Added -dd for daemon debugging.
[exim.git] / src / src / daemon.c
CommitLineData
3d235903 1/* $Cambridge: exim/src/src/daemon.c,v 1.2 2004/11/10 10:29:56 ph10 Exp $ */
059ec3d9
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2
3/*************************************************
4* Exim - an Internet mail transport agent *
5*************************************************/
6
7/* Copyright (c) University of Cambridge 1995 - 2004 */
8/* See the file NOTICE for conditions of use and distribution. */
9
10/* Functions concerned with running Exim as a daemon */
11
12
13#include "exim.h"
14
15
16/* Structure for holding data for each SMTP connection */
17
18typedef struct smtp_slot {
19 pid_t pid; /* pid of the spawned reception process */
20 uschar *host_address; /* address of the client host */
21} smtp_slot;
22
23/* An empty slot for initializing (Standard C does not allow constructor
24expressions in assigments except as initializers in declarations). */
25
26static smtp_slot empty_smtp_slot = { 0, NULL };
27
28
29
30/*************************************************
31* Local static variables *
32*************************************************/
33
34static volatile BOOL sigchld_seen;
35static volatile BOOL sighup_seen;
36
37static int accept_retry_count = 0;
38static int accept_retry_errno;
39static BOOL accept_retry_select_failed;
40
41static int queue_run_count = 0;
42static pid_t *queue_pid_slots;
43static smtp_slot *smtp_slots;
44
45static BOOL write_pid = TRUE;
46
47
48
49/*************************************************
50* SIGHUP Handler *
51*************************************************/
52
53/* All this handler does is to set a flag and re-enable the signal.
54
55Argument: the signal number
56Returns: nothing
57*/
58
59static void
60sighup_handler(int sig)
61{
62sig = sig; /* Keep picky compilers happy */
63sighup_seen = TRUE;
64signal(SIGHUP, sighup_handler);
65}
66
67
68
69/*************************************************
70* SIGCHLD handler for main daemon process *
71*************************************************/
72
73/* Don't re-enable the handler here, since we aren't doing the
74waiting here. If the signal is re-enabled, there will just be an
75infinite sequence of calls to this handler. The SIGCHLD signal is
76used just as a means of waking up the daemon so that it notices
77terminated subprocesses as soon as possible.
78
79Argument: the signal number
80Returns: nothing
81*/
82
83static void
84main_sigchld_handler(int sig)
85{
86sig = sig; /* Keep picky compilers happy */
87sigchld_seen = TRUE;
88signal(SIGCHLD, SIG_DFL);
89}
90
91
92
93
94/*************************************************
95* Unexpected errors in SMTP calls *
96*************************************************/
97
98/* This function just saves a bit of repetitious coding.
99
100Arguments:
101 log_msg Text of message to be logged
102 smtp_msg Text of SMTP error message
103 was_errno The failing errno
104
105Returns: nothing
106*/
107
108static void
109never_error(uschar *log_msg, uschar *smtp_msg, int was_errno)
110{
111uschar *emsg = (was_errno <= 0)? US"" :
112 string_sprintf(": %s", strerror(was_errno));
113log_write(0, LOG_MAIN|LOG_PANIC, "%s%s", log_msg, emsg);
114if (smtp_out != NULL) smtp_printf("421 %s\r\n", smtp_msg);
115}
116
117
118
119
120/*************************************************
121* Handle a connected SMTP call *
122*************************************************/
123
124/* This function is called when an SMTP connection has been accepted.
125If there are too many, give an error message and close down. Otherwise
126spin off a sub-process to handle the call. The list of listening sockets
127is required so that they can be closed in the sub-process. Take care not to
128leak store in this process - reset the stacking pool at the end.
129
130Arguments:
131 listen_sockets sockets which are listening for incoming calls
132 listen_socket_count count of listening sockets
133 accept_socket socket of the current accepted call
134 accepted socket information about the current call
135
136Returns: nothing
137*/
138
139static void
140handle_smtp_call(int *listen_sockets, int listen_socket_count,
141 int accept_socket, struct sockaddr *accepted)
142{
143pid_t pid;
144union sockaddr_46 interface_sockaddr;
145SOCKLEN_T ifsize = sizeof(interface_sockaddr);
146int dup_accept_socket = -1;
147int max_for_this_host = 0;
148int wfsize = 0;
149int wfptr = 0;
150int use_log_write_selector = log_write_selector;
151uschar *whofrom = NULL;
152
153void *reset_point = store_get(0);
154
155/* Make the address available in ASCII representation, and also fish out
156the remote port. */
157
158sender_host_address = host_ntoa(-1, accepted, NULL, &sender_host_port);
159DEBUG(D_any) debug_printf("Connection request from %s port %d\n",
160 sender_host_address, sender_host_port);
161
162/* Set up the output stream, check the socket has duplicated, and set up the
163input stream. These operations fail only the exceptional circumstances. Note
164that never_error() won't use smtp_out if it is NULL. */
165
166smtp_out = fdopen(accept_socket, "wb");
167if (smtp_out == NULL)
168 {
169 never_error(US"daemon: fdopen() for smtp_out failed", US"", errno);
170 goto ERROR_RETURN;
171 }
172
173dup_accept_socket = dup(accept_socket);
174if (dup_accept_socket < 0)
175 {
176 never_error(US"daemon: couldn't dup socket descriptor",
177 US"Connection setup failed", errno);
178 goto ERROR_RETURN;
179 }
180
181smtp_in = fdopen(dup_accept_socket, "rb");
182if (smtp_in == NULL)
183 {
184 never_error(US"daemon: fdopen() for smtp_in failed",
185 US"Connection setup failed", errno);
186 goto ERROR_RETURN;
187 }
188
189/* Get the data for the local interface address. */
190
191if (getsockname(accept_socket, (struct sockaddr *)(&interface_sockaddr),
192 &ifsize) < 0)
193 {
194 log_write(0, LOG_MAIN|LOG_PANIC, "getsockname() failed: %s",
195 strerror(errno));
196 smtp_printf("421 Local problem: getsockname() failed; please try again later\r\n");
197 goto ERROR_RETURN;
198 }
199
200interface_address = host_ntoa(-1, &interface_sockaddr, NULL, &interface_port);
201DEBUG(D_interface) debug_printf("interface address=%s port=%d\n",
202 interface_address, interface_port);
203
204/* Build a string identifying the remote host and, if requested, the port and
205the local interface data. This is for logging; at the end of this function the
206memory is reclaimed. */
207
208whofrom = string_append(whofrom, &wfsize, &wfptr, 3, "[", sender_host_address, "]");
209
210if ((log_extra_selector & LX_incoming_port) != 0)
211 whofrom = string_append(whofrom, &wfsize, &wfptr, 2, ":", string_sprintf("%d",
212 sender_host_port));
213
214if ((log_extra_selector & LX_incoming_interface) != 0)
215 whofrom = string_append(whofrom, &wfsize, &wfptr, 4, " I=[",
216 interface_address, "]:", string_sprintf("%d", interface_port));
217
218whofrom[wfptr] = 0; /* Terminate the newly-built string */
219
220/* Check maximum number of connections. We do not check for reserved
221connections or unacceptable hosts here. That is done in the subprocess because
222it might take some time. */
223
224if (smtp_accept_max > 0 && smtp_accept_count >= smtp_accept_max)
225 {
226 DEBUG(D_any) debug_printf("rejecting SMTP connection: count=%d max=%d\n",
227 smtp_accept_count, smtp_accept_max);
228 smtp_printf("421 Too many concurrent SMTP connections; "
229 "please try again later.\r\n");
230 log_write(L_connection_reject,
231 LOG_MAIN, "Connection from %s refused: too many connections",
232 whofrom);
