#ifndef __NET_SCHED_RED_H#define __NET_SCHED_RED_H #include <linux/types.h>#include <linux/bug.h>#include <net/pkt_sched.h>#include <net/inet_ecn.h>#include <net/dsfield.h>#include <linux/reciprocal_div.h> /*	Random Early Detection (RED) algorithm.	======================================= 	Source: Sally Floyd and Van Jacobson, "Random Early Detection Gateways	for Congestion Avoidance", 1993, IEEE/ACM Transactions on Networking. 	This file codes a "divisionless" version of RED algorithm	as written down in Fig.17 of the paper. 	Short description.	------------------ 	When a new packet arrives we calculate the average queue length: 	avg = (1-W)*avg + W*current_queue_len, 	W is the filter time constant (chosen as 2^(-Wlog)), it controls	the inertia of the algorithm. To allow larger bursts, W should be	decreased. 	if (avg > th_max) -> packet marked (dropped).	if (avg < th_min) -> packet passes.	if (th_min < avg < th_max) we calculate probability: 	Pb = max_P * (avg - th_min)/(th_max-th_min) 	and mark (drop) packet with this probability.	Pb changes from 0 (at avg==th_min) to max_P (avg==th_max).	max_P should be small (not 1), usually 0.01..0.02 is good value. 	max_P is chosen as a number, so that max_P/(th_max-th_min)	is a negative power of two in order arithmetics to contain	only shifts.  	Parameters, settable by user:	----------------------------- 	qth_min		- bytes (should be < qth_max/2)	qth_max		- bytes (should be at least 2*qth_min and less limit)	Wlog	       	- bits (<32) log(1/W).	Plog	       	- bits (<32) 	Plog is related to max_P by formula: 	max_P = (qth_max-qth_min)/2^Plog; 	F.e. if qth_max=128K and qth_min=32K, then Plog=22	corresponds to max_P=0.02 	Scell_log	Stab 	Lookup table for log((1-W)^(t/t_ave).  	NOTES: 	Upper bound on W.	----------------- 	If you want to allow bursts of L packets of size S,	you should choose W: 	L + 1 - th_min/S < (1-(1-W)^L)/W 	th_min/S = 32         th_min/S = 4 	log(W)	L	-1	33	-2	35	-3	39	-4	46	-5	57	-6	75	-7	101	-8	135	-9	190	etc. */ /* * Adaptative RED : An Algorithm for Increasing the Robustness of RED's AQM * (Sally FLoyd, Ramakrishna Gummadi, and Scott Shenker) August 2001 * * Every 500 ms: *  if (avg > target and max_p <= 0.5) *   increase max_p : max_p += alpha; *  else if (avg < target and max_p >= 0.01) *   decrease max_p : max_p *= beta; * * target :[qth_min + 0.4*(qth_min - qth_max), *          qth_min + 0.6*(qth_min - qth_max)]. * alpha : min(0.01, max_p / 4) * beta : 0.9 * max_P is a Q0.32 fixed point number (with 32 bits mantissa) * max_P between 0.01 and 0.5 (1% - 50%) [ Its no longer a negative power of two ] */#define RED_ONE_PERCENT ((u32)DIV_ROUND_CLOSEST(1ULL<<32, 100)) #define MAX_P_MIN (1 * RED_ONE_PERCENT)#define MAX_P_MAX (50 * RED_ONE_PERCENT)#define MAX_P_ALPHA(val) min(MAX_P_MIN, val / 4) #define RED_STAB_SIZE	256#define RED_STAB_MASK	(RED_STAB_SIZE - 1) struct red_stats {	u32		prob_drop;	/* Early probability drops */	u32		prob_mark;	/* Early probability marks */	u32		forced_drop;	/* Forced drops, qavg > max_thresh */	u32		forced_mark;	/* Forced marks, qavg > max_thresh */	u32		pdrop;          /* Drops due to queue limits */	u32		other;          /* Drops due to drop() calls */}; struct red_parms {	/* Parameters */	u32		qth_min;	/* Min avg length threshold: Wlog scaled */	u32		qth_max;	/* Max avg length threshold: Wlog scaled */	u32		Scell_max;	u32		max_P;		/* probability, [0 .. 