netdev - Re: [PATCH net-next 4/5] tun: Add support for SCTP checksum offload

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Date:   Mon, 16 Apr 2018 20:12:03 +0300
From:   "Michael S. Tsirkin" <mst@...hat.com>
To:     Vladislav Yasevich <vyasevich@...il.com>
Cc:     netdev@...r.kernel.org, linux-sctp@...r.kernel.org,
        virtualization@...ts.linux-foundation.org, jasowang@...hat.com,
        nhorman@...driver.com, Vladislav Yasevich <vyasevic@...hat.com>
Subject: Re: [PATCH net-next 4/5] tun: Add support for SCTP checksum offload

On Mon, Apr 02, 2018 at 09:40:05AM -0400, Vladislav Yasevich wrote:
> Adds a new tun offload flag to allow for SCTP checksum offload.
> The flag has to be set by the user and defaults to "no offload".
> 
> Signed-off-by: Vladislav Yasevich <vyasevic@...hat.com>

When would user set this flag? Wouldn't that be when
userspace is ready to get SCTP packets without a checksum?
Seems to be this is an indication that when userspace
is qemu running a guest, said guest needs to communicate
the new ability to qemu.

> ---
>  drivers/net/tun.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/drivers/net/tun.c b/drivers/net/tun.c
> index a1ba262..263bcbe 100644
> --- a/drivers/net/tun.c
> +++ b/drivers/net/tun.c
> @@ -2719,6 +2719,11 @@ static int set_offload(struct tun_struct *tun, unsigned long arg)
>  		arg &= ~TUN_F_UFO;
>  	}
>  
> +	if (arg & TUN_F_SCTP_CSUM) {
> +		features |= NETIF_F_SCTP_CRC;
> +		arg &= ~TUN_F_SCTP_CSUM;
> +	}
> +
>  	/* This gives the user a way to test for new features in future by
>  	 * trying to set them. */
>  	if (arg)
> -- 
> 2.9.5