sched: CHOKe flow scheduler

CHOKe ("CHOose and Kill" or "CHOose and Keep") is an alternative
packet scheduler based on the Random Exponential Drop (RED) algorithm.

The core idea is:
  For every packet arrival:
  	Calculate Qave
	if (Qave < minth)
	     Queue the new packet
	else
	     Select randomly a packet from the queue
	     if (both packets from same flow)
	     then Drop both the packets
	     else if (Qave > maxth)
	          Drop packet
	     else
	       	  Admit packet with proability p (same as RED)

See also:
  Rong Pan, Balaji Prabhakar, Konstantinos Psounis, "CHOKe: a stateless active
   queue management scheme for approximating fair bandwidth allocation",
  Proceeding of INFOCOM'2000, March 2000.

Help from:
     Eric Dumazet <eric.dumazet@gmail.com>
     Patrick McHardy <kaber@trash.net>

Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/pkt_sched.h

@@ -247,6 +247,35 @@ struct tc_gred_sopt {
 	__u16		pad1;
 };
 
+/* CHOKe section */
+
+enum {
+	TCA_CHOKE_UNSPEC,
+	TCA_CHOKE_PARMS,
+	TCA_CHOKE_STAB,
+	__TCA_CHOKE_MAX,
+};
+
+#define TCA_CHOKE_MAX (__TCA_CHOKE_MAX - 1)
+
+struct tc_choke_qopt {
+	__u32		limit;		/* Hard queue length (packets)	*/
+	__u32		qth_min;	/* Min average threshold (packets) */
+	__u32		qth_max;	/* Max average threshold (packets) */
+	unsigned char   Wlog;		/* log(W)		*/
+	unsigned char   Plog;		/* log(P_max/(qth_max-qth_min))	*/
+	unsigned char   Scell_log;	/* cell size for idle damping */
+	unsigned char	flags;		/* see RED flags */
+};
+
+struct tc_choke_xstats {
+	__u32		early;          /* Early drops */
+	__u32		pdrop;          /* Drops due to queue limits */
+	__u32		other;          /* Drops due to drop() calls */
+	__u32		marked;         /* Marked packets */
+	__u32		matched;	/* Drops due to flow match */
+};
+
 /* HTB section */
 #define TC_HTB_NUMPRIO		8
 #define TC_HTB_MAXDEPTH		8

net/sched/Kconfig

@@ -217,6 +217,17 @@ config NET_SCH_MQPRIO
 
 	  If unsure, say N.
 
+config NET_SCH_CHOKE
+	tristate "CHOose and Keep responsive flow scheduler (CHOKE)"
+	help
+	  Say Y here if you want to use the CHOKe packet scheduler (CHOose
+	  and Keep for responsive flows, CHOose and Kill for unresponsive
+	  flows). This is a variation of RED which trys to penalize flows
+	  that monopolize the queue.
+
+	  To compile this code as a module, choose M here: the
+	  module will be called sch_choke.
+
 config NET_SCH_INGRESS
 	tristate "Ingress Qdisc"
 	depends on NET_CLS_ACT

net/sched/Makefile

@@ -33,6 +33,8 @@ obj-$(CONFIG_NET_SCH_ATM)	+= sch_atm.o
 obj-$(CONFIG_NET_SCH_NETEM)	+= sch_netem.o
 obj-$(CONFIG_NET_SCH_DRR)	+= sch_drr.o
 obj-$(CONFIG_NET_SCH_MQPRIO)	+= sch_mqprio.o
+obj-$(CONFIG_NET_SCH_CHOKE)	+= sch_choke.o
+
 obj-$(CONFIG_NET_CLS_U32)	+= cls_u32.o
 obj-$(CONFIG_NET_CLS_ROUTE4)	+= cls_route.o
 obj-$(CONFIG_NET_CLS_FW)	+= cls_fw.o