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Date: Mon, 19 Feb 2001 17:47:37 +0530 (IST)
From: Satyajeet Seth <sseth@sasken.com>
To: Julian Elischer <julian@elischer.org>
Cc: <net@freebsd.org>
Subject: Re: Using netgraph to implement pseudo interfaces
In-Reply-To: <3A910856.CE68FEAC@elischer.org>
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Hi

A node of type ng_bpf uses BPF. How is a packet passed onto the
BPF? I believe a copy of the packet is sent. Is this correct?

Once a packet is sent to the BPF, will the driver process the
packet further and queue it to the IP layer?

If so, in our case, there will be duplication of packets. Here the BPF
will pass the packets onto pseudo ethernet interfaces.  These interfaces
will in turn queue the packets to the IP layer.

Thanks
Satya

> > I wished to implement pseudo interfaces with the following requirements:
> >
> > 1. There is a ethernet interface fxp0 having MAC address MAC0. It also
> > receives packets with destination MAC address MAC1 and MAC2.
> >
> > 2. The packets with destination MAC address MAC1 are sent to a pseudo
> > interface 1 and packets with destination MAC address MAC2 are sent to
> > pseudo interface 2.
> >
> > 3. The packets addressed to MAC0 should be sent to sent to fxp0.
> >
> > I plan to design  a netgraph as follows:
> >
> >          iface1
> >            /
> > fxp0 <-> bpf
> >            \
> >          iface2
>
> I forgot to add in my previous response that you'd have to do this like:
>
> fxp0: <--> bpf <--> bpf <--> interface0
>             \        \
>              \        ------>interface1
>               \
>                \------------>interface2
>
> as each bpfnode hook only selects between a
> "match" and "no match" hook.
>
> you could do it with one node as follows:
>
>
>             +----------------------------+
>             |                            |
>             +->(hook2)[   ]              |
> fxp0:(lower)<->(hook1)[bpf](nomatch1)----+
>                       [   ](match1)<-------->(upper)fxp0:
>                       [   ](nomatch2)<------>(hook)iface1:
>                       [   ](match2)<-------->(hook)iface2:
>
> i.e. loop the data back through the same node twice to effect two rules on
> the same data.
>
>
> >
> > fxp0, iface1, iface2, bpf are nodes of type ng_ether, ng_iface, ng_iface
> > and ng_bpf respectively.
> >
> > The packets with destination addresses MAC1 and MAC2 are sent to
> > interfaces iface1 and iface2 respectively by bpf. Remaining are sent to
> > fxp0.



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