diff --git a/cyrus-imapd-2.3.15-qos.patch b/cyrus-imapd-2.3.15-qos.patch
new file mode 100644
index 0000000..1bb28c8
--- /dev/null
+++ b/cyrus-imapd-2.3.15-qos.patch
@@ -0,0 +1,83 @@
+--- cyrus-imapd-2.3.15/lib/imapoptions.orig	2009-06-29 10:21:06.000000000 -0700
++++ cyrus-imapd-2.3.15/lib/imapoptions	2009-12-14 13:40:56.000000000 -0800
+@@ -854,6 +854,10 @@ are listed with ``<none>''.
+    strip the default realm from the userid (this does not affect the stripping
+    of realms specified by the afspts_localrealms option) */
+ 
++{ "qosmarking", "cs0", ENUM("cs0", "cs1", "cs2", "cs3", "cs4", "cs5", "cs6", "cs7", "af11", "af12", "af13", "af21", "af22", "af23", "af31", "af32", "af33", "af41", "af42", "af43", "ef") }
++/* This specifies the Class Selector or Differentiated Services Code Point
++   designation on IP headers (in the ToS field). */
++
+ { "quota_db", "quotalegacy", STRINGLIST("flat", "berkeley", "berkeley-hash", "skiplist", "sql", "quotalegacy")}
+ /* The cyrusdb backend to use for quotas. */
+ 
+--- cyrus-imapd-2.3.15/lib/libconfig.c.orig	2009-08-20 08:26:15.000000000 -0700
++++ cyrus-imapd-2.3.15/lib/libconfig.c	2009-12-13 23:37:20.000000000 -0800
+@@ -82,6 +82,7 @@ enum enum_value config_virtdomains;	    
+ enum enum_value config_mupdate_config;	/* IMAP_ENUM_MUPDATE_CONFIG_STANDARD */
+ int config_maxword;
+ int config_maxquoted;
++int config_qosmarking;
+ 
+ /* declared in each binary that uses libconfig */
+ extern const int config_need_data;
+@@ -210,11 +211,21 @@ static void config_ispartition(const cha
+     if (!strncmp("partition-", key, 10)) *found = 1;
+ }
+ 
++static const unsigned char qos[] = {
++/* cs0..cs7 */		0x00, 0x20, 0x40, 0x60, 0x80, 0xa0, 0xc0, 0xe0,
++/* af11..af13 */	0x28, 0x30, 0x38,
++/* af21..af23 */	0x48, 0x50, 0x58,
++/* af31..af33 */	0x68, 0x70, 0x78,
++/* af41..af43 */	0x88, 0x90, 0x98,
++/* ef */		0xb8
++};
++
+ void config_read(const char *alt_config)
+ {
+     enum imapopt opt = IMAPOPT_ZERO;
+     char buf[4096];
+     char *p;
++    int ival;
+ 
+     /* xxx this is leaked, this may be able to be better in 2.2 (cyrus_done) */
+     if(alt_config) config_filename = xstrdup(alt_config);
+@@ -328,6 +339,9 @@ void config_read(const char *alt_config)
+     /* set some limits */
+     config_maxquoted = config_getint(IMAPOPT_MAXQUOTED);
+     config_maxword = config_getint(IMAPOPT_MAXWORD);
++
++    ival = config_getenum(IMAPOPT_QOSMARKING);
++    config_qosmarking = qos[ival];
+ }
+ 
+ #define GROWSIZE 4096
+--- cyrus-imapd-2.3.15/lib/libconfig.h.orig	2008-09-23 10:34:38.000000000 -0700
++++ cyrus-imapd-2.3.15/lib/libconfig.h	2009-12-13 23:19:40.000000000 -0800
+@@ -80,6 +80,7 @@ extern enum enum_value config_virtdomain
+ extern enum enum_value config_mupdate_config;
+ extern int config_maxquoted;
+ extern int config_maxword;
++extern int config_qosmarking;
+ 
+ /* config requirement flags */
+ #define CONFIG_NEED_PARTITION_DATA (1<<0)
+--- cyrus-imapd-2.3.15/master/master.c.orig	2009-03-30 21:11:23.000000000 -0700
++++ cyrus-imapd-2.3.15/master/master.c	2009-12-14 14:18:24.000000000 -0800
+@@ -439,6 +439,15 @@ void service_create(struct service *s)
+ 	}
+ #endif
+ 
++	/* set IP ToS if supported */
++#if defined(SOL_IP) && defined(IP_TOS)
++	r = setsockopt(s->socket, SOL_IP, IP_TOS,
++		       (void *) &config_qosmarking, sizeof(config_qosmarking));
++	if (r < 0) {
++	    syslog(LOG_WARNING, "unable to setsocketopt(IP_TOS): %m");
++	}
++#endif
++
+ 	oldumask = umask((mode_t) 0); /* for linux */
+ 	r = bind(s->socket, res->ai_addr, res->ai_addrlen);
+ 	umask(oldumask);
diff --git a/cyrus-imapd.imap-2.3.x-conf b/cyrus-imapd.imap-2.3.x-conf
index 2579793..23a7415 100644
--- a/cyrus-imapd.imap-2.3.x-conf
+++ b/cyrus-imapd.imap-2.3.x-conf
@@ -9,3 +9,5 @@ sasl_mech_list: PLAIN
 tls_cert_file: /etc/pki/cyrus-imapd/cyrus-imapd.pem
 tls_key_file: /etc/pki/cyrus-imapd/cyrus-imapd.pem
 tls_ca_file: /etc/pki/tls/certs/ca-bundle.crt
+# uncomment this if you're operating in a DSCP environment (RFC-4594)
+# qosmarking af13
diff --git a/cyrus-imapd.spec b/cyrus-imapd.spec
index ba6301f..3d1d244 100644
--- a/cyrus-imapd.spec
+++ b/cyrus-imapd.spec
@@ -2,7 +2,7 @@
 
 Name: cyrus-imapd
 Version: 2.3.16
-Release: 2%{?dist}
+Release: 3%{?dist}
 
 %define ssl_pem_file %{_sysconfdir}/pki/%{name}/%{name}.pem
 
@@ -62,6 +62,9 @@ Patch19: cyrus-imapd-2.3.12p2-current-db.patch
 # workaround, rhbz#553011
 Patch20: cyrus-imapd-2.3.16-nodenny.patch
 
+# from upstream, rhbz#576652, for cyrus-imapd < 2.4
+Patch21: cyrus-imapd-2.3.15-qos.patch
+
 BuildRoot: %(mktemp -ud %{_tmppath}/%{name}-%{version}-%{release}-XXXXXX)
 
 BuildRequires: autoconf
@@ -151,6 +154,7 @@ one running the server.
 %patch18 -p1 -b .krb4
 %patch19 -p1 -b .db4.7
 %patch20 -p1 -b .nodenny
+%patch21 -p1 -b .qos
 
 # add additional sources
 mkdir doc/{m4,contrib}
@@ -517,6 +521,9 @@ fi
 %{_mandir}/man1/*
 
 %changelog
+* Tue Apr 20 2010 Michal Hlavinka <mhlavink@redhat.com> - 2.3.16-3
+- add support for QoS marked traffic (#576652)
+
 * Thu Jan 14 2010 Michal Hlavinka <mhlavink@redhat.com> - 2.3.16-2
 - ignore user_denny.db if missing (#553011)
 - fix location of certificates in default imapd.conf