/*
   * net/sched/sch_fq.c Fair Queue Packet Scheduler (per flow pacing)
   *
   *  Copyright (C) 2013 Eric Dumazet <edumazet@google.com>
   *
   *	This program is free software; you can redistribute it and/or
   *	modify it under the terms of the GNU General Public License
   *	as published by the Free Software Foundation; either version
   *	2 of the License, or (at your option) any later version.
   *
   *  Meant to be mostly used for localy generated traffic :
   *  Fast classification depends on skb->sk being set before reaching us.
   *  If not, (router workload), we use rxhash as fallback, with 32 bits wide hash.
   *  All packets belonging to a socket are considered as a 'flow'.
   *
   *  Flows are dynamically allocated and stored in a hash table of RB trees
   *  They are also part of one Round Robin 'queues' (new or old flows)
   *
   *  Burst avoidance (aka pacing) capability :
   *
   *  Transport (eg TCP) can set in sk->sk_pacing_rate a rate, enqueue a
   *  bunch of packets, and this packet scheduler adds delay between
   *  packets to respect rate limitation.
   *
   *  enqueue() :
   *   - lookup one RB tree (out of 1024 or more) to find the flow.
   *     If non existent flow, create it, add it to the tree.
   *     Add skb to the per flow list of skb (fifo).
   *   - Use a special fifo for high prio packets
   *
   *  dequeue() : serves flows in Round Robin
   *  Note : When a flow becomes empty, we do not immediately remove it from
   *  rb trees, for performance reasons (its expected to send additional packets,
   *  or SLAB cache will reuse socket for another flow)
   */
  
  #include <linux/module.h>
  #include <linux/types.h>
  #include <linux/kernel.h>
  #include <linux/jiffies.h>
  #include <linux/string.h>
  #include <linux/in.h>
  #include <linux/errno.h>
  #include <linux/init.h>
  #include <linux/skbuff.h>
  #include <linux/slab.h>
  #include <linux/rbtree.h>
  #include <linux/hash.h>
  #include <linux/prefetch.h>
  #include <linux/vmalloc.h>
  #include <net/netlink.h>
  #include <net/pkt_sched.h>
  #include <net/sock.h>
  #include <net/tcp_states.h>
  
  /*
   * Per flow structure, dynamically allocated
   */
  struct fq_flow {
  	struct sk_buff	*head;		/* list of skbs for this flow : first skb */
  	union {
  		struct sk_buff *tail;	/* last skb in the list */
  		unsigned long  age;	/* jiffies when flow was emptied, for gc */
  	};
  	struct rb_node	fq_node; 	/* anchor in fq_root[] trees */
  	struct sock	*sk;
  	int		qlen;		/* number of packets in flow queue */
  	int		credit;
  	u32		socket_hash;	/* sk_hash */
  	struct fq_flow *next;		/* next pointer in RR lists, or &detached */
  
  	struct rb_node  rate_node;	/* anchor in q->delayed tree */
  	u64		time_next_packet;
  };
  
  struct fq_flow_head {
  	struct fq_flow *first;
  	struct fq_flow *last;
  };
  
  struct fq_sched_data {
  	struct fq_flow_head new_flows;
  
  	struct fq_flow_head old_flows;
  
  	struct rb_root	delayed;	/* for rate limited flows */
  	u64		time_next_delayed_flow;
  
  	struct fq_flow	internal;	/* for non classified or high prio packets */
  	u32		quantum;
  	u32		initial_quantum;
  	u32		flow_refill_delay;
  	u32		flow_max_rate;	/* optional max rate per flow */
  	u32		flow_plimit;	/* max packets per flow */
  	struct rb_root	*fq_root;
  	u8		rate_enable;
  	u8		fq_trees_log;
  
  	u32		flows;
  	u32		inactive_flows;
  	u32		throttled_flows;
  
  	u64		stat_gc_flows;
  	u64		stat_internal_packets;
  	u64		stat_tcp_retrans;
  	u64		stat_throttled;
  	u64		stat_flows_plimit;
  	u64		stat_pkts_too_long;
  	u64		stat_allocation_errors;
  	struct qdisc_watchdog watchdog;
  };
  
