l2.py

# This file is part of Scapy
# See http://www.secdev.org/projects/scapy for more information
# Copyright (C) Philippe Biondi <phil@secdev.org>
# This program is published under a GPLv2 license

"""
Classes and functions for layer 2 protocols.
"""

from __future__ import absolute_import
from __future__ import print_function
import os
import struct
import time
import socket

from scapy.ansmachine import AnsweringMachine
from scapy.arch import get_if_addr, get_if_hwaddr
from scapy.base_classes import Gen, Net
from scapy.compat import chb, orb
from scapy.config import conf
from scapy import consts
from scapy.data import ARPHDR_ETHER, ARPHDR_LOOPBACK, ARPHDR_METRICOM, \
    DLT_ETHERNET_MPACKET, DLT_LINUX_IRDA, DLT_LINUX_SLL, DLT_LOOP, \
    DLT_NULL, ETHER_ANY, ETHER_BROADCAST, ETHER_TYPES, ETH_P_ARP, \
    ETH_P_MACSEC
from scapy.error import warning, ScapyNoDstMacException
from scapy.fields import BCDFloatField, BitField, ByteField, \
    ConditionalField, FieldLenField, FCSField, \
    IntEnumField, IntField, IP6Field, IPField, \
    LenField, MACField, MultipleTypeField, \
    ShortEnumField, ShortField, SourceIP6Field, SourceIPField, \
    StrFixedLenField, StrLenField, X3BytesField, XByteField, XIntField, \
    XShortEnumField, XShortField
from scapy.modules.six import viewitems
from scapy.packet import bind_layers, Packet
from scapy.plist import PacketList, SndRcvList
from scapy.sendrecv import sendp, srp, srp1
from scapy.utils import checksum, hexdump, hexstr, inet_ntoa, inet_aton, \
    mac2str, valid_mac, valid_net, valid_net6
if conf.route is None:
    # unused import, only to initialize conf.route
    import scapy.route  # noqa: F401


#################
#  Tools        #
#################


class Neighbor:
    def __init__(self):
        self.resolvers = {}

    def register_l3(self, l2, l3, resolve_method):
        self.resolvers[l2, l3] = resolve_method

    def resolve(self, l2inst, l3inst):
        k = l2inst.__class__, l3inst.__class__
        if k in self.resolvers:
            return self.resolvers[k](l2inst, l3inst)

    def __repr__(self):
        return "\n".join("%-15s -> %-15s" % (l2.__name__, l3.__name__) for l2, l3 in self.resolvers)  # noqa: E501


conf.neighbor = Neighbor()

conf.netcache.new_cache("arp_cache", 120)  # cache entries expire after 120s


@conf.commands.register
def getmacbyip(ip, chainCC=0):
    """Return MAC address corresponding to a given IP address"""
    if isinstance(ip, Net):
        ip = next(iter(ip))
    ip = inet_ntoa(inet_aton(ip or "0.0.0.0"))
    tmp = [orb(e) for e in inet_aton(ip)]
    if (tmp[0] & 0xf0) == 0xe0:  # mcast @
        return "01:00:5e:%.2x:%.2x:%.2x" % (tmp[1] & 0x7f, tmp[2], tmp[3])
    iff, _, gw = conf.route.route(ip)
    if ((iff == consts.LOOPBACK_INTERFACE) or (ip == conf.route.get_if_bcast(iff))):  # noqa: E501
        return "ff:ff:ff:ff:ff:ff"
    if gw != "0.0.0.0":
        ip = gw

    mac = conf.netcache.arp_cache.get(ip)
    if mac:
        return mac

    try:
        res = srp1(Ether(dst=ETHER_BROADCAST) / ARP(op="who-has", pdst=ip),
                   type=ETH_P_ARP,
                   iface=iff,
                   timeout=2,
                   verbose=0,
                   chainCC=chainCC,
                   nofilter=1)
    except Exception as ex:
        warning("getmacbyip failed on %s" % ex)
        return None
    if res is not None:
        mac = res.payload.hwsrc
        conf.netcache.arp_cache[ip] = mac
        return mac
    return None


