/*
 * af_can.c - Protocol family CAN core module
 *            (used by different CAN protocol modules)
 *
 * Copyright (c) 2002-2017 Volkswagen Group Electronic Research
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of Volkswagen nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * Alternatively, provided that this notice is retained in full, this
 * software may be distributed under the terms of the GNU General
 * Public License ("GPL") version 2, in which case the provisions of the
 * GPL apply INSTEAD OF those given above.
 *
 * The provided data structures and external interfaces from this code
 * are not restricted to be used by modules with a GPL compatible license.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
 * DAMAGE.
 *
 */

#include <linux/module.h>
#include <linux/stddef.h>
#include <linux/init.h>
#include <linux/kmod.h>
#include <linux/slab.h>
#include <linux/list.h>
#include <linux/spinlock.h>
#include <linux/rcupdate.h>
#include <linux/uaccess.h>
#include <linux/net.h>
#include <linux/netdevice.h>
#include <linux/socket.h>
#include <linux/if_ether.h>
#include <linux/if_arp.h>
#include <linux/skbuff.h>
#include <linux/can.h>
#include <linux/can/core.h>
#include <linux/can/skb.h>
#include <linux/ratelimit.h>
#include <net/net_namespace.h>
#include <net/sock.h>

#include "af_can.h"

MODULE_DESCRIPTION("Controller Area Network PF_CAN core");
MODULE_LICENSE("Dual BSD/GPL");
MODULE_AUTHOR("Urs Thuermann <urs.thuermann@volkswagen.de>, "
              "Oliver Hartkopp <oliver.hartkopp@volkswagen.de>");

MODULE_ALIAS_NETPROTO(PF_CAN);

static int stats_timer __read_mostly = 1;
module_param(stats_timer, int, 0444);
MODULE_PARM_DESC(stats_timer, "enable timer for statistics (default:on)");

static struct kmem_cache *rcv_cache __read_mostly;

/* table of registered CAN protocols */
static const struct can_proto __rcu *proto_tab[CAN_NPROTO] __read_mostly;
static DEFINE_MUTEX(proto_tab_lock);

static atomic_t skbcounter = ATOMIC_INIT(0);

/*
 * af_can socket functions
 */

int can_ioctl(struct socket *sock, unsigned int cmd, unsigned long arg)
{
        struct sock *sk = sock->sk;

        switch (cmd) {

        case SIOCGSTAMP:
                return sock_get_timestamp(sk, (struct timeval __user *)arg);

        default:
                return -ENOIOCTLCMD;
        }
}
EXPORT_SYMBOL(can_ioctl);

static void can_sock_destruct(struct sock *sk)
{
        skb_queue_purge(&sk->sk_receive_queue);
}

static const struct can_proto *can_get_proto(int protocol)
{
        const struct can_proto *cp;

        rcu_read_lock();
        cp = rcu_dereference(proto_tab[protocol]);
        if (cp && !try_module_get(cp->prot->owner))
                cp = NULL;
        rcu_read_unlock();

        return cp;
}

static inline void can_put_proto(const struct can_proto *cp)
{
        module_put(cp->prot->owner);
}

static int can_create(struct net *net, struct socket *sock, int protocol,
                      int kern)
{
        struct sock *sk;
        const struct can_proto *cp;
        int err = 0;

        sock->state = SS_UNCONNECTED;

        if (protocol < 0 || protocol >= CAN_NPROTO)
                return -EINVAL;

        cp = can_get_proto(protocol);

#ifdef CONFIG_MODULES
        if (!cp) {
                /* try to load protocol module if kernel is modular */

                err = request_module("can-proto-%d", protocol);

                /*
                 * In case of error we only print a message but don't
                 * return the error code immediately.  Below we will
                 * return -EPROTONOSUPPORT
                 */
                if (err)
                        printk_ratelimited(KERN_ERR "can: request_module "
                               "(can-proto-%d) failed.\n", protocol);

                cp = can_get_proto(protocol);
        }
#endif

        /* check for available protocol and correct usage */

        if (!cp)
                return -EPROTONOSUPPORT;

        if (cp->type != sock->type) {
                err = -EPROTOTYPE;
                goto errout;
        }

        sock->ops = cp->ops;

        sk = sk_alloc(net, PF_CAN, GFP_KERNEL, cp->prot, kern);
        if (!sk) {
                err = -ENOMEM;
                goto errout;
        }