  /* special value to mark a detached flow (not on old/new list) */
  static struct fq_flow detached, throttled;
  
  static void fq_flow_set_detached(struct fq_flow *f)
  {
  	f->next = &detached;
  	f->age = jiffies;
  }
  
  static bool fq_flow_is_detached(const struct fq_flow *f)
  {
  	return f->next == &detached;
  }
  
  static void fq_flow_set_throttled(struct fq_sched_data *q, struct fq_flow *f)
  {
  	struct rb_node **p = &q->delayed.rb_node, *parent = NULL;
  
  	while (*p) {
  		struct fq_flow *aux;
  
  		parent = *p;
  		aux = container_of(parent, struct fq_flow, rate_node);
  		if (f->time_next_packet >= aux->time_next_packet)
  			p = &parent->rb_right;
  		else
  			p = &parent->rb_left;
  	}
  	rb_link_node(&f->rate_node, parent, p);
  	rb_insert_color(&f->rate_node, &q->delayed);
  	q->throttled_flows++;
  	q->stat_throttled++;
  
  	f->next = &throttled;
  	if (q->time_next_delayed_flow > f->time_next_packet)
  		q->time_next_delayed_flow = f->time_next_packet;
  }
  
  
  static struct kmem_cache *fq_flow_cachep __read_mostly;
  
  static void fq_flow_add_tail(struct fq_flow_head *head, struct fq_flow *flow)
  {
  	if (head->first)
  		head->last->next = flow;
  	else
  		head->first = flow;
  	head->last = flow;
  	flow->next = NULL;
  }
  
  /* limit number of collected flows per round */
  #define FQ_GC_MAX 8
  #define FQ_GC_AGE (3*HZ)
  
  static bool fq_gc_candidate(const struct fq_flow *f)
  {
  	return fq_flow_is_detached(f) &&
  	       time_after(jiffies, f->age + FQ_GC_AGE);
  }
  
  static void fq_gc(struct fq_sched_data *q,
  		  struct rb_root *root,
  		  struct sock *sk)
  {
  	struct fq_flow *f, *tofree[FQ_GC_MAX];
  	struct rb_node **p, *parent;
  	int fcnt = 0;
  
  	p = &root->rb_node;
  	parent = NULL;
  	while (*p) {
  		parent = *p;
  
  		f = container_of(parent, struct fq_flow, fq_node);
  		if (f->sk == sk)
  			break;
  
  		if (fq_gc_candidate(f)) {
  			tofree[fcnt++] = f;
  			if (fcnt == FQ_GC_MAX)
  				break;
  		}
  
  		if (f->sk > sk)
  			p = &parent->rb_right;
  		else
  			p = &parent->rb_left;
  	}
  
  	q->flows -= fcnt;
  	q->inactive_flows -= fcnt;
  	q->stat_gc_flows += fcnt;
  	while (fcnt) {
  		struct fq_flow *f = tofree[--fcnt];
  
  		rb_erase(&f->fq_node, root);
  		kmem_cache_free(fq_flow_cachep, f);
  	}
  }
  
  static struct fq_flow *fq_classify(struct sk_buff *skb, struct fq_sched_data *q)
  {
  	struct rb_node **p, *parent;
  	struct sock *sk = skb->sk;
  	struct rb_root *root;
  	struct fq_flow *f;
  
  	/* warning: no starvation prevention... */
  	if (unlikely((skb->priority & TC_PRIO_MAX) == TC_PRIO_CONTROL))
  		return &q->internal;
  
  	if (unlikely(!sk)) {
  		/* By forcing low order bit to 1, we make sure to not
  		 * collide with a local flow (socket pointers are word aligned)
  		 */
  		sk = (struct sock *)(skb_get_hash(skb) | 1L);
  	}
  
  	root = &q->fq_root[hash_32((u32)(long)sk, q->fq_trees_log)];
  
  	if (q->flows >= (2U << q->fq_trees_log) &&
  	    q->inactive_flows > q->flows/2)
  		fq_gc(q, root, sk);
  
  	p = &root->rb_node;
  	parent = NULL;
  	while (*p) {
  		parent = *p;
  
  		f = container_of(parent, struct fq_flow, fq_node);
  		if (f->sk == sk) {
  			/* socket might have been reallocated, so check
  			 * if its sk_hash is the same.
  			 * It not, we need to refill credit with
  			 * initial quantum
  			 */
  			if (unlikely(skb->sk &&
  				     f->socket_hash != sk->sk_hash)) {
  				f->credit = q->initial_quantum;
  				f->socket_hash = sk->sk_hash;
  				f->time_next_packet = 0ULL;
  			}
  			return f;
  		}
  		if (f->sk > sk)
  			p = &parent->rb_right;
  		else
  			p = &parent->rb_left;
  	}
  
