summaryrefslogtreecommitdiff
path: root/source3/lib/messages.c
blob: 57e4514b588b7a8896452584f8a2bc70f1da69cf (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
/* 
   Unix SMB/CIFS implementation.
   Samba internal messaging functions
   Copyright (C) Andrew Tridgell 2000
   Copyright (C) 2001 by Martin Pool
   Copyright (C) 2002 by Jeremy Allison
   
   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 2 of the License, or
   (at your option) any later version.
   
   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.
   
   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software
   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/

/**
  @defgroup messages Internal messaging framework
  @{
  @file messages.c
  
  @brief  Module for internal messaging between Samba daemons. 

   The idea is that if a part of Samba wants to do communication with
   another Samba process then it will do a message_register() of a
   dispatch function, and use message_send_pid() to send messages to
   that process.

   The dispatch function is given the pid of the sender, and it can
   use that to reply by message_send_pid().  See ping_message() for a
   simple example.

   @caution Dispatch functions must be able to cope with incoming
   messages on an *odd* byte boundary.

   This system doesn't have any inherent size limitations but is not
   very efficient for large messages or when messages are sent in very
   quick succession.

*/

#include "includes.h"

/* the locking database handle */
static TDB_CONTEXT *tdb;
static int received_signal;

/* change the message version with any incompatible changes in the protocol */
#define MESSAGE_VERSION 1

struct message_rec {
	int msg_version;
	int msg_type;
	struct process_id dest;
	struct process_id src;
	size_t len;
};

/* we have a linked list of dispatch handlers */
static struct dispatch_fns {
	struct dispatch_fns *next, *prev;
	int msg_type;
	void (*fn)(int msg_type, struct process_id pid, void *buf, size_t len);
} *dispatch_fns;

/****************************************************************************
 Free global objects.
****************************************************************************/

void gfree_messages(void)
{
	struct dispatch_fns *dfn, *next;

	/* delete the dispatch_fns list */
	dfn = dispatch_fns;
	while( dfn ) {
		next = dfn->next;
		DLIST_REMOVE(dispatch_fns, dfn);
		SAFE_FREE(dfn);
		dfn = next;
	}
}

/****************************************************************************
 Notifications come in as signals.
****************************************************************************/

static void sig_usr1(void)
{
	received_signal = 1;
	sys_select_signal(SIGUSR1);
}

/****************************************************************************
 A useful function for testing the message system.
****************************************************************************/

static void ping_message(int msg_type, struct process_id src,
			 void *buf, size_t len)
{
	const char *msg = buf ? buf : "none";

	DEBUG(1,("INFO: Received PING message from PID %s [%s]\n",
		 procid_str_static(&src), msg));
	message_send_pid(src, MSG_PONG, buf, len, True);
}

/****************************************************************************
 Initialise the messaging functions. 
****************************************************************************/

BOOL message_init(void)
{
	if (tdb) return True;

	tdb = tdb_open_log(lock_path("messages.tdb"), 
		       0, TDB_CLEAR_IF_FIRST|TDB_DEFAULT, 
		       O_RDWR|O_CREAT,0600);

	if (!tdb) {
		DEBUG(0,("ERROR: Failed to initialise messages database\n"));
		return False;
	}

	CatchSignal(SIGUSR1, SIGNAL_CAST sig_usr1);

	message_register(MSG_PING, ping_message);

	/* Register some debugging related messages */

	register_msg_pool_usage();
	register_dmalloc_msgs();

	return True;
}

/*******************************************************************
 Form a static tdb key from a pid.
******************************************************************/

static TDB_DATA message_key_pid(struct process_id pid)
{
	static char key[20];
	TDB_DATA kbuf;

	slprintf(key, sizeof(key)-1, "PID/%s", procid_str_static(&pid));
	
	kbuf.dptr = (char *)key;
	kbuf.dsize = strlen(key)+1;
	return kbuf;
}

/****************************************************************************
 Notify a process that it has a message. If the process doesn't exist 
 then delete its record in the database.
****************************************************************************/

static BOOL message_notify(struct process_id procid)
{
	pid_t pid = procid.pid;
	/*
	 * Doing kill with a non-positive pid causes messages to be
	 * sent to places we don't want.
	 */

	SMB_ASSERT(pid > 0);

	if (kill(pid, SIGUSR1) == -1) {
		if (errno == ESRCH) {
			DEBUG(2,("pid %d doesn't exist - deleting messages record\n", (int)pid));
			tdb_delete(tdb, message_key_pid(procid));
		} else {
			DEBUG(2,("message to process %d failed - %s\n", (int)pid, strerror(errno)));
		}
		return False;
	}
	return True;
}

