/*

 * Copyright (c) 2000, 2019, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

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 */

package sun.nio.ch;

import java.io.FileDescriptor;

import java.io.IOException;

import java.net.InetSocketAddress;

import java.net.ServerSocket;

import java.net.SocketAddress;

import java.net.SocketOption;

import java.net.SocketTimeoutException;

import java.net.StandardSocketOptions;

import java.nio.channels.AlreadyBoundException;

import java.nio.channels.AsynchronousCloseException;

import java.nio.channels.ClosedChannelException;

import java.nio.channels.IllegalBlockingModeException;

import java.nio.channels.NotYetBoundException;

import java.nio.channels.SelectionKey;

import java.nio.channels.ServerSocketChannel;

import java.nio.channels.SocketChannel;

import java.nio.channels.spi.SelectorProvider;

import java.util.Collections;

import java.util.HashSet;

import java.util.Objects;

import java.util.Set;

import java.util.concurrent.locks.ReentrantLock;

import sun.net.NetHooks;

import sun.net.ext.ExtendedSocketOptions;

/**

 * An implementation of ServerSocketChannels

 */

class ServerSocketChannelImpl

    extends ServerSocketChannel

    implements SelChImpl

{

    // Used to make native close and configure calls

    private static final NativeDispatcher nd = new SocketDispatcher();

    // Our file descriptor

    private final FileDescriptor fd;

    private final int fdVal;

    // Lock held by thread currently blocked on this channel

    private final ReentrantLock acceptLock = new ReentrantLock();

    // Lock held by any thread that modifies the state fields declared below

    // DO NOT invoke a blocking I/O operation while holding this lock!

    private final Object stateLock = new Object();

    // -- The following fields are protected by stateLock

    // Channel state, increases monotonically

    private static final int ST_INUSE = 0;

    private static final int ST_CLOSING = 1;

    private static final int ST_CLOSED = 2;

    private int state;

    // ID of native thread currently blocked in this channel, for signalling

    private long thread;

    // Binding

    private InetSocketAddress localAddress; // null => unbound

    // set true when exclusive binding is on and SO_REUSEADDR is emulated

    private boolean isReuseAddress;

    // Our socket adaptor, if any

    private ServerSocket socket;

    // -- End of fields protected by stateLock

    ServerSocketChannelImpl(SelectorProvider sp) {

        super(sp);

        this.fd = Net.serverSocket(true);

        this.fdVal = IOUtil.fdVal(fd);

    }

    ServerSocketChannelImpl(SelectorProvider sp, FileDescriptor fd, boolean bound)

        throws IOException

    {

        super(sp);

        this.fd =  fd;

        this.fdVal = IOUtil.fdVal(fd);

        if (bound) {

            synchronized (stateLock) {

                localAddress = Net.localAddress(fd);

            }

        }

    }

    // @throws ClosedChannelException if channel is closed

    private void ensureOpen() throws ClosedChannelException {

        if (!isOpen())

            throw new ClosedChannelException();

    }

    @Override

    public ServerSocket socket() {

        synchronized (stateLock) {

            if (socket == null)

                socket = ServerSocketAdaptor.create(this);

            return socket;

        }

    }

    @Override

    public SocketAddress getLocalAddress() throws IOException {

        synchronized (stateLock) {

            ensureOpen();

            return (localAddress == null)

                    ? null

                    : Net.getRevealedLocalAddress(localAddress);

        }

    }

    @Override

    public <T> ServerSocketChannel setOption(SocketOption<T> name, T value)

        throws IOException

    {

        Objects.requireNonNull(name);

        if (!supportedOptions().contains(name))

            throw new UnsupportedOperationException("'" + name + "' not supported");

        if (!name.type().isInstance(value))

            throw new IllegalArgumentException("Invalid value '" + value + "'");

        synchronized (stateLock) {

            ensureOpen();

            if (name == StandardSocketOptions.SO_REUSEADDR && Net.useExclusiveBind()) {

                // SO_REUSEADDR emulated when using exclusive bind

                isReuseAddress = (Boolean)value;

            } else {

                // no options that require special handling

                Net.setSocketOption(fd, Net.UNSPEC, name, value);

            }

            return this;

        }

    }

    @Override

    @SuppressWarnings("unchecked")

    public <T> T getOption(SocketOption<T> name)

        throws IOException

    {

        Objects.requireNonNull(name);

        if (!supportedOptions().contains(name))

            throw new UnsupportedOperationException("'" + name + "' not supported");

        synchronized (stateLock) {

            ensureOpen();

            if (name == StandardSocketOptions.SO_REUSEADDR && Net.useExclusiveBind()) {

                // SO_REUSEADDR emulated when using exclusive bind

                return (T)Boolean.valueOf(isReuseAddress);

