[libvirt-users] LXC + USB passthrough = Operation not permitted

[Filip Maj]

Hi!

First post, kind of a noobie. I've been working with LXC and libvirt for a
few months now. Trying to do some interesting things with containers and
Android devices :D

I'm running ubuntu 13.10 with LXC 1.0.1 and tried both libvirt 1.1.1 and
1.2.2 (backported from ubuntu-trusty), but with either version of libvirt
am getting issues as soon as I try to get access to USB devices inside the
container.

Relevant versions of stuff:

$ dpkg -l | grep -i lxc
ii  liblxc1                              1.0.1-0ubuntu1~ubuntu13.10.1~ppa1
i386         Linux Containers userspace tools (library)
ii  lxc                                  1.0.1-0ubuntu1~ubuntu13.10.1~ppa1
i386         Linux Containers userspace tools
ii  lxc-templates                        1.0.1-0ubuntu1~ubuntu13.10.1~ppa1
i386         Linux Containers userspace tools (templates)
ii  python3-lxc                          1.0.1-0ubuntu1~ubuntu13.10.1~ppa1
i386         Linux Containers userspace tools (Python 3.x bindings)

$ dpkg -l | grep libvirt
ii  libvirt-bin                          1.2.2-0ubuntu12
i386         programs for the libvirt library
ii  libvirt0                             1.2.2-0ubuntu12
i386         library for interfacing with different virtualization systems
ii  python-libvirt                       1.2.2-0ubuntu1
 i386         libvirt Python bindings

Here's my entire domain definition:

<domain type='lxc'>
  <name>oshi32134</name>
  <uuid>xxxxx</uuid>
  <memory unit='KiB'>3145728</memory>
  <currentMemory unit='KiB'>3145728</currentMemory>
  <vcpu placement='static'>1</vcpu>
  <resource>
    <partition>/machine</partition>
  </resource>
  <os>
    <type arch='i686'>exe</type>
    <init>/sbin/init</init>
  </os>
  <clock offset='utc'/>
  <on_poweroff>destroy</on_poweroff>
  <on_reboot>restart</on_reboot>
  <on_crash>destroy</on_crash>
  <devices>
    <emulator>/usr/lib/libvirt/libvirt_lxc</emulator>
    <filesystem type='mount' accessmode='passthrough'>
      <source dir='/some/valid/filesystem/location'/>
      <target dir='/'/>
    </filesystem>
    <filesystem type='mount' accessmode='passthrough'>
      <source dir='/another/valid/filesystem/location'/>
      <target dir='/mnt/android'/>
    </filesystem>
    <interface type='bridge'>
      <mac address='xx:xx:xx:xx:xx:xx'/>
      <source bridge='br1'/>
    </interface>
    <console type='pty'>
      <target type='lxc' port='0'/>
    </console>
    <hostdev mode='capabilities' type='misc'>
      <source>
        <char>/dev/kvm</char>
      </source>
    </hostdev>
    <hostdev mode='subsystem' type='usb' managed='yes'>
      <source>
        <vendor id='0x04e8'/>
        <product id='0x6860'/>
  </source>
    </hostdev>
  </devices>
</domain>

Everything worked fine until I added the USB <hostdev> element. I'm
essentially trying to get access to a physical Android device connected to
the host from inside a container. When I go to start the container, I get
an error about Operation not permitted. Here's the relevant bits from
/var/log/libvirt/lxc/machine.log:

2014-04-11 22:46:40.491+0000: starting up
PATH=/usr/local/sbin:/usr/local/bin:/usr/bin:/usr/sbin:/sbin:/bin
LIBVIRT_DEBUG=3 LIBVIRT_LOG_OUTPUTS=3:stderr /usr/lib/libvirt/libvirt_lxc
--name oshi32134 --console 24 --security=none --handshake 27 --background
--veth vnet1
2014-04-11 22:46:40.597+0000: 685: info : libvirt version: 1.2.2
2014-04-11 22:46:40.597+0000: 685: error :
virLXCControllerSetupHostdevSubsysUSB:1390 : Unable to create device
//var/run/libvirt/lxc/oshi32134.dev/bus/usb//002//003: Operation not
permitted
Unable to create device
//var/run/libvirt/lxc/oshi32134.dev/bus/usb//002//003: Operation not
permitted

I get the same output above when I use libvirt 1.1.1.

Tracing down through the libvirt code it looks like it fails when calling
`mknod`. It's clear that libvirt converts the product/vendor ids I
specified in the domain definition file to the appropriate USB bus
(/dev/bus/usb/002/003, verified by comparing against output of
`usb-devices`).

In a parallel effort, a colleague of mine set up a vanilla LXContainer on a
new install of the same version of ubuntu, and successfully was able to
communicate with the Android device from a container. The only
configuration tweaks he made was make sure to whitelist the cgroup with the
appropriate major/minor device number (associated with the Android device)
inside the LXC configuration file. From there the container was able to
appropriately create the device file as you attach/detach the Android
device.

Hopefully someone can shed some light, and appreciate your patience with me
as I am learning a lot of this stuff as I go :)

Thanks in advance for any help!
Fil
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://listman.redhat.com/archives/libvirt-users/attachments/20140411/1c752b8e/attachment.htm>