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

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

Given that we haven't heard any objection from anyone in a while on
this ...can we get this in please?

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.