netdev - Re: Problems with tg3 driver after lowering the MTU

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Message-Id: <1264087643.2794.2.camel@achroite.uk.solarflarecom.com>
Date:	Thu, 21 Jan 2010 15:27:23 +0000
From:	Ben Hutchings <bhutchings@...arflare.com>
To:	Szilveszter Ordog <slipszi@...il.com>
Cc:	netdev@...r.kernel.org
Subject: Re: Problems with tg3 driver after lowering the MTU

On Thu, 2010-01-21 at 16:21 +0100, Szilveszter Ordog wrote:
> After the MTU is lowered (e.g. to 1420) on a tg3-driven interface,
> received packets larger than that (e.g. 1500 bytes) are silently
> discarded by the driver. Therefore the system doesn't send ICMP
> fragmentation-needed packets and the other side doesn't detect this
> condition.
> 
> Is this a known bug?

I don't believe this a bug.  Within a local network, MTU should be set
the same for all interfaces.  Routers that connect networks with
different MTUs will generate the fragmentation-needed message as
appropriate.

Ben.

-- 
Ben Hutchings, Senior Software Engineer, Solarflare Communications
Not speaking for my employer; that's the marketing department's job.
They asked us to note that Solarflare product names are trademarked.

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