Native Class — netty Architecture

Source Code

transport-classes-epoll/src/main/java/io/netty/channel/epoll/Native.java lines 54–349

public final class Native {
    private static final InternalLogger logger = InternalLoggerFactory.getInstance(Native.class);
    static final InetAddress INET6_ANY;
    static final InetAddress INET_ANY;

    static {
        Selector selector = null;
        try {
            // We call Selector.open() as this will under the hood cause IOUtil to be loaded.
            // This is a workaround for a possible classloader deadlock that could happen otherwise:
            //
            // See https://github.com/netty/netty/issues/10187
            selector = Selector.open();
        } catch (IOException ignore) {
            // Just ignore
        }

        try {
            INET_ANY = InetAddress.getByName("0.0.0.0");
            INET6_ANY = InetAddress.getByName("::");
        } catch (UnknownHostException e) {
            throw new ExceptionInInitializerError(e);
        }

        // Preload all classes that will be used in the OnLoad(...) function of JNI to eliminate the possiblity of a
        // class-loader deadlock. This is a workaround for https://github.com/netty/netty/issues/11209.

        // This needs to match all the classes that are loaded via NETTY_JNI_UTIL_LOAD_CLASS or looked up via
        // NETTY_JNI_UTIL_FIND_CLASS.
        ClassInitializerUtil.tryLoadClasses(Native.class,
                // netty_epoll_linuxsocket
                PeerCredentials.class, DefaultFileRegion.class, FileChannel.class, java.io.FileDescriptor.class,
                // netty_epoll_native
                NativeDatagramPacketArray.NativeDatagramPacket.class
        );

        try {
            // First, try calling a side-effect free JNI method to see if the library was already
            // loaded by the application.
            offsetofEpollData();
        } catch (UnsatisfiedLinkError ignore) {
            // The library was not previously loaded, load it now.
            loadNativeLibrary();
        } finally {
            try {
                if (selector != null) {
                    selector.close();
                }
            } catch (IOException ignore) {
                // Just ignore
            }
        }
        Unix.registerInternal(new Runnable() {
            @Override
            public void run() {
                registerUnix();
            }
        });
    }

    private static native int registerUnix();

    // EventLoop operations and constants
    public static final int EPOLLIN = epollin();
    public static final int EPOLLOUT = epollout();
    public static final int EPOLLRDHUP = epollrdhup();
    public static final int EPOLLET = epollet();
    public static final int EPOLLERR = epollerr();

    public static final boolean IS_SUPPORTING_SENDMMSG = isSupportingSendmmsg();
    static final boolean IS_SUPPORTING_RECVMMSG = isSupportingRecvmmsg();
    static final boolean IS_SUPPORTING_UDP_SEGMENT = isSupportingUdpSegment();
    private static final int TFO_ENABLED_CLIENT_MASK = 0x1;
    private static final int TFO_ENABLED_SERVER_MASK = 0x2;
    private static final int TCP_FASTOPEN_MODE = tcpFastopenMode();
    /**
     * <a href ="https://www.kernel.org/doc/Documentation/networking/ip-sysctl.txt">tcp_fastopen</a> client mode enabled
     * state.
     */
    static final boolean IS_SUPPORTING_TCP_FASTOPEN_CLIENT =
            (TCP_FASTOPEN_MODE & TFO_ENABLED_CLIENT_MASK) == TFO_ENABLED_CLIENT_MASK;