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).

AUTHOR

       Internet Systems Consortium, Inc.

COPYRIGHT

       Copyright © 2000, 2001, 2004, 2005, 2007, 2014-2016 Internet Systems Consortium, Inc.
       ("ISC")