xref: /illumos-gate/usr/src/lib/krb5/kdb/kdb_log.c (revision 437220cd296f6d8b6654d6d52508b40b1e2d1ac7)
1 /*
2  * Copyright 2007 Sun Microsystems, Inc.  All rights reserved.
3  * Use is subject to license terms.
4  */
5 
6 #pragma ident	"%Z%%M%	%I%	%E% SMI"
7 
8 #include <sys/stat.h>
9 #include <sys/types.h>
10 #include <unistd.h>
11 #include <fcntl.h>
12 #include <sys/mman.h>
13 #include <k5-int.h>
14 #include <stdlib.h>
15 #include <limits.h>
16 #include <syslog.h>
17 #include "kdb_log.h"
18 
19 /*
20  * This modules includes all the necessary functions that create and
21  * modify the Kerberos principal update and header logs.
22  */
23 
24 #define	getpagesize()	sysconf(_SC_PAGESIZE)
25 
26 static int		pagesize = 0;
27 
28 #define	INIT_ULOG(ctx)	log_ctx = ctx->kdblog_context; \
29 			ulog = log_ctx->ulog
30 /*
31  * Sync update entry to disk.
32  */
33 krb5_error_code
34 ulog_sync_update(kdb_hlog_t *ulog, kdb_ent_header_t *upd)
35 {
36 	ulong_t		start, end, size;
37 	krb5_error_code	retval;
38 
39 	if (ulog == NULL)
40 		return (KRB5_LOG_ERROR);
41 
42 	if (!pagesize)
43 		pagesize = getpagesize();
44 
45 	start = ((ulong_t)upd) & (~(pagesize-1));
46 
47 	end = (((ulong_t)upd) + ulog->kdb_block +
48 	    (pagesize-1)) & (~(pagesize-1));
49 
50 	size = end - start;
51 	if (retval = msync((caddr_t)start, size, MS_SYNC)) {
52 		return (retval);
53 	}
54 
55 	return (0);
56 }
57 
58 /*
59  * Sync memory to disk for the update log header.
60  */
61 void
62 ulog_sync_header(kdb_hlog_t *ulog)
63 {
64 
65 	if (!pagesize)
66 		pagesize = getpagesize();
67 
68 	if (msync((caddr_t)ulog, pagesize, MS_SYNC)) {
69 		/*
70 		 * Couldn't sync to disk, let's panic
71 		 */
72 		syslog(LOG_ERR, "ulog_sync_header: could not sync to disk");
73 		abort();
74 	}
75 }
76 
77 /*
78  * Resizes the array elements.  We reinitialize the update log rather than
79  * unrolling the the log and copying it over to a temporary log for obvious
80  * performance reasons.  Slaves will subsequently do a full resync, but
81  * the need for resizing should be very small.
82  */
83 krb5_error_code
84 ulog_resize(kdb_hlog_t *ulog, uint32_t ulogentries, int ulogfd, uint_t recsize)
85 {
86 	uint_t		new_block, new_size;
87 
88 	if (ulog == NULL)
89 		return (KRB5_LOG_ERROR);
90 
91 	new_size = sizeof (kdb_hlog_t);
92 
93 	new_block = (recsize / ULOG_BLOCK) + 1;
94 	new_block *= ULOG_BLOCK;
95 
96 	new_size += ulogentries * new_block;
97 
98 	if (new_size <= MAXLOGLEN) {
99 		/*
100 		 * Reinit log with new block size
101 		 */
102 		(void) memset(ulog, 0, sizeof (kdb_hlog_t));
103 
104 		ulog->kdb_hmagic = KDB_HMAGIC;
105 		ulog->db_version_num = KDB_VERSION;
106 		ulog->kdb_state = KDB_STABLE;
107 		ulog->kdb_block = new_block;
108 
109 		ulog_sync_header(ulog);
110 
111 		/*
112 		 * Time to expand log considering new block size
113 		 */
114 		if (lseek(ulogfd, new_size, SEEK_SET) == -1) {
115 			return (errno);
116 		}
117 
118 		if (write(ulogfd, "+", 1) != 1) {
119 			return (errno);
120 		}
121 	} else {
122 		/*
123 		 * Can't map into file larger than MAXLOGLEN
124 		 */
125 		return (KRB5_LOG_ERROR);
126 	}
127 
128 	return (0);
129 }
130 
131 /*
132  * Adds an entry to the update log.
