[libvirt] [PATCH v2 11/19] util: Introduce libvirt_udevhelper

[Daniel P. Berrange]

On Thu, Nov 03, 2016 at 08:19:01PM +0800, Michal Privoznik wrote:
> This is a small helper intended to be run by udev. On its input
> (either as the only command line argument or in DEVNODE
> environment vairable) it is given a device and on the output it
> will either put nothing (meaning the device is not used by any of
> the libvirt domains), or it will print out security labels in the
> following form:
> 
>   UID GID SELABEL
> 
> Signed-off-by: Michal Privoznik <mprivozn at redhat.com>
> ---
>  libvirt.spec.in       |   1 +
>  mingw-libvirt.spec.in |   2 +
>  po/POTFILES.in        |   1 +
>  src/Makefile.am       |  20 ++++++++
>  src/util/udevhelper.c | 137 ++++++++++++++++++++++++++++++++++++++++++++++++++
>  5 files changed, 161 insertions(+)
>  create mode 100644 src/util/udevhelper.c
> 

> +static int
> +printLabels(const char *device)
> +{
> +    char *filename = NULL;
> +    virUdevMgrPtr mgr = NULL;
> +    int ret = -1;
> +    virSecurityDeviceLabelDefPtr *labels = NULL;
> +    size_t i, nlabels = 0;
> +    const char *dacLabel = NULL;
> +    const char *seLabel = NULL;
> +
> +    if (virAsprintf(&filename,
> +                    "%s/run/libvirt/qemu/devices.udev", LOCALSTATEDIR) < 0)
> +        goto cleanup;
> +
> +    if (!(mgr = virUdevMgrNewFromFile(filename)))
> +        goto cleanup;
> +
> +    if (virUdevMgrLookupLabels(mgr, device, &labels, &nlabels) < 0)
> +        goto cleanup;

IIUC the 'device' here is a canonical device path, like "/dev/sda" ?

If so, then this is not going to work, because the code is recording
labels against the path seen in the XML which is not canonicalized.
eg XML could contain /dev/disk/by-path/<BLAH>, and so the lookup will
not match /dev/sda even though they point to the same device.

Regards,
Daniel
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