drivers/net/can/vxcan.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * vxcan.c - Virtual CAN Tunnel for cross namespace communication
   4  *
   5  * This code is derived from drivers/net/can/vcan.c for the virtual CAN
   6  * specific parts and from drivers/net/veth.c to implement the netlink API
   7  * for network interface pairs in a common and established way.
   8  *
   9  * Copyright (c) 2017 Oliver Hartkopp <socketcan@hartkopp.net>
  10  */
  11
  12 #include <linux/module.h>
  13 #include <linux/init.h>
  14 #include <linux/netdevice.h>
  15 #include <linux/if_arp.h>
  16 #include <linux/if_ether.h>
  17 #include <linux/can.h>
  18 #include <linux/can/dev.h>
  19 #include <linux/can/skb.h>
  20 #include <linux/can/vxcan.h>
  21 #include <linux/can/can-ml.h>
  22 #include <linux/slab.h>
  23 #include <net/rtnetlink.h>
  24
  25 #define DRV_NAME "vxcan"
  26
  27 MODULE_DESCRIPTION("Virtual CAN Tunnel");
  28 MODULE_LICENSE("GPL");
  29 MODULE_AUTHOR("Oliver Hartkopp <socketcan@hartkopp.net>");
  30 MODULE_ALIAS_RTNL_LINK(DRV_NAME);
  31
  32 struct vxcan_priv {
  33         struct net_device __rcu *peer;
  34 };
  35
  36 static netdev_tx_t vxcan_xmit(struct sk_buff *skb, struct net_device *dev)
  37 {
  38         struct vxcan_priv *priv = netdev_priv(dev);
  39         struct net_device *peer;
  40         struct canfd_frame *cfd = (struct canfd_frame *)skb->data;
  41         struct net_device_stats *peerstats, *srcstats = &dev->stats;
  42
  43         if (can_dropped_invalid_skb(dev, skb))
  44                 return NETDEV_TX_OK;
  45
  46         rcu_read_lock();
  47         peer = rcu_dereference(priv->peer);
  48         if (unlikely(!peer)) {
  49                 kfree_skb(skb);
  50                 dev->stats.tx_dropped++;
  51                 goto out_unlock;
  52         }
  53
  54         skb = can_create_echo_skb(skb);
  55         if (!skb)
  56                 goto out_unlock;
  57
  58         /* reset CAN GW hop counter */
  59         skb->csum_start = 0;
  60         skb->pkt_type   = PACKET_BROADCAST;
  61         skb->dev        = peer;
  62         skb->ip_summed  = CHECKSUM_UNNECESSARY;
  63
  64         if (netif_rx_ni(skb) == NET_RX_SUCCESS) {
  65                 srcstats->tx_packets++;
  66                 srcstats->tx_bytes += cfd->len;
  67                 peerstats = &peer->stats;
  68                 peerstats->rx_packets++;
  69                 peerstats->rx_bytes += cfd->len;
  70         }
  71
  72 out_unlock:
  73         rcu_read_unlock();
  74         return NETDEV_TX_OK;
  75 }
  76
  77
  78 static int vxcan_open(struct net_device *dev)
  79 {
  80         struct vxcan_priv *priv = netdev_priv(dev);
  81         struct net_device *peer = rtnl_dereference(priv->peer);
  82
  83         if (!peer)
  84                 return -ENOTCONN;
  85
  86         if (peer->flags & IFF_UP) {
  87                 netif_carrier_on(dev);
  88                 netif_carrier_on(peer);
  89         }
  90         return 0;
  91 }
  92
  93 static int vxcan_close(struct net_device *dev)
  94 {
  95         struct vxcan_priv *priv = netdev_priv(dev);
  96         struct net_device *peer = rtnl_dereference(priv->peer);
  97
  98         netif_carrier_off(dev);
  99         if (peer)
 100                 netif_carrier_off(peer);
 101
 102         return 0;
 103 }
 104
 105 static int vxcan_get_iflink(const struct net_device *dev)
 106 {
 107         struct vxcan_priv *priv = netdev_priv(dev);
 108         struct net_device *peer;
