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)