net/sched/sch_sfb.c - kernel/msm-4.19 - Gitiles

 /*
  * net/sched/sch_sfb.c	  Stochastic Fair Blue
  *
  * Copyright (c) 2008-2011 Juliusz Chroboczek <jch@pps.jussieu.fr>
  * Copyright (c) 2011 Eric Dumazet <eric.dumazet@gmail.com>
  *
  * This program is free software; you can redistribute it and/or
  * modify it under the terms of the GNU General Public License
  * version 2 as published by the Free Software Foundation.
  *
  * W. Feng, D. Kandlur, D. Saha, K. Shin. Blue:
  * A New Class of Active Queue Management Algorithms.
  * U. Michigan CSE-TR-387-99, April 1999.
  *
  * http://www.thefengs.com/wuchang/blue/CSE-TR-387-99.pdf
  *
  */

 #include <linux/module.h>
 #include <linux/types.h>
 #include <linux/kernel.h>
 #include <linux/errno.h>
 #include <linux/skbuff.h>
 #include <linux/random.h>
 #include <linux/jhash.h>
 #include <net/ip.h>
 #include <net/pkt_sched.h>
 #include <net/pkt_cls.h>
 #include <net/inet_ecn.h>

 /*
  * SFB uses two B[l][n] : L x N arrays of bins (L levels, N bins per level)
  * This implementation uses L = 8 and N = 16
  * This permits us to split one 32bit hash (provided per packet by rxhash or
  * external classifier) into 8 subhashes of 4 bits.
  */
 #define SFB_BUCKET_SHIFT 4
 #define SFB_NUMBUCKETS	(1 << SFB_BUCKET_SHIFT) /* N bins per Level */
 #define SFB_BUCKET_MASK (SFB_NUMBUCKETS - 1)
 #define SFB_LEVELS	(32 / SFB_BUCKET_SHIFT) /* L */

 /* SFB algo uses a virtual queue, named "bin" */
 struct sfb_bucket {
 	u16		qlen; /* length of virtual queue */
 	u16		p_mark; /* marking probability */
 };

 /* We use a double buffering right before hash change
  * (Section 4.4 of SFB reference : moving hash functions)
  */
 struct sfb_bins {
 	u32		  perturbation; /* jhash perturbation */
 	struct sfb_bucket bins[SFB_LEVELS][SFB_NUMBUCKETS];
 };

 struct sfb_sched_data {
 	struct Qdisc	*qdisc;
 	struct tcf_proto __rcu *filter_list;
 	unsigned long	rehash_interval;
 	unsigned long	warmup_time;	/* double buffering warmup time in jiffies */
 	u32		max;
 	u32		bin_size;	/* maximum queue length per bin */
 	u32		increment;	/* d1 */
 	u32		decrement;	/* d2 */
 	u32		limit;		/* HARD maximal queue length */
 	u32		penalty_rate;
 	u32		penalty_burst;
 	u32		tokens_avail;
 	unsigned long	rehash_time;
 	unsigned long	token_time;

 	u8		slot;		/* current active bins (0 or 1) */
 	bool		double_buffering;
 	struct sfb_bins bins[2];

 	struct {
 		u32	earlydrop;
 		u32	penaltydrop;
 		u32	bucketdrop;
 		u32	queuedrop;
 		u32	childdrop;	/* drops in child qdisc */
 		u32	marked;		/* ECN mark */
 	} stats;
 };

 /*
  * Each queued skb might be hashed on one or two bins
  * We store in skb_cb the two hash values.
  * (A zero value means double buffering was not used)
  */
 struct sfb_skb_cb {
 	u32 hashes[2];
 };

 static inline struct sfb_skb_cb *sfb_skb_cb(const struct sk_buff *skb)
 {
 	qdisc_cb_private_validate(skb, sizeof(struct sfb_skb_cb));
 	return (struct sfb_skb_cb *)qdisc_skb_cb(skb)->data;
 }

 /*
  * If using 'internal' SFB flow classifier, hash comes from skb rxhash
  * If using external classifier, hash comes from the classid.
  */
 static u32 sfb_hash(const struct sk_buff *skb, u32 slot)
 {
 	return sfb_skb_cb(skb)->hashes[slot];
 }

 /* Probabilities are coded as Q0.16 fixed-point values,
  * with 0xFFFF representing 65535/65536 (almost 1.0)
  * Addition and subtraction are saturating in [0, 65535]
  */
 static u32 prob_plus(u32 p1, u32 p2)
 {
 	u32 res = p1 + p2;

 	return min_t(u32, res, SFB_MAX_PROB);
 }

 static u32 prob_minus(u32 p1, u32 p2)
 {
 	return p1 > p2 ? p1 - p2 : 0;
 }

 static void increment_one_qlen(u32 sfbhash, u32 slot, struct sfb_sched_data *q)
 {
 	int i;
 	struct sfb_bucket *b = &q->bins[slot].bins[0][0];

 	for (i = 0; i < SFB_LEVELS; i++) {
 		u32 hash = sfbhash & SFB_BUCKET_MASK;

 		sfbhash >>= SFB_BUCKET_SHIFT;
 		if (b[hash].qlen < 0xFFFF)
 			b[hash].qlen++;
 		b += SFB_NUMBUCKETS; /* next level */
 	}
 }

 static void increment_qlen(const struct sk_buff *skb, struct sfb_sched_data *q)
 {
 	u32 sfbhash;

 	sfbhash = sfb_hash(skb, 0);
 	if (sfbhash)
 		increment_one_qlen(sfbhash, 0, q);

 	sfbhash = sfb_hash(skb, 1);
 	if (sfbhash)
 		increment_one_qlen(sfbhash, 1, q);
 }

 static void decrement_one_qlen(u32 sfbhash, u32 slot,
 			       struct sfb_sched_data *q)
 {
 	int i;
 	struct sfb_bucket *b = &q->bins[slot].bins[0][0];

 	for (i = 0; i < SFB_LEVELS; i++) {
 		u32 hash = sfbhash & SFB_BUCKET_MASK;

 		sfbhash >>= SFB_BUCKET_SHIFT;
 		if (b[hash].qlen > 0)
 			b[hash].qlen--;
 		b += SFB_NUMBUCKETS; /* next level */
 	}
 }

