/*
 * Copyright (c) 1996, 2016, 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.security.ssl;

import java.io.*;
import java.nio.*;
import java.net.*;
import java.security.GeneralSecurityException;
import java.security.AccessController;
import java.security.AccessControlContext;
import java.security.PrivilegedAction;
import java.security.AlgorithmConstraints;
import java.util.*;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.ReentrantLock;
import java.util.function.BiFunction;

import javax.crypto.BadPaddingException;
import javax.net.ssl.*;

import jdk.internal.misc.JavaNetInetAddressAccess;
import jdk.internal.misc.SharedSecrets;

Implementation of an SSL socket.  This is a normal connection type
socket, implementing SSL over some lower level socket, such as TCP.
Because it is layered over some lower level socket, it MUST override
all default socket methods.
 This API offers a non-traditional option for establishing SSL
connections.  You may first establish the connection directly, then pass
that connection to the SSL socket constructor with a flag saying which
role should be taken in the handshake protocol.  (The two ends of the
connection must not choose the same role!)  This allows setup of SSL
proxying or tunneling, and also allows the kind of "role reversal"
that is required for most FTP data transfers.
Author:
David Brownell
See Also:
SSLSocket
SSLServerSocket/**
 * Implementation of an SSL socket.  This is a normal connection type
 * socket, implementing SSL over some lower level socket, such as TCP.
 * Because it is layered over some lower level socket, it MUST override
 * all default socket methods.
 *
 * <P> This API offers a non-traditional option for establishing SSL
 * connections.  You may first establish the connection directly, then pass
 * that connection to the SSL socket constructor with a flag saying which
 * role should be taken in the handshake protocol.  (The two ends of the
 * connection must not choose the same role!)  This allows setup of SSL
 * proxying or tunneling, and also allows the kind of "role reversal"
 * that is required for most FTP data transfers.
 *
 * @see javax.net.ssl.SSLSocket
 * @see SSLServerSocket
 *
 * @author David Brownell
 */
public final class SSLSocketImpl extends BaseSSLSocketImpl {

    /*
     * ERROR HANDLING GUIDELINES
     * (which exceptions to throw and catch and which not to throw and catch)
     *
     * . if there is an IOException (SocketException) when accessing the
     *   underlying Socket, pass it through
     *
     * . do not throw IOExceptions, throw SSLExceptions (or a subclass)
     *
     * . for internal errors (things that indicate a bug in JSSE or a
     *   grossly misconfigured J2RE), throw either an SSLException or
     *   a RuntimeException at your convenience.
     *
     * . handshaking code (Handshaker or HandshakeMessage) should generally
     *   pass through exceptions, but can handle them if they know what to
     *   do.
     *
     * . exception chaining should be used for all new code. If you happen
     *   to touch old code that does not use chaining, you should change it.
     *
     * . there is a top level exception handler that sits at all entry
     *   points from application code to SSLSocket read/write code. It
     *   makes sure that all errors are handled (see handleException()).
     *
     * . JSSE internal code should generally not call close(), call
     *   closeInternal().
     */

    /*
     * There's a state machine associated with each connection, which
     * among other roles serves to negotiate session changes.
     *
     * - START with constructor, until the TCP connection's around.
     * - HANDSHAKE picks session parameters before allowing traffic.
     *          There are many substates due to sequencing requirements
     *          for handshake messages.
     * - DATA may be transmitted.
     * - RENEGOTIATE state allows concurrent data and handshaking
     *          traffic ("same" substates as HANDSHAKE), and terminates
     *          in selection of new session (and connection) parameters
     * - ERROR state immediately precedes abortive disconnect.
     * - SENT_CLOSE sent a close_notify to the peer. For layered,
     *          non-autoclose socket, must now read close_notify
     *          from peer before closing the connection. For nonlayered or
     *          non-autoclose socket, close connection and go onto
     *          cs_CLOSED state.
     * - CLOSED after sending close_notify alert, & socket is closed.
     *          SSL connection objects are not reused.
     * - APP_CLOSED once the application calls close(). Then it behaves like
     *          a closed socket, e.g.. getInputStream() throws an Exception.
     *
     * State affects what SSL record types may legally be sent:
     *
     * - Handshake ... only in HANDSHAKE and RENEGOTIATE states
     * - App Data ... only in DATA and RENEGOTIATE states
     * - Alert ... in HANDSHAKE, DATA, RENEGOTIATE
     *
     * Re what may be received:  same as what may be sent, except that
     * HandshakeRequest handshaking messages can come from servers even
     * in the application data state, to request entry to RENEGOTIATE.
     *
     * The state machine within HANDSHAKE and RENEGOTIATE states controls
     * the pending session, not the connection state, until the change
     * cipher spec and "Finished" handshake messages are processed and
     * make the "new" session become the current one.
     *
     * NOTE: details of the SMs always need to be nailed down better.
     * The text above illustrates the core ideas.
     *
     *                +---->-------+------>--------->-------+
     *                |            |                        |
     *     <-----<    ^            ^  <-----<               v
     *START>----->HANDSHAKE>----->DATA>----->RENEGOTIATE  SENT_CLOSE
     *                v            v               v        |   |
     *                |            |               |        |   v
     *                +------------+---------------+        v ERROR
     *                |                                     |   |
     *                v                                     |   |
     *               ERROR>------>----->CLOSED<--------<----+-- +
     *                                     |
     *                                     v
     *                                 APP_CLOSED
     *
     * ALSO, note that the purpose of handshaking (renegotiation is
     * included) is to assign a different, and perhaps new, session to
     * the connection.  The SSLv3 spec is a bit confusing on that new
     * protocol feature.
     */
    private static final int    cs_START = 0;
    private static final int    cs_HANDSHAKE = 1;
    private static final int    cs_DATA = 2;
    private static final int    cs_RENEGOTIATE = 3;
    private static final int    cs_ERROR = 4;
    private static final int    cs_SENT_CLOSE = 5;
    private static final int    cs_CLOSED = 6;
    private static final int    cs_APP_CLOSED = 7;

    /*
     * Drives the protocol state machine.
     */
    private volatile int        connectionState;

    /*
     * Flag indicating if the next record we receive MUST be a Finished
     * message. Temporarily set during the handshake to ensure that
     * a change cipher spec message is followed by a finished message.
     */
    private boolean             expectingFinished;

    /*
     * For improved diagnostics, we detail connection closure
     * If the socket is closed (connectionState >= cs_ERROR),
     * closeReason != null indicates if the socket was closed
     * because of an error or because or normal shutdown.
     */
    private SSLException        closeReason;

    /*
     * Per-connection private state that doesn't change when the
     * session is changed.
     */
    private ClientAuthType      doClientAuth =
                                        ClientAuthType.CLIENT_AUTH_NONE;
    private boolean             roleIsServer;
    private boolean             enableSessionCreation = true;
    private String              host;
    private boolean             autoClose = true;
    private AccessControlContext acc;

    // The cipher suites enabled for use on this connection.
    private CipherSuiteList     enabledCipherSuites;

    // The endpoint identification protocol
    private String              identificationProtocol = null;

    // The cryptographic algorithm constraints
    private AlgorithmConstraints    algorithmConstraints = null;

    // The server name indication and matchers
    List<SNIServerName>         serverNames =
                                    Collections.<SNIServerName>emptyList();
    Collection<SNIMatcher>      sniMatchers =
                                    Collections.<SNIMatcher>emptyList();

    // Is the serverNames set to empty with SSLParameters.setServerNames()?
    private boolean             noSniExtension = false;

    // Is the sniMatchers set to empty with SSLParameters.setSNIMatchers()?
    private boolean             noSniMatcher = false;

    // Configured application protocol values
    String[] applicationProtocols = new String[0];

    // Negotiated application protocol value.
    //
    // The value under negotiation will be obtained from handshaker.
    String applicationProtocol = null;

    // Callback function that selects the application protocol value during
    // the SSL/TLS handshake.
    BiFunction<SSLSocket, List<String>, String> applicationProtocolSelector;

    /*
     * READ ME * READ ME * READ ME * READ ME * READ ME * READ ME *
     * IMPORTANT STUFF TO UNDERSTANDING THE SYNCHRONIZATION ISSUES.
     * READ ME * READ ME * READ ME * READ ME * READ ME * READ ME *
     *
     * There are several locks here.
     *
     * The primary lock is the per-instance lock used by
     * synchronized(this) and the synchronized methods.  It controls all
     * access to things such as the connection state and variables which
     * affect handshaking.  If we are inside a synchronized method, we
     * can access the state directly, otherwise, we must use the
     * synchronized equivalents.
     *
     * The handshakeLock is used to ensure that only one thread performs
     * the *complete initial* handshake.  If someone is handshaking, any
     * stray application or startHandshake() requests who find the
     * connection state is cs_HANDSHAKE will stall on handshakeLock
     * until handshaking is done.  Once the handshake is done, we either
     * succeeded or failed, but we can never go back to the cs_HANDSHAKE
     * or cs_START state again.
     *
     * Note that the read/write() calls here in SSLSocketImpl are not
     * obviously synchronized.  In fact, it's very nonintuitive, and
     * requires careful examination of code paths.  Grab some coffee,
     * and be careful with any code changes.
     *
     * There can be only three threads active at a time in the I/O
     * subsection of this class.
     *    1.  startHandshake
     *    2.  AppInputStream
     *    3.  AppOutputStream
     * One thread could call startHandshake().
     * AppInputStream/AppOutputStream read() and write() calls are each
     * synchronized on 'this' in their respective classes, so only one
     * app. thread will be doing a SSLSocketImpl.read() or .write()'s at
     * a time.
     *
     * If handshaking is required (state cs_HANDSHAKE), and
     * getConnectionState() for some/all threads returns cs_HANDSHAKE,
     * only one can grab the handshakeLock, and the rest will stall
     * either on getConnectionState(), or on the handshakeLock if they
     * happen to successfully race through the getConnectionState().
     *
     * If a writer is doing the initial handshaking, it must create a
     * temporary reader to read the responses from the other side.  As a
     * side-effect, the writer's reader will have priority over any
     * other reader.  However, the writer's reader is not allowed to
     * consume any application data.  When handshakeLock is finally
     * released, we either have a cs_DATA connection, or a
     * cs_CLOSED/cs_ERROR socket.
     *
     * The writeLock is held while writing on a socket connection and
     * also to protect the MAC and cipher for their direction.  The
     * writeLock is package private for Handshaker which holds it while
     * writing the ChangeCipherSpec message.
     *
     * To avoid the problem of a thread trying to change operational
     * modes on a socket while handshaking is going on, we synchronize
     * on 'this'.  If handshaking has not started yet, we tell the
     * handshaker to change its mode.  If handshaking has started,
     * we simply store that request until the next pending session
     * is created, at which time the new handshaker's state is set.
     *
     * The readLock is held during readRecord(), which is responsible
     * for reading an SSLInputRecord, decrypting it, and processing it.
     * The readLock ensures that these three steps are done atomically
     * and that once started, no other thread can block on SSLInputRecord.read.
     * This is necessary so that processing of close_notify alerts
     * from the peer are handled properly.
     */
    private final Object        handshakeLock = new Object();
    final ReentrantLock         writeLock = new ReentrantLock();
    private final Object        readLock = new Object();

