# SPDX-License-Identifier: GPL-2.0-only
# This file is part of Scapy
# See https://scapy.net/ for more information
# Copyright (C) Philippe Biondi <phil@secdev.org>
# Copyright (C) 6WIND <olivier.matz@6wind.com>

"""
SCTP (Stream Control Transmission Protocol).
"""

from __future__ import absolute_import
import struct

from scapy.compat import orb, raw
from scapy.volatile import RandBin
from scapy.config import conf
from scapy.packet import Packet, bind_layers
from scapy.fields import (
    BitField,
    ByteEnumField,
    Field,
    FieldLenField,
    FieldListField,
    IPField,
    IntEnumField,
    IntField,
    MultipleTypeField,
    PacketListField,
    PadField,
    ShortEnumField,
    ShortField,
    StrFixedLenField,
    StrLenField,
    XByteField,
    XIntField,
    XShortField,
)
from scapy.data import SCTP_SERVICES
from scapy.layers.inet import IP, IPerror
from scapy.layers.inet6 import IP6Field, IPv6, IPerror6

IPPROTO_SCTP = 132

# crc32-c (Castagnoli) (crc32c_poly=0x1EDC6F41)
crc32c_table = [
    0x00000000, 0xF26B8303, 0xE13B70F7, 0x1350F3F4,
    0xC79A971F, 0x35F1141C, 0x26A1E7E8, 0xD4CA64EB,
    0x8AD958CF, 0x78B2DBCC, 0x6BE22838, 0x9989AB3B,
    0x4D43CFD0, 0xBF284CD3, 0xAC78BF27, 0x5E133C24,
    0x105EC76F, 0xE235446C, 0xF165B798, 0x030E349B,
    0xD7C45070, 0x25AFD373, 0x36FF2087, 0xC494A384,
    0x9A879FA0, 0x68EC1CA3, 0x7BBCEF57, 0x89D76C54,
    0x5D1D08BF, 0xAF768BBC, 0xBC267848, 0x4E4DFB4B,
    0x20BD8EDE, 0xD2D60DDD, 0xC186FE29, 0x33ED7D2A,
    0xE72719C1, 0x154C9AC2, 0x061C6936, 0xF477EA35,
    0xAA64D611, 0x580F5512, 0x4B5FA6E6, 0xB93425E5,
    0x6DFE410E, 0x9F95C20D, 0x8CC531F9, 0x7EAEB2FA,
    0x30E349B1, 0xC288CAB2, 0xD1D83946, 0x23B3BA45,
    0xF779DEAE, 0x05125DAD, 0x1642AE59, 0xE4292D5A,
    0xBA3A117E, 0x4851927D, 0x5B016189, 0xA96AE28A,
    0x7DA08661, 0x8FCB0562, 0x9C9BF696, 0x6EF07595,
    0x417B1DBC, 0xB3109EBF, 0xA0406D4B, 0x522BEE48,
    0x86E18AA3, 0x748A09A0, 0x67DAFA54, 0x95B17957,
    0xCBA24573, 0x39C9C670, 0x2A993584, 0xD8F2B687,
    0x0C38D26C, 0xFE53516F, 0xED03A29B, 0x1F682198,
    0x5125DAD3, 0xA34E59D0, 0xB01EAA24, 0x42752927,
    0x96BF4DCC, 0x64D4CECF, 0x77843D3B, 0x85EFBE38,
    0xDBFC821C, 0x2997011F, 0x3AC7F2EB, 0xC8AC71E8,
    0x1C661503, 0xEE0D9600, 0xFD5D65F4, 0x0F36E6F7,