 static void decrement_qlen(const struct sk_buff *skb, struct sfb_sched_data *q)
 {
 	u32 sfbhash;

 	sfbhash = sfb_hash(skb, 0);
 	if (sfbhash)
 		decrement_one_qlen(sfbhash, 0, q);

 	sfbhash = sfb_hash(skb, 1);
 	if (sfbhash)
 		decrement_one_qlen(sfbhash, 1, q);
 }

 static void decrement_prob(struct sfb_bucket *b, struct sfb_sched_data *q)
 {
 	b->p_mark = prob_minus(b->p_mark, q->decrement);
 }

 static void increment_prob(struct sfb_bucket *b, struct sfb_sched_data *q)
 {
 	b->p_mark = prob_plus(b->p_mark, q->increment);
 }

 static void sfb_zero_all_buckets(struct sfb_sched_data *q)
 {
 	memset(&q->bins, 0, sizeof(q->bins));
 }

 /*
  * compute max qlen, max p_mark, and avg p_mark
  */
 static u32 sfb_compute_qlen(u32 *prob_r, u32 *avgpm_r, const struct sfb_sched_data *q)
 {
 	int i;
 	u32 qlen = 0, prob = 0, totalpm = 0;
 	const struct sfb_bucket *b = &q->bins[q->slot].bins[0][0];

 	for (i = 0; i < SFB_LEVELS * SFB_NUMBUCKETS; i++) {
 		if (qlen < b->qlen)
 			qlen = b->qlen;
 		totalpm += b->p_mark;
 		if (prob < b->p_mark)
 			prob = b->p_mark;
 		b++;
 	}
 	*prob_r = prob;
 	*avgpm_r = totalpm / (SFB_LEVELS * SFB_NUMBUCKETS);
 	return qlen;
 }


 static void sfb_init_perturbation(u32 slot, struct sfb_sched_data *q)
 {
 	q->bins[slot].perturbation = prandom_u32();
 }

 static void sfb_swap_slot(struct sfb_sched_data *q)
 {
 	sfb_init_perturbation(q->slot, q);
 	q->slot ^= 1;
 	q->double_buffering = false;
 }

 /* Non elastic flows are allowed to use part of the bandwidth, expressed
  * in "penalty_rate" packets per second, with "penalty_burst" burst
  */
 static bool sfb_rate_limit(struct sk_buff *skb, struct sfb_sched_data *q)
 {
 	if (q->penalty_rate == 0 || q->penalty_burst == 0)
 		return true;

 	if (q->tokens_avail < 1) {
 		unsigned long age = min(10UL * HZ, jiffies - q->token_time);

 		q->tokens_avail = (age * q->penalty_rate) / HZ;
 		if (q->tokens_avail > q->penalty_burst)
 			q->tokens_avail = q->penalty_burst;
 		q->token_time = jiffies;
 		if (q->tokens_avail < 1)
 			return true;
 	}

 	q->tokens_avail--;
 	return false;
 }

 static bool sfb_classify(struct sk_buff *skb, struct tcf_proto *fl,
 			 int *qerr, u32 *salt)
 {
 	struct tcf_result res;
 	int result;

 	result = tc_classify(skb, fl, &res, false);
 	if (result >= 0) {
 #ifdef CONFIG_NET_CLS_ACT
 		switch (result) {
 		case TC_ACT_STOLEN:
 		case TC_ACT_QUEUED:
 			*qerr = NET_XMIT_SUCCESS | __NET_XMIT_STOLEN;
 		case TC_ACT_SHOT:
 			return false;
 		}
 #endif
 		*salt = TC_H_MIN(res.classid);
 		return true;
 	}
 	return false;
 }

 static int sfb_enqueue(struct sk_buff *skb, struct Qdisc *sch,
 		       struct sk_buff **to_free)
 {

 	struct sfb_sched_data *q = qdisc_priv(sch);
 	struct Qdisc *child = q->qdisc;
 	struct tcf_proto *fl;
 	int i;
 	u32 p_min = ~0;
 	u32 minqlen = ~0;
 	u32 r, sfbhash;
 	u32 slot = q->slot;
 	int ret = NET_XMIT_SUCCESS | __NET_XMIT_BYPASS;

 	if (unlikely(sch->q.qlen >= q->limit)) {
 		qdisc_qstats_overlimit(sch);
 		q->stats.queuedrop++;
 		goto drop;
 	}

 	if (q->rehash_interval > 0) {
 		unsigned long limit = q->rehash_time + q->rehash_interval;

 		if (unlikely(time_after(jiffies, limit))) {
 			sfb_swap_slot(q);
 			q->rehash_time = jiffies;
 		} else if (unlikely(!q->double_buffering && q->warmup_time > 0 &&
 				    time_after(jiffies, limit - q->warmup_time))) {
 			q->double_buffering = true;
 		}
 	}

 	fl = rcu_dereference_bh(q->filter_list);
 	if (fl) {
 		u32 salt;

 		/* If using external classifiers, get result and record it. */
 		if (!sfb_classify(skb, fl, &ret, &salt))
 			goto other_drop;
 		sfbhash = jhash_1word(salt, q->bins[slot].perturbation);
 	} else {
 		sfbhash = skb_get_hash_perturb(skb, q->bins[slot].perturbation);
 	}


 	if (!sfbhash)
 		sfbhash = 1;
 	sfb_skb_cb(skb)->hashes[slot] = sfbhash;

 	for (i = 0; i < SFB_LEVELS; i++) {
 		u32 hash = sfbhash & SFB_BUCKET_MASK;
 		struct sfb_bucket *b = &q->bins[slot].bins[i][hash];

 		sfbhash >>= SFB_BUCKET_SHIFT;
 		if (b->qlen == 0)
 			decrement_prob(b, q);
 		else if (b->qlen >= q->bin_size)
 			increment_prob(b, q);
 		if (minqlen > b->qlen)
 			minqlen = b->qlen;
 		if (p_min > b->p_mark)
 			p_min = b->p_mark;
 	}

 	slot ^= 1;
 	sfb_skb_cb(skb)->hashes[slot] = 0;

