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() */
  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 static int l2tp_eth_dev_init(struct net_device *dev)
  55 {
  56         eth_hw_addr_random(dev);
  57         eth_broadcast_addr(dev->broadcast);
  58         netdev_lockdep_set_classes(dev);
  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 netdev_tx_t 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 static const struct net_device_ops l2tp_eth_netdev_ops = {
 105         .ndo_init               = l2tp_eth_dev_init,
 106         .ndo_uninit             = l2tp_eth_dev_uninit,
 107         .ndo_start_xmit         = l2tp_eth_dev_xmit,
 108         .ndo_get_stats64        = l2tp_eth_get_stats64,
 109         .ndo_set_mac_address    = eth_mac_addr,
 110 };
 111
 112 static struct device_type l2tpeth_type = {
 113         .name = "l2tpeth",
 114 };
 115
 116 static void l2tp_eth_dev_setup(struct net_device *dev)
 117 {
 118         SET_NETDEV_DEVTYPE(dev, &l2tpeth_type);
 119         ether_setup(dev);
 120         dev->priv_flags         &= ~IFF_TX_SKB_SHARING;
 121         dev->features           |= NETIF_F_LLTX;
 122         dev->netdev_ops         = &l2tp_eth_netdev_ops;
 123         dev->needs_free_netdev  = true;
 124 }
 125
 126 static void l2tp_eth_dev_recv(struct l2tp_session *session, struct sk_buff *skb, int data_len)
 127 {
 128         struct l2tp_eth_sess *spriv = l2tp_session_priv(session);
 129         struct net_device *dev;
 130         struct l2tp_eth *priv;
 131
 132         if (session->debug & L2TP_MSG_DATA) {
 133                 unsigned int length;
 134
 135                 length = min(32u, skb->len);
 136                 if (!pskb_may_pull(skb, length))
 137                         goto error;
 138
 139                 pr_debug("%s: eth recv\n", session->name);
 140                 print_hex_dump_bytes("", DUMP_PREFIX_OFFSET, skb->data, length);
 141         }
 142
 143         if (!pskb_may_pull(skb, ETH_HLEN))
 144                 goto error;
 145
 146         secpath_reset(skb);
 147
 148         /* checksums verified by L2TP */
 149         skb->ip_summed = CHECKSUM_NONE;
 150
 151         skb_dst_drop(skb);
 152         nf_reset_ct(skb);
 153
 154         rcu_read_lock();
 155         dev = rcu_dereference(spriv->dev);
 156         if (!dev)
 157                 goto error_rcu;
 158
 159         priv = netdev_priv(dev);
 160         if (dev_forward_skb(dev, skb) == NET_RX_SUCCESS) {
 161                 atomic_long_inc(&priv->rx_packets);
 162                 atomic_long_add(data_len, &priv->rx_bytes);
 163         } else {
 164                 atomic_long_inc(&priv->rx_errors);
 165         }
 166         rcu_read_unlock();
 167
 168         return;
 169
 170 error_rcu:
 171         rcu_read_unlock();
 172 error:
 173         kfree_skb(skb);
 174 }
 175
 176 static void l2tp_eth_delete(struct l2tp_session *session)
 177 {
 178         struct l2tp_eth_sess *spriv;
 179         struct net_device *dev;
 180
 181         if (session) {
 182                 spriv = l2tp_session_priv(session);
 183
 184                 rtnl_lock();
 185                 dev = rtnl_dereference(spriv->dev);
 186                 if (dev) {
 187                         unregister_netdevice(dev);
 188                         rtnl_unlock();
 189                         module_put(THIS_MODULE);
 190                 } else {
 191                         rtnl_unlock();
 192                 }
 193         }
 194 }
 195
 196 static void l2tp_eth_show(struct seq_file *m, void *arg)
 197 {
 198         struct l2tp_session *session = arg;
 199         struct l2tp_eth_sess *spriv = l2tp_session_priv(session);
 200         struct net_device *dev;
 201
 202         rcu_read_lock();
 203         dev = rcu_dereference(spriv->dev);
 204         if (!dev) {
 205                 rcu_read_unlock();
 206                 return;
 207         }
 208         dev_hold(dev);
 209         rcu_read_unlock();
 210
 211         seq_printf(m, "   interface %s\n", dev->name);
 212
 213         dev_put(dev);
 214 }
 215
 216 static void l2tp_eth_adjust_mtu(struct l2tp_tunnel *tunnel,
 217                                 struct l2tp_session *session,
 218                                 struct net_device *dev)
 219 {
 220         unsigned int overhead = 0;
 221         u32 l3_overhead = 0;
 222         u32 mtu;
 223
 224         /* if the encap is UDP, account for UDP header size */
 225         if (tunnel->encap == L2TP_ENCAPTYPE_UDP) {
 226                 overhead += sizeof(struct udphdr);
 227                 dev->needed_headroom += sizeof(struct udphdr);
 228         }
 229
 230         lock_sock(tunnel->sock);
 231         l3_overhead = kernel_sock_ip_overhead(tunnel->sock);
 232         release_sock(tunnel->sock);
 233
 234         if (l3_overhead == 0) {
 235                 /* L3 Overhead couldn't be identified, this could be
 236                  * because tunnel->sock was NULL or the socket's
 237                  * address family was not IPv4 or IPv6,
 238                  * dev mtu stays at 1500.
