[Bug 1546565] Re: Ownership/Permissions of vhost_user sockets for openvswitch-dpdk make them unusable by libvirt/qemu/kvm

[Thiago Martins]

Hey guys,

Sorry to ask this here but, how to use the fix ?

I have the proposed repository enabled, the latest DPDK that contains
the fix is installed (apt full-upgrade on top of Proposed) but, look:

---
virsh start ubuntu16.04-1
error: Failed to start domain ubuntu16.04-1
error: internal error: process exited while connecting to monitor: 2016-04-29T23:22:57.647708Z qemu-system-x86_64: -chardev socket,id=charnet2,path=/var/run/openvswitch/vhost-user1: Failed to connect socket: Permission denied

---

ll /var/run/openvswitch/vhost-user*
srwxr-xr-x 1 root root 0 Apr 29 23:20 /var/run/openvswitch/vhost-user1=
srwxr-xr-x 1 root root 0 Apr 29 23:20 /var/run/openvswitch/vhost-user2=

---

Thanks!
Thiago

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https://bugs.launchpad.net/bugs/1546565

Title:
  Ownership/Permissions of vhost_user sockets for openvswitch-dpdk make
  them unusable by libvirt/qemu/kvm

Status in dpdk package in Ubuntu:
  Fix Released
Status in openvswitch-dpdk package in Ubuntu:
  Triaged
Status in dpdk source package in Xenial:
  Fix Committed
Status in openvswitch-dpdk source package in Xenial:
  New

Bug description:
  As of today the vhost_user sockets created by openvswitch have root:root file ownership.
  In fact creation is actually done by code the DPDK lib, but the path is passed to it from openvswitch.

  The API called to DPDK has no notion of ownership/groups.
  It just "inherits" what the current running process has.
  But due to LP:1546556 the process ownership/group can't be changed the usual way openvsiwtch would when using dpdk.

  KVM as invoked by libvirt will run under libvirt-qemu:kvm and will
  thereby be unable to access these sockets.

  The current workaround is:
     1. wait after start of openvswitch (only then the sockets exist)
     2. chown all created vhost_iuser sockets that are to be used 
        e.g. sudo chown libvirt-qemu /var/run/openvswitch/vhost-user-1 
     3. if one wants to separate vhost_user sockets from the "rest" of openvswitch /var/run files use e.g.:
        DPDK_OPTS='[...] -vhost_sock_dir /var/run/openvswitch-vhost [...]
     X. this has to be redone every start/restart of oepnvswitch
     Y. if permissions are changed in a way that openvswitch can no more remove them on shutdown they won't re-initialize properly on the next start

  That is a severe shortcoming and not really applicable to a supported production environment.
  There are discussions ongoing about providing an option to specify owner/group/permissions of vhost_user sockets which would solve the issue.
  Unfortunately the patch series is blocked by a wider discussion about moving the dpdk configuration to the ovsdb (which makes sense, but stalls the acceptance of the patches providing the interface to modify permissions.

  Link to the last thread about moving dpdk config to ovsdb: http://comments.gmane.org/gmane.network.openvswitch.devel/59186
  Link to the last thread about making vhost_user socket user/group configurable - patch 4&5 of this: http://openvswitch.org/pipermail/dev/2015-December/063568.html
  But as mentioned it was decided to get the db config discussion done first.

  It is unsure if the patches once final will make it into openvswitch 2.5 - it would be great if they would.
  But even if not they shouldn't appear too much after and we might be able to cherry pick them?

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