Permission to use, copy, modify, and distribute this software for any
purpose with or without fee is hereby granted, provided that the above
copyright notice and this permission notice appear in all copies.
THE SOFTWARE IS PROVIDED "AS IS" AND INTERNET SOFTWARE CONSORTIUM
DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL
INTERNET SOFTWARE CONSORTIUM BE LIABLE FOR ANY SPECIAL, DIRECT,
INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING
FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT,
NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION
WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
$Id: lwres_noop.3,v 1.6 2001/01/09 21:50:12 bwelling Exp $
.Dd Jun 30, 2000 .Dt LWRES_NOOP 3 .Os BIND9 9 .Sh NAME .Nm lwres_nooprequest_render , .Nm lwres_noopresponse_render , .Nm lwres_nooprequest_parse , .Nm lwres_noopresponse_parse , .Nm lwres_noopresponse_free , .Nm lwres_nooprequest_free .Nd lightweight resolver no-op message handling .Sh SYNOPSIS .Fd #include <lwres/lwres.h> .Fd .Ft lwres_result_t .Fo lwres_nooprequest_render .Fa "lwres_context_t *ctx" .Fa "lwres_nooprequest_t *req" .Fa "lwres_lwpacket_t *pkt" .Fa "lwres_buffer_t *b" .Fc .Ft lwres_result_t .Fo lwres_noopresponse_render .Fa "lwres_context_t *ctx" .Fa "lwres_noopresponse_t *req" .Fa "lwres_lwpacket_t *pkt" .Fa "lwres_buffer_t *b" .Fc .Ft lwres_result_t .Fo lwres_nooprequest_parse .Fa "lwres_context_t *ctx" .Fa "lwres_buffer_t *b" .Fa "lwres_lwpacket_t *pkt" .Fa "lwres_nooprequest_t **structp" .Fc .Ft lwres_result_t .Fo lwres_noopresponse_parse .Fa "lwres_context_t *ctx" .Fa "lwres_buffer_t *b" .Fa "lwres_lwpacket_t *pkt" .Fa "lwres_noopresponse_t **structp" .Fc .Ft void .Fo lwres_noopresponse_free .Fa "lwres_context_t *ctx" .Fa "lwres_noopresponse_t **structp" .Fc .Ft void .Fo lwres_nooprequest_free .Fa "lwres_context_t *ctx" .Fa "lwres_nooprequest_t **structp" .Fc .Sh 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 \*qping\*q 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.
p There are four main functions for the no-op opcode. One render function converts a no-op request structure - .Dv 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 - .Dv 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.
p These structures are defined in
a lwres/lwres.h . They are shown below. d -literal -offset indent #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; .Ed 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.
p .Fn lwres_nooprequest_render uses resolver context .Fa ctx to convert no-op request structure .Fa req to canonical format. The packet header structure .Fa pkt is initialised and transferred to buffer .Fa b . The contents of .Fa *req are then appended to the buffer in canonical format. .Fn lwres_noopresponse_render performs the same task, except it converts a no-op response structure .Dv lwres_noopresponse_t to the lightweight resolver's canonical format.
p .Fn lwres_nooprequest_parse uses context .Fa ctx to convert the contents of packet .Fa pkt to a .Dv lwres_nooprequest_t structure. Buffer .Fa b provides space to be used for storing this structure. When the function succeeds, the resulting .Dv lwres_nooprequest_t is made available through .Fa *structp . .Fn lwres_noopresponse_parse offers the same semantics as .Fn lwres_nooprequest_parse except it yields a .Dv lwres_noopresponse_t structure.
p .Fn lwres_noopresponse_free and .Fn lwres_nooprequest_free release the memory in resolver context .Fa ctx that was allocated to the .Dv lwres_noopresponse_t or .Dv lwres_nooprequest_t structures referenced via .Fa structp . .Sh RETURN VALUES The no-op opcode functions .Fn lwres_nooprequest_render , .Fn lwres_noopresponse_render .Fn lwres_nooprequest_parse and .Fn lwres_noopresponse_parse all return .Er LWRES_R_SUCCESS on success. They return .Er LWRES_R_NOMEMORY if memory allocation fails. .Er LWRES_R_UNEXPECTEDEND is returned if the available space in the buffer .Fa b is too small to accommodate the packet header or the .Dv lwres_nooprequest_t and .Dv lwres_noopresponse_t structures. .Fn lwres_nooprequest_parse and .Fn lwres_noopresponse_parse will return .Er LWRES_R_UNEXPECTEDEND if the buffer is not empty after decoding the received packet. These functions will return .Er LWRES_R_FAILURE if .Li pktflags in the packet header structure .Dv lwres_lwpacket_t indicate that the packet is not a response to an earlier query. .Sh SEE ALSO .Xr lwres_packet 3