  	f = kmem_cache_zalloc(fq_flow_cachep, GFP_ATOMIC | __GFP_NOWARN);
  	if (unlikely(!f)) {
  		q->stat_allocation_errors++;
  		return &q->internal;
  	}
  	fq_flow_set_detached(f);
  	f->sk = sk;
  	if (skb->sk)
  		f->socket_hash = sk->sk_hash;
  	f->credit = q->initial_quantum;
  
  	rb_link_node(&f->fq_node, parent, p);
  	rb_insert_color(&f->fq_node, root);
  
  	q->flows++;
  	q->inactive_flows++;
  	return f;
  }
  
  
  /* remove one skb from head of flow queue */
  static struct sk_buff *fq_dequeue_head(struct Qdisc *sch, struct fq_flow *flow)
  {
  	struct sk_buff *skb = flow->head;
  
  	if (skb) {
  		flow->head = skb->next;
  		skb->next = NULL;
  		flow->qlen--;
  		sch->qstats.backlog -= qdisc_pkt_len(skb);
  		sch->q.qlen--;
  	}
  	return skb;
  }
  
  /* We might add in the future detection of retransmits
   * For the time being, just return false
   */
  static bool skb_is_retransmit(struct sk_buff *skb)
  {
  	return false;
  }
  
  /* add skb to flow queue
   * flow queue is a linked list, kind of FIFO, except for TCP retransmits
   * We special case tcp retransmits to be transmitted before other packets.
   * We rely on fact that TCP retransmits are unlikely, so we do not waste
   * a separate queue or a pointer.
   * head->  [retrans pkt 1]
   *         [retrans pkt 2]
   *         [ normal pkt 1]
   *         [ normal pkt 2]
   *         [ normal pkt 3]
   * tail->  [ normal pkt 4]
   */
  static void flow_queue_add(struct fq_flow *flow, struct sk_buff *skb)
  {
  	struct sk_buff *prev, *head = flow->head;
  
  	skb->next = NULL;
  	if (!head) {
  		flow->head = skb;
  		flow->tail = skb;
  		return;
  	}
  	if (likely(!skb_is_retransmit(skb))) {
  		flow->tail->next = skb;
  		flow->tail = skb;
  		return;
  	}
  
  	/* This skb is a tcp retransmit,
  	 * find the last retrans packet in the queue
  	 */
  	prev = NULL;
  	while (skb_is_retransmit(head)) {
  		prev = head;
  		head = head->next;
  		if (!head)
  			break;
  	}
  	if (!prev) { /* no rtx packet in queue, become the new head */
  		skb->next = flow->head;
  		flow->head = skb;
  	} else {
  		if (prev == flow->tail)
  			flow->tail = skb;
  		else
  			skb->next = prev->next;
  		prev->next = skb;
  	}
  }
  
  static int fq_enqueue(struct sk_buff *skb, struct Qdisc *sch)
  {
  	struct fq_sched_data *q = qdisc_priv(sch);
  	struct fq_flow *f;
  
  	if (unlikely(sch->q.qlen >= sch->limit))
  		return qdisc_drop(skb, sch);
  
  	f = fq_classify(skb, q);
  	if (unlikely(f->qlen >= q->flow_plimit && f != &q->internal)) {
  		q->stat_flows_plimit++;
  		return qdisc_drop(skb, sch);
  	}
  
  	f->qlen++;
  	if (skb_is_retransmit(skb))
  		q->stat_tcp_retrans++;
  	sch->qstats.backlog += qdisc_pkt_len(skb);
  	if (fq_flow_is_detached(f)) {
  		fq_flow_add_tail(&q->new_flows, f);
  		if (time_after(jiffies, f->age + q->flow_refill_delay))
  			f->credit = max_t(u32, f->credit, q->quantum);
  		q->inactive_flows--;
  		qdisc_unthrottled(sch);
  	}
  
