common: Allow disabling shutdown upon close; add AFSomeSocketThing

We may not always want to call shutdown on a socket. Add an option to
disable this.

While doing this, add "AFSomeSocketThing", which defines common methods
for all sorts of junixsocket-based socket types, including channels and
servers.

junixsocket-common/src/main/java/org/newsclub/net/unix/AFDatagramChannel.java

@@ -266,4 +266,9 @@ public final boolean isDeleteOnClose() {
   public final void setDeleteOnClose(boolean b) {
     afSocket.setDeleteOnClose(b);
   }
+
+  @Override
+  public void setShutdownOnClose(boolean enabled) {
+    getAFCore().setShutdownOnClose(enabled);
+  }
 }

junixsocket-common/src/main/java/org/newsclub/net/unix/AFDatagramSocket.java

@@ -525,4 +525,9 @@ AFDatagramSocket<A> accept1(boolean throwOnFail) throws IOException {
 
     return as;
   }
+
+  @Override
+  public void setShutdownOnClose(boolean enabled) {
+    getAFImpl().getCore().setShutdownOnClose(enabled);
+  }
 }

junixsocket-common/src/main/java/org/newsclub/net/unix/AFDatagramSocketImpl.java

@@ -441,10 +441,12 @@ final boolean accept0(AFDatagramSocketImpl<A> socket) throws IOException {
         caught = e;
       } finally { // NOPMD.DoNotThrowExceptionInFinally
         if (!isBound() || isClosed()) {
-          try {
-            NativeUnixSocket.shutdown(si.fd, SHUT_RD_WR);
-          } catch (Exception e) {
-            // ignore
+          if (getCore().isShutdownOnClose()) {
+            try {
+              NativeUnixSocket.shutdown(si.fd, SHUT_RD_WR);
+            } catch (Exception e) {
+              // ignore
+            }
           }
           try {
             NativeUnixSocket.close(si.fd);

junixsocket-common/src/main/java/org/newsclub/net/unix/AFGenericSocketOptions.java

@@ -25,7 +25,7 @@
  * @author Christian Kohlschütter
  */
 @NonNullByDefault
- final class AFGenericSocketOptions {
+final class AFGenericSocketOptions {
   private AFGenericSocketOptions() {
     throw new IllegalStateException();
   }

junixsocket-common/src/main/java/org/newsclub/net/unix/AFServerSocket.java

@@ -45,7 +45,7 @@
  */
 @SuppressWarnings({"PMD.CyclomaticComplexity", "PMD.CouplingBetweenObjects"})
 public abstract class AFServerSocket<A extends AFSocketAddress> extends ServerSocket implements
-    FileDescriptorAccess {
+    AFSomeSocketThing {
   private final AFSocketImpl<A> implementation;
   private @Nullable A boundEndpoint;
   private final Closeables closeables = new Closeables();
@@ -657,6 +657,11 @@ public Set<SocketOption<?>> supportedOptions() {
     return getAFImpl().supportedOptions();
   }
 
+  @Override
+  public void setShutdownOnClose(boolean enabled) {
+    getAFImpl().getCore().setShutdownOnClose(enabled);
+  }
+
   // NOTE: We shall re-implement all methods defined in ServerSocket that internally call getImpl()
   // and call getAFImpl() here. This is not strictly necessary for environments where we can
   // override "impl"; however it's the right thing to do.

junixsocket-common/src/main/java/org/newsclub/net/unix/AFServerSocketChannel.java

@@ -111,7 +111,12 @@ public AFSocketChannel<A> accept() throws IOException {
   }
 
   @Override
-  public final @Nullable A getLocalAddress() throws IOException {
+  public final @Nullable A getLocalAddress() {
+    return getLocalSocketAddress();
+  }
+
+  @Override
+  public final @Nullable A getLocalSocketAddress() {
     return afSocket.getLocalSocketAddress();
   }
 