# Fields

class DestMACField(MACField):
    def __init__(self, name):
        MACField.__init__(self, name, None)

    def i2h(self, pkt, x):
        if x is None:
            try:
                x = conf.neighbor.resolve(pkt, pkt.payload)
            except socket.error:
                pass
            if x is None:
                if conf.raise_no_dst_mac:
                    raise ScapyNoDstMacException()
                else:
                    x = "ff:ff:ff:ff:ff:ff"
                    warning("Mac address to reach destination not found. Using broadcast.")  # noqa: E501
        return MACField.i2h(self, pkt, x)

    def i2m(self, pkt, x):
        return MACField.i2m(self, pkt, self.i2h(pkt, x))


class SourceMACField(MACField):
    __slots__ = ["getif"]

    def __init__(self, name, getif=None):
        MACField.__init__(self, name, None)
        self.getif = (lambda pkt: pkt.route()[0]) if getif is None else getif

    def i2h(self, pkt, x):
        if x is None:
            iff = self.getif(pkt)
            if iff is None:
                iff = conf.iface
            if iff:
                try:
                    x = get_if_hwaddr(iff)
                except Exception as e:
                    warning("Could not get the source MAC: %s" % e)
            if x is None:
                x = "00:00:00:00:00:00"
        return MACField.i2h(self, pkt, x)

    def i2m(self, pkt, x):
        return MACField.i2m(self, pkt, self.i2h(pkt, x))


# Layers

ETHER_TYPES['802_AD'] = 0x88a8
ETHER_TYPES['802_1AE'] = ETH_P_MACSEC


class Ether(Packet):
    name = "Ethernet"
    fields_desc = [DestMACField("dst"),
                   SourceMACField("src"),
                   XShortEnumField("type", 0x9000, ETHER_TYPES)]
    __slots__ = ["_defrag_pos"]

    def hashret(self):
        return struct.pack("H", self.type) + self.payload.hashret()

    def answers(self, other):
        if isinstance(other, Ether):
            if self.type == other.type:
                return self.payload.answers(other.payload)
        return 0

    def mysummary(self):
        return self.sprintf("%src% > %dst% (%type%)")

    @classmethod
    def dispatch_hook(cls, _pkt=None, *args, **kargs):
        if _pkt and len(_pkt) >= 14:
            if struct.unpack("!H", _pkt[12:14])[0] <= 1500:
                return Dot3
        return cls


class Dot3(Packet):
    name = "802.3"
    fields_desc = [DestMACField("dst"),
                   SourceMACField("src"),
                   LenField("len", None, "H")]

    def extract_padding(self, s):
        tmp_len = self.len
        return s[:tmp_len], s[tmp_len:]

    def answers(self, other):
        if isinstance(other, Dot3):
            return self.payload.answers(other.payload)
        return 0

    def mysummary(self):
        return "802.3 %s > %s" % (self.src, self.dst)

    @classmethod
    def dispatch_hook(cls, _pkt=None, *args, **kargs):
        if _pkt and len(_pkt) >= 14:
            if struct.unpack("!H", _pkt[12:14])[0] > 1500:
                return Ether
        return cls


class LLC(Packet):
    name = "LLC"
    fields_desc = [XByteField("dsap", 0x00),
                   XByteField("ssap", 0x00),
                   ByteField("ctrl", 0)]


def l2_register_l3(l2, l3):
    return conf.neighbor.resolve(l2, l3.payload)


conf.neighbor.register_l3(Ether, LLC, l2_register_l3)
conf.neighbor.register_l3(Dot3, LLC, l2_register_l3)


