xref: /openbmc/linux/net/l2tp/l2tp_eth.c (revision 23e25d2f)
1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /* L2TPv3 ethernet pseudowire driver
3  *
4  * Copyright (c) 2008,2009,2010 Katalix Systems Ltd
5  */
6 
7 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
8 
9 #include <linux/module.h>
10 #include <linux/skbuff.h>
11 #include <linux/socket.h>
12 #include <linux/hash.h>
13 #include <linux/l2tp.h>
14 #include <linux/in.h>
15 #include <linux/etherdevice.h>
16 #include <linux/spinlock.h>
17 #include <net/sock.h>
18 #include <net/ip.h>
19 #include <net/icmp.h>
20 #include <net/udp.h>
21 #include <net/inet_common.h>
22 #include <net/inet_hashtables.h>
23 #include <net/tcp_states.h>
24 #include <net/protocol.h>
25 #include <net/xfrm.h>
26 #include <net/net_namespace.h>
27 #include <net/netns/generic.h>
28 #include <linux/ip.h>
29 #include <linux/ipv6.h>
30 #include <linux/udp.h>
31 
32 #include "l2tp_core.h"
33 
34 /* Default device name. May be overridden by name specified by user */
35 #define L2TP_ETH_DEV_NAME	"l2tpeth%d"
36 
37 /* via netdev_priv() */
38 struct l2tp_eth {
39 	struct l2tp_session	*session;
40 	atomic_long_t		tx_bytes;
41 	atomic_long_t		tx_packets;
42 	atomic_long_t		tx_dropped;
43 	atomic_long_t		rx_bytes;
44 	atomic_long_t		rx_packets;
45 	atomic_long_t		rx_errors;
46 };
47 
48 /* via l2tp_session_priv() */
49 struct l2tp_eth_sess {
50 	struct net_device __rcu *dev;
51 };
52 
l2tp_eth_dev_init(struct net_device * dev)53 static int l2tp_eth_dev_init(struct net_device *dev)
54 {
55 	eth_hw_addr_random(dev);
56 	eth_broadcast_addr(dev->broadcast);
57 	netdev_lockdep_set_classes(dev);
58 
59 	return 0;
60 }
61 
l2tp_eth_dev_uninit(struct net_device * dev)62 static void l2tp_eth_dev_uninit(struct net_device *dev)
63 {
64 	struct l2tp_eth *priv = netdev_priv(dev);
65 	struct l2tp_eth_sess *spriv;
66 
67 	spriv = l2tp_session_priv(priv->session);
68 	RCU_INIT_POINTER(spriv->dev, NULL);
69 	/* No need for synchronize_net() here. We're called by
70 	 * unregister_netdev*(), which does the synchronisation for us.
71 	 */
72 }
73 
l2tp_eth_dev_xmit(struct sk_buff * skb,struct net_device * dev)74 static netdev_tx_t l2tp_eth_dev_xmit(struct sk_buff *skb, struct net_device *dev)
75 {
76 	struct l2tp_eth *priv = netdev_priv(dev);
77 	struct l2tp_session *session = priv->session;
78 	unsigned int len = skb->len;
79 	int ret = l2tp_xmit_skb(session, skb);
80 
81 	if (likely(ret == NET_XMIT_SUCCESS)) {
82 		atomic_long_add(len, &priv->tx_bytes);
83 		atomic_long_inc(&priv->tx_packets);
84 	} else {
85 		atomic_long_inc(&priv->tx_dropped);
86 	}
87 	return NETDEV_TX_OK;
88 }
89 
l2tp_eth_get_stats64(struct net_device * dev,struct rtnl_link_stats64 * stats)90 static void l2tp_eth_get_stats64(struct net_device *dev,
91 				 struct rtnl_link_stats64 *stats)
92 {
93 	struct l2tp_eth *priv = netdev_priv(dev);
94 
95 	stats->tx_bytes   = (unsigned long)atomic_long_read(&priv->tx_bytes);
96 	stats->tx_packets = (unsigned long)atomic_long_read(&priv->tx_packets);
97 	stats->tx_dropped = (unsigned long)atomic_long_read(&priv->tx_dropped);
98 	stats->rx_bytes   = (unsigned long)atomic_long_read(&priv->rx_bytes);
99 	stats->rx_packets = (unsigned long)atomic_long_read(&priv->rx_packets);
100 	stats->rx_errors  = (unsigned long)atomic_long_read(&priv->rx_errors);
101 }
102 
103 static const struct net_device_ops l2tp_eth_netdev_ops = {
104 	.ndo_init		= l2tp_eth_dev_init,
105 	.ndo_uninit		= l2tp_eth_dev_uninit,
106 	.ndo_start_xmit		= l2tp_eth_dev_xmit,
107 	.ndo_get_stats64	= l2tp_eth_get_stats64,
