path: root/src/qmgr/qmgr.c

/*++
/* NAME
/*	qmgr 8
/* SUMMARY
/*	Postfix queue manager
/* SYNOPSIS
/*	\fBqmgr\fR [generic Postfix daemon options]
/* DESCRIPTION
/*	The \fBqmgr\fR(8) daemon awaits the arrival of incoming mail
/*	and arranges for its delivery via Postfix delivery processes.
/*	The actual mail routing strategy is delegated to the
/*	\fBtrivial-rewrite\fR(8) daemon.
/*	This program expects to be run from the \fBmaster\fR(8) process
/*	manager.
/*
/*	Mail addressed to the local \fBdouble-bounce\fR address is
/*	logged and discarded.  This stops potential loops caused by
/*	undeliverable bounce notifications.
/* MAIL QUEUES
/* .ad
/* .fi
/*	The \fBqmgr\fR(8) daemon maintains the following queues:
/* .IP \fBincoming\fR
/*	Inbound mail from the network, or mail picked up by the
/*	local \fBpickup\fR(8) daemon from the \fBmaildrop\fR directory.
/* .IP \fBactive\fR
/*	Messages that the queue manager has opened for delivery. Only
/*	a limited number of messages is allowed to enter the \fBactive\fR
/*	queue (leaky bucket strategy, for a fixed delivery rate).
/* .IP \fBdeferred\fR
/*	Mail that could not be delivered upon the first attempt. The queue
/*	manager implements exponential backoff by doubling the time between
/*	delivery attempts.
/* .IP \fBcorrupt\fR
/*	Unreadable or damaged queue files are moved here for inspection.
/* .IP \fBhold\fR
/*	Messages that are kept "on hold" are kept here until someone
/*	sets them free.
/* DELIVERY STATUS REPORTS
/* .ad
/* .fi
/*	The \fBqmgr\fR(8) daemon keeps an eye on per-message delivery status
/*	reports in the following directories. Each status report file has
/*	the same name as the corresponding message file:
/* .IP \fBbounce\fR
/*	Per-recipient status information about why mail is bounced.
/*	These files are maintained by the \fBbounce\fR(8) daemon.
/* .IP \fBdefer\fR
/*	Per-recipient status information about why mail is delayed.
/*	These files are maintained by the \fBdefer\fR(8) daemon.
/* .IP \fBtrace\fR
/*	Per-recipient status information as requested with the
/*	Postfix "\fBsendmail -v\fR" or "\fBsendmail -bv\fR" command.
/*	These files are maintained by the \fBtrace\fR(8) daemon.
/* .PP
/*	The \fBqmgr\fR(8) daemon is responsible for asking the
/*	\fBbounce\fR(8), \fBdefer\fR(8) or \fBtrace\fR(8) daemons to
/*	send delivery reports.
/* STRATEGIES
/* .ad
/* .fi
/*	The queue manager implements a variety of strategies for
/*	either opening queue files (input) or for message delivery (output).
/* .IP "\fBleaky bucket\fR"
/*	This strategy limits the number of messages in the \fBactive\fR queue
/*	and prevents the queue manager from running out of memory under
/*	heavy load.
/* .IP \fBfairness\fR
/*	When the \fBactive\fR queue has room, the queue manager takes one
/*	message from the \fBincoming\fR queue and one from the \fBdeferred\fR
/*	queue. This prevents a large mail backlog from blocking the delivery
/*	of new mail.
/* .IP "\fBslow start\fR"
/*	This strategy eliminates "thundering herd" problems by slowly
/*	adjusting the number of parallel deliveries to the same destination.
/* .IP "\fBround robin\fR"
/*	The queue manager sorts delivery requests by destination.
/*	Round-robin selection prevents one destination from dominating
/*	deliveries to other destinations.
/* .IP "\fBexponential backoff\fR"
/*	Mail that cannot be delivered upon the first attempt is deferred.
/*	The time interval between delivery attempts is doubled after each
/*	attempt.
/* .IP "\fBdestination status cache\fR"
/*	The queue manager avoids unnecessary delivery attempts by
/*	maintaining a short-term, in-memory list of unreachable destinations.
/* .IP "\fBpreemptive message scheduling\fR"
/*	The queue manager attempts to minimize the average per-recipient delay
/*	while still preserving the correct per-message delays, using
/*	a sophisticated preemptive message scheduling.
/* TRIGGERS
/* .ad
/* .fi
/*	On an idle system, the queue manager waits for the arrival of
/*	trigger events, or it waits for a timer to go off. A trigger
/*	is a one-byte message.
/*	Depending on the message received, the queue manager performs
/*	one of the following actions (the message is followed by the
/*	symbolic constant used internally by the software):
/* .IP "\fBD (QMGR_REQ_SCAN_DEFERRED)\fR"
/*	Start a deferred queue scan.  If a deferred queue scan is already
/*	in progress, that scan will be restarted as soon as it finishes.
/* .IP "\fBI (QMGR_REQ_SCAN_INCOMING)\fR"
/*	Start an incoming queue scan. If an incoming queue scan is already
/*	in progress, that scan will be restarted as soon as it finishes.
/* .IP "\fBA (QMGR_REQ_SCAN_ALL)\fR"
/*	Ignore deferred queue file time stamps. The request affects
/*	the next deferred queue scan.
/* .IP "\fBF (QMGR_REQ_FLUSH_DEAD)\fR"
/*	Purge all information about dead transports and destinations.
/* .IP "\fBW (TRIGGER_REQ_WAKEUP)\fR"
/*	Wakeup call, This is used by the master server to instantiate
/*	servers that should not go away forever. The action is to start
