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 // SPDX-License-Identifier: GPL-2.0-or-later
 /*
  * net/sched/sch_fq.c Fair Queue Packet Scheduler (per flow pacing)
  *
  *  Copyright (C) 2013-2015 Eric Dumazet <edumazet@google.com>
  *
  *  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>
 
 struct fq_skb_cb {
     u64         time_to_send;
 };
 
 static inline struct fq_skb_cb *fq_skb_cb(struct sk_buff *skb)
 {
     qdisc_cb_private_validate(skb, sizeof(struct fq_skb_cb));
     return (struct fq_skb_cb *)qdisc_skb_cb(skb)->data;
 }
 
 /*
  * Per flow structure, dynamically allocated.
  * If packets have monotically increasing time_to_send, they are placed in O(1)
  * in linear list (head,tail), otherwise are placed in a rbtree (t_root).
  */
 struct fq_flow {
 /* First cache line : used in fq_gc(), fq_enqueue(), fq_dequeue() */
     struct rb_root  t_root;
     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 | 1UL) when flow was emptied, for gc */
     };
     struct rb_node  fq_node;    /* anchor in fq_root[] trees */
     struct sock *sk;
     u32     socket_hash;    /* sk_hash */
     int     qlen;       /* number of packets in flow queue */
 
 /* Second cache line, used in fq_dequeue() */
     int     credit;
     /* 32bit hole on 64bit arches */
 
     struct fq_flow *next;       /* next pointer in RR lists */
 
     struct rb_node  rate_node;  /* anchor in q->delayed tree */
     u64     time_next_packet;
 } ____cacheline_aligned_in_smp;
 
 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;
     u64     ktime_cache;    /* copy of last ktime_get_ns() */
     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_plimit;    /* max packets per flow */
     unsigned long   flow_max_rate;  /* optional max rate per flow */
     u64     ce_threshold;
     u64     horizon;    /* horizon in ns */
     u32     orphan_mask;    /* mask for orphaned skb */
     u32     low_rate_threshold;
     struct rb_root  *fq_root;
     u8      rate_enable;
     u8      fq_trees_log;
     u8      horizon_drop;
     u32     flows;
     u32     inactive_flows;
     u32     throttled_flows;
 
     u64     stat_gc_flows;
     u64     stat_internal_packets;
     u64     stat_throttled;
     u64     stat_ce_mark;
     u64     stat_horizon_drops;
     u64     stat_horizon_caps;
     u64     stat_flows_plimit;
     u64     stat_pkts_too_long;
     u64     stat_allocation_errors;
 
     u32     timer_slack; /* hrtimer slack in ns */
     struct qdisc_watchdog watchdog;
 };
 
 /*
  * f->tail and f->age share the same location.
  * We can use the low order bit to differentiate if this location points
  * to a sk_buff or contains a jiffies value, if we force this value to be odd.
  * This assumes f->tail low order bit must be 0 since alignof(struct sk_buff) >= 2
  */
 static void fq_flow_set_detached(struct fq_flow *f)
 {
     f->age = jiffies | 1UL;
 }
 
 static bool fq_flow_is_detached(const struct fq_flow *f)
 {
     return !!(f->age & 1UL);
 }
 
 /* special value to mark a throttled flow (not on old/new list) */
 static struct fq_flow throttled;
 
 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 rb_node **p, *parent;
     void *tofree[FQ_GC_MAX];
     struct fq_flow *f;
     int i, 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;
     }
 
     if (!fcnt)
         return;
 
     for (i = fcnt; i > 0; ) {
         f = tofree[--i];
         rb_erase(&f->fq_node, root);
     }
     q->flows -= fcnt;
     q->inactive_flows -= fcnt;
     q->stat_gc_flows += fcnt;
 
     kmem_cache_free_bulk(fq_flow_cachep, fcnt, tofree);
 }
 
 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);
     } else if (sk->sk_state == TCP_CLOSE) {
         unsigned long hash = skb_get_hash(skb) & q->orphan_mask;
         /*
          * Sockets in TCP_CLOSE are non connected.
          * Typical use case is UDP sockets, they can send packets
          * with sendto() to many different destinations.
          * We probably could use a generic bit advertising
          * non connected sockets, instead of sk_state == TCP_CLOSE,
          * if we care enough.
          */
         sk = (struct sock *)((hash << 1) | 1UL);
     }
 
