Re: [dpdk-dev] [PATCH] mbuf: fix to update documentation of QinQ stripped bit interpretation

[Olivier Matz <olivier.matz@6wind.com>]

Hi Somnath,

Sorry for the delay, please find some comments below.

I suggest the following title instead:

  mbuf: extend meaning of QinQ stripped bit

On Mon, Jan 06, 2020 at 02:04:23PM +0530, 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 and saved in mbuf->vlan_tci_outer.

To be sure we're on the same page: we are talking about case 7 of this
link: http://inbox.dpdk.org/dev/20191227145041.GQ22738@platinum/

So, even if the inner vlan_tci is not stripped from packet data, it has
to be saved in m->vlan_tci, because it is implied by PKT_RX_VLAN.

From the same link, the case where the driver only strips+saves the
outer vlan without saving or stripping the inner one is case 3.

> 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>
> ---
>  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).

their tci are -> its tci is

>   * 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.

ok

> + * 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 is correct, but I'd use a bullet list to add another sentence:

 * - If 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).
 * - If PKT_RX_QINQ_STRIPPED is set and PKT_RX_VLAN_STRIPPED is unset, only the
 *   outer vlan is removed from packet data, but both 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.

The same exact sentence is above, this one can be removed.

> + * When PKT_RX_QINQ_STRIPPED and PKT_RX_VLAN_STRIPPED are set,
> + * (PKT_RX_VLAN | PKT_RX_QINQ) must also be set.

This can be removed too as it is redundant with above sentence:

 * When PKT_RX_QINQ_STRIPPED is set, the flags (PKT_RX_VLAN |  PKT_RX_QINQ)
 * must also be set.


Thanks,
Olivier