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32 .\" @(#)resolver.3 8.1 (Berkeley) 6/4/93
33 .\" $FreeBSD: src/lib/libc/net/resolver.3,v 1.11.2.7 2001/12/14 18:33:55 ru Exp $
56 .Fa "const char *dname"
64 .Fa "const char *dname"
73 .Fa "const char *dname"
76 .Fa "const u_char *data"
78 .Fa "const u_char *newrr_in"
84 .Fa "const u_char *msg"
92 .Fa "const char *exp_dn"
96 .Fa "u_char **lastdnptr"
100 .Fa "const u_char *msg"
101 .Fa "const u_char *eomorig"
102 .Fa "const u_char *comp_dn"
107 These routines are used for making, sending and interpreting
108 query and reply messages with Internet domain name servers.
110 Global configuration and state information that is used by the
111 resolver routines is kept in the structure
113 Most of the values have reasonable defaults and can be ignored.
120 Options are stored as a simple bit mask containing the bitwise ``or''
121 of the options enabled.
122 .Bl -tag -width RES_USE_INET6
124 True if the initial name server address and default domain name are
129 Print debugging messages.
131 Accept authoritative answers only.
134 should continue until it finds an authoritative answer or finds an error.
135 Currently this is not implemented.
139 connections for queries instead of
147 connection open between
149 This is useful only in programs that regularly do many queries.
151 should be the normal mode used.
153 Unused currently (ignore truncation errors, i.e., don't retry with
156 Set the recursion-desired bit in queries.
159 does not do iterative queries and expects the name server
160 to handle recursion.)
164 will append the default domain name to single-component names
165 (those that do not contain a dot).
166 This option is enabled by default.
168 If this option is set,
170 will search for host names in the current domain and in parent domains; see
172 This is used by the standard host lookup routine
173 .Xr gethostbyname 3 .
174 This option is enabled by default.
176 This option turns off the user level aliasing feature controlled by the
178 environment variable. Network daemons should set this option.
180 Enables support for IPv6-only applications.
181 This causes IPv4 addresses to be returned as an IPv4 mapped address.
185 .Li ::ffff:10.1.1.1 .
186 The option is meaningful with certain kernel configuration only.
188 Enables support for OPT pseudo-RR for EDNS0 extension.
189 With the option, resolver code will attach OPT pseudo-RR into DNS queries,
190 to inform of our receive buffer size.
191 The option will allow DNS servers to take advantage of non-default receive
192 buffer size, and to send larger replies.
193 DNS query packets with EDNS0 extension is not compatible with
194 non-EDNS0 DNS servers.
200 reads the configuration file (if any; see
202 to get the default domain name,
204 the Internet address of the local name server(s).
205 If no server is configured, the host running
206 the resolver is tried.
207 The current domain name is defined by the hostname
208 if not specified in the configuration file;
209 it can be overridden by the environment variable
211 This environment variable may contain several blank-separated
212 tokens if you wish to override the
214 on a per-process basis. This is similar to the
216 command in the configuration file.
217 Another environment variable
220 override certain internal resolver options which are otherwise
221 set by changing fields in the
223 structure or are inherited from the configuration file's
225 command. The syntax of the
227 environment variable is explained in
229 Initialization normally occurs on the first call
230 to one of the following routines.
234 function provides an interface to the server query mechanism.
235 It constructs a query, sends it to the local server,
236 awaits a response, and makes preliminary checks on the reply.
237 The query requests information of the specified
241 for the specified fully-qualified domain name
243 The reply message is left in the
247 supplied by the caller.
251 routine makes a query and awaits a response like
253 but in addition, it implements the default and search rules
259 It returns the first successful reply.
261 The remaining routines are lower-level routines used by
266 constructs a standard query message and places it in
268 It returns the size of the query, or \-1 if the query is
275 but can be any of the query types defined in
276 .Aq Pa arpa/nameser.h .
277 The domain name for the query is given by
280 is currently unused but is intended for making update messages.
285 sends a pre-formatted query and returns an answer.
290 is not set, send the query to the local name server, and
291 handle timeouts and retries.
292 The length of the reply message is returned, or
293 \-1 if there were errors.
298 compresses the domain name
302 The size of the compressed name is returned or \-1 if there were errors.
303 The size of the array pointed to by
310 to previously-compressed names in the current message.
311 The first pointer points to
312 the beginning of the message and the list ends with
314 The limit to the array is specified by
318 is to update the list of pointers for
319 labels inserted into the message
320 as the name is compressed.
325 names are not compressed.
330 the list of labels is not updated.
335 expands the compressed domain name
337 to a full domain name
338 The compressed name is contained in a query or reply message;
340 is a pointer to the beginning of the message.
341 The uncompressed name is placed in the buffer indicated by
345 The size of compressed name is returned or \-1 if there was an error.
347 .Bl -tag -width /etc/resolv.conf
348 .It Pa /etc/resolv.conf
349 The configuration file,
354 .Xr gethostbyname 3 ,
365 .%T "Name Server Operations Guide for BIND"