1 /* $Cambridge: exim/src/src/daemon.c,v 1.20 2007/01/15 15:59:22 ph10 Exp $ */
3 /*************************************************
4 * Exim - an Internet mail transport agent *
5 *************************************************/
7 /* Copyright (c) University of Cambridge 1995 - 2007 */
8 /* See the file NOTICE for conditions of use and distribution. */
10 /* Functions concerned with running Exim as a daemon */
16 /* Structure for holding data for each SMTP connection */
18 typedef struct smtp_slot {
19 pid_t pid; /* pid of the spawned reception process */
20 uschar *host_address; /* address of the client host */
23 /* An empty slot for initializing (Standard C does not allow constructor
24 expressions in assigments except as initializers in declarations). */
26 static smtp_slot empty_smtp_slot = { 0, NULL };
30 /*************************************************
31 * Local static variables *
32 *************************************************/
34 static volatile BOOL sigchld_seen;
35 static volatile BOOL sighup_seen;
37 static int accept_retry_count = 0;
38 static int accept_retry_errno;
39 static BOOL accept_retry_select_failed;
41 static int queue_run_count = 0;
42 static pid_t *queue_pid_slots = NULL;
43 static smtp_slot *smtp_slots = NULL;
45 static BOOL write_pid = TRUE;
49 /*************************************************
51 *************************************************/
53 /* All this handler does is to set a flag and re-enable the signal.
55 Argument: the signal number
60 sighup_handler(int sig)
62 sig = sig; /* Keep picky compilers happy */
64 signal(SIGHUP, sighup_handler);
69 /*************************************************
70 * SIGCHLD handler for main daemon process *
71 *************************************************/
73 /* Don't re-enable the handler here, since we aren't doing the
74 waiting here. If the signal is re-enabled, there will just be an
75 infinite sequence of calls to this handler. The SIGCHLD signal is
76 used just as a means of waking up the daemon so that it notices
77 terminated subprocesses as soon as possible.
79 Argument: the signal number
84 main_sigchld_handler(int sig)
86 sig = sig; /* Keep picky compilers happy */
87 os_non_restarting_signal(SIGCHLD, SIG_DFL);
94 /*************************************************
95 * Unexpected errors in SMTP calls *
96 *************************************************/
98 /* This function just saves a bit of repetitious coding.
101 log_msg Text of message to be logged
102 smtp_msg Text of SMTP error message
103 was_errno The failing errno
109 never_error(uschar *log_msg, uschar *smtp_msg, int was_errno)
111 uschar *emsg = (was_errno <= 0)? US"" :
112 string_sprintf(": %s", strerror(was_errno));
113 log_write(0, LOG_MAIN|LOG_PANIC, "%s%s", log_msg, emsg);
114 if (smtp_out != NULL) smtp_printf("421 %s\r\n", smtp_msg);
120 /*************************************************
121 * Handle a connected SMTP call *
122 *************************************************/
124 /* This function is called when an SMTP connection has been accepted.
125 If there are too many, give an error message and close down. Otherwise
126 spin off a sub-process to handle the call. The list of listening sockets
127 is required so that they can be closed in the sub-process. Take care not to
128 leak store in this process - reset the stacking pool at the end.
131 listen_sockets sockets which are listening for incoming calls
132 listen_socket_count count of listening sockets
133 accept_socket socket of the current accepted call
134 accepted socket information about the current call
140 handle_smtp_call(int *listen_sockets, int listen_socket_count,
141 int accept_socket, struct sockaddr *accepted)
144 union sockaddr_46 interface_sockaddr;
145 EXIM_SOCKLEN_T ifsize = sizeof(interface_sockaddr);
146 int dup_accept_socket = -1;
147 int max_for_this_host = 0;
150 int use_log_write_selector = log_write_selector;
151 uschar *whofrom = NULL;
153 void *reset_point = store_get(0);
155 /* Make the address available in ASCII representation, and also fish out
158 sender_host_address = host_ntoa(-1, accepted, NULL, &sender_host_port);
159 DEBUG(D_any) debug_printf("Connection request from %s port %d\n",
160 sender_host_address, sender_host_port);
162 /* Set up the output stream, check the socket has duplicated, and set up the
163 input stream. These operations fail only the exceptional circumstances. Note
164 that never_error() won't use smtp_out if it is NULL. */
166 smtp_out = fdopen(accept_socket, "wb");
167 if (smtp_out == NULL)
169 never_error(US"daemon: fdopen() for smtp_out failed", US"", errno);
173 dup_accept_socket = dup(accept_socket);
174 if (dup_accept_socket < 0)
176 never_error(US"daemon: couldn't dup socket descriptor",
177 US"Connection setup failed", errno);
181 smtp_in = fdopen(dup_accept_socket, "rb");
184 never_error(US"daemon: fdopen() for smtp_in failed",
185 US"Connection setup failed", errno);
189 /* Get the data for the local interface address. Panic for most errors, but
190 "connection reset by peer" just means the connection went away. */
192 if (getsockname(accept_socket, (struct sockaddr *)(&interface_sockaddr),
195 log_write(0, LOG_MAIN | ((errno == ECONNRESET)? 0 : LOG_PANIC),
196 "getsockname() failed: %s", strerror(errno));
197 smtp_printf("421 Local problem: getsockname() failed; please try again later\r\n");
201 interface_address = host_ntoa(-1, &interface_sockaddr, NULL, &interface_port);
202 DEBUG(D_interface) debug_printf("interface address=%s port=%d\n",
203 interface_address, interface_port);
205 /* Build a string identifying the remote host and, if requested, the port and
206 the local interface data. This is for logging; at the end of this function the
207 memory is reclaimed. */
209 whofrom = string_append(whofrom, &wfsize, &wfptr, 3, "[", sender_host_address, "]");
211 if ((log_extra_selector & LX_incoming_port) != 0)
212 whofrom = string_append(whofrom, &wfsize, &wfptr, 2, ":", string_sprintf("%d",
215 if ((log_extra_selector & LX_incoming_interface) != 0)
216 whofrom = string_append(whofrom, &wfsize, &wfptr, 4, " I=[",
217 interface_address, "]:", string_sprintf("%d", interface_port));
219 whofrom[wfptr] = 0; /* Terminate the newly-built string */
221 /* Check maximum number of connections. We do not check for reserved
222 connections or unacceptable hosts here. That is done in the subprocess because
223 it might take some time. */
225 if (smtp_accept_max > 0 && smtp_accept_count >= smtp_accept_max)
227 DEBUG(D_any) debug_printf("rejecting SMTP connection: count=%d max=%d\n",
228 smtp_accept_count, smtp_accept_max);
229 smtp_printf("421 Too many concurrent SMTP connections; "
230 "please try again later.\r\n");
231 log_write(L_connection_reject,
232 LOG_MAIN, "Connection from %s refused: too many connections",
237 /* If a load limit above which only reserved hosts are acceptable is defined,
238 get the load average here, and if there are in fact no reserved hosts, do
239 the test right away (saves a fork). If there are hosts, do the check in the
240 subprocess because it might take time. */
242 if (smtp_load_reserve >= 0)
244 load_average = os_getloadavg();
245 if (smtp_reserve_hosts == NULL && load_average > smtp_load_reserve)
247 DEBUG(D_any) debug_printf("rejecting SMTP connection: load average = %.2f\n",
248 (double)load_average/1000.0);
249 smtp_printf("421 Too much load; please try again later.\r\n");
250 log_write(L_connection_reject,
251 LOG_MAIN, "Connection from %s refused: load average = %.2f",
252 whofrom, (double)load_average/1000.0);
257 /* Check that one specific host (strictly, IP address) is not hogging
258 resources. This is done here to prevent a denial of service attack by someone
259 forcing you to fork lots of times before denying service. The value of
260 smtp_accept_max_per_host is a string which is expanded. This makes it possible
261 to provide host-specific limits according to $sender_host address, but because
262 this is in the daemon mainline, only fast expansions (such as inline address
263 checks) should be used. The documentation is full of warnings. */
265 if (smtp_accept_max_per_host != NULL)
267 uschar *expanded = expand_string(smtp_accept_max_per_host);
268 if (expanded == NULL)
270 if (!expand_string_forcedfail)
