77f72a8615
Although <interface type='ethernet'> has always been able to use an
existing tap device, this is just a coincidence due to the fact that
the same ioctl is used to create a new tap device or get a handle to
an existing device.
Even then, once we have the handle to the device, we still insist on
doing extra setup to it (setting the MAC address and IFF_UP). That
*might* be okay if libvirtd is running as a privileged process, but if
libvirtd is running as an unprivileged user, those attempted
modifications to the tap device will fail (yes, even if the tap is set
to be owned by the user running libvirtd). We could avoid this if we
knew that the device already existed, but as stated above, an existing
device and new device are both accessed in the same manner, and
anyway, we need to preserve existing behavior for those who are
already using pre-existing devices with privileged libvirtd (and
allowing/expecting libvirt to configure the pre-existing device).
In order to cleanly support the idea of using a pre-existing and
pre-configured tap device, this patch introduces a new optional
attribute "managed" for the interface <target> element. This
attribute is only valid for <interface type='ethernet'> (since all
other interface types have mandatory config that doesn't apply in the
case where we expect the tap device to be setup before we
get it). The syntax would look something like this:
<interface type='ethernet'>
<target dev='mytap0' managed='no'/>
...
</interface>
This patch just adds managed to the grammar and parser for <target>,
but has no functionality behind it.
(NB: when managed='no' (the default when not specified is 'yes'), the
target dev is always a name explicitly provided, so we don't
auto-remove it from the config just because it starts with "vnet"
(VIR_NET_GENERATED_TAP_PREFIX); this makes it possible to use the
same pattern of names that libvirt itself uses when it automatically
creates the tap devices.)
Signed-off-by: Laine Stump <laine@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Libvirt API for virtualization
Libvirt provides a portable, long term stable C API for managing the virtualization technologies provided by many operating systems. It includes support for QEMU, KVM, Xen, LXC, bhyve, Virtuozzo, VMware vCenter and ESX, VMware Desktop, Hyper-V, VirtualBox and the POWER Hypervisor.
For some of these hypervisors, it provides a stateful management daemon which runs on the virtualization host allowing access to the API both by non-privileged local users and remote users.
Layered packages provide bindings of the libvirt C API into other languages including Python, Perl, PHP, Go, Java, OCaml, as well as mappings into object systems such as GObject, CIM and SNMP.
Further information about the libvirt project can be found on the website:
License
The libvirt C API is distributed under the terms of GNU Lesser General
Public License, version 2.1 (or later). Some parts of the code that are
not part of the C library may have the more restrictive GNU General
Public License, version 2.0 (or later). See the files COPYING.LESSER
and COPYING for full license terms & conditions.
Installation
Libvirt uses the GNU Autotools build system, so in general can be built and installed with the usual commands. For example, to build in a manner that is suitable for installing as root, use:
$ ./configure --prefix=/usr --sysconfdir=/etc --localstatedir=/var
$ make
$ sudo make install
While to build & install as an unprivileged user
$ ./configure --prefix=$HOME/usr
$ make
$ make install
The libvirt code relies on a large number of 3rd party libraries. These will
be detected during execution of the configure script and a summary printed
which lists any missing (optional) dependencies.
Contributing
The libvirt project welcomes contributions in many ways. For most components the best way to contribute is to send patches to the primary development mailing list. Further guidance on this can be found on the website:
https://libvirt.org/contribute.html
Contact
The libvirt project has two primary mailing lists:
- libvirt-users@redhat.com (for user discussions)
- libvir-list@redhat.com (for development only)
Further details on contacting the project are available on the website: