| // |
| // ipv4_header.hpp |
| // ~~~~~~~~~~~~~~~ |
| // |
| // Copyright (c) 2003-2010 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 |
