// SPDX-License-Identifier: GPL-2.0-only

  /*
   * 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>
   *

   * 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/siphash.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 {

  	siphash_key_t	  perturbation; /* siphash key */

  	struct sfb_bucket bins[SFB_LEVELS][SFB_NUMBUCKETS];
  };
  
  struct sfb_sched_data {
  	struct Qdisc	*qdisc;

  	struct tcf_proto __rcu *filter_list;

  	struct tcf_block *block;

  	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)
  {

  	get_random_bytes(&q->bins[slot].perturbation,
  			 sizeof(q->bins[slot].perturbation));

  }
  
  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 = tcf_classify(skb, fl, &res, false);

  	if (result >= 0) {
  #ifdef CONFIG_NET_CLS_ACT
  		switch (result) {
  		case TC_ACT_STOLEN:
  		case TC_ACT_QUEUED:

  		case TC_ACT_TRAP:

  			*qerr = NET_XMIT_SUCCESS | __NET_XMIT_STOLEN;

  			/* fall through */

  		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 = siphash_1u32(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_block_put(q->block);

  	qdisc_put(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 netlink_ext_ack *extack)

  {
  	struct sfb_sched_data *q = qdisc_priv(sch);

  	struct Qdisc *child, *old;

  	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_deprecated(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, extack);

  	if (IS_ERR(child))
  		return PTR_ERR(child);

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

  	sch_tree_lock(sch);

  	qdisc_purge_queue(q->qdisc);
  	old = 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);

  	qdisc_put(old);

  
  	return 0;
  }

  static int sfb_init(struct Qdisc *sch, struct nlattr *opt,
  		    struct netlink_ext_ack *extack)

  {
  	struct sfb_sched_data *q = qdisc_priv(sch);

  	int err;

  	err = tcf_block_get(&q->block, &q->filter_list, sch, extack);

  	if (err)
  		return err;

  
  	q->qdisc = &noop_qdisc;

  	return sfb_change(sch, opt, extack);

  }
  
  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_noflag(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 netlink_ext_ack *extack)

  {
  	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_find(struct Qdisc *sch, u32 classid)

  {
  	return 1;
  }

  static void sfb_unbind(struct Qdisc *sch, unsigned long arg)

  {
  }
  
  static int sfb_change_class(struct Qdisc *sch, u32 classid, u32 parentid,

  			    struct nlattr **tca, unsigned long *arg,
  			    struct netlink_ext_ack *extack)

  {
  	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_block *sfb_tcf_block(struct Qdisc *sch, unsigned long cl,
  				       struct netlink_ext_ack *extack)

  {
  	struct sfb_sched_data *q = qdisc_priv(sch);
  
  	if (cl)
  		return NULL;

  	return q->block;

  }
  
  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,

  	.find		=	sfb_find,

  	.change		=	sfb_change_class,
  	.delete		=	sfb_delete,
  	.walk		=	sfb_walk,

  	.tcf_block	=	sfb_tcf_block,

  	.bind_tcf	=	sfb_bind,

  	.unbind_tcf	=	sfb_unbind,

  	.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");