net/l2tp/l2tp_eth.c

   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);