Note: This bug is displayed in read-only format because
the product is no longer active in Red Hat Bugzilla.
RHEL Engineering is moving the tracking of its product development work on RHEL 6 through RHEL 9 to Red Hat Jira (issues.redhat.com). If you're a Red Hat customer, please continue to file support cases via the Red Hat customer portal. If you're not, please head to the "RHEL project" in Red Hat Jira and file new tickets here. Individual Bugzilla bugs in the statuses "NEW", "ASSIGNED", and "POST" are being migrated throughout September 2023. Bugs of Red Hat partners with an assigned Engineering Partner Manager (EPM) are migrated in late September as per pre-agreed dates. Bugs against components "kernel", "kernel-rt", and "kpatch" are only migrated if still in "NEW" or "ASSIGNED". If you cannot log in to RH Jira, please consult article #7032570. That failing, please send an e-mail to the RH Jira admins at rh-issues@redhat.com to troubleshoot your issue as a user management inquiry. The email creates a ServiceNow ticket with Red Hat. Individual Bugzilla bugs that are migrated will be moved to status "CLOSED", resolution "MIGRATED", and set with "MigratedToJIRA" in "Keywords". The link to the successor Jira issue will be found under "Links", have a little "two-footprint" icon next to it, and direct you to the "RHEL project" in Red Hat Jira (issue links are of type "https://issues.redhat.com/browse/RHEL-XXXX", where "X" is a digit). This same link will be available in a blue banner at the top of the page informing you that that bug has been migrated.
I've just pushed patches upstream:
commit 5f44d7e357f61f7be636a0e2e6d35453cbc3b589
Author: Michal Privoznik <mprivozn>
AuthorDate: Thu Jun 8 13:45:31 2017 +0200
Commit: Michal Privoznik <mprivozn>
CommitDate: Thu Jun 8 16:53:07 2017 +0200
qemuDomainChangeNet: Forbid changing MTU
https://bugzilla.redhat.com/show_bug.cgi?id=1447618
Currently, any attempt to change MTU on an interface that is
plugged to a running domain is silently ignored. We should either
do what's asked or error out. Well, we can update the host side
of the interface, but we cannot change 'host_mtu' attribute for
the virtio-net device. Therefore we have to error out.
Signed-off-by: Michal Privoznik <mprivozn>
Reviewed-by: Laine Stump <laine>
v3.4.0-82-g5f44d7e35
Comment 5yalzhang@redhat.com
2017-09-07 05:44:51 UTC
test on libvirt-3.7.0-2.el7.x86_64, the result is as expected, set this bug to be verified.
Update mtu in a running guest it will error out:
# cat interface.xml
<interface type='network'>
<mac address='52:54:00:21:e8:3f'/>
<source network='default' bridge='virbr0'/>
<target dev='vnet0'/>
<model type='virtio'/>
<mtu size='5000'/>
<alias name='net0'/>
<address type='pci' domain='0x0000' bus='0x00' slot='0x03' function='0x0'/>
</interface>
# virsh update-device rhel7.4 interface.xml
error: Failed to update device from interface.xml
error: Operation not supported: cannot modify MTU
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/RHEA-2018:0704
Description of problem: update-device failed to update the mtu of interface but return as succeed Version-Release number of selected component (if applicable): libvirt-3.2.0-3.el7.x86_64 qemu-kvm-rhev-2.9.0-2.el7.x86_64 kernel-3.10.0-640.el7.x86_64 How reproducible: 100% Steps to Reproduce: 1. # virsh net-dumpxml default <network> <name>default</name> <uuid>9feee285-f4a5-491e-a68f-0d3ee4805921</uuid> <forward mode='nat'> <nat> <port start='1024' end='65535'/> </nat> </forward> <bridge name='virbr0' stp='on' delay='0'/> <mtu size='9000'/> <mac address='52:54:00:77:9a:74'/> <ip address='192.168.122.1' netmask='255.255.255.0'> <dhcp> <range start='192.168.122.2' end='192.168.122.254'/> </dhcp> </ip> </network> # virsh dumpxml rhel7 | grep /interface -B7 <interface type='network'> <mac address='52:54:00:c2:66:40'/> <source network='default' bridge='virbr0'/> <target dev='vnet0'/> <model type='virtio'/> <alias name='net0'/> <address type='pci' domain='0x0000' bus='0x00' slot='0x03' function='0x0'/> </interface> # ifconfig | grep mtu ...... virbr0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 9000 vnet0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 9000 2. add mtu settings in the xml and update by update-device, the command succeed # cat net <interface type='network'> <mac address='52:54:00:c2:66:40'/> <source network='default' bridge='virbr0'/> <target dev='vnet0'/> <mtu size='4000'/> <model type='virtio'/> <alias name='net0'/> <address type='pci' domain='0x0000' bus='0x00' slot='0x03' function='0x0'/> </interface> # virsh update-device rhel7 net Device updated successfully # echo $? 0 3. But in fact, it fails to update the mtu of the interface # virsh dumpxml rhel7 | grep /interface -B7 <interface type='network'> <mac address='52:54:00:c2:66:40'/> <source network='default' bridge='virbr0'/> <target dev='vnet0'/> <model type='virtio'/> <alias name='net0'/> <address type='pci' domain='0x0000' bus='0x00' slot='0x03' function='0x0'/> </interface> # ifconfig | grep mtu ...... virbr0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 9000 vnet0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 9000 Actual results: The update-device failed to update mtu but return success Expected results: Should pop up error message if no support to update mtu, or update accordingly Additional info: