/*
 * net/sched/sch_fq.c Fair Queue Packet Scheduler (per flow pacing)
 *
 *  Copyright (C) 2013-2015 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 locally 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>
#include <net/tcp.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;
        unsigned long   unthrottle_latency_ns;

        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 */
        u32             orphan_mask;    /* mask for orphaned skb */
        u32             low_rate_threshold;
        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 bool fq_flow_is_throttled(const struct fq_flow *f)
{
        return f->next == &throttled;
}

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;
}

static void fq_flow_unset_throttled(struct fq_sched_data *q, struct fq_flow *f)
{
        rb_erase(&f->rate_node, &q->delayed);
        q->throttled_flows--;
        fq_flow_add_tail(&q->old_flows, f);
}

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 = rb_entry(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;


/* 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 = rb_entry(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;

        /* SYNACK messages are attached to a TCP_NEW_SYN_RECV request socket
         * or a listener (SYNCOOKIE mode)
         * 1) request sockets are not full blown,
         *    they do not contain sk_pacing_rate
         * 2) They are not part of a 'flow' yet
         * 3) We do not want to rate limit them (eg SYNFLOOD attack),
         *    especially if the listener set SO_MAX_PACING_RATE
         * 4) We pretend they are orphaned
         */
        if (!sk || sk_listener(sk)) {
                unsigned long hash = skb_get_hash(skb) & q->orphan_mask;

                /* 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 *)((hash << 1) | 1UL);
                skb_orphan(skb);
        }

        root = &q->fq_root[hash_ptr(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 = rb_entry(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;
                                if (q->rate_enable)
                                        smp_store_release(&sk->sk_pacing_status,
                                                          SK_PACING_FQ);
                                if (fq_flow_is_throttled(f))
                                        fq_flow_unset_throttled(q, f);
                                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;
                if (q->rate_enable)
                        smp_store_release(&sk->sk_pacing_status,
                                          SK_PACING_FQ);
        }
        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_mark_not_on_list(skb);
                flow->qlen--;
                qdisc_qstats_backlog_dec(sch, 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 sk_buff **to_free)
{
        struct fq_sched_data *q = qdisc_priv(sch);
        struct fq_flow *f;

        if (unlikely(sch->q.qlen >= sch->limit))
                return qdisc_drop(skb, sch, to_free);

        f = fq_classify(skb, q);
        if (unlikely(f->qlen >= q->flow_plimit && f != &q->internal)) {
                q->stat_flows_plimit++;
                return qdisc_drop(skb, sch, to_free);
        }

        f->qlen++;
        if (skb_is_retransmit(skb))
                q->stat_tcp_retrans++;
        qdisc_qstats_backlog_inc(sch, 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--;
        }

        /* Note: this overwrites f->age */
        flow_queue_add(f, skb);

        if (unlikely(f == &q->internal)) {
                q->stat_internal_packets++;
        }
        sch->q.qlen++;

        return NET_XMIT_SUCCESS;
}

static void fq_check_throttled(struct fq_sched_data *q, u64 now)
{
        unsigned long sample;
        struct rb_node *p;

        if (q->time_next_delayed_flow > now)
                return;

        /* Update unthrottle latency EWMA.
         * This is cheap and can help diagnosing timer/latency problems.
         */
        sample = (unsigned long)(now - q->time_next_delayed_flow);
        q->unthrottle_latency_ns -= q->unthrottle_latency_ns >> 3;
        q->unthrottle_latency_ns += sample >> 3;

        q->time_next_delayed_flow = ~0ULL;
        while ((p = rb_first(&q->delayed)) != NULL) {
                struct fq_flow *f = rb_entry(p, struct fq_flow, rate_node);

                if (f->time_next_packet > now) {
                        q->time_next_delayed_flow = f->time_next_packet;
                        break;
                }
                fq_flow_unset_throttled(q, f);
        }
}

static struct sk_buff *fq_dequeue(struct Qdisc *sch)
{
        struct fq_sched_data *q = qdisc_priv(sch);
        u64 now = ktime_get_ns();
        struct fq_flow_head *head;
        struct sk_buff *skb;
        struct fq_flow *f;
        u32 rate, plen;

        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;
        }

        skb = f->head;
        if (unlikely(skb && now < f->time_next_packet &&
                     !skb_is_tcp_pure_ack(skb))) {
                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->credit -= qdisc_pkt_len(skb);

        if (!q->rate_enable)
                goto out;