/*	an incoming queue scan.
/* .PP
/*	The \fBqmgr\fR(8) daemon reads an entire buffer worth of triggers.
/*	Multiple identical trigger requests are collapsed into one, and
/*	trigger requests are sorted so that \fBA\fR and \fBF\fR precede
/*	\fBD\fR and \fBI\fR. Thus, in order to force a deferred queue run,
/*	one would request \fBA F D\fR; in order to notify the queue manager
/*	of the arrival of new mail one would request \fBI\fR.
/* STANDARDS
/*	RFC 3463 (Enhanced status codes)
/*	RFC 3464 (Delivery status notifications)
/* SECURITY
/* .ad
/* .fi
/*	The \fBqmgr\fR(8) daemon is not security sensitive. It reads
/*	single-character messages from untrusted local users, and thus may
/*	be susceptible to denial of service attacks. The \fBqmgr\fR(8) daemon
/*	does not talk to the outside world, and it can be run at fixed low
/*	privilege in a chrooted environment.
/* DIAGNOSTICS
/*	Problems and transactions are logged to \fBsyslogd\fR(8)
/*	or \fBpostlogd\fR(8).
/*	Corrupted message files are saved to the \fBcorrupt\fR queue
/*	for further inspection.
/*
/*	Depending on the setting of the \fBnotify_classes\fR parameter,
/*	the postmaster is notified of bounces and of other trouble.
/* BUGS
/*	A single queue manager process has to compete for disk access with
/*	multiple front-end processes such as \fBcleanup\fR(8). A sudden burst of
/*	inbound mail can negatively impact outbound delivery rates.
/* CONFIGURATION PARAMETERS
/* .ad
/* .fi
/*	Changes to \fBmain.cf\fR are not picked up automatically
/*	as \fBqmgr\fR(8)
/*	is a persistent process. Use the "\fBpostfix reload\fR" command after
/*	a configuration change.
/*
/*	The text below provides only a parameter summary. See
/*	\fBpostconf\fR(5) for more details including examples.
/*
/*	In the text below, \fItransport\fR is the first field in a
/*	\fBmaster.cf\fR entry.
/* COMPATIBILITY CONTROLS
/* .ad
/* .fi
/*	Available before Postfix version 2.5:
/* .IP "\fBallow_min_user (no)\fR"
/*	Allow a sender or recipient address to have `-' as the first
/*	character.
/* .PP
/*	Available with Postfix version 2.7 and later:
/* .IP "\fBdefault_filter_nexthop (empty)\fR"
/*	When a content_filter or FILTER request specifies no explicit
/*	next-hop destination, use $default_filter_nexthop instead; when
/*	that value is empty, use the domain in the recipient address.
/* ACTIVE QUEUE CONTROLS
/* .ad
/* .fi
/* .IP "\fBqmgr_clog_warn_time (300s)\fR"
/*	The minimal delay between warnings that a specific destination is
/*	clogging up the Postfix active queue.
/* .IP "\fBqmgr_message_active_limit (20000)\fR"
/*	The maximal number of messages in the active queue.
/* .IP "\fBqmgr_message_recipient_limit (20000)\fR"
/*	The maximal number of recipients held in memory by the Postfix
/*	queue manager, and the maximal size of the short-term,
/*	in-memory "dead" destination status cache.
/* .IP "\fBqmgr_message_recipient_minimum (10)\fR"
/*	The minimal number of in-memory recipients for any message.
/* .IP "\fBdefault_recipient_limit (20000)\fR"
/*	The default per-transport upper limit on the number of in-memory
/*	recipients.
/* .IP "\fBtransport_recipient_limit ($default_recipient_limit)\fR"
/*	A transport-specific override for the default_recipient_limit
/*	parameter value, where \fItransport\fR is the master.cf name of
/*	the message delivery transport.
/* .IP "\fBdefault_extra_recipient_limit (1000)\fR"
/*	The default value for the extra per-transport limit imposed on the
/*	number of in-memory recipients.
/* .IP "\fBtransport_extra_recipient_limit ($default_extra_recipient_limit)\fR"
/*	A transport-specific override for the default_extra_recipient_limit
/*	parameter value, where \fItransport\fR is the master.cf name of
/*	the message delivery transport.
/* .PP
/*	Available in Postfix version 2.4 and later:
/* .IP "\fBdefault_recipient_refill_limit (100)\fR"
/*	The default per-transport limit on the number of recipients refilled at
/*	once.
/* .IP "\fBtransport_recipient_refill_limit ($default_recipient_refill_limit)\fR"
/*	A transport-specific override for the default_recipient_refill_limit
/*	parameter value, where \fItransport\fR is the master.cf name of
/*	the message delivery transport.
/* .IP "\fBdefault_recipient_refill_delay (5s)\fR"
/*	The default per-transport maximum delay between recipients refills.
/* .IP "\fBtransport_recipient_refill_delay ($default_recipient_refill_delay)\fR"
/*	A transport-specific override for the default_recipient_refill_delay
/*	parameter value, where \fItransport\fR is the master.cf name of
/*	the message delivery transport.
/* DELIVERY CONCURRENCY CONTROLS
/* .ad
/* .fi
/* .IP "\fBinitial_destination_concurrency (5)\fR"
/*	The initial per-destination concurrency level for parallel delivery
/*	to the same destination.
/* .IP "\fBdefault_destination_concurrency_limit (20)\fR"
/*	The default maximal number of parallel deliveries to the same
/*	destination.
/* .IP "\fBtransport_destination_concurrency_limit ($default_destination_concurrency_limit)\fR"
/*	A transport-specific override for the
