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1 | .\" -*- nroff -*- |
2 | .\" | |
3 | .\" Project: DHCP | |
4 | .\" File: dhcpctl.3 | |
fc06ee4f | 5 | .\" RCSId: $Id: dhcpctl.3,v 1.9 2011/04/25 23:43:16 sar Exp $ |
f6b8f48d | 6 | .\" |
9121bf67 | 7 | .\" Copyright (c) 2004-2022 by Internet Systems Consortium, Inc. ("ISC") |
98311e4b DH |
8 | .\" Copyright (c) 2000-2003 by Internet Software Consortium |
9 | .\" Copyright (c) 2000 Nominum, Inc. | |
10 | .\" | |
11 | .\" Permission to use, copy, modify, and distribute this software for any | |
12 | .\" purpose with or without fee is hereby granted, provided that the above | |
13 | .\" copyright notice and this permission notice appear in all copies. | |
14 | .\" | |
15 | .\" THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES | |
16 | .\" WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF | |
17 | .\" MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL ISC BE LIABLE FOR | |
18 | .\" ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES | |
19 | .\" WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN | |
20 | .\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT | |
21 | .\" OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. | |
22 | .\" | |
23 | .\" Internet Systems Consortium, Inc. | |
429a56d7 TM |
24 | .\" PO Box 360 |
25 | .\" Newmarket, NH 03857 USA | |
98311e4b | 26 | .\" <info@isc.org> |
2c85ac9b | 27 | .\" https://www.isc.org/ |
f6b8f48d | 28 | .\" |
45cf20c6 | 29 | .\" Description: dhcpctl man page. |
f6b8f48d | 30 | .\" |
45cf20c6 BC |
31 | .\" |
32 | .Dd Nov 15, 2000 | |
33 | .Dt DHCPCTL 3 | |
34 | .Os DHCP 3 | |
35 | .ds vT DHCP Programmer's Manual | |
36 | .\" | |
37 | .\" | |
38 | .\" | |
39 | .Sh NAME | |
40 | .Nm dhcpctl_initialize | |
41 | .Nd dhcpctl library initialization. | |
42 | .\" | |
43 | .\" | |
44 | .\" | |
45 | .Sh SYNOPSIS | |
46 | .Fd #include <dhcpctl/dhcpctl.h> | |
45cf20c6 BC |
47 | .Ft dhcpctl_status |
48 | .Fo dhcpctl_initialize | |
49 | .Fa void | |
50 | .Fc | |
51 | .\" | |
52 | .Ft dhcpctl_status | |
53 | .Fo dhcpctl_connect | |
54 | .Fa "dhcpctl_handle *cxn" | |
55 | .Fa "const char *host" | |
56 | .Fa "int port" | |
57 | .Fa "dhcpctl_handle auth" | |
58 | .Fc | |
59 | .\" | |
60 | .\" | |
61 | .\" | |
62 | .Ft dhcpctl_status | |
9121bf67 TM |
63 | .Fo dhcpctl_disconnect |
64 | .Fa "dhcpctl_handle *cxn" | |
65 | .Fa "int force" | |
66 | .Fc | |
67 | .\" | |
68 | .\" | |
69 | .\" | |
70 | .Ft dhcpctl_status | |
45cf20c6 BC |
71 | .Fo dhcpctl_wait_for_completion |
72 | .Fa "dhcpctl_handle object" | |
73 | .Fa "dhcpctl_status *status" | |
74 | .Fc | |
75 | .\" | |
76 | .\" | |
77 | .\" | |
78 | .Ft dhcpctl_status | |
9121bf67 TM |
79 | .Fo dhcpctl_timed_wait_for_completion |
80 | .Fa "dhcpctl_handle object" | |
81 | .Fa "struct timeval *timeout" | |
82 | .Fa "dhcpctl_status *status" | |
83 | .Fc | |
84 | .\" | |
85 | .\" | |
86 | .\" | |
87 | .Ft dhcpctl_status | |
45cf20c6 BC |
88 | .Fo dhcpctl_get_value |
89 | .Fa "dhcpctl_data_string *value" | |
90 | .Fa "dhcpctl_handle object" | |
91 | .Fa "const char *name" | |
92 | .Fc | |
93 | .\" | |
94 | .\" | |
95 | .\" | |
96 | .Ft dhcpctl_status | |
97 | .Fo dhcpctl_get_boolean | |
98 | .Fa "int *value" | |
99 | .Fa "dhcpctl_handle object" | |
100 | .Fa "const char *name" | |
101 | .Fc | |
102 | .\" | |
103 | .\" | |
