libs/asio/example/cpp03/icmp/ipv4_header.hpp

   1 //
   2 // ipv4_header.hpp
   3 // ~~~~~~~~~~~~~~~
   4 //
   5 // Copyright (c) 2003-2017 Christopher M. Kohlhoff (chris at kohlhoff dot com)
   6 //
   7 // Distributed under the Boost Software License, Version 1.0. (See accompanying
   8 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
   9 //
  10
  11 #ifndef IPV4_HEADER_HPP
  12 #define IPV4_HEADER_HPP
  13
  14 #include <algorithm>
  15 #include <boost/asio/ip/address_v4.hpp>
  16
  17 // Packet header for IPv4.
  18 //
  19 // The wire format of an IPv4 header is:
  20 //
  21 // 0               8               16                             31
  22 // +-------+-------+---------------+------------------------------+      ---
  23 // |       |       |               |                              |       ^
  24 // |version|header |    type of    |    total length in bytes     |       |
  25 // |  (4)  | length|    service    |                              |       |
  26 // +-------+-------+---------------+-+-+-+------------------------+       |
  27 // |                               | | | |                        |       |
  28 // |        identification         |0|D|M|    fragment offset     |       |
  29 // |                               | |F|F|                        |       |
  30 // +---------------+---------------+-+-+-+------------------------+       |
  31 // |               |               |                              |       |
  32 // | time to live  |   protocol    |       header checksum        |   20 bytes
  33 // |               |               |                              |       |
  34 // +---------------+---------------+------------------------------+       |
  35 // |                                                              |       |
  36 // |                      source IPv4 address                     |       |
  37 // |                                                              |       |
  38 // +--------------------------------------------------------------+       |
  39 // |                                                              |       |
  40 // |                   destination IPv4 address                   |       |
  41 // |                                                              |       v
  42 // +--------------------------------------------------------------+      ---
  43 // |                                                              |       ^
  44 // |                                                              |       |
  45 // /                        options (if any)                      /    0 - 40
  46 // /                                                              /     bytes
  47 // |                                                              |       |
  48 // |                                                              |       v
  49 // +--------------------------------------------------------------+      ---
  50
  51 class ipv4_header
  52 {
  53 public:
  54   ipv4_header() { std::fill(rep_, rep_ + sizeof(rep_), 0); }
  55
  56   unsigned char version() const { return (rep_[0] >> 4) & 0xF; }
  57   unsigned short header_length() const { return (rep_[0] & 0xF) * 4; }
  58   unsigned char type_of_service() const { return rep_[1]; }
  59   unsigned short total_length() const { return decode(2, 3); }
  60   unsigned short identification() const { return decode(4, 5); }
  61   bool dont_fragment() const { return (rep_[6] & 0x40) != 0; }
  62   bool more_fragments() const { return (rep_[6] & 0x20) != 0; }
  63   unsigned short fragment_offset() const { return decode(6, 7) & 0x1FFF; }
  64   unsigned int time_to_live() const { return rep_[8]; }
  65   unsigned char protocol() const { return rep_[9]; }
  66   unsigned short header_checksum() const { return decode(10, 11); }
  67
  68   boost::asio::ip::address_v4 source_address() const
  69   {
  70     boost::asio::ip::address_v4::bytes_type bytes
  71       = { { rep_[12], rep_[13], rep_[14], rep_[15] } };
  72     return boost::asio::ip::address_v4(bytes);
  73   }
  74
  75   boost::asio::ip::address_v4 destination_address() const
  76   {
  77     boost::asio::ip::address_v4::bytes_type bytes
  78       = { { rep_[16], rep_[17], rep_[18], rep_[19] } };
  79     return boost::asio::ip::address_v4(bytes);
  80   }
  81
  82   friend std::istream& operator>>(std::istream& is, ipv4_header& header)
  83   {
  84     is.read(reinterpret_cast<char*>(header.rep_), 20);
  85     if (header.version() != 4)
  86       is.setstate(std::ios::failbit);
  87     std::streamsize options_length = header.header_length() - 20;
  88     if (options_length < 0 || options_length > 40)
  89       is.setstate(std::ios::failbit);
  90     else
  91       is.read(reinterpret_cast<char*>(header.rep_) + 20, options_length);
  92     return is;
  93   }
  94
  95 private:
  96   unsigned short decode(int a, int b) const
  97     { return (rep_[a] << 8) + rep_[b]; }
  98
  99   unsigned char rep_[60];
 100 };
 101
 102 #endif // IPV4_HEADER_HPP