// SPDX-License-Identifier: GPL-2.0-only
/* net/sched/sch_atm.c - ATM VC selection "queueing discipline" */

/* Written 1998-2000 by Werner Almesberger, EPFL ICA */

#include <linux/module.h>
#include <linux/slab.h>
#include <linux/init.h>
#include <linux/interrupt.h>
#include <linux/string.h>
#include <linux/errno.h>
#include <linux/skbuff.h>
#include <linux/atmdev.h>
#include <linux/atmclip.h>
#include <linux/rtnetlink.h>
#include <linux/file.h>         /* for fput */
#include <net/netlink.h>
#include <net/pkt_sched.h>
#include <net/pkt_cls.h>

/*
 * The ATM queuing discipline provides a framework for invoking classifiers
 * (aka "filters"), which in turn select classes of this queuing discipline.
 * Each class maps the flow(s) it is handling to a given VC. Multiple classes
 * may share the same VC.
 *
 * When creating a class, VCs are specified by passing the number of the open
 * socket descriptor by which the calling process references the VC. The kernel
 * keeps the VC open at least until all classes using it are removed.
 *
 * In this file, most functions are named atm_tc_* to avoid confusion with all
 * the atm_* in net/atm. This naming convention differs from what's used in the
 * rest of net/sched.
 *
 * Known bugs:
 *  - sometimes messes up the IP stack
 *  - any manipulations besides the few operations described in the README, are
 *    untested and likely to crash the system
 *  - should lock the flow while there is data in the queue (?)
 */

#define VCC2FLOW(vcc) ((struct atm_flow_data *) ((vcc)->user_back))

struct atm_flow_data {
        struct Qdisc_class_common common;
        struct Qdisc            *q;     /* FIFO, TBF, etc. */
        struct tcf_proto __rcu  *filter_list;
        struct tcf_block        *block;
        struct atm_vcc          *vcc;   /* VCC; NULL if VCC is closed */
        void                    (*old_pop)(struct atm_vcc *vcc,
                                           struct sk_buff *skb); /* chaining */
        struct atm_qdisc_data   *parent;        /* parent qdisc */
        struct socket           *sock;          /* for closing */
        int                     ref;            /* reference count */
        struct gnet_stats_basic_packed  bstats;
        struct gnet_stats_queue qstats;
        struct list_head        list;
        struct atm_flow_data    *excess;        /* flow for excess traffic;
                                                   NULL to set CLP instead */
        int                     hdr_len;
        unsigned char           hdr[];          /* header data; MUST BE LAST */
};

struct atm_qdisc_data {
        struct atm_flow_data    link;           /* unclassified skbs go here */
        struct list_head        flows;          /* NB: "link" is also on this
                                                   list */
        struct tasklet_struct   task;           /* dequeue tasklet */
};

/* ------------------------- Class/flow operations ------------------------- */

static inline struct atm_flow_data *lookup_flow(struct Qdisc *sch, u32 classid)
{
        struct atm_qdisc_data *p = qdisc_priv(sch);
        struct atm_flow_data *flow;

        list_for_each_entry(flow, &p->flows, list) {
                if (flow->common.classid == classid)
                        return flow;
        }
        return NULL;
}

static int atm_tc_graft(struct Qdisc *sch, unsigned long arg,
                        struct Qdisc *new, struct Qdisc **old,
                        struct netlink_ext_ack *extack)
{
        struct atm_qdisc_data *p = qdisc_priv(sch);
        struct atm_flow_data *flow = (struct atm_flow_data *)arg;

        pr_debug("atm_tc_graft(sch %p,[qdisc %p],flow %p,new %p,old %p)\n",
                sch, p, flow, new, old);
        if (list_empty(&flow->list))
                return -EINVAL;
        if (!new)
                new = &noop_qdisc;
        *old = flow->q;
        flow->q = new;
        if (*old)
                qdisc_reset(*old);
        return 0;
}

