1 /* 2 * Copyright (C) 2011 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 package android.net.wifi; 18 19 import android.content.BroadcastReceiver; 20 import android.content.ContentResolver; 21 import android.content.Context; 22 import android.content.Intent; 23 import android.content.IntentFilter; 24 import android.database.ContentObserver; 25 import android.net.ConnectivityManager; 26 import android.net.LinkProperties; 27 import android.net.NetworkInfo; 28 import android.net.wifi.RssiPacketCountInfo; 29 import android.os.Message; 30 import android.os.SystemClock; 31 import android.provider.Settings; 32 import android.provider.Settings.Secure; 33 import android.util.Log; 34 import android.util.LruCache; 35 36 import com.android.internal.R; 37 import com.android.internal.util.AsyncChannel; 38 import com.android.internal.util.Protocol; 39 import com.android.internal.util.State; 40 import com.android.internal.util.StateMachine; 41 42 import java.io.FileDescriptor; 43 import java.io.PrintWriter; 44 import java.text.DecimalFormat; 45 46 /** 47 * WifiWatchdogStateMachine monitors the connection to a WiFi network. When WiFi 48 * connects at L2 layer, the beacons from access point reach the device and it 49 * can maintain a connection, but the application connectivity can be flaky (due 50 * to bigger packet size exchange). 51 * <p> 52 * We now monitor the quality of the last hop on WiFi using packet loss ratio as 53 * an indicator to decide if the link is good enough to switch to Wi-Fi as the 54 * uplink. 55 * <p> 56 * When WiFi is connected, the WiFi watchdog keeps sampling the RSSI and the 57 * instant packet loss, and record it as per-AP loss-to-rssi statistics. When 58 * the instant packet loss is higher than a threshold, the WiFi watchdog sends a 59 * poor link notification to avoid WiFi connection temporarily. 60 * <p> 61 * While WiFi is being avoided, the WiFi watchdog keep watching the RSSI to 62 * bring the WiFi connection back. Once the RSSI is high enough to achieve a 63 * lower packet loss, a good link detection is sent such that the WiFi 64 * connection become available again. 65 * <p> 66 * BSSID roaming has been taken into account. When user is moving across 67 * multiple APs, the WiFi watchdog will detect that and keep watching the 68 * currently connected AP. 69 * <p> 70 * Power impact should be minimal since much of the measurement relies on 71 * passive statistics already being tracked at the driver and the polling is 72 * done when screen is turned on and the RSSI is in a certain range. 73 * 74 * @hide 75 */ 76 public class WifiWatchdogStateMachine extends StateMachine { 77 78 /* STOPSHIP: Keep this configurable for debugging until ship */ 79 private static boolean DBG = false; 80 81 private static final int BASE = Protocol.BASE_WIFI_WATCHDOG; 82 83 /* Internal events */ 84 private static final int EVENT_WATCHDOG_TOGGLED = BASE + 1; 85 private static final int EVENT_NETWORK_STATE_CHANGE = BASE + 2; 86 private static final int EVENT_RSSI_CHANGE = BASE + 3; 87 private static final int EVENT_SUPPLICANT_STATE_CHANGE = BASE + 4; 88 private static final int EVENT_WIFI_RADIO_STATE_CHANGE = BASE + 5; 89 private static final int EVENT_WATCHDOG_SETTINGS_CHANGE = BASE + 6; 90 private static final int EVENT_BSSID_CHANGE = BASE + 7; 91 private static final int EVENT_SCREEN_ON = BASE + 8; 92 private static final int EVENT_SCREEN_OFF = BASE + 9; 93 94 /* Internal messages */ 95 private static final int CMD_RSSI_FETCH = BASE + 11; 96 97 /* Notifications from/to WifiStateMachine */ 98 static final int POOR_LINK_DETECTED = BASE + 21; 99 static final int GOOD_LINK_DETECTED = BASE + 22; 100 101 public static final boolean DEFAULT_POOR_NETWORK_AVOIDANCE_ENABLED = false; 102 103 /* 104 * RSSI levels as used by notification icon 105 * Level 4 -55 <= RSSI 106 * Level 3 -66 <= RSSI < -55 107 * Level 2 -77 <= RSSI < -67 108 * Level 1 -88 <= RSSI < -78 109 * Level 0 RSSI < -88 110 */ 111 112 /** 113 * WiFi link statistics is monitored and recorded actively below this threshold. 114 * <p> 115 * Larger threshold is more adaptive but increases sampling cost. 116 */ 117 private static final int LINK_MONITOR_LEVEL_THRESHOLD = WifiManager.RSSI_LEVELS - 1; 118 119 /** 120 * Remember packet loss statistics of how many BSSIDs. 121 * <p> 122 * Larger size is usually better but requires more space. 123 */ 124 private static final int BSSID_STAT_CACHE_SIZE = 20; 125 126 /** 127 * RSSI range of a BSSID statistics. 128 * Within the range, (RSSI -> packet loss %) mappings are stored. 129 * <p> 130 * Larger range is usually better but requires more space. 131 */ 132 private static final int BSSID_STAT_RANGE_LOW_DBM = -105; 133 134 /** 135 * See {@link #BSSID_STAT_RANGE_LOW_DBM}. 136 */ 137 private static final int BSSID_STAT_RANGE_HIGH_DBM = -45; 138 139 /** 140 * How many consecutive empty data point to trigger a empty-cache detection. 141 * In this case, a preset/default loss value (function on RSSI) is used. 142 * <p> 143 * In normal uses, some RSSI values may never be seen due to channel randomness. 