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52e8c95321
With the update to GCC 10 the compiler used to warn when using the internet
checksum functions on packet classes (like in
Net::Ipv4_packet::update_checksum):
warning: converting a packed ‘Net::[PACKET_CLASS]’ pointer
(alignment 1) to a ‘const uint16_t’ {aka ‘const short
unsigned int’} pointer (alignment 2) may result in an
unaligned pointer value
Apparently, the 'packed' attribute normally used on packet classes sets the
alignment of the packet class to 1. However, for the purpose of the
internet-checksum functions, we can assume that the packet data has no
alignment. This is expressed by casting the packet-object pointer to a pointer
of the new packed helper struct 'Packed_uint16' that contains only a single
uint16_t member before handing it over to the checksum function (instead of
casting it to a uint16_t pointer).
Ref #4109
58 lines
2.0 KiB
C++
58 lines
2.0 KiB
C++
/*
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* \brief Computing the Internet Checksum (conforms to RFC 1071)
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* \author Martin Stein
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* \date 2018-03-23
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*/
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/*
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* Copyright (C) 2018 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 _NET__INTERNET_CHECKSUM_H_
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#define _NET__INTERNET_CHECKSUM_H_
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/* Genode includes */
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#include <net/ipv4.h>
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#include <base/stdint.h>
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namespace Net {
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/**
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* This struct helps avoiding the following compiler warning when using
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* the internet checksum functions on packet classes (like
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* Net::Ipv4_packet):
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*
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* warning: converting a packed ‘Net::[PACKET_CLASS]’ pointer
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* (alignment 1) to a ‘const uint16_t’ {aka ‘const short
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* unsigned int’} pointer (alignment 2) may result in an
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* unaligned pointer value
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*
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* Apparently, the 'packed' attribute normally used on packet classes sets
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* the alignment of the packet class to 1. However, for the purpose of the
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* internet-checksum functions, we can assume that the packet data has no
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* alignment. This is expressed by casting the packet-object pointer to a
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* Packed_uint16 pointer instead of a uint16_t pointer.
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*/
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struct Packed_uint16
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{
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Genode::uint16_t value;
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} __attribute__((packed));
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Genode::uint16_t internet_checksum(Packed_uint16 const *addr,
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Genode::size_t size,
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Genode::addr_t init_sum = 0);
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Genode::uint16_t internet_checksum_pseudo_ip(Packed_uint16 const *addr,
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Genode::size_t size,
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Genode::uint16_t size_be,
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Ipv4_packet::Protocol ip_prot,
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Ipv4_address &ip_src,
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Ipv4_address &ip_dst);
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}
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#endif /* _NET__INTERNET_CHECKSUM_H_ */
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