[dpdk-dev] [PATCH] doc: refine ethernet and VLAN flow rule items

[Andrew Rybchenko]

On 4/23/20 9:30 PM, Dekel Peled wrote:
> Specified pattern may be translated in different manner.
> For example the pattern "eth / ipv4" can be translated to match
> untagged packets only, since the pattern doesn't specify a vlan item.

vlan -> VLAN

> It can also be translated to match both tagged and untagged packets,
> for the same reason.
> This patch updates the rte_flow documentation to clearly specify the
> required pattern to use.
> For example:
> To match tagged ipv4 packets, the pattern "eth type is 0x8100 /
> vlan / ipv4 / end" should be used.

Isn't eth / vlan / ipv4 /end sufficient? What's the difference?
I guess later should allow any VLAN TPID, but it is greyish
since it is HW dependent.

> To match untagged ipv4 packets, the pattern "eth type is 0x0800 /
> ipv4 / end" should be used.

What about eth / ipv4 / end?
Does usage of ipv4 assume that EtherType is 0x0800?

> To match both tagged and untagged packets, the pattern "eth / end"
> should be used.

The interesting question is what should be used if I want
either tagged or untagged IPv4 packets. I think it worse
to mention to make the picture complete.

> Signed-off-by: Dekel Peled <dekelp at mellanox.com>
> ---
>  doc/guides/prog_guide/rte_flow.rst | 8 ++++++++
>  lib/librte_ethdev/rte_flow.h       | 9 +++++++++
>  2 files changed, 17 insertions(+)
> 
> diff --git a/doc/guides/prog_guide/rte_flow.rst b/doc/guides/prog_guide/rte_flow.rst
> index cf4368e..0d1c305 100644
> --- a/doc/guides/prog_guide/rte_flow.rst
> +++ b/doc/guides/prog_guide/rte_flow.rst
> @@ -905,6 +905,12 @@ so-called layer 2.5 pattern items such as ``RTE_FLOW_ITEM_TYPE_VLAN``. In
>  the latter case, ``type`` refers to that of the outer header, with the inner
>  EtherType/TPID provided by the subsequent pattern item. This is the same
>  order as on the wire.
> +If the ``type`` field contains a TPID value, then only tagged packets will match
> +the pattern.

Shouldn't we emphasis that "tagged packets with specified TPID
will match the pattern." since tagged packets could have
various TPIDs.

> +If the ``type`` field contains another EtherType value, then only untagged
> +packets will match the pattern.

I'm afraid "another EtherType" is too ambiguous.
"non-TPID EtherType" is ambiguous as well and HW
dependent. May be it is better to remove the sentence
completely.

> +If the ``ETH`` item is the only item in the pattern, and the ``type`` field is
> +not specified, then both tagged and untagged packets will match the pattern.
>  
>  - ``dst``: destination MAC.
>  - ``src``: source MAC.
> @@ -919,6 +925,8 @@ Matches an 802.1Q/ad VLAN tag.
>  The corresponding standard outer EtherType (TPID) values are
>  ``RTE_ETHER_TYPE_VLAN`` or ``RTE_ETHER_TYPE_QINQ``. It can be overridden by the
>  preceding pattern item.
> +If a ``VLAN`` item is present in the pattern, then only tagged packets will
> +match the pattern.
>  
>  - ``tci``: tag control information.
>  - ``inner_type``: inner EtherType or TPID.
> diff --git a/lib/librte_ethdev/rte_flow.h b/lib/librte_ethdev/rte_flow.h
> index 132b44e..178e87e 100644
> --- a/lib/librte_ethdev/rte_flow.h
> +++ b/lib/librte_ethdev/rte_flow.h
> @@ -710,6 +710,13 @@ struct rte_flow_item_raw {
>   * the latter case, @p type refers to that of the outer header, with the
>   * inner EtherType/TPID provided by the subsequent pattern item. This is the
>   * same order as on the wire.
> + * If the @p type field contains a TPID value, then only tagged packets will
> + * match the pattern.
> + * If the @p type field contains another EtherType value, then only untagged
> + * packets will match the pattern.
> + * If the @p ETH item is the only item in the pattern, and the @p type field
> + * is not specified, then both tagged and untagged packets will match the
> + * pattern.
>   */
>  struct rte_flow_item_eth {
>  	struct rte_ether_addr dst; /**< Destination MAC. */
> @@ -734,6 +741,8 @@ struct rte_flow_item_eth {
>   * The corresponding standard outer EtherType (TPID) values are
>   * RTE_ETHER_TYPE_VLAN or RTE_ETHER_TYPE_QINQ. It can be overridden by
>   * the preceding pattern item.
> + * If a @p VLAN item is present in the pattern, then only tagged packets will
> + * match the pattern.
>   */
>  struct rte_flow_item_vlan {
>  	rte_be16_t tci; /**< Tag control information. */
>