144 * However, the size of such empty RSSI chunk in normal use is generally 1~2. 145 */ 146 private static final int BSSID_STAT_EMPTY_COUNT = 3; 147 148 /** 149 * Sample interval for packet loss statistics, in msec. 150 * <p> 151 * Smaller interval is more accurate but increases sampling cost (battery consumption). 152 */ 153 private static final long LINK_SAMPLING_INTERVAL_MS = 1 * 1000; 154 155 /** 156 * Coefficients (alpha) for moving average for packet loss tracking. 157 * Must be within (0.0, 1.0). 158 * <p> 159 * Equivalent number of samples: N = 2 / alpha - 1 . 160 * We want the historic loss to base on more data points to be statistically reliable. 161 * We want the current instant loss to base on less data points to be responsive. 162 */ 163 private static final double EXP_COEFFICIENT_RECORD = 0.1; 164 165 /** 166 * See {@link #EXP_COEFFICIENT_RECORD}. 167 */ 168 private static final double EXP_COEFFICIENT_MONITOR = 0.5; 169 170 /** 171 * Thresholds for sending good/poor link notifications, in packet loss %. 172 * Good threshold must be smaller than poor threshold. 173 * Use smaller poor threshold to avoid WiFi more aggressively. 174 * Use smaller good threshold to bring back WiFi more conservatively. 175 * <p> 176 * When approaching the boundary, loss ratio jumps significantly within a few dBs. 177 * 50% loss threshold is a good balance between accuracy and reponsiveness. 178 * <=10% good threshold is a safe value to avoid jumping back to WiFi too easily. 179 */ 180 private static final double POOR_LINK_LOSS_THRESHOLD = 0.5; 181 182 /** 183 * See {@link #POOR_LINK_LOSS_THRESHOLD}. 184 */ 185 private static final double GOOD_LINK_LOSS_THRESHOLD = 0.1; 186 187 /** 188 * Number of samples to confirm before sending a poor link notification. 189 * Response time = confirm_count * sample_interval . 190 * <p> 191 * A smaller threshold improves response speed but may suffer from randomness. 192 * According to experiments, 3~5 are good values to achieve a balance. 193 * These parameters should be tuned along with {@link #LINK_SAMPLING_INTERVAL_MS}. 194 */ 195 private static final int POOR_LINK_SAMPLE_COUNT = 3; 196 197 /** 198 * Minimum volume (converted from pkt/sec) to detect a poor link, to avoid randomness. 199 * <p> 200 * According to experiments, 1pkt/sec is too sensitive but 3pkt/sec is slightly unresponsive. 201 */ 202 private static final double POOR_LINK_MIN_VOLUME = 2.0 * LINK_SAMPLING_INTERVAL_MS / 1000.0; 203 204 /** 205 * When a poor link is detected, we scan over this range (based on current 206 * poor link RSSI) for a target RSSI that satisfies a target packet loss. 207 * Refer to {@link #GOOD_LINK_TARGET}. 208 * <p> 209 * We want range_min not too small to avoid jumping back to WiFi too easily. 210 */ 211 private static final int GOOD_LINK_RSSI_RANGE_MIN = 3; 212 213 /** 214 * See {@link #GOOD_LINK_RSSI_RANGE_MIN}. 215 */ 216 private static final int GOOD_LINK_RSSI_RANGE_MAX = 20; 217 218 /** 219 * Adaptive good link target to avoid flapping. 220 * When a poor link is detected, a good link target is calculated as follows: 221 * <p> 222 * targetRSSI = min { rssi | loss(rssi) < GOOD_LINK_LOSS_THRESHOLD } + rssi_adj[i], 223 * where rssi is within the above GOOD_LINK_RSSI_RANGE. 224 * targetCount = sample_count[i] . 225 * <p> 226 * While WiFi is being avoided, we keep monitoring its signal strength. 227 * Good link notification is sent when we see current RSSI >= targetRSSI 228 * for targetCount consecutive times. 229 * <p> 230 * Index i is incremented each time after a poor link detection. 231 * Index i is decreased to at most k if the last poor link was at lease reduce_time[k] ago. 232 * <p> 233 * Intuitively, larger index i makes it more difficult to get back to WiFi, avoiding flapping. 234 * In experiments, (+9 dB / 30 counts) makes it quite difficult to achieve. 235 * Avoid using it unless flapping is really bad (say, last poor link is < 1 min ago). 236 */ 237 private static final GoodLinkTarget[] GOOD_LINK_TARGET = { 238 /* rssi_adj, sample_count, reduce_time */ 239 new GoodLinkTarget( 0, 3, 30 * 60000 ), 240 new GoodLinkTarget( 3, 5, 5 * 60000 ), 241 new GoodLinkTarget( 6, 10, 1 * 60000 ), 242 new GoodLinkTarget( 9, 30, 0 * 60000 ), 243 }; 244 245 /** 246 * The max time to avoid a BSSID, to prevent avoiding forever. 247 * If current RSSI is at least min_rssi[i], the max avoidance time is at most max_time[i] 248 * <p> 249 * It is unusual to experience high packet loss at high RSSI. Something unusual must be 250 * happening (e.g. strong interference). For higher signal strengths, we set the avoidance 251 * time to be low to allow for quick turn around from temporary interference. 252 * <p> 253 * See {@link BssidStatistics#poorLinkDetected}. 