drivers/net/can/vcan.c

   1 /*
   2  * vcan.c - Virtual CAN interface
   3  *
   4  * Copyright (c) 2002-2017 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  */
  41
  42 #include <linux/module.h>
  43 #include <linux/init.h>
  44 #include <linux/netdevice.h>
  45 #include <linux/if_arp.h>
  46 #include <linux/if_ether.h>
  47 #include <linux/can.h>
  48 #include <linux/can/dev.h>
  49 #include <linux/can/skb.h>
  50 #include <linux/slab.h>
  51 #include <net/rtnetlink.h>
  52
  53 #define DRV_NAME "vcan"
  54
  55 MODULE_DESCRIPTION("virtual CAN interface");
  56 MODULE_LICENSE("Dual BSD/GPL");
  57 MODULE_AUTHOR("Urs Thuermann <urs.thuermann@volkswagen.de>");
  58 MODULE_ALIAS_RTNL_LINK(DRV_NAME);
  59
  60
  61 /*
  62  * CAN test feature:
  63  * Enable the echo on driver level for testing the CAN core echo modes.
  64  * See Documentation/networking/can.rst for details.
  65  */
  66
  67 static bool echo; /* echo testing. Default: 0 (Off) */
  68 module_param(echo, bool, 0444);
  69 MODULE_PARM_DESC(echo, "Echo sent frames (for testing). Default: 0 (Off)");
  70
  71
  72 static void vcan_rx(struct sk_buff *skb, struct net_device *dev)
  73 {
  74         struct canfd_frame *cfd = (struct canfd_frame *)skb->data;
  75         struct net_device_stats *stats = &dev->stats;
  76
  77         stats->rx_packets++;
  78         stats->rx_bytes += cfd->len;
  79
  80         skb->pkt_type  = PACKET_BROADCAST;
  81         skb->dev       = dev;
  82         skb->ip_summed = CHECKSUM_UNNECESSARY;
  83
  84         netif_rx_ni(skb);
  85 }
  86
  87 static netdev_tx_t vcan_tx(struct sk_buff *skb, struct net_device *dev)
  88 {
  89         struct canfd_frame *cfd = (struct canfd_frame *)skb->data;
  90         struct net_device_stats *stats = &dev->stats;
  91         int loop;
  92
  93         if (can_dropped_invalid_skb(dev, skb))
  94                 return NETDEV_TX_OK;
  95
  96         stats->tx_packets++;
  97         stats->tx_bytes += cfd->len;
  98
  99         /* set flag whether this packet has to be looped back */
 100         loop = skb->pkt_type == PACKET_LOOPBACK;
 101
 102         if (!echo) {
 103                 /* no echo handling available inside this driver */
 104
 105                 if (loop) {
 106                         /*
 107                          * only count the packets here, because the
 108                          * CAN core already did the echo for us
 109                          */
 110                         stats->rx_packets++;
 111                         stats->rx_bytes += cfd->len;
 112                 }
 113                 consume_skb(skb);
 114                 return NETDEV_TX_OK;
 115         }
 116
 117         /* perform standard echo handling for CAN network interfaces */
 118
 119         if (loop) {
 120
 121                 skb = can_create_echo_skb(skb);
 122                 if (!skb)
 123                         return NETDEV_TX_OK;
 124
 125                 /* receive with packet counting */
 126                 vcan_rx(skb, dev);
 127         } else {
 128                 /* no looped packets => no counting */
 129                 consume_skb(skb);
 130         }
 131         return NETDEV_TX_OK;
 132 }
 133
 134 static int vcan_change_mtu(struct net_device *dev, int new_mtu)
 135 {
 136         /* Do not allow changing the MTU while running */
 137         if (dev->flags & IFF_UP)
 138                 return -EBUSY;
 139
 140         if (new_mtu != CAN_MTU && new_mtu != CANFD_MTU)
 141                 return -EINVAL;
 142
 143         dev->mtu = new_mtu;
 144         return 0;
 145 }
 146
 147 static const struct net_device_ops vcan_netdev_ops = {
 148         .ndo_start_xmit = vcan_tx,
 149         .ndo_change_mtu = vcan_change_mtu,
 150 };
 151
 152 static void vcan_setup(struct net_device *dev)
 153 {
 154         dev->type               = ARPHRD_CAN;
 155         dev->mtu                = CANFD_MTU;
 156         dev->hard_header_len    = 0;
 157         dev->addr_len           = 0;
 158         dev->tx_queue_len       = 0;
 159         dev->flags              = IFF_NOARP;
 160
 161         /* set flags according to driver capabilities */
 162         if (echo)
 163                 dev->flags |= IFF_ECHO;
 164
 165         dev->netdev_ops         = &vcan_netdev_ops;
 166         dev->needs_free_netdev  = true;
 167 }
 168
 169 static struct rtnl_link_ops vcan_link_ops __read_mostly = {
 170         .kind   = DRV_NAME,
 171         .setup  = vcan_setup,
 172 };
 173
 174 static __init int vcan_init_module(void)
 175 {
 176         pr_info("vcan: Virtual CAN interface driver\n");
 177
 178         if (echo)
 179                 printk(KERN_INFO "vcan: enabled echo on driver level.\n");
 180
 181         return rtnl_link_register(&vcan_link_ops);
 182 }
 183
 184 static __exit void vcan_cleanup_module(void)
 185 {
 186         rtnl_link_unregister(&vcan_link_ops);
 187 }
 188
 189 module_init(vcan_init_module);
 190 module_exit(vcan_cleanup_module);