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
  52 static __initdata const char banner[] =
  53         KERN_INFO "vcan: Virtual CAN interface driver\n";
  54
  55 MODULE_DESCRIPTION("virtual CAN interface");
  56 MODULE_LICENSE("Dual BSD/GPL");
  57 MODULE_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
  66 static int echo; /* echo testing. Default: 0 (Off) */
  67 module_param(echo, bool, S_IRUGO);
  68 MODULE_PARM_DESC(echo, "Echo sent frames (for testing). Default: 0 (Off)");
  69
  70
  71 static 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(skb);
  84 }
  85
  86 static int 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
 131 static const struct net_device_ops vcan_netdev_ops = {
 132         .ndo_start_xmit = vcan_tx,
 133 };
 134
 135 static 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
 152 static struct rtnl_link_ops vcan_link_ops __read_mostly = {
 153         .kind   = "vcan",
 154         .setup  = vcan_setup,
 155 };
 156
 157 static __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
 167 static __exit void vcan_cleanup_module(void)
 168 {
 169         rtnl_link_unregister(&vcan_link_ops);
 170 }
 171
 172 module_init(vcan_init_module);
 173 module_exit(vcan_cleanup_module);