Man page for lwres_context
June 2, 2007 – 1:35 amLWRES_CONTEXT
Section: BIND9 (3)
Updated: Jun 30, 2000
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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()
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.
SEE ALSO
lwres_conf_init(3),
malloc(3),
free(3).
COPYRIGHT
Copyright © 2004, 2005, 2007 Internet Systems Consortium, Inc. ("ISC")
Copyright © 2000, 2001, 2003 Internet Software Consortium.
Index
Related posts:
- Man page for lwres_config
- Man page for lwres_gnba
- Man page for lwres_noop
- Man page for lwres_gabn
- man lwresd – Man page for lwresd
- man Net::DNS::Resolver::UNIX – Man page for Net::DNS::Resolver::UNIX
- man Net::DNS::Resolver::Base – Man page for Net::DNS::Resolver::Base
- man Net::DNS::Resolver::Base – Man page for Net::DNS::Resolver::Base
- man spi_pfree – Man page for spi_pfree
- Man page for lwres
