about the implement and design of the pfil interface

[Max Laier]

On Thursday 18 August 2005 14:02, shiner chen wrote:
> Recently ,I read the code of the pfil interface was designed and
> implemented by  Matthew R. Green. I want to get the Diagram illustrating
> the flow of TCP/IP packets through the various stages introduced by pfil
> interface and the document about the implement and design of the
> pfilinterface. Who can help me ? thanks!!

In FreeBSD we only have pfil_hooks for IP level packets.  While the 
instrumentation is there to provide other hook points with the pfil API it 
hasn't happend as it would result in performance degradation (at least one 
function call/memory read per hook point).  Unless a specific application 
makes it worthwhile to add another hookup point, I don't think it's 
worthwhile to provide such.  There is some work going on to provide L2 hooks, 
however.

More information about FreeBSD's pfil implementation can be found in 
src/sys/net/pfil.? and the pfil(9) manpage.

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