/*	default_destination_concurrency_limit parameter value, where
/*	\fItransport\fR is the master.cf name of the message delivery
/*	transport.
/* .PP
/*	Available in Postfix version 2.5 and later:
/* .IP "\fBtransport_initial_destination_concurrency ($initial_destination_concurrency)\fR"
/*	A transport-specific override for the initial_destination_concurrency
/*	parameter value, where \fItransport\fR is the master.cf name of
/*	the message delivery transport.
/* .IP "\fBdefault_destination_concurrency_failed_cohort_limit (1)\fR"
/*	How many pseudo-cohorts must suffer connection or handshake
/*	failure before a specific destination is considered unavailable
/*	(and further delivery is suspended).
/* .IP "\fBtransport_destination_concurrency_failed_cohort_limit ($default_destination_concurrency_failed_cohort_limit)\fR"
/*	A transport-specific override for the
/*	default_destination_concurrency_failed_cohort_limit parameter value,
/*	where \fItransport\fR is the master.cf name of the message delivery
/*	transport.
/* .IP "\fBdefault_destination_concurrency_negative_feedback (1)\fR"
/*	The per-destination amount of delivery concurrency negative
/*	feedback, after a delivery completes with a connection or handshake
/*	failure.
/* .IP "\fBtransport_destination_concurrency_negative_feedback ($default_destination_concurrency_negative_feedback)\fR"
/*	A transport-specific override for the
/*	default_destination_concurrency_negative_feedback parameter value,
/*	where \fItransport\fR is the master.cf name of the message delivery
/*	transport.
/* .IP "\fBdefault_destination_concurrency_positive_feedback (1)\fR"
/*	The per-destination amount of delivery concurrency positive
/*	feedback, after a delivery completes without connection or handshake
/*	failure.
/* .IP "\fBtransport_destination_concurrency_positive_feedback ($default_destination_concurrency_positive_feedback)\fR"
/*	A transport-specific override for the
/*	default_destination_concurrency_positive_feedback parameter value,
/*	where \fItransport\fR is the master.cf name of the message delivery
/*	transport.
/* .IP "\fBdestination_concurrency_feedback_debug (no)\fR"
/*	Make the queue manager's feedback algorithm verbose for performance
/*	analysis purposes.
/* RECIPIENT SCHEDULING CONTROLS
/* .ad
/* .fi
/* .IP "\fBdefault_destination_recipient_limit (50)\fR"
/*	The default maximal number of recipients per message delivery.
/* .IP "\fBtransport_destination_recipient_limit ($default_destination_recipient_limit)\fR"
/*	A transport-specific override for the
/*	default_destination_recipient_limit parameter value, where
/*	\fItransport\fR is the master.cf name of the message delivery
/*	transport.
/* MESSAGE SCHEDULING CONTROLS
/* .ad
/* .fi
/* .IP "\fBdefault_delivery_slot_cost (5)\fR"
/*	How often the Postfix queue manager's scheduler is allowed to
/*	preempt delivery of one message with another.
/* .IP "\fBtransport_delivery_slot_cost ($default_delivery_slot_cost)\fR"
/*	A transport-specific override for the default_delivery_slot_cost
/*	parameter value, where \fItransport\fR is the master.cf name of
/*	the message delivery transport.
/* .IP "\fBdefault_minimum_delivery_slots (3)\fR"
/*	How many recipients a message must have in order to invoke the
/*	Postfix queue manager's scheduling algorithm at all.
/* .IP "\fBtransport_minimum_delivery_slots ($default_minimum_delivery_slots)\fR"
/*	A transport-specific override for the default_minimum_delivery_slots
/*	parameter value, where \fItransport\fR is the master.cf name of
/*	the message delivery transport.
/* .IP "\fBdefault_delivery_slot_discount (50)\fR"
/*	The default value for transport-specific _delivery_slot_discount
/*	settings.
/* .IP "\fBtransport_delivery_slot_discount ($default_delivery_slot_discount)\fR"
/*	A transport-specific override for the default_delivery_slot_discount
/*	parameter value, where \fItransport\fR is the master.cf name of
/*	the message delivery transport.
/* .IP "\fBdefault_delivery_slot_loan (3)\fR"
/*	The default value for transport-specific _delivery_slot_loan
/*	settings.
/* .IP "\fBtransport_delivery_slot_loan ($default_delivery_slot_loan)\fR"
/*	A transport-specific override for the default_delivery_slot_loan
/*	parameter value, where \fItransport\fR is the master.cf name of
/*	the message delivery transport.
/* OTHER RESOURCE AND RATE CONTROLS
/* .ad
/* .fi
/* .IP "\fBminimal_backoff_time (300s)\fR"
/*	The minimal time between attempts to deliver a deferred message;
/*	prior to Postfix 2.4 the default value was 1000s.
/* .IP "\fBmaximal_backoff_time (4000s)\fR"
/*	The maximal time between attempts to deliver a deferred message.
/* .IP "\fBmaximal_queue_lifetime (5d)\fR"
/*	Consider a message as undeliverable, when delivery fails with a
/*	temporary error, and the time in the queue has reached the
/*	maximal_queue_lifetime limit.
/* .IP "\fBqueue_run_delay (300s)\fR"
/*	The time between deferred queue scans by the queue manager;
/*	prior to Postfix 2.4 the default value was 1000s.
