/*
 * net/sched/cls_api.c  Packet classifier API.
 *
 *              This program is free software; you can redistribute it and/or
 *              modify it under the terms of the GNU General Public License
 *              as published by the Free Software Foundation; either version
 *              2 of the License, or (at your option) any later version.
 *
 * Authors:     Alexey Kuznetsov, <kuznet@ms2.inr.ac.ru>
 *
 * Changes:
 *
 * Eduardo J. Blanco <ejbs@netlabs.com.uy> :990222: kmod support
 *
 */

#include <linux/module.h>
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/string.h>
#include <linux/errno.h>
#include <linux/err.h>
#include <linux/skbuff.h>
#include <linux/init.h>
#include <linux/kmod.h>
#include <linux/slab.h>
#include <linux/idr.h>
#include <linux/rhashtable.h>
#include <linux/jhash.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_act/tc_pedit.h>
#include <net/tc_act/tc_mirred.h>
#include <net/tc_act/tc_vlan.h>
#include <net/tc_act/tc_tunnel_key.h>
#include <net/tc_act/tc_csum.h>
#include <net/tc_act/tc_gact.h>
#include <net/tc_act/tc_police.h>
#include <net/tc_act/tc_sample.h>
#include <net/tc_act/tc_skbedit.h>
#include <net/tc_act/tc_ct.h>
#include <net/tc_act/tc_mpls.h>
#include <net/flow_offload.h>

extern const struct nla_policy rtm_tca_policy[TCA_MAX + 1];

/* The list of all installed classifier types */
static LIST_HEAD(tcf_proto_base);

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

static u32 destroy_obj_hashfn(const struct tcf_proto *tp)
{
        return jhash_3words(tp->chain->index, tp->prio,
                            (__force __u32)tp->protocol, 0);
}

static void tcf_proto_signal_destroying(struct tcf_chain *chain,
                                        struct tcf_proto *tp)
{
        struct tcf_block *block = chain->block;

        mutex_lock(&block->proto_destroy_lock);
        hash_add_rcu(block->proto_destroy_ht, &tp->destroy_ht_node,
                     destroy_obj_hashfn(tp));
        mutex_unlock(&block->proto_destroy_lock);
}

static bool tcf_proto_cmp(const struct tcf_proto *tp1,
                          const struct tcf_proto *tp2)
{
        return tp1->chain->index == tp2->chain->index &&
               tp1->prio == tp2->prio &&
               tp1->protocol == tp2->protocol;
}

static bool tcf_proto_exists_destroying(struct tcf_chain *chain,
                                        struct tcf_proto *tp)
{
        u32 hash = destroy_obj_hashfn(tp);
        struct tcf_proto *iter;
        bool found = false;

        rcu_read_lock();
        hash_for_each_possible_rcu(chain->block->proto_destroy_ht, iter,
                                   destroy_ht_node, hash) {
                if (tcf_proto_cmp(tp, iter)) {
                        found = true;
                        break;
                }
        }
        rcu_read_unlock();

        return found;
}

static void
tcf_proto_signal_destroyed(struct tcf_chain *chain, struct tcf_proto *tp)
{
        struct tcf_block *block = chain->block;

        mutex_lock(&block->proto_destroy_lock);
        if (hash_hashed(&tp->destroy_ht_node))
                hash_del_rcu(&tp->destroy_ht_node);
        mutex_unlock(&block->proto_destroy_lock);
}

/* Find classifier type by string name */

static const struct tcf_proto_ops *__tcf_proto_lookup_ops(const char *kind)
{
        const struct tcf_proto_ops *t, *res = NULL;

        if (kind) {
                read_lock(&cls_mod_lock);
                list_for_each_entry(t, &tcf_proto_base, head) {
                        if (strcmp(kind, t->kind) == 0) {
                                if (try_module_get(t->owner))
                                        res = t;
                                break;
                        }
                }
                read_unlock(&cls_mod_lock);
        }
        return res;
}

static const struct tcf_proto_ops *
tcf_proto_lookup_ops(const char *kind, bool rtnl_held,
                     struct netlink_ext_ack *extack)
{
        const struct tcf_proto_ops *ops;

        ops = __tcf_proto_lookup_ops(kind);
        if (ops)
                return ops;
#ifdef CONFIG_MODULES
        if (rtnl_held)
                rtnl_unlock();
        request_module("cls_%s", kind);
        if (rtnl_held)
                rtnl_lock();
        ops = __tcf_proto_lookup_ops(kind);
        /* We dropped the RTNL semaphore in order to perform
         * the module load. So, even if we succeeded in loading
         * the module we have to replay the request. We indicate
         * this using -EAGAIN.
         */
        if (ops) {
                module_put(ops->owner);
                return ERR_PTR(-EAGAIN);
        }
#endif
        NL_SET_ERR_MSG(extack, "TC classifier not found");
        return ERR_PTR(-ENOENT);
}

/* Register(unregister) new classifier type */

int register_tcf_proto_ops(struct tcf_proto_ops *ops)
{
        struct tcf_proto_ops *t;
        int rc = -EEXIST;

        write_lock(&cls_mod_lock);
        list_for_each_entry(t, &tcf_proto_base, head)
                if (!strcmp(ops->kind, t->kind))
                        goto out;

        list_add_tail(&ops->head, &tcf_proto_base);
        rc = 0;
out:
        write_unlock(&cls_mod_lock);
        return rc;
}
EXPORT_SYMBOL(register_tcf_proto_ops);

static struct workqueue_struct *tc_filter_wq;

int unregister_tcf_proto_ops(struct tcf_proto_ops *ops)
{
        struct tcf_proto_ops *t;
        int rc = -ENOENT;

        /* Wait for outstanding call_rcu()s, if any, from a
         * tcf_proto_ops's destroy() handler.
         */
        rcu_barrier();
        flush_workqueue(tc_filter_wq);

        write_lock(&cls_mod_lock);
        list_for_each_entry(t, &tcf_proto_base, head) {
                if (t == ops) {
                        list_del(&t->head);
                        rc = 0;
                        break;
                }
        }
        write_unlock(&cls_mod_lock);
        return rc;
}
EXPORT_SYMBOL(unregister_tcf_proto_ops);

bool tcf_queue_work(struct rcu_work *rwork, work_func_t func)
{
        INIT_RCU_WORK(rwork, func);
        return queue_rcu_work(tc_filter_wq, rwork);
}
EXPORT_SYMBOL(tcf_queue_work);

/* Select new prio value from the range, managed by kernel. */

static inline u32 tcf_auto_prio(struct tcf_proto *tp)
{
        u32 first = TC_H_MAKE(0xC0000000U, 0U);

        if (tp)
                first = tp->prio - 1;

        return TC_H_MAJ(first);
}

static bool tcf_proto_check_kind(struct nlattr *kind, char *name)
{
        if (kind)
                return nla_strlcpy(name, kind, IFNAMSIZ) >= IFNAMSIZ;
        memset(name, 0, IFNAMSIZ);
        return false;
}

static bool tcf_proto_is_unlocked(const char *kind)
{
        const struct tcf_proto_ops *ops;
        bool ret;

        if (strlen(kind) == 0)
                return false;

        ops = tcf_proto_lookup_ops(kind, false, NULL);
        /* On error return false to take rtnl lock. Proto lookup/create
         * functions will perform lookup again and properly handle errors.
         */
        if (IS_ERR(ops))
                return false;

        ret = !!(ops->flags & TCF_PROTO_OPS_DOIT_UNLOCKED);
        module_put(ops->owner);
        return ret;
}

static struct tcf_proto *tcf_proto_create(const char *kind, u32 protocol,
                                          u32 prio, struct tcf_chain *chain,
                                          bool rtnl_held,
                                          struct netlink_ext_ack *extack)
{
        struct tcf_proto *tp;
        int err;

        tp = kzalloc(sizeof(*tp), GFP_KERNEL);
        if (!tp)
                return ERR_PTR(-ENOBUFS);

        tp->ops = tcf_proto_lookup_ops(kind, rtnl_held, extack);
        if (IS_ERR(tp->ops)) {
                err = PTR_ERR(tp->ops);
                goto errout;
        }
        tp->classify = tp->ops->classify;
        tp->protocol = protocol;
        tp->prio = prio;
        tp->chain = chain;
        spin_lock_init(&tp->lock);
        refcount_set(&tp->refcnt, 1);

        err = tp->ops->init(tp);
        if (err) {
                module_put(tp->ops->owner);
                goto errout;
        }
        return tp;

errout:
        kfree(tp);
        return ERR_PTR(err);
}

static void tcf_proto_get(struct tcf_proto *tp)
{
        refcount_inc(&tp->refcnt);
}

static void tcf_chain_put(struct tcf_chain *chain);

static void tcf_proto_destroy(struct tcf_proto *tp, bool rtnl_held,
                              bool sig_destroy, struct netlink_ext_ack *extack)
{
        tp->ops->destroy(tp, rtnl_held, extack);
        if (sig_destroy)
                tcf_proto_signal_destroyed(tp->chain, tp);
        tcf_chain_put(tp->chain);
        module_put(tp->ops->owner);
        kfree_rcu(tp, rcu);
}

static void tcf_proto_put(struct tcf_proto *tp, bool rtnl_held,
                          struct netlink_ext_ack *extack)
{
        if (refcount_dec_and_test(&tp->refcnt))
                tcf_proto_destroy(tp, rtnl_held, true, extack);
}

static bool tcf_proto_check_delete(struct tcf_proto *tp)
{
        if (tp->ops->delete_empty)
                return tp->ops->delete_empty(tp);

        tp->deleting = true;
        return tp->deleting;
}

static void tcf_proto_mark_delete(struct tcf_proto *tp)
{
        spin_lock(&tp->lock);
        tp->deleting = true;
        spin_unlock(&tp->lock);
}

static bool tcf_proto_is_deleting(struct tcf_proto *tp)
{
        bool deleting;

        spin_lock(&tp->lock);
        deleting = tp->deleting;
        spin_unlock(&tp->lock);

        return deleting;
}

#define ASSERT_BLOCK_LOCKED(block)                                      \
        lockdep_assert_held(&(block)->lock)

struct tcf_filter_chain_list_item {
        struct list_head list;
        tcf_chain_head_change_t *chain_head_change;
        void *chain_head_change_priv;
};

static struct tcf_chain *tcf_chain_create(struct tcf_block *block,
                                          u32 chain_index)
{
        struct tcf_chain *chain;

        ASSERT_BLOCK_LOCKED(block);

        chain = kzalloc(sizeof(*chain), GFP_KERNEL);
        if (!chain)
                return NULL;
        list_add_tail(&chain->list, &block->chain_list);
        mutex_init(&chain->filter_chain_lock);
        chain->block = block;
        chain->index = chain_index;
        chain->refcnt = 1;
        if (!chain->index)
                block->chain0.chain = chain;
        return chain;
}

static void tcf_chain_head_change_item(struct tcf_filter_chain_list_item *item,
                                       struct tcf_proto *tp_head)
{
        if (item->chain_head_change)
                item->chain_head_change(tp_head, item->chain_head_change_priv);
}

static void tcf_chain0_head_change(struct tcf_chain *chain,
                                   struct tcf_proto *tp_head)
{
        struct tcf_filter_chain_list_item *item;
        struct tcf_block *block = chain->block;

        if (chain->index)
                return;

        mutex_lock(&block->lock);
        list_for_each_entry(item, &block->chain0.filter_chain_list, list)
                tcf_chain_head_change_item(item, tp_head);
        mutex_unlock(&block->lock);
}

/* Returns true if block can be safely freed. */

static bool tcf_chain_detach(struct tcf_chain *chain)
{
        struct tcf_block *block = chain->block;

