Performance timing measurements
[exim.git] / src / src / daemon.c
1 /*************************************************
2 * Exim - an Internet mail transport agent *
3 *************************************************/
4
5 /* Copyright (c) University of Cambridge 1995 - 2018 */
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 assignments except as initializers in declarations). */
23
24 static smtp_slot empty_smtp_slot = { .pid = 0, .host_address = 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
110 ? US"" : string_sprintf(": %s", strerror(was_errno));
111 log_write(0, LOG_MAIN|LOG_PANIC, "%s%s", log_msg, emsg);
112 if (smtp_out) smtp_printf("421 %s\r\n", FALSE, 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 save_log_selector = *log_selector;
147 gstring * whofrom;
148
149 rmark reset_point = store_mark();
150
151 /* Make the address available in ASCII representation, and also fish out
152 the remote port. */
153
154 sender_host_address = host_ntoa(-1, accepted, NULL, &sender_host_port);
155 DEBUG(D_any) debug_printf("Connection request from %s port %d\n",
156 sender_host_address, sender_host_port);
157
158 /* Set up the output stream, check the socket has duplicated, and set up the
159 input stream. These operations fail only the exceptional circumstances. Note
160 that never_error() won't use smtp_out if it is NULL. */
161
162 if (!(smtp_out = fdopen(accept_socket, "wb")))
163 {
164 never_error(US"daemon: fdopen() for smtp_out failed", US"", errno);
165 goto ERROR_RETURN;
166 }
167
168 if ((dup_accept_socket = dup(accept_socket)) < 0)
169 {
170 never_error(US"daemon: couldn't dup socket descriptor",
171 US"Connection setup failed", errno);
172 goto ERROR_RETURN;
173 }
174
175 if (!(smtp_in = fdopen(dup_accept_socket, "rb")))
176 {
177 never_error(US"daemon: fdopen() for smtp_in failed",
178 US"Connection setup failed", errno);
179 goto ERROR_RETURN;
180 }
181
182 /* Get the data for the local interface address. Panic for most errors, but
183 "connection reset by peer" just means the connection went away. */
184
185 if (getsockname(accept_socket, (struct sockaddr *)(&interface_sockaddr),
186 &ifsize) < 0)
187 {
188 log_write(0, LOG_MAIN | ((errno == ECONNRESET)? 0 : LOG_PANIC),
189 "getsockname() failed: %s", strerror(errno));
190 smtp_printf("421 Local problem: getsockname() failed; please try again later\r\n", FALSE);
191 goto ERROR_RETURN;
192 }
193
194 interface_address = host_ntoa(-1, &interface_sockaddr, NULL, &interface_port);
195 DEBUG(D_interface) debug_printf("interface address=%s port=%d\n",
196 interface_address, interface_port);
197
198 /* Build a string identifying the remote host and, if requested, the port and
199 the local interface data. This is for logging; at the end of this function the
200 memory is reclaimed. */
201
202 whofrom = string_append(NULL, 3, "[", sender_host_address, "]");
203
204 if (LOGGING(incoming_port))
205 whofrom = string_fmt_append(whofrom, ":%d", sender_host_port);
206
207 if (LOGGING(incoming_interface))
208 whofrom = string_fmt_append(whofrom, " I=[%s]:%d",
209 interface_address, interface_port);
210
211 (void) string_from_gstring(whofrom); /* Terminate the newly-built string */
212
213 /* Check maximum number of connections. We do not check for reserved
214 connections or unacceptable hosts here. That is done in the subprocess because
215 it might take some time. */
216
217 if (smtp_accept_max > 0 && smtp_accept_count >= smtp_accept_max)
218 {
219 DEBUG(D_any) debug_printf("rejecting SMTP connection: count=%d max=%d\n",
220 smtp_accept_count, smtp_accept_max);
221 smtp_printf("421 Too many concurrent SMTP connections; "
222 "please try again later.\r\n", FALSE);
223 log_write(L_connection_reject,
224 LOG_MAIN, "Connection from %s refused: too many connections",
225 whofrom->s);
226 goto ERROR_RETURN;
227 }
228
229 /* If a load limit above which only reserved hosts are acceptable is defined,
230 get the load average here, and if there are in fact no reserved hosts, do
231 the test right away (saves a fork). If there are hosts, do the check in the
232 subprocess because it might take time. */
233
234 if (smtp_load_reserve >= 0)
235 {
236 load_average = OS_GETLOADAVG();
237 if (smtp_reserve_hosts == NULL && load_average > smtp_load_reserve)
238 {
239 DEBUG(D_any) debug_printf("rejecting SMTP connection: load average = %.2f\n",
240 (double)load_average/1000.0);
241 smtp_printf("421 Too much load; please try again later.\r\n", FALSE);
242 log_write(L_connection_reject,
243 LOG_MAIN, "Connection from %s refused: load average = %.2f",
244 whofrom->s, (double)load_average/1000.0);
245 goto ERROR_RETURN;
246 }
247 }
248
249 /* Check that one specific host (strictly, IP address) is not hogging
250 resources. This is done here to prevent a denial of service attack by someone
251 forcing you to fork lots of times before denying service. The value of
252 smtp_accept_max_per_host is a string which is expanded. This makes it possible
253 to provide host-specific limits according to $sender_host address, but because
254 this is in the daemon mainline, only fast expansions (such as inline address
255 checks) should be used. The documentation is full of warnings. */
256
257 if (smtp_accept_max_per_host != NULL)
258 {
259 uschar *expanded = expand_string(smtp_accept_max_per_host);
260 if (expanded == NULL)
261 {
262 if (!f.expand_string_forcedfail)
263 log_write(0, LOG_MAIN|LOG_PANIC, "expansion of smtp_accept_max_per_host "
264 "failed for %s: %s", whofrom->s, expand_string_message);
265 }
266 /* For speed, interpret a decimal number inline here */
267 else
268 {
269 uschar *s = expanded;
270 while (isdigit(*s))
271 max_for_this_host = max_for_this_host * 10 + *s++ - '0';
272 if (*s != 0)
273 log_write(0, LOG_MAIN|LOG_PANIC, "expansion of smtp_accept_max_per_host "
274 "for %s contains non-digit: %s", whofrom->s, expanded);
275 }
276 }
277
278 /* If we have fewer connections than max_for_this_host, we can skip the tedious
279 per host_address checks. Note that at this stage smtp_accept_count contains the
280 count of *other* connections, not including this one. */
281
282 if ((max_for_this_host > 0) &&
283 (smtp_accept_count >= max_for_this_host))
284 {
285 int host_accept_count = 0;
286 int other_host_count = 0; /* keep a count of non matches to optimise */
287
288 for (int i = 0; i < smtp_accept_max; ++i)
289 if (smtp_slots[i].host_address)
290 {
291 if (Ustrcmp(sender_host_address, smtp_slots[i].host_address) == 0)
292 host_accept_count++;
293 else
294 other_host_count++;
295
296 /* Testing all these strings is expensive - see if we can drop out
297 early, either by hitting the target, or finding there are not enough
298 connections left to make the target. */
299
300 if ((host_accept_count >= max_for_this_host) ||
301 ((smtp_accept_count - other_host_count) < max_for_this_host))
302 break;
303 }
304
305 if (host_accept_count >= max_for_this_host)
306 {
307 DEBUG(D_any) debug_printf("rejecting SMTP connection: too many from this "
308 "IP address: count=%d max=%d\n",
309 host_accept_count, max_for_this_host);
310 smtp_printf("421 Too many concurrent SMTP connections "
311 "from this IP address; please try again later.\r\n", FALSE);
312 log_write(L_connection_reject,
313 LOG_MAIN, "Connection from %s refused: too many connections "
314 "from that IP address", whofrom->s);
315 goto ERROR_RETURN;
316 }
317 }
318
319 /* OK, the connection count checks have been passed. Before we can fork the
320 accepting process, we must first log the connection if requested. This logging
321 used to happen in the subprocess, but doing that means that the value of
322 smtp_accept_count can be out of step by the time it is logged. So we have to do
323 the logging here and accept the performance cost. Note that smtp_accept_count
324 hasn't yet been incremented to take account of this connection.
325
326 In order to minimize the cost (because this is going to happen for every
327 connection), do a preliminary selector test here. This saves ploughing through
328 the generalized logging code each time when the selector is false. If the
329 selector is set, check whether the host is on the list for logging. If not,
330 arrange to unset the selector in the subprocess. */
331
332 if (LOGGING(smtp_connection))
333 {
334 uschar *list = hosts_connection_nolog;
335 memset(sender_host_cache, 0, sizeof(sender_host_cache));
336 if (list != NULL && verify_check_host(&list) == OK)
337 save_log_selector &= ~L_smtp_connection;
338 else
339 log_write(L_smtp_connection, LOG_MAIN, "SMTP connection from %s "
340 "(TCP/IP connection count = %d)", whofrom->s, smtp_accept_count + 1);
341 }
342
343 /* Now we can fork the accepting process; do a lookup tidy, just in case any
344 expansion above did a lookup. */
345
346 search_tidyup();
347 pid = fork();
348
349 /* Handle the child process */
350
351 if (pid == 0)
352 {
353 int i;
354 int queue_only_reason = 0;
355 int old_pool = store_pool;
356 int save_debug_selector = debug_selector;
357 BOOL local_queue_only;
358 BOOL session_local_queue_only;
359 #ifdef SA_NOCLDWAIT
360 struct sigaction act;
361 #endif
362
363 smtp_accept_count++; /* So that it includes this process */
364
365 /* May have been modified for the subprocess */
366
367 *log_selector = save_log_selector;
368
369 /* Get the local interface address into permanent store */
370
371 store_pool = POOL_PERM;
372 interface_address = string_copy(interface_address);
373 store_pool = old_pool;
374
375 /* Check for a tls-on-connect port */
376
377 if (host_is_tls_on_connect_port(interface_port)) tls_in.on_connect = TRUE;
378
379 /* Expand smtp_active_hostname if required. We do not do this any earlier,
380 because it may depend on the local interface address (indeed, that is most
381 likely what it depends on.) */
382
383 smtp_active_hostname = primary_hostname;
384 if (raw_active_hostname)
385 {
386 uschar * nah = expand_string(raw_active_hostname);
387 if (!nah)
388 {
389 if (!f.expand_string_forcedfail)
390 {
391 log_write(0, LOG_MAIN|LOG_PANIC, "failed to expand \"%s\" "
392 "(smtp_active_hostname): %s", raw_active_hostname,
393 expand_string_message);
394 smtp_printf("421 Local configuration error; "
395 "please try again later.\r\n", FALSE);
396 mac_smtp_fflush();
397 search_tidyup();
398 exim_underbar_exit(EXIT_FAILURE);
399 }
400 }
401 else if (*nah) smtp_active_hostname = nah;
402 }
403
404 /* Initialize the queueing flags */
405
406 queue_check_only();
407 session_local_queue_only = queue_only;
408
409 /* Close the listening sockets, and set the SIGCHLD handler to SIG_IGN.
