#!/usr/bin/env python3

"""Healthchecker for exabgp.

This program is to be used as a process for exabgp. It will announce
some VIP depending on the state of a check whose a third-party program
wrapped by this program.

To use, declare this program as a process in your
:file:`/etc/exabgp/exabgp.conf`::

    neighbor 192.0.2.1 {
       router-id 192.0.2.2;
       local-as 64496;
       peer-as 64497;
    }
    process watch-haproxy {
       run python -m exabgp healthcheck --cmd "curl -sf http://127.0.0.1/healthcheck" --label haproxy;
    }
    process watch-mysql {
       run python -m exabgp healthcheck --cmd "mysql -u check -e 'SELECT 1'" --label mysql;
    }

Use :option:`--help` to get options accepted by this program. A
configuration file is also possible. Such a configuration file looks
like this::

     debug
     name = haproxy
     interval = 10
     fast-interval = 1
     command = curl -sf http://127.0.0.1/healthcheck

The left-part of each line is the corresponding long option.

When using label for loopback selection, the provided value should
match the beginning of the label without the interface prefix. In the
example above, this means that you should have addresses on lo
labelled ``lo:haproxy1``, ``lo:haproxy2``, etc.

"""

from __future__ import annotations

import sys
import os
import subprocess
import re
import logging
import logging.handlers
import argparse
import signal
import time
import collections

from ipaddress import ip_network
from ipaddress import ip_address

# Interface name validation constants
IFNAME_MAX_LENGTH = 15  # Maximum interface name length (Linux kernel limit)
IP_CMD_ADD_ERROR_CODE = 2  # Error code when 'ip address add' fails (address already exists)
IP_IFNAME_PARTS = 2  # Expected format: ip%ifname

logger = logging.getLogger('healthcheck')


def neighbor_address(value):
    """Parse a neighbor value: an IP address or '*' for all peers."""
    if value.strip() == '*':
        return '*'
    return ip_address(value)


def enum(*sequential):
    """Create a simple enumeration."""
    return type(str('Enum'), (), dict(zip(sequential, sequential)))


def setargs(parser):
    # fmt: off
    g = parser.add_mutually_exclusive_group()
    g.add_argument('--silent', '-s', action='store_true', default=False, help="don't log to console")
    g.add_argument('--syslog-facility', '-sF', metavar='FACILITY', nargs='?', const='daemon', default='daemon', help='log to syslog using FACILITY, default FACILITY is daemon')
    g.add_argument('--no-syslog', action='store_true', help='disable syslog logging')

    parser.add_argument('--debug', '-d', action='store_true', default=False, help='enable debugging')
    parser.add_argument('--no-ack', '-a', action='store_true', default=False, help='set for exabgp 3.4 or 4.x when exabgp.api.ack=false')
    parser.add_argument('--sudo', action='store_true', default=False, help='use sudo to setup ip addresses')
    parser.add_argument('--name', '-n', metavar='NAME', help='name for this healthchecker')
    parser.add_argument('--config', '-F', metavar='FILE', type=open, help='read configuration from a file')
    parser.add_argument('--pid', '-p', metavar='FILE', type=argparse.FileType('w'), help='write PID to the provided file')
    parser.add_argument('--user', metavar='USER', help='set user after setting ip addresses')
    parser.add_argument('--group', metavar='GROUP', help='set group after setting ip addresses')

    g = parser.add_argument_group('checking healthiness')
    g.add_argument('--interval', '-i', metavar='N', default=5, type=float, help='wait N seconds between each healthcheck (zero to exit after first announcement)')
    g.add_argument('--fast-interval', '-f', metavar='N', default=1, type=float, dest='fast', help='when a state change is about to occur, wait N seconds between each healthcheck')
    g.add_argument('--timeout', '-t', metavar='N', default=5, type=int, help='wait N seconds for the check command to execute')
    g.add_argument('--rise', metavar='N', default=3, type=int, help='check N times before considering the service up')
    g.add_argument('--fall', metavar='N', default=3, type=int, help='check N times before considering the service down')
    g.add_argument('--disable', metavar='FILE', type=str, help='if FILE exists, the service is considered disabled')
    g.add_argument('--command', '--cmd', '-c', metavar='CMD', type=str, help='command to use for healthcheck')