 109         int iflink;
 110
 111         rcu_read_lock();
 112         peer = rcu_dereference(priv->peer);
 113         iflink = peer ? peer->ifindex : 0;
 114         rcu_read_unlock();
 115
 116         return iflink;
 117 }
 118
 119 static int vxcan_change_mtu(struct net_device *dev, int new_mtu)
 120 {
 121         /* Do not allow changing the MTU while running */
 122         if (dev->flags & IFF_UP)
 123                 return -EBUSY;
 124
 125         if (new_mtu != CAN_MTU && new_mtu != CANFD_MTU)
 126                 return -EINVAL;
 127
 128         dev->mtu = new_mtu;
 129         return 0;
 130 }
 131
 132 static const struct net_device_ops vxcan_netdev_ops = {
 133         .ndo_open       = vxcan_open,
 134         .ndo_stop       = vxcan_close,
 135         .ndo_start_xmit = vxcan_xmit,
 136         .ndo_get_iflink = vxcan_get_iflink,
 137         .ndo_change_mtu = vxcan_change_mtu,
 138 };
 139
 140 static void vxcan_setup(struct net_device *dev)
 141 {
 142         dev->type               = ARPHRD_CAN;
 143         dev->mtu                = CANFD_MTU;
 144         dev->hard_header_len    = 0;
 145         dev->addr_len           = 0;
 146         dev->tx_queue_len       = 0;
 147         dev->flags              = (IFF_NOARP|IFF_ECHO);
 148         dev->netdev_ops         = &vxcan_netdev_ops;
 149         dev->needs_free_netdev  = true;
 150         dev->ml_priv            = netdev_priv(dev) + ALIGN(sizeof(struct vxcan_priv), NETDEV_ALIGN);
 151 }
 152
 153 /* forward declaration for rtnl_create_link() */
 154 static struct rtnl_link_ops vxcan_link_ops;
 155
 156 static int vxcan_newlink(struct net *net, struct net_device *dev,
 157                          struct nlattr *tb[], struct nlattr *data[],
 158                          struct netlink_ext_ack *extack)
 159 {
 160         struct vxcan_priv *priv;
 161         struct net_device *peer;
 162         struct net *peer_net;
 163
 164         struct nlattr *peer_tb[IFLA_MAX + 1], **tbp = tb;
 165         char ifname[IFNAMSIZ];
 166         unsigned char name_assign_type;
 167         struct ifinfomsg *ifmp = NULL;
 168         int err;
 169
 170         /* register peer device */
 171         if (data && data[VXCAN_INFO_PEER]) {
 172                 struct nlattr *nla_peer;
 173
 174                 nla_peer = data[VXCAN_INFO_PEER];
 175                 ifmp = nla_data(nla_peer);
 176                 err = rtnl_nla_parse_ifla(peer_tb,
 177                                           nla_data(nla_peer) +
 178                                           sizeof(struct ifinfomsg),
 179                                           nla_len(nla_peer) -
 180                                           sizeof(struct ifinfomsg),
 181                                           NULL);
 182                 if (err < 0)
 183                         return err;
 184
 185                 tbp = peer_tb;
 186         }
 187
 188         if (ifmp && tbp[IFLA_IFNAME]) {
 189                 nla_strlcpy(ifname, tbp[IFLA_IFNAME], IFNAMSIZ);
 190                 name_assign_type = NET_NAME_USER;
 191         } else {
 192                 snprintf(ifname, IFNAMSIZ, DRV_NAME "%%d");
 193                 name_assign_type = NET_NAME_ENUM;
 194         }
 195
 196         peer_net = rtnl_link_get_net(net, tbp);
 197         if (IS_ERR(peer_net))
 198                 return PTR_ERR(peer_net);
 199
 200         peer = rtnl_create_link(peer_net, ifname, name_assign_type,
 201                                 &vxcan_link_ops, tbp, extack);
