lldp_discovery.py

#!/usr/bin/env python
# -*- coding: utf-8 -*-

"""
Simple LLDP (Low Level Discovery Protocol) frame capture/parse script,
    designed by Hao Feng (whisperaven@gmail.com).

    1, Just read the `device name` and `portid` and `vlanid` TLV, but
        you can add your own parser by using the return value of function
        `unpack_lldp_frame`.
    2, Because it uses `socket()` with some Linux Only socket flags, so
        it should be Only work under linux.
    3, No python 3 support in mind, just want to get the job done.

    Hope that someone find it useful, but WITHOUT ANY WARRANTY;

Requirements:
pip install pyroute2 PrettyTable progressbar
"""

import re
import sys
import signal

from ctypes import c_char, c_short, Structure
from fcntl import ioctl
from socket import socket, htons, inet_ntoa
from socket import AF_PACKET, AF_INET, SOCK_DGRAM, SOCK_RAW
from socket import gaierror

from struct import pack, unpack
from pyroute2 import IPRoute
from prettytable import PrettyTable
import datetime
import logging
import logging.handlers
from progressbar import ProgressBar
import argparse
import json
import time

DEBUG = True

## Magic constants from `/usr/include/linux/if_ether.h`:
ETH_P_ALL = 0x0003
ETH_ALEN = 6
ETH_HLEN = 14

## LLDP Ethernet Protocol:
# LLDP Length:
LLDP_TLV_TYPE_BIT_LEN = 7
LLDP_TLV_LEN_BIT_LEN = 9
LLDP_TLV_HEADER_LEN = 2         # 7 + 9 = 16
LLDP_TLV_OUI_LEN = 3
LLDP_TLV_SUBTYPE_LEN = 1
# LLDP Protocol BitFiddling Mask:
LLDP_TLV_TYPE_MASK = 0xfe00
LLDP_TLV_LEN_MASK = 0x1ff
# LLDP Protocol ID:
LLDP_PROTO_ID = 0x88cc
# LLDP TLV Type:
LLDP_TLV_TYPE_CHASSISID = 0x01
LLDP_TLV_TYPE_PORTID = 0x02
LLDP_TLV_DEVICE_NAME = 0x05
LLDP_PDUEND = 0x00
LLDP_TLV_ORGANIZATIONALLY_SPECIFIC = 0x7f
# LLDP TLV OUI Type:
LLDP_TLV_OUI_802_1 = 0x0008c2
LLDP_TLV_OUI_802_3 = 0x00120f

## Magic string for unpack packet:
UNPACK_ETH_HEADER_DEST = '!%s' % ('B' * ETH_ALEN)
UNPACK_ETH_HEADER_SRC = '!%s' % ('B' * ETH_ALEN)
UNPACK_ETH_HEADER_PROTO = '!H'

## Magic string for unpack LLDP packet:
UNPACK_LLDP_TLV_TYPE = '!H'
UNPACK_LLDP_TLV_OUI = '!%s' % ('B' * LLDP_TLV_OUI_LEN)
UNPACK_LLDP_TLV_SUBTYPE = '!B'

## Other info about network under linux:
NETDEV_INFO = '/proc/net/dev'
SIOCGIFADDR = 0x8915    # Socket opt for get ip addr under linux
SIOCSIFHWADDR = 0x8927  # Socket opt for get mac addr under linux
SIOCGIFFLAGS = 0x8913   # `G` for Get socket flags
SIOCSIFFLAGS = 0x8914   # `S` for Set socket flags
IFF_PROMISC = 0x100     # Enter Promiscuous mode

## Timers
ADV_TIMER = 30        # Default LLDP advertisement timer is 30 seconds
ADV_TIMEOUT = 45      # Timeout value (seconds) for LLDP advertisements

## Defaults
PORTID = 'UNKNOWN'
SWITCH = 'UNKNOWN'
STATE = 'UNKNOWN'
VLANID = 'UNKNOWN'
INVALID_INTERFACE_TYPES = ['bridge','veth','vlan','openvswitch',
                           'tun','geneve','vxlan','gre','bond']

# Setup logging
log = logging.getLogger(__name__)
if DEBUG:
    log.setLevel(logging.DEBUG)
else:
    log.setLevel(logging.INFO)

handler = logging.handlers.SysLogHandler(address = '/dev/log')
formatter = logging.Formatter('%(module)s.%(funcName)s: %(message)s')
handler.setFormatter(formatter)

log.addHandler(handler)

class ifreq(Structure):
    """ C-compatible `ifreq` struct """
    _fields_ = [("ifr_ifrn", c_char * 16),
                ("ifr_flags", c_short)]


def detect_netdevs():
    """ Get network interface name/ip,
            ignore interface with no ip assigned """

    netdevs = list()
    netdev_regex = re.compile(r"""(.+?):[0-9]* .*$""")
    ip_gather_sock = socket(AF_INET, SOCK_DGRAM)

    fp = open(NETDEV_INFO, 'ro')
    for interface in fp:
        m = re.match(netdev_regex, interface)
        interface_ip = '0.0.0.0'
        if m and 'lo' not in m.group(1):
            interface_name = m.group(1).strip()