108 	.ndo_set_mac_address	= eth_mac_addr,
109 };
110 
111 static struct device_type l2tpeth_type = {
112 	.name = "l2tpeth",
113 };
114 
l2tp_eth_dev_setup(struct net_device * dev)115 static void l2tp_eth_dev_setup(struct net_device *dev)
116 {
117 	SET_NETDEV_DEVTYPE(dev, &l2tpeth_type);
118 	ether_setup(dev);
119 	dev->priv_flags		&= ~IFF_TX_SKB_SHARING;
120 	dev->features		|= NETIF_F_LLTX;
121 	dev->netdev_ops		= &l2tp_eth_netdev_ops;
122 	dev->needs_free_netdev	= true;
123 }
124 
l2tp_eth_dev_recv(struct l2tp_session * session,struct sk_buff * skb,int data_len)125 static void l2tp_eth_dev_recv(struct l2tp_session *session, struct sk_buff *skb, int data_len)
126 {
127 	struct l2tp_eth_sess *spriv = l2tp_session_priv(session);
128 	struct net_device *dev;
129 	struct l2tp_eth *priv;
130 
131 	if (!pskb_may_pull(skb, ETH_HLEN))
132 		goto error;
133 
134 	secpath_reset(skb);
135 
136 	/* checksums verified by L2TP */
137 	skb->ip_summed = CHECKSUM_NONE;
138 
139 	/* drop outer flow-hash */
140 	skb_clear_hash(skb);
141 
142 	skb_dst_drop(skb);
143 	nf_reset_ct(skb);
144 
145 	rcu_read_lock();
146 	dev = rcu_dereference(spriv->dev);
147 	if (!dev)
148 		goto error_rcu;
149 
150 	priv = netdev_priv(dev);
151 	if (dev_forward_skb(dev, skb) == NET_RX_SUCCESS) {
152 		atomic_long_inc(&priv->rx_packets);
153 		atomic_long_add(data_len, &priv->rx_bytes);
154 	} else {
155 		atomic_long_inc(&priv->rx_errors);
156 	}
157 	rcu_read_unlock();
158 
159 	return;
160 
161 error_rcu:
162 	rcu_read_unlock();
163 error:
164 	kfree_skb(skb);
165 }
166 
l2tp_eth_delete(struct l2tp_session * session)167 static void l2tp_eth_delete(struct l2tp_session *session)
168 {
169 	struct l2tp_eth_sess *spriv;
170 	struct net_device *dev;
171 
172 	if (session) {
173 		spriv = l2tp_session_priv(session);
174 
175 		rtnl_lock();
176 		dev = rtnl_dereference(spriv->dev);
177 		if (dev) {
178 			unregister_netdevice(dev);
179 			rtnl_unlock();
180 			module_put(THIS_MODULE);
181 		} else {
182 			rtnl_unlock();
183 		}
184 	}
185 }
186 
l2tp_eth_show(struct seq_file * m,void * arg)187 static void l2tp_eth_show(struct seq_file *m, void *arg)
188 {
189 	struct l2tp_session *session = arg;
190 	struct l2tp_eth_sess *spriv = l2tp_session_priv(session);
191 	struct net_device *dev;
192 
193 	rcu_read_lock();
194 	dev = rcu_dereference(spriv->dev);
195 	if (!dev) {
196 		rcu_read_unlock();
197 		return;
198 	}
199 	dev_hold(dev);
200 	rcu_read_unlock();
201 
202 	seq_printf(m, "   interface %s\n", dev->name);
203 
204 	dev_put(dev);
205 }
206 
l2tp_eth_adjust_mtu(struct l2tp_tunnel * tunnel,struct l2tp_session * session,struct net_device * dev)207 static void l2tp_eth_adjust_mtu(struct l2tp_tunnel *tunnel,
208 				struct l2tp_session *session,
209 				struct net_device *dev)
210 {
211 	unsigned int overhead = 0;
212 	u32 l3_overhead = 0;
213 	u32 mtu;
214 
215 	/* if the encap is UDP, account for UDP header size */
216 	if (tunnel->encap == L2TP_ENCAPTYPE_UDP) {
217 		overhead += sizeof(struct udphdr);
218 		dev->needed_headroom += sizeof(struct udphdr);
219 	}
220 
221 	lock_sock(tunnel->sock);
222 	l3_overhead = kernel_sock_ip_overhead(tunnel->sock);
223 	release_sock(tunnel->sock);
224 
225 	if (l3_overhead == 0) {
226 		/* L3 Overhead couldn't be identified, this could be
227 		 * because tunnel->sock was NULL or the socket's
228 		 * address family was not IPv4 or IPv6,
229 		 * dev mtu stays at 1500.
230 		 */
231 		return;
232 	}
233 	/* Adjust MTU, factor overhead - underlay L3, overlay L2 hdr
234 	 * UDP overhead, if any, was already factored in above.
