Implement a feedback mechanism which allows the mta to "hold" envelopes

in the scheduler when it has too many tasks for a given relay.  The
envelopes are put on a wait queue, and are not scheduled again until
the mta "releases" some envelopes from that queue.

It prevents from having too many inflight envelopes, which are out of reach
for the admin.

1 files changed, 11 insertions, 4 deletions

diff --git a/usr.sbin/smtpd/smtpd.h b/usr.sbin/smtpd/smtpd.h
index d3ac351c284..e48e756a141 100644
--- a/usr.sbin/smtpd/smtpd.h
+++ b/usr.sbin/smtpd/smtpd.h
@@ -1,4 +1,4 @@
-/*	$OpenBSD: smtpd.h,v 1.427 2013/10/27 11:01:47 eric Exp $	*/
+/*	$OpenBSD: smtpd.h,v 1.428 2013/10/27 17:47:53 eric Exp $	*/
 
 /*
  * Copyright (c) 2008 Gilles Chehade <gilles@poolp.org>
@@ -145,12 +145,11 @@ union lookup {
 	struct addrname		 addrname;
 };
 
-/* XXX */
 /*
  * Bump IMSG_VERSION whenever a change is made to enum imsg_type.
  * This will ensure that we can never use a wrong version of smtpctl with smtpd.
  */
-#define	IMSG_VERSION		5
+#define	IMSG_VERSION		6
 
 enum imsg_type {
 	IMSG_NONE,
@@ -210,6 +209,8 @@ enum imsg_type {
 	IMSG_DELIVERY_TEMPFAIL,
 	IMSG_DELIVERY_PERMFAIL,
 	IMSG_DELIVERY_LOOP,
+	IMSG_DELIVERY_HOLD,
+	IMSG_DELIVERY_RELEASE,
 
 	IMSG_BOUNCE_INJECT,
 
@@ -226,7 +227,6 @@ enum imsg_type {
 	IMSG_MFA_EVENT_COMMIT,
 	IMSG_MFA_EVENT_ROLLBACK,
 	IMSG_MFA_EVENT_DISCONNECT,
-	IMSG_MFA_SMTP_DATA,
 	IMSG_MFA_SMTP_RESPONSE,
 
 	IMSG_MTA_TRANSFER,
@@ -677,6 +677,10 @@ struct mta_limits {
 	time_t	sessdelay_keepalive;
 
 	int	family;
+
+	int	task_hiwat;
+	int	task_lowat;
+	int	task_release;
 };
 
 struct mta_relay {
@@ -697,6 +701,7 @@ struct mta_relay {
 	char			*heloname;
 	char			*secret;
 
+	int			 state;
 	size_t			 ntask;
 	TAILQ_HEAD(, mta_task)	 tasks;
 
@@ -781,6 +786,8 @@ struct scheduler_backend {
 
 	int	(*update)(struct scheduler_info *);
 	int	(*delete)(uint64_t);
+	int	(*hold)(uint64_t, uint64_t);
+	int	(*release)(uint64_t, int);
 
 	int	(*batch)(int, struct scheduler_batch *);