interface.py

#!/usr/bin/env python
# -*- coding: iso-8859-15 -*-
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# BSD 3-Clause License
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# Copyright (c) 2016, Andrés Blanco (6e726d@gmail.com)
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import os
import fcntl
import struct
import socket


SYS_NET_PATH = "/sys/class/net/"
PHY_80211_FILENAME = "phy80211"


# linux/if.h
IFNAMSIZ = 16
# linux/wireless.h
SIOCSIWFREQ = 0x8B04  # Set Channel Frequency (Hz)
SIOCGIWFREQ = 0x8B05  # Get Channel Frequency (Hz)

# 802.11 Frequency MHz
FREQUENCY_DELTA = 5
BG_BASE_FREQUENCY = 2407
BG_LOWER_FREQUENCY = 2412
BG_UPPER_FREQUENCY = 2472
BG_CH14_FREQUENCY = 2484
A_BASE_FREQUENCY = 5000
A_LOWER_FREQUENCY = 5170
A_UPPER_FREQUENCY = 5825


class InvalidIEE80211Channel(Exception):
    pass


def get_network_interfaces():
    """Returns a list with network interfaces."""
    return os.listdir(SYS_NET_PATH)


def get_wireless_interfaces():
    """Returns a list with wireless network interfaces."""
    ifaces = list()
    for iface in get_network_interfaces():
        iface_sys_path = "%s%s" % (SYS_NET_PATH, iface)
        if PHY_80211_FILENAME in os.listdir(iface_sys_path):
            ifaces.append(iface)
    return ifaces


def get_interface_channel(iface):
    """Returns channel for a wireless network interface."""
    sd = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    raw_data = fcntl.ioctl(sd.fileno(), SIOCGIWFREQ, struct.pack('256s', iface[:IFNAMSIZ-1]))[IFNAMSIZ:]
    freq = struct.unpack("I", raw_data[0:4])[0]
    return get_channel_from_frequency(freq)


def get_channel_from_frequency(freq):
    """Returns channel for a specific frequency."""
    if (freq >= BG_LOWER_FREQUENCY) and (freq <= BG_UPPER_FREQUENCY):
        return (freq - BG_BASE_FREQUENCY) / FREQUENCY_DELTA
    elif freq == BG_CH14_FREQUENCY:
        return 14
    elif (freq >= A_LOWER_FREQUENCY) and (freq <= A_UPPER_FREQUENCY):
        return (freq - A_BASE_FREQUENCY) / FREQUENCY_DELTA
    raise InvalidIEE80211Channel()