http://lxr.free-electrons.com/source/Documentation/security/tomoyo.txt

/*** tomoyo_socket_connect - Check permission for connect().** @sock:     Pointer to "struct socket".* @addr:     Pointer to "struct sockaddr".* @addr_len: Size of @addr.** Returns 0 on success, negative value otherwise.*/static int tomoyo_socket_connect(struct socket *sock, struct sockaddr *addr, int addr_len){    return tomoyo_socket_connect_permission(sock, addr, addr_len);}

/*** tomoyo_sock_family - Get socket‘s family.** @sk: Pointer to "struct sock".** Returns one of PF_INET, PF_INET6, PF_UNIX or 0.*/static u8 tomoyo_sock_family(struct sock *sk){     u8 family;    if (tomoyo_kernel_service())        return 0;    family = sk->sk_family;    switch (family)     {        case PF_INET:        case PF_INET6:        case PF_UNIX:            return family;        default:            return 0;    }}/*** tomoyo_socket_connect_permission - Check permission for setting the remote address of a socket.** @sock:     Pointer to "struct socket".* @addr:     Pointer to "struct sockaddr".* @addr_len: Size of @addr.** Returns 0 on success, negative value otherwise.*/int tomoyo_socket_connect_permission(struct socket *sock, struct sockaddr *addr, int addr_len){    struct tomoyo_addr_info address;    //Get socket‘s family.(family是链路层的概念)    const u8 family = tomoyo_sock_family(sock->sk);    //socket的类型(TCP、UDP...)(type是传输层的概念)    const unsigned int type = sock->type;    if (!family)        return 0;    address.protocol = type;    switch (type)     {        case SOCK_DGRAM:        case SOCK_RAW:            address.operation = TOMOYO_NETWORK_SEND;            break;        case SOCK_STREAM:        case SOCK_SEQPACKET:            address.operation = TOMOYO_NETWORK_CONNECT;            break;        default:            return 0;    }    if (family == PF_UNIX)        return tomoyo_check_unix_address(addr, addr_len, &address);    return tomoyo_check_inet_address(addr, addr_len, sock->sk->sk_protocol, &address);}/* Structure for holding socket address. */struct tomoyo_addr_info {    u8 protocol;    u8 operation;    struct tomoyo_inet_addr_info inet;    struct tomoyo_unix_addr_info unix0;}; static int tomoyo_check_inet_address(const struct sockaddr *addr, const unsigned int addr_len, const u16 port, struct tomoyo_addr_info *address){    struct tomoyo_inet_addr_info *i = &address->inet;        switch (addr->sa_family)     {        case AF_INET6:            if (addr_len < SIN6_LEN_RFC2133)                goto skip;            i->is_ipv6 = true;            i->address = (__be32 *)((struct sockaddr_in6 *) addr)->sin6_addr.s6_addr;            i->port = ((struct sockaddr_in6 *) addr)->sin6_port;            break;        case AF_INET:            if (addr_len < sizeof(struct sockaddr_in))                goto skip;            i->is_ipv6 = false;            i->address = (__be32 *) &((struct sockaddr_in *) addr)->sin_addr;            i->port = ((struct sockaddr_in *) addr)->sin_port;            break;        default:            goto skip;    }    if (address->protocol == SOCK_RAW)        i->port = htons(port);    return tomoyo_inet_entry(address);    skip:        return 0;}