 	if (unlikely(minqlen >= q->max)) {
 		qdisc_qstats_overlimit(sch);
 		q->stats.bucketdrop++;
 		goto drop;
 	}

 	if (unlikely(p_min >= SFB_MAX_PROB)) {
 		/* Inelastic flow */
 		if (q->double_buffering) {
 			sfbhash = skb_get_hash_perturb(skb,
 			    q->bins[slot].perturbation);
 			if (!sfbhash)
 				sfbhash = 1;
 			sfb_skb_cb(skb)->hashes[slot] = sfbhash;

 			for (i = 0; i < SFB_LEVELS; i++) {
 				u32 hash = sfbhash & SFB_BUCKET_MASK;
 				struct sfb_bucket *b = &q->bins[slot].bins[i][hash];

 				sfbhash >>= SFB_BUCKET_SHIFT;
 				if (b->qlen == 0)
 					decrement_prob(b, q);
 				else if (b->qlen >= q->bin_size)
 					increment_prob(b, q);
 			}
 		}
 		if (sfb_rate_limit(skb, q)) {
 			qdisc_qstats_overlimit(sch);
 			q->stats.penaltydrop++;
 			goto drop;
 		}
 		goto enqueue;
 	}

 	r = prandom_u32() & SFB_MAX_PROB;

 	if (unlikely(r < p_min)) {
 		if (unlikely(p_min > SFB_MAX_PROB / 2)) {
 			/* If we're marking that many packets, then either
 			 * this flow is unresponsive, or we're badly congested.
 			 * In either case, we want to start dropping packets.
 			 */
 			if (r < (p_min - SFB_MAX_PROB / 2) * 2) {
 				q->stats.earlydrop++;
 				goto drop;
 			}
 		}
 		if (INET_ECN_set_ce(skb)) {
 			q->stats.marked++;
 		} else {
 			q->stats.earlydrop++;
 			goto drop;
 		}
 	}

 enqueue:
 	ret = qdisc_enqueue(skb, child, to_free);
 	if (likely(ret == NET_XMIT_SUCCESS)) {
 		qdisc_qstats_backlog_inc(sch, skb);
 		sch->q.qlen++;
 		increment_qlen(skb, q);
 	} else if (net_xmit_drop_count(ret)) {
 		q->stats.childdrop++;
 		qdisc_qstats_drop(sch);
 	}
 	return ret;

 drop:
 	qdisc_drop(skb, sch, to_free);
 	return NET_XMIT_CN;
 other_drop:
 	if (ret & __NET_XMIT_BYPASS)
 		qdisc_qstats_drop(sch);
 	kfree_skb(skb);
 	return ret;
 }

 static struct sk_buff *sfb_dequeue(struct Qdisc *sch)
 {
 	struct sfb_sched_data *q = qdisc_priv(sch);
 	struct Qdisc *child = q->qdisc;
 	struct sk_buff *skb;

 	skb = child->dequeue(q->qdisc);

 	if (skb) {
 		qdisc_bstats_update(sch, skb);
 		qdisc_qstats_backlog_dec(sch, skb);
 		sch->q.qlen--;
 		decrement_qlen(skb, q);
 	}

 	return skb;
 }

 static struct sk_buff *sfb_peek(struct Qdisc *sch)
 {
 	struct sfb_sched_data *q = qdisc_priv(sch);
 	struct Qdisc *child = q->qdisc;

 	return child->ops->peek(child);
 }

 /* No sfb_drop -- impossible since the child doesn't return the dropped skb. */

 static void sfb_reset(struct Qdisc *sch)
 {
 	struct sfb_sched_data *q = qdisc_priv(sch);

 	qdisc_reset(q->qdisc);
 	sch->qstats.backlog = 0;
 	sch->q.qlen = 0;
 	q->slot = 0;
 	q->double_buffering = false;
 	sfb_zero_all_buckets(q);
 	sfb_init_perturbation(0, q);
 }

 static void sfb_destroy(struct Qdisc *sch)
 {
 	struct sfb_sched_data *q = qdisc_priv(sch);

 	tcf_destroy_chain(&q->filter_list);
 	qdisc_destroy(q->qdisc);
 }

 static const struct nla_policy sfb_policy[TCA_SFB_MAX + 1] = {
 	[TCA_SFB_PARMS]	= { .len = sizeof(struct tc_sfb_qopt) },
 };

 static const struct tc_sfb_qopt sfb_default_ops = {
 	.rehash_interval = 600 * MSEC_PER_SEC,
 	.warmup_time = 60 * MSEC_PER_SEC,
 	.limit = 0,
 	.max = 25,
 	.bin_size = 20,
 	.increment = (SFB_MAX_PROB + 500) / 1000, /* 0.1 % */
 	.decrement = (SFB_MAX_PROB + 3000) / 6000,
 	.penalty_rate = 10,
 	.penalty_burst = 20,
 };

 static int sfb_change(struct Qdisc *sch, struct nlattr *opt)
 {
 	struct sfb_sched_data *q = qdisc_priv(sch);
 	struct Qdisc *child;
 	struct nlattr *tb[TCA_SFB_MAX + 1];
 	const struct tc_sfb_qopt *ctl = &sfb_default_ops;
 	u32 limit;
 	int err;

 	if (opt) {
 		err = nla_parse_nested(tb, TCA_SFB_MAX, opt, sfb_policy, NULL);
 		if (err < 0)
 			return -EINVAL;

 		if (tb[TCA_SFB_PARMS] == NULL)
 			return -EINVAL;

 		ctl = nla_data(tb[TCA_SFB_PARMS]);
 	}

 	limit = ctl->limit;
 	if (limit == 0)
 		limit = qdisc_dev(sch)->tx_queue_len;

 	child = fifo_create_dflt(sch, &pfifo_qdisc_ops, limit);
 	if (IS_ERR(child))
 		return PTR_ERR(child);

 	if (child != &noop_qdisc)
 		qdisc_hash_add(child, true);
 	sch_tree_lock(sch);

 	qdisc_tree_reduce_backlog(q->qdisc, q->qdisc->q.qlen,
 				  q->qdisc->qstats.backlog);
 	qdisc_destroy(q->qdisc);
 	q->qdisc = child;

