path: root/net/sched/sch_api.c

// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * net/sched/sch_api.c	Packet scheduler API.
 *
 * Authors:	Alexey Kuznetsov, <kuznet@ms2.inr.ac.ru>
 *
 * Fixes:
 *
 * Rani Assaf <rani@magic.metawire.com> :980802: JIFFIES and CPU clock sources are repaired.
 * Eduardo J. Blanco <ejbs@netlabs.com.uy> :990222: kmod support
 * Jamal Hadi Salim <hadi@nortelnetworks.com>: 990601: ingress support
 */

#include <linux/module.h>
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/string.h>
#include <linux/errno.h>
#include <linux/skbuff.h>
#include <linux/init.h>
#include <linux/proc_fs.h>
#include <linux/seq_file.h>
#include <linux/kmod.h>
#include <linux/list.h>
#include <linux/hrtimer.h>
#include <linux/slab.h>
#include <linux/hashtable.h>

#include <net/net_namespace.h>
#include <net/sock.h>
#include <net/netlink.h>
#include <net/pkt_sched.h>
#include <net/pkt_cls.h>
#include <net/tc_wrapper.h>

#include <trace/events/qdisc.h>

/*

   Short review.
   -------------

   This file consists of two interrelated parts:

   1. queueing disciplines manager frontend.
   2. traffic classes manager frontend.

   Generally, queueing discipline ("qdisc") is a black box,
   which is able to enqueue packets and to dequeue them (when
   device is ready to send something) in order and at times
   determined by algorithm hidden in it.

   qdisc's are divided to two categories:
   - "queues", which have no internal structure visible from outside.
   - "schedulers", which split all the packets to "traffic classes",
     using "packet classifiers" (look at cls_api.c)

   In turn, classes may have child qdiscs (as rule, queues)
   attached to them etc. etc. etc.

   The goal of the routines in this file is to translate
   information supplied by user in the form of handles
   to more intelligible for kernel form, to make some sanity
   checks and part of work, which is common to all qdiscs
   and to provide rtnetlink notifications.

   All real intelligent work is done inside qdisc modules.



   Every discipline has two major routines: enqueue and dequeue.

   ---dequeue

   dequeue usually returns a skb to send. It is allowed to return NULL,
   but it does not mean that queue is empty, it just means that
   discipline does not want to send anything this time.
   Queue is really empty if q->q.qlen == 0.
   For complicated disciplines with multiple queues q->q is not
   real packet queue, but however q->q.qlen must be valid.

   ---enqueue

   enqueue returns 0, if packet was enqueued successfully.
   If packet (this one or another one) was dropped, it returns
   not zero error code.
   NET_XMIT_DROP 	- this packet dropped
     Expected action: do not backoff, but wait until queue will clear.
   NET_XMIT_CN	 	- probably this packet enqueued, but another one dropped.
     Expected action: backoff or ignore

   Auxiliary routines:

   ---peek

   like dequeue but without removing a packet from the queue

   ---reset

   returns qdisc to initial state: purge all buffers, clear all
   timers, counters (except for statistics) etc.

   ---init

   initializes newly created qdisc.

   ---destroy

   destroys resources allocated by init and during lifetime of qdisc.

   ---change

   changes qdisc parameters.
 */

/* Protects list of registered TC modules. It is pure SMP lock. */
static DEFINE_RWLOCK(qdisc_mod_lock);


/************************************************
 *	Queueing disciplines manipulation.	*
 ************************************************/


/* The list of all installed queueing disciplines. */

static struct Qdisc_ops *qdisc_base;

/* Register/unregister queueing discipline */

int register_qdisc(struct Qdisc_ops *qops)
{
	struct Qdisc_ops *q, **qp;
	int rc = -EEXIST;

	write_lock(&qdisc_mod_lock);
	for (qp = &qdisc_base; (q = *qp) != NULL; qp = &q->next)
		if (!strcmp(qops->id, q->id))
			goto out;

	if (qops->enqueue == NULL)
		qops->enqueue = noop_qdisc_ops.enqueue;
	if (qops->peek == NULL) {
		if (qops->dequeue == NULL)
			qops->peek = noop_qdisc_ops.peek;
		else
			goto out_einval;
	}
	if (qops->dequeue == NULL)
		qops->dequeue = noop_qdisc_ops.dequeue;

	if (qops->cl_ops) {
		const struct Qdisc_class_ops *cops = qops->cl_ops;

		if (!(cops->find && cops->walk && cops->leaf))
			goto out_einval;

		if (cops->tcf_block && !(cops->bind_tcf && cops->unbind_tcf))
			goto out_einval;
	}

	qops->next = NULL;
	*qp = qops;
	rc = 0;
out:
	write_unlock(&qdisc_mod_lock);
	return rc;

out_einval:
	rc = -EINVAL;
	goto out;
}
EXPORT_SYMBOL(register_qdisc);

void unregister_qdisc(struct Qdisc_ops *qops)
{
	struct Qdisc_ops *q, **qp;
	int err = -ENOENT;

	write_lock(&qdisc_mod_lock);
	for (qp = &qdisc_base; (q = *qp) != NULL; qp = &q->next)
		if (q == qops)
			break;
	if (q) {
		*qp = q->next;
		q->next = NULL;
		err = 0;
	}
	write_unlock(&qdisc_mod_lock);

	WARN(err, "unregister qdisc(%s) failed\n", qops->id);
}
EXPORT_SYMBOL(unregister_qdisc);

/* Get default qdisc if not otherwise specified */
void qdisc_get_default(char *name, size_t len)
{
	read_lock(&qdisc_mod_lock);
	strscpy(name, default_qdisc_ops->id, len);
	read_unlock(&qdisc_mod_lock);
}

static struct Qdisc_ops *qdisc_lookup_default(const char *name)
{
	struct Qdisc_ops *q = NULL;

	for (q = qdisc_base; q; q = q->next) {
		if (!strcmp(name, q->id)) {
			if (!try_module_get(q->owner))
				q = NULL;
			break;
		}
	}

	return q;
}

/* Set new default qdisc to use */
int qdisc_set_default(const char *name)
{
	const struct Qdisc_ops *ops;

	if (!capable(CAP_NET_ADMIN))
		return -EPERM;

	write_lock(&qdisc_mod_lock);
	ops = qdisc_lookup_default(name);
	if (!ops) {
		/* Not found, drop lock and try to load module */
		write_unlock(&qdisc_mod_lock);
		request_module("sch_%s", name);
		write_lock(&qdisc_mod_lock);

		ops = qdisc_lookup_default(name);
	}

	if (ops) {
		/* Set new default */
		module_put(default_qdisc_ops->owner);
		default_qdisc_ops = ops;
	}
	write_unlock(&qdisc_mod_lock);

	return ops ? 0 : -ENOENT;
}

#ifdef CONFIG_NET_SCH_DEFAULT
/* Set default value from kernel config */
static int __init sch_default_qdisc(void)
{
	return qdisc_set_default(CONFIG_DEFAULT_NET_SCH);
}
late_initcall(sch_default_qdisc);
#endif

/* We know handle. Find qdisc among all qdisc's attached to device
 * (root qdisc, all its children, children of children etc.)
 * Note: caller either uses rtnl or rcu_read_lock()
 */

static struct Qdisc *qdisc_match_from_root(struct Qdisc *root, u32 handle)
{
	struct Qdisc *q;

	if (!qdisc_dev(root))
		return (root->handle == handle ? root : NULL);

	if (!(root->flags & TCQ_F_BUILTIN) &&
	    root->handle == handle)
		return root;

	hash_for_each_possible_rcu(qdisc_dev(root)->qdisc_hash, q, hash, handle,
				   lockdep_rtnl_is_held()) {
		if (q->handle == handle)
			return q;
	}
	return NULL;
}

void qdisc_hash_add(struct Qdisc *q, bool invisible)
{
	if ((q->parent != TC_H_ROOT) && !(q->flags & TCQ_F_INGRESS)) {
		ASSERT_RTNL();
		hash_add_rcu(qdisc_dev(q)->qdisc_hash, &q->hash, q->handle);
		if (invisible)
			q->flags |= TCQ_F_INVISIBLE;
	}
}
EXPORT_SYMBOL(qdisc_hash_add);

void qdisc_hash_del(struct Qdisc *q)
{
	if ((q->parent != TC_H_ROOT) && !(q->flags & TCQ_F_INGRESS)) {
		ASSERT_RTNL();
		hash_del_rcu(&q->hash);
	}
}
EXPORT_SYMBOL(qdisc_hash_del);

struct Qdisc *qdisc_lookup(struct net_device *dev, u32 handle)
{
	struct Qdisc *q;

	if (!handle)
		return NULL;
	q = qdisc_match_from_root(rtnl_dereference(dev->qdisc), handle);
	if (q)
		goto out;

	if (dev_ingress_queue(dev))
		q = qdisc_match_from_root(
			rtnl_dereference(dev_ingress_queue(dev)->qdisc_sleeping),
			handle);
out:
	return q;
}

struct Qdisc *qdisc_lookup_rcu(struct net_device *dev, u32 handle)
{
	struct netdev_queue *nq;
	struct Qdisc *q;

	if (!handle)
		return NULL;
	q = qdisc_match_from_root(rcu_dereference(dev->qdisc), handle);
	if (q)
		goto out;

	nq = dev_ingress_queue_rcu(dev);
	if (nq)
		q = qdisc_match_from_root(rcu_dereference(nq->qdisc_sleeping),
					  handle);
out:
	return q;
}

static struct Qdisc *qdisc_leaf(struct Qdisc *p, u32 classid)
{
	unsigned long cl;
	const struct Qdisc_class_ops *cops = p->ops->cl_ops;

	if (cops == NULL)
		return NULL;
	cl = cops->find(p, classid);

	if (cl == 0)
		return NULL;
	return cops->leaf(p, cl);
}

/* Find queueing discipline by name */

static struct Qdisc_ops *qdisc_lookup_ops(struct nlattr *kind)
{
	struct Qdisc_ops *q = NULL;

	if (kind) {
		read_lock(&qdisc_mod_lock);
		for (q = qdisc_base; q; q = q->next) {
			if (nla_strcmp(kind, q->id) == 0) {
				if (!try_module_get(q->owner))
					q = NULL;
				break;
			}
		}
		read_unlock(&qdisc_mod_lock);
	}
	return q;
}

