From 621b1b743b8abee0dffc93d5c7be42e4af783ffa Mon Sep 17 00:00:00 2001
From: Paul Jensen <pauljensen@google.com>
Date: Wed, 17 Jun 2015 14:42:30 -0400
Subject: [PATCH] Speed up network transition when WiFi disconnects

Before falling back to cellular we used to first delete all the
network routing tables and rules for WiFi.  This isn't necessary
and can take significant time as it requires a lot of netd
shelling out to ip and ip[6]tables to flush routes and remove
the incoming packet mark rule.  Instead have netd delete all the
network routing tables and rules after we've either fallen back
to cellular or at least kicked off a cellular connection attempt.

Bug: 21932815
Change-Id: Iabac4a8b962492682df3073cc41a12e35bc9f1bb
---
 .../android/server/ConnectivityService.java   | 35 ++++++++++++-------
 1 file changed, 23 insertions(+), 12 deletions(-)

diff --git a/services/core/java/com/android/server/ConnectivityService.java b/services/core/java/com/android/server/ConnectivityService.java
index 9c6e16f509..8657d3bee5 100644
--- a/services/core/java/com/android/server/ConnectivityService.java
+++ b/services/core/java/com/android/server/ConnectivityService.java
@@ -2112,15 +2112,6 @@ public class ConnectivityService extends IConnectivityManager.Stub
                 log(nai.name() + " got DISCONNECTED, was satisfying " + nai.networkRequests.size());
             }
             // A network agent has disconnected.
-            if (nai.created) {
-                // Tell netd to clean up the configuration for this network
-                // (routing rules, DNS, etc).
-                try {
-                    mNetd.removeNetwork(nai.network.netId);
-                } catch (Exception e) {
-                    loge("Exception removing network: " + e);
-                }
-            }
             // TODO - if we move the logic to the network agent (have them disconnect
             // because they lost all their requests or because their score isn't good)
             // then they would disconnect organically, report their new state and then
@@ -2139,8 +2130,9 @@ public class ConnectivityService extends IConnectivityManager.Stub
             mNetworkAgentInfos.remove(msg.replyTo);
             updateClat(null, nai.linkProperties, nai);
             synchronized (mNetworkForNetId) {
+                // Remove the NetworkAgent, but don't mark the netId as
+                // available until we've told netd to delete it below.
                 mNetworkForNetId.remove(nai.network.netId);
-                mNetIdInUse.delete(nai.network.netId);
             }
             // Since we've lost the network, go through all the requests that
             // it was satisfying and see if any other factory can satisfy them.
@@ -2182,9 +2174,28 @@ public class ConnectivityService extends IConnectivityManager.Stub
                 rematchNetworkAndRequests(networkToActivate, NascentState.NOT_JUST_VALIDATED,
                         ReapUnvalidatedNetworks.DONT_REAP);
             }
+            if (nai.created) {
+                // Tell netd to clean up the configuration for this network
+                // (routing rules, DNS, etc).
+                // This may be slow as it requires a lot of netd shelling out to ip and
+                // ip[6]tables to flush routes and remove the incoming packet mark rule, so do it
+                // after we've rematched networks with requests which should make a potential
+                // fallback network the default or requested a new network from the
+                // NetworkFactories, so network traffic isn't interrupted for an unnecessarily
+                // long time.
+                try {
+                    mNetd.removeNetwork(nai.network.netId);
+                } catch (Exception e) {
+                    loge("Exception removing network: " + e);
+                }
+            }
+            synchronized (mNetworkForNetId) {
+                mNetIdInUse.delete(nai.network.netId);
+            }
+        } else {
+            NetworkFactoryInfo nfi = mNetworkFactoryInfos.remove(msg.replyTo);
+            if (DBG && nfi != null) log("unregisterNetworkFactory for " + nfi.name);
         }
-        NetworkFactoryInfo nfi = mNetworkFactoryInfos.remove(msg.replyTo);
-        if (DBG && nfi != null) log("unregisterNetworkFactory for " + nfi.name);
     }
 
     // If this method proves to be too slow then we can maintain a separate