
GETIPNODEBYNAME(3)     FreeBSD Library Functions Manual     GETIPNODEBYNAME(3)

NAME
     getipnodebyname, getipnodebyaddr - get network host entry
     freehostent - free network host entry

SYNOPSIS
     #include <netdb.h>

     struct hostent *
     getipnodebyname(const char *name, int af, int flags, int *error);

     struct hostent *
     getipnodebyaddr(const void *addr, size_t len, int af, int *error);

     void
     freehostent(struct hostent *he);

DESCRIPTION
     Getipnodebyname(), and getipnodebyaddr() each return a pointer to a hos-
     tent structure (see below) describing an internet host referenced by name
     or by address, as the function names indicate.  This structure contains
     either the information obtained from the name server, named(8),  or bro-
     ken-out fields from a line in /etc/hosts. If the local name server is not
     running, these routines do a lookup in /etc/hosts.

           struct  hostent {
                   char    *h_name;        /* official name of host */
                   char    **h_aliases;    /* alias list */
                   int     h_addrtype;     /* host address type */
                   int     h_length;       /* length of address */
                   char    **h_addr_list;  /* list of addresses from name server */
           };

           #define h_addr  h_addr_list[0]  /* address, for backward compatibility */

     The members of this structure are:

     h_name       Official name of the host.

     h_aliases    A zero-terminated array of alternate names for the host.

     h_addrtype   The type of address being returned.

     h_length     The length, in bytes, of the address.

     h_addr_list  A zero-terminated array of network addresses for the host.
                  Host addresses are returned in network byte order.

     h_addr       The first address in h_addr_list; this is for backward com-
                  patibility.

     This structure should be freed after use by calling freehostent().

     When using the nameserver, getiphostbyaddr() will search for the named
     host in each parent domain given in the ``search'' directive of re-
     solv.conf(5) unless the name contains a dot (``.''). If the name contains
     no dot, and if the environment variable HOSTALIASES contains the name of
     an alias file, the alias file will first be searched for an alias match-
     ing the input name.  See hostname(7) for the domain search procedure and
     the alias file format.

     Getiphostbyaddr() can be told to look for IPv4 addresses, IPv6 addresses
     or both IPv4 and IPv6.  If IPv4 addresses only are to be looked up then
     af should be set to AF_INET, otherwise it should be set to AF_INET6.

     There are three flags that can be set

     AI_V4MAPPED    Return IPv4 addresses if no IPv6 addresses are found.
                    This flag is ignored unless af is AF_INET6.

     AI_ALL         Return IPv4 addresses as well IPv6 addresses if
                    AI_V4MAPPED is set.  This flag is ignored unless af is
                    AF_INET6.

     AI_ADDRCONFIG  Only return addresses of a given type if the system has an
                    active interface with that type.

     Also AI_DEFAULT is defined to be (AI_V4MAPPED|AI_ADDRCONFIG).

     Getipnodebyaddr() will lookup IPv4 mapped and compatible addresses in the
     IPv4 name space and IPv6 name space

     Freehostent() frees the hostent structure allocated be getipnodebyname()
     and getipnodebyaddr().  The structures returned by gethostbyname(),
     gethostbyname2(), gethostbyaddr() and gethostent() should not be passed
     to freehostent() as they are pointers to static areas.

ENVIRONMENT
     HOSTALIASES    Name of file containing (host alias, full hostname) pairs.

FILES
     /etc/hosts     See hosts(5).

     HOSTALIASES    Name of file containing (host alias, full hostname) pairs.

DIAGNOSTICS
     Error return status from getipnodebyname() and getipnodebyaddr() is indi-
     cated by return of a null pointer.  In this case error may then be
     checked to see whether this is a temporary failure or an invalid or un-
     known host.  errno can have the following values:

           NETDB_INTERNAL    This indicates an internal error in the library,
                             unrelated to the network or name service.  errno
                             will be valid in this case; see perror(2).

           HOST_NOT_FOUND    No such host is known.

           TRY_AGAIN         This is usually a temporary error and means that
                             the local server did not receive a response from
                             an authoritative server.  A retry at some later
                             time may succeed.

           NO_RECOVERY       Some unexpected server failure was encountered.
                             This is a non-recoverable error, as one might ex-
                             pect.

           NO_ADDRESS        The requested name is valid but does not have an
                             IP address; this is not a temporary error.  This
                             means that the name is known to the name server
                             but there is no address associated with this
                             name.  Another type of request to the name server
                             using this domain name will result in an answer;
                             for example, a mail-forwarder may be registered
                             for this domain.

SEE ALSO
     hosts(5),  hostname(7),  named(8),  resolver(3),  resolver(5),
     gethostbyname(3),  RFC2553.

4th Berkeley Distribution     September 17, 1999                             2