        sock_init_data(sock, sk);
        sk->sk_destruct = can_sock_destruct;

        if (sk->sk_prot->init)
                err = sk->sk_prot->init(sk);

        if (err) {
                /* release sk on errors */
                sock_orphan(sk);
                sock_put(sk);
        }

 errout:
        can_put_proto(cp);
        return err;
}

/*
 * af_can tx path
 */

/**
 * can_send - transmit a CAN frame (optional with local loopback)
 * @skb: pointer to socket buffer with CAN frame in data section
 * @loop: loopback for listeners on local CAN sockets (recommended default!)
 *
 * Due to the loopback this routine must not be called from hardirq context.
 *
 * Return:
 *  0 on success
 *  -ENETDOWN when the selected interface is down
 *  -ENOBUFS on full driver queue (see net_xmit_errno())
 *  -ENOMEM when local loopback failed at calling skb_clone()
 *  -EPERM when trying to send on a non-CAN interface
 *  -EMSGSIZE CAN frame size is bigger than CAN interface MTU
 *  -EINVAL when the skb->data does not contain a valid CAN frame
 */
int can_send(struct sk_buff *skb, int loop)
{
        struct sk_buff *newskb = NULL;
        struct canfd_frame *cfd = (struct canfd_frame *)skb->data;
        struct s_stats *can_stats = dev_net(skb->dev)->can.can_stats;
        int err = -EINVAL;

        if (skb->len == CAN_MTU) {
                skb->protocol = htons(ETH_P_CAN);
                if (unlikely(cfd->len > CAN_MAX_DLEN))
                        goto inval_skb;
        } else if (skb->len == CANFD_MTU) {
                skb->protocol = htons(ETH_P_CANFD);
                if (unlikely(cfd->len > CANFD_MAX_DLEN))
                        goto inval_skb;
        } else
                goto inval_skb;

        /*
         * Make sure the CAN frame can pass the selected CAN netdevice.
         * As structs can_frame and canfd_frame are similar, we can provide
         * CAN FD frames to legacy CAN drivers as long as the length is <= 8
         */
        if (unlikely(skb->len > skb->dev->mtu && cfd->len > CAN_MAX_DLEN)) {
                err = -EMSGSIZE;
                goto inval_skb;
        }

        if (unlikely(skb->dev->type != ARPHRD_CAN)) {
                err = -EPERM;
                goto inval_skb;
        }

        if (unlikely(!(skb->dev->flags & IFF_UP))) {
                err = -ENETDOWN;
                goto inval_skb;
        }

        skb->ip_summed = CHECKSUM_UNNECESSARY;

        skb_reset_mac_header(skb);
        skb_reset_network_header(skb);
        skb_reset_transport_header(skb);

        if (loop) {
                /* local loopback of sent CAN frames */

                /* indication for the CAN driver: do loopback */
                skb->pkt_type = PACKET_LOOPBACK;

                /*
                 * The reference to the originating sock may be required
                 * by the receiving socket to check whether the frame is
                 * its own. Example: can_raw sockopt CAN_RAW_RECV_OWN_MSGS
                 * Therefore we have to ensure that skb->sk remains the
                 * reference to the originating sock by restoring skb->sk
                 * after each skb_clone() or skb_orphan() usage.
                 */

                if (!(skb->dev->flags & IFF_ECHO)) {
                        /*
                         * If the interface is not capable to do loopback
                         * itself, we do it here.
                         */
                        newskb = skb_clone(skb, GFP_ATOMIC);
                        if (!newskb) {
                                kfree_skb(skb);
                                return -ENOMEM;
                        }

                        can_skb_set_owner(newskb, skb->sk);
                        newskb->ip_summed = CHECKSUM_UNNECESSARY;
                        newskb->pkt_type = PACKET_BROADCAST;
                }
        } else {
                /* indication for the CAN driver: no loopback required */
                skb->pkt_type = PACKET_HOST;
        }

        /* send to netdevice */
        err = dev_queue_xmit(skb);
        if (err > 0)
                err = net_xmit_errno(err);

        if (err) {
                kfree_skb(newskb);
                return err;
        }

        if (newskb)
                netif_rx_ni(newskb);

        /* update statistics */
        can_stats->tx_frames++;
        can_stats->tx_frames_delta++;

        return 0;

inval_skb:
        kfree_skb(skb);
        return err;
}
EXPORT_SYMBOL(can_send);