133  * The layout of the update log looks like:
134  *
135  * header log -> [ update header -> xdr(kdb_incr_update_t) ], ...
136  */
137 krb5_error_code
138 ulog_add_update(krb5_context context, kdb_incr_update_t *upd)
139 {
140 	XDR		xdrs;
141 	kdbe_time_t	ktime;
142 	struct timeval	timestamp;
143 	kdb_ent_header_t *indx_log;
144 	uint_t		i, recsize;
145 	ulong_t		upd_size;
146 	krb5_error_code	retval;
147 	kdb_sno_t	cur_sno;
148 	kdb_log_context	*log_ctx;
149 	kdb_hlog_t	*ulog = NULL;
150 	uint32_t	ulogentries;
151 	int		ulogfd;
152 
153 	INIT_ULOG(context);
154 	ulogentries = log_ctx->ulogentries;
155 	ulogfd = log_ctx->ulogfd;
156 
157 	if (upd == NULL)
158 		return (KRB5_LOG_ERROR);
159 
160 	(void) gettimeofday(&timestamp, NULL);
161 	ktime.seconds = timestamp.tv_sec;
162 	ktime.useconds = timestamp.tv_usec;
163 
164 	upd_size = xdr_sizeof((xdrproc_t)xdr_kdb_incr_update_t, upd);
165 
166 	recsize = sizeof (kdb_ent_header_t) + upd_size;
167 
168 	if (recsize > ulog->kdb_block) {
169 		if (retval = ulog_resize(ulog, ulogentries, ulogfd, recsize)) {
170 			/* Resize element array failed */
171 			return (retval);
172 		}
173 	}
174 
175 	cur_sno = ulog->kdb_last_sno;
176 
177 	/*
178 	 * We need to overflow our sno, replicas will do full
179 	 * resyncs once they see their sno > than the masters.
180 	 */
181 	if (cur_sno == ULONG_MAX)
182 		cur_sno = 1;
183 	else
184 		cur_sno++;
185 
186 	/*
187 	 * We squirrel this away for finish_update() to index
188 	 */
189 	upd->kdb_entry_sno = cur_sno;
190 
191 	i = (cur_sno - 1) % ulogentries;
192 
193 	indx_log = (kdb_ent_header_t *)INDEX(ulog, i);
194 
195 	(void) memset(indx_log, 0, ulog->kdb_block);
196 
197 	indx_log->kdb_umagic = KDB_UMAGIC;
198 	indx_log->kdb_entry_size = upd_size;
199 	indx_log->kdb_entry_sno = cur_sno;
200 	indx_log->kdb_time = upd->kdb_time = ktime;
201 	indx_log->kdb_commit = upd->kdb_commit = FALSE;
202 
203 	ulog->kdb_state = KDB_UNSTABLE;
204 
205 	xdrmem_create(&xdrs, (char *)indx_log->entry_data,
206 	    indx_log->kdb_entry_size, XDR_ENCODE);
207 	if (!xdr_kdb_incr_update_t(&xdrs, upd))
208 		return (KRB5_LOG_CONV);
209 
210 	if (retval = ulog_sync_update(ulog, indx_log))
211 		return (retval);
212 
213 	if (ulog->kdb_num < ulogentries)
214 		ulog->kdb_num++;
215 
216 	ulog->kdb_last_sno = cur_sno;
217 	ulog->kdb_last_time = ktime;
218 
219 	/*
220 	 * Since this is a circular array, once we circled, kdb_first_sno is
221 	 * always kdb_entry_sno + 1.
222 	 */
223 	if (cur_sno > ulogentries) {
224 		i = upd->kdb_entry_sno % ulogentries;
225 		indx_log = (kdb_ent_header_t *)INDEX(ulog, i);
226 		ulog->kdb_first_sno = indx_log->kdb_entry_sno;
227 		ulog->kdb_first_time = indx_log->kdb_time;
228 	} else if (cur_sno == 1) {
229 		ulog->kdb_first_sno = 1;
230 		ulog->kdb_first_time = indx_log->kdb_time;
231 	}
232 
233 	ulog_sync_header(ulog);
234 
235 	return (0);
236 }
237 
238 /*
239  * Mark the log entry as committed and sync the memory mapped log
240  * to file.
