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Commit 0c455664 authored by Orion Hodson's avatar Orion Hodson
Browse files

Remove dependency on legacy jniGetFDFromFileDescriptor 

On S, use the NDK API to get the native file descriptor from a
FileDescriptor. Pre-S, fallback to implementation knowledge.

Bug: 158749603
Test: manual
Change-Id: I02b261ee2747df2637bd55b0c1ade3c62c73b17e
parent 9f48429f

jni/network_stack_utils_jni.cpp

+65 −5
Original line number Diff line number Diff line
@@ -16,6 +16,7 @@ 


#define LOG_TAG "NetworkStackUtils-JNI"



#include <dlfcn.h>

#include <errno.h>

#include <jni.h>

#include <linux/filter.h>
@@ -27,11 +28,11 @@ 
#include <netinet/ip6.h>

#include <netinet/udp.h>

#include <stdlib.h>

#include <sys/system_properties.h>



#include <string>



#include <nativehelper/JNIHelp.h>

#include <nativehelper/JNIHelpCompat.h>



#include <android/log.h>
@@ -57,6 +58,65 @@ static bool checkLenAndCopy(JNIEnv* env, const jbyteArray& addr, int len, void* 
    return true;

}



static int getNativeFileDescriptorWithoutNdk(JNIEnv* env, jobject javaFd) {

    // Prior to Android S, we need to find the descriptor field in the FileDescriptor class. The

    // symbol name has been stable in libcore, but is a private implementation detail.

    static jfieldID descriptorFieldID = nullptr;

    if (descriptorFieldID == nullptr) {

        jclass fileDescriptorClass = env->FindClass("java/io/FileDescriptor");

        descriptorFieldID = env->GetFieldID(fileDescriptorClass, "descriptor", "I");

        env->DeleteLocalRef(fileDescriptorClass);

        if (descriptorFieldID == nullptr) {

            __android_log_print(ANDROID_LOG_ERROR, LOG_TAG, "Failed to get descriptor field.");

            return -1;

        }

    }

    return javaFd != nullptr ? env->GetIntField(javaFd, descriptorFieldID) : -1;

}



static int getNativeFileDescriptorWithNdk(JNIEnv* env, jobject javaFd) {

    // Since Android S, there is an NDK API to get a file descriptor present in libnativehelper.so.

    // libnativehelper is loaded into all processes by the zygote since the zygote uses it

    // to load the Android Runtime and is also a public library (because of the NDK API).

    static int (*ndkGetFD)(JNIEnv*, jobject) = nullptr;

    if (ndkGetFD == nullptr) {

        void* handle = dlopen("libnativehelper.so", RTLD_NOLOAD | RTLD_NODELETE);

        ndkGetFD = reinterpret_cast<decltype(ndkGetFD)>(dlsym(handle, "AFileDescriptor_getFD"));

        if (ndkGetFD == nullptr) {

            __android_log_print(ANDROID_LOG_ERROR, LOG_TAG,

                                "Failed to dlsym(AFileDescriptor_getFD): %s", dlerror());

            dlclose(handle);

            return -1;

        }

        dlclose(handle);

    }

    return javaFd != nullptr ? ndkGetFD(env, javaFd) : -1;

}



static int getNativeFileDescriptor(JNIEnv* env, jobject javaFd) {

    static bool preferNdkFileDescriptorApi = false;

    static bool probeNdkFileDescriptorApi = true;



    if (probeNdkFileDescriptorApi) {

        // Check if we should use the NDK File Descriptor API introduced in S.

        preferNdkFileDescriptorApi = (android_get_device_api_level() >= __ANDROID_API_S__);

        if (!preferNdkFileDescriptorApi) {

            // Check if this is a device with Android S dogfood build.

            static constexpr const char* kCodenameProperty = "ro.build.version.codename";

            char codename[PROP_VALUE_MAX] = { 0 };

            preferNdkFileDescriptorApi = (__system_property_get(kCodenameProperty, codename) > 0 &&

                                          strncmp(codename, "S", 2) == 0);

        }

        probeNdkFileDescriptorApi = false;

    }



    if (preferNdkFileDescriptorApi) {

        return getNativeFileDescriptorWithNdk(env, javaFd);

    } else {

        return getNativeFileDescriptorWithoutNdk(env, javaFd);

    }

}



static void network_stack_utils_addArpEntry(JNIEnv *env, jobject thiz, jbyteArray ethAddr,

        jbyteArray ipv4Addr, jstring ifname, jobject javaFd) {

    arpreq req = {};
@@ -84,7 +144,7 @@ static void network_stack_utils_addArpEntry(JNIEnv *env, jobject thiz, jbyteArra 
    env->GetStringUTFRegion(ifname, 0, ifLen, req.arp_dev);



    req.arp_flags = ATF_COM;  // Completed entry (ha valid)

    int fd = jniGetFDFromFileDescriptor(env, javaFd);

    int fd = getNativeFileDescriptor(env, javaFd);

    if (fd < 0) {

        jniThrowExceptionFmt(env, "java/io/IOException", "Invalid file descriptor");

        return;
@@ -122,7 +182,7 @@ static void network_stack_utils_attachDhcpFilter(JNIEnv *env, jobject clazz, job 
        filter_code,

    };



    int fd = jniGetFDFromFileDescriptor(env, javaFd);

    int fd = getNativeFileDescriptor(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));
@@ -155,7 +215,7 @@ static void network_stack_utils_attachRaFilter(JNIEnv *env, jobject clazz, jobje 
        filter_code,

    };



    int fd = jniGetFDFromFileDescriptor(env, javaFd);

    int fd = getNativeFileDescriptor(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));
@@ -230,7 +290,7 @@ static void network_stack_utils_attachControlPacketFilter( 
        filter_code,

    };



    int fd = jniGetFDFromFileDescriptor(env, javaFd);

    int fd = getNativeFileDescriptor(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));