1 files changed, 81 insertions, 4 deletions
diff --git a/src/openvpn/block_dns.c b/src/openvpn/block_dns.c
index e31765e..d43cbcf 100644
--- a/src/openvpn/block_dns.c
+++ b/src/openvpn/block_dns.c
@@ -18,10 +18,9 @@
  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  *  GNU General Public License for more details.
  *
- *  You should have received a copy of the GNU General Public License
- *  along with this program (see the file COPYING included with this
- *  distribution); if not, write to the Free Software Foundation, Inc.,
- *  59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ *  You should have received a copy of the GNU General Public License along
+ *  with this program; if not, write to the Free Software Foundation, Inc.,
+ *  51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
 #ifdef HAVE_CONFIG_H
@@ -110,6 +109,9 @@ DEFINE_GUID(
 
 static WCHAR *FIREWALL_NAME = L"OpenVPN";
 
+VOID NETIOAPI_API_
+InitializeIpInterfaceEntry(PMIB_IPINTERFACE_ROW Row);
+
 /*
  * Default msg handler does nothing
  */
@@ -341,4 +343,79 @@ delete_block_dns_filters(HANDLE engine_handle)
     return err;
 }
 
+/*
+ * Returns interface metric value for 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.
+ */
+
+int
+get_interface_metric(const NET_IFINDEX index, const ADDRESS_FAMILY family)
+{
+    DWORD err = 0;
+    MIB_IPINTERFACE_ROW ipiface;
+    InitializeIpInterfaceEntry(&ipiface);
+    ipiface.Family = family;
+    ipiface.InterfaceIndex = index;
+    err = GetIpInterfaceEntry(&ipiface);
+    if (err == NO_ERROR)
+    {
+        if (ipiface.UseAutomaticMetric)
+        {
+            return 0;
+        }
+        return ipiface.Metric;
+    }
+    return -err;
+}
+
+/*
+ * Sets interface metric value for specified interface index.
+ *
+ * Arguments:
+ *   index         : The index of TAP adapter.
+ *   family        : Address family (AF_INET for IPv4 and AF_INET6 for IPv6).
+ *   metric        : Metric value. 0 for automatic metric.
+ * Returns 0 on success, a non-zero status code of the last failed action on failure.
+ */
+
+DWORD
+set_interface_metric(const NET_IFINDEX index, const ADDRESS_FAMILY family,
+                     const ULONG metric)
+{
+    DWORD err = 0;
+    MIB_IPINTERFACE_ROW ipiface;
+    InitializeIpInterfaceEntry(&ipiface);
+    ipiface.Family = family;
+    ipiface.InterfaceIndex = index;
+    err = GetIpInterfaceEntry(&ipiface);
+    if (err == NO_ERROR)
+    {
+        if (family == AF_INET)
+        {
+            /* required for IPv4 as per MSDN */
+            ipiface.SitePrefixLength = 0;
+        }
+        ipiface.Metric = metric;
+        if (metric == 0)
+        {
+            ipiface.UseAutomaticMetric = TRUE;
+        }
+        else
+        {
+            ipiface.UseAutomaticMetric = FALSE;
+        }
+        err = SetIpInterfaceEntry(&ipiface);
+        if (err == NO_ERROR)
+        {
+            return 0;
+        }
+    }
+    return err;
+}
+
 #endif /* ifdef _WIN32 */