IPv6 protocol stack and API

AF_INET6 address family provides similar API to AF_INET
sizeof(sockaddr_in6) > sizeof(sockaddr)

RFC2553 basic API
tcp/udp: socket, bind, connect - almost no changes
resolve host names

RFC2292 advanced API
raw/icmp, extension header manipulation
    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;
    };