netdev - Re: [PATCH net] net: Disable NETIF_F_HW_TLS_TX when HW

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Message-ID: <20201104132521.2f7c3690@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com>
Date:   Wed, 4 Nov 2020 13:25:21 -0800
From:   Jakub Kicinski <kuba@...nel.org>
To:     Tariq Toukan <tariqt@...dia.com>
Cc:     "David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
        Saeed Mahameed <saeedm@...dia.com>,
        Moshe Shemesh <moshe@...dia.com>,
        Boris Pismenny <borisp@...dia.com>
Subject: Re: [PATCH net] net: Disable NETIF_F_HW_TLS_TX when HW_CSUM is
 disabled

On Wed,  4 Nov 2020 12:21:41 +0200 Tariq Toukan wrote:
> With NETIF_F_HW_TLS_TX packets are encrypted in HW. This cannot be
> logically done when HW_CSUM offload is off.

Right. Do you expect drivers to nack clearing NETIF_F_HW_TLS_TX when
there are active connections, then?  I don't think NFP does.  We either
gotta return -EBUSY when there are offloaded connections, or at least
clearly document the expected behavior.

> Fixes: 2342a8512a1e ("net: Add TLS TX offload features")
> Signed-off-by: Tariq Toukan <tariqt@...dia.com>
> Reviewed-by: Boris Pismenny <borisp@...dia.com>

> diff --git a/net/core/dev.c b/net/core/dev.c
> index 82dc6b48e45f..5f72ea17d3f7 100644
> --- a/net/core/dev.c
> +++ b/net/core/dev.c
> @@ -9588,6 +9588,11 @@ static netdev_features_t netdev_fix_features(struct net_device *dev,
>  		}
>  	}
>  
> +	if ((features & NETIF_F_HW_TLS_TX) && !(features & NETIF_F_HW_CSUM)) {
> +		netdev_dbg(dev, "Dropping TLS TX HW offload feature since no CSUM feature.\n");
> +		features &= ~NETIF_F_HW_TLS_TX;
> +	}