 	q->rehash_interval = msecs_to_jiffies(ctl->rehash_interval);
 	q->warmup_time = msecs_to_jiffies(ctl->warmup_time);
 	q->rehash_time = jiffies;
 	q->limit = limit;
 	q->increment = ctl->increment;
 	q->decrement = ctl->decrement;
 	q->max = ctl->max;
 	q->bin_size = ctl->bin_size;
 	q->penalty_rate = ctl->penalty_rate;
 	q->penalty_burst = ctl->penalty_burst;
 	q->tokens_avail = ctl->penalty_burst;
 	q->token_time = jiffies;

 	q->slot = 0;
 	q->double_buffering = false;
 	sfb_zero_all_buckets(q);
 	sfb_init_perturbation(0, q);
 	sfb_init_perturbation(1, q);

 	sch_tree_unlock(sch);

 	return 0;
 }

 static int sfb_init(struct Qdisc *sch, struct nlattr *opt)
 {
 	struct sfb_sched_data *q = qdisc_priv(sch);

 	q->qdisc = &noop_qdisc;
 	return sfb_change(sch, opt);
 }

 static int sfb_dump(struct Qdisc *sch, struct sk_buff *skb)
 {
 	struct sfb_sched_data *q = qdisc_priv(sch);
 	struct nlattr *opts;
 	struct tc_sfb_qopt opt = {
 		.rehash_interval = jiffies_to_msecs(q->rehash_interval),
 		.warmup_time = jiffies_to_msecs(q->warmup_time),
 		.limit = q->limit,
 		.max = q->max,
 		.bin_size = q->bin_size,
 		.increment = q->increment,
 		.decrement = q->decrement,
 		.penalty_rate = q->penalty_rate,
 		.penalty_burst = q->penalty_burst,
 	};

 	sch->qstats.backlog = q->qdisc->qstats.backlog;
 	opts = nla_nest_start(skb, TCA_OPTIONS);
 	if (opts == NULL)
 		goto nla_put_failure;
 	if (nla_put(skb, TCA_SFB_PARMS, sizeof(opt), &opt))
 		goto nla_put_failure;
 	return nla_nest_end(skb, opts);

 nla_put_failure:
 	nla_nest_cancel(skb, opts);
 	return -EMSGSIZE;
 }

 static int sfb_dump_stats(struct Qdisc *sch, struct gnet_dump *d)
 {
 	struct sfb_sched_data *q = qdisc_priv(sch);
 	struct tc_sfb_xstats st = {
 		.earlydrop = q->stats.earlydrop,
 		.penaltydrop = q->stats.penaltydrop,
 		.bucketdrop = q->stats.bucketdrop,
 		.queuedrop = q->stats.queuedrop,
 		.childdrop = q->stats.childdrop,
 		.marked = q->stats.marked,
 	};

 	st.maxqlen = sfb_compute_qlen(&st.maxprob, &st.avgprob, q);

 	return gnet_stats_copy_app(d, &st, sizeof(st));
 }

 static int sfb_dump_class(struct Qdisc *sch, unsigned long cl,
 			  struct sk_buff *skb, struct tcmsg *tcm)
 {
 	return -ENOSYS;
 }

 static int sfb_graft(struct Qdisc *sch, unsigned long arg, struct Qdisc *new,
 		     struct Qdisc **old)
 {
 	struct sfb_sched_data *q = qdisc_priv(sch);

 	if (new == NULL)
 		new = &noop_qdisc;

 	*old = qdisc_replace(sch, new, &q->qdisc);
 	return 0;
 }

 static struct Qdisc *sfb_leaf(struct Qdisc *sch, unsigned long arg)
 {
 	struct sfb_sched_data *q = qdisc_priv(sch);

 	return q->qdisc;
 }

 static unsigned long sfb_get(struct Qdisc *sch, u32 classid)
 {
 	return 1;
 }

 static void sfb_put(struct Qdisc *sch, unsigned long arg)
 {
 }

 static int sfb_change_class(struct Qdisc *sch, u32 classid, u32 parentid,
 			    struct nlattr **tca, unsigned long *arg)
 {
 	return -ENOSYS;
 }

 static int sfb_delete(struct Qdisc *sch, unsigned long cl)
 {
 	return -ENOSYS;
 }

 static void sfb_walk(struct Qdisc *sch, struct qdisc_walker *walker)
 {
 	if (!walker->stop) {
 		if (walker->count >= walker->skip)
 			if (walker->fn(sch, 1, walker) < 0) {
 				walker->stop = 1;
 				return;
 			}
 		walker->count++;
 	}
 }

 static struct tcf_proto __rcu **sfb_find_tcf(struct Qdisc *sch,
 					     unsigned long cl)
 {
 	struct sfb_sched_data *q = qdisc_priv(sch);

 	if (cl)
 		return NULL;
 	return &q->filter_list;
 }

 static unsigned long sfb_bind(struct Qdisc *sch, unsigned long parent,
 			      u32 classid)
 {
 	return 0;
 }


 static const struct Qdisc_class_ops sfb_class_ops = {
 	.graft		=	sfb_graft,
 	.leaf		=	sfb_leaf,
 	.get		=	sfb_get,
 	.put		=	sfb_put,
 	.change		=	sfb_change_class,
 	.delete		=	sfb_delete,
 	.walk		=	sfb_walk,
 	.tcf_chain	=	sfb_find_tcf,
 	.bind_tcf	=	sfb_bind,
 	.unbind_tcf	=	sfb_put,
 	.dump		=	sfb_dump_class,
 };

 static struct Qdisc_ops sfb_qdisc_ops __read_mostly = {
 	.id		=	"sfb",
 	.priv_size	=	sizeof(struct sfb_sched_data),
 	.cl_ops		=	&sfb_class_ops,
 	.enqueue	=	sfb_enqueue,
 	.dequeue	=	sfb_dequeue,
 	.peek		=	sfb_peek,
 	.init		=	sfb_init,
 	.reset		=	sfb_reset,
 	.destroy	=	sfb_destroy,
 	.change		=	sfb_change,
 	.dump		=	sfb_dump,
 	.dump_stats	=	sfb_dump_stats,
 	.owner		=	THIS_MODULE,
 };

 static int __init sfb_module_init(void)
 {
 	return register_qdisc(&sfb_qdisc_ops);
 }

 static void __exit sfb_module_exit(void)
 {
 	unregister_qdisc(&sfb_qdisc_ops);
 }

 module_init(sfb_module_init)
 module_exit(sfb_module_exit)