class CookedLinux(Packet):
    # Documentation: http://www.tcpdump.org/linktypes/LINKTYPE_LINUX_SLL.html
    name = "cooked linux"
    # from wireshark's database
    fields_desc = [ShortEnumField("pkttype", 0, {0: "unicast",
                                                 1: "broadcast",
                                                 2: "multicast",
                                                 3: "unicast-to-another-host",
                                                 4: "sent-by-us"}),
                   XShortField("lladdrtype", 512),
                   ShortField("lladdrlen", 0),
                   StrFixedLenField("src", "", 8),
                   XShortEnumField("proto", 0x800, ETHER_TYPES)]


class MPacketPreamble(Packet):
    # IEEE 802.3br Figure 99-3
    name = "MPacket Preamble"
    fields_desc = [StrFixedLenField("preamble", b"", length=8),
                   FCSField("fcs", 0, fmt="!I")]


class SNAP(Packet):
    name = "SNAP"
    fields_desc = [X3BytesField("OUI", 0x000000),
                   XShortEnumField("code", 0x000, ETHER_TYPES)]


conf.neighbor.register_l3(Dot3, SNAP, l2_register_l3)


class Dot1Q(Packet):
    name = "802.1Q"
    aliastypes = [Ether]
    fields_desc = [BitField("prio", 0, 3),
                   BitField("id", 0, 1),
                   BitField("vlan", 1, 12),
                   XShortEnumField("type", 0x0000, ETHER_TYPES)]

    def answers(self, other):
        if isinstance(other, Dot1Q):
            if ((self.type == other.type) and
                    (self.vlan == other.vlan)):
                return self.payload.answers(other.payload)
        else:
            return self.payload.answers(other)
        return 0

    def default_payload_class(self, pay):
        if self.type <= 1500:
            return LLC
        return conf.raw_layer

    def extract_padding(self, s):
        if self.type <= 1500:
            return s[:self.type], s[self.type:]
        return s, None

    def mysummary(self):
        if isinstance(self.underlayer, Ether):
            return self.underlayer.sprintf("802.1q %Ether.src% > %Ether.dst% (%Dot1Q.type%) vlan %Dot1Q.vlan%")  # noqa: E501
        else:
            return self.sprintf("802.1q (%Dot1Q.type%) vlan %Dot1Q.vlan%")


conf.neighbor.register_l3(Ether, Dot1Q, l2_register_l3)


class STP(Packet):
    name = "Spanning Tree Protocol"
    fields_desc = [ShortField("proto", 0),
                   ByteField("version", 0),
                   ByteField("bpdutype", 0),
                   ByteField("bpduflags", 0),
                   ShortField("rootid", 0),
                   MACField("rootmac", ETHER_ANY),
                   IntField("pathcost", 0),
                   ShortField("bridgeid", 0),
                   MACField("bridgemac", ETHER_ANY),
                   ShortField("portid", 0),
                   BCDFloatField("age", 1),
                   BCDFloatField("maxage", 20),
                   BCDFloatField("hellotime", 2),
                   BCDFloatField("fwddelay", 15)]


