/*
 * Copyright 2013 The Netty Project
 *
 * The Netty Project licenses this file to you under the Apache License,
 * version 2.0 (the "License"); you may not use this file except in compliance
 * with the License. You may obtain a copy of the License at:
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations
 * under the License.
 */
#define _GNU_SOURCE
#include <jni.h>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <sys/epoll.h>
#include <sys/eventfd.h>
#include <sys/sendfile.h>
#include <sys/un.h>
#include <linux/tcp.h> // TCP_NOTSENT_LOWAT is a linux specific define
#include <netinet/in.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <unistd.h>
#include <arpa/inet.h>
#include <fcntl.h>
#include <sys/utsname.h>
#include <stddef.h>
#include <limits.h>
#include <inttypes.h>
#include "io_netty_channel_epoll_Native.h"
#include "netty_unix_filedescriptor.h"
#include "netty_unix_socket.h"
#include "netty_unix_errors.h"
#include "netty_unix_util.h"

// TCP_NOTSENT_LOWAT is defined in linux 3.12. We define this here so older kernels can compile.
#ifndef TCP_NOTSENT_LOWAT
#define TCP_NOTSENT_LOWAT 25
#endif

// TCP_FASTOPEN is defined in linux 3.7. We define this here so older kernels can compile.
#ifndef TCP_FASTOPEN
#define TCP_FASTOPEN 23
#endif

/**
 * On older Linux kernels, epoll can't handle timeout
 * values bigger than (LONG_MAX - 999ULL)/HZ.
 *
 * See:
 *   - https://github.com/libevent/libevent/blob/master/epoll.c#L138
 *   - http://cvs.schmorp.de/libev/ev_epoll.c?revision=1.68&view=markup
 */
#define MAX_EPOLL_TIMEOUT_MSEC (35*60*1000)

// optional
extern int epoll_create1(int flags) __attribute__((weak));

#ifdef IO_NETTY_SENDMMSG_NOT_FOUND
extern int sendmmsg(int sockfd, struct mmsghdr* msgvec, unsigned int vlen, unsigned int flags) __attribute__((weak));

#ifndef __USE_GNU
struct mmsghdr {
    struct msghdr msg_hdr;  /* Message header */
    unsigned int  msg_len;  /* Number of bytes transmitted */
};
#endif
#endif

// Those are initialized in the init(...) method and cached for performance reasons
jfieldID fileChannelFieldId = NULL;
jfieldID transferedFieldId = NULL;
jfieldID fdFieldId = NULL;
jfieldID fileDescriptorFieldId = NULL;

jfieldID packetAddrFieldId = NULL;
jfieldID packetScopeIdFieldId = NULL;
jfieldID packetPortFieldId = NULL;
jfieldID packetMemoryAddressFieldId = NULL;
jfieldID packetCountFieldId = NULL;
static jstring nettyPackagePrefixJString = NULL;
static const char* nettyPackagePrefix = NULL;
static char* nettyClassName = NULL;

// util methods
static int getSysctlValue(const char * property, int* returnValue) {
    int rc = -1;
    FILE *fd=fopen(property, "r");
    if (fd != NULL) {
      char buf[32] = {0x0};
      if (fgets(buf, 32, fd) != NULL) {
        *returnValue = atoi(buf);
        rc = 0;
      }
      fclose(fd);
    }
    return rc;
}

static inline jint epollCtl(JNIEnv* env, jint efd, int op, jint fd, jint flags) {
    uint32_t events = flags;
    struct epoll_event ev = {
        .data.fd = fd,
        .events = events
    };

    return epoll_ctl(efd, op, fd, &ev);
}
// util methods end

jint JNI_OnLoad(JavaVM* vm, void* reserved) {
    JNIEnv* env;
    if ((*vm)->GetEnv(vm, (void**) &env, JNI_VERSION_1_6) != JNI_OK) {
        return JNI_ERR;
    } else {
        // Load the prefix to use when looking for Netty classes
        jclass systemCls = (*env)->FindClass(env, "java/lang/System");
        if (systemCls == NULL) {
            return JNI_ERR;
        }
        jmethodID getPropertyMethod = (*env)->GetStaticMethodID(env, systemCls, "getProperty", "(Ljava/lang/String;)Ljava/lang/String;");
        if (getPropertyMethod == NULL) {
            return JNI_ERR;
        }
        jstring propertyName = (*env)->NewStringUTF(env, "io.netty.native.epoll.nettyPackagePrefix");
        nettyPackagePrefixJString = (*env)->CallStaticObjectMethod(env, systemCls, getPropertyMethod, propertyName);
        if (nettyPackagePrefixJString != NULL) {
            nettyPackagePrefix = (*env)->GetStringUTFChars(env, nettyPackagePrefixJString, 0);
        }

