d0f5838c61
Apply the style rule that an accessor is named similar to the the underlying value. Provide read and write accessors for each mandatory header attribute. Fix some incorrect structure in the headers like with the flags field in Ipv4_packet. Ref #2490
166 lines
4.4 KiB
C++
166 lines
4.4 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) 2010-2017 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 Affero General Public License version 3.
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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 <net/port.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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/**
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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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** Accessors **
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***************/
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Port src_port() const { return Port(host_to_big_endian(_src_port)); }
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Port dst_port() const { return Port(host_to_big_endian(_dst_port)); }
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Genode::uint16_t length() const { return host_to_big_endian(_length); }
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Genode::uint16_t checksum() const { return host_to_big_endian(_checksum); }
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template <typename T> T const * data() const { return (T const *)(_data); }
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template <typename T> T * data() { return (T *)(_data); }
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void length(Genode::uint16_t v) { _length = host_to_big_endian(v); }
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void src_port(Port p) { _src_port = host_to_big_endian(p.value); }
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void dst_port(Port p) { _dst_port = host_to_big_endian(p.value); }
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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, (Genode::uint8_t)Ipv4_packet::Protocol::UDP };
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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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/*********
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** log **
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*********/
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void print(Genode::Output &output) const;
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} __attribute__((packed));
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#endif /* _UDP_H_ */
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