gistfile1.txt

            ai_flags       The ai_flags field to which the hints parameter points
                    shall be set to zero or be the bitwise-inclusive OR of one
                    or more of the values AI_ADDRCONFIG, AI_CANONNAME,
                    AI_NUMERICHOST, AI_NUMERICSERV and AI_PASSIVE.

                    AI_ADDRCONFIG   If the AI_ADDRCONFIG bit is set, IPv4
                                    addresses shall be returned only if an
                                    IPv4 address is configured on the local
                                    system, and IPv6 addresses shall be
                                    returned only if an IPv6 address is con‐
                                    figured on the local system.

                    AI_CANONNAME    If the AI_CANONNAME bit is set, a success‐
                                    ful call to getaddrinfo() will return a
                                    NUL-terminated string containing the
                                    canonical name of the specified hostname
                                    in the ai_canonname element of the first
                                    addrinfo structure returned.

                    AI_NUMERICHOST  If the AI_NUMERICHOST bit is set, it indi‐
                                    cates that hostname should be treated as a
                                    numeric string defining an IPv4 or IPv6
                                    address and no name resolution should be
                                    attempted.

                    AI_NUMERICSERV  If the AI_NUMERICSERV bit is set, then a
                                    non-null servname string supplied shall be
                                    a numeric port string.  Otherwise, an
                                    EAI_NONAME error shall be returned.  This
                                    bit shall prevent any type of name resolu‐
                                    tion service (for example, NIS+) from
                                    being invoked.

                    AI_PASSIVE      If the AI_PASSIVE bit is set it indicates
                                    that the returned socket address structure
                                    is intended for use in a call to bind(2).
                                    In this case, if the hostname argument is
                                    the null pointer, then the IP address por‐
                                    tion of the socket address structure will
                                    be set to INADDR_ANY for an IPv4 address
                                    or IN6ADDR_ANY_INIT for an IPv6 address.

                                    If the AI_PASSIVE bit is not set, the
                                    returned socket address structure will be
                                    ready for use in a call to connect(2) for
                                    a connection-oriented protocol or
                                    connect(2), sendto(2), or sendmsg(2) if a
                                    connectionless protocol was chosen.  The
                                    IP address portion of the socket address
                                    structure will be set to the loopback
                                    address if hostname is the null pointer
                                    and AI_PASSIVE is not set.

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