LWRES_NOOP(3)							       BIND9							     LWRES_NOOP(3)

NAME

       lwres_nooprequest_render, lwres_noopresponse_render, lwres_nooprequest_parse, lwres_noopresponse_parse, lwres_noopresponse_free,
       lwres_nooprequest_free - lightweight resolver no-op message handling

SYNOPSIS

       #include <lwres/lwres.h>

       lwres_result_t lwres_nooprequest_render(lwres_context_t *ctx, lwres_nooprequest_t *req, lwres_lwpacket_t *pkt, lwres_buffer_t *b);

       lwres_result_t lwres_noopresponse_render(lwres_context_t *ctx, lwres_noopresponse_t *req, lwres_lwpacket_t *pkt, lwres_buffer_t *b);

       lwres_result_t lwres_nooprequest_parse(lwres_context_t *ctx, lwres_buffer_t *b, lwres_lwpacket_t *pkt, lwres_nooprequest_t **structp);

       lwres_result_t lwres_noopresponse_parse(lwres_context_t *ctx, lwres_buffer_t *b, lwres_lwpacket_t *pkt, lwres_noopresponse_t **structp);

       void lwres_noopresponse_free(lwres_context_t *ctx, lwres_noopresponse_t **structp);

       void lwres_nooprequest_free(lwres_context_t *ctx, lwres_nooprequest_t **structp);

DESCRIPTION

       These are low-level routines for creating and parsing lightweight resolver no-op request and response messages.

       The no-op message is analogous to a ping packet: a packet is sent to the resolver daemon and is simply echoed back. The opcode is intended
       to allow a client to determine if the server is operational or not.

       There are four main functions for the no-op opcode. One render function converts a no-op request structure -- lwres_nooprequest_t -- to the
       lighweight resolver's canonical format. It is complemented by a parse function that converts a packet in this canonical format to a no-op
       request structure. Another render function converts the no-op response structure -- lwres_noopresponse_t to the canonical format. This is
       complemented by a parse function which converts a packet in canonical format to a no-op response structure.

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

	   #define LWRES_OPCODE_NOOP	   0x00000000U

	   typedef struct {
		   lwres_uint16_t  datalength;
		   unsigned char   *data;
	   } lwres_nooprequest_t;

	   typedef struct {
		   lwres_uint16_t  datalength;
		   unsigned char   *data;
	   } lwres_noopresponse_t;

       Although the structures have different types, they are identical. This is because the no-op opcode simply echos whatever data was sent: the
       response is therefore identical to the request.

       lwres_nooprequest_render() uses resolver context ctx to convert no-op 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_noopresponse_render() performs the same task, except it converts a no-op response structure lwres_noopresponse_t to the lightweight
       resolver's canonical format.

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

       lwres_noopresponse_free() and lwres_nooprequest_free() release the memory in resolver context ctx that was allocated to the
       lwres_noopresponse_t or lwres_nooprequest_t structures referenced via structp.

RETURN VALUES

       The no-op opcode functions lwres_nooprequest_render(), lwres_noopresponse_render() lwres_nooprequest_parse() and lwres_noopresponse_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_nooprequest_t and lwres_noopresponse_t
       structures.  lwres_nooprequest_parse() and lwres_noopresponse_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.

SEE ALSO

       lwres_packet(3)

COPYRIGHT

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

BIND9								   Jun 30, 2000 						     LWRES_NOOP(3)