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

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

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?
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 ?