     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 == 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;
     }
     /* f->t_root is already zeroed after kmem_cache_zalloc() */
 
     fq_flow_set_detached(f);
     f->sk = sk;
     if (skb->sk == 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;
 }
 
 static struct sk_buff *fq_peek(struct fq_flow *flow)
 {
     struct sk_buff *skb = skb_rb_first(&flow->t_root);
     struct sk_buff *head = flow->head;
 
     if (!skb)
         return head;
 
     if (!head)
         return skb;
 
     if (fq_skb_cb(skb)->time_to_send < fq_skb_cb(head)->time_to_send)
         return skb;
     return head;
 }
 
 static void fq_erase_head(struct Qdisc *sch, struct fq_flow *flow,
               struct sk_buff *skb)
 {
     if (skb == flow->head) {
         flow->head = skb->next;
     } else {
         rb_erase(&skb->rbnode, &flow->t_root);
         skb->dev = qdisc_dev(sch);
     }
 }
 
 /* Remove one skb from flow queue.
  * This skb must be the return value of prior fq_peek().
  */
 static void fq_dequeue_skb(struct Qdisc *sch, struct fq_flow *flow,
                struct sk_buff *skb)
 {
     fq_erase_head(sch, flow, skb);
     skb_mark_not_on_list(skb);
     flow->qlen--;
     qdisc_qstats_backlog_dec(sch, skb);
     sch->q.qlen--;
 }
 
 static void flow_queue_add(struct fq_flow *flow, struct sk_buff *skb)
 {
     struct rb_node **p, *parent;
     struct sk_buff *head, *aux;
 
     head = flow->head;
     if (!head ||
         fq_skb_cb(skb)->time_to_send >= fq_skb_cb(flow->tail)->time_to_send) {
         if (!head)
             flow->head = skb;
         else
             flow->tail->next = skb;
         flow->tail = skb;
         skb->next = NULL;
         return;
     }
 
     p = &flow->t_root.rb_node;
     parent = NULL;
 
     while (*p) {
         parent = *p;
         aux = rb_to_skb(parent);
         if (fq_skb_cb(skb)->time_to_send >= fq_skb_cb(aux)->time_to_send)
             p = &parent->rb_right;
         else
             p = &parent->rb_left;
     }
     rb_link_node(&skb->rbnode, parent, p);
     rb_insert_color(&skb->rbnode, &flow->t_root);
 }
 
 static bool fq_packet_beyond_horizon(const struct sk_buff *skb,
                     const struct fq_sched_data *q)
 {
     return unlikely((s64)skb->tstamp > (s64)(q->ktime_cache + q->horizon));
 }
 
 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);
 
     if (!skb->tstamp) {
         fq_skb_cb(skb)->time_to_send = q->ktime_cache = ktime_get_ns();
     } else {
         /* Check if packet timestamp is too far in the future.
          * Try first if our cached value, to avoid ktime_get_ns()
          * cost in most cases.
          */
         if (fq_packet_beyond_horizon(skb, q)) {
             /* Refresh our cache and check another time */
             q->ktime_cache = ktime_get_ns();
             if (fq_packet_beyond_horizon(skb, q)) {
                 if (q->horizon_drop) {
                     q->stat_horizon_drops++;
                     return qdisc_drop(skb, sch, to_free);
                 }
                 q->stat_horizon_caps++;
                 skb->tstamp = q->ktime_cache + q->horizon;
             }
         }
         fq_skb_cb(skb)->time_to_send = skb->tstamp;
     }
 
     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++;
     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);
     struct fq_flow_head *head;
     struct sk_buff *skb;
     struct fq_flow *f;
     unsigned long rate;
     u32 plen;
     u64 now;
 
     if (!sch->q.qlen)
         return NULL;
 
     skb = fq_peek(&q->internal);
     if (unlikely(skb)) {
         fq_dequeue_skb(sch, &q->internal, skb);
         goto out;
     }
 
     q->ktime_cache = now = ktime_get_ns();
     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_range_ns(&q->watchdog,
                             q->time_next_delayed_flow,
                             q->timer_slack);
             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 = fq_peek(f);
     if (skb) {
         u64 time_next_packet = max_t(u64, fq_skb_cb(skb)->time_to_send,
                          f->time_next_packet);
 
         if (now < time_next_packet) {
             head->first = f->next;
             f->time_next_packet = time_next_packet;
             fq_flow_set_throttled(q, f);
             goto begin;
         }
         prefetch(&skb->end);
         if ((s64)(now - time_next_packet - q->ce_threshold) > 0) {
             INET_ECN_set_ce(skb);
             q->stat_ce_mark++;
         }
         fq_dequeue_skb(sch, f, skb);
     } else {
         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;
     }
     plen = qdisc_pkt_len(skb);
     f->credit -= plen;
 
     if (!q->rate_enable)
         goto out;
 
     rate = q->flow_max_rate;
 