/****************************************************************************
 Send a message to a particular pid.
****************************************************************************/

static BOOL message_send_pid_internal(struct process_id pid, int msg_type,
				      const void *buf, size_t len,
				      BOOL duplicates_allowed,
				      unsigned int timeout)
{
	TDB_DATA kbuf;
	TDB_DATA dbuf;
	TDB_DATA old_dbuf;
	struct message_rec rec;
	char *ptr;
	struct message_rec prec;

	/* NULL pointer means implicit length zero. */
	if (!buf) {
		SMB_ASSERT(len == 0);
	}

	/*
	 * Doing kill with a non-positive pid causes messages to be
	 * sent to places we don't want.
	 */

	SMB_ASSERT(procid_to_pid(&pid) > 0);

	rec.msg_version = MESSAGE_VERSION;
	rec.msg_type = msg_type;
	rec.dest = pid;
	rec.src = procid_self();
	rec.len = buf ? len : 0;

	kbuf = message_key_pid(pid);

	dbuf.dptr = (void *)SMB_MALLOC(len + sizeof(rec));
	if (!dbuf.dptr)
		return False;

	memcpy(dbuf.dptr, &rec, sizeof(rec));
	if (len > 0 && buf)
		memcpy((void *)((char*)dbuf.dptr+sizeof(rec)), buf, len);

	dbuf.dsize = len + sizeof(rec);

	if (duplicates_allowed) {

		/* If duplicates are allowed we can just append the message and return. */

		/* lock the record for the destination */
		if (timeout) {
			if (tdb_chainlock_with_timeout(tdb, kbuf, timeout) == -1) {
				DEBUG(0,("message_send_pid_internal: failed to get chainlock with timeout %ul.\n", timeout));
				return False;
			}
		} else {
			if (tdb_chainlock(tdb, kbuf) == -1) {
				DEBUG(0,("message_send_pid_internal: failed to get chainlock.\n"));
				return False;
			}
		}	
		tdb_append(tdb, kbuf, dbuf);
		tdb_chainunlock(tdb, kbuf);

		SAFE_FREE(dbuf.dptr);
		errno = 0;                    /* paranoia */
		return message_notify(pid);
	}

	/* lock the record for the destination */
	if (timeout) {
		if (tdb_chainlock_with_timeout(tdb, kbuf, timeout) == -1) {
			DEBUG(0,("message_send_pid_internal: failed to get chainlock with timeout %ul.\n", timeout));
			return False;
		}
	} else {
		if (tdb_chainlock(tdb, kbuf) == -1) {
			DEBUG(0,("message_send_pid_internal: failed to get chainlock.\n"));
			return False;
		}
	}	

	old_dbuf = tdb_fetch(tdb, kbuf);

	if (!old_dbuf.dptr) {
		/* its a new record */

		tdb_store(tdb, kbuf, dbuf, TDB_REPLACE);
		tdb_chainunlock(tdb, kbuf);

		SAFE_FREE(dbuf.dptr);
		errno = 0;                    /* paranoia */
		return message_notify(pid);
	}

	/* Not a new record. Check for duplicates. */

	for(ptr = (char *)old_dbuf.dptr; ptr < old_dbuf.dptr + old_dbuf.dsize; ) {
		/*
		 * First check if the message header matches, then, if it's a non-zero
		 * sized message, check if the data matches. If so it's a duplicate and
		 * we can discard it. JRA.
		 */

		if (!memcmp(ptr, &rec, sizeof(rec))) {
			if (!len || (len && !memcmp( ptr + sizeof(rec), buf, len))) {
				tdb_chainunlock(tdb, kbuf);
				DEBUG(10,("message_send_pid_internal: discarding duplicate message.\n"));
				SAFE_FREE(dbuf.dptr);
				SAFE_FREE(old_dbuf.dptr);
				return True;
			}
		}
		memcpy(&prec, ptr, sizeof(prec));
		ptr += sizeof(rec) + prec.len;
	}

	/* we're adding to an existing entry */

	tdb_append(tdb, kbuf, dbuf);
	tdb_chainunlock(tdb, kbuf);

	SAFE_FREE(old_dbuf.dptr);
	SAFE_FREE(dbuf.dptr);

	errno = 0;                    /* paranoia */
	return message_notify(pid);
}

/****************************************************************************
 Send a message to a particular pid - no timeout.
****************************************************************************/

BOOL message_send_pid(struct process_id pid, int msg_type, const void *buf, size_t len, BOOL duplicates_allowed)
{
	return message_send_pid_internal(pid, msg_type, buf, len, duplicates_allowed, 0);
}

/****************************************************************************
 Send a message to a particular pid, with timeout in seconds.
****************************************************************************/