        if (netty_unix_errors_JNI_OnLoad(env, nettyPackagePrefix) == JNI_ERR) {
            return JNI_ERR;
        }
        if (netty_unix_filedescriptor_JNI_OnLoad(env, nettyPackagePrefix) == JNI_ERR) {
            return JNI_ERR;
        }
        if (netty_unix_socket_JNI_OnLoad(env, nettyPackagePrefix) == JNI_ERR) {
            return JNI_ERR;
        }

        nettyClassName = netty_unix_util_prepend(nettyPackagePrefix, "io/netty/channel/DefaultFileRegion");
        jclass fileRegionCls = (*env)->FindClass(env, nettyClassName);
        free(nettyClassName);
        nettyClassName = NULL;
        if (fileRegionCls == NULL) {
            // pending exception...
            return JNI_ERR;
        }
        fileChannelFieldId = (*env)->GetFieldID(env, fileRegionCls, "file", "Ljava/nio/channels/FileChannel;");
        if (fileChannelFieldId == NULL) {
            netty_unix_errors_throwRuntimeException(env, "failed to get field ID: DefaultFileRegion.file");
            return JNI_ERR;
        }
        transferedFieldId = (*env)->GetFieldID(env, fileRegionCls, "transfered", "J");
        if (transferedFieldId == NULL) {
            netty_unix_errors_throwRuntimeException(env, "failed to get field ID: DefaultFileRegion.transfered");
            return JNI_ERR;
        }

        jclass fileChannelCls = (*env)->FindClass(env, "sun/nio/ch/FileChannelImpl");
        if (fileChannelCls == NULL) {
            // pending exception...
            return JNI_ERR;
        }
        fileDescriptorFieldId = (*env)->GetFieldID(env, fileChannelCls, "fd", "Ljava/io/FileDescriptor;");
        if (fileDescriptorFieldId == NULL) {
            netty_unix_errors_throwRuntimeException(env, "failed to get field ID: FileChannelImpl.fd");
            return JNI_ERR;
        }

        jclass fileDescriptorCls = (*env)->FindClass(env, "java/io/FileDescriptor");
        if (fileDescriptorCls == NULL) {
            // pending exception...
            return JNI_ERR;
        }
        fdFieldId = (*env)->GetFieldID(env, fileDescriptorCls, "fd", "I");
        if (fdFieldId == NULL) {
            netty_unix_errors_throwRuntimeException(env, "failed to get field ID: FileDescriptor.fd");
            return JNI_ERR;
        }

        nettyClassName = netty_unix_util_prepend(nettyPackagePrefix, "io/netty/channel/epoll/NativeDatagramPacketArray$NativeDatagramPacket");
        jclass nativeDatagramPacketCls = (*env)->FindClass(env, nettyClassName);
        free(nettyClassName);
        nettyClassName = NULL;
        if (nativeDatagramPacketCls == NULL) {
            // pending exception...
            return JNI_ERR;
        }

        packetAddrFieldId = (*env)->GetFieldID(env, nativeDatagramPacketCls, "addr", "[B");
        if (packetAddrFieldId == NULL) {
            netty_unix_errors_throwRuntimeException(env, "failed to get field ID: NativeDatagramPacket.addr");
            return JNI_ERR;
        }
        packetScopeIdFieldId = (*env)->GetFieldID(env, nativeDatagramPacketCls, "scopeId", "I");
        if (packetScopeIdFieldId == NULL) {
            netty_unix_errors_throwRuntimeException(env, "failed to get field ID: NativeDatagramPacket.scopeId");
            return JNI_ERR;
        }
        packetPortFieldId = (*env)->GetFieldID(env, nativeDatagramPacketCls, "port", "I");
        if (packetPortFieldId == NULL) {
            netty_unix_errors_throwRuntimeException(env, "failed to get field ID: NativeDatagramPacket.port");
            return JNI_ERR;
        }
        packetMemoryAddressFieldId = (*env)->GetFieldID(env, nativeDatagramPacketCls, "memoryAddress", "J");
        if (packetMemoryAddressFieldId == NULL) {
            netty_unix_errors_throwRuntimeException(env, "failed to get field ID: NativeDatagramPacket.memoryAddress");
            return JNI_ERR;
        }

        packetCountFieldId = (*env)->GetFieldID(env, nativeDatagramPacketCls, "count", "I");
        if (packetCountFieldId == NULL) {
            netty_unix_errors_throwRuntimeException(env, "failed to get field ID: NativeDatagramPacket.count");
            return JNI_ERR;
        }