254 */ 255 private static final MaxAvoidTime[] MAX_AVOID_TIME = { 256 /* max_time, min_rssi */ 257 new MaxAvoidTime( 30 * 60000, -200 ), 258 new MaxAvoidTime( 5 * 60000, -70 ), 259 new MaxAvoidTime( 0 * 60000, -55 ), 260 }; 261 262 /* Framework related */ 263 private Context mContext; 264 private ContentResolver mContentResolver; 265 private WifiManager mWifiManager; 266 private IntentFilter mIntentFilter; 267 private BroadcastReceiver mBroadcastReceiver; 268 private AsyncChannel mWsmChannel = new AsyncChannel(); 269 private WifiInfo mWifiInfo; 270 private LinkProperties mLinkProperties; 271 272 /* System settingss related */ 273 private static boolean sWifiOnly = false; 274 private boolean mPoorNetworkDetectionEnabled; 275 276 /* Poor link detection related */ 277 private LruCache<String, BssidStatistics> mBssidCache = 278 new LruCache<String, BssidStatistics>(BSSID_STAT_CACHE_SIZE); 279 private int mRssiFetchToken = 0; 280 private int mCurrentSignalLevel; 281 private BssidStatistics mCurrentBssid; 282 private VolumeWeightedEMA mCurrentLoss; 283 private boolean mIsScreenOn = true; 284 private static double sPresetLoss[]; 285 286 /* WiFi watchdog state machine related */ 287 private DefaultState mDefaultState = new DefaultState(); 288 private WatchdogDisabledState mWatchdogDisabledState = new WatchdogDisabledState(); 289 private WatchdogEnabledState mWatchdogEnabledState = new WatchdogEnabledState(); 290 private NotConnectedState mNotConnectedState = new NotConnectedState(); 291 private VerifyingLinkState mVerifyingLinkState = new VerifyingLinkState(); 292 private ConnectedState mConnectedState = new ConnectedState(); 293 private OnlineWatchState mOnlineWatchState = new OnlineWatchState(); 294 private LinkMonitoringState mLinkMonitoringState = new LinkMonitoringState(); 295 private OnlineState mOnlineState = new OnlineState(); 296 297 /** 298 * STATE MAP 299 * Default 300 * / \ 301 * Disabled Enabled 302 * / \ \ 303 * NotConnected Verifying Connected 304 * /---------\ 305 * (all other states) 306 */ 307 private WifiWatchdogStateMachine(Context context) { 308 super("WifiWatchdogStateMachine"); 309 mContext = context; 310 mContentResolver = context.getContentResolver(); 311 mWifiManager = (WifiManager) context.getSystemService(Context.WIFI_SERVICE); 312 mWsmChannel.connectSync(mContext, getHandler(), 313 mWifiManager.getWifiStateMachineMessenger()); 314 315 setupNetworkReceiver(); 316 317 // the content observer to listen needs a handler 318 registerForSettingsChanges(); 319 registerForWatchdogToggle(); 320 addState(mDefaultState); 321 addState(mWatchdogDisabledState, mDefaultState); 322 addState(mWatchdogEnabledState, mDefaultState); 323 addState(mNotConnectedState, mWatchdogEnabledState); 324 addState(mVerifyingLinkState, mWatchdogEnabledState); 325 addState(mConnectedState, mWatchdogEnabledState); 326 addState(mOnlineWatchState, mConnectedState); 327 addState(mLinkMonitoringState, mConnectedState); 328 addState(mOnlineState, mConnectedState); 329 330 if (isWatchdogEnabled()) { 331 setInitialState(mNotConnectedState); 332 } else { 333 setInitialState(mWatchdogDisabledState); 334 } 335 setLogRecSize(25); 336 setLogOnlyTransitions(true); 337 updateSettings(); 338 } 339 340 public static WifiWatchdogStateMachine makeWifiWatchdogStateMachine(Context context) { 341 ContentResolver contentResolver = context.getContentResolver(); 342 343 ConnectivityManager cm = (ConnectivityManager) context.getSystemService( 344 Context.CONNECTIVITY_SERVICE); 345 sWifiOnly = (cm.isNetworkSupported(ConnectivityManager.TYPE_MOBILE) == false); 346 347 // Watchdog is always enabled. Poor network detection can be seperately turned on/off 348 // TODO: Remove this setting & clean up state machine since we always have 349 // watchdog in an enabled state 350 putSettingsGlobalBoolean(contentResolver, Settings.Global.WIFI_WATCHDOG_ON, true); 351 352 WifiWatchdogStateMachine wwsm = new WifiWatchdogStateMachine(context); 353 wwsm.start(); 354 return wwsm; 355 } 356 357 private void setupNetworkReceiver() { 358 mBroadcastReceiver = new BroadcastReceiver() { 359 @Override 360 public void onReceive(Context context, Intent intent) { 361 String action = intent.getAction(); 362 if (action.equals(WifiManager.RSSI_CHANGED_ACTION)) { 363 obtainMessage(EVENT_RSSI_CHANGE, 364 intent.getIntExtra(WifiManager.EXTRA_NEW_RSSI, -200), 0).sendToTarget(); 365 } else if (action.equals(WifiManager.SUPPLICANT_STATE_CHANGED_ACTION)) { 366 sendMessage(EVENT_SUPPLICANT_STATE_CHANGE, intent); 367 } else if (action.equals(WifiManager.NETWORK_STATE_CHANGED_ACTION)) { 368 sendMessage(EVENT_NETWORK_STATE_CHANGE, intent); 369 } else if (action.equals(Intent.ACTION_SCREEN_ON)) { 370 sendMessage(EVENT_SCREEN_ON); 371 } else if (action.equals(Intent.ACTION_SCREEN_OFF)) { 372 sendMessage(EVENT_SCREEN_OFF); 373 } else if (action.equals(WifiManager.WIFI_STATE_CHANGED_ACTION)) { 374 sendMessage(EVENT_WIFI_RADIO_STATE_CHANGE,intent.getIntExtra( 375 WifiManager.EXTRA_WIFI_STATE, WifiManager.WIFI_STATE_UNKNOWN)); 376 } 377 } 378 }; 379 380 mIntentFilter = new IntentFilter(); 381 mIntentFilter.addAction(WifiManager.NETWORK_STATE_CHANGED_ACTION); 382 mIntentFilter.addAction(WifiManager.WIFI_STATE_CHANGED_ACTION); 383 mIntentFilter.addAction(WifiManager.RSSI_CHANGED_ACTION); 384 mIntentFilter.addAction(WifiManager.SUPPLICANT_STATE_CHANGED_ACTION); 385 mIntentFilter.addAction(Intent.ACTION_SCREEN_ON); 386 mIntentFilter.addAction(Intent.ACTION_SCREEN_OFF); 387 mContext.registerReceiver(mBroadcastReceiver, mIntentFilter); 388 } 389 390 /** 391 * Observes the watchdog on/off setting, and takes action when changed. 