[Qemu-devel] [RFC 0/10] Support Receive-Segment-Offload(RSC) for WHQL test of Window guest

[wexu@redhat.com]

From: Wei Xu <wexu@redhat.com>

This patch is to support WHQL test for Windows guest, while this feature also
benifits other guest works as a kernel 'gro' like feature with userspace implementation.
Feature information:
  http://msdn.microsoft.com/en-us/library/windows/hardware/jj853324

Both IPv4 and IPv6 are supported, though performance with userspace virtio
is slow than vhost-net, there is about 30-40 percent performance
improvement to userspace virtio, this is done by turning this feature on
and disable 'tso' on corresponding tap interface.

Test steps:
Although this feature is mainly used for window guest, i used linux guest to help test
the feature, to make things simple, i used 3 steps to test the patch as i moved on.
1. With a tcp socket client/server pair runnig on 2 linux guest, thus i can control
the traffic and debugging the code as i want.
2. Netperf on linux guest test the throughput.
3. WHQL test with 2 Windows guest.

Current status:
IPv4 pass all the above tests. 
IPv6 just passed test step 1 and 2 as described ahead, the virtio nic cannot receive
any packet in WHQL test, debugging on the host side shows all the packets have been
pushed to th vring, by replacing it with a linux guest, i add 10 extra packets before
sending out the real packet, tcpdump running on guest only capture 6 packets, don't
find out the root cause yet, will continue working on this.

Note:
A 'MessageDevice' nic chose as 'Realtek' will panic the system sometimes during setup,
this can be figured out by replacing it with an 'e1000' nic.

Pending issues & Todo list:
1. Dup ack count not added in the virtio_net_hdr, but WHQL test case passes,
looks like a bug in test case.
2. Missing a Feature Bit
3. Missing a few tcp/ip handling
    ECN change.
    TCP window scale.
    TCP URG packet is bypassed due to the spec, while linux guest won't accept this.

Wei Xu (10):
  'Segment', 'Chain' and 'Status' enumeration.
  Initilize & Cleanup.
  Chain lookup and packets caching.
  Tcp general data coalescing
  The draining timer
  IPv4 checksum.
  TCP control packet handling
  Sanity check & More bypass cases check.
  IPv6 support.
  Statistics.

 hw/net/virtio-net.c            | 626 ++++++++++++++++++++++++++++++++++++++++-
 include/hw/virtio/virtio-net.h |   1 +
 include/hw/virtio/virtio.h     |  67 +++++
 3 files changed, 693 insertions(+), 1 deletion(-)

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2.4.0