233 goto ERROR_RETURN;
234 }
235
236/* If a load limit above which only reserved hosts are acceptable is defined,
237get the load average here, and if there are in fact no reserved hosts, do
238the test right away (saves a fork). If there are hosts, do the check in the
239subprocess because it might take time. */
240
241if (smtp_load_reserve >= 0)
242 {
243 load_average = os_getloadavg();
244 if (smtp_reserve_hosts == NULL && load_average > smtp_load_reserve)
245 {
246 DEBUG(D_any) debug_printf("rejecting SMTP connection: load average = %.2f\n",
247 (double)load_average/1000.0);
248 smtp_printf("421 Too much load; please try again later.\r\n");
249 log_write(L_connection_reject,
250 LOG_MAIN, "Connection from %s refused: load average = %.2f",
251 whofrom, (double)load_average/1000.0);
252 goto ERROR_RETURN;
253 }
254 }
255
256/* Check that one specific host (strictly, IP address) is not hogging
257resources. This is done here to prevent a denial of service attack by someone
258forcing you to fork lots of times before denying service. The value of
259smtp_accept_max_per_host is a string which is expanded. This makes it possible
260to provide host-specific limits according to $sender_host address, but because
261this is in the daemon mainline, only fast expansions (such as inline address
262checks) should be used. The documentation is full of warnings. */
263
264if (smtp_accept_max_per_host != NULL)
265 {
266 uschar *expanded = expand_string(smtp_accept_max_per_host);
267 if (expanded == NULL)
268 {
269 if (!expand_string_forcedfail)
270 log_write(0, LOG_MAIN|LOG_PANIC, "expansion of smtp_accept_max_per_host "
271 "failed for %s: %s", whofrom, expand_string_message);
272 }
273 /* For speed, interpret a decimal number inline here */
274 else
275 {
276 uschar *s = expanded;
277 while (isdigit(*s))
278 max_for_this_host = max_for_this_host * 10 + *s++ - '0';
279 if (*s != 0)
280 log_write(0, LOG_MAIN|LOG_PANIC, "expansion of smtp_accept_max_per_host "
281 "for %s contains non-digit: %s", whofrom, expanded);
282 }
283 }
284
285/* If we have fewer connections than max_for_this_host, we can skip the tedious
286per host_address checks. Note that at this stage smtp_accept_count contains the
287count of *other* connections, not including this one. */
288
289if ((max_for_this_host > 0) &&
290 (smtp_accept_count >= max_for_this_host))
291 {
292 int i;
293 int host_accept_count = 0;
294 int other_host_count = 0; /* keep a count of non matches to optimise */
295
296 for (i = 0; i < smtp_accept_max; ++i)
297 {
298 if (smtp_slots[i].host_address != NULL)
299 {
300 if (Ustrcmp(sender_host_address, smtp_slots[i].host_address) == 0)
301 host_accept_count++;
302 else
303 other_host_count++;
304
305 /* Testing all these strings is expensive - see if we can drop out
306 early, either by hitting the target, or finding there are not enough
307 connections left to make the target. */
308
309 if ((host_accept_count >= max_for_this_host) ||
310 ((smtp_accept_count - other_host_count) < max_for_this_host))
311 break;
312 }
313 }
314
315 if (host_accept_count >= max_for_this_host)
316 {
317 DEBUG(D_any) debug_printf("rejecting SMTP connection: too many from this "
318 "IP address: count=%d max=%d\n",
319 host_accept_count, max_for_this_host);
320 smtp_printf("421 Too many concurrent SMTP connections "
321 "from this IP address; please try again later.\r\n");
322 log_write(L_connection_reject,
323 LOG_MAIN, "Connection from %s refused: too many connections "
324 "from that IP address", whofrom);
325 goto ERROR_RETURN;
326 }
327 }
328
329/* OK, the connection count checks have been passed. Before we can fork the
330accepting process, we must first log the connection if requested. This logging
331used to happen in the subprocess, but doing that means that the value of
332smtp_accept_count can be out of step by the time it is logged. So we have to do
333the logging here and accept the performance cost. Note that smtp_accept_count
334hasn't yet been incremented to take account of this connection.
335
336In order to minimize the cost (because this is going to happen for every
337connection), do a preliminary selector test here. This saves ploughing through
338the generalized logging code each time when the selector is false. If the
339selector is set, check whether the host is on the list for logging. If not,
340arrange to unset the selector in the subprocess. */
341
342if ((log_write_selector & L_smtp_connection) != 0)
343 {
344 uschar *list = hosts_connection_nolog;
345 if (list != NULL && verify_check_host(&list) == OK)
346 use_log_write_selector &= ~L_smtp_connection;
347 else
348 log_write(L_smtp_connection, LOG_MAIN, "SMTP connection from %s "
349 "(TCP/IP connection count = %d)", whofrom, smtp_accept_count + 1);
350 }
351
352/* Now we can fork the accepting process; do a lookup tidy, just in case any
353expansion above did a lookup. */
354
355search_tidyup();
356pid = fork();
357
358/* Handle the child process */
359
360if (pid == 0)
361 {
362 int i;
363 int queue_only_reason = 0;
364 int old_pool = store_pool;
3d235903 365 int save_debug_selector = debug_selector;
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366 BOOL local_queue_only;
367 #ifdef SA_NOCLDWAIT
368 struct sigaction act;
369 #endif
370
371 /* May have been modified for the subprocess */
372
373 log_write_selector = use_log_write_selector;
374
375 /* Get the local interface address into permanent store */
376
377 store_pool = POOL_PERM;
378 interface_address = string_copy(interface_address);
379 store_pool = old_pool;
380
381 /* Check for a tls-on-connect port */
382
383 if (host_is_tls_on_connect_port(interface_port)) tls_on_connect = TRUE;
384
385 /* Expand smtp_active_hostname if required. We do not do this any earlier,
386 because it may depend on the local interface address (indeed, that is most
387 likely what it depends on.) */
388
389 smtp_active_hostname = primary_hostname;
390 if (raw_active_hostname != NULL)
391 {
392 uschar *nah = expand_string(raw_active_hostname);
393 if (nah == NULL)
394 {
395 if (!expand_string_forcedfail)
396 {
397 log_write(0, LOG_MAIN|LOG_PANIC, "failed to expand \"%s\" "
398 "(smtp_active_hostname): %s", raw_active_hostname,
399 expand_string_message);
400 smtp_printf("421 Local configuration error; "
401 "please try again later.\r\n");
402 mac_smtp_fflush();
403 search_tidyup();
404 _exit(EXIT_FAILURE);
405 }
406 }
407 else if (nah[0] != 0) smtp_active_hostname = nah;
408 }
409
410 /* Initialize the queueing flags */
411
412 queue_check_only();
413 local_queue_only = queue_only;
414
415 /* Close the listening sockets, and set the SIGCHLD handler to SIG_IGN.
416 We also attempt to set things up so that children are automatically reaped,
417 but just in case this isn't available, there's a paranoid waitpid() in the
418 loop too (except for systems where we are sure it isn't needed). See the more
419 extensive comment before the reception loop in exim.c for a fuller
420 explanation of this logic. */
421
422 for (i = 0; i < listen_socket_count; i++) close(listen_sockets[i]);
423
424 #ifdef SA_NOCLDWAIT
425 act.sa_handler = SIG_IGN;
426 sigemptyset(&(act.sa_mask));
427 act.sa_flags = SA_NOCLDWAIT;
428 sigaction(SIGCHLD, &act, NULL);
429 #else
430 signal(SIGCHLD, SIG_IGN);
431 #endif
432
433 /* Attempt to get an id from the sending machine via the RFC 1413
434 protocol. We do this in the sub-process in order not to hold up the
435 main process if there is any delay. Then set up the fullhost information
3d235903
PH
436 in case there is no HELO/EHLO.
