4ac34332b84a20b01412cc283e57fa4d52e94022
[exim.git] / src / src / daemon.c
1 /*************************************************
2 * Exim - an Internet mail transport agent *
3 *************************************************/
4
5 /* Copyright (c) University of Cambridge 1995 - 2009 */
6 /* See the file NOTICE for conditions of use and distribution. */
7
8 /* Functions concerned with running Exim as a daemon */
9
10
11 #include "exim.h"
12
13
14 /* Structure for holding data for each SMTP connection */
15
16 typedef struct smtp_slot {
17 pid_t pid; /* pid of the spawned reception process */
18 uschar *host_address; /* address of the client host */
19 } smtp_slot;
20
21 /* An empty slot for initializing (Standard C does not allow constructor
22 expressions in assigments except as initializers in declarations). */
23
24 static smtp_slot empty_smtp_slot = { 0, NULL };
25
26
27
28 /*************************************************
29 * Local static variables *
30 *************************************************/
31
32 static SIGNAL_BOOL sigchld_seen;
33 static SIGNAL_BOOL sighup_seen;
34
35 static int accept_retry_count = 0;
36 static int accept_retry_errno;
37 static BOOL accept_retry_select_failed;
38
39 static int queue_run_count = 0;
40 static pid_t *queue_pid_slots = NULL;
41 static smtp_slot *smtp_slots = NULL;
42
43 static BOOL write_pid = TRUE;
44
45
46
47 /*************************************************
48 * SIGHUP Handler *
49 *************************************************/
50
51 /* All this handler does is to set a flag and re-enable the signal.
52
53 Argument: the signal number
54 Returns: nothing
55 */
56
57 static void
58 sighup_handler(int sig)
59 {
60 sig = sig; /* Keep picky compilers happy */
61 sighup_seen = TRUE;
62 signal(SIGHUP, sighup_handler);
63 }
64
65
66
67 /*************************************************
68 * SIGCHLD handler for main daemon process *
69 *************************************************/
70
71 /* Don't re-enable the handler here, since we aren't doing the
72 waiting here. If the signal is re-enabled, there will just be an
73 infinite sequence of calls to this handler. The SIGCHLD signal is
74 used just as a means of waking up the daemon so that it notices
75 terminated subprocesses as soon as possible.
76
77 Argument: the signal number
78 Returns: nothing
79 */
80
81 static void
82 main_sigchld_handler(int sig)
83 {
84 sig = sig; /* Keep picky compilers happy */
85 os_non_restarting_signal(SIGCHLD, SIG_DFL);
86 sigchld_seen = TRUE;
87 }
88
89
90
91
92 /*************************************************
93 * Unexpected errors in SMTP calls *
94 *************************************************/
95
96 /* This function just saves a bit of repetitious coding.
97
98 Arguments:
99 log_msg Text of message to be logged
100 smtp_msg Text of SMTP error message
101 was_errno The failing errno
102
103 Returns: nothing
104 */
105
106 static void
107 never_error(uschar *log_msg, uschar *smtp_msg, int was_errno)
108 {
109 uschar *emsg = (was_errno <= 0)? US"" :
110 string_sprintf(": %s", strerror(was_errno));
111 log_write(0, LOG_MAIN|LOG_PANIC, "%s%s", log_msg, emsg);
112 if (smtp_out != NULL) smtp_printf("421 %s\r\n", smtp_msg);
113 }
114
115
116
117
118 /*************************************************
119 * Handle a connected SMTP call *
120 *************************************************/
121
122 /* This function is called when an SMTP connection has been accepted.
123 If there are too many, give an error message and close down. Otherwise
124 spin off a sub-process to handle the call. The list of listening sockets
125 is required so that they can be closed in the sub-process. Take care not to
126 leak store in this process - reset the stacking pool at the end.
127
128 Arguments:
129 listen_sockets sockets which are listening for incoming calls
130 listen_socket_count count of listening sockets
131 accept_socket socket of the current accepted call
132 accepted socket information about the current call
133
134 Returns: nothing
135 */
136
137 static void
138 handle_smtp_call(int *listen_sockets, int listen_socket_count,
139 int accept_socket, struct sockaddr *accepted)
140 {
141 pid_t pid;
142 union sockaddr_46 interface_sockaddr;
143 EXIM_SOCKLEN_T ifsize = sizeof(interface_sockaddr);
144 int dup_accept_socket = -1;
145 int max_for_this_host = 0;
146 int wfsize = 0;
147 int wfptr = 0;
148 int use_log_write_selector = log_write_selector;
149 uschar *whofrom = NULL;
150
151 void *reset_point = store_get(0);
152
153 /* Make the address available in ASCII representation, and also fish out
154 the remote port. */
155
156 sender_host_address = host_ntoa(-1, accepted, NULL, &sender_host_port);
157 DEBUG(D_any) debug_printf("Connection request from %s port %d\n",
158 sender_host_address, sender_host_port);
159
160 /* Set up the output stream, check the socket has duplicated, and set up the
161 input stream. These operations fail only the exceptional circumstances. Note
162 that never_error() won't use smtp_out if it is NULL. */
163
164 smtp_out = fdopen(accept_socket, "wb");
165 if (smtp_out == NULL)
166 {
167 never_error(US"daemon: fdopen() for smtp_out failed", US"", errno);
168 goto ERROR_RETURN;
169 }
170
171 dup_accept_socket = dup(accept_socket);
172 if (dup_accept_socket < 0)
173 {
174 never_error(US"daemon: couldn't dup socket descriptor",
175 US"Connection setup failed", errno);
176 goto ERROR_RETURN;
177 }
178
179 smtp_in = fdopen(dup_accept_socket, "rb");
180 if (smtp_in == NULL)
181 {
182 never_error(US"daemon: fdopen() for smtp_in failed",
183 US"Connection setup failed", errno);
184 goto ERROR_RETURN;
185 }
186
187 /* Get the data for the local interface address. Panic for most errors, but
188 "connection reset by peer" just means the connection went away. */
189
190 if (getsockname(accept_socket, (struct sockaddr *)(&interface_sockaddr),
191 &ifsize) < 0)
192 {
193 log_write(0, LOG_MAIN | ((errno == ECONNRESET)? 0 : LOG_PANIC),
194 "getsockname() failed: %s", strerror(errno));
195 smtp_printf("421 Local problem: getsockname() failed; please try again later\r\n");
196 goto ERROR_RETURN;
197 }
198
199 interface_address = host_ntoa(-1, &interface_sockaddr, NULL, &interface_port);
200 DEBUG(D_interface) debug_printf("interface address=%s port=%d\n",
201 interface_address, interface_port);
202
203 /* Build a string identifying the remote host and, if requested, the port and
204 the local interface data. This is for logging; at the end of this function the
205 memory is reclaimed. */
206
207 whofrom = string_append(whofrom, &wfsize, &wfptr, 3, "[", sender_host_address, "]");
208
209 if ((log_extra_selector & LX_incoming_port) != 0)
210 whofrom = string_append(whofrom, &wfsize, &wfptr, 2, ":", string_sprintf("%d",
211 sender_host_port));
212
213 if ((log_extra_selector & LX_incoming_interface) != 0)
214 whofrom = string_append(whofrom, &wfsize, &wfptr, 4, " I=[",
215 interface_address, "]:", string_sprintf("%d", interface_port));
216
217 whofrom[wfptr] = 0; /* Terminate the newly-built string */
218
219 /* Check maximum number of connections. We do not check for reserved
220 connections or unacceptable hosts here. That is done in the subprocess because
221 it might take some time. */
222
223 if (smtp_accept_max > 0 && smtp_accept_count >= smtp_accept_max)
224 {
225 DEBUG(D_any) debug_printf("rejecting SMTP connection: count=%d max=%d\n",
226 smtp_accept_count, smtp_accept_max);
227 smtp_printf("421 Too many concurrent SMTP connections; "
228 "please try again later.\r\n");
229 log_write(L_connection_reject,
230 LOG_MAIN, "Connection from %s refused: too many connections",
231 whofrom);
232 goto ERROR_RETURN;
233 }
234
235 /* If a load limit above which only reserved hosts are acceptable is defined,
236 get the load average here, and if there are in fact no reserved hosts, do
237 the test right away (saves a fork). If there are hosts, do the check in the
238 subprocess because it might take time. */
239
240 if (smtp_load_reserve >= 0)
241 {
242 load_average = OS_GETLOADAVG();
243 if (smtp_reserve_hosts == NULL && load_average > smtp_load_reserve)
244 {
245 DEBUG(D_any) debug_printf("rejecting SMTP connection: load average = %.2f\n",
246 (double)load_average/1000.0);
247 smtp_printf("421 Too much load; please try again later.\r\n");
248 log_write(L_connection_reject,
249 LOG_MAIN, "Connection from %s refused: load average = %.2f",
250 whofrom, (double)load_average/1000.0);
251 goto ERROR_RETURN;
252 }
253 }
254
255 /* Check that one specific host (strictly, IP address) is not hogging