/* The linklayer setting were not transferred from iproute2, in older
 * versions, and the rate tables lookup systems have been dropped in
 * the kernel. To keep backward compatible with older iproute2 tc
 * utils, we detect the linklayer setting by detecting if the rate
 * table were modified.
 *
 * For linklayer ATM table entries, the rate table will be aligned to
 * 48 bytes, thus some table entries will contain the same value.  The
 * mpu (min packet unit) is also encoded into the old rate table, thus
 * starting from the mpu, we find low and high table entries for
 * mapping this cell.  If these entries contain the same value, when
 * the rate tables have been modified for linklayer ATM.
 *
 * This is done by rounding mpu to the nearest 48 bytes cell/entry,
 * and then roundup to the next cell, calc the table entry one below,
 * and compare.
 */
static __u8 __detect_linklayer(struct tc_ratespec *r, __u32 *rtab)
{
	int low       = roundup(r->mpu, 48);
	int high      = roundup(low+1, 48);
	int cell_low  = low >> r->cell_log;
	int cell_high = (high >> r->cell_log) - 1;

	/* rtab is too inaccurate at rates > 100Mbit/s */
	if ((r->rate > (100000000/8)) || (rtab[0] == 0)) {
		pr_debug("TC linklayer: Giving up ATM detection\n");
		return TC_LINKLAYER_ETHERNET;
	}

	if ((cell_high > cell_low) && (cell_high < 256)
	    && (rtab[cell_low] == rtab[cell_high])) {
		pr_debug("TC linklayer: Detected ATM, low(%d)=high(%d)=%u\n",
			 cell_low, cell_high, rtab[cell_high]);
		return TC_LINKLAYER_ATM;
	}
	return TC_LINKLAYER_ETHERNET;
}

static struct qdisc_rate_table *qdisc_rtab_list;

struct qdisc_rate_table *qdisc_get_rtab(struct tc_ratespec *r,
					struct nlattr *tab,
					struct netlink_ext_ack *extack)
{
	struct qdisc_rate_table *rtab;

	if (tab == NULL || r->rate == 0 ||
	    r->cell_log == 0 || r->cell_log >= 32 ||
	    nla_len(tab) != TC_RTAB_SIZE) {
		NL_SET_ERR_MSG(extack, "Invalid rate table parameters for searching");
		return NULL;
	}

	for (rtab = qdisc_rtab_list; rtab; rtab = rtab->next) {
		if (!memcmp(&rtab->rate, r, sizeof(struct tc_ratespec)) &&
		    !memcmp(&rtab->data, nla_data(tab), 1024)) {
			rtab->refcnt++;
			return rtab;
		}
	}

	rtab = kmalloc(sizeof(*rtab), GFP_KERNEL);
	if (rtab) {
		rtab->rate = *r;
		rtab->refcnt = 1;
		memcpy(rtab->data, nla_data(tab), 1024);
		if (r->linklayer == TC_LINKLAYER_UNAWARE)
			r->linklayer = __detect_linklayer(r, rtab->data);
		rtab->next = qdisc_rtab_list;
		qdisc_rtab_list = rtab;
	} else {
		NL_SET_ERR_MSG(extack, "Failed to allocate new qdisc rate table");
	}
	return rtab;
}
EXPORT_SYMBOL(qdisc_get_rtab);

void qdisc_put_rtab(struct qdisc_rate_table *tab)
{
	struct qdisc_rate_table *rtab, **rtabp;

	if (!tab || --tab->refcnt)
		return;

	for (rtabp = &qdisc_rtab_list;
	     (rtab = *rtabp) != NULL;
	     rtabp = &rtab->next) {
		if (rtab == tab) {
			*rtabp = rtab->next;
			kfree(rtab);
			return;
		}
	}
}
EXPORT_SYMBOL(qdisc_put_rtab);

static LIST_HEAD(qdisc_stab_list);

static const struct nla_policy stab_policy[TCA_STAB_MAX + 1] = {
	[TCA_STAB_BASE]	= { .len = sizeof(struct tc_sizespec) },
	[TCA_STAB_DATA] = { .type = NLA_BINARY },
};

static struct qdisc_size_table *qdisc_get_stab(struct nlattr *opt,
					       struct netlink_ext_ack *extack)
{
	struct nlattr *tb[TCA_STAB_MAX + 1];
	struct qdisc_size_table *stab;
	struct tc_sizespec *s;
	unsigned int tsize = 0;
	u16 *tab = NULL;
	int err;

	err = nla_parse_nested_deprecated(tb, TCA_STAB_MAX, opt, stab_policy,
					  extack);
	if (err < 0)
		return ERR_PTR(err);
	if (!tb[TCA_STAB_BASE]) {
		NL_SET_ERR_MSG(extack, "Size table base attribute is missing");
		return ERR_PTR(-EINVAL);
	}

	s = nla_data(tb[TCA_STAB_BASE]);

	if (s->tsize > 0) {
		if (!tb[TCA_STAB_DATA]) {
			NL_SET_ERR_MSG(extack, "Size table data attribute is missing");
			return ERR_PTR(-EINVAL);
		}
		tab = nla_data(tb[TCA_STAB_DATA]);
		tsize = nla_len(tb[TCA_STAB_DATA]) / sizeof(u16);
	}

	if (tsize != s->tsize || (!tab && tsize > 0)) {
		NL_SET_ERR_MSG(extack, "Invalid size of size table");
		return ERR_PTR(-EINVAL);
	}

	list_for_each_entry(stab, &qdisc_stab_list, list) {
		if (memcmp(&stab->szopts, s, sizeof(*s)))
			continue;
		if (tsize > 0 &&
		    memcmp(stab->data, tab, flex_array_size(stab, data, tsize)))
			continue;
		stab->refcnt++;
		return stab;
	}

	if (s->size_log > STAB_SIZE_LOG_MAX ||
	    s->cell_log > STAB_SIZE_LOG_MAX) {
		NL_SET_ERR_MSG(extack, "Invalid logarithmic size of size table");
		return ERR_PTR(-EINVAL);
	}

	stab = kmalloc(struct_size(stab, data, tsize), GFP_KERNEL);
	if (!stab)
		return ERR_PTR(-ENOMEM);

	stab->refcnt = 1;
	stab->szopts = *s;
	if (tsize > 0)
		memcpy(stab->data, tab, flex_array_size(stab, data, tsize));

	list_add_tail(&stab->list, &qdisc_stab_list);

	return stab;
}

void qdisc_put_stab(struct qdisc_size_table *tab)
{
	if (!tab)
		return;

	if (--tab->refcnt == 0) {
		list_del(&tab->list);
		kfree_rcu(tab, rcu);
	}
}
EXPORT_SYMBOL(qdisc_put_stab);

static int qdisc_dump_stab(struct sk_buff *skb, struct qdisc_size_table *stab)
{
	struct nlattr *nest;

	nest = nla_nest_start_noflag(skb, TCA_STAB);
	if (nest == NULL)
		goto nla_put_failure;
	if (nla_put(skb, TCA_STAB_BASE, sizeof(stab->szopts), &stab->szopts))
		goto nla_put_failure;
	nla_nest_end(skb, nest);

	return skb->len;

nla_put_failure:
	return -1;
}

void __qdisc_calculate_pkt_len(struct sk_buff *skb,
			       const struct qdisc_size_table *stab)
{
	int pkt_len, slot;

	pkt_len = skb->len + stab->szopts.overhead;
	if (unlikely(!stab->szopts.tsize))
		goto out;

	slot = pkt_len + stab->szopts.cell_align;
	if (unlikely(slot < 0))
		slot = 0;

	slot >>= stab->szopts.cell_log;
	if (likely(slot < stab->szopts.tsize))
		pkt_len = stab->data[slot];
	else
		pkt_len = stab->data[stab->szopts.tsize - 1] *
				(slot / stab->szopts.tsize) +
				stab->data[slot % stab->szopts.tsize];

	pkt_len <<= stab->szopts.size_log;
out:
	if (unlikely(pkt_len < 1))
		pkt_len = 1;
	qdisc_skb_cb(skb)->pkt_len = pkt_len;
}
EXPORT_SYMBOL(__qdisc_calculate_pkt_len);

void qdisc_warn_nonwc(const char *txt, struct Qdisc *qdisc)
{
	if (!(qdisc->flags & TCQ_F_WARN_NONWC)) {
		pr_warn("%s: %s qdisc %X: is non-work-conserving?\n",
			txt, qdisc->ops->id, qdisc->handle >> 16);
		qdisc->flags |= TCQ_F_WARN_NONWC;
	}
}
EXPORT_SYMBOL(qdisc_warn_nonwc);

static enum hrtimer_restart qdisc_watchdog(struct hrtimer *timer)
{
	struct qdisc_watchdog *wd = container_of(timer, struct qdisc_watchdog,
						 timer);

	rcu_read_lock();
	__netif_schedule(qdisc_root(wd->qdisc));
	rcu_read_unlock();

	return HRTIMER_NORESTART;
}

void qdisc_watchdog_init_clockid(struct qdisc_watchdog *wd, struct Qdisc *qdisc,
				 clockid_t clockid)
{
	hrtimer_init(&wd->timer, clockid, HRTIMER_MODE_ABS_PINNED);
	wd->timer.function = qdisc_watchdog;
	wd->qdisc = qdisc;
}
EXPORT_SYMBOL(qdisc_watchdog_init_clockid);

void qdisc_watchdog_init(struct qdisc_watchdog *wd, struct Qdisc *qdisc)
{
	qdisc_watchdog_init_clockid(wd, qdisc, CLOCK_MONOTONIC);
}
EXPORT_SYMBOL(qdisc_watchdog_init);

void qdisc_watchdog_schedule_range_ns(struct qdisc_watchdog *wd, u64 expires,
				      u64 delta_ns)
{
	bool deactivated;

	rcu_read_lock();
	deactivated = test_bit(__QDISC_STATE_DEACTIVATED,
			       &qdisc_root_sleeping(wd->qdisc)->state);
	rcu_read_unlock();
	if (deactivated)
		return;

