drivers/net/can/vxcan.c

   1 /*
   2  * vxcan.c - Virtual CAN Tunnel for cross namespace communication
   3  *
   4  * This code is derived from drivers/net/can/vcan.c for the virtual CAN
   5  * specific parts and from drivers/net/veth.c to implement the netlink API
   6  * for network interface pairs in a common and established way.
   7  *
   8  * Copyright (c) 2017 Oliver Hartkopp <socketcan@hartkopp.net>
   9  *
  10  * This program is free software; you can redistribute it and/or modify
  11  * it under the terms of the version 2 of the GNU General Public License
  12  * as published by the Free Software Foundation
  13  *
  14  * This program is distributed in the hope that it will be useful,
  15  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  16  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  17  * GNU General Public License for more details.
  18  *
  19  * You should have received a copy of the GNU General Public License
  20  * along with this program; if not, see <http://www.gnu.org/licenses/>.
  21  */
  22
  23 #include <linux/module.h>
  24 #include <linux/init.h>
  25 #include <linux/netdevice.h>
  26 #include <linux/if_arp.h>
  27 #include <linux/if_ether.h>
  28 #include <linux/can.h>
  29 #include <linux/can/dev.h>
  30 #include <linux/can/skb.h>
  31 #include <linux/can/vxcan.h>
  32 #include <linux/slab.h>
  33 #include <net/rtnetlink.h>
  34
  35 #define DRV_NAME "vxcan"
  36
  37 MODULE_DESCRIPTION("Virtual CAN Tunnel");
  38 MODULE_LICENSE("GPL");
  39 MODULE_AUTHOR("Oliver Hartkopp <socketcan@hartkopp.net>");
  40 MODULE_ALIAS_RTNL_LINK(DRV_NAME);
  41
  42 struct vxcan_priv {
  43         struct net_device __rcu *peer;
  44 };
  45
  46 static netdev_tx_t vxcan_xmit(struct sk_buff *skb, struct net_device *dev)
  47 {
  48         struct vxcan_priv *priv = netdev_priv(dev);
  49         struct net_device *peer;
  50         struct canfd_frame *cfd = (struct canfd_frame *)skb->data;
  51         struct net_device_stats *peerstats, *srcstats = &dev->stats;
  52
  53         if (can_dropped_invalid_skb(dev, skb))
  54                 return NETDEV_TX_OK;
  55
  56         rcu_read_lock();
  57         peer = rcu_dereference(priv->peer);
  58         if (unlikely(!peer)) {
  59                 kfree_skb(skb);
  60                 dev->stats.tx_dropped++;
  61                 goto out_unlock;
  62         }
  63
  64         skb = can_create_echo_skb(skb);
  65         if (!skb)
  66                 goto out_unlock;
  67
  68         /* reset CAN GW hop counter */
  69         skb->csum_start = 0;
  70         skb->pkt_type   = PACKET_BROADCAST;
  71         skb->dev        = peer;
  72         skb->ip_summed  = CHECKSUM_UNNECESSARY;
  73
  74         if (netif_rx_ni(skb) == NET_RX_SUCCESS) {
  75                 srcstats->tx_packets++;
  76                 srcstats->tx_bytes += cfd->len;
  77                 peerstats = &peer->stats;
  78                 peerstats->rx_packets++;
  79                 peerstats->rx_bytes += cfd->len;
  80         }
  81
  82 out_unlock:
  83         rcu_read_unlock();
  84         return NETDEV_TX_OK;
  85 }
  86
  87
  88 static int vxcan_open(struct net_device *dev)
  89 {
  90         struct vxcan_priv *priv = netdev_priv(dev);
  91         struct net_device *peer = rtnl_dereference(priv->peer);
  92
  93         if (!peer)
  94                 return -ENOTCONN;
  95
  96         if (peer->flags & IFF_UP) {
  97                 netif_carrier_on(dev);
  98                 netif_carrier_on(peer);
  99         }
 100         return 0;
 101 }
 102
 103 static int vxcan_close(struct net_device *dev)
 104 {
