Support iface_name setting for management network (#1739)

Allow setting the interface name that appears on the host for the
management network interface in the guest. This allows for more complex
networking layouts by allowiing matching against devices for vlan
configurations.

Fixes: #1701

spec/unit/action/create_network_interfaces.rb

@@ -92,6 +92,56 @@ describe VagrantPlugins::ProviderLibvirt::Action::CreateNetworkInterfaces do
       expect(subject.call(env)).to be_nil
     end
 
+    context 'management network' do
+      let(:domain_xml) {
+        # don't need full domain here, just enough for the network element to work
+        <<-EOF.unindent
+        <domain type='qemu'>
+          <devices>
+            <interface type='network'>
+              <alias name='ua-net-0'/>
+              <mac address='52:54:00:7d:14:0e'/>
+              <source network='vagrant-libvirt'/>
+              <target dev="myvnet0"></target>
+              <model type='virtio'/>
+              <driver iommu='off'/>
+              <address type='pci' domain='0x0000' bus='0x00' slot='0x05' function='0x0'/>
+            </interface>
+          </devices>
+        </domain>
+        EOF
+      }
+
+      before do
+        allow(libvirt_domain).to receive(:xml_desc).and_return(domain_xml)
+      end
+
+      context 'when iface name is set' do
+        let(:vagrantfile_providerconfig) {
+          <<-EOF
+          libvirt.management_network_iface_name = 'myvnet0'
+          EOF
+        }
+        let(:management_nic_xml) {
+          <<-EOF.unindent
+          <interface type="network">
+            <alias name="ua-net-0"></alias>
+            <source network="vagrant-libvirt"></source>
+            <target dev="myvnet0"></target>
+            <model type="virtio"></model>
+            <driver iommu="off"></driver>
+          </interface>
+          EOF
+        }
+
+        it 'should set target appropriately' do
+          expect(driver).to receive(:attach_device).with(management_nic_xml)
+
+          expect(subject.call(env)).to be_nil
+        end
+      end
+    end
+
     context 'private network' do
       let(:vagrantfile) do
         <<-EOF