        ASSERT_BLOCK_LOCKED(block);

        list_del(&chain->list);
        if (!chain->index)
                block->chain0.chain = NULL;

        if (list_empty(&block->chain_list) &&
            refcount_read(&block->refcnt) == 0)
                return true;

        return false;
}

static void tcf_block_destroy(struct tcf_block *block)
{
        mutex_destroy(&block->lock);
        mutex_destroy(&block->proto_destroy_lock);
        kfree_rcu(block, rcu);
}

static void tcf_chain_destroy(struct tcf_chain *chain, bool free_block)
{
        struct tcf_block *block = chain->block;

        mutex_destroy(&chain->filter_chain_lock);
        kfree_rcu(chain, rcu);
        if (free_block)
                tcf_block_destroy(block);
}

static void tcf_chain_hold(struct tcf_chain *chain)
{
        ASSERT_BLOCK_LOCKED(chain->block);

        ++chain->refcnt;
}

static bool tcf_chain_held_by_acts_only(struct tcf_chain *chain)
{
        ASSERT_BLOCK_LOCKED(chain->block);

        /* In case all the references are action references, this
         * chain should not be shown to the user.
         */
        return chain->refcnt == chain->action_refcnt;
}

static struct tcf_chain *tcf_chain_lookup(struct tcf_block *block,
                                          u32 chain_index)
{
        struct tcf_chain *chain;

        ASSERT_BLOCK_LOCKED(block);

        list_for_each_entry(chain, &block->chain_list, list) {
                if (chain->index == chain_index)
                        return chain;
        }
        return NULL;
}

static int tc_chain_notify(struct tcf_chain *chain, struct sk_buff *oskb,
                           u32 seq, u16 flags, int event, bool unicast);

static struct tcf_chain *__tcf_chain_get(struct tcf_block *block,
                                         u32 chain_index, bool create,
                                         bool by_act)
{
        struct tcf_chain *chain = NULL;
        bool is_first_reference;

        mutex_lock(&block->lock);
        chain = tcf_chain_lookup(block, chain_index);
        if (chain) {
                tcf_chain_hold(chain);
        } else {
                if (!create)
                        goto errout;
                chain = tcf_chain_create(block, chain_index);
                if (!chain)
                        goto errout;
        }

        if (by_act)
                ++chain->action_refcnt;
        is_first_reference = chain->refcnt - chain->action_refcnt == 1;
        mutex_unlock(&block->lock);

        /* Send notification only in case we got the first
         * non-action reference. Until then, the chain acts only as
         * a placeholder for actions pointing to it and user ought
         * not know about them.
         */
        if (is_first_reference && !by_act)
                tc_chain_notify(chain, NULL, 0, NLM_F_CREATE | NLM_F_EXCL,
                                RTM_NEWCHAIN, false);

        return chain;

errout:
        mutex_unlock(&block->lock);
        return chain;
}

static struct tcf_chain *tcf_chain_get(struct tcf_block *block, u32 chain_index,
                                       bool create)
{
        return __tcf_chain_get(block, chain_index, create, false);
}

struct tcf_chain *tcf_chain_get_by_act(struct tcf_block *block, u32 chain_index)
{
        return __tcf_chain_get(block, chain_index, true, true);
}
EXPORT_SYMBOL(tcf_chain_get_by_act);

static void tc_chain_tmplt_del(const struct tcf_proto_ops *tmplt_ops,
                               void *tmplt_priv);
static int tc_chain_notify_delete(const struct tcf_proto_ops *tmplt_ops,
                                  void *tmplt_priv, u32 chain_index,
                                  struct tcf_block *block, struct sk_buff *oskb,
                                  u32 seq, u16 flags, bool unicast);

static void __tcf_chain_put(struct tcf_chain *chain, bool by_act,
                            bool explicitly_created)
{
        struct tcf_block *block = chain->block;
        const struct tcf_proto_ops *tmplt_ops;
        bool free_block = false;
        unsigned int refcnt;
        void *tmplt_priv;

        mutex_lock(&block->lock);
        if (explicitly_created) {
                if (!chain->explicitly_created) {
                        mutex_unlock(&block->lock);
                        return;
                }
                chain->explicitly_created = false;
        }

        if (by_act)
                chain->action_refcnt--;

        /* tc_chain_notify_delete can't be called while holding block lock.
         * However, when block is unlocked chain can be changed concurrently, so
         * save these to temporary variables.
         */
        refcnt = --chain->refcnt;
        tmplt_ops = chain->tmplt_ops;
        tmplt_priv = chain->tmplt_priv;

        /* The last dropped non-action reference will trigger notification. */
        if (refcnt - chain->action_refcnt == 0 && !by_act) {
                tc_chain_notify_delete(tmplt_ops, tmplt_priv, chain->index,
                                       block, NULL, 0, 0, false);
                /* Last reference to chain, no need to lock. */
                chain->flushing = false;
        }

        if (refcnt == 0)
                free_block = tcf_chain_detach(chain);
        mutex_unlock(&block->lock);

        if (refcnt == 0) {
                tc_chain_tmplt_del(tmplt_ops, tmplt_priv);
                tcf_chain_destroy(chain, free_block);
        }
}

static void tcf_chain_put(struct tcf_chain *chain)
{
        __tcf_chain_put(chain, false, false);
}

void tcf_chain_put_by_act(struct tcf_chain *chain)
{
        __tcf_chain_put(chain, true, false);
}
EXPORT_SYMBOL(tcf_chain_put_by_act);

static void tcf_chain_put_explicitly_created(struct tcf_chain *chain)
{
        __tcf_chain_put(chain, false, true);
}

static void tcf_chain_flush(struct tcf_chain *chain, bool rtnl_held)
{
        struct tcf_proto *tp, *tp_next;

        mutex_lock(&chain->filter_chain_lock);
        tp = tcf_chain_dereference(chain->filter_chain, chain);
        while (tp) {
                tp_next = rcu_dereference_protected(tp->next, 1);
                tcf_proto_signal_destroying(chain, tp);
                tp = tp_next;
        }
        tp = tcf_chain_dereference(chain->filter_chain, chain);
        RCU_INIT_POINTER(chain->filter_chain, NULL);
        tcf_chain0_head_change(chain, NULL);
        chain->flushing = true;
        mutex_unlock(&chain->filter_chain_lock);

        while (tp) {
                tp_next = rcu_dereference_protected(tp->next, 1);
                tcf_proto_put(tp, rtnl_held, NULL);
                tp = tp_next;
        }
}

static int tcf_block_setup(struct tcf_block *block,
                           struct flow_block_offload *bo);

static void tc_indr_block_cmd(struct net_device *dev, struct tcf_block *block,
                              flow_indr_block_bind_cb_t *cb, void *cb_priv,
                              enum flow_block_command command, bool ingress)
{
        struct flow_block_offload bo = {
                .command        = command,
                .binder_type    = ingress ?
                                  FLOW_BLOCK_BINDER_TYPE_CLSACT_INGRESS :
                                  FLOW_BLOCK_BINDER_TYPE_CLSACT_EGRESS,
                .net            = dev_net(dev),
                .block_shared   = tcf_block_non_null_shared(block),
        };
        INIT_LIST_HEAD(&bo.cb_list);

        if (!block)
                return;

        bo.block = &block->flow_block;

        down_write(&block->cb_lock);
        cb(dev, cb_priv, TC_SETUP_BLOCK, &bo);

        tcf_block_setup(block, &bo);
        up_write(&block->cb_lock);
}

static struct tcf_block *tc_dev_block(struct net_device *dev, bool ingress)
{
        const struct Qdisc_class_ops *cops;
        const struct Qdisc_ops *ops;
        struct Qdisc *qdisc;

        if (!dev_ingress_queue(dev))
                return NULL;

        qdisc = dev_ingress_queue(dev)->qdisc_sleeping;
        if (!qdisc)
                return NULL;

        ops = qdisc->ops;
        if (!ops)
                return NULL;

        if (!ingress && !strcmp("ingress", ops->id))
                return NULL;

        cops = ops->cl_ops;
        if (!cops)
                return NULL;

        if (!cops->tcf_block)
                return NULL;

        return cops->tcf_block(qdisc,
                               ingress ? TC_H_MIN_INGRESS : TC_H_MIN_EGRESS,
                               NULL);
}

static void tc_indr_block_get_and_cmd(struct net_device *dev,
                                      flow_indr_block_bind_cb_t *cb,
                                      void *cb_priv,
                                      enum flow_block_command command)
{
        struct tcf_block *block;

        block = tc_dev_block(dev, true);
        tc_indr_block_cmd(dev, block, cb, cb_priv, command, true);

        block = tc_dev_block(dev, false);
        tc_indr_block_cmd(dev, block, cb, cb_priv, command, false);
}

static void tc_indr_block_call(struct tcf_block *block,
                               struct net_device *dev,
                               struct tcf_block_ext_info *ei,
                               enum flow_block_command command,
                               struct netlink_ext_ack *extack)
{
        struct flow_block_offload bo = {
                .command        = command,
                .binder_type    = ei->binder_type,
                .net            = dev_net(dev),
                .block          = &block->flow_block,
                .block_shared   = tcf_block_shared(block),
                .extack         = extack,
        };
        INIT_LIST_HEAD(&bo.cb_list);

        flow_indr_block_call(dev, &bo, command);
        tcf_block_setup(block, &bo);
}

static bool tcf_block_offload_in_use(struct tcf_block *block)
{
        return atomic_read(&block->offloadcnt);
}

static int tcf_block_offload_cmd(struct tcf_block *block,
                                 struct net_device *dev,
                                 struct tcf_block_ext_info *ei,
                                 enum flow_block_command command,
                                 struct netlink_ext_ack *extack)
{
        struct flow_block_offload bo = {};
        int err;

        bo.net = dev_net(dev);
        bo.command = command;
        bo.binder_type = ei->binder_type;
        bo.block = &block->flow_block;
        bo.block_shared = tcf_block_shared(block);
        bo.extack = extack;
        INIT_LIST_HEAD(&bo.cb_list);

        err = dev->netdev_ops->ndo_setup_tc(dev, TC_SETUP_BLOCK, &bo);
        if (err < 0)
                return err;

        return tcf_block_setup(block, &bo);
}

static int tcf_block_offload_bind(struct tcf_block *block, struct Qdisc *q,
                                  struct tcf_block_ext_info *ei,
                                  struct netlink_ext_ack *extack)
{
        struct net_device *dev = q->dev_queue->dev;
        int err;

        down_write(&block->cb_lock);
        if (!dev->netdev_ops->ndo_setup_tc)
                goto no_offload_dev_inc;

