| # Copyright 2019 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 helper for common operations in ssh forwarding""" |
| import re |
| |
| import py_utils |
| |
| def ReadRemotePort(filename): |
| """Fetches the port created remotely. |
| |
| When we specify the remote port '0' in ssh remote port forwarding, |
| the remote ssh server should return the port it binds to in stderr. |
| e.g. 'Allocated port 42360 for remote forward to localhost:12345', the port |
| 42360 is the port created remotely and the traffic to the port will be |
| relayed to localhost port 12345. |
| |
| Args: |
| filename: the file that stderr is redirected to. |
| |
| Returns: |
| The port created on the remote device. |
| """ |
| def TryReadingPort(f): |
| line = f.readline() |
| tokens = re.search(r'port (\d+) for remote forward to', line) |
| return int(tokens.group(1)) if tokens else None |
| |
| with open(filename, 'r') as f: |
| return py_utils.WaitFor(lambda: TryReadingPort(f), timeout=60) |
| |
| def GetForwardingArgs(local_port, remote_port, host_ip, port_forward): |
| """Prepare the forwarding arguments to execute for devices that connect with |
| the host via ssh. |
| |
| Args: |
| local_port: Port on the host. |
| remote_port: Port on the remote device. |
| host_ip: ip of the host. |
| port_forward: Direction of the connection. True if forwarding from the host. |
| |
| Returns: |
| List of strings, the command arguments for handling port forwarding. |
| """ |
| if port_forward: |
| arg_format = '-R{remote_port}:{host_ip}:{local_port}' |
| else: |
| arg_format = '-L{local_port}:{host_ip}:{remote_port}' |
| return [ |
| arg_format.format(host_ip=host_ip, |
| local_port=local_port, |
| remote_port=remote_port or 0) |
| ] |
