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- //
- // ipv4_header.hpp
- // ~~~~~~~~~~~~~~~
- //
- // Copyright (c) 2003-2019 Christopher M. Kohlhoff (chris at kohlhoff dot com)
- //
- // Distributed under the Boost Software License, Version 1.0. (See accompanying
- // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
- //
- #ifndef IPV4_HEADER_HPP
- #define IPV4_HEADER_HPP
- #include <algorithm>
- #include <boost/asio/ip/address_v4.hpp>
- // Packet header for IPv4.
- //
- // The wire format of an IPv4 header is:
- //
- // 0 8 16 31
- // +-------+-------+---------------+------------------------------+ ---
- // | | | | | ^
- // |version|header | type of | total length in bytes | |
- // | (4) | length| service | | |
- // +-------+-------+---------------+-+-+-+------------------------+ |
- // | | | | | | |
- // | identification |0|D|M| fragment offset | |
- // | | |F|F| | |
- // +---------------+---------------+-+-+-+------------------------+ |
- // | | | | |
- // | time to live | protocol | header checksum | 20 bytes
- // | | | | |
- // +---------------+---------------+------------------------------+ |
- // | | |
- // | source IPv4 address | |
- // | | |
- // +--------------------------------------------------------------+ |
- // | | |
- // | destination IPv4 address | |
- // | | v
- // +--------------------------------------------------------------+ ---
- // | | ^
- // | | |
- // / options (if any) / 0 - 40
- // / / bytes
- // | | |
- // | | v
- // +--------------------------------------------------------------+ ---
- class ipv4_header
- {
- public:
- ipv4_header() { std::fill(rep_, rep_ + sizeof(rep_), 0); }
- unsigned char version() const { return (rep_[0] >> 4) & 0xF; }
- unsigned short header_length() const { return (rep_[0] & 0xF) * 4; }
- unsigned char type_of_service() const { return rep_[1]; }
- unsigned short total_length() const { return decode(2, 3); }
- unsigned short identification() const { return decode(4, 5); }
- bool dont_fragment() const { return (rep_[6] & 0x40) != 0; }
- bool more_fragments() const { return (rep_[6] & 0x20) != 0; }
- unsigned short fragment_offset() const { return decode(6, 7) & 0x1FFF; }
- unsigned int time_to_live() const { return rep_[8]; }
- unsigned char protocol() const { return rep_[9]; }
- unsigned short header_checksum() const { return decode(10, 11); }
- boost::asio::ip::address_v4 source_address() const
- {
- boost::asio::ip::address_v4::bytes_type bytes
- = { { rep_[12], rep_[13], rep_[14], rep_[15] } };
- return boost::asio::ip::address_v4(bytes);
- }
- boost::asio::ip::address_v4 destination_address() const
- {
- boost::asio::ip::address_v4::bytes_type bytes
- = { { rep_[16], rep_[17], rep_[18], rep_[19] } };
- return boost::asio::ip::address_v4(bytes);
- }
- friend std::istream& operator>>(std::istream& is, ipv4_header& header)
- {
- is.read(reinterpret_cast<char*>(header.rep_), 20);
- if (header.version() != 4)
- is.setstate(std::ios::failbit);
- std::streamsize options_length = header.header_length() - 20;
- if (options_length < 0 || options_length > 40)
- is.setstate(std::ios::failbit);
- else
- is.read(reinterpret_cast<char*>(header.rep_) + 20, options_length);
- return is;
- }
- private:
- unsigned short decode(int a, int b) const
- { return (rep_[a] << 8) + rep_[b]; }
- unsigned char rep_[60];
- };
- #endif // IPV4_HEADER_HPP
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