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Bug 1456403 - Net-KVM: Implement MTU report feature of the virtio-net device
Summary: Net-KVM: Implement MTU report feature of the virtio-net device
Keywords:
Status: CLOSED ERRATA
Alias: None
Product: Red Hat Enterprise Linux 7
Classification: Red Hat
Component: virtio-win
Version: 7.5
Hardware: Unspecified
OS: Unspecified
unspecified
unspecified
Target Milestone: rc
: ---
Assignee: Sameeh Jubran
QA Contact: Virtualization Bugs
URL:
Whiteboard:
Depends On: 1452756
Blocks:
TreeView+ depends on / blocked
 
Reported: 2017-05-29 10:25 UTC by Sameeh Jubran
Modified: 2017-09-28 07:11 UTC (History)
9 users (show)

Fixed In Version:
Doc Type: Enhancement
Doc Text:
The NetKVM driver is now able to obtain the maximum transmission unit (MTU) of a host and apply it to Windows guests running on this host. As a result, the user can optimize the guest's network interface controller (NIC) when the host MTU value is different than the default 1500 bytes.
Clone Of:
Environment:
Last Closed: 2017-08-01 12:58:08 UTC
Target Upstream Version:
Embargoed:

Attachments (Terms of Use)


Links
System ID Private Priority Status Summary Last Updated
Red Hat Product Errata RHBA-2017:2341 0 normal SHIPPED_LIVE virtio-win bug fix and enhancement update 2017-08-01 16:52:38 UTC

Description Sameeh Jubran 2017-05-29 10:25:10 UTC 
The spec's documentation can be found here:
https://issues.oasis-open.org/browse/VIRTIO-152
Comment 2 Sameeh Jubran 2017-05-30 06:16:43 UTC 
In order to test the feature, the parameter "host_mtu" should be set in the virtio-net's parameters in Qemu command line.

For example:

-netdev tap,id=hostnet1,script=world_bridge_standalone.sh,downscript=no,ifname=cc1_72 \
-device virtio-net,netdev=hostnet1,mac=56:cc:c1:04:2c:21,id=cc1_72,host_mtu=4000 \

In order to verify that the feature is working correctly from the guest you should run the command "netsh interface ipv4 show subinterfaces" in the command prompt, the Net-KVM interface's MTU should be the same as whatever host_mtu is to.
Comment 3 Vadim Rozenfeld 2017-06-01 10:15:00 UTC 
should be fixed in build 139
http://download.eng.bos.redhat.com/brewroot/work/tasks/1396/13321396/virtio-win-prewhql-0.1.zip
Comment 4 lijin 2017-06-02 03:02:06 UTC 
blocked by bz1452756,will verify again after bz1452756 is fixed
Comment 5 lijin 2017-06-06 09:50:41 UTC 
steps:
1.boot guest with netkvm device and add "host_mtu=4000"
-netdev tap,id=hostnet1,script=/etc/qemu-ifup,vhost=on,queues=2 -device virtio-net-pci,host_mtu=4000,mq=on,vectors=6,netdev=hostnet1,mac=4e:63:28:bc:b1:01,id=net1
2.check guest mtu value in cmd:
# netsh interface ipv4 show subinterfaces
3.from external host,ping guest
4.from guest,ping external host

Result:
After step2,mtu is 4000 as expected: 
MTU  MediaSenseState   Bytes In  Bytes Out  Interface
------  ---------------  ---------  ---------  -------------
4294967295                1          0          0  Loopback Pseudo-Interface 1
  4000                1       5509       6678  Ethernet

ping can pass after step3 and step4,network works normally.

So this bug is fixed,thanks.
Comment 6 lijin 2017-06-06 10:05:43 UTC 
verified packages info:
virtio-win-prewhql-139
kernel-3.10.0-675.el7.x86_64
qemu-kvm-rhev-2.9.0-8.el7.x86_64
seabios-1.10.2-2.el7.x86_64
Comment 9 errata-xmlrpc 2017-08-01 12:58:08 UTC 
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://access.redhat.com/errata/RHBA-2017:2341
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