410 We also attempt to set things up so that children are automatically reaped,
411 but just in case this isn't available, there's a paranoid waitpid() in the
412 loop too (except for systems where we are sure it isn't needed). See the more
413 extensive comment before the reception loop in exim.c for a fuller
414 explanation of this logic. */
415
416 for (i = 0; i < listen_socket_count; i++) (void)close(listen_sockets[i]);
417
418 /* Set FD_CLOEXEC on the SMTP socket. We don't want any rogue child processes
419 to be able to communicate with them, under any circumstances. */
420 (void)fcntl(accept_socket, F_SETFD,
421 fcntl(accept_socket, F_GETFD) | FD_CLOEXEC);
422 (void)fcntl(dup_accept_socket, F_SETFD,
423 fcntl(dup_accept_socket, F_GETFD) | FD_CLOEXEC);
424
425 #ifdef SA_NOCLDWAIT
426 act.sa_handler = SIG_IGN;
427 sigemptyset(&(act.sa_mask));
428 act.sa_flags = SA_NOCLDWAIT;
429 sigaction(SIGCHLD, &act, NULL);
430 #else
431 signal(SIGCHLD, SIG_IGN);
432 #endif
433
434 /* Attempt to get an id from the sending machine via the RFC 1413
435 protocol. We do this in the sub-process in order not to hold up the
436 main process if there is any delay. Then set up the fullhost information
437 in case there is no HELO/EHLO.
438
439 If debugging is enabled only for the daemon, we must turn if off while
440 finding the id, but turn it on again afterwards so that information about the
441 incoming connection is output. */
442
443 if (f.debug_daemon) debug_selector = 0;
444 verify_get_ident(IDENT_PORT);
445 host_build_sender_fullhost();
446 debug_selector = save_debug_selector;
447
448 DEBUG(D_any)
449 debug_printf("Process %d is handling incoming connection from %s\n",
450 (int)getpid(), sender_fullhost);
451
452 /* Now disable debugging permanently if it's required only for the daemon
453 process. */
454
455 if (f.debug_daemon) debug_selector = 0;
456
457 /* If there are too many child processes for immediate delivery,
458 set the session_local_queue_only flag, which is initialized from the
459 configured value and may therefore already be TRUE. Leave logging
460 till later so it will have a message id attached. Note that there is no
461 possibility of re-calculating this per-message, because the value of
462 smtp_accept_count does not change in this subprocess. */
463
464 if (smtp_accept_queue > 0 && smtp_accept_count > smtp_accept_queue)
465 {
466 session_local_queue_only = TRUE;
467 queue_only_reason = 1;
468 }
469
470 /* Handle the start of the SMTP session, then loop, accepting incoming
471 messages from the SMTP connection. The end will come at the QUIT command,
472 when smtp_setup_msg() returns 0. A break in the connection causes the
473 process to die (see accept.c).
474
475 NOTE: We do *not* call smtp_log_no_mail() if smtp_start_session() fails,
476 because a log line has already been written for all its failure exists
477 (usually "connection refused: <reason>") and writing another one is
478 unnecessary clutter. */
479
480 if (!smtp_start_session())
481 {
482 mac_smtp_fflush();
483 search_tidyup();
484 exim_underbar_exit(EXIT_SUCCESS);
485 }
486
487 for (;;)
488 {
489 int rc;
490 message_id[0] = 0; /* Clear out any previous message_id */
491 reset_point = store_mark(); /* Save current store high water point */
492
493 DEBUG(D_any)
494 debug_printf("Process %d is ready for new message\n", (int)getpid());
495
496 /* Smtp_setup_msg() returns 0 on QUIT or if the call is from an
497 unacceptable host or if an ACL "drop" command was triggered, -1 on
498 connection lost, and +1 on validly reaching DATA. Receive_msg() almost
499 always returns TRUE when smtp_input is true; just retry if no message was
500 accepted (can happen for invalid message parameters). However, it can yield
501 FALSE if the connection was forcibly dropped by the DATA ACL. */
502
503 if ((rc = smtp_setup_msg()) > 0)
504 {
505 BOOL ok = receive_msg(FALSE);
506 search_tidyup(); /* Close cached databases */
507 if (!ok) /* Connection was dropped */
508 {
509 cancel_cutthrough_connection(TRUE, US"receive dropped");
510 mac_smtp_fflush();
511 smtp_log_no_mail(); /* Log no mail if configured */
512 exim_underbar_exit(EXIT_SUCCESS);
513 }
514 if (message_id[0] == 0) continue; /* No message was accepted */
515 }
516 else
517 {
518 if (smtp_out)
519 {
520 int fd = fileno(smtp_in);
521 uschar buf[128];
522
523 mac_smtp_fflush();
524 /* drain socket, for clean TCP FINs */
525 if (fcntl(fd, F_SETFL, O_NONBLOCK) == 0)
526 for(int i = 16; read(fd, buf, sizeof(buf)) > 0 && i > 0; ) i--;
527 }
528 cancel_cutthrough_connection(TRUE, US"message setup dropped");
529 search_tidyup();
530 smtp_log_no_mail(); /* Log no mail if configured */
531
532 /*XXX should we pause briefly, hoping that the client will be the
533 active TCP closer hence get the TCP_WAIT endpoint? */
534 DEBUG(D_receive) debug_printf("SMTP>>(close on process exit)\n");
535 exim_underbar_exit(rc ? EXIT_FAILURE : EXIT_SUCCESS);
536 }
537
538 /* Show the recipients when debugging */
539
540 DEBUG(D_receive)
541 {
542 if (sender_address)
543 debug_printf("Sender: %s\n", sender_address);
544 if (recipients_list)
545 {
546 debug_printf("Recipients:\n");
547 for (int i = 0; i < recipients_count; i++)
548 debug_printf(" %s\n", recipients_list[i].address);
549 }
550 }
551
552 /* A message has been accepted. Clean up any previous delivery processes
553 that have completed and are defunct, on systems where they don't go away
554 by themselves (see comments when setting SIG_IGN above). On such systems
555 (if any) these delivery processes hang around after termination until
556 the next message is received. */
557
558 #ifndef SIG_IGN_WORKS
559 while (waitpid(-1, NULL, WNOHANG) > 0);
560 #endif
561
562 /* Reclaim up the store used in accepting this message */
563
564 {
565 int r = receive_messagecount;
566 BOOL q = f.queue_only_policy;
567 smtp_reset(reset_point);
568 reset_point = NULL;
569 f.queue_only_policy = q;
570 receive_messagecount = r;
571 }
572
573 /* If queue_only is set or if there are too many incoming connections in
574 existence, session_local_queue_only will be TRUE. If it is not, check
575 whether we have received too many messages in this session for immediate
576 delivery. */
577
578 if (!session_local_queue_only &&
579 smtp_accept_queue_per_connection > 0 &&
580 receive_messagecount > smtp_accept_queue_per_connection)
581 {
582 session_local_queue_only = TRUE;
583 queue_only_reason = 2;
584 }
585
586 /* Initialize local_queue_only from session_local_queue_only. If it is not
587 true, and queue_only_load is set, check that the load average is below it.
588 If local_queue_only is set by this means, we also set if for the session if
589 queue_only_load_latch is true (the default). This means that, once set,
590 local_queue_only remains set for any subsequent messages on the same SMTP
591 connection. This is a deliberate choice; even though the load average may
592 fall, it doesn't seem right to deliver later messages on the same call when
593 not delivering earlier ones. However, the are special circumstances such as
594 very long-lived connections from scanning appliances where this is not the
595 best strategy. In such cases, queue_only_load_latch should be set false. */
596
597 if ( !(local_queue_only = session_local_queue_only)
598 && queue_only_load >= 0
599 && (local_queue_only = (load_average = OS_GETLOADAVG()) > queue_only_load)
600 )
601 {
602 queue_only_reason = 3;
603 if (queue_only_load_latch) session_local_queue_only = TRUE;
604 }
605
606 /* Log the queueing here, when it will get a message id attached, but
607 not if queue_only is set (case 0). */
608
609 if (local_queue_only) switch(queue_only_reason)
610 {
611 case 1: log_write(L_delay_delivery,
612 LOG_MAIN, "no immediate delivery: too many connections "
613 "(%d, max %d)", smtp_accept_count, smtp_accept_queue);
614 break;
615
616 case 2: log_write(L_delay_delivery,
617 LOG_MAIN, "no immediate delivery: more than %d messages "
618 "received in one connection", smtp_accept_queue_per_connection);
619 break;
620
621 case 3: log_write(L_delay_delivery,
622 LOG_MAIN, "no immediate delivery: load average %.2f",
623 (double)load_average/1000.0);
624 break;
625 }
626
627 /* If a delivery attempt is required, spin off a new process to handle it.
