doc/html/boost_asio/example/cpp03/icmp/ipv4_header.hpp
//
// ipv4_header.hpp
// ~~~~~~~~~~~~~~~
//
// Copyright (c) 2003-2023 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