        /* If tc offload feature is disabled and the block we try to bind
         * to already has some offloaded filters, forbid to bind.
         */
        if (!tc_can_offload(dev) && tcf_block_offload_in_use(block)) {
                NL_SET_ERR_MSG(extack, "Bind to offloaded block failed as dev has offload disabled");
                err = -EOPNOTSUPP;
                goto err_unlock;
        }

        err = tcf_block_offload_cmd(block, dev, ei, FLOW_BLOCK_BIND, extack);
        if (err == -EOPNOTSUPP)
                goto no_offload_dev_inc;
        if (err)
                goto err_unlock;

        tc_indr_block_call(block, dev, ei, FLOW_BLOCK_BIND, extack);
        up_write(&block->cb_lock);
        return 0;

no_offload_dev_inc:
        if (tcf_block_offload_in_use(block)) {
                err = -EOPNOTSUPP;
                goto err_unlock;
        }
        err = 0;
        block->nooffloaddevcnt++;
        tc_indr_block_call(block, dev, ei, FLOW_BLOCK_BIND, extack);
err_unlock:
        up_write(&block->cb_lock);
        return err;
}

static void tcf_block_offload_unbind(struct tcf_block *block, struct Qdisc *q,
                                     struct tcf_block_ext_info *ei)
{
        struct net_device *dev = q->dev_queue->dev;
        int err;

        down_write(&block->cb_lock);
        tc_indr_block_call(block, dev, ei, FLOW_BLOCK_UNBIND, NULL);

        if (!dev->netdev_ops->ndo_setup_tc)
                goto no_offload_dev_dec;
        err = tcf_block_offload_cmd(block, dev, ei, FLOW_BLOCK_UNBIND, NULL);
        if (err == -EOPNOTSUPP)
                goto no_offload_dev_dec;
        up_write(&block->cb_lock);
        return;

no_offload_dev_dec:
        WARN_ON(block->nooffloaddevcnt-- == 0);
        up_write(&block->cb_lock);
}

static int
tcf_chain0_head_change_cb_add(struct tcf_block *block,
                              struct tcf_block_ext_info *ei,
                              struct netlink_ext_ack *extack)
{
        struct tcf_filter_chain_list_item *item;
        struct tcf_chain *chain0;

        item = kmalloc(sizeof(*item), GFP_KERNEL);
        if (!item) {
                NL_SET_ERR_MSG(extack, "Memory allocation for head change callback item failed");
                return -ENOMEM;
        }
        item->chain_head_change = ei->chain_head_change;
        item->chain_head_change_priv = ei->chain_head_change_priv;

        mutex_lock(&block->lock);
        chain0 = block->chain0.chain;
        if (chain0)
                tcf_chain_hold(chain0);
        else
                list_add(&item->list, &block->chain0.filter_chain_list);
        mutex_unlock(&block->lock);

        if (chain0) {
                struct tcf_proto *tp_head;

                mutex_lock(&chain0->filter_chain_lock);

                tp_head = tcf_chain_dereference(chain0->filter_chain, chain0);
                if (tp_head)
                        tcf_chain_head_change_item(item, tp_head);

                mutex_lock(&block->lock);
                list_add(&item->list, &block->chain0.filter_chain_list);
                mutex_unlock(&block->lock);

                mutex_unlock(&chain0->filter_chain_lock);
                tcf_chain_put(chain0);
        }

        return 0;
}

static void
tcf_chain0_head_change_cb_del(struct tcf_block *block,
                              struct tcf_block_ext_info *ei)
{
        struct tcf_filter_chain_list_item *item;

        mutex_lock(&block->lock);
        list_for_each_entry(item, &block->chain0.filter_chain_list, list) {
                if ((!ei->chain_head_change && !ei->chain_head_change_priv) ||
                    (item->chain_head_change == ei->chain_head_change &&
                     item->chain_head_change_priv == ei->chain_head_change_priv)) {
                        if (block->chain0.chain)
                                tcf_chain_head_change_item(item, NULL);
                        list_del(&item->list);
                        mutex_unlock(&block->lock);

                        kfree(item);
                        return;
                }
        }
        mutex_unlock(&block->lock);
        WARN_ON(1);
}

struct tcf_net {
        spinlock_t idr_lock; /* Protects idr */
        struct idr idr;
};

static unsigned int tcf_net_id;

static int tcf_block_insert(struct tcf_block *block, struct net *net,
                            struct netlink_ext_ack *extack)
{
        struct tcf_net *tn = net_generic(net, tcf_net_id);
        int err;

        idr_preload(GFP_KERNEL);
        spin_lock(&tn->idr_lock);
        err = idr_alloc_u32(&tn->idr, block, &block->index, block->index,
                            GFP_NOWAIT);
        spin_unlock(&tn->idr_lock);
        idr_preload_end();

        return err;
}

static void tcf_block_remove(struct tcf_block *block, struct net *net)
{
        struct tcf_net *tn = net_generic(net, tcf_net_id);

        spin_lock(&tn->idr_lock);
        idr_remove(&tn->idr, block->index);
        spin_unlock(&tn->idr_lock);
}

static struct tcf_block *tcf_block_create(struct net *net, struct Qdisc *q,
                                          u32 block_index,
                                          struct netlink_ext_ack *extack)
{
        struct tcf_block *block;

        block = kzalloc(sizeof(*block), GFP_KERNEL);
        if (!block) {
                NL_SET_ERR_MSG(extack, "Memory allocation for block failed");
                return ERR_PTR(-ENOMEM);
        }
        mutex_init(&block->lock);
        mutex_init(&block->proto_destroy_lock);
        init_rwsem(&block->cb_lock);
        flow_block_init(&block->flow_block);
        INIT_LIST_HEAD(&block->chain_list);
        INIT_LIST_HEAD(&block->owner_list);
        INIT_LIST_HEAD(&block->chain0.filter_chain_list);

        refcount_set(&block->refcnt, 1);
        block->net = net;
        block->index = block_index;

        /* Don't store q pointer for blocks which are shared */
        if (!tcf_block_shared(block))
                block->q = q;
        return block;
}

static struct tcf_block *tcf_block_lookup(struct net *net, u32 block_index)
{
        struct tcf_net *tn = net_generic(net, tcf_net_id);

        return idr_find(&tn->idr, block_index);
}

static struct tcf_block *tcf_block_refcnt_get(struct net *net, u32 block_index)
{
        struct tcf_block *block;

        rcu_read_lock();
        block = tcf_block_lookup(net, block_index);
        if (block && !refcount_inc_not_zero(&block->refcnt))
                block = NULL;
        rcu_read_unlock();

        return block;
}

static struct tcf_chain *
__tcf_get_next_chain(struct tcf_block *block, struct tcf_chain *chain)
{
        mutex_lock(&block->lock);
        if (chain)
                chain = list_is_last(&chain->list, &block->chain_list) ?
                        NULL : list_next_entry(chain, list);
        else
                chain = list_first_entry_or_null(&block->chain_list,
                                                 struct tcf_chain, list);

        /* skip all action-only chains */
        while (chain && tcf_chain_held_by_acts_only(chain))
                chain = list_is_last(&chain->list, &block->chain_list) ?
                        NULL : list_next_entry(chain, list);

        if (chain)
                tcf_chain_hold(chain);
        mutex_unlock(&block->lock);

        return chain;
}

/* Function to be used by all clients that want to iterate over all chains on
 * block. It properly obtains block->lock and takes reference to chain before
 * returning it. Users of this function must be tolerant to concurrent chain
 * insertion/deletion or ensure that no concurrent chain modification is
 * possible. Note that all netlink dump callbacks cannot guarantee to provide
 * consistent dump because rtnl lock is released each time skb is filled with
 * data and sent to user-space.
 */

struct tcf_chain *
tcf_get_next_chain(struct tcf_block *block, struct tcf_chain *chain)
{
        struct tcf_chain *chain_next = __tcf_get_next_chain(block, chain);

        if (chain)
                tcf_chain_put(chain);

        return chain_next;
}
EXPORT_SYMBOL(tcf_get_next_chain);

static struct tcf_proto *
__tcf_get_next_proto(struct tcf_chain *chain, struct tcf_proto *tp)
{
        u32 prio = 0;

        ASSERT_RTNL();
        mutex_lock(&chain->filter_chain_lock);

        if (!tp) {

                tp = tcf_chain_dereference(chain->filter_chain, chain);
        } else if (tcf_proto_is_deleting(tp)) {
                /* 'deleting' flag is set and chain->filter_chain_lock was
                 * unlocked, which means next pointer could be invalid. Restart
                 * search.
                 */
                prio = tp->prio + 1;
                tp = tcf_chain_dereference(chain->filter_chain, chain);

                for (; tp; tp = tcf_chain_dereference(tp->next, chain))
                        if (!tp->deleting && tp->prio >= prio)
                                break;
        } else {
                tp = tcf_chain_dereference(tp->next, chain);
        }

        if (tp)
                tcf_proto_get(tp);

        mutex_unlock(&chain->filter_chain_lock);

        return tp;
}

/* Function to be used by all clients that want to iterate over all tp's on
 * chain. Users of this function must be tolerant to concurrent tp
 * insertion/deletion or ensure that no concurrent chain modification is
 * possible. Note that all netlink dump callbacks cannot guarantee to provide
 * consistent dump because rtnl lock is released each time skb is filled with
 * data and sent to user-space.
 */

struct tcf_proto *
tcf_get_next_proto(struct tcf_chain *chain, struct tcf_proto *tp,
                   bool rtnl_held)
{
        struct tcf_proto *tp_next = __tcf_get_next_proto(chain, tp);

        if (tp)
                tcf_proto_put(tp, rtnl_held, NULL);

        return tp_next;
}
EXPORT_SYMBOL(tcf_get_next_proto);

static void tcf_block_flush_all_chains(struct tcf_block *block, bool rtnl_held)
{
        struct tcf_chain *chain;

        /* Last reference to block. At this point chains cannot be added or
         * removed concurrently.
         */
        for (chain = tcf_get_next_chain(block, NULL);
             chain;
             chain = tcf_get_next_chain(block, chain)) {
                tcf_chain_put_explicitly_created(chain);
                tcf_chain_flush(chain, rtnl_held);
        }
}

/* Lookup Qdisc and increments its reference counter.
 * Set parent, if necessary.
 */

static int __tcf_qdisc_find(struct net *net, struct Qdisc **q,
                            u32 *parent, int ifindex, bool rtnl_held,
                            struct netlink_ext_ack *extack)
{
        const struct Qdisc_class_ops *cops;
        struct net_device *dev;
        int err = 0;

        if (ifindex == TCM_IFINDEX_MAGIC_BLOCK)
                return 0;

        rcu_read_lock();

        /* Find link */
        dev = dev_get_by_index_rcu(net, ifindex);
        if (!dev) {
                rcu_read_unlock();
                return -ENODEV;
        }

        /* Find qdisc */
        if (!*parent) {
                *q = dev->qdisc;
                *parent = (*q)->handle;
        } else {
                *q = qdisc_lookup_rcu(dev, TC_H_MAJ(*parent));
                if (!*q) {
                        NL_SET_ERR_MSG(extack, "Parent Qdisc doesn't exists");
                        err = -EINVAL;
                        goto errout_rcu;
                }
        }

        *q = qdisc_refcount_inc_nz(*q);
        if (!*q) {
                NL_SET_ERR_MSG(extack, "Parent Qdisc doesn't exists");
                err = -EINVAL;
                goto errout_rcu;
        }

        /* Is it classful? */
        cops = (*q)->ops->cl_ops;
        if (!cops) {
                NL_SET_ERR_MSG(extack, "Qdisc not classful");
                err = -EINVAL;
                goto errout_qdisc;
        }

        if (!cops->tcf_block) {
                NL_SET_ERR_MSG(extack, "Class doesn't support blocks");
                err = -EOPNOTSUPP;
                goto errout_qdisc;
        }

errout_rcu:
        /* At this point we know that qdisc is not noop_qdisc,
         * which means that qdisc holds a reference to net_device
         * and we hold a reference to qdisc, so it is safe to release
         * rcu read lock.
         */
        rcu_read_unlock();
        return err;

errout_qdisc:
        rcu_read_unlock();

        if (rtnl_held)
                qdisc_put(*q);
        else
                qdisc_put_unlocked(*q);
        *q = NULL;

        return err;
}

static int __tcf_qdisc_cl_find(struct Qdisc *q, u32 parent, unsigned long *cl,
                               int ifindex, struct netlink_ext_ack *extack)
{
        if (ifindex == TCM_IFINDEX_MAGIC_BLOCK)
                return 0;

        /* Do we search for filter, attached to class? */
        if (TC_H_MIN(parent)) {
                const struct Qdisc_class_ops *cops = q->ops->cl_ops;

