New Feature: Act as global resolver

- Fixes #240

Author: bitbeans

SimpleDnsCrypt/Config/Global.cs

@@ -75,6 +75,9 @@ public static class Global
 	    public const string BlacklistRuleFileName = "domain-blacklist.txt";
 	    public const string BlacklistFileName = "blacklist.txt";
 
+	    public const string GlobalResolver = "0.0.0.0:53";
+	    public const string DefaultResolverIpv4 = "127.0.0.1:53";
+	    public const string DefaultResolverIpv6 = "[::1]:53";
 
 		/// <summary>
 		///     List of files must exist.

SimpleDnsCrypt/Helper/LocalNetworkInterfaceManager.cs

@@ -4,6 +4,7 @@
 using System.Diagnostics;
 using System.Linq;
 using System.Net.NetworkInformation;
+using Caliburn.Micro;
 using SimpleDnsCrypt.Config;
 using SimpleDnsCrypt.Models;
 
@@ -14,6 +15,8 @@ namespace SimpleDnsCrypt.Helper
 	/// </summary>
 	public static class LocalNetworkInterfaceManager
 	{
+		private static readonly ILog Log = LogManagerHelper.Factory();
+
 		/// <summary>
 		///     Get a list of the local network interfaces.
 		/// </summary>
@@ -120,8 +123,9 @@ internal static List<DnsServer> GetDnsServerList(string localNetworkInterface)
 					}));
 				}
 			}
-			catch (Exception)
+			catch (Exception exception)
 			{
+				Log.Error(exception);
 			}
 			return serverAddresses;
 		}
@@ -213,8 +217,9 @@ public static bool SetNameservers(LocalNetworkInterface localNetworkInterface, L
 				}
 				return true;
 			}
-			catch (Exception)
+			catch (Exception exception)
 			{
+				Log.Error(exception);
 				return false;
 			}
 		}

SimpleDnsCrypt/ViewModels/LoaderViewModel.cs

@@ -150,8 +150,22 @@ private async void InitializeApplication()
 				}
 
 				ProgressText = LocalizationEx.GetUiString("loader_loading_network_cards", Thread.CurrentThread.CurrentCulture);
-				var localNetworkInterfaces = LocalNetworkInterfaceManager.GetLocalNetworkInterfaces(
-					DnscryptProxyConfigurationManager.DnscryptProxyConfiguration.listen_addresses.ToList());
+
+				List<LocalNetworkInterface> localNetworkInterfaces;
+				if (DnscryptProxyConfigurationManager.DnscryptProxyConfiguration.listen_addresses.Contains(Global.GlobalResolver))
+				{
+					var dnsServer = new List<string>
+					{
+						Global.DefaultResolverIpv4,
+						Global.DefaultResolverIpv6
+					};
+					localNetworkInterfaces = LocalNetworkInterfaceManager.GetLocalNetworkInterfaces(dnsServer);
+				}
+				else
+				{
+					localNetworkInterfaces = LocalNetworkInterfaceManager.GetLocalNetworkInterfaces(
+						DnscryptProxyConfigurationManager.DnscryptProxyConfiguration.listen_addresses.ToList());
+				}
 				_mainViewModel.LocalNetworkInterfaces = new BindableCollection<LocalNetworkInterface>();
 				_mainViewModel.LocalNetworkInterfaces.AddRange(localNetworkInterfaces);
 				_mainViewModel.Initialize();