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

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/ethtool.h>
#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/can-ml.h>
#include <linux/can/dev.h>
#include <linux/can/skb.h>
#include <linux/slab.h>
#include <net/rtnetlink.h>

#define DRV_NAME "vcan"

MODULE_DESCRIPTION("virtual CAN interface");
MODULE_LICENSE("Dual BSD/GPL");
MODULE_AUTHOR("Urs Thuermann <urs.thuermann@volkswagen.de>");
MODULE_ALIAS_RTNL_LINK(DRV_NAME);

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

static bool echo; /* echo testing. Default: 0 (Off) */
module_param(echo, bool, 0444);
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 net_device_stats *stats = &dev->stats;

        stats->rx_packets++;
        stats->rx_bytes += can_skb_get_data_len(skb);

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

        netif_rx(skb);
}

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

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

        len = can_skb_get_data_len(skb);
        stats->tx_packets++;
        stats->tx_bytes += len;

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

        skb_tx_timestamp(skb);

        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 += len;
                }
                consume_skb(skb);
                return NETDEV_TX_OK;
        }

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

        if (loop) {
                skb = can_create_echo_skb(skb);
                if (!skb)
                        return NETDEV_TX_OK;

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

static void vcan_set_cap_info(struct net_device *dev)
{
        u32 can_cap = CAN_CAP_CC;

        if (dev->mtu > CAN_MTU)
                can_cap |= CAN_CAP_FD;

        if (dev->mtu >= CANXL_MIN_MTU)
                can_cap |= CAN_CAP_XL;

        can_set_cap(dev, can_cap);
}

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 &&
            !can_is_canxl_dev_mtu(new_mtu))
                return -EINVAL;

        WRITE_ONCE(dev->mtu, new_mtu);
        vcan_set_cap_info(dev);
        return 0;
}

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

static const struct ethtool_ops vcan_ethtool_ops = {
        .get_ts_info = ethtool_op_get_ts_info,
};

static void vcan_setup(struct net_device *dev)
{
        dev->type               = ARPHRD_CAN;
        dev->mtu                = CANXL_MTU;
        dev->hard_header_len    = 0;
        dev->addr_len           = 0;
        dev->tx_queue_len       = 0;
        dev->flags              = IFF_NOARP;
        can_set_ml_priv(dev, netdev_priv(dev));
        vcan_set_cap_info(dev);

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

        dev->netdev_ops         = &vcan_netdev_ops;
        dev->ethtool_ops        = &vcan_ethtool_ops;
        dev->needs_free_netdev  = true;
}

static struct rtnl_link_ops vcan_link_ops __read_mostly = {
        .kind = DRV_NAME,
        .priv_size = sizeof(struct can_ml_priv),
        .setup = vcan_setup,
};

static __init int vcan_init_module(void)
{
        pr_info("Virtual CAN interface driver\n");

        if (echo)
                pr_info("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);