 MODULE_DESCRIPTION("Stochastic Fair Blue queue discipline");
 MODULE_AUTHOR("Juliusz Chroboczek");
 MODULE_AUTHOR("Eric Dumazet");
 MODULE_LICENSE("GPL");
	/*
	* net/sched/sch_sfb.c Stochastic Fair Blue
	*
	* Copyright (c) 2008-2011 Juliusz Chroboczek <jch@pps.jussieu.fr>
	* Copyright (c) 2011 Eric Dumazet <eric.dumazet@gmail.com>
	*
	* This program is free software; you can redistribute it and/or
	* modify it under the terms of the GNU General Public License
	* version 2 as published by the Free Software Foundation.
	*
	* W. Feng, D. Kandlur, D. Saha, K. Shin. Blue:
	* A New Class of Active Queue Management Algorithms.
	* U. Michigan CSE-TR-387-99, April 1999.
	*
	* http://www.thefengs.com/wuchang/blue/CSE-TR-387-99.pdf
	*
	*/

	#include <linux/module.h>
	#include <linux/types.h>
	#include <linux/kernel.h>
	#include <linux/errno.h>
	#include <linux/skbuff.h>
	#include <linux/random.h>
	#include <linux/jhash.h>
	#include <net/ip.h>
	#include <net/pkt_sched.h>
	#include <net/pkt_cls.h>
	#include <net/inet_ecn.h>

	/*
	* SFB uses two B[l][n] : L x N arrays of bins (L levels, N bins per level)
	* This implementation uses L = 8 and N = 16
	* This permits us to split one 32bit hash (provided per packet by rxhash or
	* external classifier) into 8 subhashes of 4 bits.
	*/
	#define SFB_BUCKET_SHIFT 4
	#define SFB_NUMBUCKETS (1 << SFB_BUCKET_SHIFT) /* N bins per Level */
	#define SFB_BUCKET_MASK (SFB_NUMBUCKETS - 1)
	#define SFB_LEVELS (32 / SFB_BUCKET_SHIFT) /* L */

	/* SFB algo uses a virtual queue, named "bin" */
	struct sfb_bucket {
	u16 qlen; /* length of virtual queue */
	u16 p_mark; /* marking probability */
	};

	/* We use a double buffering right before hash change
	* (Section 4.4 of SFB reference : moving hash functions)
	*/
	struct sfb_bins {
	u32 perturbation; /* jhash perturbation */
	struct sfb_bucket bins[SFB_LEVELS][SFB_NUMBUCKETS];
	};

	struct sfb_sched_data {
	struct Qdisc *qdisc;
	struct tcf_proto __rcu *filter_list;
	unsigned long rehash_interval;
	unsigned long warmup_time; /* double buffering warmup time in jiffies */
	u32 max;
	u32 bin_size; /* maximum queue length per bin */
	u32 increment; /* d1 */
	u32 decrement; /* d2 */
	u32 limit; /* HARD maximal queue length */
	u32 penalty_rate;
	u32 penalty_burst;
	u32 tokens_avail;
	unsigned long rehash_time;
	unsigned long token_time;

	u8 slot; /* current active bins (0 or 1) */
	bool double_buffering;
	struct sfb_bins bins[2];

	struct {
	u32 earlydrop;
	u32 penaltydrop;
	u32 bucketdrop;
	u32 queuedrop;
	u32 childdrop; /* drops in child qdisc */
	u32 marked; /* ECN mark */
	} stats;
	};

	/*
	* Each queued skb might be hashed on one or two bins
	* We store in skb_cb the two hash values.
	* (A zero value means double buffering was not used)
	*/
	struct sfb_skb_cb {
	u32 hashes[2];
	};

	static inline struct sfb_skb_cb sfb_skb_cb(const struct sk_buff skb)
	{
	qdisc_cb_private_validate(skb, sizeof(struct sfb_skb_cb));
	return (struct sfb_skb_cb *)qdisc_skb_cb(skb)->data;
	}

	/*
	* If using 'internal' SFB flow classifier, hash comes from skb rxhash
	* If using external classifier, hash comes from the classid.
	*/
	static u32 sfb_hash(const struct sk_buff *skb, u32 slot)
	{
	return sfb_skb_cb(skb)->hashes[slot];
	}

	/* Probabilities are coded as Q0.16 fixed-point values,
	* with 0xFFFF representing 65535/65536 (almost 1.0)
	* Addition and subtraction are saturating in [0, 65535]
	*/
	static u32 prob_plus(u32 p1, u32 p2)
	{
	u32 res = p1 + p2;

	return min_t(u32, res, SFB_MAX_PROB);
	}

	static u32 prob_minus(u32 p1, u32 p2)
	{
	return p1 > p2 ? p1 - p2 : 0;
	}

	static void increment_one_qlen(u32 sfbhash, u32 slot, struct sfb_sched_data *q)
	{
	int i;
	struct sfb_bucket *b = &q->bins[slot].bins[0][0];

	for (i = 0; i < SFB_LEVELS; i++) {
	u32 hash = sfbhash & SFB_BUCKET_MASK;

	sfbhash >>= SFB_BUCKET_SHIFT;
	if (b[hash].qlen < 0xFFFF)
	b[hash].qlen++;
	b += SFB_NUMBUCKETS; /* next level */
	}
	}

	static void increment_qlen(const struct sk_buff skb, struct sfb_sched_data q)
	{
	u32 sfbhash;

	sfbhash = sfb_hash(skb, 0);
	if (sfbhash)
	increment_one_qlen(sfbhash, 0, q);

	sfbhash = sfb_hash(skb, 1);
	if (sfbhash)
	increment_one_qlen(sfbhash, 1, q);
	}

	static void decrement_one_qlen(u32 sfbhash, u32 slot,
	struct sfb_sched_data *q)
	{
	int i;
	struct sfb_bucket *b = &q->bins[slot].bins[0][0];