static struct Qdisc *atm_tc_leaf(struct Qdisc *sch, unsigned long cl)
{
        struct atm_flow_data *flow = (struct atm_flow_data *)cl;

        pr_debug("atm_tc_leaf(sch %p,flow %p)\n", sch, flow);
        return flow ? flow->q : NULL;
}

static unsigned long atm_tc_find(struct Qdisc *sch, u32 classid)
{
        struct atm_qdisc_data *p __maybe_unused = qdisc_priv(sch);
        struct atm_flow_data *flow;

        pr_debug("%s(sch %p,[qdisc %p],classid %x)\n", __func__, sch, p, classid);
        flow = lookup_flow(sch, classid);
        pr_debug("%s: flow %p\n", __func__, flow);
        return (unsigned long)flow;
}

static unsigned long atm_tc_bind_filter(struct Qdisc *sch,
                                        unsigned long parent, u32 classid)
{
        struct atm_qdisc_data *p __maybe_unused = qdisc_priv(sch);
        struct atm_flow_data *flow;

        pr_debug("%s(sch %p,[qdisc %p],classid %x)\n", __func__, sch, p, classid);
        flow = lookup_flow(sch, classid);
        if (flow)
                flow->ref++;
        pr_debug("%s: flow %p\n", __func__, flow);
        return (unsigned long)flow;
}

/*
 * atm_tc_put handles all destructions, including the ones that are explicitly
 * requested (atm_tc_destroy, etc.). The assumption here is that we never drop
 * anything that still seems to be in use.
 */
static void atm_tc_put(struct Qdisc *sch, unsigned long cl)
{
        struct atm_qdisc_data *p = qdisc_priv(sch);
        struct atm_flow_data *flow = (struct atm_flow_data *)cl;

        pr_debug("atm_tc_put(sch %p,[qdisc %p],flow %p)\n", sch, p, flow);
        if (--flow->ref)
                return;
        pr_debug("atm_tc_put: destroying\n");
        list_del_init(&flow->list);
        pr_debug("atm_tc_put: qdisc %p\n", flow->q);
        qdisc_put(flow->q);
        tcf_block_put(flow->block);
        if (flow->sock) {
                pr_debug("atm_tc_put: f_count %ld\n",
                        file_count(flow->sock->file));
                flow->vcc->pop = flow->old_pop;
                sockfd_put(flow->sock);
        }
        if (flow->excess)
                atm_tc_put(sch, (unsigned long)flow->excess);
        if (flow != &p->link)
                kfree(flow);
        /*
         * If flow == &p->link, the qdisc no longer works at this point and
         * needs to be removed. (By the caller of atm_tc_put.)
         */
}

static void sch_atm_pop(struct atm_vcc *vcc, struct sk_buff *skb)
{
        struct atm_qdisc_data *p = VCC2FLOW(vcc)->parent;

        pr_debug("sch_atm_pop(vcc %p,skb %p,[qdisc %p])\n", vcc, skb, p);
        VCC2FLOW(vcc)->old_pop(vcc, skb);
        tasklet_schedule(&p->task);
}

static const u8 llc_oui_ip[] = {
        0xaa,                   /* DSAP: non-ISO */
        0xaa,                   /* SSAP: non-ISO */
        0x03,                   /* Ctrl: Unnumbered Information Command PDU */
        0x00,                   /* OUI: EtherType */
        0x00, 0x00,
        0x08, 0x00
};                              /* Ethertype IP (0800) */

static const struct nla_policy atm_policy[TCA_ATM_MAX + 1] = {
        [TCA_ATM_FD]            = { .type = NLA_U32 },
        [TCA_ATM_EXCESS]        = { .type = NLA_U32 },
};

