133 lines
4.1 KiB
Ruby
133 lines
4.1 KiB
Ruby
# $Id: ipv4.rb 14 2008-03-02 05:42:30Z warchild $
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#
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# Copyright (c) 2008, Jon Hart
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# All rights reserved.
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#
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# Redistribution and use in source and binary forms, with or without
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# modification, are permitted provided that the following conditions are met:
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# * Redistributions of source code must retain the above copyright
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# notice, this list of conditions and the following disclaimer.
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# * Redistributions in binary form must reproduce the above copyright
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# notice, this list of conditions and the following disclaimer in the
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# documentation and/or other materials provided with the distribution.
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# * Neither the name of the <organization> nor the
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# names of its contributors may be used to endorse or promote products
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# derived from this software without specific prior written permission.
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#
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# THIS SOFTWARE IS PROVIDED BY Jon Hart ``AS IS'' AND ANY
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# EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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# WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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# DISCLAIMED. IN NO EVENT SHALL Jon Hart BE LIABLE FOR ANY
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# DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
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# (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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# LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
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# ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
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# SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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#
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module Racket
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module L3
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# Internet Protcol Version 4 (IPV4)
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#
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# RFC791 (http://www.ietf.org/rfc/rfc791.txt)
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class IPv4 < RacketPart
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# Version (defaults to 4)
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unsigned :version, 4, { :default => 4 }
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# Header length in multiples of 4 octets (defaults to 5)
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unsigned :hlen, 4, { :default => 5 }
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# Type of Service
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unsigned :tos, 8
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# Datagram length
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unsigned :len, 16
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# Identifier
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unsigned :id, 16
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# Flags
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unsigned :flags, 3
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# Fragmentation offset
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unsigned :foffset, 13
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# Time-to-live
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unsigned :ttl, 8
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# Protocol
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unsigned :protocol, 8
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# Checksum
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unsigned :checksum, 16, "Checksum"
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# Source IP address, passed as four octets separated by periods
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# (192.168.1.2)
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octets :src_ip, 32
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# Destination IP address, passed as four octets separated by periods
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# (192.168.1.2)
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octets :dst_ip, 32
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# Payload
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rest :payload
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def initialize(*args)
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@options = []
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super
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end
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# Add an IPv4 option to this IPv4 object.
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# All rejiggering will happen when the call to fix!
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# happens automagically
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def add_option(number, value)
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t = Misc::TLV.new(1,1)
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t.type = number
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t.value = value
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t.length = value.length + 2
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@options << t.encode
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end
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# Check the checksum for this IP datagram
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def checksum?
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self.checksum == compute_checksum
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end
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# Compute and set the checksum for this IP datagram
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def checksum!
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self.checksum = compute_checksum
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end
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# Perform all the niceties necessary prior to sending
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# this IP datagram out. Append the options, update len and hlen,
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# and fix the checksum.
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def fix!
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newpayload = @options.join
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# pad to a multiple of 32 bits
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if (newpayload.length % 4 != 0)
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# fill the beginning as needed with NOPs
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while (newpayload.length % 4 != 3)
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newpayload = "\x01#{newpayload}"
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end
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# make sure the last byte is an EOL
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if (newpayload.length % 4 == 3)
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newpayload += "\x00"
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end
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end
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self.payload = newpayload + self.payload
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self.hlen += newpayload.length/4
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self.len = self.payload.length + self.class.bit_length/8
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self.checksum!
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end
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private
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# Compute the checksum for this IP datagram
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def compute_checksum
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pseudo = []
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pseudo << ((((self.version << 4) | self.hlen) << 8) | self.tos)
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pseudo << self.len
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pseudo << self.id
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pseudo << ((self.flags << 13) | self.foffset)
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pseudo << ((self.ttl << 8) | self.protocol)
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pseudo << 0
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pseudo << L3::Misc.ipv42long(self.src_ip)
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pseudo << L3::Misc.ipv42long(self.dst_ip)
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L3::Misc.checksum(pseudo.pack("nnnnnnNN"))
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end
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end
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end
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end
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# vim: set ts=2 et sw=2:
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