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

[Somnath Kotur <somnath.kotur@broadcom.com>]

On Thu, Jan 2, 2020 at 6:35 PM Andrew Rybchenko
<arybchenko@solarflare.com> wrote:
>
> Somnath,
>
> On 12/31/19 5:15 AM, Somnath Kotur wrote:
> > Andrew,
> >
> > On Tue, Dec 24, 2019 at 3:23 PM Andrew Rybchenko
> > <arybchenko@solarflare.com> wrote:
> >> 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.
> >>
> > OK, not sure I understood what is the next action here? Will you or someone
> > from the main tree maintainers be sending out a patch with this clarification?
>
> Please, send non-RCF version of the patch which fixes
> PKT_RX_QINQ_STRIPPED and PKT_RX_QINQ description.
> PKT_RX_QINQ must not claim that both VLAN headers
> have been stripped in the case of PKT_RX_QINQ_STRIPPED.
>
OK, think i've done the non-RFC patch based on my understanding here

> I think that VLAN should be used instead of "vlan" in description
> as well as TCI instead of "tci". Also vlans -> VLANs.
>
Done
> >> It sounds like change of semantics in order to resolve the
> >> problem, but anyway it is still a small change of semantics.
>
> May be dropped.
>
> >> BTW, it is better to make summary human readable and avoid
> >> PKT_RX_QINQ_STRIPPED (I guess check-git-log.sh yells on it).
>
> Please, don't forget about it as well.
Done

> >> 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.
>