    g = parser.add_argument_group('advertising options')
    g.add_argument('--next-hop', '-N', metavar='IP', type=ip_address, help='self IP address to use as next hop')
    g.add_argument('--ip', metavar='IP', type=ip_network, dest='ips', action='append', help='advertise this IP address or network (CIDR notation)')
    g.add_argument('--ip-ifname', metavar='IP%IFNAME', dest='ip_ifnames', action='append', help='bind this IP address or network (CIDR) to the given physical or logical interface (i.e. 192.165.14.1%%eth0)')
    g.add_argument('--local-preference', metavar='P', type=int, default=-1, help='advertise with local preference P')
    g.add_argument('--deaggregate-networks', dest='deaggregate_networks', action='store_true', help='Deaggregate Networks specified in --ip')
    g.add_argument('--no-ip-setup', action='store_false', dest='ip_setup', help="don't setup missing IP addresses")
    g.add_argument('--dynamic-ip-setup', default=False, action='store_true', dest='ip_dynamic', help='delete setup ips on state down and ' 'disabled, then restore them when up')
    g.add_argument('--label', default=None, help='use the provided label to match setup ip addresses')
    g.add_argument('--label-exact-match', default=False, action='store_true', help='use the provided label to exactly match setup ip addresses, not a prefix match')
    g.add_argument('--start-ip', metavar='N', type=int, default=0, help='index of the first IP in the list of IP addresses')
    g.add_argument('--up-metric', metavar='M', type=int, default=100, help='first IP get the metric M when the service is up')
    g.add_argument('--down-metric', metavar='M', type=int, default=1000, help='first IP get the metric M when the service is down')
    g.add_argument('--disabled-metric', metavar='M', type=int, default=500, help='first IP get the metric M when the service is disabled')
    g.add_argument('--increase', metavar='M', type=int, default=1, help='for each additional IP address, increase metric value by M')
    g.add_argument('--community', metavar='COMMUNITY', type=str, default=None, help='announce IPs with the supplied community')
    g.add_argument('--extended-community', metavar='EXTENDEDCOMMUNITY', type=str, default=None, help='announce IPs with the supplied extended community')
    g.add_argument('--large-community', metavar='LARGECOMMUNITY', type=str, default=None, help='announce IPs with the supplied large community')
    g.add_argument('--disabled-community', metavar='DISABLEDCOMMUNITY', type=str, default=None, help='announce IPs with the supplied community when disabled')
    g.add_argument('--as-path', metavar='ASPATH', type=str, default=None, help='announce IPs with the supplied as-path')
    g.add_argument('--up-as-path', metavar='ASPATH', type=str, default=None, help='announce IPs with the supplied as-path when the service is up')
    g.add_argument('--down-as-path', metavar='ASPATH', type=str, default=None, help='announce IPs with the supplied as-path when the service is down')
    g.add_argument('--disabled-as-path', metavar='ASPATH', type=str, default=None, help='announce IPs with the supplied as-path when the service is disabled')
    g.add_argument('--withdraw-on-down', action='store_true', help='Instead of increasing the metric on health failure, withdraw the route')
    g.add_argument('--path-id', metavar='PATHID', type=int, default=None, help='path ID to advertise for the route')
    g.add_argument('--neighbor', metavar='NEIGHBOR', type=neighbor_address, dest='neighbors', action='append', help='advertise the route to the selected neighbors (* for all)')
    g.add_argument('--debounce', action='store_true', dest='debounce', help='announce only on state changes, instead of every iteration')

    g = parser.add_argument_group('reporting')
    g.add_argument('--execute', metavar='CMD', type=str, action='append', help='execute CMD on state change')
    g.add_argument('--up-execute', metavar='CMD', type=str, action='append', help='execute CMD when the service becomes available')
    g.add_argument('--down-execute', metavar='CMD', type=str, action='append', help='execute CMD when the service becomes unavailable')
    g.add_argument('--disabled-execute', metavar='CMD', type=str, action='append', help='execute CMD when the service is disabled')
    # fmt: on


def parse():
    """Parse arguments"""