104 | .\" | |
105 | .Ft dhcpctl_status | |
106 | .Fo dhcpctl_set_value | |
107 | .Fa "dhcpctl_handle object" | |
108 | .Fa "dhcpctl_data_string value" | |
109 | .Fa "const char *name" | |
110 | .Fc | |
111 | .\" | |
112 | .\" | |
113 | .\" | |
114 | .Ft dhcpctl_status | |
115 | .Fo dhcpctl_set_string_value | |
116 | .Fa "dhcpctl_handle object" | |
117 | .Fa "const char *value" | |
118 | .Fa "const char *name" | |
119 | .Fc | |
120 | .\" | |
121 | .\" | |
122 | .\" | |
123 | .Ft dhcpctl_status | |
124 | .Fo dhcpctl_set_boolean_value | |
125 | .Fa "dhcpctl_handle object" | |
126 | .Fa "int value" | |
127 | .Fa "const char *name" | |
128 | .Fc | |
129 | .\" | |
130 | .\" | |
131 | .\" | |
132 | .Ft dhcpctl_status | |
133 | .Fo dhcpctl_set_int_value | |
134 | .Fa "dhcpctl_handle object" | |
135 | .Fa "int value" | |
136 | .Fa "const char *name" | |
137 | .Fc | |
138 | .\" | |
139 | .\" | |
140 | .\" | |
141 | .Ft dhcpctl_status | |
142 | .Fo dhcpctl_object_update | |
143 | .Fa "dhcpctl_handle connection" | |
144 | .Fa "dhcpctl_handle object" | |
145 | .Fc | |
146 | .\" | |
147 | .\" | |
148 | .\" | |
149 | .Ft dhcpctl_status | |
150 | .Fo dhcpctl_object_refresh | |
151 | .Fa "dhcpctl_handle connection" | |
152 | .Fa "dhcpctl_handle object" | |
153 | .Fc | |
154 | .\" | |
155 | .\" | |
156 | .\" | |
157 | .Ft dhcpctl_status | |
158 | .Fo dhcpctl_object_remove | |
159 | .Fa "dhcpctl_handle connection" | |
160 | .Fa "dhcpctl_handle object" | |
161 | .Fc | |
162 | .\" | |
163 | .\" | |
164 | .\" | |
165 | .Ft dhcpctl_status | |
166 | .Fo dhcpctl_set_callback | |
167 | .Fa "dhcpctl_handle object" | |
168 | .Fa "void *data" | |
169 | .Fa "void (*function) (dhcpctl_handle, dhcpctl_status, void *)" | |
170 | .Fc | |
171 | .\" | |
172 | .\" | |
173 | .\" | |
174 | .Ft dhcpctl_status | |
175 | .Fo dhcpctl_new_authenticator | |
176 | .Fa "dhcpctl_handle *object" | |
177 | .Fa "const char *name" | |
178 | .Fa "const char *algorithm" | |
179 | .Fa "const char *secret" | |
180 | .Fa "unsigned secret_len" | |
181 | .Fc | |
182 | .\" | |
183 | .\" | |
184 | .\" | |
185 | .Ft dhcpctl_status | |
186 | .Fo dhcpctl_new_object | |
187 | .Fa "dhcpctl_handle *object" | |
188 | .Fa "dhcpctl_handle connection" | |
189 | .Fa "const char *object_type" | |
190 | .Fc | |
191 | .\" | |
192 | .\" | |
193 | .\" | |
194 | .Ft dhcpctl_status | |
195 | .Fo dhcpctl_open_object | |
196 | .Fa "dhcpctl_handle object" | |
197 | .Fa "dhcpctl_handle connection" | |
198 | .Fa "int flags" | |
199 | .Fc | |
200 | .\" | |
201 | .\" | |
202 | .\" | |
203 | .Ft isc_result_t | |
204 | .Fo omapi_data_string_new | |
205 | .Fa dhcpctl_data_string *data | |
206 | .Fa unsigned int length | |
207 | .Fa const char *filename, | |
208 | .Fa int lineno | |
209 | .Fc | |
210 | .\" | |
211 | .\" | |
212 | .\" | |
213 | .Ft isc_result_t | |
214 | .Fo dhcpctl_data_string_dereference | |
215 | .Fa "dhcpctl_data_string *" | |
216 | .Fa "const char *" | |
217 | .Fa "int" | |
218 | .Fc | |
219 | .Sh DESCRIPTION | |
220 | The dhcpctl set of functions provide an API that can be used to communicate | |
221 | with and manipulate a running ISC DHCP server. All functions return a value of | |
222 | .Dv isc_result_t . | |
223 | The return values reflects the result of operations to local data | |
224 | structures. If an operation fails on the server for any reason, then the error | |
