检查对象是否在 pyshark 给出的列表中

Question

我正在尝试使用 pyshark 读取 pcap 文件。似乎 pyshark 创建了一个对象列表，其中每个对象 有关于包内每一层的信息。

我只想评估数据包中是否存在层。也许有人可以帮助我。

对象“层”的列表是这样的：

[<ETH Layer>, <IP Layer>, <SCTP Layer>, <DATA Layer>]

但是这个评估失败了，因为列表里面是对象而不是字符串。

if <ETH Layer> in layers: print "Yes, Ethernet layer exists"
if '<ETH Layer>' in layers: print "Yes, Ethernet layer exists"

以下是我的测试...

Python 2.7.10 (default, May 23 2015, 09:40:32) [MSC v.1500 32 bit (Intel)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>>
>>> import pyshark
>>> file = pyshark.FileCapture('C:\\files\\input.pcap')
>>> packet=file[0]
>>> layers=packet.layers
>>> layers
[<ETH Layer>, <IP Layer>, <SCTP Layer>, <DATA Layer>, <SCTP Layer>, <DATA Layer>]
>>> if packet.eth in layers: print "Yes, Ethernet layer exists"
...
Yes, Ethernet layer exists
>>>
Yes, Ethernet layer exists
>>> if '<ETH Layer>' in layers: print "Yes, Ethernet layer exists"
...
>>>

这个评估给出了正确的输出

if packet.eth in layers: print "Yes, Ethernet layer exists"

这两个失败，因为评估为 False

if <ETH Layer> in layers: print "Yes, Ethernet layer exists"
if '<ETH Layer>' in layers: print "Yes, Ethernet layer exists"

*更新：

如果我测试 packet.ip、packet.eth、packet.sctp，它只有在层 ip、eth 或 sctp 存在时才有效，如果某些层不存在（即 tcp），我会收到以下错误。

>>> if packet.tcp in layers: print "Yes, Ethernet layer exists"
...
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "C:\Python27\lib\site-packages\pyshark\packet\packet.py", line 110, in __getattr__
    raise AttributeError()
AttributeError

谢谢

Answer 1

<ETH Layer> 不是实际对象，它只是对象的 __repr__ 方法返回的内容。你的 Python REPL 调用它来查看如何打印出评估表达式的表示。类似地，如果您向print 表达式请求它，它可能会调用__str__。比较这些：

>> packet.layers[0]
<ETH Layer>

>> print packet.layers[0]
Layer ETH:
    Destination: 52:54:00:12:37:02 (52:54:00:12:37:02)
    .... ..1. .... .... .... .... = LG bit: Locally administered address (this is NOT the factory default)
    Address: 52:54:00:12:37:02 (52:54:00:12:37:02)
    .... ...0 .... .... .... .... = IG bit: Individual address (unicast)
    Type: IP (0x0800)
    Source: 08:00:28:1d:ae:8b (08:00:28:1d:ae:8b)
    .... ..0. .... .... .... .... = LG bit: Globally unique address (factory default)
    Address: 08:00:28:1d:ae:8b (08:00:28:1d:ae:8b)
    .... ...0 .... .... .... .... = IG bit: Individual address (unicast)

但要从功能上回答您的问题，我相信如果您想查看数据包中是否存在层，您可以执行以下操作：

if 'eth' in packet:
    # ...