Fix flakiness related to routing policy override in RNDIS forwarder.

Routing policy override is needed at the point where ping test is executed in AndroidRndisConfigurator or the ping may fail.

It's also needed after DNS is changed in AndroidRndisForwarder constructor as executing setifdns may reset the policy table.

Thus we need to make multiple calls to OverrideRoutingPolicy() during RNDIS forwarder creation lifecycle.  But this is ok since the function is idempotent.

BUG=

Review URL: https://codereview.chromium.org/577853002

Cr-Commit-Position: refs/heads/master@{#295222}

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.')