.\" Copyright (C) 2004  Internet Systems Consortium, Inc. ("ISC")
.\" Copyright (C) 2000, 2001  Internet Software Consortium.
.\"
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.\" $ISC: lwres_getipnode.3,v 1.13.2.2.4.2 2004/03/09 05:21:10 marka Exp $
.\"
.TH "LWRES_GETIPNODE" "3" "Jun 30, 2000" "BIND9" ""
.SH NAME
lwres_getipnodebyname, lwres_getipnodebyaddr, lwres_freehostent \- lightweight resolver nodename / address translation API
.SH SYNOPSIS
\fB#include <lwres/netdb.h>
.sp
.na
struct hostent *
lwres_getipnodebyname(const char *name, int af, int flags, int *error_num);
.ad
.sp
.na
struct hostent *
lwres_getipnodebyaddr(const void *src, size_t len, int af, int *error_num);
.ad
.sp
.na
void
lwres_freehostent(struct hostent *he);
.ad
\fR
.SH "DESCRIPTION"
.PP
These functions perform thread safe, protocol independent
nodename-to-address and address-to-nodename 
translation as defined in RFC2553.
.PP
They use a
\fBstruct hostent\fR
which is defined in
\fInamedb.h\fR:
.sp
.nf
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 */
.sp
.fi
.PP
The members of this structure are:
.TP
\fBh_name\fR
The official (canonical) name of the host.
.TP
\fBh_aliases\fR
A NULL-terminated array of alternate names (nicknames) for the host.
.TP
\fBh_addrtype\fR
The type of address being returned - usually
\fBPF_INET\fR
or
\fBPF_INET6\fR.
.TP
\fBh_length\fR
The length of the address in bytes.
.TP
\fBh_addr_list\fR
A
\fBNULL\fR
terminated array of network addresses for the host.
Host addresses are returned in network byte order.
.PP
\fBlwres_getipnodebyname()\fR
looks up addresses of protocol family
\fIaf\fR
for the hostname
\fIname\fR.
The
\fIflags\fR
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:
.TP
\fBAI_V4MAPPED\fR
This is used with an
\fIaf\fR
of AF_INET6, and causes IPv4 addresses to be returned as IPv4-mapped
IPv6 addresses.
.TP
\fBAI_ALL\fR
This is used with an
\fIaf\fR
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.
.TP
\fBAI_ADDRCONFIG\fR
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.
.TP
\fBAI_DEFAULT\fR
This default sets the
AI_V4MAPPED
and
AI_ADDRCONFIG
flag bits.
.PP
\fBlwres_getipnodebyaddr()\fR
performs a reverse lookup
of address
\fIsrc\fR
which is
\fIlen\fR
bytes long.
\fIaf\fR
denotes the protocol family, typically
\fBPF_INET\fR
or
\fBPF_INET6\fR.
.PP
\fBlwres_freehostent()\fR
releases all the memory associated with
the
\fBstruct hostent\fR
pointer
\fIhe\fR.
Any memory allocated for the
h_name,
h_addr_list
and
h_aliases
is freed, as is the memory for the
\fBhostent\fR
structure itself.
.SH "RETURN VALUES"
.PP
If an error occurs,
\fBlwres_getipnodebyname()\fR
and
\fBlwres_getipnodebyaddr()\fR
set
\fI*error_num\fR
to an appropriate error code and the function returns a
\fBNULL\fR
pointer.
The error codes and their meanings are defined in
\fI<lwres/netdb.h>\fR:
.TP
\fBHOST_NOT_FOUND\fR
No such host is known.
.TP
\fBNO_ADDRESS\fR
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.
.TP
\fBTRY_AGAIN\fR
A temporary and possibly transient error occurred, such as a
failure of a server to respond. The request may succeed if
retried.
.TP
\fBNO_RECOVERY\fR
An unexpected failure occurred, and retrying the request
is pointless.
.PP
\fBlwres_hstrerror\fR(3)
translates these error codes to suitable error messages.
.SH "SEE ALSO"
.PP
\fBRFC2553\fR,
\fBlwres\fR(3),
\fBlwres_gethostent\fR(3),
\fBlwres_getaddrinfo\fR(3),
\fBlwres_getnameinfo\fR(3),
\fBlwres_hstrerror\fR(3).