Re: [v4 1/3] ethdev: introduce protocol type based header split

[Jerin Jacob <jerinjacobk@gmail.com>]

On Sat, Apr 2, 2022 at 4:33 PM <wenxuanx.wu@intel.com> wrote:
>
> From: Xuan Ding <xuan.ding@intel.com>
>
> Header split consists of splitting a received packet into two separate
> regions based on the packet content. The split happens after the
> packet header and before the packet payload. Splitting is usually between
> the packet header that can be posted to a dedicated buffer and the packet
> payload that can be posted to a different buffer.
>
> Currently, Rx buffer split supports length and offset based packet split.
> Although header split is a subset of buffer split, configuring buffer
> split based on length is not suitable for NICs that do split based on
> header protocol types. Because tunneling makes the conversion from length
> to protocol type impossible.
>
> This patch extends the current buffer split to support protocol type and
> offset based header split. A new proto field is introduced in the
> rte_eth_rxseg_split structure reserved field to specify header protocol
> type. With Rx offload flag RTE_ETH_RX_OFFLOAD_HEADER_SPLIT enabled and
> protocol type configured, PMD will split the ingress packets into two
> separate regions. Currently, both inner and outer L2/L3/L4 level header
> split can be supported.
>
> For example, let's suppose we configured the Rx queue with the
> following segments:
>     seg0 - pool0, off0=2B
>     seg1 - pool1, off1=128B
>
> With header split type configured with RTE_ETH_RX_HEADER_SPLIT_UDP,
> the packet consists of MAC_IP_UDP_PAYLOAD will be split like following:
>     seg0 - udp header @ RTE_PKTMBUF_HEADROOM + 2 in mbuf from pool0

If we set rte_eth_rxseg_split::proto = RTE_ETH_RX_HEADER_SPLIT_UDP and
rte_eth_rxseg_split.offset = 2,
What will be the content for seg0,
Will it be,
- offset as Starts atUDP Header
- size of segment as MAX(size of UDP header + 2, 128(as seg 1 start from128).
Right? If not, Please describe

Also, I don't think we need duplate
rte_eth_rx_header_split_protocol_type instead we can
reuse existing RTE_PTYPE_*  flags.


>     seg1 - payload @ 128 in mbuf from pool1
>
> The memory attributes for the split parts may differ either - for example
> the mempool0 and mempool1 belong to dpdk memory and external memory,
> respectively.