# $Id: sctp.rb 162 2009-12-18 05:12:18Z jhart $
#
# Copyright (c) 2008, Jon Hart 
# All rights reserved.
# 
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions are met:
#     * Redistributions of source code must retain the above copyright
#       notice, this list of conditions and the following disclaimer.
#     * Redistributions in binary form must reproduce the above copyright
#       notice, this list of conditions and the following disclaimer in the
#       documentation and/or other materials provided with the distribution.
#     * Neither the name of the <organization> nor the
#       names of its contributors may be used to endorse or promote products
#       derived from this software without specific prior written permission.
# 
# THIS SOFTWARE IS PROVIDED BY Jon Hart ``AS IS'' AND ANY
# EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
# WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
# DISCLAIMED. IN NO EVENT SHALL Jon Hart BE LIABLE FOR ANY
# DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
# (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
# LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
# ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
# SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
#
module Racket
module L4
# Stream Control Transmission Protocol
#  http://tools.ietf.org/html/rfc4960
class SCTP < RacketPart
  # Source port
  unsigned :src_port, 16
  # Destination port
  unsigned :dst_port, 16
  # Verification tag
  unsigned :verification, 32
  # Checksum
  unsigned :checksum, 32
  rest :payload

  # Add a new SCTP chunk (see http://tools.ietf.org/html/rfc4960)
  def add_chunk(type, flags, length, data)
    @chunks << [ type, flags, length, data ]
  end

  def checksum?
    self.checksum == compute_checksum
  end

  def checksum!
    self.checksum = compute_checksum
  end

  # (really, just set the checksum)
  def fix!
    self.payload = ""
    @chunks.each do |c|
      self.payload += c.pack("CCna*")
    end
    self.checksum!
  end

  def initialize(*args)
    @chunks = []
    super
  end

private
  def compute_checksum
    crc_c = [ 
      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
      ]

    crc32 = ~0
    header = [ self.src_port, self.dst_port, self.verification, 0 ].pack("CCnn")
    (0..header.length-1).each do |b|
      crc32 = (crc32 >> 8) ^ crc_c[(crc32^header[b]) & 0xFF] 
    end

    result = ~crc32

    byte0 = result & 0xff
    byte1 = (result >> 8) & 0xff
    byte2 = (result >> 16) & 0xff
    byte3 = (result >> 24) & 0xff

    crc32 = ((byte0 << 24) |
             (byte1 << 16) |
             (byte2 << 8)  |
             byte3)
  end
end
end
end
# vim: set ts=2 et sw=2:
