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I'm using rdpcap function of Scapy to read a PCAP file. I also use the module described in a link to HTTP support in Scapy which is needed in my case, as I have to retrieve all the HTTP requests and responses and their related packets.

I noticed that parsing a large PCAP file the rdpcap function takes too much time to read it.

Is there a solution to read a pcap file faster?

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How big is your pcap file? How long does it take to read it? Is it really too long (even for loading it only once)? How many times do you want to read it (rhetorical question)? –  Jan-Philip Gehrcke May 29 '12 at 13:51
My file is greater than 300 MB, I have to launch the Python script more than once. –  auino May 29 '12 at 13:56
@auino, what specifically is the problem with the read time? Is it that it takes too long to develop your script when you're parsing a 300MB file every time you make a change, or is there some real-time processing requirement? Also, please give us a sense for what is an acceptable parse time –  Mike Pennington May 29 '12 at 14:07
It takes about 1 hours... it's not good, as I have to parse the data just loaded... –  auino May 29 '12 at 14:28
Please use upvote to thank and do not thank in question. –  ppumkin Sep 25 '13 at 12:06
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1 Answer

While I agree the load time is longer than one might expect, it is likely because the file is being parsed to generate an array of highly composed objects. What I've had to do was use editcap to chop up the packet captures to make reading them a bit easier. For example:

$ editcap -B 2013-05-2810:05:55 -i 5 -F libpcap inputcapture.pcap outputcapture.pcap

Please note: a full explanation of the switches of this command is available here.

Also, the -F libpcap part seemed to be necessary (at least for me) to get scapy's pcap function able to parse the file. (This is supposed to be the default pcap file output format, but this was not the case for me, for whatever reason. You can verify the file type of your input and output files with capinfos (e.g., simply enter capinfos your_capture.pcap).

Both capinfos and editcap are available with the WireShark distribution.

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