static int atm_tc_change(struct Qdisc *sch, u32 classid, u32 parent,
                         struct nlattr **tca, unsigned long *arg,
                         struct netlink_ext_ack *extack)
{
        struct atm_qdisc_data *p = qdisc_priv(sch);
        struct atm_flow_data *flow = (struct atm_flow_data *)*arg;
        struct atm_flow_data *excess = NULL;
        struct nlattr *opt = tca[TCA_OPTIONS];
        struct nlattr *tb[TCA_ATM_MAX + 1];
        struct socket *sock;
        int fd, error, hdr_len;
        void *hdr;

        pr_debug("atm_tc_change(sch %p,[qdisc %p],classid %x,parent %x,"
                "flow %p,opt %p)\n", sch, p, classid, parent, flow, opt);
        /*
         * The concept of parents doesn't apply for this qdisc.
         */
        if (parent && parent != TC_H_ROOT && parent != sch->handle)
                return -EINVAL;
        /*
         * ATM classes cannot be changed. In order to change properties of the
         * ATM connection, that socket needs to be modified directly (via the
         * native ATM API. In order to send a flow to a different VC, the old
         * class needs to be removed and a new one added. (This may be changed
         * later.)
         */
        if (flow)
                return -EBUSY;
        if (opt == NULL)
                return -EINVAL;

        error = nla_parse_nested_deprecated(tb, TCA_ATM_MAX, opt, atm_policy,
                                            NULL);
        if (error < 0)
                return error;

        if (!tb[TCA_ATM_FD])
                return -EINVAL;
        fd = nla_get_u32(tb[TCA_ATM_FD]);
        pr_debug("atm_tc_change: fd %d\n", fd);
        if (tb[TCA_ATM_HDR]) {
                hdr_len = nla_len(tb[TCA_ATM_HDR]);
                hdr = nla_data(tb[TCA_ATM_HDR]);
        } else {
                hdr_len = RFC1483LLC_LEN;
                hdr = NULL;     /* default LLC/SNAP for IP */
        }
        if (!tb[TCA_ATM_EXCESS])
                excess = NULL;
        else {
                excess = (struct atm_flow_data *)
                        atm_tc_find(sch, nla_get_u32(tb[TCA_ATM_EXCESS]));
                if (!excess)
                        return -ENOENT;
        }
        pr_debug("atm_tc_change: type %d, payload %d, hdr_len %d\n",
                 opt->nla_type, nla_len(opt), hdr_len);
        sock = sockfd_lookup(fd, &error);
        if (!sock)
                return error;   /* f_count++ */
        pr_debug("atm_tc_change: f_count %ld\n", file_count(sock->file));
        if (sock->ops->family != PF_ATMSVC && sock->ops->family != PF_ATMPVC) {
                error = -EPROTOTYPE;
                goto err_out;
        }
        /* @@@ should check if the socket is really operational or we'll crash
           on vcc->send */
        if (classid) {
                if (TC_H_MAJ(classid ^ sch->handle)) {
                        pr_debug("atm_tc_change: classid mismatch\n");
                        error = -EINVAL;
                        goto err_out;
                }
        } else {
                int i;
                unsigned long cl;

                for (i = 1; i < 0x8000; i++) {
                        classid = TC_H_MAKE(sch->handle, 0x8000 | i);
                        cl = atm_tc_find(sch, classid);
                        if (!cl)
                                break;
                }
        }
        pr_debug("atm_tc_change: new id %x\n", classid);
        flow = kzalloc(sizeof(struct atm_flow_data) + hdr_len, GFP_KERNEL);
        pr_debug("atm_tc_change: flow %p\n", flow);
        if (!flow) {
                error = -ENOBUFS;
                goto err_out;
        }

        error = tcf_block_get(&flow->block, &flow->filter_list, sch,
                              extack);
        if (error) {
                kfree(flow);
                goto err_out;
        }