225 | result will be returned through the | |
f6b8f48d TM |
226 | second parameter of the |
227 | .Fn dhcpctl_wait_for_completion | |
45cf20c6 BC |
228 | call. |
229 | .\" | |
230 | .\" | |
231 | .\" | |
232 | .Pp | |
233 | .Fn dhcpctl_initialize | |
234 | sets up the data structures the library needs to do its work. This function | |
235 | must be called once before any other. | |
236 | .Pp | |
237 | .Fn dhcpctl_connect | |
238 | opens a connection to the DHCP server at the given host and port. If an | |
239 | authenticator has been created for the connection, then it is given as the 4th | |
240 | argument. On a successful return the address pointed at by the first | |
241 | argument will have a new connection object assigned to it. | |
242 | .Pp | |
243 | For example: | |
244 | .Bd -literal -offset indent | |
245 | s = dhcpctl_connect(&cxn, "127.0.0.1", 7911, NULL); | |
246 | .Ed | |
247 | .Pp | |
248 | connects to the DHCP server on the localhost via port 7911 (the standard | |
249 | OMAPI port). No authentication is used for the connection. | |
250 | .\" | |
251 | .\" | |
252 | .\" | |
253 | .Pp | |
9121bf67 TM |
254 | |
255 | .Fn dhcpctl_disconnect | |
256 | closes the open connection specified by the first parameter, \fBcxn\fR. Note | |
257 | that this call will free the connection object and \fBcxn\fR will be set to | |
258 | nul. If the second parameter,\fBforce\fR, is nonzero, the connection will be | |
259 | closed immediately. Otherwise the receiving end will be shut down but any | |
260 | unsent data will be sent before actually closing the socket. Note that | |
261 | disconnecting only destroys the connection object, any other objects previously | |
262 | created will still exist. | |
263 | .Pp | |
264 | For example: | |
265 | .Bd -literal -offset indent | |
266 | s = dhcpctl_disconnect(&cxn, 1); | |
267 | .Ed | |
268 | .Pp | |
269 | will close the connection immediately. This funcion should be considered | |
270 | \fBEXPERIMENTAL\fR. | |
271 | .\" | |
272 | .\" | |
273 | .\" | |
274 | .Pp | |
45cf20c6 BC |
275 | .Fn dhcpctl_wait_for_completion |
276 | flushes a pending message to the server and waits for the response. The result | |
277 | of the request as processed on the server is returned via the second | |
278 | parameter. | |
279 | .Bd -literal -offset indent | |
280 | s = dhcpctl_wait_for_completion(cxn, &wv); | |
f6b8f48d | 281 | if (s != ISC_R_SUCCESS) |
45cf20c6 BC |
282 | local_failure(s); |
283 | else if (wv != ISC_R_SUCCESS) | |
284 | server_failure(wc); | |
285 | .Ed | |
286 | .Pp | |
f6b8f48d | 287 | The call to |
45cf20c6 BC |
288 | .Fn dhcpctl_wait_for_completion |
289 | won't return until the remote message processing completes or the connection | |
290 | to the server is lost. | |
9121bf67 TM |
291 | .\" |
292 | .\" | |
293 | .\" | |
294 | .Pp | |
295 | ||
296 | .Fn dhcpctl_timed_wait_for_completion | |
297 | flushes a pending message to the server and waits for the response. How long | |
298 | the function waits for a response is dictated by the value of the second | |
299 | parameter, \fBtimeout\fR. If the value is null, it will wait indefinetly or | |
300 | until the connection is lost. Otherwise it will wait for the amount of time | |
301 | specified by \fBtimeout\fR (tv_sec:tv_usec). Values of zero for both fields | |