class ARP(Packet):
    name = "ARP"
    fields_desc = [
        XShortField("hwtype", 0x0001),
        XShortEnumField("ptype", 0x0800, ETHER_TYPES),
        FieldLenField("hwlen", None, fmt="B", length_of="hwsrc"),
        FieldLenField("plen", None, fmt="B", length_of="psrc"),
        ShortEnumField("op", 1, {
            "who-has": 1,
            "is-at": 2,
            "RARP-req": 3,
            "RARP-rep": 4,
            "Dyn-RARP-req": 5,
            "Dyn-RAR-rep": 6,
            "Dyn-RARP-err": 7,
            "InARP-req": 8,
            "InARP-rep": 9
        }),
        MultipleTypeField(
            [
                (SourceMACField("hwsrc"),
                 (lambda pkt: pkt.hwtype == 1 and pkt.hwlen == 6,
                  lambda pkt, val: pkt.hwtype == 1 and (
                      pkt.hwlen == 6 or (pkt.hwlen is None and
                                         (val is None or len(val) == 6 or
                                          valid_mac(val)))
                  ))),
            ],
            StrFixedLenField("hwsrc", None, length_from=lambda pkt: pkt.hwlen),
        ),
        MultipleTypeField(
            [
                (SourceIPField("psrc", "pdst"),
                 (lambda pkt: pkt.ptype == 0x0800 and pkt.plen == 4,
                  lambda pkt, val: pkt.ptype == 0x0800 and (
                      pkt.plen == 4 or (pkt.plen is None and
                                        (val is None or valid_net(val)))
                  ))),
                (SourceIP6Field("psrc", "pdst"),
                 (lambda pkt: pkt.ptype == 0x86dd and pkt.plen == 16,
                  lambda pkt, val: pkt.ptype == 0x86dd and (
                      pkt.plen == 16 or (pkt.plen is None and
                                         (val is None or valid_net6(val)))
                  ))),
            ],
            StrFixedLenField("psrc", None, length_from=lambda pkt: pkt.plen),
        ),
        MultipleTypeField(
            [
                (MACField("hwdst", ETHER_ANY),
                 (lambda pkt: pkt.hwtype == 1 and pkt.hwlen == 6,
                  lambda pkt, val: pkt.hwtype == 1 and (
                      pkt.hwlen == 6 or (pkt.hwlen is None and
                                         (val is None or len(val) == 6 or
                                          valid_mac(val)))
                  ))),
            ],
            StrFixedLenField("hwdst", None, length_from=lambda pkt: pkt.hwlen),
        ),
        MultipleTypeField(
            [
                (IPField("pdst", "0.0.0.0"),
                 (lambda pkt: pkt.ptype == 0x0800 and pkt.plen == 4,
                  lambda pkt, val: pkt.ptype == 0x0800 and (
                      pkt.plen == 4 or (pkt.plen is None and
                                        (val is None or valid_net(val)))
                  ))),
                (IP6Field("pdst", "::"),
                 (lambda pkt: pkt.ptype == 0x86dd and pkt.plen == 16,
                  lambda pkt, val: pkt.ptype == 0x86dd and (
                      pkt.plen == 16 or (pkt.plen is None and
                                         (val is None or valid_net6(val)))
                  ))),
            ],
            StrFixedLenField("pdst", None, length_from=lambda pkt: pkt.plen),
        ),
    ]

    def hashret(self):
        return struct.pack(">HHH", self.hwtype, self.ptype,
                           ((self.op + 1) // 2)) + self.payload.hashret()

    def answers(self, other):
        if not isinstance(other, ARP):
            return False
        if self.op != other.op + 1:
            return False
        # We use a loose comparison on psrc vs pdst to catch answers
        # with ARP leaks
        self_psrc = self.get_field('psrc').i2m(self, self.psrc)
        other_pdst = other.get_field('pdst').i2m(other, other.pdst)
        return self_psrc[:len(other_pdst)] == other_pdst[:len(self_psrc)]

    def route(self):
        fld, dst = self.getfield_and_val("pdst")
        fld, dst = fld._find_fld_pkt_val(self, dst)
        if isinstance(dst, Gen):
            dst = next(iter(dst))
        if isinstance(fld, IP6Field):
            return conf.route6.route(dst)
        elif isinstance(fld, IPField):
            return conf.route.route(dst)
        else:
            return None, None, None

    def extract_padding(self, s):
        return "", s

    def mysummary(self):
        if self.op == 1:
            return self.sprintf("ARP who has %pdst% says %psrc%")
        if self.op == 2:
            return self.sprintf("ARP is at %hwsrc% says %psrc%")
        return self.sprintf("ARP %op% %psrc% > %pdst%")


def l2_register_l3_arp(l2, l3):
    return getmacbyip(l3.pdst)


