wifitables/sample.py

#!/usr/bin/env python

"""sample: measure wireless performance and write a report to the filesystem."""

import multiprocessing
import os
import platform
import re
import shutil
import subprocess
import sys
import tempfile
import time

import options
import report

optspec = """
sample [options...]
--
d,destination=  host to run tests against [192.168.1.143]
s,steps=        number of steps test was run from [10]
j,journal=      append to journal tracking a series of test runs
i,interface=    wireless interface to use for outgoing connections [{0}]
m,monitor=      wireless monitor interface to use [{1}]
"""


def Iperf(host, udp=False, bandwidth=20, bind=None):
  """Run iperf against host and report results."""
  line = ['iperf', '-c', host]
  prefix = 'iperf'

  if udp:
    line += ['-u', '-b', str(bandwidth * 1000000)]
    prefix += 'u'
  if bind:
    line += ['-B', bind]

  out = tempfile.NamedTemporaryFile(prefix=prefix)
  subprocess.check_call(line, stdout=out)
  return out


def MCSBackground(tcpdump, out):
  """Continually extract wireless MCS from a running `tcpdump` process.

  This function will not return as long as tcpdump is running. You probably want
  to run it in a background activity using multiprocessing.

  Args:
    tcpdump: a tcpdump process that's monitoring a wireless interface
                  and writing textual output to its stdout stream.
    out:          Python file-like object to write MCS information to.
  """
  mcs = re.compile(r'MCS (\d+)')
  x = 0

  for row in iter(tcpdump.stdout.readline, b''):
    x += 1
    match = mcs.search(row)
    if match:
      print >> out, '%2d ' % int(match.group(1)),
    else:
      print >> out, ' . ',

    if x % 25 == 0:
      print >> out


def MCS(bssid, interface):
  """Runs tcpdump in the background to gather wireless MCS."""
  print 'Please enter password for `sudo` if prompted.'
  subprocess.call(['sudo', '-v'])

  out = tempfile.NamedTemporaryFile(prefix='mcs')
  err = tempfile.NamedTemporaryFile(prefix='mcserr')

  filt = ('(not subtype beacon and not subtype ack) and '
          '(wlan addr1 {0} or wlan addr2 {0} or wlan addr3 {0})'.format(
              bssid, bssid, bssid))

  sudo_tcpdump = subprocess.Popen(['sudo', 'tcpdump', '-Z', os.getlogin(),
                                   '-Ilnei', interface, filt],
                                  stdout=subprocess.PIPE, stderr=err)
  proc = multiprocessing.Process(target=MCSBackground, args=(sudo_tcpdump, out))
  proc.start()

  return sudo_tcpdump, out, err


def IwLink(devname):
  out = tempfile.NamedTemporaryFile(prefix='iwlink')
  subprocess.check_call(['iw', 'dev', devname, 'link'], stdout=out)
  return out


def IpAddr():
  out = tempfile.NamedTemporaryFile(prefix='ipaddr')
  subprocess.check_call(['ip', '-o', '-f', 'inet', 'addr'], stdout=out)
  return out


def AirportI():
  """Gather information about the current wireless network from `airport`."""
  out = tempfile.NamedTemporaryFile(prefix='airport')
  subprocess.check_call(['airport', '-I'], stdout=out)
  return out


def AirportScan():
  """Gather information about other observable networks from `airport`."""
  out = tempfile.NamedTemporaryFile(prefix='airportscan')
  subprocess.check_call(['airport', '-s'], stdout=out)
  return out


def main():
  system = platform.system()
  defaults = {
      # on a modern MacBook, en0 is the AirPort and can monitor and send at once
      'Darwin': ['en0', 'en0'],
      # on Linux, separate client and monitor interfaces are needed.
      # these defaults are for a TV box, other platforms will be different.
      'Linux': ['wcli0', ''],
  }

  if not defaults.get(system):
    raise OSError('Running on unsupported system {0}; '
                  'supported systems are {1}'.format(system,
                                                     ' '.join(defaults.keys())))

  o = options.Options(optspec.format(*defaults[system]))
  (opt, _, extra) = o.parse(sys.argv[1:])
  if extra:
    o.fatal('did not understand supplied extra arguments.')

  # we run diagnostics, write their output to files, and gather the files into
  # a report that we present at the end of the run.
  outputs = []
  addr = ''

  if system == 'Darwin':
    ai = AirportI()
    ai.seek(0)
    bssid = report.ParseAirportI(ai.read())['BSSID']
    outputs += [ai, AirportScan()]
  elif system == 'Linux':
    # It's really likely we're running on a device with more than one interface.
    # Be sure we're using the one that we're trying to test.
    ip = IpAddr()
    ip.seek(0)
    addrmap = report.ParseIpAddr(ip.read())
    addr = addrmap.get(opt.interface)
    if not addr:
      raise ValueError('Interface {0} does not have an IPv4 address.'.format(
          opt.interface))

    # because ip addr usually includes a subnet mask, which will prevent iperf
    # from binding to the address
    mask = addr.find('/')
    if mask > -1:
      addr = addr[:mask]

    il = IwLink(opt.interface)
    il.seek(0)
    bssid = report.ParseIwLink(il.read())['BSSID']
    outputs += [ip, il]
  else:
    raise OSError('This script requires Mac OS X or Linux.')

  if opt.monitor:
    sudo_tcpdump, mcs_out, mcs_err = MCS(bssid, opt.monitor)
    print 'Gathering tcpdump in background as', sudo_tcpdump.pid
    outputs += [mcs_out, mcs_err]

  it = Iperf(opt.destination, bind=addr)

  # Empirically about 1.25x more packets make it through in UDP than TCP.
  # Try to saturate the channel by sending a bit more than that over UDP.
  it.seek(0)
  it_iperf = report.ParseIperfTCP(it.read())

  bandwidth = it_iperf.get('bandwidth', 0.01)
  outputs += [it, Iperf(opt.destination, udp=True, bandwidth=bandwidth * 1.5,
                        bind=addr)]

  if opt.monitor:
    subprocess.check_call(['sudo', 'kill', str(sudo_tcpdump.pid)])

  report_dir = 'wifi-{}-{:04}'.format(time.time(), opt.steps)
  os.mkdir(report_dir)
  for page in outputs:
    shutil.copy(page.name,
                os.path.join(report_dir, os.path.basename(page.name[:-6])))

  if opt.journal:
    with open(opt.journal, 'a') as journal:
      print >> journal, report_dir

  print 'Report written to', report_dir


if __name__ == '__main__':
  main()