302 | are valid but not recommended. The result of the request as processed on the | |
303 | server is returned via the third parameter. An example is shown below: | |
304 | .Bd -literal -offset indent | |
305 | ||
306 | struct timeval timeout; | |
307 | timeout.tv_sec = 5; /* wait for 5 seconds */ | |
308 | timeout.tv_usec = 0; | |
309 | ||
310 | s = dhcpctl_wait_for_completion(cxn, &timeout, &wv); | |
311 | if (s != ISC_R_SUCCESS) { | |
312 | local_failure(s); | |
313 | } else if (wv != ISC_R_SUCCESS) { | |
314 | server_failure(wc); | |
315 | } | |
316 | .Ed | |
317 | .Pp | |
318 | If the function times out, the status returned will be ISC_R_TIMEDOUT. Please | |
319 | note that even though the function is no longer waiting for a response, the | |
320 | server does not abandon the request and may still respond by writing the | |
321 | response to the socket. A subsequent call to either this function or | |
322 | \fBdhcpctl_wait_for_completion()\fR will see that data and read it. Depending | |
323 | on the application logic flow this may or may not be desired. Currently though | |
324 | only mechanism for "flushing" this data is to close the connection by calling | |
325 | \fBdisconnet()\fR, and then reconnecting via \fBconnect()\fR. Please note | |
326 | this function should be considered \fBEXPERIMENTAL\fR. | |
327 | ||
45cf20c6 BC |
328 | .\" |
329 | .\" | |
330 | .\" | |
331 | .Pp | |
332 | .Fn dhcpctl_get_value | |
333 | extracts a value of an attribute from the handle. The value can be of any | |
334 | length and is treated as a sequence of bytes. The handle must have been | |
335 | created first with | |
336 | .Fn dhcpctl_new_object | |
337 | and opened with | |
338 | .Fn dhcpctl_open_object . | |
339 | The value is returned via the parameter named | |
340 | .Dq value . | |
341 | The last parameter is the name of attribute to retrieve. | |
342 | .Bd -literal -offset indent | |
343 | dhcpctl_data_string value = NULL; | |
344 | dhcpctl_handle lease; | |
345 | time_t thetime; | |
346 | ||
347 | s = dhcpctl_get_value (&value, lease, "ends"); | |
348 | assert(s == ISC_R_SUCCESS && value->len == sizeof(thetime)); | |
349 | memcpy(&thetime, value->value, value->len); | |
350 | .Ed | |
351 | .\" | |
352 | .\" | |
353 | .\" | |
354 | .Pp | |
355 | .Fn dhcpctl_get_boolean | |
356 | extracts a boolean valued attribute from the object handle. | |
357 | .\" | |
358 | .\" | |
359 | .\" | |
360 | .Pp | |
361 | The | |
362 | .Fn dhcpctl_set_value , | |
363 | .Fn dhcpctl_set_string_value , | |
364 | .Fn dhcpctl_set_boolean_value , | |
365 | and | |
366 | .Fn dhcpctl_set_int_value | |
f6b8f48d | 367 | functions all set a value on the object handle. |
45cf20c6 BC |
368 | .\" |
369 | .\" | |
370 | .\" | |
371 | .Pp | |
372 | .Fn dhcpctl_object_update | |
373 | function queues a request for | |
8e112e2b JR |
374 | all the changes made to the object handle be sent to the remote |
375 | for processing. The changes made to the attributes on the handle will be | |
45cf20c6 BC |
376 | applied to remote object if permitted. |
377 | .\" | |
378 | .\" | |
379 | .\" | |
380 | .Pp | |
381 | .Fn dhcpctl_object_refresh | |
382 | queues up a request for a fresh copy of all the attribute values to be sent | |
383 | from the remote to | |
384 | refresh the values in the local object handle. | |
385 | .\" | |
386 | .\" | |
387 | .\" | |