/*
 * af_can rx path
 */

static struct can_dev_rcv_lists *find_dev_rcv_lists(struct net *net,
                                                struct net_device *dev)
{
        if (!dev)
                return net->can.can_rx_alldev_list;
        else
                return (struct can_dev_rcv_lists *)dev->ml_priv;
}

/**
 * effhash - hash function for 29 bit CAN identifier reduction
 * @can_id: 29 bit CAN identifier
 *
 * Description:
 *  To reduce the linear traversal in one linked list of _single_ EFF CAN
 *  frame subscriptions the 29 bit identifier is mapped to 10 bits.
 *  (see CAN_EFF_RCV_HASH_BITS definition)
 *
 * Return:
 *  Hash value from 0x000 - 0x3FF ( enforced by CAN_EFF_RCV_HASH_BITS mask )
 */
static unsigned int effhash(canid_t can_id)
{
        unsigned int hash;

        hash = can_id;
        hash ^= can_id >> CAN_EFF_RCV_HASH_BITS;
        hash ^= can_id >> (2 * CAN_EFF_RCV_HASH_BITS);

        return hash & ((1 << CAN_EFF_RCV_HASH_BITS) - 1);
}

/**
 * find_rcv_list - determine optimal filterlist inside device filter struct
 * @can_id: pointer to CAN identifier of a given can_filter
 * @mask: pointer to CAN mask of a given can_filter
 * @d: pointer to the device filter struct
 *
 * Description:
 *  Returns the optimal filterlist to reduce the filter handling in the
 *  receive path. This function is called by service functions that need
 *  to register or unregister a can_filter in the filter lists.
 *
 *  A filter matches in general, when
 *
 *          <received_can_id> & mask == can_id & mask
 *
 *  so every bit set in the mask (even CAN_EFF_FLAG, CAN_RTR_FLAG) describe
 *  relevant bits for the filter.
 *
 *  The filter can be inverted (CAN_INV_FILTER bit set in can_id) or it can
 *  filter for error messages (CAN_ERR_FLAG bit set in mask). For error msg
 *  frames there is a special filterlist and a special rx path filter handling.
 *
 * Return:
 *  Pointer to optimal filterlist for the given can_id/mask pair.
 *  Constistency checked mask.
 *  Reduced can_id to have a preprocessed filter compare value.
 */
static struct hlist_head *find_rcv_list(canid_t *can_id, canid_t *mask,
                                        struct can_dev_rcv_lists *d)
{
        canid_t inv = *can_id & CAN_INV_FILTER; /* save flag before masking */

        /* filter for error message frames in extra filterlist */
        if (*mask & CAN_ERR_FLAG) {
                /* clear CAN_ERR_FLAG in filter entry */
                *mask &= CAN_ERR_MASK;
                return &d->rx[RX_ERR];
        }

        /* with cleared CAN_ERR_FLAG we have a simple mask/value filterpair */

#define CAN_EFF_RTR_FLAGS (CAN_EFF_FLAG | CAN_RTR_FLAG)

        /* ensure valid values in can_mask for 'SFF only' frame filtering */
        if ((*mask & CAN_EFF_FLAG) && !(*can_id & CAN_EFF_FLAG))
                *mask &= (CAN_SFF_MASK | CAN_EFF_RTR_FLAGS);

        /* reduce condition testing at receive time */
        *can_id &= *mask;

        /* inverse can_id/can_mask filter */
        if (inv)
                return &d->rx[RX_INV];

        /* mask == 0 => no condition testing at receive time */
        if (!(*mask))
                return &d->rx[RX_ALL];

        /* extra filterlists for the subscription of a single non-RTR can_id */
        if (((*mask & CAN_EFF_RTR_FLAGS) == CAN_EFF_RTR_FLAGS) &&
            !(*can_id & CAN_RTR_FLAG)) {

                if (*can_id & CAN_EFF_FLAG) {
                        if (*mask == (CAN_EFF_MASK | CAN_EFF_RTR_FLAGS))
                                return &d->rx_eff[effhash(*can_id)];
                } else {
                        if (*mask == (CAN_SFF_MASK | CAN_EFF_RTR_FLAGS))
                                return &d->rx_sff[*can_id];
                }
        }