437
438 If debugging is enabled only for the daemon, we must turn if off while
439 finding the id, but turn it on again afterwards so that information about the
440 incoming connection is output. */
441
442 if (debug_daemon) debug_selector = 0;
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PH
443 verify_get_ident(IDENT_PORT);
444 host_build_sender_fullhost();
3d235903 445 debug_selector = save_debug_selector;
059ec3d9
PH
446
447 DEBUG(D_any)
448 debug_printf("Process %d is handling incoming connection from %s\n",
449 (int)getpid(), sender_fullhost);
450
3d235903
PH
451 /* Now disable debugging permanently if it's required only for the daemon
452 process. */
453
454 if (debug_daemon) debug_selector = 0;
455
059ec3d9
PH
456 /* If there are too many child processes for immediate delivery,
457 set the local_queue_only flag, which is initialized from the
458 configured value and may therefore already be TRUE. Leave logging
459 till later so it will have a message id attached. */
460
461 if (smtp_accept_queue > 0 && smtp_accept_count >= smtp_accept_queue)
462 {
463 local_queue_only = TRUE;
464 queue_only_reason = 1;
465 }
466
467 /* Handle the start of the SMTP session, then loop, accepting incoming
468 messages from the SMTP connection. The end will come at the QUIT command,
469 when smtp_setup_msg() returns 0. A break in the connection causes the
470 process to die (see accept.c). */
471
472 if (!smtp_start_session())
473 {
474 mac_smtp_fflush();
475 search_tidyup();
476 _exit(EXIT_SUCCESS);
477 }
478
479 for (;;)
480 {
481 int rc;
482 message_id[0] = 0; /* Clear out any previous message_id */
483 reset_point = store_get(0); /* Save current store high water point */
484
485 DEBUG(D_any)
486 debug_printf("Process %d is ready for new message\n", (int)getpid());
487
488 /* Smtp_setup_msg() returns 0 on QUIT or if the call is from an
489 unacceptable host or if an ACL "drop" command was triggered, -1 on
490 connection lost, and +1 on validly reaching DATA. Receive_msg() almost
491 always returns TRUE when smtp_input is true; just retry if no message was
492 accepted (can happen for invalid message parameters). However, it can yield
493 FALSE if the connection was forcibly dropped by the DATA ACL. */
494
495 if ((rc = smtp_setup_msg()) > 0)
496 {
497 BOOL ok = receive_msg(FALSE);
498 search_tidyup(); /* Close cached databases */
499 if (!ok) /* Connection was dropped */
500 {
501 mac_smtp_fflush();
502 _exit(EXIT_SUCCESS);
503 }
504 if (message_id[0] == 0) continue; /* No message was accepted */
505 }
506 else
507 {
508 mac_smtp_fflush();
509 search_tidyup();
510 _exit((rc == 0)? EXIT_SUCCESS : EXIT_FAILURE);
511 }
512
513 /* Show the recipients when debugging */
514
515 DEBUG(D_receive)
516 {
517 int i;
518 if (sender_address != NULL)
519 debug_printf("Sender: %s\n", sender_address);
520 if (recipients_list != NULL)
521 {
522 debug_printf("Recipients:\n");
523 for (i = 0; i < recipients_count; i++)
524 debug_printf(" %s\n", recipients_list[i].address);
525 }
526 }
527
528 /* A message has been accepted. Clean up any previous delivery processes
529 that have completed and are defunct, on systems where they don't go away
530 by themselves (see comments when setting SIG_IGN above). On such systems
531 (if any) these delivery processes hang around after termination until
532 the next message is received. */
533
534 #ifndef SIG_IGN_WORKS
535 while (waitpid(-1, NULL, WNOHANG) > 0);
536 #endif
537
538 /* Reclaim up the store used in accepting this message */
539
540 store_reset(reset_point);
541
542 /* If queue_only is set or if there are too many incoming connections in
543 existence, local_queue_only will be TRUE. If it is not, check whether we
544 have received too many messages in this session for immediate delivery. If
545 not, and queue_only_load is set, check that the load average is below it.
546 Note that, once set, local_queue_only remains set for any subsequent
547 messages on the same SMTP connection. This is a deliberate choice; even
548 though the load average may fall, it doesn't seem right to deliver later
549 messages on the same call when not delivering earlier ones. */
550
551 if (!local_queue_only)
552 {
553 if (smtp_accept_queue_per_connection > 0 &&
554 receive_messagecount > smtp_accept_queue_per_connection)
555 {
556 local_queue_only = TRUE;
557 queue_only_reason = 2;
558 }
559 else if (queue_only_load >= 0)
560 {
561 local_queue_only = (load_average = os_getloadavg()) > queue_only_load;
562 if (local_queue_only) queue_only_reason = 3;
563 }
564 }
565
566 /* Log the queueing here, when it will get a message id attached, but
567 not if queue_only is set (case 0). */
568
569 if (local_queue_only) switch(queue_only_reason)
570 {
571 case 1:
572 log_write(L_delay_delivery,
573 LOG_MAIN, "no immediate delivery: too many connections "
574 "(%d, max %d)", smtp_accept_count, smtp_accept_queue);
575 break;
576
577 case 2:
578 log_write(L_delay_delivery,
579 LOG_MAIN, "no immediate delivery: more than %d messages "
580 "received in one connection", smtp_accept_queue_per_connection);
581 break;
582
583 case 3:
584 log_write(L_delay_delivery,
585 LOG_MAIN, "no immediate delivery: load average %.2f",
586 (double)load_average/1000.0);
587 break;
588 }
589
590 /* If a delivery attempt is required, spin off a new process to handle it.
591 If we are not root, we have to re-exec exim unless deliveries are being
592 done unprivileged. */
593
594 else if (!queue_only_policy && !deliver_freeze)
595 {
596 pid_t dpid;
597
598 /* Before forking, ensure that the C output buffer is flushed. Otherwise
599 anything that it in it will get duplicated, leading to duplicate copies
600 of the pending output. */
601
602 mac_smtp_fflush();
603
604 if ((dpid = fork()) == 0)
605 {
606 fclose(smtp_in);
607 fclose(smtp_out);
608
609 /* Don't ever molest the parent's SSL connection, but do clean up
610 the data structures if necessary. */
611
612 #ifdef SUPPORT_TLS
613 tls_close(FALSE);
614 #endif
615
616 /* Reset SIGHUP and SIGCHLD in the child in both cases. */
617
618 signal(SIGHUP, SIG_DFL);
619 signal(SIGCHLD, SIG_DFL);
620
621 if (geteuid() != root_uid && !deliver_drop_privilege)
622 {
623 signal(SIGALRM, SIG_DFL);
624 (void)child_exec_exim(CEE_EXEC_PANIC, FALSE, NULL, FALSE, 2, US"-Mc",
625 message_id);
626 /* Control does not return here. */
627 }
628
629 /* No need to re-exec; SIGALRM remains set to the default handler */
630
631 (void)deliver_message(message_id, FALSE, FALSE);
632 search_tidyup();
633 _exit(EXIT_SUCCESS);
634 }
635
636 if (dpid > 0)
637 {
638 DEBUG(D_any) debug_printf("forked delivery process %d\n", (int)dpid);
639 }
640 else
641 {
642 log_write(0, LOG_MAIN|LOG_PANIC, "daemon: delivery process fork "
643 "failed: %s", strerror(errno));
644 }
645 }
646 }
647 }
648
649
650/* Carrying on in the parent daemon process... Can't do much if the fork
651failed. Otherwise, keep count of the number of accepting processes and
652remember the pid for ticking off when the child completes. */
653
654if (pid < 0)
655 {
656 never_error(US"daemon: accept process fork failed", US"Fork failed", errno);
657 }
658else
659 {
660 int i;
661 for (i = 0; i < smtp_accept_max; ++i)
662 {
663 if (smtp_slots[i].pid <= 0)
664 {
665 smtp_slots[i].pid = pid;
666 if (smtp_accept_max_per_host != NULL)
667 smtp_slots[i].host_address = string_copy_malloc(sender_host_address);
668 smtp_accept_count++;
669 break;
670 }
671 }
672 DEBUG(D_any) debug_printf("%d SMTP accept process%s running\n",
673 smtp_accept_count, (smtp_accept_count == 1)? "" : "es");
674 }
675
676/* Get here via goto in error cases */
677
678ERROR_RETURN:
679
680/* Close the streams associated with the socket which will also close the
681socket fds in this process. We can't do anything if fclose() fails, but
682logging brings it to someone's attention. However, "connection reset by peer"
683isn't really a problem, so skip that one. If the streams don't exist, something
684went wrong while setting things up. Make sure the socket descriptors are
685closed, in order to drop the connection. */
686
687if (smtp_out != NULL)
688 {
689 if (fclose(smtp_out) != 0 && errno != ECONNRESET)
690 log_write(0, LOG_MAIN|LOG_PANIC, "daemon: fclose(smtp_out) failed: %s",
691 strerror(errno));
692 smtp_out = NULL;
693 }
694else close(accept_socket);
695
696if (smtp_in != NULL)
697 {
698 if (fclose(smtp_in) != 0 && errno != ECONNRESET)
699 log_write(0, LOG_MAIN|LOG_PANIC, "daemon: fclose(smtp_in) failed: %s",
700 strerror(errno));
701 smtp_in = NULL;
702 }
703else close(dup_accept_socket);
704
705/* Release any store used in this process, including the store used for holding
706the incoming host address and an expanded active_hostname. */
707
708store_reset(reset_point);
709sender_host_address = NULL;
710}
711
712
713
714
715/*************************************************
716* Check wildcard listen special cases *
717*************************************************/
718
719/* This function is used when binding and listening on lists of addresses and
720ports. It tests for special cases of wildcard listening, when IPv4 and IPv6
721sockets may interact in different ways in different operating systems. It is
722passed an error number, the list of listening addresses, and the current
723address. Two checks are available: for a previous wildcard IPv6 address, or for
724a following wildcard IPv4 address, in both cases on the same port.
725
726In practice, pairs of wildcard addresses should be adjacent in the address list
727because they are sorted that way below.