241  */
242 krb5_error_code
243 ulog_finish_update(krb5_context context, kdb_incr_update_t *upd)
244 {
245 	krb5_error_code		retval;
246 	kdb_ent_header_t	*indx_log;
247 	uint_t			i;
248 	kdb_log_context		*log_ctx;
249 	kdb_hlog_t		*ulog = NULL;
250 	uint32_t		ulogentries;
251 
252 	INIT_ULOG(context);
253 	ulogentries = log_ctx->ulogentries;
254 
255 	i = (upd->kdb_entry_sno - 1) % ulogentries;
256 
257 	indx_log = (kdb_ent_header_t *)INDEX(ulog, i);
258 
259 	indx_log->kdb_commit = TRUE;
260 
261 	ulog->kdb_state = KDB_STABLE;
262 
263 	if (retval = ulog_sync_update(ulog, indx_log))
264 		return (retval);
265 
266 	ulog_sync_header(ulog);
267 
268 	return (0);
269 }
270 
271 /*
272  * Set the header log details on the slave and sync it to file.
273  */
274 void
275 ulog_finish_update_slave(kdb_hlog_t *ulog, kdb_last_t lastentry)
276 {
277 
278 	ulog->kdb_last_sno = lastentry.last_sno;
279 	ulog->kdb_last_time = lastentry.last_time;
280 
281 	ulog_sync_header(ulog);
282 }
283 
284 /*
285  * Delete an entry to the update log.
286  */
287 krb5_error_code
288 ulog_delete_update(krb5_context context, kdb_incr_update_t *upd)
289 {
290 
291 	upd->kdb_deleted = TRUE;
292 
293 	return (ulog_add_update(context, upd));
294 }
295 
296 /*
297  * Used by the slave or master (during ulog_check) to update it's hash db from
298  * the incr update log.
299  */
300 krb5_error_code
301 ulog_replay(krb5_context context, kdb_incr_result_t *incr_ret)
302 {
303 	krb5_db_entry		*entry = NULL;
304 	kdb_incr_update_t	*upd = NULL, *fupd;
305 	int			i, no_of_updates;
306 	krb5_error_code		retval;
307 	krb5_principal		dbprinc = NULL;
308 	kdb_last_t		errlast;
309 	char			*dbprincstr = NULL;
310 	kdb_log_context		*log_ctx;
311 	kdb_hlog_t		*ulog = NULL;
312 
313 	INIT_ULOG(context);
314 
315 	no_of_updates = incr_ret->updates.kdb_ulog_t_len;
316 	upd = incr_ret->updates.kdb_ulog_t_val;
317 	fupd = upd;
318 
319 	/*
320 	 * We reset last_sno and last_time to 0, if krb5_db_put_principal
321 	 * or krb5_db_delete_principal fail.
322 	 */
323 	errlast.last_sno = (unsigned int)0;
324 	errlast.last_time.seconds = (unsigned int)0;
325 	errlast.last_time.useconds = (unsigned int)0;
326 
327 	if ((retval = krb5_db_inited(context)))
328 		goto cleanup;
329 
330 	for (i = 0; i < no_of_updates; i++) {
331 		int nentry = 1;
332 
333 		if (!upd->kdb_commit)
334 			continue;
335 
336 		if (upd->kdb_deleted) {
337 			dbprincstr = malloc((upd->kdb_princ_name.utf8str_t_len
338 			    + 1) * sizeof (char));
339 
340 			if (dbprincstr == NULL) {
341 				retval = ENOMEM;
342 				goto cleanup;
343 			}
344 
345 			(void) strlcpy(dbprincstr,
346 			    (char *)upd->kdb_princ_name.utf8str_t_val,
347 			    (upd->kdb_princ_name.utf8str_t_len + 1));
348 
349 			if (retval = krb5_parse_name(context, dbprincstr,
350 			    &dbprinc)) {
351 				goto cleanup;
352 			}
353 
354 			if (dbprincstr)
355 				free(dbprincstr);
356 
357 			retval = krb5_db_delete_principal(context,
358 			    dbprinc, &nentry);
359 
360 			if (dbprinc)
361 				krb5_free_principal(context, dbprinc);
362 
363 			if (retval)
364 				goto cleanup;
365 		} else {
366 			entry = (krb5_db_entry *)malloc(sizeof (krb5_db_entry));
367 
368 			if (!entry) {
369 				retval = errno;
370 				goto cleanup;
371 			}
372 
373 			(void) memset(entry, 0, sizeof (krb5_db_entry));
374 
375 			if (retval = ulog_conv_2dbentry(context, entry, upd, 1))
376 				goto cleanup;
377 
378 			retval = krb5_db_put_principal(context, entry,
379 			    &nentry);
380 
381 			if (entry) {
382 				krb5_db_free_principal(context, entry, nentry);
383 				free(entry);
384 				entry = NULL;
385 			}
386 			if (retval)
387 				goto cleanup;
388 		}
389 
390 		upd++;
391 	}
392 
393 cleanup:
394 	if (fupd)
395 		ulog_free_entries(fupd, no_of_updates);
396 
397 	if (log_ctx && (log_ctx->iproprole == IPROP_SLAVE)) {
398 		if (retval)
399 			ulog_finish_update_slave(ulog, errlast);
400 		else
401 			ulog_finish_update_slave(ulog, incr_ret->lastentry);
402 	}
403 
404 	return (retval);
405 }
406 
407 /*
408  * Validate the log file and resync any uncommitted update entries
409  * to the principal database.
