.TH ONEC_SUM 3
.SH NAME
oneC_sum \- One's complement internet checksum
.SH SYNOPSIS
.ft B
.nf
#define _MINIX_SOURCE 1
#include <stddef.h>
#include <sys/types.h>

#include <net/gen/oneCsum.h>

u16_t oneC_sum(u16_t \fIprev\fP, void *\fIdata\fP, size_t \fIsize\fP)
.fi
.ft R
.SH DESCRIPTION
.B OneC_sum
is used to calculate the one's complement checksum needed for IP network
packets.
A good document about the Internet Checksum is RFC-1071 (Computing the
Internet checksum).
.PP
.B OneC_sum
expects three parameters:
.TP 10
.I prev
The checksum of previous blocks of data that are to be included in the
checksum.
The value of prev in first call to oneC_sum should be 0.
.TP
.I data
A pointer to the block of data.
The data is interpreted as a series of 16 bit numbers in network byte order, but
an odd number of bytes is also allowed.
.TP
.I size
The size of the data in bytes.
.SH "SEE ALSO"
.BR ip (4).
.br
.B RFC-1071
.SH AUTHOR
Philip Homburg (philip@cs.vu.nl)
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.\" $PchId: oneC_sum.3,v 1.3 1996/02/22 21:05:31 philip Exp $