        if (nettyPackagePrefixJString != NULL) {
            (*env)->ReleaseStringUTFChars(env, nettyPackagePrefixJString, nettyPackagePrefix);
            nettyPackagePrefix = NULL;
            nettyPackagePrefixJString = NULL;
        }

        return JNI_VERSION_1_6;
    }
}

void JNI_OnUnload(JavaVM* vm, void* reserved) {
    JNIEnv* env;
    if ((*vm)->GetEnv(vm, (void**) &env, JNI_VERSION_1_6) != JNI_OK) {
        // Something is wrong but nothing we can do about this :(
        return;
    } else {
        // delete global references so the GC can collect them
        if (nettyPackagePrefixJString != NULL) {
            (*env)->ReleaseStringUTFChars(env, nettyPackagePrefixJString, nettyPackagePrefix);
            nettyPackagePrefix = NULL;
            nettyPackagePrefixJString = NULL;
        }
        if (nettyClassName != NULL) {
            free(nettyClassName);
            nettyClassName = NULL;
        }
        netty_unix_errors_JNI_OnUnLoad(env);
        netty_unix_filedescriptor_JNI_OnUnLoad(env);
        netty_unix_socket_JNI_OnUnLoad(env);
    }
}

JNIEXPORT jint JNICALL Java_io_netty_channel_epoll_Native_eventFd(JNIEnv* env, jclass clazz) {
    jint eventFD = eventfd(0, EFD_CLOEXEC | EFD_NONBLOCK);

    if (eventFD < 0) {
        int err = errno;
        netty_unix_errors_throwChannelExceptionErrorNo(env, "eventfd() failed: ", err);
    }
    return eventFD;
}

JNIEXPORT void JNICALL Java_io_netty_channel_epoll_Native_eventFdWrite(JNIEnv* env, jclass clazz, jint fd, jlong value) {
    jint eventFD = eventfd_write(fd, (eventfd_t) value);

    if (eventFD < 0) {
        int err = errno;
        netty_unix_errors_throwChannelExceptionErrorNo(env, "eventfd_write() failed: ", err);
    }
}

JNIEXPORT void JNICALL Java_io_netty_channel_epoll_Native_eventFdRead(JNIEnv* env, jclass clazz, jint fd) {
    uint64_t eventfd_t;

    if (eventfd_read(fd, &eventfd_t) != 0) {
        // something is serious wrong
        netty_unix_errors_throwRuntimeException(env, "eventfd_read() failed");
    }
}

JNIEXPORT jint JNICALL Java_io_netty_channel_epoll_Native_epollCreate(JNIEnv* env, jclass clazz) {
    jint efd;
    if (epoll_create1) {
        efd = epoll_create1(EPOLL_CLOEXEC);
    } else {
        // size will be ignored anyway but must be positive
        efd = epoll_create(126);
    }
    if (efd < 0) {
        int err = errno;
        if (epoll_create1) {
            netty_unix_errors_throwChannelExceptionErrorNo(env, "epoll_create1() failed: ", err);
        } else {
            netty_unix_errors_throwChannelExceptionErrorNo(env, "epoll_create() failed: ", err);
        }
        return efd;
    }
    if (!epoll_create1) {
        if (fcntl(efd, F_SETFD, FD_CLOEXEC) < 0) {
            int err = errno;
            close(efd);
            netty_unix_errors_throwChannelExceptionErrorNo(env, "fcntl() failed: ", err);
            return err;
        }
    }
    return efd;
}

JNIEXPORT jint JNICALL Java_io_netty_channel_epoll_Native_epollWait0(JNIEnv* env, jclass clazz, jint efd, jlong address, jint len, jint timeout) {
    struct epoll_event *ev = (struct epoll_event*) (intptr_t) address;
    int ready;
    int err;

    if (timeout > MAX_EPOLL_TIMEOUT_MSEC) {
        // Workaround for bug in older linux kernels that can not handle bigger timeout then MAX_EPOLL_TIMEOUT_MSEC.
        timeout = MAX_EPOLL_TIMEOUT_MSEC;
    }

    do {
       ready = epoll_wait(efd, ev, len, timeout);
       // was interrupted try again.
    } while (ready == -1 && ((err = errno) == EINTR));

    if (ready < 0) {
         return -err;
    }
    return ready;
}

JNIEXPORT jint JNICALL Java_io_netty_channel_epoll_Native_epollCtlAdd0(JNIEnv* env, jclass clazz, jint efd, jint fd, jint flags) {
    int res = epollCtl(env, efd, EPOLL_CTL_ADD, fd, flags);
    if (res < 0) {
        return -errno;
    }
    return res;
}

