genode/os/include/net/udp.h
2013-01-10 21:44:47 +01:00

157 lines
3.9 KiB
C++

/*
* \brief User datagram protocol.
* \author Stefan Kalkowski
* \date 2010-08-19
*/
/*
* Copyright (C) 2010-2013 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 _UDP_H_
#define _UDP_H_
/* Genode */
#include <base/exception.h>
#include <base/stdint.h>
#include <util/endian.h>
#include <net/ethernet.h>
#include <net/ipv4.h>
namespace Net {
/**
* The data-layout of this class conforms to an UDP packet (RFC 768).
*
* UDP-header-format:
*
* -----------------------------------------------------------------------
* | source-port | destination-port | length | checksum |
* | 2 bytes | 2 bytes | 2 bytes | 2 bytes |
* -----------------------------------------------------------------------
*/
class Udp_packet
{
private:
/***********************
** UDP header fields **
***********************/
Genode::uint16_t _src_port;
Genode::uint16_t _dst_port;
Genode::uint16_t _length;
Genode::uint16_t _checksum;
unsigned _data[0];
public:
enum Protocol_id { IP_ID = 0x11 };
/**
* Exception used to indicate protocol violation.
*/
class No_udp_packet : Genode::Exception {};
/*****************
** Constructor **
*****************/
Udp_packet(Genode::size_t size) {
/* Udp header needs to fit in */
if (size < sizeof(Udp_packet))
throw No_udp_packet();
}
/******************************
** UDP field read-accessors **
******************************/
Genode::uint16_t src_port() { return bswap(_src_port); }
Genode::uint16_t dst_port() { return bswap(_dst_port); }
Genode::uint16_t length() { return bswap(_length); }
Genode::uint16_t checksum() { return bswap(_checksum); }
void* data() { return &_data; }
/***************
** Operators **
***************/
/**
* Placement new.
*/
void * operator new(Genode::size_t size, void* addr) {
return addr; }
/***************************
** Convenience functions **
***************************/
/**
* UDP checksum is calculated over the udp datagram + an IPv4
* pseudo header.
*
* IPv4 pseudo header:
*
* --------------------------------------------------------------
* | src-ipaddr | dst-ipaddr | zero-field | prot.-id | udp-length |
* | 4 bytes | 4 bytes | 1 byte | 1 byte | 2 bytes |
* --------------------------------------------------------------
*/
void calc_checksum(Ipv4_packet::Ipv4_address src,
Ipv4_packet::Ipv4_address dst)
{
/* have to reset the checksum field for calculation */
_checksum = 0;
/*
* sum up pseudo header
*/
Genode::uint32_t sum = 0;
for (unsigned i = 0; i < Ipv4_packet::ADDR_LEN; i=i+2) {
Genode::uint16_t s = src.addr[i] << 8 | src.addr[i + 1];
Genode::uint16_t d = dst.addr[i] << 8 | dst.addr[i + 1];
sum += s + d;
}
Genode::uint8_t prot[] = { 0, IP_ID };
sum += bswap(*(Genode::uint16_t*)&prot) + length();
/*
* sum up udp packet itself
*/
unsigned max = (length() & 1) ? (length() - 1) : length();
Genode::uint16_t *udp = (Genode::uint16_t*) this;
for (unsigned i = 0; i < max; i=i+2)
sum += bswap(*udp++);
/* if udp length is odd, append a zero byte */
if (length() & 1) {
Genode::uint8_t last[] =
{ *((Genode::uint8_t*)this + (length()-1)), 0 };
sum += bswap(*(Genode::uint16_t*)&last);
}
/*
* keep only the last 16 bits of the 32 bit calculated sum
* and add the carries
*/
while (sum >> 16)
sum = (sum & 0xffff) + (sum >> 16);
/* one's complement of sum */
_checksum = bswap((Genode::uint16_t) ~sum);
}
} __attribute__((packed));
}
#endif /* _UDP_H_ */