        /* default: filter via can_id/can_mask */
        return &d->rx[RX_FIL];
}

/**
 * can_rx_register - subscribe CAN frames from a specific interface
 * @dev: pointer to netdevice (NULL => subcribe from 'all' CAN devices list)
 * @can_id: CAN identifier (see description)
 * @mask: CAN mask (see description)
 * @func: callback function on filter match
 * @data: returned parameter for callback function
 * @ident: string for calling module identification
 * @sk: socket pointer (might be NULL)
 *
 * Description:
 *  Invokes the callback function with the received sk_buff and the given
 *  parameter 'data' on a matching receive filter. A filter matches, when
 *
 *          <received_can_id> & mask == can_id & mask
 *
 *  The filter can be inverted (CAN_INV_FILTER bit set in can_id) or it can
 *  filter for error message frames (CAN_ERR_FLAG bit set in mask).
 *
 *  The provided pointer to the sk_buff is guaranteed to be valid as long as
 *  the callback function is running. The callback function must *not* free
 *  the given sk_buff while processing it's task. When the given sk_buff is
 *  needed after the end of the callback function it must be cloned inside
 *  the callback function with skb_clone().
 *
 * Return:
 *  0 on success
 *  -ENOMEM on missing cache mem to create subscription entry
 *  -ENODEV unknown device
 */
int can_rx_register(struct net *net, struct net_device *dev, canid_t can_id,
                    canid_t mask, void (*func)(struct sk_buff *, void *),
                    void *data, char *ident, struct sock *sk)
{
        struct receiver *r;
        struct hlist_head *rl;
        struct can_dev_rcv_lists *d;
        struct s_pstats *can_pstats = net->can.can_pstats;
        int err = 0;

        /* insert new receiver  (dev,canid,mask) -> (func,data) */

        if (dev && dev->type != ARPHRD_CAN)
                return -ENODEV;

        if (dev && !net_eq(net, dev_net(dev)))
                return -ENODEV;

        r = kmem_cache_alloc(rcv_cache, GFP_KERNEL);
        if (!r)
                return -ENOMEM;

        spin_lock(&net->can.can_rcvlists_lock);

        d = find_dev_rcv_lists(net, dev);
        if (d) {
                rl = find_rcv_list(&can_id, &mask, d);

                r->can_id  = can_id;
                r->mask    = mask;
                r->matches = 0;
                r->func    = func;
                r->data    = data;
                r->ident   = ident;
                r->sk      = sk;

                hlist_add_head_rcu(&r->list, rl);
                d->entries++;

                can_pstats->rcv_entries++;
                if (can_pstats->rcv_entries_max < can_pstats->rcv_entries)
                        can_pstats->rcv_entries_max = can_pstats->rcv_entries;
        } else {
                kmem_cache_free(rcv_cache, r);
                err = -ENODEV;
        }

        spin_unlock(&net->can.can_rcvlists_lock);

        return err;
}
EXPORT_SYMBOL(can_rx_register);

/*
 * can_rx_delete_receiver - rcu callback for single receiver entry removal
 */
static void can_rx_delete_receiver(struct rcu_head *rp)
{
        struct receiver *r = container_of(rp, struct receiver, rcu);
        struct sock *sk = r->sk;

        kmem_cache_free(rcv_cache, r);
        if (sk)
                sock_put(sk);
}

/**
 * can_rx_unregister - unsubscribe CAN frames from a specific interface
 * @dev: pointer to netdevice (NULL => unsubscribe from 'all' CAN devices list)
 * @can_id: CAN identifier
 * @mask: CAN mask
 * @func: callback function on filter match
 * @data: returned parameter for callback function
 *
 * Description:
 *  Removes subscription entry depending on given (subscription) values.
 */
void can_rx_unregister(struct net *net, struct net_device *dev, canid_t can_id,
                       canid_t mask, void (*func)(struct sk_buff *, void *),
                       void *data)
{
        struct receiver *r = NULL;
        struct hlist_head *rl;
        struct s_pstats *can_pstats = net->can.can_pstats;
        struct can_dev_rcv_lists *d;

        if (dev && dev->type != ARPHRD_CAN)
                return;

        if (dev && !net_eq(net, dev_net(dev)))
                return;

        spin_lock(&net->can.can_rcvlists_lock);

        d = find_dev_rcv_lists(net, dev);
        if (!d) {
                pr_err("BUG: receive list not found for "
                       "dev %s, id %03X, mask %03X\n",
                       DNAME(dev), can_id, mask);
                goto out;
        }

        rl = find_rcv_list(&can_id, &mask, d);