    0x61C69362, 0x93AD1061, 0x80FDE395, 0x72966096,
    0xA65C047D, 0x5437877E, 0x4767748A, 0xB50CF789,
    0xEB1FCBAD, 0x197448AE, 0x0A24BB5A, 0xF84F3859,
    0x2C855CB2, 0xDEEEDFB1, 0xCDBE2C45, 0x3FD5AF46,
    0x7198540D, 0x83F3D70E, 0x90A324FA, 0x62C8A7F9,
    0xB602C312, 0x44694011, 0x5739B3E5, 0xA55230E6,
    0xFB410CC2, 0x092A8FC1, 0x1A7A7C35, 0xE811FF36,
    0x3CDB9BDD, 0xCEB018DE, 0xDDE0EB2A, 0x2F8B6829,
    0x82F63B78, 0x709DB87B, 0x63CD4B8F, 0x91A6C88C,
    0x456CAC67, 0xB7072F64, 0xA457DC90, 0x563C5F93,
    0x082F63B7, 0xFA44E0B4, 0xE9141340, 0x1B7F9043,
    0xCFB5F4A8, 0x3DDE77AB, 0x2E8E845F, 0xDCE5075C,
    0x92A8FC17, 0x60C37F14, 0x73938CE0, 0x81F80FE3,
    0x55326B08, 0xA759E80B, 0xB4091BFF, 0x466298FC,
    0x1871A4D8, 0xEA1A27DB, 0xF94AD42F, 0x0B21572C,
    0xDFEB33C7, 0x2D80B0C4, 0x3ED04330, 0xCCBBC033,
    0xA24BB5A6, 0x502036A5, 0x4370C551, 0xB11B4652,
    0x65D122B9, 0x97BAA1BA, 0x84EA524E, 0x7681D14D,
    0x2892ED69, 0xDAF96E6A, 0xC9A99D9E, 0x3BC21E9D,
    0xEF087A76, 0x1D63F975, 0x0E330A81, 0xFC588982,
    0xB21572C9, 0x407EF1CA, 0x532E023E, 0xA145813D,
    0x758FE5D6, 0x87E466D5, 0x94B49521, 0x66DF1622,
    0x38CC2A06, 0xCAA7A905, 0xD9F75AF1, 0x2B9CD9F2,
    0xFF56BD19, 0x0D3D3E1A, 0x1E6DCDEE, 0xEC064EED,
    0xC38D26C4, 0x31E6A5C7, 0x22B65633, 0xD0DDD530,
    0x0417B1DB, 0xF67C32D8, 0xE52CC12C, 0x1747422F,
    0x49547E0B, 0xBB3FFD08, 0xA86F0EFC, 0x5A048DFF,
    0x8ECEE914, 0x7CA56A17, 0x6FF599E3, 0x9D9E1AE0,
    0xD3D3E1AB, 0x21B862A8, 0x32E8915C, 0xC083125F,
    0x144976B4, 0xE622F5B7, 0xF5720643, 0x07198540,
    0x590AB964, 0xAB613A67, 0xB831C993, 0x4A5A4A90,
    0x9E902E7B, 0x6CFBAD78, 0x7FAB5E8C, 0x8DC0DD8F,
    0xE330A81A, 0x115B2B19, 0x020BD8ED, 0xF0605BEE,
    0x24AA3F05, 0xD6C1BC06, 0xC5914FF2, 0x37FACCF1,
    0x69E9F0D5, 0x9B8273D6, 0x88D28022, 0x7AB90321,
    0xAE7367CA, 0x5C18E4C9, 0x4F48173D, 0xBD23943E,
    0xF36E6F75, 0x0105EC76, 0x12551F82, 0xE03E9C81,
    0x34F4F86A, 0xC69F7B69, 0xD5CF889D, 0x27A40B9E,
    0x79B737BA, 0x8BDCB4B9, 0x988C474D, 0x6AE7C44E,
    0xBE2DA0A5, 0x4C4623A6, 0x5F16D052, 0xAD7D5351,
]


def crc32c(buf):
    crc = 0xffffffff
    for c in buf:
        crc = (crc >> 8) ^ crc32c_table[(crc ^ (orb(c))) & 0xFF]
    crc = (~crc) & 0xffffffff
    # reverse endianness
    return struct.unpack(">I", struct.pack("<I", crc))[0]


