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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.

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Laine Stump 13ec827052 util: set bridge device MAC address explicitly during virNetDevBridgeCreate When libvirt first implemented a stable and configurable MAC address for the bridges created for libvirt virtual networks (commit `5754dbd56d`, in libvirt v0.8.8) most distro stable releases didn't support explicitly setting the MAC address of a bridge; the bridge just always assumed the lowest numbered MAC of all attached interfaces. Because of this, we stabilized the bridge MAC address by creating a "dummy" tap interface with a MAC address guaranteed to be lower than any of the guest tap devices' MACs (which all started with 0xFE, so it's not difficult to do) and attached it to the bridge - this was the inception of the "virbr0-nic" device that has confused so many people over the years. Even though the linux kernel had recently gained support for explicitly setting a bridge MAC, we deemed it unnecessary to set the MAC that way, because the other (indirect) method worked everywhere. But recently there have been reports that the bridge MAC address was not following the setting in the network config, and mismatched the MAC of the dummy tap device (which was still correct). It turns out that this is due to a change in systemd-242 that persists whatever MAC address is set for a bridge when it's initially started. According to the systemd NEWS file entry for version 242 (https://github.com/systemd/systemd/blob/master/NEWS): "if a bridge interface is created without any slaves, and gains a slave later, then now the bridge does not inherit slave's MAC." This change was the result of: https://github.com/systemd/systemd/issues/3374 (apparently if there is no MAC saved for a bridge by the name of a bridge being created, the random MAC generated during creation is saved, and then that same MAC is used to explicitly set the MAC each time it is created). Once a bridge has an explicitly set MAC, the "use the lowest numbered MAC of attached devices" rule is ignored, so our dummy tap device is like the goggles - it does nothing! (well, almost). We could whine about changes in default behavior, etc. etc., but because the change was in response to actual user problems, that seems likely a fruitless task. Fortunately, time has marched on, and even distro releases that are old enough that they are no longer supported by upstream libvirt (e.g. RHEL6) have support for explicitly setting a bridge device MAC address, either during creation or with a separate ioctl after creation, so we can now do that. To enable explicitly setting the mac during bridge creation, we add a mac arg to virNetDevBridgeCreate(). In the case of platforms where the bridge is created with a netlink RTM_NEWLINK message, we just add that mac to the message. For platforms that still use an ioctl (either SIOCBRADDBR or SIOCIFCREATE2), we make a separate call to virNetDevSetMAC() after creating the bridge. (NB: I was unable to test the calling of virNetDevSetMAC() from the SIOCIFCREATE2 (BSD) version of virNetDevBridgeCreate(); even though I managed to get a FreeBSD system setup and libvirt built there, when I tried to start the default network the SIOCIFCREATE2 ioctl itself failed, so it never even got to the virNetDevSetMAC(). That leaves the FreeBSD implementation untested.) This makes the dummy tap pointless for purposes of setting the MAC address, but it is still useful for IPv6 DAD initialization (which apparently requires at least one interface to be attached to the bridge and online), as well as for setting an initial MTU for the bridge, so it hasn't been removed. (NB: we can safely always call virNetDevBridgeCreate() with &def->mac from the network driver because, in spite of the existence of a "mac_specified" bool in the config suggesting that it may not always be present, in reality a mac address will always be added to any network that doesn't have one - this is guaranteed in all cases by commit `a47ae7c004`) https://bugzilla.redhat.com/show_bug.cgi?id=1760851 Signed-off-by: Laine Stump <laine@redhat.com> Reviewed-by: Jiri Denemark <jdenemar@redhat.com>		2019-11-07 22:09:19 -05:00
