Date: Fri, 7 Sep 2007 16:00:49 -0700 From: Alfred Perlstein <alfred@freebsd.org> To: David Christensen <davidch@broadcom.com> Cc: FreeBSD Net <freebsd-net@freebsd.org>, Julian Elischer <julian@elischer.org> Subject: Re: FreeBSD discarding received packets > MTU Message-ID: <20070907230049.GG87451@elvis.mu.org> In-Reply-To: <09BFF2FA5EAB4A45B6655E151BBDD903051CBF54@NT-IRVA-0750.brcm.ad.broadcom.com> References: <46E0632D.8070200@elischer.org> <46E07E74.5020204@elischer.org> <09BFF2FA5EAB4A45B6655E151BBDD9030501D5C0@NT-IRVA-0750.brcm.ad.broadcom.com> <46E0A5DB.3080404@elischer.org> <09BFF2FA5EAB4A45B6655E151BBDD903051CBEB6@NT-IRVA-0750.brcm.ad.broadcom.com> <20070907194749.GD87451@elvis.mu.org> <09BFF2FA5EAB4A45B6655E151BBDD903051CBF54@NT-IRVA-0750.brcm.ad.broadcom.com>
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* David Christensen <davidch@broadcom.com> [070907 13:41] wrote: > > > I'm not completely opposed to making such a change, but I don't want > > > to make a default change in the driver's behavior that other people > > > may be depending upon (whether they are aware of it or not). A > > > tunable driver value could be the answer but I'm not entirely sure > > > how it would fare in the hardware at the high end of MTU > > values such > > > as 9000. > > > > Dave: > > > > Internet ettiquette demands being gracious in what you accept. > > The default policy of FreeBSD is to accept such packets. > > This is a really weird bug to track down. > > Other drivers support it. > > > > This isn't worth making a stand over, unless you're trying > > to hold users of YOUR driver hostage. > > > > I'm just being cautious about making changes before I understand > all of the implications. The driver's current behavior is > supported by IEEE 802.3 specification (802.3-2005, 4.2.4.2.1) > and is implemented in the same way for other operating systems > that are very widely deployed (including Windows and Linux) > without any reported problems. The existing bge driver which > was developed for FreeBSD 10 years ago also operates this way, > so all of my references for porting this driver happen to agree > on the same implementation. Which is all well and good, but the age of a bug does not a feature make. Please think of the four points I raised. I think it makes sense to possibly add a "enforce rx mtu" knob somewhere, but it should likely be turned off. -Alfred
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