# old checksum (RFC2960)
"""
BASE = 65521 # largest prime smaller than 65536
def update_adler32(adler, buf):
    s1 = adler & 0xffff
    s2 = (adler >> 16) & 0xffff
    print s1,s2

    for c in buf:
        print orb(c)
        s1 = (s1 + orb(c)) % BASE
        s2 = (s2 + s1) % BASE
        print s1,s2
    return (s2 << 16) + s1

def sctp_checksum(buf):
    return update_adler32(1, buf)
"""

hmactypes = {
    0: "Reserved1",
    1: "SHA-1",
    2: "Reserved2",
    3: "SHA-256",
}

sctpchunktypescls = {
    0: "SCTPChunkData",
    1: "SCTPChunkInit",
    2: "SCTPChunkInitAck",
    3: "SCTPChunkSACK",
    4: "SCTPChunkHeartbeatReq",
    5: "SCTPChunkHeartbeatAck",
    6: "SCTPChunkAbort",
    7: "SCTPChunkShutdown",
    8: "SCTPChunkShutdownAck",
    9: "SCTPChunkError",
    10: "SCTPChunkCookieEcho",
    11: "SCTPChunkCookieAck",
    14: "SCTPChunkShutdownComplete",
    15: "SCTPChunkAuthentication",
    0x80: "SCTPChunkAddressConfAck",
    0xc1: "SCTPChunkAddressConf",
}

sctpchunktypes = {
    0: "data",
    1: "init",
    2: "init-ack",
    3: "sack",
    4: "heartbeat-req",
    5: "heartbeat-ack",
    6: "abort",
    7: "shutdown",
    8: "shutdown-ack",
    9: "error",
    10: "cookie-echo",
    11: "cookie-ack",
    14: "shutdown-complete",
    15: "authentication",
    0x80: "address-configuration-ack",
    0xc1: "address-configuration",
}

sctpchunkparamtypescls = {
    1: "SCTPChunkParamHeartbeatInfo",
    5: "SCTPChunkParamIPv4Addr",
    6: "SCTPChunkParamIPv6Addr",
    7: "SCTPChunkParamStateCookie",
    8: "SCTPChunkParamUnrocognizedParam",
    9: "SCTPChunkParamCookiePreservative",
    11: "SCTPChunkParamHostname",
    12: "SCTPChunkParamSupportedAddrTypes",
    0x8000: "SCTPChunkParamECNCapable",
    0x8002: "SCTPChunkParamRandom",
    0x8003: "SCTPChunkParamChunkList",
    0x8004: "SCTPChunkParamRequestedHMACFunctions",
    0x8008: "SCTPChunkParamSupportedExtensions",
    0xc000: "SCTPChunkParamFwdTSN",
    0xc001: "SCTPChunkParamAddIPAddr",
    0xc002: "SCTPChunkParamDelIPAddr",
    0xc003: "SCTPChunkParamErrorIndication",
    0xc004: "SCTPChunkParamSetPrimaryAddr",
    0xc005: "SCTPChunkParamSuccessIndication",
    0xc006: "SCTPChunkParamAdaptationLayer",
}

sctpchunkparamtypes = {
    1: "heartbeat-info",
    5: "IPv4",
    6: "IPv6",
    7: "state-cookie",
    8: "unrecognized-param",
    9: "cookie-preservative",
    11: "hostname",
    12: "addrtypes",
    0x8000: "ecn-capable",
    0x8002: "random",
    0x8003: "chunk-list",
    0x8004: "requested-HMAC-functions",
    0x8008: "supported-extensions",
    0xc000: "fwd-tsn-supported",
    0xc001: "add-IP",
    0xc002: "del-IP",
    0xc003: "error-indication",
    0xc004: "set-primary-addr",
    0xc005: "success-indication",
    0xc006: "adaptation-layer",
}

