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6bde0a1a37
This patch resolves: https://bugzilla.redhat.com/show_bug.cgi?id=805071 to the extent that it can be resolved with current qemu functionality. It attempts to detect as many situations as possible when the simple operation of disconnecting an existing tap device from one bridge and attaching it to another will satisfy the change requested in virDomainUpdateDeviceFlags() for a network device. Before this patch, that situation could only be detected if the pre-change interface *and* the post-change interface definition were both "type='bridge'". After this patch, it can also be detected if the before or after interfaces are any combination of type='bridge' and type='network' (the networks can be <forward mode='nat|route|bridge'>, as long as they use a Linux host bridge and not macvtap connections). This extra effort is especially useful since the recent discovery that a netdev_del+netdev_add combo (to reconnect the network device with completely different hostside configuration) doesn't work properly with current qemu (1.2) unless it is accompanied by the matching device_del+device_add - see this mailing list message for details: http://lists.nongnu.org/archive/html/qemu-devel/2012-10/msg02355.html (A slight modification of the patch referenced there has been prepared to apply on top of this patch, but won't be pushed until qemu can be made to work with it.) * qemuDomainChangeNet needs access to the virDomainDeviceDef that holds the new netdef (so that it can clear out the virDomainDeviceDef if it ends up using the NetDef to replace the original), so the virDomainNetDefPtr arg is replaced with a virDomainDeviceDefPtr. * qemuDomainChangeNet previously checked for *some* changes to the interface config, but this check was by no means complete. It was also a bit disorganized. This refactoring of the code is (I believe) complete in its check of all NetDef attributes that might be changed, and either returns a failure (for changes that are simply impossible), or sets one of three flags: needLinkStateChange - if the device link state needs to go up/down needBridgeChange - if everything else is the same, but it needs to be connected to a difference linux host bridge needReconnect - if the entire host side of the device needs to be torn down and reconstructed (currently non-working, as mentioned above) Note that this function will refuse to make any change that requires the *guest* side of the device to be detached (e.g. changing the PCI address or mac address). Those would be disruptive enough to the guest that it's reasonable to require an explicit detach/attach sequence from the management application. * As mentioned above, qemuDomainChangeNet also does its best to understand when a simple change in attached bridge for the existing tap device will work vs. the need to completely tear down/reconstruct the host side of the device (including tap device). This patch *does not* implement the "reconnect" code anyway - there is a placeholder that turns that into an error. Rather, the purpose of this patch is to replicate existing behavior with code that is ready to have that functionality plugged in in a later patch. * The expanded uses for qemuDomainChangeNetBridge meant that it needed to be enhanced as well - it no longer replaces the original brname string in olddev with the new brname; instead, it relies on the caller to replace the *entire* olddev with newdev (since we've gone to great lengths to assure they are functionally identical other than the name of the bridge, this is now not only safe, but more correct). Additionally, qemuDomainNetChangeBridge can now set the bridge for type='network' interfaces as well as plain type='bridge' interfaces. (Note that I had to make this change simultaneous to the reorganization of qemuDomainChangeNet because the two are too closely intertwined to separate). |
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| README | ||
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| TODO | ||
LibVirt : simple API for virtualization
Libvirt is a C toolkit to interact with the virtualization capabilities
of recent versions of Linux (and other OSes). It is free software
available under the GNU Lesser General Public License. Virtualization of
the Linux Operating System means the ability to run multiple instances of
Operating Systems concurrently on a single hardware system where the basic
resources are driven by a Linux instance. The library aim at providing
long term stable C API initially for the Xen paravirtualization but
should be able to integrate other virtualization mechanisms if needed.
Daniel Veillard <veillard@redhat.com>