net/sched: add skbprio scheduler

net/sched: add skbprio scheduler

Skbprio (SKB Priority Queue) is a queueing discipline that prioritizes packets according to their skb->priority field. Under congestion, already-enqueued lower priority packets will be dropped to make space available for higher priority packets. Skbprio was conceived as a solution for denial-of-service defenses that need to route packets with different priorities as a means to overcome DoS attacks.

v5
*Do not reference qdisc_dev(sch)->tx_queue_len for setting limit. Instead set default sch->limit to 64.

v4
*Drop Documentation/networking/sch_skbprio.txt doc file to move it to tc man page for Skbprio, in iproute2.

v3
*Drop max_limit parameter in struct skbprio_sched_data and instead use sch->limit.

*Reference qdisc_dev(sch)->tx_queue_len only once, during initialisation for qdisc (previously being referenced every time qdisc changes).

*Move qdisc's detailed description from in-code to Documentation/networking.

*When qdisc is saturated, enqueue incoming packet first before dequeueing lowest priority packet in queue - improves usage of call stack registers.

*Introduce and use overlimit stat to keep track of number of dropped packets.

v2
*Use skb->priority field rather than DS field. Rename queueing discipline as SKB Priority Queue (previously Gatekeeper Priority Queue).

*Queueing discipline is made classful to expose Skbprio's internal priority queues.

---
 include/uapi/linux/pkt_sched.h |  15 ++
 net/sched/Kconfig              |  13 ++
 net/sched/Makefile             |   1 +
 net/sched/sch_skbprio.c        | 320 +++++++++++++++++++++++++++++++++++++++++
 4 files changed, 349 insertions(+)
 create mode 100644 net/sched/sch_skbprio.c

index d9cc9dc..8975fd1 100644
@@ -124,6 +124,21 @@ struct tc_fifo_qopt {
 	__u32	limit;	/* Queue length: bytes for bfifo, packets for pfifo */
 };
 
+/* SKBPRIO section */
+
+/*
+ * Priorities go from zero to (SKBPRIO_MAX_PRIORITY - 1).
+ * SKBPRIO_MAX_PRIORITY should be at least 64 in order for skbprio to be able
+ * to map one to one the DS field of IPV4 and IPV6 headers.
+ * Memory allocation grows linearly with SKBPRIO_MAX_PRIORITY.
+ */
+
+#define SKBPRIO_MAX_PRIORITY 64
+
+struct tc_skbprio_qopt {
+	__u32	limit;		/* Queue length in packets. */
+};
+
 /* PRIO section */
 
 #define TCQ_PRIO_BANDS	16

index 7af2467..7699344 100644
@@ -251,6 +251,19 @@ config NET_SCH_MQPRIO
 
 	  If unsure, say N.
 
+config NET_SCH_SKBPRIO
+	tristate "SKB priority queue scheduler (SKBPRIO)"
+	help
+	  Say Y here if you want to use the SKB priority queue
+	  scheduler. This schedules packets according to skb->priority,
+	  which is useful for request packets in DoS mitigation systems such
+	  as Gatekeeper.
+
+	  To compile this driver as a module, choose M here: the module will
+	  be called sch_skbprio.
+
+	  If unsure, say N.
+
 config NET_SCH_CHOKE
 	tristate "CHOose and Keep responsive flow scheduler (CHOKE)"
 	help

index 673ee7d..112ef70 100644
@@ -46,6 +46,7 @@ obj-$(CONFIG_NET_SCH_NETEM)	+= sch_netem.o
 obj-$(CONFIG_NET_SCH_DRR)	+= sch_drr.o
 obj-$(CONFIG_NET_SCH_PLUG)	+= sch_plug.o
 obj-$(CONFIG_NET_SCH_MQPRIO)	+= sch_mqprio.o
+obj-$(CONFIG_NET_SCH_SKBPRIO)	+= sch_skbprio.o
 obj-$(CONFIG_NET_SCH_CHOKE)	+= sch_choke.o
 obj-$(CONFIG_NET_SCH_QFQ)	+= sch_qfq.o
 obj-$(CONFIG_NET_SCH_CODEL)	+= sch_codel.o

1.9.1

Overall, it looks much better now!

Thanks the update!

From: Nishanth Devarajan <[email protected]>
Date: Mon, 23 Jul 2018 19:37:41 +0530

Applied to net-next, thank you.