lwres_resutil.3

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.\" Copyright (C) 2004, 2005 Internet Systems Consortium, Inc. ("ISC")
.\" Copyright (C) 2000, 2001 Internet Software Consortium.
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.\" $Id: lwres_resutil.3,v 1.14.2.1.8.5 2005/10/13 02:33:54 marka Exp $
.\"
.hy 0
.ad l
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.TH "LWRES_RESUTIL" "3" "Jun 30, 2000" "BIND9" "BIND9"
.\" disable hyphenation
.nh
.\" disable justification (adjust text to left margin only)
.ad l
.SH "NAME"
lwres_string_parse, lwres_addr_parse, lwres_getaddrsbyname, lwres_getnamebyaddr \- lightweight resolver utility functions
.SH "SYNOPSIS"
.nf
#include <lwres/lwres.h>
.fi
.HP 34
\fBlwres_result_t\ \fBlwres_string_parse\fR\fR\fB(\fR\fBlwres_buffer_t\ *b\fR\fB, \fR\fBchar\ **c\fR\fB, \fR\fBlwres_uint16_t\ *len\fR\fB);\fR
.HP 32
\fBlwres_result_t\ \fBlwres_addr_parse\fR\fR\fB(\fR\fBlwres_buffer_t\ *b\fR\fB, \fR\fBlwres_addr_t\ *addr\fR\fB);\fR
.HP 36
\fBlwres_result_t\ \fBlwres_getaddrsbyname\fR\fR\fB(\fR\fBlwres_context_t\ *ctx\fR\fB, \fR\fBconst\ char\ *name\fR\fB, \fR\fBlwres_uint32_t\ addrtypes\fR\fB, \fR\fBlwres_gabnresponse_t\ **structp\fR\fB);\fR
.HP 35
\fBlwres_result_t\ \fBlwres_getnamebyaddr\fR\fR\fB(\fR\fBlwres_context_t\ *ctx\fR\fB, \fR\fBlwres_uint32_t\ addrtype\fR\fB, \fR\fBlwres_uint16_t\ addrlen\fR\fB, \fR\fBconst\ unsigned\ char\ *addr\fR\fB, \fR\fBlwres_gnbaresponse_t\ **structp\fR\fB);\fR
.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's 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's 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:
.sp
.nf
typedef struct {
        lwres_uint32_t          flags;
        lwres_uint16_t          naliases;
        lwres_uint16_t          naddrs;
        char                   *realname;
        char                  **aliases;
        lwres_uint16_t          realnamelen;
        lwres_uint16_t         *aliaslen;
        lwres_addrlist_t        addrs;
        void                   *base;
        size_t                  baselen;
} lwres_gabnresponse_t;
.fi
.sp
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 foward 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).