/* .IP "\fBtransport_retry_time (60s)\fR"
/*	The time between attempts by the Postfix queue manager to contact
/*	a malfunctioning message delivery transport.
/* .PP
/*	Available in Postfix version 2.1 and later:
/* .IP "\fBbounce_queue_lifetime (5d)\fR"
/*	Consider a bounce message as undeliverable, when delivery fails
/*	with a temporary error, and the time in the queue has reached the
/*	bounce_queue_lifetime limit.
/* .PP
/*	Available in Postfix version 2.5 and later:
/* .IP "\fBdefault_destination_rate_delay (0s)\fR"
/*	The default amount of delay that is inserted between individual
/*	message deliveries to the same destination and over the same message
/*	delivery transport.
/* .IP "\fBtransport_destination_rate_delay ($default_destination_rate_delay)\fR"
/*	A transport-specific override for the default_destination_rate_delay
/*	parameter value, where \fItransport\fR is the master.cf name of
/*	the message delivery transport.
/* .PP
/*	Available in Postfix version 3.1 and later:
/* .IP "\fBdefault_transport_rate_delay (0s)\fR"
/*	The default amount of delay that is inserted between individual
/*	message deliveries over the same message delivery transport,
/*	regardless of destination.
/* .IP "\fBtransport_transport_rate_delay ($default_transport_rate_delay)\fR"
/*	A transport-specific override for the default_transport_rate_delay
/*	parameter value, where the initial \fItransport\fR in the parameter
/*	name is the master.cf name of the message delivery transport.
/* SAFETY CONTROLS
/* .ad
/* .fi
/* .IP "\fBqmgr_daemon_timeout (1000s)\fR"
/*	How much time a Postfix queue manager process may take to handle
/*	a request before it is terminated by a built-in watchdog timer.
/* .IP "\fBqmgr_ipc_timeout (60s)\fR"
/*	The time limit for the queue manager to send or receive information
/*	over an internal communication channel.
/* .PP
/*	Available in Postfix version 3.1 and later:
/* .IP "\fBaddress_verify_pending_request_limit (see 'postconf -d' output)\fR"
/*	A safety limit that prevents address verification requests from
/*	overwhelming the Postfix queue.
/* MISCELLANEOUS CONTROLS
/* .ad
/* .fi
/* .IP "\fBconfig_directory (see 'postconf -d' output)\fR"
/*	The default location of the Postfix main.cf and master.cf
/*	configuration files.
/* .IP "\fBdefer_transports (empty)\fR"
/*	The names of message delivery transports that should not deliver mail
/*	unless someone issues "\fBsendmail -q\fR" or equivalent.
/* .IP "\fBdelay_logging_resolution_limit (2)\fR"
/*	The maximal number of digits after the decimal point when logging
/*	sub-second delay values.
/* .IP "\fBhelpful_warnings (yes)\fR"
/*	Log warnings about problematic configuration settings, and provide
/*	helpful suggestions.
/* .IP "\fBprocess_id (read-only)\fR"
/*	The process ID of a Postfix command or daemon process.
/* .IP "\fBprocess_name (read-only)\fR"
/*	The process name of a Postfix command or daemon process.
/* .IP "\fBqueue_directory (see 'postconf -d' output)\fR"
/*	The location of the Postfix top-level queue directory.
/* .IP "\fBsyslog_facility (mail)\fR"
/*	The syslog facility of Postfix logging.
/* .IP "\fBsyslog_name (see 'postconf -d' output)\fR"
/*	A prefix that is prepended to the process name in syslog
/*	records, so that, for example, "smtpd" becomes "prefix/smtpd".
/* .PP
/*	Available in Postfix version 3.0 and later:
/* .IP "\fBconfirm_delay_cleared (no)\fR"
/*	After sending a "your message is delayed" notification, inform
/*	the sender when the delay clears up.
/* .PP
/*	Available in Postfix 3.3 and later:
/* .IP "\fBservice_name (read-only)\fR"
/*	The master.cf service name of a Postfix daemon process.
/* .PP
/*	Available in Postfix 3.5 and later:
/* .IP "\fBinfo_log_address_format (external)\fR"
/*	The email address form that will be used in non-debug logging
/*	(info, warning, etc.).
/* FILES
/*	/var/spool/postfix/incoming, incoming queue
/*	/var/spool/postfix/active, active queue
/*	/var/spool/postfix/deferred, deferred queue
/*	/var/spool/postfix/bounce, non-delivery status
/*	/var/spool/postfix/defer, non-delivery status
/*	/var/spool/postfix/trace, delivery status
/* SEE ALSO
/*	trivial-rewrite(8), address routing
/*	bounce(8), delivery status reports
/*	postconf(5), configuration parameters
/*	master(5), generic daemon options
/*	master(8), process manager
/*	postlogd(8), Postfix logging
/*	syslogd(8), system logging
/* README FILES
/* .ad
/* .fi
/*	Use "\fBpostconf readme_directory\fR" or
/*	"\fBpostconf html_directory\fR" to locate this information.
/* .na
/* .nf
/*	SCHEDULER_README, scheduling algorithm
/*	QSHAPE_README, Postfix queue analysis
/* LICENSE
/* .ad
/* .fi
/*	The Secure Mailer license must be distributed with this software.
/* AUTHOR(S)
/*	Wietse Venema
/*	IBM T.J. Watson Research
/*	P.O. Box 704
/*	Yorktown Heights, NY 10598, USA
/*
/*	Preemptive scheduler enhancements:
/*	Patrik Rak
/*	Modra 6
/*	155 00, Prague, Czech Republic
/*
/*	Wietse Venema
/*	Google, Inc.
/*	111 8th Avenue
/*	New York, NY 10011, USA
/*--*/

