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1 perry 1 RESOLVER
2 !!!RESOLVER
3 NAME
4 SYNOPSIS
5 DESCRIPTION
6 RETURN VALUE
7 FILES
8 CONFORMING TO
9 SEE ALSO
10 ----
11 !!NAME
12
13
14 res_init, res_query, res_search, res_querydomain, res_mkquery, res_send, dn_comp, dn_expand - resolver routines
15 !!SYNOPSIS
16
17
18 __#include
19 __''dname''__, int__ ''class''__, int__ ''type''__,
20 unsigned char *__''answer''__, int__ ''anslen''__);
21 int res_search(const char *__''dname''__, int__ ''class''__, int__ ''type''__,
22 unsigned char *__''answer''__, int__ ''anslen''__);
23 int res_querydomain(const char *__''name''__, const char *__''domain''__,
24 int__ ''class''__, int__ ''type''__, unsigned char *__''answer''__,
25 int__ ''anslen''__);
26 int res_mkquery(int__ ''op''__, const char *__''dname''__, int__ ''class''__,
27 int__ ''type''__, char *__''data''__, int__ ''datalen''__, struct rrec *__''newrr''__,
28 char *__''buf''__, int__ ''buflen''__);
29 int res_send(const char *__''msg''__, int__ ''msglen''__, char *__''answer''__,
30 int__ ''anslen''__);
31 int dn_comp(unsigned char *__''exp_dn''__, unsigned char *__''comp_dn''__,
32 int__ ''length''__, unsigned char **__''dnptrs''__, unsigned char *__''exp_dn''__,
33 unsigned char **__''lastdnptr''__);
34 int dn_expand(unsigned char *__''msg''__, unsigned char *__''eomorig''__,
35 unsigned char *__''comp_dn''__, unsigned char *__''exp_dn''__,
36 int__ ''length''__);
37 __
38 !!DESCRIPTION
39
40
41 These functions make queries to and interpret the responses
42 from Internet domain name servers.
43
44
45 The __res_init()__ function reads the configuration files
46 (see resolv+(8)) to get the default domain name, search
47 order and name server address(es). If no server is given,
48 the local host is tried. If no domain is given, that
49 associated with the local host is used. It can be overridden
50 with the environment variable LOCALDOMAIN. __res_init()__
51 is normally executed by the first call to one of the other
52 functions.
53
54
55 The __res_query()__ function queries the name server for
56 the fully-qualified domain name ''name'' of specified
57 ''type'' and ''class''. The reply is left in the
58 buffer ''answer'' of length ''anslen'' supplied by the
59 caller.
60
61
62 The __res_search()__ function makes a query and waits for
63 the response like __res_query()__, but in addition
64 implements the default and search rules controlled by
65 RES_DEFNAMES and RES_DNSRCH (see description of ''_res''
66 options below).
67
68
69 The __res_querydomain()__ function makes a query using
70 __res_query()__ on the concatenation of ''name'' and
71 ''domain''.
72
73
74 The following functions are lower-level routines used by
75 __res_query()__.
76
77
78 The __res_mkquery()__ function constructs a query message
79 in ''buf'' of length ''buflen'' for the domain name
80 ''dname''. The query type ''op'' is usually QUERY, but
81 can be any of the types defined in
82 ''''. ''newrr'' is currently
83 unused.
84
85
86 The __res_send()__ function sends a pre-formatted query
87 given in ''msg'' of length ''msglen'' and returns the
88 answer in ''answer'' which is of length ''anslen''. It
89 will call __res_init()__, if it has not already been
90 called.
91
92
93 The __dn_comp()__ function compresses the domain name
94 ''exp_dn'' and stores it in the buffer ''comp_dn'' of
95 length ''length''. The compression uses an array of
96 pointers ''dnptrs'' to previously compressed names in the
97 current message. The first pointer points to the beginning
98 of the message and the list ends with NULL. The limit of the
99 array is specified by ''lastdnptr''. if ''dnptr'' is
100 NULL, domain names are not compressed. If ''lastdnptr''
101 is NULL, the list of labels is not updated.
102
103
104 The dn_expand() function expands the compressed domain name
105 ''comp_dn'' to a full domain name, which is placed in the
106 buffer ''exp_dn'' of size ''length''. The compressed
107 name is contained in a query or reply message, and
108 ''msg'' points to the beginning of the
109 message.
110
111
112 The resolver routines use global configuration and state
113 information contained in the structure ''_res'', which is
114 defined in ''''. The only field that is
115 normally manipulated by the user is ''_res.options''.
116 This field can contain the bitwise ``or'' of the following
117 options:
118
119
120 __RES_INIT__
121
122
123 True if __res_init()__ has been called.
124
125
126 __RES_DEBUG__
127
128
129 Print debugging messages.
130
131
132 __RES_AAONLY__
133
134
135 Accept authoritative answers only. __res_send()__
136 continues until it fins an authoritative answer or returns
137 an error. [[Not currently implemented].
138
139
140 __RES_USEVC__
141
142
143 Use TCP connections for queries rather than UDP
144 datagrams.
145
146
147 __RES_PRIMARY__
148
149
150 Query primary domain name server only.
151
152
153 __RES_IGNTC__
154
155
156 Ignore truncation errors. Don't retry with TCP. [[Not
157 currently implemented].
158
159
160 __RES_RECURSE__
161
162
163 Set the recursion desired bit in queries. Recursion is
164 carried out by the domain name server, not by
165 __res_send()__. [[Enabled by default].
166
167
168 __RES_DEFNAMES__
169
170
171 If set, __res_search()__ will append the default domain
172 name to single component names, ie. those that do not
173 contain a dot. [[Enabled by default].
174
175
176 __RES_STAYOPEN__
177
178
179 Used with RES_USEVC to keep the TCP connection open between
180 queries.
181
182
183 __RES_DNSRCH__
184
185
186 If set, __res_search()__ will search for host names in
187 the current domain and in parent domains. This option is
188 used by gethostbyname(3). [[Enabled by
189 default].
190 !!RETURN VALUE
191
192
193 The __res_init()__ function returns 0 on success, or -1
194 if an error occurs.
195
196
197 The __res_query()__, __res_search()__,
198 __res_querydomain()__, __res_mkquery()__ and
199 __res_send()__ functions return the length of the
200 response, or -1 if an error occurs.
201
202
203 The __dn_comp()__ and __dn_expand()__ functions return
204 the length of the compressed name, or -1 if an error
205 occurs.
206 !!FILES
207
208
209 /etc/resolv.conf resolver configuration file
210 /etc/host.conf resolver configuration file
211 !!CONFORMING TO
212
213
214 BSD 4.3
215 !!SEE ALSO
216
217
218 gethostbyname(3), hostname(7),
219 named(8), resolv+(8)
220 ----
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