        flow->q = qdisc_create_dflt(sch->dev_queue, &pfifo_qdisc_ops, classid,
                                    extack);
        if (!flow->q)
                flow->q = &noop_qdisc;
        pr_debug("atm_tc_change: qdisc %p\n", flow->q);
        flow->sock = sock;
        flow->vcc = ATM_SD(sock);       /* speedup */
        flow->vcc->user_back = flow;
        pr_debug("atm_tc_change: vcc %p\n", flow->vcc);
        flow->old_pop = flow->vcc->pop;
        flow->parent = p;
        flow->vcc->pop = sch_atm_pop;
        flow->common.classid = classid;
        flow->ref = 1;
        flow->excess = excess;
        list_add(&flow->list, &p->link.list);
        flow->hdr_len = hdr_len;
        if (hdr)
                memcpy(flow->hdr, hdr, hdr_len);
        else
                memcpy(flow->hdr, llc_oui_ip, sizeof(llc_oui_ip));
        *arg = (unsigned long)flow;
        return 0;
err_out:
        sockfd_put(sock);
        return error;
}

static int atm_tc_delete(struct Qdisc *sch, unsigned long arg,
                         struct netlink_ext_ack *extack)
{
        struct atm_qdisc_data *p = qdisc_priv(sch);
        struct atm_flow_data *flow = (struct atm_flow_data *)arg;

        pr_debug("atm_tc_delete(sch %p,[qdisc %p],flow %p)\n", sch, p, flow);
        if (list_empty(&flow->list))
                return -EINVAL;
        if (rcu_access_pointer(flow->filter_list) || flow == &p->link)
                return -EBUSY;
        /*
         * Reference count must be 2: one for "keepalive" (set at class
         * creation), and one for the reference held when calling delete.
         */
        if (flow->ref < 2) {
                pr_err("atm_tc_delete: flow->ref == %d\n", flow->ref);
                return -EINVAL;
        }
        if (flow->ref > 2)
                return -EBUSY;  /* catch references via excess, etc. */
        atm_tc_put(sch, arg);
        return 0;
}

static void atm_tc_walk(struct Qdisc *sch, struct qdisc_walker *walker)
{
        struct atm_qdisc_data *p = qdisc_priv(sch);
        struct atm_flow_data *flow;

        pr_debug("atm_tc_walk(sch %p,[qdisc %p],walker %p)\n", sch, p, walker);
        if (walker->stop)
                return;
        list_for_each_entry(flow, &p->flows, list) {
                if (walker->count >= walker->skip &&
                    walker->fn(sch, (unsigned long)flow, walker) < 0) {
                        walker->stop = 1;
                        break;
                }
                walker->count++;
        }
}

static struct tcf_block *atm_tc_tcf_block(struct Qdisc *sch, unsigned long cl,
                                          struct netlink_ext_ack *extack)
{
        struct atm_qdisc_data *p = qdisc_priv(sch);
        struct atm_flow_data *flow = (struct atm_flow_data *)cl;

        pr_debug("atm_tc_find_tcf(sch %p,[qdisc %p],flow %p)\n", sch, p, flow);
        return flow ? flow->block : p->link.block;
}

/* --------------------------- Qdisc operations ---------------------------- */

static int atm_tc_enqueue(struct sk_buff *skb, struct Qdisc *sch,
                          struct sk_buff **to_free)
{
        struct atm_qdisc_data *p = qdisc_priv(sch);
        struct atm_flow_data *flow;
        struct tcf_result res;
        int result;
        int ret = NET_XMIT_SUCCESS | __NET_XMIT_BYPASS;

        pr_debug("atm_tc_enqueue(skb %p,sch %p,[qdisc %p])\n", skb, sch, p);
        result = TC_ACT_OK;     /* be nice to gcc */
        flow = NULL;
        if (TC_H_MAJ(skb->priority) != sch->handle ||
            !(flow = (struct atm_flow_data *)atm_tc_find(sch, skb->priority))) {
                struct tcf_proto *fl;