	if (hrtimer_is_queued(&wd->timer)) {
		u64 softexpires;

		softexpires = ktime_to_ns(hrtimer_get_softexpires(&wd->timer));
		/* If timer is already set in [expires, expires + delta_ns],
		 * do not reprogram it.
		 */
		if (softexpires - expires <= delta_ns)
			return;
	}

	hrtimer_start_range_ns(&wd->timer,
			       ns_to_ktime(expires),
			       delta_ns,
			       HRTIMER_MODE_ABS_PINNED);
}
EXPORT_SYMBOL(qdisc_watchdog_schedule_range_ns);

void qdisc_watchdog_cancel(struct qdisc_watchdog *wd)
{
	hrtimer_cancel(&wd->timer);
}
EXPORT_SYMBOL(qdisc_watchdog_cancel);

static struct hlist_head *qdisc_class_hash_alloc(unsigned int n)
{
	struct hlist_head *h;
	unsigned int i;

	h = kvmalloc_array(n, sizeof(struct hlist_head), GFP_KERNEL);

	if (h != NULL) {
		for (i = 0; i < n; i++)
			INIT_HLIST_HEAD(&h[i]);
	}
	return h;
}

void qdisc_class_hash_grow(struct Qdisc *sch, struct Qdisc_class_hash *clhash)
{
	struct Qdisc_class_common *cl;
	struct hlist_node *next;
	struct hlist_head *nhash, *ohash;
	unsigned int nsize, nmask, osize;
	unsigned int i, h;

	/* Rehash when load factor exceeds 0.75 */
	if (clhash->hashelems * 4 <= clhash->hashsize * 3)
		return;
	nsize = clhash->hashsize * 2;
	nmask = nsize - 1;
	nhash = qdisc_class_hash_alloc(nsize);
	if (nhash == NULL)
		return;

	ohash = clhash->hash;
	osize = clhash->hashsize;

	sch_tree_lock(sch);
	for (i = 0; i < osize; i++) {
		hlist_for_each_entry_safe(cl, next, &ohash[i], hnode) {
			h = qdisc_class_hash(cl->classid, nmask);
			hlist_add_head(&cl->hnode, &nhash[h]);
		}
	}
	clhash->hash     = nhash;
	clhash->hashsize = nsize;
	clhash->hashmask = nmask;
	sch_tree_unlock(sch);

	kvfree(ohash);
}
EXPORT_SYMBOL(qdisc_class_hash_grow);

int qdisc_class_hash_init(struct Qdisc_class_hash *clhash)
{
	unsigned int size = 4;

	clhash->hash = qdisc_class_hash_alloc(size);
	if (!clhash->hash)
		return -ENOMEM;
	clhash->hashsize  = size;
	clhash->hashmask  = size - 1;
	clhash->hashelems = 0;
	return 0;
}
EXPORT_SYMBOL(qdisc_class_hash_init);

void qdisc_class_hash_destroy(struct Qdisc_class_hash *clhash)
{
	kvfree(clhash->hash);
}
EXPORT_SYMBOL(qdisc_class_hash_destroy);

void qdisc_class_hash_insert(struct Qdisc_class_hash *clhash,
			     struct Qdisc_class_common *cl)
{
	unsigned int h;

	INIT_HLIST_NODE(&cl->hnode);
	h = qdisc_class_hash(cl->classid, clhash->hashmask);
	hlist_add_head(&cl->hnode, &clhash->hash[h]);
	clhash->hashelems++;
}
EXPORT_SYMBOL(qdisc_class_hash_insert);

void qdisc_class_hash_remove(struct Qdisc_class_hash *clhash,
			     struct Qdisc_class_common *cl)
{
	hlist_del(&cl->hnode);
	clhash->hashelems--;
}
EXPORT_SYMBOL(qdisc_class_hash_remove);

/* Allocate an unique handle from space managed by kernel
 * Possible range is [8000-FFFF]:0000 (0x8000 values)
 */
static u32 qdisc_alloc_handle(struct net_device *dev)
{
	int i = 0x8000;
	static u32 autohandle = TC_H_MAKE(0x80000000U, 0);

	do {
		autohandle += TC_H_MAKE(0x10000U, 0);
		if (autohandle == TC_H_MAKE(TC_H_ROOT, 0))
			autohandle = TC_H_MAKE(0x80000000U, 0);
		if (!qdisc_lookup(dev, autohandle))
			return autohandle;
		cond_resched();
	} while	(--i > 0);

	return 0;
}

void qdisc_tree_reduce_backlog(struct Qdisc *sch, int n, int len)
{
	bool qdisc_is_offloaded = sch->flags & TCQ_F_OFFLOADED;
	const struct Qdisc_class_ops *cops;
	unsigned long cl;
	u32 parentid;
	bool notify;
	int drops;

	if (n == 0 && len == 0)
		return;
	drops = max_t(int, n, 0);
	rcu_read_lock();
	while ((parentid = sch->parent)) {
		if (TC_H_MAJ(parentid) == TC_H_MAJ(TC_H_INGRESS))
			break;

		if (sch->flags & TCQ_F_NOPARENT)
			break;
		/* Notify parent qdisc only if child qdisc becomes empty.
		 *
		 * If child was empty even before update then backlog
		 * counter is screwed and we skip notification because
		 * parent class is already passive.
		 *
		 * If the original child was offloaded then it is allowed
		 * to be seem as empty, so the parent is notified anyway.
		 */
		notify = !sch->q.qlen && !WARN_ON_ONCE(!n &&
						       !qdisc_is_offloaded);
		/* TODO: perform the search on a per txq basis */
		sch = qdisc_lookup_rcu(qdisc_dev(sch), TC_H_MAJ(parentid));
		if (sch == NULL) {
			WARN_ON_ONCE(parentid != TC_H_ROOT);
			break;
		}
		cops = sch->ops->cl_ops;
		if (notify && cops->qlen_notify) {
			cl = cops->find(sch, parentid);
			cops->qlen_notify(sch, cl);
		}
		sch->q.qlen -= n;
		sch->qstats.backlog -= len;
		__qdisc_qstats_drop(sch, drops);
	}
	rcu_read_unlock();
}
EXPORT_SYMBOL(qdisc_tree_reduce_backlog);

int qdisc_offload_dump_helper(struct Qdisc *sch, enum tc_setup_type type,
			      void *type_data)
{
	struct net_device *dev = qdisc_dev(sch);
	int err;

	sch->flags &= ~TCQ_F_OFFLOADED;
	if (!tc_can_offload(dev) || !dev->netdev_ops->ndo_setup_tc)
		return 0;

	err = dev->netdev_ops->ndo_setup_tc(dev, type, type_data);
	if (err == -EOPNOTSUPP)
		return 0;

	if (!err)
		sch->flags |= TCQ_F_OFFLOADED;

	return err;
}
EXPORT_SYMBOL(qdisc_offload_dump_helper);

void qdisc_offload_graft_helper(struct net_device *dev, struct Qdisc *sch,
				struct Qdisc *new, struct Qdisc *old,
				enum tc_setup_type type, void *type_data,
				struct netlink_ext_ack *extack)
{
	bool any_qdisc_is_offloaded;
	int err;

	if (!tc_can_offload(dev) || !dev->netdev_ops->ndo_setup_tc)
		return;

	err = dev->netdev_ops->ndo_setup_tc(dev, type, type_data);

	/* Don't report error if the graft is part of destroy operation. */
	if (!err || !new || new == &noop_qdisc)
		return;

	/* Don't report error if the parent, the old child and the new
	 * one are not offloaded.
	 */
	any_qdisc_is_offloaded = new->flags & TCQ_F_OFFLOADED;
	any_qdisc_is_offloaded |= sch && sch->flags & TCQ_F_OFFLOADED;
	any_qdisc_is_offloaded |= old && old->flags & TCQ_F_OFFLOADED;

	if (any_qdisc_is_offloaded)
		NL_SET_ERR_MSG(extack, "Offloading graft operation failed.");
}
EXPORT_SYMBOL(qdisc_offload_graft_helper);

void qdisc_offload_query_caps(struct net_device *dev,
			      enum tc_setup_type type,
			      void *caps, size_t caps_len)
{
	const struct net_device_ops *ops = dev->netdev_ops;
	struct tc_query_caps_base base = {
		.type = type,
		.caps = caps,
	};

	memset(caps, 0, caps_len);

	if (ops->ndo_setup_tc)
		ops->ndo_setup_tc(dev, TC_QUERY_CAPS, &base);
}
EXPORT_SYMBOL(qdisc_offload_query_caps);

static void qdisc_offload_graft_root(struct net_device *dev,
				     struct Qdisc *new, struct Qdisc *old,
				     struct netlink_ext_ack *extack)
{
	struct tc_root_qopt_offload graft_offload = {
		.command	= TC_ROOT_GRAFT,
		.handle		= new ? new->handle : 0,
		.ingress	= (new && new->flags & TCQ_F_INGRESS) ||
				  (old && old->flags & TCQ_F_INGRESS),
	};

	qdisc_offload_graft_helper(dev, NULL, new, old,
				   TC_SETUP_ROOT_QDISC, &graft_offload, extack);
}

static int tc_fill_qdisc(struct sk_buff *skb, struct Qdisc *q, u32 clid,
			 u32 portid, u32 seq, u16 flags, int event,
			 struct netlink_ext_ack *extack)
{
	struct gnet_stats_basic_sync __percpu *cpu_bstats = NULL;
	struct gnet_stats_queue __percpu *cpu_qstats = NULL;
	struct tcmsg *tcm;
	struct nlmsghdr  *nlh;
	unsigned char *b = skb_tail_pointer(skb);
	struct gnet_dump d;
	struct qdisc_size_table *stab;
	u32 block_index;
	__u32 qlen;

