path: root/src/lib/ares_android.c

/* MIT License
 *
 * Copyright (c) John Schember
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice (including the next
 * paragraph) shall be included in all copies or substantial portions of the
 * Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 *
 * SPDX-License-Identifier: MIT
 */
#if defined(ANDROID) || defined(__ANDROID__)

#  include <jni.h>

#  include "ares_setup.h"
#  include "ares.h"
#  include "ares_android.h"
#  include "ares_private.h"

static JavaVM   *android_jvm                  = NULL;
static jobject   android_connectivity_manager = NULL;

/* ConnectivityManager.getActiveNetwork */
static jmethodID android_cm_active_net_mid = NULL;
/* ConnectivityManager.getLinkProperties */
static jmethodID android_cm_link_props_mid = NULL;
/* LinkProperties.getDnsServers */
static jmethodID android_lp_dns_servers_mid = NULL;
/* LinkProperties.getDomains */
static jmethodID android_lp_domains_mid = NULL;
/* List.size */
static jmethodID android_list_size_mid = NULL;
/* List.get */
static jmethodID android_list_get_mid = NULL;
/* InetAddress.getHostAddress */
static jmethodID android_ia_host_addr_mid = NULL;

static jclass    jni_get_class(JNIEnv *env, const char *path)
{
  jclass cls = NULL;

  if (env == NULL || path == NULL || *path == '\0') {
    return NULL;
  }

  cls = (*env)->FindClass(env, path);
  if ((*env)->ExceptionOccurred(env)) {
    (*env)->ExceptionClear(env);
    return NULL;
  }
  return cls;
}

static jmethodID jni_get_method_id(JNIEnv *env, jclass cls,
                                   const char *func_name, const char *signature)
{
  jmethodID mid = NULL;

  if (env == NULL || cls == NULL || func_name == NULL || *func_name == '\0' ||
      signature == NULL || *signature == '\0') {
    return NULL;
  }

  mid = (*env)->GetMethodID(env, cls, func_name, signature);
  if ((*env)->ExceptionOccurred(env)) {
    (*env)->ExceptionClear(env);
    return NULL;
  }

  return mid;
}

void ares_library_init_jvm(JavaVM *jvm)
{
  android_jvm = jvm;
}

int ares_library_init_android(jobject connectivity_manager)
{
  JNIEnv       *env          = NULL;
  int           need_detatch = 0;
  int           res;
  ares_status_t ret     = ARES_ENOTINITIALIZED;
  jclass        obj_cls = NULL;

  if (android_jvm == NULL) {
    goto cleanup;
  }

  res = (*android_jvm)->GetEnv(android_jvm, (void **)&env, JNI_VERSION_1_6);
  if (res == JNI_EDETACHED) {
    env          = NULL;
    res          = (*android_jvm)->AttachCurrentThread(android_jvm, &env, NULL);
    need_detatch = 1;
  }
  if (res != JNI_OK || env == NULL) {
    goto cleanup;
  }

  android_connectivity_manager =
    (*env)->NewGlobalRef(env, connectivity_manager);
  if (android_connectivity_manager == NULL) {
    goto cleanup;
  }

  /* Initialization has succeeded. Now attempt to cache the methods that will be
   * called by ares_get_android_server_list. */
  ret = ARES_SUCCESS;

  /* ConnectivityManager in API 1. */
  obj_cls = jni_get_class(env, "android/net/ConnectivityManager");
  if (obj_cls == NULL) {
    goto cleanup;
  }

  /* ConnectivityManager.getActiveNetwork in API 23. */
  android_cm_active_net_mid = jni_get_method_id(
    env, obj_cls, "getActiveNetwork", "()Landroid/net/Network;");
  if (android_cm_active_net_mid == NULL) {
    goto cleanup;
  }

  /* ConnectivityManager.getLinkProperties in API 21. */
  android_cm_link_props_mid =
    jni_get_method_id(env, obj_cls, "getLinkProperties",
                      "(Landroid/net/Network;)Landroid/net/LinkProperties;");
  if (android_cm_link_props_mid == NULL) {
    goto cleanup;
  }

  /* LinkProperties in API 21. */
  (*env)->DeleteLocalRef(env, obj_cls);
  obj_cls = jni_get_class(env, "android/net/LinkProperties");
  if (obj_cls == NULL) {
    goto cleanup;
  }

  /* getDnsServers in API 21. */
  android_lp_dns_servers_mid =
    jni_get_method_id(env, obj_cls, "getDnsServers", "()Ljava/util/List;");
  if (android_lp_dns_servers_mid == NULL) {
    goto cleanup;
  }

  /* getDomains in API 21. */
  android_lp_domains_mid =
    jni_get_method_id(env, obj_cls, "getDomains", "()Ljava/lang/String;");
  if (android_lp_domains_mid == NULL) {
    goto cleanup;
  }