.ctags.d	maint: Add support for .ctags.d	2019-05-31 17:54:28 +02:00
.gnulib@1f6fb368c0	maint: Improve use of configmake.h on mingw	2019-08-19 17:04:05 -05:00
build-aux	build-aux: rewrite po file minimizer in Python	2019-10-18 13:54:03 +01:00
ci	ci: Stop using --workdir	2019-08-21 18:58:34 +02:00
docs	news: Update for ARM CPU features	2019-11-07 16:09:25 +01:00
examples	examples: Use G_N_ELEMENTS instead of ARRAY_CARDINALITY	2019-10-15 16:14:19 +02:00
gnulib	maint: Fix VPATH build	2019-01-07 21:56:16 -06:00
include/libvirt	include: stop distributing generated source files	2019-10-23 14:45:56 +02:00
m4	build: move admin code into admin directory	2019-10-23 14:30:58 +02:00
po	build: move admin code into admin directory	2019-10-23 14:30:58 +02:00
scripts	scripts: introduce a macro file for coccinelle	2019-10-21 12:51:54 +02:00
src	util: set bridge device MAC address explicitly during virNetDevBridgeCreate	2019-11-07 22:09:19 -05:00
tests	tests: Introduce tests for ARM CPU features	2019-11-07 16:09:22 +01:00
tools	util: buffer: Remove virBufferCheckError	2019-10-24 19:35:34 +02:00
.color_coded.in
.ctags	ctags: Generate tags for headers, i.e. function prototypes	2018-09-18 14:21:33 +02:00
.dir-locals.el
.editorconfig	Add .editorconfig	2019-09-06 12:47:46 +02:00
.gitignore	.gitignore: Ignore src/admin/libvirt_admin.{def,syms}	2019-10-23 15:10:56 +02:00
.gitlab-ci.yml	gitlab: Adapt to container name changes	2019-08-20 13:08:42 +02:00
.gitmodules	gnulib: switch to use https:// instead of git:// protocol	2018-03-19 16:32:34 +00:00
.gitpublish	git: add config file telling git-publish how to send patches	2018-04-23 11:36:09 +01:00
.mailmap	mailmap: Remove some duplicates	2019-06-07 13:18:08 +02:00
.travis.yml	build: probe for glib-2 library in configure	2019-10-14 10:54:42 +01:00
.ycm_extra_conf.py.in
ABOUT-NLS	po: provide custom make rules for po file management	2018-04-19 10:35:58 +01:00
AUTHORS.in	AUTHORS: Add Katerina Koukiou	2018-07-17 17:01:19 +02:00
autogen.sh	po: provide custom make rules for po file management	2018-04-19 10:35:58 +01:00
bootstrap	maint: update gnulib for syntax-check on BSD	2019-01-07 13:54:07 -06:00
bootstrap.conf	util: drop support for stack traces with logging	2019-10-18 16:25:17 +01:00
ChangeLog	maint: Stop generating ChangeLog from git	2019-04-03 09:45:25 +02:00
config-post.h	nss: only link to yajl library and nothing else	2019-08-07 16:54:02 +01:00
configure.ac	maint: Post-release version bump to 5.10.0	2019-11-06 15:49:10 +01:00
COPYING
COPYING.LESSER
gitdm.config	gitdm: add 'ibm' file	2019-10-18 17:32:52 +02:00
GNUmakefile	build: merge all syntax-check logic into one file	2019-10-09 13:36:54 +01:00
libvirt-admin.pc.in
libvirt-lxc.pc.in
libvirt-qemu.pc.in
libvirt.pc.in
libvirt.spec.in	build: probe for glib-2 library in configure	2019-10-14 10:54:42 +01:00
Makefile.am	build-aux: rewrite po file minimizer in Python	2019-10-18 13:54:03 +01:00
Makefile.nonreentrant	Remove backslash alignment attempts	2017-11-03 13:24:12 +01:00
mingw-libvirt.spec.in	build: probe for glib-2 library in configure	2019-10-14 10:54:42 +01:00
README	Provide a useful README file	2017-05-22 17:01:37 +01:00
README-hacking	docs: update all GIT repo examples to use https:// protocol	2018-03-21 14:48:01 +00:00
README.md	README: fix license typo	2019-07-25 09:21:28 -06:00
run.in	util: activate directory override when used from library	2019-09-10 11:03:35 +01:00

README.md

Libvirt API for virtualization

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:

https://libvirt.org

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:

https://libvirt.org/contact.html