reactos/include/psdk/in6addr.h

#ifndef s6_addr

typedef struct in6_addr
{
    union
    {
        UCHAR Byte[16];
        USHORT Word[8];
    } u;
} IN6_ADDR, *PIN6_ADDR, FAR *LPIN6_ADDR;

#define in_addr6    in6_addr
#define _S6_un      u
#define _S6_u8      Byte
#define s6_addr     _S6_un._S6_u8
#define s6_bytes    u.Byte
#define s6_words    u.Word

#endif