                *cl = cops->find(q, parent);
                if (*cl == 0) {
                        NL_SET_ERR_MSG(extack, "Specified class doesn't exist");
                        return -ENOENT;
                }
        }

        return 0;
}

static struct tcf_block *__tcf_block_find(struct net *net, struct Qdisc *q,
                                          unsigned long cl, int ifindex,
                                          u32 block_index,
                                          struct netlink_ext_ack *extack)
{
        struct tcf_block *block;

        if (ifindex == TCM_IFINDEX_MAGIC_BLOCK) {
                block = tcf_block_refcnt_get(net, block_index);
                if (!block) {
                        NL_SET_ERR_MSG(extack, "Block of given index was not found");
                        return ERR_PTR(-EINVAL);
                }
        } else {
                const struct Qdisc_class_ops *cops = q->ops->cl_ops;

                block = cops->tcf_block(q, cl, extack);
                if (!block)
                        return ERR_PTR(-EINVAL);

                if (tcf_block_shared(block)) {
                        NL_SET_ERR_MSG(extack, "This filter block is shared. Please use the block index to manipulate the filters");
                        return ERR_PTR(-EOPNOTSUPP);
                }

                /* Always take reference to block in order to support execution
                 * of rules update path of cls API without rtnl lock. Caller
                 * must release block when it is finished using it. 'if' block
                 * of this conditional obtain reference to block by calling
                 * tcf_block_refcnt_get().
                 */
                refcount_inc(&block->refcnt);
        }

        return block;
}

static void __tcf_block_put(struct tcf_block *block, struct Qdisc *q,
                            struct tcf_block_ext_info *ei, bool rtnl_held)
{
        if (refcount_dec_and_mutex_lock(&block->refcnt, &block->lock)) {
                /* Flushing/putting all chains will cause the block to be
                 * deallocated when last chain is freed. However, if chain_list
                 * is empty, block has to be manually deallocated. After block
                 * reference counter reached 0, it is no longer possible to
                 * increment it or add new chains to block.
                 */
                bool free_block = list_empty(&block->chain_list);

                mutex_unlock(&block->lock);
                if (tcf_block_shared(block))
                        tcf_block_remove(block, block->net);

                if (q)
                        tcf_block_offload_unbind(block, q, ei);

                if (free_block)
                        tcf_block_destroy(block);
                else
                        tcf_block_flush_all_chains(block, rtnl_held);
        } else if (q) {
                tcf_block_offload_unbind(block, q, ei);
        }
}

static void tcf_block_refcnt_put(struct tcf_block *block, bool rtnl_held)
{
        __tcf_block_put(block, NULL, NULL, rtnl_held);
}

/* Find tcf block.
 * Set q, parent, cl when appropriate.
 */

static struct tcf_block *tcf_block_find(struct net *net, struct Qdisc **q,
                                        u32 *parent, unsigned long *cl,
                                        int ifindex, u32 block_index,
                                        struct netlink_ext_ack *extack)
{
        struct tcf_block *block;
        int err = 0;

        ASSERT_RTNL();

        err = __tcf_qdisc_find(net, q, parent, ifindex, true, extack);
        if (err)
                goto errout;

        err = __tcf_qdisc_cl_find(*q, *parent, cl, ifindex, extack);
        if (err)
                goto errout_qdisc;

        block = __tcf_block_find(net, *q, *cl, ifindex, block_index, extack);
        if (IS_ERR(block)) {
                err = PTR_ERR(block);
                goto errout_qdisc;
        }

        return block;

errout_qdisc:
        if (*q)
                qdisc_put(*q);
errout:
        *q = NULL;
        return ERR_PTR(err);
}

static void tcf_block_release(struct Qdisc *q, struct tcf_block *block,
                              bool rtnl_held)
{
        if (!IS_ERR_OR_NULL(block))
                tcf_block_refcnt_put(block, rtnl_held);

        if (q) {
                if (rtnl_held)
                        qdisc_put(q);
                else
                        qdisc_put_unlocked(q);
        }
}

struct tcf_block_owner_item {
        struct list_head list;
        struct Qdisc *q;
        enum flow_block_binder_type binder_type;
};

static void
tcf_block_owner_netif_keep_dst(struct tcf_block *block,
                               struct Qdisc *q,
                               enum flow_block_binder_type binder_type)
{
        if (block->keep_dst &&
            binder_type != FLOW_BLOCK_BINDER_TYPE_CLSACT_INGRESS &&
            binder_type != FLOW_BLOCK_BINDER_TYPE_CLSACT_EGRESS)
                netif_keep_dst(qdisc_dev(q));
}

void tcf_block_netif_keep_dst(struct tcf_block *block)
{
        struct tcf_block_owner_item *item;

        block->keep_dst = true;
        list_for_each_entry(item, &block->owner_list, list)
                tcf_block_owner_netif_keep_dst(block, item->q,
                                               item->binder_type);
}
EXPORT_SYMBOL(tcf_block_netif_keep_dst);

static int tcf_block_owner_add(struct tcf_block *block,
                               struct Qdisc *q,
                               enum flow_block_binder_type binder_type)
{
        struct tcf_block_owner_item *item;

        item = kmalloc(sizeof(*item), GFP_KERNEL);
        if (!item)
                return -ENOMEM;
        item->q = q;
        item->binder_type = binder_type;
        list_add(&item->list, &block->owner_list);
        return 0;
}

static void tcf_block_owner_del(struct tcf_block *block,
                                struct Qdisc *q,
                                enum flow_block_binder_type binder_type)
{
        struct tcf_block_owner_item *item;

        list_for_each_entry(item, &block->owner_list, list) {
                if (item->q == q && item->binder_type == binder_type) {
                        list_del(&item->list);
                        kfree(item);
                        return;
                }
        }
        WARN_ON(1);
}

int tcf_block_get_ext(struct tcf_block **p_block, struct Qdisc *q,
                      struct tcf_block_ext_info *ei,
                      struct netlink_ext_ack *extack)
{
        struct net *net = qdisc_net(q);
        struct tcf_block *block = NULL;
        int err;

        if (ei->block_index)
                /* block_index not 0 means the shared block is requested */
                block = tcf_block_refcnt_get(net, ei->block_index);

        if (!block) {
                block = tcf_block_create(net, q, ei->block_index, extack);
                if (IS_ERR(block))
                        return PTR_ERR(block);
                if (tcf_block_shared(block)) {
                        err = tcf_block_insert(block, net, extack);
                        if (err)
                                goto err_block_insert;
                }
        }

        err = tcf_block_owner_add(block, q, ei->binder_type);
        if (err)
                goto err_block_owner_add;

        tcf_block_owner_netif_keep_dst(block, q, ei->binder_type);

        err = tcf_chain0_head_change_cb_add(block, ei, extack);
        if (err)
                goto err_chain0_head_change_cb_add;

        err = tcf_block_offload_bind(block, q, ei, extack);
        if (err)
                goto err_block_offload_bind;

        *p_block = block;
        return 0;

err_block_offload_bind:
        tcf_chain0_head_change_cb_del(block, ei);
err_chain0_head_change_cb_add:
        tcf_block_owner_del(block, q, ei->binder_type);
err_block_owner_add:
err_block_insert:
        tcf_block_refcnt_put(block, true);
        return err;
}
EXPORT_SYMBOL(tcf_block_get_ext);

static void tcf_chain_head_change_dflt(struct tcf_proto *tp_head, void *priv)
{
        struct tcf_proto __rcu **p_filter_chain = priv;

        rcu_assign_pointer(*p_filter_chain, tp_head);
}

int tcf_block_get(struct tcf_block **p_block,
                  struct tcf_proto __rcu **p_filter_chain, struct Qdisc *q,
                  struct netlink_ext_ack *extack)
{
        struct tcf_block_ext_info ei = {
                .chain_head_change = tcf_chain_head_change_dflt,
                .chain_head_change_priv = p_filter_chain,
        };

        WARN_ON(!p_filter_chain);
        return tcf_block_get_ext(p_block, q, &ei, extack);
}
EXPORT_SYMBOL(tcf_block_get);

/* XXX: Standalone actions are not allowed to jump to any chain, and bound
 * actions should be all removed after flushing.
 */
void tcf_block_put_ext(struct tcf_block *block, struct Qdisc *q,
                       struct tcf_block_ext_info *ei)
{
        if (!block)
                return;
        tcf_chain0_head_change_cb_del(block, ei);
        tcf_block_owner_del(block, q, ei->binder_type);

        __tcf_block_put(block, q, ei, true);
}
EXPORT_SYMBOL(tcf_block_put_ext);

void tcf_block_put(struct tcf_block *block)
{
        struct tcf_block_ext_info ei = {0, };

        if (!block)
                return;
        tcf_block_put_ext(block, block->q, &ei);
}

EXPORT_SYMBOL(tcf_block_put);

static int
tcf_block_playback_offloads(struct tcf_block *block, flow_setup_cb_t *cb,
                            void *cb_priv, bool add, bool offload_in_use,
                            struct netlink_ext_ack *extack)
{
        struct tcf_chain *chain, *chain_prev;
        struct tcf_proto *tp, *tp_prev;
        int err;

        lockdep_assert_held(&block->cb_lock);

        for (chain = __tcf_get_next_chain(block, NULL);
             chain;
             chain_prev = chain,
                     chain = __tcf_get_next_chain(block, chain),
                     tcf_chain_put(chain_prev)) {
                for (tp = __tcf_get_next_proto(chain, NULL); tp;
                     tp_prev = tp,
                             tp = __tcf_get_next_proto(chain, tp),
                             tcf_proto_put(tp_prev, true, NULL)) {
                        if (tp->ops->reoffload) {
                                err = tp->ops->reoffload(tp, add, cb, cb_priv,
                                                         extack);
                                if (err && add)
                                        goto err_playback_remove;
                        } else if (add && offload_in_use) {
                                err = -EOPNOTSUPP;
                                NL_SET_ERR_MSG(extack, "Filter HW offload failed - classifier without re-offloading support");
                                goto err_playback_remove;
                        }
                }
        }

        return 0;

err_playback_remove:
        tcf_proto_put(tp, true, NULL);
        tcf_chain_put(chain);
        tcf_block_playback_offloads(block, cb, cb_priv, false, offload_in_use,
                                    extack);
        return err;
}

static int tcf_block_bind(struct tcf_block *block,
                          struct flow_block_offload *bo)
{
        struct flow_block_cb *block_cb, *next;
        int err, i = 0;

        lockdep_assert_held(&block->cb_lock);

        list_for_each_entry(block_cb, &bo->cb_list, list) {
                err = tcf_block_playback_offloads(block, block_cb->cb,
                                                  block_cb->cb_priv, true,
                                                  tcf_block_offload_in_use(block),
                                                  bo->extack);
                if (err)
                        goto err_unroll;
                if (!bo->unlocked_driver_cb)
                        block->lockeddevcnt++;

                i++;
        }
        list_splice(&bo->cb_list, &block->flow_block.cb_list);

        return 0;

err_unroll:
        list_for_each_entry_safe(block_cb, next, &bo->cb_list, list) {
                if (i-- > 0) {
                        list_del(&block_cb->list);
                        tcf_block_playback_offloads(block, block_cb->cb,
                                                    block_cb->cb_priv, false,
                                                    tcf_block_offload_in_use(block),
                                                    NULL);
                        if (!bo->unlocked_driver_cb)
                                block->lockeddevcnt--;
                }
                flow_block_cb_free(block_cb);
        }

        return err;
}

static void tcf_block_unbind(struct tcf_block *block,
                             struct flow_block_offload *bo)
{
        struct flow_block_cb *block_cb, *next;

        lockdep_assert_held(&block->cb_lock);

        list_for_each_entry_safe(block_cb, next, &bo->cb_list, list) {
                tcf_block_playback_offloads(block, block_cb->cb,
                                            block_cb->cb_priv, false,
                                            tcf_block_offload_in_use(block),
                                            NULL);
                list_del(&block_cb->list);
                flow_block_cb_free(block_cb);
                if (!bo->unlocked_driver_cb)
                        block->lockeddevcnt--;
        }
}

static int tcf_block_setup(struct tcf_block *block,
                           struct flow_block_offload *bo)
{
        int err;

        switch (bo->command) {
        case FLOW_BLOCK_BIND:
                err = tcf_block_bind(block, bo);
                break;
        case FLOW_BLOCK_UNBIND:
                err = 0;
                tcf_block_unbind(block, bo);
                break;
        default:
                WARN_ON_ONCE(1);
                err = -EOPNOTSUPP;
        }

        return err;
}

/* Main classifier routine: scans classifier chain attached
 * to this qdisc, (optionally) tests for protocol and asks
 * specific classifiers.
 */
int tcf_classify(struct sk_buff *skb, const struct tcf_proto *tp,
                 struct tcf_result *res, bool compat_mode)
{
#ifdef CONFIG_NET_CLS_ACT
        const int max_reclassify_loop = 4;
        const struct tcf_proto *orig_tp = tp;
        const struct tcf_proto *first_tp;
        int limit = 0;

reclassify:
#endif
        for (; tp; tp = rcu_dereference_bh(tp->next)) {
                __be16 protocol = tc_skb_protocol(skb);
                int err;

                if (tp->protocol != protocol &&
                    tp->protocol != htons(ETH_P_ALL))
                        continue;

                err = tp->classify(skb, tp, res);
#ifdef CONFIG_NET_CLS_ACT
                if (unlikely(err == TC_ACT_RECLASSIFY && !compat_mode)) {
                        first_tp = orig_tp;
                        goto reset;
                } else if (unlikely(TC_ACT_EXT_CMP(err, TC_ACT_GOTO_CHAIN))) {
                        first_tp = res->goto_tp;