271 log_write(0, LOG_MAIN|LOG_PANIC, "expansion of smtp_accept_max_per_host "
272 "failed for %s: %s", whofrom, expand_string_message);
274 /* For speed, interpret a decimal number inline here */
277 uschar *s = expanded;
279 max_for_this_host = max_for_this_host * 10 + *s++ - '0';
281 log_write(0, LOG_MAIN|LOG_PANIC, "expansion of smtp_accept_max_per_host "
282 "for %s contains non-digit: %s", whofrom, expanded);
286 /* If we have fewer connections than max_for_this_host, we can skip the tedious
287 per host_address checks. Note that at this stage smtp_accept_count contains the
288 count of *other* connections, not including this one. */
290 if ((max_for_this_host > 0) &&
291 (smtp_accept_count >= max_for_this_host))
294 int host_accept_count = 0;
295 int other_host_count = 0; /* keep a count of non matches to optimise */
297 for (i = 0; i < smtp_accept_max; ++i)
299 if (smtp_slots[i].host_address != NULL)
301 if (Ustrcmp(sender_host_address, smtp_slots[i].host_address) == 0)
306 /* Testing all these strings is expensive - see if we can drop out
307 early, either by hitting the target, or finding there are not enough
308 connections left to make the target. */
310 if ((host_accept_count >= max_for_this_host) ||
311 ((smtp_accept_count - other_host_count) < max_for_this_host))
316 if (host_accept_count >= max_for_this_host)
318 DEBUG(D_any) debug_printf("rejecting SMTP connection: too many from this "
319 "IP address: count=%d max=%d\n",
320 host_accept_count, max_for_this_host);
321 smtp_printf("421 Too many concurrent SMTP connections "
322 "from this IP address; please try again later.\r\n");
323 log_write(L_connection_reject,
324 LOG_MAIN, "Connection from %s refused: too many connections "
325 "from that IP address", whofrom);
330 /* OK, the connection count checks have been passed. Before we can fork the
331 accepting process, we must first log the connection if requested. This logging
332 used to happen in the subprocess, but doing that means that the value of
333 smtp_accept_count can be out of step by the time it is logged. So we have to do
334 the logging here and accept the performance cost. Note that smtp_accept_count
335 hasn't yet been incremented to take account of this connection.
337 In order to minimize the cost (because this is going to happen for every
338 connection), do a preliminary selector test here. This saves ploughing through
339 the generalized logging code each time when the selector is false. If the
340 selector is set, check whether the host is on the list for logging. If not,
341 arrange to unset the selector in the subprocess. */
343 if ((log_write_selector & L_smtp_connection) != 0)
345 uschar *list = hosts_connection_nolog;
346 if (list != NULL && verify_check_host(&list) == OK)
347 use_log_write_selector &= ~L_smtp_connection;
349 log_write(L_smtp_connection, LOG_MAIN, "SMTP connection from %s "
350 "(TCP/IP connection count = %d)", whofrom, smtp_accept_count + 1);
353 /* Now we can fork the accepting process; do a lookup tidy, just in case any
354 expansion above did a lookup. */
359 /* Handle the child process */
364 int queue_only_reason = 0;
365 int old_pool = store_pool;
366 int save_debug_selector = debug_selector;
367 BOOL local_queue_only;
369 struct sigaction act;
372 /* May have been modified for the subprocess */
374 log_write_selector = use_log_write_selector;
376 /* Get the local interface address into permanent store */
378 store_pool = POOL_PERM;
379 interface_address = string_copy(interface_address);
380 store_pool = old_pool;
382 /* Check for a tls-on-connect port */
384 if (host_is_tls_on_connect_port(interface_port)) tls_on_connect = TRUE;
386 /* Expand smtp_active_hostname if required. We do not do this any earlier,
387 because it may depend on the local interface address (indeed, that is most
388 likely what it depends on.) */
390 smtp_active_hostname = primary_hostname;
391 if (raw_active_hostname != NULL)
393 uschar *nah = expand_string(raw_active_hostname);
396 if (!expand_string_forcedfail)
398 log_write(0, LOG_MAIN|LOG_PANIC, "failed to expand \"%s\" "
399 "(smtp_active_hostname): %s", raw_active_hostname,
400 expand_string_message);
401 smtp_printf("421 Local configuration error; "
402 "please try again later.\r\n");
408 else if (nah[0] != 0) smtp_active_hostname = nah;
411 /* Initialize the queueing flags */
414 local_queue_only = queue_only;
416 /* Close the listening sockets, and set the SIGCHLD handler to SIG_IGN.
417 We also attempt to set things up so that children are automatically reaped,
418 but just in case this isn't available, there's a paranoid waitpid() in the
419 loop too (except for systems where we are sure it isn't needed). See the more
420 extensive comment before the reception loop in exim.c for a fuller
421 explanation of this logic. */
423 for (i = 0; i < listen_socket_count; i++) (void)close(listen_sockets[i]);
426 act.sa_handler = SIG_IGN;
427 sigemptyset(&(act.sa_mask));
428 act.sa_flags = SA_NOCLDWAIT;
429 sigaction(SIGCHLD, &act, NULL);
431 signal(SIGCHLD, SIG_IGN);
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.
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. */
443 if (debug_daemon) debug_selector = 0;
444 verify_get_ident(IDENT_PORT);
445 host_build_sender_fullhost();
446 debug_selector = save_debug_selector;
449 debug_printf("Process %d is handling incoming connection from %s\n",
450 (int)getpid(), sender_fullhost);
452 /* Now disable debugging permanently if it's required only for the daemon
455 if (debug_daemon) debug_selector = 0;
457 /* If there are too many child processes for immediate delivery,
458 set the 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. */
462 if (smtp_accept_queue > 0 && smtp_accept_count >= smtp_accept_queue)
464 local_queue_only = TRUE;
465 queue_only_reason = 1;
468 /* Handle the start of the SMTP session, then loop, accepting incoming
469 messages from the SMTP connection. The end will come at the QUIT command,
470 when smtp_setup_msg() returns 0. A break in the connection causes the
471 process to die (see accept.c). */
473 if (!smtp_start_session())
483 message_id[0] = 0; /* Clear out any previous message_id */
484 reset_point = store_get(0); /* Save current store high water point */
487 debug_printf("Process %d is ready for new message\n", (int)getpid());
489 /* Smtp_setup_msg() returns 0 on QUIT or if the call is from an
490 unacceptable host or if an ACL "drop" command was triggered, -1 on
491 connection lost, and +1 on validly reaching DATA. Receive_msg() almost
492 always returns TRUE when smtp_input is true; just retry if no message was
493 accepted (can happen for invalid message parameters). However, it can yield
494 FALSE if the connection was forcibly dropped by the DATA ACL. */
496 if ((rc = smtp_setup_msg()) > 0)
498 BOOL ok = receive_msg(FALSE);
499 search_tidyup(); /* Close cached databases */
500 if (!ok) /* Connection was dropped */
503 smtp_log_no_mail(); /* Log no mail if configured */
506 if (message_id[0] == 0) continue; /* No message was accepted */
512 smtp_log_no_mail(); /* Log no mail if configured */
513 _exit((rc == 0)? EXIT_SUCCESS : EXIT_FAILURE);
516 /* Show the recipients when debugging */
521 if (sender_address != NULL)
522 debug_printf("Sender: %s\n", sender_address);
523 if (recipients_list != NULL)
525 debug_printf("Recipients:\n");
526 for (i = 0; i < recipients_count; i++)
527 debug_printf(" %s\n", recipients_list[i].address);
531 /* A message has been accepted. Clean up any previous delivery processes
532 that have completed and are defunct, on systems where they don't go away
533 by themselves (see comments when setting SIG_IGN above). On such systems
534 (if any) these delivery processes hang around after termination until
535 the next message is received. */
537 #ifndef SIG_IGN_WORKS
538 while (waitpid(-1, NULL, WNOHANG) > 0);
541 /* Reclaim up the store used in accepting this message */
543 store_reset(reset_point);
545 /* If queue_only is set or if there are too many incoming connections in
546 existence, local_queue_only will be TRUE. If it is not, check whether we
547 have received too many messages in this session for immediate delivery. If
548 not, and queue_only_load is set, check that the load average is below it.