        /*
         * Search the receiver list for the item to delete.  This should
         * exist, since no receiver may be unregistered that hasn't
         * been registered before.
         */

        hlist_for_each_entry_rcu(r, rl, list) {
                if (r->can_id == can_id && r->mask == mask &&
                    r->func == func && r->data == data)
                        break;
        }

        /*
         * Check for bugs in CAN protocol implementations using af_can.c:
         * 'r' will be NULL if no matching list item was found for removal.
         */

        if (!r) {
                WARN(1, "BUG: receive list entry not found for dev %s, "
                     "id %03X, mask %03X\n", DNAME(dev), can_id, mask);
                goto out;
        }

        hlist_del_rcu(&r->list);
        d->entries--;

        if (can_pstats->rcv_entries > 0)
                can_pstats->rcv_entries--;

        /* remove device structure requested by NETDEV_UNREGISTER */
        if (d->remove_on_zero_entries && !d->entries) {
                kfree(d);
                dev->ml_priv = NULL;
        }

 out:
        spin_unlock(&net->can.can_rcvlists_lock);

        /* schedule the receiver item for deletion */
        if (r) {
                if (r->sk)
                        sock_hold(r->sk);
                call_rcu(&r->rcu, can_rx_delete_receiver);
        }
}
EXPORT_SYMBOL(can_rx_unregister);

static inline void deliver(struct sk_buff *skb, struct receiver *r)
{
        r->func(skb, r->data);
        r->matches++;
}

static int can_rcv_filter(struct can_dev_rcv_lists *d, struct sk_buff *skb)
{
        struct receiver *r;
        int matches = 0;
        struct can_frame *cf = (struct can_frame *)skb->data;
        canid_t can_id = cf->can_id;

        if (d->entries == 0)
                return 0;

        if (can_id & CAN_ERR_FLAG) {
                /* check for error message frame entries only */
                hlist_for_each_entry_rcu(r, &d->rx[RX_ERR], list) {
                        if (can_id & r->mask) {
                                deliver(skb, r);
                                matches++;
                        }
                }
                return matches;
        }

        /* check for unfiltered entries */
        hlist_for_each_entry_rcu(r, &d->rx[RX_ALL], list) {
                deliver(skb, r);
                matches++;
        }

        /* check for can_id/mask entries */
        hlist_for_each_entry_rcu(r, &d->rx[RX_FIL], list) {
                if ((can_id & r->mask) == r->can_id) {
                        deliver(skb, r);
                        matches++;
                }
        }

        /* check for inverted can_id/mask entries */
        hlist_for_each_entry_rcu(r, &d->rx[RX_INV], list) {
                if ((can_id & r->mask) != r->can_id) {
                        deliver(skb, r);
                        matches++;
                }
        }

        /* check filterlists for single non-RTR can_ids */
        if (can_id & CAN_RTR_FLAG)
                return matches;

        if (can_id & CAN_EFF_FLAG) {
                hlist_for_each_entry_rcu(r, &d->rx_eff[effhash(can_id)], list) {
                        if (r->can_id == can_id) {
                                deliver(skb, r);
                                matches++;
                        }
                }
        } else {
                can_id &= CAN_SFF_MASK;
                hlist_for_each_entry_rcu(r, &d->rx_sff[can_id], list) {
                        deliver(skb, r);
                        matches++;
                }
        }

        return matches;
}

static void can_receive(struct sk_buff *skb, struct net_device *dev)
{
        struct can_dev_rcv_lists *d;
        struct net *net = dev_net(dev);
        struct s_stats *can_stats = net->can.can_stats;
        int matches;

        /* update statistics */
        can_stats->rx_frames++;
        can_stats->rx_frames_delta++;

        /* create non-zero unique skb identifier together with *skb */
        while (!(can_skb_prv(skb)->skbcnt))
                can_skb_prv(skb)->skbcnt = atomic_inc_return(&skbcounter);

        rcu_read_lock();

        /* deliver the packet to sockets listening on all devices */
        matches = can_rcv_filter(net->can.can_rx_alldev_list, skb);

        /* find receive list for this device */
        d = find_dev_rcv_lists(net, dev);
        if (d)
                matches += can_rcv_filter(d, skb);

        rcu_read_unlock();

