LXR linux/drivers/net/can/vcan.c

   1/*
   2 * vcan.c - Virtual CAN interface
   3 *
   4 * Copyright (c) 2002-2007 Volkswagen Group Electronic Research
   5 * All rights reserved.
   6 *
   7 * Redistribution and use in source and binary forms, with or without
   8 * modification, are permitted provided that the following conditions
   9 * are met:
  10 * 1. Redistributions of source code must retain the above copyright
  11 *    notice, this list of conditions and the following disclaimer.
  12 * 2. Redistributions in binary form must reproduce the above copyright
  13 *    notice, this list of conditions and the following disclaimer in the
  14 *    documentation and/or other materials provided with the distribution.
  15 * 3. Neither the name of Volkswagen nor the names of its contributors
  16 *    may be used to endorse or promote products derived from this software
  17 *    without specific prior written permission.
  18 *
  19 * Alternatively, provided that this notice is retained in full, this
  20 * software may be distributed under the terms of the GNU General
  21 * Public License ("GPL") version 2, in which case the provisions of the
  22 * GPL apply INSTEAD OF those given above.
  23 *
  24 * The provided data structures and external interfaces from this code
  25 * are not restricted to be used by modules with a GPL compatible license.
  26 *
  27 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  28 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  29 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  30 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  31 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  32 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  33 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  34 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  35 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  36 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  37 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
  38 * DAMAGE.
  39 *
  40 * Send feedback to <socketcan-users@lists.berlios.de>
  41 *
  42 */
  43
  44#include <linux/module.h>
  45#include <linux/init.h>
  46#include <linux/netdevice.h>
  47#include <linux/if_arp.h>
  48#include <linux/if_ether.h>
  49#include <linux/can.h>
  50#include <net/rtnetlink.h>
  51
  52static __initdata const char banner[] =
  53        KERN_INFO "vcan: Virtual CAN interface driver\n";
  54
  55MODULE_DESCRIPTION("virtual CAN interface");
  56MODULE_LICENSE("Dual BSD/GPL");
  57MODULE_AUTHOR("Urs Thuermann <urs.thuermann@volkswagen.de>");
  58
  59
  60/*
  61 * CAN test feature:
  62 * Enable the echo on driver level for testing the CAN core echo modes.
  63 * See Documentation/networking/can.txt for details.
  64 */
  65
  66static int echo; /* echo testing. Default: 0 (Off) */
  67module_param(echo, bool, S_IRUGO);
  68MODULE_PARM_DESC(echo, "Echo sent frames (for testing). Default: 0 (Off)");
  69
  70
  71static void vcan_rx(struct sk_buff *skb, struct net_device *dev)
  72{
  73        struct net_device_stats *stats = &dev->stats;
  74
  75        stats->rx_packets++;
  76        stats->rx_bytes += skb->len;
  77
  78        skb->protocol  = htons(ETH_P_CAN);
  79        skb->pkt_type  = PACKET_BROADCAST;
  80        skb->dev       = dev;
  81        skb->ip_summed = CHECKSUM_UNNECESSARY;
  82
  83        netif_rx_ni(skb);
  84}
  85
  86static netdev_tx_t vcan_tx(struct sk_buff *skb, struct net_device *dev)
  87{
  88        struct net_device_stats *stats = &dev->stats;
  89        int loop;
  90
  91        stats->tx_packets++;
  92        stats->tx_bytes += skb->len;
  93
  94        /* set flag whether this packet has to be looped back */
  95        loop = skb->pkt_type == PACKET_LOOPBACK;
  96
  97        if (!echo) {
  98                /* no echo handling available inside this driver */
  99
 100                if (loop) {
 101                        /*
 102                         * only count the packets here, because the
 103                         * CAN core already did the echo for us
 104                         */
 105                        stats->rx_packets++;
 106                        stats->rx_bytes += skb->len;
 107                }
 108                kfree_skb(skb);
 109                return NETDEV_TX_OK;
 110        }
 111
 112        /* perform standard echo handling for CAN network interfaces */
 113
 114        if (loop) {
 115                struct sock *srcsk = skb->sk;
 116
 117                skb = skb_share_check(skb, GFP_ATOMIC);
 118                if (!skb)
 119                        return NETDEV_TX_OK;
 120
 121                /* receive with packet counting */
 122                skb->sk = srcsk;
 123                vcan_rx(skb, dev);
 124        } else {
 125                /* no looped packets => no counting */
 126                kfree_skb(skb);
 127        }
 128        return NETDEV_TX_OK;
 129}
 130
 131static const struct net_device_ops vcan_netdev_ops = {
 132        .ndo_start_xmit = vcan_tx,
 133};
 134
 135static void vcan_setup(struct net_device *dev)
 136{
 137        dev->type               = ARPHRD_CAN;
 138        dev->mtu                = sizeof(struct can_frame);
 139        dev->hard_header_len    = 0;
 140        dev->addr_len           = 0;
 141        dev->tx_queue_len       = 0;
 142        dev->flags              = IFF_NOARP;
 143
 144        /* set flags according to driver capabilities */
 145        if (echo)
 146                dev->flags |= IFF_ECHO;
 147
 148        dev->netdev_ops         = &vcan_netdev_ops;
 149        dev->destructor         = free_netdev;
 150}
 151
 152static struct rtnl_link_ops vcan_link_ops __read_mostly = {
 153        .kind   = "vcan",
 154        .setup  = vcan_setup,
 155};
 156
 157static __init int vcan_init_module(void)
 158{
 159        printk(banner);
 160
 161        if (echo)
 162                printk(KERN_INFO "vcan: enabled echo on driver level.\n");
 163
 164        return rtnl_link_register(&vcan_link_ops);
 165}
 166
 167static __exit void vcan_cleanup_module(void)
 168{
 169        rtnl_link_unregister(&vcan_link_ops);
 170}
 171
 172module_init(vcan_init_module);
 173module_exit(vcan_cleanup_module);
 174