/*
 * bcm.c - Broadcast Manager to filter/send (cyclic) CAN content
 *
 * 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/init.h>
#include <linux/interrupt.h>
#include <linux/hrtimer.h>
#include <linux/list.h>
#include <linux/proc_fs.h>
#include <linux/seq_file.h>
#include <linux/uio.h>
#include <linux/net.h>
#include <linux/netdevice.h>
#include <linux/socket.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/can/bcm.h>
#include <linux/slab.h>
#include <net/sock.h>
#include <net/net_namespace.h>

/*
 * To send multiple CAN frame content within TX_SETUP or to filter
 * CAN messages with multiplex index within RX_SETUP, the number of
 * different filters is limited to 256 due to the one byte index value.
 */
#define MAX_NFRAMES 256

/* use of last_frames[index].flags */
#define RX_RECV    0x40 /* received data for this element */
#define RX_THR     0x80 /* element not been sent due to throttle feature */
#define BCM_CAN_FLAGS_MASK 0x3F /* to clean private flags after usage */

/* get best masking value for can_rx_register() for a given single can_id */
#define REGMASK(id) ((id & CAN_EFF_FLAG) ? \
                     (CAN_EFF_MASK | CAN_EFF_FLAG | CAN_RTR_FLAG) : \
                     (CAN_SFF_MASK | CAN_EFF_FLAG | CAN_RTR_FLAG))

#define CAN_BCM_VERSION "20170425"

MODULE_DESCRIPTION("PF_CAN broadcast manager protocol");
MODULE_LICENSE("Dual BSD/GPL");
MODULE_AUTHOR("Oliver Hartkopp <oliver.hartkopp@volkswagen.de>");
MODULE_ALIAS("can-proto-2");

/*
 * easy access to the first 64 bit of can(fd)_frame payload. cp->data is
 * 64 bit aligned so the offset has to be multiples of 8 which is ensured
 * by the only callers in bcm_rx_cmp_to_index() bcm_rx_handler().
 */
static inline u64 get_u64(const struct canfd_frame *cp, int offset)
{
        return *(u64 *)(cp->data + offset);
}

struct bcm_op {
        struct list_head list;
        int ifindex;
        canid_t can_id;
        u32 flags;
        unsigned long frames_abs, frames_filtered;
        struct bcm_timeval ival1, ival2;
        struct hrtimer timer, thrtimer;
        struct tasklet_struct tsklet, thrtsklet;
        ktime_t rx_stamp, kt_ival1, kt_ival2, kt_lastmsg;
        int rx_ifindex;
        int cfsiz;
        u32 count;
        u32 nframes;
        u32 currframe;
        /* void pointers to arrays of struct can[fd]_frame */
        void *frames;
        void *last_frames;
        struct canfd_frame sframe;
        struct canfd_frame last_sframe;
        struct sock *sk;
        struct net_device *rx_reg_dev;
};

struct bcm_sock {
        struct sock sk;
        int bound;
        int ifindex;
        struct notifier_block notifier;
        struct list_head rx_ops;
        struct list_head tx_ops;
        unsigned long dropped_usr_msgs;
        struct proc_dir_entry *bcm_proc_read;
        char procname [32]; /* inode number in decimal with \0 */
};

static inline struct bcm_sock *bcm_sk(const struct sock *sk)
{
        return (struct bcm_sock *)sk;
}

static inline ktime_t bcm_timeval_to_ktime(struct bcm_timeval tv)
{
        return ktime_set(tv.tv_sec, tv.tv_usec * NSEC_PER_USEC);
}

#define CFSIZ(flags) ((flags & CAN_FD_FRAME) ? CANFD_MTU : CAN_MTU)
#define OPSIZ sizeof(struct bcm_op)
#define MHSIZ sizeof(struct bcm_msg_head)

/*
 * procfs functions
 */
#if IS_ENABLED(CONFIG_PROC_FS)
static char *bcm_proc_getifname(struct net *net, char *result, int ifindex)
{
        struct net_device *dev;

        if (!ifindex)
                return "any";

        rcu_read_lock();
        dev = dev_get_by_index_rcu(net, ifindex);
        if (dev)
                strcpy(result, dev->name);
        else
                strcpy(result, "???");
        rcu_read_unlock();

        return result;
}

static int bcm_proc_show(struct seq_file *m, void *v)
{
        char ifname[IFNAMSIZ];
        struct net *net = m->private;
        struct sock *sk = (struct sock *)PDE_DATA(m->file->f_inode);
        struct bcm_sock *bo = bcm_sk(sk);
        struct bcm_op *op;

        seq_printf(m, ">>> socket %pK", sk->sk_socket);
        seq_printf(m, " / sk %pK", sk);
        seq_printf(m, " / bo %pK", bo);
        seq_printf(m, " / dropped %lu", bo->dropped_usr_msgs);
        seq_printf(m, " / bound %s", bcm_proc_getifname(net, ifname, bo->ifindex));
        seq_printf(m, " <<<\n");

        list_for_each_entry(op, &bo->rx_ops, list) {

                unsigned long reduction;

                /* print only active entries & prevent division by zero */
                if (!op->frames_abs)
                        continue;

                seq_printf(m, "rx_op: %03X %-5s ", op->can_id,
                           bcm_proc_getifname(net, ifname, op->ifindex));

                if (op->flags & CAN_FD_FRAME)
                        seq_printf(m, "(%u)", op->nframes);
                else
                        seq_printf(m, "[%u]", op->nframes);

                seq_printf(m, "%c ", (op->flags & RX_CHECK_DLC) ? 'd' : ' ');

                if (op->kt_ival1)
                        seq_printf(m, "timeo=%lld ",
                                   (long long)ktime_to_us(op->kt_ival1));

                if (op->kt_ival2)
                        seq_printf(m, "thr=%lld ",
                                   (long long)ktime_to_us(op->kt_ival2));

                seq_printf(m, "# recv %ld (%ld) => reduction: ",
                           op->frames_filtered, op->frames_abs);

                reduction = 100 - (op->frames_filtered * 100) / op->frames_abs;

                seq_printf(m, "%s%ld%%\n",
                           (reduction == 100) ? "near " : "", reduction);
        }

        list_for_each_entry(op, &bo->tx_ops, list) {

                seq_printf(m, "tx_op: %03X %s ", op->can_id,
                           bcm_proc_getifname(net, ifname, op->ifindex));

                if (op->flags & CAN_FD_FRAME)
                        seq_printf(m, "(%u) ", op->nframes);
                else
                        seq_printf(m, "[%u] ", op->nframes);

                if (op->kt_ival1)
                        seq_printf(m, "t1=%lld ",
                                   (long long)ktime_to_us(op->kt_ival1));

                if (op->kt_ival2)
                        seq_printf(m, "t2=%lld ",
                                   (long long)ktime_to_us(op->kt_ival2));

                seq_printf(m, "# sent %ld\n", op->frames_abs);
        }
        seq_putc(m, '\n');
        return 0;
}
#endif /* CONFIG_PROC_FS */