256 resources. This is done here to prevent a denial of service attack by someone
257 forcing you to fork lots of times before denying service. The value of
258 smtp_accept_max_per_host is a string which is expanded. This makes it possible
259 to provide host-specific limits according to $sender_host address, but because
260 this is in the daemon mainline, only fast expansions (such as inline address
261 checks) should be used. The documentation is full of warnings. */
262
263 if (smtp_accept_max_per_host != NULL)
264 {
265 uschar *expanded = expand_string(smtp_accept_max_per_host);
266 if (expanded == NULL)
267 {
268 if (!expand_string_forcedfail)
269 log_write(0, LOG_MAIN|LOG_PANIC, "expansion of smtp_accept_max_per_host "
270 "failed for %s: %s", whofrom, expand_string_message);
271 }
272 /* For speed, interpret a decimal number inline here */
273 else
274 {
275 uschar *s = expanded;
276 while (isdigit(*s))
277 max_for_this_host = max_for_this_host * 10 + *s++ - '0';
278 if (*s != 0)
279 log_write(0, LOG_MAIN|LOG_PANIC, "expansion of smtp_accept_max_per_host "
280 "for %s contains non-digit: %s", whofrom, expanded);
281 }
282 }
283
284 /* If we have fewer connections than max_for_this_host, we can skip the tedious
285 per host_address checks. Note that at this stage smtp_accept_count contains the
286 count of *other* connections, not including this one. */
287
288 if ((max_for_this_host > 0) &&
289 (smtp_accept_count >= max_for_this_host))
290 {
291 int i;
292 int host_accept_count = 0;
293 int other_host_count = 0; /* keep a count of non matches to optimise */
294
295 for (i = 0; i < smtp_accept_max; ++i)
296 {
297 if (smtp_slots[i].host_address != NULL)
298 {
299 if (Ustrcmp(sender_host_address, smtp_slots[i].host_address) == 0)
300 host_accept_count++;
301 else
302 other_host_count++;
303
304 /* Testing all these strings is expensive - see if we can drop out
305 early, either by hitting the target, or finding there are not enough
306 connections left to make the target. */
307
308 if ((host_accept_count >= max_for_this_host) ||
309 ((smtp_accept_count - other_host_count) < max_for_this_host))
310 break;
311 }
312 }
313
314 if (host_accept_count >= max_for_this_host)
315 {
316 DEBUG(D_any) debug_printf("rejecting SMTP connection: too many from this "
317 "IP address: count=%d max=%d\n",
318 host_accept_count, max_for_this_host);
319 smtp_printf("421 Too many concurrent SMTP connections "
320 "from this IP address; please try again later.\r\n");
321 log_write(L_connection_reject,
322 LOG_MAIN, "Connection from %s refused: too many connections "
323 "from that IP address", whofrom);
324 goto ERROR_RETURN;
325 }
326 }
327
328 /* OK, the connection count checks have been passed. Before we can fork the
329 accepting process, we must first log the connection if requested. This logging
330 used to happen in the subprocess, but doing that means that the value of
331 smtp_accept_count can be out of step by the time it is logged. So we have to do
332 the logging here and accept the performance cost. Note that smtp_accept_count
333 hasn't yet been incremented to take account of this connection.
334
335 In order to minimize the cost (because this is going to happen for every
336 connection), do a preliminary selector test here. This saves ploughing through
337 the generalized logging code each time when the selector is false. If the
338 selector is set, check whether the host is on the list for logging. If not,
339 arrange to unset the selector in the subprocess. */
340
341 if ((log_write_selector & L_smtp_connection) != 0)
342 {
343 uschar *list = hosts_connection_nolog;
344 if (list != NULL && verify_check_host(&list) == OK)
345 use_log_write_selector &= ~L_smtp_connection;
346 else
347 log_write(L_smtp_connection, LOG_MAIN, "SMTP connection from %s "
348 "(TCP/IP connection count = %d)", whofrom, smtp_accept_count + 1);
349 }
350
351 /* Now we can fork the accepting process; do a lookup tidy, just in case any
352 expansion above did a lookup. */
353
354 search_tidyup();
355 pid = fork();
356
357 /* Handle the child process */
358
359 if (pid == 0)
360 {
361 int i;
362 int queue_only_reason = 0;
363 int old_pool = store_pool;
364 int save_debug_selector = debug_selector;
365 BOOL local_queue_only;
366 BOOL session_local_queue_only;
367 #ifdef SA_NOCLDWAIT
368 struct sigaction act;
369 #endif
370
371 smtp_accept_count++; /* So that it includes this process */
372
373 /* May have been modified for the subprocess */
374
375 log_write_selector = use_log_write_selector;
376
377 /* Get the local interface address into permanent store */
378
379 store_pool = POOL_PERM;
380 interface_address = string_copy(interface_address);
381 store_pool = old_pool;
382
383 /* Check for a tls-on-connect port */
384
385 if (host_is_tls_on_connect_port(interface_port)) tls_on_connect = TRUE;
386
387 /* Expand smtp_active_hostname if required. We do not do this any earlier,
388 because it may depend on the local interface address (indeed, that is most
389 likely what it depends on.) */
390
391 smtp_active_hostname = primary_hostname;
392 if (raw_active_hostname != NULL)
393 {
394 uschar *nah = expand_string(raw_active_hostname);
395 if (nah == NULL)
396 {
397 if (!expand_string_forcedfail)
398 {
399 log_write(0, LOG_MAIN|LOG_PANIC, "failed to expand \"%s\" "
400 "(smtp_active_hostname): %s", raw_active_hostname,
401 expand_string_message);
402 smtp_printf("421 Local configuration error; "
403 "please try again later.\r\n");
404 mac_smtp_fflush();
405 search_tidyup();
406 _exit(EXIT_FAILURE);
407 }
408 }
409 else if (nah[0] != 0) smtp_active_hostname = nah;
410 }
411
412 /* Initialize the queueing flags */
413
414 queue_check_only();
415 session_local_queue_only = queue_only;
416
417 /* Close the listening sockets, and set the SIGCHLD handler to SIG_IGN.
418 We also attempt to set things up so that children are automatically reaped,
419 but just in case this isn't available, there's a paranoid waitpid() in the
420 loop too (except for systems where we are sure it isn't needed). See the more
421 extensive comment before the reception loop in exim.c for a fuller
422 explanation of this logic. */
423
424 for (i = 0; i < listen_socket_count; i++) (void)close(listen_sockets[i]);
425
426 /* Set FD_CLOEXEC on the SMTP socket. We don't want any rogue child processes
427 to be able to communicate with them, under any circumstances. */
428 (void)fcntl(accept_socket, F_SETFD,
429 fcntl(accept_socket, F_GETFD) | FD_CLOEXEC);
430 (void)fcntl(dup_accept_socket, F_SETFD,
431 fcntl(dup_accept_socket, F_GETFD) | FD_CLOEXEC);
432
433 #ifdef SA_NOCLDWAIT
434 act.sa_handler = SIG_IGN;
435 sigemptyset(&(act.sa_mask));
436 act.sa_flags = SA_NOCLDWAIT;
437 sigaction(SIGCHLD, &act, NULL);
438 #else
439 signal(SIGCHLD, SIG_IGN);
440 #endif
441
442 /* Attempt to get an id from the sending machine via the RFC 1413
443 protocol. We do this in the sub-process in order not to hold up the
444 main process if there is any delay. Then set up the fullhost information
445 in case there is no HELO/EHLO.
446
447 If debugging is enabled only for the daemon, we must turn if off while
448 finding the id, but turn it on again afterwards so that information about the
449 incoming connection is output. */
450
451 if (debug_daemon) debug_selector = 0;
452 verify_get_ident(IDENT_PORT);
453 host_build_sender_fullhost();
454 debug_selector = save_debug_selector;
455
456 DEBUG(D_any)
457 debug_printf("Process %d is handling incoming connection from %s\n",
458 (int)getpid(), sender_fullhost);
459
460 /* Now disable debugging permanently if it's required only for the daemon
461 process. */
462
463 if (debug_daemon) debug_selector = 0;
464
465 /* If there are too many child processes for immediate delivery,
466 set the session_local_queue_only flag, which is initialized from the
467 configured value and may therefore already be TRUE. Leave logging
468 till later so it will have a message id attached. Note that there is no
469 possibility of re-calculating this per-message, because the value of
470 smtp_accept_count does not change in this subprocess. */
471
472 if (smtp_accept_queue > 0 && smtp_accept_count > smtp_accept_queue)
473 {
474 session_local_queue_only = TRUE;
475 queue_only_reason = 1;
476 }
477
478 /* Handle the start of the SMTP session, then loop, accepting incoming
479 messages from the SMTP connection. The end will come at the QUIT command,
480 when smtp_setup_msg() returns 0. A break in the connection causes the
481 process to die (see accept.c).
