Re: [dpdk-stable] [dpdk-dev] [PATCH] net/sfc: cut non VLAN ID bits from TCI

[Adrien Mazarguil <adrien.mazarguil@6wind.com>]

On Fri, Jun 29, 2018 at 04:23:31PM +0100, Andrew Rybchenko wrote:
> TCI may contain PCP or DEI bits. Matching of these bits is not
> supported, but the bits still may be set in specification value and
> not covered by mask. So, these bits should be ignored.
> 
> Fixes: 894080975e1e ("net/sfc: support VLAN in flow API filters")
> Cc: stable@dpdk.org
> 
> Signed-off-by: Andrew Rybchenko <arybchenko@solarflare.com>
> Reviewed-by: Roman Zhukov <roman.zhukov@oktetlabs.ru>
> 
> ---
>  drivers/net/sfc/sfc_flow.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/sfc/sfc_flow.c b/drivers/net/sfc/sfc_flow.c
> index 5613d59a9..18387415e 100644
> --- a/drivers/net/sfc/sfc_flow.c
> +++ b/drivers/net/sfc/sfc_flow.c
> @@ -371,7 +371,8 @@ sfc_flow_parse_vlan(const struct rte_flow_item *item,
>  	 * the outer tag and the next matches the inner tag.
>  	 */
>  	if (mask->tci == supp_mask.tci) {
> -		vid = rte_bswap16(spec->tci);
> +		/* Apply mask to keep VID only */
> +		vid = rte_bswap16(spec->tci & mask->tci);
>  
>  		if (!(efx_spec->efs_match_flags &
>  		      EFX_FILTER_MATCH_OUTER_VID)) {

I think there is an issue with this patch when spec->mask is user-provided,
PMDs have to trust it. They must not simply ignore bits they cannot handle
but explicitly reject the flow rule for correctness.

Most devices cannot match PCP and DEI, this is why the default TCI mask was
modified in v18.05 by commit 0730ab674cb1 ("ethdev: fix default VLAN TCI
mask in flow API") to cover the VID part only.

I wrote a helper for mlx5 to help with such basic sanity checks on pattern
items in a generic(ish) fashion, maybe you could reuse something. Have a
look at mlx5_nl_flow_item_mask() [1].

[1] "net/mlx5: add L2-L4 pattern items to switch flow rules"
    https://mails.dpdk.org/archives/dev/2018-June/105579.html

-- 
Adrien Mazarguil
6WIND