doc/html/boost_asio/example/cpp03/icmp/icmp_header.hpp
//
// icmp_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 ICMP_HEADER_HPP
#define ICMP_HEADER_HPP
#include <istream>
#include <ostream>
#include <algorithm>
// ICMP header for both IPv4 and IPv6.
//
// The wire format of an ICMP header is:
//
// 0 8 16 31
// +---------------+---------------+------------------------------+ ---
// | | | | ^
// | type | code | checksum | |
// | | | | |
// +---------------+---------------+------------------------------+ 8 bytes
// | | | |
// | identifier | sequence number | |
// | | | v
// +-------------------------------+------------------------------+ ---
class icmp_header
{
public:
enum { echo_reply = 0, destination_unreachable = 3, source_quench = 4,
redirect = 5, echo_request = 8, time_exceeded = 11, parameter_problem = 12,
timestamp_request = 13, timestamp_reply = 14, info_request = 15,
info_reply = 16, address_request = 17, address_reply = 18 };
icmp_header() { std::fill(rep_, rep_ + sizeof(rep_), 0); }
unsigned char type() const { return rep_[0]; }
unsigned char code() const { return rep_[1]; }
unsigned short checksum() const { return decode(2, 3); }
unsigned short identifier() const { return decode(4, 5); }
unsigned short sequence_number() const { return decode(6, 7); }
void type(unsigned char n) { rep_[0] = n; }
void code(unsigned char n) { rep_[1] = n; }
void checksum(unsigned short n) { encode(2, 3, n); }
void identifier(unsigned short n) { encode(4, 5, n); }
void sequence_number(unsigned short n) { encode(6, 7, n); }
friend std::istream& operator>>(std::istream& is, icmp_header& header)
{ return is.read(reinterpret_cast<char*>(header.rep_), 8); }
friend std::ostream& operator<<(std::ostream& os, const icmp_header& header)
{ return os.write(reinterpret_cast<const char*>(header.rep_), 8); }
private:
unsigned short decode(int a, int b) const
{ return (rep_[a] << 8) + rep_[b]; }
void encode(int a, int b, unsigned short n)
{
rep_[a] = static_cast<unsigned char>(n >> 8);
rep_[b] = static_cast<unsigned char>(n & 0xFF);
}
unsigned char rep_[8];
};
template <typename Iterator>
void compute_checksum(icmp_header& header,
Iterator body_begin, Iterator body_end)
{
unsigned int sum = (header.type() << 8) + header.code()
+ header.identifier() + header.sequence_number();
Iterator body_iter = body_begin;
while (body_iter != body_end)
{
sum += (static_cast<unsigned char>(*body_iter++) << 8);
if (body_iter != body_end)
sum += static_cast<unsigned char>(*body_iter++);
}
sum = (sum >> 16) + (sum & 0xFFFF);
sum += (sum >> 16);
header.checksum(static_cast<unsigned short>(~sum));
}
#endif // ICMP_HEADER_HPP