235 	 */
236 	overhead += session->hdr_len + ETH_HLEN + l3_overhead;
237 
238 	mtu = l2tp_tunnel_dst_mtu(tunnel) - overhead;
239 	if (mtu < dev->min_mtu || mtu > dev->max_mtu)
240 		dev->mtu = ETH_DATA_LEN - overhead;
241 	else
242 		dev->mtu = mtu;
243 
244 	dev->needed_headroom += session->hdr_len;
245 }
246 
l2tp_eth_create(struct net * net,struct l2tp_tunnel * tunnel,u32 session_id,u32 peer_session_id,struct l2tp_session_cfg * cfg)247 static int l2tp_eth_create(struct net *net, struct l2tp_tunnel *tunnel,
248 			   u32 session_id, u32 peer_session_id,
249 			   struct l2tp_session_cfg *cfg)
250 {
251 	unsigned char name_assign_type;
252 	struct net_device *dev;
253 	char name[IFNAMSIZ];
254 	struct l2tp_session *session;
255 	struct l2tp_eth *priv;
256 	struct l2tp_eth_sess *spriv;
257 	int rc;
258 
259 	if (cfg->ifname) {
260 		strscpy(name, cfg->ifname, IFNAMSIZ);
261 		name_assign_type = NET_NAME_USER;
262 	} else {
263 		strcpy(name, L2TP_ETH_DEV_NAME);
264 		name_assign_type = NET_NAME_ENUM;
265 	}
266 
267 	session = l2tp_session_create(sizeof(*spriv), tunnel, session_id,
268 				      peer_session_id, cfg);
269 	if (IS_ERR(session)) {
270 		rc = PTR_ERR(session);
271 		goto err;
272 	}
273 
274 	dev = alloc_netdev(sizeof(*priv), name, name_assign_type,
275 			   l2tp_eth_dev_setup);
276 	if (!dev) {
277 		rc = -ENOMEM;
278 		goto err_sess;
279 	}
280 
281 	dev_net_set(dev, net);
282 	dev->min_mtu = 0;
283 	dev->max_mtu = ETH_MAX_MTU;
284 	l2tp_eth_adjust_mtu(tunnel, session, dev);
285 
286 	priv = netdev_priv(dev);
287 	priv->session = session;
288 
289 	session->recv_skb = l2tp_eth_dev_recv;
290 	session->session_close = l2tp_eth_delete;
291 	if (IS_ENABLED(CONFIG_L2TP_DEBUGFS))
292 		session->show = l2tp_eth_show;
293 
294 	spriv = l2tp_session_priv(session);
295 
296 	l2tp_session_inc_refcount(session);
297 
298 	rtnl_lock();
299 
300 	/* Register both device and session while holding the rtnl lock. This
301 	 * ensures that l2tp_eth_delete() will see that there's a device to
302 	 * unregister, even if it happened to run before we assign spriv->dev.
303 	 */
304 	rc = l2tp_session_register(session, tunnel);
305 	if (rc < 0) {
306 		rtnl_unlock();
307 		goto err_sess_dev;
308 	}
309 
310 	rc = register_netdevice(dev);
311 	if (rc < 0) {
312 		rtnl_unlock();
313 		l2tp_session_delete(session);
314 		l2tp_session_dec_refcount(session);
315 		free_netdev(dev);
316 
317 		return rc;
318 	}
319 
320 	strscpy(session->ifname, dev->name, IFNAMSIZ);
321 	rcu_assign_pointer(spriv->dev, dev);
322 
323 	rtnl_unlock();
324 
325 	l2tp_session_dec_refcount(session);
326 
327 	__module_get(THIS_MODULE);
328 
329 	return 0;
330 
331 err_sess_dev:
332 	l2tp_session_dec_refcount(session);
333 	free_netdev(dev);
334 err_sess:
335 	kfree(session);
336 err:
337 	return rc;
338 }
339 
340 static const struct l2tp_nl_cmd_ops l2tp_eth_nl_cmd_ops = {
341 	.session_create	= l2tp_eth_create,
342 	.session_delete	= l2tp_session_delete,
343 };
344 
l2tp_eth_init(void)345 static int __init l2tp_eth_init(void)
346 {
347 	int err = 0;
348 
349 	err = l2tp_nl_register_ops(L2TP_PWTYPE_ETH, &l2tp_eth_nl_cmd_ops);
350 	if (err)
351 		goto err;
352 
353 	pr_info("L2TP ethernet pseudowire support (L2TPv3)\n");
354 
355 	return 0;
356 
357 err:
358 	return err;
359 }
360 
l2tp_eth_exit(void)361 static void __exit l2tp_eth_exit(void)
362 {
363 	l2tp_nl_unregister_ops(L2TP_PWTYPE_ETH);
364 }
365 
366 module_init(l2tp_eth_init);
367 module_exit(l2tp_eth_exit);
368 
369 MODULE_LICENSE("GPL");
370 MODULE_AUTHOR("James Chapman <jchapman@katalix.com>");
371 MODULE_DESCRIPTION("L2TP ethernet pseudowire driver");
372 MODULE_VERSION("1.0");
373 MODULE_ALIAS_L2TP_PWTYPE(5);
374