    def parse_ip_ifnames(ip_ifnames, ips):
        """Parse ip interfaces and return a dict of ip:ifname"""
        keyval = {}
        for val in ip_ifnames or []:
            ip_ifname = val.split(r'%')
            if len(ip_ifname) != IP_IFNAME_PARTS:
                raise ValueError(f"Expected IP to IFNAME parameter: <ip_address>%<ifname>, got '{val}'")
            # Is the ip address valid?
            try:
                ip = ip_network(ip_ifname[0])
            except ValueError as e:
                raise e
            # Is the ip address defined
            if ip not in ips:
                raise ValueError(f"No 'ip' parameter has been defined for the ip_ifname pair '{val}'")
            # Is the interface name valid?
            if not re.match(rf'^[a-zA-Z0-9._:-]{{1,{IFNAME_MAX_LENGTH}}}$', ip_ifname[1]):
                raise ValueError(f"Expected NIC interface name but got '{ip_ifname[1]}'")
            keyval[ip] = ip_ifname[1]
        return keyval

    formatter = argparse.RawDescriptionHelpFormatter
    parser = argparse.ArgumentParser(description=sys.modules[__name__].__doc__, formatter_class=formatter)
    setargs(parser)

    options = parser.parse_args()
    if options.config is not None:
        # A configuration file has been provided. Read each line and
        # build an equivalent command line.
        args = sum(
            [
                f'--{line.strip()}'.split('=', 1)
                for line in options.config.readlines()
                if not line.strip().startswith('#') and line.strip()
            ],
            [],
        )
        args = [x.strip() for x in args]
        args.extend(sys.argv[1:])
        options = parser.parse_args(args)
    options.ip_ifnames = parse_ip_ifnames(options.ip_ifnames, options.ips)
    return options


def setup_logging(debug, silent, name, syslog_facility, syslog):
    """Setup logger"""

    def syslog_address():
        """Return a sensible syslog address"""
        if sys.platform == 'darwin':
            return '/var/run/syslog'
        if sys.platform.startswith('freebsd'):
            return '/var/run/log'
        if sys.platform.startswith('netbsd'):
            return '/var/run/log'
        if sys.platform.startswith('linux'):
            return '/dev/log'
        raise OSError('Unable to guess syslog address for your platform, try to disable syslog')

    logger.setLevel(debug and logging.DEBUG or logging.INFO)
    enable_syslog = syslog and not debug
    # To syslog
    if enable_syslog:
        facility = getattr(logging.handlers.SysLogHandler, f'LOG_{syslog_facility.upper()}')
        sh = logging.handlers.SysLogHandler(address=str(syslog_address()), facility=facility)
        if name:
            healthcheck_name = f'healthcheck-{name}'
        else:
            healthcheck_name = 'healthcheck'
        sh.setFormatter(logging.Formatter(f'{healthcheck_name}[{os.getpid()}]: %(message)s'))
        logger.addHandler(sh)
    # To console
    if not silent:
        ch = logging.StreamHandler()
        ch.setFormatter(logging.Formatter('%(levelname)s[%(name)s] %(message)s'))
        logger.addHandler(ch)


def system_ips(ip_ifnames, label, label_only, label_exact_match):
    """Retrieve IP addresses for loopback and ip-ifname given interfaces"""
    logger.debug('Retrieve IP addresses for loopback and ip-ifname interfaces')
    addresses = []
    ifnames = set(ip_ifnames.values()) | {'lo'} if ip_ifnames else {'lo'}
    output = []

    if sys.platform.startswith('linux'):
        # Use "ip" (ifconfig is not able to see all addresses)
        ipre = re.compile(r'^(?P<index>\d+):\s+(?P<name>\S+)\s+inet6?\s+' r'(?P<ip>[\da-f.:]+)/(?P<mask>\d+)\s+.*')
        labelre = re.compile(r'.*\s+(?:' + '|'.join(ifnames) + r'):(?P<label>[^\\\s]+).*')
        for ifname in ifnames:
            cmd = subprocess.Popen(
                f'/sbin/ip -o address show dev {ifname}'.split(), shell=False, stdout=subprocess.PIPE
            )
            output += [line for line in cmd.stdout]
    else:
        # Try with ifconfig
        ipre = re.compile(
            r'^inet6?\s+(alias\s+)?(?P<ip>[\da-f.:]+)\s+'
            r'(?:netmask 0x(?P<netmask>[0-9a-f]+)|'
            r'prefixlen (?P<mask>\d+)).*',
        )
        labelre = re.compile(r'')
        for ifname in ifnames:
            cmd = subprocess.Popen(f'/sbin/ifconfig {ifname}'.split(), shell=False, stdout=subprocess.PIPE)
            output += [line for line in cmd.stdout]
    for line in output or []:
        line = line.decode('ascii', 'ignore').strip()
        mo = ipre.match(line)
        if not mo:
            continue
        if mo.group('mask'):
            mask = int(mo.group('mask'))
        else:
            mask = bin(int(mo.group('netmask'), 16)).count('1')
        try:
            ip = ip_network(f'{mo.group("ip")}/{mask}')
        except ValueError:
            continue
        if not ip.is_loopback:
            if label:
                lmo = labelre.match(line)
                if not lmo:
                    continue
                if label_exact_match:
                    if lmo.groupdict().get('label', '') == label:
                        addresses.append(ip)
                elif lmo.groupdict().get('label', '').startswith(label):
                    addresses.append(ip)
            elif not label_only or label is None:
                addresses.append(ip)