392 */ 393 private void registerForWatchdogToggle() { 394 ContentObserver contentObserver = new ContentObserver(this.getHandler()) { 395 @Override 396 public void onChange(boolean selfChange) { 397 sendMessage(EVENT_WATCHDOG_TOGGLED); 398 } 399 }; 400 401 mContext.getContentResolver().registerContentObserver( 402 Settings.Global.getUriFor(Settings.Global.WIFI_WATCHDOG_ON), 403 false, contentObserver); 404 } 405 406 /** 407 * Observes watchdogs secure setting changes. 408 */ 409 private void registerForSettingsChanges() { 410 ContentObserver contentObserver = new ContentObserver(this.getHandler()) { 411 @Override 412 public void onChange(boolean selfChange) { 413 sendMessage(EVENT_WATCHDOG_SETTINGS_CHANGE); 414 } 415 }; 416 417 mContext.getContentResolver().registerContentObserver( 418 Settings.Global.getUriFor(Settings.Global.WIFI_WATCHDOG_POOR_NETWORK_TEST_ENABLED), 419 false, contentObserver); 420 } 421 422 public void dump(FileDescriptor fd, PrintWriter pw, String[] args) { 423 super.dump(fd, pw, args); 424 pw.println("mWifiInfo: [" + mWifiInfo + "]"); 425 pw.println("mLinkProperties: [" + mLinkProperties + "]"); 426 pw.println("mCurrentSignalLevel: [" + mCurrentSignalLevel + "]"); 427 pw.println("mPoorNetworkDetectionEnabled: [" + mPoorNetworkDetectionEnabled + "]"); 428 } 429 430 private boolean isWatchdogEnabled() { 431 boolean ret = getSettingsGlobalBoolean( 432 mContentResolver, Settings.Global.WIFI_WATCHDOG_ON, true); 433 if (DBG) logd("Watchdog enabled " + ret); 434 return ret; 435 } 436 437 private void updateSettings() { 438 if (DBG) logd("Updating secure settings"); 439 440 // disable poor network avoidance 441 if (sWifiOnly) { 442 logd("Disabling poor network avoidance for wi-fi only device"); 443 mPoorNetworkDetectionEnabled = false; 444 } else { 445 mPoorNetworkDetectionEnabled = getSettingsGlobalBoolean(mContentResolver, 446 Settings.Global.WIFI_WATCHDOG_POOR_NETWORK_TEST_ENABLED, 447 DEFAULT_POOR_NETWORK_AVOIDANCE_ENABLED); 448 } 449 } 450 451 /** 452 * Default state, guard for unhandled messages. 453 */ 454 class DefaultState extends State { 455 @Override 456 public void enter() { 457 if (DBG) logd(getName()); 458 } 459 460 @Override 461 public boolean processMessage(Message msg) { 462 switch (msg.what) { 463 case EVENT_WATCHDOG_SETTINGS_CHANGE: 464 updateSettings(); 465 if (DBG) logd("Updating wifi-watchdog secure settings"); 466 break; 467 case EVENT_RSSI_CHANGE: 468 mCurrentSignalLevel = calculateSignalLevel(msg.arg1); 469 break; 470 case EVENT_WIFI_RADIO_STATE_CHANGE: 471 case EVENT_NETWORK_STATE_CHANGE: 472 case EVENT_SUPPLICANT_STATE_CHANGE: 473 case EVENT_BSSID_CHANGE: 474 case CMD_RSSI_FETCH: 475 case WifiManager.RSSI_PKTCNT_FETCH_SUCCEEDED: 476 case WifiManager.RSSI_PKTCNT_FETCH_FAILED: 477 // ignore 478 break; 479 case EVENT_SCREEN_ON: 480 mIsScreenOn = true; 481 break; 482 case EVENT_SCREEN_OFF: 483 mIsScreenOn = false; 484 break; 485 default: 486 loge("Unhandled message " + msg + " in state " + getCurrentState().getName()); 487 break; 488 } 489 return HANDLED; 490 } 491 } 492 493 /** 494 * WiFi watchdog is disabled by the setting. 495 */ 496 class WatchdogDisabledState extends State { 497 @Override 498 public void enter() { 499 if (DBG) logd(getName()); 500 } 501 502 @Override 503 public boolean processMessage(Message msg) { 504 switch (msg.what) { 505 case EVENT_WATCHDOG_TOGGLED: 506 if (isWatchdogEnabled()) 507 transitionTo(mNotConnectedState); 508 return HANDLED; 509 case EVENT_NETWORK_STATE_CHANGE: 510 Intent intent = (Intent) msg.obj; 511 NetworkInfo networkInfo = (NetworkInfo) 512 intent.getParcelableExtra(WifiManager.EXTRA_NETWORK_INFO); 513 514 switch (networkInfo.getDetailedState()) { 515 case VERIFYING_POOR_LINK: 516 if (DBG) logd("Watchdog disabled, verify link"); 517 sendLinkStatusNotification(true); 518 break; 519 default: 520 break; 521 } 522 break; 523 } 524 return NOT_HANDLED; 525 } 526 } 527 528 /** 529 * WiFi watchdog is enabled by the setting. 530 */ 531 class WatchdogEnabledState extends State { 532 @Override 533 public void enter() { 534 if (DBG) logd(getName()); 535 } 536 537 @Override 538 public boolean processMessage(Message msg) { 539 Intent intent; 540 switch (msg.what) { 541 case EVENT_WATCHDOG_TOGGLED: 542 if (!isWatchdogEnabled()) 543 transitionTo(mWatchdogDisabledState); 544 break; 545 546 case EVENT_NETWORK_STATE_CHANGE: 547 intent = (Intent) msg.obj; 548 NetworkInfo networkInfo = 549 (NetworkInfo) intent.getParcelableExtra(WifiManager.EXTRA_NETWORK_INFO); 550 if (DBG) logd("Network state change " + networkInfo.getDetailedState()); 551 552 mWifiInfo = (WifiInfo) intent.getParcelableExtra(WifiManager.EXTRA_WIFI_INFO); 553 updateCurrentBssid(mWifiInfo != null ? mWifiInfo.getBSSID() : null); 554 555 switch (networkInfo.getDetailedState()) { 556 case VERIFYING_POOR_LINK: 557 mLinkProperties = (LinkProperties) intent.getParcelableExtra( 558 WifiManager.EXTRA_LINK_PROPERTIES); 559 if (mPoorNetworkDetectionEnabled) { 560 if (mWifiInfo == null || mCurrentBssid == null) { 561 loge("Ignore, wifiinfo " + mWifiInfo +" bssid " + mCurrentBssid); 562 sendLinkStatusNotification(true); 563 } else { 564 transitionTo(mVerifyingLinkState); 565 } 566 } else { 567 sendLinkStatusNotification(true); 568 } 569 break; 570 case CONNECTED: 571 transitionTo(mOnlineWatchState); 572 break; 573 default: 574 transitionTo(mNotConnectedState); 575 break; 576 } 577 break; 578 579 case EVENT_SUPPLICANT_STATE_CHANGE: 580 intent = (Intent) msg.obj; 581 SupplicantState supplicantState = (SupplicantState) intent.getParcelableExtra( 582 WifiManager.EXTRA_NEW_STATE); 583 if (supplicantState == SupplicantState.COMPLETED) { 584 mWifiInfo = mWifiManager.getConnectionInfo(); 585 updateCurrentBssid(mWifiInfo.getBSSID()); 586 } 587 break; 588 589 case EVENT_WIFI_RADIO_STATE_CHANGE: 590 if (msg.arg1 == WifiManager.WIFI_STATE_DISABLING) { 591 transitionTo(mNotConnectedState); 592 } 593 break; 594 595 default: 596 return NOT_HANDLED; 597 } 598 599 return HANDLED; 600 } 601 } 602 603 /** 604 * WiFi is disconnected. 605 */ 606 class NotConnectedState extends State { 607 @Override 608 public void enter() { 609 if (DBG) logd(getName()); 610 } 611 } 612 613 /** 614 * WiFi is connected, but waiting for good link detection message. 615 */ 616 class VerifyingLinkState extends State { 617 618 private int mSampleCount; 619 620 @Override 621 public void enter() { 622 if (DBG) logd(getName()); 623 mSampleCount = 0; 624 mCurrentBssid.newLinkDetected(); 625 sendMessage(obtainMessage(CMD_RSSI_FETCH, ++mRssiFetchToken, 0)); 626 } 627 628 @Override 629 public boolean processMessage(Message msg) { 630 switch (msg.what) { 631 case EVENT_WATCHDOG_SETTINGS_CHANGE: 632 updateSettings(); 633 if (!mPoorNetworkDetectionEnabled) { 634 sendLinkStatusNotification(true); 635 } 636 break; 637 638 case EVENT_BSSID_CHANGE: 639 transitionTo(mVerifyingLinkState); 640 break; 641 642 case CMD_RSSI_FETCH: 643 if (msg.arg1 == mRssiFetchToken) { 644 mWsmChannel.sendMessage(WifiManager.RSSI_PKTCNT_FETCH); 645 sendMessageDelayed(obtainMessage(CMD_RSSI_FETCH, ++mRssiFetchToken, 0), 646 LINK_SAMPLING_INTERVAL_MS); 647 } 648 break; 649 650 case WifiManager.RSSI_PKTCNT_FETCH_SUCCEEDED: 651 RssiPacketCountInfo info = (RssiPacketCountInfo) msg.obj; 652 int rssi = info.rssi; 653 if (DBG) logd("Fetch RSSI succeed, rssi=" + rssi); 654 655 long time = mCurrentBssid.mBssidAvoidTimeMax - SystemClock.elapsedRealtime(); 656 if (time <= 0) { 657 // max avoidance time is met 658 if (DBG) logd("Max avoid time elapsed"); 659 sendLinkStatusNotification(true); 660 } else { 661 if (rssi >= mCurrentBssid.mGoodLinkTargetRssi) { 662 if (++mSampleCount >= mCurrentBssid.mGoodLinkTargetCount) { 663 // link is good again 664 if (DBG) logd("Good link detected, rssi=" + rssi); 665 mCurrentBssid.mBssidAvoidTimeMax = 0; 666 sendLinkStatusNotification(true); 667 } 668 } else { 669 mSampleCount = 0; 670 if (DBG) logd("Link is still poor, time left=" + time); 671 } 672 } 673 break; 674 675 case WifiManager.RSSI_PKTCNT_FETCH_FAILED: 676 if (DBG) logd("RSSI_FETCH_FAILED"); 677 break; 678 679 default: 680 return NOT_HANDLED; 681 } 682 return HANDLED; 683 } 684 } 685 686 /** 687 * WiFi is connected and link is verified. 688 */ 689 class ConnectedState extends State { 690 @Override 691 public void enter() { 692 if (DBG) logd(getName()); 693 } 694 695 @Override 696 public boolean processMessage(Message msg) { 697 switch (msg.what) { 698 case EVENT_WATCHDOG_SETTINGS_CHANGE: 699 updateSettings(); 700 // STOPSHIP: Remove this at ship 701 logd("Updated secure settings and turned debug on"); 702 DBG = true; 703 704 if (mPoorNetworkDetectionEnabled) { 705 transitionTo(mOnlineWatchState); 706 } else { 707 transitionTo(mOnlineState); 708 } 709 return HANDLED; 710 } 711 return NOT_HANDLED; 712 } 713 } 714 715 /** 716 * RSSI is high enough and don't need link monitoring. 717 */ 718 class OnlineWatchState extends State { 719 @Override 720 public void enter() { 721 if (DBG) logd(getName()); 722 if (mPoorNetworkDetectionEnabled) { 723 // treat entry as an rssi change 724 handleRssiChange(); 725 } else { 726 transitionTo(mOnlineState); 727 } 728 } 729 730 private void handleRssiChange() { 731 if (mCurrentSignalLevel <= LINK_MONITOR_LEVEL_THRESHOLD && mCurrentBssid != null) { 732 transitionTo(mLinkMonitoringState); 733 } else { 734 // stay here 735 } 736 } 737 738 @Override 739 public boolean processMessage(Message msg) { 740 switch (msg.what) { 741 case EVENT_RSSI_CHANGE: 742 mCurrentSignalLevel = calculateSignalLevel(msg.arg1); 743 handleRssiChange(); 744 break; 745 default: 746 return NOT_HANDLED; 747 } 748 return HANDLED; 749 } 750 } 751 752 /** 753 * Keep sampling the link and monitor any poor link situation. 