1LWRES_CONTEXT(3) BIND9 LWRES_CONTEXT(3)
2
6 lwres_context_create, lwres_context_destroy, lwres_context_nextserial,
7 lwres_context_initserial, lwres_context_freemem,
8 lwres_context_allocmem, lwres_context_sendrecv - lightweight resolver
9 context management
10
12 #include <lwres/lwres.h>
13 lwres_result_t lwres_context_create(lwres_context_t **contextp,
15 void *arg,
16 lwres_malloc_t malloc_function,
17 lwres_free_t free_function);
18 lwres_result_t lwres_context_destroy(lwres_context_t **contextp);
20 void lwres_context_initserial(lwres_context_t *ctx,
22 lwres_uint32_t serial);
23 lwres_uint32_t lwres_context_nextserial(lwres_context_t *ctx);
25 void lwres_context_freemem(lwres_context_t *ctx, void *mem,
27 size_t len);
28 void lwres_context_allocmem(lwres_context_t *ctx, size_t len);
30 void * lwres_context_sendrecv(lwres_context_t *ctx, void *sendbase,
32 int sendlen, void *recvbase, int recvlen,
33 int *recvd_len);
34
36 lwres_context_create() creates a lwres_context_t structure for use in
37 lightweight resolver operations. It holds a socket and other data
38 needed for communicating with a resolver daemon. The new
39 lwres_context_t is returned through contextp, a pointer to a
40 lwres_context_t pointer. This lwres_context_t pointer must initially be
41 NULL, and is modified to point to the newly created lwres_context_t.
42 When the lightweight resolver needs to perform dynamic memory
44 allocation, it will call malloc_function to allocate memory and
45 free_function to free it. If malloc_function and free_function are
46 NULL, memory is allocated using malloc(3). and free(3). It is not
47 permitted to have a NULL malloc_function and a non-NULL free_function
48 or vice versa. arg is passed as the first parameter to the memory
49 allocation functions. If malloc_function and free_function are NULL,
50 arg is unused and should be passed as NULL.
51 Once memory for the structure has been allocated, it is initialized
53 using lwres_conf_init(3) and returned via *contextp.
54 lwres_context_destroy() destroys a lwres_context_t, closing its socket.
56 contextp is a pointer to a pointer to the context that is to be
57 destroyed. The pointer will be set to NULL when the context has been
58 destroyed.
59 The context holds a serial number that is used to identify resolver
61 request packets and associate responses with the corresponding
62 requests. This serial number is controlled using
63 lwres_context_initserial() and lwres_context_nextserial().
64 lwres_context_initserial() sets the serial number for context *ctx to
65 serial. lwres_context_nextserial() increments the serial number and
66 returns the previous value.
67 Memory for a lightweight resolver context is allocated and freed using
69 lwres_context_allocmem() and lwres_context_freemem(). These use
70 whatever allocations were defined when the context was created with
71 lwres_context_create(). lwres_context_allocmem() allocates len bytes
72 of memory and if successful returns a pointer to the allocated storage.
73 lwres_context_freemem() frees len bytes of space starting at location
74 mem.
75 lwres_context_sendrecv() performs I/O for the context ctx. Data are
77 read and written from the context's socket. It writes data from
78 sendbase — typically a lightweight resolver query packet — and waits
79 for a reply which is copied to the receive buffer at recvbase. The
80 number of bytes that were written to this receive buffer is returned in
81 *recvd_len.
82
84 lwres_context_create() returns LWRES_R_NOMEMORY if memory for the
85 struct lwres_context could not be allocated, LWRES_R_SUCCESS otherwise.
86 Successful calls to the memory allocator lwres_context_allocmem()
88 return a pointer to the start of the allocated space. It returns NULL
89 if memory could not be allocated.
90 LWRES_R_SUCCESS is returned when lwres_context_sendrecv() completes
92 successfully. LWRES_R_IOERROR is returned if an I/O error occurs and
93 LWRES_R_TIMEOUT is returned if lwres_context_sendrecv() times out
94 waiting for a response.
95
97 lwres_conf_init(3), malloc(3), free(3).
98
100 Internet Systems Consortium, Inc.
101
103 Copyright © 2000, 2001, 2003-2005, 2007, 2014-2016, 2018 Internet
104 Systems Consortium, Inc. ("ISC")
105ISC 2007-06-18 LWRES_CONTEXT(3)