| 1 | #!/usr/bin/env python |
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| 2 | # -*- coding: utf-8 -*- |
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| 3 | |
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| 4 | # Copyright (C) 2008 Adriano Monteiro Marques. |
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| 5 | # |
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| 6 | # Author: Bartosz SKOWRON <getxsick at gmail dot com> |
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| 7 | # |
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| 8 | # This library is free software; you can redistribute it and/or modify |
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| 9 | # it under the terms of the GNU Lesser General Public License as published |
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| 10 | # by the Free Software Foundation; either version 2.1 of the License, or |
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| 11 | # (at your option) any later version. |
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| 12 | # |
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| 13 | # This library is distributed in the hope that it will be useful, but |
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| 14 | # WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY |
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| 15 | # or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public |
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| 16 | # License for more details. |
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| 17 | # |
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| 18 | # You should have received a copy of the GNU Lesser General Public License |
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| 19 | # along with this library; if not, write to the Free Software Foundation, |
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| 20 | # Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA |
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| 21 | |
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| 22 | from umpa.protocols._protocols import Protocol |
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| 23 | from umpa.protocols.IP import IP |
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| 24 | from umpa.protocols._fields import * |
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| 25 | |
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| 26 | class Layer4ChecksumField(IntField): |
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| 27 | bits = 16 |
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| 28 | auto = True |
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| 29 | def _generate_value(self): |
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| 30 | return 0 |
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| 31 | |
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| 32 | class PseudoHeader(Protocol): |
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| 33 | """This is class is useful for some protocols like TCP or UDP. |
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| 34 | It has been used to calculate checksum of those protocols. |
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| 35 | It's prefixed to the protocol header before calculating. |
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| 36 | """ |
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| 37 | _ordered_fields = ('source_address', 'destination_address', 'reserved', |
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| 38 | 'protocol_id', 'total_length') |
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| 39 | |
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| 40 | def __init__(self, protocol_id, total_length): |
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| 41 | |
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| 42 | fields_list = [ IPv4AddrField("Source Address"), |
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| 43 | IPv4AddrField("Destination Address"), |
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| 44 | IntField("Reserved", 0, bits=8), |
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| 45 | IntField("Protocol", protocol_id, bits=8), |
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| 46 | IntField("Total Length", total_length, bits=16) ] |
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| 47 | super(PseudoHeader, self).__init__(fields_list) |
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| 48 | |
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| 49 | def _pre_raw(self, raw_value, bit, protocol_container, protocol_bits): |
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| 50 | # we assign first localhost becuase if there is not IP instance |
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| 51 | # than better 0 than nothing (for nonstrict users) |
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| 52 | self.source_address = "127.0.0.1" |
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| 53 | self.destination_address = "127.0.0.1" |
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| 54 | # grabbing informations from IP's header |
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| 55 | it = iter(protocol_container) |
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| 56 | for proto in it: |
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| 57 | if isinstance(proto,IP): |
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| 58 | self.source_address = proto.source_address |
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| 59 | self.destination_address = proto.destination_address |
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| 60 | break |
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| 61 | |
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| 62 | return raw_value, bit |
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| 63 | |
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| 64 | def _post_raw(self, raw_value, bit, protocol_container, protocol_bits): |
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| 65 | return raw_value, bit |
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