	for (i = 0; i < SFB_LEVELS; i++) {
	u32 hash = sfbhash & SFB_BUCKET_MASK;

	sfbhash >>= SFB_BUCKET_SHIFT;
	if (b[hash].qlen > 0)
	b[hash].qlen--;
	b += SFB_NUMBUCKETS; /* next level */
	}
	}

	static void decrement_qlen(const struct sk_buff skb, struct sfb_sched_data q)
	{
	u32 sfbhash;

	sfbhash = sfb_hash(skb, 0);
	if (sfbhash)
	decrement_one_qlen(sfbhash, 0, q);

	sfbhash = sfb_hash(skb, 1);
	if (sfbhash)
	decrement_one_qlen(sfbhash, 1, q);
	}

	static void decrement_prob(struct sfb_bucket b, struct sfb_sched_data q)
	{
	b->p_mark = prob_minus(b->p_mark, q->decrement);
	}

	static void increment_prob(struct sfb_bucket b, struct sfb_sched_data q)
	{
	b->p_mark = prob_plus(b->p_mark, q->increment);
	}

	static void sfb_zero_all_buckets(struct sfb_sched_data *q)
	{
	memset(&q->bins, 0, sizeof(q->bins));
	}

	/*
	* compute max qlen, max p_mark, and avg p_mark
	*/
	static u32 sfb_compute_qlen(u32 prob_r, u32 avgpm_r, const struct sfb_sched_data *q)
	{
	int i;
	u32 qlen = 0, prob = 0, totalpm = 0;
	const struct sfb_bucket *b = &q->bins[q->slot].bins[0][0];

	for (i = 0; i < SFB_LEVELS * SFB_NUMBUCKETS; i++) {
	if (qlen < b->qlen)
	qlen = b->qlen;
	totalpm += b->p_mark;
	if (prob < b->p_mark)
	prob = b->p_mark;
	b++;
	}
	*prob_r = prob;
	avgpm_r = totalpm / (SFB_LEVELS SFB_NUMBUCKETS);
	return qlen;
	}


	static void sfb_init_perturbation(u32 slot, struct sfb_sched_data *q)
	{
	q->bins[slot].perturbation = prandom_u32();
	}

	static void sfb_swap_slot(struct sfb_sched_data *q)
	{
	sfb_init_perturbation(q->slot, q);
	q->slot ^= 1;
	q->double_buffering = false;
	}

	/* Non elastic flows are allowed to use part of the bandwidth, expressed
	* in "penalty_rate" packets per second, with "penalty_burst" burst
	*/
	static bool sfb_rate_limit(struct sk_buff skb, struct sfb_sched_data q)
	{
	if (q->penalty_rate == 0 \|\| q->penalty_burst == 0)
	return true;

	if (q->tokens_avail < 1) {
	unsigned long age = min(10UL * HZ, jiffies - q->token_time);

	q->tokens_avail = (age * q->penalty_rate) / HZ;
	if (q->tokens_avail > q->penalty_burst)
	q->tokens_avail = q->penalty_burst;
	q->token_time = jiffies;
	if (q->tokens_avail < 1)
	return true;
	}

	q->tokens_avail--;
	return false;
	}

	static bool sfb_classify(struct sk_buff skb, struct tcf_proto fl,
	int qerr, u32 salt)
	{
	struct tcf_result res;
	int result;

	result = tc_classify(skb, fl, &res, false);
	if (result >= 0) {
	#ifdef CONFIG_NET_CLS_ACT
	switch (result) {
	case TC_ACT_STOLEN:
	case TC_ACT_QUEUED:
	*qerr = NET_XMIT_SUCCESS \| __NET_XMIT_STOLEN;
	case TC_ACT_SHOT:
	return false;
	}
	#endif
	*salt = TC_H_MIN(res.classid);
	return true;
	}
	return false;
	}

	static int sfb_enqueue(struct sk_buff skb, struct Qdisc sch,
	struct sk_buff **to_free)
	{

	struct sfb_sched_data *q = qdisc_priv(sch);
	struct Qdisc *child = q->qdisc;
	struct tcf_proto *fl;
	int i;
	u32 p_min = ~0;
	u32 minqlen = ~0;
	u32 r, sfbhash;
	u32 slot = q->slot;
	int ret = NET_XMIT_SUCCESS \| __NET_XMIT_BYPASS;

	if (unlikely(sch->q.qlen >= q->limit)) {
	qdisc_qstats_overlimit(sch);
	q->stats.queuedrop++;
	goto drop;
	}

	if (q->rehash_interval > 0) {
	unsigned long limit = q->rehash_time + q->rehash_interval;

	if (unlikely(time_after(jiffies, limit))) {
	sfb_swap_slot(q);
	q->rehash_time = jiffies;
	} else if (unlikely(!q->double_buffering && q->warmup_time > 0 &&
	time_after(jiffies, limit - q->warmup_time))) {
	q->double_buffering = true;
	}
	}

	fl = rcu_dereference_bh(q->filter_list);
	if (fl) {
	u32 salt;

	/* If using external classifiers, get result and record it. */
	if (!sfb_classify(skb, fl, &ret, &salt))
	goto other_drop;
	sfbhash = jhash_1word(salt, q->bins[slot].perturbation);
	} else {
	sfbhash = skb_get_hash_perturb(skb, q->bins[slot].perturbation);
	}


	if (!sfbhash)
	sfbhash = 1;
	sfb_skb_cb(skb)->hashes[slot] = sfbhash;

	for (i = 0; i < SFB_LEVELS; i++) {
	u32 hash = sfbhash & SFB_BUCKET_MASK;
	struct sfb_bucket *b = &q->bins[slot].bins[i][hash];

	sfbhash >>= SFB_BUCKET_SHIFT;
	if (b->qlen == 0)
	decrement_prob(b, q);
	else if (b->qlen >= q->bin_size)
	increment_prob(b, q);
	if (minqlen > b->qlen)
	minqlen = b->qlen;
	if (p_min > b->p_mark)
	p_min = b->p_mark;
	}

