Parses received option extension headers.
    Format
      #include  <in6.h>
      int inet6_opt_next  ( void *extbuf, size_t extlen, int
                          offset, uint8_t *typep, size_t *lenp, void
                          **databufp );

1  –  Arguments

 extbuf
    Points to a buffer that contains an extension header.
 extlen
    Specifies the length, in bytes, of the extension header.
 offset
    Specifies the location in the extension header of an option.
    Valid values are either 0 for the first option or the length
    returned from a previous call to either inet6_opt_next() or
    inet6_opt_find().
 typep
    Points to the type of the option found.
 lenp
    Points to the length of the option found.
 databufp
    Points to the option data.

2  –  Description

    This function parses a received option extension header and
    returns the next option. In addition, it returns an offset to
    the next option that you specify in the offset parameter to
    subsequent calls to inet6_opt_next().
    This function does not return any PAD1 or PADN options.

3  –  Return Values

    x                  Upon successful completion, the inet6_opt_
                       next() function returns the offset for the
                       next option in the data buffer.
    -1                 Failure