net/jni/apf_jni.cpp

/*
 * Copyright 2016, 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.
 */

#include <nativehelper/JNIHelp.h>
#include <nativehelper/ScopedUtfChars.h>
#include <jni.h>
#include <pcap.h>
#include <stdlib.h>
#include <string>
#include <utils/Log.h>

#include "apf_interpreter.h"

#define ARRAY_SIZE(x) (sizeof(x) / sizeof((x)[0]))

// JNI function acting as simply call-through to native APF interpreter.
static jint com_android_server_ApfTest_apfSimulate(
        JNIEnv* env, jclass, jbyteArray program, jbyteArray packet, jint filter_age) {
    return accept_packet(
            (uint8_t*)env->GetByteArrayElements(program, NULL),
            env->GetArrayLength(program),
            (uint8_t*)env->GetByteArrayElements(packet, NULL),
            env->GetArrayLength(packet),
            filter_age);
}

class ScopedPcap {
  public:
    explicit ScopedPcap(pcap_t* pcap) : pcap_ptr(pcap) {}
    ~ScopedPcap() {
        pcap_close(pcap_ptr);
    }

    pcap_t* get() const { return pcap_ptr; };
  private:
    pcap_t* const pcap_ptr;
};

class ScopedFILE {
  public:
    explicit ScopedFILE(FILE* fp) : file(fp) {}
    ~ScopedFILE() {
        fclose(file);
    }

    FILE* get() const { return file; };
  private:
    FILE* const file;
};

static void throwException(JNIEnv* env, const std::string& error) {
    jclass newExcCls = env->FindClass("java/lang/IllegalStateException");
    if (newExcCls == 0) {
      abort();
      return;
    }
    env->ThrowNew(newExcCls, error.c_str());
}

static jstring com_android_server_ApfTest_compileToBpf(JNIEnv* env, jclass, jstring jfilter) {
    ScopedUtfChars filter(env, jfilter);
    std::string bpf_string;
    ScopedPcap pcap(pcap_open_dead(DLT_EN10MB, 65535));
    if (pcap.get() == NULL) {
        throwException(env, "pcap_open_dead failed");
        return NULL;
    }

    // Compile "filter" to a BPF program
    bpf_program bpf;
    if (pcap_compile(pcap.get(), &bpf, filter.c_str(), 0, PCAP_NETMASK_UNKNOWN)) {
        throwException(env, "pcap_compile failed");
        return NULL;
    }

    // Translate BPF program to human-readable format
    const struct bpf_insn* insn = bpf.bf_insns;
    for (uint32_t i = 0; i < bpf.bf_len; i++) {
        bpf_string += bpf_image(insn++, i);
        bpf_string += "\n";
    }

    return env->NewStringUTF(bpf_string.c_str());
}

static jboolean com_android_server_ApfTest_compareBpfApf(JNIEnv* env, jclass, jstring jfilter,
        jstring jpcap_filename, jbyteArray japf_program) {
    ScopedUtfChars filter(env, jfilter);
    ScopedUtfChars pcap_filename(env, jpcap_filename);
    const uint8_t* apf_program = (uint8_t*)env->GetByteArrayElements(japf_program, NULL);
    const uint32_t apf_program_len = env->GetArrayLength(japf_program);

    // Open pcap file for BPF filtering
    ScopedFILE bpf_fp(fopen(pcap_filename.c_str(), "rb"));
    char pcap_error[PCAP_ERRBUF_SIZE];
    ScopedPcap bpf_pcap(pcap_fopen_offline(bpf_fp.get(), pcap_error));
    if (bpf_pcap.get() == NULL) {
        throwException(env, "pcap_fopen_offline failed: " + std::string(pcap_error));
        return false;
    }

    // Open pcap file for APF filtering
    ScopedFILE apf_fp(fopen(pcap_filename.c_str(), "rb"));
    ScopedPcap apf_pcap(pcap_fopen_offline(apf_fp.get(), pcap_error));
    if (apf_pcap.get() == NULL) {
        throwException(env, "pcap_fopen_offline failed: " + std::string(pcap_error));
        return false;
    }

    // Compile "filter" to a BPF program
    bpf_program bpf;
    if (pcap_compile(bpf_pcap.get(), &bpf, filter.c_str(), 0, PCAP_NETMASK_UNKNOWN)) {
        throwException(env, "pcap_compile failed");
        return false;
    }

    // Install BPF filter on bpf_pcap
    if (pcap_setfilter(bpf_pcap.get(), &bpf)) {
        throwException(env, "pcap_setfilter failed");
        return false;
    }

    while (1) {
        pcap_pkthdr bpf_header, apf_header;
        // Run BPF filter to the next matching packet.
        const uint8_t* bpf_packet = pcap_next(bpf_pcap.get(), &bpf_header);

        // Run APF filter to the next matching packet.
        const uint8_t* apf_packet;
        do {
            apf_packet = pcap_next(apf_pcap.get(), &apf_header);
        } while (apf_packet != NULL && !accept_packet(
                apf_program, apf_program_len, apf_packet, apf_header.len, 0));

        // Make sure both filters matched the same packet.
        if (apf_packet == NULL && bpf_packet == NULL)
             break;
        if (apf_packet == NULL || bpf_packet == NULL)
             return false;
        if (apf_header.len != bpf_header.len ||
                apf_header.ts.tv_sec != bpf_header.ts.tv_sec ||
                apf_header.ts.tv_usec != bpf_header.ts.tv_usec ||
                memcmp(apf_packet, bpf_packet, apf_header.len))
            return false;
    }
    return true;
}

extern "C" jint JNI_OnLoad(JavaVM* vm, void*) {
    JNIEnv *env;
    if (vm->GetEnv(reinterpret_cast<void**>(&env), JNI_VERSION_1_6) != JNI_OK) {
        ALOGE("ERROR: GetEnv failed");
        return -1;
    }

    static JNINativeMethod gMethods[] = {
            { "apfSimulate", "([B[BI)I",
                    (void*)com_android_server_ApfTest_apfSimulate },
            { "compileToBpf", "(Ljava/lang/String;)Ljava/lang/String;",
                    (void*)com_android_server_ApfTest_compileToBpf },
            { "compareBpfApf", "(Ljava/lang/String;Ljava/lang/String;[B)Z",
                    (void*)com_android_server_ApfTest_compareBpfApf },
    };

    jniRegisterNativeMethods(env, "android/net/apf/ApfTest",
            gMethods, ARRAY_SIZE(gMethods));

    return JNI_VERSION_1_6;
}