webrtc: Fix missing port forwarding on CrOS

telemetry/telemetry/core/cros_interface.py

 # Copyright 2013 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 """A wrapper around ssh for common operations on a CrOS-based device"""
 import logging
 import os
 import re
 import shutil
 import stat
 import subprocess
@@ skipping 124 matching lines @@
     return not self._hostname
 
   @property
   def hostname(self):
     return self._hostname
 
   @property
   def ssh_port(self):
     return self._ssh_port
 
-  def FormSSHCommandLine(self, args, extra_ssh_args=None):
+  def FormSSHCommandLine(self, args, extra_ssh_args=None, port_forward=False):
     """Constructs a subprocess-suitable command line for `ssh'.
     """
     if self.local:
       # We run the command through the shell locally for consistency with
       # how commands are run through SSH (crbug.com/239161). This work
       # around will be unnecessary once we implement a persistent SSH
       # connection to run remote commands (crbug.com/239607).
       return ['sh', '-c', " ".join(args)]
 
-    full_args = ['ssh', '-o ForwardX11=no', '-o ForwardX11Trusted=no', '-n',
-                 '-S', self._ssh_control_file] + self._ssh_args
+    full_args = ['ssh', '-o ForwardX11=no', '-o ForwardX11Trusted=no', '-n']
+    # As remote port forwarding might conflict with the control socket
+    # sharing, skip the control socket args if it is for remote port forwarding.
+    if not port_forward:
+      full_args += ['-S', self._ssh_control_file]
+    full_args += self._ssh_args
     if self._ssh_identity is not None:
       full_args.extend(['-i', self._ssh_identity])
     if extra_ssh_args:
       full_args.extend(extra_ssh_args)
     full_args.append('root@%s' % self._hostname)
     full_args.append('-p%d' % self._ssh_port)
     full_args.extend(args)
     return full_args
 
   def _FormSCPCommandLine(self, src, dst, extra_scp_args=None):
@@ skipping 394 matching lines @@
     else:
       self.RunCmdOnDevice(start_cmd)
 
   def CloseConnection(self):
     if not self.local:
       with open(os.devnull, 'w') as devnull:
         subprocess.call(
             self.FormSSHCommandLine(['-O', 'exit', self._hostname]),
             stdout=devnull,
             stderr=devnull)