qvm-prefs: allow for on the fly netvm switch

[joanna]

When the user types:

qvm-prefs -s SomeAppVM netvm SomeNetVM

and if the SomeAppVM already is running, qvm-prefs should automatically re-attach the SomeAppVM to the new SomeNetVM (also making sure to reinitialize networking in SomeAppVM). This seems simple, yet would be extremely useful for users that decided to have a separate UsbVM and keep their 3G modem there. Then switching between WiFi? and 3G modem would be just a matter of setting a different netvm for the firewallvm.

[rafal]

implemented in
​http://git.qubes-os.org/?p=rafal/core.git;a=commit;h=d2301ab125949d6ec3b5986fa9159bc112912982
prebeta2 branch.
Requires fixed #316.

[joanna]

It doesn't seem to be working. I created an additional NetVM that I call 'usbvm' (which has 3G modem).

Now I did:

[joanna@dom0 ~]$ qvm-prefs -s firewallvm netvm usbvm

and got the following error:

Traceback (most recent call last):
  File "/usr/bin/qvm-prefs", line 318, in <module>
    main()
  File "/usr/bin/qvm-prefs", line 309, in main
    do_set(qvm_collection, vm, property, args[2:])
  File "/usr/bin/qvm-prefs", line 261, in do_set
    return properties[property](vms, vm, args)
  File "/usr/bin/qvm-prefs", line 139, in set_netvm
    "script=/etc/xen/scripts/vif-route-qubes"])
  File "/usr/lib64/python2.6/subprocess.py", line 488, in check_call
    raise CalledProcessError(retcode, cmd)
subprocess.CalledProcessError: Command '['xl', 'network-attach', 'firewallvm', 'ip=10.137.3.5', 'backend=usbvm', 'script=/etc/xen/scripts/vif-route-qubes']' returned non-zero exit status -11

[joanna]

I'm using xen 4.1.0-8 packages, and qubes core 1.6.17-dom0, BTW.

[rafal]

Missing spec line added at
​http://git.qubes-os.org/?p=rafal/xen.git;a=commit;h=1404651045e51baea108c35de27bc352ce42c0fa
prebeta2 branch.

[joanna]

After dynamic global netvm switch:

qvm-prefs -s netvm netvm <newnetvm>

• DNS resolving doesn't work (one needs to manually fix resolv.conf in each AppVM).
• TCP doesn't work (curl google.com), even though ICMP works fine.

[joanna]

Works now with 1.6.19-vm rpms :)