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

#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); .SH "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

     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.

     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