lwres_getipnode(3)

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 (C) 2004, 2005, 2007, 2014-2016 Internet Systems Consortium,
       Inc. ("ISC")
       Copyright (C) 2000, 2001, 2003 Internet Software Consortium.

ISC                               2007-06-18                LWRES_GETIPNODE(3)