628 If we are not root, we have to re-exec exim unless deliveries are being
629 done unprivileged. */
630
631 else if (!f.queue_only_policy && !f.deliver_freeze)
632 {
633 pid_t dpid;
634
635 /* Before forking, ensure that the C output buffer is flushed. Otherwise
636 anything that it in it will get duplicated, leading to duplicate copies
637 of the pending output. */
638
639 mac_smtp_fflush();
640
641 if ((dpid = fork()) == 0)
642 {
643 (void)fclose(smtp_in);
644 (void)fclose(smtp_out);
645
646 /* Don't ever molest the parent's SSL connection, but do clean up
647 the data structures if necessary. */
648
649 #ifndef DISABLE_TLS
650 tls_close(NULL, TLS_NO_SHUTDOWN);
651 #endif
652
653 /* Reset SIGHUP and SIGCHLD in the child in both cases. */
654
655 signal(SIGHUP, SIG_DFL);
656 signal(SIGCHLD, SIG_DFL);
657
658 if (geteuid() != root_uid && !deliver_drop_privilege)
659 {
660 signal(SIGALRM, SIG_DFL);
661 delivery_re_exec(CEE_EXEC_PANIC);
662 /* Control does not return here. */
663 }
664
665 /* No need to re-exec; SIGALRM remains set to the default handler */
666
667 (void) deliver_message(message_id, FALSE, FALSE);
668 search_tidyup();
669 exim_underbar_exit(EXIT_SUCCESS);
670 }
671
672 if (dpid > 0)
673 {
674 release_cutthrough_connection(US"passed for delivery");
675 DEBUG(D_any) debug_printf("forked delivery process %d\n", (int)dpid);
676 }
677 else
678 {
679 cancel_cutthrough_connection(TRUE, US"delivery fork failed");
680 log_write(0, LOG_MAIN|LOG_PANIC, "daemon: delivery process fork "
681 "failed: %s", strerror(errno));
682 }
683 }
684 }
685 }
686
687
688 /* Carrying on in the parent daemon process... Can't do much if the fork
689 failed. Otherwise, keep count of the number of accepting processes and
690 remember the pid for ticking off when the child completes. */
691
692 if (pid < 0)
693 never_error(US"daemon: accept process fork failed", US"Fork failed", errno);
694 else
695 {
696 for (int i = 0; i < smtp_accept_max; ++i)
697 if (smtp_slots[i].pid <= 0)
698 {
699 smtp_slots[i].pid = pid;
700 /* Connection closes come asyncronously, so we cannot stack this store */
701 if (smtp_accept_max_per_host)
702 smtp_slots[i].host_address = string_copy_malloc(sender_host_address);
703 smtp_accept_count++;
704 break;
705 }
706 DEBUG(D_any) debug_printf("%d SMTP accept process%s running\n",
707 smtp_accept_count, smtp_accept_count == 1 ? "" : "es");
708 }
709
710 /* Get here via goto in error cases */
711
712 ERROR_RETURN:
713
714 /* Close the streams associated with the socket which will also close the
715 socket fds in this process. We can't do anything if fclose() fails, but
716 logging brings it to someone's attention. However, "connection reset by peer"
717 isn't really a problem, so skip that one. On Solaris, a dropped connection can
718 manifest itself as a broken pipe, so drop that one too. If the streams don't
719 exist, something went wrong while setting things up. Make sure the socket
720 descriptors are closed, in order to drop the connection. */
721
722 if (smtp_out)
723 {
724 if (fclose(smtp_out) != 0 && errno != ECONNRESET && errno != EPIPE)
725 log_write(0, LOG_MAIN|LOG_PANIC, "daemon: fclose(smtp_out) failed: %s",
726 strerror(errno));
727 smtp_out = NULL;
728 }
729 else (void)close(accept_socket);
730
731 if (smtp_in)
732 {
733 if (fclose(smtp_in) != 0 && errno != ECONNRESET && errno != EPIPE)
734 log_write(0, LOG_MAIN|LOG_PANIC, "daemon: fclose(smtp_in) failed: %s",
735 strerror(errno));
736 smtp_in = NULL;
737 }
738 else (void)close(dup_accept_socket);
739
740 /* Release any store used in this process, including the store used for holding
741 the incoming host address and an expanded active_hostname. */
742
743 log_close_all();
744 interface_address =
745 sender_host_address = NULL;
746 store_reset(reset_point);
747 sender_host_address = NULL;
748 }
749
750
751
752
753 /*************************************************
754 * Check wildcard listen special cases *
755 *************************************************/
756
757 /* This function is used when binding and listening on lists of addresses and
758 ports. It tests for special cases of wildcard listening, when IPv4 and IPv6
759 sockets may interact in different ways in different operating systems. It is
760 passed an error number, the list of listening addresses, and the current
761 address. Two checks are available: for a previous wildcard IPv6 address, or for
762 a following wildcard IPv4 address, in both cases on the same port.
763
764 In practice, pairs of wildcard addresses should be adjacent in the address list
765 because they are sorted that way below.
766
767 Arguments:
768 eno the error number
769 addresses the list of addresses
770 ipa the current IP address
771 back if TRUE, check for previous wildcard IPv6 address
772 if FALSE, check for a following wildcard IPv4 address
773
774 Returns: TRUE or FALSE
775 */
776
777 static BOOL
778 check_special_case(int eno, ip_address_item *addresses, ip_address_item *ipa,
779 BOOL back)
780 {
781 ip_address_item *ipa2;
782
783 /* For the "back" case, if the failure was "address in use" for a wildcard IPv4
784 address, seek a previous IPv6 wildcard address on the same port. As it is
785 previous, it must have been successfully bound and be listening. Flag it as a
786 "6 including 4" listener. */
787
788 if (back)
789 {
790 if (eno != EADDRINUSE || ipa->address[0] != 0) return FALSE;
791 for (ipa2 = addresses; ipa2 != ipa; ipa2 = ipa2->next)
792 {
793 if (ipa2->address[1] == 0 && ipa2->port == ipa->port)
794 {
795 ipa2->v6_include_v4 = TRUE;
796 return TRUE;
797 }
798 }
799 }
800
801 /* For the "forward" case, if the current address is a wildcard IPv6 address,
802 we seek a following wildcard IPv4 address on the same port. */
803
804 else
805 {
806 if (ipa->address[0] != ':' || ipa->address[1] != 0) return FALSE;
807 for (ipa2 = ipa->next; ipa2 != NULL; ipa2 = ipa2->next)
808 if (ipa2->address[0] == 0 && ipa->port == ipa2->port) return TRUE;
809 }
810
811 return FALSE;
812 }
813
814
815
816
817 /*************************************************
818 * Handle terminating subprocesses *
819 *************************************************/
820
821 /* Handle the termination of child processes. Theoretically, this need be done
822 only when sigchld_seen is TRUE, but rumour has it that some systems lose
823 SIGCHLD signals at busy times, so to be on the safe side, this function is
824 called each time round. It shouldn't be too expensive.
825
826 Arguments: none
827 Returns: nothing
828 */
829
830 static void
831 handle_ending_processes(void)
832 {
833 int status;
834 pid_t pid;
835
836 while ((pid = waitpid(-1, &status, WNOHANG)) > 0)
837 {
838 DEBUG(D_any)
839 {
840 debug_printf("child %d ended: status=0x%x\n", (int)pid, status);
841 #ifdef WCOREDUMP
842 if (WIFEXITED(status))
843 debug_printf(" normal exit, %d\n", WEXITSTATUS(status));
844 else if (WIFSIGNALED(status))
845 debug_printf(" signal exit, signal %d%s\n", WTERMSIG(status),
846 WCOREDUMP(status) ? " (core dumped)" : "");
847 #endif
848 }
849
850 /* If it's a listening daemon for which we are keeping track of individual
851 subprocesses, deal with an accepting process that has terminated. */
852
853 if (smtp_slots)
854 {
855 int i;
856 for (i = 0; i < smtp_accept_max; i++)
857 if (smtp_slots[i].pid == pid)
858 {
859 if (smtp_slots[i].host_address)
860 store_free(smtp_slots[i].host_address);
861 smtp_slots[i] = empty_smtp_slot;
862 if (--smtp_accept_count < 0) smtp_accept_count = 0;
863 DEBUG(D_any) debug_printf("%d SMTP accept process%s now running\n",
864 smtp_accept_count, (smtp_accept_count == 1)? "" : "es");
865 break;
866 }
867 if (i < smtp_accept_max) continue; /* Found an accepting process */
868 }
869
870 /* If it wasn't an accepting process, see if it was a queue-runner
871 process that we are tracking. */
872
873 if (queue_pid_slots)
874 {
875 int max = atoi(CS expand_string(queue_run_max));
876 for (int i = 0; i < max; i++)
877 if (queue_pid_slots[i] == pid)
878 {
879 queue_pid_slots[i] = 0;
880 if (--queue_run_count < 0) queue_run_count = 0;
881 DEBUG(D_any) debug_printf("%d queue-runner process%s now running\n",
882 queue_run_count, (queue_run_count == 1)? "" : "es");
883 break;
884 }
885 }
886 }
887 }
888
889
890
891 /*************************************************
892 * Exim Daemon Mainline *
893 *************************************************/
894
895 /* The daemon can do two jobs, either of which is optional:
896
897 (1) Listens for incoming SMTP calls and spawns off a sub-process to handle
898 each one. This is requested by the -bd option, with -oX specifying the SMTP
899 port on which to listen (for testing).
900
901 (2) Spawns a queue-running process every so often. This is controlled by the
902 -q option with a an interval time. (If no time is given, a single queue run
903 is done from the main function, and control doesn't get here.)
904
905 Root privilege is required in order to attach to port 25. Some systems require
906 it when calling socket() rather than bind(). To cope with all cases, we run as
907 root for both socket() and bind(). Some systems also require root in order to
908 write to the pid file directory. This function must therefore be called as root
909 if it is to work properly in all circumstances. Once the socket is bound and
910 the pid file written, root privilege is given up if there is an exim uid.