410  */
411 krb5_error_code
412 ulog_check(krb5_context context, kdb_hlog_t *ulog)
413 {
414 	XDR			xdrs;
415 	krb5_error_code		retval = 0;
416 	int			i;
417 	kdb_ent_header_t	*indx_log;
418 	kdb_incr_update_t	*upd = NULL;
419 	kdb_incr_result_t	*incr_ret = NULL;
420 
421 	ulog->kdb_state = KDB_STABLE;
422 
423 	for (i = 0; i < ulog->kdb_num; i++) {
424 		indx_log = (kdb_ent_header_t *)INDEX(ulog, i);
425 
426 		if (indx_log->kdb_umagic != KDB_UMAGIC) {
427 			/*
428 			 * Update entry corrupted we should scream and die
429 			 */
430 			ulog->kdb_state = KDB_CORRUPT;
431 			retval = KRB5_LOG_CORRUPT;
432 			break;
433 		}
434 
435 		if (indx_log->kdb_commit == FALSE) {
436 			ulog->kdb_state = KDB_UNSTABLE;
437 
438 			incr_ret = (kdb_incr_result_t *)
439 			    malloc(sizeof (kdb_incr_result_t));
440 			if (incr_ret == NULL) {
441 				retval = errno;
442 				goto error;
443 			}
444 
445 			upd = (kdb_incr_update_t *)
446 			    malloc(sizeof (kdb_incr_update_t));
447 			if (upd == NULL) {
448 				retval = errno;
449 				goto error;
450 			}
451 
452 			(void) memset(upd, 0, sizeof (kdb_incr_update_t));
453 			xdrmem_create(&xdrs, (char *)indx_log->entry_data,
454 			    indx_log->kdb_entry_size, XDR_DECODE);
455 			if (!xdr_kdb_incr_update_t(&xdrs, upd)) {
456 				retval = KRB5_LOG_CONV;
457 				goto error;
458 			}
459 
460 			incr_ret->updates.kdb_ulog_t_len = 1;
461 			incr_ret->updates.kdb_ulog_t_val = upd;
462 
463 			upd->kdb_commit = TRUE;
464 
465 			/*
466 			 * We don't want to readd this update and just use the
467 			 * existing update to be propagated later on
468 			 */
469 			ulog_set_role(context, IPROP_NULL);
470 			retval = ulog_replay(context, incr_ret);
471 
472 			/*
473 			 * upd was freed by ulog_replay, we NULL
474 			 * the pointer in case we subsequently break from loop.
475 			 */
476 			upd = NULL;
477 			if (incr_ret) {
478 				free(incr_ret);
479 				incr_ret = NULL;
480 			}
481 			ulog_set_role(context, IPROP_MASTER);
482 
483 			if (retval)
484 				goto error;
485 
486 			/*
487 			 * We flag this as committed since this was
488 			 * the last entry before kadmind crashed, ergo
489 			 * the slaves have not seen this update before
490 			 */
491 			indx_log->kdb_commit = TRUE;
492 			retval = ulog_sync_update(ulog, indx_log);
493 			if (retval)
494 				goto error;
495 
496 			ulog->kdb_state = KDB_STABLE;
497 		}
498 	}
499 
500 error:
501 	if (upd)
502 		ulog_free_entries(upd, 1);
503 
504 	if (incr_ret)
505 		free(incr_ret);
506 
507 	ulog_sync_header(ulog);
508 
509 	return (retval);
510 }
511 
512 /*
513  * Map the log file to memory for performance and simplicity.