754 */ 755 class LinkMonitoringState extends State { 756 757 private int mSampleCount; 758 759 private int mLastRssi; 760 private int mLastTxGood; 761 private int mLastTxBad; 762 763 @Override 764 public void enter() { 765 if (DBG) logd(getName()); 766 mSampleCount = 0; 767 mCurrentLoss = new VolumeWeightedEMA(EXP_COEFFICIENT_MONITOR); 768 sendMessage(obtainMessage(CMD_RSSI_FETCH, ++mRssiFetchToken, 0)); 769 } 770 771 @Override 772 public boolean processMessage(Message msg) { 773 switch (msg.what) { 774 case EVENT_RSSI_CHANGE: 775 mCurrentSignalLevel = calculateSignalLevel(msg.arg1); 776 if (mCurrentSignalLevel <= LINK_MONITOR_LEVEL_THRESHOLD) { 777 // stay here; 778 } else { 779 // we don't need frequent RSSI monitoring any more 780 transitionTo(mOnlineWatchState); 781 } 782 break; 783 784 case EVENT_BSSID_CHANGE: 785 transitionTo(mLinkMonitoringState); 786 break; 787 788 case CMD_RSSI_FETCH: 789 if (!mIsScreenOn) { 790 transitionTo(mOnlineState); 791 } else if (msg.arg1 == mRssiFetchToken) { 792 mWsmChannel.sendMessage(WifiManager.RSSI_PKTCNT_FETCH); 793 sendMessageDelayed(obtainMessage(CMD_RSSI_FETCH, ++mRssiFetchToken, 0), 794 LINK_SAMPLING_INTERVAL_MS); 795 } 796 break; 797 798 case WifiManager.RSSI_PKTCNT_FETCH_SUCCEEDED: 799 RssiPacketCountInfo info = (RssiPacketCountInfo) msg.obj; 800 int rssi = info.rssi; 801 int mrssi = (mLastRssi + rssi) / 2; 802 int txbad = info.txbad; 803 int txgood = info.txgood; 804 if (DBG) logd("Fetch RSSI succeed, rssi=" + rssi + " mrssi=" + mrssi + " txbad=" 805 + txbad + " txgood=" + txgood); 806 807 // skip the first data point as we want incremental values 808 long now = SystemClock.elapsedRealtime(); 809 if (now - mCurrentBssid.mLastTimeSample < LINK_SAMPLING_INTERVAL_MS * 2) { 810 811 // update packet loss statistics 812 int dbad = txbad - mLastTxBad; 813 int dgood = txgood - mLastTxGood; 814 int dtotal = dbad + dgood; 815 816 if (dtotal > 0) { 817 // calculate packet loss in the last sampling interval 818 double loss = ((double) dbad) / ((double) dtotal); 819 820 mCurrentLoss.update(loss, dtotal); 821 822 if (DBG) { 823 DecimalFormat df = new DecimalFormat("#.##"); 824 logd("Incremental loss=" + dbad + "/" + dtotal + " Current loss=" 825 + df.format(mCurrentLoss.mValue * 100) + "% volume=" 826 + df.format(mCurrentLoss.mVolume)); 827 } 828 829 mCurrentBssid.updateLoss(mrssi, loss, dtotal); 830 831 // check for high packet loss and send poor link notification 832 if (mCurrentLoss.mValue > POOR_LINK_LOSS_THRESHOLD 833 && mCurrentLoss.mVolume > POOR_LINK_MIN_VOLUME) { 834 if (++mSampleCount >= POOR_LINK_SAMPLE_COUNT) 835 if (mCurrentBssid.poorLinkDetected(rssi)) { 836 sendLinkStatusNotification(false); 837 ++mRssiFetchToken; 838 } 839 } else { 840 mSampleCount = 0; 841 } 842 } 843 } 844 845 mCurrentBssid.mLastTimeSample = now; 846 mLastTxBad = txbad; 847 mLastTxGood = txgood; 848 mLastRssi = rssi; 849 break; 850 851 case WifiManager.RSSI_PKTCNT_FETCH_FAILED: 852 // can happen if we are waiting to get a disconnect notification 853 if (DBG) logd("RSSI_FETCH_FAILED"); 854 break; 855 856 default: 857 return NOT_HANDLED; 858 } 859 return HANDLED; 860 } 861 } 862 863 /** 864 * Child state of ConnectedState indicating that we are online and there is nothing to do. 865 */ 866 class OnlineState extends State { 867 @Override 868 public void enter() { 869 if (DBG) logd(getName()); 870 } 871 872 @Override 873 public boolean processMessage(Message msg) { 874 switch (msg.what) { 875 case EVENT_SCREEN_ON: 876 mIsScreenOn = true; 877 if (mPoorNetworkDetectionEnabled) 878 transitionTo(mOnlineWatchState); 879 break; 880 default: 881 return NOT_HANDLED; 882 } 883 return HANDLED; 884 } 885 } 886 887 private void updateCurrentBssid(String bssid) { 888 if (DBG) logd("Update current BSSID to " + (bssid != null ? bssid : "null")); 889 890 // if currently not connected, then set current BSSID to null 891 if (bssid == null) { 892 if (mCurrentBssid == null) return; 893 mCurrentBssid = null; 894 if (DBG) logd("BSSID changed"); 895 sendMessage(EVENT_BSSID_CHANGE); 896 return; 897 } 898 899 // if it is already the current BSSID, then done 900 if (mCurrentBssid != null && bssid.equals(mCurrentBssid.mBssid)) return; 901 902 // search for the new BSSID in the cache, add to cache if not found 903 mCurrentBssid = mBssidCache.get(bssid); 904 if (mCurrentBssid == null) { 905 mCurrentBssid = new BssidStatistics(bssid); 906 mBssidCache.put(bssid, mCurrentBssid); 907 } 908 909 // send BSSID change notification 910 if (DBG) logd("BSSID changed"); 911 sendMessage(EVENT_BSSID_CHANGE); 912 } 913 914 private int calculateSignalLevel(int rssi) { 915 int signalLevel = WifiManager.calculateSignalLevel(rssi, WifiManager.RSSI_LEVELS); 916 if (DBG) 917 logd("RSSI current: " + mCurrentSignalLevel + " new: " + rssi + ", " + signalLevel); 918 return signalLevel; 919 } 920 921 private void sendLinkStatusNotification(boolean isGood) { 922 if (DBG) logd("########################################"); 923 if (isGood) { 924 mWsmChannel.sendMessage(GOOD_LINK_DETECTED); 925 if (mCurrentBssid != null) { 926 mCurrentBssid.mLastTimeGood = SystemClock.elapsedRealtime(); 927 } 928 if (DBG) logd("Good link notification is sent"); 929 } else { 930 mWsmChannel.sendMessage(POOR_LINK_DETECTED); 931 if (mCurrentBssid != null) { 932 mCurrentBssid.mLastTimePoor = SystemClock.elapsedRealtime(); 933 } 934 logd("Poor link notification is sent"); 935 } 936 } 937 938 /** 939 * Convenience function for retrieving a single secure settings value as a 940 * boolean. Note that internally setting values are always stored as 941 * strings; this function converts the string to a boolean for you. The 942 * default value will be returned if the setting is not defined or not a 943 * valid boolean. 