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Libvirt native C API and daemons
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Laine Stump 282d135ddb conf: properly clear out autogenerated macvtap names when formatting/parsing 
Back when macvtap support was added in commit 315baab944 in Feb. 2010
(libvirt-0.7.7), it was setup to autogenerate a name for the device if
one wasn't supplied, in the pattern "macvtap%d" (or "macvlan%d"),
similar to the way an unspecified standard tap device name will lead
to an autogenerated "vnet%d".

As a matter of fact, in commit ca1b7cc8e4 added in May 2010, the code
was changed to *always* ignore a supplied device name for macvtap
interfaces by deleting *any* name immediately during the <interface>
parsing (this was intended to prevent one domain which had failed to
completely start from deleting the macvtap device of another domain
which had subsequently been provided the same device name (this will
seem mildly ironic later). This was later fixed to only clear the
device name when inactive XML was being parsed. HOWEVER - this was
only done if the xml was <interface type='direct'> - autogenerated
names were not cleared for <interface type='network'> (which could
also result in a macvtap device).

Although the names of "vnetX" tap devices had always been
automatically cleared when parsing <interface> (see commit d1304583d
from July 2008 (!)), at the time macvtap support was added, both vnetX
and macvtapX device names were always included when formatting the
XML.

Then in commit a8be259d0c (July 2011, libvirt-0.9.4), <interface>
formatting was changed to also clear out "vnetX" device names during
XML formatting as well. However the same treatment wasn't given to
"macvtapX".

Now in 2020, there has been a report that a failed migration leads to
the macvtap device of some other unrelated guest on the destination
host losing its network connectivity. It was determined that this was
due to the domain XML in the migration containing a macvtap device
name, e.g. "macvtap0", that was already in use by the other guest on
the destination. Normally this wouldn't be a problem, because libvirt
would see that the device was already in use, and then find a
different unused name. But in this case, other external problems were
causing the migration to fail prior to selecting a macvtap device and
successfully opening it, and during error recovery, qemuProcessStop()
was called, which went through all def->nets objects and (if they were
macvtap) deleted the device specified in net->ifname; since libvirt
hadn't gotten to the point of replacing the incoming "macvtap0" with
the name of a device it actually created for this guest, that meant
that "macvtap0" was deleted, *even though it was currently in use by a
different guest*!

Whew!

So, it turns out that when formatting "migratable" XML, "vnetX"
devices are omitted, just as when formatting "inactive" XML. By making
the code in both interface parsing and formatting consistent for
"vnetX", "macvtapX", and "macvlanX", we can thus make sure that the
autogenerated (and unneeded / completely *not* wanted) macvtap device
name will not be sent with the migration XML. This way when a
migration fails, net->ifname will be NULL, and libvirt won't have any
device to try and (erroneously) delete.