/*
 * bcm_can_tx - send the (next) CAN frame to the appropriate CAN interface
 *              of the given bcm tx op
 */
static void bcm_can_tx(struct bcm_op *op)
{
        struct sk_buff *skb;
        struct net_device *dev;
        struct canfd_frame *cf = op->frames + op->cfsiz * op->currframe;

        /* no target device? => exit */
        if (!op->ifindex)
                return;

        dev = dev_get_by_index(sock_net(op->sk), op->ifindex);
        if (!dev) {
                /* RFC: should this bcm_op remove itself here? */
                return;
        }

        skb = alloc_skb(op->cfsiz + sizeof(struct can_skb_priv), gfp_any());
        if (!skb)
                goto out;

        can_skb_reserve(skb);
        can_skb_prv(skb)->ifindex = dev->ifindex;
        can_skb_prv(skb)->skbcnt = 0;

        skb_put_data(skb, cf, op->cfsiz);

        /* send with loopback */
        skb->dev = dev;
        can_skb_set_owner(skb, op->sk);
        can_send(skb, 1);

        /* update statistics */
        op->currframe++;
        op->frames_abs++;

        /* reached last frame? */
        if (op->currframe >= op->nframes)
                op->currframe = 0;
out:
        dev_put(dev);
}

/*
 * bcm_send_to_user - send a BCM message to the userspace
 *                    (consisting of bcm_msg_head + x CAN frames)
 */
static void bcm_send_to_user(struct bcm_op *op, struct bcm_msg_head *head,
                             struct canfd_frame *frames, int has_timestamp)
{
        struct sk_buff *skb;
        struct canfd_frame *firstframe;
        struct sockaddr_can *addr;
        struct sock *sk = op->sk;
        unsigned int datalen = head->nframes * op->cfsiz;
        int err;

        skb = alloc_skb(sizeof(*head) + datalen, gfp_any());
        if (!skb)
                return;

        skb_put_data(skb, head, sizeof(*head));

        if (head->nframes) {
                /* CAN frames starting here */
                firstframe = (struct canfd_frame *)skb_tail_pointer(skb);

                skb_put_data(skb, frames, datalen);

                /*
                 * the BCM uses the flags-element of the canfd_frame
                 * structure for internal purposes. This is only
                 * relevant for updates that are generated by the
                 * BCM, where nframes is 1
                 */
                if (head->nframes == 1)
                        firstframe->flags &= BCM_CAN_FLAGS_MASK;
        }

        if (has_timestamp) {
                /* restore rx timestamp */
                skb->tstamp = op->rx_stamp;
        }

        /*
         *  Put the datagram to the queue so that bcm_recvmsg() can
         *  get it from there.  We need to pass the interface index to
         *  bcm_recvmsg().  We pass a whole struct sockaddr_can in skb->cb
         *  containing the interface index.
         */

        sock_skb_cb_check_size(sizeof(struct sockaddr_can));
        addr = (struct sockaddr_can *)skb->cb;
        memset(addr, 0, sizeof(*addr));
        addr->can_family  = AF_CAN;
        addr->can_ifindex = op->rx_ifindex;

        err = sock_queue_rcv_skb(sk, skb);
        if (err < 0) {
                struct bcm_sock *bo = bcm_sk(sk);

                kfree_skb(skb);
                /* don't care about overflows in this statistic */
                bo->dropped_usr_msgs++;
        }
}

static void bcm_tx_start_timer(struct bcm_op *op)
{
        if (op->kt_ival1 && op->count)
                hrtimer_start(&op->timer,
                              ktime_add(ktime_get(), op->kt_ival1),
                              HRTIMER_MODE_ABS);
        else if (op->kt_ival2)
                hrtimer_start(&op->timer,
                              ktime_add(ktime_get(), op->kt_ival2),
                              HRTIMER_MODE_ABS);
}

static void bcm_tx_timeout_tsklet(unsigned long data)
{
        struct bcm_op *op = (struct bcm_op *)data;
        struct bcm_msg_head msg_head;

        if (op->kt_ival1 && (op->count > 0)) {

                op->count--;
                if (!op->count && (op->flags & TX_COUNTEVT)) {

                        /* create notification to user */
                        msg_head.opcode  = TX_EXPIRED;
                        msg_head.flags   = op->flags;
                        msg_head.count   = op->count;
                        msg_head.ival1   = op->ival1;
                        msg_head.ival2   = op->ival2;
                        msg_head.can_id  = op->can_id;
                        msg_head.nframes = 0;

                        bcm_send_to_user(op, &msg_head, NULL, 0);
                }
                bcm_can_tx(op);

        } else if (op->kt_ival2)
                bcm_can_tx(op);

        bcm_tx_start_timer(op);
}

/*
 * bcm_tx_timeout_handler - performs cyclic CAN frame transmissions
 */
static enum hrtimer_restart bcm_tx_timeout_handler(struct hrtimer *hrtimer)
{
        struct bcm_op *op = container_of(hrtimer, struct bcm_op, timer);

        tasklet_schedule(&op->tsklet);

        return HRTIMER_NORESTART;
}

/*
 * bcm_rx_changed - create a RX_CHANGED notification due to changed content
 */
static void bcm_rx_changed(struct bcm_op *op, struct canfd_frame *data)
{
        struct bcm_msg_head head;

        /* update statistics */
        op->frames_filtered++;

        /* prevent statistics overflow */
        if (op->frames_filtered > ULONG_MAX/100)
                op->frames_filtered = op->frames_abs = 0;

        /* this element is not throttled anymore */
        data->flags &= (BCM_CAN_FLAGS_MASK|RX_RECV);

        head.opcode  = RX_CHANGED;
        head.flags   = op->flags;
        head.count   = op->count;
        head.ival1   = op->ival1;
        head.ival2   = op->ival2;
        head.can_id  = op->can_id;
        head.nframes = 1;

        bcm_send_to_user(op, &head, data, 1);
}

/*
 * bcm_rx_update_and_send - process a detected relevant receive content change
 *                          1. update the last received data
 *                          2. send a notification to the user (if possible)
 */
static void bcm_rx_update_and_send(struct bcm_op *op,
                                   struct canfd_frame *lastdata,
                                   const struct canfd_frame *rxdata)
{
        memcpy(lastdata, rxdata, op->cfsiz);

