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
  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         netdev_lockdep_set_classes(dev);
  60
  61         return 0;
  62 }
  63
  64 static void l2tp_eth_dev_uninit(struct net_device *dev)
  65 {
  66         struct l2tp_eth *priv = netdev_priv(dev);
  67         struct l2tp_eth_sess *spriv;
  68
  69         spriv = l2tp_session_priv(priv->session);
  70         RCU_INIT_POINTER(spriv->dev, NULL);
  71         /* No need for synchronize_net() here. We're called by
  72          * unregister_netdev*(), which does the synchronisation for us.
  73          */
  74 }
  75
  76 static int l2tp_eth_dev_xmit(struct sk_buff *skb, struct net_device *dev)
  77 {
  78         struct l2tp_eth *priv = netdev_priv(dev);
  79         struct l2tp_session *session = priv->session;
  80         unsigned int len = skb->len;
  81         int ret = l2tp_xmit_skb(session, skb, session->hdr_len);
  82
  83         if (likely(ret == NET_XMIT_SUCCESS)) {
  84                 atomic_long_add(len, &priv->tx_bytes);
  85                 atomic_long_inc(&priv->tx_packets);
  86         } else {
  87                 atomic_long_inc(&priv->tx_dropped);
  88         }
  89         return NETDEV_TX_OK;
  90 }
  91
  92 static void l2tp_eth_get_stats64(struct net_device *dev,
  93                                  struct rtnl_link_stats64 *stats)
  94 {
  95         struct l2tp_eth *priv = netdev_priv(dev);
  96
  97         stats->tx_bytes   = (unsigned long) atomic_long_read(&priv->tx_bytes);
  98         stats->tx_packets = (unsigned long) atomic_long_read(&priv->tx_packets);
  99         stats->tx_dropped = (unsigned long) atomic_long_read(&priv->tx_dropped);
 100         stats->rx_bytes   = (unsigned long) atomic_long_read(&priv->rx_bytes);
 101         stats->rx_packets = (unsigned long) atomic_long_read(&priv->rx_packets);
 102         stats->rx_errors  = (unsigned long) atomic_long_read(&priv->rx_errors);
 103
 104 }
 105
 106 static const struct net_device_ops l2tp_eth_netdev_ops = {
 107         .ndo_init               = l2tp_eth_dev_init,
 108         .ndo_uninit             = l2tp_eth_dev_uninit,
 109         .ndo_start_xmit         = l2tp_eth_dev_xmit,
 110         .ndo_get_stats64        = l2tp_eth_get_stats64,
 111         .ndo_set_mac_address    = eth_mac_addr,
 112 };
 113
 114 static struct device_type l2tpeth_type = {
 115         .name = "l2tpeth",
 116 };
 117
 118 static void l2tp_eth_dev_setup(struct net_device *dev)
 119 {
 120         SET_NETDEV_DEVTYPE(dev, &l2tpeth_type);
 121         ether_setup(dev);
 122         dev->priv_flags         &= ~IFF_TX_SKB_SHARING;
 123         dev->features           |= NETIF_F_LLTX;
 124         dev->netdev_ops         = &l2tp_eth_netdev_ops;
 125         dev->needs_free_netdev  = true;
 126 }
 127
 128 static void l2tp_eth_dev_recv(struct l2tp_session *session, struct sk_buff *skb, int data_len)
 129 {
 130         struct l2tp_eth_sess *spriv = l2tp_session_priv(session);
 131         struct net_device *dev;
 132         struct l2tp_eth *priv;
 133
 134         if (session->debug & L2TP_MSG_DATA) {
 135                 unsigned int length;
 136
 137                 length = min(32u, skb->len);
 138                 if (!pskb_may_pull(skb, length))
 139                         goto error;
 140
 141                 pr_debug("%s: eth recv\n", session->name);
