genode/repos/os/include/net/udp.h

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/*
* \brief User datagram protocol.
* \author Stefan Kalkowski
* \date 2010-08-19
*/
/*
* Copyright (C) 2010-2017 Genode Labs GmbH
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*
* This file is part of the Genode OS framework, which is distributed
* under the terms of the GNU Affero General Public License version 3.
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*/
#ifndef _UDP_H_
#define _UDP_H_
/* Genode */
#include <base/exception.h>
#include <base/stdint.h>
#include <net/port.h>
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#include <util/endian.h>
#include <net/ethernet.h>
#include <net/ipv4.h>
namespace Net { class Udp_packet; }
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/**
* 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 Net::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:
struct Bad_data_type : Genode::Exception { };
template <typename T> T const *data(Genode::size_t data_size) const
{
if (data_size < sizeof(T)) {
throw Bad_data_type();
}
return (T const *)(_data);
}
template <typename T> T *data(Genode::size_t data_size)
{
if (data_size < sizeof(T)) {
throw Bad_data_type();
}
return (T *)(_data);
}
/***************
** Accessors **
***************/
Port src_port() const { return Port(host_to_big_endian(_src_port)); }
Port dst_port() const { return Port(host_to_big_endian(_dst_port)); }
Genode::uint16_t length() const { return host_to_big_endian(_length); }
Genode::uint16_t checksum() const { return host_to_big_endian(_checksum); }
void length(Genode::uint16_t v) { _length = host_to_big_endian(v); }
void src_port(Port p) { _src_port = host_to_big_endian(p.value); }
void dst_port(Port p) { _dst_port = host_to_big_endian(p.value); }
/***************
** Operators **
***************/
/**
* Placement new.
*/
void * operator new(__SIZE_TYPE__, 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 update_checksum(Ipv4_address src,
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;
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}
Genode::uint8_t prot[] = { 0, (Genode::uint8_t)Ipv4_packet::Protocol::UDP };
sum += host_to_big_endian(*(Genode::uint16_t*)&prot) + length();
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/*
* sum up udp packet itself
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*/
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 += host_to_big_endian(*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 += host_to_big_endian(*(Genode::uint16_t*)&last);
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}
/*
* 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 = host_to_big_endian((Genode::uint16_t) ~sum);
}
/*********
** log **
*********/
void print(Genode::Output &output) const;
} __attribute__((packed));
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#endif /* _UDP_H_ */