        /* mark as used and throttled by default */
        lastdata->flags |= (RX_RECV|RX_THR);

        /* throttling mode inactive ? */
        if (!op->kt_ival2) {
                /* send RX_CHANGED to the user immediately */
                bcm_rx_changed(op, lastdata);
                return;
        }

        /* with active throttling timer we are just done here */
        if (hrtimer_active(&op->thrtimer))
                return;

        /* first reception with enabled throttling mode */
        if (!op->kt_lastmsg)
                goto rx_changed_settime;

        /* got a second frame inside a potential throttle period? */
        if (ktime_us_delta(ktime_get(), op->kt_lastmsg) <
            ktime_to_us(op->kt_ival2)) {
                /* do not send the saved data - only start throttle timer */
                hrtimer_start(&op->thrtimer,
                              ktime_add(op->kt_lastmsg, op->kt_ival2),
                              HRTIMER_MODE_ABS);
                return;
        }

        /* the gap was that big, that throttling was not needed here */
rx_changed_settime:
        bcm_rx_changed(op, lastdata);
        op->kt_lastmsg = ktime_get();
}

/*
 * bcm_rx_cmp_to_index - (bit)compares the currently received data to formerly
 *                       received data stored in op->last_frames[]
 */
static void bcm_rx_cmp_to_index(struct bcm_op *op, unsigned int index,
                                const struct canfd_frame *rxdata)
{
        struct canfd_frame *cf = op->frames + op->cfsiz * index;
        struct canfd_frame *lcf = op->last_frames + op->cfsiz * index;
        int i;

        /*
         * no one uses the MSBs of flags for comparison,
         * so we use it here to detect the first time of reception
         */

        if (!(lcf->flags & RX_RECV)) {
                /* received data for the first time => send update to user */
                bcm_rx_update_and_send(op, lcf, rxdata);
                return;
        }

        /* do a real check in CAN frame data section */
        for (i = 0; i < rxdata->len; i += 8) {
                if ((get_u64(cf, i) & get_u64(rxdata, i)) !=
                    (get_u64(cf, i) & get_u64(lcf, i))) {
                        bcm_rx_update_and_send(op, lcf, rxdata);
                        return;
                }
        }

        if (op->flags & RX_CHECK_DLC) {
                /* do a real check in CAN frame length */
                if (rxdata->len != lcf->len) {
                        bcm_rx_update_and_send(op, lcf, rxdata);
                        return;
                }
        }
}

/*
 * bcm_rx_starttimer - enable timeout monitoring for CAN frame reception
 */
static void bcm_rx_starttimer(struct bcm_op *op)
{
        if (op->flags & RX_NO_AUTOTIMER)
                return;

        if (op->kt_ival1)
                hrtimer_start(&op->timer, op->kt_ival1, HRTIMER_MODE_REL);
}

static void bcm_rx_timeout_tsklet(unsigned long data)
{
        struct bcm_op *op = (struct bcm_op *)data;
        struct bcm_msg_head msg_head;

        /* create notification to user */
        msg_head.opcode  = RX_TIMEOUT;
        msg_head.flags   = op->flags;
        msg_head.count   = op->count;
        msg_head.ival1   = op->ival1;
        msg_head.ival2   = op->ival2;
        msg_head.can_id  = op->can_id;
        msg_head.nframes = 0;

        bcm_send_to_user(op, &msg_head, NULL, 0);
}

/*
 * bcm_rx_timeout_handler - when the (cyclic) CAN frame reception timed out
 */
static enum hrtimer_restart bcm_rx_timeout_handler(struct hrtimer *hrtimer)
{
        struct bcm_op *op = container_of(hrtimer, struct bcm_op, timer);

        /* schedule before NET_RX_SOFTIRQ */
        tasklet_hi_schedule(&op->tsklet);

        /* no restart of the timer is done here! */

        /* if user wants to be informed, when cyclic CAN-Messages come back */
        if ((op->flags & RX_ANNOUNCE_RESUME) && op->last_frames) {
                /* clear received CAN frames to indicate 'nothing received' */
                memset(op->last_frames, 0, op->nframes * op->cfsiz);
        }

        return HRTIMER_NORESTART;
}

/*
 * bcm_rx_do_flush - helper for bcm_rx_thr_flush
 */
static inline int bcm_rx_do_flush(struct bcm_op *op, int update,
                                  unsigned int index)
{
        struct canfd_frame *lcf = op->last_frames + op->cfsiz * index;

        if ((op->last_frames) && (lcf->flags & RX_THR)) {
                if (update)
                        bcm_rx_changed(op, lcf);
                return 1;
        }
        return 0;
}

/*
 * bcm_rx_thr_flush - Check for throttled data and send it to the userspace
 *
 * update == 0 : just check if throttled data is available  (any irq context)
 * update == 1 : check and send throttled data to userspace (soft_irq context)
 */
static int bcm_rx_thr_flush(struct bcm_op *op, int update)
{
        int updated = 0;

        if (op->nframes > 1) {
                unsigned int i;

                /* for MUX filter we start at index 1 */
                for (i = 1; i < op->nframes; i++)
                        updated += bcm_rx_do_flush(op, update, i);

        } else {
                /* for RX_FILTER_ID and simple filter */
                updated += bcm_rx_do_flush(op, update, 0);
        }

        return updated;
}

static void bcm_rx_thr_tsklet(unsigned long data)
{
        struct bcm_op *op = (struct bcm_op *)data;

        /* push the changed data to the userspace */
        bcm_rx_thr_flush(op, 1);
}

/*
 * bcm_rx_thr_handler - the time for blocked content updates is over now:
 *                      Check for throttled data and send it to the userspace
 */
static enum hrtimer_restart bcm_rx_thr_handler(struct hrtimer *hrtimer)
{
        struct bcm_op *op = container_of(hrtimer, struct bcm_op, thrtimer);

        tasklet_schedule(&op->thrtsklet);

        if (bcm_rx_thr_flush(op, 0)) {
                hrtimer_forward(hrtimer, ktime_get(), op->kt_ival2);
                return HRTIMER_RESTART;
        } else {
                /* rearm throttle handling */
                op->kt_lastmsg = 0;
                return HRTIMER_NORESTART;
        }
}

/*
 * bcm_rx_handler - handle a CAN frame reception
 */
static void bcm_rx_handler(struct sk_buff *skb, void *data)
{
        struct bcm_op *op = (struct bcm_op *)data;
        const struct canfd_frame *rxframe = (struct canfd_frame *)skb->data;
        unsigned int i;

        if (op->can_id != rxframe->can_id)
                return;

