Get fragments from reassembly table

[Anton Glukhov <anton.a.glukhov () gmail com>]

I have dissector which works with fragments and reassembling by using
fragment_add_check() and process_reassembled_data() functions. Now I got
one problem. Each new fragment must be validated thought CRC32 calculation,
but not for itself but for all previous fragments together. Here is an
example: imagine that we received 3 fragments and now they are already in
fragment_table. Next 4th fragment is coming and we need to verify it. In
order to verify it we have to take all previous fragments(all 3 previous)
out, concatenate them, calculate crc32 for all _four_ fragments together
and put 4th fragment into fragment_table by using function
fragment_add_check(). So, it looks like we do "temporary" reassemble for
each new packet with all previous packet. Could you help me with ideas how
to design it better?

My thoughts so far: I can reassemble them manually by allocate new buffer,
getting fragment_head and going through linked list. But I don't think this
is the best choice here.

Best regards,
Anton

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