# SCTP header

# Dummy class to guess payload type (variable parameters)


class _SCTPChunkGuessPayload:
    def default_payload_class(self, p):
        if len(p) < 4:
            return conf.padding_layer
        else:
            t = orb(p[0])
            return globals().get(sctpchunktypescls.get(t, "Raw"), conf.raw_layer)  # noqa: E501


class SCTP(_SCTPChunkGuessPayload, Packet):
    fields_desc = [ShortEnumField("sport", 0, SCTP_SERVICES),
                   ShortEnumField("dport", 0, SCTP_SERVICES),
                   XIntField("tag", 0),
                   XIntField("chksum", None), ]

    def answers(self, other):
        if not isinstance(other, SCTP):
            return 0
        if conf.checkIPsrc:
            if not ((self.sport == other.dport) and
                    (self.dport == other.sport)):
                return 0
        return 1

    def post_build(self, p, pay):
        p += pay
        if self.chksum is None:
            crc = crc32c(raw(p))
            p = p[:8] + struct.pack(">I", crc) + p[12:]
        return p


class SCTPerror(SCTP):
    name = "SCTP in ICMP"

    def answers(self, other):
        if not isinstance(other, SCTP):
            return 0
        if conf.checkIPsrc:
            if not ((self.sport == other.sport) and
                    (self.dport == other.dport)):
                return 0
        return 1

    def mysummary(self):
        return Packet.mysummary(self)


# SCTP Chunk variable params


class ChunkParamField(PacketListField):
    def __init__(self, name, default, count_from=None, length_from=None):
        PacketListField.__init__(self, name, default, conf.raw_layer, count_from=count_from, length_from=length_from)  # noqa: E501

    def m2i(self, p, m):
        cls = conf.raw_layer
        if len(m) >= 4:
            t = orb(m[0]) * 256 + orb(m[1])
            cls = globals().get(sctpchunkparamtypescls.get(t, "Raw"), conf.raw_layer)  # noqa: E501
        return cls(m)

# dummy class to avoid Raw() after Chunk params


class _SCTPChunkParam:
    def extract_padding(self, s):
        return b"", s[:]


class SCTPChunkParamHeartbeatInfo(_SCTPChunkParam, Packet):
    fields_desc = [ShortEnumField("type", 1, sctpchunkparamtypes),
                   FieldLenField("len", None, length_of="data",
                                 adjust=lambda pkt, x:x + 4),
                   PadField(StrLenField("data", "",
                                        length_from=lambda pkt: pkt.len - 4),
                            4, padwith=b"\x00"), ]


class SCTPChunkParamIPv4Addr(_SCTPChunkParam, Packet):
    fields_desc = [ShortEnumField("type", 5, sctpchunkparamtypes),
                   ShortField("len", 8),
                   IPField("addr", "127.0.0.1"), ]


class SCTPChunkParamIPv6Addr(_SCTPChunkParam, Packet):
    fields_desc = [ShortEnumField("type", 6, sctpchunkparamtypes),
                   ShortField("len", 20),
                   IP6Field("addr", "::1"), ]


class SCTPChunkParamStateCookie(_SCTPChunkParam, Packet):
    fields_desc = [ShortEnumField("type", 7, sctpchunkparamtypes),
                   FieldLenField("len", None, length_of="cookie",
                                 adjust=lambda pkt, x:x + 4),
                   PadField(StrLenField("cookie", "",
                                        length_from=lambda pkt: pkt.len - 4),
                            4, padwith=b"\x00"), ]


class SCTPChunkParamUnrocognizedParam(_SCTPChunkParam, Packet):
    fields_desc = [ShortEnumField("type", 8, sctpchunkparamtypes),
                   FieldLenField("len", None, length_of="param",
                                 adjust=lambda pkt, x:x + 4),
                   PadField(StrLenField("param", "",
                                        length_from=lambda pkt: pkt.len - 4),
                            4, padwith=b"\x00"), ]


class SCTPChunkParamCookiePreservative(_SCTPChunkParam, Packet):
    fields_desc = [ShortEnumField("type", 9, sctpchunkparamtypes),
                   ShortField("len", 8),
                   XIntField("sug_cookie_inc", None), ]