        /* Do not pace locally generated ack packets */
        if (skb_is_tcp_pure_ack(skb))
                goto out;

        rate = q->flow_max_rate;
        if (skb->sk)
                rate = min(skb->sk->sk_pacing_rate, rate);

        if (rate <= q->low_rate_threshold) {
                f->credit = 0;
                plen = qdisc_pkt_len(skb);
        } else {
                plen = max(qdisc_pkt_len(skb), q->quantum);
                if (f->credit > 0)
                        goto out;
        }
        if (rate != ~0U) {
                u64 len = (u64)plen * NSEC_PER_SEC;

                if (likely(rate))
                        do_div(len, rate);
                /* Since socket rate can change later,
                 * clamp the delay to 1 second.
                 * Really, providers of too big packets should be fixed !
                 */
                if (unlikely(len > NSEC_PER_SEC)) {
                        len = NSEC_PER_SEC;
                        q->stat_pkts_too_long++;
                }
                /* Account for schedule/timers drifts.
                 * f->time_next_packet was set when prior packet was sent,
                 * and current time (@now) can be too late by tens of us.
                 */
                if (f->time_next_packet)
                        len -= min(len/2, now - f->time_next_packet);
                f->time_next_packet = now + len;
        }
out:
        qdisc_bstats_update(sch, skb);
        return skb;
}

static void fq_flow_purge(struct fq_flow *flow)
{
        rtnl_kfree_skbs(flow->head, flow->tail);
        flow->head = NULL;
        flow->qlen = 0;
}

static void fq_reset(struct Qdisc *sch)
{
        struct fq_sched_data *q = qdisc_priv(sch);
        struct rb_root *root;
        struct rb_node *p;
        struct fq_flow *f;
        unsigned int idx;

        sch->q.qlen = 0;
        sch->qstats.backlog = 0;

        fq_flow_purge(&q->internal);

        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 = rb_entry(p, struct fq_flow, fq_node);
                        rb_erase(p, root);

                        fq_flow_purge(f);

                        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 = rb_entry(op, struct fq_flow, fq_node);
                        if (fq_gc_candidate(of)) {
                                fcnt++;
                                kmem_cache_free(fq_flow_cachep, of);
                                continue;
                        }
                        nroot = &new_array[hash_ptr(of->sk, new_log)];

                        np = &nroot->rb_node;
                        parent = NULL;
                        while (*np) {
                                parent = *np;

                                nf = rb_entry(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_free(void *addr)
{
        kvfree(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 = kvmalloc_node(sizeof(struct rb_root) << log, GFP_KERNEL | __GFP_RETRY_MAYFAIL,
                              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 },
        [TCA_FQ_LOW_RATE_THRESHOLD]     = { .type = NLA_U32 },
};

static int fq_change(struct Qdisc *sch, struct nlattr *opt,
                     struct netlink_ext_ack *extack)
{
        struct fq_sched_data *q = qdisc_priv(sch);
        struct nlattr *tb[TCA_FQ_MAX + 1];
        int err, drop_count = 0;
        unsigned drop_len = 0;
        u32 fq_log;

        if (!opt)
                return -EINVAL;

        err = nla_parse_nested_deprecated(tb, TCA_FQ_MAX, opt, fq_policy,
                                          NULL);
        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]) {
                u32 quantum = nla_get_u32(tb[TCA_FQ_QUANTUM]);

                if (quantum > 0 && quantum <= (1 << 20)) {
                        q->quantum = quantum;
                } else {
                        NL_SET_ERR_MSG_MOD(extack, "invalid quantum");
                        err = -EINVAL;
                }
        }

        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.\n",
                                    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_LOW_RATE_THRESHOLD])
                q->low_rate_threshold =
                        nla_get_u32(tb[TCA_FQ_LOW_RATE_THRESHOLD]);

        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 (tb[TCA_FQ_ORPHAN_MASK])
                q->orphan_mask = nla_get_u32(tb[TCA_FQ_ORPHAN_MASK]);

        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;
                drop_len += qdisc_pkt_len(skb);
                rtnl_kfree_skbs(skb, skb);
                drop_count++;
        }
        qdisc_tree_reduce_backlog(sch, drop_count, drop_len);

        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 netlink_ext_ack *extack)
{
        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->time_next_delayed_flow = ~0ULL;
        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);
        q->orphan_mask          = 1024 - 1;
        q->low_rate_threshold   = 550000 / 8;
        qdisc_watchdog_init(&q->watchdog, sch);

        if (opt)
                err = fq_change(sch, opt, extack);
        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_noflag(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_ORPHAN_MASK, q->orphan_mask) ||
            nla_put_u32(skb, TCA_FQ_LOW_RATE_THRESHOLD,
                        q->low_rate_threshold) ||
            nla_put_u32(skb, TCA_FQ_BUCKETS_LOG, q->fq_trees_log))
                goto nla_put_failure;

        return nla_nest_end(skb, opts);

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);
        struct tc_fq_qd_stats st;

        sch_tree_lock(sch);

        st.gc_flows               = q->stat_gc_flows;
        st.highprio_packets       = q->stat_internal_packets;
        st.tcp_retrans            = q->stat_tcp_retrans;
        st.throttled              = q->stat_throttled;
        st.flows_plimit           = q->stat_flows_plimit;
        st.pkts_too_long          = q->stat_pkts_too_long;
        st.allocation_errors      = q->stat_allocation_errors;
        st.time_next_delayed_flow = q->time_next_delayed_flow - ktime_get_ns();
        st.flows                  = q->flows;
        st.inactive_flows         = q->inactive_flows;
        st.throttled_flows        = q->throttled_flows;
        st.unthrottle_latency_ns  = min_t(unsigned long,
                                          q->unthrottle_latency_ns, ~0U);
        sch_tree_unlock(sch);

        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");