        /* consume the skbuff allocated by the netdevice driver */
        consume_skb(skb);

        if (matches > 0) {
                can_stats->matches++;
                can_stats->matches_delta++;
        }
}

static int can_rcv(struct sk_buff *skb, struct net_device *dev,
                   struct packet_type *pt, struct net_device *orig_dev)
{
        struct canfd_frame *cfd = (struct canfd_frame *)skb->data;

        if (unlikely(dev->type != ARPHRD_CAN || skb->len != CAN_MTU ||
                     cfd->len > CAN_MAX_DLEN)) {
                pr_warn_once("PF_CAN: dropped non conform CAN skbuf: dev type %d, len %d, datalen %d\n",
                             dev->type, skb->len, cfd->len);
                kfree_skb(skb);
                return NET_RX_DROP;
        }

        can_receive(skb, dev);
        return NET_RX_SUCCESS;
}

static int canfd_rcv(struct sk_buff *skb, struct net_device *dev,
                   struct packet_type *pt, struct net_device *orig_dev)
{
        struct canfd_frame *cfd = (struct canfd_frame *)skb->data;

        if (unlikely(dev->type != ARPHRD_CAN || skb->len != CANFD_MTU ||
                     cfd->len > CANFD_MAX_DLEN)) {
                pr_warn_once("PF_CAN: dropped non conform CAN FD skbuf: dev type %d, len %d, datalen %d\n",
                             dev->type, skb->len, cfd->len);
                kfree_skb(skb);
                return NET_RX_DROP;
        }

        can_receive(skb, dev);
        return NET_RX_SUCCESS;
}

/*
 * af_can protocol functions
 */

/**
 * can_proto_register - register CAN transport protocol
 * @cp: pointer to CAN protocol structure
 *
 * Return:
 *  0 on success
 *  -EINVAL invalid (out of range) protocol number
 *  -EBUSY  protocol already in use
 *  -ENOBUF if proto_register() fails
 */
int can_proto_register(const struct can_proto *cp)
{
        int proto = cp->protocol;
        int err = 0;

        if (proto < 0 || proto >= CAN_NPROTO) {
                pr_err("can: protocol number %d out of range\n", proto);
                return -EINVAL;
        }

        err = proto_register(cp->prot, 0);
        if (err < 0)
                return err;

        mutex_lock(&proto_tab_lock);

        if (rcu_access_pointer(proto_tab[proto])) {
                pr_err("can: protocol %d already registered\n", proto);
                err = -EBUSY;
        } else
                RCU_INIT_POINTER(proto_tab[proto], cp);

        mutex_unlock(&proto_tab_lock);

        if (err < 0)
                proto_unregister(cp->prot);

        return err;
}
EXPORT_SYMBOL(can_proto_register);

/**
 * can_proto_unregister - unregister CAN transport protocol
 * @cp: pointer to CAN protocol structure
 */
void can_proto_unregister(const struct can_proto *cp)
{
        int proto = cp->protocol;

        mutex_lock(&proto_tab_lock);
        BUG_ON(rcu_access_pointer(proto_tab[proto]) != cp);
        RCU_INIT_POINTER(proto_tab[proto], NULL);
        mutex_unlock(&proto_tab_lock);

        synchronize_rcu();

        proto_unregister(cp->prot);
}
EXPORT_SYMBOL(can_proto_unregister);

/*
 * af_can notifier to create/remove CAN netdevice specific structs
 */
static int can_notifier(struct notifier_block *nb, unsigned long msg,
                        void *ptr)
{
        struct net_device *dev = netdev_notifier_info_to_dev(ptr);
        struct can_dev_rcv_lists *d;

        if (dev->type != ARPHRD_CAN)
                return NOTIFY_DONE;

        switch (msg) {

        case NETDEV_REGISTER:

                /* create new dev_rcv_lists for this device */
                d = kzalloc(sizeof(*d), GFP_KERNEL);
                if (!d)
                        return NOTIFY_DONE;
                BUG_ON(dev->ml_priv);
                dev->ml_priv = d;

                break;

        case NETDEV_UNREGISTER:
                spin_lock(&dev_net(dev)->can.can_rcvlists_lock);

                d = dev->ml_priv;
                if (d) {
                        if (d->entries)
                                d->remove_on_zero_entries = 1;
                        else {
                                kfree(d);
                                dev->ml_priv = NULL;
                        }
                } else
                        pr_err("can: notifier: receive list not found for dev "
                               "%s\n", dev->name);

