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/ethtool.h>
 13#include <linux/module.h>
 14#include <linux/init.h>
 15#include <linux/netdevice.h>
 16#include <linux/if_arp.h>
 17#include <linux/if_ether.h>
 18#include <linux/can.h>
 19#include <linux/can/dev.h>
 20#include <linux/can/skb.h>
 21#include <linux/can/vxcan.h>
 22#include <linux/can/can-ml.h>
 23#include <linux/slab.h>
 24#include <net/rtnetlink.h>
 25
 26#define DRV_NAME "vxcan"
 27
 28MODULE_DESCRIPTION("Virtual CAN Tunnel");
 29MODULE_LICENSE("GPL");
 30MODULE_AUTHOR("Oliver Hartkopp <socketcan@hartkopp.net>");
 31MODULE_ALIAS_RTNL_LINK(DRV_NAME);
 32
 33struct vxcan_priv {
 34	struct net_device __rcu	*peer;
 35};
 36
 37static netdev_tx_t vxcan_xmit(struct sk_buff *oskb, struct net_device *dev)
 38{
 39	struct vxcan_priv *priv = netdev_priv(dev);
 40	struct net_device *peer;
 41	struct net_device_stats *peerstats, *srcstats = &dev->stats;
 42	struct sk_buff *skb;
 43	unsigned int len;
 44
 45	if (can_dropped_invalid_skb(dev, oskb))
 46		return NETDEV_TX_OK;
 47
 48	rcu_read_lock();
 49	peer = rcu_dereference(priv->peer);
 50	if (unlikely(!peer)) {
 51		kfree_skb(oskb);
 52		dev->stats.tx_dropped++;
 53		goto out_unlock;
 54	}
 55
 56	skb_tx_timestamp(oskb);
 57
 58	skb = skb_clone(oskb, GFP_ATOMIC);
 59	if (skb) {
 60		consume_skb(oskb);
 61	} else {
 62		kfree_skb(oskb);
 63		goto out_unlock;
 64	}
 65
 66	/* reset CAN GW hop counter */
 67	skb->csum_start = 0;
 68	skb->pkt_type   = PACKET_BROADCAST;
 69	skb->dev        = peer;
 70	skb->ip_summed  = CHECKSUM_UNNECESSARY;
 71
 72	len = can_skb_get_data_len(skb);
 73	if (netif_rx(skb) == NET_RX_SUCCESS) {
 74		srcstats->tx_packets++;
 75		srcstats->tx_bytes += len;
 76		peerstats = &peer->stats;
 77		peerstats->rx_packets++;
 78		peerstats->rx_bytes += len;
 79	}
 80
 81out_unlock:
 82	rcu_read_unlock();
 83	return NETDEV_TX_OK;
 84}
 85
 86
 87static int vxcan_open(struct net_device *dev)
 88{
 89	struct vxcan_priv *priv = netdev_priv(dev);
 90	struct net_device *peer = rtnl_dereference(priv->peer);
 91
 92	if (!peer)
 93		return -ENOTCONN;
 94
 95	if (peer->flags & IFF_UP) {
 96		netif_carrier_on(dev);
 97		netif_carrier_on(peer);
 98	}
 99	return 0;
100}
101
102static int vxcan_close(struct net_device *dev)
103{
104	struct vxcan_priv *priv = netdev_priv(dev);
105	struct net_device *peer = rtnl_dereference(priv->peer);
106
107	netif_carrier_off(dev);
108	if (peer)
109		netif_carrier_off(peer);
110
111	return 0;
112}
113
114static int vxcan_get_iflink(const struct net_device *dev)
115{
116	struct vxcan_priv *priv = netdev_priv(dev);
117	struct net_device *peer;
118	int iflink;
119
120	rcu_read_lock();
121	peer = rcu_dereference(priv->peer);
122	iflink = peer ? READ_ONCE(peer->ifindex) : 0;
123	rcu_read_unlock();
124
125	return iflink;
126}
127
128static void vxcan_set_cap_info(struct net_device *dev)
129{
130	u32 can_cap = CAN_CAP_CC;
131
132	if (dev->mtu > CAN_MTU)
133		can_cap |= CAN_CAP_FD;
134
135	if (dev->mtu >= CANXL_MIN_MTU)
136		can_cap |= CAN_CAP_XL;
137
138	can_set_cap(dev, can_cap);
139}
140
141static int vxcan_change_mtu(struct net_device *dev, int new_mtu)
142{
143	/* Do not allow changing the MTU while running */
144	if (dev->flags & IFF_UP)
145		return -EBUSY;
146
147	if (new_mtu != CAN_MTU && new_mtu != CANFD_MTU &&
148	    !can_is_canxl_dev_mtu(new_mtu))
149		return -EINVAL;
150
151	WRITE_ONCE(dev->mtu, new_mtu);
152	vxcan_set_cap_info(dev);
153	return 0;
154}
155
156static const struct net_device_ops vxcan_netdev_ops = {
157	.ndo_open	= vxcan_open,
158	.ndo_stop	= vxcan_close,
159	.ndo_start_xmit	= vxcan_xmit,
160	.ndo_get_iflink	= vxcan_get_iflink,
161	.ndo_change_mtu = vxcan_change_mtu,
162};
163
164static const struct ethtool_ops vxcan_ethtool_ops = {
165	.get_ts_info = ethtool_op_get_ts_info,
166};
167
168static void vxcan_setup(struct net_device *dev)
169{
170	struct can_ml_priv *can_ml;
171
172	dev->type		= ARPHRD_CAN;
173	dev->mtu		= CANXL_MTU;
174	dev->hard_header_len	= 0;
175	dev->addr_len		= 0;
176	dev->tx_queue_len	= 0;
177	dev->flags		= IFF_NOARP;
178	dev->netdev_ops		= &vxcan_netdev_ops;