    logger.debug(f'System addresses ({ifnames}) detected: {addresses}')
    return addresses


def ip_ifname(ip, ip_ifnames):
    ifname = ip_ifnames.get(ip)
    if not ifname:
        ifname = 'lo0'
        if sys.platform.startswith('linux'):
            ifname = 'lo'
    return ifname


def setup_ips(ips, ip_ifnames, label, label_exact_match, sudo=False):
    """Setup missing IP on loopback or physical interface"""

    existing = set(system_ips(ip_ifnames, label, False, label_exact_match))
    toadd = set([ip_network(ip) for net in ips for ip in net]) - existing
    for ip in toadd:
        ifname = ip_ifname(ip, ip_ifnames)
        logger.debug('Setup %s IP address %s', ifname, ip)
        with open(os.devnull, 'w') as fnull:
            cmd = ['ip', 'address', 'add', str(ip), 'dev', ifname]
            if sudo:
                cmd.insert(0, 'sudo')
            if label:
                cmd += ['label', f'{ifname}:{label}']
            try:
                subprocess.check_call(cmd, stdout=fnull, stderr=fnull)
            except subprocess.CalledProcessError as e:
                # the IP address is already setup, ignoring
                if cmd[0] == 'ip' and cmd[2] == 'add' and e.returncode == IP_CMD_ADD_ERROR_CODE:
                    continue
                raise e


def remove_ips(ips, ip_ifnames, label, label_exact_match, sudo=False):
    """Remove added IP on loopback or physical interface"""
    existing = set(system_ips(ip_ifnames, label, True, label_exact_match))

    # Get intersection of IPs (ips setup, and IPs configured by ExaBGP)
    toremove = set([ip_network(ip) for net in ips for ip in net]) & existing
    for ip in toremove:
        ifname = ip_ifname(ip, ip_ifnames)
        logger.debug('Remove %s IP address %s', ifname, ip)
        with open(os.devnull, 'w') as fnull:
            cmd = ['ip', 'address', 'delete', str(ip), 'dev', ifname]
            if sudo:
                cmd.insert(0, 'sudo')
            if label:
                cmd += ['label', f'{ifname}:{label}']
            try:
                subprocess.check_call(cmd, stdout=fnull, stderr=fnull)
            except subprocess.CalledProcessError:
                logger.warning(
                    'Unable to remove %s IP address %s - is \
                    healthcheck running as root?',
                    ifname,
                    str(ip),
                )


def drop_privileges(user, group):
    """Drop privileges to specified user and group"""
    if group is not None:
        import grp

        gid = grp.getgrnam(group).gr_gid
        logger.debug(f'Dropping privileges to group {group}/{gid}')
        try:
            os.setresgid(gid, gid, gid)
        except AttributeError:
            os.setregid(gid, gid)
    if user is not None:
        import pwd

        uid = pwd.getpwnam(user).pw_uid
        logger.debug(f'Dropping privileges to user {user}/{uid}')
        try:
            os.setresuid(uid, uid, uid)
        except AttributeError:
            os.setreuid(uid, uid)


def check(cmd, timeout):
    """Check the return code of the given command.

