Enable custom socket end points and allow Unix Domain Sockets

With code separation into System.Net.Primitives and System.Net.Sockets,
EndPoint extensibility was broken because System.Net.Sockets started to
use its own copy of SocketAddress and didn't respect SocketAddress that
a custom EndPoint may provide.

The fix is to allow conversion between SocketAddress from System.Net.Primitives
and System.Net.Sockets. This way custom implementations of EndPoint will
be able to provide their own SocketAddress and it'll be honored by the
Socket APIs.

The fix also allows sockets to use 'Unspecified' protocol type which is
needed for Unix Domain Sockets. There are several changes in socket test
server to allow tests pass protocol type.

Add new unit tests that use end point extensibility to implement Unix
Domain Sockets.

Fix #4777

Author: IlyaBiryukov

src/Common/src/System/Net/Internals/IPEndPointExtensions.cs

@@ -9,28 +9,65 @@ internal static class IPEndPointExtensions
     {
         public static Internals.SocketAddress Serialize(EndPoint endpoint)
         {
-            Debug.Assert(endpoint is IPEndPoint);
+            Debug.Assert(!(endpoint is DnsEndPoint));
 
-            return new Internals.SocketAddress(((IPEndPoint)endpoint).Address, ((IPEndPoint)endpoint).Port);
+            var ipEndPoint = endpoint as IPEndPoint;
+            if (ipEndPoint != null)
+            {
+                return new Internals.SocketAddress(ipEndPoint.Address, ipEndPoint.Port);
+            }
+
+            System.Net.SocketAddress address = endpoint.Serialize();
+            return GetInternalSocketAddress(address);
         }
 
         public static EndPoint Create(this EndPoint thisObj, Internals.SocketAddress socketAddress)
         {
-            if (socketAddress.Family != thisObj.AddressFamily)
+            AddressFamily family = socketAddress.Family;
+            if (family != thisObj.AddressFamily)
             {
-                throw new ArgumentException(SR.Format(SR.net_InvalidAddressFamily, socketAddress.Family.ToString(), thisObj.GetType().FullName, thisObj.AddressFamily.ToString()), "socketAddress");
+                throw new ArgumentException(SR.Format(SR.net_InvalidAddressFamily, family.ToString(), thisObj.GetType().FullName, thisObj.AddressFamily.ToString()), "socketAddress");
             }
-            if (socketAddress.Size < 8)
+
+            if (family == AddressFamily.InterNetwork || family == AddressFamily.InterNetworkV6)
             {
-                throw new ArgumentException(SR.Format(SR.net_InvalidSocketAddressSize, socketAddress.GetType().FullName, thisObj.GetType().FullName), "socketAddress");
+                if (socketAddress.Size < 8)
+                {
+                    throw new ArgumentException(SR.Format(SR.net_InvalidSocketAddressSize, socketAddress.GetType().FullName, thisObj.GetType().FullName), "socketAddress");
+                }
+
+                return socketAddress.GetIPEndPoint();
             }
 
-            return socketAddress.GetIPEndPoint();
+            System.Net.SocketAddress address = GetNetSocketAddress(socketAddress);
+            return thisObj.Create(address);
         }
 
         internal static IPEndPoint Snapshot(this IPEndPoint thisObj)
         {
             return new IPEndPoint(thisObj.Address.Snapshot(), thisObj.Port);
         }
+
+        private static Internals.SocketAddress GetInternalSocketAddress(System.Net.SocketAddress address)
+        {
+            var result = new Internals.SocketAddress(address.Family, address.Size);
+            for (int index = 0; index < address.Size; index++)
+            {
+                result[index] = address[index];
+            }
+
+            return result;
+        }
+
+        private static System.Net.SocketAddress GetNetSocketAddress(Internals.SocketAddress address)
+        {
+            var result = new System.Net.SocketAddress(address.Family, address.Size);
+            for (int index = 0; index < address.Size; index++)
+            {
+                result[index] = address[index];
+            }
+
+            return result;
+        }
     }
 }

src/Common/tests/System/Net/Sockets/SocketTestServer.cs

@@ -12,9 +12,9 @@ public abstract partial class SocketTestServer : IDisposable
 
         protected abstract int Port { get; }
 
-        public static SocketTestServer SocketTestServerFactory(EndPoint endpoint)
+        public static SocketTestServer SocketTestServerFactory(EndPoint endpoint, ProtocolType protocolType = ProtocolType.Tcp)
         {
-            return SocketTestServerFactory(DefaultNumConnections, DefaultReceiveBufferSize, endpoint);
+            return SocketTestServerFactory(DefaultNumConnections, DefaultReceiveBufferSize, endpoint, protocolType);
         }
 
         public static SocketTestServer SocketTestServerFactory(IPAddress address, out int port)
@@ -25,13 +25,15 @@ public static SocketTestServer SocketTestServerFactory(IPAddress address, out in
         public static SocketTestServer SocketTestServerFactory(
             int numConnections,
             int receiveBufferSize,
-            EndPoint localEndPoint)
+            EndPoint localEndPoint,
+            ProtocolType protocolType = ProtocolType.Tcp)
         {
             return SocketTestServerFactory(
                 s_implementationType,
                 numConnections,
                 receiveBufferSize,
-                localEndPoint);
+                localEndPoint,
+                protocolType);
         }
 
