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
 27MODULE_DESCRIPTION("Virtual CAN Tunnel");
 28MODULE_LICENSE("GPL");
 29MODULE_AUTHOR("Oliver Hartkopp <socketcan@hartkopp.net>");
 30MODULE_ALIAS_RTNL_LINK(DRV_NAME);
 31
 32struct vxcan_priv {
 33	struct net_device __rcu	*peer;
 34};
 35
 36static 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	u8 len;
 43
 44	if (can_dropped_invalid_skb(dev, skb))
 45		return NETDEV_TX_OK;
 46
 47	rcu_read_lock();
 48	peer = rcu_dereference(priv->peer);
 49	if (unlikely(!peer)) {
 50		kfree_skb(skb);
 51		dev->stats.tx_dropped++;
 52		goto out_unlock;
 53	}
 54
 55	skb = can_create_echo_skb(skb);
 56	if (!skb)
 57		goto out_unlock;
 58
 59	/* reset CAN GW hop counter */
 60	skb->csum_start = 0;
 61	skb->pkt_type   = PACKET_BROADCAST;
 62	skb->dev        = peer;
 63	skb->ip_summed  = CHECKSUM_UNNECESSARY;
 64
 65	len = cfd->len;
 66	if (netif_rx_ni(skb) == NET_RX_SUCCESS) {
 67		srcstats->tx_packets++;
 68		srcstats->tx_bytes += len;
 69		peerstats = &peer->stats;
 70		peerstats->rx_packets++;
 71		peerstats->rx_bytes += len;
 72	}
 73
 74out_unlock:
 75	rcu_read_unlock();
 76	return NETDEV_TX_OK;
 77}
 78
 79
 80static int vxcan_open(struct net_device *dev)
 81{
 82	struct vxcan_priv *priv = netdev_priv(dev);
 83	struct net_device *peer = rtnl_dereference(priv->peer);
 84
 85	if (!peer)
 86		return -ENOTCONN;
 87
 88	if (peer->flags & IFF_UP) {
 89		netif_carrier_on(dev);
 90		netif_carrier_on(peer);
 91	}
 92	return 0;
 93}
 94
 95static int vxcan_close(struct net_device *dev)
 96{
 97	struct vxcan_priv *priv = netdev_priv(dev);
 98	struct net_device *peer = rtnl_dereference(priv->peer);
 99
100	netif_carrier_off(dev);
101	if (peer)
102		netif_carrier_off(peer);
103
104	return 0;
105}
106
107static int vxcan_get_iflink(const struct net_device *dev)
108{
109	struct vxcan_priv *priv = netdev_priv(dev);
110	struct net_device *peer;
111	int iflink;
112
113	rcu_read_lock();
114	peer = rcu_dereference(priv->peer);
115	iflink = peer ? peer->ifindex : 0;
116	rcu_read_unlock();
117
118	return iflink;
119}
120
121static int vxcan_change_mtu(struct net_device *dev, int new_mtu)
122{
123	/* Do not allow changing the MTU while running */
124	if (dev->flags & IFF_UP)
125		return -EBUSY;
126
127	if (new_mtu != CAN_MTU && new_mtu != CANFD_MTU)
128		return -EINVAL;
129
130	dev->mtu = new_mtu;
131	return 0;
132}
133
134static const struct net_device_ops vxcan_netdev_ops = {
135	.ndo_open	= vxcan_open,
136	.ndo_stop	= vxcan_close,
137	.ndo_start_xmit	= vxcan_xmit,
138	.ndo_get_iflink	= vxcan_get_iflink,
139	.ndo_change_mtu = vxcan_change_mtu,
140};
141
142static void vxcan_setup(struct net_device *dev)
143{
144	struct can_ml_priv *can_ml;
145
146	dev->type		= ARPHRD_CAN;
147	dev->mtu		= CANFD_MTU;
148	dev->hard_header_len	= 0;
149	dev->addr_len		= 0;
150	dev->tx_queue_len	= 0;
151	dev->flags		= (IFF_NOARP|IFF_ECHO);
152	dev->netdev_ops		= &vxcan_netdev_ops;
153	dev->needs_free_netdev	= true;
154
155	can_ml = netdev_priv(dev) + ALIGN(sizeof(struct vxcan_priv), NETDEV_ALIGN);
156	can_set_ml_priv(dev, can_ml);
157}
158
159/* forward declaration for rtnl_create_link() */
160static struct rtnl_link_ops vxcan_link_ops;
161
162static int vxcan_newlink(struct net *net, struct net_device *dev,
163			 struct nlattr *tb[], struct nlattr *data[],
164			 struct netlink_ext_ack *extack)
165{
166	struct vxcan_priv *priv;
167	struct net_device *peer;
168	struct net *peer_net;
169
170	struct nlattr *peer_tb[IFLA_MAX + 1], **tbp = tb;
171	char ifname[IFNAMSIZ];
172	unsigned char name_assign_type;
173	struct ifinfomsg *ifmp = NULL;
174	int err;
175