    :param cmd: command to execute. If :keyword:`None`, no command is executed.
    :param timeout: how much time we should wait for command completion.
    :return: :keyword:`True` if the command was successful or
             :keyword:`False` if not or if the timeout was triggered.
    """
    if cmd is None:
        return True

    class Alarm(Exception):
        """Exception to signal an alarm condition."""

    def alarm_handler(number, frame):  # pylint: disable=W0613
        """Handle SIGALRM signal."""
        raise Alarm

    logger.debug('Checking command %s', repr(cmd))
    p = subprocess.Popen(cmd, shell=True, stdout=subprocess.PIPE, stderr=subprocess.STDOUT, preexec_fn=os.setpgrp)
    if timeout:
        signal.signal(signal.SIGALRM, alarm_handler)
        signal.alarm(timeout)
    try:
        stdout = None
        stdout, _ = p.communicate()
        if timeout:
            signal.alarm(0)
        if p.returncode != 0:
            logger.warning('Check command was unsuccessful: %s', p.returncode)
            if stdout.strip():
                logger.info('Output of check command: %s', stdout)
            return False
        logger.debug('Command was executed successfully %s %s', p.returncode, stdout)
        return True
    except Alarm:
        logger.warning('Timeout (%s) while running check command %s', timeout, cmd)
        os.killpg(p.pid, signal.SIGKILL)
        return False


def loop(options):
    """Main loop."""
    states = enum(
        'INIT',  # Initial state
        'DISABLED',  # Disabled state
        'RISING',  # Checks are currently succeeding.
        'FALLING',  # Checks are currently failing.
        'UP',  # Service is considered as up.
        'DOWN',  # Service is considered as down.
        'EXIT',  # Exit state
        'END',  # End state, exiting but without removing setup ips and/or announced routes
    )

    def exabgp(target):
        """Communicate new state to ExaBGP"""
        if target not in (states.UP, states.DOWN, states.DISABLED, states.EXIT, states.END):
            return
        if target in (states.END,):
            return
        # if ips was deleted with dyn ip, re-setup them
        if target == states.UP and options.ip_dynamic:
            logger.info('service up, restoring loopback and ip-ifname ips')
            setup_ips(options.ips, options.ip_ifnames, options.label, options.label_exact_match, options.sudo)

        logger.info(f'send announces for {target} state to ExaBGP')
        metric = vars(options).get(f'{str(target).lower()}_metric', 0)
        as_path = vars(options).get(f'{str(target).lower()}_as_path', None)
        if as_path is None:
            as_path = options.as_path
        if options.neighbors and not any(n == '*' for n in options.neighbors):
            prefix = ', '.join(f'neighbor {neighbor}' for neighbor in options.neighbors)
        else:
            prefix = 'neighbor *'
        for ip in options.ips:
            if options.withdraw_on_down or target is states.EXIT:
                action = 'announce' if target is states.UP else 'withdraw'
            else:
                action = 'announce'
            command = f'{prefix} {action}'
            announce = f'route {ip} next-hop {options.next_hop or "self"}'

            if action == 'announce':
                announce = f'{announce} med {metric}'
                if options.local_preference >= 0:
                    announce = f'{announce} local-preference {options.local_preference}'
                if options.community or options.disabled_community:
                    community = options.community
                    if target in (states.DOWN, states.DISABLED):
                        if options.disabled_community:
                            community = options.disabled_community
                    if community:
                        announce = f'{announce} community [ {community} ]'
                if options.extended_community:
                    announce = f'{announce} extended-community [ {options.extended_community} ]'
                if options.large_community:
                    announce = f'{announce} large-community [ {options.large_community} ]'
                if as_path:
                    announce = f'{announce} as-path [ {as_path} ]'

            # append path ID if required
            if options.path_id:
                announce = f'{announce} path-information {options.path_id}'

            metric += options.increase

            # Send and flush command
            logger.debug(f'exabgp: {command} {announce}')
            sys.stdout.write(f'{command} {announce}\n')
            sys.stdout.flush()

            # Wait for confirmation from ExaBGP if expected
            if options.no_ack:
                continue
            # if the program is not ran manually, do not read the input
            if hasattr(sys.stdout, 'isatty') and sys.stdout.isatty():
                continue
            sys.stdin.readline()

        # dynamic ip management. When the service fail, remove the setup ips
        if target in (states.EXIT,) and (options.ip_dynamic or options.ip_setup):
            logger.info('exiting, deleting setup ips')
            remove_ips(options.ips, options.ip_ifnames, options.label, options.label_exact_match, options.sudo)
        # dynamic ip management. When the service fail, remove the setup ips
        if target in (states.DOWN, states.DISABLED) and options.ip_dynamic:
            logger.info('service down, deleting setup ips')
            remove_ips(options.ips, options.ip_ifnames, options.label, options.label_exact_match, options.sudo)

    def trigger(target):
        """Trigger a state change and execute the appropriate commands"""
        # Shortcut for RISING->UP and FALLING->UP
        if target == states.RISING and options.rise <= 1:
            target = states.UP
        elif target == states.FALLING and options.fall <= 1:
            target = states.DOWN