JNIEXPORT jint JNICALL Java_io_netty_channel_epoll_Native_epollCtlMod0(JNIEnv* env, jclass clazz, jint efd, jint fd, jint flags) {
    int res = epollCtl(env, efd, EPOLL_CTL_MOD, fd, flags);
    if (res < 0) {
        return -errno;
    }
    return res;
}

JNIEXPORT jint JNICALL Java_io_netty_channel_epoll_Native_epollCtlDel0(JNIEnv* env, jclass clazz, jint efd, jint fd) {
    // Create an empty event to workaround a bug in older kernels which can not handle NULL.
    struct epoll_event event = { 0 };
    int res = epoll_ctl(efd, EPOLL_CTL_DEL, fd, &event);
    if (res < 0) {
        return -errno;
    }
    return res;
}

JNIEXPORT jint JNICALL Java_io_netty_channel_epoll_Native_sendmmsg0(JNIEnv* env, jclass clazz, jint fd, jobjectArray packets, jint offset, jint len) {
    struct mmsghdr msg[len];
    int i;

    memset(msg, 0, sizeof(msg));

    for (i = 0; i < len; i++) {
        struct sockaddr_storage addr;

        jobject packet = (*env)->GetObjectArrayElement(env, packets, i + offset);
        jbyteArray address = (jbyteArray) (*env)->GetObjectField(env, packet, packetAddrFieldId);
        jint scopeId = (*env)->GetIntField(env, packet, packetScopeIdFieldId);
        jint port = (*env)->GetIntField(env, packet, packetPortFieldId);

        if (netty_unix_socket_initSockaddr(env, address, scopeId, port, &addr) == -1) {
            return -1;
        }

        msg[i].msg_hdr.msg_name = &addr;
        msg[i].msg_hdr.msg_namelen = sizeof(addr);

        msg[i].msg_hdr.msg_iov = (struct iovec*) (intptr_t) (*env)->GetLongField(env, packet, packetMemoryAddressFieldId);
        msg[i].msg_hdr.msg_iovlen = (*env)->GetIntField(env, packet, packetCountFieldId);;
    }

    ssize_t res;
    int err;
    do {
       res = sendmmsg(fd, msg, len, 0);
       // keep on writing if it was interrupted
    } while (res == -1 && ((err = errno) == EINTR));

    if (res < 0) {
        return -err;
    }
    return (jint) res;
}

JNIEXPORT jlong JNICALL Java_io_netty_channel_epoll_Native_sendfile0(JNIEnv* env, jclass clazz, jint fd, jobject fileRegion, jlong base_off, jlong off, jlong len) {
    jobject fileChannel = (*env)->GetObjectField(env, fileRegion, fileChannelFieldId);
    if (fileChannel == NULL) {
        netty_unix_errors_throwRuntimeException(env, "failed to get DefaultFileRegion.file");
        return -1;
    }
    jobject fileDescriptor = (*env)->GetObjectField(env, fileChannel, fileDescriptorFieldId);
    if (fileDescriptor == NULL) {
        netty_unix_errors_throwRuntimeException(env, "failed to get FileChannelImpl.fd");
        return -1;
    }
    jint srcFd = (*env)->GetIntField(env, fileDescriptor, fdFieldId);
    if (srcFd == -1) {
        netty_unix_errors_throwRuntimeException(env, "failed to get FileDescriptor.fd");
        return -1;
    }
    ssize_t res;
    off_t offset = base_off + off;
    int err;
    do {
      res = sendfile(fd, srcFd, &offset, (size_t) len);
    } while (res == -1 && ((err = errno) == EINTR));
    if (res < 0) {
        return -err;
    }
    if (res > 0) {
        // update the transfered field in DefaultFileRegion
        (*env)->SetLongField(env, fileRegion, transferedFieldId, off + res);
    }

    return res;
}

JNIEXPORT void JNICALL Java_io_netty_channel_epoll_Native_setReuseAddress(JNIEnv* env, jclass clazz, jint fd, jint optval) {
    netty_unix_socket_setOption(env, fd, SOL_SOCKET, SO_REUSEADDR, &optval, sizeof(optval));
}

JNIEXPORT void JNICALL Java_io_netty_channel_epoll_Native_setReusePort(JNIEnv* env, jclass clazz, jint fd, jint optval) {
    netty_unix_socket_setOption(env, fd, SOL_SOCKET, SO_REUSEPORT, &optval, sizeof(optval));
}

JNIEXPORT void JNICALL Java_io_netty_channel_epoll_Native_setTcpFastopen(JNIEnv* env, jclass clazz, jint fd, jint optval) {
    netty_unix_socket_setOption(env, fd, IPPROTO_TCP, TCP_FASTOPEN, &optval, sizeof(optval));
}

