[PKT_SCHED]: Blackhole queueing discipline

Useful in combination with classful qdiscs to drop or
temporary disable certain flows, e.g. one could block
specific ds flows with dsmark.

Unlike the noop qdisc it can be controlled by the user and
statistic accounting is done.

Signed-off-by: Thomas Graf <[email protected]>
Signed-off-by: David S. Miller <[email protected]>

net/sched/Makefile

@@ -4,7 +4,7 @@
 
 obj-y	:= sch_generic.o
 
-obj-$(CONFIG_NET_SCHED)		+= sch_api.o sch_fifo.o
+obj-$(CONFIG_NET_SCHED)		+= sch_api.o sch_fifo.o sch_blackhole.o
 obj-$(CONFIG_NET_CLS)		+= cls_api.o
 obj-$(CONFIG_NET_CLS_ACT)	+= act_api.o
 obj-$(CONFIG_NET_ACT_POLICE)	+= police.o

net/sched/sch_blackhole.c

@@ -0,0 +1,54 @@
+/*
+ * net/sched/sch_blackhole.c	Black hole queue
+ *
+ *		This program is free software; you can redistribute it and/or
+ *		modify it under the terms of the GNU General Public License
+ *		as published by the Free Software Foundation; either version
+ *		2 of the License, or (at your option) any later version.
+ *
+ * Authors:	Thomas Graf <[email protected]>
+ *
+ * Note: Quantum tunneling is not supported.
+ */
+
+#include <linux/config.h>
+#include <linux/module.h>
+#include <linux/types.h>
+#include <linux/kernel.h>
+#include <linux/netdevice.h>
+#include <linux/skbuff.h>
+#include <net/pkt_sched.h>
+
+static int blackhole_enqueue(struct sk_buff *skb, struct Qdisc *sch)
+{
+	qdisc_drop(skb, sch);
+	return NET_XMIT_SUCCESS;
+}
+
+static struct sk_buff *blackhole_dequeue(struct Qdisc *sch)
+{
+	return NULL;
+}
+
+static struct Qdisc_ops blackhole_qdisc_ops = {
+	.id		= "blackhole",
+	.priv_size	= 0,
+	.enqueue	= blackhole_enqueue,
+	.dequeue	= blackhole_dequeue,
+	.owner		= THIS_MODULE,
+};
+
+static int __init blackhole_module_init(void)
+{
+	return register_qdisc(&blackhole_qdisc_ops);
+}
+
+static void __exit blackhole_module_exit(void)
+{
+	unregister_qdisc(&blackhole_qdisc_ops);
+}
+
+module_init(blackhole_module_init)
+module_exit(blackhole_module_exit)
+
+MODULE_LICENSE("GPL");