    InputRecord                 inputRecord;
    OutputRecord                outputRecord;

    /*
     * security parameters for secure renegotiation.
     */
    private boolean             secureRenegotiation;
    private byte[]              clientVerifyData;
    private byte[]              serverVerifyData;

    /*
     * The authentication context holds all information used to establish
     * who this end of the connection is (certificate chains, private keys,
     * etc) and who is trusted (e.g. as CAs or websites).
     */
    private SSLContextImpl      sslContext;


    /*
     * This connection is one of (potentially) many associated with
     * any given session.  The output of the handshake protocol is a
     * new session ... although all the protocol description talks
     * about changing the cipher spec (and it does change), in fact
     * that's incidental since it's done by changing everything that
     * is associated with a session at the same time.  (TLS/IETF may
     * change that to add client authentication w/o new key exchg.)
     */
    private Handshaker                  handshaker;
    private SSLSessionImpl              sess;
    private volatile SSLSessionImpl     handshakeSession;


    /*
     * If anyone wants to get notified about handshake completions,
     * they'll show up on this list.
     */
    private HashMap<HandshakeCompletedListener, AccessControlContext>
                                                        handshakeListeners;

    /*
     * Reuse the same internal input/output streams.
     */
    private InputStream         sockInput;
    private OutputStream        sockOutput;


    /*
     * These input and output streams block their data in SSL records,
     * and usually arrange integrity and privacy protection for those
     * records.  The guts of the SSL protocol are wrapped up in these
     * streams, and in the handshaking that establishes the details of
     * that integrity and privacy protection.
     */
    private AppInputStream      input;
    private AppOutputStream     output;

    /*
     * The protocol versions enabled for use on this connection.
     *
     * Note: we support a pseudo protocol called SSLv2Hello which when
     * set will result in an SSL v2 Hello being sent with SSL (version 3.0)
     * or TLS (version 3.1, 3.2, etc.) version info.
     */
    private ProtocolList enabledProtocols;

    /*
     * The SSL version associated with this connection.
     */
    private ProtocolVersion     protocolVersion = ProtocolVersion.DEFAULT_TLS;

    /* Class and subclass dynamic debugging support */
    private static final Debug debug = Debug.getInstance("ssl");

    /*
     * Whether local cipher suites preference in server side should be
     * honored during handshaking?
     */
    private boolean preferLocalCipherSuites = false;

    /*
     * The maximum expected network packet size for SSL/TLS/DTLS records.
     */
    private int maximumPacketSize = 0;

    /*
     * Is the local name service trustworthy?
     *
     * If the local name service is not trustworthy, reverse host name
     * resolution should not be performed for endpoint identification.
     */
    static final boolean trustNameService =
            Debug.getBooleanProperty("jdk.tls.trustNameService", false);

    //
    // CONSTRUCTORS AND INITIALIZATION CODE
    //

    
Constructs an SSL connection to a named host at a specified port,
using the authentication context provided.  This endpoint acts as
the client, and may rejoin an existing SSL session if appropriate.
Params:
context – authentication context to use
host – name of the host with which to connect
port – number of the server's port/**
     * Constructs an SSL connection to a named host at a specified port,
     * using the authentication context provided.  This endpoint acts as
     * the client, and may rejoin an existing SSL session if appropriate.
     *
     * @param context authentication context to use
     * @param host name of the host with which to connect
     * @param port number of the server's port
     */
    SSLSocketImpl(SSLContextImpl context, String host, int port)
            throws IOException, UnknownHostException {
        super();
        this.host = host;
        this.serverNames =
            Utilities.addToSNIServerNameList(this.serverNames, this.host);
        init(context, false);
        SocketAddress socketAddress =
               host != null ? new InetSocketAddress(host, port) :
               new InetSocketAddress(InetAddress.getByName(null), port);
        connect(socketAddress, 0);
    }


    
Constructs an SSL connection to a server at a specified address.
and TCP port, using the authentication context provided.  This
endpoint acts as the client, and may rejoin an existing SSL session
if appropriate.
Params:
context – authentication context to use
address – the server's host
port – its port/**
     * Constructs an SSL connection to a server at a specified address.
     * and TCP port, using the authentication context provided.  This
     * endpoint acts as the client, and may rejoin an existing SSL session
     * if appropriate.
     *
     * @param context authentication context to use
     * @param address the server's host
     * @param port its port
     */
    SSLSocketImpl(SSLContextImpl context, InetAddress host, int port)
            throws IOException {
        super();
        init(context, false);
        SocketAddress socketAddress = new InetSocketAddress(host, port);
        connect(socketAddress, 0);
    }

    
Constructs an SSL connection to a named host at a specified port,
using the authentication context provided.  This endpoint acts as
the client, and may rejoin an existing SSL session if appropriate.
Params:
context – authentication context to use
host – name of the host with which to connect
port – number of the server's port
localAddr – the local address the socket is bound to
localPort – the local port the socket is bound to/**
     * Constructs an SSL connection to a named host at a specified port,
     * using the authentication context provided.  This endpoint acts as
     * the client, and may rejoin an existing SSL session if appropriate.
     *
     * @param context authentication context to use
     * @param host name of the host with which to connect
     * @param port number of the server's port
     * @param localAddr the local address the socket is bound to
     * @param localPort the local port the socket is bound to
     */
    SSLSocketImpl(SSLContextImpl context, String host, int port,
            InetAddress localAddr, int localPort)
            throws IOException, UnknownHostException {
        super();
        this.host = host;
        this.serverNames =
            Utilities.addToSNIServerNameList(this.serverNames, this.host);
        init(context, false);
        bind(new InetSocketAddress(localAddr, localPort));
        SocketAddress socketAddress =
               host != null ? new InetSocketAddress(host, port) :
               new InetSocketAddress(InetAddress.getByName(null), port);
        connect(socketAddress, 0);
    }


    
Constructs an SSL connection to a server at a specified address.
and TCP port, using the authentication context provided.  This
endpoint acts as the client, and may rejoin an existing SSL session
if appropriate.
Params:
context – authentication context to use
address – the server's host
port – its port
localAddr – the local address the socket is bound to
localPort – the local port the socket is bound to/**
     * Constructs an SSL connection to a server at a specified address.
     * and TCP port, using the authentication context provided.  This
     * endpoint acts as the client, and may rejoin an existing SSL session
     * if appropriate.
     *
     * @param context authentication context to use
     * @param address the server's host
     * @param port its port
     * @param localAddr the local address the socket is bound to
     * @param localPort the local port the socket is bound to
     */
    SSLSocketImpl(SSLContextImpl context, InetAddress host, int port,
            InetAddress localAddr, int localPort)
            throws IOException {
        super();
        init(context, false);
        bind(new InetSocketAddress(localAddr, localPort));
        SocketAddress socketAddress = new InetSocketAddress(host, port);
        connect(socketAddress, 0);
    }

    /*
     * Package-private constructor used ONLY by SSLServerSocket.  The
     * java.net package accepts the TCP connection after this call is
     * made.  This just initializes handshake state to use "server mode",
     * giving control over the use of SSL client authentication.
     */
    SSLSocketImpl(SSLContextImpl context, boolean serverMode,
            CipherSuiteList suites, ClientAuthType clientAuth,
            boolean sessionCreation, ProtocolList protocols,
            String identificationProtocol,
            AlgorithmConstraints algorithmConstraints,
            Collection<SNIMatcher> sniMatchers,
            boolean preferLocalCipherSuites,
            String[] applicationProtocols) throws IOException {

        super();
        doClientAuth = clientAuth;
        enableSessionCreation = sessionCreation;
        this.identificationProtocol = identificationProtocol;
        this.algorithmConstraints = algorithmConstraints;
        this.sniMatchers = sniMatchers;
        this.preferLocalCipherSuites = preferLocalCipherSuites;
        this.applicationProtocols = applicationProtocols;
        init(context, serverMode);

        /*
         * Override what was picked out for us.
         */
        enabledCipherSuites = suites;
        enabledProtocols = protocols;
    }


    
Package-private constructor used to instantiate an unconnected
socket. The java.net package will connect it, either when the
connect() call is made by the application.  This instance is
meant to set handshake state to use "client mode".
/**
     * Package-private constructor used to instantiate an unconnected
     * socket. The java.net package will connect it, either when the
     * connect() call is made by the application.  This instance is
     * meant to set handshake state to use "client mode".
     */
    SSLSocketImpl(SSLContextImpl context) {
        super();
        init(context, false);
    }


    
Layer SSL traffic over an existing connection, rather than creating
a new connection.  The existing connection may be used only for SSL
traffic (using this SSLSocket) until the SSLSocket.close() call
returns. However, if a protocol error is detected, that existing
connection is automatically closed.
 This particular constructor always uses the socket in the
role of an SSL client. It may be useful in cases which start
using SSL after some initial data transfers, for example in some
SSL tunneling applications or as part of some kinds of application
protocols which negotiate use of a SSL based security.
Params:
sock – the existing connection
context – the authentication context to use/**
     * Layer SSL traffic over an existing connection, rather than creating
     * a new connection.  The existing connection may be used only for SSL
     * traffic (using this SSLSocket) until the SSLSocket.close() call
     * returns. However, if a protocol error is detected, that existing
     * connection is automatically closed.
     *
     * <P> This particular constructor always uses the socket in the
     * role of an SSL client. It may be useful in cases which start
     * using SSL after some initial data transfers, for example in some
     * SSL tunneling applications or as part of some kinds of application
     * protocols which negotiate use of a SSL based security.
     *
     * @param sock the existing connection
     * @param context the authentication context to use
     */
    SSLSocketImpl(SSLContextImpl context, Socket sock, String host,
            int port, boolean autoClose) throws IOException {
        super(sock);
        // We always layer over a connected socket
        if (!sock.isConnected()) {
            throw new SocketException("Underlying socket is not connected");
        }
        this.host = host;
        this.serverNames =
            Utilities.addToSNIServerNameList(this.serverNames, this.host);
        init(context, false);
        this.autoClose = autoClose;
        doneConnect();
    }

    
Creates a server mode Socket layered over an existing connected socket, and is able to read data which has already been consumed/removed from the Socket's underlying InputStream. /**
     * Creates a server mode {@link Socket} layered over an
     * existing connected socket, and is able to read data which has
     * already been consumed/removed from the {@link Socket}'s
     * underlying {@link InputStream}.
     */
    SSLSocketImpl(SSLContextImpl context, Socket sock,
            InputStream consumed, boolean autoClose) throws IOException {
        super(sock, consumed);
        // We always layer over a connected socket
        if (!sock.isConnected()) {
            throw new SocketException("Underlying socket is not connected");
        }

        // In server mode, it is not necessary to set host and serverNames.
        // Otherwise, would require a reverse DNS lookup to get the hostname.

        init(context, true);
        this.autoClose = autoClose;
        doneConnect();
    }

    
Initializes the client socket.
/**
     * Initializes the client socket.
     */
    private void init(SSLContextImpl context, boolean isServer) {
        sslContext = context;
        sess = SSLSessionImpl.nullSession;
        handshakeSession = null;

        /*
         * role is as specified, state is START until after
         * the low level connection's established.
         */
        roleIsServer = isServer;
        connectionState = cs_START;