176	/* register peer device */
177	if (data && data[VXCAN_INFO_PEER]) {
178		struct nlattr *nla_peer;
179
180		nla_peer = data[VXCAN_INFO_PEER];
181		ifmp = nla_data(nla_peer);
182		err = rtnl_nla_parse_ifla(peer_tb,
183					  nla_data(nla_peer) +
184					  sizeof(struct ifinfomsg),
185					  nla_len(nla_peer) -
186					  sizeof(struct ifinfomsg),
187					  NULL);
188		if (err < 0)
189			return err;
190
191		tbp = peer_tb;
192	}
193
194	if (ifmp && tbp[IFLA_IFNAME]) {
195		nla_strscpy(ifname, tbp[IFLA_IFNAME], IFNAMSIZ);
196		name_assign_type = NET_NAME_USER;
197	} else {
198		snprintf(ifname, IFNAMSIZ, DRV_NAME "%%d");
199		name_assign_type = NET_NAME_ENUM;
200	}
201
202	peer_net = rtnl_link_get_net(net, tbp);
203	if (IS_ERR(peer_net))
204		return PTR_ERR(peer_net);
205
206	peer = rtnl_create_link(peer_net, ifname, name_assign_type,
207				&vxcan_link_ops, tbp, extack);
208	if (IS_ERR(peer)) {
209		put_net(peer_net);
210		return PTR_ERR(peer);
211	}
212
213	if (ifmp && dev->ifindex)
214		peer->ifindex = ifmp->ifi_index;
215
216	err = register_netdevice(peer);
217	put_net(peer_net);
218	peer_net = NULL;
219	if (err < 0) {
220		free_netdev(peer);
221		return err;
222	}
223
224	netif_carrier_off(peer);
225
226	err = rtnl_configure_link(peer, ifmp);
227	if (err < 0)
228		goto unregister_network_device;
229
230	/* register first device */
231	if (tb[IFLA_IFNAME])
232		nla_strscpy(dev->name, tb[IFLA_IFNAME], IFNAMSIZ);
233	else
234		snprintf(dev->name, IFNAMSIZ, DRV_NAME "%%d");
235
236	err = register_netdevice(dev);
237	if (err < 0)
238		goto unregister_network_device;
239
240	netif_carrier_off(dev);
241
242	/* cross link the device pair */
243	priv = netdev_priv(dev);
244	rcu_assign_pointer(priv->peer, peer);
245
246	priv = netdev_priv(peer);
247	rcu_assign_pointer(priv->peer, dev);
248
249	return 0;
250
251unregister_network_device:
252	unregister_netdevice(peer);
253	return err;
254}
255
256static void vxcan_dellink(struct net_device *dev, struct list_head *head)
257{
258	struct vxcan_priv *priv;
259	struct net_device *peer;
260
261	priv = netdev_priv(dev);
262	peer = rtnl_dereference(priv->peer);
263
264	/* Note : dellink() is called from default_device_exit_batch(),
265	 * before a rcu_synchronize() point. The devices are guaranteed
266	 * not being freed before one RCU grace period.
267	 */
268	RCU_INIT_POINTER(priv->peer, NULL);
269	unregister_netdevice_queue(dev, head);
270
271	if (peer) {
272		priv = netdev_priv(peer);
273		RCU_INIT_POINTER(priv->peer, NULL);
274		unregister_netdevice_queue(peer, head);
275	}
276}
277
278static const struct nla_policy vxcan_policy[VXCAN_INFO_MAX + 1] = {
279	[VXCAN_INFO_PEER] = { .len = sizeof(struct ifinfomsg) },
280};
281
282static struct net *vxcan_get_link_net(const struct net_device *dev)
283{
284	struct vxcan_priv *priv = netdev_priv(dev);
285	struct net_device *peer = rtnl_dereference(priv->peer);
286
287	return peer ? dev_net(peer) : dev_net(dev);
288}
289
290static struct rtnl_link_ops vxcan_link_ops = {
291	.kind		= DRV_NAME,
292	.priv_size	= ALIGN(sizeof(struct vxcan_priv), NETDEV_ALIGN) + sizeof(struct can_ml_priv),
293	.setup		= vxcan_setup,
294	.newlink	= vxcan_newlink,
295	.dellink	= vxcan_dellink,
296	.policy		= vxcan_policy,
297	.maxtype	= VXCAN_INFO_MAX,
298	.get_link_net	= vxcan_get_link_net,
299};
300
301static __init int vxcan_init(void)
302{
303	pr_info("vxcan: Virtual CAN Tunnel driver\n");
304
305	return rtnl_link_register(&vxcan_link_ops);
306}
307
308static __exit void vxcan_exit(void)
309{
310	rtnl_link_unregister(&vxcan_link_ops);
311}
312
313module_init(vxcan_init);
314module_exit(vxcan_exit);