549 Note that, once set, local_queue_only remains set for any subsequent
550 messages on the same SMTP connection. This is a deliberate choice; even
551 though the load average may fall, it doesn't seem right to deliver later
552 messages on the same call when not delivering earlier ones. */
554 if (!local_queue_only)
556 if (smtp_accept_queue_per_connection > 0 &&
557 receive_messagecount > smtp_accept_queue_per_connection)
559 local_queue_only = TRUE;
560 queue_only_reason = 2;
562 else if (queue_only_load >= 0)
564 local_queue_only = (load_average = os_getloadavg()) > queue_only_load;
565 if (local_queue_only) queue_only_reason = 3;
569 /* Log the queueing here, when it will get a message id attached, but
570 not if queue_only is set (case 0). */
572 if (local_queue_only) switch(queue_only_reason)
575 log_write(L_delay_delivery,
576 LOG_MAIN, "no immediate delivery: too many connections "
577 "(%d, max %d)", smtp_accept_count, smtp_accept_queue);
581 log_write(L_delay_delivery,
582 LOG_MAIN, "no immediate delivery: more than %d messages "
583 "received in one connection", smtp_accept_queue_per_connection);
587 log_write(L_delay_delivery,
588 LOG_MAIN, "no immediate delivery: load average %.2f",
589 (double)load_average/1000.0);
593 /* If a delivery attempt is required, spin off a new process to handle it.
594 If we are not root, we have to re-exec exim unless deliveries are being
595 done unprivileged. */
597 else if (!queue_only_policy && !deliver_freeze)
601 /* Before forking, ensure that the C output buffer is flushed. Otherwise
602 anything that it in it will get duplicated, leading to duplicate copies
603 of the pending output. */
607 if ((dpid = fork()) == 0)
609 (void)fclose(smtp_in);
610 (void)fclose(smtp_out);
612 /* Don't ever molest the parent's SSL connection, but do clean up
613 the data structures if necessary. */
619 /* Reset SIGHUP and SIGCHLD in the child in both cases. */
621 signal(SIGHUP, SIG_DFL);
622 signal(SIGCHLD, SIG_DFL);
624 if (geteuid() != root_uid && !deliver_drop_privilege)
626 signal(SIGALRM, SIG_DFL);
627 (void)child_exec_exim(CEE_EXEC_PANIC, FALSE, NULL, FALSE, 2, US"-Mc",
629 /* Control does not return here. */
632 /* No need to re-exec; SIGALRM remains set to the default handler */
634 (void)deliver_message(message_id, FALSE, FALSE);
641 DEBUG(D_any) debug_printf("forked delivery process %d\n", (int)dpid);
645 log_write(0, LOG_MAIN|LOG_PANIC, "daemon: delivery process fork "
646 "failed: %s", strerror(errno));
653 /* Carrying on in the parent daemon process... Can't do much if the fork
654 failed. Otherwise, keep count of the number of accepting processes and
655 remember the pid for ticking off when the child completes. */
659 never_error(US"daemon: accept process fork failed", US"Fork failed", errno);
664 for (i = 0; i < smtp_accept_max; ++i)
666 if (smtp_slots[i].pid <= 0)
668 smtp_slots[i].pid = pid;
669 if (smtp_accept_max_per_host != NULL)
670 smtp_slots[i].host_address = string_copy_malloc(sender_host_address);
675 DEBUG(D_any) debug_printf("%d SMTP accept process%s running\n",
676 smtp_accept_count, (smtp_accept_count == 1)? "" : "es");
679 /* Get here via goto in error cases */
683 /* Close the streams associated with the socket which will also close the
684 socket fds in this process. We can't do anything if fclose() fails, but
685 logging brings it to someone's attention. However, "connection reset by peer"
686 isn't really a problem, so skip that one. On Solaris, a dropped connection can
687 manifest itself as a broken pipe, so drop that one too. If the streams don't
688 exist, something went wrong while setting things up. Make sure the socket
689 descriptors are closed, in order to drop the connection. */
691 if (smtp_out != NULL)
693 if (fclose(smtp_out) != 0 && errno != ECONNRESET && errno != EPIPE)
694 log_write(0, LOG_MAIN|LOG_PANIC, "daemon: fclose(smtp_out) failed: %s",
698 else (void)close(accept_socket);
702 if (fclose(smtp_in) != 0 && errno != ECONNRESET && errno != EPIPE)
703 log_write(0, LOG_MAIN|LOG_PANIC, "daemon: fclose(smtp_in) failed: %s",
707 else (void)close(dup_accept_socket);
709 /* Release any store used in this process, including the store used for holding
710 the incoming host address and an expanded active_hostname. */
712 store_reset(reset_point);
713 sender_host_address = NULL;
719 /*************************************************
720 * Check wildcard listen special cases *
721 *************************************************/
723 /* This function is used when binding and listening on lists of addresses and
724 ports. It tests for special cases of wildcard listening, when IPv4 and IPv6
725 sockets may interact in different ways in different operating systems. It is
726 passed an error number, the list of listening addresses, and the current
727 address. Two checks are available: for a previous wildcard IPv6 address, or for
728 a following wildcard IPv4 address, in both cases on the same port.
730 In practice, pairs of wildcard addresses should be adjacent in the address list
731 because they are sorted that way below.
735 addresses the list of addresses
736 ipa the current IP address
737 back if TRUE, check for previous wildcard IPv6 address
738 if FALSE, check for a following wildcard IPv4 address
740 Returns: TRUE or FALSE
744 check_special_case(int eno, ip_address_item *addresses, ip_address_item *ipa,
747 ip_address_item *ipa2;
749 /* For the "back" case, if the failure was "address in use" for a wildcard IPv4
750 address, seek a previous IPv6 wildcard address on the same port. As it is
751 previous, it must have been successfully bound and be listening. Flag it as a
752 "6 including 4" listener. */
756 if (eno != EADDRINUSE || ipa->address[0] != 0) return FALSE;
757 for (ipa2 = addresses; ipa2 != ipa; ipa2 = ipa2->next)
759 if (ipa2->address[1] == 0 && ipa2->port == ipa->port)
761 ipa2->v6_include_v4 = TRUE;
767 /* For the "forward" case, if the current address is a wildcard IPv6 address,
768 we seek a following wildcard IPv4 address on the same port. */
772 if (ipa->address[0] != ':' || ipa->address[1] != 0) return FALSE;
773 for (ipa2 = ipa->next; ipa2 != NULL; ipa2 = ipa2->next)
774 if (ipa2->address[0] == 0 && ipa->port == ipa2->port) return TRUE;
783 /*************************************************
784 * Handle terminating subprocesses *
785 *************************************************/
787 /* Handle the termination of child processes. Theoretically, this need be done
788 only when sigchld_seen is TRUE, but rumour has it that some systems lose
789 SIGCHLD signals at busy times, so to be on the safe side, this function is
790 called each time round. It shouldn't be too expensive.
