private static IPAddress RequestControlSystemEndpointAddress(string appID, NetworkInterface nic)
{
IPAddress address = null;
DhcpRequestFailedException requestException = null;
var thread = new Thread(() =>
{
try
{
using (var client = new DhcpClient()
{
ApplicationID = appID
})
{
// get DHCP option data
byte[] data = client.DhcpRequestParams(nic.Id, ControlSystemDhcpOptionID);
if (data == null || data.Length <= 0)
{
requestException = new DhcpRequestFailedException("Empty DHCP option data returned");
return;
}
if (data.Length != 4)
{
requestException = new DhcpRequestFailedException("DHCP option data size is not valid");
return;
}
address = new IPAddress(data);
}
}
catch (Exception e)
{
// We can catch all exceptions here and not re-throw because the caller knows how to handle a null return value.
requestException = new DhcpRequestFailedException(e.Message);
return;
}
});
thread.Start();
// wait no more than 3 minutes, to compensate for win7 bug 699003 (timezone issue
// causing DHCP service to malfunction, leading to infinite blocking of DHCP API calls)
if (thread.Join(TimeSpan.FromMinutes(3)) == false)
{
// Timed out waiting for DHCP response
throw new DhcpRequestFailedException("Timed out while waiting for DHCP to respond");
}
if (requestException != null)
{
throw requestException;
}
return(address);
}
// This implementation is copied from the Windows GuestAgent implementation
private static IPAddress GetDhcpAddress()
{
foreach (NetworkInterface nic in DhcpClient.GetDhcpInterfaces())
{
if (nic.OperationalStatus != OperationalStatus.Up)
{
continue;
}
try
{
IPAddress address = RequestControlSystemEndpointAddress("WindowsAzureGuestAgent", nic);
return(address);
}
catch (DhcpRequestFailedException e)
{
}
}
return(null);
}
