Public bug reported: == Comment: #0 - BRYANT G. LY <b...@us.ibm.com> - 2017-05-22 08:40:16 == ---Problem Description---
- Issue 1: ibmveth doesn't support largesend and checksum offload features when configured as "Trunk". Driver has explicit checks to prevent enabling these offloads. - Issue 2: SYN packet drops seen at destination VM. When the packet originates, it has CHECKSUM_PARTIAL flag set and as it gets delivered to IO server's inbound Trunk ibmveth, on validating "checksum good" bits in ibmveth receive routine, SKB's ip_summed field is set with CHECKSUM_UNNECESSARY flag. This packet is then bridged by OVS (or Linux Bridge) and delivered to outbound Trunk ibmveth. At this point the outbound ibmveth transmit routine will not set "no checksum" and "checksum good" bits in transmit buffer descriptor, as it does so only when the ip_summed field is CHECKSUM_PARTIAL. When this packet gets delivered to destination VM, TCP layer receives the packet with checksum value of 0 and with no checksum related flags in ip_summed field. This leads to packet drops. So, TCP connections never goes through fine. - Issue 3: First packet of a TCP connection will be dropped, if there is no OVS flow cached in datapath. OVS while trying to identify the flow, computes the checksum. The computed checksum will be invalid at the receiving end, as ibmveth transmit routine zeroes out the pseudo checksum value in the packet. This leads to packet drop. - Issue 4: ibmveth driver doesn't have support for SKB's with frag_list. When Physical NIC has GRO enabled and when OVS bridges these packets, OVS vport send code will end up calling dev_queue_xmit, which in turn calls validate_xmit_skb. In validate_xmit_skb routine, the larger packets will get segmented into MSS sized segments, if SKB has a frag_list and if the driver to which they are delivered to doesn't support NETIF_F_FRAGLIST feature. Contact Information = Bryant G. Ly/b...@us.ibm.com ---uname output--- 4.8.0-51.54 Machine Type = p8 ---Debugger--- A debugger is not configured ---Steps to Reproduce--- Increases performance greatly The patch has been accepted upstream: https://patchwork.ozlabs.org/patch/764533/ ** Affects: linux (Ubuntu) Importance: Undecided Assignee: Ubuntu on IBM Power Systems Bug Triage (ubuntu-power-triage) Status: New ** Tags: architecture-ppc64le bugnameltc-154875 severity-critical targetmilestone-inin16042 ** Tags added: architecture-ppc64le bugnameltc-154875 severity-critical targetmilestone-inin16042 ** Changed in: ubuntu Assignee: (unassigned) => Ubuntu on IBM Power Systems Bug Triage (ubuntu-power-triage) ** Package changed: ubuntu => linux (Ubuntu) -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1692538 Title: Ubuntu 16.04.02: ibmveth: Support to enable LSO/CSO for Trunk VEA To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1692538/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
