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
  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);