	cond_resched();
	nlh = nlmsg_put(skb, portid, seq, event, sizeof(*tcm), flags);
	if (!nlh)
		goto out_nlmsg_trim;
	tcm = nlmsg_data(nlh);
	tcm->tcm_family = AF_UNSPEC;
	tcm->tcm__pad1 = 0;
	tcm->tcm__pad2 = 0;
	tcm->tcm_ifindex = qdisc_dev(q)->ifindex;
	tcm->tcm_parent = clid;
	tcm->tcm_handle = q->handle;
	tcm->tcm_info = refcount_read(&q->refcnt);
	if (nla_put_string(skb, TCA_KIND, q->ops->id))
		goto nla_put_failure;
	if (q->ops->ingress_block_get) {
		block_index = q->ops->ingress_block_get(q);
		if (block_index &&
		    nla_put_u32(skb, TCA_INGRESS_BLOCK, block_index))
			goto nla_put_failure;
	}
	if (q->ops->egress_block_get) {
		block_index = q->ops->egress_block_get(q);
		if (block_index &&
		    nla_put_u32(skb, TCA_EGRESS_BLOCK, block_index))
			goto nla_put_failure;
	}
	if (q->ops->dump && q->ops->dump(q, skb) < 0)
		goto nla_put_failure;
	if (nla_put_u8(skb, TCA_HW_OFFLOAD, !!(q->flags & TCQ_F_OFFLOADED)))
		goto nla_put_failure;
	qlen = qdisc_qlen_sum(q);

	stab = rtnl_dereference(q->stab);
	if (stab && qdisc_dump_stab(skb, stab) < 0)
		goto nla_put_failure;

	if (gnet_stats_start_copy_compat(skb, TCA_STATS2, TCA_STATS, TCA_XSTATS,
					 NULL, &d, TCA_PAD) < 0)
		goto nla_put_failure;

	if (q->ops->dump_stats && q->ops->dump_stats(q, &d) < 0)
		goto nla_put_failure;

	if (qdisc_is_percpu_stats(q)) {
		cpu_bstats = q->cpu_bstats;
		cpu_qstats = q->cpu_qstats;
	}

	if (gnet_stats_copy_basic(&d, cpu_bstats, &q->bstats, true) < 0 ||
	    gnet_stats_copy_rate_est(&d, &q->rate_est) < 0 ||
	    gnet_stats_copy_queue(&d, cpu_qstats, &q->qstats, qlen) < 0)
		goto nla_put_failure;

	if (gnet_stats_finish_copy(&d) < 0)
		goto nla_put_failure;

	if (extack && extack->_msg &&
	    nla_put_string(skb, TCA_EXT_WARN_MSG, extack->_msg))
		goto out_nlmsg_trim;

	nlh->nlmsg_len = skb_tail_pointer(skb) - b;

	return skb->len;

out_nlmsg_trim:
nla_put_failure:
	nlmsg_trim(skb, b);
	return -1;
}

static bool tc_qdisc_dump_ignore(struct Qdisc *q, bool dump_invisible)
{
	if (q->flags & TCQ_F_BUILTIN)
		return true;
	if ((q->flags & TCQ_F_INVISIBLE) && !dump_invisible)
		return true;

	return false;
}

static int qdisc_get_notify(struct net *net, struct sk_buff *oskb,
			    struct nlmsghdr *n, u32 clid, struct Qdisc *q,
			    struct netlink_ext_ack *extack)
{
	struct sk_buff *skb;
	u32 portid = oskb ? NETLINK_CB(oskb).portid : 0;

	skb = alloc_skb(NLMSG_GOODSIZE, GFP_KERNEL);
	if (!skb)
		return -ENOBUFS;

	if (!tc_qdisc_dump_ignore(q, false)) {
		if (tc_fill_qdisc(skb, q, clid, portid, n->nlmsg_seq, 0,
				  RTM_NEWQDISC, extack) < 0)
			goto err_out;
	}

	if (skb->len)
		return rtnetlink_send(skb, net, portid, RTNLGRP_TC,
				      n->nlmsg_flags & NLM_F_ECHO);

err_out:
	kfree_skb(skb);
	return -EINVAL;
}

static int qdisc_notify(struct net *net, struct sk_buff *oskb,
			struct nlmsghdr *n, u32 clid,
			struct Qdisc *old, struct Qdisc *new,
			struct netlink_ext_ack *extack)
{
	struct sk_buff *skb;
	u32 portid = oskb ? NETLINK_CB(oskb).portid : 0;

	if (!rtnl_notify_needed(net, n->nlmsg_flags, RTNLGRP_TC))
		return 0;

	skb = alloc_skb(NLMSG_GOODSIZE, GFP_KERNEL);
	if (!skb)
		return -ENOBUFS;

	if (old && !tc_qdisc_dump_ignore(old, false)) {
		if (tc_fill_qdisc(skb, old, clid, portid, n->nlmsg_seq,
				  0, RTM_DELQDISC, extack) < 0)
			goto err_out;
	}
	if (new && !tc_qdisc_dump_ignore(new, false)) {
		if (tc_fill_qdisc(skb, new, clid, portid, n->nlmsg_seq,
				  old ? NLM_F_REPLACE : 0, RTM_NEWQDISC, extack) < 0)
			goto err_out;
	}

	if (skb->len)
		return rtnetlink_send(skb, net, portid, RTNLGRP_TC,
				      n->nlmsg_flags & NLM_F_ECHO);

err_out:
	kfree_skb(skb);
	return -EINVAL;
}

static void notify_and_destroy(struct net *net, struct sk_buff *skb,
			       struct nlmsghdr *n, u32 clid,
			       struct Qdisc *old, struct Qdisc *new,
			       struct netlink_ext_ack *extack)
{
	if (new || old)
		qdisc_notify(net, skb, n, clid, old, new, extack);

	if (old)
		qdisc_put(old);
}

static void qdisc_clear_nolock(struct Qdisc *sch)
{
	sch->flags &= ~TCQ_F_NOLOCK;
	if (!(sch->flags & TCQ_F_CPUSTATS))
		return;

	free_percpu(sch->cpu_bstats);
	free_percpu(sch->cpu_qstats);
	sch->cpu_bstats = NULL;
	sch->cpu_qstats = NULL;
	sch->flags &= ~TCQ_F_CPUSTATS;
}

/* Graft qdisc "new" to class "classid" of qdisc "parent" or
 * to device "dev".
 *
 * When appropriate send a netlink notification using 'skb'
 * and "n".
 *
 * On success, destroy old qdisc.
 */

static int qdisc_graft(struct net_device *dev, struct Qdisc *parent,
		       struct sk_buff *skb, struct nlmsghdr *n, u32 classid,
		       struct Qdisc *new, struct Qdisc *old,
		       struct netlink_ext_ack *extack)
{
	struct Qdisc *q = old;
	struct net *net = dev_net(dev);

	if (parent == NULL) {
		unsigned int i, num_q, ingress;
		struct netdev_queue *dev_queue;

		ingress = 0;
		num_q = dev->num_tx_queues;
		if ((q && q->flags & TCQ_F_INGRESS) ||
		    (new && new->flags & TCQ_F_INGRESS)) {
			ingress = 1;
			dev_queue = dev_ingress_queue(dev);
			if (!dev_queue) {
				NL_SET_ERR_MSG(extack, "Device does not have an ingress queue");
				return -ENOENT;
			}

			q = rtnl_dereference(dev_queue->qdisc_sleeping);

			/* This is the counterpart of that qdisc_refcount_inc_nz() call in
			 * __tcf_qdisc_find() for filter requests.
			 */
			if (!qdisc_refcount_dec_if_one(q)) {
				NL_SET_ERR_MSG(extack,
					       "Current ingress or clsact Qdisc has ongoing filter requests");
				return -EBUSY;
			}
		}

		if (dev->flags & IFF_UP)
			dev_deactivate(dev);

		qdisc_offload_graft_root(dev, new, old, extack);

		if (new && new->ops->attach && !ingress)
			goto skip;

		if (!ingress) {
			for (i = 0; i < num_q; i++) {
				dev_queue = netdev_get_tx_queue(dev, i);
				old = dev_graft_qdisc(dev_queue, new);

				if (new && i > 0)
					qdisc_refcount_inc(new);
				qdisc_put(old);
			}
		} else {
			old = dev_graft_qdisc(dev_queue, NULL);

			/* {ingress,clsact}_destroy() @old before grafting @new to avoid
			 * unprotected concurrent accesses to net_device::miniq_{in,e}gress
			 * pointer(s) in mini_qdisc_pair_swap().
			 */
			qdisc_notify(net, skb, n, classid, old, new, extack);
			qdisc_destroy(old);

			dev_graft_qdisc(dev_queue, new);
		}

skip:
		if (!ingress) {
			old = rtnl_dereference(dev->qdisc);
			if (new && !new->ops->attach)
				qdisc_refcount_inc(new);
			rcu_assign_pointer(dev->qdisc, new ? : &noop_qdisc);

			notify_and_destroy(net, skb, n, classid, old, new, extack);

			if (new && new->ops->attach)
				new->ops->attach(new);
		}

		if (dev->flags & IFF_UP)
			dev_activate(dev);
	} else {
		const struct Qdisc_class_ops *cops = parent->ops->cl_ops;
		unsigned long cl;
		int err;

		/* Only support running class lockless if parent is lockless */
		if (new && (new->flags & TCQ_F_NOLOCK) && !(parent->flags & TCQ_F_NOLOCK))
			qdisc_clear_nolock(new);

		if (!cops || !cops->graft)
			return -EOPNOTSUPP;

		cl = cops->find(parent, classid);
		if (!cl) {
			NL_SET_ERR_MSG(extack, "Specified class not found");
			return -ENOENT;
		}

		if (new && new->ops == &noqueue_qdisc_ops) {
			NL_SET_ERR_MSG(extack, "Cannot assign noqueue to a class");
			return -EINVAL;
		}

		err = cops->graft(parent, cl, new, &old, extack);
		if (err)
			return err;
		notify_and_destroy(net, skb, n, classid, old, new, extack);
	}
	return 0;
}

static int qdisc_block_indexes_set(struct Qdisc *sch, struct nlattr **tca,
				   struct netlink_ext_ack *extack)
{
	u32 block_index;

	if (tca[TCA_INGRESS_BLOCK]) {
		block_index = nla_get_u32(tca[TCA_INGRESS_BLOCK]);

		if (!block_index) {
			NL_SET_ERR_MSG(extack, "Ingress block index cannot be 0");
			return -EINVAL;
		}
		if (!sch->ops->ingress_block_set) {
			NL_SET_ERR_MSG(extack, "Ingress block sharing is not supported");
			return -EOPNOTSUPP;
		}
		sch->ops->ingress_block_set(sch, block_index);
	}
	if (tca[TCA_EGRESS_BLOCK]) {
		block_index = nla_get_u32(tca[TCA_EGRESS_BLOCK]);

		if (!block_index) {
			NL_SET_ERR_MSG(extack, "Egress block index cannot be 0");
			return -EINVAL;
		}
		if (!sch->ops->egress_block_set) {
			NL_SET_ERR_MSG(extack, "Egress block sharing is not supported");
			return -EOPNOTSUPP;
		}
		sch->ops->egress_block_set(sch, block_index);
	}
	return 0;
}

/*
   Allocate and initialize new qdisc.