 239                  */
 240                 return;
 241         }
 242         /* Adjust MTU, factor overhead - underlay L3, overlay L2 hdr
 243          * UDP overhead, if any, was already factored in above.
 244          */
 245         overhead += session->hdr_len + ETH_HLEN + l3_overhead;
 246
 247         mtu = l2tp_tunnel_dst_mtu(tunnel) - overhead;
 248         if (mtu < dev->min_mtu || mtu > dev->max_mtu)
 249                 dev->mtu = ETH_DATA_LEN - overhead;
 250         else
 251                 dev->mtu = mtu;
 252
 253         dev->needed_headroom += session->hdr_len;
 254 }
 255
 256 static int l2tp_eth_create(struct net *net, struct l2tp_tunnel *tunnel,
 257                            u32 session_id, u32 peer_session_id,
 258                            struct l2tp_session_cfg *cfg)
 259 {
 260         unsigned char name_assign_type;
 261         struct net_device *dev;
 262         char name[IFNAMSIZ];
 263         struct l2tp_session *session;
 264         struct l2tp_eth *priv;
 265         struct l2tp_eth_sess *spriv;
 266         int rc;
 267
 268         if (cfg->ifname) {
 269                 strlcpy(name, cfg->ifname, IFNAMSIZ);
 270                 name_assign_type = NET_NAME_USER;
 271         } else {
 272                 strcpy(name, L2TP_ETH_DEV_NAME);
 273                 name_assign_type = NET_NAME_ENUM;
 274         }
 275
 276         session = l2tp_session_create(sizeof(*spriv), tunnel, session_id,
 277                                       peer_session_id, cfg);
 278         if (IS_ERR(session)) {
 279                 rc = PTR_ERR(session);
 280                 goto err;
 281         }
 282
 283         dev = alloc_netdev(sizeof(*priv), name, name_assign_type,
 284                            l2tp_eth_dev_setup);
 285         if (!dev) {
 286                 rc = -ENOMEM;
 287                 goto err_sess;
 288         }
 289
 290         dev_net_set(dev, net);
 291         dev->min_mtu = 0;
 292         dev->max_mtu = ETH_MAX_MTU;
 293         l2tp_eth_adjust_mtu(tunnel, session, dev);
 294
 295         priv = netdev_priv(dev);
 296         priv->session = session;
 297
 298         session->recv_skb = l2tp_eth_dev_recv;
 299         session->session_close = l2tp_eth_delete;
 300         if (IS_ENABLED(CONFIG_L2TP_DEBUGFS))
 301                 session->show = l2tp_eth_show;
 302
 303         spriv = l2tp_session_priv(session);
 304
 305         l2tp_session_inc_refcount(session);
 306
 307         rtnl_lock();
 308
 309         /* Register both device and session while holding the rtnl lock. This
 310          * ensures that l2tp_eth_delete() will see that there's a device to
 311          * unregister, even if it happened to run before we assign spriv->dev.
 312          */
 313         rc = l2tp_session_register(session, tunnel);
 314         if (rc < 0) {
 315                 rtnl_unlock();
 316                 goto err_sess_dev;
 317         }
 318
 319         rc = register_netdevice(dev);
 320         if (rc < 0) {
 321                 rtnl_unlock();
 322                 l2tp_session_delete(session);
 323                 l2tp_session_dec_refcount(session);
 324                 free_netdev(dev);
 325
 326                 return rc;
 327         }
 328
 329         strlcpy(session->ifname, dev->name, IFNAMSIZ);
 330         rcu_assign_pointer(spriv->dev, dev);
 331
 332         rtnl_unlock();
 333
 334         l2tp_session_dec_refcount(session);
 335
 336         __module_get(THIS_MODULE);
 337
 338         return 0;
 339
 340 err_sess_dev:
 341         l2tp_session_dec_refcount(session);
 342         free_netdev(dev);
 343 err_sess:
 344         kfree(session);
 345 err:
 346         return rc;
 347 }
 348
 349 static const struct l2tp_nl_cmd_ops l2tp_eth_nl_cmd_ops = {
 350         .session_create = l2tp_eth_create,
 351         .session_delete = l2tp_session_delete,
 352 };
 353
 354 static int __init l2tp_eth_init(void)
 355 {
 356         int err = 0;
 357
 358         err = l2tp_nl_register_ops(L2TP_PWTYPE_ETH, &l2tp_eth_nl_cmd_ops);
 359         if (err)
 360                 goto err;
 361
 362         pr_info("L2TP ethernet pseudowire support (L2TPv3)\n");
 363
 364         return 0;
 365
 366 err:
 367         return err;
 368 }
 369
 370 static void __exit l2tp_eth_exit(void)
 371 {
 372         l2tp_nl_unregister_ops(L2TP_PWTYPE_ETH);
 373 }
 374
 375 module_init(l2tp_eth_init);
 376 module_exit(l2tp_eth_exit);
 377
 378 MODULE_LICENSE("GPL");
 379 MODULE_AUTHOR("James Chapman <jchapman@katalix.com>");
 380 MODULE_DESCRIPTION("L2TP ethernet pseudowire driver");
 381 MODULE_VERSION("1.0");
 382 MODULE_ALIAS_L2TP_PWTYPE(5);