path: root/framework/jni/android_net_NetworkUtils.cpp

/*
 * Copyright 2020, 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_TAG "NetworkUtils"

#include <android/file_descriptor_jni.h>
#include <android/multinetwork.h>
#include <linux/filter.h>
#include <linux/tcp.h>
#include <netinet/in.h>
#include <string.h>

#include <DnsProxydProtocol.h> // NETID_USE_LOCAL_NAMESERVERS
#include <nativehelper/JNIPlatformHelp.h>
#include <utils/Log.h>

#include "jni.h"

#define NETUTILS_PKG_NAME "android/net/NetworkUtils"

namespace android {

constexpr int MAXPACKETSIZE = 8 * 1024;
// FrameworkListener limits the size of commands to 4096 bytes.
constexpr int MAXCMDSIZE = 4096;

static volatile jclass class_Network = 0;
static volatile jmethodID method_fromNetworkHandle = 0;

static inline jclass FindClassOrDie(JNIEnv* env, const char* class_name) {
    jclass clazz = env->FindClass(class_name);
    LOG_ALWAYS_FATAL_IF(clazz == NULL, "Unable to find class %s", class_name);
    return clazz;
}

template <typename T>
static inline T MakeGlobalRefOrDie(JNIEnv* env, T in) {
    jobject res = env->NewGlobalRef(in);
    LOG_ALWAYS_FATAL_IF(res == NULL, "Unable to create global reference.");
    return static_cast<T>(res);
}

static void android_net_utils_attachDropAllBPFFilter(JNIEnv *env, jobject clazz, jobject javaFd)
{
    struct sock_filter filter_code[] = {
        // Reject all.
        BPF_STMT(BPF_RET | BPF_K, 0)
    };
    struct sock_fprog filter = {
        sizeof(filter_code) / sizeof(filter_code[0]),
        filter_code,
    };

    int fd = AFileDescriptor_getFd(env, javaFd);
    if (setsockopt(fd, SOL_SOCKET, SO_ATTACH_FILTER, &filter, sizeof(filter)) != 0) {
        jniThrowExceptionFmt(env, "java/net/SocketException",
                "setsockopt(SO_ATTACH_FILTER): %s", strerror(errno));
    }
}

static void android_net_utils_detachBPFFilter(JNIEnv *env, jobject clazz, jobject javaFd)
{
    int optval_ignored = 0;
    int fd = AFileDescriptor_getFd(env, javaFd);
    if (setsockopt(fd, SOL_SOCKET, SO_DETACH_FILTER, &optval_ignored, sizeof(optval_ignored)) !=
        0) {
        jniThrowExceptionFmt(env, "java/net/SocketException",
                "setsockopt(SO_DETACH_FILTER): %s", strerror(errno));
    }
}

static jboolean android_net_utils_bindProcessToNetworkHandle(JNIEnv *env, jobject thiz,
        jlong netHandle)
{
    return (jboolean) !android_setprocnetwork(netHandle);
}

static jlong android_net_utils_getBoundNetworkHandleForProcess(JNIEnv *env, jobject thiz)
{
    net_handle_t network;
    if (android_getprocnetwork(&network) != 0) {
        jniThrowExceptionFmt(env, "java/lang/IllegalStateException",
                "android_getprocnetwork(): %s", strerror(errno));
        return NETWORK_UNSPECIFIED;
    }
    return (jlong) network;
}

static jboolean android_net_utils_bindProcessToNetworkForHostResolution(JNIEnv *env, jobject thiz,
        jint netId, jlong netHandle)
{
    return (jboolean) !android_setprocdns(netHandle);
}

static jint android_net_utils_bindSocketToNetworkHandle(JNIEnv *env, jobject thiz, jobject javaFd,
                                                  jlong netHandle) {
    return android_setsocknetwork(netHandle, AFileDescriptor_getFd(env, javaFd));
}

static bool checkLenAndCopy(JNIEnv* env, const jbyteArray& addr, int len, void* dst)
{
    if (env->GetArrayLength(addr) != len) {
        return false;
    }
    env->GetByteArrayRegion(addr, 0, len, reinterpret_cast<jbyte*>(dst));
    return true;
}

static jobject android_net_utils_resNetworkQuery(JNIEnv *env, jobject thiz, jlong netHandle,
        jstring dname, jint ns_class, jint ns_type, jint flags) {
    const jsize javaCharsCount = env->GetStringLength(dname);
    const jsize byteCountUTF8 = env->GetStringUTFLength(dname);