797 handle_ending_processes(void)
802 while ((pid = waitpid(-1, &status, WNOHANG)) > 0)
805 DEBUG(D_any) debug_printf("child %d ended: status=0x%x\n", (int)pid,
808 /* If it's a listening daemon for which we are keeping track of individual
809 subprocesses, deal with an accepting process that has terminated. */
811 if (smtp_slots != NULL)
813 for (i = 0; i < smtp_accept_max; i++)
815 if (smtp_slots[i].pid == pid)
817 if (smtp_slots[i].host_address != NULL)
818 store_free(smtp_slots[i].host_address);
819 smtp_slots[i] = empty_smtp_slot;
820 if (--smtp_accept_count < 0) smtp_accept_count = 0;
821 DEBUG(D_any) debug_printf("%d SMTP accept process%s now running\n",
822 smtp_accept_count, (smtp_accept_count == 1)? "" : "es");
826 if (i < smtp_accept_max) continue; /* Found an accepting process */
829 /* If it wasn't an accepting process, see if it was a queue-runner
830 process that we are tracking. */
832 if (queue_pid_slots != NULL)
834 for (i = 0; i < queue_run_max; i++)
836 if (queue_pid_slots[i] == pid)
838 queue_pid_slots[i] = 0;
839 if (--queue_run_count < 0) queue_run_count = 0;
840 DEBUG(D_any) debug_printf("%d queue-runner process%s now running\n",
841 queue_run_count, (queue_run_count == 1)? "" : "es");
851 /*************************************************
852 * Exim Daemon Mainline *
853 *************************************************/
855 /* The daemon can do two jobs, either of which is optional:
857 (1) Listens for incoming SMTP calls and spawns off a sub-process to handle
858 each one. This is requested by the -bd option, with -oX specifying the SMTP
859 port on which to listen (for testing).
861 (2) Spawns a queue-running process every so often. This is controlled by the
862 -q option with a an interval time. (If no time is given, a single queue run
863 is done from the main function, and control doesn't get here.)
865 Root privilege is required in order to attach to port 25. Some systems require
866 it when calling socket() rather than bind(). To cope with all cases, we run as
867 root for both socket() and bind(). Some systems also require root in order to
868 write to the pid file directory. This function must therefore be called as root
869 if it is to work properly in all circumstances. Once the socket is bound and
870 the pid file written, root privilege is given up if there is an exim uid.
872 There are no arguments to this function, and it never returns. */
877 int *listen_sockets = NULL;
878 int listen_socket_count = 0;
879 ip_address_item *addresses = NULL;
881 /* If any debugging options are set, turn on the D_pid bit so that all
882 debugging lines get the pid added. */
884 DEBUG(D_any|D_v) debug_selector |= D_pid;
887 /* Do the preparation for setting up a listener on one or more interfaces, and
888 possible on various ports. This is controlled by the combination of
889 local_interfaces (which can set IP addresses and ports) and daemon_smtp_port
890 (which is a list of default ports to use for those items in local_interfaces
891 that do not specify a port). The -oX command line option can be used to
892 override one or both of these options.
894 If local_interfaces is not set, the default is to listen on all interfaces.
895 When it is set, it can include "all IPvx interfaces" as an item. This is useful
896 when different ports are in use.
898 It turns out that listening on all interfaces is messy in an IPv6 world,
899 because several different implementation approaches have been taken. This code
900 is now supposed to work with all of them. The point of difference is whether an
901 IPv6 socket that is listening on all interfaces will receive incoming IPv4
902 calls or not. We also have to cope with the case when IPv6 libraries exist, but
903 there is no IPv6 support in the kernel.
905 . On Solaris, an IPv6 socket will accept IPv4 calls, and give them as mapped
906 addresses. However, if an IPv4 socket is also listening on all interfaces,
907 calls are directed to the appropriate socket.
909 . On (some versions of) Linux, an IPv6 socket will accept IPv4 calls, and
910 give them as mapped addresses, but an attempt also to listen on an IPv4
911 socket on all interfaces causes an error.
913 . On OpenBSD, an IPv6 socket will not accept IPv4 calls. You have to set up
914 two sockets if you want to accept both kinds of call.
916 . FreeBSD is like OpenBSD, but it has the IPV6_V6ONLY socket option, which
917 can be turned off, to make it behave like the versions of Linux described
920 . I heard a report that the USAGI IPv6 stack for Linux has implemented
923 So, what we do when IPv6 is supported is as follows:
925 (1) After it is set up, the list of interfaces is scanned for wildcard
926 addresses. If an IPv6 and an IPv4 wildcard are both found for the same
927 port, the list is re-arranged so that they are together, with the IPv6
930 (2) If the creation of a wildcard IPv6 socket fails, we just log the error and
931 carry on if an IPv4 wildcard socket for the same port follows later in the
932 list. This allows Exim to carry on in the case when the kernel has no IPv6
935 (3) Having created an IPv6 wildcard socket, we try to set IPV6_V6ONLY if that
936 option is defined. However, if setting fails, carry on regardless (but log
939 (4) If binding or listening on an IPv6 wildcard socket fails, it is a serious
942 (5) If binding or listening on an IPv4 wildcard socket fails with the error
943 EADDRINUSE, and a previous interface was an IPv6 wildcard for the same
944 port (which must have succeeded or we wouldn't have got this far), we
945 assume we are in the situation where just a single socket is permitted,
946 and ignore the error.
950 The preparation code decodes options and sets up the relevant data. We do this
951 first, so that we can return non-zero if there are any syntax errors, and also
956 int *default_smtp_port;
961 uschar *local_iface_source = US"local_interfaces";
962 ip_address_item *ipa;
963 ip_address_item **pipa;
965 /* If any option requiring a load average to be available during the
966 reception of a message is set, call os_getloadavg() while we are root
967 for those OS for which this is necessary the first time it is called (in
968 order to perform an "open" on the kernel memory file). */
970 #ifdef LOAD_AVG_NEEDS_ROOT
971 if (queue_only_load >= 0 || smtp_load_reserve >= 0 ||
972 (deliver_queue_load_max >= 0 && deliver_drop_privilege))
973 (void)os_getloadavg();
976 /* If -oX was used, disable the writing of a pid file unless -oP was
977 explicitly used to force it. Then scan the string given to -oX. Any items
978 that contain neither a dot nor a colon are used to override daemon_smtp_port.