482
483 NOTE: We do *not* call smtp_log_no_mail() if smtp_start_session() fails,
484 because a log line has already been written for all its failure exists
485 (usually "connection refused: <reason>") and writing another one is
486 unnecessary clutter. */
487
488 if (!smtp_start_session())
489 {
490 mac_smtp_fflush();
491 search_tidyup();
492 _exit(EXIT_SUCCESS);
493 }
494
495 for (;;)
496 {
497 int rc;
498 message_id[0] = 0; /* Clear out any previous message_id */
499 reset_point = store_get(0); /* Save current store high water point */
500
501 DEBUG(D_any)
502 debug_printf("Process %d is ready for new message\n", (int)getpid());
503
504 /* Smtp_setup_msg() returns 0 on QUIT or if the call is from an
505 unacceptable host or if an ACL "drop" command was triggered, -1 on
506 connection lost, and +1 on validly reaching DATA. Receive_msg() almost
507 always returns TRUE when smtp_input is true; just retry if no message was
508 accepted (can happen for invalid message parameters). However, it can yield
509 FALSE if the connection was forcibly dropped by the DATA ACL. */
510
511 if ((rc = smtp_setup_msg()) > 0)
512 {
513 BOOL ok = receive_msg(FALSE);
514 search_tidyup(); /* Close cached databases */
515 if (!ok) /* Connection was dropped */
516 {
517 mac_smtp_fflush();
518 smtp_log_no_mail(); /* Log no mail if configured */
519 _exit(EXIT_SUCCESS);
520 }
521 if (message_id[0] == 0) continue; /* No message was accepted */
522 }
523 else
524 {
525 mac_smtp_fflush();
526 search_tidyup();
527 smtp_log_no_mail(); /* Log no mail if configured */
528 _exit((rc == 0)? EXIT_SUCCESS : EXIT_FAILURE);
529 }
530
531 /* Show the recipients when debugging */
532
533 DEBUG(D_receive)
534 {
535 int i;
536 if (sender_address != NULL)
537 debug_printf("Sender: %s\n", sender_address);
538 if (recipients_list != NULL)
539 {
540 debug_printf("Recipients:\n");
541 for (i = 0; i < recipients_count; i++)
542 debug_printf(" %s\n", recipients_list[i].address);
543 }
544 }
545
546 /* A message has been accepted. Clean up any previous delivery processes
547 that have completed and are defunct, on systems where they don't go away
548 by themselves (see comments when setting SIG_IGN above). On such systems
549 (if any) these delivery processes hang around after termination until
550 the next message is received. */
551
552 #ifndef SIG_IGN_WORKS
553 while (waitpid(-1, NULL, WNOHANG) > 0);
554 #endif
555
556 /* Reclaim up the store used in accepting this message */
557
558 store_reset(reset_point);
559
560 /* If queue_only is set or if there are too many incoming connections in
561 existence, session_local_queue_only will be TRUE. If it is not, check
562 whether we have received too many messages in this session for immediate
563 delivery. */
564
565 if (!session_local_queue_only &&
566 smtp_accept_queue_per_connection > 0 &&
567 receive_messagecount > smtp_accept_queue_per_connection)
568 {
569 session_local_queue_only = TRUE;
570 queue_only_reason = 2;
571 }
572
573 /* Initialize local_queue_only from session_local_queue_only. If it is not
574 true, and queue_only_load is set, check that the load average is below it.
575 If local_queue_only is set by this means, we also set if for the session if
576 queue_only_load_latch is true (the default). This means that, once set,
577 local_queue_only remains set for any subsequent messages on the same SMTP
578 connection. This is a deliberate choice; even though the load average may
579 fall, it doesn't seem right to deliver later messages on the same call when
580 not delivering earlier ones. However, the are special circumstances such as
581 very long-lived connections from scanning appliances where this is not the
582 best strategy. In such cases, queue_only_load_latch should be set false. */
583
584 local_queue_only = session_local_queue_only;
585 if (!local_queue_only && queue_only_load >= 0)
586 {
587 local_queue_only = (load_average = OS_GETLOADAVG()) > queue_only_load;
588 if (local_queue_only)
589 {
590 queue_only_reason = 3;
591 if (queue_only_load_latch) session_local_queue_only = TRUE;
592 }
593 }
594
595 /* Log the queueing here, when it will get a message id attached, but
596 not if queue_only is set (case 0). */
597
598 if (local_queue_only) switch(queue_only_reason)
599 {
600 case 1:
601 log_write(L_delay_delivery,
602 LOG_MAIN, "no immediate delivery: too many connections "
603 "(%d, max %d)", smtp_accept_count, smtp_accept_queue);
604 break;
605
606 case 2:
607 log_write(L_delay_delivery,
608 LOG_MAIN, "no immediate delivery: more than %d messages "
609 "received in one connection", smtp_accept_queue_per_connection);
610 break;
611
612 case 3:
613 log_write(L_delay_delivery,
614 LOG_MAIN, "no immediate delivery: load average %.2f",
615 (double)load_average/1000.0);
616 break;
617 }
618
619 /* If a delivery attempt is required, spin off a new process to handle it.
620 If we are not root, we have to re-exec exim unless deliveries are being
621 done unprivileged. */
622
623 else if (!queue_only_policy && !deliver_freeze)
624 {
625 pid_t dpid;
626
627 /* Before forking, ensure that the C output buffer is flushed. Otherwise
628 anything that it in it will get duplicated, leading to duplicate copies
629 of the pending output. */
630
631 mac_smtp_fflush();
632
633 if ((dpid = fork()) == 0)
634 {
635 (void)fclose(smtp_in);
636 (void)fclose(smtp_out);
637
638 /* Don't ever molest the parent's SSL connection, but do clean up
639 the data structures if necessary. */
640
641 #ifdef SUPPORT_TLS
642 tls_close(FALSE);
643 #endif
644
645 /* Reset SIGHUP and SIGCHLD in the child in both cases. */
646
647 signal(SIGHUP, SIG_DFL);
648 signal(SIGCHLD, SIG_DFL);
649
650 if (geteuid() != root_uid && !deliver_drop_privilege)
651 {
652 signal(SIGALRM, SIG_DFL);
653 (void)child_exec_exim(CEE_EXEC_PANIC, FALSE, NULL, FALSE, 2, US"-Mc",
654 message_id);
655 /* Control does not return here. */
656 }
657
658 /* No need to re-exec; SIGALRM remains set to the default handler */
659
660 (void)deliver_message(message_id, FALSE, FALSE);
661 search_tidyup();
662 _exit(EXIT_SUCCESS);
663 }
664
665 if (dpid > 0)
666 {
667 DEBUG(D_any) debug_printf("forked delivery process %d\n", (int)dpid);
668 }
669 else
670 {
671 log_write(0, LOG_MAIN|LOG_PANIC, "daemon: delivery process fork "
672 "failed: %s", strerror(errno));
673 }
674 }
675 }
676 }
677
678
679 /* Carrying on in the parent daemon process... Can't do much if the fork
680 failed. Otherwise, keep count of the number of accepting processes and
681 remember the pid for ticking off when the child completes. */
682
683 if (pid < 0)
684 {
685 never_error(US"daemon: accept process fork failed", US"Fork failed", errno);
686 }
687 else
688 {
689 int i;
690 for (i = 0; i < smtp_accept_max; ++i)
691 {
692 if (smtp_slots[i].pid <= 0)
693 {
694 smtp_slots[i].pid = pid;
695 if (smtp_accept_max_per_host != NULL)
696 smtp_slots[i].host_address = string_copy_malloc(sender_host_address);
697 smtp_accept_count++;
698 break;
699 }
700 }
701 DEBUG(D_any) debug_printf("%d SMTP accept process%s running\n",
702 smtp_accept_count, (smtp_accept_count == 1)? "" : "es");
703 }
704
705 /* Get here via goto in error cases */
706
707 ERROR_RETURN:
708
709 /* Close the streams associated with the socket which will also close the
710 socket fds in this process. We can't do anything if fclose() fails, but
711 logging brings it to someone's attention. However, "connection reset by peer"
712 isn't really a problem, so skip that one. On Solaris, a dropped connection can
713 manifest itself as a broken pipe, so drop that one too. If the streams don't
714 exist, something went wrong while setting things up. Make sure the socket
715 descriptors are closed, in order to drop the connection. */
716
717 if (smtp_out != NULL)
718 {
719 if (fclose(smtp_out) != 0 && errno != ECONNRESET && errno != EPIPE)
720 log_write(0, LOG_MAIN|LOG_PANIC, "daemon: fclose(smtp_out) failed: %s",
721 strerror(errno));
722 smtp_out = NULL;
723 }
724 else (void)close(accept_socket);
725
726 if (smtp_in != NULL)
727 {
728 if (fclose(smtp_in) != 0 && errno != ECONNRESET && errno != EPIPE)
729 log_write(0, LOG_MAIN|LOG_PANIC, "daemon: fclose(smtp_in) failed: %s",
730 strerror(errno));
731 smtp_in = NULL;
732 }
733 else (void)close(dup_accept_socket);
734
735 /* Release any store used in this process, including the store used for holding
736 the incoming host address and an expanded active_hostname. */
737
738 store_reset(reset_point);
739 sender_host_address = NULL;
740 }
741
742
743
744
745 /*************************************************
746 * Check wildcard listen special cases *
747 *************************************************/
748
749 /* This function is used when binding and listening on lists of addresses and
750 ports. It tests for special cases of wildcard listening, when IPv4 and IPv6
751 sockets may interact in different ways in different operating systems. It is
752 passed an error number, the list of listening addresses, and the current
753 address. Two checks are available: for a previous wildcard IPv6 address, or for
754 a following wildcard IPv4 address, in both cases on the same port.
755
756 In practice, pairs of wildcard addresses should be adjacent in the address list
757 because they are sorted that way below.