514  *
515  * Called by: if iprop_enabled then ulog_map();
516  * Assumes that the caller will terminate on ulog_map, hence munmap and
517  * closing of the fd are implicitly performed by the caller.
518  * Returns 0 on success else failure.
519  */
520 krb5_error_code
521 ulog_map(krb5_context context, kadm5_config_params *params, int caller)
522 {
523 	struct stat	st;
524 	krb5_error_code	retval;
525 	uint32_t	ulog_filesize;
526 	char		logname[MAX_FILENAME];
527 	kdb_log_context	*log_ctx;
528 	kdb_hlog_t	*ulog = NULL;
529 	uint32_t	ulogentries;
530 	int		ulogfd = -1;
531 
532 	if ((caller == FKADMIND) || (caller == FKCOMMAND))
533 		ulogentries = params->iprop_ulogsize;
534 
535 	ulog_filesize = sizeof (kdb_hlog_t);
536 
537 	if (strlcpy(logname, params->dbname, MAX_FILENAME) >= MAX_FILENAME)
538 		return (KRB5_LOG_ERROR);
539 	if (strlcat(logname, ".ulog", MAX_FILENAME) >= MAX_FILENAME)
540 		return (KRB5_LOG_ERROR);
541 
542 	if (stat(logname, &st) == -1) {
543 
544 		if (caller == FKPROPLOG) {
545 			/*
546 			 * File doesn't exist so we exit with kproplog
547 			 */
548 			return (errno);
549 		}
550 
551 		if ((ulogfd = open(logname, O_RDWR+O_CREAT, 0600)) == -1) {
552 			return (errno);
553 		}
554 
555 		if (lseek(ulogfd, 0L, SEEK_CUR) == -1) {
556 			return (errno);
557 		}
558 
559 		if ((caller == FKADMIND) || (caller == FKCOMMAND))
560 			ulog_filesize += ulogentries * ULOG_BLOCK;
561 
562 		if (lseek(ulogfd, ulog_filesize, SEEK_SET) == -1) {
563 			return (errno);
564 		}
565 
566 		if (write(ulogfd, "+", 1) != 1) {
567 			return (errno);
568 		}
569 
570 	} else {
571 
572 		if ((ulogfd = open(logname, O_RDWR, 0600)) == -1) {
573 			/*
574 			 * Can't open existing log file
575 			 */
576 			return (errno);
577 		}
578 	}
579 
580 	if (caller == FKPROPLOG) {
581 		fstat(ulogfd, &st);
582 		ulog_filesize = st.st_size;
583 
584 		ulog = (kdb_hlog_t *)mmap(0, ulog_filesize,
585 		    PROT_READ+PROT_WRITE, MAP_PRIVATE, ulogfd, 0);
586 	} else {
587 		/*
588 		 * else kadmind, kpropd, & kcommands should udpate stores
589 		 */
590 		ulog = (kdb_hlog_t *)mmap(0, MAXLOGLEN,
591 		    PROT_READ+PROT_WRITE, MAP_SHARED, ulogfd, 0);
592 	}
593 
594 	if ((int)(ulog) == -1) {
595 		/*
596 		 * Can't map update log file to memory
597 		 */
598 		return (errno);
599 	}
600 
601 	if (!context->kdblog_context) {
602 		if (!(log_ctx = malloc(sizeof (kdb_log_context))))
603 			return (errno);
604 		context->kdblog_context = (void *)log_ctx;
605 	} else
606 		log_ctx = context->kdblog_context;
607 	log_ctx->ulog = ulog;
608 	log_ctx->ulogentries = ulogentries;
609 	log_ctx->ulogfd = ulogfd;
610 
611 	if (ulog->kdb_hmagic != KDB_HMAGIC) {
612 		if (ulog->kdb_hmagic == 0) {
613 			/*
614 			 * New update log
615 			 */
616 			(void) memset(ulog, 0, sizeof (kdb_hlog_t));
617 
618 			ulog->kdb_hmagic = KDB_HMAGIC;
619 			ulog->db_version_num = KDB_VERSION;
620 			ulog->kdb_state = KDB_STABLE;
621 			ulog->kdb_block = ULOG_BLOCK;
622 			if (!(caller == FKPROPLOG))
623 				ulog_sync_header(ulog);
624 		} else {
625 			return (KRB5_LOG_CORRUPT);
626 		}
627 	}
628 
629 	if (caller == FKADMIND) {
630 		switch (ulog->kdb_state) {
631 			case KDB_STABLE:
632 			case KDB_UNSTABLE:
633 				/*
634 				 * Log is currently un/stable, check anyway
635 				 */
636 				retval = ulog_check(context, ulog);
637 				if (retval == KRB5_LOG_CORRUPT) {
638 					return (retval);
639 				}
640 				break;
641 			case KDB_CORRUPT:
642 				return (KRB5_LOG_CORRUPT);
643 			default:
644 				/*
645 				 * Invalid db state
646 				 */
647 				return (KRB5_LOG_ERROR);
648 		}
649 	} else if ((caller == FKPROPLOG) || (caller == FKPROPD)) {
650 		/*
651 		 * kproplog and kpropd don't need to do anything else
652 		 */
653 		return (0);
654 	}
655 
656 	/*
657 	 * Reinit ulog if the log is being truncated or expanded after
658 	 * we have circled.