911
912 There are no arguments to this function, and it never returns. */
913
914 void
915 daemon_go(void)
916 {
917 struct passwd *pw;
918 int *listen_sockets = NULL;
919 int listen_socket_count = 0;
920 ip_address_item *addresses = NULL;
921 time_t last_connection_time = (time_t)0;
922 int local_queue_run_max = atoi(CS expand_string(queue_run_max));
923
924 /* If any debugging options are set, turn on the D_pid bit so that all
925 debugging lines get the pid added. */
926
927 DEBUG(D_any|D_v) debug_selector |= D_pid;
928
929 if (f.inetd_wait_mode)
930 {
931 listen_socket_count = 1;
932 listen_sockets = store_get(sizeof(int), FALSE);
933 (void) close(3);
934 if (dup2(0, 3) == -1)
935 log_write(0, LOG_MAIN|LOG_PANIC_DIE,
936 "failed to dup inetd socket safely away: %s", strerror(errno));
937
938 listen_sockets[0] = 3;
939 (void) close(0);
940 (void) close(1);
941 (void) close(2);
942 exim_nullstd();
943
944 if (debug_file == stderr)
945 {
946 /* need a call to log_write before call to open debug_file, so that
947 log.c:file_path has been initialised. This is unfortunate. */
948 log_write(0, LOG_MAIN, "debugging Exim in inetd wait mode starting");
949
950 fclose(debug_file);
951 debug_file = NULL;
952 exim_nullstd(); /* re-open fd2 after we just closed it again */
953 debug_logging_activate(US"-wait", NULL);
954 }
955
956 DEBUG(D_any) debug_printf("running in inetd wait mode\n");
957
958 /* As per below, when creating sockets ourselves, we handle tcp_nodelay for
959 our own buffering; we assume though that inetd set the socket REUSEADDR. */
960
961 if (tcp_nodelay)
962 if (setsockopt(3, IPPROTO_TCP, TCP_NODELAY, US &on, sizeof(on)))
963 log_write(0, LOG_MAIN|LOG_PANIC_DIE, "failed to set socket NODELAY: %s",
964 strerror(errno));
965 }
966
967
968 if (f.inetd_wait_mode || f.daemon_listen)
969 {
970 /* If any option requiring a load average to be available during the
971 reception of a message is set, call os_getloadavg() while we are root
972 for those OS for which this is necessary the first time it is called (in
973 order to perform an "open" on the kernel memory file). */
974
975 #ifdef LOAD_AVG_NEEDS_ROOT
976 if (queue_only_load >= 0 || smtp_load_reserve >= 0 ||
977 (deliver_queue_load_max >= 0 && deliver_drop_privilege))
978 (void)os_getloadavg();
979 #endif
980 }
981
982
983 /* Do the preparation for setting up a listener on one or more interfaces, and
984 possible on various ports. This is controlled by the combination of
985 local_interfaces (which can set IP addresses and ports) and daemon_smtp_port
986 (which is a list of default ports to use for those items in local_interfaces
987 that do not specify a port). The -oX command line option can be used to
988 override one or both of these options.
989
990 If local_interfaces is not set, the default is to listen on all interfaces.
991 When it is set, it can include "all IPvx interfaces" as an item. This is useful
992 when different ports are in use.
993
994 It turns out that listening on all interfaces is messy in an IPv6 world,
995 because several different implementation approaches have been taken. This code
996 is now supposed to work with all of them. The point of difference is whether an
997 IPv6 socket that is listening on all interfaces will receive incoming IPv4
998 calls or not. We also have to cope with the case when IPv6 libraries exist, but
999 there is no IPv6 support in the kernel.
1000
1001 . On Solaris, an IPv6 socket will accept IPv4 calls, and give them as mapped
1002 addresses. However, if an IPv4 socket is also listening on all interfaces,
1003 calls are directed to the appropriate socket.
1004
1005 . On (some versions of) Linux, an IPv6 socket will accept IPv4 calls, and
1006 give them as mapped addresses, but an attempt also to listen on an IPv4
1007 socket on all interfaces causes an error.
1008
1009 . On OpenBSD, an IPv6 socket will not accept IPv4 calls. You have to set up
1010 two sockets if you want to accept both kinds of call.
1011
1012 . FreeBSD is like OpenBSD, but it has the IPV6_V6ONLY socket option, which
1013 can be turned off, to make it behave like the versions of Linux described
1014 above.
1015
1016 . I heard a report that the USAGI IPv6 stack for Linux has implemented
1017 IPV6_V6ONLY.
1018
1019 So, what we do when IPv6 is supported is as follows:
1020
1021 (1) After it is set up, the list of interfaces is scanned for wildcard
1022 addresses. If an IPv6 and an IPv4 wildcard are both found for the same
1023 port, the list is re-arranged so that they are together, with the IPv6
1024 wildcard first.
1025
1026 (2) If the creation of a wildcard IPv6 socket fails, we just log the error and
1027 carry on if an IPv4 wildcard socket for the same port follows later in the
1028 list. This allows Exim to carry on in the case when the kernel has no IPv6
1029 support.
1030
1031 (3) Having created an IPv6 wildcard socket, we try to set IPV6_V6ONLY if that
1032 option is defined. However, if setting fails, carry on regardless (but log
1033 the incident).
1034
1035 (4) If binding or listening on an IPv6 wildcard socket fails, it is a serious
1036 error.
1037
1038 (5) If binding or listening on an IPv4 wildcard socket fails with the error
1039 EADDRINUSE, and a previous interface was an IPv6 wildcard for the same
1040 port (which must have succeeded or we wouldn't have got this far), we
1041 assume we are in the situation where just a single socket is permitted,
1042 and ignore the error.
1043
1044 Phew!
1045
1046 The preparation code decodes options and sets up the relevant data. We do this
1047 first, so that we can return non-zero if there are any syntax errors, and also
1048 write to stderr. */
1049
1050 if (f.daemon_listen && !f.inetd_wait_mode)
1051 {
1052 int *default_smtp_port;
1053 int sep;
1054 int pct = 0;
1055 uschar *s;
1056 const uschar * list;
1057 uschar *local_iface_source = US"local_interfaces";
1058 ip_address_item *ipa;
1059 ip_address_item **pipa;
1060
1061 /* If -oX was used, disable the writing of a pid file unless -oP was
1062 explicitly used to force it. Then scan the string given to -oX. Any items
1063 that contain neither a dot nor a colon are used to override daemon_smtp_port.
1064 Any other items are used to override local_interfaces. */
1065
1066 if (override_local_interfaces)
1067 {
1068 gstring * new_smtp_port = NULL;
1069 gstring * new_local_interfaces = NULL;
1070
1071 if (override_pid_file_path == NULL) write_pid = FALSE;
1072
1073 list = override_local_interfaces;
1074 sep = 0;
1075 while ((s = string_nextinlist(&list, &sep, big_buffer, big_buffer_size)))
1076 {
1077 uschar joinstr[4];
1078 gstring ** gp;
1079
1080 if (Ustrpbrk(s, ".:") == NULL)
1081 gp = &new_smtp_port;
1082 else
1083 gp = &new_local_interfaces;
1084
1085 if (!*gp)
1086 {
1087 joinstr[0] = sep;
1088 joinstr[1] = ' ';
1089 *gp = string_catn(*gp, US"<", 1);
1090 }
1091
1092 *gp = string_catn(*gp, joinstr, 2);
1093 *gp = string_cat (*gp, s);
1094 }
1095
1096 if (new_smtp_port)
1097 {
1098 daemon_smtp_port = string_from_gstring(new_smtp_port);
1099 DEBUG(D_any) debug_printf("daemon_smtp_port overridden by -oX:\n %s\n",
1100 daemon_smtp_port);
1101 }
1102
1103 if (new_local_interfaces)
1104 {
1105 local_interfaces = string_from_gstring(new_local_interfaces);
1106 local_iface_source = US"-oX data";
1107 DEBUG(D_any) debug_printf("local_interfaces overridden by -oX:\n %s\n",
1108 local_interfaces);
1109 }
1110 }
1111
1112 /* Create a list of default SMTP ports, to be used if local_interfaces
1113 contains entries without explicit ports. First count the number of ports, then
1114 build a translated list in a vector. */
1115
1116 list = daemon_smtp_port;
1117 sep = 0;
1118 while ((s = string_nextinlist(&list, &sep, big_buffer, big_buffer_size)))
1119 pct++;
1120 default_smtp_port = store_get((pct+1) * sizeof(int), FALSE);
1121 list = daemon_smtp_port;
1122 sep = 0;
1123 for (pct = 0;
1124 (s = string_nextinlist(&list, &sep, big_buffer, big_buffer_size));
1125 pct++)
1126 {
1127 if (isdigit(*s))
1128 {
1129 uschar *end;
1130 default_smtp_port[pct] = Ustrtol(s, &end, 0);
1131 if (end != s + Ustrlen(s))
1132 log_write(0, LOG_PANIC_DIE|LOG_CONFIG, "invalid SMTP port: %s", s);
1133 }
1134 else
1135 {
1136 struct servent *smtp_service = getservbyname(CS s, "tcp");
1137 if (!smtp_service)
1138 log_write(0, LOG_PANIC_DIE|LOG_CONFIG, "TCP port \"%s\" not found", s);
1139 default_smtp_port[pct] = ntohs(smtp_service->s_port);
1140 }
1141 }
1142 default_smtp_port[pct] = 0;
1143
1144 /* Check the list of TLS-on-connect ports and do name lookups if needed */
1145
1146 list = tls_in.on_connect_ports;
1147 sep = 0;
1148 while ((s = string_nextinlist(&list, &sep, big_buffer, big_buffer_size)))
1149 if (!isdigit(*s))
1150 {
1151 gstring * g = NULL;
1152
1153 list = tls_in.on_connect_ports;
1154 tls_in.on_connect_ports = NULL;
1155 sep = 0;
1156 while ((s = string_nextinlist(&list, &sep, big_buffer, big_buffer_size)))
1157 {
1158 if (!isdigit(*s))
1159 {
1160 struct servent * smtp_service = getservbyname(CS s, "tcp");
1161 if (!smtp_service)
1162 log_write(0, LOG_PANIC_DIE|LOG_CONFIG, "TCP port \"%s\" not found", s);
1163 s = string_sprintf("%d", (int)ntohs(smtp_service->s_port));
1164 }
1165 g = string_append_listele(g, ':', s);
1166 }
1167 if (g)
1168 tls_in.on_connect_ports = g->s;
1169 break;
1170 }
1171
1172 /* Create the list of local interfaces, possibly with ports included. This
1173 list may contain references to 0.0.0.0 and ::0 as wildcards. These special
1174 values are converted below. */
1175
1176 addresses = host_build_ifacelist(local_interfaces, local_iface_source);
1177
1178 /* In the list of IP addresses, convert 0.0.0.0 into an empty string, and ::0
1179 into the string ":". We use these to recognize wildcards in IPv4 and IPv6. In
1180 fact, many IP stacks recognize 0.0.0.0 and ::0 and handle them as wildcards
1181 anyway, but we need to know which are the wildcard addresses, and the shorter
1182 strings are neater.