  	/* Note: this overwrites f->age */
  	flow_queue_add(f, skb);
  
  	if (unlikely(f == &q->internal)) {
  		q->stat_internal_packets++;
  		qdisc_unthrottled(sch);
  	}
  	sch->q.qlen++;
  
  	return NET_XMIT_SUCCESS;
  }
  
  static void fq_check_throttled(struct fq_sched_data *q, u64 now)
  {
  	struct rb_node *p;
  
  	if (q->time_next_delayed_flow > now)
  		return;
  
  	q->time_next_delayed_flow = ~0ULL;
  	while ((p = rb_first(&q->delayed)) != NULL) {
  		struct fq_flow *f = container_of(p, struct fq_flow, rate_node);
  
  		if (f->time_next_packet > now) {
  			q->time_next_delayed_flow = f->time_next_packet;
  			break;
  		}
  		rb_erase(p, &q->delayed);
  		q->throttled_flows--;
  		fq_flow_add_tail(&q->old_flows, f);
  	}
  }
  
  static struct sk_buff *fq_dequeue(struct Qdisc *sch)
  {
  	struct fq_sched_data *q = qdisc_priv(sch);
  	u64 now = ktime_to_ns(ktime_get());
  	struct fq_flow_head *head;
  	struct sk_buff *skb;
  	struct fq_flow *f;
  	u32 rate;
  
  	skb = fq_dequeue_head(sch, &q->internal);
  	if (skb)
  		goto out;
  	fq_check_throttled(q, now);
  begin:
  	head = &q->new_flows;
  	if (!head->first) {
  		head = &q->old_flows;
  		if (!head->first) {
  			if (q->time_next_delayed_flow != ~0ULL)
  				qdisc_watchdog_schedule_ns(&q->watchdog,
  							   q->time_next_delayed_flow);
  			return NULL;
  		}
  	}
  	f = head->first;
  
  	if (f->credit <= 0) {
  		f->credit += q->quantum;
  		head->first = f->next;
  		fq_flow_add_tail(&q->old_flows, f);
  		goto begin;
  	}
  
  	if (unlikely(f->head && now < f->time_next_packet)) {
  		head->first = f->next;
  		fq_flow_set_throttled(q, f);
  		goto begin;
  	}
  
  	skb = fq_dequeue_head(sch, f);
  	if (!skb) {
  		head->first = f->next;
  		/* force a pass through old_flows to prevent starvation */
  		if ((head == &q->new_flows) && q->old_flows.first) {
  			fq_flow_add_tail(&q->old_flows, f);
  		} else {
  			fq_flow_set_detached(f);
  			q->inactive_flows++;
  		}
  		goto begin;
  	}
  	prefetch(&skb->end);
  	f->time_next_packet = now;
  	f->credit -= qdisc_pkt_len(skb);
  
  	if (f->credit > 0 || !q->rate_enable)
  		goto out;
  
  	rate = q->flow_max_rate;
  	if (skb->sk && skb->sk->sk_state != TCP_TIME_WAIT)
  		rate = min(skb->sk->sk_pacing_rate, rate);
  
  	if (rate != ~0U) {
  		u32 plen = max(qdisc_pkt_len(skb), q->quantum);
  		u64 len = (u64)plen * NSEC_PER_SEC;
  
  		if (likely(rate))
  			do_div(len, rate);
  		/* Since socket rate can change later,
  		 * clamp the delay to 125 ms.
  		 * TODO: maybe segment the too big skb, as in commit
  		 * e43ac79a4bc ("sch_tbf: segment too big GSO packets")
  		 */
  		if (unlikely(len > 125 * NSEC_PER_MSEC)) {
  			len = 125 * NSEC_PER_MSEC;
  			q->stat_pkts_too_long++;
  		}
  
  		f->time_next_packet = now + len;
  	}
  out:
  	qdisc_bstats_update(sch, skb);
  	qdisc_unthrottled(sch);
  	return skb;
  }
  
  static void fq_reset(struct Qdisc *sch)
  {
  	struct fq_sched_data *q = qdisc_priv(sch);
  	struct rb_root *root;
  	struct sk_buff *skb;
  	struct rb_node *p;
  	struct fq_flow *f;
  	unsigned int idx;
  
  	while ((skb = fq_dequeue_head(sch, &q->internal)) != NULL)
  		kfree_skb(skb);
  
  	if (!q->fq_root)
  		return;
  
  	for (idx = 0; idx < (1U << q->fq_trees_log); idx++) {
  		root = &q->fq_root[idx];
  		while ((p = rb_first(root)) != NULL) {
  			f = container_of(p, struct fq_flow, fq_node);
  			rb_erase(p, root);
  
