Wireshark · Wireshark-dev: [Wireshark-dev] Writing NoOp PCAP-NG Records

[Paul Offord <Paul.Offord@xxxxxxxxxxxx>]

Hi,

 

I am writing a small utility that converts .etl network trace files produced by netsh trace into pcapng format.  The interface information is right at the end of the ETL file, but I need to create IDBs near the start of the pcapng file.  I don’t want to hold a whole converted trace file in memory and I’d prefer not to shuffle the data around in the pcapng file.  My plan is:

 

·        Write an “IDB segment” of null bytes where the IDB will go – enough to accomodate the maximum anticipated IDB blocks, say 2 KB

·        Once I get to the interface data in the ETL, seek back to the “IDB Segment”

·        Write the IDBs

·        Pad the “IDB segment” with the equivalent of NoOps

 

There is no NoOp block type and so I’m thinking of using a Custom Block

 

·        Would using a Custom Block in this way cause problems?

·        What value should I use for the Private Enterprise Number (PEN)?

·        Is there a better way of doing this?

 

Thanks and regards…Paul

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