388 | .Pp | |
389 | .Fn dhcpctl_object_remove | |
390 | queues a request for the removal on the server of the object referenced by the | |
391 | handle. | |
392 | .\" | |
393 | .\" | |
394 | .\" | |
395 | .Pp | |
f6b8f48d | 396 | The |
45cf20c6 BC |
397 | .Fn dhcpctl_set_callback |
398 | function sets up a user-defined function to be called when an event completes | |
399 | on the given object handle. This is needed for asynchronous handling of | |
400 | events, versus the synchronous handling given by | |
401 | .Fn dhcpctl_wait_for_completion . | |
402 | When the function is called the first parameter is the object the event | |
403 | arrived for, the second is the status of the message that was processed, the | |
f6b8f48d | 404 | third is the same value as the second parameter given to |
45cf20c6 BC |
405 | .Fn dhcpctl_set_callback . |
406 | .\" | |
407 | .\" | |
408 | .\" | |
409 | .Pp | |
f6b8f48d | 410 | The |
45cf20c6 BC |
411 | .Fn dhcpctl_new_authenticator |
412 | creates a new authenticator object to be used for signing the messages | |
f6b8f48d | 413 | that cross over the network. The |
45cf20c6 BC |
414 | .Dq name , |
415 | .Dq algorithm , | |
f6b8f48d | 416 | and |
45cf20c6 BC |
417 | .Dq secret |
418 | values must all match what the server uses and are defined in its | |
419 | configuration file. The created object is returned through the first parameter | |
f6b8f48d | 420 | and must be used as the 4th parameter to |
45cf20c6 | 421 | .Fn dhcpctl_connect . |
98311e4b DH |
422 | Note that the 'secret' value must not be base64 encoded, which is different |
423 | from how the value appears in the dhcpd.conf file. | |
45cf20c6 BC |
424 | .\" |
425 | .\" | |
426 | .\" | |
427 | .Pp | |
428 | .Fn dhcpctl_new_object | |
f6b8f48d | 429 | creates a local handle for an object on the server. The |
45cf20c6 | 430 | .Dq object_type |
f6b8f48d | 431 | parameter is the ascii name of the type of object being accessed. e.g. |
45cf20c6 | 432 | .Qq lease . |
f6b8f48d | 433 | This function only sets up local data structures, it does not queue any |
45cf20c6 BC |
434 | messages |
435 | to be sent to the remote side, | |
436 | .Fn dhcpctl_open_object | |
437 | does that. | |
438 | .\" | |
439 | .\" | |
440 | .\" | |
441 | .Pp | |
442 | .Fn dhcpctl_open_object | |
443 | builds and queues the request to the remote side. This function is used with | |
444 | handle created via | |
445 | .Fn dhcpctl_new_object . | |
446 | The flags argument is a bit mask with the following values available for | |
447 | setting: | |
448 | .Bl -tag -offset indent -width 20 | |
449 | .It DHCPCTL_CREATE | |
450 | if the object does not exist then the remote will create it | |
451 | .It DHCPCTL_UPDATE | |
452 | update the object on the remote side using the | |
453 | attributes already set in the handle. | |
454 | .It DHCPCTL_EXCL | |
455 | return and error if the object exists and DHCPCTL_CREATE | |
456 | was also specified | |
457 | .El | |
458 | .\" | |
459 | .\" | |
460 | .\" | |
461 | .Pp | |
f6b8f48d | 462 | The |
45cf20c6 BC |
463 | .Fn omapi_data_string_new |
464 | function allocates a new | |
465 | .Ft dhcpctl_data_string | |
f6b8f48d | 466 | object. The data string will be large enough to hold |
45cf20c6 BC |
467 | .Dq length |
468 | bytes of data. The | |
f6b8f48d | 469 | .Dq file |
45cf20c6 BC |
470 | and |
