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Message-ID: <35dc2a59-7e6b-224d-49da-085d3f140fe7@redhat.com> Date: Tue, 23 May 2017 08:59:45 -0400 From: Vlad Yasevich <vyasevic@...hat.com> To: David Miller <davem@...emloft.net>, vyasevich@...il.com Cc: netdev@...r.kernel.org, makita.toshiaki@....ntt.co.jp Subject: Re: [PATCH net 1/3] vlan: Fix tcp checksums offloads for Q-in-Q vlan. On 05/22/2017 07:59 PM, David Miller wrote: > From: Vladislav Yasevich <vyasevich@...il.com> > Date: Thu, 18 May 2017 09:31:03 -0400 > >> It appears that since commit 8cb65d000, Q-in-Q vlans have been >> broken. The series that commit is part of enabled TSO and checksum >> offloading on Q-in-Q vlans. However, most HW we support can't handle >> it. To work around the issue, the above commit added a function that >> turns off offloads on Q-in-Q devices, but it left the checksum offload. >> That will cause issues with most older devices that supprort very basic >> checksum offload capabilities as well as some newer devices (we've >> reproduced te problem with both be2net and bnx). >> >> To solve this for everyone, turn off checksum offloading feature >> by default when sending Q-in-Q traffic. Devices that are proven to >> work can provided a corrected ndo_features_check implemetation. >> >> Fixes: 8cb65d000 ("net: Move check for multiple vlans to drivers") >> CC: Toshiaki Makita <makita.toshiaki@....ntt.co.jp> >> Signed-off-by: Vladislav Yasevich <vyasevic@...hat.com> > > This is a tough one. I can certainly sympathize with your frustration > trying to track this down. > > Clearing NETIF_F_HW_CSUM completely is the most conservative change. > > However, for all the (perhaps many) cards upon which the checksumming > does work properly in Q-in-Q situations, this change could be > introducing non-trivial performance regressions. > > So I think Toshiaki's suggestion to drop IP_CSUM and IPV6_CSUM is, > on balance, the best way forward. > Thanks. I'll update and re-submit. -vlad > Thanks. >
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