758
759 Arguments:
760 eno the error number
761 addresses the list of addresses
762 ipa the current IP address
763 back if TRUE, check for previous wildcard IPv6 address
764 if FALSE, check for a following wildcard IPv4 address
765
766 Returns: TRUE or FALSE
767 */
768
769 static BOOL
770 check_special_case(int eno, ip_address_item *addresses, ip_address_item *ipa,
771 BOOL back)
772 {
773 ip_address_item *ipa2;
774
775 /* For the "back" case, if the failure was "address in use" for a wildcard IPv4
776 address, seek a previous IPv6 wildcard address on the same port. As it is
777 previous, it must have been successfully bound and be listening. Flag it as a
778 "6 including 4" listener. */
779
780 if (back)
781 {
782 if (eno != EADDRINUSE || ipa->address[0] != 0) return FALSE;
783 for (ipa2 = addresses; ipa2 != ipa; ipa2 = ipa2->next)
784 {
785 if (ipa2->address[1] == 0 && ipa2->port == ipa->port)
786 {
787 ipa2->v6_include_v4 = TRUE;
788 return TRUE;
789 }
790 }
791 }
792
793 /* For the "forward" case, if the current address is a wildcard IPv6 address,
794 we seek a following wildcard IPv4 address on the same port. */
795
796 else
797 {
798 if (ipa->address[0] != ':' || ipa->address[1] != 0) return FALSE;
799 for (ipa2 = ipa->next; ipa2 != NULL; ipa2 = ipa2->next)
800 if (ipa2->address[0] == 0 && ipa->port == ipa2->port) return TRUE;
801 }
802
803 return FALSE;
804 }
805
806
807
808
809 /*************************************************
810 * Handle terminating subprocesses *
811 *************************************************/
812
813 /* Handle the termination of child processes. Theoretically, this need be done
814 only when sigchld_seen is TRUE, but rumour has it that some systems lose
815 SIGCHLD signals at busy times, so to be on the safe side, this function is
816 called each time round. It shouldn't be too expensive.
817
818 Arguments: none
819 Returns: nothing
820 */
821
822 static void
823 handle_ending_processes(void)
824 {
825 int status;
826 pid_t pid;
827
828 while ((pid = waitpid(-1, &status, WNOHANG)) > 0)
829 {
830 int i;
831 DEBUG(D_any) debug_printf("child %d ended: status=0x%x\n", (int)pid,
832 status);
833
834 /* If it's a listening daemon for which we are keeping track of individual
835 subprocesses, deal with an accepting process that has terminated. */
836
837 if (smtp_slots != NULL)
838 {
839 for (i = 0; i < smtp_accept_max; i++)
840 {
841 if (smtp_slots[i].pid == pid)
842 {
843 if (smtp_slots[i].host_address != NULL)
844 store_free(smtp_slots[i].host_address);
845 smtp_slots[i] = empty_smtp_slot;
846 if (--smtp_accept_count < 0) smtp_accept_count = 0;
847 DEBUG(D_any) debug_printf("%d SMTP accept process%s now running\n",
848 smtp_accept_count, (smtp_accept_count == 1)? "" : "es");
849 break;
850 }
851 }
852 if (i < smtp_accept_max) continue; /* Found an accepting process */
853 }
854
855 /* If it wasn't an accepting process, see if it was a queue-runner
856 process that we are tracking. */
857
858 if (queue_pid_slots != NULL)
859 {
860 for (i = 0; i < queue_run_max; i++)
861 {
862 if (queue_pid_slots[i] == pid)
863 {
864 queue_pid_slots[i] = 0;
865 if (--queue_run_count < 0) queue_run_count = 0;
866 DEBUG(D_any) debug_printf("%d queue-runner process%s now running\n",
867 queue_run_count, (queue_run_count == 1)? "" : "es");
868 break;
869 }
870 }
871 }
872 }
873 }
874
875
876
877 /*************************************************
878 * Exim Daemon Mainline *
879 *************************************************/
880
881 /* The daemon can do two jobs, either of which is optional:
882
883 (1) Listens for incoming SMTP calls and spawns off a sub-process to handle
884 each one. This is requested by the -bd option, with -oX specifying the SMTP
885 port on which to listen (for testing).
886
887 (2) Spawns a queue-running process every so often. This is controlled by the
888 -q option with a an interval time. (If no time is given, a single queue run
889 is done from the main function, and control doesn't get here.)
890
891 Root privilege is required in order to attach to port 25. Some systems require
892 it when calling socket() rather than bind(). To cope with all cases, we run as
893 root for both socket() and bind(). Some systems also require root in order to
894 write to the pid file directory. This function must therefore be called as root
895 if it is to work properly in all circumstances. Once the socket is bound and
896 the pid file written, root privilege is given up if there is an exim uid.
897
898 There are no arguments to this function, and it never returns. */
899
900 void
901 daemon_go(void)
902 {
903 struct passwd *pw;
904 int *listen_sockets = NULL;
905 int listen_socket_count = 0;
906 ip_address_item *addresses = NULL;
907
908 /* If any debugging options are set, turn on the D_pid bit so that all
909 debugging lines get the pid added. */
910
911 DEBUG(D_any|D_v) debug_selector |= D_pid;
912
913
914 /* Do the preparation for setting up a listener on one or more interfaces, and
915 possible on various ports. This is controlled by the combination of
916 local_interfaces (which can set IP addresses and ports) and daemon_smtp_port
917 (which is a list of default ports to use for those items in local_interfaces
918 that do not specify a port). The -oX command line option can be used to
919 override one or both of these options.
920
921 If local_interfaces is not set, the default is to listen on all interfaces.
922 When it is set, it can include "all IPvx interfaces" as an item. This is useful
923 when different ports are in use.
924
925 It turns out that listening on all interfaces is messy in an IPv6 world,
926 because several different implementation approaches have been taken. This code
927 is now supposed to work with all of them. The point of difference is whether an
928 IPv6 socket that is listening on all interfaces will receive incoming IPv4
929 calls or not. We also have to cope with the case when IPv6 libraries exist, but
930 there is no IPv6 support in the kernel.
931
932 . On Solaris, an IPv6 socket will accept IPv4 calls, and give them as mapped
933 addresses. However, if an IPv4 socket is also listening on all interfaces,
934 calls are directed to the appropriate socket.
935
936 . On (some versions of) Linux, an IPv6 socket will accept IPv4 calls, and
937 give them as mapped addresses, but an attempt also to listen on an IPv4
938 socket on all interfaces causes an error.
939
940 . On OpenBSD, an IPv6 socket will not accept IPv4 calls. You have to set up
941 two sockets if you want to accept both kinds of call.
942
943 . FreeBSD is like OpenBSD, but it has the IPV6_V6ONLY socket option, which
944 can be turned off, to make it behave like the versions of Linux described
945 above.
946
947 . I heard a report that the USAGI IPv6 stack for Linux has implemented
948 IPV6_V6ONLY.
949
950 So, what we do when IPv6 is supported is as follows:
951
952 (1) After it is set up, the list of interfaces is scanned for wildcard
953 addresses. If an IPv6 and an IPv4 wildcard are both found for the same
954 port, the list is re-arranged so that they are together, with the IPv6
955 wildcard first.
956
957 (2) If the creation of a wildcard IPv6 socket fails, we just log the error and
958 carry on if an IPv4 wildcard socket for the same port follows later in the
959 list. This allows Exim to carry on in the case when the kernel has no IPv6
960 support.
961
962 (3) Having created an IPv6 wildcard socket, we try to set IPV6_V6ONLY if that
963 option is defined. However, if setting fails, carry on regardless (but log
964 the incident).
965
966 (4) If binding or listening on an IPv6 wildcard socket fails, it is a serious
967 error.
968
969 (5) If binding or listening on an IPv4 wildcard socket fails with the error
970 EADDRINUSE, and a previous interface was an IPv6 wildcard for the same
971 port (which must have succeeded or we wouldn't have got this far), we
972 assume we are in the situation where just a single socket is permitted,
973 and ignore the error.
974
975 Phew!
976
977 The preparation code decodes options and sets up the relevant data. We do this
978 first, so that we can return non-zero if there are any syntax errors, and also
979 write to stderr. */
980
981 if (daemon_listen)
982 {
983 int *default_smtp_port;
984 int sep;
985 int pct = 0;
986 uschar *s;
987 uschar *list;
988 uschar *local_iface_source = US"local_interfaces";
989 ip_address_item *ipa;
990 ip_address_item **pipa;
991
992 /* If any option requiring a load average to be available during the
993 reception of a message is set, call os_getloadavg() while we are root
994 for those OS for which this is necessary the first time it is called (in
995 order to perform an "open" on the kernel memory file). */
996
997 #ifdef LOAD_AVG_NEEDS_ROOT
998 if (queue_only_load >= 0 || smtp_load_reserve >= 0 ||
999 (deliver_queue_load_max >= 0 && deliver_drop_privilege))
1000 (void)os_getloadavg();
1001 #endif
1002
1003 /* If -oX was used, disable the writing of a pid file unless -oP was
1004 explicitly used to force it. Then scan the string given to -oX. Any items
1005 that contain neither a dot nor a colon are used to override daemon_smtp_port.
