/*
* af_can.c - Protocol family CAN core module
* (used by different CAN protocol modules)
*
* Copyright (c) 2002-2007 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.
*
* Send feedback to <socketcan-users@lists.berlios.de>
*
*/
#include <linux/module.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 <net/net_namespace.h>
#include <net/sock.h>
#include "af_can.h"
static __initdata const char banner[] = KERN_INFO
"can: controller area network core (" CAN_VERSION_STRING ")\n";
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, S_IRUGO);
MODULE_PARM_DESC(stats_timer, "enable timer for statistics (default:on)");
/* receive filters subscribed for 'all' CAN devices */
struct dev_rcv_lists can_rx_alldev_list;
static DEFINE_SPINLOCK(can_rcvlists_lock);
static struct kmem_cache *rcv_cache __read_mostly;
/* table of registered CAN protocols */
static const struct can_proto *proto_tab[CAN_NPROTO] __read_mostly;
static DEFINE_MUTEX(proto_tab_lock);
struct timer_list can_stattimer; /* timer for statistics update */
struct s_stats can_stats; /* packet statistics */
struct s_pstats can_pstats; /* receive list statistics */
/*
* 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;
if (!net_eq(net, &init_net))
return -EAFNOSUPPORT;
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_ratelimit())
printk(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);
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
* -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 can_frame *cf = (struct can_frame *)skb->data;
int err;
if (skb->len != sizeof(struct can_frame) || cf->can_dlc > 8) {
kfree_skb(skb);
return -EINVAL;
}
if (skb->dev->type != ARPHRD_CAN) {
kfree_skb(skb);
return -EPERM;
}
if (!(skb->dev->flags & IFF_UP)) {
kfree_skb(skb);
return -ENETDOWN;
}
skb->protocol = htons(ETH_P_CAN);
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;
}
newskb->sk = 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;
}
EXPORT_SYMBOL(can_send);
/*
* af_can rx path
*/
static struct dev_rcv_lists *find_dev_rcv_lists(struct net_device *dev)
{
if (!dev)
return &can_rx_alldev_list;
else
return (struct dev_rcv_lists *)dev->ml_priv;
}
/**
* 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 frames (CAN_ERR_FLAG bit set in mask). For error 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 dev_rcv_lists *d)
{
canid_t inv = *can_id & CAN_INV_FILTER; /* save flag before masking */
/* filter for error 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)) {
/* RFC: a future use-case for hash-tables? */
return &d->rx[RX_EFF];
}
} 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 indentification
*
* 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 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_device *dev, canid_t can_id, canid_t mask,
void (*func)(struct sk_buff *, void *), void *data,
char *ident)
{
struct receiver *r;
struct hlist_head *rl;
struct dev_rcv_lists *d;
int err = 0;
/* insert new receiver (dev,canid,mask) -> (func,data) */
if (dev && dev->type != ARPHRD_CAN)
return -ENODEV;
r = kmem_cache_alloc(rcv_cache, GFP_KERNEL);
if (!r)
return -ENOMEM;
spin_lock(&can_rcvlists_lock);
d = find_dev_rcv_lists(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;
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(&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);
kmem_cache_free(rcv_cache, r);
}
/**
* can_rx_unregister - unsubscribe CAN frames from a specific interface
* @dev: pointer to netdevice (NULL => unsubcribe 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_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 hlist_node *next;
struct dev_rcv_lists *d;
if (dev && dev->type != ARPHRD_CAN)
return;
spin_lock(&can_rcvlists_lock);
d = find_dev_rcv_lists(dev);
if (!d) {
printk(KERN_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, next, 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:
* If no matching list item was found, the list cursor variable next
* will be NULL, while r will point to the last item of the list.
