BUG REPORT : IP Address parsing (.NET 2.0 and log4net 1.2.10) causes UdpAppender to crash

[Olivier DALET <od...@gmail.com>]

Hi,

I've detected a bug in IPAddressConverter.ConvertFrom
(log4net-1.2.10\src\Util\TypeConverters\IPAddressConverter.cs):

If compiled with .NET framework 2.0, the IP is resolved via dns using this code:

IPHostEntry host = Dns.GetHostEntry(str);

then the first address in the  host.AddressList array is returned.
When executed on my computer, this array contains the following items:

+        [0]    {::1}    System.Net.IPAddress
+        [1]    {192.168.0.2 }    System.Net.IPAddress
+        [2]    {192.168.206.1}    System.Net.IPAddress
+        [3]    {192.168.114.1}    System.Net.IPAddress

 So, with the existing code, the address ::1 is selected... and the
UdpAppender throws an Exception :-(

log4net:ERROR [UdpAppender] Unable to send logging event to remote
host ::1 on port 1234.
System.Net.Sockets.SocketException : Une adresse incompatible avec le
protocole demandé a été utilisée (*)
  à System.Net.Sockets.Socket.SendTo(Byte[] buffer, Int32 offset,
Int32 size, SocketFlags socketFlags, EndPoint remoteEP)
  à System.Net.Sockets.UdpClient.Send (Byte[] dgram, Int32 bytes,
IPEndPoint endPoint)
  à log4net.Appender.UdpAppender.Append(LoggingEvent loggingEvent)

To avoid this:

- first I added this property to IPAddressConverter:

public bool IsIPv6Supported { get { return false; } }

note that I'm not networking aware, and thus this may be replaced by
some code able to detect wether or not IP v6 is supported...

- then I replaced "return host.AddressList[0];" with:

foreach (IPAddress address in  host.AddressList)
{
   if ((address.AddressFamily ==
System.Net.Sockets.AddressFamily.InterNetworkV6) && !IsIPv6Supported)
       continue;

   return address;
}

This way, I return the first IPv4 address.

Hope this helps

(*) aproximatively translated from French into English: The used
address is incompatible with the requested protocol

PS: log4net is really fantastic a library. I knew it existed for a
long time but am just using it for a few months. I love it.
--
Olivier DALET
---------------------------------
http://odalet.wordpress.com
http://aspadvice.com/blogs/oliviers_net_blog