lwres_noop (3)
NAME
lwres_nooprequest_render, lwres_noopresponse_render, lwres_noopre-
quest_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 func-
tion 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 {
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_noopre-
sponse_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_noopre-
quest_parse() except it yields a lwres_noopresponse_t structure.
lwres_noopresponse_free() and lwres_nooprequest_free() release the mem-
ory in resolver context ctx that was allocated to the lwres_noopre-
sponse_t or lwres_nooprequest_t structures referenced via structp.
RETURN VALUES
The no-op opcode functions lwres_nooprequest_render(), lwres_noopre-
sponse_render() lwres_nooprequest_parse() and lwres_noopre-
sponse_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 accom-
modate the packet header or the lwres_nooprequest_t and lwres_noopre-
sponse_t structures. lwres_nooprequest_parse() and lwres_noopre-
sponse_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 ear-
lier query.
SEE ALSO
lwres_packet(3)
BIND9 Jun 30, 2000 lwres_noop(3)