Renamed to Network Emulator and improved error handling.
Changed default start port of the port-range to 32768.
BUG=None
TEST=Tested locally.
Review URL: https://webrtc-codereview.appspot.com/627004
git-svn-id: http://webrtc.googlecode.com/svn/trunk@2338 4adac7df-926f-26a2-2b94-8c16560cd09d
diff --git a/tools/network_emulator/network_emulator.py b/tools/network_emulator/network_emulator.py
new file mode 100644
index 0000000..2876939
--- /dev/null
+++ b/tools/network_emulator/network_emulator.py
@@ -0,0 +1,178 @@
+#!/usr/bin/env python
+# Copyright (c) 2012 The WebRTC project authors. All Rights Reserved.
+#
+# Use of this source code is governed by a BSD-style license
+# that can be found in the LICENSE file in the root of the source
+# tree. An additional intellectual property rights grant can be found
+# in the file PATENTS. All contributing project authors may
+# be found in the AUTHORS file in the root of the source tree.
+
+"""Script for constraining traffic on the local machine."""
+
+import logging
+import os
+import subprocess
+import sys
+
+
+class NetworkEmulatorError(BaseException):
+ """Exception raised for errors in the network emulator.
+
+ Attributes:
+ msg: User defined error message.
+ cmd: Command for which the exception was raised.
+ returncode: Return code of running the command.
+ stdout: Output of running the command.
+ stderr: Error output of running the command.
+ """
+
+ def __init__(self, msg, cmd=None, returncode=None, output=None,
+ error=None):
+ BaseException.__init__(self, msg)
+ self.msg = msg
+ self.cmd = cmd
+ self.returncode = returncode
+ self.output = output
+ self.error = error
+
+
+class NetworkEmulator(object):
+ """A network emulator that can constrain the network using Dummynet."""
+
+ def __init__(self, connection_config, port_range):
+ """Constructor.
+
+ Args:
+ connection_config: A config.ConnectionConfig object containing the
+ characteristics for the connection to be emulation.
+ port_range: Tuple containing two integers defining the port range.
+ """
+ self._pipe_counter = 0
+ self._rule_counter = 0
+ self._port_range = port_range
+ self._connection_config = connection_config
+
+ def emulate(self, target_ip):
+ """Starts a network emulation by setting up Dummynet rules.
+
+ Args:
+ target_ip: The IP address of the interface that shall be that have the
+ network constraints applied to it.
+ """
+ receive_pipe_id = self._create_dummynet_pipe(
+ self._connection_config.receive_bw_kbps,
+ self._connection_config.delay_ms,
+ self._connection_config.packet_loss_percent,
+ self._connection_config.queue_slots)
+ logging.debug('Created receive pipe: %s', receive_pipe_id)
+ send_pipe_id = self._create_dummynet_pipe(
+ self._connection_config.send_bw_kbps,
+ self._connection_config.delay_ms,
+ self._connection_config.packet_loss_percent,
+ self._connection_config.queue_slots)
+ logging.debug('Created send pipe: %s', send_pipe_id)
+
+ # Adding the rules will start the emulation.
+ incoming_rule_id = self._create_dummynet_rule(receive_pipe_id, 'any',
+ target_ip, self._port_range)
+ logging.debug('Created incoming rule: %s', incoming_rule_id)
+ outgoing_rule_id = self._create_dummynet_rule(send_pipe_id, target_ip,
+ 'any', self._port_range)
+ logging.debug('Created outgoing rule: %s', outgoing_rule_id)
+
+ def check_permissions(self):
+ """Checks if permissions are available to run Dummynet commands.
+
+ Raises:
+ NetworkEmulatorError: If permissions to run Dummynet commands are not
+ available.
+ """
+ if os.geteuid() != 0:
+ self._run_shell_command(
+ ['sudo', '-n', 'ipfw', '-h'],
+ msg=('Cannot run \'ipfw\' command. This script must be run as '
+ 'root or have password-less sudo access to this command.'))
+
+ def cleanup(self):
+ """Stops the network emulation by flushing all Dummynet rules.
+
+ Notice that this will flush any rules that may have been created previously
+ before starting the emulation.
+ """
+ self._run_shell_command(['sudo', 'ipfw', '-f', 'flush'],
+ 'Failed to flush Dummynet rules!')
+
+ def _create_dummynet_rule(self, pipe_id, from_address, to_address,
+ port_range):
+ """Creates a network emulation rule and returns its ID.
+
+ Args:
+ pipe_id: integer ID of the pipe.
+ from_address: The IP address to match source address. May be an IP or
+ 'any'.
+ to_address: The IP address to match destination address. May be an IP or
+ 'any'.
+ port_range: The range of ports the rule shall be applied on. Must be
+ specified as a tuple of with two integers.
+ Returns:
+ The ID of the rule, starting at 100. The rule ID increments with 100 for
+ each rule being added.
+ """
+ self._rule_counter += 100
+ add_part = ['sudo', 'ipfw', 'add', self._rule_counter, 'pipe', pipe_id,
+ 'ip', 'from', from_address, 'to', to_address]
+ self._run_shell_command(add_part + ['src-port', '%s-%s' % port_range],
+ 'Failed to add Dummynet src-port rule.')
+ self._run_shell_command(add_part + ['dst-port', '%s-%s' % port_range],
+ 'Failed to add Dummynet dst-port rule.')
+ return self._rule_counter
+
+ def _create_dummynet_pipe(self, bandwidth_kbps, delay_ms, packet_loss_percent,
+ queue_slots):
+ """Creates a Dummynet pipe and return its ID.
+
+ Args:
+ bandwidth_kbps: Bandwidth.
+ delay_ms: Delay for a one-way trip of a packet.
+ packet_loss_percent: Float value of packet loss, in percent.
+ queue_slots: Size of the queue.
+ Returns:
+ The ID of the pipe, starting at 1.
+ """
+ self._pipe_counter += 1
+ cmd = ['sudo', 'ipfw', 'pipe', self._pipe_counter, 'config',
+ 'bw', str(bandwidth_kbps/8) + 'KByte/s',
+ 'delay', '%sms' % delay_ms,
+ 'plr', (packet_loss_percent/100.0),
+ 'queue', queue_slots]
+ error_message = 'Failed to create Dummynet pipe. '
+ if sys.platform.startswith('linux'):
+ error_message += ('Make sure you have loaded the ipfw_mod.ko module to '
+ 'your kernel (sudo insmod /path/to/ipfw_mod.ko)')
+ self._run_shell_command(cmd, error_message)
+ return self._pipe_counter
+
+ def _run_shell_command(self, command, msg=None):
+ """Executes a command.
+
+ Args:
+ command: Command list to execute.
+ msg: Message describing the error in case the command fails.
+
+ Returns:
+ The standard output from running the command.
+
+ Raises:
+ NetworkEmulatorError: If command fails. Message is set by the msg
+ parameter.
+ """
+ cmd_list = [str(x) for x in command]
+ cmd = ' '.join(cmd_list)
+ logging.debug('Running command: %s', cmd)
+
+ process = subprocess.Popen(cmd_list, stdout=subprocess.PIPE,
+ stderr=subprocess.PIPE)
+ output, error = process.communicate()
+ if process.returncode != 0:
+ raise NetworkEmulatorError(msg, cmd, process.returncode, output, error)
+ return output.strip()