        // initial security parameters for secure renegotiation
        secureRenegotiation = false;
        clientVerifyData = new byte[0];
        serverVerifyData = new byte[0];

        enabledCipherSuites =
                sslContext.getDefaultCipherSuiteList(roleIsServer);
        enabledProtocols =
                sslContext.getDefaultProtocolList(roleIsServer);

        inputRecord = new SSLSocketInputRecord();;
        outputRecord = new SSLSocketOutputRecord();

        maximumPacketSize = outputRecord.getMaxPacketSize();

        // save the acc
        acc = AccessController.getContext();

        input = new AppInputStream(this);
        output = new AppOutputStream(this);
    }

    
Connects this socket to the server with a specified timeout
value.
This method is either called on an unconnected SSLSocketImpl by the
application, or it is called in the constructor of a regular
SSLSocketImpl. If we are layering on top on another socket, then
this method should not be called, because we assume that the
underlying socket is already connected by the time it is passed to
us.
Params:
endpoint – the SocketAddress
timeout –  the timeout value to be used, 0 is no timeout
Throws:
IOException – if an error occurs during the connection
SocketTimeoutException – if timeout expires before connecting/**
     * Connects this socket to the server with a specified timeout
     * value.
     *
     * This method is either called on an unconnected SSLSocketImpl by the
     * application, or it is called in the constructor of a regular
     * SSLSocketImpl. If we are layering on top on another socket, then
     * this method should not be called, because we assume that the
     * underlying socket is already connected by the time it is passed to
     * us.
     *
     * @param   endpoint the <code>SocketAddress</code>
     * @param   timeout  the timeout value to be used, 0 is no timeout
     * @throws  IOException if an error occurs during the connection
     * @throws  SocketTimeoutException if timeout expires before connecting
     */
    @Override
    public void connect(SocketAddress endpoint, int timeout)
            throws IOException {

        if (isLayered()) {
            throw new SocketException("Already connected");
        }

        if (!(endpoint instanceof InetSocketAddress)) {
            throw new SocketException(
                                  "Cannot handle non-Inet socket addresses.");
        }

        super.connect(endpoint, timeout);

        if (host == null || host.length() == 0) {
            useImplicitHost(false);
        }

        doneConnect();
    }

    
Initialize the handshaker and socket streams.
Called by connect, the layered constructor, and SSLServerSocket.
/**
     * Initialize the handshaker and socket streams.
     *
     * Called by connect, the layered constructor, and SSLServerSocket.
     */
    void doneConnect() throws IOException {
        /*
         * Save the input and output streams.  May be done only after
         * java.net actually connects using the socket "self", else
         * we get some pretty bizarre failure modes.
         */
        sockInput = super.getInputStream();
        sockOutput = super.getOutputStream();

        inputRecord.setDeliverStream(sockOutput);
        outputRecord.setDeliverStream(sockOutput);

        /*
         * Move to handshaking state, with pending session initialized
         * to defaults and the appropriate kind of handshaker set up.
         */
        initHandshaker();
    }

    private synchronized int getConnectionState() {
        return connectionState;
    }

    private synchronized void setConnectionState(int state) {
        connectionState = state;
    }

    AccessControlContext getAcc() {
        return acc;
    }

    //
    // READING AND WRITING RECORDS
    //

    /*
     * Application data record output.
     *
     * Application data can't be sent until the first handshake establishes
     * a session.
     */
    void writeRecord(byte[] source, int offset, int length) throws IOException {
        /*
         * The loop is in case of HANDSHAKE --> ERROR transitions, etc
         */
        // Don't bother to check the emptiness of source applicatoin data
        // before the security connection established.
        for (boolean readyForApp = false; !readyForApp;) {
            /*
             * Not all states support passing application data.  We
             * synchronize access to the connection state, so that
             * synchronous handshakes can complete cleanly.
             */
            switch (getConnectionState()) {

                /*
                 * We've deferred the initial handshaking till just now,
                 * when presumably a thread's decided it's OK to block for
                 * longish periods of time for I/O purposes (as well as
                 * configured the cipher suites it wants to use).
                 */
                case cs_HANDSHAKE:
                    performInitialHandshake();
                    break;

                case cs_DATA:
                case cs_RENEGOTIATE:
                    readyForApp = true;
                    break;

                case cs_ERROR:
                    fatal(Alerts.alert_close_notify,
                            "error while writing to socket");
                    break; // dummy

                case cs_SENT_CLOSE:
                case cs_CLOSED:
                case cs_APP_CLOSED:
                    // we should never get here (check in AppOutputStream)
                    // this is just a fallback
                    if (closeReason != null) {
                        throw closeReason;
                    } else {
                        throw new SocketException("Socket closed");
                    }

                /*
                 * Else something's goofy in this state machine's use.
                 */
                default:
                    throw new SSLProtocolException(
                            "State error, send app data");
            }
        }

        //
        // Don't bother to really write empty records.  We went this
        // far to drive the handshake machinery, for correctness; not
        // writing empty records improves performance by cutting CPU
        // time and network resource usage.  However, some protocol
        // implementations are fragile and don't like to see empty
        // records, so this also increases robustness.
        //
        if (length > 0) {
            IOException ioe = null;
            byte description = 0;    // 0: never used, make the compiler happy
            writeLock.lock();
            try {
                outputRecord.deliver(source, offset, length);
            } catch (SSLHandshakeException she) {
                // may be record sequence number overflow
                description = Alerts.alert_handshake_failure;
                ioe = she;
            } catch (IOException e) {
                description = Alerts.alert_unexpected_message;
                ioe = e;
            } finally {
                writeLock.unlock();
            }

            // Be care of deadlock. Please don't place the call to fatal()
            // into the writeLock locked block.
            if (ioe != null) {
                fatal(description, ioe);
            }
        }

        /*
         * Check the sequence number state
         *
         * Note that in order to maintain the connection I/O
         * properly, we check the sequence number after the last
         * record writing process. As we request renegotiation
         * or close the connection for wrapped sequence number
         * when there is enough sequence number space left to
         * handle a few more records, so the sequence number
         * of the last record cannot be wrapped.
         *
         * Don't bother to kickstart the renegotiation when the
         * local is asking for it.
         */
        if ((connectionState == cs_DATA) && outputRecord.seqNumIsHuge()) {
            /*
             * Ask for renegotiation when need to renew sequence number.
             *
             * Don't bother to kickstart the renegotiation when the local is
             * asking for it.
             */
            if (debug != null && Debug.isOn("ssl")) {
                System.out.println(Thread.currentThread().getName() +
                        ", request renegotiation " +
                        "to avoid sequence number overflow");
            }

            startHandshake();
        }
    }

    /*
     * Alert record output.
     */
    void writeAlert(byte level, byte description) throws IOException {

        // If the record is a close notify alert, we need to honor
        // socket option SO_LINGER. Note that we will try to send
        // the close notify even if the SO_LINGER set to zero.
        if ((description == Alerts.alert_close_notify) && getSoLinger() >= 0) {

            // keep and clear the current thread interruption status.
            boolean interrupted = Thread.interrupted();
            try {
                if (writeLock.tryLock(getSoLinger(), TimeUnit.SECONDS)) {
                    try {
                        outputRecord.encodeAlert(level, description);
                    } finally {
                        writeLock.unlock();
                    }
                } else {
                    SSLException ssle = new SSLException(
                            "SO_LINGER timeout," +
                            " close_notify message cannot be sent.");


                    // For layered, non-autoclose sockets, we are not
                    // able to bring them into a usable state, so we
                    // treat it as fatal error.
                    if (isLayered() && !autoClose) {
                        // Note that the alert description is
                        // specified as -1, so no message will be send
                        // to peer anymore.
                        fatal((byte)(-1), ssle);
                    } else if ((debug != null) && Debug.isOn("ssl")) {
                        System.out.println(
                            Thread.currentThread().getName() +
                            ", received Exception: " + ssle);
                    }

                    // RFC2246 requires that the session becomes
                    // unresumable if any connection is terminated
                    // without proper close_notify messages with
                    // level equal to warning.
                    //
                    // RFC4346 no longer requires that a session not be
                    // resumed if failure to properly close a connection.
                    //
                    // We choose to make the session unresumable if
                    // failed to send the close_notify message.
                    //
                    sess.invalidate();
                }
            } catch (InterruptedException ie) {
                // keep interrupted status
                interrupted = true;
            }

            // restore the interrupted status
            if (interrupted) {
                Thread.currentThread().interrupt();
            }
        } else {
            writeLock.lock();
            try {
                outputRecord.encodeAlert(level, description);
            } finally {
                writeLock.unlock();
            }
        }

        // Don't bother to check sequence number overlap here.  If sequence
        // number is huge, there should be enough sequence number space to
        // request renegotiation in next application data read and write.
    }


    int bytesInCompletePacket() throws IOException {
        if (getConnectionState() == cs_HANDSHAKE) {
            performInitialHandshake();
        }

        synchronized (readLock) {
            int state = getConnectionState();
            if ((state == cs_CLOSED) ||
                    (state == cs_ERROR) || (state == cs_APP_CLOSED)) {
                return -1;
            }

            try {
                return inputRecord.bytesInCompletePacket(sockInput);
            } catch (EOFException eofe) {
                boolean handshaking = (connectionState <= cs_HANDSHAKE);
                boolean rethrow = requireCloseNotify || handshaking;
                if ((debug != null) && Debug.isOn("ssl")) {
                    System.out.println(Thread.currentThread().getName() +
                        ", received EOFException: "
                        + (rethrow ? "error" : "ignored"));
                }

                if (!rethrow) {
                    // treat as if we had received a close_notify
                    closeInternal(false);
                } else {
                    SSLException e;
                    if (handshaking) {
                        e = new SSLHandshakeException(
                            "Remote host terminated the handshake");
                    } else {
                        e = new SSLProtocolException(
                            "Remote host terminated the handshake");
                    }
                    e.initCause(eofe);
                    throw e;
                }
            }

            return -1;
        }
    }

    // the caller have synchronized readLock
    void expectingFinishFlight() {
        inputRecord.expectingFinishFlight();
    }

    /*
     * Read an application data record.
     *
     * Alerts and handshake messages are internally handled directly.
     */
    int readRecord(ByteBuffer buffer) throws IOException {
        if (getConnectionState() == cs_HANDSHAKE) {
            performInitialHandshake();
        }

        return readRecord(buffer, true);
    }

    /*
     * Read a record, no application data input required.
     *
     * Alerts and handshake messages are internally handled directly.
     */
    int readRecord(boolean needAppData) throws IOException {
        return readRecord(null, needAppData);
    }

    /*
     * Clear the pipeline of records from the peer, optionally returning
     * application data.   Caller is responsible for knowing that it's
     * possible to do this kind of clearing, if they don't want app
     * data -- e.g. since it's the initial SSL handshake.
     *
     * Don't synchronize (this) during a blocking read() since it
     * protects data which is accessed on the write side as well.
     */
    private int readRecord(ByteBuffer buffer, boolean needAppData)
            throws IOException {
        int state;

