aggressively blacklist WifiConfiguration for the purpose of switching networklollipop-mr1-dev

In cases where networks are not properly configured, WiFi might tries to repeatdly
switch from one network to a bad network, or might try to roam and renew DHCP which can fail.
In KK, WiFi autojoin would try other networks (by cycling to network it sees) and
end up associated to a "good" network. In L release even thought WiFi might pick
a good network it will still repeatedly try to switch to what it thinks is a better
network and fail, thus annoying the user whose connection becomes unstable.

This CL tries to remember networks that have seen multiple DHCP or auth failure in
the past and for those networks it disable roaming temporarily.
That is, if wifi is not associated to any network, it will tries to join a network
aggressively, however if wifi is currently associated to a network, it will not try
to switch to a new network if that new network has seen multiple failure in the past.

The maximum blacklist time is set to 2 days for now.
An example of such situation is:
- user has multiple SSID at home, one of which is incorrectly configured with a wrong password
- broken DHCP situation (potentially: multiple servers on home network, broken implementation incorrecting NAK'ing DHCP requests but properly serving DHCP offer...)
Bug:18792931

Change-Id: Ib09eaaea978c772f630e86696f9a49f18ad708e2

3 files changed, 56 insertions, 1 deletions

diff --git a/service/java/com/android/server/wifi/WifiAutoJoinController.java b/service/java/com/android/server/wifi/WifiAutoJoinController.java
index b86f77681..c7da1794e 100644
--- a/service/java/com/android/server/wifi/WifiAutoJoinController.java
+++ b/service/java/com/android/server/wifi/WifiAutoJoinController.java
@@ -1520,6 +1520,29 @@ public class WifiAutoJoinController {
             if (config.visibility == null) {
                 continue;
             }
+
+            if (config.lastRoamingFailure != 0
+                    && currentConfiguration != null
+                    && (lastSelectedConfiguration == null
+                    || !config.configKey().equals(lastSelectedConfiguration))) {
+                // Apply blacklisting for roaming to this config if:
+                //   - the target config had a recent roaming failure
+                //   - we are currently associated
+                //   - the target config is not the last selected
+                if (now > config.lastRoamingFailure
+                        && (now - config.lastRoamingFailure)
+                        < config.roamingFailureBlackListTimeMilli) {
+                    if (DBG) {
+                        logDbg("compareNetwork not switching to " + config.configKey()
+                                + " from current " + currentConfiguration.configKey()
+                                + " because it is blacklisted due to roam failure, "
+                                + " blacklist remain time = "
+                                + (now - config.lastRoamingFailure) + " ms");
+                    }
+                    continue;
+                }
+            }
+
             int boost = config.autoJoinUseAggressiveJoinAttemptThreshold + weakRssiBailCount;
             if ((config.visibility.rssi5 + boost)
                         < mWifiConfigStore.thresholdInitialAutoJoinAttemptMin5RSSI
diff --git a/service/java/com/android/server/wifi/WifiConfigStore.java b/service/java/com/android/server/wifi/WifiConfigStore.java
index f347d56d7..94752d369 100644
--- a/service/java/com/android/server/wifi/WifiConfigStore.java
+++ b/service/java/com/android/server/wifi/WifiConfigStore.java
@@ -342,6 +342,10 @@ public class WifiConfigStore extends IpConfigStore {
 
     public int associatedPartialScanPeriodMilli;
 
+    // Sane value for roam blacklisting (not switching to a network if already associated)
+    // 2 days
+    public int networkSwitchingBlackListPeriodMilli = 2 * 24 * 60 * 60 * 1000;
+
     public int bandPreferenceBoostFactor5 = 5; // Boost by 5 dB per dB above threshold
     public int bandPreferencePenaltyFactor5 = 2; // Penalize by 2 dB per dB below threshold
     public int bandPreferencePenaltyThreshold5 = WifiConfiguration.G_BAND_PREFERENCE_RSSI_THRESHOLD;
@@ -548,6 +552,9 @@ public class WifiConfigStore extends IpConfigStore {
 
         scanResultRssiLevelPatchUp = mContext.getResources().getInteger(
                 R.integer.config_wifi_framework_scan_result_rssi_level_patchup_value);
+
+        networkSwitchingBlackListPeriodMilli = mContext.getResources().getInteger(
+                R.integer.config_wifi_network_switching_blacklist_time);
     }
 
     void enableVerboseLogging(int verbose) {
@@ -928,6 +935,19 @@ public class WifiConfigStore extends IpConfigStore {
         }
     }
 
+    void noteRoamingFailure(WifiConfiguration config, int reason) {
+        if (config == null) return;
+        config.lastRoamingFailure = System.currentTimeMillis();
+        config.roamingFailureBlackListTimeMilli
+                = 2 * (config.roamingFailureBlackListTimeMilli + 1000);
+        if (config.roamingFailureBlackListTimeMilli
+                > networkSwitchingBlackListPeriodMilli) {
+            config.roamingFailureBlackListTimeMilli =
+                    networkSwitchingBlackListPeriodMilli;
+        }
+        config.lastRoamingFailureReason = reason;
+    }
+
     void saveWifiConfigBSSID(WifiConfiguration config) {
         // Sanity check the config is valid
         if (config == null || (config.networkId == INVALID_NETWORK_ID &&
diff --git a/service/java/com/android/server/wifi/WifiStateMachine.java b/service/java/com/android/server/wifi/WifiStateMachine.java
index 2311e34ae..fb9e9fd5b 100644
--- a/service/java/com/android/server/wifi/WifiStateMachine.java
+++ b/service/java/com/android/server/wifi/WifiStateMachine.java
@@ -7470,8 +7470,15 @@ public class WifiStateMachine extends StateMachine {
         @Override
         public boolean processMessage(Message message) {
             logStateAndMessage(message, getClass().getSimpleName());
-
+            WifiConfiguration config;
             switch (message.what) {
+                case CMD_IP_CONFIGURATION_LOST:
+                    config = getCurrentWifiConfiguration();
+                    if (config != null) {
+                        mWifiConfigStore.noteRoamingFailure(config,
+                                WifiConfiguration.ROAMING_FAILURE_IP_CONFIG);
+                    }
+                    return NOT_HANDLED;
                case WifiWatchdogStateMachine.POOR_LINK_DETECTED:
                     if (DBG) log("Roaming and Watchdog reports poor link -> ignore");
                     return HANDLED;
@@ -7557,6 +7564,11 @@ public class WifiStateMachine extends StateMachine {
                             + " isRoaming=" + isRoaming()
                             + " roam=" + Integer.toString(mAutoRoaming));
                     if (message.arg1 == mLastNetworkId) {
+                        config = getCurrentWifiConfiguration();
+                        if (config != null) {
+                            mWifiConfigStore.noteRoamingFailure(config,
+                                    WifiConfiguration.ROAMING_FAILURE_AUTH_FAILURE);
+                        }
                         handleNetworkDisconnect();
                         transitionTo(mDisconnectingState);
                     }