                spin_unlock(&dev_net(dev)->can.can_rcvlists_lock);

                break;
        }

        return NOTIFY_DONE;
}

static int can_pernet_init(struct net *net)
{
        spin_lock_init(&net->can.can_rcvlists_lock);
        net->can.can_rx_alldev_list =
                kzalloc(sizeof(struct can_dev_rcv_lists), GFP_KERNEL);
        if (!net->can.can_rx_alldev_list)
                goto out;
        net->can.can_stats = kzalloc(sizeof(struct s_stats), GFP_KERNEL);
        if (!net->can.can_stats)
                goto out_free_alldev_list;
        net->can.can_pstats = kzalloc(sizeof(struct s_pstats), GFP_KERNEL);
        if (!net->can.can_pstats)
                goto out_free_can_stats;

        if (IS_ENABLED(CONFIG_PROC_FS)) {
                /* the statistics are updated every second (timer triggered) */
                if (stats_timer) {
                        timer_setup(&net->can.can_stattimer, can_stat_update,
                                    0);
                        mod_timer(&net->can.can_stattimer,
                                  round_jiffies(jiffies + HZ));
                }
                net->can.can_stats->jiffies_init = jiffies;
                can_init_proc(net);
        }

        return 0;

 out_free_can_stats:
        kfree(net->can.can_stats);
 out_free_alldev_list:
        kfree(net->can.can_rx_alldev_list);
 out:
        return -ENOMEM;
}

static void can_pernet_exit(struct net *net)
{
        struct net_device *dev;

        if (IS_ENABLED(CONFIG_PROC_FS)) {
                can_remove_proc(net);
                if (stats_timer)
                        del_timer_sync(&net->can.can_stattimer);
        }

        /* remove created dev_rcv_lists from still registered CAN devices */
        rcu_read_lock();
        for_each_netdev_rcu(net, dev) {
                if (dev->type == ARPHRD_CAN && dev->ml_priv) {
                        struct can_dev_rcv_lists *d = dev->ml_priv;

                        BUG_ON(d->entries);
                        kfree(d);
                        dev->ml_priv = NULL;
                }
        }
        rcu_read_unlock();

        kfree(net->can.can_rx_alldev_list);
        kfree(net->can.can_stats);
        kfree(net->can.can_pstats);
}

/*
 * af_can module init/exit functions
 */

static struct packet_type can_packet __read_mostly = {
        .type = cpu_to_be16(ETH_P_CAN),
        .func = can_rcv,
};

static struct packet_type canfd_packet __read_mostly = {
        .type = cpu_to_be16(ETH_P_CANFD),
        .func = canfd_rcv,
};

static const struct net_proto_family can_family_ops = {
        .family = PF_CAN,
        .create = can_create,
        .owner  = THIS_MODULE,
};

/* notifier block for netdevice event */
static struct notifier_block can_netdev_notifier __read_mostly = {
        .notifier_call = can_notifier,
};

static struct pernet_operations can_pernet_ops __read_mostly = {
        .init = can_pernet_init,
        .exit = can_pernet_exit,
};

static __init int can_init(void)
{
        /* check for correct padding to be able to use the structs similarly */
        BUILD_BUG_ON(offsetof(struct can_frame, can_dlc) !=
                     offsetof(struct canfd_frame, len) ||
                     offsetof(struct can_frame, data) !=
                     offsetof(struct canfd_frame, data));

        pr_info("can: controller area network core (" CAN_VERSION_STRING ")\n");

        rcv_cache = kmem_cache_create("can_receiver", sizeof(struct receiver),
                                      0, 0, NULL);
        if (!rcv_cache)
                return -ENOMEM;

        register_pernet_subsys(&can_pernet_ops);

        /* protocol register */
        sock_register(&can_family_ops);
        register_netdevice_notifier(&can_netdev_notifier);
        dev_add_pack(&can_packet);
        dev_add_pack(&canfd_packet);

        return 0;
}

static __exit void can_exit(void)
{
        /* protocol unregister */
        dev_remove_pack(&canfd_packet);
        dev_remove_pack(&can_packet);
        unregister_netdevice_notifier(&can_netdev_notifier);
        sock_unregister(PF_CAN);

        unregister_pernet_subsys(&can_pernet_ops);

        rcu_barrier(); /* Wait for completion of call_rcu()'s */

        kmem_cache_destroy(rcv_cache);
}

module_init(can_init);

module_exit(can_exit);