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Date:      Thu, 22 Mar 2007 18:39:26 +0300
From:      Yar Tikhiy <yar@comp.chem.msu.su>
To:        Julian Elischer <julian@elischer.org>
Cc:        Luigi Rizzo <rizzo@icir.org>, net@freebsd.org
Subject:   Re: A dummy Ethernet driver
Message-ID:  <20070322153926.GY41715@comp.chem.msu.su>
In-Reply-To: <4601B28B.7090204@elischer.org>
References:  <20070321201936.GN41715@comp.chem.msu.su> <20070321132306.A1936@xorpc.icir.org> <4601B28B.7090204@elischer.org>

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On Wed, Mar 21, 2007 at 03:32:43PM -0700, Julian Elischer wrote:
> Luigi Rizzo wrote:
> >On Wed, Mar 21, 2007 at 11:19:36PM +0300, Yar Tikhiy wrote:
> >>Hi folks,
> >>
> >>We have disc(4) for testing and benchmarking.  However, it's a
> >>loopback driver, so such things as vlan or bridge cannot attach to
> >>it.  I needed a similar dummy interface mimicing Ethernet and failed
> >>to find a ready solution.  I tried ng_eiface+ng_hole, but it just
> >>couldn't keep up with gigabit rates.  So I knocked up a new dummy
> >>driver, edsc(4): Ethernet discard interface.  I'd like to commit it
> >>if there are no objections.  Then it could also serve as the bones
> >>of an Ethernet driver for those who study kernel internals or want
> >>to write a new driver.
> >
> >seems like a good idea.
> >
> 
> I think the question I have is why eiface couldn't cope..?
> I think it should have so I'll look at it..

I believe that it can't keep pace because the packet isn't passed
straight from if_start() to Netgraph due to some reservations about
locking.  A callback is used intead, which may introduce a delay.

-- 
Yar



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