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Linux/net/l2tp/l2tp_eth.c

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  1 /*
  2  * L2TPv3 ethernet pseudowire driver
  3  *
  4  * Copyright (c) 2008,2009,2010 Katalix Systems Ltd
  5  *
  6  *      This program is free software; you can redistribute it and/or
  7  *      modify it under the terms of the GNU General Public License
  8  *      as published by the Free Software Foundation; either version
  9  *      2 of the License, or (at your option) any later version.
 10  */
 11 
 12 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
 13 
 14 #include <linux/module.h>
 15 #include <linux/skbuff.h>
 16 #include <linux/socket.h>
 17 #include <linux/hash.h>
 18 #include <linux/l2tp.h>
 19 #include <linux/in.h>
 20 #include <linux/etherdevice.h>
 21 #include <linux/spinlock.h>
 22 #include <net/sock.h>
 23 #include <net/ip.h>
 24 #include <net/icmp.h>
 25 #include <net/udp.h>
 26 #include <net/inet_common.h>
 27 #include <net/inet_hashtables.h>
 28 #include <net/tcp_states.h>
 29 #include <net/protocol.h>
 30 #include <net/xfrm.h>
 31 #include <net/net_namespace.h>
 32 #include <net/netns/generic.h>
 33 #include <linux/ip.h>
 34 #include <linux/ipv6.h>
 35 #include <linux/udp.h>
 36 
 37 #include "l2tp_core.h"
 38 
 39 /* Default device name. May be overridden by name specified by user */
 40 #define L2TP_ETH_DEV_NAME       "l2tpeth%d"
 41 
 42 /* via netdev_priv() */
 43 struct l2tp_eth {
 44         struct l2tp_session     *session;
 45         atomic_long_t           tx_bytes;
 46         atomic_long_t           tx_packets;
 47         atomic_long_t           tx_dropped;
 48         atomic_long_t           rx_bytes;
 49         atomic_long_t           rx_packets;
 50         atomic_long_t           rx_errors;
 51 };
 52 
 53 /* via l2tp_session_priv() */
 54 struct l2tp_eth_sess {
 55         struct net_device __rcu *dev;
 56 };
 57 
 58 
 59 static int l2tp_eth_dev_init(struct net_device *dev)
 60 {
 61         eth_hw_addr_random(dev);
 62         eth_broadcast_addr(dev->broadcast);
 63         netdev_lockdep_set_classes(dev);
 64 
 65         return 0;
 66 }
 67 
 68 static void l2tp_eth_dev_uninit(struct net_device *dev)
 69 {
 70         struct l2tp_eth *priv = netdev_priv(dev);
 71         struct l2tp_eth_sess *spriv;
 72 
 73         spriv = l2tp_session_priv(priv->session);
 74         RCU_INIT_POINTER(spriv->dev, NULL);
 75         /* No need for synchronize_net() here. We're called by
 76          * unregister_netdev*(), which does the synchronisation for us.
 77          */
 78 }
 79 
 80 static int l2tp_eth_dev_xmit(struct sk_buff *skb, struct net_device *dev)
 81 {
 82         struct l2tp_eth *priv = netdev_priv(dev);
 83         struct l2tp_session *session = priv->session;
 84         unsigned int len = skb->len;
 85         int ret = l2tp_xmit_skb(session, skb, session->hdr_len);
 86 
 87         if (likely(ret == NET_XMIT_SUCCESS)) {
 88                 atomic_long_add(len, &priv->tx_bytes);
 89                 atomic_long_inc(&priv->tx_packets);
 90         } else {
 91                 atomic_long_inc(&priv->tx_dropped);
 92         }
 93         return NETDEV_TX_OK;
 94 }
 95 
 96 static void l2tp_eth_get_stats64(struct net_device *dev,
 97                                  struct rtnl_link_stats64 *stats)
 98 {
 99         struct l2tp_eth *priv = netdev_priv(dev);
100 
101         stats->tx_bytes   = (unsigned long) atomic_long_read(&priv->tx_bytes);
102         stats->tx_packets = (unsigned long) atomic_long_read(&priv->tx_packets);
103         stats->tx_dropped = (unsigned long) atomic_long_read(&priv->tx_dropped);
104         stats->rx_bytes   = (unsigned long) atomic_long_read(&priv->rx_bytes);
105         stats->rx_packets = (unsigned long) atomic_long_read(&priv->rx_packets);
106         stats->rx_errors  = (unsigned long) atomic_long_read(&priv->rx_errors);
107 
108 }
109 
110 static const struct net_device_ops l2tp_eth_netdev_ops = {
111         .ndo_init               = l2tp_eth_dev_init,
112         .ndo_uninit             = l2tp_eth_dev_uninit,
113         .ndo_start_xmit         = l2tp_eth_dev_xmit,
114         .ndo_get_stats64        = l2tp_eth_get_stats64,
115         .ndo_set_mac_address    = eth_mac_addr,
116 };
117 
118 static struct device_type l2tpeth_type = {
119         .name = "l2tpeth",
120 };
121 
122 static void l2tp_eth_dev_setup(struct net_device *dev)
123 {
