Ubuntu Manpage: lwres_context_create, lwres_context_destroy, lwres_context

Provided by: libbind-dev_9.11.3+dfsg-1ubuntu1.18_amd64

NAME

       lwres_context_create, lwres_context_destroy, lwres_context_nextserial,
       lwres_context_initserial, lwres_context_freemem, lwres_context_allocmem,
       lwres_context_sendrecv - lightweight resolver context management

SYNOPSIS

       #include <lwres/lwres.h>

       lwres_result_t lwres_context_create(lwres_context_t **contextp, void *arg,
                                           lwres_malloc_t malloc_function,
                                           lwres_free_t free_function);

       lwres_result_t lwres_context_destroy(lwres_context_t **contextp);

       void lwres_context_initserial(lwres_context_t *ctx, lwres_uint32_t serial);

       lwres_uint32_t lwres_context_nextserial(lwres_context_t *ctx);

       void lwres_context_freemem(lwres_context_t *ctx, void *mem, size_t len);

       void lwres_context_allocmem(lwres_context_t *ctx, size_t len);

       void * lwres_context_sendrecv(lwres_context_t *ctx, void *sendbase, int sendlen,
                                     void *recvbase, int recvlen, int *recvd_len);

DESCRIPTION

lwres_context_create() creates a lwres_context_t structure for use in lightweight resolver
operations. It holds a socket and other data needed for communicating with a resolver
daemon. The new lwres_context_t is returned through contextp, a pointer to a
lwres_context_t pointer. This lwres_context_t pointer must initially be NULL, and is
modified to point to the newly created lwres_context_t.

When the lightweight resolver needs to perform dynamic memory allocation, it will call
malloc_function to allocate memory and free_function to free it. If malloc_function and
free_function are NULL, memory is allocated using malloc(3). and free(3). It is not
permitted to have a NULL malloc_function and a non-NULL free_function or vice versa. arg
is passed as the first parameter to the memory allocation functions. If malloc_function
and free_function are NULL, arg is unused and should be passed as NULL.

Once memory for the structure has been allocated, it is initialized using
lwres_conf_init(3) and returned via *contextp.

lwres_context_destroy() destroys a lwres_context_t, closing its socket. contextp is a
pointer to a pointer to the context that is to be destroyed. The pointer will be set to
NULL when the context has been destroyed.

The context holds a serial number that is used to identify resolver request packets and
associate responses with the corresponding requests. This serial number is controlled
using lwres_context_initserial() and lwres_context_nextserial().
lwres_context_initserial() sets the serial number for context *ctx to serial.
lwres_context_nextserial() increments the serial number and returns the previous value.

Memory for a lightweight resolver context is allocated and freed using
lwres_context_allocmem() and lwres_context_freemem(). These use whatever allocations were
defined when the context was created with lwres_context_create().
lwres_context_allocmem() allocates len bytes of memory and if successful returns a pointer
to the allocated storage. lwres_context_freemem() frees len bytes of space starting at
location mem.

lwres_context_sendrecv() performs I/O for the context ctx. Data are read and written from
the context's socket. It writes data from sendbase — typically a lightweight resolver
query packet — and waits for a reply which is copied to the receive buffer at recvbase.
The number of bytes that were written to this receive buffer is returned in *recvd_len.

RETURN VALUES

       lwres_context_create() returns LWRES_R_NOMEMORY if memory for the struct lwres_context
       could not be allocated, LWRES_R_SUCCESS otherwise.

       Successful calls to the memory allocator lwres_context_allocmem() return a pointer to the
       start of the allocated space. It returns NULL if memory could not be allocated.

       LWRES_R_SUCCESS is returned when lwres_context_sendrecv() completes successfully.
       LWRES_R_IOERROR is returned if an I/O error occurs and LWRES_R_TIMEOUT is returned if
       lwres_context_sendrecv() times out waiting for a response.

AUTHOR

       Internet Systems Consortium, Inc.

COPYRIGHT