*/
if (!next) {
printk(KERN_ERR "BUG: receive list entry not found for "
"dev %s, id %03X, mask %03X\n",
DNAME(dev), can_id, mask);
r = NULL;
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(&can_rcvlists_lock);
/* schedule the receiver item for deletion */
if (r)
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 dev_rcv_lists *d, struct sk_buff *skb)
{
struct receiver *r;
struct hlist_node *n;
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 frame entries only */
hlist_for_each_entry_rcu(r, n, &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, n, &d->rx[RX_ALL], list) {
deliver(skb, r);
matches++;
}
/* check for can_id/mask entries */
hlist_for_each_entry_rcu(r, n, &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, n, &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, n, &d->rx[RX_EFF], list) {
if (r->can_id == can_id) {
deliver(skb, r);
matches++;
}
}
} else {
can_id &= CAN_SFF_MASK;
hlist_for_each_entry_rcu(r, n, &d->rx_sff[can_id], list) {
deliver(skb, r);
matches++;
}
}
return matches;
}
static int can_rcv(struct sk_buff *skb, struct net_device *dev,
struct packet_type *pt, struct net_device *orig_dev)
{
struct dev_rcv_lists *d;
struct can_frame *cf = (struct can_frame *)skb->data;
int matches;
if (!net_eq(dev_net(dev), &init_net))
goto drop;
if (WARN_ONCE(dev->type != ARPHRD_CAN ||
skb->len != sizeof(struct can_frame) ||
cf->can_dlc > 8,
"PF_CAN: dropped non conform skbuf: "
"dev type %d, len %d, can_dlc %d\n",
dev->type, skb->len, cf->can_dlc))
goto drop;
/* update statistics */
can_stats.rx_frames++;
can_stats.rx_frames_delta++;
rcu_read_lock();
/* deliver the packet to sockets listening on all devices */
matches = can_rcv_filter(&can_rx_alldev_list, skb);
/* find receive list for this device */
d = find_dev_rcv_lists(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++;
}
return NET_RX_SUCCESS;
drop:
kfree_skb(skb);
return NET_RX_DROP;
}
/*
* 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) {
printk(KERN_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 (proto_tab[proto]) {
printk(KERN_ERR "can: protocol %d already registered\n",
proto);
err = -EBUSY;
} else
rcu_assign_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(proto_tab[proto] != cp);
rcu_assign_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 *data)
{
struct net_device *dev = (struct net_device *)data;
struct dev_rcv_lists *d;
if (!net_eq(dev_net(dev), &init_net))
return NOTIFY_DONE;
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) {
printk(KERN_ERR
"can: allocation of receive list failed\n");
return NOTIFY_DONE;
}
BUG_ON(dev->ml_priv);
dev->ml_priv = d;
break;
case NETDEV_UNREGISTER:
spin_lock(&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
printk(KERN_ERR "can: notifier: receive list not "
"found for dev %s\n", dev->name);
spin_unlock(&can_rcvlists_lock);
break;
}
return NOTIFY_DONE;
}
/*
* af_can module init/exit functions
*/
static struct packet_type can_packet __read_mostly = {
.type = cpu_to_be16(ETH_P_CAN),
.dev = NULL,
.func = can_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 __init int can_init(void)
{
printk(banner);
memset(&can_rx_alldev_list, 0, sizeof(can_rx_alldev_list));
rcv_cache = kmem_cache_create("can_receiver", sizeof(struct receiver),
0, 0, NULL);
if (!rcv_cache)
return -ENOMEM;
if (stats_timer) {
/* the statistics are updated every second (timer triggered) */
setup_timer(&can_stattimer, can_stat_update, 0);
mod_timer(&can_stattimer, round_jiffies(jiffies + HZ));
} else
can_stattimer.function = NULL;
can_init_proc();
/* protocol register */
sock_register(&can_family_ops);
register_netdevice_notifier(&can_netdev_notifier);
dev_add_pack(&can_packet);
return 0;
}
static __exit void can_exit(void)
{
struct net_device *dev;
if (stats_timer)
del_timer(&can_stattimer);
can_remove_proc();
/* protocol unregister */
dev_remove_pack(&can_packet);
unregister_netdevice_notifier(&can_netdev_notifier);
sock_unregister(PF_CAN);
/* remove created dev_rcv_lists from still registered CAN devices */
rcu_read_lock();
for_each_netdev_rcu(&init_net, dev) {
if (dev->type == ARPHRD_CAN && dev->ml_priv){
struct dev_rcv_lists *d = dev->ml_priv;
BUG_ON(d->entries);
kfree(d);
dev->ml_priv = NULL;
}
}
rcu_read_unlock();
rcu_barrier(); /* Wait for completion of call_rcu()'s */
kmem_cache_destroy(rcv_cache);
}
module_init(can_init);
module_exit(can_exit);
