Re: [dpdk-dev] [PATCH] ethdev: extend flow metadata

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

Hi Yongseok,

On Thu, Jul 04, 2019 at 04:21:22PM -0700, Yongseok Koh wrote:
> Currently, metadata can be set on egress path via mbuf tx_meatadata field
> with PKT_TX_METADATA flag and RTE_FLOW_ITEM_TYPE_RX_META matches metadata.
> 
> This patch extends the usability.
> 
> 1) RTE_FLOW_ACTION_TYPE_SET_META
> 
> When supporting multiple tables, Tx metadata can also be set by a rule and
> matched by another rule. This new action allows metadata to be set as a
> result of flow match.
> 
> 2) Metadata on ingress
> 
> There's also need to support metadata on packet Rx. Metadata can be set by
> SET_META action and matched by META item like Tx. The final value set by
> the action will be delivered to application via mbuf metadata field with
> PKT_RX_METADATA ol_flag.
> 
> For this purpose, mbuf->tx_metadata is moved as a separate new field and
> renamed to 'metadata' to support both Rx and Tx metadata.
> 
> For loopback/hairpin packet, metadata set on Rx/Tx may or may not be
> propagated to the other path depending on HW capability.
> 
> Signed-off-by: Yongseok Koh <yskoh@mellanox.com>

(...)

> --- a/lib/librte_mbuf/rte_mbuf.h
> +++ b/lib/librte_mbuf/rte_mbuf.h
> @@ -200,6 +200,11 @@ extern "C" {
>  
>  /* add new RX flags here */
>  
> +/**
> + * Indicate that mbuf has metadata from device.
> + */
> +#define PKT_RX_METADATA	(1ULL << 23)
> +
>  /* add new TX flags here */
>  
>  /**
> @@ -648,17 +653,6 @@ struct rte_mbuf {
>  			/**< User defined tags. See rte_distributor_process() */
>  			uint32_t usr;
>  		} hash;                   /**< hash information */
> -		struct {
> -			/**
> -			 * Application specific metadata value
> -			 * for egress flow rule match.
> -			 * Valid if PKT_TX_METADATA is set.
> -			 * Located here to allow conjunct use
> -			 * with hash.sched.hi.
> -			 */
> -			uint32_t tx_metadata;
> -			uint32_t reserved;
> -		};
>  	};
>  
>  	/** Outer VLAN TCI (CPU order), valid if PKT_RX_QINQ is set. */
> @@ -727,6 +721,11 @@ struct rte_mbuf {
>  	 */
>  	struct rte_mbuf_ext_shared_info *shinfo;
>  
> +	/** Application specific metadata value for flow rule match.
> +	 * Valid if PKT_RX_METADATA or PKT_TX_METADATA is set.
> +	 */
> +	uint32_t metadata;
> +
>  } __rte_cache_aligned;

This will break the ABI, so we cannot put it in 19.08, and we need a
deprecation notice.

That said, it shows again that we need something to make the addition of
fields in mbufs more flexible. Knowing that Thomas will present
something about it at next userspace [1], I drafted something in a RFC
[2]. It is simpler than I expected, and I think your commit could be
a good candidate for a first user. Do you mind having a try? Feedback
and comment is of course welcome.

If it fits your needs, we can target its introduction for 19.11. Having
a user for this new feature would be a plus for its introduction :)

Thanks,
Olivier

[1] https://dpdkbordeaux2019.sched.com/
[2] http://mails.dpdk.org/archives/dev/2019-July/137772.html