  (*env)->DeleteLocalRef(env, obj_cls);
  obj_cls = jni_get_class(env, "java/util/List");
  if (obj_cls == NULL) {
    goto cleanup;
  }

  android_list_size_mid = jni_get_method_id(env, obj_cls, "size", "()I");
  if (android_list_size_mid == NULL) {
    goto cleanup;
  }

  android_list_get_mid =
    jni_get_method_id(env, obj_cls, "get", "(I)Ljava/lang/Object;");
  if (android_list_get_mid == NULL) {
    goto cleanup;
  }

  (*env)->DeleteLocalRef(env, obj_cls);
  obj_cls = jni_get_class(env, "java/net/InetAddress");
  if (obj_cls == NULL) {
    goto cleanup;
  }

  android_ia_host_addr_mid =
    jni_get_method_id(env, obj_cls, "getHostAddress", "()Ljava/lang/String;");
  if (android_ia_host_addr_mid == NULL) {
    goto cleanup;
  }

  (*env)->DeleteLocalRef(env, obj_cls);
  goto done;

cleanup:
  if (obj_cls != NULL) {
    (*env)->DeleteLocalRef(env, obj_cls);
  }

  android_cm_active_net_mid  = NULL;
  android_cm_link_props_mid  = NULL;
  android_lp_dns_servers_mid = NULL;
  android_lp_domains_mid     = NULL;
  android_list_size_mid      = NULL;
  android_list_get_mid       = NULL;
  android_ia_host_addr_mid   = NULL;

done:
  if (need_detatch) {
    (*android_jvm)->DetachCurrentThread(android_jvm);
  }

  return ret;
}

int ares_library_android_initialized(void)
{
  if (android_jvm == NULL || android_connectivity_manager == NULL) {
    return ARES_ENOTINITIALIZED;
  }
  return ARES_SUCCESS;
}

void ares_library_cleanup_android(void)
{
  JNIEnv *env          = NULL;
  int     need_detatch = 0;
  int     res;

  if (android_jvm == NULL || android_connectivity_manager == NULL) {
    return;
  }

  res = (*android_jvm)->GetEnv(android_jvm, (void **)&env, JNI_VERSION_1_6);
  if (res == JNI_EDETACHED) {
    env          = NULL;
    res          = (*android_jvm)->AttachCurrentThread(android_jvm, &env, NULL);
    need_detatch = 1;
  }
  if (res != JNI_OK || env == NULL) {
    return;
  }

  android_cm_active_net_mid  = NULL;
  android_cm_link_props_mid  = NULL;
  android_lp_dns_servers_mid = NULL;
  android_lp_domains_mid     = NULL;
  android_list_size_mid      = NULL;
  android_list_get_mid       = NULL;
  android_ia_host_addr_mid   = NULL;

  (*env)->DeleteGlobalRef(env, android_connectivity_manager);
  android_connectivity_manager = NULL;

  if (need_detatch) {
    (*android_jvm)->DetachCurrentThread(android_jvm);
  }
}

char **ares_get_android_server_list(size_t max_servers, size_t *num_servers)
{
  JNIEnv     *env             = NULL;
  jobject     active_network  = NULL;
  jobject     link_properties = NULL;
  jobject     server_list     = NULL;
  jobject     server          = NULL;
  jstring     str             = NULL;
  jint        nserv;
  const char *ch_server_address;
  int         res;
  size_t      i;
  char      **dns_list     = NULL;
  int         need_detatch = 0;

  if (android_jvm == NULL || android_connectivity_manager == NULL ||
      max_servers == 0 || num_servers == NULL) {
    return NULL;
  }

  if (android_cm_active_net_mid == NULL || android_cm_link_props_mid == NULL ||
      android_lp_dns_servers_mid == NULL || android_list_size_mid == NULL ||
      android_list_get_mid == NULL || android_ia_host_addr_mid == NULL) {
    return NULL;
  }

  res = (*android_jvm)->GetEnv(android_jvm, (void **)&env, JNI_VERSION_1_6);
  if (res == JNI_EDETACHED) {
    env          = NULL;
    res          = (*android_jvm)->AttachCurrentThread(android_jvm, &env, NULL);
    need_detatch = 1;
  }
  if (res != JNI_OK || env == NULL) {
    goto done;
  }

  /* JNI below is equivalent to this Java code.
     import android.content.Context;
     import android.net.ConnectivityManager;
     import android.net.LinkProperties;
     import android.net.Network;
     import java.net.InetAddress;
     import java.util.List;

     ConnectivityManager cm = (ConnectivityManager)this.getApplicationContext()
       .getSystemService(Context.CONNECTIVITY_SERVICE);
     Network an = cm.getActiveNetwork();
     LinkProperties lp = cm.getLinkProperties(an);
     List<InetAddress> dns = lp.getDnsServers();
     for (InetAddress ia: dns) {
       String ha = ia.getHostAddress();
     }