        /* make sure to handle the correct frame type (CAN / CAN FD) */
        if (skb->len != op->cfsiz)
                return;

        /* disable timeout */
        hrtimer_cancel(&op->timer);

        /* save rx timestamp */
        op->rx_stamp = skb->tstamp;
        /* save originator for recvfrom() */
        op->rx_ifindex = skb->dev->ifindex;
        /* update statistics */
        op->frames_abs++;

        if (op->flags & RX_RTR_FRAME) {
                /* send reply for RTR-request (placed in op->frames[0]) */
                bcm_can_tx(op);
                return;
        }

        if (op->flags & RX_FILTER_ID) {
                /* the easiest case */
                bcm_rx_update_and_send(op, op->last_frames, rxframe);
                goto rx_starttimer;
        }

        if (op->nframes == 1) {
                /* simple compare with index 0 */
                bcm_rx_cmp_to_index(op, 0, rxframe);
                goto rx_starttimer;
        }

        if (op->nframes > 1) {
                /*
                 * multiplex compare
                 *
                 * find the first multiplex mask that fits.
                 * Remark: The MUX-mask is stored in index 0 - but only the
                 * first 64 bits of the frame data[] are relevant (CAN FD)
                 */

                for (i = 1; i < op->nframes; i++) {
                        if ((get_u64(op->frames, 0) & get_u64(rxframe, 0)) ==
                            (get_u64(op->frames, 0) &
                             get_u64(op->frames + op->cfsiz * i, 0))) {
                                bcm_rx_cmp_to_index(op, i, rxframe);
                                break;
                        }
                }
        }

rx_starttimer:
        bcm_rx_starttimer(op);
}

/*
 * helpers for bcm_op handling: find & delete bcm [rx|tx] op elements
 */
static struct bcm_op *bcm_find_op(struct list_head *ops,
                                  struct bcm_msg_head *mh, int ifindex)
{
        struct bcm_op *op;

        list_for_each_entry(op, ops, list) {
                if ((op->can_id == mh->can_id) && (op->ifindex == ifindex) &&
                    (op->flags & CAN_FD_FRAME) == (mh->flags & CAN_FD_FRAME))
                        return op;
        }

        return NULL;
}

static void bcm_remove_op(struct bcm_op *op)
{
        if (op->tsklet.func) {
                while (test_bit(TASKLET_STATE_SCHED, &op->tsklet.state) ||
                       test_bit(TASKLET_STATE_RUN, &op->tsklet.state) ||
                       hrtimer_active(&op->timer)) {
                        hrtimer_cancel(&op->timer);
                        tasklet_kill(&op->tsklet);
                }
        }

        if (op->thrtsklet.func) {
                while (test_bit(TASKLET_STATE_SCHED, &op->thrtsklet.state) ||
                       test_bit(TASKLET_STATE_RUN, &op->thrtsklet.state) ||
                       hrtimer_active(&op->thrtimer)) {
                        hrtimer_cancel(&op->thrtimer);
                        tasklet_kill(&op->thrtsklet);
                }
        }

        if ((op->frames) && (op->frames != &op->sframe))
                kfree(op->frames);

        if ((op->last_frames) && (op->last_frames != &op->last_sframe))
                kfree(op->last_frames);

        kfree(op);
}

static void bcm_rx_unreg(struct net_device *dev, struct bcm_op *op)
{
        if (op->rx_reg_dev == dev) {
                can_rx_unregister(dev_net(dev), dev, op->can_id,
                                  REGMASK(op->can_id), bcm_rx_handler, op);

                /* mark as removed subscription */
                op->rx_reg_dev = NULL;
        } else
                printk(KERN_ERR "can-bcm: bcm_rx_unreg: registered device "
                       "mismatch %p %p\n", op->rx_reg_dev, dev);
}

/*
 * bcm_delete_rx_op - find and remove a rx op (returns number of removed ops)
 */
static int bcm_delete_rx_op(struct list_head *ops, struct bcm_msg_head *mh,
                            int ifindex)
{
        struct bcm_op *op, *n;

        list_for_each_entry_safe(op, n, ops, list) {
                if ((op->can_id == mh->can_id) && (op->ifindex == ifindex) &&
                    (op->flags & CAN_FD_FRAME) == (mh->flags & CAN_FD_FRAME)) {

                        /*
                         * Don't care if we're bound or not (due to netdev
                         * problems) can_rx_unregister() is always a save
                         * thing to do here.
                         */
                        if (op->ifindex) {
                                /*
                                 * Only remove subscriptions that had not
                                 * been removed due to NETDEV_UNREGISTER
                                 * in bcm_notifier()
                                 */
                                if (op->rx_reg_dev) {
                                        struct net_device *dev;

                                        dev = dev_get_by_index(sock_net(op->sk),
                                                               op->ifindex);
                                        if (dev) {
                                                bcm_rx_unreg(dev, op);
                                                dev_put(dev);
                                        }
                                }
                        } else
                                can_rx_unregister(sock_net(op->sk), NULL,
                                                  op->can_id,
                                                  REGMASK(op->can_id),
                                                  bcm_rx_handler, op);

                        list_del(&op->list);
                        bcm_remove_op(op);
                        return 1; /* done */
                }
        }

        return 0; /* not found */
}

/*
 * bcm_delete_tx_op - find and remove a tx op (returns number of removed ops)
 */
static int bcm_delete_tx_op(struct list_head *ops, struct bcm_msg_head *mh,
                            int ifindex)
{
        struct bcm_op *op, *n;

        list_for_each_entry_safe(op, n, ops, list) {
                if ((op->can_id == mh->can_id) && (op->ifindex == ifindex) &&
                    (op->flags & CAN_FD_FRAME) == (mh->flags & CAN_FD_FRAME)) {
                        list_del(&op->list);
                        bcm_remove_op(op);
                        return 1; /* done */
                }
        }

        return 0; /* not found */
}

/*
 * bcm_read_op - read out a bcm_op and send it to the user (for bcm_sendmsg)
 */
static int bcm_read_op(struct list_head *ops, struct bcm_msg_head *msg_head,
                       int ifindex)
{
        struct bcm_op *op = bcm_find_op(ops, msg_head, ifindex);

        if (!op)
                return -EINVAL;

