Detailed Explanation of Android WiFi forget() Operation Example

Detailed Explanation of Android Wifi's forget() Operation

When handling a certain Wifi connection, we sometimes need to forget the current connection password information. To perform this operation, we need to call the WifiManager::forget() function:

/** 
 * Delete the network in the supplicant config. 
 * 
 * This function is used instead of a sequence of removeNetwork() 
 * and saveConfiguration(). 
 * 
 * @param config the set of variables that describe the configuration, 
 *      contained in a {@link WifiConfiguration} object. 
 * @param listener for callbacks on success or failure. Can be null. 
 * @throws IllegalStateException if the WifiManager instance needs to be 
 * initialized again 
 * @hide 
 */ 
public void forget(int netId, ActionListener listener) { 
  if (netId < 0) throw new IllegalArgumentException("Network id cannot be negative"); 
  validateChannel(); 
  sAsyncChannel.sendMessage(FORGET_NETWORK, netId, putListener(listener)); 
} 

From the function description, calling the forget() function will delete the configuration information of the current network connection from wpa_supplicant.conf; after that, this network will not have the action of automatic reconnection because there is no configuration information of this network in the conf file.

Track the FORGET_NETWORK message, the ClientHandler in WifiServiceImpl handles:

case WifiManager.FORGET_NETWORK: 
  if (isOwner(msg.sendingUid)) { 
    mWifiStateMachine.sendMessage(Message.obtain(msg)); 
  } else { 
    Slog.e(TAG, "Forget is not authorized for user"); 
    replyFailed(msg, WifiManager.FORGET_NETWORK_FAILED, 
        WifiManager.NOT_AUTHORIZED); 
  } 
  break; 

Simply forward the message to WifiStateMachine. At this time, the Wi-Fi is connected, the current state in WifiStateMachine is ConnectedState, and its parent state ConnectModeState handles:

case WifiManager.FORGET_NETWORK: 
  // Debug only, remember last configuration that was forgotten 
  WifiConfiguration toRemove 
      = mWifiConfigStore.getWifiConfiguration(message.arg1); 
  if (toRemove == null) { 
    lastForgetConfigurationAttempt = null; 
  } else { 
    lastForgetConfigurationAttempt = new WifiConfiguration(toRemove); 
  } 
  // check that the caller owns this network 
  netId = message.arg1; 
  if (!mWifiConfigStore.canModifyNetwork(message.sendingUid, netId, 
      /* onlyAnnotate */ false)) { 
    logw("Not authorized to forget network " 
       + " cnid=" + netId 
       + " uid=" + message.sendingUid); 
    replyToMessage(message, WifiManager.FORGET_NETWORK_FAILED, 
        WifiManager.NOT_AUTHORIZED); 
    break; 
  } 
  if (mWifiConfigStore.forgetNetwork(message.arg1)) { 
    replyToMessage(message, WifiManager.FORGET_NETWORK_SUCCEEDED); 
    broadcastWifiCredentialChanged(WifiManager.WIFI_CREDENTIAL_FORGOT, 
        (WifiConfiguration) message.obj); 
  } else { 
    loge("Failed to forget network"); 
    replyToMessage(message, WifiManager.FORGET_NETWORK_FAILED, 
        WifiManager.ERROR); 
  } 
  break; 

mWifiConfigStore.forgetNetwork()：

/** 
 * Forget the specified network and save config 
 * 
 * @param netId network to forget 
 * @return {@code true} if it succeeds, {@code false} otherwise 
 */ 
boolean forgetNetwork(int netId) { 
  if (showNetworks) localLog("forgetNetwork", netId); 
  WifiConfiguration config = mConfiguredNetworks.get(netId); 
  boolean remove = removeConfigAndSendBroadcastIfNeeded(netId); 
  if (!remove) { 
    //success but we don't want to remove the network from the supplicant conf file 
    return true; 
  } 
  if (mWifiNative.removeNetwork(netId)) { 
    if (config != null && config.isPasspoint()) { 
      writePasspointConfigs(config.FQDN, null); 
    } 
    mWifiNative.saveConfig(); 
    writeKnownNetworkHistory(true); 
    return true; 
  } else { 
    log("Failed to remove network ") + netId); 
    return false; 
  } 
} 

According to the current network netId passed in, the removeNetwork() and saveConfig() methods of WifiNative are called respectively to delete the configuration information of the conf file and save it; after the execution is completed, the forget() function ends. Through the code, we find that executing the forget() function does not cause a state change in the WifiStateMachine.

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