            # Check to see if the interface is interesting to us
            # and append to list of interfaces to query
            if get_interface_kind(interface_name) not in INVALID_INTERFACE_TYPES:
                netdevs.append((interface_name, interface_ip))

    return netdevs


def promiscuous_mode(interface, sock, enable=False):
    """ Enable/Disable NIC promiscuous mode via `ioctl` system call
            with c-compatible `ifreq` struct and `SIOC[G|S]IFFLAGS` """

    ifr = ifreq()
    ifr.ifr_ifrn = interface
    ioctl(sock.fileno(), SIOCGIFFLAGS, ifr)

    if enable:
        ifr.ifr_flags |= IFF_PROMISC
    else:
        ifr.ifr_flags &= ~IFF_PROMISC
    ioctl(sock.fileno(), SIOCSIFFLAGS, ifr)


def toggle_interface(interface_name, state='up'):
    """ Toggle interface """

    ipr = IPRoute()

    # lookup the index
    dev = ipr.link_lookup(ifname=interface_name)[0]
    ipr.link('set', index=dev, state=state)

    log.debug("Interface %s is being toggled %s" % (interface_name, state))
    ipr.close()


def unpack_ethernet_frame(packet):
    """ Unpack ethernet frame """

    eth_header = packet[0:ETH_HLEN]
    eth_dest_mac = unpack(UNPACK_ETH_HEADER_DEST, eth_header[0:ETH_ALEN])
    eth_src_mac = unpack(UNPACK_ETH_HEADER_SRC, eth_header[ETH_ALEN:ETH_ALEN*2])
    eth_protocol = unpack(UNPACK_ETH_HEADER_PROTO, eth_header[ETH_ALEN*2:ETH_HLEN])[0]
    eth_payload = packet[ETH_HLEN:]

    return (eth_header, eth_dest_mac, eth_src_mac, eth_protocol, eth_payload)


def covert_hex_string(decimals):
    """ Covert decimals to hex string which start with `0x`, 
            and `strip` by `0x` """
    return [ hex(decimal).strip('0x').rjust(2, '0') for decimal in decimals ]


def unpack_lldp_frame(eth_payload):
    """ Unpack lldp frame """

    while eth_payload:

        tlv_header = unpack(UNPACK_LLDP_TLV_TYPE, eth_payload[:LLDP_TLV_HEADER_LEN])
        tlv_type = (tlv_header[0] & LLDP_TLV_TYPE_MASK) >> LLDP_TLV_LEN_BIT_LEN
        tlv_data_len = (tlv_header[0] & LLDP_TLV_LEN_MASK)
        tlv_payload = eth_payload[LLDP_TLV_HEADER_LEN:LLDP_TLV_HEADER_LEN + tlv_data_len]

        # These headers only available with
        #   `LLDP_TLV_ORGANIZATIONALLY_SPECIFIC` TLV
        tlv_oui = None
        tlv_subtype = None

        if tlv_type == LLDP_TLV_ORGANIZATIONALLY_SPECIFIC:
            _tlv_oui = unpack(UNPACK_LLDP_TLV_OUI, tlv_payload[:LLDP_TLV_OUI_LEN])
            tlv_subtype = unpack(UNPACK_LLDP_TLV_SUBTYPE,
                            tlv_payload[LLDP_TLV_OUI_LEN:LLDP_TLV_OUI_LEN + LLDP_TLV_SUBTYPE_LEN])[0]
            tlv_payload = tlv_payload[LLDP_TLV_OUI_LEN + LLDP_TLV_SUBTYPE_LEN:]

            # Covert oui from list to hex/decimals
            tlv_oui = str()
            for bit in _tlv_oui:
                tlv_oui += hex(bit).strip('0x').rjust(2, '0')
            tlv_oui = int(tlv_oui, 16)

        elif tlv_type == LLDP_PDUEND:
            break

        eth_payload = eth_payload[LLDP_TLV_HEADER_LEN + tlv_data_len:]

        yield (tlv_header, tlv_type, tlv_data_len, tlv_oui, \
                                        tlv_subtype, tlv_payload)


def exit_handler(signum, frame):
    """ Exit signal handler """

    capture_sock = frame.f_locals['capture_sock']
    interface_name = frame.f_locals['interface_name']

    promiscuous_mode(interface_name, capture_sock, False)
    print("Abort, %s exit promiscuous mode." % interface_name)

    sys.exit(1)


def get_interface_state(interface_name):

