Re: Playing with mbuf in userland

From: Bosko Milekic (bmilekic_at_FreeBSD.org)
Date: 08/22/04

  • Next message: Kevin Brunelle: "Re: Fatal trap 12: page fault while in kernel mode" 
    Date: Sun, 22 Aug 2004 14:12:53 +0000
To: Paolo Pisati <flag@oltrelinux.com>, FreeBSD_Hackers <freebsd-hackers@freebsd.org>

    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
     
    _______________________________________________
    freebsd-hackers@freebsd.org mailing list
    http://lists.freebsd.org/mailman/listinfo/freebsd-hackers
    To unsubscribe, send any mail to "freebsd-hackers-unsubscribe@freebsd.org"

  • Next message: Kevin Brunelle: "Re: Fatal trap 12: page fault while in kernel mode"