    // Only allow dname which could be simply formatted to UTF8.
    // In native layer, res_mkquery would re-format the input char array to packet.
    char queryname[byteCountUTF8 + 1];
    memset(queryname, 0, (byteCountUTF8 + 1) * sizeof(char));

    env->GetStringUTFRegion(dname, 0, javaCharsCount, queryname);
    int fd = android_res_nquery(netHandle, queryname, ns_class, ns_type, flags);

    if (fd < 0) {
        jniThrowErrnoException(env, "resNetworkQuery", -fd);
        return nullptr;
    }

    return jniCreateFileDescriptor(env, fd);
}

static jobject android_net_utils_resNetworkSend(JNIEnv *env, jobject thiz, jlong netHandle,
        jbyteArray msg, jint msgLen, jint flags) {
    uint8_t data[MAXCMDSIZE];

    checkLenAndCopy(env, msg, msgLen, data);
    int fd = android_res_nsend(netHandle, data, msgLen, flags);

    if (fd < 0) {
        jniThrowErrnoException(env, "resNetworkSend", -fd);
        return nullptr;
    }

    return jniCreateFileDescriptor(env, fd);
}

static jobject android_net_utils_resNetworkResult(JNIEnv *env, jobject thiz, jobject javaFd) {
    int fd = AFileDescriptor_getFd(env, javaFd);
    int rcode;
    uint8_t buf[MAXPACKETSIZE] = {0};

    int res = android_res_nresult(fd, &rcode, buf, MAXPACKETSIZE);
    jniSetFileDescriptorOfFD(env, javaFd, -1);
    if (res < 0) {
        jniThrowErrnoException(env, "resNetworkResult", -res);
        return nullptr;
    }

    jbyteArray answer = env->NewByteArray(res);
    if (answer == nullptr) {
        jniThrowErrnoException(env, "resNetworkResult", ENOMEM);
        return nullptr;
    } else {
        env->SetByteArrayRegion(answer, 0, res, reinterpret_cast<jbyte*>(buf));
    }

    jclass class_DnsResponse = env->FindClass("android/net/DnsResolver$DnsResponse");
    jmethodID ctor = env->GetMethodID(class_DnsResponse, "<init>", "([BI)V");

    return env->NewObject(class_DnsResponse, ctor, answer, rcode);
}

static void android_net_utils_resNetworkCancel(JNIEnv *env, jobject thiz, jobject javaFd) {
    int fd = AFileDescriptor_getFd(env, javaFd);
    android_res_cancel(fd);
    jniSetFileDescriptorOfFD(env, javaFd, -1);
}

static jobject android_net_utils_getDnsNetwork(JNIEnv *env, jobject thiz) {
    net_handle_t dnsNetHandle = NETWORK_UNSPECIFIED;
    if (int res = android_getprocdns(&dnsNetHandle) < 0) {
        jniThrowErrnoException(env, "getDnsNetwork", -res);
        return nullptr;
    }

    if (method_fromNetworkHandle == 0) {
        // This may be called multiple times concurrently but that is fine
        class_Network = MakeGlobalRefOrDie(env, FindClassOrDie(env, "android/net/Network"));
        method_fromNetworkHandle = env->GetStaticMethodID(class_Network, "fromNetworkHandle",
                "(J)Landroid/net/Network;");
    }
    return env->CallStaticObjectMethod(class_Network, method_fromNetworkHandle,
            static_cast<jlong>(dnsNetHandle));
}

static jobject android_net_utils_getTcpRepairWindow(JNIEnv *env, jobject thiz, jobject javaFd) {
    if (javaFd == NULL) {
        jniThrowNullPointerException(env, NULL);
        return NULL;
    }

    int fd = AFileDescriptor_getFd(env, javaFd);
    struct tcp_repair_window trw = {};
    socklen_t size = sizeof(trw);

