# oneC_sum(3)

    NAME
         oneC_sum - One's complement internet checksum

    SYNOPSIS
         #define _MINIX_SOURCE 1
         #include <stddef.h>
         #include <sys/types.h>

         #include <net/gen/oneCsum.h>

         u16_t oneC_sum(u16_t prev, void *data, size_t size)

    DESCRIPTION
         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).

         OneC_sum expects three parameters:

         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.

         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.

         size      The size of the data in bytes.

    SEE ALSO
         ip(4).
         RFC-1071

    AUTHOR
         Philip Homburg (philip@cs.vu.nl)