728
729Arguments:
730 eno the error number
731 addresses the list of addresses
732 ipa the current IP address
733 back if TRUE, check for previous wildcard IPv6 address
734 if FALSE, check for a following wildcard IPv4 address
735
736Returns: TRUE or FALSE
737*/
738
739static BOOL
740check_special_case(int eno, ip_address_item *addresses, ip_address_item *ipa,
741 BOOL back)
742{
743ip_address_item *ipa2;
744
745/* For the "back" case, if the failure was "address in use" for a wildcard IPv4
746address, seek a previous IPv6 wildcard address on the same port. As it is
747previous, it must have been successfully bound and be listening. Flag it as a
748"6 including 4" listener. */
749
750if (back)
751 {
752 if (eno != EADDRINUSE || ipa->address[0] != 0) return FALSE;
753 for (ipa2 = addresses; ipa2 != ipa; ipa2 = ipa2->next)
754 {
755 if (ipa2->address[1] == 0 && ipa2->port == ipa->port)
756 {
757 ipa2->v6_include_v4 = TRUE;
758 return TRUE;
759 }
760 }
761 }
762
763/* For the "forward" case, if the current address is a wildcard IPv6 address,
764we seek a following wildcard IPv4 address on the same port. */
765
766else
767 {
768 if (ipa->address[0] != ':' || ipa->address[1] != 0) return FALSE;
769 for (ipa2 = ipa->next; ipa2 != NULL; ipa2 = ipa2->next)
770 if (ipa2->address[0] == 0 && ipa->port == ipa2->port) return TRUE;
771 }
772
773return FALSE;
774}
775
776
777
778
779
780
781/*************************************************
782* Exim Daemon Mainline *
783*************************************************/
784
785/* The daemon can do two jobs, either of which is optional:
786
787(1) Listens for incoming SMTP calls and spawns off a sub-process to handle
788each one. This is requested by the -bd option, with -oX specifying the SMTP
789port on which to listen (for testing).
790
791(2) Spawns a queue-running process every so often. This is controlled by the
792-q option with a an interval time. (If no time is given, a single queue run
793is done from the main function, and control doesn't get here.)
794
795Root privilege is required in order to attach to port 25. Some systems require
796it when calling socket() rather than bind(). To cope with all cases, we run as
797root for both socket() and bind(). Some systems also require root in order to
798write to the pid file directory. This function must therefore be called as root
799if it is to work properly in all circumstances. Once the socket is bound and
800the pid file written, root privilege is given up if there is an exim uid.
801
802There are no arguments to this function, and it never returns. */
803
804void
805daemon_go(void)
806{
807int *listen_sockets = NULL;
808int listen_socket_count = 0;
809ip_address_item *addresses = NULL;
810
811/* If any debugging options are set, turn on the D_pid bit so that all
812debugging lines get the pid added. */
813
814DEBUG(D_any|D_v) debug_selector |= D_pid;
815
816
817/* Do the preparation for setting up a listener on one or more interfaces, and
818possible on various ports. This is controlled by the combination of
819local_interfaces (which can set IP addresses and ports) and daemon_smtp_port
820(which is a list of default ports to use for those items in local_interfaces
821that do not specify a port). The -oX command line option can be used to
822override one or both of these options.
823
824If local_interfaces is not set, the default is to listen on all interfaces.
825When it is set, it can include "all IPvx interfaces" as an item. This is useful
826when different ports are in use.
827
828It turns out that listening on all interfaces is messy in an IPv6 world,
829because several different implementation approaches have been taken. This code
830is now supposed to work with all of them. The point of difference is whether an
831IPv6 socket that is listening on all interfaces will receive incoming IPv4
832calls or not. We also have to cope with the case when IPv6 libraries exist, but
833there is no IPv6 support in the kernel.
834
835. On Solaris, an IPv6 socket will accept IPv4 calls, and give them as mapped
836 addresses. However, if an IPv4 socket is also listening on all interfaces,
837 calls are directed to the appropriate socket.
838
839. On (some versions of) Linux, an IPv6 socket will accept IPv4 calls, and
840 give them as mapped addresses, but an attempt also to listen on an IPv4
841 socket on all interfaces causes an error.
842
843. On OpenBSD, an IPv6 socket will not accept IPv4 calls. You have to set up
844 two sockets if you want to accept both kinds of call.
845
846. FreeBSD is like OpenBSD, but it has the IPV6_V6ONLY socket option, which
847 can be turned off, to make it behave like the versions of Linux described
848 above.
849
850. I heard a report that the USAGI IPv6 stack for Linux has implemented
851 IPV6_V6ONLY.
852
853So, what we do when IPv6 is supported is as follows:
854
855 (1) After it is set up, the list of interfaces is scanned for wildcard
856 addresses. If an IPv6 and an IPv4 wildcard are both found for the same
857 port, the list is re-arranged so that they are together, with the IPv6
858 wildcard first.
859
860 (2) If the creation of a wildcard IPv6 socket fails, we just log the error and
861 carry on if an IPv4 wildcard socket for the same port follows later in the
862 list. This allows Exim to carry on in the case when the kernel has no IPv6
863 support.
864
865 (3) Having created an IPv6 wildcard socket, we try to set IPV6_V6ONLY if that
866 option is defined. However, if setting fails, carry on regardless (but log
867 the incident).
868
869 (4) If binding or listening on an IPv6 wildcard socket fails, it is a serious
870 error.
871
872 (5) If binding or listening on an IPv4 wildcard socket fails with the error
873 EADDRINUSE, and a previous interface was an IPv6 wildcard for the same
874 port (which must have succeeded or we wouldn't have got this far), we
875 assume we are in the situation where just a single socket is permitted,
876 and ignore the error.
877
878Phew!
879
880The preparation code decodes options and sets up the relevant data. We do this
881first, so that we can return non-zero if there are any syntax errors, and also
882write to stderr. */
883
884if (daemon_listen)
885 {
886 int *default_smtp_port;
887 int sep;
888 int pct = 0;
889 uschar *s;
890 uschar *list;
891 uschar *local_iface_source = US"local_interfaces";
892 ip_address_item *ipa;
893 ip_address_item **pipa;
894
895 /* If any option requiring a load average to be available during the
896 reception of a message is set, call os_getloadavg() while we are root
897 for those OS for which this is necessary the first time it is called (in
898 order to perform an "open" on the kernel memory file). */
899
900 #ifdef LOAD_AVG_NEEDS_ROOT
901 if (queue_only_load >= 0 || smtp_load_reserve >= 0) (void)os_getloadavg();
902 #endif
903
904 /* If -oX was used, disable the writing of a pid file unless -oP was
905 explicitly used to force it. Then scan the string given to -oX. Any items
906 that contain neither a dot nor a colon are used to override daemon_smtp_port.
907 Any other items are used to override local_interfaces. */
908
909 if (override_local_interfaces != NULL)
910 {
911 uschar *new_smtp_port = NULL;
912 uschar *new_local_interfaces = NULL;
913 int portsize = 0;
914 int portptr = 0;
915 int ifacesize = 0;
916 int ifaceptr = 0;
917
918 if (override_pid_file_path == NULL) write_pid = FALSE;
919
920 list = override_local_interfaces;
921 sep = 0;
922 while ((s = string_nextinlist(&list,&sep,big_buffer,big_buffer_size))
923 != NULL)
924 {
925 uschar joinstr[4];
926 uschar **ptr;
927 int *sizeptr;
928 int *ptrptr;
929
930 if (Ustrpbrk(s, ".:") == NULL)
931 {
932 ptr = &new_smtp_port;
933 sizeptr = &portsize;
934 ptrptr = &portptr;
935 }
936 else
937 {
938 ptr = &new_local_interfaces;
939 sizeptr = &ifacesize;
940 ptrptr = &ifaceptr;
941 }
942
943 if (*ptr == NULL)
944 {
945 joinstr[0] = sep;
946 joinstr[1] = ' ';
947 *ptr = string_cat(*ptr, sizeptr, ptrptr, US"<", 1);
948 }
949
950 *ptr = string_cat(*ptr, sizeptr, ptrptr, joinstr, 2);
951 *ptr = string_cat(*ptr, sizeptr, ptrptr, s, Ustrlen(s));
952 }
953
954 if (new_smtp_port != NULL)
955 {
956 new_smtp_port[portptr] = 0;
957 daemon_smtp_port = new_smtp_port;
958 DEBUG(D_any) debug_printf("daemon_smtp_port overridden by -oX:\n %s\n",
959 daemon_smtp_port);
960 }
961
962 if (new_local_interfaces != NULL)
963 {
964 new_local_interfaces[ifaceptr] = 0;
965 local_interfaces = new_local_interfaces;
966 local_iface_source = US"-oX data";
967 DEBUG(D_any) debug_printf("local_interfaces overridden by -oX:\n %s\n",
968 local_interfaces);
969 }
970 }
971
972 /* Create a list of default SMTP ports, to be used if local_interfaces
973 contains entries without explict ports. First count the number of ports, then
974 build a translated list in a vector. */
975
976 list = daemon_smtp_port;
977 sep = 0;
978 while ((s = string_nextinlist(&list,&sep,big_buffer,big_buffer_size)) != NULL)
979 pct++;
980 default_smtp_port = store_get((pct+1) * sizeof(int));
981 list = daemon_smtp_port;
982 sep = 0;
983 for (pct = 0;
984 (s = string_nextinlist(&list,&sep,big_buffer,big_buffer_size)) != NULL;
985 pct++)
986 {
987 if (isdigit(*s))
988 {
989 uschar *end;
990 default_smtp_port[pct] = Ustrtol(s, &end, 0);
991 if (end != s + Ustrlen(s))
992 log_write(0, LOG_PANIC_DIE|LOG_CONFIG, "invalid SMTP port: %s", s);
993 }
994 else
995 {
996 struct servent *smtp_service = getservbyname(CS s, "tcp");
997 if (smtp_service == NULL)
998 log_write(0, LOG_PANIC_DIE|LOG_CONFIG, "TCP port \"%s\" not found", s);
999 default_smtp_port[pct] = ntohs(smtp_service->s_port);
1000 }
1001 }
1002 default_smtp_port[pct] = 0;
1003
1004 /* Create the list of local interfaces, possibly with ports included. This
1005 list may contain references to 0.0.0.0 and ::0 as wildcards. These special
1006 values are converted below. */
1007
1008 addresses = host_build_ifacelist(local_interfaces, local_iface_source);
1009
1010 /* In the list of IP addresses, convert 0.0.0.0 into an empty string, and ::0
1011 into the string ":". We use these to recognize wildcards in IPv4 and IPv6. In
1012 fact, many IP stacks recognize 0.0.0.0 and ::0 and handle them as wildcards
1013 anyway, but we need to know which are the wildcard addresses, and the shorter
1014 strings are neater.
