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 check-
     sum).

     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 net-
               work 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)