   Parameters are passed via opt.
 */

static struct Qdisc *qdisc_create(struct net_device *dev,
				  struct netdev_queue *dev_queue,
				  u32 parent, u32 handle,
				  struct nlattr **tca, int *errp,
				  struct netlink_ext_ack *extack)
{
	int err;
	struct nlattr *kind = tca[TCA_KIND];
	struct Qdisc *sch;
	struct Qdisc_ops *ops;
	struct qdisc_size_table *stab;

	ops = qdisc_lookup_ops(kind);
#ifdef CONFIG_MODULES
	if (ops == NULL && kind != NULL) {
		char name[IFNAMSIZ];
		if (nla_strscpy(name, kind, IFNAMSIZ) >= 0) {
			/* We dropped the RTNL semaphore in order to
			 * perform the module load.  So, even if we
			 * succeeded in loading the module we have to
			 * tell the caller to replay the request.  We
			 * indicate this using -EAGAIN.
			 * We replay the request because the device may
			 * go away in the mean time.
			 */
			rtnl_unlock();
			request_module("sch_%s", name);
			rtnl_lock();
			ops = qdisc_lookup_ops(kind);
			if (ops != NULL) {
				/* We will try again qdisc_lookup_ops,
				 * so don't keep a reference.
				 */
				module_put(ops->owner);
				err = -EAGAIN;
				goto err_out;
			}
		}
	}
#endif

	err = -ENOENT;
	if (!ops) {
		NL_SET_ERR_MSG(extack, "Specified qdisc kind is unknown");
		goto err_out;
	}

	sch = qdisc_alloc(dev_queue, ops, extack);
	if (IS_ERR(sch)) {
		err = PTR_ERR(sch);
		goto err_out2;
	}

	sch->parent = parent;

	if (handle == TC_H_INGRESS) {
		if (!(sch->flags & TCQ_F_INGRESS)) {
			NL_SET_ERR_MSG(extack,
				       "Specified parent ID is reserved for ingress and clsact Qdiscs");
			err = -EINVAL;
			goto err_out3;
		}
		handle = TC_H_MAKE(TC_H_INGRESS, 0);
	} else {
		if (handle == 0) {
			handle = qdisc_alloc_handle(dev);
			if (handle == 0) {
				NL_SET_ERR_MSG(extack, "Maximum number of qdisc handles was exceeded");
				err = -ENOSPC;
				goto err_out3;
			}
		}
		if (!netif_is_multiqueue(dev))
			sch->flags |= TCQ_F_ONETXQUEUE;
	}

	sch->handle = handle;

	/* This exist to keep backward compatible with a userspace
	 * loophole, what allowed userspace to get IFF_NO_QUEUE
	 * facility on older kernels by setting tx_queue_len=0 (prior
	 * to qdisc init), and then forgot to reinit tx_queue_len
	 * before again attaching a qdisc.
	 */
	if ((dev->priv_flags & IFF_NO_QUEUE) && (dev->tx_queue_len == 0)) {
		dev->tx_queue_len = DEFAULT_TX_QUEUE_LEN;
		netdev_info(dev, "Caught tx_queue_len zero misconfig\n");
	}

	err = qdisc_block_indexes_set(sch, tca, extack);
	if (err)
		goto err_out3;

	if (tca[TCA_STAB]) {
		stab = qdisc_get_stab(tca[TCA_STAB], extack);
		if (IS_ERR(stab)) {
			err = PTR_ERR(stab);
			goto err_out3;
		}
		rcu_assign_pointer(sch->stab, stab);
	}

	if (ops->init) {
		err = ops->init(sch, tca[TCA_OPTIONS], extack);
		if (err != 0)
			goto err_out4;
	}

	if (tca[TCA_RATE]) {
		err = -EOPNOTSUPP;
		if (sch->flags & TCQ_F_MQROOT) {
			NL_SET_ERR_MSG(extack, "Cannot attach rate estimator to a multi-queue root qdisc");
			goto err_out4;
		}

		err = gen_new_estimator(&sch->bstats,
					sch->cpu_bstats,
					&sch->rate_est,
					NULL,
					true,
					tca[TCA_RATE]);
		if (err) {
			NL_SET_ERR_MSG(extack, "Failed to generate new estimator");
			goto err_out4;
		}
	}

	qdisc_hash_add(sch, false);
	trace_qdisc_create(ops, dev, parent);

	return sch;

err_out4:
	/* Even if ops->init() failed, we call ops->destroy()
	 * like qdisc_create_dflt().
	 */
	if (ops->destroy)
		ops->destroy(sch);
	qdisc_put_stab(rtnl_dereference(sch->stab));
err_out3:
	netdev_put(dev, &sch->dev_tracker);
	qdisc_free(sch);
err_out2:
	module_put(ops->owner);
err_out:
	*errp = err;
	return NULL;
}

static int qdisc_change(struct Qdisc *sch, struct nlattr **tca,
			struct netlink_ext_ack *extack)
{
	struct qdisc_size_table *ostab, *stab = NULL;
	int err = 0;

	if (tca[TCA_OPTIONS]) {
		if (!sch->ops->change) {
			NL_SET_ERR_MSG(extack, "Change operation not supported by specified qdisc");
			return -EINVAL;
		}
		if (tca[TCA_INGRESS_BLOCK] || tca[TCA_EGRESS_BLOCK]) {
			NL_SET_ERR_MSG(extack, "Change of blocks is not supported");
			return -EOPNOTSUPP;
		}
		err = sch->ops->change(sch, tca[TCA_OPTIONS], extack);
		if (err)
			return err;
	}

	if (tca[TCA_STAB]) {
		stab = qdisc_get_stab(tca[TCA_STAB], extack);
		if (IS_ERR(stab))
			return PTR_ERR(stab);
	}

	ostab = rtnl_dereference(sch->stab);
	rcu_assign_pointer(sch->stab, stab);
	qdisc_put_stab(ostab);

	if (tca[TCA_RATE]) {
		/* NB: ignores errors from replace_estimator
		   because change can't be undone. */
		if (sch->flags & TCQ_F_MQROOT)
			goto out;
		gen_replace_estimator(&sch->bstats,
				      sch->cpu_bstats,
				      &sch->rate_est,
				      NULL,
				      true,
				      tca[TCA_RATE]);
	}
out:
	return 0;
}

struct check_loop_arg {
	struct qdisc_walker	w;
	struct Qdisc		*p;
	int			depth;
};

static int check_loop_fn(struct Qdisc *q, unsigned long cl,
			 struct qdisc_walker *w);

static int check_loop(struct Qdisc *q, struct Qdisc *p, int depth)
{
	struct check_loop_arg	arg;

	if (q->ops->cl_ops == NULL)
		return 0;

	arg.w.stop = arg.w.skip = arg.w.count = 0;
	arg.w.fn = check_loop_fn;
	arg.depth = depth;
	arg.p = p;
	q->ops->cl_ops->walk(q, &arg.w);
	return arg.w.stop ? -ELOOP : 0;
}

static int
check_loop_fn(struct Qdisc *q, unsigned long cl, struct qdisc_walker *w)
{
	struct Qdisc *leaf;
	const struct Qdisc_class_ops *cops = q->ops->cl_ops;
	struct check_loop_arg *arg = (struct check_loop_arg *)w;

	leaf = cops->leaf(q, cl);
	if (leaf) {
		if (leaf == arg->p || arg->depth > 7)
			return -ELOOP;
		return check_loop(leaf, arg->p, arg->depth + 1);
	}
	return 0;
}

const struct nla_policy rtm_tca_policy[TCA_MAX + 1] = {
	[TCA_KIND]		= { .type = NLA_STRING },
	[TCA_RATE]		= { .type = NLA_BINARY,
				    .len = sizeof(struct tc_estimator) },
	[TCA_STAB]		= { .type = NLA_NESTED },
	[TCA_DUMP_INVISIBLE]	= { .type = NLA_FLAG },
	[TCA_CHAIN]		= { .type = NLA_U32 },
	[TCA_INGRESS_BLOCK]	= { .type = NLA_U32 },
	[TCA_EGRESS_BLOCK]	= { .type = NLA_U32 },
};