         public static SocketTestServer SocketTestServerFactory(
@@ -52,14 +54,15 @@ public static SocketTestServer SocketTestServerFactory(
             SocketImplementationType type,
             int numConnections,
             int receiveBufferSize,
-            EndPoint localEndPoint)
+            EndPoint localEndPoint,
+            ProtocolType protocolType = ProtocolType.Tcp)
         {
             switch (type)
             {
                 case SocketImplementationType.APM:
                     return new SocketTestServerAPM(numConnections, receiveBufferSize, localEndPoint);
                 case SocketImplementationType.Async:
-                    return new SocketTestServerAsync(numConnections, receiveBufferSize, localEndPoint);
+                    return new SocketTestServerAsync(numConnections, receiveBufferSize, localEndPoint, protocolType);
                 default:
                     throw new ArgumentOutOfRangeException("type");
             }

src/Common/tests/System/Net/Sockets/SocketTestServerAsync.cs

@@ -31,12 +31,13 @@ public class SocketTestServerAsync : SocketTestServer
         private int _numConnectedSockets;     // The total number of clients connected to the server.
         private Semaphore _maxNumberAcceptedClientsSemaphore;
         private int _acceptRetryCount = 10;
+        private ProtocolType _protocolType;
 
         private object _listenSocketLock = new object();
 
         protected sealed override int Port { get { return ((IPEndPoint)_listenSocket.LocalEndPoint).Port; } }
 
-        public SocketTestServerAsync(int numConnections, int receiveBufferSize, EndPoint localEndPoint)
+        public SocketTestServerAsync(int numConnections, int receiveBufferSize, EndPoint localEndPoint, ProtocolType protocolType = ProtocolType.Tcp)
         {
             _log = VerboseTestLogging.GetInstance();
             _totalBytesRead = 0;
@@ -51,6 +52,7 @@ public SocketTestServerAsync(int numConnections, int receiveBufferSize, EndPoint
 
             _readWritePool = new SocketAsyncEventArgsPool(numConnections);
             _maxNumberAcceptedClientsSemaphore = new Semaphore(numConnections, numConnections);
+            _protocolType = protocolType;
             Init();
             Start(localEndPoint);
         }
@@ -108,7 +110,7 @@ private void Init()
         private void Start(EndPoint localEndPoint)
         {
             // Create the socket which listens for incoming connections.
-            _listenSocket = new Socket(localEndPoint.AddressFamily, SocketType.Stream, ProtocolType.Tcp);
+            _listenSocket = new Socket(localEndPoint.AddressFamily, SocketType.Stream, _protocolType);
             _listenSocket.Bind(localEndPoint);
 
             // Start the server with a listen backlog of 100 connections.

src/Native/System.Native/pal_networking.cpp

@@ -1863,6 +1863,10 @@ static bool TryConvertProtocolTypePalToPlatform(int32_t palProtocolType, int* pl
 
     switch (palProtocolType)
     {
+        case PAL_PT_UNSPECIFIED:
+            *platformProtocolType = 0;
+            return true;
+
         case PAL_PT_ICMP:
             *platformProtocolType = IPPROTO_ICMP;
             return true;

src/Native/System.Native/pal_networking.h

@@ -81,6 +81,7 @@ enum SocketType : int32_t
  */
 enum ProtocolType : int32_t
 {
+    PAL_PT_UNSPECIFIED = 0, // System.Net.ProtocolType.Unspecified
     PAL_PT_ICMP = 1,        // System.Net.ProtocolType.Icmp
     PAL_PT_TCP = 6,         // System.Net.ProtocolType.Tcp
     PAL_PT_UDP = 17,        // System.Net.ProtocolType.Udp

src/System.Net.Sockets/src/System/Net/Sockets/Socket.cs

@@ -4231,7 +4231,7 @@ public bool ConnectAsync(SocketAsyncEventArgs e)
                     {
                         InternalBind(new IPEndPoint(IPAddress.Any, 0));
                     }
-                    else
+                    else if (endPointSnapshot.AddressFamily != AddressFamily.Unix)
                     {
                         InternalBind(new IPEndPoint(IPAddress.IPv6Any, 0));
                     }

src/System.Net.Sockets/tests/FunctionalTests/System.Net.Sockets.Tests.csproj

@@ -27,7 +27,8 @@
     <Compile Include="SocketAsyncExtensions.cs" />
     <Compile Include="SocketOptionNameTest.cs" />
     <Compile Include="SocketTestServerAPMMock.cs" />
-    
+    <Compile Include="UnixDomainSocketTest.cs" />
+
     <!-- Common Sockets files -->
     <Compile Include="$(CommonTestPath)\System\Net\Sockets\Configuration.cs">
       <Link>SocketCommon\Configuration.cs</Link>
@@ -77,7 +78,7 @@
       <Name>System.Net.Sockets</Name>
     </ProjectReference>
   </ItemGroup>
-  
+
   <ItemGroup>
     <None Include="project.json" />
   </ItemGroup>