179	dev->ethtool_ops	= &vxcan_ethtool_ops;
180	dev->needs_free_netdev	= true;
181
182	can_ml = netdev_priv(dev) + ALIGN(sizeof(struct vxcan_priv), NETDEV_ALIGN);
183	can_set_ml_priv(dev, can_ml);
184	vxcan_set_cap_info(dev);
185}
186
187/* forward declaration for rtnl_create_link() */
188static struct rtnl_link_ops vxcan_link_ops;
189
190static int vxcan_newlink(struct net_device *dev,
191			 struct rtnl_newlink_params *params,
192			 struct netlink_ext_ack *extack)
193{
194	struct net *peer_net = rtnl_newlink_peer_net(params);
195	struct nlattr **data = params->data;
196	struct nlattr **tb = params->tb;
197	struct vxcan_priv *priv;
198	struct net_device *peer;
199
200	struct nlattr *peer_tb[IFLA_MAX + 1], **tbp = tb;
201	char ifname[IFNAMSIZ];
202	unsigned char name_assign_type;
203	struct ifinfomsg *ifmp = NULL;
204	int err;
205
206	/* register peer device */
207	if (data && data[VXCAN_INFO_PEER]) {
208		struct nlattr *nla_peer = data[VXCAN_INFO_PEER];
209
210		ifmp = nla_data(nla_peer);
211		rtnl_nla_parse_ifinfomsg(peer_tb, nla_peer, extack);
212		tbp = peer_tb;
213	}
214
215	if (ifmp && tbp[IFLA_IFNAME]) {
216		nla_strscpy(ifname, tbp[IFLA_IFNAME], IFNAMSIZ);
217		name_assign_type = NET_NAME_USER;
218	} else {
219		snprintf(ifname, IFNAMSIZ, DRV_NAME "%%d");
220		name_assign_type = NET_NAME_ENUM;
221	}
222
223	peer = rtnl_create_link(peer_net, ifname, name_assign_type,
224				&vxcan_link_ops, tbp, extack);
225	if (IS_ERR(peer))
226		return PTR_ERR(peer);
227
228	if (ifmp && dev->ifindex)
229		peer->ifindex = ifmp->ifi_index;
230
231	err = register_netdevice(peer);
232	if (err < 0) {
233		free_netdev(peer);
234		return err;
235	}
236
237	netif_carrier_off(peer);
238
239	err = rtnl_configure_link(peer, ifmp, 0, NULL);
240	if (err < 0)
241		goto unregister_network_device;
242
243	/* register first device */
244	if (tb[IFLA_IFNAME])
245		nla_strscpy(dev->name, tb[IFLA_IFNAME], IFNAMSIZ);
246	else
247		snprintf(dev->name, IFNAMSIZ, DRV_NAME "%%d");
248
249	err = register_netdevice(dev);
250	if (err < 0)
251		goto unregister_network_device;
252
253	netif_carrier_off(dev);
254
255	/* cross link the device pair */
256	priv = netdev_priv(dev);
257	rcu_assign_pointer(priv->peer, peer);
258
259	priv = netdev_priv(peer);
260	rcu_assign_pointer(priv->peer, dev);
261
262	return 0;
263
264unregister_network_device:
265	unregister_netdevice(peer);
266	return err;
267}
268
269static void vxcan_dellink(struct net_device *dev, struct list_head *head)
270{
271	struct vxcan_priv *priv;
272	struct net_device *peer;
273
274	priv = netdev_priv(dev);
275	peer = rtnl_dereference(priv->peer);
276
277	/* Note : dellink() is called from default_device_exit_batch(),
278	 * before a rcu_synchronize() point. The devices are guaranteed
279	 * not being freed before one RCU grace period.
280	 */
281	RCU_INIT_POINTER(priv->peer, NULL);
282	unregister_netdevice_queue(dev, head);
283
284	if (peer) {
285		priv = netdev_priv(peer);
286		RCU_INIT_POINTER(priv->peer, NULL);
287		unregister_netdevice_queue(peer, head);
288	}
289}
290
291static const struct nla_policy vxcan_policy[VXCAN_INFO_MAX + 1] = {
292	[VXCAN_INFO_PEER] = { .len = sizeof(struct ifinfomsg) },
293};
294
295static struct net *vxcan_get_link_net(const struct net_device *dev)
296{
297	struct vxcan_priv *priv = netdev_priv(dev);
298	struct net_device *peer = rtnl_dereference(priv->peer);
299
300	return peer ? dev_net(peer) : dev_net(dev);
301}
302
303static struct rtnl_link_ops vxcan_link_ops = {
304	.kind		= DRV_NAME,
305	.priv_size	= ALIGN(sizeof(struct vxcan_priv), NETDEV_ALIGN) + sizeof(struct can_ml_priv),
306	.setup		= vxcan_setup,
307	.newlink	= vxcan_newlink,
308	.dellink	= vxcan_dellink,
309	.policy		= vxcan_policy,
310	.peer_type	= VXCAN_INFO_PEER,
311	.maxtype	= VXCAN_INFO_MAX,
312	.get_link_net	= vxcan_get_link_net,
313};
314
315static __init int vxcan_init(void)
316{
317	pr_info("vxcan: Virtual CAN Tunnel driver\n");
318
319	return rtnl_link_register(&vxcan_link_ops);
320}
321
322static __exit void vxcan_exit(void)
323{
324	rtnl_link_unregister(&vxcan_link_ops);
325}
326
327module_init(vxcan_init);
328module_exit(vxcan_exit);