#if IS_ENABLED(CONFIG_NET_TC_SKB_EXT)
                        {
                                struct tc_skb_ext *ext;

                                ext = skb_ext_add(skb, TC_SKB_EXT);
                                if (WARN_ON_ONCE(!ext))
                                        return TC_ACT_SHOT;

                                ext->chain = err & TC_ACT_EXT_VAL_MASK;
                        }
#endif
                        goto reset;
                }
#endif
                if (err >= 0)
                        return err;
        }

        return TC_ACT_UNSPEC; /* signal: continue lookup */
#ifdef CONFIG_NET_CLS_ACT
reset:
        if (unlikely(limit++ >= max_reclassify_loop)) {
                net_notice_ratelimited("%u: reclassify loop, rule prio %u, protocol %02x\n",
                                       tp->chain->block->index,
                                       tp->prio & 0xffff,
                                       ntohs(tp->protocol));
                return TC_ACT_SHOT;
        }

        tp = first_tp;
        goto reclassify;
#endif
}
EXPORT_SYMBOL(tcf_classify);

struct tcf_chain_info {
        struct tcf_proto __rcu **pprev;
        struct tcf_proto __rcu *next;
};

static struct tcf_proto *tcf_chain_tp_prev(struct tcf_chain *chain,
                                           struct tcf_chain_info *chain_info)
{
        return tcf_chain_dereference(*chain_info->pprev, chain);
}

static int tcf_chain_tp_insert(struct tcf_chain *chain,
                               struct tcf_chain_info *chain_info,
                               struct tcf_proto *tp)
{
        if (chain->flushing)
                return -EAGAIN;

        if (*chain_info->pprev == chain->filter_chain)
                tcf_chain0_head_change(chain, tp);
        tcf_proto_get(tp);
        RCU_INIT_POINTER(tp->next, tcf_chain_tp_prev(chain, chain_info));
        rcu_assign_pointer(*chain_info->pprev, tp);

        return 0;
}

static void tcf_chain_tp_remove(struct tcf_chain *chain,
                                struct tcf_chain_info *chain_info,
                                struct tcf_proto *tp)
{
        struct tcf_proto *next = tcf_chain_dereference(chain_info->next, chain);

        tcf_proto_mark_delete(tp);
        if (tp == chain->filter_chain)
                tcf_chain0_head_change(chain, next);
        RCU_INIT_POINTER(*chain_info->pprev, next);
}

static struct tcf_proto *tcf_chain_tp_find(struct tcf_chain *chain,
                                           struct tcf_chain_info *chain_info,
                                           u32 protocol, u32 prio,
                                           bool prio_allocate);

/* Try to insert new proto.
 * If proto with specified priority already exists, free new proto
 * and return existing one.
 */

static struct tcf_proto *tcf_chain_tp_insert_unique(struct tcf_chain *chain,
                                                    struct tcf_proto *tp_new,
                                                    u32 protocol, u32 prio,
                                                    bool rtnl_held)
{
        struct tcf_chain_info chain_info;
        struct tcf_proto *tp;
        int err = 0;

        mutex_lock(&chain->filter_chain_lock);

        if (tcf_proto_exists_destroying(chain, tp_new)) {
                mutex_unlock(&chain->filter_chain_lock);
                tcf_proto_destroy(tp_new, rtnl_held, false, NULL);
                return ERR_PTR(-EAGAIN);
        }

        tp = tcf_chain_tp_find(chain, &chain_info,
                               protocol, prio, false);
        if (!tp)
                err = tcf_chain_tp_insert(chain, &chain_info, tp_new);
        mutex_unlock(&chain->filter_chain_lock);

        if (tp) {
                tcf_proto_destroy(tp_new, rtnl_held, false, NULL);
                tp_new = tp;
        } else if (err) {
                tcf_proto_destroy(tp_new, rtnl_held, false, NULL);
                tp_new = ERR_PTR(err);
        }

        return tp_new;
}

static void tcf_chain_tp_delete_empty(struct tcf_chain *chain,
                                      struct tcf_proto *tp, bool rtnl_held,
                                      struct netlink_ext_ack *extack)
{
        struct tcf_chain_info chain_info;
        struct tcf_proto *tp_iter;
        struct tcf_proto **pprev;
        struct tcf_proto *next;

        mutex_lock(&chain->filter_chain_lock);

        /* Atomically find and remove tp from chain. */
        for (pprev = &chain->filter_chain;
             (tp_iter = tcf_chain_dereference(*pprev, chain));
             pprev = &tp_iter->next) {
                if (tp_iter == tp) {
                        chain_info.pprev = pprev;
                        chain_info.next = tp_iter->next;
                        WARN_ON(tp_iter->deleting);
                        break;
                }
        }
        /* Verify that tp still exists and no new filters were inserted
         * concurrently.
         * Mark tp for deletion if it is empty.
         */
        if (!tp_iter || !tcf_proto_check_delete(tp)) {
                mutex_unlock(&chain->filter_chain_lock);
                return;
        }

        tcf_proto_signal_destroying(chain, tp);
        next = tcf_chain_dereference(chain_info.next, chain);
        if (tp == chain->filter_chain)
                tcf_chain0_head_change(chain, next);
        RCU_INIT_POINTER(*chain_info.pprev, next);
        mutex_unlock(&chain->filter_chain_lock);

        tcf_proto_put(tp, rtnl_held, extack);
}

static struct tcf_proto *tcf_chain_tp_find(struct tcf_chain *chain,
                                           struct tcf_chain_info *chain_info,
                                           u32 protocol, u32 prio,
                                           bool prio_allocate)
{
        struct tcf_proto **pprev;
        struct tcf_proto *tp;

        /* Check the chain for existence of proto-tcf with this priority */
        for (pprev = &chain->filter_chain;
             (tp = tcf_chain_dereference(*pprev, chain));
             pprev = &tp->next) {
                if (tp->prio >= prio) {
                        if (tp->prio == prio) {
                                if (prio_allocate ||
                                    (tp->protocol != protocol && protocol))
                                        return ERR_PTR(-EINVAL);
                        } else {
                                tp = NULL;
                        }
                        break;
                }
        }
        chain_info->pprev = pprev;
        if (tp) {
                chain_info->next = tp->next;
                tcf_proto_get(tp);
        } else {
                chain_info->next = NULL;
        }
        return tp;
}

static int tcf_fill_node(struct net *net, struct sk_buff *skb,
                         struct tcf_proto *tp, struct tcf_block *block,
                         struct Qdisc *q, u32 parent, void *fh,
                         u32 portid, u32 seq, u16 flags, int event,
                         bool rtnl_held)
{
        struct tcmsg *tcm;
        struct nlmsghdr  *nlh;
        unsigned char *b = skb_tail_pointer(skb);

        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;
        if (q) {
                tcm->tcm_ifindex = qdisc_dev(q)->ifindex;
                tcm->tcm_parent = parent;
        } else {
                tcm->tcm_ifindex = TCM_IFINDEX_MAGIC_BLOCK;
                tcm->tcm_block_index = block->index;
        }
        tcm->tcm_info = TC_H_MAKE(tp->prio, tp->protocol);
        if (nla_put_string(skb, TCA_KIND, tp->ops->kind))
                goto nla_put_failure;
        if (nla_put_u32(skb, TCA_CHAIN, tp->chain->index))
                goto nla_put_failure;
        if (!fh) {
                tcm->tcm_handle = 0;
        } else {
                if (tp->ops->dump &&
                    tp->ops->dump(net, tp, fh, skb, tcm, rtnl_held) < 0)
                        goto nla_put_failure;
        }
        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 tfilter_notify(struct net *net, struct sk_buff *oskb,
                          struct nlmsghdr *n, struct tcf_proto *tp,
                          struct tcf_block *block, struct Qdisc *q,
                          u32 parent, void *fh, int event, bool unicast,
                          bool rtnl_held)
{
        struct sk_buff *skb;
        u32 portid = oskb ? NETLINK_CB(oskb).portid : 0;
        int err = 0;

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

        if (tcf_fill_node(net, skb, tp, block, q, parent, fh, portid,
                          n->nlmsg_seq, n->nlmsg_flags, event,
                          rtnl_held) <= 0) {
                kfree_skb(skb);
                return -EINVAL;
        }

        if (unicast)
                err = netlink_unicast(net->rtnl, skb, portid, MSG_DONTWAIT);
        else
                err = rtnetlink_send(skb, net, portid, RTNLGRP_TC,
                                     n->nlmsg_flags & NLM_F_ECHO);

        if (err > 0)
                err = 0;
        return err;
}

static int tfilter_del_notify(struct net *net, struct sk_buff *oskb,
                              struct nlmsghdr *n, struct tcf_proto *tp,
                              struct tcf_block *block, struct Qdisc *q,
                              u32 parent, void *fh, bool unicast, bool *last,
                              bool rtnl_held, struct netlink_ext_ack *extack)
{
        struct sk_buff *skb;
        u32 portid = oskb ? NETLINK_CB(oskb).portid : 0;
        int err;

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

        if (tcf_fill_node(net, skb, tp, block, q, parent, fh, portid,
                          n->nlmsg_seq, n->nlmsg_flags, RTM_DELTFILTER,
                          rtnl_held) <= 0) {
                NL_SET_ERR_MSG(extack, "Failed to build del event notification");
                kfree_skb(skb);
                return -EINVAL;
        }

        err = tp->ops->delete(tp, fh, last, rtnl_held, extack);
        if (err) {
                kfree_skb(skb);
                return err;
        }

        if (unicast)
                err = netlink_unicast(net->rtnl, skb, portid, MSG_DONTWAIT);
        else
                err = rtnetlink_send(skb, net, portid, RTNLGRP_TC,
                                     n->nlmsg_flags & NLM_F_ECHO);
        if (err < 0)
                NL_SET_ERR_MSG(extack, "Failed to send filter delete notification");

        if (err > 0)
                err = 0;
        return err;
}

static void tfilter_notify_chain(struct net *net, struct sk_buff *oskb,
                                 struct tcf_block *block, struct Qdisc *q,
                                 u32 parent, struct nlmsghdr *n,
                                 struct tcf_chain *chain, int event,
                                 bool rtnl_held)
{
        struct tcf_proto *tp;

        for (tp = tcf_get_next_proto(chain, NULL, rtnl_held);
             tp; tp = tcf_get_next_proto(chain, tp, rtnl_held))
                tfilter_notify(net, oskb, n, tp, block,
                               q, parent, NULL, event, false, rtnl_held);
}

static void tfilter_put(struct tcf_proto *tp, void *fh)
{
        if (tp->ops->put && fh)
                tp->ops->put(tp, fh);
}

static int tc_new_tfilter(struct sk_buff *skb, struct nlmsghdr *n,
                          struct netlink_ext_ack *extack)
{
        struct net *net = sock_net(skb->sk);
        struct nlattr *tca[TCA_MAX + 1];
        char name[IFNAMSIZ];
        struct tcmsg *t;
        u32 protocol;
        u32 prio;
        bool prio_allocate;
        u32 parent;
        u32 chain_index;
        struct Qdisc *q = NULL;
        struct tcf_chain_info chain_info;
        struct tcf_chain *chain = NULL;
        struct tcf_block *block;
        struct tcf_proto *tp;
        unsigned long cl;
        void *fh;
        int err;
        int tp_created;
        bool rtnl_held = false;

        if (!netlink_ns_capable(skb, net->user_ns, CAP_NET_ADMIN))
                return -EPERM;

replay:
        tp_created = 0;