class SCTPChunkParamHostname(_SCTPChunkParam, Packet):
    fields_desc = [ShortEnumField("type", 11, sctpchunkparamtypes),
                   FieldLenField("len", None, length_of="hostname",
                                 adjust=lambda pkt, x:x + 4),
                   PadField(StrLenField("hostname", "",
                                        length_from=lambda pkt: pkt.len - 4),
                            4, padwith=b"\x00"), ]


class SCTPChunkParamSupportedAddrTypes(_SCTPChunkParam, Packet):
    fields_desc = [ShortEnumField("type", 12, sctpchunkparamtypes),
                   FieldLenField("len", None, length_of="addr_type_list",
                                 adjust=lambda pkt, x:x + 4),
                   PadField(FieldListField("addr_type_list", ["IPv4"],
                                           ShortEnumField("addr_type", 5, sctpchunkparamtypes),  # noqa: E501
                                           length_from=lambda pkt: pkt.len - 4),  # noqa: E501
                            4, padwith=b"\x00"), ]


class SCTPChunkParamECNCapable(_SCTPChunkParam, Packet):
    fields_desc = [ShortEnumField("type", 0x8000, sctpchunkparamtypes),
                   ShortField("len", 4), ]


class SCTPChunkParamRandom(_SCTPChunkParam, Packet):
    fields_desc = [ShortEnumField("type", 0x8002, sctpchunkparamtypes),
                   FieldLenField("len", None, length_of="random",
                                 adjust=lambda pkt, x:x + 4),
                   PadField(StrLenField("random", RandBin(32),
                                        length_from=lambda pkt: pkt.len - 4),
                            4, padwith=b"\x00"), ]


class SCTPChunkParamChunkList(_SCTPChunkParam, Packet):
    fields_desc = [ShortEnumField("type", 0x8003, sctpchunkparamtypes),
                   FieldLenField("len", None, length_of="chunk_list",
                                 adjust=lambda pkt, x:x + 4),
                   PadField(FieldListField("chunk_list", None,
                                           ByteEnumField("chunk", None, sctpchunktypes),  # noqa: E501
                                           length_from=lambda pkt: pkt.len - 4),  # noqa: E501
                            4, padwith=b"\x00"), ]


class SCTPChunkParamRequestedHMACFunctions(_SCTPChunkParam, Packet):
    fields_desc = [ShortEnumField("type", 0x8004, sctpchunkparamtypes),
                   FieldLenField("len", None, length_of="HMAC_functions_list",
                                 adjust=lambda pkt, x:x + 4),
                   PadField(FieldListField("HMAC_functions_list", ["SHA-1"],
                                           ShortEnumField("HMAC_function", 1, hmactypes),  # noqa: E501
                                           length_from=lambda pkt: pkt.len - 4),  # noqa: E501
                            4, padwith=b"\x00"), ]


class SCTPChunkParamSupportedExtensions(_SCTPChunkParam, Packet):
    fields_desc = [ShortEnumField("type", 0x8008, sctpchunkparamtypes),
                   FieldLenField("len", None, length_of="supported_extensions",
                                 adjust=lambda pkt, x:x + 4),
                   PadField(FieldListField("supported_extensions",
                                           ["authentication",
                                            "address-configuration",
                                            "address-configuration-ack"],
                                           ByteEnumField("supported_extensions",  # noqa: E501
                                                         None, sctpchunktypes),
                                           length_from=lambda pkt: pkt.len - 4),  # noqa: E501
                            4, padwith=b"\x00"), ]


class SCTPChunkParamFwdTSN(_SCTPChunkParam, Packet):
    fields_desc = [ShortEnumField("type", 0xc000, sctpchunkparamtypes),
                   ShortField("len", 4), ]