JNIEXPORT void JNICALL Java_io_netty_channel_epoll_Native_setTcpNotSentLowAt(JNIEnv* env, jclass clazz, jint fd, jint optval) {
    netty_unix_socket_setOption(env, fd, IPPROTO_TCP, TCP_NOTSENT_LOWAT, &optval, sizeof(optval));
}

JNIEXPORT void JNICALL Java_io_netty_channel_epoll_Native_setTrafficClass(JNIEnv* env, jclass clazz, jint fd, jint optval) {
    netty_unix_socket_setOption(env, fd, IPPROTO_IP, IP_TOS, &optval, sizeof(optval));

    /* Try to set the ipv6 equivalent, but don't throw if this is an ipv4 only socket. */
    int rc = setsockopt(fd, IPPROTO_IPV6, IPV6_TCLASS, &optval, sizeof(optval));
    if (rc < 0 && errno != ENOPROTOOPT) {
        netty_unix_errors_throwChannelExceptionErrorNo(env, "setting ipv6 dscp failed: ", errno);
    }
}

JNIEXPORT void JNICALL Java_io_netty_channel_epoll_Native_setBroadcast(JNIEnv* env, jclass clazz, jint fd, jint optval) {
    netty_unix_socket_setOption(env, fd, SOL_SOCKET, SO_BROADCAST, &optval, sizeof(optval));
}

JNIEXPORT void JNICALL Java_io_netty_channel_epoll_Native_setTcpKeepIdle(JNIEnv* env, jclass clazz, jint fd, jint optval) {
    netty_unix_socket_setOption(env, fd, IPPROTO_TCP, TCP_KEEPIDLE, &optval, sizeof(optval));
}

JNIEXPORT void JNICALL Java_io_netty_channel_epoll_Native_setTcpKeepIntvl(JNIEnv* env, jclass clazz, jint fd, jint optval) {
    netty_unix_socket_setOption(env, fd, IPPROTO_TCP, TCP_KEEPINTVL, &optval, sizeof(optval));
}

JNIEXPORT void Java_io_netty_channel_epoll_Native_setTcpKeepCnt(JNIEnv* env, jclass clazz, jint fd, jint optval) {
    netty_unix_socket_setOption(env, fd, IPPROTO_TCP, TCP_KEEPCNT, &optval, sizeof(optval));
}

JNIEXPORT void Java_io_netty_channel_epoll_Native_setTcpUserTimeout(JNIEnv* env, jclass clazz, jint fd, jint optval) {
    netty_unix_socket_setOption(env, fd, IPPROTO_TCP, TCP_USER_TIMEOUT, &optval, sizeof(optval));
}

JNIEXPORT void JNICALL Java_io_netty_channel_epoll_Native_setIpFreeBind(JNIEnv* env, jclass clazz, jint fd, jint optval) {
    netty_unix_socket_setOption(env, fd, IPPROTO_IP, IP_FREEBIND, &optval, sizeof(optval));
}

JNIEXPORT jint JNICALL Java_io_netty_channel_epoll_Native_isReuseAddresss(JNIEnv* env, jclass clazz, jint fd) {
    int optval;
    if (netty_unix_socket_getOption(env, fd, SOL_SOCKET, SO_REUSEADDR, &optval, sizeof(optval)) == -1) {
        return -1;
    }
    return optval;
}

JNIEXPORT jint JNICALL Java_io_netty_channel_epoll_Native_isReusePort(JNIEnv* env, jclass clazz, jint fd) {
    int optval;
    if (netty_unix_socket_getOption(env, fd, SOL_SOCKET, SO_REUSEPORT, &optval, sizeof(optval)) == -1) {
        return -1;
    }
    return optval;
}

JNIEXPORT jint JNICALL Java_io_netty_channel_epoll_Native_getTcpNotSentLowAt(JNIEnv* env, jclass clazz, jint fd) {
    int optval;
    if (netty_unix_socket_getOption(env, fd, IPPROTO_TCP, TCP_NOTSENT_LOWAT, &optval, sizeof(optval)) == -1) {
        return -1;
    }
    return optval;
}

JNIEXPORT jint JNICALL Java_io_netty_channel_epoll_Native_getTrafficClass(JNIEnv* env, jclass clazz, jint fd) {
    int optval;
    if (netty_unix_socket_getOption(env, fd, IPPROTO_IP, IP_TOS, &optval, sizeof(optval)) == -1) {
        return -1;
    }
    return optval;
}

