/*

 * Copyright (c) 2003, 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

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 */

package sun.nio.ch;

import java.lang.reflect.Constructor;

import java.io.FileDescriptor;

import java.io.IOException;

import java.io.UncheckedIOException;

import java.net.InetAddress;

import java.net.InetSocketAddress;

import java.net.Socket;

import java.net.SocketAddress;

import java.net.SocketOption;

import java.nio.ByteBuffer;

import java.nio.channels.Channel;

import java.nio.channels.SocketChannel;

import java.nio.channels.ServerSocketChannel;

import java.nio.channels.DatagramChannel;

import java.nio.channels.spi.SelectorProvider;

    // the "types" of socket returned by soType0

    private static final int UNKNOWN            = -1;

    private static final int SOCK_STREAM        = 1;

    private static final int SOCK_DGRAM         = 2;

    // socket address type

    private static final int AF_UNKNOWN         = -1;

    private static final int AF_INET            = 1;

    private static final int AF_INET6           = 2;

    private static final int AF_UNIX            = 3;

    // oflag values when opening a file

    private static final int O_RDONLY           = 0;

    private static final int O_WRONLY           = 1;

    private static final int O_RDWR             = 2;

    /*

     * In order to "detach" the standard streams we dup them to /dev/null.

     * In order to reduce the possibility of an error at close time we

     * open /dev/null early - that way we know we won't run out of file

     * descriptors at close time. This makes the close operation a

     * simple dup2 operation for each of the standard streams.

     */

    private static int devnull = -1;

    private static void detachIOStreams() {

        try {

            dup2(devnull, 0);

            dup2(devnull, 1);

            dup2(devnull, 2);

        } catch (IOException ioe) {

            // this shouldn't happen

            throw new InternalError(ioe);

        }

    }

    /*

     * Override the implCloseSelectableChannel for each channel type - this

     * allows us to "detach" the standard streams after closing and ensures

     * that the underlying socket really closes.

     */

    public static class InheritedInetSocketChannelImpl extends InetSocketChannelImpl {

        InheritedInetSocketChannelImpl(SelectorProvider sp,

                                   FileDescriptor fd,

                                   InetSocketAddress remote)

            throws IOException

        {

            super(sp, fd, remote);

        }

        protected void implCloseSelectableChannel() throws IOException {

            super.implCloseSelectableChannel();

            detachIOStreams();

        }

    }

    public static class InheritedUnixSocketChannelImpl extends UnixDomainSocketChannelImpl {

        InheritedUnixSocketChannelImpl(SelectorProvider sp, FileDescriptor fd)

            throws IOException

        {

            super(sp, fd, true);

        }

        @Override

        protected void implCloseSelectableChannel() throws IOException {

            detachIOStreams();

        }

    }

    public static class InheritedInetServerSocketChannelImpl extends

        InetServerSocketChannelImpl {

        InheritedInetServerSocketChannelImpl(SelectorProvider sp,

                                         FileDescriptor fd)

            throws IOException

        {

            super(sp, fd, true);

        }

        protected void implCloseSelectableChannel() throws IOException {

            super.implCloseSelectableChannel();

            detachIOStreams();

        }

    }

    public static class InheritedDatagramChannelImpl extends

        DatagramChannelImpl {

        InheritedDatagramChannelImpl(SelectorProvider sp,

                                     FileDescriptor fd)

            throws IOException

        {

            super(sp, fd);

        }

        protected void implCloseSelectableChannel() throws IOException {

            super.implCloseSelectableChannel();

            detachIOStreams();

        }

    }

    /*

     * If there's a SecurityManager then check for the appropriate

     * RuntimePermission.

     */

    private static void checkAccess(Channel c) {

        SecurityManager sm = System.getSecurityManager();

        if (sm != null) {

            sm.checkPermission(

                new RuntimePermission("inheritedChannel")

            );

        }

    }

    /*

     * If standard inherited channel is connected to a socket then return a Channel

     * of the appropriate type based standard input.

     */

    private static Channel createChannel() throws IOException {

        // dup the file descriptor - we do this so that for two reasons :-

        // 1. Avoids any timing issues with FileDescriptor.in being closed

        //    or redirected while we create the channel.

        // 2. Allows streams based on file descriptor 0 to co-exist with

        //    the channel (closing one doesn't impact the other)

        int fdVal = dup(0);

        // Examine the file descriptor - if it's not a socket then we don't

        // create a channel so we release the file descriptor.

        int st;

        st = soType0(fdVal);

        if (st != SOCK_STREAM && st != SOCK_DGRAM) {

            close0(fdVal);

            return null;

        }

        // Next we create a FileDescriptor for the dup'ed file descriptor

        // Have to use reflection and also make assumption on how FD

        // is implemented.

        Class<?> paramTypes[] = { int.class };

        Constructor<?> ctr = Reflect.lookupConstructor("java.io.FileDescriptor",

                                                       paramTypes);

        Object args[] = { Integer.valueOf(fdVal) };

        FileDescriptor fd = (FileDescriptor)Reflect.invoke(ctr, args);

        // Now create the channel. If the socket is a streams socket then

        // we see if tthere is a peer (ie: connected). If so, then we

        // create a SocketChannel, otherwise a ServerSocketChannel.

        // If the socket is a datagram socket then create a DatagramChannel

        SelectorProvider provider = SelectorProvider.provider();

        assert provider instanceof sun.nio.ch.SelectorProviderImpl;

        Channel c;

        if (st == SOCK_STREAM) {

            int family = addressFamily(fdVal);

            if (family == AF_UNKNOWN)

                return null;

            if (family == AF_UNIX) {

                if (isConnected(fdVal)) {

                    return new InheritedUnixSocketChannelImpl(provider, fd);

                } else {

                    // listener. unsupported.

                    return null;

                }

            }

            InetAddress ia = peerAddress0(fdVal);

            if (ia == null) {

               c = new InheritedInetServerSocketChannelImpl(provider, fd);

            } else {

               int port = peerPort0(fdVal);

               assert port > 0;

               InetSocketAddress isa = new InetSocketAddress(ia, port);

               c = new InheritedInetSocketChannelImpl(provider, fd, isa);

            }

        } else {

            c = new InheritedDatagramChannelImpl(provider, fd);

        }

        return c;

    }

    private static boolean haveChannel = false;

    private static Channel channel = null;

    /*

     * Returns a Channel representing the inherited channel if the

     * inherited channel is a stream connected to a network socket.

     */

    public static synchronized Channel getChannel() throws IOException {

        if (devnull < 0) {

            devnull = open0("/dev/null", O_RDWR);

        }

        // If we don't have the channel try to create it

        if (!haveChannel) {

            channel = createChannel();

            haveChannel = true;

        }

        // if there is a channel then do the security check before

        // returning it.

        if (channel != null) {

            checkAccess(channel);

        }

        return channel;

    }

    // -- Native methods --

    private static native void initIDs();

    private static native int dup(int fd) throws IOException;

    private static native void dup2(int fd, int fd2) throws IOException;

    private static native int open0(String path, int oflag) throws IOException;

    private static native void close0(int fd) throws IOException;

    private static native int soType0(int fd);

    private static native int addressFamily(int fd);

    private static native InetAddress peerAddress0(int fd);

    private static native int peerPort0(int fd);

    // return true if socket is connected to a peer

    private static native boolean isConnected(int fd);

    static {

        IOUtil.load();

        initIDs();

    }

}