Re: [dpdk-dev] [PATCH 0/3] i40e VXLAN TX checksum rework

["Liu, Jijiang" <jijiang.liu@intel.com>]

Could you review this patch today ? 
If possible, I hope this patch set can be included RC2.


> -----Original Message-----
> From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Jijiang Liu
> Sent: Thursday, November 27, 2014 4:19 PM
> To: dev@dpdk.org
> Subject: [dpdk-dev] [PATCH 0/3] 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 2 new flags: PKT_TX_OUT_IP_CKSUM,
> 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.
> 
> The existing flags are listed below,
> PKT_TX_IP_CKSUM:     HW IPv4 checksum for non-tunnelling packet/ HW inner
> IPv4 checksum for tunnelling packet
> PKT_TX_TCP_CKSUM:    HW TCP checksum for non-tunnelling packet/ HW inner
> TCP checksum for tunnelling packet
> PKT_TX_SCTP_CKSUM:   HW SCTP checksum for non-tunnelling packet/ HW inner
> SCTP checksum for tunnelling packet
> PKT_TX_UDP_CKSUM:    HW SCTP checksum for non-tunnelling packet/ HW inner
> SCTP checksum for tunnelling packet
> PKT_TX_IPV4:        IPv4 with no HW checksum offload for non-tunnelling
> packet/inner IPv4 with no HW checksum offload for tunnelling packet
> PKT_TX_IPV6:        IPv6 non-tunnelling packet/ inner IPv6 with no HW checksum
> offload for tunnelling packet
> 
> let's use a few examples to demonstrate how to use these flags:
> 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;
> 
> Jijiang Liu (3):
>   mbuf change
>   i40e PMD change in i40e_rxtx.c
>   rework csum forward engine
> 
>  app/test-pmd/csumonly.c         |   55 +++++++++++++++++++++-----------------
>  lib/librte_mbuf/rte_mbuf.c      |    2 +-
>  lib/librte_mbuf/rte_mbuf.h      |   23 ++++++++++------
>  lib/librte_pmd_i40e/i40e_rxtx.c |   40 ++++++++++++---------------
>  4 files changed, 63 insertions(+), 57 deletions(-)
> 
> --
> 1.7.7.6