IPv6 protocol stack and API

AF_INET6: similar to AF_INET
sizeof(sockaddr_in6) > sizeof(sockaddr_in) = sizeof(sockaddr)

RFC2553/3493 basic API
TCP/UDP: socket, bind, connect - same
address family independent hostname lookup (getaddrinfo, getnameinfo)
RFC2292/3542 advanced API
raw/ICMPv6, extension headers handling (ping, traceroute)
(only very few apps need this)

IPv6 support = rewrite apps to use RFC2553-based API
    struct sockaddr_in6 {
        u_int8_t sin6_len;
        u_int8_t sin6_family;
        u_int16_t sin6_port;
        u_int32_t sin6_flowinfo;
        struct in6_addr sin6_addr;
        u_int32_t sin6_scope_id;
    };