LWRES_GABN(3)

NAME

lwres_gabnrequest_render, lwres_gabnresponse_render,
lwres_gabnrequest_parse, lwres_gabnresponse_parse,
lwres_gabnresponse_free, lwres_gabnrequest_free - lightweight resolver getaddrbyname message handling

SYNOPSIS

#include <lwres/lwres.h>

lwres_result_t lwres_gabnrequest_render(lwres_context_t *ctx,
                                        lwres_gabnrequest_t *req,
                                        lwres_lwpacket_t *pkt,
                                        lwres_buffer_t *b);

lwres_result_t lwres_gabnresponse_render(lwres_context_t *ctx,
                                         lwres_gabnresponse_t *req,
                                         lwres_lwpacket_t *pkt,
                                         lwres_buffer_t *b);

lwres_result_t lwres_gabnrequest_parse(lwres_context_t *ctx,
                                       lwres_buffer_t *b,
                                       lwres_lwpacket_t *pkt,
                                       lwres_gabnrequest_t **structp);

lwres_result_t lwres_gabnresponse_parse(lwres_context_t *ctx,
                                        lwres_buffer_t *b,
                                        lwres_lwpacket_t *pkt,
                                        lwres_gabnresponse_t **structp);

void lwres_gabnresponse_free(lwres_context_t *ctx,
                             lwres_gabnresponse_t **structp);

void lwres_gabnrequest_free(lwres_context_t *ctx,
                            lwres_gabnrequest_t **structp);

DESCRIPTION

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

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

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

#define LWRES_OPCODE_GETADDRSBYNAME 0x00010001U

typedef struct lwres_addr lwres_addr_t;
typedef LWRES_LIST(lwres_addr_t) lwres_addrlist_t;

typedef struct {

lwres_uint32_t flags;
lwres_uint32_t addrtypes;
lwres_uint16_t namelen;
char *name;

} lwres_gabnrequest_t;

typedef struct {

lwres_uint32_t flags;
lwres_uint16_t naliases;
lwres_uint16_t naddrs;
char *realname;
char **aliases;
lwres_uint16_t realnamelen;
lwres_uint16_t *aliaslen;
lwres_addrlist_t addrs;
void *base;
size_t baselen;

} lwres_gabnresponse_t;

lwres_gabnrequest_render() uses resolver context ctx to convert getaddrbyname 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_gabnresponse_render() performs the same task, except it converts a getaddrbyname response structure lwres_gabnresponse_t to the lightweight resolver's canonical format.

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

lwres_gabnresponse_free() and lwres_gabnrequest_free() release the memory in resolver context ctx that was allocated to the
lwres_gabnresponse_t or lwres_gabnrequest_t structures referenced via structp. Any memory associated with ancillary buffers and strings for those structures is also discarded.

RETURN VALUES

The getaddrbyname opcode functions lwres_gabnrequest_render(), lwres_gabnresponse_render() lwres_gabnrequest_parse() and lwres_gabnresponse_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_gabnrequest_t and lwres_gabnresponse_t structures. lwres_gabnrequest_parse() and lwres_gabnresponse_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 Internet Systems Consortium, Inc.
("ISC")
Copyright (C) 2000, 2001 Internet Software Consortium.

BIND9 Jun 30, 2000 LWRES_GABN(3)