Allow setting virt-bridge to "none" to disable all network configuration

[opoplawski]

I'm still kind of mulling this over, but figured I would get it out there for more comments.

My use case is that I want to install VMs with SR-IOV hostdev interfaces. Unfortunately, virt-install does not yet support this (see virt-manager/virt-manager#500), so the only way I've figured to do this is as follows:

sudo koan --server=${COBBLER_SERVER} --virt --system ${name} --graphics spice --virt-type kvm --qemu-disk-type scsi ${opts}

# Remove any bridged interface setup for the hostdev MAC and attach the hostdev interface
if [ -n "$hostdev" ]
then
   virsh detach-interface ${name} bridge --mac ${hostdev_mac} --live --config || :
   virsh nodedev-detach pci_0000_${hostdev//[:.]/_}
   virsh attach-interface ${name} hostdev 0000:${hostdev} --mac ${hostdev_mac}
fi

It's somewhat cleaner and I can ditch the detach-interface call if I don't have any networks configured for the VM in the first place.

I'm not sure if there are any other use-cases for configuring a VM without a network interface.

The other TODO is to get cobbler to be able to save the information needed for hostdev interface configurations, namely the PCI ID and that it is the type hostdev. But that isn't really useful until virt-install supports it.

[SchoolGuy]

I like the idea of being able to handle an "empty" network interface. As such please go ahead with your plan from my side.

[opoplawski]

Trying to enumerate various uses cases:

• Normal - every interface has an associated virt_bridge
• No network config at all. Options for configuring;
  • A system level virt option to disable networking. Probably best?
  • Specify 'none' for virt_bridge. What to do if one interface is 'none' and another has a bridge specified?
• Partial - some interfaces have bridges, some are blank
• Hostdev only interface
• Mixed bridged and hostdev interfaces

[SchoolGuy]

So far my experience with Koan & Virtualization is limited. I will ask at work if this would cover all cases our virt team can imagine.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 0% with 9 lines in your changes are missing coverage. Please review.

Project coverage is 4.08%. Comparing base (34360a8) to head (b39c4c8).

❗ Current head b39c4c8 differs from pull request most recent head 792c74b. Consider uploading reports for the commit 792c74b to get more accurate results

Files	Patch %	Lines
koan/virtinstall.py	0.00%	9 Missing ⚠️

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@@           Coverage Diff            @@
##            main     #96      +/-   ##
========================================
- Coverage   4.08%   4.08%   -0.01%     
========================================
  Files         12      12              
  Lines       2152    2154       +2     
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  Hits          88      88              
- Misses      2064    2066       +2     

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