    // Obtain the parameters of the TCP repair window.
    int rc = getsockopt(fd, IPPROTO_TCP, TCP_REPAIR_WINDOW, &trw, &size);
    if (rc == -1) {
        jniThrowErrnoException(env, "getsockopt : TCP_REPAIR_WINDOW", errno);
        return NULL;
    }

    struct tcp_info tcpinfo = {};
    socklen_t tcpinfo_size = sizeof(tcp_info);

    // Obtain the window scale from the tcp info structure. This contains a scale factor that
    // should be applied to the window size.
    rc = getsockopt(fd, IPPROTO_TCP, TCP_INFO, &tcpinfo, &tcpinfo_size);
    if (rc == -1) {
        jniThrowErrnoException(env, "getsockopt : TCP_INFO", errno);
        return NULL;
    }

    jclass class_TcpRepairWindow = env->FindClass("android/net/TcpRepairWindow");
    jmethodID ctor = env->GetMethodID(class_TcpRepairWindow, "<init>", "(IIIIII)V");

    return env->NewObject(class_TcpRepairWindow, ctor, trw.snd_wl1, trw.snd_wnd, trw.max_window,
            trw.rcv_wnd, trw.rcv_wup, tcpinfo.tcpi_rcv_wscale);
}

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

/*
 * JNI registration.
 */
// clang-format off
static const JNINativeMethod gNetworkUtilMethods[] = {
    /* name, signature, funcPtr */
    { "bindProcessToNetworkHandle", "(J)Z", (void*) android_net_utils_bindProcessToNetworkHandle },
    { "getBoundNetworkHandleForProcess", "()J", (void*) android_net_utils_getBoundNetworkHandleForProcess },
    { "bindProcessToNetworkForHostResolution", "(I)Z", (void*) android_net_utils_bindProcessToNetworkForHostResolution },
    { "bindSocketToNetworkHandle", "(Ljava/io/FileDescriptor;J)I", (void*) android_net_utils_bindSocketToNetworkHandle },
    { "attachDropAllBPFFilter", "(Ljava/io/FileDescriptor;)V", (void*) android_net_utils_attachDropAllBPFFilter },
    { "detachBPFFilter", "(Ljava/io/FileDescriptor;)V", (void*) android_net_utils_detachBPFFilter },
    { "getTcpRepairWindow", "(Ljava/io/FileDescriptor;)Landroid/net/TcpRepairWindow;", (void*) android_net_utils_getTcpRepairWindow },
    { "resNetworkSend", "(J[BII)Ljava/io/FileDescriptor;", (void*) android_net_utils_resNetworkSend },
    { "resNetworkQuery", "(JLjava/lang/String;III)Ljava/io/FileDescriptor;", (void*) android_net_utils_resNetworkQuery },
    { "resNetworkResult", "(Ljava/io/FileDescriptor;)Landroid/net/DnsResolver$DnsResponse;", (void*) android_net_utils_resNetworkResult },
    { "resNetworkCancel", "(Ljava/io/FileDescriptor;)V", (void*) android_net_utils_resNetworkCancel },
    { "getDnsNetwork", "()Landroid/net/Network;", (void*) android_net_utils_getDnsNetwork },
};
// clang-format on

int register_android_net_NetworkUtils(JNIEnv* env)
{
    return jniRegisterNativeMethods(env, NETUTILS_PKG_NAME, gNetworkUtilMethods,
                                    NELEM(gNetworkUtilMethods));
}

}; // namespace android