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

[Andrew Rybchenko <arybchenko@solarflare.com>]

On 05.07.2018 22:23, Adrien Mazarguil wrote:
> On Thu, Jul 05, 2018 at 01:14:49PM +0200, Adrien Mazarguil wrote:
>> 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
> Seems like I misread the original patch and PMD code, both are in fact
> correct.
>
> Please ignore my previous comment, sorry for the noise!

No problem. Many thanks for reviewing it.

Andrew.