        # Log and execute commands
        logger.debug(f'Transition to {target}')
        cmds = []
        cmds.extend(vars(options).get(f'{str(target).lower()}_execute', []) or [])
        cmds.extend(vars(options).get('execute', []) or [])
        for cmd in cmds:
            logger.debug(f'Transition to {target}, execute `{cmd}`')
            env = os.environ.copy()
            env.update({'STATE': str(target)})
            with open(os.devnull, 'w') as fnull:
                subprocess.call(cmd, shell=True, stdout=fnull, stderr=fnull, env=env)

        return target

    def one(checks, state):
        """Execute one loop iteration."""
        disabled = options.disable is not None and os.path.exists(options.disable)
        successful = disabled or check(options.command, options.timeout)
        state_before_iteration = state
        # FSM
        if state != states.DISABLED and disabled:
            state = trigger(states.DISABLED)
        elif state == states.INIT:
            if successful and options.rise <= 1:
                state = trigger(states.UP)
            elif successful:
                state = trigger(states.RISING)
                checks = 1
            else:
                state = trigger(states.FALLING)
                checks = 1
        elif state == states.DISABLED:
            if not disabled:
                state = trigger(states.INIT)
        elif state == states.RISING:
            if successful:
                checks += 1
                if checks >= options.rise:
                    state = trigger(states.UP)
            else:
                state = trigger(states.FALLING)
                checks = 1
        elif state == states.FALLING:
            if not successful:
                checks += 1
                if checks >= options.fall:
                    state = trigger(states.DOWN)
            else:
                state = trigger(states.RISING)
                checks = 1
        elif state == states.UP:
            if not successful:
                state = trigger(states.FALLING)
                checks = 1
        elif state == states.DOWN:
            if successful:
                state = trigger(states.RISING)
                checks = 1
        else:
            raise ValueError(f'Unhandled state: {state}')

        # Send announces. We announce them on a regular basis (unless --debounce flag is set),
        # in case we lose connection with a peer and the adj-rib-out is disabled.
        if not options.debounce or state != state_before_iteration:
            exabgp(state)

        return checks, state

    checks = 0
    state = states.INIT

    # Do cleanups on SIGTERM
    def sigterm_handler(signum, frame):  # pylint: disable=W0612,W0613
        exabgp(states.EXIT)
        sys.exit(0)

    signal.signal(signal.SIGTERM, sigterm_handler)

    while True:
        checks, state = one(checks, state)

        try:
            # How much we should sleep?
            if state in (states.FALLING, states.RISING):
                time.sleep(options.fast)
            elif options.interval == 0:
                logger.info('interval set to zero, exiting after the announcement')
                exabgp(states.END)
                break
            else:
                time.sleep(options.interval)
        except KeyboardInterrupt:
            exabgp(states.EXIT)
            break


def cmdline(cmdarg):
    sys.argv = [f'{sys.argv[0]} {sys.argv[1]}'] + sys.argv[2:]
    main()


def main():
    """Entry point."""
    options = parse()
    setup_logging(options.debug, options.silent, options.name, options.syslog_facility, not options.no_syslog)
    if options.pid:
        options.pid.write(f'{os.getpid()}\n')
        options.pid.close()
    try:
        # Setup IP to use
        options.ips = options.ips or system_ips(None, options.label, False, options.label_exact_match)
        if not options.ips:
            logger.error('No IP found')
            sys.exit(1)
        if options.ip_setup:
            setup_ips(options.ips, options.ip_ifnames, options.label, options.label_exact_match, options.sudo)
        drop_privileges(options.user, options.group)

        # Parse defined networks into a list of IPs for advertisement
        if options.deaggregate_networks:
            options.ips = [ip_network(ip) for net in options.ips for ip in net]

        options.ips = collections.deque(options.ips)
        options.ips.rotate(-options.start_ip)
        options.ips = list(options.ips)
        # Main loop
        loop(options)
    except Exception as e:  # pylint: disable=W0703
        logger.exception(f'Uncaught exception: {e}')
        sys.exit(1)


if __name__ == '__main__':
    main()
