Darren Reed wrote:
> 
> In some email I received from Gunther Schadow, sie wrote:
> > Gunther Schadow wrote:
> > [snip]
> >
> > .... to make things even more complicated, we also have the
> > berkeley packet filter (BPF) mechanism. Heck! How could
> > so many things evolve that all do essentially the same
> > thing? The interesting thing about the BPF mechanism is
> > that it is very generic. Filter rules are instructions
> > of a virtual von-Neumann-machine (reminds me of 6502
> > assembler :-). Tcpdump uses BPF, at least on FreeBSD.
> > But I think BPF is available on all 4.4 BSD derivatives.
> >
> > where does this fit in the crowd?
> 
> BPF uses a byte-code language, like Java, to tell the
> matching routine what bits to compare and return a "true or
> false".  i.e. you need to build things around it if you want
> to use it for packet matching, etc.

netgraph has a bpf node that can be programmed with BPF codes to do almost 
any filtereing required. 

(Netgraph can be used to do in-kernel tunnelling of almost any type
if you are willing to figure ot how to use it.)

> 
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