NAME

       lwres_getipnodebyname, lwres_getipnodebyaddr, lwres_freehostent - lightweight resolver
       nodename / address translation API

SYNOPSIS

       #include <lwres/netdb.h>

       struct hostent * lwres_getipnodebyname(const char *name, int af, int flags,
                                              int *error_num);

       struct hostent * lwres_getipnodebyaddr(const void *src, size_t len, int af,
                                              int *error_num);

       void lwres_freehostent(struct hostent *he);

DESCRIPTION

       These functions perform thread safe, protocol independent nodename-to-address and
       address-to-nodename translation as defined in RFC2553.

       They use a struct hostent which is defined in namedb.h:

           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
           The official (canonical) name of the host.

       h_aliases
           A NULL-terminated array of alternate names (nicknames) for the host.

       h_addrtype
           The type of address being returned - usually PF_INET or PF_INET6.

       h_length
           The length of the address in bytes.

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

       lwres_getipnodebyname() looks up addresses of protocol family af for the hostname name.
       The flags parameter contains ORed flag bits to specify the types of addresses that are
       searched for, and the types of addresses that are returned. The flag bits are:

       AI_V4MAPPED
           This is used with an af of AF_INET6, and causes IPv4 addresses to be returned as
           IPv4-mapped IPv6 addresses.

       AI_ALL
           This is used with an af of AF_INET6, and causes all known addresses (IPv6 and IPv4) to
           be returned. If AI_V4MAPPED is also set, the IPv4 addresses are return as mapped IPv6
           addresses.

       AI_ADDRCONFIG
           Only return an IPv6 or IPv4 address if here is an active network interface of that
           type. This is not currently implemented in the BIND 9 lightweight resolver, and the
           flag is ignored.

       AI_DEFAULT
           This default sets the AI_V4MAPPED and AI_ADDRCONFIG flag bits.

       lwres_getipnodebyaddr() performs a reverse lookup of address src which is len bytes long.
       af denotes the protocol family, typically PF_INET or PF_INET6.

       lwres_freehostent() releases all the memory associated with the struct hostent pointer he.
       Any memory allocated for the h_name, h_addr_list and h_aliases is freed, as is the memory
       for the hostent structure itself.

RETURN VALUES

       If an error occurs, lwres_getipnodebyname() and lwres_getipnodebyaddr() set *error_num to
       an appropriate error code and the function returns a NULL pointer. The error codes and
       their meanings are defined in <lwres/netdb.h>:

       HOST_NOT_FOUND
           No such host is known.

       NO_ADDRESS
           The server recognised the request and the name but no address is available. Another
           type of request to the name server for the domain might return an answer.

       TRY_AGAIN
           A temporary and possibly transient error occurred, such as a failure of a server to
           respond. The request may succeed if retried.

       NO_RECOVERY
           An unexpected failure occurred, and retrying the request is pointless.

       lwres_hstrerror(3) translates these error codes to suitable error messages.

SEE ALSO

       RFC2553(), lwres(3), lwres_gethostent(3), lwres_getaddrinfo(3), lwres_getnameinfo(3),
       lwres_hstrerror(3).

AUTHOR

       Internet Systems Consortium, Inc.

COPYRIGHT

       Copyright © 2000, 2001, 2003-2005, 2007, 2014-2016 Internet Systems Consortium, Inc.
       ("ISC")