From eef0aa8dfaf6928394a5465603d5390895a7e743 Mon Sep 17 00:00:00 2001
From: Wilfried Goesgens <dothebart@citadel.org>
Date: Tue, 21 Feb 2012 23:42:09 +0100
Subject: [PATCH] SMTP-Client: implement tactics not to overload our peers

  - local context overload protection: try not to exceed our session limit (not possible if more mailinglist recipients than contexts)
  - rate limiting to reduce threat on DNS and Peers
---
 citadel/modules/smtp/serv_smtpqueue.c | 57 +++++++++++++++++++++++++++
 1 file changed, 57 insertions(+)

diff --git a/citadel/modules/smtp/serv_smtpqueue.c b/citadel/modules/smtp/serv_smtpqueue.c
index 485395044..2d406f2e3 100644
--- a/citadel/modules/smtp/serv_smtpqueue.c
+++ b/citadel/modules/smtp/serv_smtpqueue.c
@@ -93,6 +93,9 @@ struct CitContext smtp_queue_CC;
 pthread_mutex_t ActiveQItemsLock;
 HashList *ActiveQItems  = NULL;
 HashList *QItemHandlers = NULL;
+int max_sessions_for_outbound_smtp = 500; /* how many sessions might be active till we stop adding more smtp jobs */
+int ndelay_count = 50; /* every n queued messages we will sleep... */
+int delay_msec = 5000; /* this many seconds. */
 
 static const long MaxRetry = SMTP_RETRY_INTERVAL * 2 * 2 * 2 * 2 * 2 * 2 * 2 * 2 * 2 * 2 * 2 * 2 * 2 * 2;
 int MsgCount            = 0;
@@ -612,6 +615,7 @@ void smtpq_do_bounce(OneQueItem *MyQItem, StrBuf *OMsgTxt)
  * Called by smtp_do_queue() to handle an individual message.
  */
 void smtp_do_procmsg(long msgnum, void *userdata) {
+	int mynumsessions = num_sessions;
 	struct CtdlMessage *msg = NULL;
 	char *instr = NULL;
 	StrBuf *PlainQItem;
@@ -626,6 +630,13 @@ void smtp_do_procmsg(long msgnum, void *userdata) {
 	int HaveBuffers = 0;
 	StrBuf *Msg =NULL;
 
+	if (mynumsessions > max_sessions_for_outbound_smtp) {
+		syslog(LOG_DEBUG,
+		       "SMTP Queue: skipping because of num jobs %d > %d max_sessions_for_outbound_smtp",
+		       mynumsessions,
+		       max_sessions_for_outbound_smtp);
+	}
+
 	syslog(LOG_DEBUG, "SMTP Queue: smtp_do_procmsg(%ld)\n", msgnum);
 	///strcpy(envelope_from, "");
 
@@ -770,8 +781,32 @@ void smtp_do_procmsg(long msgnum, void *userdata) {
 	DeleteHashPos(&It);
 
 	MyQItem->ActiveDeliveries = CountActiveQueueEntries(MyQItem);
+
+	/* failsafe against overload: 
+	 * will we exceed the limit set? 
+	 */
+	if ((MyQItem->ActiveDeliveries + mynumsessions > max_sessions_for_outbound_smtp) && 
+	    /* if yes, did we reach more than half of the quota? */
+	    ((mynumsessions * 2) > max_sessions_for_outbound_smtp) && 
+	    /* if... would we ever fit into half of the quota?? */
+	    (((MyQItem->ActiveDeliveries * 2)  < max_sessions_for_outbound_smtp)))
+	{
+		/* abort delivery for another time. */
+		syslog(LOG_DEBUG,
+		       "SMTP Queue: skipping because of num jobs %d + %ld > %d max_sessions_for_outbound_smtp",
+		       mynumsessions,
+		       MyQItem->ActiveDeliveries,
+		       max_sessions_for_outbound_smtp);
+
+		FreeQueItem(&MyQItem);
+
+		return;
+	}
+
+
 	if (MyQItem->ActiveDeliveries > 0)
 	{
+		int nActivated = 0;
 		int n = MsgCount++;
 		int m = MyQItem->ActiveDeliveries;
 		int i = 1;
@@ -786,6 +821,11 @@ void smtp_do_procmsg(long msgnum, void *userdata) {
 			if (ThisItem->Active == 1)
 			{
 				int KeepBuffers = (i == m);
+
+				nActivated++;
+				if (nActivated % ndelay_count == 0)
+					usleep(delay_msec);
+
 				if (i > 1) n = MsgCount++;
 				syslog(LOG_DEBUG,
 				       "SMTPQ: Trying <%ld> <%s> %d / %d \n",
@@ -962,8 +1002,25 @@ void cmd_smtp(char *argbuf) {
 
 CTDL_MODULE_INIT(smtp_queu)
 {
+	char *pstr;
+
 	if (!threading)
 	{
+		pstr = getenv("CITSERVER_n_session_max");
+		if ((pstr != NULL) && (*pstr != '\0'))
+			max_sessions_for_outbound_smtp = atol(pstr); /* how many sessions might be active till we stop adding more smtp jobs */
+
+		pstr = getenv("CITSERVER_smtp_n_delay_count");
+		if ((pstr != NULL) && (*pstr != '\0'))
+			ndelay_count = atol(pstr); /* every n queued messages we will sleep... */
+
+		pstr = getenv("CITSERVER_smtp_delay");
+		if ((pstr != NULL) && (*pstr != '\0'))
+			delay_msec = atol(pstr) * 1000; /* this many seconds. */
+
+
+
+
 		CtdlFillSystemContext(&smtp_queue_CC, "SMTP_Send");
 		ActiveQItems = NewHash(1, lFlathash);
 		pthread_mutex_init(&ActiveQItemsLock, NULL);
-- 
2.30.2