1183
1184 In the same scan, fill in missing port numbers from the default list. When
1185 there is more than one item in the list, extra items are created. */
1186
1187 for (ipa = addresses; ipa; ipa = ipa->next)
1188 {
1189 if (Ustrcmp(ipa->address, "0.0.0.0") == 0)
1190 ipa->address[0] = 0;
1191 else if (Ustrcmp(ipa->address, "::0") == 0)
1192 {
1193 ipa->address[0] = ':';
1194 ipa->address[1] = 0;
1195 }
1196
1197 if (ipa->port > 0) continue;
1198
1199 if (daemon_smtp_port[0] <= 0)
1200 log_write(0, LOG_MAIN|LOG_PANIC_DIE, "no port specified for interface "
1201 "%s and daemon_smtp_port is unset; cannot start daemon",
1202 ipa->address[0] == 0 ? US"\"all IPv4\"" :
1203 ipa->address[1] == 0 ? US"\"all IPv6\"" : ipa->address);
1204
1205 ipa->port = default_smtp_port[0];
1206 for (int i = 1; default_smtp_port[i] > 0; i++)
1207 {
1208 ip_address_item *new = store_get(sizeof(ip_address_item), FALSE);
1209
1210 memcpy(new->address, ipa->address, Ustrlen(ipa->address) + 1);
1211 new->port = default_smtp_port[i];
1212 new->next = ipa->next;
1213 ipa->next = new;
1214 ipa = new;
1215 }
1216 }
1217
1218 /* Scan the list of addresses for wildcards. If we find an IPv4 and an IPv6
1219 wildcard for the same port, ensure that (a) they are together and (b) the
1220 IPv6 address comes first. This makes handling the messy features easier, and
1221 also simplifies the construction of the "daemon started" log line. */
1222
1223 pipa = &addresses;
1224 for (ipa = addresses; ipa; pipa = &ipa->next, ipa = ipa->next)
1225 {
1226 ip_address_item *ipa2;
1227
1228 /* Handle an IPv4 wildcard */
1229
1230 if (ipa->address[0] == 0)
1231 for (ipa2 = ipa; ipa2->next; ipa2 = ipa2->next)
1232 {
1233 ip_address_item *ipa3 = ipa2->next;
1234 if (ipa3->address[0] == ':' &&
1235 ipa3->address[1] == 0 &&
1236 ipa3->port == ipa->port)
1237 {
1238 ipa2->next = ipa3->next;
1239 ipa3->next = ipa;
1240 *pipa = ipa3;
1241 break;
1242 }
1243 }
1244
1245 /* Handle an IPv6 wildcard. */
1246
1247 else if (ipa->address[0] == ':' && ipa->address[1] == 0)
1248 for (ipa2 = ipa; ipa2->next; ipa2 = ipa2->next)
1249 {
1250 ip_address_item *ipa3 = ipa2->next;
1251 if (ipa3->address[0] == 0 && ipa3->port == ipa->port)
1252 {
1253 ipa2->next = ipa3->next;
1254 ipa3->next = ipa->next;
1255 ipa->next = ipa3;
1256 ipa = ipa3;
1257 break;
1258 }
1259 }
1260 }
1261
1262 /* Get a vector to remember all the sockets in */
1263
1264 for (ipa = addresses; ipa; ipa = ipa->next)
1265 listen_socket_count++;
1266 listen_sockets = store_get(sizeof(int) * listen_socket_count, FALSE);
1267
1268 } /* daemon_listen but not inetd_wait_mode */
1269
1270 if (f.daemon_listen)
1271 {
1272
1273 /* Do a sanity check on the max connects value just to save us from getting
1274 a huge amount of store. */
1275
1276 if (smtp_accept_max > 4095) smtp_accept_max = 4096;
1277
1278 /* There's no point setting smtp_accept_queue unless it is less than the max
1279 connects limit. The configuration reader ensures that the max is set if the
1280 queue-only option is set. */
1281
1282 if (smtp_accept_queue > smtp_accept_max) smtp_accept_queue = 0;
1283
1284 /* Get somewhere to keep the list of SMTP accepting pids if we are keeping
1285 track of them for total number and queue/host limits. */
1286
1287 if (smtp_accept_max > 0)
1288 {
1289 smtp_slots = store_get(smtp_accept_max * sizeof(smtp_slot), FALSE);
1290 for (int i = 0; i < smtp_accept_max; i++) smtp_slots[i] = empty_smtp_slot;
1291 }
1292 }
1293
1294 /* The variable background_daemon is always false when debugging, but
1295 can also be forced false in order to keep a non-debugging daemon in the
1296 foreground. If background_daemon is true, close all open file descriptors that
1297 we know about, but then re-open stdin, stdout, and stderr to /dev/null. Also
1298 do this for inetd_wait mode.
1299
1300 This is protection against any called functions (in libraries, or in
1301 Perl, or whatever) that think they can write to stderr (or stdout). Before this
1302 was added, it was quite likely that an SMTP connection would use one of these
1303 file descriptors, in which case writing random stuff to it caused chaos.
1304
1305 Then disconnect from the controlling terminal, Most modern Unixes seem to have
1306 setsid() for getting rid of the controlling terminal. For any OS that doesn't,
1307 setsid() can be #defined as a no-op, or as something else. */
1308
1309 if (f.background_daemon || f.inetd_wait_mode)
1310 {
1311 log_close_all(); /* Just in case anything was logged earlier */
1312 search_tidyup(); /* Just in case any were used in reading the config. */
1313 (void)close(0); /* Get rid of stdin/stdout/stderr */
1314 (void)close(1);
1315 (void)close(2);
1316 exim_nullstd(); /* Connect stdin/stdout/stderr to /dev/null */
1317 log_stderr = NULL; /* So no attempt to copy paniclog output */
1318 }
1319
1320 if (f.background_daemon)
1321 {
1322 /* If the parent process of this one has pid == 1, we are re-initializing the
1323 daemon as the result of a SIGHUP. In this case, there is no need to do
1324 anything, because the controlling terminal has long gone. Otherwise, fork, in
1325 case current process is a process group leader (see 'man setsid' for an
1326 explanation) before calling setsid(). */
1327
1328 if (getppid() != 1)
1329 {
1330 pid_t pid = fork();
1331 if (pid < 0) log_write(0, LOG_MAIN|LOG_PANIC_DIE,
1332 "fork() failed when starting daemon: %s", strerror(errno));
1333 if (pid > 0) exit(EXIT_SUCCESS); /* in parent process, just exit */
1334 (void)setsid(); /* release controlling terminal */
1335 }
1336 }
1337
1338 /* We are now in the disconnected, daemon process (unless debugging). Set up
1339 the listening sockets if required. */
1340
1341 if (f.daemon_listen && !f.inetd_wait_mode)
1342 {
1343 int sk;
1344 ip_address_item *ipa;
1345
1346 /* For each IP address, create a socket, bind it to the appropriate port, and
1347 start listening. See comments above about IPv6 sockets that may or may not
1348 accept IPv4 calls when listening on all interfaces. We also have to cope with
1349 the case of a system with IPv6 libraries, but no IPv6 support in the kernel.
