80 lines
2.7 KiB
Ruby
80 lines
2.7 KiB
Ruby
# $Id: igmpv1.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 L4
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# Internet Group Management Protocol, Version 1
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#
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# RFC1112 (http://www.faqs.org/rfcs/rfc1112.html)
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#
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class IGMPv1 < RacketPart
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# Version (defaults to 1)
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unsigned :version, 4, { :default => 1 }
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# Type
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unsigned :type, 4
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# Unused
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unsigned :unused, 8
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# Checksum
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unsigned :checksum, 16
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# Group Address
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octets :gaddr, 32
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# Payload
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rest :payload
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# Check the checksum for this IGMP message
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def checksum?
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self.checksum == 0 || (self.checksum == compute_checksum)
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end
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# Compute and set the checkum for this IGMP message
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def checksum!
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self.checksum = compute_checksum
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end
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# Do whatever 'fixing' is neccessary in preparation
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# for being sent
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def fix!
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self.checksum!
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end
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private
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def compute_checksum
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# The checksum is the 16-bit one's complement of the one's complement sum
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# of the 8-octet IGMP message. For computing the checksum, the checksum
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# field is zeroed.
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tmp = []
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tmp << ((((self.version << 4) | self.type) << 8) | self.unused)
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tmp << 0
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tmp << L3::Misc.ipv42long(self.gaddr)
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tmp << self.payload
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L3::Misc.checksum(tmp.pack("nnNa*"))
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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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