 105         struct vxcan_priv *priv = netdev_priv(dev);
 106         struct net_device *peer = rtnl_dereference(priv->peer);
 107
 108         netif_carrier_off(dev);
 109         if (peer)
 110                 netif_carrier_off(peer);
 111
 112         return 0;
 113 }
 114
 115 static int vxcan_get_iflink(const struct net_device *dev)
 116 {
 117         struct vxcan_priv *priv = netdev_priv(dev);
 118         struct net_device *peer;
 119         int iflink;
 120
 121         rcu_read_lock();
 122         peer = rcu_dereference(priv->peer);
 123         iflink = peer ? peer->ifindex : 0;
 124         rcu_read_unlock();
 125
 126         return iflink;
 127 }
 128
 129 static int vxcan_change_mtu(struct net_device *dev, int new_mtu)
 130 {
 131         /* Do not allow changing the MTU while running */
 132         if (dev->flags & IFF_UP)
 133                 return -EBUSY;
 134
 135         if (new_mtu != CAN_MTU && new_mtu != CANFD_MTU)
 136                 return -EINVAL;
 137
 138         dev->mtu = new_mtu;
 139         return 0;
 140 }
 141
 142 static const struct net_device_ops vxcan_netdev_ops = {
 143         .ndo_open       = vxcan_open,
 144         .ndo_stop       = vxcan_close,
 145         .ndo_start_xmit = vxcan_xmit,
 146         .ndo_get_iflink = vxcan_get_iflink,
 147         .ndo_change_mtu = vxcan_change_mtu,
 148 };
 149
 150 static void vxcan_setup(struct net_device *dev)
 151 {
 152         dev->type               = ARPHRD_CAN;
 153         dev->mtu                = CANFD_MTU;
 154         dev->hard_header_len    = 0;
 155         dev->addr_len           = 0;
 156         dev->tx_queue_len       = 0;
 157         dev->flags              = (IFF_NOARP|IFF_ECHO);
 158         dev->netdev_ops         = &vxcan_netdev_ops;
 159         dev->needs_free_netdev  = true;
 160 }
 161
 162 /* forward declaration for rtnl_create_link() */
 163 static struct rtnl_link_ops vxcan_link_ops;
 164
 165 static int vxcan_newlink(struct net *net, struct net_device *dev,
 166                          struct nlattr *tb[], struct nlattr *data[],
 167                          struct netlink_ext_ack *extack)
 168 {
 169         struct vxcan_priv *priv;
 170         struct net_device *peer;
 171         struct net *peer_net;
 172
 173         struct nlattr *peer_tb[IFLA_MAX + 1], **tbp = tb;
 174         char ifname[IFNAMSIZ];
 175         unsigned char name_assign_type;
 176         struct ifinfomsg *ifmp = NULL;
 177         int err;
 178
 179         /* register peer device */
 180         if (data && data[VXCAN_INFO_PEER]) {
 181                 struct nlattr *nla_peer;
 182
 183                 nla_peer = data[VXCAN_INFO_PEER];
 184                 ifmp = nla_data(nla_peer);
 185                 err = rtnl_nla_parse_ifla(peer_tb,
 186                                           nla_data(nla_peer) +
 187                                           sizeof(struct ifinfomsg),
 188                                           nla_len(nla_peer) -
 189                                           sizeof(struct ifinfomsg),
 190                                           NULL);
 191                 if (err < 0)
 192                         return err;
 193
 194                 tbp = peer_tb;
 195         }
 196
 197         if (tbp[IFLA_IFNAME]) {
 198                 nla_strlcpy(ifname, tbp[IFLA_IFNAME], IFNAMSIZ);
 199                 name_assign_type = NET_NAME_USER;
 200         } else {
 201                 snprintf(ifname, IFNAMSIZ, DRV_NAME "%%d");
 202                 name_assign_type = NET_NAME_ENUM;
 203         }
 204
 205         peer_net = rtnl_link_get_net(net, tbp);
 206         if (IS_ERR(peer_net))