979 Any other items are used to override local_interfaces. */
981 if (override_local_interfaces != NULL)
983 uschar *new_smtp_port = NULL;
984 uschar *new_local_interfaces = NULL;
990 if (override_pid_file_path == NULL) write_pid = FALSE;
992 list = override_local_interfaces;
994 while ((s = string_nextinlist(&list,&sep,big_buffer,big_buffer_size))
1002 if (Ustrpbrk(s, ".:") == NULL)
1004 ptr = &new_smtp_port;
1005 sizeptr = &portsize;
1010 ptr = &new_local_interfaces;
1011 sizeptr = &ifacesize;
1019 *ptr = string_cat(*ptr, sizeptr, ptrptr, US"<", 1);
1022 *ptr = string_cat(*ptr, sizeptr, ptrptr, joinstr, 2);
1023 *ptr = string_cat(*ptr, sizeptr, ptrptr, s, Ustrlen(s));
1026 if (new_smtp_port != NULL)
1028 new_smtp_port[portptr] = 0;
1029 daemon_smtp_port = new_smtp_port;
1030 DEBUG(D_any) debug_printf("daemon_smtp_port overridden by -oX:\n %s\n",
1034 if (new_local_interfaces != NULL)
1036 new_local_interfaces[ifaceptr] = 0;
1037 local_interfaces = new_local_interfaces;
1038 local_iface_source = US"-oX data";
1039 DEBUG(D_any) debug_printf("local_interfaces overridden by -oX:\n %s\n",
1044 /* Create a list of default SMTP ports, to be used if local_interfaces
1045 contains entries without explict ports. First count the number of ports, then
1046 build a translated list in a vector. */
1048 list = daemon_smtp_port;
1050 while ((s = string_nextinlist(&list,&sep,big_buffer,big_buffer_size)) != NULL)
1052 default_smtp_port = store_get((pct+1) * sizeof(int));
1053 list = daemon_smtp_port;
1056 (s = string_nextinlist(&list,&sep,big_buffer,big_buffer_size)) != NULL;
1062 default_smtp_port[pct] = Ustrtol(s, &end, 0);
1063 if (end != s + Ustrlen(s))
1064 log_write(0, LOG_PANIC_DIE|LOG_CONFIG, "invalid SMTP port: %s", s);
1068 struct servent *smtp_service = getservbyname(CS s, "tcp");
1069 if (smtp_service == NULL)
1070 log_write(0, LOG_PANIC_DIE|LOG_CONFIG, "TCP port \"%s\" not found", s);
1071 default_smtp_port[pct] = ntohs(smtp_service->s_port);
1074 default_smtp_port[pct] = 0;
1076 /* Create the list of local interfaces, possibly with ports included. This
1077 list may contain references to 0.0.0.0 and ::0 as wildcards. These special
1078 values are converted below. */
1080 addresses = host_build_ifacelist(local_interfaces, local_iface_source);
1082 /* In the list of IP addresses, convert 0.0.0.0 into an empty string, and ::0
1083 into the string ":". We use these to recognize wildcards in IPv4 and IPv6. In
1084 fact, many IP stacks recognize 0.0.0.0 and ::0 and handle them as wildcards
1085 anyway, but we need to know which are the wildcard addresses, and the shorter
1088 In the same scan, fill in missing port numbers from the default list. When
1089 there is more than one item in the list, extra items are created. */
1091 for (ipa = addresses; ipa != NULL; ipa = ipa->next)
1095 if (Ustrcmp(ipa->address, "0.0.0.0") == 0) ipa->address[0] = 0;
1096 else if (Ustrcmp(ipa->address, "::0") == 0)
1098 ipa->address[0] = ':';
1099 ipa->address[1] = 0;
1102 if (ipa->port > 0) continue;
1104 if (daemon_smtp_port[0] <= 0)
1105 log_write(0, LOG_MAIN|LOG_PANIC_DIE, "no port specified for interface "
1106 "%s and daemon_smtp_port is unset; cannot start daemon",
1107 (ipa->address[0] == 0)? US"\"all IPv4\"" :
1108 (ipa->address[1] == 0)? US"\"all IPv6\"" : ipa->address);
1109 ipa->port = default_smtp_port[0];
1110 for (i = 1; default_smtp_port[i] > 0; i++)
1112 ip_address_item *new = store_get(sizeof(ip_address_item));
1113 memcpy(new->address, ipa->address, Ustrlen(ipa->address) + 1);
1114 new->port = default_smtp_port[i];
1115 new->next = ipa->next;
1121 /* Scan the list of addresses for wildcards. If we find an IPv4 and an IPv6
1122 wildcard for the same port, ensure that (a) they are together and (b) the
1123 IPv6 address comes first. This makes handling the messy features easier, and
1124 also simplifies the construction of the "daemon started" log line. */
1127 for (ipa = addresses; ipa != NULL; pipa = &(ipa->next), ipa = ipa->next)
1129 ip_address_item *ipa2;
1131 /* Handle an IPv4 wildcard */
1133 if (ipa->address[0] == 0)
1135 for (ipa2 = ipa; ipa2->next != NULL; ipa2 = ipa2->next)
1137 ip_address_item *ipa3 = ipa2->next;
1138 if (ipa3->address[0] == ':' &&
1139 ipa3->address[1] == 0 &&
1140 ipa3->port == ipa->port)
1142 ipa2->next = ipa3->next;
1150 /* Handle an IPv6 wildcard. */
1152 else if (ipa->address[0] == ':' && ipa->address[1] == 0)
1154 for (ipa2 = ipa; ipa2->next != NULL; ipa2 = ipa2->next)
1156 ip_address_item *ipa3 = ipa2->next;
1157 if (ipa3->address[0] == 0 && ipa3->port == ipa->port)
1159 ipa2->next = ipa3->next;
1160 ipa3->next = ipa->next;
1169 /* Get a vector to remember all the sockets in */
1171 for (ipa = addresses; ipa != NULL; ipa = ipa->next)
1172 listen_socket_count++;
1173 listen_sockets = store_get(sizeof(int *) * listen_socket_count);
1175 /* Do a sanity check on the max connects value just to save us from getting
1176 a huge amount of store. */
1178 if (smtp_accept_max > 4095) smtp_accept_max = 4096;
1180 /* There's no point setting smtp_accept_queue unless it is less than the max
1181 connects limit. The configuration reader ensures that the max is set if the
1182 queue-only option is set. */
1184 if (smtp_accept_queue > smtp_accept_max) smtp_accept_queue = 0;
1186 /* Get somewhere to keep the list of SMTP accepting pids if we are keeping
1187 track of them for total number and queue/host limits. */
1189 if (smtp_accept_max > 0)
1192 smtp_slots = store_get(smtp_accept_max * sizeof(smtp_slot));
1193 for (i = 0; i < smtp_accept_max; i++) smtp_slots[i] = empty_smtp_slot;
1197 /* The variable background_daemon is always false when debugging, but
1198 can also be forced false in order to keep a non-debugging daemon in the
1199 foreground. If background_daemon is true, close all open file descriptors that
1200 we know about, but then re-open stdin, stdout, and stderr to /dev/null.
1202 This is protection against any called functions (in libraries, or in
1203 Perl, or whatever) that think they can write to stderr (or stdout). Before this
1204 was added, it was quite likely that an SMTP connection would use one of these
1205 file descriptors, in which case writing random stuff to it caused chaos.