class SCTPChunkParamAddIPAddr(_SCTPChunkParam, Packet):
    fields_desc = [ShortEnumField("type", 0xc001, sctpchunkparamtypes),
                   FieldLenField("len", None, length_of="addr",
                                 adjust=lambda pkt, x:x + 12),
                   XIntField("correlation_id", None),
                   ShortEnumField("addr_type", 5, sctpchunkparamtypes),
                   FieldLenField("addr_len", None, length_of="addr",
                                 adjust=lambda pkt, x:x + 4),
                   MultipleTypeField(
                       [
                           (IPField("addr", "127.0.0.1"),
                            lambda p: p.addr_type == 5),
                           (IP6Field("addr", "::1"),
                            lambda p: p.addr_type == 6),
                       ],
                       StrFixedLenField("addr", "",
                                        length_from=lambda pkt: pkt.addr_len))
                   ]


class SCTPChunkParamDelIPAddr(SCTPChunkParamAddIPAddr):
    type = 0xc002


class SCTPChunkParamErrorIndication(_SCTPChunkParam, Packet):
    fields_desc = [ShortEnumField("type", 0xc003, sctpchunkparamtypes),
                   FieldLenField("len", None, length_of="error_causes",
                                 adjust=lambda pkt, x:x + 8),
                   XIntField("correlation_id", None),
                   PadField(StrLenField("error_causes", "",
                                        length_from=lambda pkt: pkt.len - 4),
                            4, padwith=b"\x00"), ]


class SCTPChunkParamSetPrimaryAddr(SCTPChunkParamAddIPAddr):
    type = 0xc004


class SCTPChunkParamSuccessIndication(_SCTPChunkParam, Packet):
    fields_desc = [ShortEnumField("type", 0xc005, sctpchunkparamtypes),
                   ShortField("len", 8),
                   XIntField("correlation_id", None), ]


class SCTPChunkParamAdaptationLayer(_SCTPChunkParam, Packet):
    fields_desc = [ShortEnumField("type", 0xc006, sctpchunkparamtypes),
                   ShortField("len", 8),
                   XIntField("indication", None), ]

# SCTP Chunks


# Dictionary taken from: http://www.iana.org/assignments/sctp-parameters/sctp-parameters.xhtml  # noqa: E501
SCTP_PAYLOAD_PROTOCOL_INDENTIFIERS = {
    0: 'Reserved',
    1: 'IUA',
    2: 'M2UA',
    3: 'M3UA',
    4: 'SUA',
    5: 'M2PA',
    6: 'V5UA',
    7: 'H.248',
    8: 'BICC/Q.2150.3',
    9: 'TALI',
    10: 'DUA',
    11: 'ASAP',
    12: 'ENRP',
    13: 'H.323',
    14: 'Q.IPC/Q.2150.3',
    15: 'SIMCO',
    16: 'DDP Segment Chunk',
    17: 'DDP Stream Session Control',
    18: 'S1AP',
    19: 'RUA',
    20: 'HNBAP',
    21: 'ForCES-HP',
    22: 'ForCES-MP',
    23: 'ForCES-LP',
    24: 'SBc-AP',
    25: 'NBAP',
    26: 'Unassigned',
    27: 'X2AP',
    28: 'IRCP',
    29: 'LCS-AP',
    30: 'MPICH2',
    31: 'SABP',
    32: 'FGP',
    33: 'PPP',
    34: 'CALCAPP',
    35: 'SSP',
    36: 'NPMP-CONTROL',
    37: 'NPMP-DATA',
    38: 'ECHO',
    39: 'DISCARD',
    40: 'DAYTIME',
    41: 'CHARGEN',
    42: '3GPP RNA',
    43: '3GPP M2AP',
    44: '3GPP M3AP',
    45: 'SSH/SCTP',
    46: 'Diameter/SCTP',
    47: 'Diameter/DTLS/SCTP',
    48: 'R14P',
    49: 'Unassigned',
    50: 'WebRTC DCEP',
    51: 'WebRTC String',
    52: 'WebRTC Binary Partial',
    53: 'WebRTC Binary',
    54: 'WebRTC String Partial',
    55: '3GPP PUA',
    56: 'WebRTC String Empty',
    57: 'WebRTC Binary Empty'
}