            }

            // no options that require special handling

            return (T) Net.getSocketOption(fd, Net.UNSPEC, name);

        }

    }

    private static class DefaultOptionsHolder {

        static final Set<SocketOption<?>> defaultOptions = defaultOptions();

        private static Set<SocketOption<?>> defaultOptions() {

            HashSet<SocketOption<?>> set = new HashSet<>();

            set.add(StandardSocketOptions.SO_RCVBUF);

            set.add(StandardSocketOptions.SO_REUSEADDR);

            if (Net.isReusePortAvailable()) {

                set.add(StandardSocketOptions.SO_REUSEPORT);

            }

            set.addAll(ExtendedSocketOptions.serverSocketOptions());

            return Collections.unmodifiableSet(set);

        }

    }

    @Override

    public final Set<SocketOption<?>> supportedOptions() {

        return DefaultOptionsHolder.defaultOptions;

    }

    @Override

    public ServerSocketChannel bind(SocketAddress local, int backlog) throws IOException {

        synchronized (stateLock) {

            ensureOpen();

            if (localAddress != null)

                throw new AlreadyBoundException();

            InetSocketAddress isa = (local == null)

                                    ? new InetSocketAddress(0)

                                    : Net.checkAddress(local);

            SecurityManager sm = System.getSecurityManager();

            if (sm != null)

                sm.checkListen(isa.getPort());

            NetHooks.beforeTcpBind(fd, isa.getAddress(), isa.getPort());

            Net.bind(fd, isa.getAddress(), isa.getPort());

            Net.listen(fd, backlog < 1 ? 50 : backlog);

            localAddress = Net.localAddress(fd);

        }

        return this;

    }

    /**

     * Marks the beginning of an I/O operation that might block.

     *

     * @throws ClosedChannelException if the channel is closed

     * @throws NotYetBoundException if the channel's socket has not been bound yet

     */

    private void begin(boolean blocking) throws ClosedChannelException {

        if (blocking)

            begin();  // set blocker to close channel if interrupted

        synchronized (stateLock) {

            ensureOpen();

            if (localAddress == null)

                throw new NotYetBoundException();

            if (blocking)

                thread = NativeThread.current();

        }

    }

    /**

     * Marks the end of an I/O operation that may have blocked.

     *

     * @throws AsynchronousCloseException if the channel was closed due to this

     * thread being interrupted on a blocking I/O operation.

     */

    private void end(boolean blocking, boolean completed)

        throws AsynchronousCloseException

    {

        if (blocking) {

            synchronized (stateLock) {

                thread = 0;

                if (state == ST_CLOSING) {

                    tryFinishClose();

                }

            }

            end(completed);

        }

    }

    @Override

    public SocketChannel accept() throws IOException {

        int n = 0;

        FileDescriptor newfd = new FileDescriptor();

        InetSocketAddress[] isaa = new InetSocketAddress[1];

        acceptLock.lock();

        try {

            boolean blocking = isBlocking();

            try {

                begin(blocking);

                n = Net.accept(this.fd, newfd, isaa);

                if (blocking) {

                    while (IOStatus.okayToRetry(n) && isOpen()) {

                        park(Net.POLLIN);

                        n = Net.accept(this.fd, newfd, isaa);

                    }

                }

            } finally {

                end(blocking, n > 0);

                assert IOStatus.check(n);

            }

        } finally {

            acceptLock.unlock();

        }

        if (n > 0) {

            return finishAccept(newfd, isaa[0]);

        } else {

            return null;

        }

    }

    /**

     * Accepts a new connection with a given timeout. This method requires the

     * channel to be configured in blocking mode.

     *

     * @apiNote This method is for use by the socket adaptor.

     *

     * @param nanos the timeout, in nanoseconds

     * @throws IllegalBlockingModeException if the channel is configured non-blocking

     * @throws SocketTimeoutException if the timeout expires

     */

    SocketChannel blockingAccept(long nanos) throws IOException {

        int n = 0;

        FileDescriptor newfd = new FileDescriptor();

        InetSocketAddress[] isaa = new InetSocketAddress[1];

        acceptLock.lock();

        try {

            // check that channel is configured blocking

            if (!isBlocking())

                throw new IllegalBlockingModeException();

            try {

                begin(true);

