Reassembly packet fragments

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This topic contains 3 replies, has 2 voices, and was last updated by  Vadim Smirnov 7 years, 9 months ago.

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    Hello sir,
    I am using winpkfilter to change some payload contents and the length using visual C++.NET. However everything is going well, recompute the checksum, … etc.
    The problem is that when I receive UDP fragments (packet fragmentation), the packet dropped. This is due that when I compute the checksum (of course it is wrong) because the true checksum is for all the fragment not that fragment alone.
    So, I need to reasseble these fragments when I receive them and do the change (legnth and payload) then recompute the checksum and finally refragment again and send to the upper layer.
    Q1) can I do that in winpkfilter??? reassemble many packets and then refragment them and send them again as fragmented packets???
    Q2) Can you help me??? if there is any source code that help me, I will be very appreciated.
    Thank you very much sir.
    I am waiting your kindly reply as soon as possible.


    Vadim Smirnov

    1) Yes, of course this is possible to do with WinpkFilter.
    2) We don’t have defragment/fragment sample code we can send to you. Although we can develop one as a small consulting project if you agree to pay the development effort.



    how much is the price for the fragment and Defragment code??? and how long is it take of time???


    Vadim Smirnov

    Please address such questions to support(at)

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