                list_for_each_entry(flow, &p->flows, list) {
                        fl = rcu_dereference_bh(flow->filter_list);
                        if (fl) {
                                result = tcf_classify(skb, fl, &res, true);
                                if (result < 0)
                                        continue;
                                flow = (struct atm_flow_data *)res.class;
                                if (!flow)
                                        flow = lookup_flow(sch, res.classid);
                                goto done;
                        }
                }
                flow = NULL;
done:
                ;
        }
        if (!flow) {
                flow = &p->link;
        } else {
                if (flow->vcc)
                        ATM_SKB(skb)->atm_options = flow->vcc->atm_options;
                /*@@@ looks good ... but it's not supposed to work :-) */
#ifdef CONFIG_NET_CLS_ACT
                switch (result) {
                case TC_ACT_QUEUED:
                case TC_ACT_STOLEN:
                case TC_ACT_TRAP:
                        __qdisc_drop(skb, to_free);
                        return NET_XMIT_SUCCESS | __NET_XMIT_STOLEN;
                case TC_ACT_SHOT:
                        __qdisc_drop(skb, to_free);
                        goto drop;
                case TC_ACT_RECLASSIFY:
                        if (flow->excess)
                                flow = flow->excess;
                        else
                                ATM_SKB(skb)->atm_options |= ATM_ATMOPT_CLP;
                        break;
                }
#endif
        }

        ret = qdisc_enqueue(skb, flow->q, to_free);
        if (ret != NET_XMIT_SUCCESS) {
drop: __maybe_unused
                if (net_xmit_drop_count(ret)) {
                        qdisc_qstats_drop(sch);
                        if (flow)
                                flow->qstats.drops++;
                }
                return ret;
        }
        /*
         * Okay, this may seem weird. We pretend we've dropped the packet if
         * it goes via ATM. The reason for this is that the outer qdisc
         * expects to be able to q->dequeue the packet later on if we return
         * success at this place. Also, sch->q.qdisc needs to reflect whether
         * there is a packet egligible for dequeuing or not. Note that the
         * statistics of the outer qdisc are necessarily wrong because of all
         * this. There's currently no correct solution for this.
         */
        if (flow == &p->link) {
                sch->q.qlen++;
                return NET_XMIT_SUCCESS;
        }
        tasklet_schedule(&p->task);
        return NET_XMIT_SUCCESS | __NET_XMIT_BYPASS;
}

/*
 * Dequeue packets and send them over ATM. Note that we quite deliberately
 * avoid checking net_device's flow control here, simply because sch_atm
 * uses its own channels, which have nothing to do with any CLIP/LANE/or
 * non-ATM interfaces.
 */

static void sch_atm_dequeue(struct tasklet_struct *t)
{
        struct atm_qdisc_data *p = from_tasklet(p, t, task);
        struct Qdisc *sch = qdisc_from_priv(p);
        struct atm_flow_data *flow;
        struct sk_buff *skb;

        pr_debug("sch_atm_dequeue(sch %p,[qdisc %p])\n", sch, p);
        list_for_each_entry(flow, &p->flows, list) {
                if (flow == &p->link)
                        continue;
                /*
                 * If traffic is properly shaped, this won't generate nasty
                 * little bursts. Otherwise, it may ... (but that's okay)
                 */
                while ((skb = flow->q->ops->peek(flow->q))) {
                        if (!atm_may_send(flow->vcc, skb->truesize))
                                break;

                        skb = qdisc_dequeue_peeked(flow->q);
                        if (unlikely(!skb))
                                break;

                        qdisc_bstats_update(sch, skb);
                        bstats_update(&flow->bstats, skb);
                        pr_debug("atm_tc_dequeue: sending on class %p\n", flow);
                        /* remove any LL header somebody else has attached */
                        skb_pull(skb, skb_network_offset(skb));
                        if (skb_headroom(skb) < flow->hdr_len) {
                                struct sk_buff *new;