BOOL message_send_pid_with_timeout(struct process_id pid, int msg_type, const void *buf, size_t len,
		BOOL duplicates_allowed, unsigned int timeout)
{
	return message_send_pid_internal(pid, msg_type, buf, len, duplicates_allowed, timeout);
}

/****************************************************************************
 Count the messages pending for a particular pid. Expensive....
****************************************************************************/

unsigned int messages_pending_for_pid(struct process_id pid)
{
	TDB_DATA kbuf;
	TDB_DATA dbuf;
	char *buf;
	unsigned int message_count = 0;

	kbuf = message_key_pid(pid);

	dbuf = tdb_fetch(tdb, kbuf);
	if (dbuf.dptr == NULL || dbuf.dsize == 0) {
		SAFE_FREE(dbuf.dptr);
		return 0;
	}

	for (buf = dbuf.dptr; dbuf.dsize > sizeof(struct message_rec);) {
		struct message_rec rec;
		memcpy(&rec, buf, sizeof(rec));
		buf += (sizeof(rec) + rec.len);
		dbuf.dsize -= (sizeof(rec) + rec.len);
		message_count++;
	}

	SAFE_FREE(dbuf.dptr);
	return message_count;
}

/****************************************************************************
 Retrieve all messages for the current process.
****************************************************************************/

static BOOL retrieve_all_messages(char **msgs_buf, size_t *total_len)
{
	TDB_DATA kbuf;
	TDB_DATA dbuf;
	TDB_DATA null_dbuf;

	ZERO_STRUCT(null_dbuf);

	*msgs_buf = NULL;
	*total_len = 0;

	kbuf = message_key_pid(pid_to_procid(sys_getpid()));

	if (tdb_chainlock(tdb, kbuf) == -1)
		return False;

	dbuf = tdb_fetch(tdb, kbuf);
	/*
	 * Replace with an empty record to keep the allocated
	 * space in the tdb.
	 */
	tdb_store(tdb, kbuf, null_dbuf, TDB_REPLACE);
	tdb_chainunlock(tdb, kbuf);

	if (dbuf.dptr == NULL || dbuf.dsize == 0) {
		SAFE_FREE(dbuf.dptr);
		return False;
	}

	*msgs_buf = dbuf.dptr;
	*total_len = dbuf.dsize;

	return True;
}

/****************************************************************************
 Parse out the next message for the current process.
****************************************************************************/

static BOOL message_recv(char *msgs_buf, size_t total_len, int *msg_type,
			 struct process_id *src, char **buf, size_t *len)
{
	struct message_rec rec;
	char *ret_buf = *buf;

	*buf = NULL;
	*len = 0;

	if (total_len - (ret_buf - msgs_buf) < sizeof(rec))
		return False;

	memcpy(&rec, ret_buf, sizeof(rec));
	ret_buf += sizeof(rec);

	if (rec.msg_version != MESSAGE_VERSION) {
		DEBUG(0,("message version %d received (expected %d)\n", rec.msg_version, MESSAGE_VERSION));
		return False;
	}

	if (rec.len > 0) {
		if (total_len - (ret_buf - msgs_buf) < rec.len)
			return False;
	}

	*len = rec.len;
	*msg_type = rec.msg_type;
	*src = rec.src;
	*buf = ret_buf;

	return True;
}

/****************************************************************************
 Receive and dispatch any messages pending for this process.
 Notice that all dispatch handlers for a particular msg_type get called,
 so you can register multiple handlers for a message.
 *NOTE*: Dispatch functions must be able to cope with incoming
 messages on an *odd* byte boundary.
****************************************************************************/

void message_dispatch(void)
{
	int msg_type;
	struct process_id src;
	char *buf;
	char *msgs_buf;
	size_t len, total_len;
	struct dispatch_fns *dfn;
	int n_handled;

	if (!received_signal)
		return;

	DEBUG(10,("message_dispatch: received_signal = %d\n", received_signal));

	received_signal = 0;

	if (!retrieve_all_messages(&msgs_buf, &total_len))
		return;

	for (buf = msgs_buf; message_recv(msgs_buf, total_len, &msg_type, &src, &buf, &len); buf += len) {
		DEBUG(10,("message_dispatch: received msg_type=%d "
			  "src_pid=%u\n", msg_type,
			  (unsigned int) procid_to_pid(&src)));
		n_handled = 0;
		for (dfn = dispatch_fns; dfn; dfn = dfn->next) {
			if (dfn->msg_type == msg_type) {
				DEBUG(10,("message_dispatch: processing message of type %d.\n", msg_type));
				dfn->fn(msg_type, src, len ? (void *)buf : NULL, len);
				n_handled++;
			}
		}
		if (!n_handled) {
			DEBUG(5,("message_dispatch: warning: no handlers registed for "
				 "msg_type %d in pid %u\n",
				 msg_type, (unsigned int)sys_getpid()));
		}
	}
	SAFE_FREE(msgs_buf);
}

