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Linux/net/l2tp/l2tp_eth.c

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  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() */
 39 struct 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() */
 50 struct l2tp_eth_sess {
 51         struct net_device __rcu *dev;
 52 };
 53 
 54 
 55 static 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 
 63 static 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 
 75 static 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 
 91 static 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 
105 static 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 
113 static struct device_type l2tpeth_type = {
114         .name = "l2tpeth",
115 };
116 
117 static 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 
127 static 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 
171 error_rcu:
172         rcu_read_unlock();
173 error:
174         kfree_skb(skb);
175 }
176 
177 static 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 
197 static 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 
217 static 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 
257 static 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 
341 err_sess_dev:
342         l2tp_session_dec_refcount(session);
343         free_netdev(dev);
344 err_sess:
345         kfree(session);
346 err:
347         return rc;
348 }
349 
350 
351 static 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 
357 static 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 
369 err:
370         return err;
371 }
372 
373 static void __exit l2tp_eth_exit(void)
374 {
375         l2tp_nl_unregister_ops(L2TP_PWTYPE_ETH);
376 }
377 
378 module_init(l2tp_eth_init);
379 module_exit(l2tp_eth_exit);
380 
381 MODULE_LICENSE("GPL");
382 MODULE_AUTHOR("James Chapman <jchapman@katalix.com>");
383 MODULE_DESCRIPTION("L2TP ethernet pseudowire driver");
384 MODULE_VERSION("1.0");
385 MODULE_ALIAS_L2TP_PWTYPE(5);
386 

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