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       lwres_gabnrequest_render, lwres_gabnresponse_render,
       lwres_gabnrequest_parse,	lwres_gabnresponse_parse,
       lwres_gabnresponse_free,	lwres_gabnrequest_free - lightweight resolver
       getaddrbyname message handling

       #include	<lwres/lwres.h>

       lwres_result_t lwres_gabnrequest_render(lwres_context_t *ctx,
					       lwres_gabnrequest_t *req,
					       lwres_lwpacket_t	*pkt,
					       lwres_buffer_t *b);

       lwres_result_t lwres_gabnresponse_render(lwres_context_t	*ctx,
						lwres_gabnresponse_t *req,
						lwres_lwpacket_t *pkt,
						lwres_buffer_t *b);

       lwres_result_t lwres_gabnrequest_parse(lwres_context_t *ctx,
					      lwres_buffer_t *b,
					      lwres_lwpacket_t *pkt,
					      lwres_gabnrequest_t **structp);

       lwres_result_t lwres_gabnresponse_parse(lwres_context_t *ctx,
					       lwres_buffer_t *b,
					       lwres_lwpacket_t	*pkt,
					       lwres_gabnresponse_t **structp);

       void lwres_gabnresponse_free(lwres_context_t *ctx,
				    lwres_gabnresponse_t **structp);

       void lwres_gabnrequest_free(lwres_context_t *ctx,
				   lwres_gabnrequest_t **structp);

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

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

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

	   #define LWRES_OPCODE_GETADDRSBYNAME	   0x00010001U

	   typedef struct lwres_addr lwres_addr_t;
	   typedef LWRES_LIST(lwres_addr_t) lwres_addrlist_t;

	   typedef struct {
		   uint32_t  flags;
		   uint32_t  addrtypes;
		   uint16_t  namelen;
		   char		  *name;
	   } lwres_gabnrequest_t;

	   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;

       lwres_gabnrequest_render() uses resolver	context	ctx to convert
       getaddrbyname 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_gabnresponse_render() performs the	same task, except it converts
       a getaddrbyname response	structure lwres_gabnresponse_t to the
       lightweight resolver's canonical	format.

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

       lwres_gabnresponse_free() and lwres_gabnrequest_free() release the
       memory in resolver context ctx that was allocated to the
       lwres_gabnresponse_t or lwres_gabnrequest_t structures referenced via
       structp.	Any memory associated with ancillary buffers and strings for
       those structures	is also	discarded.

       The getaddrbyname opcode	functions lwres_gabnrequest_render(),
       lwres_gabnresponse_render()lwres_gabnrequest_parse() and
       lwres_gabnresponse_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_gabnrequest_t and lwres_gabnresponse_t structures.
       lwres_gabnrequest_parse() and lwres_gabnresponse_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.


       Internet	Systems	Consortium, Inc.

       Copyright (C) 2000, 2001, 2004, 2005, 2007, 2014-2016, 2018-2020
       Internet	Systems	Consortium, Inc. ("ISC")

ISC				  2007-06-18			 LWRES_GABN(3)


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