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

        t = nlmsg_data(n);
        protocol = TC_H_MIN(t->tcm_info);
        prio = TC_H_MAJ(t->tcm_info);
        prio_allocate = false;
        parent = t->tcm_parent;
        tp = NULL;
        cl = 0;
        block = NULL;

        if (prio == 0) {
                /* If no priority is provided by the user,
                 * we allocate one.
                 */
                if (n->nlmsg_flags & NLM_F_CREATE) {
                        prio = TC_H_MAKE(0x80000000U, 0U);
                        prio_allocate = true;
                } else {
                        NL_SET_ERR_MSG(extack, "Invalid filter command with priority of zero");
                        return -ENOENT;
                }
        }

        /* Find head of filter chain. */

        err = __tcf_qdisc_find(net, &q, &parent, t->tcm_ifindex, false, extack);
        if (err)
                return err;

        if (tcf_proto_check_kind(tca[TCA_KIND], name)) {
                NL_SET_ERR_MSG(extack, "Specified TC filter name too long");
                err = -EINVAL;
                goto errout;
        }

        /* Take rtnl mutex if rtnl_held was set to true on previous iteration,
         * block is shared (no qdisc found), qdisc is not unlocked, classifier
         * type is not specified, classifier is not unlocked.
         */
        if (rtnl_held ||
            (q && !(q->ops->cl_ops->flags & QDISC_CLASS_OPS_DOIT_UNLOCKED)) ||
            !tcf_proto_is_unlocked(name)) {
                rtnl_held = true;
                rtnl_lock();

        }

        err = __tcf_qdisc_cl_find(q, parent, &cl, t->tcm_ifindex, extack);
        if (err)
                goto errout;

        block = __tcf_block_find(net, q, cl, t->tcm_ifindex, t->tcm_block_index,
                                 extack);
        if (IS_ERR(block)) {
                err = PTR_ERR(block);
                goto errout;
        }

        chain_index = tca[TCA_CHAIN] ? nla_get_u32(tca[TCA_CHAIN]) : 0;
        if (chain_index > TC_ACT_EXT_VAL_MASK) {
                NL_SET_ERR_MSG(extack, "Specified chain index exceeds upper limit");
                err = -EINVAL;
                goto errout;
        }
        chain = tcf_chain_get(block, chain_index, true);
        if (!chain) {
                NL_SET_ERR_MSG(extack, "Cannot create specified filter chain");
                err = -ENOMEM;
                goto errout;
        }

        mutex_lock(&chain->filter_chain_lock);
        tp = tcf_chain_tp_find(chain, &chain_info, protocol,
                               prio, prio_allocate);
        if (IS_ERR(tp)) {
                NL_SET_ERR_MSG(extack, "Filter with specified priority/protocol not found");
                err = PTR_ERR(tp);
                goto errout_locked;
        }

        if (tp == NULL) {
                struct tcf_proto *tp_new = NULL;

                if (chain->flushing) {
                        err = -EAGAIN;
                        goto errout_locked;
                }

                /* Proto-tcf does not exist, create new one */

                if (tca[TCA_KIND] == NULL || !protocol) {
                        NL_SET_ERR_MSG(extack, "Filter kind and protocol must be specified");
                        err = -EINVAL;
                        goto errout_locked;
                }

                if (!(n->nlmsg_flags & NLM_F_CREATE)) {
                        NL_SET_ERR_MSG(extack, "Need both RTM_NEWTFILTER and NLM_F_CREATE to create a new filter");
                        err = -ENOENT;
                        goto errout_locked;
                }

                if (prio_allocate)
                        prio = tcf_auto_prio(tcf_chain_tp_prev(chain,
                                                               &chain_info));

                mutex_unlock(&chain->filter_chain_lock);
                tp_new = tcf_proto_create(name, protocol, prio, chain,
                                          rtnl_held, extack);
                if (IS_ERR(tp_new)) {
                        err = PTR_ERR(tp_new);
                        goto errout_tp;
                }

                tp_created = 1;
                tp = tcf_chain_tp_insert_unique(chain, tp_new, protocol, prio,
                                                rtnl_held);
                if (IS_ERR(tp)) {
                        err = PTR_ERR(tp);
                        goto errout_tp;
                }
        } else {
                mutex_unlock(&chain->filter_chain_lock);
        }

        if (tca[TCA_KIND] && nla_strcmp(tca[TCA_KIND], tp->ops->kind)) {
                NL_SET_ERR_MSG(extack, "Specified filter kind does not match existing one");
                err = -EINVAL;
                goto errout;
        }

        fh = tp->ops->get(tp, t->tcm_handle);

        if (!fh) {
                if (!(n->nlmsg_flags & NLM_F_CREATE)) {
                        NL_SET_ERR_MSG(extack, "Need both RTM_NEWTFILTER and NLM_F_CREATE to create a new filter");
                        err = -ENOENT;
                        goto errout;
                }
        } else if (n->nlmsg_flags & NLM_F_EXCL) {
                tfilter_put(tp, fh);
                NL_SET_ERR_MSG(extack, "Filter already exists");
                err = -EEXIST;
                goto errout;
        }

        if (chain->tmplt_ops && chain->tmplt_ops != tp->ops) {
                NL_SET_ERR_MSG(extack, "Chain template is set to a different filter kind");
                err = -EINVAL;
                goto errout;
        }

        err = tp->ops->change(net, skb, tp, cl, t->tcm_handle, tca, &fh,
                              n->nlmsg_flags & NLM_F_CREATE ? TCA_ACT_NOREPLACE : TCA_ACT_REPLACE,
                              rtnl_held, extack);
        if (err == 0) {
                tfilter_notify(net, skb, n, tp, block, q, parent, fh,
                               RTM_NEWTFILTER, false, rtnl_held);
                tfilter_put(tp, fh);
                /* q pointer is NULL for shared blocks */
                if (q)
                        q->flags &= ~TCQ_F_CAN_BYPASS;
        }

errout:
        if (err && tp_created)
                tcf_chain_tp_delete_empty(chain, tp, rtnl_held, NULL);
errout_tp:
        if (chain) {
                if (tp && !IS_ERR(tp))
                        tcf_proto_put(tp, rtnl_held, NULL);
                if (!tp_created)
                        tcf_chain_put(chain);
        }
        tcf_block_release(q, block, rtnl_held);

        if (rtnl_held)
                rtnl_unlock();

        if (err == -EAGAIN) {
                /* Take rtnl lock in case EAGAIN is caused by concurrent flush
                 * of target chain.
                 */
                rtnl_held = true;
                /* Replay the request. */
                goto replay;
        }
        return err;

errout_locked:
        mutex_unlock(&chain->filter_chain_lock);
        goto errout;
}

static int tc_del_tfilter(struct sk_buff *skb, struct nlmsghdr *n,
                          struct netlink_ext_ack *extack)
{
        struct net *net = sock_net(skb->sk);
        struct nlattr *tca[TCA_MAX + 1];
        char name[IFNAMSIZ];
        struct tcmsg *t;
        u32 protocol;
        u32 prio;
        u32 parent;
        u32 chain_index;
        struct Qdisc *q = NULL;
        struct tcf_chain_info chain_info;
        struct tcf_chain *chain = NULL;
        struct tcf_block *block = NULL;
        struct tcf_proto *tp = NULL;
        unsigned long cl = 0;
        void *fh = NULL;
        int err;
        bool rtnl_held = false;

        if (!netlink_ns_capable(skb, net->user_ns, CAP_NET_ADMIN))
                return -EPERM;

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

        t = nlmsg_data(n);
        protocol = TC_H_MIN(t->tcm_info);
        prio = TC_H_MAJ(t->tcm_info);
        parent = t->tcm_parent;

        if (prio == 0 && (protocol || t->tcm_handle || tca[TCA_KIND])) {
                NL_SET_ERR_MSG(extack, "Cannot flush filters with protocol, handle or kind set");
                return -ENOENT;
        }

        /* Find head of filter chain. */

        err = __tcf_qdisc_find(net, &q, &parent, t->tcm_ifindex, false, extack);
        if (err)
                return err;

        if (tcf_proto_check_kind(tca[TCA_KIND], name)) {
                NL_SET_ERR_MSG(extack, "Specified TC filter name too long");
                err = -EINVAL;
                goto errout;
        }
        /* Take rtnl mutex if flushing whole chain, block is shared (no qdisc
         * found), qdisc is not unlocked, classifier type is not specified,
         * classifier is not unlocked.
         */
        if (!prio ||
            (q && !(q->ops->cl_ops->flags & QDISC_CLASS_OPS_DOIT_UNLOCKED)) ||
            !tcf_proto_is_unlocked(name)) {
                rtnl_held = true;
                rtnl_lock();
        }

        err = __tcf_qdisc_cl_find(q, parent, &cl, t->tcm_ifindex, extack);
        if (err)
                goto errout;

        block = __tcf_block_find(net, q, cl, t->tcm_ifindex, t->tcm_block_index,
                                 extack);
        if (IS_ERR(block)) {
                err = PTR_ERR(block);
                goto errout;
        }

        chain_index = tca[TCA_CHAIN] ? nla_get_u32(tca[TCA_CHAIN]) : 0;
        if (chain_index > TC_ACT_EXT_VAL_MASK) {
                NL_SET_ERR_MSG(extack, "Specified chain index exceeds upper limit");
                err = -EINVAL;
                goto errout;
        }
        chain = tcf_chain_get(block, chain_index, false);
        if (!chain) {
                /* User requested flush on non-existent chain. Nothing to do,
                 * so just return success.
                 */
                if (prio == 0) {
                        err = 0;
                        goto errout;
                }
                NL_SET_ERR_MSG(extack, "Cannot find specified filter chain");
                err = -ENOENT;
                goto errout;
        }

        if (prio == 0) {
                tfilter_notify_chain(net, skb, block, q, parent, n,
                                     chain, RTM_DELTFILTER, rtnl_held);
                tcf_chain_flush(chain, rtnl_held);
                err = 0;
                goto errout;
        }

        mutex_lock(&chain->filter_chain_lock);
        tp = tcf_chain_tp_find(chain, &chain_info, protocol,
                               prio, false);
        if (!tp || IS_ERR(tp)) {
                NL_SET_ERR_MSG(extack, "Filter with specified priority/protocol not found");
                err = tp ? PTR_ERR(tp) : -ENOENT;
                goto errout_locked;
        } else if (tca[TCA_KIND] && nla_strcmp(tca[TCA_KIND], tp->ops->kind)) {
                NL_SET_ERR_MSG(extack, "Specified filter kind does not match existing one");
                err = -EINVAL;
                goto errout_locked;
        } else if (t->tcm_handle == 0) {
                tcf_proto_signal_destroying(chain, tp);
                tcf_chain_tp_remove(chain, &chain_info, tp);
                mutex_unlock(&chain->filter_chain_lock);