1006 Any other items are used to override local_interfaces. */
1007
1008 if (override_local_interfaces != NULL)
1009 {
1010 uschar *new_smtp_port = NULL;
1011 uschar *new_local_interfaces = NULL;
1012 int portsize = 0;
1013 int portptr = 0;
1014 int ifacesize = 0;
1015 int ifaceptr = 0;
1016
1017 if (override_pid_file_path == NULL) write_pid = FALSE;
1018
1019 list = override_local_interfaces;
1020 sep = 0;
1021 while ((s = string_nextinlist(&list,&sep,big_buffer,big_buffer_size))
1022 != NULL)
1023 {
1024 uschar joinstr[4];
1025 uschar **ptr;
1026 int *sizeptr;
1027 int *ptrptr;
1028
1029 if (Ustrpbrk(s, ".:") == NULL)
1030 {
1031 ptr = &new_smtp_port;
1032 sizeptr = &portsize;
1033 ptrptr = &portptr;
1034 }
1035 else
1036 {
1037 ptr = &new_local_interfaces;
1038 sizeptr = &ifacesize;
1039 ptrptr = &ifaceptr;
1040 }
1041
1042 if (*ptr == NULL)
1043 {
1044 joinstr[0] = sep;
1045 joinstr[1] = ' ';
1046 *ptr = string_cat(*ptr, sizeptr, ptrptr, US"<", 1);
1047 }
1048
1049 *ptr = string_cat(*ptr, sizeptr, ptrptr, joinstr, 2);
1050 *ptr = string_cat(*ptr, sizeptr, ptrptr, s, Ustrlen(s));
1051 }
1052
1053 if (new_smtp_port != NULL)
1054 {
1055 new_smtp_port[portptr] = 0;
1056 daemon_smtp_port = new_smtp_port;
1057 DEBUG(D_any) debug_printf("daemon_smtp_port overridden by -oX:\n %s\n",
1058 daemon_smtp_port);
1059 }
1060
1061 if (new_local_interfaces != NULL)
1062 {
1063 new_local_interfaces[ifaceptr] = 0;
1064 local_interfaces = new_local_interfaces;
1065 local_iface_source = US"-oX data";
1066 DEBUG(D_any) debug_printf("local_interfaces overridden by -oX:\n %s\n",
1067 local_interfaces);
1068 }
1069 }
1070
1071 /* Create a list of default SMTP ports, to be used if local_interfaces
1072 contains entries without explict ports. First count the number of ports, then
1073 build a translated list in a vector. */
1074
1075 list = daemon_smtp_port;
1076 sep = 0;
1077 while ((s = string_nextinlist(&list,&sep,big_buffer,big_buffer_size)) != NULL)
1078 pct++;
1079 default_smtp_port = store_get((pct+1) * sizeof(int));
1080 list = daemon_smtp_port;
1081 sep = 0;
1082 for (pct = 0;
1083 (s = string_nextinlist(&list,&sep,big_buffer,big_buffer_size)) != NULL;
1084 pct++)
1085 {
1086 if (isdigit(*s))
1087 {
1088 uschar *end;
1089 default_smtp_port[pct] = Ustrtol(s, &end, 0);
1090 if (end != s + Ustrlen(s))
1091 log_write(0, LOG_PANIC_DIE|LOG_CONFIG, "invalid SMTP port: %s", s);
1092 }
1093 else
1094 {
1095 struct servent *smtp_service = getservbyname(CS s, "tcp");
1096 if (smtp_service == NULL)
1097 log_write(0, LOG_PANIC_DIE|LOG_CONFIG, "TCP port \"%s\" not found", s);
1098 default_smtp_port[pct] = ntohs(smtp_service->s_port);
1099 }
1100 }
1101 default_smtp_port[pct] = 0;
1102
1103 /* Create the list of local interfaces, possibly with ports included. This
1104 list may contain references to 0.0.0.0 and ::0 as wildcards. These special
1105 values are converted below. */
1106
1107 addresses = host_build_ifacelist(local_interfaces, local_iface_source);
1108
1109 /* In the list of IP addresses, convert 0.0.0.0 into an empty string, and ::0
1110 into the string ":". We use these to recognize wildcards in IPv4 and IPv6. In
1111 fact, many IP stacks recognize 0.0.0.0 and ::0 and handle them as wildcards
1112 anyway, but we need to know which are the wildcard addresses, and the shorter
1113 strings are neater.
1114
1115 In the same scan, fill in missing port numbers from the default list. When
1116 there is more than one item in the list, extra items are created. */
1117
1118 for (ipa = addresses; ipa != NULL; ipa = ipa->next)
1119 {
1120 int i;
1121
1122 if (Ustrcmp(ipa->address, "0.0.0.0") == 0) ipa->address[0] = 0;
1123 else if (Ustrcmp(ipa->address, "::0") == 0)
1124 {
1125 ipa->address[0] = ':';
1126 ipa->address[1] = 0;
1127 }
1128
1129 if (ipa->port > 0) continue;
1130
1131 if (daemon_smtp_port[0] <= 0)
1132 log_write(0, LOG_MAIN|LOG_PANIC_DIE, "no port specified for interface "
1133 "%s and daemon_smtp_port is unset; cannot start daemon",
1134 (ipa->address[0] == 0)? US"\"all IPv4\"" :
1135 (ipa->address[1] == 0)? US"\"all IPv6\"" : ipa->address);
1136 ipa->port = default_smtp_port[0];
1137 for (i = 1; default_smtp_port[i] > 0; i++)
1138 {
1139 ip_address_item *new = store_get(sizeof(ip_address_item));
1140 memcpy(new->address, ipa->address, Ustrlen(ipa->address) + 1);
1141 new->port = default_smtp_port[i];
1142 new->next = ipa->next;
1143 ipa->next = new;
1144 ipa = new;
1145 }
1146 }
1147
1148 /* Scan the list of addresses for wildcards. If we find an IPv4 and an IPv6
1149 wildcard for the same port, ensure that (a) they are together and (b) the
1150 IPv6 address comes first. This makes handling the messy features easier, and
1151 also simplifies the construction of the "daemon started" log line. */
1152
1153 pipa = &addresses;
1154 for (ipa = addresses; ipa != NULL; pipa = &(ipa->next), ipa = ipa->next)
1155 {
1156 ip_address_item *ipa2;
1157
1158 /* Handle an IPv4 wildcard */
1159
1160 if (ipa->address[0] == 0)
1161 {
1162 for (ipa2 = ipa; ipa2->next != NULL; ipa2 = ipa2->next)
1163 {
1164 ip_address_item *ipa3 = ipa2->next;
1165 if (ipa3->address[0] == ':' &&
1166 ipa3->address[1] == 0 &&
1167 ipa3->port == ipa->port)
1168 {
1169 ipa2->next = ipa3->next;
1170 ipa3->next = ipa;
1171 *pipa = ipa3;
1172 break;
1173 }
1174 }
1175 }
1176
1177 /* Handle an IPv6 wildcard. */
1178
1179 else if (ipa->address[0] == ':' && ipa->address[1] == 0)
1180 {
1181 for (ipa2 = ipa; ipa2->next != NULL; ipa2 = ipa2->next)
1182 {
1183 ip_address_item *ipa3 = ipa2->next;
1184 if (ipa3->address[0] == 0 && ipa3->port == ipa->port)
1185 {
1186 ipa2->next = ipa3->next;
1187 ipa3->next = ipa->next;
1188 ipa->next = ipa3;
1189 ipa = ipa3;
1190 break;
1191 }
1192 }
1193 }
1194 }
1195
1196 /* Get a vector to remember all the sockets in */
1197
1198 for (ipa = addresses; ipa != NULL; ipa = ipa->next)
1199 listen_socket_count++;
1200 listen_sockets = store_get(sizeof(int *) * listen_socket_count);
1201
1202 /* Do a sanity check on the max connects value just to save us from getting
1203 a huge amount of store. */
1204
1205 if (smtp_accept_max > 4095) smtp_accept_max = 4096;
1206
1207 /* There's no point setting smtp_accept_queue unless it is less than the max
1208 connects limit. The configuration reader ensures that the max is set if the
1209 queue-only option is set. */
1210
1211 if (smtp_accept_queue > smtp_accept_max) smtp_accept_queue = 0;
1212
1213 /* Get somewhere to keep the list of SMTP accepting pids if we are keeping
1214 track of them for total number and queue/host limits. */
1215
1216 if (smtp_accept_max > 0)
1217 {
1218 int i;
1219 smtp_slots = store_get(smtp_accept_max * sizeof(smtp_slot));
1220 for (i = 0; i < smtp_accept_max; i++) smtp_slots[i] = empty_smtp_slot;
1221 }
1222 }
1223
1224 /* The variable background_daemon is always false when debugging, but
1225 can also be forced false in order to keep a non-debugging daemon in the
1226 foreground. If background_daemon is true, close all open file descriptors that
1227 we know about, but then re-open stdin, stdout, and stderr to /dev/null.
1228
1229 This is protection against any called functions (in libraries, or in
1230 Perl, or whatever) that think they can write to stderr (or stdout). Before this
1231 was added, it was quite likely that an SMTP connection would use one of these
1232 file descriptors, in which case writing random stuff to it caused chaos.