1015
1016 In the same scan, fill in missing port numbers from the default list. When
1017 there is more than one item in the list, extra items are created. */
1018
1019 for (ipa = addresses; ipa != NULL; ipa = ipa->next)
1020 {
1021 int i;
1022
1023 if (Ustrcmp(ipa->address, "0.0.0.0") == 0) ipa->address[0] = 0;
1024 else if (Ustrcmp(ipa->address, "::0") == 0)
1025 {
1026 ipa->address[0] = ':';
1027 ipa->address[1] = 0;
1028 }
1029
1030 if (ipa->port > 0) continue;
1031
1032 if (daemon_smtp_port[0] <= 0)
1033 log_write(0, LOG_MAIN|LOG_PANIC_DIE, "no port specified for interface "
1034 "%s and daemon_smtp_port is unset; cannot start daemon",
1035 (ipa->address[0] == 0)? US"\"all IPv4\"" :
1036 (ipa->address[1] == 0)? US"\"all IPv6\"" : ipa->address);
1037 ipa->port = default_smtp_port[0];
1038 for (i = 1; default_smtp_port[i] > 0; i++)
1039 {
1040 ip_address_item *new = store_get(sizeof(ip_address_item));
1041 memcpy(new->address, ipa->address, Ustrlen(ipa->address) + 1);
1042 new->port = default_smtp_port[i];
1043 new->next = ipa->next;
1044 ipa->next = new;
1045 ipa = new;
1046 }
1047 }
1048
1049 /* Scan the list of addresses for wildcards. If we find an IPv4 and an IPv6
1050 wildcard for the same port, ensure that (a) they are together and (b) the
1051 IPv6 address comes first. This makes handling the messy features easier, and
1052 also simplifies the construction of the "daemon started" log line. */
1053
1054 pipa = &addresses;
1055 for (ipa = addresses; ipa != NULL; pipa = &(ipa->next), ipa = ipa->next)
1056 {
1057 ip_address_item *ipa2;
1058
1059 /* Handle an IPv4 wildcard */
1060
1061 if (ipa->address[0] == 0)
1062 {
1063 for (ipa2 = ipa; ipa2->next != NULL; ipa2 = ipa2->next)
1064 {
1065 ip_address_item *ipa3 = ipa2->next;
1066 if (ipa3->address[0] == ':' &&
1067 ipa3->address[1] == 0 &&
1068 ipa3->port == ipa->port)
1069 {
1070 ipa2->next = ipa3->next;
1071 ipa3->next = ipa;
1072 *pipa = ipa3;
1073 break;
1074 }
1075 }
1076 }
1077
1078 /* Handle an IPv6 wildcard. */
1079
1080 else if (ipa->address[0] == ':' && ipa->address[1] == 0)
1081 {
1082 for (ipa2 = ipa; ipa2->next != NULL; ipa2 = ipa2->next)
1083 {
1084 ip_address_item *ipa3 = ipa2->next;
1085 if (ipa3->address[0] == 0 && ipa3->port == ipa->port)
1086 {
1087 ipa2->next = ipa3->next;
1088 ipa3->next = ipa->next;
1089 ipa->next = ipa3;
1090 ipa = ipa3;
1091 break;
1092 }
1093 }
1094 }
1095 }
1096
1097 /* Get a vector to remember all the sockets in */
1098
1099 for (ipa = addresses; ipa != NULL; ipa = ipa->next)
1100 listen_socket_count++;
1101 listen_sockets = store_get(sizeof(int *) * listen_socket_count);
1102
1103 /* Do a sanity check on the max connects value just to save us from getting
1104 a huge amount of store. */
1105
1106 if (smtp_accept_max > 4095) smtp_accept_max = 4096;
1107
1108 /* There's no point setting smtp_accept_queue unless it is less than the max
1109 connects limit. The configuration reader ensures that the max is set if the
1110 queue-only option is set. */
1111
1112 if (smtp_accept_queue > smtp_accept_max) smtp_accept_queue = 0;
1113
1114 /* Get somewhere to keep the list of SMTP accepting pids if we are keeping
1115 track of them for total number and queue/host limits. */
1116
1117 if (smtp_accept_max > 0)
1118 {
1119 int i;
1120 smtp_slots = store_get(smtp_accept_max * sizeof(smtp_slot));
1121 for (i = 0; i < smtp_accept_max; i++) smtp_slots[i] = empty_smtp_slot;
1122 }
1123 }
1124
1125/* We now close all open file descriptors that we know about, and disconnect
1126from the controlling terminal, unless background_daemon is unset. This is
1127always unset when debugging, but can also be forced. Most modern Unixes seem to
1128have setsid() for getting rid of the controlling terminal. For any OS that
1129doesn't, setsid() can be #defined as a no-op, or as something else. */
1130
1131if (background_daemon)
1132 {
1133 log_close_all(); /* Just in case anything was logged earlier */
1134 search_tidyup(); /* Just in case any were used in reading the config. */
1135 close(0); /* Get rid of stdin/stdout/stderr */
1136 close(1);
1137 close(2);
1138 log_stderr = NULL; /* So no attempt to copy paniclog output */
1139
1140 /* If the parent process of this one has pid == 1, we are re-initializing the
1141 daemon as the result of a SIGHUP. In this case, there is no need to do any
1142 forking, because the controlling terminal has long gone. Otherwise, fork,
1143 in case current process is a process group leader (see 'man setsid' for an
1144 explanation). */
1145
1146 if (getppid() != 1)
1147 {
1148 pid_t pid = fork();
1149 if (pid < 0) log_write(0, LOG_MAIN|LOG_PANIC_DIE,
1150 "fork() failed when starting daemon: %s", strerror(errno));
1151 if (pid > 0) exit(EXIT_SUCCESS); /* in parent process, just exit */
1152 (void)setsid(); /* release controlling terminal */
1153 }
1154 }
1155
1156/* We are now in the disconnected, daemon process (unless debugging). Set up
1157the listening sockets if required. */
1158
1159if (daemon_listen)
1160 {
1161 int sk;
1162 int on = 1;
1163 ip_address_item *ipa;
1164
1165 /* For each IP address, create a socket, bind it to the appropriate port, and
1166 start listening. See comments above about IPv6 sockets that may or may not
1167 accept IPv4 calls when listening on all interfaces. We also have to cope with
1168 the case of a system with IPv6 libraries, but no IPv6 support in the kernel.