                tcf_proto_put(tp, rtnl_held, NULL);
                tfilter_notify(net, skb, n, tp, block, q, parent, fh,
                               RTM_DELTFILTER, false, rtnl_held);
                err = 0;
                goto errout;
        }
        mutex_unlock(&chain->filter_chain_lock);

        fh = tp->ops->get(tp, t->tcm_handle);

        if (!fh) {
                NL_SET_ERR_MSG(extack, "Specified filter handle not found");
                err = -ENOENT;
        } else {
                bool last;

                err = tfilter_del_notify(net, skb, n, tp, block,
                                         q, parent, fh, false, &last,
                                         rtnl_held, extack);

                if (err)
                        goto errout;
                if (last)
                        tcf_chain_tp_delete_empty(chain, tp, rtnl_held, extack);
        }

errout:
        if (chain) {
                if (tp && !IS_ERR(tp))
                        tcf_proto_put(tp, rtnl_held, NULL);
                tcf_chain_put(chain);
        }
        tcf_block_release(q, block, rtnl_held);

        if (rtnl_held)
                rtnl_unlock();

        return err;

errout_locked:
        mutex_unlock(&chain->filter_chain_lock);
        goto errout;
}

static int tc_get_tfilter(struct sk_buff *skb, struct nlmsghdr *n,
                          struct netlink_ext_ack *extack)
{
        struct net *net = sock_net(skb->sk);
        struct nlattr *tca[TCA_MAX + 1];
        char name[IFNAMSIZ];
        struct tcmsg *t;
        u32 protocol;
        u32 prio;
        u32 parent;
        u32 chain_index;
        struct Qdisc *q = NULL;
        struct tcf_chain_info chain_info;
        struct tcf_chain *chain = NULL;
        struct tcf_block *block = NULL;
        struct tcf_proto *tp = NULL;
        unsigned long cl = 0;
        void *fh = NULL;
        int err;
        bool rtnl_held = false;

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

        t = nlmsg_data(n);
        protocol = TC_H_MIN(t->tcm_info);
        prio = TC_H_MAJ(t->tcm_info);
        parent = t->tcm_parent;

        if (prio == 0) {
                NL_SET_ERR_MSG(extack, "Invalid filter command with priority of zero");
                return -ENOENT;
        }

        /* Find head of filter chain. */

        err = __tcf_qdisc_find(net, &q, &parent, t->tcm_ifindex, false, extack);
        if (err)
                return err;

        if (tcf_proto_check_kind(tca[TCA_KIND], name)) {
                NL_SET_ERR_MSG(extack, "Specified TC filter name too long");
                err = -EINVAL;
                goto errout;
        }
        /* Take rtnl mutex if block is shared (no qdisc found), qdisc is not
         * unlocked, classifier type is not specified, classifier is not
         * unlocked.
         */
        if ((q && !(q->ops->cl_ops->flags & QDISC_CLASS_OPS_DOIT_UNLOCKED)) ||
            !tcf_proto_is_unlocked(name)) {
                rtnl_held = true;
                rtnl_lock();
        }

        err = __tcf_qdisc_cl_find(q, parent, &cl, t->tcm_ifindex, extack);
        if (err)
                goto errout;

        block = __tcf_block_find(net, q, cl, t->tcm_ifindex, t->tcm_block_index,
                                 extack);
        if (IS_ERR(block)) {
                err = PTR_ERR(block);
                goto errout;
        }

        chain_index = tca[TCA_CHAIN] ? nla_get_u32(tca[TCA_CHAIN]) : 0;
        if (chain_index > TC_ACT_EXT_VAL_MASK) {
                NL_SET_ERR_MSG(extack, "Specified chain index exceeds upper limit");
                err = -EINVAL;
                goto errout;
        }
        chain = tcf_chain_get(block, chain_index, false);
        if (!chain) {
                NL_SET_ERR_MSG(extack, "Cannot find specified filter chain");
                err = -EINVAL;
                goto errout;
        }

        mutex_lock(&chain->filter_chain_lock);
        tp = tcf_chain_tp_find(chain, &chain_info, protocol,
                               prio, false);
        mutex_unlock(&chain->filter_chain_lock);
        if (!tp || IS_ERR(tp)) {
                NL_SET_ERR_MSG(extack, "Filter with specified priority/protocol not found");
                err = tp ? PTR_ERR(tp) : -ENOENT;
                goto errout;
        } else if (tca[TCA_KIND] && nla_strcmp(tca[TCA_KIND], tp->ops->kind)) {
                NL_SET_ERR_MSG(extack, "Specified filter kind does not match existing one");
                err = -EINVAL;
                goto errout;
        }

        fh = tp->ops->get(tp, t->tcm_handle);

        if (!fh) {
                NL_SET_ERR_MSG(extack, "Specified filter handle not found");
                err = -ENOENT;
        } else {
                err = tfilter_notify(net, skb, n, tp, block, q, parent,
                                     fh, RTM_NEWTFILTER, true, rtnl_held);
                if (err < 0)
                        NL_SET_ERR_MSG(extack, "Failed to send filter notify message");
        }

        tfilter_put(tp, fh);
errout:
        if (chain) {
                if (tp && !IS_ERR(tp))
                        tcf_proto_put(tp, rtnl_held, NULL);
                tcf_chain_put(chain);
        }
        tcf_block_release(q, block, rtnl_held);

        if (rtnl_held)
                rtnl_unlock();

        return err;
}

struct tcf_dump_args {
        struct tcf_walker w;
        struct sk_buff *skb;
        struct netlink_callback *cb;
        struct tcf_block *block;
        struct Qdisc *q;
        u32 parent;
};

static int tcf_node_dump(struct tcf_proto *tp, void *n, struct tcf_walker *arg)
{
        struct tcf_dump_args *a = (void *)arg;
        struct net *net = sock_net(a->skb->sk);

        return tcf_fill_node(net, a->skb, tp, a->block, a->q, a->parent,
                             n, NETLINK_CB(a->cb->skb).portid,
                             a->cb->nlh->nlmsg_seq, NLM_F_MULTI,
                             RTM_NEWTFILTER, true);
}

static bool tcf_chain_dump(struct tcf_chain *chain, struct Qdisc *q, u32 parent,
                           struct sk_buff *skb, struct netlink_callback *cb,
                           long index_start, long *p_index)
{
        struct net *net = sock_net(skb->sk);
        struct tcf_block *block = chain->block;
        struct tcmsg *tcm = nlmsg_data(cb->nlh);
        struct tcf_proto *tp, *tp_prev;
        struct tcf_dump_args arg;

        for (tp = __tcf_get_next_proto(chain, NULL);
             tp;
             tp_prev = tp,
                     tp = __tcf_get_next_proto(chain, tp),
                     tcf_proto_put(tp_prev, true, NULL),
                     (*p_index)++) {
                if (*p_index < index_start)
                        continue;
                if (TC_H_MAJ(tcm->tcm_info) &&
                    TC_H_MAJ(tcm->tcm_info) != tp->prio)
                        continue;
                if (TC_H_MIN(tcm->tcm_info) &&
                    TC_H_MIN(tcm->tcm_info) != tp->protocol)
                        continue;
                if (*p_index > index_start)
                        memset(&cb->args[1], 0,
                               sizeof(cb->args) - sizeof(cb->args[0]));
                if (cb->args[1] == 0) {
                        if (tcf_fill_node(net, skb, tp, block, q, parent, NULL,
                                          NETLINK_CB(cb->skb).portid,
                                          cb->nlh->nlmsg_seq, NLM_F_MULTI,
                                          RTM_NEWTFILTER, true) <= 0)
                                goto errout;
                        cb->args[1] = 1;
                }
                if (!tp->ops->walk)
                        continue;
                arg.w.fn = tcf_node_dump;
                arg.skb = skb;
                arg.cb = cb;
                arg.block = block;
                arg.q = q;
                arg.parent = parent;
                arg.w.stop = 0;
                arg.w.skip = cb->args[1] - 1;
                arg.w.count = 0;
                arg.w.cookie = cb->args[2];
                tp->ops->walk(tp, &arg.w, true);
                cb->args[2] = arg.w.cookie;
                cb->args[1] = arg.w.count + 1;
                if (arg.w.stop)
                        goto errout;
        }
        return true;

errout:
        tcf_proto_put(tp, true, NULL);
        return false;
}

/* called with RTNL */
static int tc_dump_tfilter(struct sk_buff *skb, struct netlink_callback *cb)
{
        struct tcf_chain *chain, *chain_prev;
        struct net *net = sock_net(skb->sk);
        struct nlattr *tca[TCA_MAX + 1];
        struct Qdisc *q = NULL;
        struct tcf_block *block;
        struct tcmsg *tcm = nlmsg_data(cb->nlh);
        long index_start;
        long index;
        u32 parent;
        int err;

        if (nlmsg_len(cb->nlh) < sizeof(*tcm))
                return skb->len;

        err = nlmsg_parse_deprecated(cb->nlh, sizeof(*tcm), tca, TCA_MAX,
                                     NULL, cb->extack);
        if (err)
                return err;

        if (tcm->tcm_ifindex == TCM_IFINDEX_MAGIC_BLOCK) {
                block = tcf_block_refcnt_get(net, tcm->tcm_block_index);
                if (!block)
                        goto out;
                /* If we work with block index, q is NULL and parent value
                 * will never be used in the following code. The check
                 * in tcf_fill_node prevents it. However, compiler does not
                 * see that far, so set parent to zero to silence the warning
                 * about parent being uninitialized.
                 */
                parent = 0;
        } else {
                const struct Qdisc_class_ops *cops;
                struct net_device *dev;
                unsigned long cl = 0;

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

                parent = tcm->tcm_parent;
                if (!parent) {
                        q = dev->qdisc;
                        parent = q->handle;
                } else {
                        q = qdisc_lookup(dev, TC_H_MAJ(tcm->tcm_parent));
                }
                if (!q)
                        goto out;
                cops = q->ops->cl_ops;
                if (!cops)
                        goto out;
                if (!cops->tcf_block)
                        goto out;
                if (TC_H_MIN(tcm->tcm_parent)) {
                        cl = cops->find(q, tcm->tcm_parent);
                        if (cl == 0)
                                goto out;
                }
                block = cops->tcf_block(q, cl, NULL);
                if (!block)
                        goto out;
                if (tcf_block_shared(block))
                        q = NULL;
        }

        index_start = cb->args[0];
        index = 0;

        for (chain = __tcf_get_next_chain(block, NULL);
             chain;
             chain_prev = chain,
                     chain = __tcf_get_next_chain(block, chain),
                     tcf_chain_put(chain_prev)) {
                if (tca[TCA_CHAIN] &&
                    nla_get_u32(tca[TCA_CHAIN]) != chain->index)
                        continue;
                if (!tcf_chain_dump(chain, q, parent, skb, cb,
                                    index_start, &index)) {
                        tcf_chain_put(chain);
                        err = -EMSGSIZE;
                        break;
                }
        }

        if (tcm->tcm_ifindex == TCM_IFINDEX_MAGIC_BLOCK)
                tcf_block_refcnt_put(block, true);
        cb->args[0] = index;

out:
        /* If we did no progress, the error (EMSGSIZE) is real */
        if (skb->len == 0 && err)
                return err;
        return skb->len;
}

static int tc_chain_fill_node(const struct tcf_proto_ops *tmplt_ops,
                              void *tmplt_priv, u32 chain_index,
                              struct net *net, struct sk_buff *skb,
                              struct tcf_block *block,
                              u32 portid, u32 seq, u16 flags, int event)
{
        unsigned char *b = skb_tail_pointer(skb);
        const struct tcf_proto_ops *ops;
        struct nlmsghdr *nlh;
        struct tcmsg *tcm;
        void *priv;

        ops = tmplt_ops;
        priv = tmplt_priv;