 202         if (IS_ERR(peer)) {
 203                 put_net(peer_net);
 204                 return PTR_ERR(peer);
 205         }
 206
 207         if (ifmp && dev->ifindex)
 208                 peer->ifindex = ifmp->ifi_index;
 209
 210         err = register_netdevice(peer);
 211         put_net(peer_net);
 212         peer_net = NULL;
 213         if (err < 0) {
 214                 free_netdev(peer);
 215                 return err;
 216         }
 217
 218         netif_carrier_off(peer);
 219
 220         err = rtnl_configure_link(peer, ifmp);
 221         if (err < 0)
 222                 goto unregister_network_device;
 223
 224         /* register first device */
 225         if (tb[IFLA_IFNAME])
 226                 nla_strlcpy(dev->name, tb[IFLA_IFNAME], IFNAMSIZ);
 227         else
 228                 snprintf(dev->name, IFNAMSIZ, DRV_NAME "%%d");
 229
 230         err = register_netdevice(dev);
 231         if (err < 0)
 232                 goto unregister_network_device;
 233
 234         netif_carrier_off(dev);
 235
 236         /* cross link the device pair */
 237         priv = netdev_priv(dev);
 238         rcu_assign_pointer(priv->peer, peer);
 239
 240         priv = netdev_priv(peer);
 241         rcu_assign_pointer(priv->peer, dev);
 242
 243         return 0;
 244
 245 unregister_network_device:
 246         unregister_netdevice(peer);
 247         return err;
 248 }
 249
 250 static void vxcan_dellink(struct net_device *dev, struct list_head *head)
 251 {
 252         struct vxcan_priv *priv;
 253         struct net_device *peer;
 254
 255         priv = netdev_priv(dev);
 256         peer = rtnl_dereference(priv->peer);
 257
 258         /* Note : dellink() is called from default_device_exit_batch(),
 259          * before a rcu_synchronize() point. The devices are guaranteed
 260          * not being freed before one RCU grace period.
 261          */
 262         RCU_INIT_POINTER(priv->peer, NULL);
 263         unregister_netdevice_queue(dev, head);
 264
 265         if (peer) {
 266                 priv = netdev_priv(peer);
 267                 RCU_INIT_POINTER(priv->peer, NULL);
 268                 unregister_netdevice_queue(peer, head);
 269         }
 270 }
 271
 272 static const struct nla_policy vxcan_policy[VXCAN_INFO_MAX + 1] = {
 273         [VXCAN_INFO_PEER] = { .len = sizeof(struct ifinfomsg) },
 274 };
 275
 276 static struct net *vxcan_get_link_net(const struct net_device *dev)
 277 {
 278         struct vxcan_priv *priv = netdev_priv(dev);
 279         struct net_device *peer = rtnl_dereference(priv->peer);
 280
 281         return peer ? dev_net(peer) : dev_net(dev);
 282 }
 283
 284 static struct rtnl_link_ops vxcan_link_ops = {
 285         .kind           = DRV_NAME,
 286         .priv_size      = ALIGN(sizeof(struct vxcan_priv), NETDEV_ALIGN) + sizeof(struct can_ml_priv),
 287         .setup          = vxcan_setup,
 288         .newlink        = vxcan_newlink,
 289         .dellink        = vxcan_dellink,
 290         .policy         = vxcan_policy,
 291         .maxtype        = VXCAN_INFO_MAX,
 292         .get_link_net   = vxcan_get_link_net,
 293 };
 294
 295 static __init int vxcan_init(void)
 296 {
 297         pr_info("vxcan: Virtual CAN Tunnel driver\n");
 298
 299         return rtnl_link_register(&vxcan_link_ops);
 300 }
 301
 302 static __exit void vxcan_exit(void)
 303 {
 304         rtnl_link_unregister(&vxcan_link_ops);
 305 }
 306
 307 module_init(vxcan_init);
 308 module_exit(vxcan_exit);