/net/l2tp/l2tp_eth.c

  1// SPDX-License-Identifier: GPL-2.0-or-later
  2/*
  3 * L2TPv3 ethernet pseudowire driver
  4 *
  5 * Copyright (c) 2008,2009,2010 Katalix Systems Ltd
  6 */
  7
  8#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  9
 10#include <linux/module.h>
 11#include <linux/skbuff.h>
 12#include <linux/socket.h>
 13#include <linux/hash.h>
 14#include <linux/l2tp.h>
 15#include <linux/in.h>
 16#include <linux/etherdevice.h>
 17#include <linux/spinlock.h>
 18#include <net/sock.h>
 19#include <net/ip.h>
 20#include <net/icmp.h>
 21#include <net/udp.h>
 22#include <net/inet_common.h>
 23#include <net/inet_hashtables.h>
 24#include <net/tcp_states.h>
 25#include <net/protocol.h>
 26#include <net/xfrm.h>
 27#include <net/net_namespace.h>
 28#include <net/netns/generic.h>
 29#include <linux/ip.h>
 30#include <linux/ipv6.h>
 31#include <linux/udp.h>
 32
 33#include "l2tp_core.h"
 34
 35/* Default device name. May be overridden by name specified by user */
 36#define L2TP_ETH_DEV_NAME	"l2tpeth%d"
 37
 38/* via netdev_priv() */
 39struct l2tp_eth {
 40	struct l2tp_session	*session;
 41	atomic_long_t		tx_bytes;
 42	atomic_long_t		tx_packets;
 43	atomic_long_t		tx_dropped;
 44	atomic_long_t		rx_bytes;
 45	atomic_long_t		rx_packets;
 46	atomic_long_t		rx_errors;
 47};
 48
 49/* via l2tp_session_priv() */
 50struct l2tp_eth_sess {
 51	struct net_device __rcu *dev;
 52};
 53
 54
 55static int l2tp_eth_dev_init(struct net_device *dev)
 56{
 57	eth_hw_addr_random(dev);
 58	eth_broadcast_addr(dev->broadcast);
 59
 60	return 0;
 61}
 62
 63static void l2tp_eth_dev_uninit(struct net_device *dev)
 64{
 65	struct l2tp_eth *priv = netdev_priv(dev);
 66	struct l2tp_eth_sess *spriv;
 67
 68	spriv = l2tp_session_priv(priv->session);
 69	RCU_INIT_POINTER(spriv->dev, NULL);
 70	/* No need for synchronize_net() here. We're called by
 71	 * unregister_netdev*(), which does the synchronisation for us.
 72	 */
 73}
 74
 75static int l2tp_eth_dev_xmit(struct sk_buff *skb, struct net_device *dev)
 76{
 77	struct l2tp_eth *priv = netdev_priv(dev);
 78	struct l2tp_session *session = priv->session;
 79	unsigned int len = skb->len;
 80	int ret = l2tp_xmit_skb(session, skb, session->hdr_len);
 81
 82	if (likely(ret == NET_XMIT_SUCCESS)) {
 83		atomic_long_add(len, &priv->tx_bytes);
 84		atomic_long_inc(&priv->tx_packets);
 85	} else {
 86		atomic_long_inc(&priv->tx_dropped);
 87	}
 88	return NETDEV_TX_OK;
 89}
 90
 91static void l2tp_eth_get_stats64(struct net_device *dev,
 92				 struct rtnl_link_stats64 *stats)
 93{
 94	struct l2tp_eth *priv = netdev_priv(dev);
 95
 96	stats->tx_bytes   = (unsigned long) atomic_long_read(&priv->tx_bytes);
 97	stats->tx_packets = (unsigned long) atomic_long_read(&priv->tx_packets);
 98	stats->tx_dropped = (unsigned long) atomic_long_read(&priv->tx_dropped);
 99	stats->rx_bytes   = (unsigned long) atomic_long_read(&priv->rx_bytes);
100	stats->rx_packets = (unsigned long) atomic_long_read(&priv->rx_packets);
101	stats->rx_errors  = (unsigned long) atomic_long_read(&priv->rx_errors);
102
103}
104
105static const struct net_device_ops l2tp_eth_netdev_ops = {
106	.ndo_init		= l2tp_eth_dev_init,
107	.ndo_uninit		= l2tp_eth_dev_uninit,
108	.ndo_start_xmit		= l2tp_eth_dev_xmit,
109	.ndo_get_stats64	= l2tp_eth_get_stats64,
110	.ndo_set_mac_address	= eth_mac_addr,