1233
1234 Then disconnect from the controlling terminal, Most modern Unixes seem to have
1235 setsid() for getting rid of the controlling terminal. For any OS that doesn't,
1236 setsid() can be #defined as a no-op, or as something else. */
1237
1238 if (background_daemon)
1239 {
1240 log_close_all(); /* Just in case anything was logged earlier */
1241 search_tidyup(); /* Just in case any were used in reading the config. */
1242 (void)close(0); /* Get rid of stdin/stdout/stderr */
1243 (void)close(1);
1244 (void)close(2);
1245 exim_nullstd(); /* Connect stdin/stdout/stderr to /dev/null */
1246 log_stderr = NULL; /* So no attempt to copy paniclog output */
1247
1248 /* If the parent process of this one has pid == 1, we are re-initializing the
1249 daemon as the result of a SIGHUP. In this case, there is no need to do
1250 anything, because the controlling terminal has long gone. Otherwise, fork, in
1251 case current process is a process group leader (see 'man setsid' for an
1252 explanation) before calling setsid(). */
1253
1254 if (getppid() != 1)
1255 {
1256 pid_t pid = fork();
1257 if (pid < 0) log_write(0, LOG_MAIN|LOG_PANIC_DIE,
1258 "fork() failed when starting daemon: %s", strerror(errno));
1259 if (pid > 0) exit(EXIT_SUCCESS); /* in parent process, just exit */
1260 (void)setsid(); /* release controlling terminal */
1261 }
1262 }
1263
1264 /* We are now in the disconnected, daemon process (unless debugging). Set up
1265 the listening sockets if required. */
1266
1267 if (daemon_listen)
1268 {
1269 int sk;
1270 int on = 1;
1271 ip_address_item *ipa;
1272
1273 /* For each IP address, create a socket, bind it to the appropriate port, and
1274 start listening. See comments above about IPv6 sockets that may or may not
1275 accept IPv4 calls when listening on all interfaces. We also have to cope with
1276 the case of a system with IPv6 libraries, but no IPv6 support in the kernel.
1277 listening, provided a wildcard IPv4 socket for the same port follows. */
1278
1279 for (ipa = addresses, sk = 0; sk < listen_socket_count; ipa = ipa->next, sk++)
1280 {
1281 BOOL wildcard;
1282 ip_address_item *ipa2;
1283 int af;
1284
1285 if (Ustrchr(ipa->address, ':') != NULL)
1286 {
1287 af = AF_INET6;
1288 wildcard = ipa->address[1] == 0;
1289 }
1290 else
1291 {
1292 af = AF_INET;
1293 wildcard = ipa->address[0] == 0;
1294 }
1295
1296 listen_sockets[sk] = ip_socket(SOCK_STREAM, af);
1297 if (listen_sockets[sk] < 0)
1298 {
1299 if (check_special_case(0, addresses, ipa, FALSE))
1300 {
1301 log_write(0, LOG_MAIN, "Failed to create IPv6 socket for wildcard "
1302 "listening (%s): will use IPv4", strerror(errno));
1303 goto SKIP_SOCKET;
1304 }
1305 log_write(0, LOG_PANIC_DIE, "IPv%c socket creation failed: %s",
1306 (af == AF_INET6)? '6' : '4', strerror(errno));
1307 }
1308
1309 /* If this is an IPv6 wildcard socket, set IPV6_V6ONLY if that option is
1310 available. Just log failure (can get protocol not available, just like
1311 socket creation can). */
1312
1313 #ifdef IPV6_V6ONLY
1314 if (af == AF_INET6 && wildcard &&
1315 setsockopt(listen_sockets[sk], IPPROTO_IPV6, IPV6_V6ONLY, (char *)(&on),
1316 sizeof(on)) < 0)
1317 log_write(0, LOG_MAIN, "Setting IPV6_V6ONLY on daemon's IPv6 wildcard "
1318 "socket failed (%s): carrying on without it", strerror(errno));
1319 #endif /* IPV6_V6ONLY */
1320
1321 /* Set SO_REUSEADDR so that the daemon can be restarted while a connection
1322 is being handled. Without this, a connection will prevent reuse of the
1323 smtp port for listening. */
1324
1325 if (setsockopt(listen_sockets[sk], SOL_SOCKET, SO_REUSEADDR,
1326 (uschar *)(&on), sizeof(on)) < 0)
1327 log_write(0, LOG_MAIN|LOG_PANIC_DIE, "setting SO_REUSEADDR on socket "
1328 "failed when starting daemon: %s", strerror(errno));
1329
1330 /* Set TCP_NODELAY; Exim does its own buffering. There is a switch to
1331 disable this because it breaks some broken clients. */
1332
1333 if (tcp_nodelay) setsockopt(listen_sockets[sk], IPPROTO_TCP, TCP_NODELAY,
1334 (uschar *)(&on), sizeof(on));
1335
1336 /* Now bind the socket to the required port; if Exim is being restarted
1337 it may not always be possible to bind immediately, even with SO_REUSEADDR
1338 set, so try 10 times, waiting between each try. After 10 failures, we give
1339 up. In an IPv6 environment, if bind () fails with the error EADDRINUSE and
1340 we are doing wildcard IPv4 listening and there was a previous IPv6 wildcard
1341 address for the same port, ignore the error on the grounds that we must be
1342 in a system where the IPv6 socket accepts both kinds of call. This is
1343 necessary for (some release of) USAGI Linux; other IP stacks fail at the
1344 listen() stage instead. */
1345
1346 for(;;)
1347 {
1348 uschar *msg, *addr;
1349 if (ip_bind(listen_sockets[sk], af, ipa->address, ipa->port) >= 0) break;
1350 if (check_special_case(errno, addresses, ipa, TRUE))
1351 {
1352 DEBUG(D_any) debug_printf("wildcard IPv4 bind() failed after IPv6 "
1353 "listen() success; EADDRINUSE ignored\n");
1354 (void)close(listen_sockets[sk]);
1355 goto SKIP_SOCKET;
1356 }
1357 msg = US strerror(errno);
1358 addr = wildcard? ((af == AF_INET6)? US"(any IPv6)" : US"(any IPv4)") :
1359 ipa->address;
1360 if (daemon_startup_retries <= 0)
1361 log_write(0, LOG_MAIN|LOG_PANIC_DIE,
1362 "socket bind() to port %d for address %s failed: %s: "
1363 "daemon abandoned", ipa->port, addr, msg);
1364 log_write(0, LOG_MAIN, "socket bind() to port %d for address %s "
1365 "failed: %s: waiting %s before trying again (%d more %s)",
1366 ipa->port, addr, msg, readconf_printtime(daemon_startup_sleep),
1367 daemon_startup_retries, (daemon_startup_retries > 1)? "tries" : "try");
1368 daemon_startup_retries--;
1369 sleep(daemon_startup_sleep);
1370 }
1371
1372 DEBUG(D_any)
1373 {
1374 if (wildcard)
1375 debug_printf("listening on all interfaces (IPv%c) port %d\n",
1376 (af == AF_INET6)? '6' : '4', ipa->port);
1377 else
1378 debug_printf("listening on %s port %d\n", ipa->address, ipa->port);
1379 }
1380
1381 /* Start listening on the bound socket, establishing the maximum backlog of
1382 connections that is allowed. On success, continue to the next address. */
1383
1384 if (listen(listen_sockets[sk], smtp_connect_backlog) >= 0) continue;
1385
1386 /* Listening has failed. In an IPv6 environment, as for bind(), if listen()
1387 fails with the error EADDRINUSE and we are doing IPv4 wildcard listening
1388 and there was a previous successful IPv6 wildcard listen on the same port,
1389 we want to ignore the error on the grounds that we must be in a system
1390 where the IPv6 socket accepts both kinds of call. */
1391
1392 if (!check_special_case(errno, addresses, ipa, TRUE))
1393 log_write(0, LOG_PANIC_DIE, "listen() failed on interface %s: %s",
1394 wildcard? ((af == AF_INET6)? US"(any IPv6)" : US"(any IPv4)") :
1395 ipa->address,
1396 strerror(errno));
1397
1398 DEBUG(D_any) debug_printf("wildcard IPv4 listen() failed after IPv6 "
1399 "listen() success; EADDRINUSE ignored\n");
1400 (void)close(listen_sockets[sk]);
1401
1402 /* Come here if there has been a problem with the socket which we
1403 are going to ignore. We remove the address from the chain, and back up the
1404 counts. */
1405
1406 SKIP_SOCKET:
1407 sk--; /* Back up the count */
1408 listen_socket_count--; /* Reduce the total */
1409 if (ipa == addresses) addresses = ipa->next; else
1410 {
1411 for (ipa2 = addresses; ipa2->next != ipa; ipa2 = ipa2->next);
1412 ipa2->next = ipa->next;
1413 ipa = ipa2;
1414 }
1415 } /* End of bind/listen loop for each address */
1416 } /* End of setup for listening */
1417
1418
1419 /* If we are not listening, we want to write a pid file only if -oP was
1420 explicitly given. */
1421
1422 else if (override_pid_file_path == NULL) write_pid = FALSE;
1423
1424 /* Write the pid to a known file for assistance in identification, if required.
1425 We do this before giving up root privilege, because on some systems it is
1426 necessary to be root in order to write into the pid file directory. There's
1427 nothing to stop multiple daemons running, as long as no more than one listens
1428 on a given TCP/IP port on the same interface(s). However, in these
1429 circumstances it gets far too complicated to mess with pid file names
1430 automatically. Consequently, Exim 4 writes a pid file only
1431
1432 (a) When running in the test harness, or
1433 (b) When -bd is used and -oX is not used, or
1434 (c) When -oP is used to supply a path.
