Re: [PATCH v2] can: raw: fix CAN FD frame transmissions over CAN XL devices

[Marc Kleine-Budde <mkl@pengutronix.de>]

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On 31.01.2023 10:18:24, Oliver Hartkopp wrote:
> A CAN XL device is always capable to process CAN FD frames. The former
> check when sending CAN FD frames relied on the existence of a CAN FD
> device and did not check for a CAN XL device that would be correct too.
> 
> With this patch the CAN FD feature is enabled automatically when CAN XL
> is switched on - and CAN FD cannot be switch off while CAN XL is enabled.
> 
> This precondition also leads to a clean up and reduction of checks in the
> hot path in raw_rcv() and raw_sendmsg().
> 
> Fixes: 626332696d75 ("can: raw: add CAN XL support")
> Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>
> ---
> 
> V2: fixed typo: devive -> device
> 
> net/can/raw.c | 45 ++++++++++++++++++++++++++++++---------------
>  1 file changed, 30 insertions(+), 15 deletions(-)
> 
> diff --git a/net/can/raw.c b/net/can/raw.c
> index 81071cdb0301..c505d315a7a9 100644
> --- a/net/can/raw.c
> +++ b/net/can/raw.c
> @@ -130,11 +130,11 @@ static void raw_rcv(struct sk_buff *oskb, void *data)
>  	/* check the received tx sock reference */
>  	if (!ro->recv_own_msgs && oskb->sk == sk)
>  		return;
>  
>  	/* make sure to not pass oversized frames to the socket */
> -	if ((can_is_canfd_skb(oskb) && !ro->fd_frames && !ro->xl_frames) ||
> +	if ((can_is_canfd_skb(oskb) && !ro->fd_frames) ||
>  	    (can_is_canxl_skb(oskb) && !ro->xl_frames))
>  		return;
>  
>  	/* eliminate multiple filter matches for the same skb */
>  	if (this_cpu_ptr(ro->uniq)->skb == oskb &&
> @@ -668,19 +668,27 @@ static int raw_setsockopt(struct socket *sock, int level, int optname,
>  			return -EINVAL;
>  
>  		if (copy_from_sockptr(&ro->fd_frames, optval, optlen))
>  			return -EFAULT;
>  
> +		/* Enabling CAN XL includes CAN FD */
> +		if (ro->xl_frames && !ro->fd_frames) {
> +			ro->fd_frames = ro->xl_frames;
> +			return -EINVAL;
> +		}

This looks a bit weird. Maybe copy to a local variable first, then
check, then assign ->fd_frames or exit with error (instead of rolling
back)?

Marc

-- 
Pengutronix e.K.                 | Marc Kleine-Budde           |
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