     /* If EDT time was provided for this skb, we need to
      * update f->time_next_packet only if this qdisc enforces
      * a flow max rate.
      */
     if (!skb->tstamp) {
         if (skb->sk)
             rate = min(skb->sk->sk_pacing_rate, rate);
 
         if (rate <= q->low_rate_threshold) {
             f->credit = 0;
         } else {
             plen = max(plen, q->quantum);
             if (f->credit > 0)
                 goto out;
         }
     }
     if (rate != ~0UL) {
         u64 len = (u64)plen * NSEC_PER_SEC;
 
         if (likely(rate))
             len = div64_ul(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)
 {
     struct rb_node *p = rb_first(&flow->t_root);
 
     while (p) {
         struct sk_buff *skb = rb_to_skb(p);
 
         p = rb_next(p);
         rb_erase(&skb->rbnode, &flow->t_root);
         rtnl_kfree_skbs(skb, skb);
     }
     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_UNSPEC]         = { .strict_start_type = TCA_FQ_TIMER_SLACK },
 
     [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_ORPHAN_MASK]        = { .type = NLA_U32 },
     [TCA_FQ_LOW_RATE_THRESHOLD] = { .type = NLA_U32 },
     [TCA_FQ_CE_THRESHOLD]       = { .type = NLA_U32 },
     [TCA_FQ_TIMER_SLACK]        = { .type = NLA_U32 },
     [TCA_FQ_HORIZON]        = { .type = NLA_U32 },
     [TCA_FQ_HORIZON_DROP]       = { .type = NLA_U8 },
 };
 
 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]) {
         u32 rate = nla_get_u32(tb[TCA_FQ_FLOW_MAX_RATE]);
 
         q->flow_max_rate = (rate == ~0U) ? ~0UL : 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 (tb[TCA_FQ_CE_THRESHOLD])
         q->ce_threshold = (u64)NSEC_PER_USEC *
                   nla_get_u32(tb[TCA_FQ_CE_THRESHOLD]);
 
     if (tb[TCA_FQ_TIMER_SLACK])
         q->timer_slack = nla_get_u32(tb[TCA_FQ_TIMER_SLACK]);
 
     if (tb[TCA_FQ_HORIZON])
         q->horizon = (u64)NSEC_PER_USEC *
                   nla_get_u32(tb[TCA_FQ_HORIZON]);
 
     if (tb[TCA_FQ_HORIZON_DROP])
         q->horizon_drop = nla_get_u8(tb[TCA_FQ_HORIZON_DROP]);
 
     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    = ~0UL;
     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;
 
     q->timer_slack = 10 * NSEC_PER_USEC; /* 10 usec of hrtimer slack */
 
     q->horizon = 10ULL * NSEC_PER_SEC; /* 10 seconds */
     q->horizon_drop = 1; /* by default, drop packets beyond horizon */
 
     /* Default ce_threshold of 4294 seconds */
     q->ce_threshold     = (u64)NSEC_PER_USEC * ~0U;
 
     qdisc_watchdog_init_clockid(&q->watchdog, sch, CLOCK_MONOTONIC);
 
     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);
     u64 ce_threshold = q->ce_threshold;
     u64 horizon = q->horizon;
     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 */
 
     do_div(ce_threshold, NSEC_PER_USEC);
     do_div(horizon, NSEC_PER_USEC);
 
     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,
             min_t(unsigned long, q->flow_max_rate, ~0U)) ||
         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_CE_THRESHOLD, (u32)ce_threshold) ||
         nla_put_u32(skb, TCA_FQ_BUCKETS_LOG, q->fq_trees_log) ||
         nla_put_u32(skb, TCA_FQ_TIMER_SLACK, q->timer_slack) ||
         nla_put_u32(skb, TCA_FQ_HORIZON, (u32)horizon) ||
         nla_put_u8(skb, TCA_FQ_HORIZON_DROP, q->horizon_drop))
         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        = 0;
     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 + q->timer_slack -
                     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);
     st.ce_mark        = q->stat_ce_mark;
     st.horizon_drops      = q->stat_horizon_drops;
     st.horizon_caps       = q->stat_horizon_caps;
     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");
 MODULE_DESCRIPTION("Fair Queue Packet Scheduler");

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