interface: Refactor interface vlan to helper func

Mechanical move to break up udevIfaceGetIfaceDef() into different
helpers for each of the interface types to hopefully make the code
easier to follow. This moves the vlan code to
udevIfaceGetIfaceDefVlan().

src/interface/interface_backend_udev.c

@@ -654,6 +654,51 @@ error:
     return -1;
 }
 
+static int
+ATTRIBUTE_NONNULL(1) ATTRIBUTE_NONNULL(2) ATTRIBUTE_NONNULL(3)
+ATTRIBUTE_NONNULL(4) ATTRIBUTE_RETURN_CHECK
+udevIfaceGetIfaceDefVlan(struct udev *udev ATTRIBUTE_UNUSED,
+                         struct udev_device *dev ATTRIBUTE_UNUSED,
+                         const char *name,
+                         virInterfaceDef *ifacedef)
+{
+    char *vid;
+    char *vlan_parent_dev = NULL;
+
+    vlan_parent_dev = strdup(name);
+    if (!vlan_parent_dev) {
+        virReportOOMError();
+        goto cleanup;
+    }
+
+    /* Find the DEVICE.VID again */
+    vid = strrchr(vlan_parent_dev, '.');
+    if (!vid) {
+        virReportError(VIR_ERR_INTERNAL_ERROR,
+                _("failed to find the VID for the VLAN device '%s'"),
+                name);
+        goto cleanup;
+        }
+
+    /* Replace the dot with a NULL so we can have the device and VID */
+    vid[0] = '\0';
+    vid++;
+
+    /* Set our type to VLAN  */
+    ifacedef->type = VIR_INTERFACE_TYPE_VLAN;
+
+    /* Set the VLAN specifics */
+    ifacedef->data.vlan.tag = vid;
+    ifacedef->data.vlan.devname = vlan_parent_dev;
+
+    return 0;
+
+cleanup:
+    VIR_FREE(vlan_parent_dev);
+
+    return -1;
+}
+
 static virInterfaceDef * ATTRIBUTE_NONNULL(1)
 udevIfaceGetIfaceDef(struct udev *udev, const char *name)
 {
@@ -712,34 +757,8 @@ udevIfaceGetIfaceDef(struct udev *udev, const char *name)
      * other devices */
     vlan_parent_dev = strrchr(name, '.');
     if (vlan_parent_dev) {
-        /* Found the VLAN dot */
-        char *vid;
-
-        vlan_parent_dev = strdup(name);
-        if (!vlan_parent_dev) {
-            virReportOOMError();
+        if (udevIfaceGetIfaceDefVlan(udev, dev, name, ifacedef))
             goto cleanup;
-        }
-
-        /* Find the DEVICE.VID separator again */
-        vid = strrchr(vlan_parent_dev, '.');
-        if (!vid) {
-            virReportError(VIR_ERR_INTERNAL_ERROR,
-                           _("failed to find the VID for the VLAN device '%s'"),
-                           name);
-            goto cleanup;
-        }
-
-        /* Replace the dot with a NULL so we can have the device and VID */
-        vid[0] = '\0';
-        vid++;
-
-        /* Set our type to VLAN  */
-        ifacedef->type = VIR_INTERFACE_TYPE_VLAN;
-
-        /* Set the VLAN specifics */
-        ifacedef->data.vlan.tag = vid;
-        ifacedef->data.vlan.devname = vlan_parent_dev;
     } else if (STREQ_NULLABLE(udev_device_get_devtype(dev), "bridge")) {
         if (udevIfaceGetIfaceDefBridge(udev, dev, name, ifacedef) < 0)
             goto cleanup;