1LWRES_NOOP(3)                        BIND9                       LWRES_NOOP(3)
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3
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NAME

6       lwres_nooprequest_render, lwres_noopresponse_render,
7       lwres_nooprequest_parse, lwres_noopresponse_parse,
8       lwres_noopresponse_free, lwres_nooprequest_free - lightweight resolver
9       no-op message handling
10

SYNOPSIS

12       #include <lwres/lwres.h>
13
14       lwres_result_t lwres_nooprequest_render(lwres_context_t *ctx,
15                                               lwres_nooprequest_t *req,
16                                               lwres_lwpacket_t *pkt,
17                                               lwres_buffer_t *b);
18
19       lwres_result_t lwres_noopresponse_render(lwres_context_t *ctx,
20                                                lwres_noopresponse_t *req,
21                                                lwres_lwpacket_t *pkt,
22                                                lwres_buffer_t *b);
23
24       lwres_result_t lwres_nooprequest_parse(lwres_context_t *ctx,
25                                              lwres_buffer_t *b,
26                                              lwres_lwpacket_t *pkt,
27                                              lwres_nooprequest_t **structp);
28
29       lwres_result_t lwres_noopresponse_parse(lwres_context_t *ctx,
30                                               lwres_buffer_t *b,
31                                               lwres_lwpacket_t *pkt,
32                                               lwres_noopresponse_t **structp);
33
34       void lwres_noopresponse_free(lwres_context_t *ctx,
35                                    lwres_noopresponse_t **structp);
36
37       void lwres_nooprequest_free(lwres_context_t *ctx,
38                                   lwres_nooprequest_t **structp);
39

DESCRIPTION

41       These are low-level routines for creating and parsing lightweight
42       resolver no-op request and response messages.
43
44       The no-op message is analogous to a ping packet: a packet is sent to
45       the resolver daemon and is simply echoed back. The opcode is intended
46       to allow a client to determine if the server is operational or not.
47
48       There are four main functions for the no-op opcode. One render function
49       converts a no-op request structure — lwres_nooprequest_t — to the
50       lighweight resolver's canonical format. It is complemented by a parse
51       function that converts a packet in this canonical format to a no-op
52       request structure. Another render function converts the no-op response
53       structure — lwres_noopresponse_t to the canonical format. This is
54       complemented by a parse function which converts a packet in canonical
55       format to a no-op response structure.
56
57       These structures are defined in lwres/lwres.h. They are shown below.
58
59           #define LWRES_OPCODE_NOOP       0x00000000U
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61
62           typedef struct {
63                   lwres_uint16_t  datalength;
64                   unsigned char   *data;
65           } lwres_nooprequest_t;
66
67
68           typedef struct {
69                   lwres_uint16_t  datalength;
70                   unsigned char   *data;
71           } lwres_noopresponse_t;
72
73
74       Although the structures have different types, they are identical. This
75       is because the no-op opcode simply echos whatever data was sent: the
76       response is therefore identical to the request.
77
78       lwres_nooprequest_render() uses resolver context ctx to convert no-op
79       request structure req to canonical format. The packet header structure
80       pkt is initialised and transferred to buffer b. The contents of *req
81       are then appended to the buffer in canonical format.
82       lwres_noopresponse_render() performs the same task, except it converts
83       a no-op response structure lwres_noopresponse_t to the lightweight
84       resolver's canonical format.
85
86       lwres_nooprequest_parse() uses context ctx to convert the contents of
87       packet pkt to a lwres_nooprequest_t structure. Buffer b provides space
88       to be used for storing this structure. When the function succeeds, the
89       resulting lwres_nooprequest_t is made available through *structp.
90       lwres_noopresponse_parse() offers the same semantics as
91       lwres_nooprequest_parse() except it yields a lwres_noopresponse_t
92       structure.
93
94       lwres_noopresponse_free() and lwres_nooprequest_free() release the
95       memory in resolver context ctx that was allocated to the
96       lwres_noopresponse_t or lwres_nooprequest_t structures referenced via
97       structp.
98

RETURN VALUES

100       The no-op opcode functions lwres_nooprequest_render(),
101       lwres_noopresponse_render() lwres_nooprequest_parse() and
102       lwres_noopresponse_parse() all return LWRES_R_SUCCESS on success. They
103       return LWRES_R_NOMEMORY if memory allocation fails.
104       LWRES_R_UNEXPECTEDEND is returned if the available space in the buffer
105       b is too small to accommodate the packet header or the
106       lwres_nooprequest_t and lwres_noopresponse_t structures.
107       lwres_nooprequest_parse() and lwres_noopresponse_parse() will return
108       LWRES_R_UNEXPECTEDEND if the buffer is not empty after decoding the
109       received packet. These functions will return LWRES_R_FAILURE if
110       pktflags in the packet header structure lwres_lwpacket_t indicate that
111       the packet is not a response to an earlier query.
112

SEE ALSO

114       lwres_packet(3)
115
117       Copyright © 2004, 2005, 2007 Internet Systems Consortium, Inc. ("ISC")
118       Copyright © 2000, 2001 Internet Software Consortium.
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122BIND9                            Jun 30, 2000                    LWRES_NOOP(3)
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