/* System library. */

#include <sys_defs.h>
#include <stdlib.h>
#include <unistd.h>
#include <ctype.h>

/* Utility library. */

#include <msg.h>
#include <events.h>
#include <vstream.h>
#include <dict.h>

/* Global library. */

#include <mail_queue.h>
#include <recipient_list.h>
#include <mail_conf.h>
#include <mail_params.h>
#include <mail_version.h>
#include <mail_proto.h>			/* QMGR_SCAN constants */
#include <mail_flow.h>
#include <flush_clnt.h>

/* Master process interface */

#include <master_proto.h>
#include <mail_server.h>

/* Application-specific. */

#include "qmgr.h"

 /*
  * Tunables.
  */
int     var_queue_run_delay;
int     var_min_backoff_time;
int     var_max_backoff_time;
int     var_max_queue_time;
int     var_dsn_queue_time;
int     var_qmgr_active_limit;
int     var_qmgr_rcpt_limit;
int     var_qmgr_msg_rcpt_limit;
int     var_xport_rcpt_limit;
int     var_stack_rcpt_limit;
int     var_xport_refill_limit;
int     var_xport_refill_delay;
int     var_delivery_slot_cost;
int     var_delivery_slot_loan;
int     var_delivery_slot_discount;
int     var_min_delivery_slots;
int     var_init_dest_concurrency;
int     var_transport_retry_time;
int     var_dest_con_limit;
int     var_dest_rcpt_limit;
char   *var_defer_xports;
int     var_local_con_lim;
int     var_local_rcpt_lim;
bool    var_verp_bounce_off;
int     var_qmgr_clog_warn_time;
char   *var_conc_pos_feedback;
char   *var_conc_neg_feedback;
int     var_conc_cohort_limit;
int     var_conc_feedback_debug;
int     var_xport_rate_delay;
int     var_dest_rate_delay;
char   *var_def_filter_nexthop;
int     var_qmgr_daemon_timeout;
int     var_qmgr_ipc_timeout;
int     var_dsn_delay_cleared;
int     var_vrfy_pend_limit;

static QMGR_SCAN *qmgr_scans[2];

#define QMGR_SCAN_IDX_INCOMING 0
#define QMGR_SCAN_IDX_DEFERRED 1
#define QMGR_SCAN_IDX_COUNT (sizeof(qmgr_scans) / sizeof(qmgr_scans[0]))

/* qmgr_deferred_run_event - queue manager heartbeat */

static void qmgr_deferred_run_event(int unused_event, void *dummy)
{

    /*
     * This routine runs when it is time for another deferred queue scan.
     * Make sure this routine gets called again in the future.
     */
    qmgr_scan_request(qmgr_scans[QMGR_SCAN_IDX_DEFERRED], QMGR_SCAN_START);
    event_request_timer(qmgr_deferred_run_event, dummy, var_queue_run_delay);
}

