lwres_gnbaresponse_parse (3) Linux Manual Page

There are four main functions for the getnamebyaddr opcode. One render function converts a getnamebyaddr request structure — lwres_gnbarequest_t — to the lightweight resolver’s canonical format. It is complemented by a parse function that converts a packet in this canonical format to a getnamebyaddr request structure. Another render function converts the getnamebyaddr response structure — lwres_gnbaresponse_t to the canonical format. This is complemented by a parse function which converts a packet in canonical format to a getnamebyaddr response structure.

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

#define LWRES_OPCODE_GETNAMEBYADDR 0x00010002U

typedef struct {
lwres_uint32_t flags;
lwres_addr_t addr;
} lwres_gnbarequest_t;

typedef struct {
    lwres_uint32_t flags;
    lwres_uint16_t naliases;
    char *realname;
    char **aliases;
    lwres_uint16_t realnamelen;
    lwres_uint16_t *aliaslen;
    void *base;
    size_t baselen;
} lwres_gnbaresponse_t;

lwres_gnbarequest_render() uses resolver context ctx to convert getnamebyaddr 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_gnbaresponse_render() performs the same task, except it converts a getnamebyaddr response structure lwres_gnbaresponse_t to the lightweight resolver’s canonical format.

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

lwres_gnbaresponse_free() and lwres_gnbarequest_free() release the memory in resolver context ctx that was allocated to the lwres_gnbaresponse_t or lwres_gnbarequest_t structures referenced via structp. Any memory associated with ancillary buffers and strings for those structures is also discarded.

RETURN VALUES

The getnamebyaddr opcode functions lwres_gnbarequest_render(), lwres_gnbaresponse_render() lwres_gnbarequest_parse() and lwres_gnbaresponse_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_gnbarequest_t and lwres_gnbaresponse_t structures. lwres_gnbarequest_parse() and lwres_gnbaresponse_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, 2007 Internet Systems Consortium, Inc. ("ISC")
Copyright © 2000, 2001 Internet Software Consortium.

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