78 lines
2.9 KiB
Ruby
78 lines
2.9 KiB
Ruby
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# $Id: udp.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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# User Datagram Protocol: UDP
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#
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# RFC768 (http://www.faqs.org/rfcs/rfc768.html)
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class UDP < RacketPart
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# Source Port
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unsigned :src_port, 16
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# Destination Port
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unsigned :dst_port, 16
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# Datagram Length
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unsigned :len, 16
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# Checksum
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unsigned :csum, 16
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# Payload
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rest :payload
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# Check the checksum for this UDP datagram
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def checksum?(src_ip, dst_ip)
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self.csum == 0 || (self.csum == compute_checksum(src_ip, dst_ip))
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end
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# Compute and set the checksum for this UDP datagram
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def checksum!(src_ip, dst_ip)
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# set the checksum to 0 for usage in the pseudo header...
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self.csum = 0
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self.csum = compute_checksum(src_ip, dst_ip)
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end
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# Fix this packet up for proper sending. Sets the length
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# and checksum properly.
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def fix!(src_ip, dst_ip)
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self.len = self.class.bit_length/8 + self.payload.length
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self.checksum!(src_ip, dst_ip)
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end
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def initialize(*args)
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super
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@autofix = false
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end
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private
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# Compute the checksum for this UDP datagram
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def compute_checksum(src_ip, dst_ip)
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# pseudo header used for checksum calculation as per RFC 768
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pseudo = [L3::Misc.ipv42long(src_ip), L3::Misc.ipv42long(dst_ip), 17, self.payload.length + self.class.bit_length/8 ]
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header = [self.src_port, self.dst_port, self.payload.length + self.class.bit_length/8, 0, self.payload]
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L3::Misc.checksum((pseudo << header).flatten.pack("NNnnnnnna*"))
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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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