【转】Android软件限制AP的最大连接数

最近有个需要是要做成AP的最大连接数用户可配置，此处不讨论硬件限制，仅仅从软件方面去对Android源码做修改。

让/data/misc/wifi/hostapd.conf里面带上max_num_sta参数即可达到目的，例如要限制成10个，则max_num_sta=10。

Android原生代码不包含此参数，/data/misc/wifi/hostapd.conf会在AP开启的时候由/system/bin/netd通过softap set参数设置下去，查看netd相关源码，可以看到最后的配置文件是由system/netd/SoftapController.cpp中的SoftapController::setSoftap()函数根据java层传过来的参数设置的。

最简单的方式是使用原有的argv[5]，也就是Channel值，修改成包含Channel和max_num_sta两个值的参数，上层传参数时把这两个值合成，SoftapController::setSoftap()函数再把值解析出来即可，修改如下：

/*

• Arguments:

• argv[2] - wlan interface

• argv[3] - SSID

• argv[4] - Broadcast/Hidden

• argv[5] - Channel

• argv[6] - Security

• argv[7] - Key
  */
  int SoftapController::setSoftap(int argc, char *argv[]) {
  int hidden = 0;
  int channel = AP_CHANNEL_DEFAULT;
  int max_num_sta = 0;//add for sta limit 20180921

  if (argc < 5) {
  ALOGE("Softap set is missing arguments. Please use:");
  ALOGE("softap <wlan iface> <SSID> <hidden/broadcast> <channel> <wpa2?-psk|open> <passphrase>");
  return ResponseCode::CommandSyntaxError;
  }

  if (!strcasecmp(argv[4], "hidden"))
  hidden = 1;

  if (argc >= 5) {
  channel = atoi(argv[5]);
  //start add for sta limit 20180921
  char buf[PROPERTY_VALUE_MAX] = {'\0',};
  if (property_get("persist.sys.softap.limit", buf, "0")) {
  max_num_sta = (channel >> 16) & 0xFFFF;
  channel &= 0xFFFF;
  }
  //end add for sta limit 20180921
  if (channel <= 0)
  channel = AP_CHANNEL_DEFAULT;
  }

  std::string wbuf;
  if(max_num_sta) {
  std::string wbuf_tmp(StringPrintf("interface=%s\n"
  "driver=nl80211\n"
  "ctrl_interface=/data/misc/wifi/hostapd\n"
  "ssid=%s\n"
  "channel=%d\n"
  "ieee80211n=1\n"
  "hw_mode=%c\n"
  "ignore_broadcast_ssid=%d\n"
  "wowlan_triggers=any\n"
  "max_num_sta=%d\n",
  argv[2], argv[3], channel, (channel <= 14) ? 'g' : 'a', hidden, max_num_sta));
  wbuf = wbuf_tmp;
  }
  else {
  std::string wbuf_tmp(StringPrintf("interface=%s\n"
  "driver=nl80211\n"
  "ctrl_interface=/data/misc/wifi/hostapd\n"
  "ssid=%s\n"
  "channel=%d\n"
  "ieee80211n=1\n"
  "hw_mode=%c\n"
  "ignore_broadcast_ssid=%d\n"
  "wowlan_triggers=any\n",
  argv[2], argv[3], channel, (channel <= 14) ? 'g' : 'a', hidden));
  wbuf = wbuf_tmp;
  }

  std::string fbuf;
  if (argc > 7) {
  char psk_str[2*SHA256_DIGEST_LENGTH+1];
  if (!strcmp(argv[6], "wpa-psk")) {
  generatePsk(argv[3], argv[7], psk_str);
  fbuf = StringPrintf("%swpa=3\nwpa_pairwise=TKIP CCMP\nwpa_psk=%s\n", wbuf.c_str(), psk_str);
  } else if (!strcmp(argv[6], "wpa2-psk")) {
  generatePsk(argv[3], argv[7], psk_str);
  fbuf = StringPrintf("%swpa=2\nrsn_pairwise=CCMP\nwpa_psk=%s\n", wbuf.c_str(), psk_str);
  } else if (!strcmp(argv[6], "open")) {
  fbuf = wbuf;
  }
  } else if (argc > 6) {
  if (!strcmp(argv[6], "open")) {
  fbuf = wbuf;
  }
  } else {
  fbuf = wbuf;
  }

  if (!WriteStringToFile(fbuf, HOSTAPD_CONF_FILE, 0660, AID_SYSTEM, AID_WIFI)) {
  ALOGE("Cannot write to "%s": %s", HOSTAPD_CONF_FILE, strerror(errno));
  return ResponseCode::OperationFailed;
  }
  return ResponseCode::SoftapStatusResult;
  }
  至于java层的修改则是修改WifiConfiguration类，添加一个apMaxNumSta字段，并修改WifiConfiguration相关操作函数增加对此值的处理，最后通过NetworkManagementService.startAccessPoint把值传下去，修改如下：

