@@ -344,33 +344,43 @@ delete_block_dns_filters(HANDLE engine_handle)

 }

 /*

- * Returns interface metric value for specified interface index.

+ * Return interface metric value for the specified interface index.

  *

  * Arguments:

  *   index         : The index of TAP adapter.

  *   family        : Address family (AF_INET for IPv4 and AF_INET6 for IPv6).

- * Returns positive metric value or zero for automatic metric on success,

- * a less then zero error code on failure.

+ *   is_auto       : On return set to true if automatic metric is in use.

+ *                   Unused if NULL.

+ *

+ * Returns positive metric value or -1 on error.

  */

-

 int

-get_interface_metric(const NET_IFINDEX index, const ADDRESS_FAMILY family)

+get_interface_metric(const NET_IFINDEX index, const ADDRESS_FAMILY family, int *is_auto)

 {

     DWORD err = 0;

     MIB_IPINTERFACE_ROW ipiface;

     InitializeIpInterfaceEntry(&ipiface);

     ipiface.Family = family;

     ipiface.InterfaceIndex = index;

+

+    if (is_auto)

+    {

+        *is_auto = 0;

+    }

     err = GetIpInterfaceEntry(&ipiface);

-    if (err == NO_ERROR)

+

+    /* On Windows metric is never > INT_MAX so return value of int is ok.

+     * But we check for overflow nevertheless.

+     */

+    if (err == NO_ERROR && ipiface.Metric <= INT_MAX)

     {

-        if (ipiface.UseAutomaticMetric)

+        if (is_auto)

         {

-            return 0;

+            *is_auto = ipiface.UseAutomaticMetric;

         }

-        return ipiface.Metric;

+        return (int)ipiface.Metric;

     }

-    return -err;

+    return -1;

 }

 /*

@@ -39,17 +39,17 @@ add_block_dns_filters(HANDLE *engine, int iface_index, const WCHAR *exe_path,

                       block_dns_msg_handler_t msg_handler_callback);

 /**

- * Returns interface metric value for specified interface index.

+ * Return interface metric value for the specified interface index.

  *

- * @param index The index of TAP adapter

- * @param family Address family (AF_INET for IPv4 and AF_INET6 for IPv6)

+ * @param index         The index of TAP adapter.

+ * @param family        Address family (AF_INET for IPv4 and AF_INET6 for IPv6).

+ * @param is_auto       On return set to true if automatic metric is in use.

+ *                      Unused if NULL.

  *

- * @return positive metric value or zero for automatic metric on success,

- * a less then zero error code on failure.

+ * @return positive interface metric on success or -1 on error

  */

-

 int

-get_interface_metric(const NET_IFINDEX index, const ADDRESS_FAMILY family);

+get_interface_metric(const NET_IFINDEX index, const ADDRESS_FAMILY family, int *is_auto);

 /**

  * Sets interface metric value for specified interface index.

@@ -1344,17 +1344,16 @@ win_wfp_block_dns(const NET_IFINDEX index, const HANDLE msg_channel)

                                    block_dns_msg_handler);

     if (status == 0)

     {

-        tap_metric_v4 = get_interface_metric(index, AF_INET);

-        tap_metric_v6 = get_interface_metric(index, AF_INET6);

-        if (tap_metric_v4 < 0)

+        int is_auto = 0;

+        tap_metric_v4 = get_interface_metric(index, AF_INET, &is_auto);

+        if (is_auto)

         {

-            /* error, should not restore metric */

-            tap_metric_v4 = -1;

+            tap_metric_v4 = 0;

         }

-        if (tap_metric_v6 < 0)

+        tap_metric_v6 = get_interface_metric(index, AF_INET6, &is_auto);

+        if (is_auto)

         {

-            /* error, should not restore metric */

-            tap_metric_v6 = -1;

+            tap_metric_v6 = 0;

         }

         status = set_interface_metric(index, AF_INET, BLOCK_DNS_IFACE_METRIC);

         if (!status)

@@ -804,17 +804,18 @@ HandleBlockDNSMessage(const block_dns_message_t *msg, undo_lists_t *lists)

             }

             interface_data->engine = engine;

             interface_data->index = msg->iface.index;

+            int is_auto = 0;

             interface_data->metric_v4 = get_interface_metric(msg->iface.index,

-                                                             AF_INET);

-            if (interface_data->metric_v4 < 0)

+                                                             AF_INET, &is_auto);

+            if (is_auto)

             {

-                interface_data->metric_v4 = -1;

+                interface_data->metric_v4 = 0;

             }

             interface_data->metric_v6 = get_interface_metric(msg->iface.index,

-                                                             AF_INET6);

-            if (interface_data->metric_v6 < 0)

+                                                             AF_INET6, &is_auto);

+            if (is_auto)

             {

-                interface_data->metric_v6 = -1;

+                interface_data->metric_v6 = 0;

             }

             err = AddListItem(&(*lists)[block_dns], interface_data);

             if (!err)