[PATCH 20/36] lib: Introduce virDomainFDAssociate API

[Peter Krempa]

On Fri, Jan 06, 2023 at 13:40:03 +0100, Pavel Hrdina wrote:
> On Thu, Jan 05, 2023 at 05:30:09PM +0100, Peter Krempa wrote:
> > The API can be used to associate one or more (e.g. a RO and RW fd for a
> > disk backend image) FDs to a VM. They can be then used per definition.
> > 
> > The primary use case for now is for complex deployment where
> > libvirtd/virtqemud may be run inside a container and getting the image
> > into the container is complicated.
> > 
> > In the future it will also allow passing e.g. vhost FDs and other
> > resources to a VM without the need to have a filesystem representation
> > for it.
> > 
> > Passing raw FDs has few intricacies and thus libvirt will by default not
> > restore security labels.
> > 
> > Signed-off-by: Peter Krempa <pkrempa at redhat.com>
> > ---
> >  include/libvirt/libvirt-domain.h    | 22 ++++++++
> >  src/driver-hypervisor.h             |  8 +++
> >  src/libvirt-domain.c                | 82 +++++++++++++++++++++++++++++
> >  src/libvirt_public.syms             |  5 ++
> >  src/remote/remote_daemon_dispatch.c | 40 ++++++++++++++
> >  src/remote/remote_driver.c          | 27 ++++++++++
> >  src/remote/remote_protocol.x        | 14 ++++-
> >  src/remote_protocol-structs         |  6 +++
> >  8 files changed, 203 insertions(+), 1 deletion(-)
> > 
> > diff --git a/include/libvirt/libvirt-domain.h b/include/libvirt/libvirt-domain.h
> > index 295fd30c93..a1e39f2f70 100644
> > --- a/include/libvirt/libvirt-domain.h
> > +++ b/include/libvirt/libvirt-domain.h
> > @@ -6457,4 +6457,26 @@ int virDomainStartDirtyRateCalc(virDomainPtr domain,
> >                                  int seconds,
> >                                  unsigned int flags);
> > 
> > +
> > +/**
> > + * virDomainFDAssociateFlags:
> > + *
> > + * Since: 9.0.0
> > + */
> > +typedef enum {
> > +    /* Attempt a best-effort restore of security labels after use (Since: 9.0.0) */
> > +    VIR_DOMAIN_FD_ASSOCIATE_SECLABEL_RESTORE = (1 << 0),
> > +    /* Require mandatory restore of security labels after use (Since: 9.0.0) */
> > +    VIR_DOMAIN_FD_ASSOCIATE_SECLABEL_RESTORE_REQUIRE = (1 << 1),
> > +    /* Use a seclabel allowing writes for the FD even if usage implies read-only mode (Since: 9.0.0) */
> > +    VIR_DOMAIN_FD_ASSOCIATE_SECLABEL_WRITABLE = (1 << 2),
> > +} virDomainFDAssociateFlags;
> 
> Do we need to introduce flag that is not supported by any hypervisor? It
> should be perfectly fine to introduce the flag once there is actual
> usage for it or am I missing something?

No, VIR_DOMAIN_FD_ASSOCIATE_SECLABEL_RESTORE_REQUIRE can be actually
deleted for now and re-introduced once it's implemented.