  			while ((skb = fq_dequeue_head(sch, f)) != NULL)
  				kfree_skb(skb);
  
  			kmem_cache_free(fq_flow_cachep, f);
  		}
  	}
  	q->new_flows.first	= NULL;
  	q->old_flows.first	= NULL;
  	q->delayed		= RB_ROOT;
  	q->flows		= 0;
  	q->inactive_flows	= 0;
  	q->throttled_flows	= 0;
  }
  
  static void fq_rehash(struct fq_sched_data *q,
  		      struct rb_root *old_array, u32 old_log,
  		      struct rb_root *new_array, u32 new_log)
  {
  	struct rb_node *op, **np, *parent;
  	struct rb_root *oroot, *nroot;
  	struct fq_flow *of, *nf;
  	int fcnt = 0;
  	u32 idx;
  
  	for (idx = 0; idx < (1U << old_log); idx++) {
  		oroot = &old_array[idx];
  		while ((op = rb_first(oroot)) != NULL) {
  			rb_erase(op, oroot);
  			of = container_of(op, struct fq_flow, fq_node);
  			if (fq_gc_candidate(of)) {
  				fcnt++;
  				kmem_cache_free(fq_flow_cachep, of);
  				continue;
  			}
  			nroot = &new_array[hash_32((u32)(long)of->sk, new_log)];
  
  			np = &nroot->rb_node;
  			parent = NULL;
  			while (*np) {
  				parent = *np;
  
  				nf = container_of(parent, struct fq_flow, fq_node);
  				BUG_ON(nf->sk == of->sk);
  
  				if (nf->sk > of->sk)
  					np = &parent->rb_right;
  				else
  					np = &parent->rb_left;
  			}
  
  			rb_link_node(&of->fq_node, parent, np);
  			rb_insert_color(&of->fq_node, nroot);
  		}
  	}
  	q->flows -= fcnt;
  	q->inactive_flows -= fcnt;
  	q->stat_gc_flows += fcnt;
  }
  
  static void *fq_alloc_node(size_t sz, int node)
  {
  	void *ptr;
  
  	ptr = kmalloc_node(sz, GFP_KERNEL | __GFP_REPEAT | __GFP_NOWARN, node);
  	if (!ptr)
  		ptr = vmalloc_node(sz, node);
  	return ptr;
  }
  
  static void fq_free(void *addr)
  {
  	if (addr && is_vmalloc_addr(addr))
  		vfree(addr);
  	else
  		kfree(addr);
  }
  
  static int fq_resize(struct Qdisc *sch, u32 log)
  {
  	struct fq_sched_data *q = qdisc_priv(sch);
  	struct rb_root *array;
  	void *old_fq_root;
  	u32 idx;
  
  	if (q->fq_root && log == q->fq_trees_log)
  		return 0;
  
  	/* If XPS was setup, we can allocate memory on right NUMA node */
  	array = fq_alloc_node(sizeof(struct rb_root) << log,
  			      netdev_queue_numa_node_read(sch->dev_queue));
  	if (!array)
  		return -ENOMEM;
  
  	for (idx = 0; idx < (1U << log); idx++)
  		array[idx] = RB_ROOT;
  
  	sch_tree_lock(sch);
  
  	old_fq_root = q->fq_root;
  	if (old_fq_root)
  		fq_rehash(q, old_fq_root, q->fq_trees_log, array, log);
  
  	q->fq_root = array;
  	q->fq_trees_log = log;
  
  	sch_tree_unlock(sch);
  
  	fq_free(old_fq_root);
  
  	return 0;
  }
  
  static const struct nla_policy fq_policy[TCA_FQ_MAX + 1] = {
  	[TCA_FQ_PLIMIT]			= { .type = NLA_U32 },
  	[TCA_FQ_FLOW_PLIMIT]		= { .type = NLA_U32 },
  	[TCA_FQ_QUANTUM]		= { .type = NLA_U32 },
  	[TCA_FQ_INITIAL_QUANTUM]	= { .type = NLA_U32 },
  	[TCA_FQ_RATE_ENABLE]		= { .type = NLA_U32 },
  	[TCA_FQ_FLOW_DEFAULT_RATE]	= { .type = NLA_U32 },
  	[TCA_FQ_FLOW_MAX_RATE]		= { .type = NLA_U32 },
  	[TCA_FQ_BUCKETS_LOG]		= { .type = NLA_U32 },
  	[TCA_FQ_FLOW_REFILL_DELAY]	= { .type = NLA_U32 },
  };
  