@@ -170,4 +175,10 @@ public final boolean isDeleteOnClose() {
   public final void setDeleteOnClose(boolean b) {
     socket().setDeleteOnClose(b);
   }
+
+  @Override
+  public void setShutdownOnClose(boolean enabled) {
+    socket().setShutdownOnClose(enabled);
+  }
+
 }

junixsocket-common/src/main/java/org/newsclub/net/unix/AFSocket.java

@@ -620,4 +620,9 @@ public boolean checkConnectionClosed() throws IOException {
   public static boolean isRunningOnAndroid() {
     return NativeLibraryLoader.isAndroid();
   }
+
+  @Override
+  public void setShutdownOnClose(boolean enabled) {
+    getAFImpl().getCore().setShutdownOnClose(enabled);
+  }
 }

junixsocket-common/src/main/java/org/newsclub/net/unix/AFSocketChannel.java

@@ -304,4 +304,9 @@ public final FileDescriptor getFileDescriptor() throws IOException {
   public final String toString() {
     return super.toString() + afSocket.toStringSuffix();
   }
+
+  @Override
+  public void setShutdownOnClose(boolean enabled) {
+    getAFCore().setShutdownOnClose(enabled);
+  }
 }

junixsocket-common/src/main/java/org/newsclub/net/unix/AFSocketCore.java

@@ -42,6 +42,7 @@ class AFSocketCore extends AFCore {
   AFSocketAddress socketAddress;
 
   private final AFAddressFamily<?> af;
+  private boolean shutdownOnClose = true;
 
   protected AFSocketCore(Object observed, FileDescriptor fd,
       AncillaryDataSupport ancillaryDataSupport, AFAddressFamily<?> af, boolean datagramMode) {
@@ -56,8 +57,10 @@ protected AFAddressFamily<?> addressFamily() {
   @Override
   @SuppressWarnings("UnsafeFinalization" /* errorprone */)
   protected void doClose() throws IOException {
-    NativeUnixSocket.shutdown(fd, SHUT_RD_WR);
-    unblockAccepts();
+    if (isShutdownOnClose()) {
+      NativeUnixSocket.shutdown(fd, SHUT_RD_WR);
+      unblockAccepts();
+    }
 
     super.doClose();
   }
@@ -151,4 +154,12 @@ protected void decPendingAccepts() throws SocketException {
   protected boolean hasPendingAccepts() {
     return pendingAccepts.get() > 0;
   }
+
+  boolean isShutdownOnClose() {
+    return shutdownOnClose;
+  }
+
+  void setShutdownOnClose(boolean enabled) {
+    this.shutdownOnClose = enabled;
+  }
 }

junixsocket-common/src/main/java/org/newsclub/net/unix/AFSocketImpl.java

@@ -115,10 +115,12 @@ protected void unblockAccepts() {
             // (e.g., SocketException: No such file or directory)
             return;
           }
-          try {
-            NativeUnixSocket.shutdown(tmpFd, SHUT_RD_WR);
-          } catch (Exception e) {
-            // ignore
+          if (isShutdownOnClose()) {
+            try {
+              NativeUnixSocket.shutdown(tmpFd, SHUT_RD_WR);
+            } catch (Exception e) {
+              // ignore
+            }
           }
           try {
             NativeUnixSocket.close(tmpFd);
@@ -256,10 +258,12 @@ final boolean accept0(SocketImpl socket) throws IOException {
         caught = e;
       } finally { // NOPMD.DoNotThrowExceptionInFinally
         if (!isBound() || isClosed()) {
-          try {
-            NativeUnixSocket.shutdown(si.fd, SHUT_RD_WR);
-          } catch (Exception e) {
-            // ignore
+          if (getCore().isShutdownOnClose()) {
+            try {
+              NativeUnixSocket.shutdown(si.fd, SHUT_RD_WR);
+            } catch (Exception e) {
+              // ignore
+            }
           }
           try {
             NativeUnixSocket.close(si.fd);
@@ -517,7 +521,7 @@ public int read() throws IOException {
     public synchronized void close() throws IOException {
       streamClosed = true;
       FileDescriptor fdesc = core.validFd();
-      if (fdesc != null) {
+      if (fdesc != null && getCore().isShutdownOnClose()) {
         NativeUnixSocket.shutdown(fdesc, SHUT_RD);
       }
 