1435
1436 The variable daemon_write_pid is used to control this. */
1437
1438 if (running_in_test_harness || write_pid)
1439 {
1440 FILE *f;
1441
1442 if (override_pid_file_path != NULL)
1443 pid_file_path = override_pid_file_path;
1444
1445 if (pid_file_path[0] == 0)
1446 pid_file_path = string_sprintf("%s/exim-daemon.pid", spool_directory);
1447
1448 f = modefopen(pid_file_path, "wb", 0644);
1449 if (f != NULL)
1450 {
1451 (void)fprintf(f, "%d\n", (int)getpid());
1452 (void)fclose(f);
1453 DEBUG(D_any) debug_printf("pid written to %s\n", pid_file_path);
1454 }
1455 else
1456 {
1457 DEBUG(D_any)
1458 debug_printf("%s\n", string_open_failed(errno, "pid file %s",
1459 pid_file_path));
1460 }
1461 }
1462
1463 /* Set up the handler for SIGHUP, which causes a restart of the daemon. */
1464
1465 sighup_seen = FALSE;
1466 signal(SIGHUP, sighup_handler);
1467
1468 /* Give up root privilege at this point (assuming that exim_uid and exim_gid
1469 are not root). The third argument controls the running of initgroups().
1470 Normally we do this, in order to set up the groups for the Exim user. However,
1471 if we are not root at this time - some odd installations run that way - we
1472 cannot do this. */
1473
1474 exim_setugid(exim_uid, exim_gid, geteuid()==root_uid, US"running as a daemon");
1475
1476 /* Update the originator_xxx fields so that received messages as listed as
1477 coming from Exim, not whoever started the daemon. */
1478
1479 originator_uid = exim_uid;
1480 originator_gid = exim_gid;
1481 originator_login = ((pw = getpwuid(exim_uid)) != NULL)?
1482 string_copy_malloc(US pw->pw_name) : US"exim";
1483
1484 /* Get somewhere to keep the list of queue-runner pids if we are keeping track
1485 of them (and also if we are doing queue runs). */
1486
1487 if (queue_interval > 0 && queue_run_max > 0)
1488 {
1489 int i;
1490 queue_pid_slots = store_get(queue_run_max * sizeof(pid_t));
1491 for (i = 0; i < queue_run_max; i++) queue_pid_slots[i] = 0;
1492 }
1493
1494 /* Set up the handler for termination of child processes. */
1495
1496 sigchld_seen = FALSE;
1497 os_non_restarting_signal(SIGCHLD, main_sigchld_handler);
1498
1499 /* If we are to run the queue periodically, pretend the alarm has just gone
1500 off. This will cause the first queue-runner to get kicked off straight away. */
1501
1502 sigalrm_seen = (queue_interval > 0);
1503
1504 /* Log the start up of a daemon - at least one of listening or queue running
1505 must be set up. */
1506
1507 if (daemon_listen)
1508 {
1509 int i, j;
1510 int smtp_ports = 0;
1511 int smtps_ports = 0;
1512 ip_address_item *ipa;
1513 uschar *p = big_buffer;
1514 uschar *qinfo = (queue_interval > 0)?
1515 string_sprintf("-q%s", readconf_printtime(queue_interval))
1516 :
1517 US"no queue runs";
1518
1519 /* Build a list of listening addresses in big_buffer, but limit it to 10
1520 items. The style is for backwards compatibility.
1521
1522 It is now possible to have some ports listening for SMTPS (the old,
1523 deprecated protocol that starts TLS without using STARTTLS), and others
1524 listening for standard SMTP. Keep their listings separate. */
1525
1526 for (j = 0; j < 2; j++)
1527 {
1528 for (i = 0, ipa = addresses; i < 10 && ipa != NULL; i++, ipa = ipa->next)
1529 {
1530 /* First time round, look for SMTP ports; second time round, look for
1531 SMTPS ports. For the first one of each, insert leading text. */
1532
1533 if (host_is_tls_on_connect_port(ipa->port) == (j > 0))
1534 {
1535 if (j == 0)
1536 {
1537 if (smtp_ports++ == 0)
1538 {
1539 memcpy(p, "SMTP on", 8);
1540 p += 7;
1541 }
1542 }
1543 else
1544 {
1545 if (smtps_ports++ == 0)
1546 {
1547 (void)sprintf(CS p, "%sSMTPS on",
1548 (smtp_ports == 0)? "":" and for ");
1549 while (*p != 0) p++;
1550 }
1551 }
1552
1553 /* Now the information about the port (and sometimes interface) */
1554
1555 if (ipa->address[0] == ':' && ipa->address[1] == 0)
1556 {
1557 if (ipa->next != NULL && ipa->next->address[0] == 0 &&
1558 ipa->next->port == ipa->port)
1559 {
1560 (void)sprintf(CS p, " port %d (IPv6 and IPv4)", ipa->port);
1561 ipa = ipa->next;
1562 }
1563 else if (ipa->v6_include_v4)
1564 (void)sprintf(CS p, " port %d (IPv6 with IPv4)", ipa->port);
1565 else
1566 (void)sprintf(CS p, " port %d (IPv6)", ipa->port);
1567 }
1568 else if (ipa->address[0] == 0)
1569 (void)sprintf(CS p, " port %d (IPv4)", ipa->port);
1570 else
1571 (void)sprintf(CS p, " [%s]:%d", ipa->address, ipa->port);
1572 while (*p != 0) p++;
1573 }
1574 }
1575
1576 if (ipa != NULL)
1577 {
1578 memcpy(p, " ...", 5);
1579 p += 4;
1580 }
1581 }
1582
1583 log_write(0, LOG_MAIN,
1584 "exim %s daemon started: pid=%d, %s, listening for %s",
1585 version_string, getpid(), qinfo, big_buffer);
1586 set_process_info("daemon: %s, listening for %s", qinfo, big_buffer);
1587 }
1588
1589 else
1590 {
1591 log_write(0, LOG_MAIN,
1592 "exim %s daemon started: pid=%d, -q%s, not listening for SMTP",
1593 version_string, getpid(), readconf_printtime(queue_interval));
1594 set_process_info("daemon: -q%s, not listening",
1595 readconf_printtime(queue_interval));
1596 }
1597
1598
1599 /* Close the log so it can be renamed and moved. In the few cases below where
1600 this long-running process writes to the log (always exceptional conditions), it
1601 closes the log afterwards, for the same reason. */
1602
1603 log_close_all();
1604
1605 DEBUG(D_any) debug_print_ids(US"daemon running with");
1606
1607 /* Any messages accepted via this route are going to be SMTP. */
1608
1609 smtp_input = TRUE;
1610
1611 /* Enter the never-ending loop... */
1612
1613 for (;;)
1614 {
1615 #if HAVE_IPV6
1616 struct sockaddr_in6 accepted;
1617 #else
1618 struct sockaddr_in accepted;
1619 #endif
1620
1621 EXIM_SOCKLEN_T len;
1622 pid_t pid;
1623
1624 /* This code is placed first in the loop, so that it gets obeyed at the
1625 start, before the first wait. This causes the first queue-runner to be
1626 started immediately. */
1627
1628 if (sigalrm_seen)
1629 {
1630 DEBUG(D_any) debug_printf("SIGALRM received\n");
1631
1632 /* Do a full queue run in a child process, if required, unless we already
1633 have enough queue runners on the go. If we are not running as root, a
1634 re-exec is required. */
1635
1636 if (queue_interval > 0 &&
1637 (queue_run_max <= 0 || queue_run_count < queue_run_max))
1638 {
1639 if ((pid = fork()) == 0)
1640 {
1641 int sk;
1642
1643 DEBUG(D_any) debug_printf("Starting queue-runner: pid %d\n",
1644 (int)getpid());
1645
1646 /* Disable debugging if it's required only for the daemon process. We
1647 leave the above message, because it ties up with the "child ended"
1648 debugging messages. */
1649
1650 if (debug_daemon) debug_selector = 0;
1651
1652 /* Close any open listening sockets in the child */
1653
1654 for (sk = 0; sk < listen_socket_count; sk++)
1655 (void)close(listen_sockets[sk]);
1656
1657 /* Reset SIGHUP and SIGCHLD in the child in both cases. */
1658
1659 signal(SIGHUP, SIG_DFL);
1660 signal(SIGCHLD, SIG_DFL);
1661
1662 /* Re-exec if privilege has been given up, unless deliver_drop_
1663 privilege is set. Reset SIGALRM before exec(). */
1664
1665 if (geteuid() != root_uid && !deliver_drop_privilege)
1666 {
1667 uschar opt[8];
1668 uschar *p = opt;
1669 uschar *extra[5];
1670 int extracount = 1;
1671
1672 signal(SIGALRM, SIG_DFL);
1673 *p++ = '-';
1674 *p++ = 'q';
1675 if (queue_2stage) *p++ = 'q';
1676 if (queue_run_first_delivery) *p++ = 'i';
1677 if (queue_run_force) *p++ = 'f';
1678 if (deliver_force_thaw) *p++ = 'f';
1679 if (queue_run_local) *p++ = 'l';
1680 *p = 0;
1681 extra[0] = opt;
1682
1683 /* If -R or -S were on the original command line, ensure they get
1684 passed on. */
1685
1686 if (deliver_selectstring != NULL)
1687 {
1688 extra[extracount++] = deliver_selectstring_regex? US"-Rr" : US"-R";
1689 extra[extracount++] = deliver_selectstring;
1690 }
1691
1692 if (deliver_selectstring_sender != NULL)
1693 {
1694 extra[extracount++] = deliver_selectstring_sender_regex?