        /* put current values into msg_head */
        msg_head->flags   = op->flags;
        msg_head->count   = op->count;
        msg_head->ival1   = op->ival1;
        msg_head->ival2   = op->ival2;
        msg_head->nframes = op->nframes;

        bcm_send_to_user(op, msg_head, op->frames, 0);

        return MHSIZ;
}

/*
 * bcm_tx_setup - create or update a bcm tx op (for bcm_sendmsg)
 */
static int bcm_tx_setup(struct bcm_msg_head *msg_head, struct msghdr *msg,
                        int ifindex, struct sock *sk)
{
        struct bcm_sock *bo = bcm_sk(sk);
        struct bcm_op *op;
        struct canfd_frame *cf;
        unsigned int i;
        int err;

        /* we need a real device to send frames */
        if (!ifindex)
                return -ENODEV;

        /* check nframes boundaries - we need at least one CAN frame */
        if (msg_head->nframes < 1 || msg_head->nframes > MAX_NFRAMES)
                return -EINVAL;

        /* check the given can_id */
        op = bcm_find_op(&bo->tx_ops, msg_head, ifindex);
        if (op) {
                /* update existing BCM operation */

                /*
                 * Do we need more space for the CAN frames than currently
                 * allocated? -> This is a _really_ unusual use-case and
                 * therefore (complexity / locking) it is not supported.
                 */
                if (msg_head->nframes > op->nframes)
                        return -E2BIG;

                /* update CAN frames content */
                for (i = 0; i < msg_head->nframes; i++) {

                        cf = op->frames + op->cfsiz * i;
                        err = memcpy_from_msg((u8 *)cf, msg, op->cfsiz);

                        if (op->flags & CAN_FD_FRAME) {
                                if (cf->len > 64)
                                        err = -EINVAL;
                        } else {
                                if (cf->len > 8)
                                        err = -EINVAL;
                        }

                        if (err < 0)
                                return err;

                        if (msg_head->flags & TX_CP_CAN_ID) {
                                /* copy can_id into frame */
                                cf->can_id = msg_head->can_id;
                        }
                }
                op->flags = msg_head->flags;

        } else {
                /* insert new BCM operation for the given can_id */

                op = kzalloc(OPSIZ, GFP_KERNEL);
                if (!op)
                        return -ENOMEM;

                op->can_id = msg_head->can_id;
                op->cfsiz = CFSIZ(msg_head->flags);
                op->flags = msg_head->flags;

                /* create array for CAN frames and copy the data */
                if (msg_head->nframes > 1) {
                        op->frames = kmalloc_array(msg_head->nframes,
                                                   op->cfsiz,
                                                   GFP_KERNEL);
                        if (!op->frames) {
                                kfree(op);
                                return -ENOMEM;
                        }
                } else
                        op->frames = &op->sframe;

                for (i = 0; i < msg_head->nframes; i++) {

                        cf = op->frames + op->cfsiz * i;
                        err = memcpy_from_msg((u8 *)cf, msg, op->cfsiz);

                        if (op->flags & CAN_FD_FRAME) {
                                if (cf->len > 64)
                                        err = -EINVAL;
                        } else {
                                if (cf->len > 8)
                                        err = -EINVAL;
                        }

                        if (err < 0) {
                                if (op->frames != &op->sframe)
                                        kfree(op->frames);
                                kfree(op);
                                return err;
                        }

                        if (msg_head->flags & TX_CP_CAN_ID) {
                                /* copy can_id into frame */
                                cf->can_id = msg_head->can_id;
                        }
                }

                /* tx_ops never compare with previous received messages */
                op->last_frames = NULL;

                /* bcm_can_tx / bcm_tx_timeout_handler needs this */
                op->sk = sk;
                op->ifindex = ifindex;

                /* initialize uninitialized (kzalloc) structure */
                hrtimer_init(&op->timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
                op->timer.function = bcm_tx_timeout_handler;

                /* initialize tasklet for tx countevent notification */
                tasklet_init(&op->tsklet, bcm_tx_timeout_tsklet,
                             (unsigned long) op);

                /* currently unused in tx_ops */
                hrtimer_init(&op->thrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);

                /* add this bcm_op to the list of the tx_ops */
                list_add(&op->list, &bo->tx_ops);

        } /* if ((op = bcm_find_op(&bo->tx_ops, msg_head->can_id, ifindex))) */

        if (op->nframes != msg_head->nframes) {
                op->nframes   = msg_head->nframes;
                /* start multiple frame transmission with index 0 */
                op->currframe = 0;
        }

        /* check flags */

        if (op->flags & TX_RESET_MULTI_IDX) {
                /* start multiple frame transmission with index 0 */
                op->currframe = 0;
        }

        if (op->flags & SETTIMER) {
                /* set timer values */
                op->count = msg_head->count;

                op->ival1 = msg_head->ival1;
                op->ival2 = msg_head->ival2;
                op->kt_ival1 = bcm_timeval_to_ktime(msg_head->ival1);
                op->kt_ival2 = bcm_timeval_to_ktime(msg_head->ival2);

                /* disable an active timer due to zero values? */
                if (!op->kt_ival1 && !op->kt_ival2)
                        hrtimer_cancel(&op->timer);
        }

        if (op->flags & STARTTIMER) {
                hrtimer_cancel(&op->timer);
                /* spec: send CAN frame when starting timer */
                op->flags |= TX_ANNOUNCE;
        }

        if (op->flags & TX_ANNOUNCE) {
                bcm_can_tx(op);
                if (op->count)
                        op->count--;
        }

        if (op->flags & STARTTIMER)
                bcm_tx_start_timer(op);

        return msg_head->nframes * op->cfsiz + MHSIZ;
}

/*
 * bcm_rx_setup - create or update a bcm rx op (for bcm_sendmsg)
 */
static int bcm_rx_setup(struct bcm_msg_head *msg_head, struct msghdr *msg,
                        int ifindex, struct sock *sk)
{
        struct bcm_sock *bo = bcm_sk(sk);
        struct bcm_op *op;
        int do_rx_register;
        int err = 0;

        if ((msg_head->flags & RX_FILTER_ID) || (!(msg_head->nframes))) {
                /* be robust against wrong usage ... */
                msg_head->flags |= RX_FILTER_ID;
                /* ignore trailing garbage */
                msg_head->nframes = 0;
        }

        /* the first element contains the mux-mask => MAX_NFRAMES + 1  */
        if (msg_head->nframes > MAX_NFRAMES + 1)
                return -EINVAL;

        if ((msg_head->flags & RX_RTR_FRAME) &&
            ((msg_head->nframes != 1) ||
             (!(msg_head->can_id & CAN_RTR_FLAG))))
                return -EINVAL;

        /* check the given can_id */
        op = bcm_find_op(&bo->rx_ops, msg_head, ifindex);
        if (op) {
                /* update existing BCM operation */

