netinet: Deduplicate most in_cksum() implementations
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Authored by markj on Nov 23 2021, 2:29 PM.

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manu
kp
glebius

Group Reviewers

network

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rGecbbe831445a: netinet: Deduplicate most in_cksum() implementations

Summary

in_cksum() and related routines are implemented separately for each
platform, but only i386 and arm have optimized versions. Other
platforms' copies of in_cksum.c are identical except for style
differences and support for big-endian CPUs.

Deduplicate the implementations for the rest of the platforms. This
will make it easier to implement in_cksum() for unmapped mbufs. On arm
and i386, define HAVE_MD_IN_CKSUM to mean that the MI implementation is
not to be compiled.

No functional change intended.

MFC after: 1 week
Sponsored by: The FreeBSD Foundation

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Repository

rG FreeBSD src repository

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Tests Not Applicable

Event Timeline

markj created this revision.Nov 23 2021, 2:29 PM

Herald added a reviewer: manu. · View Herald TranscriptNov 23 2021, 2:29 PM

Herald added subscribers: glebius, melifaro, jhibbits and 3 others. · View Herald Transcript

markj requested review of this revision.Nov 23 2021, 2:29 PM

Harbormaster completed remote builds in B42936: Diff 98874.Nov 23 2021, 2:29 PM

markj added a parent revision: D33094: netinet: Remove in_cksum.c.Nov 23 2021, 2:30 PM

markj added a child revision: D33096: netinet: Implement in_cksum_skip() using m_apply().

kp accepted this revision as: kp.Nov 23 2021, 4:34 PM

This revision is now accepted and ready to land.Nov 23 2021, 4:34 PM

P.S., I spent some time trying to replace this implementation with an updated one from NetBSD. Theirs is easier to read and is licensed under BSD 2-clause. It got somewhat messy, though, and wasn't important to my immediate goal, so I dropped it. I think there's also some room for micro-optimizations here, for instance in_pseudo() and in_addword() should probably be inlines. in_pseudo() in particular is dead simple, it's just a ones complement sum:

static inline uint16_t
in_addword(uint16_t a, uint16_t b)
{
    uint32_t sum;

    sum = (uint32_t)a + b;
    return ((sum >> 16) + (sum & 0xffff));
}

in_pseudo() is similar. If anyone's interested in working further on this, I'm happy to help.

glebius accepted this revision.Nov 23 2021, 8:31 PM

Closed by commit rGecbbe831445a: netinet: Deduplicate most in_cksum() implementations (authored by markj). · Explain WhyNov 24 2021, 6:40 PM

This revision was automatically updated to reflect the committed changes.

markj added a commit: rGecbbe831445a: netinet: Deduplicate most in_cksum() implementations.