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Date: Wed, 08 Apr 2015 23:48:51 -0500 From: Michael Cronenworth <mike@...tml.com> To: Alexander Duyck <alexander.h.duyck@...hat.com>, intel-wired-lan@...ts.osuosl.org, jeffrey.t.kirsher@...el.com CC: netdev@...r.kernel.org, htodd@...fifty.com Subject: Re: [PATCH] e1000e: Cleanup handling of VLAN_HLEN as a part of max frame size On 04/08/2015 04:02 PM, Alexander Duyck wrote: > When the VLAN_HLEN was added to the calculation for the maximum frame size > there seems to have been a number of issues added to the driver. > > The first issue is that in some cases the maximum frame size for a device > never really reached the actual maximum frame size as the VLAN header > length was not included the calculation for that value. As a result some > parts only supported a maximum frame size of either 1496 in the case of > parts that didn't support jumbo frames, and 8996 in the case of the parts > that do. > > The second issue is the fact that there were several checks that weren't > updated so as a result setting an MTU of 1500 was treated as enabling jumbo > frames as the calculated value was 1522 instead of 1518. I have addressed > those by replacing ETH_FRAME_LEN with VLAN_ETH_FRAME_LEN where appropriate. > > The final issue was the fact that lowering the MTU below 1500 would cause > the driver to allocate 2K buffers for the rings. This is an old issue that > was fixed several years ago in igb/ixgbe and I am addressing now by just > replacing == with a <= so that we always just round up to 1522 for anything > that isn't a jumbo frame. Alex, Thanks taking the time to work on a patch. I have tested this patch in 4.0 on i218-v hardware and it is working. I see 9000 in tcpdump (tso/gso off) and my switch blocks packets if I set the max frame size to 9017 down from 9018. I also played with a VLAN real quick, and did not encounter any problems, but I don't normally use VLANs so it may need further testing. Thanks, Michael -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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