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libvirt/m4/virt-driver-remote.m4
Daniel P. Berrangé b18c273a24 remote: enable connecting to the per-driver daemons
Historically URIs handled by the remote driver will always connect to
the libvirtd UNIX socket. There will now be one daemon per driver, and
each of these has its own UNIX sockets to connect to.

It will still be possible to run the traditional monolithic libvirtd
though, which will have the original UNIX socket path.

In addition there is a virproxyd daemon that doesn't run any drivers,
but provides proxying for clients accessing libvirt over IP sockets, or
tunnelling to the legacy libvirtd UNIX socket path.

Finally when running inside a daemon, the remote driver must not reject
connections unconditionally. For example, the QEMU driver needs to be
able to connect to the network driver. The remote driver must thus be
willing to handle connections even when inside the daemon, provided no
local driver is registered.

This refactoring enables the remote driver to be able to connect to the
per-driver daemons. The URI parameter "mode" accepts the values "auto",
"direct" and "legacy" to control which daemons are connected to.

The client side libvirt.conf config file also supports a "remote_mode"
setting which is used if the URI parameter is not set.

If neither the config file or URI parameter set a mode, then "auto"
is used, whereby the client looks to see which sockets actually exist
right now.

The remote driver will only ever spawn the per-driver daemons, or
the legacy libvirtd. It won't ever try to spawn virtproxyd, as
that is only there for IP based connectivity, or for access from
legacy remote clients.

If connecting to a remote host over any kind of ssh tunnel, for now we
must assume only the legacy socket exists. A future patch will introduce
a netcat replacement that is tailored for libvirt to make remote
tunnelling easier.

The configure arg '--with-remote-default-mode=legacy|direct' allows
packagers to set a default at build time. If not given, it will default
to legacy mode.

Eventually the default will switch to direct mode. Distros can choose
to do the switch earlier if desired. The main blocker is testing and
suitable SELinux/AppArmor policies.

Reviewed-by: Andrea Bolognani <abologna@redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
2019-08-09 14:06:31 +01:00

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dnl The remote driver
dnl
dnl Copyright (C) 2016 Red Hat, Inc.
dnl
dnl This library is free software; you can redistribute it and/or
dnl modify it under the terms of the GNU Lesser General Public
dnl License as published by the Free Software Foundation; either
dnl version 2.1 of the License, or (at your option) any later version.
dnl
dnl This library is distributed in the hope that it will be useful,
dnl but WITHOUT ANY WARRANTY; without even the implied warranty of
dnl MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
dnl Lesser General Public License for more details.
dnl
dnl You should have received a copy of the GNU Lesser General Public
dnl License along with this library. If not, see
dnl <http://www.gnu.org/licenses/>.
dnl
AC_DEFUN([LIBVIRT_DRIVER_ARG_REMOTE], [
LIBVIRT_ARG_WITH_FEATURE([REMOTE], [remote driver], [yes])
LIBVIRT_ARG_WITH([REMOTE_DEFAULT_MODE], [remote driver default mode], [legacy])
])
AC_DEFUN([LIBVIRT_DRIVER_CHECK_REMOTE], [
if test "$with_remote" = "yes" ; then
AC_DEFINE_UNQUOTED([WITH_REMOTE], 1, [whether Remote driver is enabled])
fi
AM_CONDITIONAL([WITH_REMOTE], [test "$with_remote" = "yes"])
case "$with_remote_default_mode" in
legacy)
REMOTE_DRIVER_MODE_DEFAULT=REMOTE_DRIVER_MODE_LEGACY
;;
direct)
REMOTE_DRIVER_MODE_DEFAULT=REMOTE_DRIVER_MODE_DIRECT
;;
*)
AC_MSG_ERROR([Unknown remote mode '$with_remote_default_mode'])
;;
esac
AC_DEFINE_UNQUOTED([REMOTE_DRIVER_MODE_DEFAULT],[$REMOTE_DRIVER_MODE_DEFAULT], [Default remote driver mode])
])
AC_DEFUN([LIBVIRT_DRIVER_RESULT_REMOTE], [
LIBVIRT_RESULT([Remote], [$with_remote])
])