class SCTPChunkData(_SCTPChunkGuessPayload, Packet):
    # TODO : add a padding function in post build if this layer is used to generate SCTP chunk data  # noqa: E501
    fields_desc = [ByteEnumField("type", 0, sctpchunktypes),
                   BitField("reserved", None, 4),
                   BitField("delay_sack", 0, 1),
                   BitField("unordered", 0, 1),
                   BitField("beginning", 0, 1),
                   BitField("ending", 0, 1),
                   FieldLenField("len", None, length_of="data", adjust=lambda pkt, x:x + 16),  # noqa: E501
                   XIntField("tsn", None),
                   XShortField("stream_id", None),
                   XShortField("stream_seq", None),
                   IntEnumField("proto_id", None, SCTP_PAYLOAD_PROTOCOL_INDENTIFIERS),  # noqa: E501
                   PadField(StrLenField("data", None, length_from=lambda pkt: pkt.len - 16),  # noqa: E501
                            4, padwith=b"\x00"),
                   ]


class SCTPChunkInit(_SCTPChunkGuessPayload, Packet):
    fields_desc = [ByteEnumField("type", 1, sctpchunktypes),
                   XByteField("flags", None),
                   FieldLenField("len", None, length_of="params", adjust=lambda pkt, x:x + 20),  # noqa: E501
                   XIntField("init_tag", None),
                   IntField("a_rwnd", None),
                   ShortField("n_out_streams", None),
                   ShortField("n_in_streams", None),
                   XIntField("init_tsn", None),
                   ChunkParamField("params", None, length_from=lambda pkt:pkt.len - 20),  # noqa: E501
                   ]


class SCTPChunkInitAck(SCTPChunkInit):
    type = 2


class GapAckField(Field):
    def __init__(self, name, default):
        Field.__init__(self, name, default, "4s")

    def i2m(self, pkt, x):
        if x is None:
            return b"\0\0\0\0"
        sta, end = [int(e) for e in x.split(':')]
        args = tuple([">HH", sta, end])
        return struct.pack(*args)

    def m2i(self, pkt, x):
        return "%d:%d" % (struct.unpack(">HH", x))

    def any2i(self, pkt, x):
        if isinstance(x, tuple) and len(x) == 2:
            return "%d:%d" % (x)
        return x


class SCTPChunkSACK(_SCTPChunkGuessPayload, Packet):
    fields_desc = [ByteEnumField("type", 3, sctpchunktypes),
                   XByteField("flags", None),
                   ShortField("len", None),
                   XIntField("cumul_tsn_ack", None),
                   IntField("a_rwnd", None),
                   FieldLenField("n_gap_ack", None, count_of="gap_ack_list"),
                   FieldLenField("n_dup_tsn", None, count_of="dup_tsn_list"),
                   FieldListField("gap_ack_list", [], GapAckField("gap_ack", None), count_from=lambda pkt:pkt.n_gap_ack),  # noqa: E501
                   FieldListField("dup_tsn_list", [], XIntField("dup_tsn", None), count_from=lambda pkt:pkt.n_dup_tsn),  # noqa: E501
                   ]

    def post_build(self, p, pay):
        if self.len is None:
            p = p[:2] + struct.pack(">H", len(p)) + p[4:]
        return p + pay


class SCTPChunkHeartbeatReq(_SCTPChunkGuessPayload, Packet):
    fields_desc = [ByteEnumField("type", 4, sctpchunktypes),
                   XByteField("flags", None),
                   FieldLenField("len", None, length_of="params", adjust=lambda pkt, x:x + 4),  # noqa: E501
                   ChunkParamField("params", None, length_from=lambda pkt:pkt.len - 4),  # noqa: E501
                   ]