@@ -617,7 +621,7 @@ public synchronized void close() throws IOException {
       }
       streamClosed = true;
       FileDescriptor fdesc = core.validFd();
-      if (fdesc != null) {
+      if (fdesc != null && getCore().isShutdownOnClose()) {
         NativeUnixSocket.shutdown(fdesc, SHUT_WR);
       }
       closedOutputStream = true;

junixsocket-common/src/main/java/org/newsclub/net/unix/AFSomeSocket.java

@@ -17,7 +17,6 @@
  */
 package org.newsclub.net.unix;
 
-import java.io.Closeable;
 import java.net.DatagramSocket;
 import java.net.Socket;
 import java.net.SocketAddress;
@@ -37,16 +36,7 @@
  * @see AFDatagramSocket
  * @see AFDatagramChannel
  */
-public interface AFSomeSocket extends Closeable, FileDescriptorAccess {
-  /**
-   * Returns the socket's local socket address, or {@code null} if unavailable or if there was a
-   * problem retrieving it.
-   *
-   * @return The local socket address, or {@code null}.
-   */
-  @Nullable
-  SocketAddress getLocalSocketAddress();
-
+public interface AFSomeSocket extends AFSomeSocketThing {
   /**
    * Returns the socket's remote socket address, or {@code null} if unavailable/not connected, or if
    * there was a problem retrieving it.

junixsocket-common/src/main/java/org/newsclub/net/unix/AFSomeSocketChannel.java

@@ -33,11 +33,11 @@
  * @see AFServerSocketChannel
  * @see AFDatagramChannel
  */
-public interface AFSomeSocketChannel extends Closeable, FileDescriptorAccess {
+public interface AFSomeSocketChannel extends Closeable, FileDescriptorAccess, AFSomeSocketThing {
   /**
    * Checks if the channel is configured blocking. The result may be cached, and therefore not
    * invoke native code to check if the underlying socket is actually configured that way.
-   * 
+   *
    * @return {@code true} if blocking.
    */
   boolean isBlocking();
@@ -49,7 +49,7 @@ public interface AFSomeSocketChannel extends Closeable, FileDescriptorAccess {
    * If the given blocking mode is different from the currently cached blocking mode then this
    * method native code to change it.
    * </p>
-   * 
+   *
    * @param block {@code true} if blocking is desired.
    * @return This channel.
    * @throws IOException on error.

junixsocket-common/src/main/java/org/newsclub/net/unix/AFSomeSocketThing.java

@@ -0,0 +1,61 @@
+/*
+ * junixsocket
+ *
+ * Copyright 2009-2023 Christian Kohlschütter
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.newsclub.net.unix;
+
+import java.io.Closeable;
+import java.net.DatagramSocket;
+import java.net.ServerSocket;
+import java.net.Socket;
+import java.net.SocketAddress;
+import java.nio.channels.DatagramChannel;
+import java.nio.channels.ServerSocketChannel;
+import java.nio.channels.SocketChannel;
+
+import org.eclipse.jdt.annotation.Nullable;
+
+/**
+ * Marker interface that combines junixsocket-based {@link SocketChannel}s, {@link Socket}s,
+ * {@link DatagramChannel}s and {@link DatagramSocket}s, as well as {@link ServerSocket}s and
+ * {@link ServerSocketChannel}s.
+ *
+ * @author Christian Kohlschütter
+ * @see AFSocketPair
+ * @see AFSocket
+ * @see AFSocketChannel
+ * @see AFDatagramSocket
+ * @see AFDatagramChannel
+ * @see AFServerSocket
+ * @see AFServerSocketChannel
+ */
+public interface AFSomeSocketThing extends Closeable, FileDescriptorAccess {
+  /**
+   * Returns the socket's local socket address, or {@code null} if unavailable or if there was a
+   * problem retrieving it.
+   *
+   * @return The local socket address, or {@code null}.
+   */
+  @Nullable
+  SocketAddress getLocalSocketAddress();
+
+  /**
+   * Configures whether the socket should be shutdown upon {@link #close()}, which is the default.
+   *
+   * @param enabled {@code true} if enabled.
+   */
+  void setShutdownOnClose(boolean enabled);
+}