111};
112
113static struct device_type l2tpeth_type = {
114	.name = "l2tpeth",
115};
116
117static void l2tp_eth_dev_setup(struct net_device *dev)
118{
119	SET_NETDEV_DEVTYPE(dev, &l2tpeth_type);
120	ether_setup(dev);
121	dev->priv_flags		&= ~IFF_TX_SKB_SHARING;
122	dev->features		|= NETIF_F_LLTX;
123	dev->netdev_ops		= &l2tp_eth_netdev_ops;
124	dev->needs_free_netdev	= true;
125}
126
127static void l2tp_eth_dev_recv(struct l2tp_session *session, struct sk_buff *skb, int data_len)
128{
129	struct l2tp_eth_sess *spriv = l2tp_session_priv(session);
130	struct net_device *dev;
131	struct l2tp_eth *priv;
132
133	if (session->debug & L2TP_MSG_DATA) {
134		unsigned int length;
135
136		length = min(32u, skb->len);
137		if (!pskb_may_pull(skb, length))
138			goto error;
139
140		pr_debug("%s: eth recv\n", session->name);
141		print_hex_dump_bytes("", DUMP_PREFIX_OFFSET, skb->data, length);
142	}
143
144	if (!pskb_may_pull(skb, ETH_HLEN))
145		goto error;
146
147	secpath_reset(skb);
148
149	/* checksums verified by L2TP */
150	skb->ip_summed = CHECKSUM_NONE;
151
152	skb_dst_drop(skb);
153	nf_reset_ct(skb);
154
155	rcu_read_lock();
156	dev = rcu_dereference(spriv->dev);
157	if (!dev)
158		goto error_rcu;
159
160	priv = netdev_priv(dev);
161	if (dev_forward_skb(dev, skb) == NET_RX_SUCCESS) {
162		atomic_long_inc(&priv->rx_packets);
163		atomic_long_add(data_len, &priv->rx_bytes);
164	} else {
165		atomic_long_inc(&priv->rx_errors);
166	}
167	rcu_read_unlock();
168
169	return;
170
171error_rcu:
172	rcu_read_unlock();
173error:
174	kfree_skb(skb);
175}
176
177static void l2tp_eth_delete(struct l2tp_session *session)
178{
179	struct l2tp_eth_sess *spriv;
180	struct net_device *dev;
181
182	if (session) {
183		spriv = l2tp_session_priv(session);
184
185		rtnl_lock();
186		dev = rtnl_dereference(spriv->dev);
187		if (dev) {
188			unregister_netdevice(dev);
189			rtnl_unlock();
190			module_put(THIS_MODULE);
191		} else {
192			rtnl_unlock();
193		}
194	}
195}
196
197static void l2tp_eth_show(struct seq_file *m, void *arg)
198{
199	struct l2tp_session *session = arg;
200	struct l2tp_eth_sess *spriv = l2tp_session_priv(session);
201	struct net_device *dev;
202
203	rcu_read_lock();
204	dev = rcu_dereference(spriv->dev);
205	if (!dev) {
206		rcu_read_unlock();
207		return;
208	}
209	dev_hold(dev);
210	rcu_read_unlock();
211
212	seq_printf(m, "   interface %s\n", dev->name);
213
214	dev_put(dev);
215}
216
217static void l2tp_eth_adjust_mtu(struct l2tp_tunnel *tunnel,
218				struct l2tp_session *session,
219				struct net_device *dev)
220{
221	unsigned int overhead = 0;
222	u32 l3_overhead = 0;
223	u32 mtu;
224
225	/* if the encap is UDP, account for UDP header size */
226	if (tunnel->encap == L2TP_ENCAPTYPE_UDP) {
227		overhead += sizeof(struct udphdr);
228		dev->needed_headroom += sizeof(struct udphdr);
229	}
230
231	lock_sock(tunnel->sock);
232	l3_overhead = kernel_sock_ip_overhead(tunnel->sock);
233	release_sock(tunnel->sock);
234
235	if (l3_overhead == 0) {
236		/* L3 Overhead couldn't be identified, this could be
237		 * because tunnel->sock was NULL or the socket's
238		 * address family was not IPv4 or IPv6,
239		 * dev mtu stays at 1500.
240		 */
241		return;
242	}
243	/* Adjust MTU, factor overhead - underlay L3, overlay L2 hdr
244	 * UDP overhead, if any, was already factored in above.
