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LWRES_GNBA(3)                        BIND9                       LWRES_GNBA(3)

NAME
       lwres_gnbarequest_render, lwres_gnbaresponse_render,
       lwres_gnbarequest_parse, lwres_gnbaresponse_parse,
       lwres_gnbaresponse_free, lwres_gnbarequest_free - lightweight resolver
       getnamebyaddress message handling

SYNOPSIS
       #include <lwres/lwres.h>

       lwres_result_t lwres_gnbarequest_render(lwres_context_t *ctx,
                                               lwres_gnbarequest_t *req,
                                               lwres_lwpacket_t *pkt,
                                               lwres_buffer_t *b);

       lwres_result_t lwres_gnbaresponse_render(lwres_context_t *ctx,
                                                lwres_gnbaresponse_t *req,
                                                lwres_lwpacket_t *pkt,
                                                lwres_buffer_t *b);

       lwres_result_t lwres_gnbarequest_parse(lwres_context_t *ctx,
                                              lwres_buffer_t *b,
                                              lwres_lwpacket_t *pkt,
                                              lwres_gnbarequest_t **structp);

       lwres_result_t lwres_gnbaresponse_parse(lwres_context_t *ctx,
                                               lwres_buffer_t *b,
                                               lwres_lwpacket_t *pkt,
                                               lwres_gnbaresponse_t **structp);

       void lwres_gnbaresponse_free(lwres_context_t *ctx,
                                    lwres_gnbaresponse_t **structp);

       void lwres_gnbarequest_free(lwres_context_t *ctx,
                                   lwres_gnbarequest_t **structp);

DESCRIPTION
       These are low-level routines for creating and parsing lightweight
       resolver address-to-name lookup request and response messages.

       There are four main functions for the getnamebyaddr opcode. One render
       function converts a getnamebyaddr request structure --
       lwres_gnbarequest_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 getnamebyaddr request structure. Another render
       function converts the getnamebyaddr response structure --
       lwres_gnbaresponse_t to the canonical format. This is complemented by a
       parse function which converts a packet in canonical format to a
       getnamebyaddr response structure.

       These structures are defined in lwres/lwres.h. They are shown below.

           #define LWRES_OPCODE_GETNAMEBYADDR      0x00010002U

           typedef struct {
                   lwres_uint32_t  flags;
                   lwres_addr_t    addr;
           } lwres_gnbarequest_t;

           typedef struct {
                   lwres_uint32_t  flags;
                   lwres_uint16_t  naliases;
                   char           *realname;
                   char          **aliases;
                   lwres_uint16_t  realnamelen;
                   lwres_uint16_t *aliaslen;
                   void           *base;
                   size_t          baselen;
           } lwres_gnbaresponse_t;

       lwres_gnbarequest_render() uses resolver context ctx to convert
       getnamebyaddr 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_gnbaresponse_render() performs the same task, except it converts
       a getnamebyaddr response structure lwres_gnbaresponse_t to the
       lightweight resolver's canonical format.

       lwres_gnbarequest_parse() uses context ctx to convert the contents of
       packet pkt to a lwres_gnbarequest_t structure. Buffer b provides space
       to be used for storing this structure. When the function succeeds, the
       resulting lwres_gnbarequest_t is made available through *structp.
       lwres_gnbaresponse_parse() offers the same semantics as
       lwres_gnbarequest_parse() except it yields a lwres_gnbaresponse_t
       structure.

       lwres_gnbaresponse_free() and lwres_gnbarequest_free() release the
       memory in resolver context ctx that was allocated to the
       lwres_gnbaresponse_t or lwres_gnbarequest_t structures referenced via
       structp. Any memory associated with ancillary buffers and strings for
       those structures is also discarded.

RETURN VALUES
       The getnamebyaddr opcode functions lwres_gnbarequest_render(),
       lwres_gnbaresponse_render() lwres_gnbarequest_parse() and
       lwres_gnbaresponse_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_gnbarequest_t and lwres_gnbaresponse_t structures.
       lwres_gnbarequest_parse() and lwres_gnbaresponse_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).

COPYRIGHT
       Copyright (C) 2004, 2005, 2007, 2014 Internet Systems Consortium, Inc.
       ("ISC")
       Copyright (C) 2000, 2001 Internet Software Consortium.

BIND9                            June 18, 2007                   LWRES_GNBA(3)