                                new = skb_realloc_headroom(skb, flow->hdr_len);
                                dev_kfree_skb(skb);
                                if (!new)
                                        continue;
                                skb = new;
                        }
                        pr_debug("sch_atm_dequeue: ip %p, data %p\n",
                                 skb_network_header(skb), skb->data);
                        ATM_SKB(skb)->vcc = flow->vcc;
                        memcpy(skb_push(skb, flow->hdr_len), flow->hdr,
                               flow->hdr_len);
                        refcount_add(skb->truesize,
                                   &sk_atm(flow->vcc)->sk_wmem_alloc);
                        /* atm.atm_options are already set by atm_tc_enqueue */
                        flow->vcc->send(flow->vcc, skb);
                }
        }
}

static struct sk_buff *atm_tc_dequeue(struct Qdisc *sch)
{
        struct atm_qdisc_data *p = qdisc_priv(sch);
        struct sk_buff *skb;

        pr_debug("atm_tc_dequeue(sch %p,[qdisc %p])\n", sch, p);
        tasklet_schedule(&p->task);
        skb = qdisc_dequeue_peeked(p->link.q);
        if (skb)
                sch->q.qlen--;
        return skb;
}

static struct sk_buff *atm_tc_peek(struct Qdisc *sch)
{
        struct atm_qdisc_data *p = qdisc_priv(sch);

        pr_debug("atm_tc_peek(sch %p,[qdisc %p])\n", sch, p);

        return p->link.q->ops->peek(p->link.q);
}

static int atm_tc_init(struct Qdisc *sch, struct nlattr *opt,
                       struct netlink_ext_ack *extack)
{
        struct atm_qdisc_data *p = qdisc_priv(sch);
        int err;

        pr_debug("atm_tc_init(sch %p,[qdisc %p],opt %p)\n", sch, p, opt);
        INIT_LIST_HEAD(&p->flows);
        INIT_LIST_HEAD(&p->link.list);
        list_add(&p->link.list, &p->flows);
        p->link.q = qdisc_create_dflt(sch->dev_queue,
                                      &pfifo_qdisc_ops, sch->handle, extack);
        if (!p->link.q)
                p->link.q = &noop_qdisc;
        pr_debug("atm_tc_init: link (%p) qdisc %p\n", &p->link, p->link.q);
        p->link.vcc = NULL;
        p->link.sock = NULL;
        p->link.common.classid = sch->handle;
        p->link.ref = 1;

        err = tcf_block_get(&p->link.block, &p->link.filter_list, sch,
                            extack);
        if (err)
                return err;

        tasklet_setup(&p->task, sch_atm_dequeue);
        return 0;
}

static void atm_tc_reset(struct Qdisc *sch)
{
        struct atm_qdisc_data *p = qdisc_priv(sch);
        struct atm_flow_data *flow;

        pr_debug("atm_tc_reset(sch %p,[qdisc %p])\n", sch, p);
        list_for_each_entry(flow, &p->flows, list)
                qdisc_reset(flow->q);
        sch->q.qlen = 0;
}

static void atm_tc_destroy(struct Qdisc *sch)
{
        struct atm_qdisc_data *p = qdisc_priv(sch);
        struct atm_flow_data *flow, *tmp;

        pr_debug("atm_tc_destroy(sch %p,[qdisc %p])\n", sch, p);
        list_for_each_entry(flow, &p->flows, list) {
                tcf_block_put(flow->block);
                flow->block = NULL;
        }

        list_for_each_entry_safe(flow, tmp, &p->flows, list) {
                if (flow->ref > 1)
                        pr_err("atm_destroy: %p->ref = %d\n", flow, flow->ref);
                atm_tc_put(sch, (unsigned long)flow);
        }
        tasklet_kill(&p->task);
}

static int atm_tc_dump_class(struct Qdisc *sch, unsigned long cl,
                             struct sk_buff *skb, struct tcmsg *tcm)
{
        struct atm_qdisc_data *p = qdisc_priv(sch);
        struct atm_flow_data *flow = (struct atm_flow_data *)cl;
        struct nlattr *nest;

