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
lightweight 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)
AUTHOR
Internet Systems Consortium, Inc.
COPYRIGHT
Copyright (C) 2004, 2005, 2007, 2014, 2015 Internet Systems Consortium,
Inc. ("ISC")
Copyright (C) 2000, 2001 Internet Software Consortium.
ISC 2007-06-18 lwres_noop(3)
bind 9.10.4 - Generated Fri Apr 29 20:49:37 CDT 2016