1# Copyright (c) 2014 The Chromium OS Authors. All rights reserved. 2# Use of this source code is governed by a BSD-style license that can be 3# found in the LICENSE file. 4 5import logging 6import random 7import string 8import time 9 10from autotest_lib.server.cros.network import frame_sender 11from autotest_lib.server.cros.network import hostap_config 12from autotest_lib.server.cros.network import wifi_interface_claim_context 13from autotest_lib.server import site_linux_system 14from autotest_lib.client.common_lib import error 15from autotest_lib.client.common_lib.cros.network import tcpdump_analyzer 16from autotest_lib.server.cros.network import wifi_cell_test_base 17 18 19class network_WiFi_ChannelScanDwellTime(wifi_cell_test_base.WiFiCellTestBase): 20 """Test for determine channel scan dwell time.""" 21 version = 1 22 23 KNOWN_TEST_PREFIX = 'network_WiFi' 24 SUFFIX_LETTERS = string.ascii_lowercase + string.digits 25 DELAY_INTERVAL_MILLISECONDS = 1 26 SCAN_RETRY_TIMEOUT_SECONDS = 10 27 NUM_BSS = 1024 28 MISSING_BEACON_THRESHOLD = 2 29 FREQUENCY_MHZ = 2412 30 MSEC_PER_SEC = 1000 31 32 def _build_ssid_prefix(self): 33 """Build ssid prefix.""" 34 unique_salt = ''.join([random.choice(self.SUFFIX_LETTERS) 35 for x in range(5)]) 36 prefix = self.__class__.__name__[len(self.KNOWN_TEST_PREFIX):] 37 prefix = prefix.lstrip('_') 38 prefix += '_' + unique_salt + '_' 39 return prefix[-23:] 40 41 42 def _get_ssid_index(self, ssid): 43 """Return the SSID index from an SSID string. 44 45 Given an SSID of the form [testName]_[salt]_[index], returns |index|. 46 47 @param ssid: full SSID, as received in scan results. 48 @return int SSID index. 49 """ 50 return int(ssid.split('_')[-1], 16) 51 52 53 def _get_beacon_timestamp(self, beacon_frames, ssid_num): 54 """Return the time at which the beacon with |ssid_num| was transmitted. 55 56 If multiple beacons match |ssid_num|, return the time of the first 57 matching beacon. 58 59 @param beacon_frames: List of Frames. 60 @param ssid_num: int SSID number to match. 61 @return datetime time at which beacon was transmitted. 62 """ 63 for frame in beacon_frames: 64 if self._get_ssid_index(frame.ssid) == ssid_num: 65 return frame.time_datetime 66 else: 67 raise error.TestFail('Failed to find SSID %d in pcap.' % ssid_num) 68 69 70 def _get_dwell_time(self, bss_list, sent_beacon_frames): 71 """Parse scan result to get dwell time. 72 73 Calculate dwell time based on the SSIDs in the scan result. 74 75 @param bss_list: List of BSSs. 76 @param sent_beacon_frames: List of Frames, as captured on sender. 77 78 @return int dwell time in ms. 79 """ 80 ssid_index = [self._get_ssid_index(bss) for bss in bss_list] 81 # Calculate dwell time based on the start ssid index and end ssid index. 82 ssid_index.sort() 83 index_diff = ssid_index[-1] - ssid_index[0] 84 85 # Check if number of missed beacon frames exceed the test threshold. 86 missed_beacons = index_diff - (len(ssid_index) - 1) 87 if missed_beacons > self.MISSING_BEACON_THRESHOLD: 88 logging.info('Missed %d beacon frames, SSID Index: %r', 89 missed_beacons, ssid_index) 90 raise error.TestFail('DUT missed more than %d beacon frames' % 91 missed_beacons) 92 93 first_ssid_tstamp = self._get_beacon_timestamp( 94 sent_beacon_frames, ssid_index[0]) 95 last_ssid_tstamp = self._get_beacon_timestamp( 96 sent_beacon_frames, ssid_index[-1]) 97 return int(round( 98 (last_ssid_tstamp - first_ssid_tstamp).total_seconds() * 99 self.MSEC_PER_SEC)) 100 101 102 def _channel_dwell_time_test(self, single_channel): 103 """Perform test to determine channel dwell time. 104 105 This function invoke FrameSender to continuously send beacon frames 106 for specific number of BSSs with specific delay, the SSIDs of the 107 BSS are in hex numerical order. And at the same time, perform wifi scan 108 on the DUT. The index in the SSIDs of the scan result will be used to 109 interpret the relative start time and end time of the channel scan. 110 111 @param single_channel: bool perform single channel scan if true. 112 113 @return int dwell time in ms. 114 115 """ 116 dwell_time = 0 117 channel = hostap_config.HostapConfig.get_channel_for_frequency( 118 self.FREQUENCY_MHZ) 119 self.context.router.start_capture(self.FREQUENCY_MHZ) 120 ssid_prefix = self._build_ssid_prefix() 121 122 with frame_sender.FrameSender(self.context.router, 'beacon', channel, 123 ssid_prefix=ssid_prefix, 124 num_bss=self.NUM_BSS, 125 frame_count=0, 126 delay=self.DELAY_INTERVAL_MILLISECONDS): 127 if single_channel: 128 frequencies = [self.FREQUENCY_MHZ] 129 else: 130 frequencies = [] 131 # Perform scan 132 start_time = time.time() 133 while time.time() - start_time < self.SCAN_RETRY_TIMEOUT_SECONDS: 134 bss_list = self.context.client.iw_runner.scan( 135 self.context.client.wifi_if, frequencies=frequencies) 136 137 if bss_list is not None: 138 break 139 140 time.sleep(0.5) 141 else: 142 raise error.TestFail('Unable to trigger scan on client.') 143 if not bss_list: 144 raise error.TestFail('Failed to find any BSS') 145 146 # Remaining work is done outside the FrameSender 147 # context. This is to ensure that no additional frames are 148 # transmitted while we're waiting for the packet capture 149 # to complete. 150 151 pcap_path = self.context.router.stop_capture()[0].local_pcap_path 152 153 # Filter scan result based on ssid prefix to remove any cached 154 # BSSs from previous run. 155 result_list = [bss.ssid for bss in bss_list if 156 bss.ssid.startswith(ssid_prefix)] 157 if result_list is None: 158 raise error.TestFail('Failed to find any BSS for this test') 159 160 beacon_frames = tcpdump_analyzer.get_frames( 161 pcap_path, tcpdump_analyzer.WLAN_BEACON_ACCEPTOR, bad_fcs='include') 162 # Filter beacon frames based on ssid prefix. 163 result_beacon_frames = [beacon_frame for beacon_frame in beacon_frames if 164 beacon_frame.ssid.startswith(ssid_prefix)] 165 if result_beacon_frames is None: 166 raise error.TestFail('Failed to find any beacons for this test') 167 return self._get_dwell_time(result_list, result_beacon_frames) 168 169 170 def run_once(self): 171 if self.context.router.board == "panther": 172 raise error.TestNAError('Panther router does not support manual ' 173 'beacon frame generation') 174 self.context.router.require_capabilities( 175 [site_linux_system.LinuxSystem. 176 CAPABILITY_SEND_MANAGEMENT_FRAME]) 177 # Claim the control over the wifi interface from WiFiClient, which 178 # will prevent shill and wpa_supplicant from managing that interface. 179 # So this test can have the sole ownership of the interface and can 180 # perform scans without interference from shill and wpa_supplicant. 181 with wifi_interface_claim_context.WiFiInterfaceClaimContext( 182 self.context.client): 183 # Get channel dwell time for single-channel scan 184 dwell_time = self._channel_dwell_time_test(True) 185 logging.info('Channel dwell time for single-channel scan: %d ms', 186 dwell_time) 187 self.write_perf_keyval( 188 {'dwell_time_single_channel_scan': dwell_time}) 189