/*
 * \brief  Internet protocol version 4.
 * \author Stefan Kalkowski
 * \date   2010-08-19
 */

/*
 * Copyright (C) 2010-2012 Genode Labs GmbH
 *
 * This file is part of the Genode OS framework, which is distributed
 * under the terms of the GNU General Public License version 2.
 */

#ifndef _IPV4_H_
#define _IPV4_H_

/* Genode */
#include <base/exception.h>
#include <util/string.h>

#include <util/endian.h>
#include <net/netaddress.h>

namespace Net {

	/**
	 * The data-layout of this class conforms to an IPv4 packet (RFC 791).
	 *
	 * IPv4-header-format:
	 *
	 *  ----------------------------------------------------------------
	 * |   0-3   |  4-7  | 8-11 | 12-15 | 16-18 | 19-23 | 24-27 | 28-31 |
	 *  ----------------------------------------------------------------
	 * | version |  IHL  | service-type |         total-length          |
	 *  ----------------------------------------------------------------
	 * |         identifikation         | flags |     fragment-offset   |
	 *  ----------------------------------------------------------------
	 * |        ttl      |   protocol   |       header-checksum         |
	 *  ----------------------------------------------------------------
	 * |                       source-ip-address                        |
	 *  ----------------------------------------------------------------
	 * |                     destination-ip-address                     |
	 *  ----------------------------------------------------------------
	 * |                            options ...                         |
	 *  ----------------------------------------------------------------
	 */
	class Ipv4_packet
	{
		public:

			enum Size {
				ADDR_LEN = 4, /* Ip address length in bytes */
			};

			typedef Network_address<ADDR_LEN> Ipv4_address;

			static const Ipv4_address CURRENT;    /* current network   */
			static const Ipv4_address BROADCAST;  /* broadcast address */

		private:

			/************************
			 ** IPv4 header fields **
			 ************************/

			unsigned         _version         : 4;
			unsigned         _header_length   : 4;
			Genode::uint8_t  _diff_service;
			Genode::uint16_t _total_length;
			Genode::uint16_t _identification;
			unsigned         _flags           : 3;
			unsigned         _fragment_offset : 13;
			Genode::uint8_t  _time_to_live;
			Genode::uint8_t  _protocol;
			Genode::uint16_t _header_checksum;
			Genode::uint8_t  _src_addr[ADDR_LEN];
			Genode::uint8_t  _dst_addr[ADDR_LEN];
			unsigned         _data[0];

			/**
			 * Bitmasks for differentiated services field.
			 */
			enum Differentiated_services {
				PRECEDENCE  = 0x7,
				DELAY       = 0x8,
				THROUGHPUT  = 0x10,
				RELIABILITY = 0x20,
				COST        = 0x40
			};

		public:

			enum Precedence {
				NETWORK_CONTROL      = 7,
				INTERNETWORK_CONTROL = 6,
				CRITIC_ECP           = 5,
				FLASH_OVERRIDE       = 4,
				FLASH                = 3,
				IMMEDIATE            = 2,
				PRIORITY             = 1,
				ROUTINE              = 0
			};

			enum Flags {
				NO_FRAGMENT    = 0x2,
				MORE_FRAGMENTS = 0x4
			};


			/**
			 * Exception used to indicate protocol violation.
			 */
			class No_ip_packet : Genode::Exception {};


			/*****************
			 ** Constructor **
			 *****************/

			Ipv4_packet(Genode::size_t size) {
				/* ip header needs to fit in */
				if (size < sizeof(Ipv4_packet))
					throw No_ip_packet();
			}


			/*******************************
			 ** IPv4 field read-accessors **
			 *******************************/

			Genode::size_t  version()     { return _version;                   }
			Genode::size_t  header_length() { return _header_length / 4;       }
			Genode::uint8_t precedence()  { return _diff_service & PRECEDENCE; }

			bool low_delay()              { return _diff_service & DELAY;      }
			bool high_throughput()        { return _diff_service & THROUGHPUT; }
			bool high_reliability()       { return _diff_service & RELIABILITY;}
			bool minimize_monetary_cost() { return _diff_service & COST;       }

			Genode::uint16_t total_length()   { return bswap(_total_length);   }
			Genode::uint16_t identification() { return bswap(_identification); }

			bool no_fragmentation() { return _flags & NO_FRAGMENT;             }
			bool more_fragments()   { return _flags & MORE_FRAGMENTS;          }

			Genode::size_t   fragment_offset() { return _fragment_offset;      }
			Genode::uint8_t  time_to_live()    { return _time_to_live;         }
			Genode::uint8_t  protocol()        { return _protocol;             }

			Genode::uint16_t checksum() { return bswap(_header_checksum);      }

			Ipv4_address dst() { return Ipv4_address(&_dst_addr); }
			Ipv4_address src() { return Ipv4_address(&_src_addr); }

			void *data() { return &_data; }


			/***************
			 ** Operators **
			 ***************/

			/**
			 * Placement new.
			 */
			void * operator new(Genode::size_t size, void* addr) {
				return addr; }

	} __attribute__((packed));
}

#endif /* _IPV4_H_ */