/*
 * Delete/get qdisc.
 */

static int tc_get_qdisc(struct sk_buff *skb, struct nlmsghdr *n,
			struct netlink_ext_ack *extack)
{
	struct net *net = sock_net(skb->sk);
	struct tcmsg *tcm = nlmsg_data(n);
	struct nlattr *tca[TCA_MAX + 1];
	struct net_device *dev;
	u32 clid;
	struct Qdisc *q = NULL;
	struct Qdisc *p = NULL;
	int err;

	err = nlmsg_parse_deprecated(n, sizeof(*tcm), tca, TCA_MAX,
				     rtm_tca_policy, extack);
	if (err < 0)
		return err;

	dev = __dev_get_by_index(net, tcm->tcm_ifindex);
	if (!dev)
		return -ENODEV;

	clid = tcm->tcm_parent;
	if (clid) {
		if (clid != TC_H_ROOT) {
			if (TC_H_MAJ(clid) != TC_H_MAJ(TC_H_INGRESS)) {
				p = qdisc_lookup(dev, TC_H_MAJ(clid));
				if (!p) {
					NL_SET_ERR_MSG(extack, "Failed to find qdisc with specified classid");
					return -ENOENT;
				}
				q = qdisc_leaf(p, clid);
			} else if (dev_ingress_queue(dev)) {
				q = rtnl_dereference(dev_ingress_queue(dev)->qdisc_sleeping);
			}
		} else {
			q = rtnl_dereference(dev->qdisc);
		}
		if (!q) {
			NL_SET_ERR_MSG(extack, "Cannot find specified qdisc on specified device");
			return -ENOENT;
		}

		if (tcm->tcm_handle && q->handle != tcm->tcm_handle) {
			NL_SET_ERR_MSG(extack, "Invalid handle");
			return -EINVAL;
		}
	} else {
		q = qdisc_lookup(dev, tcm->tcm_handle);
		if (!q) {
			NL_SET_ERR_MSG(extack, "Failed to find qdisc with specified handle");
			return -ENOENT;
		}
	}

	if (tca[TCA_KIND] && nla_strcmp(tca[TCA_KIND], q->ops->id)) {
		NL_SET_ERR_MSG(extack, "Invalid qdisc name");
		return -EINVAL;
	}

	if (n->nlmsg_type == RTM_DELQDISC) {
		if (!clid) {
			NL_SET_ERR_MSG(extack, "Classid cannot be zero");
			return -EINVAL;
		}
		if (q->handle == 0) {
			NL_SET_ERR_MSG(extack, "Cannot delete qdisc with handle of zero");
			return -ENOENT;
		}
		err = qdisc_graft(dev, p, skb, n, clid, NULL, q, extack);
		if (err != 0)
			return err;
	} else {
		qdisc_get_notify(net, skb, n, clid, q, NULL);
	}
	return 0;
}

static bool req_create_or_replace(struct nlmsghdr *n)
{
	return (n->nlmsg_flags & NLM_F_CREATE &&
		n->nlmsg_flags & NLM_F_REPLACE);
}

static bool req_create_exclusive(struct nlmsghdr *n)
{
	return (n->nlmsg_flags & NLM_F_CREATE &&
		n->nlmsg_flags & NLM_F_EXCL);
}

static bool req_change(struct nlmsghdr *n)
{
	return (!(n->nlmsg_flags & NLM_F_CREATE) &&
		!(n->nlmsg_flags & NLM_F_REPLACE) &&
		!(n->nlmsg_flags & NLM_F_EXCL));
}

/*
 * Create/change qdisc.
 */
static int tc_modify_qdisc(struct sk_buff *skb, struct nlmsghdr *n,
			   struct netlink_ext_ack *extack)
{
	struct net *net = sock_net(skb->sk);
	struct tcmsg *tcm;
	struct nlattr *tca[TCA_MAX + 1];
	struct net_device *dev;
	u32 clid;
	struct Qdisc *q, *p;
	int err;

replay:
	/* Reinit, just in case something touches this. */
	err = nlmsg_parse_deprecated(n, sizeof(*tcm), tca, TCA_MAX,
				     rtm_tca_policy, extack);
	if (err < 0)
		return err;

	tcm = nlmsg_data(n);
	clid = tcm->tcm_parent;
	q = p = NULL;

	dev = __dev_get_by_index(net, tcm->tcm_ifindex);
	if (!dev)
		return -ENODEV;


	if (clid) {
		if (clid != TC_H_ROOT) {
			if (clid != TC_H_INGRESS) {
				p = qdisc_lookup(dev, TC_H_MAJ(clid));
				if (!p) {
					NL_SET_ERR_MSG(extack, "Failed to find specified qdisc");
					return -ENOENT;
				}
				q = qdisc_leaf(p, clid);
			} else if (dev_ingress_queue_create(dev)) {
				q = rtnl_dereference(dev_ingress_queue(dev)->qdisc_sleeping);
			}
		} else {
			q = rtnl_dereference(dev->qdisc);
		}

		/* It may be default qdisc, ignore it */
		if (q && q->handle == 0)
			q = NULL;

		if (!q || !tcm->tcm_handle || q->handle != tcm->tcm_handle) {
			if (tcm->tcm_handle) {
				if (q && !(n->nlmsg_flags & NLM_F_REPLACE)) {
					NL_SET_ERR_MSG(extack, "NLM_F_REPLACE needed to override");
					return -EEXIST;
				}
				if (TC_H_MIN(tcm->tcm_handle)) {
					NL_SET_ERR_MSG(extack, "Invalid minor handle");
					return -EINVAL;
				}
				q = qdisc_lookup(dev, tcm->tcm_handle);
				if (!q)
					goto create_n_graft;
				if (n->nlmsg_flags & NLM_F_EXCL) {
					NL_SET_ERR_MSG(extack, "Exclusivity flag on, cannot override");
					return -EEXIST;
				}
				if (tca[TCA_KIND] &&
				    nla_strcmp(tca[TCA_KIND], q->ops->id)) {
					NL_SET_ERR_MSG(extack, "Invalid qdisc name");
					return -EINVAL;
				}
				if (q->flags & TCQ_F_INGRESS) {
					NL_SET_ERR_MSG(extack,
						       "Cannot regraft ingress or clsact Qdiscs");
					return -EINVAL;
				}
				if (q == p ||
				    (p && check_loop(q, p, 0))) {
					NL_SET_ERR_MSG(extack, "Qdisc parent/child loop detected");
					return -ELOOP;
				}
				if (clid == TC_H_INGRESS) {
					NL_SET_ERR_MSG(extack, "Ingress cannot graft directly");
					return -EINVAL;
				}
				qdisc_refcount_inc(q);
				goto graft;
			} else {
				if (!q)
					goto create_n_graft;

				/* This magic test requires explanation.
				 *
				 *   We know, that some child q is already
				 *   attached to this parent and have choice:
				 *   1) change it or 2) create/graft new one.
				 *   If the requested qdisc kind is different
				 *   than the existing one, then we choose graft.
				 *   If they are the same then this is "change"
				 *   operation - just let it fallthrough..
				 *
				 *   1. We are allowed to create/graft only
				 *   if the request is explicitly stating
				 *   "please create if it doesn't exist".
				 *
				 *   2. If the request is to exclusive create
				 *   then the qdisc tcm_handle is not expected
				 *   to exist, so that we choose create/graft too.
				 *
				 *   3. The last case is when no flags are set.
				 *   This will happen when for example tc
				 *   utility issues a "change" command.
				 *   Alas, it is sort of hole in API, we
				 *   cannot decide what to do unambiguously.
				 *   For now we select create/graft.
				 */
				if (tca[TCA_KIND] &&
				    nla_strcmp(tca[TCA_KIND], q->ops->id)) {
					if (req_create_or_replace(n) ||
					    req_create_exclusive(n))
						goto create_n_graft;
					else if (req_change(n))
						goto create_n_graft2;
				}
			}
		}
	} else {
		if (!tcm->tcm_handle) {
			NL_SET_ERR_MSG(extack, "Handle cannot be zero");
			return -EINVAL;
		}
		q = qdisc_lookup(dev, tcm->tcm_handle);
	}

	/* Change qdisc parameters */
	if (!q) {
		NL_SET_ERR_MSG(extack, "Specified qdisc not found");
		return -ENOENT;
	}
	if (n->nlmsg_flags & NLM_F_EXCL) {
		NL_SET_ERR_MSG(extack, "Exclusivity flag on, cannot modify");
		return -EEXIST;
	}
	if (tca[TCA_KIND] && nla_strcmp(tca[TCA_KIND], q->ops->id)) {
		NL_SET_ERR_MSG(extack, "Invalid qdisc name");
		return -EINVAL;
	}
	err = qdisc_change(q, tca, extack);
	if (err == 0)
		qdisc_notify(net, skb, n, clid, NULL, q, extack);
	return err;

create_n_graft:
	if (!(n->nlmsg_flags & NLM_F_CREATE)) {
		NL_SET_ERR_MSG(extack, "Qdisc not found. To create specify NLM_F_CREATE flag");
		return -ENOENT;
	}
create_n_graft2:
	if (clid == TC_H_INGRESS) {
		if (dev_ingress_queue(dev)) {
			q = qdisc_create(dev, dev_ingress_queue(dev),
					 tcm->tcm_parent, tcm->tcm_parent,
					 tca, &err, extack);
		} else {
			NL_SET_ERR_MSG(extack, "Cannot find ingress queue for specified device");
			err = -ENOENT;
		}
	} else {
		struct netdev_queue *dev_queue;

		if (p && p->ops->cl_ops && p->ops->cl_ops->select_queue)
			dev_queue = p->ops->cl_ops->select_queue(p, tcm);
		else if (p)
			dev_queue = p->dev_queue;
		else
			dev_queue = netdev_get_tx_queue(dev, 0);

		q = qdisc_create(dev, dev_queue,
				 tcm->tcm_parent, tcm->tcm_handle,
				 tca, &err, extack);
	}
	if (q == NULL) {
		if (err == -EAGAIN)
			goto replay;
		return err;
	}

graft:
	err = qdisc_graft(dev, p, skb, n, clid, q, NULL, extack);
	if (err) {
		if (q)
			qdisc_put(q);
		return err;
	}

	return 0;
}

static int tc_dump_qdisc_root(struct Qdisc *root, struct sk_buff *skb,
			      struct netlink_callback *cb,
			      int *q_idx_p, int s_q_idx, bool recur,
			      bool dump_invisible)
{
	int ret = 0, q_idx = *q_idx_p;
	struct Qdisc *q;
	int b;

	if (!root)
		return 0;

	q = root;
	if (q_idx < s_q_idx) {
		q_idx++;
	} else {
		if (!tc_qdisc_dump_ignore(q, dump_invisible) &&
		    tc_fill_qdisc(skb, q, q->parent, NETLINK_CB(cb->skb).portid,
				  cb->nlh->nlmsg_seq, NLM_F_MULTI,
				  RTM_NEWQDISC, NULL) <= 0)
			goto done;
		q_idx++;
	}