/* qmgr_trigger_event - respond to external trigger(s) */

static void qmgr_trigger_event(char *buf, ssize_t len,
			               char *unused_service, char **argv)
{
    int     incoming_flag = 0;
    int     deferred_flag = 0;
    int     i;

    /*
     * Sanity check. This service takes no command-line arguments.
     */
    if (argv[0])
	msg_fatal("unexpected command-line argument: %s", argv[0]);

    /*
     * Collapse identical requests that have arrived since we looked last
     * time. There is no client feedback so there is no need to process each
     * request in order. And as long as we don't have conflicting requests we
     * are free to sort them into the most suitable order.
     */
#define QMGR_FLUSH_BEFORE	(QMGR_FLUSH_ONCE | QMGR_FLUSH_DFXP)

    for (i = 0; i < len; i++) {
	if (msg_verbose)
	    msg_info("request: %d (%c)",
		     buf[i], ISALNUM(buf[i]) ? buf[i] : '?');
	switch (buf[i]) {
	case TRIGGER_REQ_WAKEUP:
	case QMGR_REQ_SCAN_INCOMING:
	    incoming_flag |= QMGR_SCAN_START;
	    break;
	case QMGR_REQ_SCAN_DEFERRED:
	    deferred_flag |= QMGR_SCAN_START;
	    break;
	case QMGR_REQ_FLUSH_DEAD:
	    deferred_flag |= QMGR_FLUSH_BEFORE;
	    incoming_flag |= QMGR_FLUSH_BEFORE;
	    break;
	case QMGR_REQ_SCAN_ALL:
	    deferred_flag |= QMGR_SCAN_ALL;
	    incoming_flag |= QMGR_SCAN_ALL;
	    break;
	default:
	    if (msg_verbose)
		msg_info("request ignored");
	    break;
	}
    }

    /*
     * Process each request type at most once. Modifiers take effect upon the
     * next queue run. If no queue run is in progress, and a queue scan is
     * requested, the request takes effect immediately.
     */
    if (incoming_flag != 0)
	qmgr_scan_request(qmgr_scans[QMGR_SCAN_IDX_INCOMING], incoming_flag);
    if (deferred_flag != 0)
	qmgr_scan_request(qmgr_scans[QMGR_SCAN_IDX_DEFERRED], deferred_flag);
}

/* qmgr_loop - queue manager main loop */

static int qmgr_loop(char *unused_name, char **unused_argv)
{
    char   *path;
    ssize_t token_count;
    int     feed = 0;
    int     scan_idx;			/* Priority order scan index */
    static int first_scan_idx = QMGR_SCAN_IDX_INCOMING;
    int     last_scan_idx = QMGR_SCAN_IDX_COUNT - 1;
    int     delay;

    /*
     * This routine runs as part of the event handling loop, after the event
     * manager has delivered a timer or I/O event (including the completion
     * of a connection to a delivery process), or after it has waited for a
     * specified amount of time. The result value of qmgr_loop() specifies
     * how long the event manager should wait for the next event.
     */
#define DONT_WAIT	0
#define WAIT_FOR_EVENT	(-1)

    /*
     * Attempt to drain the active queue by allocating a suitable delivery
     * process and by delivering mail via it. Delivery process allocation and
     * mail delivery are asynchronous.
     */
    qmgr_active_drain();

    /*
     * Let some new blood into the active queue when the queue size is
     * smaller than some configurable limit.
     * 
     * We import one message per interrupt, to optimally tune the input count
     * for the number of delivery agent protocol wait states, as explained in
     * qmgr_transport.c.
     */
    delay = WAIT_FOR_EVENT;
    for (scan_idx = 0; qmgr_message_count < var_qmgr_active_limit
	 && scan_idx < QMGR_SCAN_IDX_COUNT; ++scan_idx) {
	last_scan_idx = (scan_idx + first_scan_idx) % QMGR_SCAN_IDX_COUNT;
	if ((path = qmgr_scan_next(qmgr_scans[last_scan_idx])) != 0) {
	    delay = DONT_WAIT;
	    if ((feed = qmgr_active_feed(qmgr_scans[last_scan_idx], path)) != 0)
		break;
	}
    }

    /*
     * Round-robin the queue scans. When the active queue becomes full,
     * prefer new mail over deferred mail.
     */
    if (qmgr_message_count < var_qmgr_active_limit) {
	first_scan_idx = (last_scan_idx + 1) % QMGR_SCAN_IDX_COUNT;
    } else if (first_scan_idx != QMGR_SCAN_IDX_INCOMING) {
	first_scan_idx = QMGR_SCAN_IDX_INCOMING;
    }

    /*
     * Global flow control. If enabled, slow down receiving processes that
     * get ahead of the queue manager, but don't block them completely.
     */
    if (var_in_flow_delay > 0) {
	token_count = mail_flow_count();
	if (token_count < var_proc_limit) {
	    if (feed != 0 && last_scan_idx == QMGR_SCAN_IDX_INCOMING)
		mail_flow_put(1);
	    else if (qmgr_scans[QMGR_SCAN_IDX_INCOMING]->handle == 0)
		mail_flow_put(var_proc_limit - token_count);
	} else if (token_count > var_proc_limit) {
	    mail_flow_get(token_count - var_proc_limit);
	}
    }
    return (delay);
}

