Courier does so-called tarpitting on connections that are considered spam. That means it keeps the tcp connection open for a while and is meant to eat ressources from spammers.
We had the problem on our servers that it was eating too much of our ressources. Also I'm unsure if this is generally a useful idea. But others may have a different opinion on that, so I think this should be made optional. See attached patch, adds an option TARPIT to esmtpd config. -- Hanno Böck Blog: http://www.hboeck.de/ GPG: 3DBD3B20 Jabber/Mail: ha...@hboeck.de http://schokokeks.org - professional webhosting
diff -Naur courier-0.64.0/courier/module.esmtp/courieresmtpd.c courier-0.64.0-1/courier/module.esmtp/courieresmtpd.c
--- courier-0.64.0/courier/module.esmtp/courieresmtpd.c 2009-08-23 12:26:34.000000000 +0200
+++ courier-0.64.0-1/courier/module.esmtp/courieresmtpd.c 2010-01-31 19:46:52.000000000 +0100
@@ -81,10 +81,14 @@
static void tarpit()
{
- sleep(teergrube);
- teergrube *= 2;
- if (teergrube > MAX_TEERGRUBE)
- teergrube=MAX_TEERGRUBE;
+ const char *p;
+ if ((p=getenv("TARPIT")) && atoi(p))
+ {
+ sleep(teergrube);
+ teergrube *= 2;
+ if (teergrube > MAX_TEERGRUBE)
+ teergrube=MAX_TEERGRUBE;
+ }
}
void iov_logerror(const char *q, const char *p)
diff -Naur courier-0.64.0/courier/module.esmtp/esmtpd.dist.in courier-0.64.0-1/courier/module.esmtp/esmtpd.dist.in
--- courier-0.64.0/courier/module.esmtp/esmtpd.dist.in 2009-08-13 00:25:49.000000000 +0200
+++ courier-0.64.0-1/courier/module.esmtp/esmtpd.dist.in 2010-01-31 19:41:17.000000000 +0100
@@ -51,6 +51,12 @@
BOFHNOVRFY=0
+##NAME: TARPIT:1
+#
+# Set TARPIT to 0 to disable tarpitting
+
+TARPIT=1
+
##NAME: NOADDMSGID:0
#
# The following environment variables keep Courier from adding
diff -Naur courier-0.64.0/courier/module.esmtp/esmtpd-ssl.dist.in courier-0.64.0-1/courier/module.esmtp/esmtpd-ssl.dist.in
--- courier-0.64.0/courier/module.esmtp/esmtpd-ssl.dist.in 2009-08-13 00:25:49.000000000 +0200
+++ courier-0.64.0-1/courier/module.esmtp/esmtpd-ssl.dist.in 2010-01-31 19:41:49.000000000 +0100
@@ -44,6 +44,12 @@
BOFHNOVRFY=0
+##NAME: TARPIT:1
+#
+# Set TARPIT to 0 to disable tarpitting
+
+TARPIT=1
+
##NAME: NOADDMSGID:0
#
# The following environment variables keep Courier from adding
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