel & _const):
_bit = True
print _name,_bit
return _bit
TURBO = 0x0010
CCK = 0x0020
OFDM = 0x0040
GHz_2 = 0x0080
GHz_5 = 0x0100
PASSI = 0x0200
DYNAM = 0x0400
GFSK = 0x0800
variant = None
turbo = check("turbo", TURBO)
cck = check("cck", CCK)
ofdm = check("ofdm", OFDM)
ghz_2 = check("ghz_2", GHz_2)
ghz_5 = check("ghz_5", GHz_5)
passi = check("passi", PASSI)
dynam = check("dynam", DYNAM)
gfsk = check("gfsk", GFSK)
if ghz_5 and ofdm:
variant = "802.11a"
elif ghz_2 and cck:
variant = "802.11b"
elif ghz_2 and ofdm:
variant = "802.11g"
elif ghz_2 and dynam:
variant = "802.11g"
print "variant",variant
return variant
PCAPNG = "/cygdrive/c/tmp/trace3.pcapng"
MAX = 5
INTERFACEDESCRIPTION = 1
ENHANCEDPACKET = 6
LINKTYPE_IEEE802_11_RADIOTAP = 127
with open(PCAPNG, "r") as pcapng_file:
scanner = FileScanner(pcapng_file)
counter = MAX
link_type = None
for block in scanner:
print
print "magic_number",hex(block.magic_number)
print block
if block.magic_number == ENHANCEDPACKET:
if link_type == LINKTYPE_IEEE802_11_RADIOTAP:
payload_data = block.packet_payload_info[2]
print "packet_payload_data (hex):",hex_str_to_num(payload_data,"X")
radiotap_dict = radiotap.parse(payload_data)
radiotap_hedear_len = radiotap.get_length(payload_data)
print "radiotap_dict",radiotap_dict
channel = radiotap_dict[radiotap.RTAP_CHANNEL]
protocol_variant = get_protocol_variant(channel)
print "protocol_variant",protocol_variant
"""
print "channel",channel,hex(channel),bin(channel)
print "radiotap_hedear_len",radiotap_hedear_len
payload_802_11 = payload_data[radiotap_hedear_len+1:]
print "payload_802_11 (hex)",hex_str_to_num(payload_802_11,"X")
"""
elif block.magic_number == INTERFACEDESCRIPTION:
link_type = block.link_type
counter -= 1
if not counter:
break
它的输出是：
magic_number 0xa0d0d0a
SectionHeader(version_major=1, version_minor=0, section_length=-1, options=Options({'shb_userappl': [u'Dumpcap 1.12.4 (v1.12.4-0-gb4861da from master-1.12)'], 'shb_os': [u'Mac OS X 10.10.2, build 14C109 (Darwin 14.1.0)']}))
magic_number 0x1
InterfaceDescription(link_type=127, reserved='\x00\x00', snaplen=262144, options=Options({'if_os': [u'Mac OS X 10.10.2, build 14C109 (Darwin 14.1.0)'], 'if_tsresol': [6], 'if_name': [u'en1']}))
magic_number 0x6
EnhancedPacket(interface_id=0, timestamp_high=332139, timestamp_low=2801116064L, packet_payload_info=(45, 45, '\x00\x00\x19\x00o\x08\x00\x00`I\xb2&\x00\x00\x00\x00\x12\x18q\x16@\x01\xb1\xaa\x00\xb4\x00\x90\x00\xf4\x0f\x1b\xb8sL`\x92\x175\x00\x01\xe3\xcf\x00\x12'), options=Options({}))
packet_payload_data (hex): 00 00 19 00 6F 08 00 00 60 49 B2 26 00 00 00 00 12 18 71 16 40 01 B1 AA 00 B4 00 90 00 F4 0F 1B B8 73 4C 60 92 17 35 00 01 E3 CF 00 12
radiotap_dict {0: 649218400, 1: 18, 2: 24, 3: 20977265, 5: -79, 6: -86, 11: 0}
turbo True
cck True
ofdm True
passi True
dynam True
variant None
protocol_variant None
magic_number 0x6
EnhancedPacket(interface_id=0, timestamp_high=332139, timestamp_low=2801116070L, packet_payload_info=(39, 39, '\x00\x00\x19\x00o\x08\x00\x00\x92I\xb2&\x00\x00\x00\x00\x12\x18q\x16@\x01\xcd\xaa\x00\xc4\x00`\x00`\x92\x175\x00\x01\xf7eny'), options=Options({}))
packet_payload_data (hex): 00 00 19 00 6F 08 00 00 92 49 B2 26 00 00 00 00 12 18 71 16 40 01 CD AA 00 C4 00 60 00 60 92 17 35 00 01 F7 65 6E 79
radiotap_dict {0: 649218450, 1: 18, 2: 24, 3: 20977265, 5: -51, 6: -86, 11: 0}
turbo True
cck True
ofdm True
passi True
dynam True
variant None
protocol_variant None
magic_number 0x6
EnhancedPacket(interface_id=0, timestamp_high=332139, timestamp_low=2801116213L, packet_payload_info=(57, 57, '\x00\x00\x19\x00o\x08\x00\x00\tJ\xb2&\x00\x00\x00\x00\x12\x18q\x16@\x01\xca\xaa\x00\x94\x00\x00\x00`\x92\x175\x00\x01\xf4\x0f\x1b\xb8sL\x04\x00\xc0#\xff\xff\xff\xff\xff\xff\xff\xffX\xd0Y\\'), options=Options({}))
packet_payload_data (hex): 00 00 19 00 6F 08 00 00 09 4A B2 26 00 00 00 00 12 18 71 16 40 01 CA AA 00 94 00 00 00 60 92 17 35 00 01 F4 0F 1B B8 73 4C 04 00 C0 23 FF FF FF FF FF FF FF FF 58 D0 59 5C
radiotap_dict {0: 649218569, 1: 18, 2: 24, 3: 20977265, 5: -54, 6: -86, 11: 0}
turbo True
cck True
ofdm True
passi True
dynam True
variant None
protocol_variant None