/* pre_accept - see if tables have changed */

static void pre_accept(char *unused_name, char **unused_argv)
{
    const char *table;

    if ((table = dict_changed_name()) != 0) {
	msg_info("table %s has changed -- restarting", table);
	exit(0);
    }
}

/* qmgr_pre_init - pre-jail initialization */

static void qmgr_pre_init(char *unused_name, char **unused_argv)
{
    flush_init();
}

/* qmgr_post_init - post-jail initialization */

static void qmgr_post_init(char *name, char **unused_argv)
{

    /*
     * Backwards compatibility.
     */
    if (strcmp(var_procname, "nqmgr") == 0) {
	msg_warn("please update the %s/%s file; the new queue manager",
		 var_config_dir, MASTER_CONF_FILE);
	msg_warn("(old name: nqmgr) has become the standard queue manager (new name: qmgr)");
	msg_warn("support for the name old name (nqmgr) will be removed from Postfix");
    }

    /*
     * Sanity check.
     */
    if (var_qmgr_rcpt_limit < var_qmgr_active_limit) {
	msg_warn("%s is smaller than %s - adjusting %s",
	      VAR_QMGR_RCPT_LIMIT, VAR_QMGR_ACT_LIMIT, VAR_QMGR_RCPT_LIMIT);
	var_qmgr_rcpt_limit = var_qmgr_active_limit;
    }
    if (var_dsn_queue_time > var_max_queue_time) {
	msg_warn("%s is larger than %s - adjusting %s",
		 VAR_DSN_QUEUE_TIME, VAR_MAX_QUEUE_TIME, VAR_DSN_QUEUE_TIME);
	var_dsn_queue_time = var_max_queue_time;
    }

    /*
     * This routine runs after the skeleton code has entered the chroot jail.
     * Prevent automatic process suicide after a limited number of client
     * requests or after a limited amount of idle time. Move any left-over
     * entries from the active queue to the incoming queue, and give them a
     * time stamp into the future, in order to allow ongoing deliveries to
     * finish first. Start scanning the incoming and deferred queues.
     * Left-over active queue entries are moved to the incoming queue because
     * the incoming queue has priority; moving left-overs to the deferred
     * queue could cause anomalous delays when "postfix reload/start" are
     * issued often. Override the IPC timeout (default 3600s) so that the
     * queue manager can reset a broken IPC channel before the watchdog timer
     * goes off.
     */
    var_ipc_timeout = var_qmgr_ipc_timeout;
    var_use_limit = 0;
    var_idle_limit = 0;
    qmgr_move(MAIL_QUEUE_ACTIVE, MAIL_QUEUE_INCOMING, event_time());
    qmgr_scans[QMGR_SCAN_IDX_INCOMING] = qmgr_scan_create(MAIL_QUEUE_INCOMING);
    qmgr_scans[QMGR_SCAN_IDX_DEFERRED] = qmgr_scan_create(MAIL_QUEUE_DEFERRED);
    qmgr_scan_request(qmgr_scans[QMGR_SCAN_IDX_INCOMING], QMGR_SCAN_START);
    qmgr_deferred_run_event(0, (void *) 0);
}

MAIL_VERSION_STAMP_DECLARE;

