Update to Drupal 8.1.8. For more information, see https://www.drupal.org/project/drupal/releases/8.1.8

core/modules/link/src/Plugin/Field/FieldType/LinkItem.php

@@ -169,7 +169,7 @@ class LinkItem extends FieldItemBase implements LinkItemInterface {
    * {@inheritdoc}
    */
   public function getUrl() {
-    return Url::fromUri($this->uri);
+    return Url::fromUri($this->uri, $this->options);
   }
 
   /**

core/modules/link/src/Plugin/migrate/cckfield/d7/LinkField.php

@@ -0,0 +1,30 @@
+<?php
+
+namespace Drupal\link\Plugin\migrate\cckfield\d7;
+
+use Drupal\link\Plugin\migrate\cckfield\LinkField as D6LinkField;
+
+/**
+ * @MigrateCckField(
+ *   id = "link_field",
+ *   core = {7},
+ *   type_map = {
+ *     "link_field" = "link"
+ *   }
+ * )
+ *
+ * This plugin provides the exact same functionality as the Drupal 6 "link"
+ * plugin with the exception that the plugin ID "link_field" is used in the
+ * field type map.
+ */
+class LinkField extends D6LinkField {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getFieldWidgetMap() {
+    // By default, use the plugin ID for the widget types.
+    return ['link_field' => 'link_default'];
+  }
+
+}

core/modules/link/tests/src/Kernel/LinkItemTest.php

@@ -78,6 +78,13 @@ class LinkItemTest extends FieldKernelTestBase {
     $entity->field_test->title = $title;
     $entity->field_test->first()->get('options')->set('query', $parsed_url['query']);
     $entity->field_test->first()->get('options')->set('attributes', array('class' => $class));
+    $this->assertEquals([
+      'query' => $parsed_url['query'],
+      'attributes' => [
+        'class' => $class,
+      ],
+      'external' => TRUE,
+    ], $entity->field_test->first()->getUrl()->getOptions());
     $entity->name->value = $this->randomMachineName();
     $entity->save();