                /*
                 * Do we need more space for the CAN frames than currently
                 * allocated? -> This is a _really_ unusual use-case and
                 * therefore (complexity / locking) it is not supported.
                 */
                if (msg_head->nframes > op->nframes)
                        return -E2BIG;

                if (msg_head->nframes) {
                        /* update CAN frames content */
                        err = memcpy_from_msg(op->frames, msg,
                                              msg_head->nframes * op->cfsiz);
                        if (err < 0)
                                return err;

                        /* clear last_frames to indicate 'nothing received' */
                        memset(op->last_frames, 0, msg_head->nframes * op->cfsiz);
                }

                op->nframes = msg_head->nframes;
                op->flags = msg_head->flags;

                /* Only an update -> do not call can_rx_register() */
                do_rx_register = 0;

        } else {
                /* insert new BCM operation for the given can_id */
                op = kzalloc(OPSIZ, GFP_KERNEL);
                if (!op)
                        return -ENOMEM;

                op->can_id = msg_head->can_id;
                op->nframes = msg_head->nframes;
                op->cfsiz = CFSIZ(msg_head->flags);
                op->flags = msg_head->flags;

                if (msg_head->nframes > 1) {
                        /* create array for CAN frames and copy the data */
                        op->frames = kmalloc_array(msg_head->nframes,
                                                   op->cfsiz,
                                                   GFP_KERNEL);
                        if (!op->frames) {
                                kfree(op);
                                return -ENOMEM;
                        }

                        /* create and init array for received CAN frames */
                        op->last_frames = kcalloc(msg_head->nframes,
                                                  op->cfsiz,
                                                  GFP_KERNEL);
                        if (!op->last_frames) {
                                kfree(op->frames);
                                kfree(op);
                                return -ENOMEM;
                        }

                } else {
                        op->frames = &op->sframe;
                        op->last_frames = &op->last_sframe;
                }

                if (msg_head->nframes) {
                        err = memcpy_from_msg(op->frames, msg,
                                              msg_head->nframes * op->cfsiz);
                        if (err < 0) {
                                if (op->frames != &op->sframe)
                                        kfree(op->frames);
                                if (op->last_frames != &op->last_sframe)
                                        kfree(op->last_frames);
                                kfree(op);
                                return err;
                        }
                }

                /* bcm_can_tx / bcm_tx_timeout_handler needs this */
                op->sk = sk;
                op->ifindex = ifindex;

                /* ifindex for timeout events w/o previous frame reception */
                op->rx_ifindex = ifindex;

                /* initialize uninitialized (kzalloc) structure */
                hrtimer_init(&op->timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
                op->timer.function = bcm_rx_timeout_handler;

                /* initialize tasklet for rx timeout notification */
                tasklet_init(&op->tsklet, bcm_rx_timeout_tsklet,
                             (unsigned long) op);

                hrtimer_init(&op->thrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
                op->thrtimer.function = bcm_rx_thr_handler;

                /* initialize tasklet for rx throttle handling */
                tasklet_init(&op->thrtsklet, bcm_rx_thr_tsklet,
                             (unsigned long) op);

                /* add this bcm_op to the list of the rx_ops */
                list_add(&op->list, &bo->rx_ops);

                /* call can_rx_register() */
                do_rx_register = 1;

        } /* if ((op = bcm_find_op(&bo->rx_ops, msg_head->can_id, ifindex))) */

        /* check flags */

        if (op->flags & RX_RTR_FRAME) {
                struct canfd_frame *frame0 = op->frames;

                /* no timers in RTR-mode */
                hrtimer_cancel(&op->thrtimer);
                hrtimer_cancel(&op->timer);

                /*
                 * funny feature in RX(!)_SETUP only for RTR-mode:
                 * copy can_id into frame BUT without RTR-flag to
                 * prevent a full-load-loopback-test ... ;-]
                 */
                if ((op->flags & TX_CP_CAN_ID) ||
                    (frame0->can_id == op->can_id))
                        frame0->can_id = op->can_id & ~CAN_RTR_FLAG;

        } else {
                if (op->flags & SETTIMER) {

                        /* set timer value */
                        op->ival1 = msg_head->ival1;
                        op->ival2 = msg_head->ival2;
                        op->kt_ival1 = bcm_timeval_to_ktime(msg_head->ival1);
                        op->kt_ival2 = bcm_timeval_to_ktime(msg_head->ival2);

                        /* disable an active timer due to zero value? */
                        if (!op->kt_ival1)
                                hrtimer_cancel(&op->timer);

                        /*
                         * In any case cancel the throttle timer, flush
                         * potentially blocked msgs and reset throttle handling
                         */
                        op->kt_lastmsg = 0;
                        hrtimer_cancel(&op->thrtimer);
                        bcm_rx_thr_flush(op, 1);
                }

                if ((op->flags & STARTTIMER) && op->kt_ival1)
                        hrtimer_start(&op->timer, op->kt_ival1,
                                      HRTIMER_MODE_REL);
        }

        /* now we can register for can_ids, if we added a new bcm_op */
        if (do_rx_register) {
                if (ifindex) {
                        struct net_device *dev;

                        dev = dev_get_by_index(sock_net(sk), ifindex);
                        if (dev) {
                                err = can_rx_register(sock_net(sk), dev,
                                                      op->can_id,
                                                      REGMASK(op->can_id),
                                                      bcm_rx_handler, op,
                                                      "bcm", sk);

                                op->rx_reg_dev = dev;
                                dev_put(dev);
                        }

                } else
                        err = can_rx_register(sock_net(sk), NULL, op->can_id,
                                              REGMASK(op->can_id),
                                              bcm_rx_handler, op, "bcm", sk);
                if (err) {
                        /* this bcm rx op is broken -> remove it */
                        list_del(&op->list);
                        bcm_remove_op(op);
                        return err;
                }
        }

        return msg_head->nframes * op->cfsiz + MHSIZ;
}

/*
 * bcm_tx_send - send a single CAN frame to the CAN interface (for bcm_sendmsg)
 */
static int bcm_tx_send(struct msghdr *msg, int ifindex, struct sock *sk,
                       int cfsiz)
{
        struct sk_buff *skb;
        struct net_device *dev;
        int err;

