Hi Oliver, > -----Original Message----- > From: dev [mailto:dev-bounces at dpdk.org] On Behalf Of Olivier MATZ > Sent: Thursday, November 27, 2014 9:45 AM > To: Liu, Jijiang; dev at dpdk.org > Subject: Re: [dpdk-dev] [PATCH 0/3] i40e VXLAN TX checksum rework > > 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.
FVL HW don't support outer L4 checksum offload. But to calculate inner checksums correctly, it needs a hint from SW about L4 Tunnelling Type. > > > > 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. No, no big difference here, but I still think it will be a bit cleaner if all 3 flags would be nutually exclusive. In fact, we can unite all 3 of them them into 2 bits, same as we doing for L4 checksum flags. > > > > 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. You mean a new DEV_TX_OFFLOAD_* value, right? Something like: DEV_TX_OFFLOAD_UDP_TUNNEL? And make i40e_dev_info_get() to return it? Yes, forgot about it, sounds like a proper thing to do. Konstantin > > > Regards, > Olivier
