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* TAP-Win32 -- A kernel driver to provide virtual tap device functionality
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* on Windows. Originally derived from the CIPE-Win32
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* project by Damion K. Wilson, with extensive modifications by
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* All source code which derives from the CIPE-Win32 project is
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* Copyright (C) Damion K. Wilson, 2003, and is released under the
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* GPL version 2 (see below).
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* All other source code is Copyright (C) 2002-2005 OpenVPN Solutions LLC,
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* and is released under the GPL version 2 (see below).
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2
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* as published by the Free Software Foundation.
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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* You should have received a copy of the GNU General Public License
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* along with this program (see the file COPYING included with this
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* distribution); if not, write to the Free Software Foundation, Inc.,
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* 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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HexStringToDecimalInt (const int p_Character)
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if (p_Character >= 'A' && p_Character <= 'F')
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l_Value = (p_Character - 'A') + 10;
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else if (p_Character >= 'a' && p_Character <= 'f')
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l_Value = (p_Character - 'a') + 10;
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else if (p_Character >= '0' && p_Character <= '9')
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l_Value = p_Character - '0';
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ParseMAC (MACADDR dest, const char *src)
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BOOLEAN high_digit = FALSE;
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if (IsMacDelimiter (c))
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mac_index += delim_action;
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else if (IsHexDigit (c))
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const int digit = HexStringToDecimalInt (c);
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if (mac_index < sizeof (MACADDR))
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dest[mac_index] = (char)(digit);
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dest[mac_index] = (char)(dest[mac_index] * 16 + digit);
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return (mac_index + delim_action) >= sizeof (MACADDR);
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* Generate a MAC using the GUID in the adapter name.
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* The mac is constructed as 00:FF:xx:xx:xx:xx where
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* the Xs are taken from the first 32 bits of the GUID in the
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* adapter name. This is similar to the Linux 2.4 tap MAC
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* generator, except linux uses 32 random bits for the Xs.
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* In general, this solution is reasonable for most
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* applications except for very large bridged TAP networks,
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* where the probability of address collisions becomes more
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* Using the well-known "birthday paradox", on a 1000 node
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* network the probability of collision would be
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* 0.000116292153. On a 10,000 node network, the probability
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* of collision would be 0.01157288998621678766.
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VOID GenerateRandomMac (MACADDR mac, const unsigned char *adapter_name)
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unsigned const char *cp = adapter_name;
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unsigned int byte = 0;
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if (i >= sizeof (MACADDR))
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if (IsHexDigit (c) && brace)
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const unsigned int digit = HexStringToDecimalInt (c);
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mac[i++] = (unsigned char) byte;
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VOID GenerateRelatedMAC (MACADDR dest, const MACADDR src, const int delta)
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COPY_MAC (dest, src);
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dest[2] += (UCHAR) delta;