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_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 )



BIND9                      Jun 30, 2000             LWRES_NOOP(3)