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<HTML
><HEAD
><TITLE
>lwres_gnba</TITLE
><META
NAME="GENERATOR"
CONTENT="Modular DocBook HTML Stylesheet Version 1.79"></HEAD
><BODY
CLASS="REFENTRY"
BGCOLOR="#FFFFFF"
TEXT="#000000"
LINK="#0000FF"
VLINK="#840084"
ALINK="#0000FF"
><H1
><A
NAME="AEN1"
></A
>lwres_gnba</H1
><DIV
CLASS="REFNAMEDIV"
><A
NAME="AEN8"
></A
><H2
>Name</H2
>lwres_gnbarequest_render, lwres_gnbaresponse_render, lwres_gnbarequest_parse, lwres_gnbaresponse_parse, lwres_gnbaresponse_free, lwres_gnbarequest_free&nbsp;--&nbsp;lightweight resolver getnamebyaddress message handling</DIV
><DIV
CLASS="REFSYNOPSISDIV"
><A
NAME="AEN16"
></A
><H2
>Synopsis</H2
><DIV
CLASS="FUNCSYNOPSIS"
><P
></P
><A
NAME="AEN17"
></A
><PRE
CLASS="FUNCSYNOPSISINFO"
>#include &lt;lwres/lwres.h&gt;</PRE
><P
><CODE
><CODE
CLASS="FUNCDEF"
>lwres_result_t
lwres_gnbarequest_render</CODE
>(lwres_context_t *ctx, lwres_gnbarequest_t *req, lwres_lwpacket_t *pkt, lwres_buffer_t *b);</CODE
></P
><P
><CODE
><CODE
CLASS="FUNCDEF"
>lwres_result_t
lwres_gnbaresponse_render</CODE
>(lwres_context_t *ctx, lwres_gnbaresponse_t *req, lwres_lwpacket_t *pkt, lwres_buffer_t *b);</CODE
></P
><P
><CODE
><CODE
CLASS="FUNCDEF"
>lwres_result_t
lwres_gnbarequest_parse</CODE
>(lwres_context_t *ctx, lwres_buffer_t *b, lwres_lwpacket_t *pkt, lwres_gnbarequest_t **structp);</CODE
></P
><P
><CODE
><CODE
CLASS="FUNCDEF"
>lwres_result_t
lwres_gnbaresponse_parse</CODE
>(lwres_context_t *ctx, lwres_buffer_t *b, lwres_lwpacket_t *pkt, lwres_gnbaresponse_t **structp);</CODE
></P
><P
><CODE
><CODE
CLASS="FUNCDEF"
>void
lwres_gnbaresponse_free</CODE
>(lwres_context_t *ctx, lwres_gnbaresponse_t **structp);</CODE
></P
><P
><CODE
><CODE
CLASS="FUNCDEF"
>void
lwres_gnbarequest_free</CODE
>(lwres_context_t *ctx, lwres_gnbarequest_t **structp);</CODE
></P
><P
></P
></DIV
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN61"
></A
><H2
>DESCRIPTION</H2
><P
>These are low-level routines for creating and parsing
lightweight resolver address-to-name lookup request and
response messages.</P
><P
>There are four main functions for the getnamebyaddr opcode.
One render function converts a getnamebyaddr request structure &mdash;
<SPAN
CLASS="TYPE"
>lwres_gnbarequest_t</SPAN
> &mdash;
to the lightweight resolver's canonical format.
It is complemented by a parse function that converts a packet in this
canonical format to a getnamebyaddr request structure.
Another render function converts the getnamebyaddr response structure &mdash;
<SPAN
CLASS="TYPE"
>lwres_gnbaresponse_t</SPAN
>
to the canonical format.
This is complemented by a parse function which converts a packet in
canonical format to a getnamebyaddr response structure.</P
><P
>These structures are defined in
<TT
CLASS="FILENAME"
>lwres/lwres.h</TT
>.
They are shown below.
<PRE
CLASS="PROGRAMLISTING"
>#define LWRES_OPCODE_GETNAMEBYADDR 0x00010002U
typedef struct {
lwres_uint32_t flags;
lwres_addr_t addr;
} lwres_gnbarequest_t;
typedef struct {
lwres_uint32_t flags;
lwres_uint16_t naliases;
char *realname;
char **aliases;
lwres_uint16_t realnamelen;
lwres_uint16_t *aliaslen;
void *base;
size_t baselen;
} lwres_gnbaresponse_t;</PRE
></P
><P
><CODE
CLASS="FUNCTION"
>lwres_gnbarequest_render()</CODE
>
uses resolver context
<CODE
CLASS="VARNAME"
>ctx</CODE
>
to convert getnamebyaddr request structure
<CODE
CLASS="VARNAME"
>req</CODE
>
to canonical format.
