5 // Copyright (c) 2003-2017 Christopher M. Kohlhoff (chris at kohlhoff dot com)
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)
11 #ifndef IPV4_HEADER_HPP
12 #define IPV4_HEADER_HPP
15 #include <boost/asio/ip/address_v4.hpp>
17 // Packet header for IPv4.
19 // The wire format of an IPv4 header is:
22 // +-------+-------+---------------+------------------------------+ ---
24 // |version|header | type of | total length in bytes | |
25 // | (4) | length| service | | |
26 // +-------+-------+---------------+-+-+-+------------------------+ |
28 // | identification |0|D|M| fragment offset | |
30 // +---------------+---------------+-+-+-+------------------------+ |
32 // | time to live | protocol | header checksum | 20 bytes
34 // +---------------+---------------+------------------------------+ |
36 // | source IPv4 address | |
38 // +--------------------------------------------------------------+ |
40 // | destination IPv4 address | |
42 // +--------------------------------------------------------------+ ---
45 // / options (if any) / 0 - 40
49 // +--------------------------------------------------------------+ ---
54 ipv4_header() { std::fill(rep_, rep_ + sizeof(rep_), 0); }
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); }
68 boost::asio::ip::address_v4 source_address() const
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);
75 boost::asio::ip::address_v4 destination_address() const
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);
82 friend std::istream& operator>>(std::istream& is, ipv4_header& header)
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);
91 is.read(reinterpret_cast<char*>(header.rep_) + 20, options_length);
96 unsigned short decode(int a, int b) const
97 { return (rep_[a] << 8) + rep_[b]; }
99 unsigned char rep_[60];
102 #endif // IPV4_HEADER_HPP