	slot ^= 1;
	sfb_skb_cb(skb)->hashes[slot] = 0;

	if (unlikely(minqlen >= q->max)) {
	qdisc_qstats_overlimit(sch);
	q->stats.bucketdrop++;
	goto drop;
	}

	if (unlikely(p_min >= SFB_MAX_PROB)) {
	/* Inelastic flow */
	if (q->double_buffering) {
	sfbhash = skb_get_hash_perturb(skb,
	q->bins[slot].perturbation);
	if (!sfbhash)
	sfbhash = 1;
	sfb_skb_cb(skb)->hashes[slot] = sfbhash;

	for (i = 0; i < SFB_LEVELS; i++) {
	u32 hash = sfbhash & SFB_BUCKET_MASK;
	struct sfb_bucket *b = &q->bins[slot].bins[i][hash];

	sfbhash >>= SFB_BUCKET_SHIFT;
	if (b->qlen == 0)
	decrement_prob(b, q);
	else if (b->qlen >= q->bin_size)
	increment_prob(b, q);
	}
	}
	if (sfb_rate_limit(skb, q)) {
	qdisc_qstats_overlimit(sch);
	q->stats.penaltydrop++;
	goto drop;
	}
	goto enqueue;
	}

	r = prandom_u32() & SFB_MAX_PROB;

	if (unlikely(r < p_min)) {
	if (unlikely(p_min > SFB_MAX_PROB / 2)) {
	/* If we're marking that many packets, then either
	* this flow is unresponsive, or we're badly congested.
	* In either case, we want to start dropping packets.
	*/
	if (r < (p_min - SFB_MAX_PROB / 2) * 2) {
	q->stats.earlydrop++;
	goto drop;
	}
	}
	if (INET_ECN_set_ce(skb)) {
	q->stats.marked++;
	} else {
	q->stats.earlydrop++;
	goto drop;
	}
	}

	enqueue:
	ret = qdisc_enqueue(skb, child, to_free);
	if (likely(ret == NET_XMIT_SUCCESS)) {
	qdisc_qstats_backlog_inc(sch, skb);
	sch->q.qlen++;
	increment_qlen(skb, q);
	} else if (net_xmit_drop_count(ret)) {
	q->stats.childdrop++;
	qdisc_qstats_drop(sch);
	}
	return ret;

	drop:
	qdisc_drop(skb, sch, to_free);
	return NET_XMIT_CN;
	other_drop:
	if (ret & __NET_XMIT_BYPASS)
	qdisc_qstats_drop(sch);
	kfree_skb(skb);
	return ret;
	}

	static struct sk_buff sfb_dequeue(struct Qdisc sch)
	{
	struct sfb_sched_data *q = qdisc_priv(sch);
	struct Qdisc *child = q->qdisc;
	struct sk_buff *skb;

	skb = child->dequeue(q->qdisc);

	if (skb) {
	qdisc_bstats_update(sch, skb);
	qdisc_qstats_backlog_dec(sch, skb);
	sch->q.qlen--;
	decrement_qlen(skb, q);
	}

	return skb;
	}

	static struct sk_buff sfb_peek(struct Qdisc sch)
	{
	struct sfb_sched_data *q = qdisc_priv(sch);
	struct Qdisc *child = q->qdisc;

	return child->ops->peek(child);
	}

	/* No sfb_drop -- impossible since the child doesn't return the dropped skb. */

	static void sfb_reset(struct Qdisc *sch)
	{
	struct sfb_sched_data *q = qdisc_priv(sch);

	qdisc_reset(q->qdisc);
	sch->qstats.backlog = 0;
	sch->q.qlen = 0;
	q->slot = 0;
	q->double_buffering = false;
	sfb_zero_all_buckets(q);
	sfb_init_perturbation(0, q);
	}

	static void sfb_destroy(struct Qdisc *sch)
	{
	struct sfb_sched_data *q = qdisc_priv(sch);

	tcf_destroy_chain(&q->filter_list);
	qdisc_destroy(q->qdisc);
	}

	static const struct nla_policy sfb_policy[TCA_SFB_MAX + 1] = {
	[TCA_SFB_PARMS] = { .len = sizeof(struct tc_sfb_qopt) },
	};

	static const struct tc_sfb_qopt sfb_default_ops = {
	.rehash_interval = 600 * MSEC_PER_SEC,
	.warmup_time = 60 * MSEC_PER_SEC,
	.limit = 0,
	.max = 25,
	.bin_size = 20,
	.increment = (SFB_MAX_PROB + 500) / 1000, /* 0.1 % */
	.decrement = (SFB_MAX_PROB + 3000) / 6000,
	.penalty_rate = 10,
	.penalty_burst = 20,
	};

	static int sfb_change(struct Qdisc sch, struct nlattr opt)
	{
	struct sfb_sched_data *q = qdisc_priv(sch);
	struct Qdisc *child;
	struct nlattr *tb[TCA_SFB_MAX + 1];
	const struct tc_sfb_qopt *ctl = &sfb_default_ops;
	u32 limit;
	int err;

	if (opt) {
	err = nla_parse_nested(tb, TCA_SFB_MAX, opt, sfb_policy, NULL);
	if (err < 0)
	return -EINVAL;

	if (tb[TCA_SFB_PARMS] == NULL)
	return -EINVAL;

	ctl = nla_data(tb[TCA_SFB_PARMS]);
	}

	limit = ctl->limit;
	if (limit == 0)
	limit = qdisc_dev(sch)->tx_queue_len;

	child = fifo_create_dflt(sch, &pfifo_qdisc_ops, limit);
	if (IS_ERR(child))
	return PTR_ERR(child);

	if (child != &noop_qdisc)
	qdisc_hash_add(child, true);
	sch_tree_lock(sch);

	qdisc_tree_reduce_backlog(q->qdisc, q->qdisc->q.qlen,
	q->qdisc->qstats.backlog);
	qdisc_destroy(q->qdisc);
	q->qdisc = child;

