vxcan.c
// SPDX-License-Identifier: GPL-2.0-only
/*
* vxcan.c - Virtual CAN Tunnel for cross namespace communication
*
* This code is derived from drivers/net/can/vcan.c for the virtual CAN
* specific parts and from drivers/net/veth.c to implement the netlink API
* for network interface pairs in a common and established way.
*
* Copyright (c) 2017 Oliver Hartkopp <socketcan@hartkopp.net>
*/
#include <linux/module.h>
#include <linux/init.h>
#include <linux/netdevice.h>
#include <linux/if_arp.h>
#include <linux/if_ether.h>
#include <linux/can.h>
#include <linux/can/dev.h>
#include <linux/can/skb.h>
#include <linux/can/vxcan.h>
#include <linux/can/can-ml.h>
#include <linux/slab.h>
#include <net/rtnetlink.h>
#define DRV_NAME "vxcan"
MODULE_DESCRIPTION("Virtual CAN Tunnel");
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Oliver Hartkopp <socketcan@hartkopp.net>");
MODULE_ALIAS_RTNL_LINK(DRV_NAME);
struct vxcan_priv {
struct net_device __rcu *peer;
};
static netdev_tx_t vxcan_xmit(struct sk_buff *skb, struct net_device *dev)
{
struct vxcan_priv *priv = netdev_priv(dev);
struct net_device *peer;
struct canfd_frame *cfd = (struct canfd_frame *)skb->data;
struct net_device_stats *peerstats, *srcstats = &dev->stats;
u8 len;
if (can_dropped_invalid_skb(dev, skb))
return NETDEV_TX_OK;
rcu_read_lock();
peer = rcu_dereference(priv->peer);
if (unlikely(!peer)) {
kfree_skb(skb);
dev->stats.tx_dropped++;
goto out_unlock;
}
skb = can_create_echo_skb(skb);
if (!skb)
goto out_unlock;
/* reset CAN GW hop counter */
skb->csum_start = 0;
skb->pkt_type = PACKET_BROADCAST;
skb->dev = peer;
skb->ip_summed = CHECKSUM_UNNECESSARY;
len = cfd->len;
if (netif_rx_ni(skb) == NET_RX_SUCCESS) {
srcstats->tx_packets++;
srcstats->tx_bytes += len;
peerstats = &peer->stats;
peerstats->rx_packets++;
peerstats->rx_bytes += len;
}
out_unlock:
rcu_read_unlock();
return NETDEV_TX_OK;
}
static int vxcan_open(struct net_device *dev)
{
struct vxcan_priv *priv = netdev_priv(dev);
struct net_device *peer = rtnl_dereference(priv->peer);
if (!peer)
return -ENOTCONN;
if (peer->flags & IFF_UP) {
netif_carrier_on(dev);
netif_carrier_on(peer);
}
return 0;
}
static int vxcan_close(struct net_device *dev)
{
struct vxcan_priv *priv = netdev_priv(dev);
struct net_device *peer = rtnl_dereference(priv->peer);
netif_carrier_off(dev);
if (peer)
netif_carrier_off(peer);
return 0;
}
static int vxcan_get_iflink(const struct net_device *dev)
{
struct vxcan_priv *priv = netdev_priv(dev);
struct net_device *peer;
int iflink;
rcu_read_lock();
peer = rcu_dereference(priv->peer);
iflink = peer ? peer->ifindex : 0;
rcu_read_unlock();
return iflink;
}
static int vxcan_change_mtu(struct net_device *dev, int new_mtu)
{
/* Do not allow changing the MTU while running */
if (dev->flags & IFF_UP)
return -EBUSY;
if (new_mtu != CAN_MTU && new_mtu != CANFD_MTU)
return -EINVAL;
dev->mtu = new_mtu;
return 0;
}
static const struct net_device_ops vxcan_netdev_ops = {
.ndo_open = vxcan_open,
.ndo_stop = vxcan_close,
.ndo_start_xmit = vxcan_xmit,
.ndo_get_iflink = vxcan_get_iflink,
.ndo_change_mtu = vxcan_change_mtu,
};
static void vxcan_setup(struct net_device *dev)
{
struct can_ml_priv *can_ml;
dev->type = ARPHRD_CAN;
dev->mtu = CANFD_MTU;
dev->hard_header_len = 0;
dev->addr_len = 0;
dev->tx_queue_len = 0;
dev->flags = (IFF_NOARP|IFF_ECHO);
dev->netdev_ops = &vxcan_netdev_ops;
dev->needs_free_netdev = true;
can_ml = netdev_priv(dev) + ALIGN(sizeof(struct vxcan_priv), NETDEV_ALIGN);
can_set_ml_priv(dev, can_ml);