659 	 */
660 	if (ulog->kdb_num != ulogentries) {
661 		if ((ulog->kdb_num != 0) &&
662 		    ((ulog->kdb_last_sno > ulog->kdb_num) ||
663 		    (ulog->kdb_num > ulogentries))) {
664 			(void) memset(ulog, 0, sizeof (kdb_hlog_t));
665 
666 			ulog->kdb_hmagic = KDB_HMAGIC;
667 			ulog->db_version_num = KDB_VERSION;
668 			ulog->kdb_state = KDB_STABLE;
669 			ulog->kdb_block = ULOG_BLOCK;
670 
671 			ulog_sync_header(ulog);
672 		}
673 
674 		/*
675 		 * Expand ulog if we have specified a greater size
676 		 */
677 		if (ulog->kdb_num < ulogentries) {
678 			ulog_filesize += ulogentries * ulog->kdb_block;
679 
680 			if (lseek(ulogfd, ulog_filesize, SEEK_SET) == -1) {
681 				return (errno);
682 			}
683 
684 			if (write(ulogfd, "+", 1) != 1) {
685 				return (errno);
686 			}
687 		}
688 	}
689 
690 	return (0);
691 }
692 
693 /*
694  * Get the last set of updates seen, (last+1) to n is returned.
695  */
696 krb5_error_code
697 ulog_get_entries(
698 	krb5_context context,		/* input - krb5 lib config */
699 	kdb_last_t last,		/* input - slave's last sno */
700 	kdb_incr_result_t *ulog_handle)	/* output - incr result for slave */
701 {
702 	XDR			xdrs;
703 	kdb_ent_header_t	*indx_log;
704 	kdb_incr_update_t	*upd;
705 	uint_t			indx, count, tdiff;
706 	uint32_t		sno;
707 	krb5_error_code		retval;
708 	struct timeval		timestamp;
709 	kdb_log_context		*log_ctx;
710 	kdb_hlog_t		*ulog = NULL;
711 	uint32_t		ulogentries;
712 
713 	INIT_ULOG(context);
714 	ulogentries = log_ctx->ulogentries;
715 
716 	/*
717 	 * Check to make sure we don't have a corrupt ulog first.
718 	 */
719 	if (ulog->kdb_state == KDB_CORRUPT) {
720 		ulog_handle->ret = UPDATE_ERROR;
721 		return (KRB5_LOG_CORRUPT);
722 	}
723 
724 	gettimeofday(&timestamp, NULL);
725 
726 	tdiff = timestamp.tv_sec - ulog->kdb_last_time.seconds;
727 	if (tdiff <= ULOG_IDLE_TIME) {
728 		ulog_handle->ret = UPDATE_BUSY;
729 		return (0);
730 	}
731 
732 	/*
733 	 * We need to lock out other processes here, such as kadmin.local,
734 	 * since we are looking at the last_sno and looking up updates.  So
735 	 * we can share with other readers.
736 	 */
737 	retval = krb5_db_lock(context, KRB5_LOCKMODE_SHARED);
738 	if (retval)
739 		return (retval);
740 
741 	/*
742 	 * We may have overflowed the update log or we shrunk the log, or
743 	 * the client's ulog has just been created.