	/* If dumping singletons, there is no qdisc_dev(root) and the singleton
	 * itself has already been dumped.
	 *
	 * If we've already dumped the top-level (ingress) qdisc above and the global
	 * qdisc hashtable, we don't want to hit it again
	 */
	if (!qdisc_dev(root) || !recur)
		goto out;

	hash_for_each(qdisc_dev(root)->qdisc_hash, b, q, hash) {
		if (q_idx < s_q_idx) {
			q_idx++;
			continue;
		}
		if (!tc_qdisc_dump_ignore(q, dump_invisible) &&
		    tc_fill_qdisc(skb, q, q->parent, NETLINK_CB(cb->skb).portid,
				  cb->nlh->nlmsg_seq, NLM_F_MULTI,
				  RTM_NEWQDISC, NULL) <= 0)
			goto done;
		q_idx++;
	}

out:
	*q_idx_p = q_idx;
	return ret;
done:
	ret = -1;
	goto out;
}

static int tc_dump_qdisc(struct sk_buff *skb, struct netlink_callback *cb)
{
	struct net *net = sock_net(skb->sk);
	int idx, q_idx;
	int s_idx, s_q_idx;
	struct net_device *dev;
	const struct nlmsghdr *nlh = cb->nlh;
	struct nlattr *tca[TCA_MAX + 1];
	int err;

	s_idx = cb->args[0];
	s_q_idx = q_idx = cb->args[1];

	idx = 0;
	ASSERT_RTNL();

	err = nlmsg_parse_deprecated(nlh, sizeof(struct tcmsg), tca, TCA_MAX,
				     rtm_tca_policy, cb->extack);
	if (err < 0)
		return err;

	for_each_netdev(net, dev) {
		struct netdev_queue *dev_queue;

		if (idx < s_idx)
			goto cont;
		if (idx > s_idx)
			s_q_idx = 0;
		q_idx = 0;

		if (tc_dump_qdisc_root(rtnl_dereference(dev->qdisc),
				       skb, cb, &q_idx, s_q_idx,
				       true, tca[TCA_DUMP_INVISIBLE]) < 0)
			goto done;

		dev_queue = dev_ingress_queue(dev);
		if (dev_queue &&
		    tc_dump_qdisc_root(rtnl_dereference(dev_queue->qdisc_sleeping),
				       skb, cb, &q_idx, s_q_idx, false,
				       tca[TCA_DUMP_INVISIBLE]) < 0)
			goto done;

cont:
		idx++;
	}

done:
	cb->args[0] = idx;
	cb->args[1] = q_idx;

	return skb->len;
}



/************************************************
 *	Traffic classes manipulation.		*
 ************************************************/

static int tc_fill_tclass(struct sk_buff *skb, struct Qdisc *q,
			  unsigned long cl, u32 portid, u32 seq, u16 flags,
			  int event, struct netlink_ext_ack *extack)
{
	struct tcmsg *tcm;
	struct nlmsghdr  *nlh;
	unsigned char *b = skb_tail_pointer(skb);
	struct gnet_dump d;
	const struct Qdisc_class_ops *cl_ops = q->ops->cl_ops;

	cond_resched();
	nlh = nlmsg_put(skb, portid, seq, event, sizeof(*tcm), flags);
	if (!nlh)
		goto out_nlmsg_trim;
	tcm = nlmsg_data(nlh);
	tcm->tcm_family = AF_UNSPEC;
	tcm->tcm__pad1 = 0;
	tcm->tcm__pad2 = 0;
	tcm->tcm_ifindex = qdisc_dev(q)->ifindex;
	tcm->tcm_parent = q->handle;
	tcm->tcm_handle = q->handle;
	tcm->tcm_info = 0;
	if (nla_put_string(skb, TCA_KIND, q->ops->id))
		goto nla_put_failure;
	if (cl_ops->dump && cl_ops->dump(q, cl, skb, tcm) < 0)
		goto nla_put_failure;

	if (gnet_stats_start_copy_compat(skb, TCA_STATS2, TCA_STATS, TCA_XSTATS,
					 NULL, &d, TCA_PAD) < 0)
		goto nla_put_failure;

	if (cl_ops->dump_stats && cl_ops->dump_stats(q, cl, &d) < 0)
		goto nla_put_failure;

	if (gnet_stats_finish_copy(&d) < 0)
		goto nla_put_failure;

	if (extack && extack->_msg &&
	    nla_put_string(skb, TCA_EXT_WARN_MSG, extack->_msg))
		goto out_nlmsg_trim;

	nlh->nlmsg_len = skb_tail_pointer(skb) - b;

	return skb->len;

out_nlmsg_trim:
nla_put_failure:
	nlmsg_trim(skb, b);
	return -1;
}

static int tclass_notify(struct net *net, struct sk_buff *oskb,
			 struct nlmsghdr *n, struct Qdisc *q,
			 unsigned long cl, int event, struct netlink_ext_ack *extack)
{
	struct sk_buff *skb;
	u32 portid = oskb ? NETLINK_CB(oskb).portid : 0;

	if (!rtnl_notify_needed(net, n->nlmsg_flags, RTNLGRP_TC))
		return 0;

	skb = alloc_skb(NLMSG_GOODSIZE, GFP_KERNEL);
	if (!skb)
		return -ENOBUFS;

	if (tc_fill_tclass(skb, q, cl, portid, n->nlmsg_seq, 0, event, extack) < 0) {
		kfree_skb(skb);
		return -EINVAL;
	}

	return rtnetlink_send(skb, net, portid, RTNLGRP_TC,
			      n->nlmsg_flags & NLM_F_ECHO);
}

static int tclass_get_notify(struct net *net, struct sk_buff *oskb,
			     struct nlmsghdr *n, struct Qdisc *q,
			     unsigned long cl, struct netlink_ext_ack *extack)
{
	struct sk_buff *skb;
	u32 portid = oskb ? NETLINK_CB(oskb).portid : 0;

	skb = alloc_skb(NLMSG_GOODSIZE, GFP_KERNEL);
	if (!skb)
		return -ENOBUFS;

	if (tc_fill_tclass(skb, q, cl, portid, n->nlmsg_seq, 0, RTM_NEWTCLASS,
			   extack) < 0) {
		kfree_skb(skb);
		return -EINVAL;
	}

	return rtnetlink_send(skb, net, portid, RTNLGRP_TC,
			      n->nlmsg_flags & NLM_F_ECHO);
}

static int tclass_del_notify(struct net *net,
			     const struct Qdisc_class_ops *cops,
			     struct sk_buff *oskb, struct nlmsghdr *n,
			     struct Qdisc *q, unsigned long cl,
			     struct netlink_ext_ack *extack)
{
	u32 portid = oskb ? NETLINK_CB(oskb).portid : 0;
	struct sk_buff *skb;
	int err = 0;

	if (!cops->delete)
		return -EOPNOTSUPP;

	if (rtnl_notify_needed(net, n->nlmsg_flags, RTNLGRP_TC)) {
		skb = alloc_skb(NLMSG_GOODSIZE, GFP_KERNEL);
		if (!skb)
			return -ENOBUFS;

		if (tc_fill_tclass(skb, q, cl, portid, n->nlmsg_seq, 0,
				   RTM_DELTCLASS, extack) < 0) {
			kfree_skb(skb);
			return -EINVAL;
		}
	} else {
		skb = NULL;
	}

	err = cops->delete(q, cl, extack);
	if (err) {
		kfree_skb(skb);
		return err;
	}

	err = rtnetlink_maybe_send(skb, net, portid, RTNLGRP_TC,
				   n->nlmsg_flags & NLM_F_ECHO);
	return err;
}

#ifdef CONFIG_NET_CLS

struct tcf_bind_args {
	struct tcf_walker w;
	unsigned long base;
	unsigned long cl;
	u32 classid;
};

static int tcf_node_bind(struct tcf_proto *tp, void *n, struct tcf_walker *arg)
{
	struct tcf_bind_args *a = (void *)arg;

	if (n && tp->ops->bind_class) {
		struct Qdisc *q = tcf_block_q(tp->chain->block);

		sch_tree_lock(q);
		tp->ops->bind_class(n, a->classid, a->cl, q, a->base);
		sch_tree_unlock(q);
	}
	return 0;
}

struct tc_bind_class_args {
	struct qdisc_walker w;
	unsigned long new_cl;
	u32 portid;
	u32 clid;
};

static int tc_bind_class_walker(struct Qdisc *q, unsigned long cl,
				struct qdisc_walker *w)
{
	struct tc_bind_class_args *a = (struct tc_bind_class_args *)w;
	const struct Qdisc_class_ops *cops = q->ops->cl_ops;
	struct tcf_block *block;
	struct tcf_chain *chain;

	block = cops->tcf_block(q, cl, NULL);
	if (!block)
		return 0;
	for (chain = tcf_get_next_chain(block, NULL);
	     chain;
	     chain = tcf_get_next_chain(block, chain)) {
		struct tcf_proto *tp;

		for (tp = tcf_get_next_proto(chain, NULL);
		     tp; tp = tcf_get_next_proto(chain, tp)) {
			struct tcf_bind_args arg = {};

			arg.w.fn = tcf_node_bind;
			arg.classid = a->clid;
			arg.base = cl;
			arg.cl = a->new_cl;
			tp->ops->walk(tp, &arg.w, true);
		}
	}

	return 0;
}

static void tc_bind_tclass(struct Qdisc *q, u32 portid, u32 clid,
			   unsigned long new_cl)
{
	const struct Qdisc_class_ops *cops = q->ops->cl_ops;
	struct tc_bind_class_args args = {};

	if (!cops->tcf_block)
		return;
	args.portid = portid;
	args.clid = clid;
	args.new_cl = new_cl;
	args.w.fn = tc_bind_class_walker;
	q->ops->cl_ops->walk(q, &args.w);
}

#else

static void tc_bind_tclass(struct Qdisc *q, u32 portid, u32 clid,
			   unsigned long new_cl)
{
}

