ExtendedSocketOptions.java

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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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 * accompanied this code).
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package jdk.net;

import java.io.FileDescriptor;
import java.net.SocketException;
import java.net.SocketOption;
import java.security.AccessController;
import java.security.PrivilegedAction;
import java.util.Collections;
import java.util.HashSet;
import java.util.Set;
import jdk.internal.misc.JavaIOFileDescriptorAccess;
import jdk.internal.misc.SharedSecrets;

/**
 * Defines extended socket options, beyond those defined in {@link java.net.StandardSocketOptions}.
 * These options may be platform specific.
 *
 * @since 1.8
 */
// 扩展的Socket参数， 这里的Socket参数可能是依赖平台实现的
public final class ExtendedSocketOptions {
    
    /**
     * Service level properties. When a security manager is installed,
     * setting or getting this option requires a {@link NetworkPermission}
     * {@code ("setOption.SO_FLOW_SLA")} or {@code "getOption.SO_FLOW_SLA"}
     * respectively.
     */
    public static final SocketOption<SocketFlow> SO_FLOW_SLA = new ExtSocketOption<>("SO_FLOW_SLA", SocketFlow.class);
    
    /**
     * Disable Delayed Acknowledgements.
     *
     * <p>
     * This socket option can be used to reduce or disable delayed
     * acknowledgments (ACKs). When {@code TCP_QUICKACK} is enabled, ACKs are
     * sent immediately, rather than delayed if needed in accordance to normal
     * TCP operation. This option is not permanent, it only enables a switch to
     * or from {@code TCP_QUICKACK} mode. Subsequent operations of the TCP
     * protocol will once again disable/enable {@code TCP_QUICKACK} mode
     * depending on internal protocol processing and factors such as delayed ACK
     * timeouts occurring and data transfer, therefore this option needs to be
     * set with {@code setOption} after each operation of TCP on a given socket.
     *
     * <p>
     * The value of this socket option is a {@code Boolean} that represents
     * whether the option is enabled or disabled. The socket option is specific
     * to stream-oriented sockets using the TCP/IP protocol. The exact semantics
     * of this socket option are socket type and system dependent.
     *
     * @since 10
     */
    public static final SocketOption<Boolean> TCP_QUICKACK = new ExtSocketOption<>("TCP_QUICKACK", Boolean.class);
    
    /**
     * Keep-Alive idle time.
     *
     * <p>
     * The value of this socket option is an {@code Integer} that is the number
     * of seconds of idle time before keep-alive initiates a probe. The socket
     * option is specific to stream-oriented sockets using the TCP/IP protocol.
     * The exact semantics of this socket option are system dependent.
     *
     * <p>
     * When the {@link java.net.StandardSocketOptions#SO_KEEPALIVE
     * SO_KEEPALIVE} option is enabled, TCP probes a connection that has been
     * idle for some amount of time. The default value for this idle period is
     * system dependent, but is typically 2 hours. The {@code TCP_KEEPIDLE}
     * option can be used to affect this value for a given socket.
     *
     * @since 11
     */
    public static final SocketOption<Integer> TCP_KEEPIDLE = new ExtSocketOption<>("TCP_KEEPIDLE", Integer.class);
    
    /**
     * Keep-Alive retransmission interval time.
     *
     * <p>
     * The value of this socket option is an {@code Integer} that is the number
     * of seconds to wait before retransmitting a keep-alive probe. The socket
     * option is specific to stream-oriented sockets using the TCP/IP protocol.
     * The exact semantics of this socket option are system dependent.
     *
     * <p>
     * When the {@link java.net.StandardSocketOptions#SO_KEEPALIVE
     * SO_KEEPALIVE} option is enabled, TCP probes a connection that has been
     * idle for some amount of time. If the remote system does not respond to a
     * keep-alive probe, TCP retransmits the probe after some amount of time.
     * The default value for this retransmission interval is system dependent,
     * but is typically 75 seconds. The {@code TCP_KEEPINTERVAL} option can be
     * used to affect this value for a given socket.
     *
     * @since 11
     */
    public static final SocketOption<Integer> TCP_KEEPINTERVAL = new ExtSocketOption<>("TCP_KEEPINTERVAL", Integer.class);
    
    /**
     * Keep-Alive retransmission maximum limit.
     *
     * <p>
     * The value of this socket option is an {@code Integer} that is the maximum
     * number of keep-alive probes to be sent. The socket option is specific to
     * stream-oriented sockets using the TCP/IP protocol. The exact semantics of
     * this socket option are system dependent.
     *
     * <p>
     * When the {@link java.net.StandardSocketOptions#SO_KEEPALIVE
     * SO_KEEPALIVE} option is enabled, TCP probes a connection that has been
     * idle for some amount of time. If the remote system does not respond to a
     * keep-alive probe, TCP retransmits the probe a certain number of times
     * before a connection is considered to be broken. The default value for
     * this keep-alive probe retransmit limit is system dependent, but is
     * typically 8. The {@code TCP_KEEPCOUNT} option can be used to affect this
     * value for a given socket.
     *
     * @since 11
     */
    public static final SocketOption<Integer> TCP_KEEPCOUNT = new ExtSocketOption<>("TCP_KEEPCOUNT", Integer.class);
    
    private static final PlatformSocketOptions platformSocketOptions = PlatformSocketOptions.get();
    
    private static final boolean flowSupported = platformSocketOptions.flowSupported();
    private static final boolean quickAckSupported = platformSocketOptions.quickAckSupported();
    private static final boolean keepAliveOptSupported = platformSocketOptions.keepAliveOptionsSupported();
    
