Playing with mbuf in userland

[Bosko Milekic]

I wrote:
  Another option to look into would be to implement a sysctl(8)-exported
  handler that iterates over the mbuf chain and prints out the mbuf chains
  in something like XML, which your userland application can then more or less
  easily parse, and reproduce the chain ("fake it up") in userland.  This
  solution is rather attractive because you can do all sorts of things
  with the intermediate-parsing-language right from the kernel, as well
  as from userland (at the parsing stages).  To see an example of a sysctl(8)
  handler, refer to src/sys/vm/uma_core.c (the bottom) in FreeBSD 5.x.

    I should also add: you should have various sysctl OIDs that call this
    handler passing, say, the mbuf chain as an argument (a reference to the
    top mbuf).  This way certain OIDs can send out a snapshot of an mbuf
    chain at a particular point in the stack, and others can send snapshots
    from the socket buffer and driver entry-points (you can get some perception
    of how the chain changes as it makes its way up-and-down the layers).

    -Bosko