1169 listening, provided a wildcard IPv4 socket for the same port follows. */
1170
1171 for (ipa = addresses, sk = 0; sk < listen_socket_count; ipa = ipa->next, sk++)
1172 {
1173 BOOL wildcard;
1174 ip_address_item *ipa2;
1175 int retries = 9;
1176 int af;
1177
1178 if (Ustrchr(ipa->address, ':') != NULL)
1179 {
1180 af = AF_INET6;
1181 wildcard = ipa->address[1] == 0;
1182 }
1183 else
1184 {
1185 af = AF_INET;
1186 wildcard = ipa->address[0] == 0;
1187 }
1188
1189 listen_sockets[sk] = ip_socket(SOCK_STREAM, af);
1190 if (listen_sockets[sk] < 0)
1191 {
1192 if (check_special_case(0, addresses, ipa, FALSE))
1193 {
1194 log_write(0, LOG_MAIN, "Failed to create IPv6 socket for wildcard "
1195 "listening (%s): will use IPv4", strerror(errno));
1196 goto SKIP_SOCKET;
1197 }
1198 log_write(0, LOG_PANIC_DIE, "IPv%c socket creation failed: %s",
1199 (af == AF_INET6)? '6' : '4', strerror(errno));
1200 }
1201
1202 /* If this is an IPv6 wildcard socket, set IPV6_V6ONLY if that option is
1203 available. Just log failure (can get protocol not available, just like
1204 socket creation can). */
1205
1206 #ifdef IPV6_V6ONLY
1207 if (af == AF_INET6 && wildcard &&
1208 setsockopt(listen_sockets[sk], IPPROTO_IPV6, IPV6_V6ONLY, (char *)(&on),
1209 sizeof(on)) < 0)
1210 log_write(0, LOG_MAIN, "Setting IPV6_V6ONLY on daemon's IPv6 wildcard "
1211 "socket failed (%s): carrying on without it", strerror(errno));
1212 #endif /* IPV6_V6ONLY */
1213
1214 /* Set SO_REUSEADDR so that the daemon can be restarted while a connection
1215 is being handled. Without this, a connection will prevent reuse of the
1216 smtp port for listening. */
1217
1218 if (setsockopt(listen_sockets[sk], SOL_SOCKET, SO_REUSEADDR,
1219 (uschar *)(&on), sizeof(on)) < 0)
1220 log_write(0, LOG_MAIN|LOG_PANIC_DIE, "setting SO_REUSEADDR on socket "
1221 "failed when starting daemon: %s", strerror(errno));
1222
1223 /* Set TCP_NODELAY; Exim does its own buffering. There is a switch to
1224 disable this because it breaks some broken clients. */
1225
1226 if (tcp_nodelay) setsockopt(listen_sockets[sk], IPPROTO_TCP, TCP_NODELAY,
1227 (uschar *)(&on), sizeof(on));
1228
1229 /* Now bind the socket to the required port; if Exim is being restarted
1230 it may not always be possible to bind immediately, even with SO_REUSEADDR
1231 set, so try 10 times, waiting between each try. After 10 failures, we give
1232 up. In an IPv6 environment, if bind () fails with the error EADDRINUSE and
1233 we are doing wildcard IPv4 listening and there was a previous IPv6 wildcard
1234 address for the same port, ignore the error on the grounds that we must be
1235 in a system where the IPv6 socket accepts both kinds of call. This is
1236 necessary for (some release of) USAGI Linux; other IP stacks fail at the
1237 listen() stage instead. */
1238
1239 for(;;)
1240 {
1241 uschar *msg, *addr;
1242 if (ip_bind(listen_sockets[sk], af, ipa->address, ipa->port) >= 0) break;
1243 if (check_special_case(errno, addresses, ipa, TRUE))
1244 {
1245 DEBUG(D_any) debug_printf("wildcard IPv4 bind() failed after IPv6 "
1246 "listen() success; EADDRINUSE ignored\n");
1247 close(listen_sockets[sk]);
1248 goto SKIP_SOCKET;
1249 }
1250 msg = US strerror(errno);
1251 addr = wildcard? ((af == AF_INET6)? US"(any IPv6)" : US"(any IPv4)") :
1252 ipa->address;
1253 if (retries-- <= 0)
1254 log_write(0, LOG_MAIN|LOG_PANIC_DIE,
1255 "socket bind() to port %d for address %s failed: %s: "
1256 "daemon abandoned", ipa->port, addr, msg);
1257 log_write(0, LOG_MAIN, "socket bind() to port %d for address %s "
1258 "failed: %s: waiting before trying again", ipa->port, addr, msg);
1259 sleep(30);
1260 }
1261
1262 DEBUG(D_any)
1263 {
1264 if (wildcard)
1265 debug_printf("listening on all interfaces (IPv%c) port %d\n",
1266 (af == AF_INET6)? '6' : '4', ipa->port);
1267 else
1268 debug_printf("listening on %s port %d\n", ipa->address, ipa->port);
1269 }
1270
1271 /* Start listening on the bound socket, establishing the maximum backlog of
1272 connections that is allowed. On success, continue to the next address. */
1273
1274 if (listen(listen_sockets[sk], smtp_connect_backlog) >= 0) continue;
1275
1276 /* Listening has failed. In an IPv6 environment, as for bind(), if listen()
1277 fails with the error EADDRINUSE and we are doing IPv4 wildcard listening
1278 and there was a previous successful IPv6 wildcard listen on the same port,
1279 we want to ignore the error on the grounds that we must be in a system
1280 where the IPv6 socket accepts both kinds of call. */
1281
1282 if (!check_special_case(errno, addresses, ipa, TRUE))
1283 log_write(0, LOG_PANIC_DIE, "listen() failed on interface %s: %s",
1284 wildcard? ((af == AF_INET6)? US"(any IPv6)" : US"(any IPv4)") :
1285 ipa->address,
1286 strerror(errno));
1287
1288 DEBUG(D_any) debug_printf("wildcard IPv4 listen() failed after IPv6 "
1289 "listen() success; EADDRINUSE ignored\n");
1290 close(listen_sockets[sk]);
1291
1292 /* Come here if there has been a problem with the socket which we
1293 are going to ignore. We remove the address from the chain, and back up the
1294 counts. */
1295
1296 SKIP_SOCKET:
1297 sk--; /* Back up the count */
1298 listen_socket_count--; /* Reduce the total */
1299 if (ipa == addresses) addresses = ipa->next; else
1300 {
1301 for (ipa2 = addresses; ipa2->next != ipa; ipa2 = ipa2->next);
1302 ipa2->next = ipa->next;
1303 ipa = ipa2;
1304 }
1305 } /* End of bind/listen loop for each address */
1306 } /* End of setup for listening */
1307
1308
1309/* If we are not listening, we want to write a pid file only if -oP was
1310explicitly given. */
1311
1312else if (override_pid_file_path == NULL) write_pid = FALSE;
1313
1314/* Write the pid to a known file for assistance in identification, if required.
1315We do this before giving up root privilege, because on some systems it is
1316necessary to be root in order to write into the pid file directory. There's
1317nothing to stop multiple daemons running, as long as no more than one listens
1318on a given TCP/IP port on the same interface(s). However, in these
1319circumstances it gets far too complicated to mess with pid file names
1320automatically. Consequently, Exim 4 writes a pid file only
1321
1322 (a) When running in the test harness, or
1323 (b) When -bd is used and -oX is not used, or
1324 (c) When -oP is used to supply a path.
1325
1326The variable daemon_write_pid is used to control this. */
1327
1328if (running_in_test_harness || write_pid)
1329 {
1330 FILE *f;
1331
1332 if (override_pid_file_path != NULL)
1333 pid_file_path = override_pid_file_path;
1334
1335 if (pid_file_path[0] == 0)
1336 pid_file_path = string_sprintf("%s/exim-daemon.pid", spool_directory);
1337
1338 f = Ufopen(pid_file_path, "wb");
1339 if (f != NULL)
1340 {
1341 fprintf(f, "%d\n", (int)getpid());
1342 fchmod(fileno(f), 0644);
1343 fclose(f);
1344 DEBUG(D_any) debug_printf("pid written to %s\n", pid_file_path);
1345 }
1346 else
1347 {
1348 DEBUG(D_any)
1349 debug_printf("%s\n", string_open_failed(errno, "pid file %s",
1350 pid_file_path));
1351 }
1352 }
1353
1354/* Set up the handler for SIGHUP, which causes a restart of the daemon. */
1355
1356sighup_seen = FALSE;
1357signal(SIGHUP, sighup_handler);
1358
1359/* Give up root privilege at this point (assuming that exim_uid and exim_gid
1360are not root). The third argument controls the running of initgroups().