conf.neighbor.register_l3(Ether, ARP, l2_register_l3_arp)


class ERSPAN(Packet):
    name = "ERSPAN"
    fields_desc = [BitField("ver", 0, 4),
                   BitField("vlan", 0, 12),
                   BitField("cos", 0, 3),
                   BitField("en", 0, 2),
                   BitField("t", 0, 1),
                   BitField("session_id", 0, 10),
                   BitField("reserved", 0, 12),
                   BitField("index", 0, 20),
                   ]


class GRErouting(Packet):
    name = "GRE routing information"
    fields_desc = [ShortField("address_family", 0),
                   ByteField("SRE_offset", 0),
                   FieldLenField("SRE_len", None, "routing_info", "B"),
                   StrLenField("routing_info", "", "SRE_len"),
                   ]


class GRE(Packet):
    name = "GRE"
    deprecated_fields = {
        "seqence_number": ("sequence_number", "2.4.4"),
    }
    fields_desc = [BitField("chksum_present", 0, 1),
                   BitField("routing_present", 0, 1),
                   BitField("key_present", 0, 1),
                   BitField("seqnum_present", 0, 1),
                   BitField("strict_route_source", 0, 1),
                   BitField("recursion_control", 0, 3),
                   BitField("flags", 0, 5),
                   BitField("version", 0, 3),
                   XShortEnumField("proto", 0x0000, ETHER_TYPES),
                   ConditionalField(XShortField("chksum", None), lambda pkt:pkt.chksum_present == 1 or pkt.routing_present == 1),  # noqa: E501
                   ConditionalField(XShortField("offset", None), lambda pkt:pkt.chksum_present == 1 or pkt.routing_present == 1),  # noqa: E501
                   ConditionalField(XIntField("key", None), lambda pkt:pkt.key_present == 1),  # noqa: E501
                   ConditionalField(XIntField("sequence_number", None), lambda pkt:pkt.seqnum_present == 1),  # noqa: E501
                   ]

    @classmethod
    def dispatch_hook(cls, _pkt=None, *args, **kargs):
        if _pkt and struct.unpack("!H", _pkt[2:4])[0] == 0x880b:
            return GRE_PPTP
        return cls

    def post_build(self, p, pay):
        p += pay
        if self.chksum_present and self.chksum is None:
            c = checksum(p)
            p = p[:4] + chb((c >> 8) & 0xff) + chb(c & 0xff) + p[6:]
        return p


class GRE_PPTP(GRE):

    """
    Enhanced GRE header used with PPTP
    RFC 2637
    """

    name = "GRE PPTP"
    deprecated_fields = {
        "seqence_number": ("sequence_number", "2.4.4"),
    }
    fields_desc = [BitField("chksum_present", 0, 1),
                   BitField("routing_present", 0, 1),
                   BitField("key_present", 1, 1),
                   BitField("seqnum_present", 0, 1),
                   BitField("strict_route_source", 0, 1),
                   BitField("recursion_control", 0, 3),
                   BitField("acknum_present", 0, 1),
                   BitField("flags", 0, 4),
                   BitField("version", 1, 3),
                   XShortEnumField("proto", 0x880b, ETHER_TYPES),
                   ShortField("payload_len", None),
                   ShortField("call_id", None),
                   ConditionalField(XIntField("sequence_number", None), lambda pkt: pkt.seqnum_present == 1),  # noqa: E501
                   ConditionalField(XIntField("ack_number", None), lambda pkt: pkt.acknum_present == 1)]  # noqa: E501

    def post_build(self, p, pay):
        p += pay
        if self.payload_len is None:
            pay_len = len(pay)
            p = p[:4] + chb((pay_len >> 8) & 0xff) + chb(pay_len & 0xff) + p[6:]  # noqa: E501
        return p