1695 US"-Sr" : US"-S";
1696 extra[extracount++] = deliver_selectstring_sender;
1697 }
1698
1699 /* Overlay this process with a new execution. */
1700
1701 (void)child_exec_exim(CEE_EXEC_PANIC, FALSE, NULL, TRUE, extracount,
1702 extra[0], extra[1], extra[2], extra[3], extra[4]);
1703
1704 /* Control never returns here. */
1705 }
1706
1707 /* No need to re-exec; SIGALRM remains set to the default handler */
1708
1709 queue_run(NULL, NULL, FALSE);
1710 _exit(EXIT_SUCCESS);
1711 }
1712
1713 if (pid < 0)
1714 {
1715 log_write(0, LOG_MAIN|LOG_PANIC, "daemon: fork of queue-runner "
1716 "process failed: %s", strerror(errno));
1717 log_close_all();
1718 }
1719 else
1720 {
1721 int i;
1722 for (i = 0; i < queue_run_max; ++i)
1723 {
1724 if (queue_pid_slots[i] <= 0)
1725 {
1726 queue_pid_slots[i] = pid;
1727 queue_run_count++;
1728 break;
1729 }
1730 }
1731 DEBUG(D_any) debug_printf("%d queue-runner process%s running\n",
1732 queue_run_count, (queue_run_count == 1)? "" : "es");
1733 }
1734 }
1735
1736 /* Reset the alarm clock */
1737
1738 sigalrm_seen = FALSE;
1739 alarm(queue_interval);
1740 }
1741
1742
1743 /* Sleep till a connection happens if listening, and handle the connection if
1744 that is why we woke up. The FreeBSD operating system requires the use of
1745 select() before accept() because the latter function is not interrupted by
1746 a signal, and we want to wake up for SIGCHLD and SIGALRM signals. Some other
1747 OS do notice signals in accept() but it does no harm to have the select()
1748 in for all of them - and it won't then be a lurking problem for ports to
1749 new OS. In fact, the later addition of listening on specific interfaces only
1750 requires this way of working anyway. */
1751
1752 if (daemon_listen)
1753 {
1754 int sk, lcount, select_errno;
1755 int max_socket = 0;
1756 BOOL select_failed = FALSE;
1757 fd_set select_listen;
1758
1759 FD_ZERO(&select_listen);
1760 for (sk = 0; sk < listen_socket_count; sk++)
1761 {
1762 FD_SET(listen_sockets[sk], &select_listen);
1763 if (listen_sockets[sk] > max_socket) max_socket = listen_sockets[sk];
1764 }
1765
1766 DEBUG(D_any) debug_printf("Listening...\n");
1767
1768 /* In rare cases we may have had a SIGCHLD signal in the time between
1769 setting the handler (below) and getting back here. If so, pretend that the
1770 select() was interrupted so that we reap the child. This might still leave
1771 a small window when a SIGCHLD could get lost. However, since we use SIGCHLD
1772 only to do the reaping more quickly, it shouldn't result in anything other
1773 than a delay until something else causes a wake-up. */
1774
1775 if (sigchld_seen)
1776 {
1777 lcount = -1;
1778 errno = EINTR;
1779 }
1780 else
1781 {
1782 lcount = select(max_socket + 1, (SELECT_ARG2_TYPE *)&select_listen,
1783 NULL, NULL, NULL);
1784 }
1785
1786 if (lcount < 0)
1787 {
1788 select_failed = TRUE;
1789 lcount = 1;
1790 }
1791
1792 /* Clean up any subprocesses that may have terminated. We need to do this
1793 here so that smtp_accept_max_per_host works when a connection to that host
1794 has completed, and we are about to accept a new one. When this code was
1795 later in the sequence, a new connection could be rejected, even though an
1796 old one had just finished. Preserve the errno from any select() failure for
1797 the use of the common select/accept error processing below. */
1798
1799 select_errno = errno;
1800 handle_ending_processes();
1801 errno = select_errno;
1802
1803 /* Loop for all the sockets that are currently ready to go. If select
1804 actually failed, we have set the count to 1 and select_failed=TRUE, so as
1805 to use the common error code for select/accept below. */
1806
1807 while (lcount-- > 0)
1808 {
1809 int accept_socket = -1;
1810 if (!select_failed)
1811 {
1812 for (sk = 0; sk < listen_socket_count; sk++)
1813 {
1814 if (FD_ISSET(listen_sockets[sk], &select_listen))
1815 {
1816 len = sizeof(accepted);
1817 accept_socket = accept(listen_sockets[sk],
1818 (struct sockaddr *)&accepted, &len);
1819 FD_CLR(listen_sockets[sk], &select_listen);
1820 break;
1821 }
1822 }
1823 }
1824
1825 /* If select or accept has failed and this was not caused by an
1826 interruption, log the incident and try again. With asymmetric TCP/IP
1827 routing errors such as "No route to network" have been seen here. Also
1828 "connection reset by peer" has been seen. These cannot be classed as
1829 disastrous errors, but they could fill up a lot of log. The code in smail
1830 crashes the daemon after 10 successive failures of accept, on the grounds
1831 that some OS fail continuously. Exim originally followed suit, but this
1832 appears to have caused problems. Now it just keeps going, but instead of
1833 logging each error, it batches them up when they are continuous. */
1834
1835 if (accept_socket < 0 && errno != EINTR)
1836 {
1837 if (accept_retry_count == 0)
1838 {
1839 accept_retry_errno = errno;
1840 accept_retry_select_failed = select_failed;
1841 }
1842 else
1843 {
1844 if (errno != accept_retry_errno ||
1845 select_failed != accept_retry_select_failed ||
1846 accept_retry_count >= 50)
1847 {
1848 log_write(0, LOG_MAIN | ((accept_retry_count >= 50)? LOG_PANIC : 0),
1849 "%d %s() failure%s: %s",
1850 accept_retry_count,
1851 accept_retry_select_failed? "select" : "accept",
1852 (accept_retry_count == 1)? "" : "s",
1853 strerror(accept_retry_errno));
1854 log_close_all();
1855 accept_retry_count = 0;
1856 accept_retry_errno = errno;
1857 accept_retry_select_failed = select_failed;
1858 }
1859 }
1860 accept_retry_count++;
1861 }
1862
1863 else
1864 {
1865 if (accept_retry_count > 0)
1866 {
1867 log_write(0, LOG_MAIN, "%d %s() failure%s: %s",
1868 accept_retry_count,
1869 accept_retry_select_failed? "select" : "accept",
1870 (accept_retry_count == 1)? "" : "s",
1871 strerror(accept_retry_errno));
1872 log_close_all();
1873 accept_retry_count = 0;
1874 }
1875 }
1876
1877 /* If select/accept succeeded, deal with the connection. */
1878
1879 if (accept_socket >= 0)
1880 handle_smtp_call(listen_sockets, listen_socket_count, accept_socket,
1881 (struct sockaddr *)&accepted);
1882 }
1883 }
1884
1885 /* If not listening, then just sleep for the queue interval. If we woke
1886 up early the last time for some other signal, it won't matter because
1887 the alarm signal will wake at the right time. This code originally used
1888 sleep() but it turns out that on the FreeBSD system, sleep() is not inter-
1889 rupted by signals, so it wasn't waking up for SIGALRM or SIGCHLD. Luckily
1890 select() can be used as an interruptible sleep() on all versions of Unix. */
1891
1892 else
1893 {
1894 struct timeval tv;
1895 tv.tv_sec = queue_interval;
1896 tv.tv_usec = 0;
1897 select(0, NULL, NULL, NULL, &tv);
1898 handle_ending_processes();
1899 }
1900
1901 /* Re-enable the SIGCHLD handler if it has been run. It can't do it
1902 for itself, because it isn't doing the waiting itself. */
1903
1904 if (sigchld_seen)
1905 {
1906 sigchld_seen = FALSE;
1907 os_non_restarting_signal(SIGCHLD, main_sigchld_handler);
1908 }
1909
1910 /* Handle being woken by SIGHUP. We know at this point that the result
1911 of accept() has been dealt with, so we can re-exec exim safely, first
1912 closing the listening sockets so that they can be reused. Cancel any pending
1913 alarm in case it is just about to go off, and set SIGHUP to be ignored so
1914 that another HUP in quick succession doesn't clobber the new daemon before it
1915 gets going. All log files get closed by the close-on-exec flag; however, if
1916 the exec fails, we need to close the logs. */
1917
1918 if (sighup_seen)
1919 {
1920 int sk;
1921 log_write(0, LOG_MAIN, "pid %d: SIGHUP received: re-exec daemon",
1922 getpid());
1923 for (sk = 0; sk < listen_socket_count; sk++)
1924 (void)close(listen_sockets[sk]);
1925 alarm(0);
1926 signal(SIGHUP, SIG_IGN);
1927 sighup_argv[0] = exim_path;
1928 exim_nullstd();
1929 execv(CS exim_path, (char *const *)sighup_argv);
1930 log_write(0, LOG_MAIN|LOG_PANIC_DIE, "pid %d: exec of %s failed: %s",
1931 getpid(), exim_path, strerror(errno));
1932 log_close_all();
1933 }
1934
1935 } /* End of main loop */
1936
1937 /* Control never reaches here */
1938 }
1939
1940 /* End of exim_daemon.c */
1941