netdev - Re: [PATCH net 1/3] vlan: Fix tcp checksums offloads for Q-in-Q vlan.

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Date:   Fri, 19 May 2017 10:04:20 +0900
From:   Toshiaki Makita <makita.toshiaki@....ntt.co.jp>
To:     Vladislav Yasevich <vyasevich@...il.com>, netdev@...r.kernel.org
Cc:     Vladislav Yasevich <vyasevic@...hat.com>
Subject: Re: [PATCH net 1/3] vlan: Fix tcp checksums offloads for Q-in-Q vlan.

On 2017/05/18 22:31, Vladislav Yasevich wrote:
> 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>

The patch looks ok, but why do you think 8cb65d000 is wrong?
The same check was there before my patch set.

kernel v4.0:
> netdev_features_t netif_skb_features(struct sk_buff *skb)
...
> 	if (protocol == htons(ETH_P_8021Q) || protocol == htons(ETH_P_8021AD))
> 		features = netdev_intersect_features(features,
> 						     NETIF_F_SG |
> 						     NETIF_F_HIGHDMA |
> 						     NETIF_F_FRAGLIST |
> 						     NETIF_F_GEN_CSUM |
> 						     NETIF_F_HW_VLAN_CTAG_TX |
> 						     NETIF_F_HW_VLAN_STAG_TX);

The commit just moved the check into another function.


Toshiaki Makita