Add MacOS fix for serving DHCP IP broadcast (#1990)

* Add MacOS fix for serving DHCP IP broadcast

* Remove setting socket options

* Remove comment

---------

Co-authored-by: Nicholas Shi <nicholas@Nicholass-MacBook-Pro.local>

Author: nicholas-shi

DnsServerCore/Dhcp/DhcpServer.cs

@@ -261,7 +261,14 @@ private async Task ProcessDhcpRequestAsync(DhcpMessage request, IPEndPoint remot
                         else
                             udpSocket = udpListener; //no appropriate socket found so use default socket
 
-                        await udpSocket.SendToAsync(new ArraySegment<byte>(sendBuffer, 0, (int)sendBufferStream.Position), SocketFlags.DontRoute, new IPEndPoint(IPAddress.Broadcast, 68)); //no routing for broadcast
+						if (OperatingSystem.IsMacOS())
+						{
+                            await udpSocket.SendToAsync(new ArraySegment<byte>(sendBuffer, 0, (int)sendBufferStream.Position), SocketFlags.None, new IPEndPoint(IPAddress.Broadcast, 68));
+						}
+						else
+						{
+							await udpSocket.SendToAsync(new ArraySegment<byte>(sendBuffer, 0, (int)sendBufferStream.Position), SocketFlags.DontRoute, new IPEndPoint(IPAddress.Broadcast, 68)); //no routing for broadcast
+						}
                     }
                 }
             }