  static int fq_change(struct Qdisc *sch, struct nlattr *opt)
  {
  	struct fq_sched_data *q = qdisc_priv(sch);
  	struct nlattr *tb[TCA_FQ_MAX + 1];
  	int err, drop_count = 0;
  	u32 fq_log;
  
  	if (!opt)
  		return -EINVAL;
  
  	err = nla_parse_nested(tb, TCA_FQ_MAX, opt, fq_policy);
  	if (err < 0)
  		return err;
  
  	sch_tree_lock(sch);
  
  	fq_log = q->fq_trees_log;
  
  	if (tb[TCA_FQ_BUCKETS_LOG]) {
  		u32 nval = nla_get_u32(tb[TCA_FQ_BUCKETS_LOG]);
  
  		if (nval >= 1 && nval <= ilog2(256*1024))
  			fq_log = nval;
  		else
  			err = -EINVAL;
  	}
  	if (tb[TCA_FQ_PLIMIT])
  		sch->limit = nla_get_u32(tb[TCA_FQ_PLIMIT]);
  
  	if (tb[TCA_FQ_FLOW_PLIMIT])
  		q->flow_plimit = nla_get_u32(tb[TCA_FQ_FLOW_PLIMIT]);
  
  	if (tb[TCA_FQ_QUANTUM])
  		q->quantum = nla_get_u32(tb[TCA_FQ_QUANTUM]);
  
  	if (tb[TCA_FQ_INITIAL_QUANTUM])
  		q->initial_quantum = nla_get_u32(tb[TCA_FQ_INITIAL_QUANTUM]);
  
  	if (tb[TCA_FQ_FLOW_DEFAULT_RATE])
  		pr_warn_ratelimited("sch_fq: defrate %u ignored.
  ",
  				    nla_get_u32(tb[TCA_FQ_FLOW_DEFAULT_RATE]));
  
  	if (tb[TCA_FQ_FLOW_MAX_RATE])
  		q->flow_max_rate = nla_get_u32(tb[TCA_FQ_FLOW_MAX_RATE]);
  
  	if (tb[TCA_FQ_RATE_ENABLE]) {
  		u32 enable = nla_get_u32(tb[TCA_FQ_RATE_ENABLE]);
  
  		if (enable <= 1)
  			q->rate_enable = enable;
  		else
  			err = -EINVAL;
  	}
  
  	if (tb[TCA_FQ_FLOW_REFILL_DELAY]) {
  		u32 usecs_delay = nla_get_u32(tb[TCA_FQ_FLOW_REFILL_DELAY]) ;
  
  		q->flow_refill_delay = usecs_to_jiffies(usecs_delay);
  	}
  
  	if (!err) {
  		sch_tree_unlock(sch);
  		err = fq_resize(sch, fq_log);
  		sch_tree_lock(sch);
  	}
  	while (sch->q.qlen > sch->limit) {
  		struct sk_buff *skb = fq_dequeue(sch);
  
  		if (!skb)
  			break;
  		kfree_skb(skb);
  		drop_count++;
  	}
  	qdisc_tree_decrease_qlen(sch, drop_count);
  
  	sch_tree_unlock(sch);
  	return err;
  }
  
  static void fq_destroy(struct Qdisc *sch)
  {
  	struct fq_sched_data *q = qdisc_priv(sch);
  
  	fq_reset(sch);
  	fq_free(q->fq_root);
  	qdisc_watchdog_cancel(&q->watchdog);
  }
  
  static int fq_init(struct Qdisc *sch, struct nlattr *opt)
  {
  	struct fq_sched_data *q = qdisc_priv(sch);
  	int err;
  
  	sch->limit		= 10000;
  	q->flow_plimit		= 100;
  	q->quantum		= 2 * psched_mtu(qdisc_dev(sch));
  	q->initial_quantum	= 10 * psched_mtu(qdisc_dev(sch));
  	q->flow_refill_delay	= msecs_to_jiffies(40);
  	q->flow_max_rate	= ~0U;
  	q->rate_enable		= 1;
  	q->new_flows.first	= NULL;
  	q->old_flows.first	= NULL;
  	q->delayed		= RB_ROOT;
  	q->fq_root		= NULL;
  	q->fq_trees_log		= ilog2(1024);
  	qdisc_watchdog_init(&q->watchdog, sch);
  
