vcan.c

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/*
 * vcan.c - Virtual CAN interface
 *
 * 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.
 *
 */

#include <linux/module.h>
#include <linux/init.h>
#include <linux/netdevice.h>
#include <linux/if_arp.h>
#include <linux/if_ether.h>
#include <linux/can.h>
#include <linux/can/dev.h>
#include <linux/slab.h>
#include <net/rtnetlink.h>

static __initconst const char banner[] =
    KERN_INFO "vcan: Virtual CAN interface driver\n";

MODULE_DESCRIPTION("virtual CAN interface");
MODULE_LICENSE("Dual BSD/GPL");
MODULE_AUTHOR("Urs Thuermann <[email protected]>");


/*
 * CAN test feature:
 * Enable the echo on driver level for testing the CAN core echo modes.
 * See Documentation/networking/can.txt for details.
 */

static bool echo; /* echo testing. Default: 0 (Off) */
module_param(echo, bool, S_IRUGO);
MODULE_PARM_DESC(echo, "Echo sent frames (for testing). Default: 0 (Off)");


static void vcan_rx(struct sk_buff *skb, struct net_device *dev)
{
    struct canfd_frame *cfd = (struct canfd_frame *)skb->data;
    struct net_device_stats *stats = &dev->stats;

    stats->rx_packets++;
    stats->rx_bytes += cfd->len;

    skb->pkt_type  = PACKET_BROADCAST;
    skb->dev       = dev;
    skb->ip_summed = CHECKSUM_UNNECESSARY;

    netif_rx_ni(skb);
}

static netdev_tx_t vcan_tx(struct sk_buff *skb, struct net_device *dev)
{
    struct canfd_frame *cfd = (struct canfd_frame *)skb->data;
    struct net_device_stats *stats = &dev->stats;
    int loop;

    if (can_dropped_invalid_skb(dev, skb))
        return NETDEV_TX_OK;

    stats->tx_packets++;
    stats->tx_bytes += cfd->len;

    /* set flag whether this packet has to be looped back */
    loop = skb->pkt_type == PACKET_LOOPBACK;

    if (!echo) {
        /* no echo handling available inside this driver */

        if (loop) {
            /*
             * only count the packets here, because the
             * CAN core already did the echo for us
             */
            stats->rx_packets++;
            stats->rx_bytes += cfd->len;
        }
        kfree_skb(skb);
        return NETDEV_TX_OK;
    }

    /* perform standard echo handling for CAN network interfaces */

    if (loop) {
        struct sock *srcsk = skb->sk;

        skb = skb_share_check(skb, GFP_ATOMIC);
        if (!skb)
            return NETDEV_TX_OK;

        /* receive with packet counting */
        skb->sk = srcsk;
        vcan_rx(skb, dev);
    } else {
        /* no looped packets => no counting */
        kfree_skb(skb);
    }
    return NETDEV_TX_OK;
}

static int vcan_change_mtu(struct net_device *dev, int new_mtu)
{
    /* Do not allow changing the MTU while running */
    if (dev->flags & IFF_UP)
        return -EBUSY;

    if (new_mtu != CAN_MTU && new_mtu != CANFD_MTU)
        return -EINVAL;

    dev->mtu = new_mtu;
    return 0;
}

static const struct net_device_ops vcan_netdev_ops = {
    .ndo_start_xmit = vcan_tx,
    .ndo_change_mtu = vcan_change_mtu,
};

static void vcan_setup(struct net_device *dev)
{
    dev->type       = ARPHRD_CAN;
    dev->mtu        = CAN_MTU;
    dev->hard_header_len    = 0;
    dev->addr_len       = 0;
    dev->tx_queue_len   = 0;
    dev->flags      = IFF_NOARP;

    /* set flags according to driver capabilities */
    if (echo)
        dev->flags |= IFF_ECHO;

    dev->netdev_ops     = &vcan_netdev_ops;
    dev->destructor     = free_netdev;
}

static struct rtnl_link_ops vcan_link_ops __read_mostly = {
    .kind   = "vcan",
    .setup  = vcan_setup,
};

static __init int vcan_init_module(void)
{
    printk(banner);

    if (echo)
        printk(KERN_INFO "vcan: enabled echo on driver level.\n");

    return rtnl_link_register(&vcan_link_ops);
}

static __exit void vcan_cleanup_module(void)
{
    rtnl_link_unregister(&vcan_link_ops);
}

module_init(vcan_init_module);
module_exit(vcan_cleanup_module);