JNIEXPORT jint JNICALL Java_io_netty_channel_epoll_Native_isBroadcast(JNIEnv* env, jclass clazz, jint fd) {
    int optval;
    if (netty_unix_socket_getOption(env, fd, SOL_SOCKET, SO_BROADCAST, &optval, sizeof(optval)) == -1) {
        return -1;
    }
    return optval;
}

JNIEXPORT jint JNICALL Java_io_netty_channel_epoll_Native_getTcpKeepIdle(JNIEnv* env, jclass clazz, jint fd) {
    int optval;
    if (netty_unix_socket_getOption(env, fd, IPPROTO_TCP, TCP_KEEPIDLE, &optval, sizeof(optval)) == -1) {
        return -1;
    }
    return optval;
}

JNIEXPORT jint JNICALL Java_io_netty_channel_epoll_Native_getTcpKeepIntvl(JNIEnv* env, jclass clazz, jint fd) {
    int optval;
    if (netty_unix_socket_getOption(env, fd, IPPROTO_TCP, TCP_KEEPINTVL, &optval, sizeof(optval)) == -1) {
        return -1;
    }
    return optval;
}

JNIEXPORT jint JNICALL Java_io_netty_channel_epoll_Native_getTcpKeepCnt(JNIEnv* env, jclass clazz, jint fd) {
     int optval;
     if (netty_unix_socket_getOption(env, fd, IPPROTO_TCP, TCP_KEEPCNT, &optval, sizeof(optval)) == -1) {
         return -1;
     }
     return optval;
}

JNIEXPORT jint JNICALL Java_io_netty_channel_epoll_Native_getTcpUserTimeout(JNIEnv* env, jclass clazz, jint fd) {
     int optval;
     if (netty_unix_socket_getOption(env, fd, IPPROTO_TCP, TCP_USER_TIMEOUT, &optval, sizeof(optval)) == -1) {
         return -1;
     }
     return optval;
}

JNIEXPORT jint JNICALL Java_io_netty_channel_epoll_Native_isIpFreeBind(JNIEnv* env, jclass clazz, jint fd) {
     int optval;
     if (netty_unix_socket_getOption(env, fd, IPPROTO_TCP, IP_FREEBIND, &optval, sizeof(optval)) == -1) {
         return -1;
     }
     return optval;
}

JNIEXPORT void JNICALL Java_io_netty_channel_epoll_Native_tcpInfo0(JNIEnv* env, jclass clazz, jint fd, jintArray array) {
     struct tcp_info tcp_info;
     if (netty_unix_socket_getOption(env, fd, IPPROTO_TCP, TCP_INFO, &tcp_info, sizeof(tcp_info)) == -1) {
         return;
     }
     unsigned int cArray[32];
     cArray[0] = tcp_info.tcpi_state;
     cArray[1] = tcp_info.tcpi_ca_state;
     cArray[2] = tcp_info.tcpi_retransmits;
     cArray[3] = tcp_info.tcpi_probes;
     cArray[4] = tcp_info.tcpi_backoff;
     cArray[5] = tcp_info.tcpi_options;
     cArray[6] = tcp_info.tcpi_snd_wscale;
     cArray[7] = tcp_info.tcpi_rcv_wscale;
     cArray[8] = tcp_info.tcpi_rto;
     cArray[9] = tcp_info.tcpi_ato;
     cArray[10] = tcp_info.tcpi_snd_mss;
     cArray[11] = tcp_info.tcpi_rcv_mss;
     cArray[12] = tcp_info.tcpi_unacked;
     cArray[13] = tcp_info.tcpi_sacked;
     cArray[14] = tcp_info.tcpi_lost;
     cArray[15] = tcp_info.tcpi_retrans;
     cArray[16] = tcp_info.tcpi_fackets;
     cArray[17] = tcp_info.tcpi_last_data_sent;
     cArray[18] = tcp_info.tcpi_last_ack_sent;
     cArray[19] = tcp_info.tcpi_last_data_recv;
     cArray[20] = tcp_info.tcpi_last_ack_recv;
     cArray[21] = tcp_info.tcpi_pmtu;
     cArray[22] = tcp_info.tcpi_rcv_ssthresh;
     cArray[23] = tcp_info.tcpi_rtt;
     cArray[24] = tcp_info.tcpi_rttvar;
     cArray[25] = tcp_info.tcpi_snd_ssthresh;
     cArray[26] = tcp_info.tcpi_snd_cwnd;
     cArray[27] = tcp_info.tcpi_advmss;
     cArray[28] = tcp_info.tcpi_reordering;
     cArray[29] = tcp_info.tcpi_rcv_rtt;
     cArray[30] = tcp_info.tcpi_rcv_space;
     cArray[31] = tcp_info.tcpi_total_retrans;

