LWRES_NOOP(3)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 canon-
ical 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 func-
tion 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 identi-
cal 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 trans-
ferred to buffer b. The contents of *req are then appended
to the buffer in canonical format. lwres_noopresponse_ren-
der() 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 struc-
ture. 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_noopre-
sponse_t structure.
lwres_noopresponse_free() and lwres_nooprequest_free()
release the memory in resolver context ctx that was allo-
cated 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 alloca-
tion fails. LWRES_R_UNEXPECTEDEND is returned if the
available space in the buffer b is too small to accommo-
date the packet header or the lwres_nooprequest_t and
lwres_noopresponse_t structures. lwres_noopre-
quest_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 ALSOlwres_packet(3)BIND9 Jun 30, 2000 LWRES_NOOP(3)
