.\" Copyright (C) 2000, 2001, 2003-2005, 2007, 2014-2016, 2018 Internet Systems Consortium, Inc. ("ISC")
.\" 
.\" This Source Code Form is subject to the terms of the Mozilla Public
.\" License, v. 2.0. If a copy of the MPL was not distributed with this
.\" file, You can obtain one at http://mozilla.org/MPL/2.0/.
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.\"     Title: lwres_getipnode
.\"    Author: 
.\" Generator: DocBook XSL Stylesheets v1.78.1 <http://docbook.sf.net/>
.\"      Date: 2007-06-18
.\"    Manual: BIND9
.\"    Source: ISC
.\"  Language: English
.\"
.TH "LWRES_GETIPNODE" "3" "2007\-06\-18" "ISC" "BIND9"
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.SH "NAME"
lwres_getipnodebyname, lwres_getipnodebyaddr, lwres_freehostent \- lightweight resolver nodename / address translation API
.SH "SYNOPSIS"
.sp
.ft B
.nf
#include <lwres/netdb\&.h>
.fi
.ft
.HP \w'struct\ hostent\ *\ lwres_getipnodebyname('u
.BI "struct hostent * lwres_getipnodebyname(const\ char\ *" "name" ", int\ " "af" ", int\ " "flags" ", int\ *" "error_num" ");"
.HP \w'struct\ hostent\ *\ lwres_getipnodebyaddr('u
.BI "struct hostent * lwres_getipnodebyaddr(const\ void\ *" "src" ", size_t\ " "len" ", int\ " "af" ", int\ *" "error_num" ");"
.HP \w'void\ lwres_freehostent('u
.BI "void lwres_freehostent(struct\ hostent\ *" "he" ");"
.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
namedb\&.h:
.PP
.if n \{\
.RS 4
.\}
.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 */
.fi
.if n \{\
.RE
.\}
.PP
The members of this structure are:
.PP
\fBh_name\fR
.RS 4
The official (canonical) name of the host\&.
.RE
.PP
\fBh_aliases\fR
.RS 4
A NULL\-terminated array of alternate names (nicknames) for the host\&.
.RE
.PP
\fBh_addrtype\fR
.RS 4
The type of address being returned \- usually
\fBPF_INET\fR
or
\fBPF_INET6\fR\&.
.RE
.PP
\fBh_length\fR
.RS 4
The length of the address in bytes\&.
.RE
.PP
\fBh_addr_list\fR
.RS 4
A
\fBNULL\fR
terminated array of network addresses for the host\&. Host addresses are returned in network byte order\&.
.RE
.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:
.PP
\fBAI_V4MAPPED\fR
.RS 4
This is used with an
\fIaf\fR
of AF_INET6, and causes IPv4 addresses to be returned as IPv4\-mapped IPv6 addresses\&.
.RE
.PP
\fBAI_ALL\fR
.RS 4
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\&.
.RE
.PP
\fBAI_ADDRCONFIG\fR
.RS 4
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\&.
.RE
.PP
\fBAI_DEFAULT\fR
.RS 4
This default sets the
\fBAI_V4MAPPED\fR
and
\fBAI_ADDRCONFIG\fR
flag bits\&.
.RE
.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
\fBh_name\fR,
\fBh_addr_list\fR
and
\fBh_aliases\fR
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
<lwres/netdb\&.h>:
.PP
\fBHOST_NOT_FOUND\fR
.RS 4
No such host is known\&.
.RE
.PP
\fBNO_ADDRESS\fR
.RS 4
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\&.
.RE
.PP
\fBTRY_AGAIN\fR
.RS 4
A temporary and possibly transient error occurred, such as a failure of a server to respond\&. The request may succeed if retried\&.
.RE
.PP
\fBNO_RECOVERY\fR
.RS 4
An unexpected failure occurred, and retrying the request is pointless\&.
.RE
.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)\&.
.SH "AUTHOR"
.PP
\fBInternet Systems Consortium, Inc\&.\fR
.SH "COPYRIGHT"
.br
Copyright \(co 2000, 2001, 2003-2005, 2007, 2014-2016, 2018 Internet Systems Consortium, Inc. ("ISC")
.br