  	if (opt)
  		err = fq_change(sch, opt);
  	else
  		err = fq_resize(sch, q->fq_trees_log);
  
  	return err;
  }
  
  static int fq_dump(struct Qdisc *sch, struct sk_buff *skb)
  {
  	struct fq_sched_data *q = qdisc_priv(sch);
  	struct nlattr *opts;
  
  	opts = nla_nest_start(skb, TCA_OPTIONS);
  	if (opts == NULL)
  		goto nla_put_failure;
  
  	/* TCA_FQ_FLOW_DEFAULT_RATE is not used anymore */
  
  	if (nla_put_u32(skb, TCA_FQ_PLIMIT, sch->limit) ||
  	    nla_put_u32(skb, TCA_FQ_FLOW_PLIMIT, q->flow_plimit) ||
  	    nla_put_u32(skb, TCA_FQ_QUANTUM, q->quantum) ||
  	    nla_put_u32(skb, TCA_FQ_INITIAL_QUANTUM, q->initial_quantum) ||
  	    nla_put_u32(skb, TCA_FQ_RATE_ENABLE, q->rate_enable) ||
  	    nla_put_u32(skb, TCA_FQ_FLOW_MAX_RATE, q->flow_max_rate) ||
  	    nla_put_u32(skb, TCA_FQ_FLOW_REFILL_DELAY,
  			jiffies_to_usecs(q->flow_refill_delay)) ||
  	    nla_put_u32(skb, TCA_FQ_BUCKETS_LOG, q->fq_trees_log))
  		goto nla_put_failure;
  
  	nla_nest_end(skb, opts);
  	return skb->len;
  
  nla_put_failure:
  	return -1;
  }
  
  static int fq_dump_stats(struct Qdisc *sch, struct gnet_dump *d)
  {
  	struct fq_sched_data *q = qdisc_priv(sch);
  	u64 now = ktime_to_ns(ktime_get());
  	struct tc_fq_qd_stats st = {
  		.gc_flows		= q->stat_gc_flows,
  		.highprio_packets	= q->stat_internal_packets,
  		.tcp_retrans		= q->stat_tcp_retrans,
  		.throttled		= q->stat_throttled,
  		.flows_plimit		= q->stat_flows_plimit,
  		.pkts_too_long		= q->stat_pkts_too_long,
  		.allocation_errors	= q->stat_allocation_errors,
  		.flows			= q->flows,
  		.inactive_flows		= q->inactive_flows,
  		.throttled_flows	= q->throttled_flows,
  		.time_next_delayed_flow	= q->time_next_delayed_flow - now,
  	};
  
  	return gnet_stats_copy_app(d, &st, sizeof(st));
  }
  
  static struct Qdisc_ops fq_qdisc_ops __read_mostly = {
  	.id		=	"fq",
  	.priv_size	=	sizeof(struct fq_sched_data),
  
  	.enqueue	=	fq_enqueue,
  	.dequeue	=	fq_dequeue,
  	.peek		=	qdisc_peek_dequeued,
  	.init		=	fq_init,
  	.reset		=	fq_reset,
  	.destroy	=	fq_destroy,
  	.change		=	fq_change,
  	.dump		=	fq_dump,
  	.dump_stats	=	fq_dump_stats,
  	.owner		=	THIS_MODULE,
  };
  
  static int __init fq_module_init(void)
  {
  	int ret;
  
  	fq_flow_cachep = kmem_cache_create("fq_flow_cache",
  					   sizeof(struct fq_flow),
  					   0, 0, NULL);
  	if (!fq_flow_cachep)
  		return -ENOMEM;
  
  	ret = register_qdisc(&fq_qdisc_ops);
  	if (ret)
  		kmem_cache_destroy(fq_flow_cachep);
  	return ret;
  }
  
  static void __exit fq_module_exit(void)
  {
  	unregister_qdisc(&fq_qdisc_ops);
  	kmem_cache_destroy(fq_flow_cachep);
  }
  
  module_init(fq_module_init)
  module_exit(fq_module_exit)
  MODULE_AUTHOR("Eric Dumazet");
  MODULE_LICENSE("GPL");