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       lwres_gnbarequest_render, lwres_gnbaresponse_render,
       lwres_gnbarequest_parse,	lwres_gnbaresponse_parse,
       lwres_gnbaresponse_free,	lwres_gnbarequest_free - lightweight resolver
       getnamebyaddress	message	handling

       #include	<lwres/lwres.h>

       lwres_result_t lwres_gnbarequest_render(lwres_context_t *ctx,
					       lwres_gnbarequest_t *req,
					       lwres_lwpacket_t	*pkt,
					       lwres_buffer_t *b);

       lwres_result_t lwres_gnbaresponse_render(lwres_context_t	*ctx,
						lwres_gnbaresponse_t *req,
						lwres_lwpacket_t *pkt,
						lwres_buffer_t *b);

       lwres_result_t lwres_gnbarequest_parse(lwres_context_t *ctx,
					      lwres_buffer_t *b,
					      lwres_lwpacket_t *pkt,
					      lwres_gnbarequest_t **structp);

       lwres_result_t lwres_gnbaresponse_parse(lwres_context_t *ctx,
					       lwres_buffer_t *b,
					       lwres_lwpacket_t	*pkt,
					       lwres_gnbaresponse_t **structp);

       void lwres_gnbaresponse_free(lwres_context_t *ctx,
				    lwres_gnbaresponse_t **structp);

       void lwres_gnbarequest_free(lwres_context_t *ctx,
				   lwres_gnbarequest_t **structp);

       These are low-level routines for	creating and parsing lightweight
       resolver	address-to-name	lookup request and response messages.

       There are four main functions for the getnamebyaddr opcode. One render
       function	converts a getnamebyaddr request structure --
       lwres_gnbarequest_t -- 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 --
       lwres_gnbaresponse_t to the canonical format. This is complemented by a
       parse function which converts a packet in canonical format to a
       getnamebyaddr response structure.

       These structures	are defined in lwres/lwres.h. They are shown below.

	   #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;

       lwres_gnbarequest_render() uses resolver	context	ctx to convert
       getnamebyaddr request structure req to canonical	format.	The packet
       header structure	pkt is initialised and transferred to buffer b.	The
       contents	of *req	are then appended to the buffer	in canonical format.
       lwres_gnbaresponse_render() performs the	same task, except it converts
       a getnamebyaddr response	structure lwres_gnbaresponse_t to the
       lightweight resolver's canonical	format.

       lwres_gnbarequest_parse() uses context ctx to convert the contents of
       packet pkt to a lwres_gnbarequest_t structure. Buffer b provides	space
       to be used for storing this structure. When the function	succeeds, the
       resulting lwres_gnbarequest_t is	made available through *structp.
       lwres_gnbaresponse_parse() offers the same semantics as
       lwres_gnbarequest_parse() except	it yields a lwres_gnbaresponse_t

       lwres_gnbaresponse_free() and lwres_gnbarequest_free() release the
       memory in resolver context ctx that was allocated to the
       lwres_gnbaresponse_t or lwres_gnbarequest_t structures referenced via
       structp.	Any memory associated with ancillary buffers and strings for
       those structures	is also	discarded.

       The getnamebyaddr opcode	functions lwres_gnbarequest_render(),
       lwres_gnbaresponse_render() lwres_gnbarequest_parse() and
       lwres_gnbaresponse_parse() all return LWRES_R_SUCCESS on	success. They
       return LWRES_R_NOMEMORY if memory allocation fails.
       LWRES_R_UNEXPECTEDEND is	returned if the	available space	in the buffer
       b is too	small to accommodate the packet	header or the
       lwres_gnbarequest_t and lwres_gnbaresponse_t structures.
       lwres_gnbarequest_parse() and lwres_gnbaresponse_parse()	will return
       LWRES_R_UNEXPECTEDEND if	the buffer is not empty	after decoding the
       received	packet.	These functions	will return LWRES_R_FAILURE if
       pktflags	in the packet header structure lwres_lwpacket_t	indicate that
       the packet is not a response to an earlier query.


       Copyright (C) 2004, 2005, 2007, 2012 Internet Systems Consortium, Inc.
       Copyright (C) 2000, 2001	Internet Software Consortium.

BIND9				 Jun 30, 2000			 LWRES_GNBA(3)


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