     (*env)->SetIntArrayRegion(env, array, 0, 32, cArray);
}

JNIEXPORT jstring JNICALL Java_io_netty_channel_epoll_Native_kernelVersion(JNIEnv* env, jclass clazz) {
    struct utsname name;

    int res = uname(&name);
    if (res == 0) {
        return (*env)->NewStringUTF(env, name.release);
    }
    int err = errno;
    netty_unix_errors_throwRuntimeExceptionErrorNo(env, "uname() failed: ", err);
    return NULL;
}

JNIEXPORT jint JNICALL Java_io_netty_channel_epoll_Native_iovMax(JNIEnv* env, jclass clazz) {
    return IOV_MAX;
}

JNIEXPORT jint JNICALL Java_io_netty_channel_epoll_Native_uioMaxIov(JNIEnv* env, jclass clazz) {
    return UIO_MAXIOV;
}

JNIEXPORT jboolean JNICALL Java_io_netty_channel_epoll_Native_isSupportingSendmmsg(JNIEnv* env, jclass clazz) {
    if (sendmmsg) {
        return JNI_TRUE;
    }
    return JNI_FALSE;
}

JNIEXPORT jboolean JNICALL Java_io_netty_channel_epoll_Native_isSupportingTcpFastopen(JNIEnv* env, jclass clazz) {
    int fastopen = 0;
    getSysctlValue("/proc/sys/net/ipv4/tcp_fastopen", &fastopen);
    if (fastopen > 0) {
        return JNI_TRUE;
    }
    return JNI_FALSE;
}

JNIEXPORT jint JNICALL Java_io_netty_channel_epoll_Native_recvFd0(JNIEnv* env, jclass clazz, jint fd) {
    int socketFd;
    struct msghdr descriptorMessage = { 0 };
    struct iovec iov[1] = { 0 };
    char control[CMSG_SPACE(sizeof(int))] = { 0 };
    char iovecData[1];

    descriptorMessage.msg_control = control;
    descriptorMessage.msg_controllen = sizeof(control);
    descriptorMessage.msg_iov = iov;
    descriptorMessage.msg_iovlen = 1;
    iov[0].iov_base = iovecData;
    iov[0].iov_len = sizeof(iovecData);

    ssize_t res;
    int err;

    for (;;) {
        do {
            res = recvmsg(fd, &descriptorMessage, 0);
            // Keep on reading if we was interrupted
        } while (res == -1 && ((err = errno) == EINTR));

        if (res == 0) {
            return 0;
        }

        if (res < 0) {
            return -err;
        }

        struct cmsghdr* cmsg = CMSG_FIRSTHDR(&descriptorMessage);
        if (!cmsg) {
            return -errno;
        }

        if ((cmsg->cmsg_len == CMSG_LEN(sizeof(int))) && (cmsg->cmsg_level == SOL_SOCKET) && (cmsg->cmsg_type == SCM_RIGHTS)) {
            socketFd = *((int *) CMSG_DATA(cmsg));
            // set as non blocking as we want to use it with epoll
            if (fcntl(socketFd, F_SETFL, O_NONBLOCK) == -1) {
                err = errno;
                close(socketFd);
                return -err;
            }
            return socketFd;
        }
    }
}

JNIEXPORT jint JNICALL Java_io_netty_channel_epoll_Native_sendFd0(JNIEnv* env, jclass clazz, jint socketFd, jint fd) {
    struct msghdr descriptorMessage = { 0 };
    struct iovec iov[1] = { 0 };
    char control[CMSG_SPACE(sizeof(int))] = { 0 };
    char iovecData[1];

    descriptorMessage.msg_control = control;
    descriptorMessage.msg_controllen = sizeof(control);
    struct cmsghdr* cmsg = CMSG_FIRSTHDR(&descriptorMessage);

    if (cmsg) {
        cmsg->cmsg_len = CMSG_LEN(sizeof(int));
        cmsg->cmsg_level = SOL_SOCKET;
        cmsg->cmsg_type = SCM_RIGHTS;
        *((int *)CMSG_DATA(cmsg)) = fd;
        descriptorMessage.msg_iov = iov;
        descriptorMessage.msg_iovlen = 1;
        iov[0].iov_base = iovecData;
        iov[0].iov_len = sizeof(iovecData);

        ssize_t res;
        int err;
        do {
            res = sendmsg(socketFd, &descriptorMessage, 0);
        // keep on writing if it was interrupted
        } while (res == -1 && ((err = errno) == EINTR));

        if (res < 0) {
            return -err;
        }
        return (jint) res;
    }
    return -1;
}