        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_handle = 0;
        if (block->q) {
                tcm->tcm_ifindex = qdisc_dev(block->q)->ifindex;
                tcm->tcm_parent = block->q->handle;
        } else {
                tcm->tcm_ifindex = TCM_IFINDEX_MAGIC_BLOCK;
                tcm->tcm_block_index = block->index;
        }

        if (nla_put_u32(skb, TCA_CHAIN, chain_index))
                goto nla_put_failure;

        if (ops) {
                if (nla_put_string(skb, TCA_KIND, ops->kind))
                        goto nla_put_failure;
                if (ops->tmplt_dump(skb, net, priv) < 0)
                        goto nla_put_failure;
        }

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

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

static int tc_chain_notify(struct tcf_chain *chain, struct sk_buff *oskb,
                           u32 seq, u16 flags, int event, bool unicast)
{
        u32 portid = oskb ? NETLINK_CB(oskb).portid : 0;
        struct tcf_block *block = chain->block;
        struct net *net = block->net;
        struct sk_buff *skb;
        int err = 0;

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

        if (tc_chain_fill_node(chain->tmplt_ops, chain->tmplt_priv,
                               chain->index, net, skb, block, portid,
                               seq, flags, event) <= 0) {
                kfree_skb(skb);
                return -EINVAL;
        }

        if (unicast)
                err = netlink_unicast(net->rtnl, skb, portid, MSG_DONTWAIT);
        else
                err = rtnetlink_send(skb, net, portid, RTNLGRP_TC,
                                     flags & NLM_F_ECHO);

        if (err > 0)
                err = 0;
        return err;
}

static int tc_chain_notify_delete(const struct tcf_proto_ops *tmplt_ops,
                                  void *tmplt_priv, u32 chain_index,
                                  struct tcf_block *block, struct sk_buff *oskb,
                                  u32 seq, u16 flags, bool unicast)
{
        u32 portid = oskb ? NETLINK_CB(oskb).portid : 0;
        struct net *net = block->net;
        struct sk_buff *skb;

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

        if (tc_chain_fill_node(tmplt_ops, tmplt_priv, chain_index, net, skb,
                               block, portid, seq, flags, RTM_DELCHAIN) <= 0) {
                kfree_skb(skb);
                return -EINVAL;
        }

        if (unicast)
                return netlink_unicast(net->rtnl, skb, portid, MSG_DONTWAIT);

        return rtnetlink_send(skb, net, portid, RTNLGRP_TC, flags & NLM_F_ECHO);
}

static int tc_chain_tmplt_add(struct tcf_chain *chain, struct net *net,
                              struct nlattr **tca,
                              struct netlink_ext_ack *extack)
{
        const struct tcf_proto_ops *ops;
        char name[IFNAMSIZ];
        void *tmplt_priv;

        /* If kind is not set, user did not specify template. */
        if (!tca[TCA_KIND])
                return 0;

        if (tcf_proto_check_kind(tca[TCA_KIND], name)) {
                NL_SET_ERR_MSG(extack, "Specified TC chain template name too long");
                return -EINVAL;
        }

        ops = tcf_proto_lookup_ops(name, true, extack);
        if (IS_ERR(ops))
                return PTR_ERR(ops);
        if (!ops->tmplt_create || !ops->tmplt_destroy || !ops->tmplt_dump) {
                NL_SET_ERR_MSG(extack, "Chain templates are not supported with specified classifier");
                return -EOPNOTSUPP;
        }

        tmplt_priv = ops->tmplt_create(net, chain, tca, extack);
        if (IS_ERR(tmplt_priv)) {
                module_put(ops->owner);
                return PTR_ERR(tmplt_priv);
        }
        chain->tmplt_ops = ops;
        chain->tmplt_priv = tmplt_priv;
        return 0;
}

static void tc_chain_tmplt_del(const struct tcf_proto_ops *tmplt_ops,
                               void *tmplt_priv)
{
        /* If template ops are set, no work to do for us. */
        if (!tmplt_ops)
                return;

        tmplt_ops->tmplt_destroy(tmplt_priv);
        module_put(tmplt_ops->owner);
}

/* Add/delete/get a chain */

static int tc_ctl_chain(struct sk_buff *skb, struct nlmsghdr *n,
                        struct netlink_ext_ack *extack)
{
        struct net *net = sock_net(skb->sk);
        struct nlattr *tca[TCA_MAX + 1];
        struct tcmsg *t;
        u32 parent;
        u32 chain_index;
        struct Qdisc *q = NULL;
        struct tcf_chain *chain = NULL;
        struct tcf_block *block;
        unsigned long cl;
        int err;

        if (n->nlmsg_type != RTM_GETCHAIN &&
            !netlink_ns_capable(skb, net->user_ns, CAP_NET_ADMIN))
                return -EPERM;

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

        t = nlmsg_data(n);
        parent = t->tcm_parent;
        cl = 0;

        block = tcf_block_find(net, &q, &parent, &cl,
                               t->tcm_ifindex, t->tcm_block_index, extack);
        if (IS_ERR(block))
                return PTR_ERR(block);

        chain_index = tca[TCA_CHAIN] ? nla_get_u32(tca[TCA_CHAIN]) : 0;
        if (chain_index > TC_ACT_EXT_VAL_MASK) {
                NL_SET_ERR_MSG(extack, "Specified chain index exceeds upper limit");
                err = -EINVAL;
                goto errout_block;
        }

        mutex_lock(&block->lock);
        chain = tcf_chain_lookup(block, chain_index);
        if (n->nlmsg_type == RTM_NEWCHAIN) {
                if (chain) {
                        if (tcf_chain_held_by_acts_only(chain)) {
                                /* The chain exists only because there is
                                 * some action referencing it.
                                 */
                                tcf_chain_hold(chain);
                        } else {
                                NL_SET_ERR_MSG(extack, "Filter chain already exists");
                                err = -EEXIST;
                                goto errout_block_locked;
                        }
                } else {
                        if (!(n->nlmsg_flags & NLM_F_CREATE)) {
                                NL_SET_ERR_MSG(extack, "Need both RTM_NEWCHAIN and NLM_F_CREATE to create a new chain");
                                err = -ENOENT;
                                goto errout_block_locked;
                        }
                        chain = tcf_chain_create(block, chain_index);
                        if (!chain) {
                                NL_SET_ERR_MSG(extack, "Failed to create filter chain");
                                err = -ENOMEM;
                                goto errout_block_locked;
                        }
                }
        } else {
                if (!chain || tcf_chain_held_by_acts_only(chain)) {
                        NL_SET_ERR_MSG(extack, "Cannot find specified filter chain");
                        err = -EINVAL;
                        goto errout_block_locked;
                }
                tcf_chain_hold(chain);
        }

        if (n->nlmsg_type == RTM_NEWCHAIN) {
                /* Modifying chain requires holding parent block lock. In case
                 * the chain was successfully added, take a reference to the
                 * chain. This ensures that an empty chain does not disappear at
                 * the end of this function.
                 */
                tcf_chain_hold(chain);
                chain->explicitly_created = true;
        }
        mutex_unlock(&block->lock);

        switch (n->nlmsg_type) {
        case RTM_NEWCHAIN:
                err = tc_chain_tmplt_add(chain, net, tca, extack);
                if (err) {
                        tcf_chain_put_explicitly_created(chain);
                        goto errout;
                }

                tc_chain_notify(chain, NULL, 0, NLM_F_CREATE | NLM_F_EXCL,
                                RTM_NEWCHAIN, false);
                break;
        case RTM_DELCHAIN:
                tfilter_notify_chain(net, skb, block, q, parent, n,
                                     chain, RTM_DELTFILTER, true);
                /* Flush the chain first as the user requested chain removal. */
                tcf_chain_flush(chain, true);
                /* In case the chain was successfully deleted, put a reference
                 * to the chain previously taken during addition.
                 */
                tcf_chain_put_explicitly_created(chain);
                break;
        case RTM_GETCHAIN:
                err = tc_chain_notify(chain, skb, n->nlmsg_seq,
                                      n->nlmsg_seq, n->nlmsg_type, true);
                if (err < 0)
                        NL_SET_ERR_MSG(extack, "Failed to send chain notify message");
                break;
        default:
                err = -EOPNOTSUPP;
                NL_SET_ERR_MSG(extack, "Unsupported message type");
                goto errout;
        }

errout:
        tcf_chain_put(chain);
errout_block:
        tcf_block_release(q, block, true);
        if (err == -EAGAIN)
                /* Replay the request. */
                goto replay;
        return err;

errout_block_locked:
        mutex_unlock(&block->lock);
        goto errout_block;
}

/* called with RTNL */
static int tc_dump_chain(struct sk_buff *skb, struct netlink_callback *cb)
{
        struct net *net = sock_net(skb->sk);
        struct nlattr *tca[TCA_MAX + 1];
        struct Qdisc *q = NULL;
        struct tcf_block *block;
        struct tcmsg *tcm = nlmsg_data(cb->nlh);
        struct tcf_chain *chain;
        long index_start;
        long index;
        u32 parent;
        int err;

        if (nlmsg_len(cb->nlh) < sizeof(*tcm))
                return skb->len;

        err = nlmsg_parse_deprecated(cb->nlh, sizeof(*tcm), tca, TCA_MAX,
                                     rtm_tca_policy, cb->extack);
        if (err)
                return err;

        if (tcm->tcm_ifindex == TCM_IFINDEX_MAGIC_BLOCK) {
                block = tcf_block_refcnt_get(net, tcm->tcm_block_index);
                if (!block)
                        goto out;
                /* If we work with block index, q is NULL and parent value
                 * will never be used in the following code. The check
                 * in tcf_fill_node prevents it. However, compiler does not
                 * see that far, so set parent to zero to silence the warning
                 * about parent being uninitialized.
                 */
                parent = 0;
        } else {
                const struct Qdisc_class_ops *cops;
                struct net_device *dev;
                unsigned long cl = 0;

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

                parent = tcm->tcm_parent;
                if (!parent) {
                        q = dev->qdisc;
                        parent = q->handle;
                } else {
                        q = qdisc_lookup(dev, TC_H_MAJ(tcm->tcm_parent));
                }
                if (!q)
                        goto out;
                cops = q->ops->cl_ops;
                if (!cops)
                        goto out;
                if (!cops->tcf_block)
                        goto out;
                if (TC_H_MIN(tcm->tcm_parent)) {
                        cl = cops->find(q, tcm->tcm_parent);
                        if (cl == 0)
                                goto out;
                }
                block = cops->tcf_block(q, cl, NULL);
                if (!block)
                        goto out;
                if (tcf_block_shared(block))
                        q = NULL;
        }

        index_start = cb->args[0];
        index = 0;

        mutex_lock(&block->lock);
        list_for_each_entry(chain, &block->chain_list, list) {
                if ((tca[TCA_CHAIN] &&
                     nla_get_u32(tca[TCA_CHAIN]) != chain->index))
                        continue;
                if (index < index_start) {
                        index++;
                        continue;
                }
                if (tcf_chain_held_by_acts_only(chain))
                        continue;
                err = tc_chain_fill_node(chain->tmplt_ops, chain->tmplt_priv,
                                         chain->index, net, skb, block,
                                         NETLINK_CB(cb->skb).portid,
                                         cb->nlh->nlmsg_seq, NLM_F_MULTI,
                                         RTM_NEWCHAIN);
                if (err <= 0)
                        break;
                index++;
        }
        mutex_unlock(&block->lock);

        if (tcm->tcm_ifindex == TCM_IFINDEX_MAGIC_BLOCK)
                tcf_block_refcnt_put(block, true);
        cb->args[0] = index;

out:
        /* If we did no progress, the error (EMSGSIZE) is real */
        if (skb->len == 0 && err)
                return err;
        return skb->len;
}