/* main - the main program */

int     main(int argc, char **argv)
{
    static const CONFIG_STR_TABLE str_table[] = {
	VAR_DEFER_XPORTS, DEF_DEFER_XPORTS, &var_defer_xports, 0, 0,
	VAR_CONC_POS_FDBACK, DEF_CONC_POS_FDBACK, &var_conc_pos_feedback, 1, 0,
	VAR_CONC_NEG_FDBACK, DEF_CONC_NEG_FDBACK, &var_conc_neg_feedback, 1, 0,
	VAR_DEF_FILTER_NEXTHOP, DEF_DEF_FILTER_NEXTHOP, &var_def_filter_nexthop, 0, 0,
	0,
    };
    static const CONFIG_TIME_TABLE time_table[] = {
	VAR_QUEUE_RUN_DELAY, DEF_QUEUE_RUN_DELAY, &var_queue_run_delay, 1, 0,
	VAR_MIN_BACKOFF_TIME, DEF_MIN_BACKOFF_TIME, &var_min_backoff_time, 1, 0,
	VAR_MAX_BACKOFF_TIME, DEF_MAX_BACKOFF_TIME, &var_max_backoff_time, 1, 0,
	VAR_MAX_QUEUE_TIME, DEF_MAX_QUEUE_TIME, &var_max_queue_time, 0, 8640000,
	VAR_DSN_QUEUE_TIME, DEF_DSN_QUEUE_TIME, &var_dsn_queue_time, 0, 8640000,
	VAR_XPORT_RETRY_TIME, DEF_XPORT_RETRY_TIME, &var_transport_retry_time, 1, 0,
	VAR_QMGR_CLOG_WARN_TIME, DEF_QMGR_CLOG_WARN_TIME, &var_qmgr_clog_warn_time, 0, 0,
	VAR_XPORT_REFILL_DELAY, DEF_XPORT_REFILL_DELAY, &var_xport_refill_delay, 1, 0,
	VAR_XPORT_RATE_DELAY, DEF_XPORT_RATE_DELAY, &var_xport_rate_delay, 0, 0,
	VAR_DEST_RATE_DELAY, DEF_DEST_RATE_DELAY, &var_dest_rate_delay, 0, 0,
	VAR_QMGR_DAEMON_TIMEOUT, DEF_QMGR_DAEMON_TIMEOUT, &var_qmgr_daemon_timeout, 1, 0,
	VAR_QMGR_IPC_TIMEOUT, DEF_QMGR_IPC_TIMEOUT, &var_qmgr_ipc_timeout, 1, 0,
	0,
    };
    static const CONFIG_INT_TABLE int_table[] = {
	VAR_QMGR_ACT_LIMIT, DEF_QMGR_ACT_LIMIT, &var_qmgr_active_limit, 1, 0,
	VAR_QMGR_RCPT_LIMIT, DEF_QMGR_RCPT_LIMIT, &var_qmgr_rcpt_limit, 1, 0,
	VAR_QMGR_MSG_RCPT_LIMIT, DEF_QMGR_MSG_RCPT_LIMIT, &var_qmgr_msg_rcpt_limit, 1, 0,
	VAR_XPORT_RCPT_LIMIT, DEF_XPORT_RCPT_LIMIT, &var_xport_rcpt_limit, 0, 0,
	VAR_STACK_RCPT_LIMIT, DEF_STACK_RCPT_LIMIT, &var_stack_rcpt_limit, 0, 0,
	VAR_XPORT_REFILL_LIMIT, DEF_XPORT_REFILL_LIMIT, &var_xport_refill_limit, 1, 0,
	VAR_DELIVERY_SLOT_COST, DEF_DELIVERY_SLOT_COST, &var_delivery_slot_cost, 0, 0,
	VAR_DELIVERY_SLOT_LOAN, DEF_DELIVERY_SLOT_LOAN, &var_delivery_slot_loan, 0, 0,
	VAR_DELIVERY_SLOT_DISCOUNT, DEF_DELIVERY_SLOT_DISCOUNT, &var_delivery_slot_discount, 0, 100,
	VAR_MIN_DELIVERY_SLOTS, DEF_MIN_DELIVERY_SLOTS, &var_min_delivery_slots, 0, 0,
	VAR_INIT_DEST_CON, DEF_INIT_DEST_CON, &var_init_dest_concurrency, 1, 0,
	VAR_DEST_CON_LIMIT, DEF_DEST_CON_LIMIT, &var_dest_con_limit, 0, 0,
	VAR_DEST_RCPT_LIMIT, DEF_DEST_RCPT_LIMIT, &var_dest_rcpt_limit, 0, 0,
	VAR_LOCAL_RCPT_LIMIT, DEF_LOCAL_RCPT_LIMIT, &var_local_rcpt_lim, 0, 0,
	VAR_LOCAL_CON_LIMIT, DEF_LOCAL_CON_LIMIT, &var_local_con_lim, 0, 0,
	VAR_CONC_COHORT_LIM, DEF_CONC_COHORT_LIM, &var_conc_cohort_limit, 0, 0,
	VAR_VRFY_PEND_LIMIT, DEF_VRFY_PEND_LIMIT, &var_vrfy_pend_limit, 1, 0,
	0,
    };
    static const CONFIG_BOOL_TABLE bool_table[] = {
	VAR_VERP_BOUNCE_OFF, DEF_VERP_BOUNCE_OFF, &var_verp_bounce_off,
	VAR_CONC_FDBACK_DEBUG, DEF_CONC_FDBACK_DEBUG, &var_conc_feedback_debug,
	VAR_DSN_DELAY_CLEARED, DEF_DSN_DELAY_CLEARED, &var_dsn_delay_cleared,
	0,
    };

    /*
     * Fingerprint executables and core dumps.
     */
    MAIL_VERSION_STAMP_ALLOCATE;

    /*
     * Use the trigger service skeleton, because no-one else should be
     * monitoring our service port while this process runs, and because we do
     * not talk back to the client.
     */
    trigger_server_main(argc, argv, qmgr_trigger_event,
			CA_MAIL_SERVER_INT_TABLE(int_table),
			CA_MAIL_SERVER_STR_TABLE(str_table),
			CA_MAIL_SERVER_BOOL_TABLE(bool_table),
			CA_MAIL_SERVER_TIME_TABLE(time_table),
			CA_MAIL_SERVER_PRE_INIT(qmgr_pre_init),
			CA_MAIL_SERVER_POST_INIT(qmgr_post_init),
			CA_MAIL_SERVER_LOOP(qmgr_loop),
			CA_MAIL_SERVER_PRE_ACCEPT(pre_accept),
			CA_MAIL_SERVER_SOLITARY,
			CA_MAIL_SERVER_WATCHDOG(&var_qmgr_daemon_timeout),
			0);
}