The checksums for forwarded/routed UDP, TCP and ICMP, used to be always
re-calculated from scratch in the NIC router although the router changes only
a few packet fields. This commit replaces the old approach whereever sensible
with an algorithm for incremental checksum updates suggested in RFC 1071.
The goal is to improve router performance.
Ref #4555
The checksums for forwarded/routed IPv4, used to be always re-calculated from
scratch in the NIC router although the router changes only a few packet fields.
This commit replaces the old approach whereever sensible with an algorithm for
incremental checksum updates suggested in RFC 1071. The goal is to improve
router performance.
Ref #4555
Prevent public reflection of the only internally used 'init_sum' argument in
'uint16_t internet_checksum(...)' that, in addition, added a default value to
the function interface.
Ref #4555
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
This reduces the redundant implementations of checksum calculation to
one generic implementation, makes the checksum interface conform over
all protocols, and brings performance optimizations. For instance,
the checksum is now calculated directly in big endian which saves us
most of the previously done byte-re-ordering.
Issue #2775
