When starting an LXC container, the /dev entries are created
under temp root (/var/run/libvirt/lxc/$name.dev), relabelled and
then the root is pivoted. However, when it comes to USB devices
which keep path to the device in the structure we need a way to
override the default /dev/usb/... path because we want to work
with the one under temp root. That's what @vroot argument is for
in virUSBDeviceNew. However, what is being passed there is:

  vroot = /var/run/libvirt/lxc/lxc_0.dev/bus/usb

Therefore, constructed path is wrong:

  dev->path = //var/run/libvirt/lxc/lxc_0.dev/bus/usb//dev/bus/usb/002/002

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
---
 src/util/virusb.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/src/util/virusb.c b/src/util/virusb.c
index 6359235ff..f06639eec 100644
--- a/src/util/virusb.c
+++ b/src/util/virusb.c
@@ -343,9 +343,13 @@ virUSBDeviceNew(unsigned int bus,
         virUSBDeviceFree(dev);
         return NULL;
     }
-    if (virAsprintf(&dev->path, "%s" USB_DEVFS "%03d/%03d",
-                    vroot ? vroot : "",
-                    dev->bus, dev->dev) < 0) {
+
+    if ((vroot &&
+         virAsprintf(&dev->path, "%s/%03d/%03d",
+                     vroot, dev->bus, dev->dev) < 0) ||
+        (!vroot &&
+         virAsprintf(&dev->path, USB_DEVFS "%03d/%03d",
+                     dev->bus, dev->dev) < 0)) {
         virUSBDeviceFree(dev);
         return NULL;
     }
-- 
2.13.6

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On 01/24/2018 04:37 AM, Michal Privoznik wrote:
> When starting an LXC container, the /dev entries are created
> under temp root (/var/run/libvirt/lxc/$name.dev), relabelled and
> then the root is pivoted. However, when it comes to USB devices
> which keep path to the device in the structure we need a way to
> override the default /dev/usb/... path because we want to work
> with the one under temp root. That's what @vroot argument is for
> in virUSBDeviceNew. However, what is being passed there is:
> 
>   vroot = /var/run/libvirt/lxc/lxc_0.dev/bus/usb
> 
> Therefore, constructed path is wrong:
> 
>   dev->path = //var/run/libvirt/lxc/lxc_0.dev/bus/usb//dev/bus/usb/002/002
> 
> Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
> ---
>  src/util/virusb.c | 10 +++++++---
>  1 file changed, 7 insertions(+), 3 deletions(-)
> 

Reviewed-by: John Ferlan <jferlan@redhat.com>

> diff --git a/src/util/virusb.c b/src/util/virusb.c
> index 6359235ff..f06639eec 100644
> --- a/src/util/virusb.c
> +++ b/src/util/virusb.c
> @@ -343,9 +343,13 @@ virUSBDeviceNew(unsigned int bus,
>          virUSBDeviceFree(dev);
>          return NULL;
>      }
> -    if (virAsprintf(&dev->path, "%s" USB_DEVFS "%03d/%03d",
> -                    vroot ? vroot : "",
> -                    dev->bus, dev->dev) < 0) {
> +
> +    if ((vroot &&
> +         virAsprintf(&dev->path, "%s/%03d/%03d",
> +                     vroot, dev->bus, dev->dev) < 0) ||
> +        (!vroot &&
> +         virAsprintf(&dev->path, USB_DEVFS "%03d/%03d",
> +                     dev->bus, dev->dev) < 0)) {

This I think is of those cases where something like:

if (vroot)
    rc = virAsprintf()
else
    rc = virAsprintf()
if (rc < 0)

just is easier to read.  Your call - the code works, just causes
personal eye irritation ;-)

John

>          virUSBDeviceFree(dev);
>          return NULL;
>      }
> 

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