Re: [dpdk-dev] [PATCH v3 0/4] i40e VXLAN TX checksum rework

["Ananyev, Konstantin" <konstantin.ananyev@intel.com>]

> -----Original Message-----
> From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Jijiang Liu
> Sent: Thursday, November 27, 2014 5:03 PM
> To: dev@dpdk.org
> Subject: [dpdk-dev] [PATCH v3 0/4] i40e VXLAN TX checksum rework
> 
> We have got some feedback about backward compatibility of VXLAN TX checksum offload API with 1G/10G NIC after the i40e VXLAN
> TX checksum codes were applied, so we have to rework the APIs on i40e, including the changes of mbuf, i40e PMD and csum engine.
> 
> The main changes in mbuf are as follows,
> In place of removing PKT_TX_VXLAN_CKSUM, we introducing 3 new flags: PKT_TX_OUTER_IP_CKSUM,PKT_TX_OUTER_IPV6 and
> PKT_TX_UDP_TUNNEL_PKT, and a new field: l4_tun_len.
> Replace the inner_l2_len and the inner_l3_len field with the outer_l2_len and outer_l3_len field.
> 
> let's use a few examples to demonstrate how to use these new flags and existing flags in rte_mbuf.h
> Let say we have a tunnel packet: eth_hdr_out/ipv4_hdr_out/udp_hdr_out/vxlan_hdr/ehtr_hdr_in/ipv4_hdr_in/tcp_hdr_in.There
> could be several scenarios:
> 
> A) User requests HW offload for ipv4_hdr_out checksum.
> He doesn't care is it a tunnelled packet or not.
> So he sets:
> 
> mb->l2_len =  eth_hdr_out;
> mb->l3_len = ipv4_hdr_out;
> mb->ol_flags |= PKT_TX_IPV4_CSUM;
> 
> B) User is aware that it is a tunnelled packet and requests HW offload for ipv4_hdr_in and tcp_hdr_in *only*.
> He doesn't care about outer IP checksum offload.
> In that case, for FVL  he has 2 choices:
>    1. Treat that packet as a 'proper' tunnelled packet, and fill all the fields:
>      mb->l2_len =  eth_hdr_in;
>      mb->l3_len = ipv4_hdr_in;
>      mb->outer_l2_len = eth_hdr_out;
>      mb->outer_l3_len = ipv4_hdr_out;
>      mb->l4tun_len = vxlan_hdr;
>      mb->ol_flags |= PKT_TX_UDP_TUNNEL_PKT | PKT_TX_IP_CKSUM |  PKT_TX_TCP_CKSUM;
> 
>    2. As user doesn't care about outer IP hdr checksum, he can treat everything before ipv4_hdr_in as L2 header.
>    So he knows, that it is a tunnelled packet, but makes HW to treat it as ordinary (non-tunnelled) packet:
>      mb->l2_len = eth_hdr_out + ipv4_hdr_out + udp_hdr_out + vxlan_hdr + ehtr_hdr_in;
>      mb->l3_len = ipv4_hdr_in;
>      mb->ol_flags |= PKT_TX_IP_CKSUM |  PKT_TX_TCP_CKSUM;
> 
> i40e PMD will support both B.1 and B.2.
> ixgbe/igb/em PMD supports only B.2.
> if HW supports both - it will be up to user app which method to choose.
> tespmd will support both methods, and it should be configurable by user which approach to use (cmdline parameter).
> So the user can try/test both methods and select an appropriate for him.
> 
> Now, B.2 is exactly what Oliver suggested.
> I think it has few important advantages over B.1:
> First of all - compatibility. It works across all HW we currently support (i40e/ixgbe/igb/em).
> Second - it is probably faster even on FVL, as for it we have to fill only TXD, while with approach #2 we have to fill both TCD and TXD.
> 
> C) User knows that is a tunnelled packet, and wants HW offload for all 3 checksums:  outer IP hdr checksum, inner IP checksum, inner
> TCP checksum.
> Then he has to setup all TX checksum fields:
>      mb->l2_len =  eth_hdr_in;
>      mb->l3_len = ipv4_hdr_in;
>      mb->outer_l2_len = eth_hdr_out;
>      mb->outer_l3_len = ipv4_hdr_out;
>      mb->l4tun_len = vxlan_hdr;
>      mb->ol_flags |= PKT_TX_OUT_IP_CKSUM  | PKT_TX_UDP_TUNNEL | PKT_TX_IP_CKSUM |  PKT_TX_TCP_CKSUM;
> 
> v2 changes:
>      remove PKT_TX_IP_CKSUM alias.
>      add PKT_TX_OUT_IP_CKSUM and PKT_TX_OUTER_IPV6 in rte_get_tx_ol_flag_name.
>      spliting mbuf changes into two patches.
>      fix MACLEN caculation issue in i40e driver
>      fix some issues in csumonly.c
>      change cover letter.
> v3 changes:
>      fix MACLEN caculation issue in i40e driver when non-tunneling packet
> 
> Jijiang Liu (4):
>   mbuf change for 3 new flags and 3 fields
>   mbuf change for PKT_TX_IPV4 and PKT_TX_IPV6
>   i40e PMD change in i40e_rxtx.c
>   rework csum forward engine
> 
> 
>  app/test-pmd/csumonly.c         |   65 ++++++++++++++++++++++-----------------
>  lib/librte_mbuf/rte_mbuf.c      |    6 +++-
>  lib/librte_mbuf/rte_mbuf.h      |   22 ++++++++-----
>  lib/librte_pmd_i40e/i40e_rxtx.c |   49 ++++++++++++++++-------------
>  4 files changed, 82 insertions(+), 60 deletions(-)
> 
> --
> 1.7.7.6

Acked-by: Konstantin Ananyev <konstantin.ananyev@intel.com>