# *BSD loopback layer

class LoIntEnumField(IntEnumField):

    def m2i(self, pkt, x):
        return x >> 24

    def i2m(self, pkt, x):
        return x << 24


# https://github.com/wireshark/wireshark/blob/fe219637a6748130266a0b0278166046e60a2d68/epan/dissectors/packet-null.c
# https://www.wireshark.org/docs/wsar_html/epan/aftypes_8h.html
LOOPBACK_TYPES = {0x2: "IPv4",
                  0x7: "OSI",
                  0x10: "Appletalk",
                  0x17: "Netware IPX/SPX",
                  0x18: "IPv6", 0x1c: "IPv6", 0x1e: "IPv6"}


class Loopback(Packet):
    r"""\*BSD loopback layer"""

    name = "Loopback"
    if consts.OPENBSD:
        fields_desc = [IntEnumField("type", 0x2, LOOPBACK_TYPES)]
    else:
        fields_desc = [LoIntEnumField("type", 0x2, LOOPBACK_TYPES)]
    __slots__ = ["_defrag_pos"]


class Dot1AD(Dot1Q):
    name = '802_1AD'


bind_layers(Dot3, LLC)
bind_layers(Ether, LLC, type=122)
bind_layers(Ether, LLC, type=34928)
bind_layers(Ether, Dot1Q, type=33024)
bind_layers(Ether, Dot1AD, type=0x88a8)
bind_layers(Dot1AD, Dot1AD, type=0x88a8)
bind_layers(Dot1AD, Dot1Q, type=0x8100)
bind_layers(Dot1Q, Dot1AD, type=0x88a8)
bind_layers(ERSPAN, Ether)
bind_layers(Ether, Ether, type=1)
bind_layers(Ether, ARP, type=2054)
bind_layers(CookedLinux, LLC, proto=122)
bind_layers(CookedLinux, Dot1Q, proto=33024)
bind_layers(CookedLinux, Dot1AD, type=0x88a8)
bind_layers(CookedLinux, Ether, proto=1)
bind_layers(CookedLinux, ARP, proto=2054)
bind_layers(MPacketPreamble, Ether)
bind_layers(GRE, LLC, proto=122)
bind_layers(GRE, Dot1Q, proto=33024)
bind_layers(GRE, Dot1AD, type=0x88a8)
bind_layers(GRE, Ether, proto=0x6558)
bind_layers(GRE, ARP, proto=2054)
bind_layers(GRE, ERSPAN, proto=0x88be, seqnum_present=1)
bind_layers(GRE, GRErouting, {"routing_present": 1})
bind_layers(GRErouting, conf.raw_layer, {"address_family": 0, "SRE_len": 0})
bind_layers(GRErouting, GRErouting)
bind_layers(LLC, STP, dsap=66, ssap=66, ctrl=3)
bind_layers(LLC, SNAP, dsap=170, ssap=170, ctrl=3)
bind_layers(SNAP, Dot1Q, code=33024)
bind_layers(SNAP, Dot1AD, type=0x88a8)
bind_layers(SNAP, Ether, code=1)
bind_layers(SNAP, ARP, code=2054)
bind_layers(SNAP, STP, code=267)

conf.l2types.register(ARPHDR_ETHER, Ether)
conf.l2types.register_num2layer(ARPHDR_METRICOM, Ether)
conf.l2types.register_num2layer(ARPHDR_LOOPBACK, Ether)
conf.l2types.register_layer2num(ARPHDR_ETHER, Dot3)
conf.l2types.register(DLT_LINUX_SLL, CookedLinux)
conf.l2types.register(DLT_ETHERNET_MPACKET, MPacketPreamble)
conf.l2types.register_num2layer(DLT_LINUX_IRDA, CookedLinux)
conf.l2types.register(DLT_LOOP, Loopback)
conf.l2types.register_num2layer(DLT_NULL, Loopback)

conf.l3types.register(ETH_P_ARP, ARP)