}
/* forward declaration for rtnl_create_link() */
static struct rtnl_link_ops vxcan_link_ops;
static int vxcan_newlink(struct net *net, struct net_device *dev,
struct nlattr *tb[], struct nlattr *data[],
struct netlink_ext_ack *extack)
{
struct vxcan_priv *priv;
struct net_device *peer;
struct net *peer_net;
struct nlattr *peer_tb[IFLA_MAX + 1], **tbp = tb;
char ifname[IFNAMSIZ];
unsigned char name_assign_type;
struct ifinfomsg *ifmp = NULL;
int err;
/* register peer device */
if (data && data[VXCAN_INFO_PEER]) {
struct nlattr *nla_peer;
nla_peer = data[VXCAN_INFO_PEER];
ifmp = nla_data(nla_peer);
err = rtnl_nla_parse_ifla(peer_tb,
nla_data(nla_peer) +
sizeof(struct ifinfomsg),
nla_len(nla_peer) -
sizeof(struct ifinfomsg),
NULL);
if (err < 0)
return err;
tbp = peer_tb;
}
if (ifmp && tbp[IFLA_IFNAME]) {
nla_strscpy(ifname, tbp[IFLA_IFNAME], IFNAMSIZ);
name_assign_type = NET_NAME_USER;
} else {
snprintf(ifname, IFNAMSIZ, DRV_NAME "%%d");
name_assign_type = NET_NAME_ENUM;
}
peer_net = rtnl_link_get_net(net, tbp);
if (IS_ERR(peer_net))
return PTR_ERR(peer_net);
peer = rtnl_create_link(peer_net, ifname, name_assign_type,
&vxcan_link_ops, tbp, extack);
if (IS_ERR(peer)) {
put_net(peer_net);
return PTR_ERR(peer);
}
if (ifmp && dev->ifindex)
peer->ifindex = ifmp->ifi_index;
err = register_netdevice(peer);
put_net(peer_net);
peer_net = NULL;
if (err < 0) {
free_netdev(peer);
return err;
}
netif_carrier_off(peer);
err = rtnl_configure_link(peer, ifmp);
if (err < 0)
goto unregister_network_device;
/* register first device */
if (tb[IFLA_IFNAME])
nla_strscpy(dev->name, tb[IFLA_IFNAME], IFNAMSIZ);
else
snprintf(dev->name, IFNAMSIZ, DRV_NAME "%%d");
err = register_netdevice(dev);
if (err < 0)
goto unregister_network_device;
netif_carrier_off(dev);
/* cross link the device pair */
priv = netdev_priv(dev);
rcu_assign_pointer(priv->peer, peer);
priv = netdev_priv(peer);
rcu_assign_pointer(priv->peer, dev);
return 0;
unregister_network_device:
unregister_netdevice(peer);
return err;
}
static void vxcan_dellink(struct net_device *dev, struct list_head *head)
{
struct vxcan_priv *priv;
struct net_device *peer;
priv = netdev_priv(dev);
peer = rtnl_dereference(priv->peer);
/* Note : dellink() is called from default_device_exit_batch(),
* before a rcu_synchronize() point. The devices are guaranteed
* not being freed before one RCU grace period.
*/
RCU_INIT_POINTER(priv->peer, NULL);
unregister_netdevice_queue(dev, head);
if (peer) {
priv = netdev_priv(peer);
RCU_INIT_POINTER(priv->peer, NULL);
unregister_netdevice_queue(peer, head);
}
}
static const struct nla_policy vxcan_policy[VXCAN_INFO_MAX + 1] = {
[VXCAN_INFO_PEER] = { .len = sizeof(struct ifinfomsg) },
};
static struct net *vxcan_get_link_net(const struct net_device *dev)
{
struct vxcan_priv *priv = netdev_priv(dev);
struct net_device *peer = rtnl_dereference(priv->peer);
return peer ? dev_net(peer) : dev_net(dev);
}
static struct rtnl_link_ops vxcan_link_ops = {
.kind = DRV_NAME,
.priv_size = ALIGN(sizeof(struct vxcan_priv), NETDEV_ALIGN) + sizeof(struct can_ml_priv),
.setup = vxcan_setup,
.newlink = vxcan_newlink,
.dellink = vxcan_dellink,
.policy = vxcan_policy,
.maxtype = VXCAN_INFO_MAX,
.get_link_net = vxcan_get_link_net,
};
static __init int vxcan_init(void)
{
pr_info("vxcan: Virtual CAN Tunnel driver\n");
return rtnl_link_register(&vxcan_link_ops);
}
static __exit void vxcan_exit(void)
{
rtnl_link_unregister(&vxcan_link_ops);
}
module_init(vxcan_init);
module_exit(vxcan_exit);