 142                 print_hex_dump_bytes("", DUMP_PREFIX_OFFSET, skb->data, length);
 143         }
 144
 145         if (!pskb_may_pull(skb, ETH_HLEN))
 146                 goto error;
 147
 148         secpath_reset(skb);
 149
 150         /* checksums verified by L2TP */
 151         skb->ip_summed = CHECKSUM_NONE;
 152
 153         skb_dst_drop(skb);
 154         nf_reset(skb);
 155
 156         rcu_read_lock();
 157         dev = rcu_dereference(spriv->dev);
 158         if (!dev)
 159                 goto error_rcu;
 160
 161         priv = netdev_priv(dev);
 162         if (dev_forward_skb(dev, skb) == NET_RX_SUCCESS) {
 163                 atomic_long_inc(&priv->rx_packets);
 164                 atomic_long_add(data_len, &priv->rx_bytes);
 165         } else {
 166                 atomic_long_inc(&priv->rx_errors);
 167         }
 168         rcu_read_unlock();
 169
 170         return;
 171
 172 error_rcu:
 173         rcu_read_unlock();
 174 error:
 175         kfree_skb(skb);
 176 }
 177
 178 static void l2tp_eth_delete(struct l2tp_session *session)
 179 {
 180         struct l2tp_eth_sess *spriv;
 181         struct net_device *dev;
 182
 183         if (session) {
 184                 spriv = l2tp_session_priv(session);
 185
 186                 rtnl_lock();
 187                 dev = rtnl_dereference(spriv->dev);
 188                 if (dev) {
 189                         unregister_netdevice(dev);
 190                         rtnl_unlock();
 191                         module_put(THIS_MODULE);
 192                 } else {
 193                         rtnl_unlock();
 194                 }
 195         }
 196 }
 197
 198 static void l2tp_eth_show(struct seq_file *m, void *arg)
 199 {
 200         struct l2tp_session *session = arg;
 201         struct l2tp_eth_sess *spriv = l2tp_session_priv(session);
 202         struct net_device *dev;
 203
 204         rcu_read_lock();
 205         dev = rcu_dereference(spriv->dev);
 206         if (!dev) {
 207                 rcu_read_unlock();
 208                 return;
 209         }
 210         dev_hold(dev);
 211         rcu_read_unlock();
 212
 213         seq_printf(m, "   interface %s\n", dev->name);
 214
 215         dev_put(dev);
 216 }
 217
 218 static void l2tp_eth_adjust_mtu(struct l2tp_tunnel *tunnel,
 219                                 struct l2tp_session *session,
 220                                 struct net_device *dev)
 221 {
 222         unsigned int overhead = 0;
 223         u32 l3_overhead = 0;
 224         u32 mtu;
 225
 226         /* if the encap is UDP, account for UDP header size */
 227         if (tunnel->encap == L2TP_ENCAPTYPE_UDP) {
 228                 overhead += sizeof(struct udphdr);
 229                 dev->needed_headroom += sizeof(struct udphdr);
 230         }
 231
 232         lock_sock(tunnel->sock);
 233         l3_overhead = kernel_sock_ip_overhead(tunnel->sock);
 234         release_sock(tunnel->sock);
 235
 236         if (l3_overhead == 0) {
 237                 /* L3 Overhead couldn't be identified, this could be
 238                  * because tunnel->sock was NULL or the socket's
 239                  * address family was not IPv4 or IPv6,
 240                  * dev mtu stays at 1500.
 241                  */
 242                 return;
 243         }
 244         /* Adjust MTU, factor overhead - underlay L3, overlay L2 hdr
 245          * UDP overhead, if any, was already factored in above.