The packet header structure
<CODE
CLASS="VARNAME"
>pkt</CODE
>
is initialised and transferred to
buffer
<CODE
CLASS="VARNAME"
>b</CODE
>.
The contents of
<CODE
CLASS="VARNAME"
>*req</CODE
>
are then appended to the buffer in canonical format.
<CODE
CLASS="FUNCTION"
>lwres_gnbaresponse_render()</CODE
>
performs the same task, except it converts a getnamebyaddr response structure
<SPAN
CLASS="TYPE"
>lwres_gnbaresponse_t</SPAN
>
to the lightweight resolver's canonical format.</P
><P
><CODE
CLASS="FUNCTION"
>lwres_gnbarequest_parse()</CODE
>
uses context
<CODE
CLASS="VARNAME"
>ctx</CODE
>
to convert the contents of packet
<CODE
CLASS="VARNAME"
>pkt</CODE
>
to a
<SPAN
CLASS="TYPE"
>lwres_gnbarequest_t</SPAN
>
structure.
Buffer
<CODE
CLASS="VARNAME"
>b</CODE
>
provides space to be used for storing this structure.
When the function succeeds, the resulting
<SPAN
CLASS="TYPE"
>lwres_gnbarequest_t</SPAN
>
is made available through
<CODE
CLASS="VARNAME"
>*structp</CODE
>.
<CODE
CLASS="FUNCTION"
>lwres_gnbaresponse_parse()</CODE
>
offers the same semantics as
<CODE
CLASS="FUNCTION"
>lwres_gnbarequest_parse()</CODE
>
except it yields a
<SPAN
CLASS="TYPE"
>lwres_gnbaresponse_t</SPAN
>
structure.</P
><P
><CODE
CLASS="FUNCTION"
>lwres_gnbaresponse_free()</CODE
>
and
<CODE
CLASS="FUNCTION"
>lwres_gnbarequest_free()</CODE
>
release the memory in resolver context
<CODE
CLASS="VARNAME"
>ctx</CODE
>
that was allocated to the
<SPAN
CLASS="TYPE"
>lwres_gnbaresponse_t</SPAN
>
or
<SPAN
CLASS="TYPE"
>lwres_gnbarequest_t</SPAN
>
structures referenced via
<CODE
CLASS="VARNAME"
>structp</CODE
>.
Any memory associated with ancillary buffers and strings for those
structures is also discarded.</P
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN97"
></A
><H2
>RETURN VALUES</H2
><P
>The getnamebyaddr opcode functions
<CODE
CLASS="FUNCTION"
>lwres_gnbarequest_render()</CODE
>,
<CODE
CLASS="FUNCTION"
>lwres_gnbaresponse_render()</CODE
>
<CODE
CLASS="FUNCTION"
>lwres_gnbarequest_parse()</CODE
>
and
<CODE
CLASS="FUNCTION"
>lwres_gnbaresponse_parse()</CODE
>
all return
<SPAN
CLASS="ERRORCODE"
>LWRES_R_SUCCESS</SPAN
>
on success.
They return
<SPAN
CLASS="ERRORCODE"
>LWRES_R_NOMEMORY</SPAN
>
if memory allocation fails.
<SPAN
CLASS="ERRORCODE"
>LWRES_R_UNEXPECTEDEND</SPAN
>
is returned if the available space in the buffer
<CODE
CLASS="VARNAME"
>b</CODE
>
is too small to accommodate the packet header or the
<SPAN
CLASS="TYPE"
>lwres_gnbarequest_t</SPAN
>
and
<SPAN
CLASS="TYPE"
>lwres_gnbaresponse_t</SPAN
>
structures.
<CODE
CLASS="FUNCTION"
>lwres_gnbarequest_parse()</CODE
>
and
<CODE
CLASS="FUNCTION"
>lwres_gnbaresponse_parse()</CODE
>
will return
<SPAN
CLASS="ERRORCODE"
>LWRES_R_UNEXPECTEDEND</SPAN
>
if the buffer is not empty after decoding the received packet.
These functions will return
<SPAN
CLASS="ERRORCODE"
>LWRES_R_FAILURE</SPAN
>
if
<CODE
CLASS="STRUCTFIELD"
>pktflags</CODE
>
in the packet header structure
<SPAN
CLASS="TYPE"
>lwres_lwpacket_t</SPAN
>
indicate that the packet is not a response to an earlier query.</P
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN116"
></A
><H2
>SEE ALSO</H2
><P
><SPAN
CLASS="CITEREFENTRY"
><SPAN
CLASS="REFENTRYTITLE"
>lwres_packet</SPAN
>(3)</SPAN
>.</P
></DIV
></BODY
></HTML
>