     Note: The JNI ConnectivityManager object and all method IDs were previously
           initialized in ares_library_init_android.
   */

  active_network = (*env)->CallObjectMethod(env, android_connectivity_manager,
                                            android_cm_active_net_mid);
  if (active_network == NULL) {
    goto done;
  }

  link_properties =
    (*env)->CallObjectMethod(env, android_connectivity_manager,
                             android_cm_link_props_mid, active_network);
  if (link_properties == NULL) {
    goto done;
  }

  server_list =
    (*env)->CallObjectMethod(env, link_properties, android_lp_dns_servers_mid);
  if (server_list == NULL) {
    goto done;
  }

  nserv = (*env)->CallIntMethod(env, server_list, android_list_size_mid);
  if (nserv > (jint)max_servers) {
    nserv = (jint)max_servers;
  }
  if (nserv <= 0) {
    goto done;
  }
  *num_servers = (size_t)nserv;

  dns_list = ares_malloc(sizeof(*dns_list) * (*num_servers));
  for (i = 0; i < *num_servers; i++) {
    size_t len = 64;
    server =
      (*env)->CallObjectMethod(env, server_list, android_list_get_mid, (jint)i);
    dns_list[i]    = ares_malloc(len);
    dns_list[i][0] = 0;
    if (server == NULL) {
      continue;
    }
    str = (*env)->CallObjectMethod(env, server, android_ia_host_addr_mid);
    ch_server_address = (*env)->GetStringUTFChars(env, str, 0);
    ares_strcpy(dns_list[i], ch_server_address, len);
    (*env)->ReleaseStringUTFChars(env, str, ch_server_address);
    (*env)->DeleteLocalRef(env, str);
    (*env)->DeleteLocalRef(env, server);
  }

done:
  if ((*env)->ExceptionOccurred(env)) {
    (*env)->ExceptionClear(env);
  }

  if (server_list != NULL) {
    (*env)->DeleteLocalRef(env, server_list);
  }
  if (link_properties != NULL) {
    (*env)->DeleteLocalRef(env, link_properties);
  }
  if (active_network != NULL) {
    (*env)->DeleteLocalRef(env, active_network);
  }

  if (need_detatch) {
    (*android_jvm)->DetachCurrentThread(android_jvm);
  }
  return dns_list;
}

char *ares_get_android_search_domains_list(void)
{
  JNIEnv     *env             = NULL;
  jobject     active_network  = NULL;
  jobject     link_properties = NULL;
  jstring     domains         = NULL;
  const char *domain;
  int         res;
  char       *domain_list  = NULL;
  int         need_detatch = 0;

  if (android_jvm == NULL || android_connectivity_manager == NULL) {
    return NULL;
  }

  if (android_cm_active_net_mid == NULL || android_cm_link_props_mid == NULL ||
      android_lp_domains_mid == NULL) {
    return NULL;
  }

  res = (*android_jvm)->GetEnv(android_jvm, (void **)&env, JNI_VERSION_1_6);
  if (res == JNI_EDETACHED) {
    env          = NULL;
    res          = (*android_jvm)->AttachCurrentThread(android_jvm, &env, NULL);
    need_detatch = 1;
  }
  if (res != JNI_OK || env == NULL) {
    goto done;
  }

  /* JNI below is equivalent to this Java code.
     import android.content.Context;
     import android.net.ConnectivityManager;
     import android.net.LinkProperties;

     ConnectivityManager cm = (ConnectivityManager)this.getApplicationContext()
       .getSystemService(Context.CONNECTIVITY_SERVICE);
     Network an = cm.getActiveNetwork();
     LinkProperties lp = cm.getLinkProperties(an);
   String domains = lp.getDomains();
     for (String domain: domains.split(",")) {
       String d = domain;
     }

     Note: The JNI ConnectivityManager object and all method IDs were previously
           initialized in ares_library_init_android.
   */

  active_network = (*env)->CallObjectMethod(env, android_connectivity_manager,
                                            android_cm_active_net_mid);
  if (active_network == NULL) {
    goto done;
  }

  link_properties =
    (*env)->CallObjectMethod(env, android_connectivity_manager,
                             android_cm_link_props_mid, active_network);
  if (link_properties == NULL) {
    goto done;
  }

  /* Get the domains. It is a common separated list of domains to search. */
  domains =
    (*env)->CallObjectMethod(env, link_properties, android_lp_domains_mid);
  if (domains == NULL) {
    goto done;
  }

  /* Split on , */
  domain      = (*env)->GetStringUTFChars(env, domains, 0);
  domain_list = ares_strdup(domain);
  (*env)->ReleaseStringUTFChars(env, domains, domain);
  (*env)->DeleteLocalRef(env, domains);

done:
  if ((*env)->ExceptionOccurred(env)) {
    (*env)->ExceptionClear(env);
  }

  if (link_properties != NULL) {
    (*env)->DeleteLocalRef(env, link_properties);
  }
  if (active_network != NULL) {
    (*env)->DeleteLocalRef(env, active_network);
  }

  if (need_detatch) {
    (*android_jvm)->DetachCurrentThread(android_jvm);
  }
  return domain_list;
}
#else
/* warning: ISO C forbids an empty translation unit */
typedef int dummy_make_iso_compilers_happy;
#endif