245	 */
246	overhead += session->hdr_len + ETH_HLEN + l3_overhead;
247
248	mtu = l2tp_tunnel_dst_mtu(tunnel) - overhead;
249	if (mtu < dev->min_mtu || mtu > dev->max_mtu)
250		dev->mtu = ETH_DATA_LEN - overhead;
251	else
252		dev->mtu = mtu;
253
254	dev->needed_headroom += session->hdr_len;
255}
256
257static int l2tp_eth_create(struct net *net, struct l2tp_tunnel *tunnel,
258			   u32 session_id, u32 peer_session_id,
259			   struct l2tp_session_cfg *cfg)
260{
261	unsigned char name_assign_type;
262	struct net_device *dev;
263	char name[IFNAMSIZ];
264	struct l2tp_session *session;
265	struct l2tp_eth *priv;
266	struct l2tp_eth_sess *spriv;
267	int rc;
268
269	if (cfg->ifname) {
270		strlcpy(name, cfg->ifname, IFNAMSIZ);
271		name_assign_type = NET_NAME_USER;
272	} else {
273		strcpy(name, L2TP_ETH_DEV_NAME);
274		name_assign_type = NET_NAME_ENUM;
275	}
276
277	session = l2tp_session_create(sizeof(*spriv), tunnel, session_id,
278				      peer_session_id, cfg);
279	if (IS_ERR(session)) {
280		rc = PTR_ERR(session);
281		goto err;
282	}
283
284	dev = alloc_netdev(sizeof(*priv), name, name_assign_type,
285			   l2tp_eth_dev_setup);
286	if (!dev) {
287		rc = -ENOMEM;
288		goto err_sess;
289	}
290
291	dev_net_set(dev, net);
292	dev->min_mtu = 0;
293	dev->max_mtu = ETH_MAX_MTU;
294	l2tp_eth_adjust_mtu(tunnel, session, dev);
295
296	priv = netdev_priv(dev);
297	priv->session = session;
298
299	session->recv_skb = l2tp_eth_dev_recv;
300	session->session_close = l2tp_eth_delete;
301	if (IS_ENABLED(CONFIG_L2TP_DEBUGFS))
302		session->show = l2tp_eth_show;
303
304	spriv = l2tp_session_priv(session);
305
306	l2tp_session_inc_refcount(session);
307
308	rtnl_lock();
309
310	/* Register both device and session while holding the rtnl lock. This
311	 * ensures that l2tp_eth_delete() will see that there's a device to
312	 * unregister, even if it happened to run before we assign spriv->dev.
313	 */
314	rc = l2tp_session_register(session, tunnel);
315	if (rc < 0) {
316		rtnl_unlock();
317		goto err_sess_dev;
318	}
319
320	rc = register_netdevice(dev);
321	if (rc < 0) {
322		rtnl_unlock();
323		l2tp_session_delete(session);
324		l2tp_session_dec_refcount(session);
325		free_netdev(dev);
326
327		return rc;
328	}
329
330	strlcpy(session->ifname, dev->name, IFNAMSIZ);
331	rcu_assign_pointer(spriv->dev, dev);
332
333	rtnl_unlock();
334
335	l2tp_session_dec_refcount(session);
336
337	__module_get(THIS_MODULE);
338
339	return 0;
340
341err_sess_dev:
342	l2tp_session_dec_refcount(session);
343	free_netdev(dev);
344err_sess:
345	kfree(session);
346err:
347	return rc;
348}
349
350
351static const struct l2tp_nl_cmd_ops l2tp_eth_nl_cmd_ops = {
352	.session_create	= l2tp_eth_create,
353	.session_delete	= l2tp_session_delete,
354};
355
356
357static int __init l2tp_eth_init(void)
358{
359	int err = 0;
360
361	err = l2tp_nl_register_ops(L2TP_PWTYPE_ETH, &l2tp_eth_nl_cmd_ops);
362	if (err)
363		goto err;
364
365	pr_info("L2TP ethernet pseudowire support (L2TPv3)\n");
366
367	return 0;
368
369err:
370	return err;
371}
372
373static void __exit l2tp_eth_exit(void)
374{
375	l2tp_nl_unregister_ops(L2TP_PWTYPE_ETH);
376}
377
378module_init(l2tp_eth_init);
379module_exit(l2tp_eth_exit);
380
381MODULE_LICENSE("GPL");
382MODULE_AUTHOR("James Chapman <jchapman@katalix.com>");
383MODULE_DESCRIPTION("L2TP ethernet pseudowire driver");
384MODULE_VERSION("1.0");
385MODULE_ALIAS_L2TP_PWTYPE(5);