BCE on FreeBSD and oversized packet acceptance.

[Mike Karels]

> 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.

I can provide diffs if they are of interest.  As you say, this is
driver-by-driver.  We have done only em at this point, as we don't
support 9K clusters.  (Long story, has to do with resource management.)

		Mike