sockaddr_union.h

/*
** This puts different kinds of IP addresses in one place.
** Here we can put IPv4 and IPv6 addresses.
*/
typedef union sockaddr_union {
    struct sockaddr sa;
    struct sockaddr_in in;
#if defined(USE_IPv6)
    struct sockaddr_in6 in6;
#endif
} SOCKADDR_UNION;

/* 
Notes: 

- sizeof sockaddr_union will reflect the size of the biggest member of the union (so the actual size of this union heavily depends on USE_IPv6)
- Linux tolerates wrong size specs in connect() and bind() calls:
   connect(AF_INET, ..., sizeof(struct sockaddr_in6))
  But Solaris does not (runtime error: invalid argument).
*/