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.\" Copyright (C) 2000, 2001, 2004, 2005, 2007, 2014-2016, 2018, 2019 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/.
.\"
.hy 0
.ad l
'\" t
.\" Title: lwres_resutil
.\" Author:
.\" Generator: DocBook XSL Stylesheets v1.78.1 <http://docbook.sf.net/>
.\" Date: 2007-06-18
.\" Manual: BIND9
.\" Source: ISC
.\" Language: English
.\"
.TH "LWRES_RESUTIL" "3" "2007\-06\-18" "ISC" "BIND9"
.\" -----------------------------------------------------------------
.\" * Define some portability stuff
.\" -----------------------------------------------------------------
.\" ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
.\" http://bugs.debian.org/507673
.\" http://lists.gnu.org/archive/html/groff/2009-02/msg00013.html
.\" ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
.ie \n(.g .ds Aq \(aq
.el .ds Aq '
.\" -----------------------------------------------------------------
.\" * set default formatting
.\" -----------------------------------------------------------------
.\" disable hyphenation
.nh
.\" disable justification (adjust text to left margin only)
.ad l
.\" -----------------------------------------------------------------
.\" * MAIN CONTENT STARTS HERE *
.\" -----------------------------------------------------------------
.SH "NAME"
lwres_string_parse, lwres_addr_parse, lwres_getaddrsbyname, lwres_getnamebyaddr \- lightweight resolver utility functions
.SH "SYNOPSIS"
.sp
.ft B
.nf
#include <lwres/lwres\&.h>
.fi
.ft
.HP \w'lwres_result_t\ lwres_string_parse('u
.BI "lwres_result_t lwres_string_parse(lwres_buffer_t\ *" "b" ", char\ **" "c" ", uint16_t\ *" "len" ");"
.HP \w'lwres_result_t\ lwres_addr_parse('u
.BI "lwres_result_t lwres_addr_parse(lwres_buffer_t\ *" "b" ", lwres_addr_t\ *" "addr" ");"
.HP \w'lwres_result_t\ lwres_getaddrsbyname('u
.BI "lwres_result_t lwres_getaddrsbyname(lwres_context_t\ *" "ctx" ", const\ char\ *" "name" ", uint32_t\ " "addrtypes" ", lwres_gabnresponse_t\ **" "structp" ");"
.HP \w'lwres_result_t\ lwres_getnamebyaddr('u
.BI "lwres_result_t lwres_getnamebyaddr(lwres_context_t\ *" "ctx" ", uint32_t\ " "addrtype" ", uint16_t\ " "addrlen" ", const\ unsigned\ char\ *" "addr" ", lwres_gnbaresponse_t\ **" "structp" ");"
.SH "DESCRIPTION"
.PP
\fBlwres_string_parse()\fR
retrieves a DNS\-encoded string starting the current pointer of lightweight resolver buffer
\fIb\fR: i\&.e\&.
\fBb\->current\fR\&. When the function returns, the address of the first byte of the encoded string is returned via
\fI*c\fR
and the length of that string is given by
\fI*len\fR\&. The buffer\*(Aqs current pointer is advanced to point at the character following the string length, the encoded string, and the trailing
\fBNULL\fR
character\&.
.PP
\fBlwres_addr_parse()\fR
extracts an address from the buffer
\fIb\fR\&. The buffer\*(Aqs current pointer
\fBb\->current\fR
is presumed to point at an encoded address: the address preceded by a 32\-bit protocol family identifier and a 16\-bit length field\&. The encoded address is copied to
\fBaddr\->address\fR
and
\fBaddr\->length\fR
indicates the size in bytes of the address that was copied\&.
\fBb\->current\fR
is advanced to point at the next byte of available data in the buffer following the encoded address\&.
.PP
\fBlwres_getaddrsbyname()\fR
and
\fBlwres_getnamebyaddr()\fR
use the
\fBlwres_gnbaresponse_t\fR
structure defined below:
.PP
.if n \{\
.RS 4
.\}
.nf
typedef struct {
uint32_t flags;
uint16_t naliases;
uint16_t naddrs;
char *realname;
char **aliases;
uint16_t realnamelen;
uint16_t *aliaslen;
lwres_addrlist_t addrs;
void *base;
size_t baselen;
} lwres_gabnresponse_t;
.fi
.if n \{\
.RE
.\}
.PP
The contents of this structure are not manipulated directly but they are controlled through the
\fBlwres_gabn\fR(3)
functions\&.
.PP
The lightweight resolver uses
\fBlwres_getaddrsbyname()\fR
to perform forward lookups\&. Hostname
\fIname\fR
is looked up using the resolver context
\fIctx\fR
for memory allocation\&.
\fIaddrtypes\fR
is a bitmask indicating which type of addresses are to be looked up\&. Current values for this bitmask are
\fBLWRES_ADDRTYPE_V4\fR
for IPv4 addresses and
\fBLWRES_ADDRTYPE_V6\fR
for IPv6 addresses\&. Results of the lookup are returned in
\fI*structp\fR\&.
.PP
\fBlwres_getnamebyaddr()\fR
performs reverse lookups\&. Resolver context
\fIctx\fR
is used for memory allocation\&. The address type is indicated by
\fIaddrtype\fR:
\fBLWRES_ADDRTYPE_V4\fR
or
\fBLWRES_ADDRTYPE_V6\fR\&. The address to be looked up is given by
\fIaddr\fR
and its length is
\fIaddrlen\fR
bytes\&. The result of the function call is made available through
\fI*structp\fR\&.
.SH "RETURN VALUES"
.PP
Successful calls to
\fBlwres_string_parse()\fR
and
\fBlwres_addr_parse()\fR
return
\fBLWRES_R_SUCCESS\&.\fR
Both functions return
\fBLWRES_R_FAILURE\fR
if the buffer is corrupt or
\fBLWRES_R_UNEXPECTEDEND\fR
if the buffer has less space than expected for the components of the encoded string or address\&.
.PP
\fBlwres_getaddrsbyname()\fR
returns
\fBLWRES_R_SUCCESS\fR
on success and it returns
\fBLWRES_R_NOTFOUND\fR
if the hostname
\fIname\fR
could not be found\&.
.PP
\fBLWRES_R_SUCCESS\fR
is returned by a successful call to
\fBlwres_getnamebyaddr()\fR\&.
.PP
Both
\fBlwres_getaddrsbyname()\fR
and
\fBlwres_getnamebyaddr()\fR
return
\fBLWRES_R_NOMEMORY\fR
when memory allocation requests fail and
\fBLWRES_R_UNEXPECTEDEND\fR
if the buffers used for sending queries and receiving replies are too small\&.
.SH "SEE ALSO"
.PP
\fBlwres_buffer\fR(3),
\fBlwres_gabn\fR(3)\&.
.SH "AUTHOR"
.PP
\fBInternet Systems Consortium, Inc\&.\fR
.SH "COPYRIGHT"
.br
Copyright \(co 2000, 2001, 2004, 2005, 2007, 2014-2016, 2018, 2019 Internet Systems Consortium, Inc. ("ISC")
.br
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