1361Normally we do this, in order to set up the groups for the Exim user. However,
1362if we are not root at this time - some odd installations run that way - we
1363cannot do this. */
1364
1365exim_setugid(exim_uid, exim_gid, geteuid()==root_uid, US"running as a daemon");
1366
1367/* Get somewhere to keep the list of queue-runner pids if we are keeping track
1368of them (and also if we are doing queue runs). */
1369
1370if (queue_interval > 0 && queue_run_max > 0)
1371 {
1372 int i;
1373 queue_pid_slots = store_get(queue_run_max * sizeof(pid_t));
1374 for (i = 0; i < queue_run_max; i++) queue_pid_slots[i] = 0;
1375 }
1376
1377/* Set up the handler for termination of child processes. */
1378
1379sigchld_seen = FALSE;
1380signal(SIGCHLD, main_sigchld_handler);
1381
1382/* If we are to run the queue periodically, pretend the alarm has just gone
1383off. This will cause the first queue-runner to get kicked off straight away. */
1384
1385sigalrm_seen = (queue_interval > 0);
1386
1387/* Log the start up of a daemon - at least one of listening or queue running
1388must be set up. */
1389
1390if (daemon_listen)
1391 {
1392 int i, j;
1393 int smtp_ports = 0;
1394 int smtps_ports = 0;
1395 ip_address_item *ipa;
1396 uschar *p = big_buffer;
1397 uschar *qinfo = (queue_interval > 0)?
1398 string_sprintf("-q%s", readconf_printtime(queue_interval))
1399 :
1400 US"no queue runs";
1401
1402 /* Build a list of listening addresses in big_buffer, but limit it to 10
1403 items. The style is for backwards compatibility.
1404
1405 It is now possible to have some ports listening for SMTPS (the old,
1406 deprecated protocol that starts TLS without using STARTTLS), and others
1407 listening for standard SMTP. Keep their listings separate. */
1408
1409 for (j = 0; j < 2; j++)
1410 {
1411 for (i = 0, ipa = addresses; i < 10 && ipa != NULL; i++, ipa = ipa->next)
1412 {
1413 /* First time round, look for SMTP ports; second time round, look for
1414 SMTPS ports. For the first one of each, insert leading text. */
1415
1416 if (host_is_tls_on_connect_port(ipa->port) == (j > 0))
1417 {
1418 if (j == 0)
1419 {
1420 if (smtp_ports++ == 0)
1421 {
1422 memcpy(p, "SMTP on", 8);
1423 p += 7;
1424 }
1425 }
1426 else
1427 {
1428 if (smtps_ports++ == 0)
1429 {
1430 (void)sprintf(CS p, "%sSMTPS on",
1431 (smtp_ports == 0)? "":" and for ");
1432 while (*p != 0) p++;
1433 }
1434 }
1435
1436 /* Now the information about the port (and sometimes interface) */
1437
1438 if (ipa->address[0] == ':' && ipa->address[1] == 0)
1439 {
1440 if (ipa->next != NULL && ipa->next->address[0] == 0 &&
1441 ipa->next->port == ipa->port)
1442 {
1443 (void)sprintf(CS p, " port %d (IPv6 and IPv4)", ipa->port);
1444 ipa = ipa->next;
1445 }
1446 else if (ipa->v6_include_v4)
1447 (void)sprintf(CS p, " port %d (IPv6 with IPv4)", ipa->port);
1448 else
1449 (void)sprintf(CS p, " port %d (IPv6)", ipa->port);
1450 }
1451 else if (ipa->address[0] == 0)
1452 (void)sprintf(CS p, " port %d (IPv4)", ipa->port);
1453 else
1454 (void)sprintf(CS p, " [%s]:%d", ipa->address, ipa->port);
1455 while (*p != 0) p++;
1456 }
1457 }
1458
1459 if (ipa != NULL)
1460 {
1461 memcpy(p, " ...", 5);
1462 p += 4;
1463 }
1464 }
1465
1466 log_write(0, LOG_MAIN,
1467 "exim %s daemon started: pid=%d, %s, listening for %s",
1468 version_string, getpid(), qinfo, big_buffer);
1469 set_process_info("daemon: %s, listening for %s", qinfo, big_buffer);
1470 }
1471
1472else
1473 {
1474 log_write(0, LOG_MAIN,
1475 "exim %s daemon started: pid=%d, -q%s, not listening for SMTP",
1476 version_string, getpid(), readconf_printtime(queue_interval));
1477 set_process_info("daemon: -q%s, not listening",
1478 readconf_printtime(queue_interval));
1479 }
1480
1481
1482/* Close the log so it can be renamed and moved. In the few cases below where
1483this long-running process writes to the log (always exceptional conditions), it
1484closes the log afterwards, for the same reason. */
1485
1486log_close_all();
1487
1488DEBUG(D_any) debug_print_ids(US"daemon running with");
1489
1490/* Any messages accepted via this route are going to be SMTP. */
1491
1492smtp_input = TRUE;
1493
1494/* Enter the never-ending loop... */
1495
1496for (;;)
1497 {
1498 #if HAVE_IPV6
1499 struct sockaddr_in6 accepted;
1500 #else
1501 struct sockaddr_in accepted;
1502 #endif
1503
1504 SOCKLEN_T len = sizeof(accepted);
1505 int status;
1506 pid_t pid;
1507
1508 /* This code is placed first in the loop, so that it gets obeyed at the
1509 start, before the first wait. This causes the first queue-runner to be
1510 started immediately. */
1511
1512 if (sigalrm_seen)
1513 {
1514 DEBUG(D_any) debug_printf("SIGALRM received\n");
1515
1516 /* Do a full queue run in a child process, if required, unless we already
1517 have enough queue runners on the go. If we are not running as root, a
1518 re-exec is required. */
1519
1520 if (queue_interval > 0 &&
1521 (queue_run_max <= 0 || queue_run_count < queue_run_max))
1522 {
1523 if ((pid = fork()) == 0)
1524 {
1525 int sk;
3d235903 1526
059ec3d9
PH
1527 DEBUG(D_any) debug_printf("Starting queue-runner: pid %d\n",
1528 (int)getpid());
1529
3d235903
PH
1530 /* Disable debugging if it's required only for the daemon process. We
1531 leave the above message, because it ties up with the "child ended"
1532 debugging messages. */
1533
1534 if (debug_daemon) debug_selector = 0;
1535
059ec3d9
PH
1536 /* Close any open listening sockets in the child */
1537
1538 for (sk = 0; sk < listen_socket_count; sk++) close(listen_sockets[sk]);
1539
1540 /* Reset SIGHUP and SIGCHLD in the child in both cases. */
1541
1542 signal(SIGHUP, SIG_DFL);
1543 signal(SIGCHLD, SIG_DFL);
1544
1545 /* Re-exec if privilege has been given up, unless deliver_drop_
1546 privilege is set. Reset SIGALRM before exec(). */
1547
1548 if (geteuid() != root_uid && !deliver_drop_privilege)
1549 {
1550 uschar opt[8];
1551 uschar *p = opt;
1552
1553 signal(SIGALRM, SIG_DFL);
1554 *p++ = '-';
1555 *p++ = 'q';
1556 if (queue_2stage) *p++ = 'q';
1557 if (queue_run_first_delivery) *p++ = 'i';
1558 if (queue_run_force) *p++ = 'f';
1559 if (deliver_force_thaw) *p++ = 'f';
1560 if (queue_run_local) *p++ = 'l';
1561 *p = 0;
1562
1563 (void)child_exec_exim(CEE_EXEC_PANIC, FALSE, NULL, TRUE, 1, opt);
1564 /* Control never returns here. */
1565 }
1566
1567 /* No need to re-exec; SIGALRM remains set to the default handler */
1568
1569 queue_run(NULL, NULL, FALSE);
1570 _exit(EXIT_SUCCESS);
1571 }
1572
1573 if (pid < 0)
1574 {
1575 log_write(0, LOG_MAIN|LOG_PANIC, "daemon: fork of queue-runner "
1576 "process failed: %s", strerror(errno));
1577 log_close_all();
1578 }
1579 else
1580 {
1581 int i;
1582 for (i = 0; i < queue_run_max; ++i)
1583 {
1584 if (queue_pid_slots[i] <= 0)
1585 {
1586 queue_pid_slots[i] = pid;
1587 queue_run_count++;
1588 break;
1589 }
1590 }
1591 DEBUG(D_any) debug_printf("%d queue-runner process%s running\n",
1592 queue_run_count, (queue_run_count == 1)? "" : "es");
1593 }
1594 }
1595
1596 /* Reset the alarm clock */
1597
1598 sigalrm_seen = FALSE;
1599 alarm(queue_interval);
1600 }
1601
1602
1603 /* Sleep till a connection happens if listening, and handle the connection if
1604 that is why we woke up. The FreeBSD operating system requires the use of
1605 select() before accept() because the latter function is not interrupted by
