server/site_tests/network_WiFi_BgscanBackoff/network_WiFi_BgscanBackoff.py

# Copyright (c) 2013 The Chromium OS Authors. All rights reserved.
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.

import logging
import time

from autotest_lib.client.common_lib import error
from autotest_lib.client.common_lib.cros.network import iw_runner
from autotest_lib.client.common_lib.cros.network import ping_runner
from autotest_lib.client.common_lib.cros.network import xmlrpc_datatypes
from autotest_lib.server.cros.network import hostap_config
from autotest_lib.server.cros.network import wifi_cell_test_base


class network_WiFi_BgscanBackoff(wifi_cell_test_base.WiFiCellTestBase):
    """Test that background scan backs off when there is foreground traffic."""
    version = 1

    BGSCAN_SAMPLE_PERIOD_SECONDS = 100
    NO_BGSCAN_SAMPLE_PERIOD_SECONDS = 10
    CONFIGURED_BGSCAN_INTERVAL_SECONDS = 7
    PING_INTERVAL_SECONDS = 0.1
    LATENCY_MARGIN_MS = 200
    THRESHOLD_BASELINE_LATENCY_MS = 100


    def run_once(self):
        """Body of the test."""
        get_assoc_params = lambda conf: xmlrpc_datatypes.AssociationParameters(
                ssid=self.context.router.get_ssid(instance=0),
                bgscan_config=conf)
        get_ping_config = lambda period: ping_runner.PingConfig(
                self.context.get_wifi_addr(),
                interval=self.PING_INTERVAL_SECONDS,
                count=int(period / self.PING_INTERVAL_SECONDS))
        self.context.configure(hostap_config.HostapConfig(channel=1))
        bgscan_config = xmlrpc_datatypes.BgscanConfiguration(
                short_interval=self.CONFIGURED_BGSCAN_INTERVAL_SECONDS,
                long_interval=self.CONFIGURED_BGSCAN_INTERVAL_SECONDS,
                method=xmlrpc_datatypes.BgscanConfiguration.SCAN_METHOD_SIMPLE)
        self.context.assert_connect_wifi(get_assoc_params(bgscan_config))
        logging.info('Pinging router with background scans for %d seconds.',
                     self.BGSCAN_SAMPLE_PERIOD_SECONDS)
        result_bgscan = self.context.client.ping(
                get_ping_config(self.BGSCAN_SAMPLE_PERIOD_SECONDS))
        logging.info('Ping statistics with bgscan: %r', result_bgscan)
        # Bring up a second AP, make sure that it shows up in bgscans.
        self.context.configure(
                hostap_config.HostapConfig(channel=11,
                                           ssid=self.context.router.get_ssid()),
                multi_interface=True)
        logging.info('Without a ping running, ensure that bgscans succeed.')
        ap_mac = self.context.router.get_hostapd_mac(ap_num=1)
        logging.debug('Looking for BSS %s', ap_mac)
        iw = iw_runner.IwRunner(remote_host=self.context.client.host)
        start_time = time.time()
        while time.time() - start_time < self.BGSCAN_SAMPLE_PERIOD_SECONDS:
            bsses = iw.scan_dump(self.context.client.wifi_if)
            logging.debug('Found BSSes: %r', bsses)
            if filter(lambda bss: bss.bss == ap_mac, bsses):
                break

            time.sleep(1)
        else:
            raise error.TestFail('Background scans should detect new BSSes '
                                 'within an associated ESS.')

        self.context.router.deconfig_aps(instance=1)
        self.context.client.shill.disconnect(
                self.context.router.get_ssid(instance=0))
        # Reconfigure AP, so the new bgscan setting can be correctly applied.
        self.context.configure(hostap_config.HostapConfig(channel=1))
        # Gather some statistics about ping latencies without scanning going on.
        self.context.assert_connect_wifi(get_assoc_params(None))
        logging.info('Pinging router without background scans for %d seconds.',
                     self.NO_BGSCAN_SAMPLE_PERIOD_SECONDS)
        result_no_bgscan = self.context.client.ping(
                get_ping_config(self.NO_BGSCAN_SAMPLE_PERIOD_SECONDS))
        logging.info('Ping statistics without bgscan: %r', result_no_bgscan)
        if result_no_bgscan.max_latency > self.THRESHOLD_BASELINE_LATENCY_MS:
            raise error.TestFail('RTT latency is too high even without '
                                 'background scans: %f' %
                                 result_no_bgscan.max_latency)

        # Dwell time for scanning is usually configured to be around 100 ms,
        # since this is also the standard beacon interval.  Tolerate spikes in
        # latency up to 200 ms as a way of asking that our PHY be servicing
        # foreground traffic regularly during background scans.
        if (result_bgscan.max_latency >
                self.LATENCY_MARGIN_MS + result_no_bgscan.avg_latency):
            raise error.TestFail('Significant difference in rtt due to bgscan: '
                                 '%.1f > %.1f + %d' %
                                 (result_bgscan.max_latency,
                                  result_no_bgscan.avg_latency,
                                  self.LATENCY_MARGIN_MS))