124         SET_NETDEV_DEVTYPE(dev, &l2tpeth_type);
125         ether_setup(dev);
126         dev->priv_flags         &= ~IFF_TX_SKB_SHARING;
127         dev->features           |= NETIF_F_LLTX;
128         dev->netdev_ops         = &l2tp_eth_netdev_ops;
129         dev->needs_free_netdev  = true;
130 }
131 
132 static void l2tp_eth_dev_recv(struct l2tp_session *session, struct sk_buff *skb, int data_len)
133 {
134         struct l2tp_eth_sess *spriv = l2tp_session_priv(session);
135         struct net_device *dev;
136         struct l2tp_eth *priv;
137 
138         if (session->debug & L2TP_MSG_DATA) {
139                 unsigned int length;
140 
141                 length = min(32u, skb->len);
142                 if (!pskb_may_pull(skb, length))
143                         goto error;
144 
145                 pr_debug("%s: eth recv\n", session->name);
146                 print_hex_dump_bytes("", DUMP_PREFIX_OFFSET, skb->data, length);
147         }
148 
149         if (!pskb_may_pull(skb, ETH_HLEN))
150                 goto error;
151 
152         secpath_reset(skb);
153 
154         /* checksums verified by L2TP */
155         skb->ip_summed = CHECKSUM_NONE;
156 
157         skb_dst_drop(skb);
158         nf_reset(skb);
159 
160         rcu_read_lock();
161         dev = rcu_dereference(spriv->dev);
162         if (!dev)
163                 goto error_rcu;
164 
165         priv = netdev_priv(dev);
166         if (dev_forward_skb(dev, skb) == NET_RX_SUCCESS) {
167                 atomic_long_inc(&priv->rx_packets);
168                 atomic_long_add(data_len, &priv->rx_bytes);
169         } else {
170                 atomic_long_inc(&priv->rx_errors);
171         }
172         rcu_read_unlock();
173 
174         return;
175 
176 error_rcu:
177         rcu_read_unlock();
178 error:
179         kfree_skb(skb);
180 }
181 
182 static void l2tp_eth_delete(struct l2tp_session *session)
183 {
184         struct l2tp_eth_sess *spriv;
185         struct net_device *dev;
186 
187         if (session) {
188                 spriv = l2tp_session_priv(session);
189 
190                 rtnl_lock();
191                 dev = rtnl_dereference(spriv->dev);
192                 if (dev) {
193                         unregister_netdevice(dev);
194                         rtnl_unlock();
195                         module_put(THIS_MODULE);
196                 } else {
197                         rtnl_unlock();
198                 }
199         }
200 }
201 
202 #if IS_ENABLED(CONFIG_L2TP_DEBUGFS)
203 static void l2tp_eth_show(struct seq_file *m, void *arg)
204 {
205         struct l2tp_session *session = arg;
206         struct l2tp_eth_sess *spriv = l2tp_session_priv(session);
207         struct net_device *dev;
208 
209         rcu_read_lock();
210         dev = rcu_dereference(spriv->dev);
211         if (!dev) {
212                 rcu_read_unlock();
213                 return;
214         }
215         dev_hold(dev);
216         rcu_read_unlock();
217 
218         seq_printf(m, "   interface %s\n", dev->name);
219 
220         dev_put(dev);
221 }
222 #endif
223 
224 static void l2tp_eth_adjust_mtu(struct l2tp_tunnel *tunnel,
225                                 struct l2tp_session *session,
226                                 struct net_device *dev)
227 {
228         unsigned int overhead = 0;
229         struct dst_entry *dst;
230         u32 l3_overhead = 0;
231 
232         /* if the encap is UDP, account for UDP header size */
233         if (tunnel->encap == L2TP_ENCAPTYPE_UDP) {
234                 overhead += sizeof(struct udphdr);
235                 dev->needed_headroom += sizeof(struct udphdr);
236         }
237         if (session->mtu != 0) {
238                 dev->mtu = session->mtu;
239                 dev->needed_headroom += session->hdr_len;
240                 return;
241         }
242         lock_sock(tunnel->sock);
243         l3_overhead = kernel_sock_ip_overhead(tunnel->sock);
244         release_sock(tunnel->sock);
245         if (l3_overhead == 0) {
246                 /* L3 Overhead couldn't be identified, this could be
247                  * because tunnel->sock was NULL or the socket's
248                  * address family was not IPv4 or IPv6,
249                  * dev mtu stays at 1500.
250                  */
251                 return;
252         }
253         /* Adjust MTU, factor overhead - underlay L3, overlay L2 hdr
254          * UDP overhead, if any, was already factored in above.