1207 Then disconnect from the controlling terminal, Most modern Unixes seem to have
1208 setsid() for getting rid of the controlling terminal. For any OS that doesn't,
1209 setsid() can be #defined as a no-op, or as something else. */
1211 if (background_daemon)
1213 log_close_all(); /* Just in case anything was logged earlier */
1214 search_tidyup(); /* Just in case any were used in reading the config. */
1215 (void)close(0); /* Get rid of stdin/stdout/stderr */
1218 exim_nullstd(); /* Connect stdin/stdout/stderr to /dev/null */
1219 log_stderr = NULL; /* So no attempt to copy paniclog output */
1221 /* If the parent process of this one has pid == 1, we are re-initializing the
1222 daemon as the result of a SIGHUP. In this case, there is no need to do
1223 anything, because the controlling terminal has long gone. Otherwise, fork, in
1224 case current process is a process group leader (see 'man setsid' for an
1225 explanation) before calling setsid(). */
1230 if (pid < 0) log_write(0, LOG_MAIN|LOG_PANIC_DIE,
1231 "fork() failed when starting daemon: %s", strerror(errno));
1232 if (pid > 0) exit(EXIT_SUCCESS); /* in parent process, just exit */
1233 (void)setsid(); /* release controlling terminal */
1237 /* We are now in the disconnected, daemon process (unless debugging). Set up
1238 the listening sockets if required. */
1244 ip_address_item *ipa;
1246 /* For each IP address, create a socket, bind it to the appropriate port, and
1247 start listening. See comments above about IPv6 sockets that may or may not
1248 accept IPv4 calls when listening on all interfaces. We also have to cope with
1249 the case of a system with IPv6 libraries, but no IPv6 support in the kernel.
1250 listening, provided a wildcard IPv4 socket for the same port follows. */
1252 for (ipa = addresses, sk = 0; sk < listen_socket_count; ipa = ipa->next, sk++)
1255 ip_address_item *ipa2;
1258 if (Ustrchr(ipa->address, ':') != NULL)
1261 wildcard = ipa->address[1] == 0;
1266 wildcard = ipa->address[0] == 0;
1269 listen_sockets[sk] = ip_socket(SOCK_STREAM, af);
1270 if (listen_sockets[sk] < 0)
1272 if (check_special_case(0, addresses, ipa, FALSE))
1274 log_write(0, LOG_MAIN, "Failed to create IPv6 socket for wildcard "
1275 "listening (%s): will use IPv4", strerror(errno));
1278 log_write(0, LOG_PANIC_DIE, "IPv%c socket creation failed: %s",
1279 (af == AF_INET6)? '6' : '4', strerror(errno));
1282 /* If this is an IPv6 wildcard socket, set IPV6_V6ONLY if that option is
1283 available. Just log failure (can get protocol not available, just like
1284 socket creation can). */
1287 if (af == AF_INET6 && wildcard &&
1288 setsockopt(listen_sockets[sk], IPPROTO_IPV6, IPV6_V6ONLY, (char *)(&on),
1290 log_write(0, LOG_MAIN, "Setting IPV6_V6ONLY on daemon's IPv6 wildcard "
1291 "socket failed (%s): carrying on without it", strerror(errno));
1292 #endif /* IPV6_V6ONLY */
1294 /* Set SO_REUSEADDR so that the daemon can be restarted while a connection
1295 is being handled. Without this, a connection will prevent reuse of the
1296 smtp port for listening. */
1298 if (setsockopt(listen_sockets[sk], SOL_SOCKET, SO_REUSEADDR,
1299 (uschar *)(&on), sizeof(on)) < 0)
1300 log_write(0, LOG_MAIN|LOG_PANIC_DIE, "setting SO_REUSEADDR on socket "
1301 "failed when starting daemon: %s", strerror(errno));
1303 /* Set TCP_NODELAY; Exim does its own buffering. There is a switch to
1304 disable this because it breaks some broken clients. */
1306 if (tcp_nodelay) setsockopt(listen_sockets[sk], IPPROTO_TCP, TCP_NODELAY,
1307 (uschar *)(&on), sizeof(on));
1309 /* Now bind the socket to the required port; if Exim is being restarted
1310 it may not always be possible to bind immediately, even with SO_REUSEADDR
1311 set, so try 10 times, waiting between each try. After 10 failures, we give
1312 up. In an IPv6 environment, if bind () fails with the error EADDRINUSE and
1313 we are doing wildcard IPv4 listening and there was a previous IPv6 wildcard
1314 address for the same port, ignore the error on the grounds that we must be
1315 in a system where the IPv6 socket accepts both kinds of call. This is
1316 necessary for (some release of) USAGI Linux; other IP stacks fail at the
1317 listen() stage instead. */
1322 if (ip_bind(listen_sockets[sk], af, ipa->address, ipa->port) >= 0) break;
1323 if (check_special_case(errno, addresses, ipa, TRUE))
1325 DEBUG(D_any) debug_printf("wildcard IPv4 bind() failed after IPv6 "
1326 "listen() success; EADDRINUSE ignored\n");
1327 (void)close(listen_sockets[sk]);
1330 msg = US strerror(errno);
1331 addr = wildcard? ((af == AF_INET6)? US"(any IPv6)" : US"(any IPv4)") :
1333 if (daemon_startup_retries <= 0)
1334 log_write(0, LOG_MAIN|LOG_PANIC_DIE,
1335 "socket bind() to port %d for address %s failed: %s: "
1336 "daemon abandoned", ipa->port, addr, msg);
1337 log_write(0, LOG_MAIN, "socket bind() to port %d for address %s "
1338 "failed: %s: waiting %s before trying again (%d more %s)",
1339 ipa->port, addr, msg, readconf_printtime(daemon_startup_sleep),
1340 daemon_startup_retries, (daemon_startup_retries > 1)? "tries" : "try");
1341 daemon_startup_retries--;
1342 sleep(daemon_startup_sleep);
1348 debug_printf("listening on all interfaces (IPv%c) port %d\n",
1349 (af == AF_INET6)? '6' : '4', ipa->port);
1351 debug_printf("listening on %s port %d\n", ipa->address, ipa->port);
1354 /* Start listening on the bound socket, establishing the maximum backlog of
1355 connections that is allowed. On success, continue to the next address. */
1357 if (listen(listen_sockets[sk], smtp_connect_backlog) >= 0) continue;
1359 /* Listening has failed. In an IPv6 environment, as for bind(), if listen()
1360 fails with the error EADDRINUSE and we are doing IPv4 wildcard listening
1361 and there was a previous successful IPv6 wildcard listen on the same port,
1362 we want to ignore the error on the grounds that we must be in a system
1363 where the IPv6 socket accepts both kinds of call. */
1365 if (!check_special_case(errno, addresses, ipa, TRUE))
1366 log_write(0, LOG_PANIC_DIE, "listen() failed on interface %s: %s",
1367 wildcard? ((af == AF_INET6)? US"(any IPv6)" : US"(any IPv4)") :
1371 DEBUG(D_any) debug_printf("wildcard IPv4 listen() failed after IPv6 "
1372 "listen() success; EADDRINUSE ignored\n");
1373 (void)close(listen_sockets[sk]);
1375 /* Come here if there has been a problem with the socket which we
1376 are going to ignore. We remove the address from the chain, and back up the
1380 sk--; /* Back up the count */
1381 listen_socket_count--; /* Reduce the total */
1382 if (ipa == addresses) addresses = ipa->next; else
1384 for (ipa2 = addresses; ipa2->next != ipa; ipa2 = ipa2->next);
1385 ipa2->next = ipa->next;
1388 } /* End of bind/listen loop for each address */
1389 } /* End of setup for listening */
1392 /* If we are not listening, we want to write a pid file only if -oP was
1393 explicitly given. */
1395 else if (override_pid_file_path == NULL) write_pid = FALSE;
1397 /* Write the pid to a known file for assistance in identification, if required.
1398 We do this before giving up root privilege, because on some systems it is
1399 necessary to be root in order to write into the pid file directory. There's
1400 nothing to stop multiple daemons running, as long as no more than one listens
1401 on a given TCP/IP port on the same interface(s). However, in these
1402 circumstances it gets far too complicated to mess with pid file names
1403 automatically. Consequently, Exim 4 writes a pid file only
1405 (a) When running in the test harness, or
1406 (b) When -bd is used and -oX is not used, or
1407 (c) When -oP is used to supply a path.
