Hi Jijiang,
Please find below some comments about the specifications. The global
picture looks fine to me.
I've not reviewed the patch right now, but it's in the pipe.
On 11/27/2014 09:18 AM, Jijiang Liu wrote:
> 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.
What about PKT_TX_OUT_UDP_CKSUM instead of PKT_TX_UDP_TUNNEL_PKT? It's
maybe more coherent with the other names.
> 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
As I suggested in the TSO thread, I think the following semantics
is easier to understand for the user:
- PKT_TX_IP_CKSUM: tell the NIC to compute IP cksum
- PKT_TX_IPV4: tell the NIC it's an IPv4 packet. Required for L4
checksum offload or TSO.
- PKT_TX_IPV6: tell the NIC it's an IPv6 packet. Required for L4
checksum offload or TSO.
I think it won't make a big difference in the FVL driver.
> 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.
I think we should have a flag to advertise outer ip and outer udp
checksum offload support, so the application knows which mode can
be used.
Regards,
Olivier
