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U32 allows you to extract quantities of up to 4 bytes from a packet,
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AND them with specified masks, shift them by specified amounts and
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test whether the results are in any of a set of specified ranges.
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The specification of what to extract is general enough to skip over
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headers with lengths stored in the packet, as in IP or TCP header
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(Please note: This match requires kernel support that
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might not be available in official Linux kernel sources or
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Debian's packaged Linux kernel sources.
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And if support for this match is available for the
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specific Linux kernel source version, that support might
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not be enabled in the current Linux kernel binary.)
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Details and examples are in the kernel module source.