  @Override
  public void startAccessPoint(
  WifiConfiguration wifiConfig, String wlanIface) {
  mContext.enforceCallingOrSelfPermission(CONNECTIVITY_INTERNAL, TAG);
  try {
  if (wifiConfig == null) {
  mConnector.execute("softap", "set", wlanIface);
  } else {
  if (SystemProperties.getInt("persist.sys.softap.limit", 0) != 0 && wifiConfig.apMaxNumSta != 0) {
  int mix = (wifiConfig.apMaxNumSta << 16) | wifiConfig.apChannel ;
  //start add by gerhard.lao for sta limit 20180921
  Slog.d(TAG, "startAccessPoint apMaxNumSta " + wifiConfig.apMaxNumSta +
  "apChannel " + wifiConfig.apChannel + "mix " + mix);
  mConnector.execute("softap", "set", wlanIface, wifiConfig.SSID,
  "broadcast", Integer.toString(mix),
  getSecurityType(wifiConfig),
  new SensitiveArg(wifiConfig.preSharedKey));
  //end add by gerhard.lao for sta limit 20180921
  } else {
  mConnector.execute("softap", "set", wlanIface, wifiConfig.SSID,
  "broadcast", Integer.toString(wifiConfig.apChannel),
  getSecurityType(wifiConfig),
  new SensitiveArg(wifiConfig.preSharedKey));
  }
  }
  mConnector.execute("softap", "startap");
  } catch (NativeDaemonConnectorException e) {
  throw e.rethrowAsParcelableException();
  }
  }
  这样，上层使用的时候设置apMaxNumSta即可带到native层然后写/data/misc/wifi/hostapd.conf，最终开启AP的时候会根据此参数限制最大连接数。

或者使用更简单直接的方式：

SoftapController::setSoftap()读取persist.sys.softap.limit值然后如果是非0值就应用到配置里面：

/*

• Arguments:

• argv[2] - wlan interface

• argv[3] - SSID

• argv[4] - Broadcast/Hidden

• argv[5] - Channel

• argv[6] - Security

• argv[7] - Key
  */
  int SoftapController::setSoftap(int argc, char *argv[]) {
  int hidden = 0;
  int channel = AP_CHANNEL_DEFAULT;

  if (argc < 5) {
  ALOGE("Softap set is missing arguments. Please use:");
  ALOGE("softap <wlan iface> <SSID> <hidden/broadcast> <channel> <wpa2?-psk|open> <passphrase>");
  return ResponseCode::CommandSyntaxError;
  }

  if (!strcasecmp(argv[4], "hidden"))
  hidden = 1;

  if (argc >= 5) {
  channel = atoi(argv[5]);
  if (channel <= 0)
  channel = AP_CHANNEL_DEFAULT;
  }

  //start add for sta limit 20180921
  int max_num_sta = 0;
  char buf[PROPERTY_VALUE_MAX] = {'\0',};
  if (property_get("persist.sys.softap.limit", buf, "0")) {
  max_num_sta = atoi(buf);
  if(max_num_sta != 0) {
  if(max_num_sta < 0 || max_num_sta > 255)
  max_num_sta = 0;
  }
  }
  //end add for sta limit 20180921

  std::string wbuf;
  if(max_num_sta) {
  std::string wbuf_tmp(StringPrintf("interface=%s\n"
  "driver=nl80211\n"
  "ctrl_interface=/data/misc/wifi/hostapd\n"
  "ssid=%s\n"
  "channel=%d\n"
  "ieee80211n=1\n"
  "hw_mode=%c\n"
  "ignore_broadcast_ssid=%d\n"
  "wowlan_triggers=any\n"
  "max_num_sta=%d\n",
  argv[2], argv[3], channel, (channel <= 14) ? 'g' : 'a', hidden, max_num_sta));
  wbuf = wbuf_tmp;
  }
  else {
  std::string wbuf_tmp(StringPrintf("interface=%s\n"
  "driver=nl80211\n"
  "ctrl_interface=/data/misc/wifi/hostapd\n"
  "ssid=%s\n"
  "channel=%d\n"
  "ieee80211n=1\n"
  "hw_mode=%c\n"
  "ignore_broadcast_ssid=%d\n"
  "wowlan_triggers=any\n",
  argv[2], argv[3], channel, (channel <= 14) ? 'g' : 'a', hidden));
  wbuf = wbuf_tmp;
  }

  std::string fbuf;
  if (argc > 7) {
  char psk_str[2*SHA256_DIGEST_LENGTH+1];
  if (!strcmp(argv[6], "wpa-psk")) {
  generatePsk(argv[3], argv[7], psk_str);
  fbuf = StringPrintf("%swpa=3\nwpa_pairwise=TKIP CCMP\nwpa_psk=%s\n", wbuf.c_str(), psk_str);
  } else if (!strcmp(argv[6], "wpa2-psk")) {
  generatePsk(argv[3], argv[7], psk_str);
  fbuf = StringPrintf("%swpa=2\nrsn_pairwise=CCMP\nwpa_psk=%s\n", wbuf.c_str(), psk_str);
  } else if (!strcmp(argv[6], "open")) {
  fbuf = wbuf;
  }
  } else if (argc > 6) {
  if (!strcmp(argv[6], "open")) {
  fbuf = wbuf;
  }
  } else {
  fbuf = wbuf;
  }

  if (!WriteStringToFile(fbuf, HOSTAPD_CONF_FILE, 0660, AID_SYSTEM, AID_WIFI)) {
  ALOGE("Cannot write to "%s": %s", HOSTAPD_CONF_FILE, strerror(errno));
  return ResponseCode::OperationFailed;
  }
  return ResponseCode::SoftapStatusResult;
  }
  ————————————————
  版权声明：本文为CSDN博主「觅风者」的原创文章，遵循 CC 4.0 BY-SA 版权协议，转载请附上原文出处链接及本声明。
  原文链接：https://blog.csdn.net/laoguanhua/article/details/82810386