Re: [RFC] ethdev: support metadata as flow rule criteria

[Andrew Rybchenko <arybchenko@solarflare.com>]

On 13.08.2018 10:46, Dekel Peled wrote:
> Current implementation of rte_flow allows match pattern of flow rule,
> based on packet data or header fields.
> This limits the application use of match patterns.
>
> For example, consider a vswitch application which controls a set of VMs,
> connected with virtio, in a fabric with overlay of VXLAN.
> Several VMs can have the same inner tuple, while the outer tuple is
> different and controlled by the vswitch (encap action).
> For the vswtich to be able to offload the rule to the NIC, it must use a
> unique match criteria, independent from the inner tuple, to perform the
> encap action.
>
> This RFC adds support for additional metadata to use as match pattern.
> The metadata is an opaque item, fully controlled by the application.
>
> The use of metadata is relevant for egress rules only.
> It can be set in the flow rule using the RTE_FLOW_ITEM_META.
>
> Application should set the packet metdata in the mbuf->metadata field,
> and set the PKT_TX_METADATA flag in the mbuf->ol_flags.
> The NIC will use the packet metadata as match criteria for relevant flow
> rules.
>
> For example, to do an encap action depending on the VM id, the
> application needs to configure 'match on metadata' rte_flow rule with
> VM id as metadata, along with desired encap action.
> When preparing an egress data packet, application will set VM id data in
> mbuf metadata field and set PKT_TX_METADATA flag.
>
> PMD will send data packets to NIC, with VM id as metadata.
> Egress flow on NIC will match metadata as done with other criteria.
> Upon match on metadata (VM id) the appropriate encap action will be
> performed.
>
> This RFC introduces metadata item type for rte_flow RTE_FLOW_ITEM_META,
> along with corresponding struct rte_flow_item_meta and ol_flag
> PKT_TX_METADATA.
> It also enhances struct rte_mbuf with new data item, uint64_t metadata.
>
> Comments are welcome.
>
> Signed-off-by: Dekel Peled <dekelp@mellanox.com>
> ---
>   doc/guides/prog_guide/rte_flow.rst | 21 +++++++++++++++++++++
>   lib/librte_ethdev/rte_flow.c       |  1 +
>   lib/librte_ethdev/rte_flow.h       | 25 +++++++++++++++++++++++++
>   lib/librte_mbuf/rte_mbuf.h         | 11 +++++++++++
>   4 files changed, 58 insertions(+)
>
> diff --git a/doc/guides/prog_guide/rte_flow.rst b/doc/guides/prog_guide/rte_flow.rst
> index b305a72..b6e35f1 100644
> --- a/doc/guides/prog_guide/rte_flow.rst
> +++ b/doc/guides/prog_guide/rte_flow.rst
> @@ -1191,6 +1191,27 @@ Normally preceded by any of:
>   - `Item: ICMP6_ND_NS`_
>   - `Item: ICMP6_ND_OPT`_
>   
> +Item: ``META``
> +^^^^^^^^^^^^^^
> +
> +Matches an application specific 64 bit metadata item.
> +
> +- Default ``mask`` matches any 64 bit value.
> +
> +.. _table_rte_flow_item_meta:
> +
> +.. table:: META
> +
> +   +----------+----------+---------------------------+
> +   | Field    | Subfield | Value                     |
> +   +==========+==========+===========================+
> +   | ``spec`` | ``data`` | 64 bit metadata value     |
> +   +----------+--------------------------------------+
> +   | ``last`` | ``data`` | upper range value         |
> +   +----------+----------+---------------------------+
> +   | ``mask`` | ``data`` | zeroed to match any value |
> +   +----------+----------+---------------------------+
> +
>   Actions
>   ~~~~~~~
>   
> diff --git a/lib/librte_ethdev/rte_flow.c b/lib/librte_ethdev/rte_flow.c
> index cff4b52..54e5ef8 100644
> --- a/lib/librte_ethdev/rte_flow.c
> +++ b/lib/librte_ethdev/rte_flow.c
> @@ -66,6 +66,7 @@ struct rte_flow_desc_data {
>   		     sizeof(struct rte_flow_item_icmp6_nd_opt_sla_eth)),
>   	MK_FLOW_ITEM(ICMP6_ND_OPT_TLA_ETH,
>   		     sizeof(struct rte_flow_item_icmp6_nd_opt_tla_eth)),
> +	MK_FLOW_ITEM(META, sizeof(struct rte_flow_item_meta)),
>   };
>   
>   /** Generate flow_action[] entry. */
> diff --git a/lib/librte_ethdev/rte_flow.h b/lib/librte_ethdev/rte_flow.h
> index f8ba71c..b81c816 100644
> --- a/lib/librte_ethdev/rte_flow.h
> +++ b/lib/librte_ethdev/rte_flow.h
> @@ -413,6 +413,15 @@ enum rte_flow_item_type {
>   	 * See struct rte_flow_item_mark.
>   	 */
>   	RTE_FLOW_ITEM_TYPE_MARK,
> +
> +	/**
> +	 * [META]
> +	 *
> +	 * Matches a metadata value specified in mbuf metadata field.
> +	 *
> +	 * See struct rte_flow_item_meta.
> +	 */
> +	RTE_FLOW_ITEM_TYPE_META,
>   };
>   
>   /**
> @@ -849,6 +858,22 @@ struct rte_flow_item_gre {
>   #endif
>   
>   /**
> + * RTE_FLOW_ITEM_TYPE_META.
> + *
> + * Matches a specified metadata value.
> + */
> +struct rte_flow_item_meta {
> +	uint64_t data;
> +};
> +
> +/** Default mask for RTE_FLOW_ITEM_TYPE_META. */
> +#ifndef __cplusplus
> +static const struct rte_flow_item_meta rte_flow_item_meta_mask = {
> +	.data = RTE_BE64(UINT64_MAX),
> +};
> +#endif
> +
> +/**
>    * RTE_FLOW_ITEM_TYPE_FUZZY
>    *
>    * Fuzzy pattern match, expect faster than default.
> diff --git a/lib/librte_mbuf/rte_mbuf.h b/lib/librte_mbuf/rte_mbuf.h
> index 9ce5d76..8f06a78 100644
> --- a/lib/librte_mbuf/rte_mbuf.h
> +++ b/lib/librte_mbuf/rte_mbuf.h
> @@ -182,6 +182,11 @@
>   /* add new TX flags here */
>   
>   /**
> + * This flag indicates that the metadata field in the mbuf is in use.
> + */
> +#define PKT_TX_METADATA		(1ULL << 41)
> +
> +/**
>    * UDP Fragmentation Offload flag. This flag is used for enabling UDP
>    * fragmentation in SW or in HW. When use UFO, mbuf->tso_segsz is used
>    * to store the MSS of UDP fragments.
> @@ -593,6 +598,12 @@ struct rte_mbuf {
>   	 */
>   	struct rte_mbuf_ext_shared_info *shinfo;
>   
> +	/**
> +	 * Application specific metadata value for flow rule match.
> +	 * Valid if PKT_TX_METADATA is set.
> +	 */
> +	uint64_t metadata;
> +

I don't see the difference from hash union which is 64-bit wide as well.
hash.fdir.hi is used by flow mark action and mark match item (but just 
32-bit).

>   } __rte_cache_aligned;
>   
>   /**