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From: Julian Elischer <julian@elischer.org>
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Cc: FreeBSD Net <freebsd-net@freebsd.org>,
	David Christensen <davidch@broadcom.com>, Jack Vogel <jfvogel@gmail.com>
Subject: Re: BCE on FreeBSD and oversized packet acceptance.
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Mike Karels wrote:
>>> Secure Computing (my employer) has a modification that seems reasonable
>>> to me (well, I guess I wouldn't have done it otherwise).  We adopted the
>>> existing but unused JUMBO_MTU capability flag, and, if enabled, instructs
>>> the driver to receive jumbo frames according to the hardware limits.  With
>>> that flag, the MTU may be 1500, but the driver is still instructed to
>>> receive jumbo frames even without sending them.  The reason for this
>>> is the lack of a way to negotiate the use of jumbo frames per host
>>> (as far as I know; such a thing would certainly be useful, though).
> 
>> certainly the adoption of that flag is reasonable.
>> is it settable from ifconfig?
>> it's probably better than saying "enable jumbo reception 
>> if mtu is greater than 1600 bytes" or whatever.. 
> 
> Yes, the flag is settable with ifconfig.  It expands the "accept
> what is convenient" to "and also accept whatever is reasonable
> for jumbo" (for this NIC).
> 
> 		Mike

It would be interesting to get patches to look at....
Does it require changing all the drivers?
I assume that if so, you'd only patch those you are interested in.