1409 The variable daemon_write_pid is used to control this. */
1411 if (running_in_test_harness || write_pid)
1415 if (override_pid_file_path != NULL)
1416 pid_file_path = override_pid_file_path;
1418 if (pid_file_path[0] == 0)
1419 pid_file_path = string_sprintf("%s/exim-daemon.pid", spool_directory);
1421 f = modefopen(pid_file_path, "wb", 0644);
1424 (void)fprintf(f, "%d\n", (int)getpid());
1426 DEBUG(D_any) debug_printf("pid written to %s\n", pid_file_path);
1431 debug_printf("%s\n", string_open_failed(errno, "pid file %s",
1436 /* Set up the handler for SIGHUP, which causes a restart of the daemon. */
1438 sighup_seen = FALSE;
1439 signal(SIGHUP, sighup_handler);
1441 /* Give up root privilege at this point (assuming that exim_uid and exim_gid
1442 are not root). The third argument controls the running of initgroups().
1443 Normally we do this, in order to set up the groups for the Exim user. However,
1444 if we are not root at this time - some odd installations run that way - we
1447 exim_setugid(exim_uid, exim_gid, geteuid()==root_uid, US"running as a daemon");
1449 /* Get somewhere to keep the list of queue-runner pids if we are keeping track
1450 of them (and also if we are doing queue runs). */
1452 if (queue_interval > 0 && queue_run_max > 0)
1455 queue_pid_slots = store_get(queue_run_max * sizeof(pid_t));
1456 for (i = 0; i < queue_run_max; i++) queue_pid_slots[i] = 0;
1459 /* Set up the handler for termination of child processes. */
1461 sigchld_seen = FALSE;
1462 os_non_restarting_signal(SIGCHLD, main_sigchld_handler);
1464 /* If we are to run the queue periodically, pretend the alarm has just gone
1465 off. This will cause the first queue-runner to get kicked off straight away. */
1467 sigalrm_seen = (queue_interval > 0);
1469 /* Log the start up of a daemon - at least one of listening or queue running
1476 int smtps_ports = 0;
1477 ip_address_item *ipa;
1478 uschar *p = big_buffer;
1479 uschar *qinfo = (queue_interval > 0)?
1480 string_sprintf("-q%s", readconf_printtime(queue_interval))
1484 /* Build a list of listening addresses in big_buffer, but limit it to 10
1485 items. The style is for backwards compatibility.
1487 It is now possible to have some ports listening for SMTPS (the old,
1488 deprecated protocol that starts TLS without using STARTTLS), and others
1489 listening for standard SMTP. Keep their listings separate. */
1491 for (j = 0; j < 2; j++)
1493 for (i = 0, ipa = addresses; i < 10 && ipa != NULL; i++, ipa = ipa->next)
1495 /* First time round, look for SMTP ports; second time round, look for
1496 SMTPS ports. For the first one of each, insert leading text. */
1498 if (host_is_tls_on_connect_port(ipa->port) == (j > 0))
1502 if (smtp_ports++ == 0)
1504 memcpy(p, "SMTP on", 8);
1510 if (smtps_ports++ == 0)
1512 (void)sprintf(CS p, "%sSMTPS on",
1513 (smtp_ports == 0)? "":" and for ");
1514 while (*p != 0) p++;
1518 /* Now the information about the port (and sometimes interface) */
1520 if (ipa->address[0] == ':' && ipa->address[1] == 0)
1522 if (ipa->next != NULL && ipa->next->address[0] == 0 &&
1523 ipa->next->port == ipa->port)
1525 (void)sprintf(CS p, " port %d (IPv6 and IPv4)", ipa->port);
1528 else if (ipa->v6_include_v4)
1529 (void)sprintf(CS p, " port %d (IPv6 with IPv4)", ipa->port);
1531 (void)sprintf(CS p, " port %d (IPv6)", ipa->port);
1533 else if (ipa->address[0] == 0)
1534 (void)sprintf(CS p, " port %d (IPv4)", ipa->port);
1536 (void)sprintf(CS p, " [%s]:%d", ipa->address, ipa->port);
1537 while (*p != 0) p++;
1543 memcpy(p, " ...", 5);
1548 log_write(0, LOG_MAIN,
1549 "exim %s daemon started: pid=%d, %s, listening for %s",
1550 version_string, getpid(), qinfo, big_buffer);
1551 set_process_info("daemon: %s, listening for %s", qinfo, big_buffer);
1556 log_write(0, LOG_MAIN,
1557 "exim %s daemon started: pid=%d, -q%s, not listening for SMTP",
1558 version_string, getpid(), readconf_printtime(queue_interval));
1559 set_process_info("daemon: -q%s, not listening",
1560 readconf_printtime(queue_interval));
1564 /* Close the log so it can be renamed and moved. In the few cases below where
1565 this long-running process writes to the log (always exceptional conditions), it
1566 closes the log afterwards, for the same reason. */
1570 DEBUG(D_any) debug_print_ids(US"daemon running with");
1572 /* Any messages accepted via this route are going to be SMTP. */
1576 /* Enter the never-ending loop... */
1581 struct sockaddr_in6 accepted;
1583 struct sockaddr_in accepted;
1586 EXIM_SOCKLEN_T len = sizeof(accepted);
1589 /* This code is placed first in the loop, so that it gets obeyed at the
1590 start, before the first wait. This causes the first queue-runner to be
1591 started immediately. */
1595 DEBUG(D_any) debug_printf("SIGALRM received\n");
1597 /* Do a full queue run in a child process, if required, unless we already
1598 have enough queue runners on the go. If we are not running as root, a
1599 re-exec is required. */
1601 if (queue_interval > 0 &&
1602 (queue_run_max <= 0 || queue_run_count < queue_run_max))
1604 if ((pid = fork()) == 0)
1608 DEBUG(D_any) debug_printf("Starting queue-runner: pid %d\n",
1611 /* Disable debugging if it's required only for the daemon process. We
1612 leave the above message, because it ties up with the "child ended"
1613 debugging messages. */
1615 if (debug_daemon) debug_selector = 0;
1617 /* Close any open listening sockets in the child */
1619 for (sk = 0; sk < listen_socket_count; sk++)
1620 (void)close(listen_sockets[sk]);
1622 /* Reset SIGHUP and SIGCHLD in the child in both cases. */
1624 signal(SIGHUP, SIG_DFL);
1625 signal(SIGCHLD, SIG_DFL);
1627 /* Re-exec if privilege has been given up, unless deliver_drop_
1628 privilege is set. Reset SIGALRM before exec(). */
1630 if (geteuid() != root_uid && !deliver_drop_privilege)
1637 signal(SIGALRM, SIG_DFL);
1640 if (queue_2stage) *p++ = 'q';
1641 if (queue_run_first_delivery) *p++ = 'i';
1642 if (queue_run_force) *p++ = 'f';
1643 if (deliver_force_thaw) *p++ = 'f';
1644 if (queue_run_local) *p++ = 'l';
1648 /* If -R or -S were on the original command line, ensure they get
1651 if (deliver_selectstring != NULL)
1653 extra[extracount++] = deliver_selectstring_regex? US"-Rr" : US"-R";
1654 extra[extracount++] = deliver_selectstring;
1657 if (deliver_selectstring_sender != NULL)
1659 extra[extracount++] = deliver_selectstring_sender_regex?