471 | .Dq lineno | |
472 | arguments are the source file location the call is made from, typically by | |
f6b8f48d | 473 | using the |
45cf20c6 BC |
474 | .Dv __FILE__ |
475 | and | |
476 | .Dv __LINE__ | |
f6b8f48d | 477 | macros or the |
45cf20c6 BC |
478 | .Dv MDL |
479 | macro defined in | |
480 | . | |
481 | .\" | |
482 | .\" | |
483 | .\" | |
484 | .Pp | |
485 | .Fn dhcpctl_data_string_dereference | |
486 | deallocates a data string created by | |
487 | .Fn omapi_data_string_new . | |
d758ad8c TL |
488 | The memory for the object won't be freed until the last reference is |
489 | released. | |
45cf20c6 | 490 | .Sh EXAMPLES |
f6b8f48d | 491 | .Pp |
45cf20c6 BC |
492 | The following program will connect to the DHCP server running on the local |
493 | host and will get the details of the existing lease for IP address | |
494 | 10.0.0.101. It will then print out the time the lease is due to expire. Note | |
f6b8f48d | 495 | that most error checking has been omitted for brevity. |
45cf20c6 | 496 | .Bd -literal -offset indent |
45cf20c6 | 497 | #include <sys/time.h> |
45cf20c6 | 498 | #include <stdio.h> |
fc06ee4f SR |
499 | #include <stdlib.h> |
500 | #include <string.h> | |
501 | #include <stdarg.h> | |
502 | ||
503 | #include <sys/socket.h> | |
45cf20c6 | 504 | #include <netinet/in.h> |
fc06ee4f | 505 | #include <arpa/inet.h> |
45cf20c6 | 506 | |
fc06ee4f SR |
507 | #include "omapip/result.h" |
508 | #include "dhcpctl.h" | |
45cf20c6 BC |
509 | |
510 | int main (int argc, char **argv) { | |
511 | dhcpctl_data_string ipaddrstring = NULL; | |
512 | dhcpctl_data_string value = NULL; | |
513 | dhcpctl_handle connection = NULL; | |
514 | dhcpctl_handle lease = NULL; | |
515 | isc_result_t waitstatus; | |
516 | struct in_addr convaddr; | |
517 | time_t thetime; | |
518 | ||
519 | dhcpctl_initialize (); | |
520 | ||
521 | dhcpctl_connect (&connection, "127.0.0.1", | |
522 | 7911, 0); | |
f6b8f48d | 523 | |
45cf20c6 BC |
524 | dhcpctl_new_object (&lease, connection, |
525 | "lease"); | |
526 | ||
527 | memset (&ipaddrstring, 0, sizeof | |
528 | ipaddrstring); | |
529 | ||
530 | inet_pton(AF_INET, "10.0.0.101", | |
531 | &convaddr); | |
532 | ||
533 | omapi_data_string_new (&ipaddrstring, | |
534 | 4, MDL); | |
535 | memcpy(ipaddrstring->value, &convaddr.s_addr, 4); | |
536 | ||
537 | dhcpctl_set_value (lease, ipaddrstring, | |
538 | "ip-address"); | |
539 | ||
540 | dhcpctl_open_object (lease, connection, 0); | |
541 | ||
542 | dhcpctl_wait_for_completion (lease, | |
543 | &waitstatus); | |
544 | if (waitstatus != ISC_R_SUCCESS) { | |
545 | /* server not authoritative */ | |
546 | exit (0); | |
547 | } | |
548 | ||
549 | dhcpctl_data_string_dereference(&ipaddrstring, | |
550 | MDL); | |
551 | ||
552 | dhcpctl_get_value (&value, lease, "ends"); | |
553 | ||
554 | memcpy(&thetime, value->value, value->len); | |
555 | ||
556 | dhcpctl_data_string_dereference(&value, MDL); | |
557 | ||
558 | fprintf (stdout, "ending time is %s", | |
559 | ctime(&thetime)); | |
560 | } | |
561 | .Ed | |
562 | .Sh SEE ALSO | |
fac2bbb0 | 563 | omapi(3), omshell(1), dhcpd(8), dhclient(8), dhcpd.conf(5), dhclient.conf(5). |
98311e4b DH |
564 | .Sh AUTHOR |
565 | .Em dhcpctl | |
edad9be5 SR |
566 | is maintained by ISC. To learn more about Internet Systems Consortium, |
567 | see | |
568 | .B https://www.isc.org |