        /* we need a real device to send frames */
        if (!ifindex)
                return -ENODEV;

        skb = alloc_skb(cfsiz + sizeof(struct can_skb_priv), GFP_KERNEL);
        if (!skb)
                return -ENOMEM;

        can_skb_reserve(skb);

        err = memcpy_from_msg(skb_put(skb, cfsiz), msg, cfsiz);
        if (err < 0) {
                kfree_skb(skb);
                return err;
        }

        dev = dev_get_by_index(sock_net(sk), ifindex);
        if (!dev) {
                kfree_skb(skb);
                return -ENODEV;
        }

        can_skb_prv(skb)->ifindex = dev->ifindex;
        can_skb_prv(skb)->skbcnt = 0;
        skb->dev = dev;
        can_skb_set_owner(skb, sk);
        err = can_send(skb, 1); /* send with loopback */
        dev_put(dev);

        if (err)
                return err;

        return cfsiz + MHSIZ;
}

/*
 * bcm_sendmsg - process BCM commands (opcodes) from the userspace
 */
static int bcm_sendmsg(struct socket *sock, struct msghdr *msg, size_t size)
{
        struct sock *sk = sock->sk;
        struct bcm_sock *bo = bcm_sk(sk);
        int ifindex = bo->ifindex; /* default ifindex for this bcm_op */
        struct bcm_msg_head msg_head;
        int cfsiz;
        int ret; /* read bytes or error codes as return value */

        if (!bo->bound)
                return -ENOTCONN;

        /* check for valid message length from userspace */
        if (size < MHSIZ)
                return -EINVAL;

        /* read message head information */
        ret = memcpy_from_msg((u8 *)&msg_head, msg, MHSIZ);
        if (ret < 0)
                return ret;

        cfsiz = CFSIZ(msg_head.flags);
        if ((size - MHSIZ) % cfsiz)
                return -EINVAL;

        /* check for alternative ifindex for this bcm_op */

        if (!ifindex && msg->msg_name) {
                /* no bound device as default => check msg_name */
                DECLARE_SOCKADDR(struct sockaddr_can *, addr, msg->msg_name);

                if (msg->msg_namelen < sizeof(*addr))
                        return -EINVAL;

                if (addr->can_family != AF_CAN)
                        return -EINVAL;

                /* ifindex from sendto() */
                ifindex = addr->can_ifindex;

                if (ifindex) {
                        struct net_device *dev;

                        dev = dev_get_by_index(sock_net(sk), ifindex);
                        if (!dev)
                                return -ENODEV;

                        if (dev->type != ARPHRD_CAN) {
                                dev_put(dev);
                                return -ENODEV;
                        }

                        dev_put(dev);
                }
        }

        lock_sock(sk);

        switch (msg_head.opcode) {

        case TX_SETUP:
                ret = bcm_tx_setup(&msg_head, msg, ifindex, sk);
                break;

        case RX_SETUP:
                ret = bcm_rx_setup(&msg_head, msg, ifindex, sk);
                break;

        case TX_DELETE:
                if (bcm_delete_tx_op(&bo->tx_ops, &msg_head, ifindex))
                        ret = MHSIZ;
                else
                        ret = -EINVAL;
                break;

        case RX_DELETE:
                if (bcm_delete_rx_op(&bo->rx_ops, &msg_head, ifindex))
                        ret = MHSIZ;
                else
                        ret = -EINVAL;
                break;

        case TX_READ:
                /* reuse msg_head for the reply to TX_READ */
                msg_head.opcode  = TX_STATUS;
                ret = bcm_read_op(&bo->tx_ops, &msg_head, ifindex);
                break;

        case RX_READ:
                /* reuse msg_head for the reply to RX_READ */
                msg_head.opcode  = RX_STATUS;
                ret = bcm_read_op(&bo->rx_ops, &msg_head, ifindex);
                break;

        case TX_SEND:
                /* we need exactly one CAN frame behind the msg head */
                if ((msg_head.nframes != 1) || (size != cfsiz + MHSIZ))
                        ret = -EINVAL;
                else
                        ret = bcm_tx_send(msg, ifindex, sk, cfsiz);
                break;

        default:
                ret = -EINVAL;
                break;
        }

        release_sock(sk);

        return ret;
}

/*
 * notification handler for netdevice status changes
 */
static int bcm_notifier(struct notifier_block *nb, unsigned long msg,
                        void *ptr)
{
        struct net_device *dev = netdev_notifier_info_to_dev(ptr);
        struct bcm_sock *bo = container_of(nb, struct bcm_sock, notifier);
        struct sock *sk = &bo->sk;
        struct bcm_op *op;
        int notify_enodev = 0;

        if (!net_eq(dev_net(dev), sock_net(sk)))
                return NOTIFY_DONE;

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

        switch (msg) {

        case NETDEV_UNREGISTER:
                lock_sock(sk);

                /* remove device specific receive entries */
                list_for_each_entry(op, &bo->rx_ops, list)
                        if (op->rx_reg_dev == dev)
                                bcm_rx_unreg(dev, op);

                /* remove device reference, if this is our bound device */
                if (bo->bound && bo->ifindex == dev->ifindex) {
                        bo->bound   = 0;
                        bo->ifindex = 0;
                        notify_enodev = 1;
                }

                release_sock(sk);

                if (notify_enodev) {
                        sk->sk_err = ENODEV;
                        if (!sock_flag(sk, SOCK_DEAD))
                                sk->sk_error_report(sk);
                }
                break;

        case NETDEV_DOWN:
                if (bo->bound && bo->ifindex == dev->ifindex) {
                        sk->sk_err = ENETDOWN;
                        if (!sock_flag(sk, SOCK_DEAD))
                                sk->sk_error_report(sk);
                }
        }

        return NOTIFY_DONE;
}

/*
 * initial settings for all BCM sockets to be set at socket creation time
 */
static int bcm_init(struct sock *sk)
{
        struct bcm_sock *bo = bcm_sk(sk);

        bo->bound            = 0;
        bo->ifindex          = 0;
        bo->dropped_usr_msgs = 0;
        bo->bcm_proc_read    = NULL;

        INIT_LIST_HEAD(&bo->tx_ops);
        INIT_LIST_HEAD(&bo->rx_ops);

        /* set notifier */
        bo->notifier.notifier_call = bcm_notifier;

        register_netdevice_notifier(&bo->notifier);

        return 0;
}

/*
 * standard socket functions
 */
static int bcm_release(struct socket *sock)
{
        struct sock *sk = sock->sk;
        struct net *net;
        struct bcm_sock *bo;
        struct bcm_op *op, *next;

        if (!sk)
                return 0;

        net = sock_net(sk);
        bo = bcm_sk(sk);

        /* remove bcm_ops, timer, rx_unregister(), etc. */

        unregister_netdevice_notifier(&bo->notifier);

        lock_sock(sk);

        list_for_each_entry_safe(op, next, &bo->tx_ops, list)
                bcm_remove_op(op);

        list_for_each_entry_safe(op, next, &bo->rx_ops, list) {
                /*
                 * Don't care if we're bound or not (due to netdev problems)
                 * can_rx_unregister() is always a save thing to do here.
                 */
                if (op->ifindex) {
                        /*
                         * Only remove subscriptions that had not
                         * been removed due to NETDEV_UNREGISTER
                         * in bcm_notifier()
                         */
                        if (op->rx_reg_dev) {
                                struct net_device *dev;