1661 extra[extracount++] = deliver_selectstring_sender;
1664 /* Overlay this process with a new execution. */
1666 (void)child_exec_exim(CEE_EXEC_PANIC, FALSE, NULL, TRUE, extracount,
1667 extra[0], extra[1], extra[2], extra[3], extra[4]);
1669 /* Control never returns here. */
1672 /* No need to re-exec; SIGALRM remains set to the default handler */
1674 queue_run(NULL, NULL, FALSE);
1675 _exit(EXIT_SUCCESS);
1680 log_write(0, LOG_MAIN|LOG_PANIC, "daemon: fork of queue-runner "
1681 "process failed: %s", strerror(errno));
1687 for (i = 0; i < queue_run_max; ++i)
1689 if (queue_pid_slots[i] <= 0)
1691 queue_pid_slots[i] = pid;
1696 DEBUG(D_any) debug_printf("%d queue-runner process%s running\n",
1697 queue_run_count, (queue_run_count == 1)? "" : "es");
1701 /* Reset the alarm clock */
1703 sigalrm_seen = FALSE;
1704 alarm(queue_interval);
1708 /* Sleep till a connection happens if listening, and handle the connection if
1709 that is why we woke up. The FreeBSD operating system requires the use of
1710 select() before accept() because the latter function is not interrupted by
1711 a signal, and we want to wake up for SIGCHLD and SIGALRM signals. Some other
1712 OS do notice signals in accept() but it does no harm to have the select()
1713 in for all of them - and it won't then be a lurking problem for ports to
1714 new OS. In fact, the later addition of listening on specific interfaces only
1715 requires this way of working anyway. */
1719 int sk, lcount, select_errno;
1721 BOOL select_failed = FALSE;
1722 fd_set select_listen;
1724 FD_ZERO(&select_listen);
1725 for (sk = 0; sk < listen_socket_count; sk++)
1727 FD_SET(listen_sockets[sk], &select_listen);
1728 if (listen_sockets[sk] > max_socket) max_socket = listen_sockets[sk];
1731 DEBUG(D_any) debug_printf("Listening...\n");
1733 /* In rare cases we may have had a SIGCHLD signal in the time between
1734 setting the handler (below) and getting back here. If so, pretend that the
1735 select() was interrupted so that we reap the child. This might still leave
1736 a small window when a SIGCHLD could get lost. However, since we use SIGCHLD
1737 only to do the reaping more quickly, it shouldn't result in anything other
1738 than a delay until something else causes a wake-up. */
1747 lcount = select(max_socket + 1, (SELECT_ARG2_TYPE *)&select_listen,
1753 select_failed = TRUE;
1757 /* Clean up any subprocesses that may have terminated. We need to do this
1758 here so that smtp_accept_max_per_host works when a connection to that host
1759 has completed, and we are about to accept a new one. When this code was
1760 later in the sequence, a new connection could be rejected, even though an
1761 old one had just finished. Preserve the errno from any select() failure for
1762 the use of the common select/accept error processing below. */
1764 select_errno = errno;
1765 handle_ending_processes();
1766 errno = select_errno;
1768 /* Loop for all the sockets that are currently ready to go. If select
1769 actually failed, we have set the count to 1 and select_failed=TRUE, so as
1770 to use the common error code for select/accept below. */
1772 while (lcount-- > 0)
1774 int accept_socket = -1;
1777 for (sk = 0; sk < listen_socket_count; sk++)
1779 if (FD_ISSET(listen_sockets[sk], &select_listen))
1781 accept_socket = accept(listen_sockets[sk],
1782 (struct sockaddr *)&accepted, &len);
1783 FD_CLR(listen_sockets[sk], &select_listen);
1789 /* If select or accept has failed and this was not caused by an
1790 interruption, log the incident and try again. With asymmetric TCP/IP
1791 routing errors such as "No route to network" have been seen here. Also
1792 "connection reset by peer" has been seen. These cannot be classed as
1793 disastrous errors, but they could fill up a lot of log. The code in smail
1794 crashes the daemon after 10 successive failures of accept, on the grounds
1795 that some OS fail continuously. Exim originally followed suit, but this
1796 appears to have caused problems. Now it just keeps going, but instead of
1797 logging each error, it batches them up when they are continuous. */
1799 if (accept_socket < 0 && errno != EINTR)
1801 if (accept_retry_count == 0)
1803 accept_retry_errno = errno;
1804 accept_retry_select_failed = select_failed;
1808 if (errno != accept_retry_errno ||
1809 select_failed != accept_retry_select_failed ||
1810 accept_retry_count >= 50)
1812 log_write(0, LOG_MAIN | ((accept_retry_count >= 50)? LOG_PANIC : 0),
1813 "%d %s() failure%s: %s",
1815 accept_retry_select_failed? "select" : "accept",
1816 (accept_retry_count == 1)? "" : "s",
1817 strerror(accept_retry_errno));
1819 accept_retry_count = 0;
1820 accept_retry_errno = errno;
1821 accept_retry_select_failed = select_failed;
1824 accept_retry_count++;
1829 if (accept_retry_count > 0)
1831 log_write(0, LOG_MAIN, "%d %s() failure%s: %s",
1833 accept_retry_select_failed? "select" : "accept",
1834 (accept_retry_count == 1)? "" : "s",
1835 strerror(accept_retry_errno));
1837 accept_retry_count = 0;
1841 /* If select/accept succeeded, deal with the connection. */
1843 if (accept_socket >= 0)
1844 handle_smtp_call(listen_sockets, listen_socket_count, accept_socket,
1845 (struct sockaddr *)&accepted);
1849 /* If not listening, then just sleep for the queue interval. If we woke
1850 up early the last time for some other signal, it won't matter because
1851 the alarm signal will wake at the right time. This code originally used
1852 sleep() but it turns out that on the FreeBSD system, sleep() is not inter-
1853 rupted by signals, so it wasn't waking up for SIGALRM or SIGCHLD. Luckily
1854 select() can be used as an interruptible sleep() on all versions of Unix. */
1859 tv.tv_sec = queue_interval;
1861 select(0, NULL, NULL, NULL, &tv);
1862 handle_ending_processes();
1865 /* Re-enable the SIGCHLD handler if it has been run. It can't do it
1866 for itself, because it isn't doing the waiting itself. */
1870 sigchld_seen = FALSE;
1871 os_non_restarting_signal(SIGCHLD, main_sigchld_handler);
1874 /* Handle being woken by SIGHUP. We know at this point that the result
1875 of accept() has been dealt with, so we can re-exec exim safely, first
1876 closing the listening sockets so that they can be reused. Cancel any pending
1877 alarm in case it is just about to go off, and set SIGHUP to be ignored so
1878 that another HUP in quick succession doesn't clobber the new daemon before it
1879 gets going. All log files get closed by the close-on-exec flag; however, if
1880 the exec fails, we need to close the logs. */
1885 log_write(0, LOG_MAIN, "pid %d: SIGHUP received: re-exec daemon",
1887 for (sk = 0; sk < listen_socket_count; sk++)
1888 (void)close(listen_sockets[sk]);
1890 signal(SIGHUP, SIG_IGN);
1891 sighup_argv[0] = exim_path;
1893 execv(CS exim_path, (char *const *)sighup_argv);
1894 log_write(0, LOG_MAIN|LOG_PANIC_DIE, "pid %d: exec of %s failed: %s",
1895 getpid(), exim_path, strerror(errno));
1899 } /* End of main loop */
1901 /* Control never reaches here */
1904 /* End of exim_daemon.c */