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32 .\" @(#)resolver.3 8.1 (Berkeley) 6/4/93
61 .Fa "const char *dname"
69 .Fa "const char *dname"
78 .Fa "const char *dname"
81 .Fa "const u_char *data"
83 .Fa "const u_char *newrr_in"
89 .Fa "const u_char *msg"
98 .Fa "const char *exp_dn"
101 .Fa "u_char **dnptrs"
102 .Fa "u_char **lastdnptr"
106 .Fa "const u_char *msg"
107 .Fa "const u_char *eomorig"
108 .Fa "const u_char *comp_dn"
113 .Fn dn_skipname "const u_char *comp_dn" "const u_char *eom"
115 .Fn ns_get16 "const u_char *src"
117 .Fn ns_get32 "const u_char *src"
119 .Fn ns_put16 "u_int src" "u_char *dst"
121 .Fn ns_put32 "u_long src" "u_char *dst"
123 These routines are used for making, sending and interpreting
124 query and reply messages with Internet domain name servers.
126 Global configuration and state information that is used by the
127 resolver routines is kept in the structure
129 Most of the values have reasonable defaults and can be ignored.
136 Options are stored as a simple bit mask containing the bitwise ``or''
137 of the options enabled.
138 .Bl -tag -width RES_USE_INET6
140 True if the initial name server address and default domain name are
145 Print debugging messages.
147 Accept authoritative answers only.
150 should continue until it finds an authoritative answer or finds an error.
151 Currently this is not implemented.
155 connections for queries instead of
163 connection open between
165 This is useful only in programs that regularly do many queries.
167 should be the normal mode used.
169 Unused currently (ignore truncation errors, i.e., do not retry with
172 Set the recursion-desired bit in queries.
175 does not do iterative queries and expects the name server
176 to handle recursion.)
180 will append the default domain name to single-component names
181 (those that do not contain a dot).
182 This option is enabled by default.
184 If this option is set,
186 will search for host names in the current domain and in parent domains; see
188 This is used by the standard host lookup routine
189 .Xr gethostbyname 3 .
190 This option is enabled by default.
192 This option turns off the user level aliasing feature controlled by the
194 environment variable.
195 Network daemons should set this option.
197 Enables support for IPv6-only applications.
198 This causes IPv4 addresses to be returned as an IPv4 mapped address.
202 .Li ::ffff:10.1.1.1 .
203 The option is meaningful with certain kernel configuration only.
205 Enables support for OPT pseudo-RR for EDNS0 extension.
206 With the option, resolver code will attach OPT pseudo-RR into DNS queries,
207 to inform of our receive buffer size.
208 The option will allow DNS servers to take advantage of non-default receive
209 buffer size, and to send larger replies.
210 DNS query packets with EDNS0 extension is not compatible with
211 non-EDNS0 DNS servers.
217 reads the configuration file (if any; see
219 to get the default domain name,
221 the Internet address of the local name server(s).
222 If no server is configured, the host running
223 the resolver is tried.
224 The current domain name is defined by the hostname
225 if not specified in the configuration file;
226 it can be overridden by the environment variable
228 This environment variable may contain several blank-separated
229 tokens if you wish to override the
231 on a per-process basis.
232 This is similar to the
234 command in the configuration file.
235 Another environment variable
238 override certain internal resolver options which are otherwise
239 set by changing fields in the
241 structure or are inherited from the configuration file's
246 environment variable is explained in
248 Initialization normally occurs on the first call
249 to one of the following routines.
253 function provides an interface to the server query mechanism.
254 It constructs a query, sends it to the local server,
255 awaits a response, and makes preliminary checks on the reply.
256 The query requests information of the specified
260 for the specified fully-qualified domain name
262 The reply message is left in the
266 supplied by the caller.
270 routine makes a query and awaits a response like
272 but in addition, it implements the default and search rules
278 It returns the first successful reply.
280 The remaining routines are lower-level routines used by
285 constructs a standard query message and places it in
287 It returns the size of the query, or \-1 if the query is
294 but can be any of the query types defined in
296 The domain name for the query is given by
301 is currently unused but is intended for making update messages.
306 sends a pre-formatted query and returns an answer.
311 is not set, send the query to the local name server, and
312 handle timeouts and retries.
313 The length of the reply message is returned, or
314 \-1 if there were errors.
319 compresses the domain name
323 The size of the compressed name is returned or \-1 if there were errors.
324 The size of the array pointed to by
331 to previously-compressed names in the current message.
332 The first pointer points to
333 the beginning of the message and the list ends with
335 The limit to the array is specified by
339 is to update the list of pointers for
340 labels inserted into the message
341 as the name is compressed.
346 names are not compressed.
351 the list of labels is not updated.
356 expands the compressed domain name
358 to a full domain name
359 The compressed name is contained in a query or reply message;
361 is a pointer to the beginning of the message.
362 The uncompressed name is placed in the buffer indicated by
366 The size of compressed name is returned or \-1 if there was an error.
370 function skips over a compressed domain name, which starts at a location
373 The compressed name is contained in a query or reply message;
375 is a pointer to the end of the message.
376 The size of compressed name is returned or \-1 if there was
381 function gets a 16-bit quantity from a buffer pointed to by
386 function gets a 32-bit quantity from a buffer pointed to by
391 function puts a 16-bit quantity
393 to a buffer pointed to by
398 function puts a 32-bit quantity
400 to a buffer pointed to by
402 .Sh IMPLEMENTATION NOTES
403 This implementation of the resolver is thread-safe, but it will not
404 function properly if the programmer attempts to declare his or her own
406 structure in an attempt to replace the per-thread version referred to
411 function will return 0 on success, or \-1 in a threaded program if
412 per-thread storage could not be allocated.
414 .Bl -tag -width /etc/resolv.conf
415 .It Pa /etc/resolv.conf
416 The configuration file,
421 .Xr gethostbyname 3 ,
432 .%T "Name Server Operations Guide for BIND"