JNIEXPORT jint JNICALL Java_io_netty_channel_epoll_Native_epollet(JNIEnv* env, jclass clazz) {
    return EPOLLET;
}

JNIEXPORT jint JNICALL Java_io_netty_channel_epoll_Native_epollin(JNIEnv* env, jclass clazz) {
    return EPOLLIN;
}

JNIEXPORT jint JNICALL Java_io_netty_channel_epoll_Native_epollout(JNIEnv* env, jclass clazz) {
    return EPOLLOUT;
}

JNIEXPORT jint JNICALL Java_io_netty_channel_epoll_Native_epollrdhup(JNIEnv* env, jclass clazz) {
    return EPOLLRDHUP;
}

JNIEXPORT jint JNICALL Java_io_netty_channel_epoll_Native_epollerr(JNIEnv* env, jclass clazz) {
    return EPOLLERR;
}

JNIEXPORT jint JNICALL Java_io_netty_channel_epoll_Native_sizeofEpollEvent(JNIEnv* env, jclass clazz) {
    return sizeof(struct epoll_event);
}

JNIEXPORT jint JNICALL Java_io_netty_channel_epoll_Native_offsetofEpollData(JNIEnv* env, jclass clazz) {
    return offsetof(struct epoll_event, data);
}

JNIEXPORT jint JNICALL Java_io_netty_channel_epoll_Native_splice0(JNIEnv* env, jclass clazz, jint fd, jlong offIn, jint fdOut, jlong offOut, jlong len) {
    ssize_t res;
    int err;
    loff_t off_in = (loff_t) offIn;
    loff_t off_out = (loff_t) offOut;

    loff_t* p_off_in = off_in >= 0 ? &off_in : NULL;
    loff_t* p_off_out = off_in >= 0 ? &off_out : NULL;

    do {
       res = splice(fd, p_off_in, fdOut, p_off_out, (size_t) len, SPLICE_F_NONBLOCK | SPLICE_F_MOVE);
       // keep on splicing if it was interrupted
    } while (res == -1 && ((err = errno) == EINTR));

    if (res < 0) {
        return -err;
    }
    return (jint) res;
}

JNIEXPORT jlong JNICALL Java_io_netty_channel_epoll_Native_ssizeMax(JNIEnv* env, jclass clazz) {
    return SSIZE_MAX;
}

JNIEXPORT jint JNICALL Java_io_netty_channel_epoll_Native_tcpMd5SigMaxKeyLen(JNIEnv* env, jclass clazz) {
    struct tcp_md5sig md5sig;

    // Defensive size check
    if (sizeof(md5sig.tcpm_key) < TCP_MD5SIG_MAXKEYLEN) {
        return sizeof(md5sig.tcpm_key);
    }

    return TCP_MD5SIG_MAXKEYLEN;
}

JNIEXPORT void JNICALL Java_io_netty_channel_epoll_Native_setTcpMd5Sig0(JNIEnv* env, jclass clazz, jint fd, jbyteArray address, jint scopeId, jbyteArray key) {
    struct sockaddr_storage addr;
    if (netty_unix_socket_initSockaddr(env, address, scopeId, 0, &addr) == -1) {
        return;
    }

    struct tcp_md5sig md5sig;
    memset(&md5sig, 0, sizeof(md5sig));
    md5sig.tcpm_addr.ss_family = addr.ss_family;

    struct sockaddr_in* ipaddr;
    struct sockaddr_in6* ip6addr;

    switch (addr.ss_family) {
    case AF_INET:
        ipaddr = (struct sockaddr_in*) &addr;
        memcpy(&((struct sockaddr_in *) &md5sig.tcpm_addr)->sin_addr, &ipaddr->sin_addr, sizeof(ipaddr->sin_addr));
        break;
    case AF_INET6:
        ip6addr = (struct sockaddr_in6*) &addr;
        memcpy(&((struct sockaddr_in6 *) &md5sig.tcpm_addr)->sin6_addr, &ip6addr->sin6_addr, sizeof(ip6addr->sin6_addr));
        break;
    }

    if (key != NULL) {
        md5sig.tcpm_keylen = (*env)->GetArrayLength(env, key);
        (*env)->GetByteArrayRegion(env, key, 0, md5sig.tcpm_keylen, (void *) &md5sig.tcpm_key);
        if ((*env)->ExceptionCheck(env) == JNI_TRUE) {
            return;
        }
    }

    if (setsockopt(fd, IPPROTO_TCP, TCP_MD5SIG, &md5sig, sizeof(md5sig)) < 0) {
        netty_unix_errors_throwChannelExceptionErrorNo(env, "setsockopt() failed: ", errno);
    }
}