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lwres_gabn

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 © 2004, 2005 Internet Systems Consortium, Inc. ("ISC")