                                dev = dev_get_by_index(net, op->ifindex);
                                if (dev) {
                                        bcm_rx_unreg(dev, op);
                                        dev_put(dev);
                                }
                        }
                } else
                        can_rx_unregister(net, NULL, op->can_id,
                                          REGMASK(op->can_id),
                                          bcm_rx_handler, op);

                bcm_remove_op(op);
        }

#if IS_ENABLED(CONFIG_PROC_FS)
        /* remove procfs entry */
        if (net->can.bcmproc_dir && bo->bcm_proc_read)
                remove_proc_entry(bo->procname, net->can.bcmproc_dir);
#endif /* CONFIG_PROC_FS */

        /* remove device reference */
        if (bo->bound) {
                bo->bound   = 0;
                bo->ifindex = 0;
        }

        sock_orphan(sk);
        sock->sk = NULL;

        release_sock(sk);
        sock_put(sk);

        return 0;
}

static int bcm_connect(struct socket *sock, struct sockaddr *uaddr, int len,
                       int flags)
{
        struct sockaddr_can *addr = (struct sockaddr_can *)uaddr;
        struct sock *sk = sock->sk;
        struct bcm_sock *bo = bcm_sk(sk);
        struct net *net = sock_net(sk);
        int ret = 0;

        if (len < sizeof(*addr))
                return -EINVAL;

        lock_sock(sk);

        if (bo->bound) {
                ret = -EISCONN;
                goto fail;
        }

        /* bind a device to this socket */
        if (addr->can_ifindex) {
                struct net_device *dev;

                dev = dev_get_by_index(net, addr->can_ifindex);
                if (!dev) {
                        ret = -ENODEV;
                        goto fail;
                }
                if (dev->type != ARPHRD_CAN) {
                        dev_put(dev);
                        ret = -ENODEV;
                        goto fail;
                }

                bo->ifindex = dev->ifindex;
                dev_put(dev);

        } else {
                /* no interface reference for ifindex = 0 ('any' CAN device) */
                bo->ifindex = 0;
        }

#if IS_ENABLED(CONFIG_PROC_FS)
        if (net->can.bcmproc_dir) {
                /* unique socket address as filename */
                sprintf(bo->procname, "%lu", sock_i_ino(sk));
                bo->bcm_proc_read = proc_create_net_single(bo->procname, 0644,
                                                     net->can.bcmproc_dir,
                                                     bcm_proc_show, sk);
                if (!bo->bcm_proc_read) {
                        ret = -ENOMEM;
                        goto fail;
                }
        }
#endif /* CONFIG_PROC_FS */

        bo->bound = 1;

fail:
        release_sock(sk);

        return ret;
}

static int bcm_recvmsg(struct socket *sock, struct msghdr *msg, size_t size,
                       int flags)
{
        struct sock *sk = sock->sk;
        struct sk_buff *skb;
        int error = 0;
        int noblock;
        int err;

        noblock =  flags & MSG_DONTWAIT;
        flags   &= ~MSG_DONTWAIT;
        skb = skb_recv_datagram(sk, flags, noblock, &error);
        if (!skb)
                return error;

        if (skb->len < size)
                size = skb->len;

        err = memcpy_to_msg(msg, skb->data, size);
        if (err < 0) {
                skb_free_datagram(sk, skb);
                return err;
        }

        sock_recv_ts_and_drops(msg, sk, skb);

        if (msg->msg_name) {
                __sockaddr_check_size(sizeof(struct sockaddr_can));
                msg->msg_namelen = sizeof(struct sockaddr_can);
                memcpy(msg->msg_name, skb->cb, msg->msg_namelen);
        }

        skb_free_datagram(sk, skb);

        return size;
}

static const struct proto_ops bcm_ops = {
        .family        = PF_CAN,
        .release       = bcm_release,
        .bind          = sock_no_bind,
        .connect       = bcm_connect,
        .socketpair    = sock_no_socketpair,
        .accept        = sock_no_accept,
        .getname       = sock_no_getname,
        .poll          = datagram_poll,
        .ioctl         = can_ioctl,     /* use can_ioctl() from af_can.c */
        .listen        = sock_no_listen,
        .shutdown      = sock_no_shutdown,
        .setsockopt    = sock_no_setsockopt,
        .getsockopt    = sock_no_getsockopt,
        .sendmsg       = bcm_sendmsg,
        .recvmsg       = bcm_recvmsg,
        .mmap          = sock_no_mmap,
        .sendpage      = sock_no_sendpage,
};

static struct proto bcm_proto __read_mostly = {
        .name       = "CAN_BCM",
        .owner      = THIS_MODULE,
        .obj_size   = sizeof(struct bcm_sock),
        .init       = bcm_init,
};

static const struct can_proto bcm_can_proto = {
        .type       = SOCK_DGRAM,
        .protocol   = CAN_BCM,
        .ops        = &bcm_ops,
        .prot       = &bcm_proto,
};

static int canbcm_pernet_init(struct net *net)
{
#if IS_ENABLED(CONFIG_PROC_FS)
        /* create /proc/net/can-bcm directory */
        net->can.bcmproc_dir = proc_net_mkdir(net, "can-bcm", net->proc_net);
#endif /* CONFIG_PROC_FS */

        return 0;
}

static void canbcm_pernet_exit(struct net *net)
{
#if IS_ENABLED(CONFIG_PROC_FS)
        /* remove /proc/net/can-bcm directory */
        if (net->can.bcmproc_dir)
                remove_proc_entry("can-bcm", net->proc_net);
#endif /* CONFIG_PROC_FS */
}

static struct pernet_operations canbcm_pernet_ops __read_mostly = {
        .init = canbcm_pernet_init,
        .exit = canbcm_pernet_exit,
};

static int __init bcm_module_init(void)
{
        int err;

        pr_info("can: broadcast manager protocol (rev " CAN_BCM_VERSION " t)\n");

        err = can_proto_register(&bcm_can_proto);
        if (err < 0) {
                printk(KERN_ERR "can: registration of bcm protocol failed\n");
                return err;
        }

        register_pernet_subsys(&canbcm_pernet_ops);
        return 0;
}

static void __exit bcm_module_exit(void)
{
        can_proto_unregister(&bcm_can_proto);
        unregister_pernet_subsys(&canbcm_pernet_ops);
}

module_init(bcm_module_init);
module_exit(bcm_module_exit);