From mboxrd@z Thu Jan 1 00:00:00 1970 From: Olivier MATZ Subject: Re: [PATCH 0/3] i40e VXLAN TX checksum rework Date: Thu, 27 Nov 2014 10:44:47 +0100 Message-ID: <5476F28F.7010802@6wind.com> References: <1417076319-629-1-git-send-email-jijiang.liu@intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit To: Jijiang Liu , dev-VfR2kkLFssw@public.gmane.org Return-path: In-Reply-To: <1417076319-629-1-git-send-email-jijiang.liu-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org> List-Id: patches and discussions about DPDK List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces-VfR2kkLFssw@public.gmane.org Sender: "dev" 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