        // readLock protects reading and processing of an SSLInputRecord.
        // It keeps the reading from sockInput and processing of the record
        // atomic so that no two threads can be blocked on the
        // read from the same input stream at the same time.
        // This is required for example when a reader thread is
        // blocked on the read and another thread is trying to
        // close the socket. For a non-autoclose, layered socket,
        // the thread performing the close needs to read the close_notify.
        //
        // Use readLock instead of 'this' for locking because
        // 'this' also protects data accessed during writing.
        synchronized (readLock) {
            /*
             * Read and handle records ... return application data
             * ONLY if it's needed.
             */
            Plaintext plainText = null;
            while (((state = getConnectionState()) != cs_CLOSED) &&
                    (state != cs_ERROR) && (state != cs_APP_CLOSED)) {

                /*
                 * clean the buffer and check if it is too small, e.g. because
                 * the AppInputStream did not have the chance to see the
                 * current packet length but rather something like that of the
                 * handshake before. In that case we return 0 at this point to
                 * give the caller the chance to adjust the buffer.
                 */
                if (buffer != null) {
                    buffer.clear();

                    if (buffer.remaining() <
                            inputRecord.bytesInCompletePacket(sockInput)) {
                        return 0;
                    }
                }

                /*
                 * Read a record ... maybe emitting an alert if we get a
                 * comprehensible but unsupported "hello" message during
                 * format checking (e.g. V2).
                 */
                try {
                    plainText = inputRecord.decode(sockInput, buffer);
                } catch (BadPaddingException bpe) {
                    byte alertType = (state != cs_DATA) ?
                            Alerts.alert_handshake_failure :
                            Alerts.alert_bad_record_mac;
                    fatal(alertType, bpe.getMessage(), bpe);
                } catch (SSLProtocolException spe) {
                    try {
                        fatal(Alerts.alert_unexpected_message, spe);
                    } catch (IOException x) {
                        // discard this exception, throw the original exception
                    }
                    throw spe;
                } catch (SSLHandshakeException she) {
                    // may be record sequence number overflow
                    fatal(Alerts.alert_handshake_failure, she);
                } catch (EOFException eof) {
                    boolean handshaking = (connectionState <= cs_HANDSHAKE);
                    boolean rethrow = requireCloseNotify || handshaking;
                    if ((debug != null) && Debug.isOn("ssl")) {
                        System.out.println(Thread.currentThread().getName() +
                            ", received EOFException: "
                            + (rethrow ? "error" : "ignored"));
                    }
                    if (rethrow) {
                        SSLException e;
                        if (handshaking) {
                            e = new SSLHandshakeException(
                                    "Remote host terminated the handshake");
                        } else {
                            e = new SSLProtocolException(
                                    "Remote host terminated the connection");
                        }
                        e.initCause(eof);
                        throw e;
                    } else {
                        // treat as if we had received a close_notify
                        closeInternal(false);
                        continue;
                    }
                }

                // PlainText should never be null. Process input record.
                int volume = processInputRecord(plainText, needAppData);

                if (plainText.contentType == Record.ct_application_data) {
                    return volume;
                }

                if (plainText.contentType == Record.ct_handshake) {
                    if (!needAppData && connectionState == cs_DATA) {
                        return volume;
                    }   // otherwise, need to read more for app data.
                }

                // continue to read more net data
            }   // while

            //
            // couldn't read, due to some kind of error
            //
            return -1;
        }  // readLock synchronization
    }

    /*
     * Process the plainText input record.
     */
    private synchronized int processInputRecord(
            Plaintext plainText, boolean needAppData) throws IOException {

        /*
         * Process the record.
         */
        int volume = 0;    // no application data
        switch (plainText.contentType) {
            case Record.ct_handshake:
                /*
                 * Handshake messages always go to a pending session
                 * handshaker ... if there isn't one, create one.  This
                 * must work asynchronously, for renegotiation.
                 *
                 * NOTE that handshaking will either resume a session
                 * which was in the cache (and which might have other
                 * connections in it already), or else will start a new
                 * session (new keys exchanged) with just this connection
                 * in it.
                 */
                initHandshaker();
                if (!handshaker.activated()) {
                    // prior to handshaking, activate the handshake
                    if (connectionState == cs_RENEGOTIATE) {
                        // don't use SSLv2Hello when renegotiating
                        handshaker.activate(protocolVersion);
                    } else {
                        handshaker.activate(null);
                    }
                }

                /*
                 * process the handshake record ... may contain just
                 * a partial handshake message or multiple messages.
                 *
                 * The handshaker state machine will ensure that it's
                 * a finished message.
                 */
                handshaker.processRecord(plainText.fragment, expectingFinished);
                expectingFinished = false;

                if (handshaker.invalidated) {
                    handshaker = null;
                    inputRecord.setHandshakeHash(null);
                    outputRecord.setHandshakeHash(null);

                    // if state is cs_RENEGOTIATE, revert it to cs_DATA
                    if (connectionState == cs_RENEGOTIATE) {
                        connectionState = cs_DATA;
                    }
                } else if (handshaker.isDone()) {
                    // reset the parameters for secure renegotiation.
                    secureRenegotiation =
                                    handshaker.isSecureRenegotiation();
                    clientVerifyData = handshaker.getClientVerifyData();
                    serverVerifyData = handshaker.getServerVerifyData();
                    // set connection ALPN value
                    applicationProtocol =
                        handshaker.getHandshakeApplicationProtocol();

                    sess = handshaker.getSession();
                    handshakeSession = null;
                    handshaker = null;
                    inputRecord.setHandshakeHash(null);
                    outputRecord.setHandshakeHash(null);
                    connectionState = cs_DATA;

                    //
                    // Tell folk about handshake completion, but do
                    // it in a separate thread.
                    //
                    if (handshakeListeners != null) {
                        HandshakeCompletedEvent event =
                            new HandshakeCompletedEvent(this, sess);

                        Thread thread = new Thread(
                            null,
                            new NotifyHandshake(
                                handshakeListeners.entrySet(), event),
                            "HandshakeCompletedNotify-Thread",
                            0,
                            false);
                        thread.start();
                    }
                }

                break;

            case Record.ct_application_data:
                if (connectionState != cs_DATA
                        && connectionState != cs_RENEGOTIATE
                        && connectionState != cs_SENT_CLOSE) {
                    throw new SSLProtocolException(
                        "Data received in non-data state: " +
                        connectionState);
                }
                if (expectingFinished) {
                    throw new SSLProtocolException
                            ("Expecting finished message, received data");
                }
                if (!needAppData) {
                    throw new SSLException("Discarding app data");
                }

                volume = plainText.fragment.remaining();
                break;

            case Record.ct_alert:
                recvAlert(plainText.fragment);
                break;

            case Record.ct_change_cipher_spec:
                if ((connectionState != cs_HANDSHAKE
                        && connectionState != cs_RENEGOTIATE)) {
                    // For the CCS message arriving in the wrong state
                    fatal(Alerts.alert_unexpected_message,
                            "illegal change cipher spec msg, conn state = "
                            + connectionState);
                } else if (plainText.fragment.remaining() != 1
                        || plainText.fragment.get() != 1) {
                    // For structural/content issues with the CCS
                    fatal(Alerts.alert_unexpected_message,
                            "Malformed change cipher spec msg");
                }

                //
                // The first message after a change_cipher_spec
                // record MUST be a "Finished" handshake record,
                // else it's a protocol violation.  We force this
                // to be checked by a minor tweak to the state
                // machine.
                //
                handshaker.receiveChangeCipherSpec();

                CipherBox readCipher;
                Authenticator readAuthenticator;
                try {
                    readCipher = handshaker.newReadCipher();
                    readAuthenticator = handshaker.newReadAuthenticator();
                } catch (GeneralSecurityException e) {
                    // can't happen
                    throw new SSLException("Algorithm missing:  ", e);
                }
                inputRecord.changeReadCiphers(readAuthenticator, readCipher);

                // next message MUST be a finished message
                expectingFinished = true;

                break;

            default:
                //
                // TLS requires that unrecognized records be ignored.
                //
                if (debug != null && Debug.isOn("ssl")) {
                    System.out.println(Thread.currentThread().getName() +
                        ", Received record type: " + plainText.contentType);
                }
                break;
        }

        /*
         * Check the sequence number state
         *
         * Note that in order to maintain the connection I/O
         * properly, we check the sequence number after the last
         * record reading process. As we request renegotiation
         * or close the connection for wrapped sequence number
         * when there is enough sequence number space left to
         * handle a few more records, so the sequence number
         * of the last record cannot be wrapped.
         *
         * Don't bother to kickstart the renegotiation when the
         * local is asking for it.
         */
        if ((connectionState == cs_DATA) && inputRecord.seqNumIsHuge()) {
            /*
             * Ask for renegotiation when need to renew sequence number.
             *
             * Don't bother to kickstart the renegotiation when the local is
             * asking for it.
             */
            if (debug != null && Debug.isOn("ssl")) {
                System.out.println(Thread.currentThread().getName() +
                        ", request renegotiation " +
                        "to avoid sequence number overflow");
            }

            startHandshake();
        }

        return volume;
    }


    //
    // HANDSHAKE RELATED CODE
    //

    
Return the AppInputStream. For use by Handshaker only.
/**
     * Return the AppInputStream. For use by Handshaker only.
     */
    AppInputStream getAppInputStream() {
        return input;
    }

    
Return the AppOutputStream. For use by Handshaker only.
/**
     * Return the AppOutputStream. For use by Handshaker only.
     */
    AppOutputStream getAppOutputStream() {
        return output;
    }

    
Initialize the handshaker object. This means:
 . if a handshake is already in progress (state is cs_HANDSHAKE
   or cs_RENEGOTIATE), do nothing and return
 . if the socket is already closed, throw an Exception (internal error)
 . otherwise (cs_START or cs_DATA), create the appropriate handshaker
   object, and advance the connection state (to cs_HANDSHAKE or
   cs_RENEGOTIATE, respectively).
This method is called right after a new socket is created, when
starting renegotiation, or when changing client/ server mode of the
socket.
/**
     * Initialize the handshaker object. This means:
     *
     *  . if a handshake is already in progress (state is cs_HANDSHAKE
     *    or cs_RENEGOTIATE), do nothing and return
     *
     *  . if the socket is already closed, throw an Exception (internal error)
     *
     *  . otherwise (cs_START or cs_DATA), create the appropriate handshaker
     *    object, and advance the connection state (to cs_HANDSHAKE or
     *    cs_RENEGOTIATE, respectively).
     *
     * This method is called right after a new socket is created, when
     * starting renegotiation, or when changing client/ server mode of the
     * socket.
     */
    private void initHandshaker() {
        switch (connectionState) {

        //
        // Starting a new handshake.
        //
        case cs_START:
        case cs_DATA:
            break;

        //
        // We're already in the middle of a handshake.
        //
        case cs_HANDSHAKE:
        case cs_RENEGOTIATE:
            return;

        //
        // Anyone allowed to call this routine is required to
        // do so ONLY if the connection state is reasonable...
        //
        default:
            throw new IllegalStateException("Internal error");
        }

