Bug 41616

Mono 4.4.0 crashes when using Socket.ConnectAsync to a unix domain socket if the path doesn't exist. I created following console app as test code:

using System;
using System.Net.Sockets;
using System.Threading.Tasks;

namespace MonoSocketConnectBug
{
    class Program
    {
        static void Main(string[] args)
        {
            string socketPath = (args.Length == 0) ? "/tmp/foo" : args[0];

            Task t = Task.Run(async () =>
            {
                var endPoint = new Mono.Unix.UnixEndPoint(socketPath);
                var socket = new Socket(endPoint.AddressFamily, SocketType.Stream, ProtocolType.Unspecified);
                var tcs = new TaskCompletionSource<SocketError>();
                var socketArgs = new SocketAsyncEventArgs();

                socketArgs.RemoteEndPoint = endPoint;
                socketArgs.UserToken = tcs;
                socketArgs.Completed += (sender, e) => ((TaskCompletionSource<SocketError>)e.UserToken).SetResult(e.SocketError);
                SocketError error = socket.ConnectAsync(socketArgs) ? await tcs.Task.ConfigureAwait(false) : socketArgs.SocketError;

                Console.WriteLine("SocketError={0}, Socket.Connected={1}", error, socket.Connected);
            });

            t.GetAwaiter().GetResult();
        }
    }
}

On Mono 4.4.0 the above console app crashes with following call stack:
Unhandled Exception:
System.InvalidOperationException: No operation in progress
  at System.Net.Sockets.Socket.<ConnectAsyncCallback>m__3 (IAsyncResult ares) <0x7e3ea0 + 0x0019f> in <filename unknown>:0 
  at System.Net.Sockets.SocketAsyncResult+<Complete>c__AnonStorey0.<>m__0 (System.Object _) <0x7e3de0 + 0x0001b> in <filename unknown>:0 
  at System.Threading.QueueUserWorkItemCallback.System.Threading.IThreadPoolWorkItem.ExecuteWorkItem () <0x1970810 + 0x00035> in <filename unknown>:0 
  at System.Threading.ThreadPoolWorkQueue.Dispatch () <0x196ee40 + 0x001d8> in <filename unknown>:0 
  at System.Threading._ThreadPoolWaitCallback.PerformWaitCallback () <0x1970680 + 0x00017> in <filename unknown>:0 

This is a regression from Mono 4.2.3 where this same console app runs successfully without any crashes. Here's the output from 4.2.3 runtime:
SocketError=Success, Socket.Connected=False