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161 lines
4.1 KiB
C++
161 lines
4.1 KiB
C++
/*
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* \brief User datagram protocol.
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* \author Stefan Kalkowski
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* \date 2010-08-19
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*/
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/*
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* Copyright (C) 2010-2013 Genode Labs GmbH
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*
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* This file is part of the Genode OS framework, which is distributed
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* under the terms of the GNU General Public License version 2.
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*/
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#ifndef _UDP_H_
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#define _UDP_H_
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/* Genode */
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#include <base/exception.h>
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#include <base/stdint.h>
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#include <util/endian.h>
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#include <net/ethernet.h>
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#include <net/ipv4.h>
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namespace Net { class Udp_packet; }
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/**
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* Data layout of this class conforms to an UDP packet (RFC 768)
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*
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* UDP-header-format:
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*
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* -----------------------------------------------------------------------
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* | source-port | destination-port | length | checksum |
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* | 2 bytes | 2 bytes | 2 bytes | 2 bytes |
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* -----------------------------------------------------------------------
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*/
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class Net::Udp_packet
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{
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private:
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/***********************
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** UDP header fields **
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***********************/
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Genode::uint16_t _src_port;
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Genode::uint16_t _dst_port;
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Genode::uint16_t _length;
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Genode::uint16_t _checksum;
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unsigned _data[0];
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public:
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enum Protocol_id { IP_ID = 0x11 };
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/**
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* Exception used to indicate protocol violation.
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*/
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class No_udp_packet : Genode::Exception {};
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/*****************
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** Constructor **
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*****************/
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Udp_packet(Genode::size_t size) {
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/* Udp header needs to fit in */
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if (size < sizeof(Udp_packet))
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throw No_udp_packet();
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}
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/******************************
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** UDP field read-accessors **
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******************************/
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Genode::uint16_t src_port() { return host_to_big_endian(_src_port); }
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Genode::uint16_t dst_port() { return host_to_big_endian(_dst_port); }
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Genode::uint16_t length() { return host_to_big_endian(_length); }
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Genode::uint16_t checksum() { return host_to_big_endian(_checksum); }
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void src_port(Genode::uint16_t p) { _src_port = host_to_big_endian(p); }
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void dst_port(Genode::uint16_t p) { _dst_port = host_to_big_endian(p); }
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template <typename T> T * data() { return (T *)(_data); }
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template <typename T> T const * data() const { return (T const *)(_data); }
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/***************
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** Operators **
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***************/
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/**
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* Placement new.
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*/
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void * operator new(__SIZE_TYPE__, void* addr) { return addr; }
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/***************************
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** Convenience functions **
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***************************/
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/**
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* UDP checksum is calculated over the udp datagram + an IPv4
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* pseudo header.
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*
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* IPv4 pseudo header:
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*
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* --------------------------------------------------------------
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* | src-ipaddr | dst-ipaddr | zero-field | prot.-id | udp-length |
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* | 4 bytes | 4 bytes | 1 byte | 1 byte | 2 bytes |
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* --------------------------------------------------------------
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*/
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void update_checksum(Ipv4_address src,
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Ipv4_address dst)
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{
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/* have to reset the checksum field for calculation */
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_checksum = 0;
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/*
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* sum up pseudo header
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*/
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Genode::uint32_t sum = 0;
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for (unsigned i = 0; i < Ipv4_packet::ADDR_LEN; i=i+2) {
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Genode::uint16_t s = src.addr[i] << 8 | src.addr[i + 1];
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Genode::uint16_t d = dst.addr[i] << 8 | dst.addr[i + 1];
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sum += s + d;
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}
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Genode::uint8_t prot[] = { 0, IP_ID };
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sum += host_to_big_endian(*(Genode::uint16_t*)&prot) + length();
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/*
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* sum up udp packet itself
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*/
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unsigned max = (length() & 1) ? (length() - 1) : length();
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Genode::uint16_t *udp = (Genode::uint16_t*) this;
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for (unsigned i = 0; i < max; i=i+2)
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sum += host_to_big_endian(*udp++);
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/* if udp length is odd, append a zero byte */
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if (length() & 1) {
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Genode::uint8_t last[] =
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{ *((Genode::uint8_t*)this + (length()-1)), 0 };
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sum += host_to_big_endian(*(Genode::uint16_t*)&last);
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}
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/*
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* keep only the last 16 bits of the 32 bit calculated sum
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* and add the carries
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*/
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while (sum >> 16)
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sum = (sum & 0xffff) + (sum >> 16);
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/* one's complement of sum */
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_checksum = host_to_big_endian((Genode::uint16_t) ~sum);
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}
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} __attribute__((packed));
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#endif /* _UDP_H_ */
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