/*
 * Copyright (C) 2018 The Android Open Source Project
 *
 * Licensed 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 LOG_NDEBUG 0

#define LOG_TAG "TestNetworkServiceJni"

#include <arpa/inet.h>
#include <errno.h>
#include <fcntl.h>
#include <linux/if.h>
#include <linux/if_tun.h>
#include <linux/ipv6_route.h>
#include <linux/route.h>
#include <netinet/in.h>
#include <stdio.h>
#include <string.h>
#include <sys/ioctl.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/types.h>

#include <log/log.h>

#include "jni.h"
#include <android-base/stringprintf.h>
#include <android-base/unique_fd.h>
#include <bpf/KernelUtils.h>
#include <nativehelper/JNIHelp.h>
#include <nativehelper/ScopedUtfChars.h>

#ifndef IFF_NO_CARRIER
#define IFF_NO_CARRIER 0x0040
#endif

namespace android {

//------------------------------------------------------------------------------

static void throwException(JNIEnv* env, int error, const char* action, const char* iface) {
    const std::string& msg = "Error: " + std::string(action) + " " + std::string(iface) +  ": "
                + std::string(strerror(error));
    jniThrowException(env, "java/lang/IllegalStateException", msg.c_str());
}

// enable or disable  carrier on tun / tap interface.
static void setTunTapCarrierEnabledImpl(JNIEnv* env, const char* iface, int tunFd, bool enabled) {
    uint32_t carrierOn = enabled;
    if (ioctl(tunFd, TUNSETCARRIER, &carrierOn)) {
        throwException(env, errno, "set carrier", iface);
    }
}

static int createTunTapImpl(JNIEnv* env, bool isTun, bool hasCarrier, bool setIffMulticast,
                            const char* iface) {
    base::unique_fd tun(open("/dev/tun", O_RDWR | O_NONBLOCK));
    ifreq ifr{};

    // Allocate interface.
    ifr.ifr_flags = (isTun ? IFF_TUN : IFF_TAP) | IFF_NO_PI;
    if (!hasCarrier) {
        // Using IFF_NO_CARRIER is supported starting in kernel version >= 6.0
        // Up until then, unsupported flags are ignored.
        if (!bpf::isAtLeastKernelVersion(6, 0, 0)) {
            throwException(env, EOPNOTSUPP, "IFF_NO_CARRIER not supported", ifr.ifr_name);
            return -1;
        }
        ifr.ifr_flags |= IFF_NO_CARRIER;
    }
    strlcpy(ifr.ifr_name, iface, IFNAMSIZ);
    if (ioctl(tun.get(), TUNSETIFF, &ifr)) {
        throwException(env, errno, "allocating", ifr.ifr_name);
        return -1;
    }

    // Mark some TAP interfaces as supporting multicast
    if (setIffMulticast && !isTun) {
        base::unique_fd inet6CtrlSock(socket(AF_INET6, SOCK_DGRAM, 0));
        ifr.ifr_flags = IFF_MULTICAST;

        if (ioctl(inet6CtrlSock.get(), SIOCSIFFLAGS, &ifr)) {
            throwException(env, errno, "set IFF_MULTICAST", ifr.ifr_name);
            return -1;
        }
    }

    return tun.release();
}

static void bringUpInterfaceImpl(JNIEnv* env, const char* iface) {
    // Activate interface using an unconnected datagram socket.
    base::unique_fd inet6CtrlSock(socket(AF_INET6, SOCK_DGRAM, 0));

    ifreq ifr{};
    strlcpy(ifr.ifr_name, iface, IFNAMSIZ);
    if (ioctl(inet6CtrlSock.get(), SIOCGIFFLAGS, &ifr)) {
        throwException(env, errno, "read flags", iface);
        return;
    }
    ifr.ifr_flags |= IFF_UP;
    if (ioctl(inet6CtrlSock.get(), SIOCSIFFLAGS, &ifr)) {
        throwException(env, errno, "set IFF_UP", iface);
        return;
    }
}

//------------------------------------------------------------------------------



static void setTunTapCarrierEnabled(JNIEnv* env, jclass /* clazz */, jstring
                                    jIface, jint tunFd, jboolean enabled) {
    ScopedUtfChars iface(env, jIface);
    if (!iface.c_str()) {
        jniThrowNullPointerException(env, "iface");
        return;
    }
    setTunTapCarrierEnabledImpl(env, iface.c_str(), tunFd, enabled);
}

static jint createTunTap(JNIEnv* env, jclass /* clazz */, jboolean isTun,
                             jboolean hasCarrier, jboolean setIffMulticast, jstring jIface) {
    ScopedUtfChars iface(env, jIface);
    if (!iface.c_str()) {
        jniThrowNullPointerException(env, "iface");
        return -1;
    }

    return createTunTapImpl(env, isTun, hasCarrier, setIffMulticast, iface.c_str());
}

static void bringUpInterface(JNIEnv* env, jclass /* clazz */, jstring jIface) {
    ScopedUtfChars iface(env, jIface);
    if (!iface.c_str()) {
        jniThrowNullPointerException(env, "iface");
        return;
    }
    bringUpInterfaceImpl(env, iface.c_str());
}

//------------------------------------------------------------------------------

static const JNINativeMethod gMethods[] = {
    {"nativeSetTunTapCarrierEnabled", "(Ljava/lang/String;IZ)V", (void*)setTunTapCarrierEnabled},
    {"nativeCreateTunTap", "(ZZZLjava/lang/String;)I", (void*)createTunTap},
    {"nativeBringUpInterface", "(Ljava/lang/String;)V", (void*)bringUpInterface},
};

int register_com_android_server_TestNetworkService(JNIEnv* env) {
    return jniRegisterNativeMethods(env,
            "android/net/connectivity/com/android/server/TestNetworkService", gMethods,
            NELEM(gMethods));
}

}; // namespace android