** Changed in: linux (Ubuntu Zesty)
Status: In Progress => Fix Committed
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Ubuntu 16.04.02: ibmveth: Support to enable LSO/CSO for Trunk VEA
Status in The Ubuntu-power-systems project:
Status in linux package in Ubuntu:
Status in linux source package in Xenial:
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== Comment: #0 - BRYANT G. LY <b...@us.ibm.com> - 2017-05-22 08:40:16 ==
- 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
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
Machine Type = p8
A debugger is not configured
---Steps to Reproduce---
Increases performance greatly
The patch has been accepted upstream:
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