255          */
256         overhead += session->hdr_len + ETH_HLEN + l3_overhead;
257 
258         /* If PMTU discovery was enabled, use discovered MTU on L2TP device */
259         dst = sk_dst_get(tunnel->sock);
260         if (dst) {
261                 /* dst_mtu will use PMTU if found, else fallback to intf MTU */
262                 u32 pmtu = dst_mtu(dst);
263 
264                 if (pmtu != 0)
265                         dev->mtu = pmtu;
266                 dst_release(dst);
267         }
268         session->mtu = dev->mtu - overhead;
269         dev->mtu = session->mtu;
270         dev->needed_headroom += session->hdr_len;
271 }
272 
273 static int l2tp_eth_create(struct net *net, struct l2tp_tunnel *tunnel,
274                            u32 session_id, u32 peer_session_id,
275                            struct l2tp_session_cfg *cfg)
276 {
277         unsigned char name_assign_type;
278         struct net_device *dev;
279         char name[IFNAMSIZ];
280         struct l2tp_session *session;
281         struct l2tp_eth *priv;
282         struct l2tp_eth_sess *spriv;
283         int rc;
284 
285         if (cfg->ifname) {
286                 strlcpy(name, cfg->ifname, IFNAMSIZ);
287                 name_assign_type = NET_NAME_USER;
288         } else {
289                 strcpy(name, L2TP_ETH_DEV_NAME);
290                 name_assign_type = NET_NAME_ENUM;
291         }
292 
293         session = l2tp_session_create(sizeof(*spriv), tunnel, session_id,
294                                       peer_session_id, cfg);
295         if (IS_ERR(session)) {
296                 rc = PTR_ERR(session);
297                 goto err;
298         }
299 
300         dev = alloc_netdev(sizeof(*priv), name, name_assign_type,
301                            l2tp_eth_dev_setup);
302         if (!dev) {
303                 rc = -ENOMEM;
304                 goto err_sess;
305         }
306 
307         dev_net_set(dev, net);
308         dev->min_mtu = 0;
309         dev->max_mtu = ETH_MAX_MTU;
310         l2tp_eth_adjust_mtu(tunnel, session, dev);
311 
312         priv = netdev_priv(dev);
313         priv->session = session;
314 
315         session->recv_skb = l2tp_eth_dev_recv;
316         session->session_close = l2tp_eth_delete;
317 #if IS_ENABLED(CONFIG_L2TP_DEBUGFS)
318         session->show = l2tp_eth_show;
319 #endif
320 
321         spriv = l2tp_session_priv(session);
322 
323         l2tp_session_inc_refcount(session);
324 
325         rtnl_lock();
326 
327         /* Register both device and session while holding the rtnl lock. This
328          * ensures that l2tp_eth_delete() will see that there's a device to
329          * unregister, even if it happened to run before we assign spriv->dev.
330          */
331         rc = l2tp_session_register(session, tunnel);
332         if (rc < 0) {
333                 rtnl_unlock();
334                 goto err_sess_dev;
335         }
336 
337         rc = register_netdevice(dev);
338         if (rc < 0) {
339                 rtnl_unlock();
340                 l2tp_session_delete(session);
341                 l2tp_session_dec_refcount(session);
342                 free_netdev(dev);
343 
344                 return rc;
345         }
346 
347         strlcpy(session->ifname, dev->name, IFNAMSIZ);
348         rcu_assign_pointer(spriv->dev, dev);
349 
350         rtnl_unlock();
351 
352         l2tp_session_dec_refcount(session);
353 
354         __module_get(THIS_MODULE);
355 
356         return 0;
357 
358 err_sess_dev:
359         l2tp_session_dec_refcount(session);
360         free_netdev(dev);
361 err_sess:
362         kfree(session);
363 err:
364         return rc;
365 }
366 
367 
368 static const struct l2tp_nl_cmd_ops l2tp_eth_nl_cmd_ops = {
369         .session_create = l2tp_eth_create,
370         .session_delete = l2tp_session_delete,
371 };
372 
373 
374 static int __init l2tp_eth_init(void)
375 {
376         int err = 0;
377 
378         err = l2tp_nl_register_ops(L2TP_PWTYPE_ETH, &l2tp_eth_nl_cmd_ops);
379         if (err)
380                 goto err;
381 
382         pr_info("L2TP ethernet pseudowire support (L2TPv3)\n");
383 
384         return 0;
385 
386 err:
387         return err;
388 }
389 
390 static void __exit l2tp_eth_exit(void)
391 {
392         l2tp_nl_unregister_ops(L2TP_PWTYPE_ETH);
393 }
394 
395 module_init(l2tp_eth_init);
396 module_exit(l2tp_eth_exit);
397 
398 MODULE_LICENSE("GPL");
399 MODULE_AUTHOR("James Chapman <jchapman@katalix.com>");
400 MODULE_DESCRIPTION("L2TP ethernet pseudowire driver");
401 MODULE_VERSION("1.0");
402 MODULE_ALIAS_L2TP_PWTYPE(5);
403 

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