Vagrant+Docker networking problems.

Vagrantfile

# The two above specifies which version of the vagrant API is used.
Vagrant.configure('2') do |config|

  # This is a hack around the networking slowness in the VM.
  config.vm.provider 'virtualbox' do |vb|
    vb.customize ['modifyvm', :id, '--natdnshostresolver1', 'on']
    vb.customize ['modifyvm', :id, '--natdnsproxy1', 'on']
    vb.customize ['modifyvm', :id, '--natpf1', 'app,tcp,,9977,,9977']
  end

  # TODO: move to using Quay
  config.vm.synced_folder '../docker', '/docker'
  config.vm.synced_folder '.', '/app'


  # Forward port 80 to dev port 9977
  #config.vm.network 'forwarded_port', guest: 9977, host: 9977, auto_correct: true
  config.vm.network :private_network, ip: "192.168.50.4"

  # This is the main app container
  config.vm.define 'app' do |app|

    # Each docker container here gets a `provider` block.
    app.vm.provider 'docker' do |d|
      d.build_dir = '../docker/rack-app'
      d.ports     = ['9977:80']
      d.volumes   = ['/app']
      d.cmd       = ['bash', '-l', '-c', 'echo "Launching server." && bundle install; ' +
                     'bundle exec thin -R config.ru -p 80 start']
    end


  end

  # This is just a dummy container we can use to interact with the box above.
  config.vm.define 'test' do |app|
    app.vm.provider 'docker' do |d|
      d.image = 'ubuntu'
      d.create_args = %w(--link api-internal_app_1399599910:app)
    end
  end
end