# Techniques


@conf.commands.register
def arpcachepoison(target, victim, interval=60):
    """Poison target's cache with (your MAC,victim's IP) couple
arpcachepoison(target, victim, [interval=60]) -> None
"""
    tmac = getmacbyip(target)
    p = Ether(dst=tmac) / ARP(op="who-has", psrc=victim, pdst=target)
    try:
        while True:
            sendp(p, iface_hint=target)
            if conf.verb > 1:
                os.write(1, b".")
            time.sleep(interval)
    except KeyboardInterrupt:
        pass


class ARPingResult(SndRcvList):
    def __init__(self, res=None, name="ARPing", stats=None):
        SndRcvList.__init__(self, res, name, stats)

    def show(self):
        """
        Print the list of discovered MAC addresses.
        """

        data = list()
        padding = 0

        for s, r in self.res:
            manuf = conf.manufdb._get_short_manuf(r.src)
            manuf = "unknown" if manuf == r.src else manuf
            padding = max(padding, len(manuf))
            data.append((r[Ether].src, manuf, r[ARP].psrc))

        for src, manuf, psrc in data:
            print("  %-17s %-*s %s" % (src, padding, manuf, psrc))


@conf.commands.register
def arping(net, timeout=2, cache=0, verbose=None, **kargs):
    """Send ARP who-has requests to determine which hosts are up
arping(net, [cache=0,] [iface=conf.iface,] [verbose=conf.verb]) -> None
Set cache=True if you want arping to modify internal ARP-Cache"""
    if verbose is None:
        verbose = conf.verb
    ans, unans = srp(Ether(dst="ff:ff:ff:ff:ff:ff") / ARP(pdst=net), verbose=verbose,  # noqa: E501
                     filter="arp and arp[7] = 2", timeout=timeout, iface_hint=net, **kargs)  # noqa: E501
    ans = ARPingResult(ans.res)

    if cache and ans is not None:
        for pair in ans:
            conf.netcache.arp_cache[pair[1].psrc] = (pair[1].hwsrc, time.time())  # noqa: E501
    if ans is not None and verbose:
        ans.show()
    return ans, unans


@conf.commands.register
def is_promisc(ip, fake_bcast="ff:ff:00:00:00:00", **kargs):
    """Try to guess if target is in Promisc mode. The target is provided by its ip."""  # noqa: E501

    responses = srp1(Ether(dst=fake_bcast) / ARP(op="who-has", pdst=ip), type=ETH_P_ARP, iface_hint=ip, timeout=1, verbose=0, **kargs)  # noqa: E501

    return responses is not None


@conf.commands.register
def promiscping(net, timeout=2, fake_bcast="ff:ff:ff:ff:ff:fe", **kargs):
    """Send ARP who-has requests to determine which hosts are in promiscuous mode
    promiscping(net, iface=conf.iface)"""
    ans, unans = srp(Ether(dst=fake_bcast) / ARP(pdst=net),
                     filter="arp and arp[7] = 2", timeout=timeout, iface_hint=net, **kargs)  # noqa: E501
    ans = ARPingResult(ans.res, name="PROMISCPing")

    ans.display()
    return ans, unans


class ARP_am(AnsweringMachine):
    """Fake ARP Relay Daemon (farpd)

    example:
    To respond to an ARP request for 192.168.100 replying on the
    ingress interface::

      farpd(IP_addr='192.168.1.100',ARP_addr='00:01:02:03:04:05')

    To respond on a different interface add the interface parameter::

      farpd(IP_addr='192.168.1.100',ARP_addr='00:01:02:03:04:05',iface='eth0')

    To respond on ANY arp request on an interface with mac address ARP_addr::

      farpd(ARP_addr='00:01:02:03:04:05',iface='eth1')

    To respond on ANY arp request with my mac addr on the given interface::

      farpd(iface='eth1')

