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ISC Internet Systems Consortium, Inc. lwres_gabn 3 BIND9 2000 2001 2004 2005 2007 2014 2015 2016 2018 2019 2020 Internet Systems Consortium, Inc. ("ISC") 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


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 lightweight 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.

typedef struct lwres_addr lwres_addr_t;
typedef LWRES_LIST(lwres_addr_t) lwres_addrlist_t;
typedef struct {
        uint32_t  flags;
        uint32_t  addrtypes;
        uint16_t  namelen;
        char           *name;
} lwres_gabnrequest_t;
typedef struct {
        uint32_t          flags;
        uint16_t          naliases;
        uint16_t          naddrs;
        char                   *realname;
        char                  **aliases;
        uint16_t          realnamelen;
        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.


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.