#!/usr/bin/env python
# Copyright (c) 2016 Cisco and/or its affiliates.
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at:
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

"""Router solicitation check script."""

import sys
import ipaddress

from scapy.layers.l2 import Ether
from scapy.layers.inet6 import IPv6, ICMPv6ND_RA, ICMPv6ND_RS, ICMPv6ND_NS

from resources.libraries.python.PacketVerifier import RxQueue, TxQueue
from resources.libraries.python.TrafficScriptArg import TrafficScriptArg


def mac_to_ipv6_linklocal(mac):
    """Transfer MAC address into specific link-local IPv6 address.

    :param mac: MAC address to be transferred.
    :type mac: str
    :return: IPv6 link-local address.
    :rtype: str
    """
    # Remove the most common delimiters: dots, dashes, etc.
    mac_value = int(mac.translate(None, ' .:-'), 16)

    # Split out the bytes that slot into the IPv6 address
    # XOR the most significant byte with 0x02, inverting the
    # Universal / Local bit
    high2 = mac_value >> 32 & 0xffff ^ 0x0200
    high1 = mac_value >> 24 & 0xff
    low1 = mac_value >> 16 & 0xff
    low2 = mac_value & 0xffff

    return 'fe80::{:04x}:{:02x}ff:fe{:02x}:{:04x}'.format(
        high2, high1, low1, low2)


def main():
    """Send Router Solicitation packet, check if the received response\
     is a Router Advertisement packet and verify."""

    args = TrafficScriptArg(
        ['src_mac', 'dst_mac', 'src_ip']
    )

    router_mac = args.get_arg('dst_mac')
    src_mac = args.get_arg('src_mac')
    src_ip = args.get_arg('src_ip')
    if not src_ip:
        src_ip = mac_to_ipv6_linklocal(src_mac)
    tx_if = args.get_arg('tx_if')

    txq = TxQueue(tx_if)
    rxq = RxQueue(tx_if)

    pkt_raw = (Ether(src=src_mac, dst='33:33:00:00:00:02') /
               IPv6(src=src_ip, dst='ff02::2') /
               ICMPv6ND_RS())

    sent_packets = [pkt_raw]
    txq.send(pkt_raw)

    while True:
        ether = rxq.recv(2, sent_packets)
        if ether is None:
            raise RuntimeError('ICMP echo Rx timeout')

        if ether.haslayer(ICMPv6ND_NS):
            # read another packet in the queue if the current one is ICMPv6ND_NS
            continue
        else:
            # otherwise process the current packet
            break

    # Check whether received packet contains layer RA and check other values
    if ether.src != router_mac:
        raise RuntimeError('Packet source MAC ({0}) does not match router MAC '
                           '({1}).'.format(ether.src, router_mac))
    if ether.dst != src_mac:
        raise RuntimeError('Packet destination MAC ({0}) does not match RS '
                           'source MAC ({1}).'.format(ether.dst, src_mac))

    if not ether.haslayer(ICMPv6ND_RA):
        raise RuntimeError('Not an RA packet received {0}'.
                           format(ether.__repr__()))

    src_address = ipaddress.IPv6Address(unicode(ether['IPv6'].src))
    dst_address = ipaddress.IPv6Address(unicode(ether['IPv6'].dst))
    router_link_local = ipaddress.IPv6Address(unicode(
        mac_to_ipv6_linklocal(router_mac)))
    rs_src_address = ipaddress.IPv6Address(unicode(src_ip))

    if src_address != router_link_local:
        raise RuntimeError('Packet source address ({0}) does not match link '
                           'local address({1})'.
                           format(src_address, router_link_local))

    if dst_address != rs_src_address:
        raise RuntimeError('Packet destination address ({0}) does not match '
                           'RS source address ({1}).'.
                           format(dst_address, rs_src_address))

    if ether['IPv6'].hlim != 255:
        raise RuntimeError('Hop limit not correct: {0}!=255'.
                           format(ether['IPv6'].hlim))

    ra_code = ether[ICMPv6ND_RA].code
    if ra_code != 0:
        raise RuntimeError('ICMP code: {0} not correct. '.format(ra_code))

    sys.exit(0)


if __name__ == "__main__":
    main()