| #!/usr/bin/python -S |
| |
| """Utils related to automatic channel selection.""" |
| |
| import random |
| import subprocess |
| import time |
| |
| import utils |
| |
| |
| MODES = { |
| '24MAIN_20': '2412 2432 2462', |
| '24MAIN_40': '2412', |
| '24MAIN_80': '', |
| '24OVERLAP_20': '2412 2417 2422 2427 2432 2437 2442 2447 2452 2457 2462', |
| '24OVERLAP_40': '2412', |
| '24OVERLAP_80': '', |
| '5LOW_20': '5180 5200 5220 5240', |
| '5LOW_40': '5180 5220', |
| '5LOW_80': '5180', |
| '5HIGH_20': '5745 5765 5785 5805 5825', |
| '5HIGH_40': '5745 5785', |
| '5HIGH_80': '5745', |
| '5DFS_20': '5260 5280 5300 5320 5500 5520 5540 5560 5580 5660 5680 5700', |
| '5DFS_40': '5260 5300 5500 5540 5660', |
| '5DFS_80': '5260 5500', |
| } |
| |
| |
| def get_permitted_frequencies(band, autotype, width): |
| try: |
| return { |
| ('2.4', 'LOW', '20'): MODES['24MAIN_20'], |
| ('2.4', 'LOW', '40'): MODES['24MAIN_40'], |
| ('2.4', 'HIGH', '20'): MODES['24MAIN_20'], |
| ('2.4', 'HIGH', '40'): MODES['24MAIN_40'], |
| ('2.4', 'NONDFS', '20'): MODES['24MAIN_20'], |
| ('2.4', 'NONDFS', '40'): MODES['24MAIN_40'], |
| ('2.4', 'ANY', '20'): MODES['24MAIN_20'], |
| ('2.4', 'ANY', '40'): MODES['24MAIN_40'], |
| ('2.4', 'OVERLAP', '20'): MODES['24OVERLAP_20'], |
| ('2.4', 'OVERLAP', '40'): MODES['24OVERLAP_40'], |
| ('5', 'LOW', '20'): MODES['5LOW_20'], |
| ('5', 'LOW', '40'): MODES['5LOW_40'], |
| ('5', 'LOW', '80'): MODES['5LOW_80'], |
| ('5', 'HIGH', '20'): MODES['5HIGH_20'], |
| ('5', 'HIGH', '40'): MODES['5HIGH_40'], |
| ('5', 'HIGH', '80'): MODES['5HIGH_80'], |
| ('5', 'DFS', '20'): MODES['5DFS_20'], |
| ('5', 'DFS', '40'): MODES['5DFS_40'], |
| ('5', 'DFS', '80'): MODES['5DFS_80'], |
| ('5', 'NONDFS', '20'): ' '.join((MODES['5LOW_20'], MODES['5HIGH_20'])), |
| ('5', 'NONDFS', '40'): ' '.join((MODES['5LOW_40'], MODES['5HIGH_40'])), |
| ('5', 'NONDFS', '80'): ' '.join((MODES['5LOW_80'], MODES['5HIGH_80'])), |
| ('5', 'ANY', '20'): ' '.join((MODES['5LOW_20'], MODES['5HIGH_20'], |
| MODES['5DFS_20'])), |
| ('5', 'ANY', '40'): ' '.join((MODES['5LOW_40'], MODES['5HIGH_40'], |
| MODES['5DFS_40'])), |
| ('5', 'ANY', '80'): ' '.join((MODES['5LOW_80'], MODES['5HIGH_80'], |
| MODES['5DFS_80'])), |
| }[(band, autotype, width)] |
| except KeyError: |
| raise ValueError('Unknown autochannel type: band=%s autotype=%s width=%s' |
| % (band, autotype, width)) |
| |
| |
| def get_all_frequencies(band): |
| """Get all 802.11 frequencies for the given band.""" |
| return get_permitted_frequencies(band, 'OVERLAP' if band == '2.4' else 'ANY', |
| '20').split() |
| |
| |
| def scan(interface, band, autotype, width): |
| """Do an autochannel scan and return the recommended channel. |
| |
| Args: |
| interface: The interface on which to scan. |
| band: The band on which to scan. |
| autotype: Determines permitted frequencies. See get_permitted_frequencies |
| for valid values. |
| width: Determines permitted frequencies. See get_permitted_frequencies for |
| valid values. |
| |
| Returns: |
| The channel to use, or None if no recommendation can be made. |
| """ |
| utils.log('Doing autochannel scan.') |
| |
| permitted_frequencies = get_permitted_frequencies(band, autotype, width) |
| |
| subprocess.call(('ip', 'link', 'set', interface, 'up')) |
| |
| # TODO(apenwarr): We really want to clear any old survey results first. But |