        # Get interface state
        ip = IPRoute()
        state = ip.get_links(ip.link_lookup(ifname=interface_name))[0].get_attr('IFLA_OPERSTATE')
        log.debug("Interface %s state is %s." % (interface_name, state))
        ip.close()

        return state

def get_interface_kind(interface_name):

        # Get interface state
        ip = IPRoute()

        linkinfo = ip.get_links(ip.link_lookup(ifname=interface_name))[0].get_attr('IFLA_LINKINFO')
        if linkinfo is not None:
            kind = linkinfo.get_attr('IFLA_INFO_KIND')
        else:
            kind = 'n/a'
        ip.close()

        return kind

def main():
    """ Low Level Discovery Protocol """

    parser = argparse.ArgumentParser()
    output = parser.add_mutually_exclusive_group(required=False)
    output.add_argument("-p", "--pretty", action="store_true",
                    help="Prints output to table")
    output.add_argument("-j", "--json", action="store_true",
                    help="Prints output to json")
    args = parser.parse_args()

    rv = dict()

    netdevs = detect_netdevs()

    # Build a table if asked
    if args.pretty:
        print "Polling interfaces for LLDP. This may take a bit..."

    for interface_name, interface_ip in netdevs:

        rv[interface_name] = dict()

        state = get_interface_state(interface_name)
        rv[interface_name]['state'] = state
        kind = get_interface_kind(interface_name)
        rv[interface_name]['kind'] = kind

        # Toggle if DOWN
        if state is 'DOWN':
            toggle = True
            next_state = 'down'
            toggle_interface(interface_name, 'up')
            time.sleep(10)    # sleep to allow interface to change
            state = get_interface_state(interface_name)
        else:
            toggle = False

        capture_sock = socket(AF_PACKET, SOCK_RAW, htons(ETH_P_ALL))
        capture_sock.bind((interface_name, 0))

        promiscuous_mode(interface_name, capture_sock, True)

        signal.signal(signal.SIGINT, exit_handler)
        signal.signal(signal.SIGALRM, exit_handler)
        signal.alarm(ADV_TIMEOUT)

        # Set defaults
        rv[interface_name]['portid'] = PORTID
        rv[interface_name]['switch'] = SWITCH
        rv[interface_name]['vlan'] = VLANID

        while True and state is 'UP':

            packet = capture_sock.recvfrom(65565)
            packet = packet[0]

            eth_dest_mac, eth_src_mac, eth_protocol, eth_payload = unpack_ethernet_frame(packet)[1:]

            # Convert tuple MAC to hex MAC
            hex_src_mac = ':'.join(covert_hex_string(list(eth_src_mac)))
            hex_dest_mac = ':'.join(covert_hex_string(list(eth_dest_mac)))

            if eth_protocol == LLDP_PROTO_ID:

                log.debug("%s %s - SRC: %s, DEST: %s, Ethernet Protocol: %s" %
                                (datetime.datetime.utcnow(),interface_name,
                                hex_src_mac,hex_dest_mac,eth_protocol))

                promiscuous_mode(interface_name, capture_sock, False)
                signal.signal(signal.SIGINT, signal.SIG_DFL)
                signal.signal(signal.SIGALRM, signal.SIG_DFL)
                signal.alarm(0)

                for tlv_parse_rv in unpack_lldp_frame(eth_payload):

                    tlv_header, tlv_type, tlv_data_len, tlv_oui, tlv_subtype, tlv_payload \
                                                                            = tlv_parse_rv

                    log.debug("%s, %s, %s, %s, %s, %s" %
                                    (tlv_header, tlv_type, tlv_data_len, tlv_oui, tlv_subtype, tlv_payload))

                    if tlv_type == LLDP_TLV_TYPE_PORTID:
                        rv[interface_name]['portid'] = re.sub(r'[\x00-\x08]', '', tlv_payload).strip()
                    elif tlv_type == LLDP_TLV_DEVICE_NAME:
                        rv[interface_name]['switch'] = tlv_payload
                    elif tlv_type == LLDP_TLV_ORGANIZATIONALLY_SPECIFIC:
                        if tlv_oui == LLDP_TLV_OUI_802_1 and tlv_subtype == 3:
                            rv[interface_name]['vlan'] = re.sub(r'[\x00-\x08]', '', tlv_payload).strip()

                break

        # Reset interface state
        if toggle:
            toggle_interface(interface_name, state=next_state)

    # Build a table of results
    if args.pretty:
        x = PrettyTable(["Interface", "State", "Kind", "Switch", "Port", "VLAN"])
        x.padding_width = 1

        for int_name, int_details in rv.items():
            x.add_row([int_name, int_details['state'], int_details['kind'],
                       int_details['switch'], int_details['portid'], int_details['vlan']])

        print x
    elif args.json:
        print json.dumps(rv)

# Start:
if __name__ == '__main__':
    main()