Jun 30, 2000
lwres_gabn
3
BIND9
2004
2005
2007
2012
Internet Systems Consortium, Inc. ("ISC")
2000
2001
Internet Software Consortium.

# lwres_gabnrequest_render

# lwres_gabnresponse_render

# lwres_gabnrequest_parse

# lwres_gabnresponse_parse

# lwres_gabnresponse_free

# lwres_gabnrequest_free

lightweight resolver getaddrbyname message handling

    #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 &mdash; lwres_gabnrequest_t &mdash; 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 &mdash; lwres_gabnresponse_t &mdash; 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