Class TCP
In: lib/l4/tcp.rb  (CVS)
Parent: RacketPart

$Id: tcp.rb 14 2008-03-02 05:42:30Z warchild $

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.

Transmission Control Protocol: TCP

RFC793 (www.faqs.org/rfcs/rfc793.html)

Methods

add_option   checksum!   checksum?   fix!   new  

Attributes

ack    Acknowledgement number
csum    Checksum
dst_port    Destination port
flag_ack    ACK
flag_cwr    CWR
flag_ece    ECE
flag_fin    FIN
flag_psh    PSH
flag_rst    RST
flag_syn    SYN
flag_urg    URG
offset    Data Offset
payload    Payload
reserved    Reserved
seq    Sequence number
src_port    Source port
urg    Urgent pointer
window    Window size

Public Class methods

new(*args)

[Source]

# File lib/l4/tcp.rb, line 109
  def initialize(*args)
    @options = []
    super
    @autofix = false
  end

Public Instance methods

add_option(number, value)

Add an TCP option to this TCP object. All rejiggering will happen when the call to fix! happens automagically.

[Source]

# File lib/l4/tcp.rb, line 72
  def add_option(number, value)
    t = TLV.new(1,1)
    t.type = number
    t.value = value
    t.length = value.length + 2
    @options << t.encode
  end
checksum!(ip_src, ip_dst)

Compute and set the checksum for this TCP packet

[Source]

# File lib/l4/tcp.rb, line 86
  def checksum!(ip_src, ip_dst)
    self.csum = compute_checksum(ip_src, ip_dst)
  end
checksum?(ip_src, ip_dst)

Check the checksum for this TCP packet

[Source]

# File lib/l4/tcp.rb, line 81
  def checksum?(ip_src, ip_dst)
    self.csum == compute_checksum(ip_src, ip_dst)
  end
fix!(ip_src, ip_dst, next_payload)

Fix this packet up for proper sending. Sets the length and checksum properly.

[Source]

# File lib/l4/tcp.rb, line 92
  def fix!(ip_src, ip_dst, next_payload)
    newpayload = @options.join
    
    # pad to a multiple of 32 bits
    if ((self.class.bit_length/8 + newpayload.length) % 4 != 0) 
      # fill the beginning as needed with NOPs
      while ((self.class.bit_length/8 + newpayload.length) % 4 != 4)
        newpayload = "\x01#{newpayload}"
      end
    end

    self.payload = newpayload + self.payload + next_payload
    self.offset = self.class.bit_length/32 + newpayload.length/4
    self.checksum!(ip_src, ip_dst)
    self.payload = newpayload
  end

[Validate]