        // state is either cs_START or cs_DATA
        if (connectionState == cs_START) {
            connectionState = cs_HANDSHAKE;
        } else { // cs_DATA
            connectionState = cs_RENEGOTIATE;
        }

        if (roleIsServer) {
            handshaker = new ServerHandshaker(this, sslContext,
                    enabledProtocols, doClientAuth,
                    protocolVersion, connectionState == cs_HANDSHAKE,
                    secureRenegotiation, clientVerifyData, serverVerifyData);
            handshaker.setSNIMatchers(sniMatchers);
            handshaker.setUseCipherSuitesOrder(preferLocalCipherSuites);
        } else {
            handshaker = new ClientHandshaker(this, sslContext,
                    enabledProtocols,
                    protocolVersion, connectionState == cs_HANDSHAKE,
                    secureRenegotiation, clientVerifyData, serverVerifyData);
            handshaker.setSNIServerNames(serverNames);
        }
        handshaker.setMaximumPacketSize(maximumPacketSize);
        handshaker.setEnabledCipherSuites(enabledCipherSuites);
        handshaker.setEnableSessionCreation(enableSessionCreation);
        handshaker.setApplicationProtocols(applicationProtocols);
        handshaker.setApplicationProtocolSelectorSSLSocket(
            applicationProtocolSelector);
    }

    
Synchronously perform the initial handshake.
If the handshake is already in progress, this method blocks until it
is completed. If the initial handshake has already been completed,
it returns immediately.
/**
     * Synchronously perform the initial handshake.
     *
     * If the handshake is already in progress, this method blocks until it
     * is completed. If the initial handshake has already been completed,
     * it returns immediately.
     */
    private void performInitialHandshake() throws IOException {
        // use handshakeLock and the state check to make sure only
        // one thread performs the handshake
        synchronized (handshakeLock) {
            if (getConnectionState() == cs_HANDSHAKE) {
                kickstartHandshake();

                /*
                 * All initial handshaking goes through this operation
                 * until we have a valid SSL connection.
                 *
                 * Handle handshake messages only, need no application data.
                 */
                readRecord(false);
            }
        }
    }

    
Starts an SSL handshake on this connection.
/**
     * Starts an SSL handshake on this connection.
     */
    @Override
    public void startHandshake() throws IOException {
        // start an ssl handshake that could be resumed from timeout exception
        startHandshake(true);
    }

    
Starts an ssl handshake on this connection.
Params:
resumable – indicates the handshake process is resumable from a
         certain exception. If resumable, the socket will
         be reserved for exceptions like timeout; otherwise, the socket
         will be closed, no further communications could be done./**
     * Starts an ssl handshake on this connection.
     *
     * @param resumable indicates the handshake process is resumable from a
     *          certain exception. If <code>resumable</code>, the socket will
     *          be reserved for exceptions like timeout; otherwise, the socket
     *          will be closed, no further communications could be done.
     */
    private void startHandshake(boolean resumable) throws IOException {
        checkWrite();
        try {
            if (getConnectionState() == cs_HANDSHAKE) {
                // do initial handshake
                performInitialHandshake();
            } else {
                // start renegotiation
                kickstartHandshake();
            }
        } catch (Exception e) {
            // shutdown and rethrow (wrapped) exception as appropriate
            handleException(e, resumable);
        }
    }

    
Kickstart the handshake if it is not already in progress.
This means:
 . if handshaking is already underway, do nothing and return
 . if the socket is not connected or already closed, throw an
   Exception.
 . otherwise, call initHandshake() to initialize the handshaker
   object and progress the state. Then, send the initial
   handshaking message if appropriate (always on clients and
   on servers when renegotiating).
/**
     * Kickstart the handshake if it is not already in progress.
     * This means:
     *
     *  . if handshaking is already underway, do nothing and return
     *
     *  . if the socket is not connected or already closed, throw an
     *    Exception.
     *
     *  . otherwise, call initHandshake() to initialize the handshaker
     *    object and progress the state. Then, send the initial
     *    handshaking message if appropriate (always on clients and
     *    on servers when renegotiating).
     */
    private synchronized void kickstartHandshake() throws IOException {

        switch (connectionState) {

        case cs_HANDSHAKE:
            // handshaker already setup, proceed
            break;

        case cs_DATA:
            if (!secureRenegotiation && !Handshaker.allowUnsafeRenegotiation) {
                throw new SSLHandshakeException(
                        "Insecure renegotiation is not allowed");
            }

            if (!secureRenegotiation) {
                if (debug != null && Debug.isOn("handshake")) {
                    System.out.println(
                        "Warning: Using insecure renegotiation");
                }
            }

            // initialize the handshaker, move to cs_RENEGOTIATE
            initHandshaker();
            break;

        case cs_RENEGOTIATE:
            // handshaking already in progress, return
            return;

        /*
         * The only way to get a socket in the state is when
         * you have an unconnected socket.
         */
        case cs_START:
            throw new SocketException(
                "handshaking attempted on unconnected socket");

        default:
            throw new SocketException("connection is closed");
        }

        //
        // Kickstart handshake state machine if we need to ...
        //
        // Note that handshaker.kickstart() writes the message
        // to its HandshakeOutStream, which calls back into
        // SSLSocketImpl.writeRecord() to send it.
        //
        if (!handshaker.activated()) {
             // prior to handshaking, activate the handshake
            if (connectionState == cs_RENEGOTIATE) {
                // don't use SSLv2Hello when renegotiating
                handshaker.activate(protocolVersion);
            } else {
                handshaker.activate(null);
            }

            if (handshaker instanceof ClientHandshaker) {
                // send client hello
                handshaker.kickstart();
            } else {
                if (connectionState == cs_HANDSHAKE) {
                    // initial handshake, no kickstart message to send
                } else {
                    // we want to renegotiate, send hello request
                    handshaker.kickstart();
                }
            }
        }
    }

    //
    // CLOSURE RELATED CALLS
    //

    
Return whether the socket has been explicitly closed by the application.
/**
     * Return whether the socket has been explicitly closed by the application.
     */
    @Override
    public boolean isClosed() {
        return connectionState == cs_APP_CLOSED;
    }

    
Return whether we have reached end-of-file.
If the socket is not connected, has been shutdown because of an error
or has been closed, throw an Exception.
/**
     * Return whether we have reached end-of-file.
     *
     * If the socket is not connected, has been shutdown because of an error
     * or has been closed, throw an Exception.
     */
    boolean checkEOF() throws IOException {
        switch (getConnectionState()) {
        case cs_START:
            throw new SocketException("Socket is not connected");

        case cs_HANDSHAKE:
        case cs_DATA:
        case cs_RENEGOTIATE:
        case cs_SENT_CLOSE:
            return false;

        case cs_APP_CLOSED:
            throw new SocketException("Socket is closed");

        case cs_ERROR:
        case cs_CLOSED:
        default:
            // either closed because of error, or normal EOF
            if (closeReason == null) {
                return true;
            }
            IOException e = new SSLException
                        ("Connection has been shutdown: " + closeReason);
            e.initCause(closeReason);
            throw e;

        }
    }

    
Check if we can write data to this socket. If not, throw an IOException.
/**
     * Check if we can write data to this socket. If not, throw an IOException.
     */
    void checkWrite() throws IOException {
        if (checkEOF() || (getConnectionState() == cs_SENT_CLOSE)) {
            // we are at EOF, write must throw Exception
            throw new SocketException("Connection closed by remote host");
        }
    }

    private void closeSocket() throws IOException {

        if ((debug != null) && Debug.isOn("ssl")) {
            System.out.println(Thread.currentThread().getName() +
                                                ", called closeSocket()");
        }

        super.close();
    }

    private void closeSocket(boolean selfInitiated) throws IOException {
        if ((debug != null) && Debug.isOn("ssl")) {
            System.out.println(Thread.currentThread().getName() +
                ", called closeSocket(" + selfInitiated + ")");
        }
        if (!isLayered() || autoClose) {
            super.close();
        } else if (selfInitiated) {
            // layered && non-autoclose
            // read close_notify alert to clear input stream
            waitForClose(false);
        }
    }

    /*
     * Closing the connection is tricky ... we can't officially close the
     * connection until we know the other end is ready to go away too,
     * and if ever the connection gets aborted we must forget session
     * state (it becomes invalid).
     */

    
Closes the SSL connection.  SSL includes an application level
shutdown handshake; you should close SSL sockets explicitly
rather than leaving it for finalization, so that your remote
peer does not experience a protocol error.
/**
     * Closes the SSL connection.  SSL includes an application level
     * shutdown handshake; you should close SSL sockets explicitly
     * rather than leaving it for finalization, so that your remote
     * peer does not experience a protocol error.
     */
    @Override
    public void close() throws IOException {
        if ((debug != null) && Debug.isOn("ssl")) {
            System.out.println(Thread.currentThread().getName() +
                                                    ", called close()");
        }
        closeInternal(true);  // caller is initiating close

        // Clearup the resources.
        try {
            synchronized (readLock) {
                inputRecord.close();
            }

            writeLock.lock();
            try {
                outputRecord.close();
            } finally {
                writeLock.unlock();
            }
        } catch (IOException ioe) {
           // ignore
        }

        setConnectionState(cs_APP_CLOSED);
    }

    
Don't synchronize the whole method because waitForClose()
(which calls readRecord()) might be called.
Params:
selfInitiated – Indicates which party initiated the close.
If selfInitiated, this side is initiating a close; for layered and
non-autoclose socket, wait for close_notify response.
If !selfInitiated, peer sent close_notify; we reciprocate but
no need to wait for response./**
     * Don't synchronize the whole method because waitForClose()
     * (which calls readRecord()) might be called.
     *
     * @param selfInitiated Indicates which party initiated the close.
     * If selfInitiated, this side is initiating a close; for layered and
     * non-autoclose socket, wait for close_notify response.
     * If !selfInitiated, peer sent close_notify; we reciprocate but
     * no need to wait for response.
     */
    private void closeInternal(boolean selfInitiated) throws IOException {
        if ((debug != null) && Debug.isOn("ssl")) {
            System.out.println(Thread.currentThread().getName() +
                        ", called closeInternal(" + selfInitiated + ")");
        }

        int state = getConnectionState();
        boolean closeSocketCalled = false;
        Throwable cachedThrowable = null;
        try {
            switch (state) {
            case cs_START:
                // unconnected socket or handshaking has not been initialized
                closeSocket(selfInitiated);
                break;

            /*
             * If we're closing down due to error, we already sent (or else
             * received) the fatal alert ... no niceties, blow the connection
             * away as quickly as possible (even if we didn't allocate the
             * socket ourselves; it's unusable, regardless).
             */
            case cs_ERROR:
                closeSocket();
                break;

            /*
             * Sometimes close() gets called more than once.
             */
            case cs_CLOSED:
            case cs_APP_CLOSED:
                 break;

