[pcap-ng-format] Reading and writing blocks you don't understand

[Michael Richardson]

Michael Tuexen <tuexen at wireshark.org> wrote:
    >>> Yes, have a critical bit in the option space.
    >>
    >> By "critical bit" do you mean "if you can't understand this block, you
    >> can't understand the file", so that if you're reading the file and see
    >> a block with that bit set, you have to stop processing the file"?  An
    >> IDB would be such a block, as you can't interpret packet blocks
    >> without knowing the link-layer header type for the interface for the
    >> packet, and one might consider packet blocks to be critical, too, as
    >> there's not much to analyzer if you can't read a packet block. :-)

    >> Ideally, we wouldn't introduce those, as that'd mean there'd be
    >> pcap-ng files that no old software could read, even with a loss of
    >> information.

    > So if we require "ignore if not known", then the only bit we need
    > means, copy when writing vs.  ignore when writing. This is something
    > you know when specifying the option/block.

Yes, that's my point.
We would know when assigning the option # if the info is critical.

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