CONFIG_IP_NF_MATCH_LENGTH
U32 patch support
CONFIG_IP_NF_MATCH_U32
  U32 allows you to extract quantities of up to 4 bytes from a packet,
  AND them with specified masks, shift them by specified amounts and
  test whether the results are in any of a set of specified ranges.
  The specification of what to extract is general enough to skip over
  headers with lengths stored in the packet, as in IP or TCP header
  lengths.

  Details and examples are in the kernel module source.

