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List:       linux-bridge
Subject:    Re: [Bridge] Switch chip support
From:       Lennert Buytenhek <buytenh () gnu ! org>
Date:       2002-06-24 14:51:48
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On Mon, Jun 24, 2002 at 04:47:09PM +0200, Georg Klug wrote:

> Hi Lennert et. al.,

Hello,


> > Will the hardware do just switching, or also routing?  Does
> > the hardware have some kind of built-in ethernet address table?
> > Inhowfar is the chip programmable, i.e., can you upload code
> > into it?  
> 
> The chip is just a Layer 2 switching chip. It has an built-in 
> ethernet address table, which will be maintained in hardware.
> Software can only send and receive packets (on every individual
> port), read statistic counters and configure ports and the 
> switching engine. The port states supported by the hardware match
> the Spanning Tree port states so that the spanning tree protocol
> can be easily adopted to the hardware. There is no firmware on 
> that hardware so there is no upload/download functionality.

Ok.  What would make the most sense to me then is to put hooks into
the bridge code for uploading MAC entries to the chip (or if the
switch chip auto-learns MAC addresses, do it the other way round),
and implement hooks for setting STP port states.  But do expose the
eth0-23 devices to linux.  Add the regular hooks for promiscuous
mode, so that something like 'tcpdump -i eth12' still works.  Every
now and then, poll the statistics counters, and update the host
counters.  Seems fairly straightforward all.

For multicast, you'd have to fall back to broadcasting, because
the linux bridge stuff is unfortunately not very intelligent about
this yet.


cheers,
Lennert
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