netdev - Re: [PATCH net-next] net: vlan: add support for tunnel offload

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Date:   Wed, 07 Nov 2018 22:23:53 -0800 (PST)
From:   David Miller <davem@...emloft.net>
To:     dcaratti@...hat.com
Cc:     xiyou.wangcong@...il.com, netdev@...r.kernel.org, fbl@...hat.com,
        fw@...len.de
Subject: Re: [PATCH net-next] net: vlan: add support for tunnel offload

From: Davide Caratti <dcaratti@...hat.com>
Date: Wed,  7 Nov 2018 11:28:18 +0100

> GSO tunneled packets are always segmented in software before they are
> transmitted by a VLAN, even when the lower device can offload tunnel
> encapsulation and VLAN together (i.e., some bits in NETIF_F_GSO_ENCAP_ALL
> mask are set in the lower device 'vlan_features'). If we let VLANs have
> the same tunnel offload capabilities as their lower device, throughput
> can improve significantly when CPU is limited on the transmitter side.
> 
>  - set NETIF_F_GSO_ENCAP_ALL bits in the VLAN 'hw_features', to ensure
>  that 'features' will have those bits zeroed only when the lower device
>  has no hardware support for tunnel encapsulation.
>  - for the same reason, copy GSO-related bits of 'hw_enc_features' from
>  lower device to VLAN, and ensure to update that value when the lower
>  device changes its features.
>  - set NETIF_F_HW_CSUM bit in the VLAN 'hw_enc_features' if 'real_dev'
>  is able to compute checksums at least for a kind of packets, like done
>  with commit 8403debeead8 ("vlan: Keep NETIF_F_HW_CSUM similar to other
>  software devices"). This avoids software segmentation due to mismatching
>  checksum capabilities between VLAN's 'features' and 'hw_enc_features'.
> 
> Reported-by: Flavio Leitner <fbl@...hat.com>
> Signed-off-by: Davide Caratti <dcaratti@...hat.com>

Applied.