            /*
             * Otherwise we indicate clean termination.
             */
            // case cs_HANDSHAKE:
            // case cs_DATA:
            // case cs_RENEGOTIATE:
            // case cs_SENT_CLOSE:
            default:
                synchronized (this) {
                    if (((state = getConnectionState()) == cs_CLOSED) ||
                       (state == cs_ERROR) || (state == cs_APP_CLOSED)) {
                        return;  // connection was closed while we waited
                    }
                    if (state != cs_SENT_CLOSE) {
                        try {
                            warning(Alerts.alert_close_notify);
                            connectionState = cs_SENT_CLOSE;
                        } catch (Throwable th) {
                            // we need to ensure socket is closed out
                            // if we encounter any errors.
                            connectionState = cs_ERROR;
                            // cache this for later use
                            cachedThrowable = th;
                            closeSocketCalled = true;
                            closeSocket(selfInitiated);
                        }
                    }
                }
                // If state was cs_SENT_CLOSE before, we don't do the actual
                // closing since it is already in progress.
                if (state == cs_SENT_CLOSE) {
                    if (debug != null && Debug.isOn("ssl")) {
                        System.out.println(Thread.currentThread().getName() +
                            ", close invoked again; state = " +
                            getConnectionState());
                    }
                    if (selfInitiated == false) {
                        // We were called because a close_notify message was
                        // received. This may be due to another thread calling
                        // read() or due to our call to waitForClose() below.
                        // In either case, just return.
                        return;
                    }
                    // Another thread explicitly called close(). We need to
                    // wait for the closing to complete before returning.
                    synchronized (this) {
                        while (connectionState < cs_CLOSED) {
                            try {
                                this.wait();
                            } catch (InterruptedException e) {
                                // ignore
                            }
                        }
                    }
                    if ((debug != null) && Debug.isOn("ssl")) {
                        System.out.println(Thread.currentThread().getName() +
                            ", after primary close; state = " +
                            getConnectionState());
                    }
                    return;
                }

                if (!closeSocketCalled)  {
                    closeSocketCalled = true;
                    closeSocket(selfInitiated);
                }

                break;
            }
        } finally {
            synchronized (this) {
                // Upon exit from this method, the state is always >= cs_CLOSED
                connectionState = (connectionState == cs_APP_CLOSED)
                                ? cs_APP_CLOSED : cs_CLOSED;
                // notify any threads waiting for the closing to finish
                this.notifyAll();
            }

            if (cachedThrowable != null) {
               /*
                * Rethrow the error to the calling method
                * The Throwable caught can only be an Error or RuntimeException
                */
                if (cachedThrowable instanceof Error) {
                    throw (Error)cachedThrowable;
                } else if (cachedThrowable instanceof RuntimeException) {
                    throw (RuntimeException)cachedThrowable;
                }   // Otherwise, unlikely
            }
        }
    }

    
Reads a close_notify or a fatal alert from the input stream.
Keep reading records until we get a close_notify or until
the connection is otherwise closed.  The close_notify or alert
might be read by another reader,
which will then process the close and set the connection state.
/**
     * Reads a close_notify or a fatal alert from the input stream.
     * Keep reading records until we get a close_notify or until
     * the connection is otherwise closed.  The close_notify or alert
     * might be read by another reader,
     * which will then process the close and set the connection state.
     */
    void waitForClose(boolean rethrow) throws IOException {
        if (debug != null && Debug.isOn("ssl")) {
            System.out.println(Thread.currentThread().getName() +
                ", waiting for close_notify or alert: state "
                + getConnectionState());
        }

        try {
            int state;

            while (((state = getConnectionState()) != cs_CLOSED) &&
                   (state != cs_ERROR) && (state != cs_APP_CLOSED)) {

                // Ask for app data and then throw it away
                try {
                    readRecord(true);
                } catch (SocketTimeoutException e) {
                    if ((debug != null) && Debug.isOn("ssl")) {
                        System.out.println(
                            Thread.currentThread().getName() +
                            ", received Exception: " + e);
                    }
                    fatal((byte)(-1), "Did not receive close_notify from peer", e);
                }
            }
        } catch (IOException e) {
            if (debug != null && Debug.isOn("ssl")) {
                System.out.println(Thread.currentThread().getName() +
                    ", Exception while waiting for close " +e);
            }
            if (rethrow) {
                throw e; // pass exception up
            }
        }
    }

    //
    // EXCEPTION AND ALERT HANDLING
    //

    
Handle an exception. This method is called by top level exception
handlers (in read(), write()) to make sure we always shutdown the
connection correctly and do not pass runtime exception to the
application.
/**
     * Handle an exception. This method is called by top level exception
     * handlers (in read(), write()) to make sure we always shutdown the
     * connection correctly and do not pass runtime exception to the
     * application.
     */
    void handleException(Exception e) throws IOException {
        handleException(e, true);
    }

    
Handle an exception. This method is called by top level exception
handlers (in read(), write(), startHandshake()) to make sure we
always shutdown the connection correctly and do not pass runtime
exception to the application.
This method never returns normally, it always throws an IOException.
We first check if the socket has already been shutdown because of an
error. If so, we just rethrow the exception. If the socket has not
been shutdown, we sent a fatal alert and remember the exception.
Params:
e – the Exception
resumable – indicates the caller process is resumable from the
         exception. If resumable, the socket will be
         reserved for exceptions like timeout; otherwise, the socket
         will be closed, no further communications could be done./**
     * Handle an exception. This method is called by top level exception
     * handlers (in read(), write(), startHandshake()) to make sure we
     * always shutdown the connection correctly and do not pass runtime
     * exception to the application.
     *
     * This method never returns normally, it always throws an IOException.
     *
     * We first check if the socket has already been shutdown because of an
     * error. If so, we just rethrow the exception. If the socket has not
     * been shutdown, we sent a fatal alert and remember the exception.
     *
     * @param e the Exception
     * @param resumable indicates the caller process is resumable from the
     *          exception. If <code>resumable</code>, the socket will be
     *          reserved for exceptions like timeout; otherwise, the socket
     *          will be closed, no further communications could be done.
     */
    private synchronized void handleException(Exception e, boolean resumable)
        throws IOException {
        if ((debug != null) && Debug.isOn("ssl")) {
            System.out.println(Thread.currentThread().getName() +
                        ", handling exception: " + e.toString());
        }

        // don't close the Socket in case of timeouts or interrupts if
        // the process is resumable.
        if (e instanceof InterruptedIOException && resumable) {
            throw (IOException)e;
        }

        // if we've already shutdown because of an error,
        // there is nothing to do except rethrow the exception
        if (closeReason != null) {
            if (e instanceof IOException) { // includes SSLException
                throw (IOException)e;
            } else {
                // this is odd, not an IOException.
                // normally, this should not happen
                // if closeReason has been already been set
                throw Alerts.getSSLException(Alerts.alert_internal_error, e,
                                      "Unexpected exception");
            }
        }

        // need to perform error shutdown
        boolean isSSLException = (e instanceof SSLException);
        if ((!isSSLException) && (e instanceof IOException)) {
            // IOException from the socket
            // this means the TCP connection is already dead
            // we call fatal just to set the error status
            try {
                fatal(Alerts.alert_unexpected_message, e);
            } catch (IOException ee) {
                // ignore (IOException wrapped in SSLException)
            }
            // rethrow original IOException
            throw (IOException)e;
        }

        // must be SSLException or RuntimeException
        byte alertType;
        if (isSSLException) {
            if (e instanceof SSLHandshakeException) {
                alertType = Alerts.alert_handshake_failure;
            } else {
                alertType = Alerts.alert_unexpected_message;
            }
        } else {
            alertType = Alerts.alert_internal_error;
        }
        fatal(alertType, e);
    }

    /*
     * Send a warning alert.
     */
    void warning(byte description) {
        sendAlert(Alerts.alert_warning, description);
    }

    synchronized void fatal(byte description, String diagnostic)
            throws IOException {
        fatal(description, diagnostic, null);
    }

    synchronized void fatal(byte description, Throwable cause)
            throws IOException {
        fatal(description, null, cause);
    }

    /*
     * Send a fatal alert, and throw an exception so that callers will
     * need to stand on their heads to accidentally continue processing.
     */
    synchronized void fatal(byte description, String diagnostic,
            Throwable cause) throws IOException {

        // Be care of deadlock. Please don't synchronize readLock.
        try {
            inputRecord.close();
        } catch (IOException ioe) {
            // ignore
        }

        sess.invalidate();
        if (handshakeSession != null) {
            handshakeSession.invalidate();
        }

        int oldState = connectionState;
        if (connectionState < cs_ERROR) {
            connectionState = cs_ERROR;
        }

        /*
         * Has there been an error received yet?  If not, remember it.
         * By RFC 2246, we don't bother waiting for a response.
         * Fatal errors require immediate shutdown.
         */
        if (closeReason == null) {
            /*
             * Try to clear the kernel buffer to avoid TCP connection resets.
             */
            if (oldState == cs_HANDSHAKE) {
                sockInput.skip(sockInput.available());
            }

            // If the description equals -1, the alert won't be sent to peer.
            if (description != -1) {
                sendAlert(Alerts.alert_fatal, description);
            }
            if (cause instanceof SSLException) { // only true if != null
                closeReason = (SSLException)cause;
            } else {
                closeReason =
                    Alerts.getSSLException(description, cause, diagnostic);
            }
        }

        /*
         * Clean up our side.
         */
        closeSocket();

        // Be care of deadlock. Please don't synchronize writeLock.
        try {
            outputRecord.close();
        } catch (IOException ioe) {
            // ignore
        }

        throw closeReason;
    }


    /*
     * Process an incoming alert ... caller must already have synchronized
     * access to "this".
     */
    private void recvAlert(ByteBuffer fragment) throws IOException {
        byte level = fragment.get();
        byte description = fragment.get();

        if (description == -1) { // check for short message
            fatal(Alerts.alert_illegal_parameter, "Short alert message");
        }

        if (debug != null && (Debug.isOn("record") ||
                Debug.isOn("handshake"))) {
            synchronized (System.out) {
                System.out.print(Thread.currentThread().getName());
                System.out.print(", RECV " + protocolVersion + " ALERT:  ");
                if (level == Alerts.alert_fatal) {
                    System.out.print("fatal, ");
                } else if (level == Alerts.alert_warning) {
                    System.out.print("warning, ");
                } else {
                    System.out.print("<level " + (0x0ff & level) + ">, ");
                }
                System.out.println(Alerts.alertDescription(description));
            }
        }

        if (level == Alerts.alert_warning) {
            if (description == Alerts.alert_close_notify) {
                if (connectionState == cs_HANDSHAKE) {
                    fatal(Alerts.alert_unexpected_message,
                                "Received close_notify during handshake");
                } else {
                    closeInternal(false);  // reply to close
                }
            } else {

                //
                // The other legal warnings relate to certificates,
                // e.g. no_certificate, bad_certificate, etc; these
                // are important to the handshaking code, which can
                // also handle illegal protocol alerts if needed.
                //
                if (handshaker != null) {
                    handshaker.handshakeAlert(description);
                }
            }
        } else { // fatal or unknown level
            String reason = "Received fatal alert: "
                + Alerts.alertDescription(description);
            if (closeReason == null) {
                closeReason = Alerts.getSSLException(description, reason);
            }
            fatal(Alerts.alert_unexpected_message, reason);
        }
    }


    /*
     * Emit alerts.  Caller must have synchronized with "this".
     */
    private void sendAlert(byte level, byte description) {
        // the connectionState cannot be cs_START
        if (connectionState >= cs_SENT_CLOSE) {
            return;
        }

