Tumbleweed currently ships VirtualBox 5.1, but vagrant 1.8.1 cannot use it.
It's difficult to install old VirtualBox RPMs on Tumbleweed, because of kmp
packages not matching the new kernel.

Updating to vagrant 1.8.5 fixes this:
https://build.opensuse.org/package/show/Virtualization/vagrant

Output:

  % vagrant up --provider=virtualbox
  The provider 'virtualbox' that was requested to back the machine
  'default' is reporting that it isn't usable on this system. The
  reason is shown below:

  Vagrant has detected that you have a version of VirtualBox installed
  that is not supported by this version of Vagrant. Please install one of
  the supported versions listed below to use Vagrant:

  4.0, 4.1, 4.2, 4.3, 5.0

  A Vagrant update may also be available that adds support for the version
  you specified. Please check www.vagrantup.com/downloads.html to download
  the latest version.