        pr_debug("atm_tc_dump_class(sch %p,[qdisc %p],flow %p,skb %p,tcm %p)\n",
                sch, p, flow, skb, tcm);
        if (list_empty(&flow->list))
                return -EINVAL;
        tcm->tcm_handle = flow->common.classid;
        tcm->tcm_info = flow->q->handle;

        nest = nla_nest_start_noflag(skb, TCA_OPTIONS);
        if (nest == NULL)
                goto nla_put_failure;

        if (nla_put(skb, TCA_ATM_HDR, flow->hdr_len, flow->hdr))
                goto nla_put_failure;
        if (flow->vcc) {
                struct sockaddr_atmpvc pvc;
                int state;

                memset(&pvc, 0, sizeof(pvc));
                pvc.sap_family = AF_ATMPVC;
                pvc.sap_addr.itf = flow->vcc->dev ? flow->vcc->dev->number : -1;
                pvc.sap_addr.vpi = flow->vcc->vpi;
                pvc.sap_addr.vci = flow->vcc->vci;
                if (nla_put(skb, TCA_ATM_ADDR, sizeof(pvc), &pvc))
                        goto nla_put_failure;
                state = ATM_VF2VS(flow->vcc->flags);
                if (nla_put_u32(skb, TCA_ATM_STATE, state))
                        goto nla_put_failure;
        }
        if (flow->excess) {
                if (nla_put_u32(skb, TCA_ATM_EXCESS, flow->common.classid))
                        goto nla_put_failure;
        } else {
                if (nla_put_u32(skb, TCA_ATM_EXCESS, 0))
                        goto nla_put_failure;
        }
        return nla_nest_end(skb, nest);

nla_put_failure:
        nla_nest_cancel(skb, nest);
        return -1;
}
static int
atm_tc_dump_class_stats(struct Qdisc *sch, unsigned long arg,
                        struct gnet_dump *d)
{
        struct atm_flow_data *flow = (struct atm_flow_data *)arg;

        if (gnet_stats_copy_basic(qdisc_root_sleeping_running(sch),
                                  d, NULL, &flow->bstats) < 0 ||
            gnet_stats_copy_queue(d, NULL, &flow->qstats, flow->q->q.qlen) < 0)
                return -1;

        return 0;
}

static int atm_tc_dump(struct Qdisc *sch, struct sk_buff *skb)
{
        return 0;
}

static const struct Qdisc_class_ops atm_class_ops = {
        .graft          = atm_tc_graft,
        .leaf           = atm_tc_leaf,
        .find           = atm_tc_find,
        .change         = atm_tc_change,
        .delete         = atm_tc_delete,
        .walk           = atm_tc_walk,
        .tcf_block      = atm_tc_tcf_block,
        .bind_tcf       = atm_tc_bind_filter,
        .unbind_tcf     = atm_tc_put,
        .dump           = atm_tc_dump_class,
        .dump_stats     = atm_tc_dump_class_stats,
};

static struct Qdisc_ops atm_qdisc_ops __read_mostly = {
        .cl_ops         = &atm_class_ops,
        .id             = "atm",
        .priv_size      = sizeof(struct atm_qdisc_data),
        .enqueue        = atm_tc_enqueue,
        .dequeue        = atm_tc_dequeue,
        .peek           = atm_tc_peek,
        .init           = atm_tc_init,
        .reset          = atm_tc_reset,
        .destroy        = atm_tc_destroy,
        .dump           = atm_tc_dump,
        .owner          = THIS_MODULE,
};

static int __init atm_init(void)
{
        return register_qdisc(&atm_qdisc_ops);
}

static void __exit atm_exit(void)
{
        unregister_qdisc(&atm_qdisc_ops);
}

module_init(atm_init)
module_exit(atm_exit)
MODULE_LICENSE("GPL");