        // For initial handshaking, don't send alert message to peer if
        // handshaker has not started.
        //
        // Shall we send an fatal alter to terminate the connection gracefully?
        if (connectionState <= cs_HANDSHAKE &&
                (handshaker == null || !handshaker.started() ||
                        !handshaker.activated())) {
            return;
        }

        boolean useDebug = debug != null && Debug.isOn("ssl");
        if (useDebug) {
            synchronized (System.out) {
                System.out.print(Thread.currentThread().getName());
                System.out.print(", SEND " + protocolVersion + " ALERT:  ");
                if (level == Alerts.alert_fatal) {
                    System.out.print("fatal, ");
                } else if (level == Alerts.alert_warning) {
                    System.out.print("warning, ");
                } else {
                    System.out.print("<level = " + (0x0ff & level) + ">, ");
                }
                System.out.println("description = "
                        + Alerts.alertDescription(description));
            }
        }

        try {
            writeAlert(level, description);
        } catch (IOException e) {
            if (useDebug) {
                System.out.println(Thread.currentThread().getName() +
                    ", Exception sending alert: " + e);
            }
        }
    }

    //
    // VARIOUS OTHER METHODS
    //

    // used by Handshaker
    void changeWriteCiphers() throws IOException {
        Authenticator writeAuthenticator;
        CipherBox writeCipher;
        try {
            writeCipher = handshaker.newWriteCipher();
            writeAuthenticator = handshaker.newWriteAuthenticator();
        } catch (GeneralSecurityException e) {
            // "can't happen"
            throw new SSLException("Algorithm missing:  ", e);
        }
        outputRecord.changeWriteCiphers(writeAuthenticator, writeCipher);
    }

    /*
     * Updates the SSL version associated with this connection.
     * Called from Handshaker once it has determined the negotiated version.
     */
    synchronized void setVersion(ProtocolVersion protocolVersion) {
        this.protocolVersion = protocolVersion;
        outputRecord.setVersion(protocolVersion);
    }

    //
    // ONLY used by ClientHandshaker for the server hostname during handshaking
    //
    synchronized String getHost() {
        // Note that the host may be null or empty for localhost.
        if (host == null || host.length() == 0) {
            useImplicitHost(true);
        }

        return host;
    }

    /*
     * Try to set and use the implicit specified hostname
     */
    private synchronized void useImplicitHost(boolean noSniUpdate) {

        // Note: If the local name service is not trustworthy, reverse
        // host name resolution should not be performed for endpoint
        // identification.  Use the application original specified
        // hostname or IP address instead.

        // Get the original hostname via jdk.internal.misc.SharedSecrets
        InetAddress inetAddress = getInetAddress();
        if (inetAddress == null) {      // not connected
            return;
        }

        JavaNetInetAddressAccess jna =
                SharedSecrets.getJavaNetInetAddressAccess();
        String originalHostname = jna.getOriginalHostName(inetAddress);
        if ((originalHostname != null) &&
                (originalHostname.length() != 0)) {

            host = originalHostname;
            if (!noSniUpdate && serverNames.isEmpty() && !noSniExtension) {
                serverNames =
                        Utilities.addToSNIServerNameList(serverNames, host);

                if (!roleIsServer &&
                        (handshaker != null) && !handshaker.activated()) {
                    handshaker.setSNIServerNames(serverNames);
                }
            }

            return;
        }

        // No explicitly specified hostname, no server name indication.
        if (!trustNameService) {
            // The local name service is not trustworthy, use IP address.
            host = inetAddress.getHostAddress();
        } else {
            // Use the underlying reverse host name resolution service.
            host = getInetAddress().getHostName();
        }
    }

    // ONLY used by HttpsClient to setup the URI specified hostname
    //
    // Please NOTE that this method MUST be called before calling to
    // SSLSocket.setSSLParameters(). Otherwise, the {@code host} parameter
    // may override SNIHostName in the customized server name indication.
    public synchronized void setHost(String host) {
        this.host = host;
        this.serverNames =
            Utilities.addToSNIServerNameList(this.serverNames, this.host);

        if (!roleIsServer && (handshaker != null) && !handshaker.activated()) {
            handshaker.setSNIServerNames(serverNames);
        }
    }

    
Gets an input stream to read from the peer on the other side.
Data read from this stream was always integrity protected in
transit, and will usually have been confidentiality protected.
/**
     * Gets an input stream to read from the peer on the other side.
     * Data read from this stream was always integrity protected in
     * transit, and will usually have been confidentiality protected.
     */
    @Override
    public synchronized InputStream getInputStream() throws IOException {
        if (isClosed()) {
            throw new SocketException("Socket is closed");
        }

        /*
         * Can't call isConnected() here, because the Handshakers
         * do some initialization before we actually connect.
         */
        if (connectionState == cs_START) {
            throw new SocketException("Socket is not connected");
        }

        return input;
    }

    
Gets an output stream to write to the peer on the other side.
Data written on this stream is always integrity protected, and
will usually be confidentiality protected.
/**
     * Gets an output stream to write to the peer on the other side.
     * Data written on this stream is always integrity protected, and
     * will usually be confidentiality protected.
     */
    @Override
    public synchronized OutputStream getOutputStream() throws IOException {
        if (isClosed()) {
            throw new SocketException("Socket is closed");
        }

        /*
         * Can't call isConnected() here, because the Handshakers
         * do some initialization before we actually connect.
         */
        if (connectionState == cs_START) {
            throw new SocketException("Socket is not connected");
        }

        return output;
    }

    
Returns the SSL Session in use by this connection.  These can
be long lived, and frequently correspond to an entire login session
for some user.
/**
     * Returns the SSL Session in use by this connection.  These can
     * be long lived, and frequently correspond to an entire login session
     * for some user.
     */
    @Override
    public SSLSession getSession() {
        /*
         * Force a synchronous handshake, if appropriate.
         */
        if (getConnectionState() == cs_HANDSHAKE) {
            try {
                // start handshaking, if failed, the connection will be closed.
                startHandshake(false);
            } catch (IOException e) {
                // handshake failed. log and return a nullSession
                if (debug != null && Debug.isOn("handshake")) {
                      System.out.println(Thread.currentThread().getName() +
                          ", IOException in getSession():  " + e);
                }
            }
        }
        synchronized (this) {
            return sess;
        }
    }

    @Override
    public synchronized SSLSession getHandshakeSession() {
        return handshakeSession;
    }

    synchronized void setHandshakeSession(SSLSessionImpl session) {
        // update the fragment size, which may be negotiated during handshaking
        inputRecord.changeFragmentSize(session.getNegotiatedMaxFragSize());
        outputRecord.changeFragmentSize(session.getNegotiatedMaxFragSize());

        handshakeSession = session;
    }

    
Controls whether new connections may cause creation of new SSL
sessions.
As long as handshaking has not started, we can change
whether we enable session creations.  Otherwise,
we will need to wait for the next handshake.
/**
     * Controls whether new connections may cause creation of new SSL
     * sessions.
     *
     * As long as handshaking has not started, we can change
     * whether we enable session creations.  Otherwise,
     * we will need to wait for the next handshake.
     */
    @Override
    public synchronized void setEnableSessionCreation(boolean flag) {
        enableSessionCreation = flag;

        if ((handshaker != null) && !handshaker.activated()) {
            handshaker.setEnableSessionCreation(enableSessionCreation);
        }
    }

    
Returns true if new connections may cause creation of new SSL
sessions.
/**
     * Returns true if new connections may cause creation of new SSL
     * sessions.
     */
    @Override
    public synchronized boolean getEnableSessionCreation() {
        return enableSessionCreation;
    }


    
Sets the flag controlling whether a server mode socket
 *REQUIRES* SSL client authentication.
As long as handshaking has not started, we can change
whether client authentication is needed.  Otherwise,
we will need to wait for the next handshake.
/**
     * Sets the flag controlling whether a server mode socket
     * *REQUIRES* SSL client authentication.
     *
     * As long as handshaking has not started, we can change
     * whether client authentication is needed.  Otherwise,
     * we will need to wait for the next handshake.
     */
    @Override
    public synchronized void setNeedClientAuth(boolean flag) {
        doClientAuth = (flag ? ClientAuthType.CLIENT_AUTH_REQUIRED :
                ClientAuthType.CLIENT_AUTH_NONE);

        if ((handshaker != null) &&
                (handshaker instanceof ServerHandshaker) &&
                !handshaker.activated()) {
            ((ServerHandshaker) handshaker).setClientAuth(doClientAuth);
        }
    }

    @Override
    public synchronized boolean getNeedClientAuth() {
        return (doClientAuth == ClientAuthType.CLIENT_AUTH_REQUIRED);
    }

    
Sets the flag controlling whether a server mode socket
 *REQUESTS* SSL client authentication.
As long as handshaking has not started, we can change
whether client authentication is requested.  Otherwise,
we will need to wait for the next handshake.
/**
     * Sets the flag controlling whether a server mode socket
     * *REQUESTS* SSL client authentication.
     *
     * As long as handshaking has not started, we can change
     * whether client authentication is requested.  Otherwise,
     * we will need to wait for the next handshake.
     */
    @Override
    public synchronized void setWantClientAuth(boolean flag) {
        doClientAuth = (flag ? ClientAuthType.CLIENT_AUTH_REQUESTED :
                ClientAuthType.CLIENT_AUTH_NONE);

        if ((handshaker != null) &&
                (handshaker instanceof ServerHandshaker) &&
                !handshaker.activated()) {
            ((ServerHandshaker) handshaker).setClientAuth(doClientAuth);
        }
    }

    @Override
    public synchronized boolean getWantClientAuth() {
        return (doClientAuth == ClientAuthType.CLIENT_AUTH_REQUESTED);
    }


    
Sets the flag controlling whether the socket is in SSL
client or server mode.  Must be called before any SSL
traffic has started.
/**
     * Sets the flag controlling whether the socket is in SSL
     * client or server mode.  Must be called before any SSL
     * traffic has started.
     */
    @Override
    @SuppressWarnings("fallthrough")
    public synchronized void setUseClientMode(boolean flag) {
        switch (connectionState) {

        case cs_START:
            /*
             * If we need to change the socket mode and the enabled
             * protocols and cipher suites haven't specifically been
             * set by the user, change them to the corresponding
             * default ones.
             */
            if (roleIsServer != (!flag)) {
                if (sslContext.isDefaultProtocolList(enabledProtocols)) {
                    enabledProtocols =
                            sslContext.getDefaultProtocolList(!flag);
                }

                if (sslContext.isDefaultCipherSuiteList(enabledCipherSuites)) {
                    enabledCipherSuites =
                            sslContext.getDefaultCipherSuiteList(!flag);
                }
            }

            roleIsServer = !flag;
            break;

        case cs_HANDSHAKE:
            /*
             * If we have a handshaker, but haven't started
             * SSL traffic, we can throw away our current
             * handshaker, and start from scratch.  Don't
             * need to call doneConnect() again, we already
             * have the streams.
             */
            assert(handshaker != null);
            if (!handshaker.activated()) {
                /*
                 * If we need to change the socket mode and the enabled
                 * protocols and cipher suites haven't specifically been
                 * set by the user, change them to the corresponding
                 * default ones.
                 */
                if (roleIsServer != (!flag)) {
                    if (sslContext.isDefaultProtocolList(enabledProtocols)) {
                        enabledProtocols =
                                sslContext.getDefaultProtocolList(!flag);
                    }

                    if (sslContext.isDefaultCipherSuiteList(
                                                    enabledCipherSuites)) {
                        enabledCipherSuites =
                            sslContext.getDefaultCipherSuiteList(!flag);
                    }
                }

                roleIsServer = !flag;
                connectionState = cs_START;
                initHandshaker();
                break;
            }