#endif

static int tc_ctl_tclass(struct sk_buff *skb, struct nlmsghdr *n,
			 struct netlink_ext_ack *extack)
{
	struct net *net = sock_net(skb->sk);
	struct tcmsg *tcm = nlmsg_data(n);
	struct nlattr *tca[TCA_MAX + 1];
	struct net_device *dev;
	struct Qdisc *q = NULL;
	const struct Qdisc_class_ops *cops;
	unsigned long cl = 0;
	unsigned long new_cl;
	u32 portid;
	u32 clid;
	u32 qid;
	int err;

	err = nlmsg_parse_deprecated(n, sizeof(*tcm), tca, TCA_MAX,
				     rtm_tca_policy, extack);
	if (err < 0)
		return err;

	dev = __dev_get_by_index(net, tcm->tcm_ifindex);
	if (!dev)
		return -ENODEV;

	/*
	   parent == TC_H_UNSPEC - unspecified parent.
	   parent == TC_H_ROOT   - class is root, which has no parent.
	   parent == X:0	 - parent is root class.
	   parent == X:Y	 - parent is a node in hierarchy.
	   parent == 0:Y	 - parent is X:Y, where X:0 is qdisc.

	   handle == 0:0	 - generate handle from kernel pool.
	   handle == 0:Y	 - class is X:Y, where X:0 is qdisc.
	   handle == X:Y	 - clear.
	   handle == X:0	 - root class.
	 */

	/* Step 1. Determine qdisc handle X:0 */

	portid = tcm->tcm_parent;
	clid = tcm->tcm_handle;
	qid = TC_H_MAJ(clid);

	if (portid != TC_H_ROOT) {
		u32 qid1 = TC_H_MAJ(portid);

		if (qid && qid1) {
			/* If both majors are known, they must be identical. */
			if (qid != qid1)
				return -EINVAL;
		} else if (qid1) {
			qid = qid1;
		} else if (qid == 0)
			qid = rtnl_dereference(dev->qdisc)->handle;

		/* Now qid is genuine qdisc handle consistent
		 * both with parent and child.
		 *
		 * TC_H_MAJ(portid) still may be unspecified, complete it now.
		 */
		if (portid)
			portid = TC_H_MAKE(qid, portid);
	} else {
		if (qid == 0)
			qid = rtnl_dereference(dev->qdisc)->handle;
	}

	/* OK. Locate qdisc */
	q = qdisc_lookup(dev, qid);
	if (!q)
		return -ENOENT;

	/* An check that it supports classes */
	cops = q->ops->cl_ops;
	if (cops == NULL)
		return -EINVAL;

	/* Now try to get class */
	if (clid == 0) {
		if (portid == TC_H_ROOT)
			clid = qid;
	} else
		clid = TC_H_MAKE(qid, clid);

	if (clid)
		cl = cops->find(q, clid);

	if (cl == 0) {
		err = -ENOENT;
		if (n->nlmsg_type != RTM_NEWTCLASS ||
		    !(n->nlmsg_flags & NLM_F_CREATE))
			goto out;
	} else {
		switch (n->nlmsg_type) {
		case RTM_NEWTCLASS:
			err = -EEXIST;
			if (n->nlmsg_flags & NLM_F_EXCL)
				goto out;
			break;
		case RTM_DELTCLASS:
			err = tclass_del_notify(net, cops, skb, n, q, cl, extack);
			/* Unbind the class with flilters with 0 */
			tc_bind_tclass(q, portid, clid, 0);
			goto out;
		case RTM_GETTCLASS:
			err = tclass_get_notify(net, skb, n, q, cl, extack);
			goto out;
		default:
			err = -EINVAL;
			goto out;
		}
	}

	if (tca[TCA_INGRESS_BLOCK] || tca[TCA_EGRESS_BLOCK]) {
		NL_SET_ERR_MSG(extack, "Shared blocks are not supported for classes");
		return -EOPNOTSUPP;
	}

	new_cl = cl;
	err = -EOPNOTSUPP;
	if (cops->change)
		err = cops->change(q, clid, portid, tca, &new_cl, extack);
	if (err == 0) {
		tclass_notify(net, skb, n, q, new_cl, RTM_NEWTCLASS, extack);
		/* We just create a new class, need to do reverse binding. */
		if (cl != new_cl)
			tc_bind_tclass(q, portid, clid, new_cl);
	}
out:
	return err;
}

struct qdisc_dump_args {
	struct qdisc_walker	w;
	struct sk_buff		*skb;
	struct netlink_callback	*cb;
};

static int qdisc_class_dump(struct Qdisc *q, unsigned long cl,
			    struct qdisc_walker *arg)
{
	struct qdisc_dump_args *a = (struct qdisc_dump_args *)arg;

	return tc_fill_tclass(a->skb, q, cl, NETLINK_CB(a->cb->skb).portid,
			      a->cb->nlh->nlmsg_seq, NLM_F_MULTI,
			      RTM_NEWTCLASS, NULL);
}

static int tc_dump_tclass_qdisc(struct Qdisc *q, struct sk_buff *skb,
				struct tcmsg *tcm, struct netlink_callback *cb,
				int *t_p, int s_t)
{
	struct qdisc_dump_args arg;

	if (tc_qdisc_dump_ignore(q, false) ||
	    *t_p < s_t || !q->ops->cl_ops ||
	    (tcm->tcm_parent &&
	     TC_H_MAJ(tcm->tcm_parent) != q->handle)) {
		(*t_p)++;
		return 0;
	}
	if (*t_p > s_t)
		memset(&cb->args[1], 0, sizeof(cb->args)-sizeof(cb->args[0]));
	arg.w.fn = qdisc_class_dump;
	arg.skb = skb;
	arg.cb = cb;
	arg.w.stop  = 0;
	arg.w.skip = cb->args[1];
	arg.w.count = 0;
	q->ops->cl_ops->walk(q, &arg.w);
	cb->args[1] = arg.w.count;
	if (arg.w.stop)
		return -1;
	(*t_p)++;
	return 0;
}

static int tc_dump_tclass_root(struct Qdisc *root, struct sk_buff *skb,
			       struct tcmsg *tcm, struct netlink_callback *cb,
			       int *t_p, int s_t, bool recur)
{
	struct Qdisc *q;
	int b;

	if (!root)
		return 0;

	if (tc_dump_tclass_qdisc(root, skb, tcm, cb, t_p, s_t) < 0)
		return -1;

	if (!qdisc_dev(root) || !recur)
		return 0;

	if (tcm->tcm_parent) {
		q = qdisc_match_from_root(root, TC_H_MAJ(tcm->tcm_parent));
		if (q && q != root &&
		    tc_dump_tclass_qdisc(q, skb, tcm, cb, t_p, s_t) < 0)
			return -1;
		return 0;
	}
	hash_for_each(qdisc_dev(root)->qdisc_hash, b, q, hash) {
		if (tc_dump_tclass_qdisc(q, skb, tcm, cb, t_p, s_t) < 0)
			return -1;
	}

	return 0;
}

static int tc_dump_tclass(struct sk_buff *skb, struct netlink_callback *cb)
{
	struct tcmsg *tcm = nlmsg_data(cb->nlh);
	struct net *net = sock_net(skb->sk);
	struct netdev_queue *dev_queue;
	struct net_device *dev;
	int t, s_t;

	if (nlmsg_len(cb->nlh) < sizeof(*tcm))
		return 0;
	dev = dev_get_by_index(net, tcm->tcm_ifindex);
	if (!dev)
		return 0;

	s_t = cb->args[0];
	t = 0;

	if (tc_dump_tclass_root(rtnl_dereference(dev->qdisc),
				skb, tcm, cb, &t, s_t, true) < 0)
		goto done;

	dev_queue = dev_ingress_queue(dev);
	if (dev_queue &&
	    tc_dump_tclass_root(rtnl_dereference(dev_queue->qdisc_sleeping),
				skb, tcm, cb, &t, s_t, false) < 0)
		goto done;

done:
	cb->args[0] = t;

	dev_put(dev);
	return skb->len;
}

#ifdef CONFIG_PROC_FS
static int psched_show(struct seq_file *seq, void *v)
{
	seq_printf(seq, "%08x %08x %08x %08x\n",
		   (u32)NSEC_PER_USEC, (u32)PSCHED_TICKS2NS(1),
		   1000000,
		   (u32)NSEC_PER_SEC / hrtimer_resolution);

	return 0;
}

static int __net_init psched_net_init(struct net *net)
{
	struct proc_dir_entry *e;

	e = proc_create_single("psched", 0, net->proc_net, psched_show);
	if (e == NULL)
		return -ENOMEM;

	return 0;
}

static void __net_exit psched_net_exit(struct net *net)
{
	remove_proc_entry("psched", net->proc_net);
}
#else
static int __net_init psched_net_init(struct net *net)
{
	return 0;
}

static void __net_exit psched_net_exit(struct net *net)
{
}
#endif

static struct pernet_operations psched_net_ops = {
	.init = psched_net_init,
	.exit = psched_net_exit,
};

#if IS_ENABLED(CONFIG_RETPOLINE)
DEFINE_STATIC_KEY_FALSE(tc_skip_wrapper);
#endif

static int __init pktsched_init(void)
{
	int err;

	err = register_pernet_subsys(&psched_net_ops);
	if (err) {
		pr_err("pktsched_init: "
		       "cannot initialize per netns operations\n");
		return err;
	}

	register_qdisc(&pfifo_fast_ops);
	register_qdisc(&pfifo_qdisc_ops);
	register_qdisc(&bfifo_qdisc_ops);
	register_qdisc(&pfifo_head_drop_qdisc_ops);
	register_qdisc(&mq_qdisc_ops);
	register_qdisc(&noqueue_qdisc_ops);

	rtnl_register(PF_UNSPEC, RTM_NEWQDISC, tc_modify_qdisc, NULL, 0);
	rtnl_register(PF_UNSPEC, RTM_DELQDISC, tc_get_qdisc, NULL, 0);
	rtnl_register(PF_UNSPEC, RTM_GETQDISC, tc_get_qdisc, tc_dump_qdisc,
		      0);
	rtnl_register(PF_UNSPEC, RTM_NEWTCLASS, tc_ctl_tclass, NULL, 0);
	rtnl_register(PF_UNSPEC, RTM_DELTCLASS, tc_ctl_tclass, NULL, 0);
	rtnl_register(PF_UNSPEC, RTM_GETTCLASS, tc_ctl_tclass, tc_dump_tclass,
		      0);

	tc_wrapper_init();

	return 0;
}

subsys_initcall(pktsched_init);