1350 listening, provided a wildcard IPv4 socket for the same port follows. */
1351
1352 for (ipa = addresses, sk = 0; sk < listen_socket_count; ipa = ipa->next, sk++)
1353 {
1354 BOOL wildcard;
1355 ip_address_item *ipa2;
1356 int af;
1357
1358 if (Ustrchr(ipa->address, ':') != NULL)
1359 {
1360 af = AF_INET6;
1361 wildcard = ipa->address[1] == 0;
1362 }
1363 else
1364 {
1365 af = AF_INET;
1366 wildcard = ipa->address[0] == 0;
1367 }
1368
1369 if ((listen_sockets[sk] = ip_socket(SOCK_STREAM, af)) < 0)
1370 {
1371 if (check_special_case(0, addresses, ipa, FALSE))
1372 {
1373 log_write(0, LOG_MAIN, "Failed to create IPv6 socket for wildcard "
1374 "listening (%s): will use IPv4", strerror(errno));
1375 goto SKIP_SOCKET;
1376 }
1377 log_write(0, LOG_PANIC_DIE, "IPv%c socket creation failed: %s",
1378 (af == AF_INET6)? '6' : '4', strerror(errno));
1379 }
1380
1381 /* If this is an IPv6 wildcard socket, set IPV6_V6ONLY if that option is
1382 available. Just log failure (can get protocol not available, just like
1383 socket creation can). */
1384
1385 #ifdef IPV6_V6ONLY
1386 if (af == AF_INET6 && wildcard &&
1387 setsockopt(listen_sockets[sk], IPPROTO_IPV6, IPV6_V6ONLY, CS (&on),
1388 sizeof(on)) < 0)
1389 log_write(0, LOG_MAIN, "Setting IPV6_V6ONLY on daemon's IPv6 wildcard "
1390 "socket failed (%s): carrying on without it", strerror(errno));
1391 #endif /* IPV6_V6ONLY */
1392
1393 /* Set SO_REUSEADDR so that the daemon can be restarted while a connection
1394 is being handled. Without this, a connection will prevent reuse of the
1395 smtp port for listening. */
1396
1397 if (setsockopt(listen_sockets[sk], SOL_SOCKET, SO_REUSEADDR,
1398 US (&on), sizeof(on)) < 0)
1399 log_write(0, LOG_MAIN|LOG_PANIC_DIE, "setting SO_REUSEADDR on socket "
1400 "failed when starting daemon: %s", strerror(errno));
1401
1402 /* Set TCP_NODELAY; Exim does its own buffering. There is a switch to
1403 disable this because it breaks some broken clients. */
1404
1405 if (tcp_nodelay) setsockopt(listen_sockets[sk], IPPROTO_TCP, TCP_NODELAY,
1406 US (&on), sizeof(on));
1407
1408 /* Now bind the socket to the required port; if Exim is being restarted
1409 it may not always be possible to bind immediately, even with SO_REUSEADDR
1410 set, so try 10 times, waiting between each try. After 10 failures, we give
1411 up. In an IPv6 environment, if bind () fails with the error EADDRINUSE and
1412 we are doing wildcard IPv4 listening and there was a previous IPv6 wildcard
1413 address for the same port, ignore the error on the grounds that we must be
1414 in a system where the IPv6 socket accepts both kinds of call. This is
1415 necessary for (some release of) USAGI Linux; other IP stacks fail at the
1416 listen() stage instead. */
1417
1418 #ifdef TCP_FASTOPEN
1419 f.tcp_fastopen_ok = TRUE;
1420 #endif
1421 for(;;)
1422 {
1423 uschar *msg, *addr;
1424 if (ip_bind(listen_sockets[sk], af, ipa->address, ipa->port) >= 0) break;
1425 if (check_special_case(errno, addresses, ipa, TRUE))
1426 {
1427 DEBUG(D_any) debug_printf("wildcard IPv4 bind() failed after IPv6 "
1428 "listen() success; EADDRINUSE ignored\n");
1429 (void)close(listen_sockets[sk]);
1430 goto SKIP_SOCKET;
1431 }
1432 msg = US strerror(errno);
1433 addr = wildcard
1434 ? af == AF_INET6
1435 ? US"(any IPv6)"
1436 : US"(any IPv4)"
1437 : ipa->address;
1438 if (daemon_startup_retries <= 0)
1439 log_write(0, LOG_MAIN|LOG_PANIC_DIE,
1440 "socket bind() to port %d for address %s failed: %s: "
1441 "daemon abandoned", ipa->port, addr, msg);
1442 log_write(0, LOG_MAIN, "socket bind() to port %d for address %s "
1443 "failed: %s: waiting %s before trying again (%d more %s)",
1444 ipa->port, addr, msg, readconf_printtime(daemon_startup_sleep),
1445 daemon_startup_retries, (daemon_startup_retries > 1)? "tries" : "try");
1446 daemon_startup_retries--;
1447 sleep(daemon_startup_sleep);
1448 }
1449
1450 DEBUG(D_any)
1451 if (wildcard)
1452 debug_printf("listening on all interfaces (IPv%c) port %d\n",
1453 af == AF_INET6 ? '6' : '4', ipa->port);
1454 else
1455 debug_printf("listening on %s port %d\n", ipa->address, ipa->port);
1456
1457 #if defined(TCP_FASTOPEN) && !defined(__APPLE__)
1458 if ( f.tcp_fastopen_ok
1459 && setsockopt(listen_sockets[sk], IPPROTO_TCP, TCP_FASTOPEN,
1460 &smtp_connect_backlog, sizeof(smtp_connect_backlog)))
1461 {
1462 DEBUG(D_any) debug_printf("setsockopt FASTOPEN: %s\n", strerror(errno));
1463 f.tcp_fastopen_ok = FALSE;
1464 }
1465 #endif
1466
1467 /* Start listening on the bound socket, establishing the maximum backlog of
1468 connections that is allowed. On success, continue to the next address. */
1469
1470 if (listen(listen_sockets[sk], smtp_connect_backlog) >= 0)
1471 {
1472 #if defined(TCP_FASTOPEN) && defined(__APPLE__)
1473 if ( f.tcp_fastopen_ok
1474 && setsockopt(listen_sockets[sk], IPPROTO_TCP, TCP_FASTOPEN,
1475 &on, sizeof(on)))
1476 {
1477 DEBUG(D_any) debug_printf("setsockopt FASTOPEN: %s\n", strerror(errno));
1478 f.tcp_fastopen_ok = FALSE;
1479 }
1480 #endif
1481 continue;
1482 }
1483
1484 /* Listening has failed. In an IPv6 environment, as for bind(), if listen()
1485 fails with the error EADDRINUSE and we are doing IPv4 wildcard listening
1486 and there was a previous successful IPv6 wildcard listen on the same port,
1487 we want to ignore the error on the grounds that we must be in a system
1488 where the IPv6 socket accepts both kinds of call. */
1489
1490 if (!check_special_case(errno, addresses, ipa, TRUE))
1491 log_write(0, LOG_PANIC_DIE, "listen() failed on interface %s: %s",
1492 wildcard
1493 ? af == AF_INET6 ? US"(any IPv6)" : US"(any IPv4)" : ipa->address,
1494 strerror(errno));
1495
1496 DEBUG(D_any) debug_printf("wildcard IPv4 listen() failed after IPv6 "
1497 "listen() success; EADDRINUSE ignored\n");
1498 (void)close(listen_sockets[sk]);
1499
1500 /* Come here if there has been a problem with the socket which we
1501 are going to ignore. We remove the address from the chain, and back up the
1502 counts. */
1503
1504 SKIP_SOCKET:
1505 sk--; /* Back up the count */
1506 listen_socket_count--; /* Reduce the total */
1507 if (ipa == addresses) addresses = ipa->next; else
1508 {
1509 for (ipa2 = addresses; ipa2->next != ipa; ipa2 = ipa2->next);
1510 ipa2->next = ipa->next;
1511 ipa = ipa2;
1512 }
1513 } /* End of bind/listen loop for each address */
1514 } /* End of setup for listening */
1515
1516
1517 /* If we are not listening, we want to write a pid file only if -oP was
1518 explicitly given. */
1519
1520 else if (!override_pid_file_path)
1521 write_pid = FALSE;
1522
1523 /* Write the pid to a known file for assistance in identification, if required.
1524 We do this before giving up root privilege, because on some systems it is
1525 necessary to be root in order to write into the pid file directory. There's
1526 nothing to stop multiple daemons running, as long as no more than one listens
1527 on a given TCP/IP port on the same interface(s). However, in these
1528 circumstances it gets far too complicated to mess with pid file names
1529 automatically. Consequently, Exim 4 writes a pid file only
1530
1531 (a) When running in the test harness, or
1532 (b) When -bd is used and -oX is not used, or
1533 (c) When -oP is used to supply a path.
1534
1535 The variable daemon_write_pid is used to control this. */
1536
1537 if (f.running_in_test_harness || write_pid)
1538 {
1539 FILE *f;
1540
1541 if (override_pid_file_path)
1542 pid_file_path = override_pid_file_path;
1543
1544 if (pid_file_path[0] == 0)
1545 pid_file_path = string_sprintf("%s/exim-daemon.pid", spool_directory);
1546
1547 if ((f = modefopen(pid_file_path, "wb", 0644)))
1548 {
1549 (void)fprintf(f, "%d\n", (int)getpid());
1550 (void)fclose(f);
1551 DEBUG(D_any) debug_printf("pid written to %s\n", pid_file_path);
1552 }
1553 else
1554 DEBUG(D_any)
1555 debug_printf("%s\n", string_open_failed(errno, "pid file %s",
1556 pid_file_path));
1557 }
1558
1559 /* Set up the handler for SIGHUP, which causes a restart of the daemon. */
1560
1561 sighup_seen = FALSE;
1562 signal(SIGHUP, sighup_handler);
1563
1564 /* Give up root privilege at this point (assuming that exim_uid and exim_gid
1565 are not root). The third argument controls the running of initgroups().
1566 Normally we do this, in order to set up the groups for the Exim user. However,
1567 if we are not root at this time - some odd installations run that way - we
1568 cannot do this. */
1569
1570 exim_setugid(exim_uid, exim_gid, geteuid()==root_uid, US"running as a daemon");
1571
1572 /* Update the originator_xxx fields so that received messages as listed as
1573 coming from Exim, not whoever started the daemon. */
1574
1575 originator_uid = exim_uid;
1576 originator_gid = exim_gid;
1577 originator_login = (pw = getpwuid(exim_uid))
1578 ? string_copy_perm(US pw->pw_name, FALSE) : US"exim";
1579
1580 /* Get somewhere to keep the list of queue-runner pids if we are keeping track
1581 of them (and also if we are doing queue runs). */
1582
1583 if (queue_interval > 0 && local_queue_run_max > 0)
1584 {
1585 queue_pid_slots = store_get(local_queue_run_max * sizeof(pid_t), FALSE);
1586 for (int i = 0; i < local_queue_run_max; i++) queue_pid_slots[i] = 0;
1587 }
1588
1589 /* Set up the handler for termination of child processes. */
1590
1591 sigchld_seen = FALSE;
1592 os_non_restarting_signal(SIGCHLD, main_sigchld_handler);
1593
1594 /* If we are to run the queue periodically, pretend the alarm has just gone
1595 off. This will cause the first queue-runner to get kicked off straight away. */
1596
1597 sigalrm_seen = (queue_interval > 0);
1598
1599 /* Log the start up of a daemon - at least one of listening or queue running
1600 must be set up. */
1601
1602 if (f.inetd_wait_mode)
1603 {
1604 uschar *p = big_buffer;
1605
1606 if (inetd_wait_timeout >= 0)
1607 sprintf(CS p, "terminating after %d seconds", inetd_wait_timeout);
1608 else
1609 sprintf(CS p, "with no wait timeout");
1610
1611 log_write(0, LOG_MAIN,
1612 "exim %s daemon started: pid=%d, launched with listening socket, %s",
1613 version_string, getpid(), big_buffer);
1614 set_process_info("daemon(%s): pre-listening socket", version_string);
1615
1616 /* set up the timeout logic */
1617 sigalrm_seen = 1;
1618 }
1619
1620 else if (f.daemon_listen)
1621 {
1622 int smtp_ports = 0;
1623 int smtps_ports = 0;
1624 ip_address_item * ipa;
1625 uschar * p;
1626 uschar * qinfo = queue_interval > 0
1627 ? string_sprintf("-q%s", readconf_printtime(queue_interval))
1628 : US"no queue runs";
1629
1630 /* Build a list of listening addresses in big_buffer, but limit it to 10
1631 items. The style is for backwards compatibility.