/****************************************************************************
 Register a dispatch function for a particular message type.
 *NOTE*: Dispatch functions must be able to cope with incoming
 messages on an *odd* byte boundary.
****************************************************************************/

void message_register(int msg_type, 
		      void (*fn)(int msg_type, struct process_id pid,
				 void *buf, size_t len))
{
	struct dispatch_fns *dfn;

	dfn = SMB_MALLOC_P(struct dispatch_fns);

	if (dfn != NULL) {

		ZERO_STRUCTPN(dfn);

		dfn->msg_type = msg_type;
		dfn->fn = fn;

		DLIST_ADD(dispatch_fns, dfn);
	}
	else {
	
		DEBUG(0,("message_register: Not enough memory. malloc failed!\n"));
	}
}

/****************************************************************************
 De-register the function for a particular message type.
****************************************************************************/

void message_deregister(int msg_type)
{
	struct dispatch_fns *dfn, *next;

	for (dfn = dispatch_fns; dfn; dfn = next) {
		next = dfn->next;
		if (dfn->msg_type == msg_type) {
			DLIST_REMOVE(dispatch_fns, dfn);
			SAFE_FREE(dfn);
		}
	}	
}

struct msg_all {
	int msg_type;
	uint32 msg_flag;
	const void *buf;
	size_t len;
	BOOL duplicates;
	int n_sent;
};

/****************************************************************************
 Send one of the messages for the broadcast.
****************************************************************************/

static int traverse_fn(TDB_CONTEXT *the_tdb, TDB_DATA kbuf, TDB_DATA dbuf, void *state)
{
	struct connections_data crec;
	struct msg_all *msg_all = (struct msg_all *)state;

	if (dbuf.dsize != sizeof(crec))
		return 0;

	memcpy(&crec, dbuf.dptr, sizeof(crec));

	if (crec.cnum != -1)
		return 0;

	/* Don't send if the receiver hasn't registered an interest. */

	if(!(crec.bcast_msg_flags & msg_all->msg_flag))
		return 0;

	/* If the msg send fails because the pid was not found (i.e. smbd died), 
	 * the msg has already been deleted from the messages.tdb.*/

	if (!message_send_pid(crec.pid, msg_all->msg_type,
			      msg_all->buf, msg_all->len,
			      msg_all->duplicates)) {
		
		/* If the pid was not found delete the entry from connections.tdb */

		if (errno == ESRCH) {
			DEBUG(2,("pid %s doesn't exist - deleting connections %d [%s]\n",
				 procid_str_static(&crec.pid),
				 crec.cnum, crec.name));
			tdb_delete(the_tdb, kbuf);
		}
	}
	msg_all->n_sent++;
	return 0;
}

/**
 * Send a message to all smbd processes.
 *
 * It isn't very efficient, but should be OK for the sorts of
 * applications that use it. When we need efficient broadcast we can add
 * it.
 *
 * @param n_sent Set to the number of messages sent.  This should be
 * equal to the number of processes, but be careful for races.
 *
 * @retval True for success.
 **/
BOOL message_send_all(TDB_CONTEXT *conn_tdb, int msg_type,
		      const void *buf, size_t len,
		      BOOL duplicates_allowed,
		      int *n_sent)
{
	struct msg_all msg_all;

	msg_all.msg_type = msg_type;
	if (msg_type < 1000)
		msg_all.msg_flag = FLAG_MSG_GENERAL;
	else if (msg_type > 1000 && msg_type < 2000)
		msg_all.msg_flag = FLAG_MSG_NMBD;
	else if (msg_type > 2000 && msg_type < 2100)
		msg_all.msg_flag = FLAG_MSG_PRINT_NOTIFY;
	else if (msg_type > 2100 && msg_type < 3000)
		msg_all.msg_flag = FLAG_MSG_PRINT_GENERAL;
	else if (msg_type > 3000 && msg_type < 4000)
		msg_all.msg_flag = FLAG_MSG_SMBD;
	else
		return False;

	msg_all.buf = buf;
	msg_all.len = len;
	msg_all.duplicates = duplicates_allowed;
	msg_all.n_sent = 0;

	tdb_traverse(conn_tdb, traverse_fn, &msg_all);
	if (n_sent)
		*n_sent = msg_all.n_sent;
	return True;
}

/*
 * Block and unblock receiving of messages. Allows removal of race conditions
 * when doing a fork and changing message disposition.
 */

void message_block(void)
{
	BlockSignals(True, SIGUSR1);
}

void message_unblock(void)
{
	BlockSignals(False, SIGUSR1);
}
/** @} **/