    // 获取平台支持的socket扩展参数
    private static final Set<SocketOption<?>> extendedOptions = options();
    
    // FileDescriptor后门
    private static final JavaIOFileDescriptorAccess fdAccess = SharedSecrets.getJavaIOFileDescriptorAccess();
    
    
    static {
        /* Registers the extended socket options with the base module. */
        sun.net.ext.ExtendedSocketOptions.register(new sun.net.ext.ExtendedSocketOptions(extendedOptions) {
            
            // 返回socket指定参数的值
            @Override
            public Object getOption(FileDescriptor socket, SocketOption<?> option) throws SocketException {
                SecurityManager sm = System.getSecurityManager();
                if(sm != null) {
                    sm.checkPermission(new NetworkPermission("getOption." + option.name()));
                }
                
                if(socket == null || !socket.valid()) {
                    throw new SocketException("socket closed");
                }
                
                if(option == SO_FLOW_SLA) {
                    assert flowSupported;
                    SocketFlow flow = SocketFlow.create();
                    getFlowOption(socket, flow);
                    return flow;
                } else if(option == TCP_QUICKACK) {
                    return getQuickAckOption(socket);
                } else if(option == TCP_KEEPCOUNT) {
                    return getTcpkeepAliveProbes(socket);
                } else if(option == TCP_KEEPIDLE) {
                    return getTcpKeepAliveTime(socket);
                } else if(option == TCP_KEEPINTERVAL) {
                    return getTcpKeepAliveIntvl(socket);
                } else {
                    throw new InternalError("Unexpected option " + option);
                }
            }
            
            // 为socket的指定参数设置值
            @Override
            public void setOption(FileDescriptor socket, SocketOption<?> option, Object value) throws SocketException {
                SecurityManager sm = System.getSecurityManager();
                if(sm != null) {
                    sm.checkPermission(new NetworkPermission("setOption." + option.name()));
                }
                
                if(socket == null || !socket.valid()) {
                    throw new SocketException("socket closed");
                }
                
                if(option == SO_FLOW_SLA) {
                    assert flowSupported;
                    SocketFlow flow = checkValueType(value, option.type());
                    setFlowOption(socket, flow);
                } else if(option == TCP_QUICKACK) {
                    setQuickAckOption(socket, (boolean) value);
                } else if(option == TCP_KEEPCOUNT) {
                    setTcpkeepAliveProbes(socket, (Integer) value);
                } else if(option == TCP_KEEPIDLE) {
                    setTcpKeepAliveTime(socket, (Integer) value);
                } else if(option == TCP_KEEPINTERVAL) {
                    setTcpKeepAliveIntvl(socket, (Integer) value);
                } else {
                    throw new InternalError("Unexpected option " + option);
                }
            }
            
        });
    }
    
    
    private ExtendedSocketOptions() {
    }
    
    
    // 返回平台支持的socket扩展参数
    static Set<SocketOption<?>> options() {
        Set<SocketOption<?>> options = new HashSet<>();
        
        if(flowSupported) {
            options.add(SO_FLOW_SLA);
        }
        
        if(quickAckSupported) {
            options.add(TCP_QUICKACK);
        }
        
        if(keepAliveOptSupported) {
            options.addAll(Set.of(TCP_KEEPCOUNT, TCP_KEEPIDLE, TCP_KEEPINTERVAL));
        }
        
        return Collections.unmodifiableSet(options);
    }
    
    @SuppressWarnings("unchecked")
    private static <T> T checkValueType(Object value, Class<?> type) {
        if(!type.isAssignableFrom(value.getClass())) {
            String s = "Found: " + value.getClass() + ", Expected: " + type;
            throw new IllegalArgumentException(s);
        }
        
        return (T) value;
    }
    
    private static void getFlowOption(FileDescriptor socket, SocketFlow flow) throws SocketException {
        int status = platformSocketOptions.getFlowOption(fdAccess.get(socket), flow);
        flow.status(status);  // augment the given flow with the status
    }
    
    private static void setFlowOption(FileDescriptor socket, SocketFlow flow) throws SocketException {
        int status = platformSocketOptions.setFlowOption(fdAccess.get(socket), flow.priority(), flow.bandwidth());
        flow.status(status);  // augment the given flow with the status
    }
    
    private static Object getQuickAckOption(FileDescriptor socket) throws SocketException {
        return platformSocketOptions.getQuickAck(fdAccess.get(socket));
    }
    
