mirror of
https://github.com/libvirt/libvirt.git
synced 2025-02-25 18:55:26 -06:00
370608b4c7
This patch creates two bitmaps, one for macvlan device names and one for macvtap. The bitmap position is used to indicate that libvirt is currently using a device with the name macvtap%d/macvlan%d, where %d is the position in the bitmap. When requested to create a new macvtap/macvlan device, libvirt will now look for the first clear bit in the appropriate bitmap and derive the device name from that rather than just starting at 0 and counting up until one works. When libvirtd is restarted, the qemu driver code that reattaches to active domains calls the appropriate function to "re-reserve" the device names as it is scanning the status of running domains. Note that it may seem strange that the retry counter now starts at 8191 instead of 5. This is because we now don't do a "pre-check" for the existence of a device once we've reserved it in the bitmap - we move straight to creating it; although very unlikely, it's possible that someone has a running system where they have a large number of network devices *created outside libvirt* named "macvtap%d" or "macvlan%d" - such a setup would still allow creating more devices with the old code, while a low retry max in the new code would cause a failure. Since the objective of the retry max is just to prevent an infinite loop, and it's highly unlikely to do more than 1 iteration anyway, having a high max is a reasonable concession in order to prevent lots of new failures.
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>