class SCTPChunkHeartbeatAck(SCTPChunkHeartbeatReq):
    type = 5


class SCTPChunkAbort(_SCTPChunkGuessPayload, Packet):
    fields_desc = [ByteEnumField("type", 6, sctpchunktypes),
                   BitField("reserved", None, 7),
                   BitField("TCB", 0, 1),
                   FieldLenField("len", None, length_of="error_causes", adjust=lambda pkt, x:x + 4),  # noqa: E501
                   PadField(StrLenField("error_causes", "", length_from=lambda pkt: pkt.len - 4),  # noqa: E501
                            4, padwith=b"\x00"),
                   ]


class SCTPChunkShutdown(_SCTPChunkGuessPayload, Packet):
    fields_desc = [ByteEnumField("type", 7, sctpchunktypes),
                   XByteField("flags", None),
                   ShortField("len", 8),
                   XIntField("cumul_tsn_ack", None),
                   ]


class SCTPChunkShutdownAck(_SCTPChunkGuessPayload, Packet):
    fields_desc = [ByteEnumField("type", 8, sctpchunktypes),
                   XByteField("flags", None),
                   ShortField("len", 4),
                   ]


class SCTPChunkError(_SCTPChunkGuessPayload, Packet):
    fields_desc = [ByteEnumField("type", 9, sctpchunktypes),
                   XByteField("flags", None),
                   FieldLenField("len", None, length_of="error_causes", adjust=lambda pkt, x:x + 4),  # noqa: E501
                   PadField(StrLenField("error_causes", "", length_from=lambda pkt: pkt.len - 4),  # noqa: E501
                            4, padwith=b"\x00"),
                   ]


class SCTPChunkCookieEcho(SCTPChunkError):
    fields_desc = [ByteEnumField("type", 10, sctpchunktypes),
                   XByteField("flags", None),
                   FieldLenField("len", None, length_of="cookie", adjust=lambda pkt, x:x + 4),  # noqa: E501
                   PadField(StrLenField("cookie", "", length_from=lambda pkt: pkt.len - 4),  # noqa: E501
                            4, padwith=b"\x00"),
                   ]


class SCTPChunkCookieAck(_SCTPChunkGuessPayload, Packet):
    fields_desc = [ByteEnumField("type", 11, sctpchunktypes),
                   XByteField("flags", None),
                   ShortField("len", 4),
                   ]


class SCTPChunkShutdownComplete(_SCTPChunkGuessPayload, Packet):
    fields_desc = [ByteEnumField("type", 14, sctpchunktypes),
                   BitField("reserved", None, 7),
                   BitField("TCB", 0, 1),
                   ShortField("len", 4),
                   ]


class SCTPChunkAuthentication(_SCTPChunkGuessPayload, Packet):
    fields_desc = [ByteEnumField("type", 15, sctpchunktypes),
                   XByteField("flags", None),
                   FieldLenField("len", None, length_of="HMAC",
                                 adjust=lambda pkt, x:x + 8),
                   ShortField("shared_key_id", None),
                   ShortField("HMAC_function", None),
                   PadField(StrLenField("HMAC", "", length_from=lambda pkt: pkt.len - 8),  # noqa: E501
                            4, padwith=b"\x00"),
                   ]


class SCTPChunkAddressConf(_SCTPChunkGuessPayload, Packet):
    fields_desc = [ByteEnumField("type", 0xc1, sctpchunktypes),
                   XByteField("flags", None),
                   FieldLenField("len", None, length_of="params",
                                 adjust=lambda pkt, x:x + 8),
                   IntField("seq", 0),
                   ChunkParamField("params", None, length_from=lambda pkt:pkt.len - 8),  # noqa: E501
                   ]


class SCTPChunkAddressConfAck(SCTPChunkAddressConf):
    type = 0x80


bind_layers(IP, SCTP, proto=IPPROTO_SCTP)
bind_layers(IPerror, SCTPerror, proto=IPPROTO_SCTP)
bind_layers(IPv6, SCTP, nh=IPPROTO_SCTP)
bind_layers(IPerror6, SCTPerror, proto=IPPROTO_SCTP)