944 * 945 * @param cr The ContentResolver to access. 946 * @param name The name of the setting to retrieve. 947 * @param def Value to return if the setting is not defined. 948 * @return The setting's current value, or 'def' if it is not defined or not 949 * a valid boolean. 950 */ 951 private static boolean getSettingsGlobalBoolean(ContentResolver cr, String name, boolean def) { 952 return Settings.Global.getInt(cr, name, def ? 1 : 0) == 1; 953 } 954 955 /** 956 * Convenience function for updating a single settings value as an integer. 957 * This will either create a new entry in the table if the given name does 958 * not exist, or modify the value of the existing row with that name. Note 959 * that internally setting values are always stored as strings, so this 960 * function converts the given value to a string before storing it. 961 * 962 * @param cr The ContentResolver to access. 963 * @param name The name of the setting to modify. 964 * @param value The new value for the setting. 965 * @return true if the value was set, false on database errors 966 */ 967 private static boolean putSettingsGlobalBoolean(ContentResolver cr, String name, boolean value) { 968 return Settings.Global.putInt(cr, name, value ? 1 : 0); 969 } 970 971 /** 972 * Bundle of good link count parameters 973 */ 974 private static class GoodLinkTarget { 975 public final int RSSI_ADJ_DBM; 976 public final int SAMPLE_COUNT; 977 public final int REDUCE_TIME_MS; 978 public GoodLinkTarget(int adj, int count, int time) { 979 RSSI_ADJ_DBM = adj; 980 SAMPLE_COUNT = count; 981 REDUCE_TIME_MS = time; 982 } 983 } 984 985 /** 986 * Bundle of max avoidance time parameters 987 */ 988 private static class MaxAvoidTime { 989 public final int TIME_MS; 990 public final int MIN_RSSI_DBM; 991 public MaxAvoidTime(int time, int rssi) { 992 TIME_MS = time; 993 MIN_RSSI_DBM = rssi; 994 } 995 } 996 997 /** 998 * Volume-weighted Exponential Moving Average (V-EMA) 999 * - volume-weighted: each update has its own weight (number of packets) 1000 * - exponential: O(1) time and O(1) space for both update and query 1001 * - moving average: reflect most recent results and expire old ones 1002 */ 1003 private class VolumeWeightedEMA { 1004 private double mValue; 1005 private double mVolume; 1006 private double mProduct; 1007 private final double mAlpha; 1008 1009 public VolumeWeightedEMA(double coefficient) { 1010 mValue = 0.0; 1011 mVolume = 0.0; 1012 mProduct = 0.0; 1013 mAlpha = coefficient; 1014 } 1015 1016 public void update(double newValue, int newVolume) { 1017 if (newVolume <= 0) return; 1018 // core update formulas 1019 double newProduct = newValue * newVolume; 1020 mProduct = mAlpha * newProduct + (1 - mAlpha) * mProduct; 1021 mVolume = mAlpha * newVolume + (1 - mAlpha) * mVolume; 1022 mValue = mProduct / mVolume; 1023 } 1024 } 1025 1026 /** 1027 * Record (RSSI -> pakce loss %) mappings of one BSSID 1028 */ 1029 private class BssidStatistics { 1030 1031 /* MAC address of this BSSID */ 1032 private final String mBssid; 1033 1034 /* RSSI -> packet loss % mappings */ 1035 private VolumeWeightedEMA[] mEntries; 1036 private int mRssiBase; 1037 private int mEntriesSize; 1038 1039 /* Target to send good link notification, set when poor link is detected */ 1040 private int mGoodLinkTargetRssi; 1041 private int mGoodLinkTargetCount; 1042 1043 /* Index of GOOD_LINK_TARGET array */ 1044 private int mGoodLinkTargetIndex; 1045 1046 /* Timestamps of some last events */ 1047 private long mLastTimeSample; 1048 private long mLastTimeGood; 1049 private long mLastTimePoor; 1050 1051 /* Max time to avoid this BSSID */ 1052 private long mBssidAvoidTimeMax; 1053 1054 /** 1055 * Constructor 1056 * 1057 * @param bssid is the address of this BSSID 1058 */ 1059 public BssidStatistics(String bssid) { 1060 this.mBssid = bssid; 1061 mRssiBase = BSSID_STAT_RANGE_LOW_DBM; 1062 mEntriesSize = BSSID_STAT_RANGE_HIGH_DBM - BSSID_STAT_RANGE_LOW_DBM + 1; 1063 mEntries = new VolumeWeightedEMA[mEntriesSize]; 1064 for (int i = 0; i < mEntriesSize; i++) 1065 mEntries[i] = new VolumeWeightedEMA(EXP_COEFFICIENT_RECORD); 1066 } 1067 1068 /** 1069 * Update this BSSID cache 1070 * 1071 * @param rssi is the RSSI 1072 * @param value is the new instant loss value at this RSSI 1073 * @param volume is the volume for this single update 1074 */ 1075 public void updateLoss(int rssi, double value, int volume) { 1076 if (volume <= 0) return; 1077 int index = rssi - mRssiBase; 1078 if (index < 0 || index >= mEntriesSize) return; 1079 mEntries[index].update(value, volume); 1080 if (DBG) { 1081 DecimalFormat df = new DecimalFormat("#.