Fix flakiness related to routing policy override in RNDIS forwarder.

tools/telemetry/telemetry/core/forwarders/android_forwarder.py

Index: tools/telemetry/telemetry/core/forwarders/android_forwarder.py
diff --git a/tools/telemetry/telemetry/core/forwarders/android_forwarder.py b/tools/telemetry/telemetry/core/forwarders/android_forwarder.py
index a3c3b1959a22096da5808137192d6b9c10e23a41..c522c3c8b9487ba75a0271ddb77e56f725e8cfd7 100644
--- a/tools/telemetry/telemetry/core/forwarders/android_forwarder.py
+++ b/tools/telemetry/telemetry/core/forwarders/android_forwarder.py
@@ -34,8 +34,7 @@ class AndroidForwarderFactory(forwarders.ForwarderFactory):
 
   def Create(self, port_pairs):
     if self._rndis_configurator:
-      return AndroidRndisForwarder(self._adb, self.host_ip,
-                                   self._rndis_configurator.device_iface,
+      return AndroidRndisForwarder(self._adb, self._rndis_configurator,
                                    port_pairs)
     return AndroidForwarder(self._adb, port_pairs)
 
@@ -68,17 +67,20 @@ class AndroidForwarder(forwarders.Forwarder):
 class AndroidRndisForwarder(forwarders.Forwarder):
   """Forwards traffic using RNDIS. Assumes the device has root access."""
 
-  def __init__(self, adb, host_ip, device_iface, port_pairs):
+  def __init__(self, adb, rndis_configurator, port_pairs):
     super(AndroidRndisForwarder, self).__init__(port_pairs)
 
     self._adb = adb
-    self._device_iface = device_iface
-    self._host_ip = host_ip
+    self._rndis_configurator = rndis_configurator
+    self._device_iface = rndis_configurator.device_iface
+    self._host_ip = rndis_configurator.host_ip
     self._original_dns = None, None, None
     self._RedirectPorts(port_pairs)
     if port_pairs.dns:
       self._OverrideDns()
-    self._OverrideRoutingPolicy()
+      # Need to override routing policy again since call to setifdns
+      # sometimes resets policy table
+      self._rndis_configurator.OverrideRoutingPolicy()
     # TODO(tonyg): Verify that each port can connect to host.
 
   @property
@@ -86,8 +88,8 @@ class AndroidRndisForwarder(forwarders.Forwarder):
     return self._host_ip
 
   def Close(self):
+    self._rndis_configurator.RestoreRoutingPolicy()
     self._SetDns(*self._original_dns)
-    self._RestoreRoutingPolicy()
     super(AndroidRndisForwarder, self).Close()
 
   def _RedirectPorts(self, port_pairs):
@@ -146,21 +148,6 @@ class AndroidRndisForwarder(forwarders.Forwarder):
       self._adb.device().GetProp('net.dns2'),
     )
 
-  def _OverrideRoutingPolicy(self):
-    """Override any routing policy that could prevent
-    packets from reaching the rndis interface
-    """
-    policies = self._adb.RunShellCommand('ip rule')
-    if len(policies) > 1 and not ('lookup main' in policies[1]):
-      self._adb.RunShellCommand('ip rule add prio 1 from all table main')
-      self._adb.RunShellCommand('ip route flush cache')
-
-  def _RestoreRoutingPolicy(self):
-    policies = self._adb.RunShellCommand('ip rule')
-    if len(policies) > 1 and re.match("^1:.*lookup main", policies[1]):
-      self._adb.RunShellCommand('ip rule del prio 1')
-      self._adb.RunShellCommand('ip route flush cache')
-
 
 class AndroidRndisConfigurator(object):
   """Configures a linux host to connect to an android device via RNDIS.
@@ -473,13 +460,30 @@ doit &
       return subprocess.call(['ping', '-q', '-c1', '-W1', self._device_ip],
                              stdout=devnull) == 0
 
+  def OverrideRoutingPolicy(self):
+    """Override any routing policy that could prevent
+    packets from reaching the rndis interface
+    """
+    policies = self._device.RunShellCommand('ip rule')
+    if len(policies) > 1 and not ('lookup main' in policies[1]):
+      self._device.RunShellCommand('ip rule add prio 1 from all table main')
+      self._device.RunShellCommand('ip route flush cache')
+
+  def RestoreRoutingPolicy(self):
+    policies = self._device.RunShellCommand('ip rule')
+    if len(policies) > 1 and re.match("^1:.*lookup main", policies[1]):
+      self._device.RunShellCommand('ip rule del prio 1')
+      self._device.RunShellCommand('ip route flush cache')
+
   def _CheckConfigureNetwork(self):
     """Enables RNDIS and configures it, retrying until we have connectivity."""
     force = False
     for _ in range(3):
       device_iface, host_iface = self._CheckEnableRndis(force)
       self._ConfigureNetwork(device_iface, host_iface)
+      self.OverrideRoutingPolicy()
       if self._TestConnectivity():
         return
       force = True
+    self.RestoreRoutingPolicy()
     raise Exception('No connectivity, giving up.')