 207                 return PTR_ERR(peer_net);
 208
 209         peer = rtnl_create_link(peer_net, ifname, name_assign_type,
 210                                 &vxcan_link_ops, tbp);
 211         if (IS_ERR(peer)) {
 212                 put_net(peer_net);
 213                 return PTR_ERR(peer);
 214         }
 215
 216         if (ifmp && dev->ifindex)
 217                 peer->ifindex = ifmp->ifi_index;
 218
 219         err = register_netdevice(peer);
 220         put_net(peer_net);
 221         peer_net = NULL;
 222         if (err < 0) {
 223                 free_netdev(peer);
 224                 return err;
 225         }
 226
 227         netif_carrier_off(peer);
 228
 229         err = rtnl_configure_link(peer, ifmp);
 230         if (err < 0) {
 231                 unregister_netdevice(peer);
 232                 return err;
 233         }
 234
 235         /* register first device */
 236         if (tb[IFLA_IFNAME])
 237                 nla_strlcpy(dev->name, tb[IFLA_IFNAME], IFNAMSIZ);
 238         else
 239                 snprintf(dev->name, IFNAMSIZ, DRV_NAME "%%d");
 240
 241         err = register_netdevice(dev);
 242         if (err < 0) {
 243                 unregister_netdevice(peer);
 244                 return err;
 245         }
 246
 247         netif_carrier_off(dev);
 248
 249         /* cross link the device pair */
 250         priv = netdev_priv(dev);
 251         rcu_assign_pointer(priv->peer, peer);
 252
 253         priv = netdev_priv(peer);
 254         rcu_assign_pointer(priv->peer, dev);
 255
 256         return 0;
 257 }
 258
 259 static void vxcan_dellink(struct net_device *dev, struct list_head *head)
 260 {
 261         struct vxcan_priv *priv;
 262         struct net_device *peer;
 263
 264         priv = netdev_priv(dev);
 265         peer = rtnl_dereference(priv->peer);
 266
 267         /* Note : dellink() is called from default_device_exit_batch(),
 268          * before a rcu_synchronize() point. The devices are guaranteed
 269          * not being freed before one RCU grace period.
 270          */
 271         RCU_INIT_POINTER(priv->peer, NULL);
 272         unregister_netdevice_queue(dev, head);
 273
 274         if (peer) {
 275                 priv = netdev_priv(peer);
 276                 RCU_INIT_POINTER(priv->peer, NULL);
 277                 unregister_netdevice_queue(peer, head);
 278         }
 279 }
 280
 281 static const struct nla_policy vxcan_policy[VXCAN_INFO_MAX + 1] = {
 282         [VXCAN_INFO_PEER] = { .len = sizeof(struct ifinfomsg) },
 283 };
 284
 285 static struct net *vxcan_get_link_net(const struct net_device *dev)
 286 {
 287         struct vxcan_priv *priv = netdev_priv(dev);
 288         struct net_device *peer = rtnl_dereference(priv->peer);
 289
 290         return peer ? dev_net(peer) : dev_net(dev);
 291 }
 292
 293 static struct rtnl_link_ops vxcan_link_ops = {
 294         .kind           = DRV_NAME,
 295         .priv_size      = sizeof(struct vxcan_priv),
 296         .setup          = vxcan_setup,
 297         .newlink        = vxcan_newlink,
 298         .dellink        = vxcan_dellink,
 299         .policy         = vxcan_policy,
 300         .maxtype        = VXCAN_INFO_MAX,
 301         .get_link_net   = vxcan_get_link_net,
 302 };
 303
 304 static __init int vxcan_init(void)
 305 {
 306         pr_info("vxcan: Virtual CAN Tunnel driver\n");
 307
 308         return rtnl_link_register(&vxcan_link_ops);
 309 }
 310
 311 static __exit void vxcan_exit(void)
 312 {
 313         rtnl_link_unregister(&vxcan_link_ops);
 314 }
 315
 316 module_init(vxcan_init);
 317 module_exit(vxcan_exit);