| # there seems to be no iw command for that yet... |
| # |
| # TODO(apenwarr): This only scans each channel for 100ms. Ideally it should |
| # scan for longer, to get a better activity sample. It would also be nice to |
| # continue scanning in the background while hostapd is running, using 'iw |
| # offchannel'. Retry this a few times if it fails, just in case there was a |
| # scan already in progress started somewhere else (e.g. from waveguide). |
| for _ in xrange(9): |
| if utils.subprocess_quiet(('iw', 'dev', interface, 'scan', 'passive'), |
| no_stdout=True) == 0: |
| break |
| time.sleep(0.5) |
| |
| # TODO(apenwarr): This algorithm doesn't deal with overlapping channels. Just |
| # because channel 1 looks good doesn't mean we should use it; activity in |
| # overlapping channels could destroy performance. In fact, overlapping |
| # channel activity is much worse than activity on the main channel. Also, if |
| # using 40 MHz or 80 MHz channel width, we should count activity in all the 20 |
| # MHz sub-channels separately, and choose the least-active sub-channel as the |
| # primary. |
| best_frequency = best_noise = best_ratio = frequency = None |
| for tokens in utils.subprocess_line_tokens( |
| ('iw', 'dev', interface, 'survey', 'dump')): |
| # TODO(apenwarr): Randomize the order of channels. Otherwise when channels |
| # are all about equally good, we would always choose exactly the same |
| # channel, which might be bad in the case of hidden nodes. |
| if len(tokens) >= 2 and tokens[0] == 'frequency:': |
| frequency = tokens[1] |
| noise = active = busy = None |
| elif len(tokens) >= 2 and tokens[0] == 'noise:': |
| noise = int(tokens[1]) |
| elif len(tokens) >= 4 and tokens[:3] == ('channel', 'active', 'time:'): |
| active = int(tokens[3]) |
| elif len(tokens) >= 4 and tokens[:3] == ('channel', 'receive', 'time:'): |
| busy = int(tokens[3]) |
| # TODO(rofrankel): busy or 1 might make more sense than busy + 1 here; |
| # need to discuss with apenwarr@. |
| ratio = (active + 1) * 1000 / (busy + 1) |
| |
| if frequency not in permitted_frequencies.split(): |
| continue |
| |
| # Some radios support both bands, but we only want to match channels on |
| # the band we have chosen. |
| if band[0] != frequency[0]: |
| continue |
| |
| utils.log('freq=%s ratio=%s noise=%s', frequency, ratio, noise) |
| |
| if best_noise is None or best_noise - 15 > noise or best_ratio < ratio: |
| best_frequency, best_ratio, best_noise = frequency, ratio, noise |
| |
| if not best_frequency: |
| utils.log('Autoscan did not find any channel, picking random channel.') |
| utils.log('Permitted frequencies: %s', permitted_frequencies) |
| if not permitted_frequencies: |
| utils.log('No default channel: type=%s band=%s width=%s', |
| autotype, band, width) |
| return None |
| best_frequency = random.choice(permitted_frequencies.split()) |
| |
| utils.log('autofreq=%s', best_frequency) |
| |
| for tokens in utils.subprocess_line_tokens(('iw', 'phy')): |
| if len(tokens) >= 4 and tokens[2] == 'MHz': |
| frequency = tokens[1] |
| if frequency == best_frequency: |
| channel = tokens[3].strip('[]') |
| break |
| |
| if not channel: |
| utils.log('No channel number matched freq=%s.', best_frequency) |
| return None |
| |
| utils.log('autochannel=%s', channel) |
| |
| return channel |