1632
1633 It is now possible to have some ports listening for SMTPS (the old,
1634 deprecated protocol that starts TLS without using STARTTLS), and others
1635 listening for standard SMTP. Keep their listings separate. */
1636
1637 for (int j = 0, i; j < 2; j++)
1638 {
1639 for (i = 0, ipa = addresses; i < 10 && ipa; i++, ipa = ipa->next)
1640 {
1641 /* First time round, look for SMTP ports; second time round, look for
1642 SMTPS ports. Build IP+port strings. */
1643
1644 if (host_is_tls_on_connect_port(ipa->port) == (j > 0))
1645 {
1646 if (j == 0)
1647 smtp_ports++;
1648 else
1649 smtps_ports++;
1650
1651 /* Now the information about the port (and sometimes interface) */
1652
1653 if (ipa->address[0] == ':' && ipa->address[1] == 0)
1654 { /* v6 wildcard */
1655 if (ipa->next && ipa->next->address[0] == 0 &&
1656 ipa->next->port == ipa->port)
1657 {
1658 ipa->log = string_sprintf(" port %d (IPv6 and IPv4)", ipa->port);
1659 (ipa = ipa->next)->log = NULL;
1660 }
1661 else if (ipa->v6_include_v4)
1662 ipa->log = string_sprintf(" port %d (IPv6 with IPv4)", ipa->port);
1663 else
1664 ipa->log = string_sprintf(" port %d (IPv6)", ipa->port);
1665 }
1666 else if (ipa->address[0] == 0) /* v4 wildcard */
1667 ipa->log = string_sprintf(" port %d (IPv4)", ipa->port);
1668 else /* check for previously-seen IP */
1669 {
1670 ip_address_item * i2;
1671 for (i2 = addresses; i2 != ipa; i2 = i2->next)
1672 if ( host_is_tls_on_connect_port(i2->port) == (j > 0)
1673 && Ustrcmp(ipa->address, i2->address) == 0
1674 )
1675 { /* found; append port to list */
1676 for (p = i2->log; *p; ) p++; /* end of existing string */
1677 if (*--p == '}') *p = '\0'; /* drop EOL */
1678 while (isdigit(*--p)) ; /* char before port */
1679
1680 i2->log = *p == ':' /* no list yet? */
1681 ? string_sprintf("%.*s{%s,%d}",
1682 (int)(p - i2->log + 1), i2->log, p+1, ipa->port)
1683 : string_sprintf("%s,%d}", i2->log, ipa->port);
1684 ipa->log = NULL;
1685 break;
1686 }
1687 if (i2 == ipa) /* first-time IP */
1688 ipa->log = string_sprintf(" [%s]:%d", ipa->address, ipa->port);
1689 }
1690 }
1691 }
1692 }
1693
1694 p = big_buffer;
1695 for (int j = 0, i; j < 2; j++)
1696 {
1697 /* First time round, look for SMTP ports; second time round, look for
1698 SMTPS ports. For the first one of each, insert leading text. */
1699
1700 if (j == 0)
1701 {
1702 if (smtp_ports > 0)
1703 p += sprintf(CS p, "SMTP on");
1704 }
1705 else
1706 if (smtps_ports > 0)
1707 p += sprintf(CS p, "%sSMTPS on",
1708 smtp_ports == 0 ? "" : " and for ");
1709
1710 /* Now the information about the port (and sometimes interface) */
1711
1712 for (i = 0, ipa = addresses; i < 10 && ipa; i++, ipa = ipa->next)
1713 if (host_is_tls_on_connect_port(ipa->port) == (j > 0))
1714 if (ipa->log)
1715 p += sprintf(CS p, "%s", ipa->log);
1716
1717 if (ipa)
1718 p += sprintf(CS p, " ...");
1719 }
1720
1721 log_write(0, LOG_MAIN,
1722 "exim %s daemon started: pid=%d, %s, listening for %s",
1723 version_string, getpid(), qinfo, big_buffer);
1724 set_process_info("daemon(%s): %s, listening for %s",
1725 version_string, qinfo, big_buffer);
1726 }
1727
1728 else
1729 {
1730 uschar * s = *queue_name
1731 ? string_sprintf("-qG%s/%s", queue_name, readconf_printtime(queue_interval))
1732 : string_sprintf("-q%s", readconf_printtime(queue_interval));
1733 log_write(0, LOG_MAIN,
1734 "exim %s daemon started: pid=%d, %s, not listening for SMTP",
1735 version_string, getpid(), s);
1736 set_process_info("daemon(%s): %s, not listening", version_string, s);
1737 }
1738
1739 /* Do any work it might be useful to amortize over our children
1740 (eg: compile regex) */
1741
1742 dns_pattern_init();
1743
1744 #ifdef WITH_CONTENT_SCAN
1745 malware_init();
1746 #endif
1747 #ifdef SUPPORT_SPF
1748 spf_init();
1749 #endif
1750
1751 /* Close the log so it can be renamed and moved. In the few cases below where
1752 this long-running process writes to the log (always exceptional conditions), it
1753 closes the log afterwards, for the same reason. */
1754
1755 log_close_all();
1756
1757 DEBUG(D_any) debug_print_ids(US"daemon running with");
1758
1759 /* Any messages accepted via this route are going to be SMTP. */
1760
1761 smtp_input = TRUE;
1762
1763 #ifdef MEASURE_TIMING
1764 report_time_since(&timestamp_startup, US"daemon loop start"); /* testcase 0022 */
1765 #endif
1766
1767 /* Enter the never-ending loop... */
1768
1769 for (;;)
1770 {
1771 #if HAVE_IPV6
1772 struct sockaddr_in6 accepted;
1773 #else
1774 struct sockaddr_in accepted;
1775 #endif
1776
1777 EXIM_SOCKLEN_T len;
1778 pid_t pid;
1779
1780 /* This code is placed first in the loop, so that it gets obeyed at the
1781 start, before the first wait, for the queue-runner case, so that the first
1782 one can be started immediately.
1783
1784 The other option is that we have an inetd wait timeout specified to -bw. */
1785
1786 if (sigalrm_seen)
1787 {
1788 if (inetd_wait_timeout > 0)
1789 {
1790 time_t resignal_interval = inetd_wait_timeout;
1791
1792 if (last_connection_time == (time_t)0)
1793 {
1794 DEBUG(D_any)
1795 debug_printf("inetd wait timeout expired, but still not seen first message, ignoring\n");
1796 }
1797 else
1798 {
1799 time_t now = time(NULL);
1800 if (now == (time_t)-1)
1801 {
1802 DEBUG(D_any) debug_printf("failed to get time: %s\n", strerror(errno));
1803 }
1804 else
1805 {
1806 if ((now - last_connection_time) >= inetd_wait_timeout)
1807 {
1808 DEBUG(D_any)
1809 debug_printf("inetd wait timeout %d expired, ending daemon\n",
1810 inetd_wait_timeout);
1811 log_write(0, LOG_MAIN, "exim %s daemon terminating, inetd wait timeout reached.\n",
1812 version_string);
1813 exit(EXIT_SUCCESS);
1814 }
1815 else
1816 {
1817 resignal_interval -= (now - last_connection_time);
1818 }
1819 }
1820 }
1821
1822 sigalrm_seen = FALSE;
1823 ALARM(resignal_interval);
1824 }
1825
1826 else
1827 {
1828 DEBUG(D_any) debug_printf("SIGALRM received\n");
1829
1830 /* Do a full queue run in a child process, if required, unless we already
1831 have enough queue runners on the go. If we are not running as root, a
1832 re-exec is required. */
1833
1834 if (queue_interval > 0 &&
1835 (local_queue_run_max <= 0 || queue_run_count < local_queue_run_max))
1836 {
1837 if ((pid = fork()) == 0)
1838 {
1839 DEBUG(D_any) debug_printf("Starting queue-runner: pid %d\n",
1840 (int)getpid());
1841
1842 /* Disable debugging if it's required only for the daemon process. We
1843 leave the above message, because it ties up with the "child ended"
1844 debugging messages. */
1845
1846 if (f.debug_daemon) debug_selector = 0;
1847
1848 /* Close any open listening sockets in the child */
1849
1850 for (int sk = 0; sk < listen_socket_count; sk++)
1851 (void)close(listen_sockets[sk]);
1852
1853 /* Reset SIGHUP and SIGCHLD in the child in both cases. */
1854
1855 signal(SIGHUP, SIG_DFL);
1856 signal(SIGCHLD, SIG_DFL);
1857
1858 /* Re-exec if privilege has been given up, unless deliver_drop_
1859 privilege is set. Reset SIGALRM before exec(). */
1860
1861 if (geteuid() != root_uid && !deliver_drop_privilege)
1862 {
1863 uschar opt[8];
1864 uschar *p = opt;
1865 uschar *extra[5];
1866 int extracount = 1;
1867
1868 signal(SIGALRM, SIG_DFL);
1869 *p++ = '-';
1870 *p++ = 'q';
1871 if (f.queue_2stage) *p++ = 'q';
1872 if (f.queue_run_first_delivery) *p++ = 'i';
1873 if (f.queue_run_force) *p++ = 'f';
1874 if (f.deliver_force_thaw) *p++ = 'f';
1875 if (f.queue_run_local) *p++ = 'l';
1876 *p = 0;
1877 extra[0] = queue_name
1878 ? string_sprintf("%sG%s", opt, queue_name) : opt;
1879
1880 /* If -R or -S were on the original command line, ensure they get
1881 passed on. */
1882
1883 if (deliver_selectstring)
1884 {
1885 extra[extracount++] = f.deliver_selectstring_regex ? US"-Rr" : US"-R";
1886 extra[extracount++] = deliver_selectstring;
1887 }
1888
1889 if (deliver_selectstring_sender)
1890 {
1891 extra[extracount++] = f.deliver_selectstring_sender_regex
1892 ? US"-Sr" : US"-S";
1893 extra[extracount++] = deliver_selectstring_sender;
1894 }
1895
1896 /* Overlay this process with a new execution. */
1897
1898 (void)child_exec_exim(CEE_EXEC_PANIC, FALSE, NULL, TRUE, extracount,
1899 extra[0], extra[1], extra[2], extra[3], extra[4]);