1606 a signal, and we want to wake up for SIGCHLD and SIGALRM signals. Some other
1607 OS do notice signals in accept() but it does no harm to have the select()
1608 in for all of them - and it won't then be a lurking problem for ports to
1609 new OS. In fact, the later addition of listening on specific interfaces only
1610 requires this way of working anyway. */
1611
1612 if (daemon_listen)
1613 {
1614 int sk, lcount;
1615 int max_socket = 0;
1616 BOOL select_failed = FALSE;
1617 fd_set select_listen;
1618
1619 FD_ZERO(&select_listen);
1620 for (sk = 0; sk < listen_socket_count; sk++)
1621 {
1622 FD_SET(listen_sockets[sk], &select_listen);
1623 if (listen_sockets[sk] > max_socket) max_socket = listen_sockets[sk];
1624 }
1625
1626 DEBUG(D_any) debug_printf("Listening...\n");
1627
1628 if ((lcount = select(max_socket + 1, (SELECT_ARG2_TYPE *)&select_listen,
1629 NULL, NULL, NULL)) < 0)
1630 {
1631 select_failed = TRUE;
1632 lcount = 1;
1633 }
1634
1635 /* Loop for all the sockets that are currently ready to go. If select
1636 actually failed, we have set the count to 1 and a flag, so as to use the
1637 common error code for select/accept below. */
1638
1639 while (lcount-- > 0)
1640 {
1641 int accept_socket = -1;
1642 if (!select_failed)
1643 {
1644 for (sk = 0; sk < listen_socket_count; sk++)
1645 {
1646 if (FD_ISSET(listen_sockets[sk], &select_listen))
1647 {
1648 accept_socket = accept(listen_sockets[sk],
1649 (struct sockaddr *)&accepted, &len);
1650 FD_CLR(listen_sockets[sk], &select_listen);
1651 break;
1652 }
1653 }
1654 }
1655
1656 /* If select or accept has failed and this was not caused by an
1657 interruption, log the incident and try again. With asymmetric TCP/IP
1658 routing errors such as "No route to network" have been seen here. Also
1659 "connection reset by peer" has been seen. These cannot be classed as
1660 disastrous errors, but they could fill up a lot of log. The code in smail
1661 crashes the daemon after 10 successive failures of accept, on the grounds
1662 that some OS fail continuously. Exim originally followed suit, but this
1663 appears to have caused problems. Now it just keeps going, but instead of
1664 logging each error, it batches them up when they are continuous. */
1665
1666 if (accept_socket < 0 && errno != EINTR)
1667 {
1668 if (accept_retry_count == 0)
1669 {
1670 accept_retry_errno = errno;
1671 accept_retry_select_failed = select_failed;
1672 }
1673 else
1674 {
1675 if (errno != accept_retry_errno ||
1676 select_failed != accept_retry_select_failed ||
1677 accept_retry_count >= 50)
1678 {
1679 log_write(0, LOG_MAIN | ((accept_retry_count >= 50)? LOG_PANIC : 0),
1680 "%d %s() failure%s: %s",
1681 accept_retry_count,
1682 accept_retry_select_failed? "select" : "accept",
1683 (accept_retry_count == 1)? "" : "s",
1684 strerror(accept_retry_errno));
1685 log_close_all();
1686 accept_retry_count = 0;
1687 accept_retry_errno = errno;
1688 accept_retry_select_failed = select_failed;
1689 }
1690 }
1691 accept_retry_count++;
1692 }
1693
1694 else
1695 {
1696 if (accept_retry_count > 0)
1697 {
1698 log_write(0, LOG_MAIN, "%d %s() failure%s: %s",
1699 accept_retry_count,
1700 accept_retry_select_failed? "select" : "accept",
1701 (accept_retry_count == 1)? "" : "s",
1702 strerror(accept_retry_errno));
1703 log_close_all();
1704 accept_retry_count = 0;
1705 }
1706 }
1707
1708 /* If select/accept succeeded, deal with the connection. */
1709
1710 if (accept_socket >= 0)
1711 handle_smtp_call(listen_sockets, listen_socket_count, accept_socket,
1712 (struct sockaddr *)&accepted);
1713 }
1714 }
1715
1716 /* If not listening, then just sleep for the queue interval. If we woke
1717 up early the last time for some other signal, it won't matter because
1718 the alarm signal will wake at the right time. This code originally used
1719 sleep() but it turns out that on the FreeBSD system, sleep() is not inter-
1720 rupted by signals, so it wasn't waking up for SIGALRM or SIGCHLD. Luckily
1721 select() can be used as an interruptible sleep() on all versions of Unix. */
1722
1723 else
1724 {
1725 struct timeval tv;
1726 tv.tv_sec = queue_interval;
1727 tv.tv_usec = 0;
1728 select(0, NULL, NULL, NULL, &tv);
1729 }
1730
1731 /* Handle the termination of a child process. Theoretically, this need
1732 be done only when sigchld_seen is TRUE, but rumour has it that some systems
1733 lose SIGCHLD signals at busy times, so to be on the safe side, just
1734 do it each time round. It shouldn't be too expensive. */
1735
1736 while ((pid = waitpid(-1, &status, WNOHANG)) > 0)
1737 {
1738 int i;
1739 DEBUG(D_any) debug_printf("child %d ended: status=0x%x\n", (int)pid,
1740 status);
1741
1742 /* If it's a listening daemon, deal with an accepting process that has
1743 terminated. */
1744
1745 if (daemon_listen)
1746 {
1747 for (i = 0; i < smtp_accept_max; i++)
1748 {
1749 if (smtp_slots[i].pid == pid)
1750 {
1751 if (smtp_slots[i].host_address != NULL)
1752 store_free(smtp_slots[i].host_address);
1753 smtp_slots[i] = empty_smtp_slot;
1754 if (--smtp_accept_count < 0) smtp_accept_count = 0;
1755 DEBUG(D_any) debug_printf("%d SMTP accept process%s now running\n",
1756 smtp_accept_count, (smtp_accept_count == 1)? "" : "es");
1757 break;
1758 }
1759 }
1760 if (i < smtp_accept_max) continue; /* Found an accepting process */
1761 }
1762
1763 /* If it wasn't an accepting process, see if it was a queue-runner
1764 process, if we are keeping track of them. */
1765
1766 if (queue_interval > 0)
1767 {
1768 for (i = 0; i < queue_run_max; i++)
1769 {
1770 if (queue_pid_slots[i] == pid)
1771 {
1772 queue_pid_slots[i] = 0;
1773 if (--queue_run_count < 0) queue_run_count = 0;
1774 DEBUG(D_any) debug_printf("%d queue-runner process%s now running\n",
1775 queue_run_count, (queue_run_count == 1)? "" : "es");
1776 break;
1777 }
1778 }
1779 }
1780 }
1781
1782 /* Re-enable the SIGCHLD handler if it has been run. It can't do it
1783 for itself, because it isn't doing the waiting itself. */
1784
1785 if (sigchld_seen)
1786 {
1787 sigchld_seen = FALSE;
1788 signal(SIGCHLD, main_sigchld_handler);
1789 }
1790
1791 /* Handle being woken by SIGHUP. We know at this point that the result
1792 of accept() has been dealt with, so we can re-exec exim safely, first
1793 closing the listening sockets so that they can be reused. Cancel any pending
1794 alarm in case it is just about to go off, and set SIGHUP to be ignored so
1795 that another HUP in quick succession doesn't clobber the new daemon before it
1796 gets going. All log files get closed by the close-on-exec flag; however, if
1797 the exec fails, we need to close the logs. */
1798
1799 if (sighup_seen)
1800 {
1801 int sk;
1802 log_write(0, LOG_MAIN, "pid %d: SIGHUP received: re-exec daemon",
1803 getpid());
1804 for (sk = 0; sk < listen_socket_count; sk++) close(listen_sockets[sk]);
1805 alarm(0);
1806 signal(SIGHUP, SIG_IGN);
1807 sighup_argv[0] = exim_path;
1808 exim_nullstd();
1809 execv(CS exim_path, (char *const *)sighup_argv);
1810 log_write(0, LOG_MAIN|LOG_PANIC_DIE, "pid %d: exec of %s failed: %s",
1811 getpid(), exim_path, strerror(errno));
1812 log_close_all();
1813 }
1814
1815 } /* End of main loop */
1816
1817/* Control never reaches here */
1818}
1819
1820/* End of exim_daemon.c */
1821