Python 使用 Scapy 创建空 pcap 文件时抑制警告

Question

I want to create an empty pcap file. I'm using wrpcap module of 'Scapy'. But wrpcap takes exactly 2 arguments : one is the file name and other is the packet list like:

wrpcap("my.pcap",my_pkt_list)

Since I want to make it, empty and I don't have a packet list, I'm writing an empty string to the pcap file. Which is creating the file but also giving a warning as well as errors since a string doesn't match to a packet type.

WARNING: PcapWriter: unknown LL type for str. Using type 1 (Ethernet)
Traceback (most recent call last):
  File "test.py", line 35, in <module>
    wrpcap("pcap/FU.pcap","")
  File "/usr/lib/python2.7/site-packages/scapy/utils.py", line 466, in wrpcap
    PcapWriter(filename, *args, **kargs).write(pkt)
  File "/usr/lib/python2.7/site-packages/scapy/utils.py", line 646, in write
    self._write_packet(pkt)
  File "/usr/lib/python2.7/site-packages/scapy/utils.py", line 688, in _write_packet
    sec = int(packet.time)
AttributeError: 'str' object has no attribute 'time'

For now, I'm able to suppress the errors with try and except but unable to suppress the warning.

Code

from scapy.all import *
try:
    wrpcap("my.pcap","")
except:
    pass

and the warning is still there:

WARNING: PcapWriter: unknown LL type for str. Using type 1 (Ethernet)

How to suppress it from inside the python code?

Answer 1

Python has a built in method in the standard library for supressing warnings:

import warnings
warnings.simplefilter("ignore", Warning)

You can read more about the warnings library in the docs .

EDIT

It doesn't look like scapy uses the warnings library to generate this. Instead it logs them to a logger called scapy.runtime with a level of warning . There's obviously some default logging config to echo that to stdout . You could add your own logging handler for scapy.runtime to supress them.

Answer 2

You can avoid that warning by using PcapWriter method of scapy.

from scapy.all import *
try:
    writer=PcapWriter("my.pcap")
except:
    pass

This creates your empty pcap file. When you want to write some packets to it, just use the following code:

writer.write(<Your_packets>)
writer.flush()

Answer 3

You can suppress this warning by disabling warning logging before the call wrpcap :

import logging
logging.getLogger("scapy.runtime").setLevel(logging.ERROR)

Answer 4

The text "WARNING: ..." is not part of the exception and will thus not be surpressed by your try clause.

An idea I got was to redirect stdout during the call

from scapy.all import *
try:
    old_stdout = sys.stdout
    sys.stdout = None
    wrpcap("my.pcap","")
    sys.stdout = old_stdout
except:
    pass

that should surpress any and all output during the call