            // If handshake has started, that's an error.  Fall through...

        default:
            if (debug != null && Debug.isOn("ssl")) {
                System.out.println(Thread.currentThread().getName() +
                    ", setUseClientMode() invoked in state = " +
                    connectionState);
            }
            throw new IllegalArgumentException(
                "Cannot change mode after SSL traffic has started");
        }
    }

    @Override
    public synchronized boolean getUseClientMode() {
        return !roleIsServer;
    }


    
Returns the names of the cipher suites which could be enabled for use
on an SSL connection.  Normally, only a subset of these will actually
be enabled by default, since this list may include cipher suites which
do not support the mutual authentication of servers and clients, or
which do not protect data confidentiality.  Servers may also need
certain kinds of certificates to use certain cipher suites.
Returns:
an array of cipher suite names/**
     * Returns the names of the cipher suites which could be enabled for use
     * on an SSL connection.  Normally, only a subset of these will actually
     * be enabled by default, since this list may include cipher suites which
     * do not support the mutual authentication of servers and clients, or
     * which do not protect data confidentiality.  Servers may also need
     * certain kinds of certificates to use certain cipher suites.
     *
     * @return an array of cipher suite names
     */
    @Override
    public String[] getSupportedCipherSuites() {
        return sslContext.getSupportedCipherSuiteList().toStringArray();
    }

    
Controls which particular cipher suites are enabled for use on
this connection.  The cipher suites must have been listed by
getCipherSuites() as being supported.  Even if a suite has been
enabled, it might never be used if no peer supports it or the
requisite certificates (and private keys) are not available.
Params:
suites – Names of all the cipher suites to enable./**
     * Controls which particular cipher suites are enabled for use on
     * this connection.  The cipher suites must have been listed by
     * getCipherSuites() as being supported.  Even if a suite has been
     * enabled, it might never be used if no peer supports it or the
     * requisite certificates (and private keys) are not available.
     *
     * @param suites Names of all the cipher suites to enable.
     */
    @Override
    public synchronized void setEnabledCipherSuites(String[] suites) {
        enabledCipherSuites = new CipherSuiteList(suites);
        if ((handshaker != null) && !handshaker.activated()) {
            handshaker.setEnabledCipherSuites(enabledCipherSuites);
        }
    }

    
Returns the names of the SSL cipher suites which are currently enabled
for use on this connection.  When an SSL socket is first created,
all enabled cipher suites (a) protect data confidentiality,
by traffic encryption, and (b) can mutually authenticate
both clients and servers.  Thus, in some environments, this value
might be empty.
Returns:
an array of cipher suite names/**
     * Returns the names of the SSL cipher suites which are currently enabled
     * for use on this connection.  When an SSL socket is first created,
     * all enabled cipher suites <em>(a)</em> protect data confidentiality,
     * by traffic encryption, and <em>(b)</em> can mutually authenticate
     * both clients and servers.  Thus, in some environments, this value
     * might be empty.
     *
     * @return an array of cipher suite names
     */
    @Override
    public synchronized String[] getEnabledCipherSuites() {
        return enabledCipherSuites.toStringArray();
    }


    
Returns the protocols that are supported by this implementation.
A subset of the supported protocols may be enabled for this connection
Returns:
an array of protocol names./**
     * Returns the protocols that are supported by this implementation.
     * A subset of the supported protocols may be enabled for this connection
     * @return an array of protocol names.
     */
    @Override
    public String[] getSupportedProtocols() {
        return sslContext.getSuportedProtocolList().toStringArray();
    }

    
Controls which protocols are enabled for use on
this connection.  The protocols must have been listed by
getSupportedProtocols() as being supported.
Params:
protocols – protocols to enable.
Throws:
IllegalArgumentException – when one of the protocols
 named by the parameter is not supported./**
     * Controls which protocols are enabled for use on
     * this connection.  The protocols must have been listed by
     * getSupportedProtocols() as being supported.
     *
     * @param protocols protocols to enable.
     * @exception IllegalArgumentException when one of the protocols
     *  named by the parameter is not supported.
     */
    @Override
    public synchronized void setEnabledProtocols(String[] protocols) {
        enabledProtocols = new ProtocolList(protocols);
        if ((handshaker != null) && !handshaker.activated()) {
            handshaker.setEnabledProtocols(enabledProtocols);
        }
    }

    @Override
    public synchronized String[] getEnabledProtocols() {
        return enabledProtocols.toStringArray();
    }

    
Assigns the socket timeout.
See Also:
setSoTimeout.setSoTimeout/**
     * Assigns the socket timeout.
     * @see java.net.Socket#setSoTimeout
     */
    @Override
    public void setSoTimeout(int timeout) throws SocketException {
        if ((debug != null) && Debug.isOn("ssl")) {
            System.out.println(Thread.currentThread().getName() +
                ", setSoTimeout(" + timeout + ") called");
        }

        super.setSoTimeout(timeout);
    }

    
Registers an event listener to receive notifications that an
SSL handshake has completed on this connection.
/**
     * Registers an event listener to receive notifications that an
     * SSL handshake has completed on this connection.
     */
    @Override
    public synchronized void addHandshakeCompletedListener(
            HandshakeCompletedListener listener) {
        if (listener == null) {
            throw new IllegalArgumentException("listener is null");
        }
        if (handshakeListeners == null) {
            handshakeListeners = new
                HashMap<HandshakeCompletedListener, AccessControlContext>(4);
        }
        handshakeListeners.put(listener, AccessController.getContext());
    }


    
Removes a previously registered handshake completion listener.
/**
     * Removes a previously registered handshake completion listener.
     */
    @Override
    public synchronized void removeHandshakeCompletedListener(
            HandshakeCompletedListener listener) {
        if (handshakeListeners == null) {
            throw new IllegalArgumentException("no listeners");
        }
        if (handshakeListeners.remove(listener) == null) {
            throw new IllegalArgumentException("listener not registered");
        }
        if (handshakeListeners.isEmpty()) {
            handshakeListeners = null;
        }
    }

    
Returns the SSLParameters in effect for this SSLSocket.
/**
     * Returns the SSLParameters in effect for this SSLSocket.
     */
    @Override
    public synchronized SSLParameters getSSLParameters() {
        SSLParameters params = super.getSSLParameters();

        // the super implementation does not handle the following parameters
        params.setEndpointIdentificationAlgorithm(identificationProtocol);
        params.setAlgorithmConstraints(algorithmConstraints);

        if (sniMatchers.isEmpty() && !noSniMatcher) {
            // 'null' indicates none has been set
            params.setSNIMatchers(null);
        } else {
            params.setSNIMatchers(sniMatchers);
        }

        if (serverNames.isEmpty() && !noSniExtension) {
            // 'null' indicates none has been set
            params.setServerNames(null);
        } else {
            params.setServerNames(serverNames);
        }

        params.setUseCipherSuitesOrder(preferLocalCipherSuites);
        params.setMaximumPacketSize(maximumPacketSize);
        params.setApplicationProtocols(applicationProtocols);

        // DTLS handshake retransmissions parameter does not apply here.

        return params;
    }

    
Applies SSLParameters to this socket.
/**
     * Applies SSLParameters to this socket.
     */
    @Override
    public synchronized void setSSLParameters(SSLParameters params) {
        super.setSSLParameters(params);

        // the super implementation does not handle the following parameters
        identificationProtocol = params.getEndpointIdentificationAlgorithm();
        algorithmConstraints = params.getAlgorithmConstraints();
        preferLocalCipherSuites = params.getUseCipherSuitesOrder();
        maximumPacketSize = params.getMaximumPacketSize();

        // DTLS handshake retransmissions parameter does not apply here.

        if (maximumPacketSize != 0) {
            outputRecord.changePacketSize(maximumPacketSize);
        } else {
            // use the implicit maximum packet size.
            maximumPacketSize = outputRecord.getMaxPacketSize();
        }

        List<SNIServerName> sniNames = params.getServerNames();
        if (sniNames != null) {
            noSniExtension = sniNames.isEmpty();
            serverNames = sniNames;
        }

        Collection<SNIMatcher> matchers = params.getSNIMatchers();
        if (matchers != null) {
            noSniMatcher = matchers.isEmpty();
            sniMatchers = matchers;
        }

        applicationProtocols = params.getApplicationProtocols();

        if ((handshaker != null) && !handshaker.activated()) {
            handshaker.setIdentificationProtocol(identificationProtocol);
            handshaker.setAlgorithmConstraints(algorithmConstraints);
            handshaker.setMaximumPacketSize(maximumPacketSize);
            handshaker.setApplicationProtocols(applicationProtocols);
            if (roleIsServer) {
                handshaker.setSNIMatchers(sniMatchers);
                handshaker.setUseCipherSuitesOrder(preferLocalCipherSuites);
            } else {
                handshaker.setSNIServerNames(serverNames);
            }
        }
    }

    @Override
    public synchronized String getApplicationProtocol() {
        return applicationProtocol;
    }

    @Override
    public synchronized String getHandshakeApplicationProtocol() {
        if ((handshaker != null) && handshaker.started()) {
            return handshaker.getHandshakeApplicationProtocol();
        }
        return null;
    }

    @Override
    public synchronized void setHandshakeApplicationProtocolSelector(
        BiFunction<SSLSocket, List<String>, String> selector) {
        applicationProtocolSelector = selector;
        if ((handshaker != null) && !handshaker.activated()) {
            handshaker.setApplicationProtocolSelectorSSLSocket(selector);
        }
    }

    @Override
    public synchronized BiFunction<SSLSocket, List<String>, String>
        getHandshakeApplicationProtocolSelector() {
        return this.applicationProtocolSelector;
    }

    //
    // We allocate a separate thread to deliver handshake completion
    // events.  This ensures that the notifications don't block the
    // protocol state machine.
    //
    private static class NotifyHandshake implements Runnable {

        private Set<Map.Entry<HandshakeCompletedListener,AccessControlContext>>
                targets;        // who gets notified
        private HandshakeCompletedEvent event;          // the notification

        NotifyHandshake(
            Set<Map.Entry<HandshakeCompletedListener,AccessControlContext>>
            entrySet, HandshakeCompletedEvent e) {

            targets = new HashSet<>(entrySet);          // clone the entry set
            event = e;
        }

        @Override
        public void run() {
            // Don't need to synchronize, as it only runs in one thread.
            for (Map.Entry<HandshakeCompletedListener,AccessControlContext>
                entry : targets) {

                final HandshakeCompletedListener l = entry.getKey();
                AccessControlContext acc = entry.getValue();
                AccessController.doPrivileged(new PrivilegedAction<Void>() {
                    @Override
                    public Void run() {
                        l.handshakeCompleted(event);
                        return null;
                    }
                }, acc);
            }
        }
    }

    
Returns a printable representation of this end of the connection.
/**
     * Returns a printable representation of this end of the connection.
     */
    @Override
    public String toString() {
        StringBuilder retval = new StringBuilder(80);

        retval.append(Integer.toHexString(hashCode()));
        retval.append("[");
        retval.append(sess.getCipherSuite());
        retval.append(": ");

        retval.append(super.toString());
        retval.append("]");

        return retval.toString();
    }
}