    private static void setQuickAckOption(FileDescriptor socket, boolean enable) throws SocketException {
        platformSocketOptions.setQuickAck(fdAccess.get(socket), enable);
    }
    
    private static int getTcpkeepAliveProbes(FileDescriptor socket) throws SocketException {
        return platformSocketOptions.getTcpkeepAliveProbes(fdAccess.get(socket));
    }
    
    private static void setTcpkeepAliveProbes(FileDescriptor socket, int value) throws SocketException {
        platformSocketOptions.setTcpkeepAliveProbes(fdAccess.get(socket), value);
    }
    
    private static int getTcpKeepAliveIntvl(FileDescriptor socket) throws SocketException {
        return platformSocketOptions.getTcpKeepAliveIntvl(fdAccess.get(socket));
    }
    
    private static void setTcpKeepAliveIntvl(FileDescriptor socket, int value) throws SocketException {
        platformSocketOptions.setTcpKeepAliveIntvl(fdAccess.get(socket), value);
    }
    
    private static int getTcpKeepAliveTime(FileDescriptor socket) throws SocketException {
        return platformSocketOptions.getTcpKeepAliveTime(fdAccess.get(socket));
    }
    
    private static void setTcpKeepAliveTime(FileDescriptor socket, int value) throws SocketException {
        platformSocketOptions.setTcpKeepAliveTime(fdAccess.get(socket), value);
    }
    
    
    // windows平台的socket扩展参数
    static class PlatformSocketOptions {
        
        private static final PlatformSocketOptions instance = create();
        
        protected PlatformSocketOptions() {
        }
        
        static PlatformSocketOptions get() {
            return instance;
        }
        
        int getFlowOption(int fd, SocketFlow f) throws SocketException {
            throw new UnsupportedOperationException("unsupported socket option");
        }
        
        int setFlowOption(int fd, int priority, long bandwidth) throws SocketException {
            throw new UnsupportedOperationException("unsupported socket option");
        }
        
        boolean flowSupported() {
            return false;
        }
        
        boolean quickAckSupported() {
            return false;
        }
        
        boolean keepAliveOptionsSupported() {
            return false;
        }
        
        boolean getQuickAck(int fd) throws SocketException {
            throw new UnsupportedOperationException("unsupported TCP_QUICKACK option");
        }
        
        void setQuickAck(int fd, boolean on) throws SocketException {
            throw new UnsupportedOperationException("unsupported TCP_QUICKACK option");
        }
        
        int getTcpkeepAliveProbes(int socket) throws SocketException {
            throw new UnsupportedOperationException("unsupported TCP_KEEPCNT option");
        }
        
        void setTcpkeepAliveProbes(int socket, final int value) throws SocketException {
            throw new UnsupportedOperationException("unsupported TCP_KEEPCNT option");
        }
        
        int getTcpKeepAliveTime(int socket) throws SocketException {
            throw new UnsupportedOperationException("unsupported TCP_KEEPIDLE option");
        }
        
        void setTcpKeepAliveTime(int socket, final int value) throws SocketException {
            throw new UnsupportedOperationException("unsupported TCP_KEEPIDLE option");
        }
        
        int getTcpKeepAliveIntvl(int socket) throws SocketException {
            throw new UnsupportedOperationException("unsupported TCP_KEEPINTVL option");
        }
        
        void setTcpKeepAliveIntvl(int socket, final int value) throws SocketException {
            throw new UnsupportedOperationException("unsupported TCP_KEEPINTVL option");
        }
        
        @SuppressWarnings("unchecked")
        private static PlatformSocketOptions newInstance(String cn) {
            Class<PlatformSocketOptions> c;
            try {
                c = (Class<PlatformSocketOptions>) Class.forName(cn);
                return c.getConstructor(new Class<?>[]{}).newInstance();
            } catch(ReflectiveOperationException x) {
                throw new AssertionError(x);
            }
        }
        
        // 根据当前平台类型，返回对应的平台参数集
        private static PlatformSocketOptions create() {
            String osname = AccessController.doPrivileged(new PrivilegedAction<String>() {
                public String run() {
                    return System.getProperty("os.name");
                }
            });
            
            if("SunOS".equals(osname)) {
                return newInstance("jdk.net.SolarisSocketOptions");
            } else if("Linux".equals(osname)) {
                return newInstance("jdk.net.LinuxSocketOptions");
            } else if(osname.startsWith("Mac")) {
                return newInstance("jdk.net.MacOSXSocketOptions");
            } else {
                return new PlatformSocketOptions();
            }
        }
    }
    
    private static class ExtSocketOption<T> implements SocketOption<T> {
        private final String name;
        private final Class<T> type;
        
        ExtSocketOption(String name, Class<T> type) {
            this.name = name;
            this.type = type;
        }
        
        @Override
        public String name() {
            return name;
        }
        
        @Override
        public Class<T> type() {
            return type;
        }
        
        @Override
        public String toString() {
            return name;
        }
    }
    
}