Reland of "[telemetry] Wire TsProxy through telemetry's network stack."

telemetry/telemetry/internal/forwarders/do_nothing_forwarder.py

Index: telemetry/telemetry/internal/forwarders/do_nothing_forwarder.py
diff --git a/telemetry/telemetry/internal/forwarders/do_nothing_forwarder.py b/telemetry/telemetry/internal/forwarders/do_nothing_forwarder.py
index d254cfbc049d82abe83c2ce4c55a6fc1db2024eb..901c8e953701cc80faec50dbec4c9a0484d18b6c 100644
--- a/telemetry/telemetry/internal/forwarders/do_nothing_forwarder.py
+++ b/telemetry/telemetry/internal/forwarders/do_nothing_forwarder.py
@@ -28,8 +28,8 @@
 
 class DoNothingForwarderFactory(forwarders.ForwarderFactory):
 
-  def Create(self, port_pair):
-    return DoNothingForwarder(port_pair)
+  def Create(self, port_pairs):
+    return DoNothingForwarder(port_pairs)
 
 
 class DoNothingForwarder(forwarders.Forwarder):
@@ -41,23 +41,37 @@
   Also, check that all TCP ports support connections.  (Raises ConnectionError.)
   """
 
-  def __init__(self, port_pair):
-    super(DoNothingForwarder, self).__init__(port_pair)
-    self._CheckPortPair()
+  def __init__(self, port_pairs):
+    super(DoNothingForwarder, self).__init__(
+        forwarders.PortPairs(*[
+            forwarders.PortPair(p.local_port, p.remote_port or p.local_port)
+            if p else None for p in port_pairs]))
+    self._CheckPortPairs()
 
-  def _CheckPortPair(self):
-    if self._port_pair.local_port != self._port_pair.remote_port:
-      raise PortsMismatchError('Local port forwarding is not supported')
-    try:
-      self._WaitForConnectionEstablished(
-          (self.host_ip, self._port_pair.local_port), timeout=10)
-      logging.debug(
-          'Connection test succeeded for %s:%d',
-          self.host_ip, self._port_pair.local_port)
-    except exceptions.TimeoutException:
-      raise ConnectionError(
-          'Unable to connect to address: %s:%d',
-          self.host_ip, self._port_pair.local_port)
+  def _CheckPortPairs(self):
+    # namedtuple._asdict() is a public method. The method starts with an
+    # underscore to avoid conflicts with attribute names.
+    # pylint: disable=protected-access
+    for protocol, port_pair in self._port_pairs._asdict().items():
+      if not port_pair:
+        continue
+      local_port, remote_port = port_pair
+      if local_port != remote_port:
+        raise PortsMismatchError('Local port forwarding is not supported')
+      if protocol == 'dns':
+        logging.debug('Connection test SKIPPED for DNS: %s:%d',
+                      self.host_ip, local_port)
+        continue
+      try:
+        self._WaitForConnectionEstablished(
+            (self.host_ip, local_port), timeout=10)
+        logging.debug(
+            'Connection test succeeded for %s: %s:%d',
+            protocol.upper(), self.host_ip, local_port)
+      except exceptions.TimeoutException:
+        raise ConnectionError(
+            'Unable to connect to %s address: %s:%d',
+            protocol.upper(), self.host_ip, local_port)
 
   def _WaitForConnectionEstablished(self, address, timeout):
     def CanConnect():