1900
1901 /* Control never returns here. */
1902 }
1903
1904 /* No need to re-exec; SIGALRM remains set to the default handler */
1905
1906 queue_run(NULL, NULL, FALSE);
1907 exim_underbar_exit(EXIT_SUCCESS);
1908 }
1909
1910 if (pid < 0)
1911 {
1912 log_write(0, LOG_MAIN|LOG_PANIC, "daemon: fork of queue-runner "
1913 "process failed: %s", strerror(errno));
1914 log_close_all();
1915 }
1916 else
1917 {
1918 for (int i = 0; i < local_queue_run_max; ++i)
1919 if (queue_pid_slots[i] <= 0)
1920 {
1921 queue_pid_slots[i] = pid;
1922 queue_run_count++;
1923 break;
1924 }
1925 DEBUG(D_any) debug_printf("%d queue-runner process%s running\n",
1926 queue_run_count, queue_run_count == 1 ? "" : "es");
1927 }
1928 }
1929
1930 /* Reset the alarm clock */
1931
1932 sigalrm_seen = FALSE;
1933 ALARM(queue_interval);
1934 }
1935
1936 } /* sigalrm_seen */
1937
1938
1939 /* Sleep till a connection happens if listening, and handle the connection if
1940 that is why we woke up. The FreeBSD operating system requires the use of
1941 select() before accept() because the latter function is not interrupted by
1942 a signal, and we want to wake up for SIGCHLD and SIGALRM signals. Some other
1943 OS do notice signals in accept() but it does no harm to have the select()
1944 in for all of them - and it won't then be a lurking problem for ports to
1945 new OS. In fact, the later addition of listening on specific interfaces only
1946 requires this way of working anyway. */
1947
1948 if (f.daemon_listen)
1949 {
1950 int lcount, select_errno;
1951 int max_socket = 0;
1952 BOOL select_failed = FALSE;
1953 fd_set select_listen;
1954
1955 FD_ZERO(&select_listen);
1956 for (int sk = 0; sk < listen_socket_count; sk++)
1957 {
1958 FD_SET(listen_sockets[sk], &select_listen);
1959 if (listen_sockets[sk] > max_socket) max_socket = listen_sockets[sk];
1960 }
1961
1962 DEBUG(D_any) debug_printf("Listening...\n");
1963
1964 /* In rare cases we may have had a SIGCHLD signal in the time between
1965 setting the handler (below) and getting back here. If so, pretend that the
1966 select() was interrupted so that we reap the child. This might still leave
1967 a small window when a SIGCHLD could get lost. However, since we use SIGCHLD
1968 only to do the reaping more quickly, it shouldn't result in anything other
1969 than a delay until something else causes a wake-up. */
1970
1971 if (sigchld_seen)
1972 {
1973 lcount = -1;
1974 errno = EINTR;
1975 }
1976 else
1977 lcount = select(max_socket + 1, (SELECT_ARG2_TYPE *)&select_listen,
1978 NULL, NULL, NULL);
1979
1980 if (lcount < 0)
1981 {
1982 select_failed = TRUE;
1983 lcount = 1;
1984 }
1985
1986 /* Clean up any subprocesses that may have terminated. We need to do this
1987 here so that smtp_accept_max_per_host works when a connection to that host
1988 has completed, and we are about to accept a new one. When this code was
1989 later in the sequence, a new connection could be rejected, even though an
1990 old one had just finished. Preserve the errno from any select() failure for
1991 the use of the common select/accept error processing below. */
1992
1993 select_errno = errno;
1994 handle_ending_processes();
1995 errno = select_errno;
1996
1997 #ifndef DISABLE_TLS
1998 /* Create or rotate any required keys */
1999 tls_daemon_init();
2000 #endif
2001
2002 /* Loop for all the sockets that are currently ready to go. If select
2003 actually failed, we have set the count to 1 and select_failed=TRUE, so as
2004 to use the common error code for select/accept below. */
2005
2006 while (lcount-- > 0)
2007 {
2008 int accept_socket = -1;
2009
2010 if (!select_failed)
2011 for (int sk = 0; sk < listen_socket_count; sk++)
2012 if (FD_ISSET(listen_sockets[sk], &select_listen))
2013 {
2014 len = sizeof(accepted);
2015 accept_socket = accept(listen_sockets[sk],
2016 (struct sockaddr *)&accepted, &len);
2017 FD_CLR(listen_sockets[sk], &select_listen);
2018 break;
2019 }
2020
2021 /* If select or accept has failed and this was not caused by an
2022 interruption, log the incident and try again. With asymmetric TCP/IP
2023 routing errors such as "No route to network" have been seen here. Also
2024 "connection reset by peer" has been seen. These cannot be classed as
2025 disastrous errors, but they could fill up a lot of log. The code in smail
2026 crashes the daemon after 10 successive failures of accept, on the grounds
2027 that some OS fail continuously. Exim originally followed suit, but this
2028 appears to have caused problems. Now it just keeps going, but instead of
2029 logging each error, it batches them up when they are continuous. */
2030
2031 if (accept_socket < 0 && errno != EINTR)
2032 {
2033 if (accept_retry_count == 0)
2034 {
2035 accept_retry_errno = errno;
2036 accept_retry_select_failed = select_failed;
2037 }
2038 else
2039 {
2040 if (errno != accept_retry_errno ||
2041 select_failed != accept_retry_select_failed ||
2042 accept_retry_count >= 50)
2043 {
2044 log_write(0, LOG_MAIN | ((accept_retry_count >= 50)? LOG_PANIC : 0),
2045 "%d %s() failure%s: %s",
2046 accept_retry_count,
2047 accept_retry_select_failed? "select" : "accept",
2048 (accept_retry_count == 1)? "" : "s",
2049 strerror(accept_retry_errno));
2050 log_close_all();
2051 accept_retry_count = 0;
2052 accept_retry_errno = errno;
2053 accept_retry_select_failed = select_failed;
2054 }
2055 }
2056 accept_retry_count++;
2057 }
2058
2059 else
2060 {
2061 if (accept_retry_count > 0)
2062 {
2063 log_write(0, LOG_MAIN, "%d %s() failure%s: %s",
2064 accept_retry_count,
2065 accept_retry_select_failed? "select" : "accept",
2066 (accept_retry_count == 1)? "" : "s",
2067 strerror(accept_retry_errno));
2068 log_close_all();
2069 accept_retry_count = 0;
2070 }
2071 }
2072
2073 /* If select/accept succeeded, deal with the connection. */
2074
2075 if (accept_socket >= 0)
2076 {
2077 if (inetd_wait_timeout)
2078 last_connection_time = time(NULL);
2079 handle_smtp_call(listen_sockets, listen_socket_count, accept_socket,
2080 (struct sockaddr *)&accepted);
2081 }
2082 }
2083 }
2084
2085 /* If not listening, then just sleep for the queue interval. If we woke
2086 up early the last time for some other signal, it won't matter because
2087 the alarm signal will wake at the right time. This code originally used
2088 sleep() but it turns out that on the FreeBSD system, sleep() is not inter-
2089 rupted by signals, so it wasn't waking up for SIGALRM or SIGCHLD. Luckily
2090 select() can be used as an interruptible sleep() on all versions of Unix. */
2091
2092 else
2093 {
2094 struct timeval tv;
2095 tv.tv_sec = queue_interval;
2096 tv.tv_usec = 0;
2097 select(0, NULL, NULL, NULL, &tv);
2098 handle_ending_processes();
2099 }
2100
2101 /* Re-enable the SIGCHLD handler if it has been run. It can't do it
2102 for itself, because it isn't doing the waiting itself. */
2103
2104 if (sigchld_seen)
2105 {
2106 sigchld_seen = FALSE;
2107 os_non_restarting_signal(SIGCHLD, main_sigchld_handler);
2108 }
2109
2110 /* Handle being woken by SIGHUP. We know at this point that the result
2111 of accept() has been dealt with, so we can re-exec exim safely, first
2112 closing the listening sockets so that they can be reused. Cancel any pending
2113 alarm in case it is just about to go off, and set SIGHUP to be ignored so
2114 that another HUP in quick succession doesn't clobber the new daemon before it
2115 gets going. All log files get closed by the close-on-exec flag; however, if
2116 the exec fails, we need to close the logs. */
2117
2118 if (sighup_seen)
2119 {
2120 log_write(0, LOG_MAIN, "pid %d: SIGHUP received: re-exec daemon",
2121 getpid());
2122 for (int sk = 0; sk < listen_socket_count; sk++)
2123 (void)close(listen_sockets[sk]);
2124 ALARM_CLR(0);
2125 signal(SIGHUP, SIG_IGN);
2126 sighup_argv[0] = exim_path;
2127 exim_nullstd();
2128 execv(CS exim_path, (char *const *)sighup_argv);
2129 log_write(0, LOG_MAIN|LOG_PANIC_DIE, "pid %d: exec of %s failed: %s",
2130 getpid(), exim_path, strerror(errno));
2131 log_close_all();
2132 }
2133
2134 } /* End of main loop */
2135
2136 /* Control never reaches here */
2137 }
2138
2139 /* vi: aw ai sw=2
2140 */
2141 /* End of exim_daemon.c */