Re: bpf, ipfw and before-and-after

From: Barney Wolff (barney_at_databus.com)
Date: 08/06/03

  • Next message: John Polstra: "Re: bpf, ipfw and before-and-after" 
    Date: Tue, 5 Aug 2003 20:29:45 -0400
To: Edwin Groothuis <edwin@freebsd.org>

    On Wed, Aug 06, 2003 at 09:54:11AM +1000, Edwin Groothuis wrote:
    > On Tue, Aug 05, 2003 at 10:31:01AM -0400, Barney Wolff wrote:
    > > Seems to me that with ipfw logging and tcpdump packet selection this
    > > is largely a non-issue. We should be wary of adding complexity to
    > > what's already at the limits of human comprehension.
    >
    > Could you explain that first line a little bit more verbose?

    ipfw can log packets, giving source ip/port, dest ip/port, proto
    and interface which is at least some of the info that tcpdump would supply.

    tcpdump can take quite complex selection criteria to determine whether
    to log a packet. So your complaint that tcpdump logs stuff that ipfw
    is going to drop can be substantially mitigated.

    > About the second one, given the fact that I could find out how it
    > works (more or less) and where to add the statements, makes me think
    > that despite the complexity of the thing being achieved, the
    > implementation in the code is pretty neat and structured.

    The issue is not that the addition would be complex, but that every
    addition to a system already very complex must be carefully weighed
    against the claimed benefits. Does the expression "creeping featurism"
    sound familiar? Every feature of the Win32 API, OS/360 and the US
    Federal Tax Code was added because somebody thought it was a good idea.

    "Perfection in design is achieved not when there is nothing left to add,
    but when there is nothing left to take away." 

    -- 
Barney Wolff         http://www.databus.com/bwresume.pdf
I'm available by contract or FT, in the NYC metro area or via the 'Net.
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