744 	 */
745 	if ((last.last_sno > ulog->kdb_last_sno) ||
746 	    (last.last_sno < ulog->kdb_first_sno) ||
747 	    (last.last_sno == 0)) {
748 		ulog_handle->lastentry.last_sno = ulog->kdb_last_sno;
749 		(void) krb5_db_unlock(context);
750 		ulog_handle->ret = UPDATE_FULL_RESYNC_NEEDED;
751 		return (0);
752 	} else if (last.last_sno <= ulog->kdb_last_sno) {
753 		sno = last.last_sno;
754 
755 		indx = (sno - 1) % ulogentries;
756 
757 		indx_log = (kdb_ent_header_t *)INDEX(ulog, indx);
758 
759 		/*
760 		 * Validate the time stamp just to make sure it was the same sno
761 		 */
762 		if ((indx_log->kdb_time.seconds == last.last_time.seconds) &&
763 		    (indx_log->kdb_time.useconds == last.last_time.useconds)) {
764 
765 			/*
766 			 * If we have the same sno we return success
767 			 */
768 			if (last.last_sno == ulog->kdb_last_sno) {
769 				(void) krb5_db_unlock(context);
770 				ulog_handle->ret = UPDATE_NIL;
771 				return (0);
772 			}
773 
774 			count = ulog->kdb_last_sno - sno;
775 
776 			ulog_handle->updates.kdb_ulog_t_val =
777 			    (kdb_incr_update_t *)malloc(
778 			    sizeof (kdb_incr_update_t) * count);
779 
780 			upd = ulog_handle->updates.kdb_ulog_t_val;
781 
782 			if (upd == NULL) {
783 				(void) krb5_db_unlock(context);
784 				ulog_handle->ret = UPDATE_ERROR;
785 				return (errno);
786 			}
787 
788 			while (sno < ulog->kdb_last_sno) {
789 				indx = sno % ulogentries;
790 
791 				indx_log = (kdb_ent_header_t *)
792 				    INDEX(ulog, indx);
793 
794 				(void) memset(upd, 0,
795 				    sizeof (kdb_incr_update_t));
796 				xdrmem_create(&xdrs,
797 				    (char *)indx_log->entry_data,
798 				    indx_log->kdb_entry_size, XDR_DECODE);
799 				if (!xdr_kdb_incr_update_t(&xdrs, upd)) {
800 					(void) krb5_db_unlock(context);
801 					ulog_handle->ret = UPDATE_ERROR;
802 					return (KRB5_LOG_CONV);
803 				}
804 				/*
805 				 * Mark commitment since we didn't
806 				 * want to decode and encode the
807 				 * incr update record the first time.
808 				 */
809 				upd->kdb_commit = indx_log->kdb_commit;
810 
811 				upd++;
812 				sno++;
813 			} /* while */
814 
815 			ulog_handle->updates.kdb_ulog_t_len = count;
816 
817 			ulog_handle->lastentry.last_sno = ulog->kdb_last_sno;
818 			ulog_handle->lastentry.last_time.seconds =
819 			    ulog->kdb_last_time.seconds;
820 			ulog_handle->lastentry.last_time.useconds =
821 			    ulog->kdb_last_time.useconds;
822 			ulog_handle->ret = UPDATE_OK;
823 
824 			(void) krb5_db_unlock(context);
825 
826 			return (0);
827 		} else {
828 			/*
829 			 * We have time stamp mismatch or we no longer have
830 			 * the slave's last sno, so we brute force it
831 			 */
832 			(void) krb5_db_unlock(context);
833 			ulog_handle->ret = UPDATE_FULL_RESYNC_NEEDED;
834 
835 			return (0);
836 		}
837 	}
838 
839 	/*
840 	 * Should never get here, return error
841 	 */
842 	ulog_handle->ret = UPDATE_ERROR;
843 	return (KRB5_LOG_ERROR);
844 }
845 
846 krb5_error_code
847 ulog_set_role(krb5_context ctx, iprop_role role)
848 {
849 	kdb_log_context	*log_ctx;
850 
851 	if (!ctx->kdblog_context) {
852 		if (!(log_ctx = malloc(sizeof (kdb_log_context))))
853 			return (errno);
854 		ctx->kdblog_context = (void *)log_ctx;
855 	} else
856 		log_ctx = ctx->kdblog_context;
857 
858 	log_ctx->iproprole = role;
859 
860 	return (0);
861 }
862