1LWRES_NOOP(3)                        BIND9                       LWRES_NOOP(3)
2
3
4

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       lightweight 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
60
61           typedef struct {
62                   uint16_t  datalength;
63                   unsigned char   *data;
64           } lwres_nooprequest_t;
65
66           typedef struct {
67                   uint16_t  datalength;
68                   unsigned char   *data;
69           } lwres_noopresponse_t;
70
71       Although the structures have different types, they are identical. This
72       is because the no-op opcode simply echos whatever data was sent: the
73       response is therefore identical to the request.
74
75       lwres_nooprequest_render() uses resolver context ctx to convert no-op
76       request structure req to canonical format. The packet header structure
77       pkt is initialised and transferred to buffer b. The contents of *req
78       are then appended to the buffer in canonical format.
79       lwres_noopresponse_render() performs the same task, except it converts
80       a no-op response structure lwres_noopresponse_t to the lightweight
81       resolver's canonical format.
82
83       lwres_nooprequest_parse() uses context ctx to convert the contents of
84       packet pkt to a lwres_nooprequest_t structure. Buffer b provides space
85       to be used for storing this structure. When the function succeeds, the
86       resulting lwres_nooprequest_t is made available through *structp.
87       lwres_noopresponse_parse() offers the same semantics as
88       lwres_nooprequest_parse() except it yields a lwres_noopresponse_t
89       structure.
90
91       lwres_noopresponse_free() and lwres_nooprequest_free() release the
92       memory in resolver context ctx that was allocated to the
93       lwres_noopresponse_t or lwres_nooprequest_t structures referenced via
94       structp.
95

RETURN VALUES

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

SEE ALSO

111       lwres_packet(3)
112

AUTHOR

114       Internet Systems Consortium, Inc.
115
117       Copyright © 2000, 2001, 2004, 2005, 2007, 2014-2016, 2018-2020 Internet
118       Systems Consortium, Inc. ("ISC")
119
120
121
122ISC                               2007-06-18                     LWRES_NOOP(3)
Impressum