[dpdk-dev] [RFC 04/16] i40e: remove the use of PKT_TX_UDP_TUNNEL_PKT flag

[Liu, Jijiang]

Hi,

> -----Original Message-----
> From: Olivier Matz [mailto:olivier.matz at 6wind.com]
> Sent: Thursday, January 22, 2015 7:36 AM
> To: dev at dpdk.org
> Cc: olivier.matz at 6wind.com; Ananyev, Konstantin; Liu, Jijiang
> Subject: [RFC 04/16] i40e: remove the use of PKT_TX_UDP_TUNNEL_PKT flag
> 
> The definition of the flag in rte_mbuf.h was:
>   TX packet is an UDP tunneled packet. It must be specified when using
>   outer checksum offload (PKT_TX_OUTER_IP_CKSUM)
> 
> This flag was used to tell the NIC that the offload type is UDP
> (I40E_TXD_CTX_UDP_TUNNELING flag). In the datasheet, it says it's required
> to specify the tunnel type in the register. However, some tests (see [1])
> showed that it also works without this flag.
> 
> Moreover, it is not explained how the hardware use this information. From a
> network perspective, this information is useless for calculating the outer IP
> checksum as it does not depend on the payload.
> 
> Having this flag in the API would force the application to specify the tunnel
> type for something that looks only useful for this PMD. It will limit the
> number of possible tunnel types (we would need a flag for each tunnel type)
> and therefore prevent to support outer IP checksum for proprietary tunnels.
> 
> Finally, if a hardware advertises "I support outer IP checksum", it must be
> supported for any payload types.
> 
> [1] http://dpdk.org/ml/archives/dev/2015-January/011380.html
> 
> Signed-off-by: Olivier Matz <olivier.matz at 6wind.com>
> ---
>  lib/librte_pmd_i40e/i40e_rxtx.c | 6 ++----
>  1 file changed, 2 insertions(+), 4 deletions(-)
> 
> diff --git a/lib/librte_pmd_i40e/i40e_rxtx.c b/lib/librte_pmd_i40e/i40e_rxtx.c
> index 9acdeee..0786255 100644
> --- a/lib/librte_pmd_i40e/i40e_rxtx.c
> +++ b/lib/librte_pmd_i40e/i40e_rxtx.c
> @@ -482,7 +482,7 @@ i40e_txd_enable_checksum(uint64_t ol_flags,
>  	}
> 
>  	/* UDP tunneling packet TX checksum offload */
> -	if (unlikely(ol_flags & PKT_TX_UDP_TUNNEL_PKT)) {
> +	if (unlikely(ol_flags & PKT_TX_OUTER_IP_CKSUM)) {

This way will disable  FVL TX checksum offload capability of inner IP and inner L4 using B.1 method.

Again, the B.1 in http://dpdk.org/ml/archives/dev/2014-December/009213.html should be supported and allowed.

Helin, you are i40e maintainer, what's your point?


>  		*td_offset |= (outer_l2_len >> 1)
>  				<< I40E_TX_DESC_LENGTH_MACLEN_SHIFT;
> @@ -497,7 +497,6 @@ i40e_txd_enable_checksum(uint64_t ol_flags,
>  		/* Now set the ctx descriptor fields */
>  		*cd_tunneling |= (outer_l3_len >> 2) <<
>  				I40E_TXD_CTX_QW0_EXT_IPLEN_SHIFT |
> -				I40E_TXD_CTX_UDP_TUNNELING |
>  				(l2_len >> 1) <<
>  				I40E_TXD_CTX_QW0_NATLEN_SHIFT;
> 



> @@ -1165,8 +1164,7 @@ i40e_calc_context_desc(uint64_t flags)  {
>  	uint64_t mask = 0ULL;
> 
> -	if (flags | PKT_TX_UDP_TUNNEL_PKT)
> -		mask |= PKT_TX_UDP_TUNNEL_PKT;
> +	mask |= PKT_TX_OUTER_IP_CKSUM;
> 
>  #ifdef RTE_LIBRTE_IEEE1588
>  	mask |= PKT_TX_IEEE1588_TMST;
> --
> 2.1.3