1.0] 32 scaled */	/* reciprocal_value(max_P / qth_delta) */	struct reciprocal_value	max_P_reciprocal;	u32		qth_delta;	/* max_th - min_th */	u32		target_min;	/* min_th + 0.4*(max_th - min_th) */	u32		target_max;	/* min_th + 0.6*(max_th - min_th) */	u8		Scell_log;	u8		Wlog;		/* log(W)		*/	u8		Plog;		/* random number bits	*/	u8		Stab[RED_STAB_SIZE];}; struct red_vars {	/* Variables */	int		qcount;		/* Number of packets since last random					   number generation */	u32		qR;		/* Cached random number */ 	unsigned long	qavg;		/* Average queue length: Wlog scaled */	ktime_t		qidlestart;	/* Start of current idle period */}; static inline u32 red_maxp(u8 Plog){	return Plog < 32 ? (~0U >> Plog) : ~0U;} static inline void red_set_vars(struct red_vars *v){	/* Reset average queue length, the value is strictly bound	 * to the parameters below, reseting hurts a bit but leaving	 * it might result in an unreasonable qavg for a while. --TGR	 */	v->qavg		= 0; 	v->qcount	= -1;} static inline void red_set_parms(struct red_parms *p,				 u32 qth_min, u32 qth_max, u8 Wlog, u8 Plog,				 u8 Scell_log, u8 *stab, u32 max_P){	int delta = qth_max - qth_min;	u32 max_p_delta; 	p->qth_min	= qth_min << Wlog;	p->qth_max	= qth_max << Wlog;	p->Wlog		= Wlog;	p->Plog		= Plog;	if (delta < 0)		delta = 1;	p->qth_delta	= delta;	if (!max_P) {		max_P = red_maxp(Plog);		max_P *= delta; /* max_P = (qth_max - qth_min)/2^Plog */	}	p->max_P = max_P;	max_p_delta = max_P / delta;	max_p_delta = max(max_p_delta, 1U);	p->max_P_reciprocal  = reciprocal_value(max_p_delta); 	/* RED Adaptative target :	 * [min_th + 0.4*(min_th - max_th),	 *  min_th + 0.6*(min_th - max_th)].	 */	delta /= 5;	p->target_min = qth_min + 2*delta;	p->target_max = qth_min + 3*delta; 	p->Scell_log	= Scell_log;	p->Scell_max	= (255 << Scell_log); 	if (stab)		memcpy(p->Stab, stab, sizeof(p->Stab));} static inline int red_is_idling(const struct red_vars *v){	return v->qidlestart != 0;} static inline void red_start_of_idle_period(struct red_vars *v){	v->qidlestart = ktime_get();} static inline void red_end_of_idle_period(struct red_vars *v){	v->qidlestart = 0;} static inline void red_restart(struct red_vars *v){	red_end_of_idle_period(v);	v->qavg = 0;	v->qcount = -1;} static inline unsigned long red_calc_qavg_from_idle_time(const struct red_parms *p,							 const struct red_vars *v){	s64 delta = ktime_us_delta(ktime_get(), v->qidlestart);	long us_idle = min_t(s64, delta, p->Scell_max);	int  shift; 	/*	 * The problem: ideally, average length queue recalcultion should	 * be done over constant clock intervals. This is too expensive, so	 * that the calculation is driven by outgoing packets.	 * When the queue is idle we have to model this clock by hand.	 *	 * SF+VJ proposed to "generate":	 *	 *	m = idletime / (average_pkt_size / bandwidth)	 *	 * dummy packets as a burst after idle time, i.e.	 *	 * 	v->qavg *= (1-W)^m	 *	 * This is an apparently overcomplicated solution (f.e. we have to	 * precompute a table to make this calculation in reasonable time)	 * I believe that a simpler model may be used here,	 * but it is field for experiments.	 */ 	shift = p->Stab[(us_idle >> p->Scell_log) & RED_STAB_MASK]; 	if (shift)		return v->qavg >> shift;	else {		/* Approximate initial part of exponent with linear function:		 *		 * 	(1-W)^m ~= 1-mW + ...		 *		 * Seems, it is the best solution to		 * problem of too coarse exponent tabulation.		 */		us_idle = (v->qavg * (u64)us_idle) >> p->Scell_log; 		if (us_idle < (v->qavg >> 1))			return v->qavg - us_idle;		else			return v->qavg >> 1;	}} static inline unsigned long red_calc_qavg_no_idle_time(const struct red_parms *p,						       const struct red_vars *v,						       unsigned int backlog){	/*	 * NOTE: v->qavg is fixed point number with point at Wlog.	 * The formula below is equvalent to floating point	 * version:	 *	 * 	qavg = qavg*(1-W) + backlog*W;	 *	 * --ANK (980924)	 */	return v->qavg + (backlog - (v->qavg >> p->Wlog));} static inline unsigned long red_calc_qavg(const struct red_parms *p,					  const struct red_vars *v,					  unsigned int backlog){	if (!red_is_idling(v))		return red_calc_qavg_no_idle_time(p, v, backlog);	else		return red_calc_qavg_from_idle_time(p, v);}  static inline u32 red_random(const struct red_parms *p){	return reciprocal_divide(prandom_u32(), p->max_P_reciprocal);} static inline int red_mark_probability(const struct red_parms *p,				       const struct red_vars *v,				       unsigned long qavg){	/* The formula used below causes questions. 	   OK. qR is random number in the interval		(0..1/max_P)*(qth_max-qth_min)	   i.e. 0..(2^Plog). If we used floating point	   arithmetics, it would be: (2^Plog)*rnd_num,	   where rnd_num is less 1. 	   Taking into account, that qavg have fixed	   point at Wlog, two lines	   below have the following floating point equivalent: 	   max_P*(qavg - qth_min)/(qth_max-qth_min) < rnd/qcount 	   Any questions? --ANK (980924)	 */	return !(((qavg - p->qth_min) >> p->Wlog) * v->qcount < v->qR);} enum {	RED_BELOW_MIN_THRESH,	RED_BETWEEN_TRESH,	RED_ABOVE_MAX_TRESH,}; static inline int red_cmp_thresh(const struct red_parms *p, unsigned long qavg){	if (qavg < p->qth_min)		return RED_BELOW_MIN_THRESH;	else if (qavg >= p->qth_max)		return RED_ABOVE_MAX_TRESH;	else		return RED_BETWEEN_TRESH;} enum {	RED_DONT_MARK,	RED_PROB_MARK,	RED_HARD_MARK,}; static inline int red_action(const struct red_parms *p,			     struct red_vars *v,			     unsigned long qavg){	switch (red_cmp_thresh(p, qavg)) {		case RED_BELOW_MIN_THRESH:			v->qcount = -1;			return RED_DONT_MARK; 		case RED_BETWEEN_TRESH:			if (++v->qcount) {				if (red_mark_probability(p, v, qavg)) {					v->qcount = 0;					v->qR = red_random(p);					return RED_PROB_MARK;				}			} else				v->qR = red_random(p); 			return RED_DONT_MARK; 		case RED_ABOVE_MAX_TRESH:			v->qcount = -1;			return RED_HARD_MARK;	} 	BUG();	return RED_DONT_MARK;} static inline void red_adaptative_algo(struct red_parms *p, struct red_vars *v){	unsigned long qavg;	u32 max_p_delta; 	qavg = v->qavg;	if (red_is_idling(v))		qavg = red_calc_qavg_from_idle_time(p, v); 	/* v->qavg is fixed point number with point at Wlog */	qavg >>= p->Wlog; 	if (qavg > p->target_max && p->max_P <= MAX_P_MAX)		p->max_P += MAX_P_ALPHA(p->max_P); /* maxp = maxp + alpha */	else if (qavg < p->target_min && p->max_P >= MAX_P_MIN)		p->max_P = (p->max_P/10)*9; /* maxp = maxp * Beta */ 	max_p_delta = DIV_ROUND_CLOSEST(p->max_P, p->qth_delta);	max_p_delta = max(max_p_delta, 1U);	p->max_P_reciprocal = reciprocal_value(max_p_delta);}#endif