Signed-off-by: Laine Stump <laine@redhat.com>
Reviewed-by: Daniel Henrique Barboza <danielhb413@gmail.com>
2020-08-24 23:49:16 -04:00
.ctags.d maint: Add support for .ctags.d 2019-05-31 17:54:28 +02:00
.github github: skip lockdown of old issues/prs 2020-04-07 17:50:54 +01:00
build-aux build-aux: Get rid of 'make syntax-check' reference 2020-08-17 08:49:59 +02:00
ci ci/Makefile: get rid of 'make check' references 2020-08-17 08:42:47 +02:00
docs Revert "formatdomain.html.in: mention pSeries NVDIMM 'align down' mechanic" 2020-08-24 18:41:38 +02:00
examples examples: Use GLib event loop impl in events.stp 2020-08-21 11:34:23 +01:00
include meson: add include directory 2020-08-03 09:26:59 +02:00
po qemu: Extract snapshot related code to a separate file 2020-08-24 16:42:29 +02:00
scripts scripts: Fix meson-install-symlink.py overwriting existing links 2020-08-05 13:11:16 +02:00
src conf: properly clear out autogenerated macvtap names when formatting/parsing 2020-08-24 23:49:16 -04:00
tests qemu_validate.c: add pSeries NVDIMM size alignment validation 2020-08-24 18:41:28 +02:00
tools virshStreamInData: Handle block devices 2020-08-24 13:39:55 +02:00
.color_coded.in gnulib: delete all gnulib integration 2020-02-07 15:03:54 +00:00
.ctags ctags: Generate tags for headers, i.e. function prototypes 2018-09-18 14:21:33 +02:00
.dir-locals.el build: avoid tabs that failed syntax-check 2012-09-06 09:43:46 -06:00
.editorconfig Add .editorconfig 2019-09-06 12:47:46 +02:00
.gitignore Ignore clangd-related files and folders 2020-08-03 10:57:47 +02:00
.gitlab-ci.yml ci: Temporarily enable verbose mode for cirrus-run 2020-08-04 13:29:34 +02:00
.gitmodules gnulib: delete all gnulib integration 2020-02-07 15:03:54 +00:00
.gitpublish gitpublish: add a subject prefix 2020-01-16 13:04:11 +00:00
.mailmap mailmap: Remove some duplicates 2019-06-07 13:18:08 +02:00
.ycm_extra_conf.py.in gnulib: delete all gnulib integration 2020-02-07 15:03:54 +00:00
AUTHORS.in meson: generate and distribute spec files and AUTHORS 2020-08-03 09:27:06 +02:00
config.h config.h: add a copyright blurb 2020-08-03 13:54:15 +02:00
configmake.h.in meson: generate configmake.h 2020-08-03 09:26:48 +02:00
CONTRIBUTING.rst meson: adjust our documentation to mention meson instead of autoconf 2020-08-03 09:27:09 +02:00
COPYING maint: follow recommended practice for using LGPL 2013-05-20 14:15:21 -06:00
COPYING.LESSER maint: Remove control characters from LGPL license file 2015-09-25 09:16:24 +02:00
gitdm.config gitdm: add 'ibm' file 2019-10-18 17:32:52 +02:00
libvirt-admin.pc.in Add libvirt-admin library 2015-06-16 13:46:20 +02:00
libvirt-lxc.pc.in Add pkg-config files for libvirt-qemu & libvirt-lxc 2014-06-23 16:17:27 +01:00
libvirt-qemu.pc.in Add pkg-config files for libvirt-qemu & libvirt-lxc 2014-06-23 16:17:27 +01:00
libvirt.pc.in Add pkg-config files for libvirt-qemu & libvirt-lxc 2014-06-23 16:17:27 +01:00
libvirt.spec.in README: Drop symlink 2020-08-24 09:32:08 +02:00
meson_options.txt meson: Improve RPATH handling 2020-08-24 12:58:51 +02:00
meson.build meson: Improve RPATH handling 2020-08-24 12:58:51 +02:00
mingw-libvirt.spec.in spec: Require Fedora 31 2020-06-17 12:59:08 +02:00
NEWS.rst news: Document sparse streams for block devices 2020-08-24 15:16:43 +02:00
README.rst README: drop Travis CI badge 2020-08-03 15:08:28 +02:00
run.in meson: generate run helper 2020-08-03 09:27:06 +02:00

README.rst 

.. image:: https://gitlab.com/libvirt/libvirt/badges/master/pipeline.svg
     :target: https://gitlab.com/libvirt/libvirt/pipelines
     :alt: GitLab CI Build Status
.. image:: https://bestpractices.coreinfrastructure.org/projects/355/badge
     :target: https://bestpractices.coreinfrastructure.org/projects/355
     :alt: CII Best Practices
.. image:: https://translate.fedoraproject.org/widgets/libvirt/-/libvirt/svg-badge.svg
     :target: https://translate.fedoraproject.org/engage/libvirt/
     :alt: Translation status

==============================
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:

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
============

Instructions on building and installing libvirt can be found on the website:

https://libvirt.org/compiling.html

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