                // change socket to non-blocking

                lockedConfigureBlocking(false);

                try {

                    long startNanos = System.nanoTime();

                    n = Net.accept(fd, newfd, isaa);

                    while (n == IOStatus.UNAVAILABLE && isOpen()) {

                        long remainingNanos = nanos - (System.nanoTime() - startNanos);

                        if (remainingNanos <= 0) {

                            throw new SocketTimeoutException("Accept timed out");

                        }

                        park(Net.POLLIN, remainingNanos);

                        n = Net.accept(fd, newfd, isaa);

                    }

                } finally {

                    // restore socket to blocking mode (if channel is open)

                    tryLockedConfigureBlocking(true);

                }

            } finally {

                end(true, n > 0);

            }

        } finally {

            acceptLock.unlock();

        }

        assert n > 0;

        return finishAccept(newfd, isaa[0]);

    }

    private SocketChannel finishAccept(FileDescriptor newfd, InetSocketAddress isa)

        throws IOException

    {

        try {

            // newly accepted socket is initially in blocking mode

            IOUtil.configureBlocking(newfd, true);

            // check permitted to accept connections from the remote address

            SecurityManager sm = System.getSecurityManager();

            if (sm != null) {

                sm.checkAccept(isa.getAddress().getHostAddress(), isa.getPort());

            }

            return new SocketChannelImpl(provider(), newfd, isa);

        } catch (Exception e) {

            nd.close(newfd);

            throw e;

        }

    }

    @Override

    protected void implConfigureBlocking(boolean block) throws IOException {

        acceptLock.lock();

        try {

            lockedConfigureBlocking(block);

        } finally {

            acceptLock.unlock();

        }

    }

    /**

     * Adjust the blocking. acceptLock must already be held.

     */

    private void lockedConfigureBlocking(boolean block) throws IOException {

        assert acceptLock.isHeldByCurrentThread();

        synchronized (stateLock) {

            ensureOpen();

            IOUtil.configureBlocking(fd, block);

        }

    }

    /**

     * Adjusts the blocking mode if the channel is open. acceptLock must already

     * be held.

     *

     * @return {@code true} if the blocking mode was adjusted, {@code false} if

     *         the blocking mode was not adjusted because the channel is closed

     */

    private boolean tryLockedConfigureBlocking(boolean block) throws IOException {

        assert acceptLock.isHeldByCurrentThread();

        synchronized (stateLock) {

            if (isOpen()) {

                IOUtil.configureBlocking(fd, block);

                return true;

            } else {

                return false;

            }

        }

    }

    /**

     * Closes the socket if there are no accept in progress and the channel is

     * not registered with a Selector.

     */

    private boolean tryClose() throws IOException {

        assert Thread.holdsLock(stateLock) && state == ST_CLOSING;

        if ((thread == 0) && !isRegistered()) {

            state = ST_CLOSED;

            nd.close(fd);

            return true;

        } else {

            return false;

        }

    }

    /**

     * Invokes tryClose to attempt to close the socket.

     *

     * This method is used for deferred closing by I/O and Selector operations.

     */

    private void tryFinishClose() {

        try {

            tryClose();

        } catch (IOException ignore) { }

    }

    /**

     * Closes this channel when configured in blocking mode.

     *

     * If there is an accept in progress then the socket is pre-closed and the

     * accept thread is signalled, in which case the final close is deferred

     * until the accept aborts.

     */

    private void implCloseBlockingMode() throws IOException {

        synchronized (stateLock) {

            assert state < ST_CLOSING;

            state = ST_CLOSING;

            if (!tryClose()) {

                long th = thread;

                if (th != 0) {

                    nd.preClose(fd);

                    NativeThread.signal(th);

                }

            }

        }

    }

    /**

     * Closes this channel when configured in non-blocking mode.

     *

     * If the channel is registered with a Selector then the close is deferred

     * until the channel is flushed from all Selectors.

     */

    private void implCloseNonBlockingMode() throws IOException {

        synchronized (stateLock) {

            assert state < ST_CLOSING;

            state = ST_CLOSING;

        }

        // wait for any accept to complete before trying to close

        acceptLock.lock();

        acceptLock.unlock();

        synchronized (stateLock) {

            if (state == ST_CLOSING) {

                tryClose();

            }

        }

    }

    /**

     * Invoked by implCloseChannel to close the channel.

     */

    @Override

    protected void implCloseSelectableChannel() throws IOException {

        assert !isOpen();

        if (isBlocking()) {

            implCloseBlockingMode();

        } else {

            implCloseNonBlockingMode();

        }

    }

    @Override

    public void kill() {

        synchronized (stateLock) {

            if (state == ST_CLOSING) {