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Optimise checksum fixup routines:

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- npf_fixup16_cksum: 1's complement sum is endian-independent.
- npf_fixup32_cksum: the first 32->16 bit reduction is not needed.

Pointed out by Valery Ushakov.
This commit is contained in:
rmind 2013-11-22 01:48:36 +00:00
parent 1c6c349315
commit 85c1b3a579
1 changed files with 20 additions and 9 deletions
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29
sys/net/npf/npf_inet.c
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@ -1,4 +1,4 @@
/* $NetBSD: npf_inet.c,v 1.26 2013/11/22 01:24:21 rmind Exp $ */
/* $NetBSD: npf_inet.c,v 1.27 2013/11/22 01:48:36 rmind Exp $ */
/*-
* Copyright (c) 2009-2012 The NetBSD Foundation, Inc.
@ -39,7 +39,7 @@
*/
#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: npf_inet.c,v 1.26 2013/11/22 01:24:21 rmind Exp $");
__KERNEL_RCSID(0, "$NetBSD: npf_inet.c,v 1.27 2013/11/22 01:48:36 rmind Exp $");
#include <sys/param.h>
#include <sys/types.h>
@ -60,7 +60,7 @@ __KERNEL_RCSID(0, "$NetBSD: npf_inet.c,v 1.26 2013/11/22 01:24:21 rmind Exp $");
#include "npf_impl.h"
/*
* npf_fixup{16,32}_cksum: update IPv4 checksum.
* npf_fixup{16,32}_cksum: incremental update of the Internet checksum.
*/
uint16_t
@ -71,22 +71,33 @@ npf_fixup16_cksum(uint16_t cksum, uint16_t odatum, uint16_t ndatum)
/*
* RFC 1624:
* HC' = ~(~HC + ~m + m')
*
* Note: 1's complement sum is endian-independent (RFC 1071, page 2).
*/
sum = ~ntohs(cksum) & 0xffff;
sum += (~ntohs(odatum) & 0xffff) + ntohs(ndatum);
sum = ~cksum & 0xffff;
sum += (~odatum & 0xffff) + ndatum;
sum = (sum >> 16) + (sum & 0xffff);
sum += (sum >> 16);
return htons(~sum & 0xffff);
return ~sum & 0xffff;
}
uint16_t
npf_fixup32_cksum(uint16_t cksum, uint32_t odatum, uint32_t ndatum)
{
uint32_t sum;
cksum = npf_fixup16_cksum(cksum, odatum & 0xffff, ndatum & 0xffff);
cksum = npf_fixup16_cksum(cksum, odatum >> 16, ndatum >> 16);
return cksum;
/*
* Checksum 32-bit datum as as two 16-bit. Note, the first
* 32->16 bit reduction is not necessary.
*/
sum = ~cksum & 0xffff;
sum += (~odatum & 0xffff) + (ndatum & 0xffff);
sum += (~odatum >> 16) + (ndatum >> 16);
sum = (sum >> 16) + (sum & 0xffff);
sum += (sum >> 16);
return ~sum & 0xffff;
}
/*