 246          */
 247         overhead += session->hdr_len + ETH_HLEN + l3_overhead;
 248
 249         mtu = l2tp_tunnel_dst_mtu(tunnel) - overhead;
 250         if (mtu < dev->min_mtu || mtu > dev->max_mtu)
 251                 dev->mtu = ETH_DATA_LEN - overhead;
 252         else
 253                 dev->mtu = mtu;
 254
 255         dev->needed_headroom += session->hdr_len;
 256 }
 257
 258 static int l2tp_eth_create(struct net *net, struct l2tp_tunnel *tunnel,
 259                            u32 session_id, u32 peer_session_id,
 260                            struct l2tp_session_cfg *cfg)
 261 {
 262         unsigned char name_assign_type;
 263         struct net_device *dev;
 264         char name[IFNAMSIZ];
 265         struct l2tp_session *session;
 266         struct l2tp_eth *priv;
 267         struct l2tp_eth_sess *spriv;
 268         int rc;
 269
 270         if (cfg->ifname) {
 271                 strlcpy(name, cfg->ifname, IFNAMSIZ);
 272                 name_assign_type = NET_NAME_USER;
 273         } else {
 274                 strcpy(name, L2TP_ETH_DEV_NAME);
 275                 name_assign_type = NET_NAME_ENUM;
 276         }
 277
 278         session = l2tp_session_create(sizeof(*spriv), tunnel, session_id,
 279                                       peer_session_id, cfg);
 280         if (IS_ERR(session)) {
 281                 rc = PTR_ERR(session);
 282                 goto err;
 283         }
 284
 285         dev = alloc_netdev(sizeof(*priv), name, name_assign_type,
 286                            l2tp_eth_dev_setup);
 287         if (!dev) {
 288                 rc = -ENOMEM;
 289                 goto err_sess;
 290         }
 291
 292         dev_net_set(dev, net);
 293         dev->min_mtu = 0;
 294         dev->max_mtu = ETH_MAX_MTU;
 295         l2tp_eth_adjust_mtu(tunnel, session, dev);
 296
 297         priv = netdev_priv(dev);
 298         priv->session = session;
 299
 300         session->recv_skb = l2tp_eth_dev_recv;
 301         session->session_close = l2tp_eth_delete;
 302         if (IS_ENABLED(CONFIG_L2TP_DEBUGFS))
 303                 session->show = l2tp_eth_show;
 304
 305         spriv = l2tp_session_priv(session);
 306
 307         l2tp_session_inc_refcount(session);
 308
 309         rtnl_lock();
 310
 311         /* Register both device and session while holding the rtnl lock. This
 312          * ensures that l2tp_eth_delete() will see that there's a device to
 313          * unregister, even if it happened to run before we assign spriv->dev.
 314          */
 315         rc = l2tp_session_register(session, tunnel);
 316         if (rc < 0) {
 317                 rtnl_unlock();
 318                 goto err_sess_dev;
 319         }
 320
 321         rc = register_netdevice(dev);
 322         if (rc < 0) {
 323                 rtnl_unlock();
 324                 l2tp_session_delete(session);
 325                 l2tp_session_dec_refcount(session);
 326                 free_netdev(dev);
 327
 328                 return rc;
 329         }
 330
 331         strlcpy(session->ifname, dev->name, IFNAMSIZ);
 332         rcu_assign_pointer(spriv->dev, dev);
 333
 334         rtnl_unlock();
 335
 336         l2tp_session_dec_refcount(session);
 337
 338         __module_get(THIS_MODULE);
 339
 340         return 0;
 341
 342 err_sess_dev:
 343         l2tp_session_dec_refcount(session);
 344         free_netdev(dev);
 345 err_sess:
 346         kfree(session);
 347 err:
 348         return rc;
 349 }
 350
 351
 352 static const struct l2tp_nl_cmd_ops l2tp_eth_nl_cmd_ops = {
 353         .session_create = l2tp_eth_create,
 354         .session_delete = l2tp_session_delete,
 355 };
 356
 357
 358 static int __init l2tp_eth_init(void)
 359 {
 360         int err = 0;
 361
 362         err = l2tp_nl_register_ops(L2TP_PWTYPE_ETH, &l2tp_eth_nl_cmd_ops);
 363         if (err)
 364                 goto err;
 365
 366         pr_info("L2TP ethernet pseudowire support (L2TPv3)\n");
 367
 368         return 0;
 369
 370 err:
 371         return err;
 372 }
 373
 374 static void __exit l2tp_eth_exit(void)
 375 {
 376         l2tp_nl_unregister_ops(L2TP_PWTYPE_ETH);
 377 }
 378
 379 module_init(l2tp_eth_init);
 380 module_exit(l2tp_eth_exit);
 381
 382 MODULE_LICENSE("GPL");
 383 MODULE_AUTHOR("James Chapman <jchapman@katalix.com>");
 384 MODULE_DESCRIPTION("L2TP ethernet pseudowire driver");
 385 MODULE_VERSION("1.0");
 386 MODULE_ALIAS_L2TP_PWTYPE(5);