	q->rehash_interval = msecs_to_jiffies(ctl->rehash_interval);
	q->warmup_time = msecs_to_jiffies(ctl->warmup_time);
	q->rehash_time = jiffies;
	q->limit = limit;
	q->increment = ctl->increment;
	q->decrement = ctl->decrement;
	q->max = ctl->max;
	q->bin_size = ctl->bin_size;
	q->penalty_rate = ctl->penalty_rate;
	q->penalty_burst = ctl->penalty_burst;
	q->tokens_avail = ctl->penalty_burst;
	q->token_time = jiffies;

	q->slot = 0;
	q->double_buffering = false;
	sfb_zero_all_buckets(q);
	sfb_init_perturbation(0, q);
	sfb_init_perturbation(1, q);

	sch_tree_unlock(sch);

	return 0;
	}

	static int sfb_init(struct Qdisc sch, struct nlattr opt)
	{
	struct sfb_sched_data *q = qdisc_priv(sch);

	q->qdisc = &noop_qdisc;
	return sfb_change(sch, opt);
	}

	static int sfb_dump(struct Qdisc sch, struct sk_buff skb)
	{
	struct sfb_sched_data *q = qdisc_priv(sch);
	struct nlattr *opts;
	struct tc_sfb_qopt opt = {
	.rehash_interval = jiffies_to_msecs(q->rehash_interval),
	.warmup_time = jiffies_to_msecs(q->warmup_time),
	.limit = q->limit,
	.max = q->max,
	.bin_size = q->bin_size,
	.increment = q->increment,
	.decrement = q->decrement,
	.penalty_rate = q->penalty_rate,
	.penalty_burst = q->penalty_burst,
	};

	sch->qstats.backlog = q->qdisc->qstats.backlog;
	opts = nla_nest_start(skb, TCA_OPTIONS);
	if (opts == NULL)
	goto nla_put_failure;
	if (nla_put(skb, TCA_SFB_PARMS, sizeof(opt), &opt))
	goto nla_put_failure;
	return nla_nest_end(skb, opts);

	nla_put_failure:
	nla_nest_cancel(skb, opts);
	return -EMSGSIZE;
	}

	static int sfb_dump_stats(struct Qdisc sch, struct gnet_dump d)
	{
	struct sfb_sched_data *q = qdisc_priv(sch);
	struct tc_sfb_xstats st = {
	.earlydrop = q->stats.earlydrop,
	.penaltydrop = q->stats.penaltydrop,
	.bucketdrop = q->stats.bucketdrop,
	.queuedrop = q->stats.queuedrop,
	.childdrop = q->stats.childdrop,
	.marked = q->stats.marked,
	};

	st.maxqlen = sfb_compute_qlen(&st.maxprob, &st.avgprob, q);

	return gnet_stats_copy_app(d, &st, sizeof(st));
	}

	static int sfb_dump_class(struct Qdisc *sch, unsigned long cl,
	struct sk_buff skb, struct tcmsg tcm)
	{
	return -ENOSYS;
	}

	static int sfb_graft(struct Qdisc sch, unsigned long arg, struct Qdisc new,
	struct Qdisc **old)
	{
	struct sfb_sched_data *q = qdisc_priv(sch);

	if (new == NULL)
	new = &noop_qdisc;

	*old = qdisc_replace(sch, new, &q->qdisc);
	return 0;
	}

	static struct Qdisc sfb_leaf(struct Qdisc sch, unsigned long arg)
	{
	struct sfb_sched_data *q = qdisc_priv(sch);

	return q->qdisc;
	}

	static unsigned long sfb_get(struct Qdisc *sch, u32 classid)
	{
	return 1;
	}

	static void sfb_put(struct Qdisc *sch, unsigned long arg)
	{
	}

	static int sfb_change_class(struct Qdisc *sch, u32 classid, u32 parentid,
	struct nlattr *tca, unsigned long arg)
	{
	return -ENOSYS;
	}

	static int sfb_delete(struct Qdisc *sch, unsigned long cl)
	{
	return -ENOSYS;
	}

	static void sfb_walk(struct Qdisc sch, struct qdisc_walker walker)
	{
	if (!walker->stop) {
	if (walker->count >= walker->skip)
	if (walker->fn(sch, 1, walker) < 0) {
	walker->stop = 1;
	return;
	}
	walker->count++;
	}
	}

	static struct tcf_proto __rcu *sfb_find_tcf(struct Qdisc sch,
	unsigned long cl)
	{
	struct sfb_sched_data *q = qdisc_priv(sch);

	if (cl)
	return NULL;
	return &q->filter_list;
	}

	static unsigned long sfb_bind(struct Qdisc *sch, unsigned long parent,
	u32 classid)
	{
	return 0;
	}


	static const struct Qdisc_class_ops sfb_class_ops = {
	.graft = sfb_graft,
	.leaf = sfb_leaf,
	.get = sfb_get,
	.put = sfb_put,
	.change = sfb_change_class,
	.delete = sfb_delete,
	.walk = sfb_walk,
	.tcf_chain = sfb_find_tcf,
	.bind_tcf = sfb_bind,
	.unbind_tcf = sfb_put,
	.dump = sfb_dump_class,
	};

	static struct Qdisc_ops sfb_qdisc_ops __read_mostly = {
	.id = "sfb",
	.priv_size = sizeof(struct sfb_sched_data),
	.cl_ops = &sfb_class_ops,
	.enqueue = sfb_enqueue,
	.dequeue = sfb_dequeue,
	.peek = sfb_peek,
	.init = sfb_init,
	.reset = sfb_reset,
	.destroy = sfb_destroy,
	.change = sfb_change,
	.dump = sfb_dump,
	.dump_stats = sfb_dump_stats,
	.owner = THIS_MODULE,
	};

	static int __init sfb_module_init(void)
	{
	return register_qdisc(&sfb_qdisc_ops);
	}

	static void __exit sfb_module_exit(void)
	{
	unregister_qdisc(&sfb_qdisc_ops);
	}

	module_init(sfb_module_init)
	module_exit(sfb_module_exit)

	MODULE_DESCRIPTION("Stochastic Fair Blue queue discipline");
	MODULE_AUTHOR("Juliusz Chroboczek");
	MODULE_AUTHOR("Eric Dumazet");
	MODULE_LICENSE("GPL");