Re: [dpdk-dev] [RFC PATCH] mbuf: fix to update documentation of PKT_RX_QINQ_STRIPPED

[Andrew Rybchenko <arybchenko@solarflare.com>]

On 12/24/19 6:16 AM, Somnath Kotur wrote:
> Given that we haven't heard any objection from anyone in a while on
> this ...can we get this in please?

I'm sorry, but have you seen below?
It means that PKT_RX_QINQ_STRIPPED, PKT_RX_QINQ, PKT_RX_VLAN
and PKT_RX_VLAN_STRIPPED must be clarified.

It sounds like change of semantics in order to resolve the
problem, but anyway it is still a small change of semantics.

BTW, it is better to make summary human readable and avoid
PKT_RX_QINQ_STRIPPED (I guess check-git-log.sh yells on it).

Also RFC patch cannot be applied, non-RFC version is required.

CC main tree maintainers.

> Thanks
> 
> On Mon, Dec 16, 2019 at 2:43 PM Andrew Rybchenko
> <arybchenko@solarflare.com> wrote:
>>
>> On 12/16/19 11:47 AM, Somnath Kotur wrote:
>>> On Mon, Dec 16, 2019 at 12:01 PM Andrew Rybchenko
>>> <arybchenko@solarflare.com> wrote:
>>>>
>>>> On 12/16/19 6:16 AM, Somnath Kotur wrote:
>>>>> Certain hardware may be able to strip and/or save only the outermost
>>>>> VLAN instead of both the VLANs in the mbuf in a QinQ scenario.
>>>>> To handle such cases, we could re-interpret setting of just PKT_RX_QINQ_STRIPPED
>>>>> to indicate that only the outermost VLAN has been stripped by the hardware and
>>>>> saved in mbuf->vlan_tci_outer.
>>>>> Only When both PKT_RX_QINQ_STRIPPED and PKT_RX_VLAN_STRIPPED are set, the 2 vlans
>>>>> have been stripped by the hardware and their tci are saved in mbuf->vlan_tci (inner)
>>>>> and mbuf->vlan_tci_outer (outer).
>>>>>
>>>>> Signed-off-by: Somnath Kotur <somnath.kotur@broadcom.com>
>>>>> Signed-off-by: JP Lee <jongpil.lee@broadcom.com>
>>>>> ---
>>>>>  lib/librte_mbuf/rte_mbuf_core.h | 15 +++++++++++----
>>>>>  1 file changed, 11 insertions(+), 4 deletions(-)
>>>>>
>>>>> diff --git a/lib/librte_mbuf/rte_mbuf_core.h b/lib/librte_mbuf/rte_mbuf_core.h
>>>>> index 9a8557d..db1070b 100644
>>>>> --- a/lib/librte_mbuf/rte_mbuf_core.h
>>>>> +++ b/lib/librte_mbuf/rte_mbuf_core.h
>>>>> @@ -124,12 +124,19 @@
>>>>>  #define PKT_RX_FDIR_FLX      (1ULL << 14)
>>>>>
>>>>>  /**
>>>>> - * The 2 vlans have been stripped by the hardware and their tci are
>>>>> - * saved in mbuf->vlan_tci (inner) and mbuf->vlan_tci_outer (outer).
>>>>> + * The outer vlan has been stripped by the hardware and their tci are
>>>>> + * saved in mbuf->vlan_tci_outer (outer).
>>>>>   * This can only happen if vlan stripping is enabled in the RX
>>>>>   * configuration of the PMD.
>>>>> - * When PKT_RX_QINQ_STRIPPED is set, the flags (PKT_RX_VLAN |
>>>>> - * PKT_RX_VLAN_STRIPPED | PKT_RX_QINQ) must also be set.
>>>>> + * When PKT_RX_QINQ_STRIPPED is set, the flags (PKT_RX_VLAN |  PKT_RX_QINQ)
>>>>> + * must also be set.
>>>>> + * When both PKT_RX_QINQ_STRIPPED and PKT_RX_VLAN_STRIPPED are set, the 2 vlans
>>>>> + * have been stripped by the hardware and their tci are saved in
>>>>> + * mbuf->vlan_tci (inner) and mbuf->vlan_tci_outer (outer).
>>>>> + * This can only happen if vlan stripping is enabled in the RX configuration
>>>>> + * of the PMD.
>>>>> + * When PKT_RX_QINQ_STRIPPED and PKT_RX_VLAN_STRIPPED are set,
>>>>> + * (PKT_RX_VLAN | PKT_RX_QINQ) must also be set.
>>>>>   */
>>>>>  #define PKT_RX_QINQ_STRIPPED (1ULL << 15)
>>>>>
>>>>
>>>> I always thought that PKT_RX_VLAN_STRIPPED means *one* VLAN
>>>> stripped regardless if it is outer (if the packet is double
>>>> tagged) or inner (if only one VLAN tag was present).
>>>>
>>>> That's why PKT_RX_QINQ_STRIPPED description says that *two*
>>>> VLANs have been stripped.
>>>>
>>>> What is the problem with such approach?
>>> The problem is that RX_VLAN_STRIPPED implies that the stripped VLAN
>>> (outer or inner) is saved in mbuf->vlan_tci, correct?
>>
>> Yes.
>>
>>> There is no way to convey that it is in QinQ mode and yet only outer
>>> VLAN has been stripped and saved in mbuf->vlan_tci_outer ?
>>
>> Ah, it looks like I understand now that the problem is in
>> PKT_RX_QINQ description which claims that TCI is saved in
>> mbuf->vlan_tci_outer and PKT_RX_QINQ_STRIPPED means that
>> both VLAN tags are stripped regardless (PKT_RX_VLAN_STRIPPED).
>> Moreover PKT_RX_QINQ_STRIPPED requires PKT_RX_VLAN_STRIPPED.
>>
>> It means that PKT_RX_QINQ_STRIPPED, PKT_RX_QINQ, PKT_RX_VLAN
>> and PKT_RX_VLAN_STRIPPED must be clarified.
>>
>> I'm not sure, but it looks like it could affect net/dpaa2,
>> so I'm including driver maintainers in CC.