Fix for Bug #29682333 UNABLE TO CONNECT USING IPV6(::1) PROTOCOL IN C…

…LASSIC CONNECTION (Enhancement)

This change gives priority to IPv4 when resolving a host name.

MySQL.Data/src/Resources.resx

@@ -553,4 +553,7 @@
   <data name="LocalInfileDisabled" xml:space="preserve">
     <value>Server asked for stream in response to LOAD DATA LOCAL INFILE, but the functionality is disabled by the client setting 'allowlocalinfile' to 'false'.</value>
   </data>
+  <data name="InvalidHostNameOrAddress" xml:space="preserve">
+    <value>The host name or IP address is invalid.</value>
+  </data>
 </root>

MySQL.Data/src/common/StreamCreator.cs

@@ -29,6 +29,7 @@
 using MySql.Data.MySqlClient;
 using System.IO.Pipes;
 using System.Net;
+using System.Linq;
 #if !NETSTANDARD1_3
 using MySql.Data.MySqlClient.Common;
 using System.IO.MemoryMappedFiles;
@@ -77,7 +78,7 @@ public static Stream GetStream(MySqlConnectionStringBuilder settings)
       switch (settings.ConnectionProtocol)
       {
         case MySqlConnectionProtocol.Tcp: return GetTcpStream(settings);
-        case MySqlConnectionProtocol.UnixSocket: return GetUnixSocketStream(settings);        
+        case MySqlConnectionProtocol.UnixSocket: return GetUnixSocketStream(settings);
         case MySqlConnectionProtocol.SharedMemory: return GetSharedMemoryStream(settings);
         case MySqlConnectionProtocol.NamedPipe: return GetNamedPipeStream(settings);
       }
@@ -88,7 +89,11 @@ private static Stream GetTcpStream(MySqlConnectionStringBuilder settings)
     {
       Task<IPAddress[]> dnsTask = Dns.GetHostAddressesAsync(settings.Server);
       dnsTask.Wait();
-      IPAddress addr = dnsTask.Result?[0] ?? null;
+      if (dnsTask.Result == null || dnsTask.Result.Length == 0)
+        throw new ArgumentException(Resources.InvalidHostNameOrAddress);
+      IPAddress addr = dnsTask.Result.SingleOrDefault(c => c.AddressFamily == AddressFamily.InterNetwork);
+      if (addr == null)
+        addr = dnsTask.Result[0];
       TcpClient client = new TcpClient(addr.AddressFamily);
       Task task = client.ConnectAsync(settings.Server, (int)settings.Port);