mirror of
https://github.com/OpenVPN/openvpn3.git
synced 2024-09-20 12:12:15 +02:00
84 lines
2.5 KiB
C++
84 lines
2.5 KiB
C++
// OpenVPN -- An application to securely tunnel IP networks
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// over a single port, with support for SSL/TLS-based
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// session authentication and key exchange,
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// packet encryption, packet authentication, and
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// packet compression.
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//
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// Copyright (C) 2012-2016 OpenVPN Technologies, Inc.
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//
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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 3
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// as published by the Free Software Foundation.
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//
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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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//
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// You should have received a copy of the GNU General Public License
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// along with this program in the COPYING file.
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// If not, see <http://www.gnu.org/licenses/>.
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// Define the UDP header
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#ifndef OPENVPN_IP_UDP_H
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#define OPENVPN_IP_UDP_H
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#include <openvpn/ip/ip.hpp>
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namespace openvpn {
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#pragma pack(push)
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#pragma pack(1)
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struct UDPHeader {
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std::uint16_t source;
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std::uint16_t dest;
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std::uint16_t len;
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std::uint16_t check;
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};
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#pragma pack(pop)
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inline std::uint16_t udp_checksum (const std::uint8_t *buf,
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const unsigned int len_udp,
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const std::uint8_t *src_addr,
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const std::uint8_t *dest_addr)
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{
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std::uint32_t sum = 0;
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/* make 16 bit words out of every two adjacent 8 bit words and */
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/* calculate the sum of all 16 bit words */
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for (unsigned int i = 0; i < len_udp; i += 2)
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{
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std::uint16_t word16 = ((buf[i] << 8) & 0xFF00) + ((i + 1 < len_udp) ? (buf[i+1] & 0xFF) : 0);
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sum += word16;
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}
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/* add the UDP pseudo header which contains the IP source and destination addresses */
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for (unsigned int i = 0; i < 4; i += 2)
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{
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std::uint16_t word16 =((src_addr[i] << 8) & 0xFF00) + (src_addr[i+1] & 0xFF);
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sum += word16;
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}
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for (unsigned int i = 0; i < 4; i += 2)
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{
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std::uint16_t word16 =((dest_addr[i] << 8) & 0xFF00) + (dest_addr[i+1] & 0xFF);
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sum += word16;
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}
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/* the protocol number and the length of the UDP packet */
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sum += (std::uint16_t)IPHeader::UDP + (std::uint16_t)len_udp;
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/* keep only the last 16 bits of the 32 bit calculated sum and add the carries */
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while (sum >> 16)
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sum = (sum & 0xFFFF) + (sum >> 16);
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/* take the one's complement of sum */
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return std::uint16_t(~sum);
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}
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}
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#endif
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