8280944: Enable Unix domain sockets in Windows Selector notification mechanism

Backport-of: 87ab0994ded3b535a160bb87b6540bd072042c44

Author: RealCLanger

src/java.base/windows/classes/sun/nio/ch/PipeImpl.java

@@ -33,6 +33,7 @@
 import java.net.InetSocketAddress;
 import java.net.SocketAddress;
 import java.net.StandardSocketOptions;
+import java.net.UnixDomainSocketAddress;
 import java.nio.*;
 import java.nio.channels.*;
 import java.nio.file.Files;
@@ -44,6 +45,7 @@
 import java.security.SecureRandom;
 import java.util.Random;
 
+import static java.net.StandardProtocolFamily.UNIX;
 
 /**
  * A simple Pipe implementation based on a socket connection.
@@ -67,12 +69,14 @@ private static class Initializer
     {
 
         private final SelectorProvider sp;
+        private final boolean preferUnixDomain;
         private IOException ioe;
         SourceChannelImpl source;
         SinkChannelImpl sink;
 
-        private Initializer(SelectorProvider sp) {
+        private Initializer(SelectorProvider sp, boolean preferUnixDomain) {
             this.sp = sp;
+            this.preferUnixDomain = preferUnixDomain;
         }
 
         @Override
@@ -120,7 +124,7 @@ public void run() {
                         // Bind ServerSocketChannel to a port on the loopback
                         // address
                         if (ssc == null || !ssc.isOpen()) {
-                            ssc = createListener();
+                            ssc = createListener(preferUnixDomain);
                             sa = ssc.getLocalAddress();
                         }
 
@@ -162,28 +166,34 @@ public void run() {
                     try {
                         if (ssc != null)
                             ssc.close();
+                        if (sa instanceof UnixDomainSocketAddress uaddr) {
+                            Files.deleteIfExists(uaddr.getPath());
+                        }
                     } catch (IOException e2) {}
                 }
             }
         }
     }
 
     /**
-     * Creates a Pipe implementation that supports buffering.
+     * Creates a (TCP) Pipe implementation that supports buffering.
      */
     PipeImpl(SelectorProvider sp) throws IOException {
-        this(sp, true);
+        this(sp, true, false);
     }
 
     /**
-     * Creates Pipe implementation that supports optionally buffering.
+     * Creates Pipe implementation that supports optionally buffering
+     * and is TCP by default, but if Unix domain is supported and
+     * preferAfUnix is true, then Unix domain sockets are used.
+     *
+     * @param preferAfUnix use Unix domain sockets if supported
      *
-     * @implNote Uses a loopback connection. When buffering is
-     * disabled then it sets TCP_NODELAY on the sink channel.
+     * @param buffering if false set TCP_NODELAY on TCP sockets
      */
     @SuppressWarnings("removal")
-    PipeImpl(SelectorProvider sp, boolean buffering) throws IOException {
-        Initializer initializer = new Initializer(sp);
+    PipeImpl(SelectorProvider sp, boolean preferAfUnix, boolean buffering) throws IOException {
+        Initializer initializer = new Initializer(sp, preferAfUnix);
         try {
             AccessController.doPrivileged(initializer);
             SinkChannelImpl sink = initializer.sink;
@@ -205,8 +215,19 @@ public SinkChannelImpl sink() {
         return sink;
     }
 
-    private static ServerSocketChannel createListener() throws IOException {
-        ServerSocketChannel listener = ServerSocketChannel.open();
+    private static ServerSocketChannel createListener(boolean preferUnixDomain) throws IOException {
+        ServerSocketChannel listener = null;
+        if (preferUnixDomain && UnixDomainSockets.isSupported()) {
+            try {
+                listener = ServerSocketChannel.open(UNIX);
+                listener.bind(null);
+                return listener;
+            } catch (IOException | UnsupportedOperationException e) {
+                if (listener != null)
+                    listener.close();
+            }
+        }
+        listener = ServerSocketChannel.open();
         InetAddress lb = InetAddress.getLoopbackAddress();
         listener.bind(new InetSocketAddress(lb, 0));
         return listener;

src/java.base/windows/classes/sun/nio/ch/WEPollSelectorImpl.java

@@ -75,7 +75,7 @@ class WEPollSelectorImpl extends SelectorImpl {
 
         // wakeup support
         try {
-            this.pipe = new PipeImpl(sp, /*buffering*/ false);
+            this.pipe = new PipeImpl(sp, /* AF_UNIX */ true, /*buffering*/ false);
         } catch (IOException ioe) {
             WEPoll.freePollArray(pollArrayAddress);
             WEPoll.close(eph);

src/java.base/windows/classes/sun/nio/ch/WindowsSelectorImpl.java

@@ -139,7 +139,7 @@ private static final class MapEntry {
     WindowsSelectorImpl(SelectorProvider sp) throws IOException {
         super(sp);
         pollWrapper = new PollArrayWrapper(INIT_CAP);
-        wakeupPipe = new PipeImpl(sp, false);
+        wakeupPipe = new PipeImpl(sp, /* AF_UNIX */ true, /*buffering*/ false);
         wakeupSourceFd = ((SelChImpl)wakeupPipe.source()).getFDVal();
         wakeupSinkFd = ((SelChImpl)wakeupPipe.sink()).getFDVal();
         pollWrapper.addWakeupSocket(wakeupSourceFd, 0);