##"); 1082 logd("Cache updated: loss[" + rssi + "]=" + df.format(mEntries[index].mValue * 100) 1083 + "% volume=" + df.format(mEntries[index].mVolume)); 1084 } 1085 } 1086 1087 /** 1088 * Get preset loss if the cache has insufficient data, observed from experiments. 1089 * 1090 * @param rssi is the input RSSI 1091 * @return preset loss of the given RSSI 1092 */ 1093 public double presetLoss(int rssi) { 1094 if (rssi <= -90) return 1.0; 1095 if (rssi > 0) return 0.0; 1096 1097 if (sPresetLoss == null) { 1098 // pre-calculate all preset losses only once, then reuse them 1099 final int size = 90; 1100 sPresetLoss = new double[size]; 1101 for (int i = 0; i < size; i++) sPresetLoss[i] = 1.0 / Math.pow(90 - i, 1.5); 1102 } 1103 return sPresetLoss[-rssi]; 1104 } 1105 1106 /** 1107 * A poor link is detected, calculate a target RSSI to bring WiFi back. 1108 * 1109 * @param rssi is the current RSSI 1110 * @return true iff the current BSSID should be avoided 1111 */ 1112 public boolean poorLinkDetected(int rssi) { 1113 if (DBG) logd("Poor link detected, rssi=" + rssi); 1114 1115 long now = SystemClock.elapsedRealtime(); 1116 long lastGood = now - mLastTimeGood; 1117 long lastPoor = now - mLastTimePoor; 1118 1119 // reduce the difficulty of good link target if last avoidance was long time ago 1120 while (mGoodLinkTargetIndex > 0 1121 && lastPoor >= GOOD_LINK_TARGET[mGoodLinkTargetIndex - 1].REDUCE_TIME_MS) 1122 mGoodLinkTargetIndex--; 1123 mGoodLinkTargetCount = GOOD_LINK_TARGET[mGoodLinkTargetIndex].SAMPLE_COUNT; 1124 1125 // scan for a target RSSI at which the link is good 1126 int from = rssi + GOOD_LINK_RSSI_RANGE_MIN; 1127 int to = rssi + GOOD_LINK_RSSI_RANGE_MAX; 1128 mGoodLinkTargetRssi = findRssiTarget(from, to, GOOD_LINK_LOSS_THRESHOLD); 1129 mGoodLinkTargetRssi += GOOD_LINK_TARGET[mGoodLinkTargetIndex].RSSI_ADJ_DBM; 1130 if (mGoodLinkTargetIndex < GOOD_LINK_TARGET.length - 1) mGoodLinkTargetIndex++; 1131 1132 // calculate max avoidance time to prevent avoiding forever 1133 int p = 0, pmax = MAX_AVOID_TIME.length - 1; 1134 while (p < pmax && rssi >= MAX_AVOID_TIME[p + 1].MIN_RSSI_DBM) p++; 1135 long avoidMax = MAX_AVOID_TIME[p].TIME_MS; 1136 1137 // don't avoid if max avoidance time is 0 (RSSI is super high) 1138 if (avoidMax <= 0) return false; 1139 1140 // set max avoidance time, send poor link notification 1141 mBssidAvoidTimeMax = now + avoidMax; 1142 1143 if (DBG) logd("goodRssi=" + mGoodLinkTargetRssi + " goodCount=" + mGoodLinkTargetCount 1144 + " lastGood=" + lastGood + " lastPoor=" + lastPoor + " avoidMax=" + avoidMax); 1145 1146 return true; 1147 } 1148 1149 /** 1150 * A new BSSID is connected, recalculate target RSSI threshold 1151 */ 1152 public void newLinkDetected() { 1153 // if this BSSID is currently being avoided, the reuse those values 1154 if (mBssidAvoidTimeMax > 0) { 1155 if (DBG) logd("Previous avoidance still in effect, rssi=" + mGoodLinkTargetRssi 1156 + " count=" + mGoodLinkTargetCount); 1157 return; 1158 } 1159 1160 // calculate a new RSSI threshold for new link verifying 1161 int from = BSSID_STAT_RANGE_LOW_DBM; 1162 int to = BSSID_STAT_RANGE_HIGH_DBM; 1163 mGoodLinkTargetRssi = findRssiTarget(from, to, GOOD_LINK_LOSS_THRESHOLD); 1164 mGoodLinkTargetCount = 1; 1165 mBssidAvoidTimeMax = SystemClock.elapsedRealtime() + MAX_AVOID_TIME[0].TIME_MS; 1166 if (DBG) logd("New link verifying target set, rssi=" + mGoodLinkTargetRssi + " count=" 1167 + mGoodLinkTargetCount); 1168 } 1169 1170 /** 1171 * Return the first RSSI within the range where loss[rssi] < threshold 1172 * 1173 * @param from start scanning from this RSSI 1174 * @param to stop scanning at this RSSI 1175 * @param threshold target threshold for scanning 1176 * @return target RSSI 1177 */ 1178 public int findRssiTarget(int from, int to, double threshold) { 1179 from -= mRssiBase; 1180 to -= mRssiBase; 1181 int emptyCount = 0; 1182 int d = from < to ? 1 : -1; 1183 for (int i = from; i != to; i += d) 1184 // don't use a data point if it volume is too small (statistically unreliable) 1185 if (i >= 0 && i < mEntriesSize && mEntries[i].mVolume > 1.0) { 1186 emptyCount = 0; 1187 if (mEntries[i].mValue < threshold) { 1188 // scan target found 1189 int rssi = mRssiBase + i; 1190 if (DBG) { 1191 DecimalFormat df = new DecimalFormat("#.##"); 1192 logd("Scan target found: rssi=" + rssi + " threshold=" 1193 + df.format(threshold * 100) + "% value=" 1194 + df.format(mEntries[i].mValue * 100) + "% volume=" 1195 + df.format(mEntries[i].mVolume)); 1196 } 1197 return rssi; 1198 } 1199 } else if (++emptyCount >= BSSID_STAT_EMPTY_COUNT) { 1200 // cache has insufficient data around this RSSI, use preset loss instead 1201 int rssi = mRssiBase + i; 1202 double lossPreset = presetLoss(rssi); 1203 if (lossPreset < threshold) { 1204 if (DBG) { 1205 DecimalFormat df = new DecimalFormat("#.##"); 1206 logd("Scan target found: rssi=" + rssi + " threshold=" 1207 + df.format(threshold * 100) + "% value=" 1208 + df.format(lossPreset * 100) + "% volume=preset"); 1209 } 1210 return rssi; 1211 } 1212 } 1213 1214 return mRssiBase + to; 1215 } 1216 } 1217 } 1218