    Optional Args::

     inter=<n>   Interval in seconds between ARP replies being sent

    """

    function_name = "farpd"
    filter = "arp"
    send_function = staticmethod(sendp)

    def parse_options(self, IP_addr=None, ARP_addr=None):
        self.IP_addr = IP_addr
        self.ARP_addr = ARP_addr

    def is_request(self, req):
        return (req.haslayer(ARP) and
                req.getlayer(ARP).op == 1 and
                (self.IP_addr is None or self.IP_addr == req.getlayer(ARP).pdst))  # noqa: E501

    def make_reply(self, req):
        ether = req.getlayer(Ether)
        arp = req.getlayer(ARP)

        if 'iface' in self.optsend:
            iff = self.optsend.get('iface')
        else:
            iff, a, gw = conf.route.route(arp.psrc)
        self.iff = iff
        if self.ARP_addr is None:
            try:
                ARP_addr = get_if_hwaddr(iff)
            except Exception:
                ARP_addr = "00:00:00:00:00:00"
        else:
            ARP_addr = self.ARP_addr
        resp = Ether(dst=ether.src,
                     src=ARP_addr) / ARP(op="is-at",
                                         hwsrc=ARP_addr,
                                         psrc=arp.pdst,
                                         hwdst=arp.hwsrc,
                                         pdst=arp.psrc)
        return resp

    def send_reply(self, reply):
        if 'iface' in self.optsend:
            self.send_function(reply, **self.optsend)
        else:
            self.send_function(reply, iface=self.iff, **self.optsend)

    def print_reply(self, req, reply):
        print("%s ==> %s on %s" % (req.summary(), reply.summary(), self.iff))


@conf.commands.register
def etherleak(target, **kargs):
    """Exploit Etherleak flaw"""
    return srp(Ether() / ARP(pdst=target),
               prn=lambda s_r: conf.padding_layer in s_r[1] and hexstr(s_r[1][conf.padding_layer].load),  # noqa: E501
               filter="arp", **kargs)


@conf.commands.register
def arpleak(target, plen=255, hwlen=255, **kargs):
    """Exploit ARP leak flaws, like NetBSD-SA2017-002.

https://ftp.netbsd.org/pub/NetBSD/security/advisories/NetBSD-SA2017-002.txt.asc

    """
    # We want explicit packets
    pkts_iface = {}
    for pkt in ARP(pdst=target):
        # We have to do some of Scapy's work since we mess with
        # important values
        iface = conf.route.route(pkt.pdst)[0]
        psrc = get_if_addr(iface)
        hwsrc = get_if_hwaddr(iface)
        pkt.plen = plen
        pkt.hwlen = hwlen
        if plen == 4:
            pkt.psrc = psrc
        else:
            pkt.psrc = inet_aton(psrc)[:plen]
            pkt.pdst = inet_aton(pkt.pdst)[:plen]
        if hwlen == 6:
            pkt.hwsrc = hwsrc
        else:
            pkt.hwsrc = mac2str(hwsrc)[:hwlen]
        pkts_iface.setdefault(iface, []).append(
            Ether(src=hwsrc, dst=ETHER_BROADCAST) / pkt
        )
    ans, unans = SndRcvList(), PacketList(name="Unanswered")
    for iface, pkts in viewitems(pkts_iface):
        ans_new, unans_new = srp(pkts, iface=iface, filter="arp", **kargs)
        ans += ans_new
        unans += unans_new
        ans.listname = "Results"
        unans.listname = "Unanswered"
    for _, rcv in ans:
        if ARP not in rcv:
            continue
        rcv = rcv[ARP]
        psrc = rcv.get_field('psrc').i2m(rcv, rcv.psrc)
        if plen > 4 and len(psrc) > 4:
            print("psrc")
            hexdump(psrc[4:])
            print()
        hwsrc = rcv.get_field('hwsrc').i2m(rcv, rcv.hwsrc)
        if hwlen > 6 and len(hwsrc) > 6:
            print("hwsrc")
            hexdump(hwsrc[6:])
            print()
    return ans, unans