net/l2tp/l2tp_eth.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /* L2TPv3 ethernet pseudowire driver
   3  *
   4  * Copyright (c) 2008,2009,2010 Katalix Systems Ltd
   5  */
   6
   7 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
   8
   9 #include <linux/module.h>
  10 #include <linux/skbuff.h>
  11 #include <linux/socket.h>
  12 #include <linux/hash.h>
  13 #include <linux/l2tp.h>
  14 #include <linux/in.h>
  15 #include <linux/etherdevice.h>
  16 #include <linux/spinlock.h>
  17 #include <net/sock.h>
  18 #include <net/ip.h>
  19 #include <net/icmp.h>
  20 #include <net/udp.h>
  21 #include <net/inet_common.h>
  22 #include <net/inet_hashtables.h>
  23 #include <net/tcp_states.h>
  24 #include <net/protocol.h>
  25 #include <net/xfrm.h>
  26 #include <net/net_namespace.h>
  27 #include <net/netns/generic.h>
  28 #include <linux/ip.h>
  29 #include <linux/ipv6.h>
  30 #include <linux/udp.h>
  31
  32 #include "l2tp_core.h"
  33
  34 /* Default device name. May be overridden by name specified by user */
  35 #define L2TP_ETH_DEV_NAME       "l2tpeth%d"
  36
  37 /* via netdev_priv() */
  38 struct l2tp_eth {
  39         struct l2tp_session     *session;
  40         atomic_long_t           tx_bytes;
  41         atomic_long_t           tx_packets;
  42         atomic_long_t           tx_dropped;
  43         atomic_long_t           rx_bytes;
  44         atomic_long_t           rx_packets;
  45         atomic_long_t           rx_errors;
  46 };
  47
  48 /* via l2tp_session_priv() */
  49 struct l2tp_eth_sess {
  50         struct net_device __rcu *dev;
  51 };
  52
  53 static int l2tp_eth_dev_init(struct net_device *dev)
  54 {
  55         eth_hw_addr_random(dev);
  56         eth_broadcast_addr(dev->broadcast);
  57         netdev_lockdep_set_classes(dev);
  58
  59         return 0;
  60 }
  61
  62 static void l2tp_eth_dev_uninit(struct net_device *dev)
  63 {
  64         struct l2tp_eth *priv = netdev_priv(dev);
  65         struct l2tp_eth_sess *spriv;
  66
  67         spriv = l2tp_session_priv(priv->session);
  68         RCU_INIT_POINTER(spriv->dev, NULL);
  69         /* No need for synchronize_net() here. We're called by
  70          * unregister_netdev*(), which does the synchronisation for us.
  71          */
  72 }
  73
  74 static netdev_tx_t l2tp_eth_dev_xmit(struct sk_buff *skb, struct net_device *dev)
  75 {
  76         struct l2tp_eth *priv = netdev_priv(dev);
  77         struct l2tp_session *session = priv->session;
  78         unsigned int len = skb->len;
  79         int ret = l2tp_xmit_skb(session, skb);
  80
  81         if (likely(ret == NET_XMIT_SUCCESS)) {
  82                 atomic_long_add(len, &priv->tx_bytes);
  83                 atomic_long_inc(&priv->tx_packets);
  84         } else {
  85                 atomic_long_inc(&priv->tx_dropped);
  86         }
  87         return NETDEV_TX_OK;
  88 }
  89
  90 static void l2tp_eth_get_stats64(struct net_device *dev,
  91                                  struct rtnl_link_stats64 *stats)
  92 {
  93         struct l2tp_eth *priv = netdev_priv(dev);
  94
  95         stats->tx_bytes   = (unsigned long)atomic_long_read(&priv->tx_bytes);
  96         stats->tx_packets = (unsigned long)atomic_long_read(&priv->tx_packets);
  97         stats->tx_dropped = (unsigned long)atomic_long_read(&priv->tx_dropped);
  98         stats->rx_bytes   = (unsigned long)atomic_long_read(&priv->rx_bytes);
  99         stats->rx_packets = (unsigned long)atomic_long_read(&priv->rx_packets);
 100         stats->rx_errors  = (unsigned long)atomic_long_read(&priv->rx_errors);
 101 }
 102
 103 static const struct net_device_ops l2tp_eth_netdev_ops = {
 104         .ndo_init               = l2tp_eth_dev_init,
 105         .ndo_uninit             = l2tp_eth_dev_uninit,
 106         .ndo_start_xmit         = l2tp_eth_dev_xmit,
 107         .ndo_get_stats64        = l2tp_eth_get_stats64,
 108         .ndo_set_mac_address    = eth_mac_addr,
 109 };
 110
 111 static struct device_type l2tpeth_type = {
 112         .name = "l2tpeth",
 113 };
 114
 115 static void l2tp_eth_dev_setup(struct net_device *dev)
 116 {
 117         SET_NETDEV_DEVTYPE(dev, &l2tpeth_type);
 118         ether_setup(dev);
 119         dev->priv_flags         &= ~IFF_TX_SKB_SHARING;
 120         dev->features           |= NETIF_F_LLTX;
 121         dev->netdev_ops         = &l2tp_eth_netdev_ops;
 122         dev->needs_free_netdev  = true;
 123 }
 124
 125 static void l2tp_eth_dev_recv(struct l2tp_session *session, struct sk_buff *skb, int data_len)
 126 {
 127         struct l2tp_eth_sess *spriv = l2tp_session_priv(session);
 128         struct net_device *dev;
 129         struct l2tp_eth *priv;
 130
 131         if (!pskb_may_pull(skb, ETH_HLEN))
 132                 goto error;
 133
 134         secpath_reset(skb);
 135
 136         /* checksums verified by L2TP */
 137         skb->ip_summed = CHECKSUM_NONE;
 138
 139         skb_dst_drop(skb);
 140         nf_reset_ct(skb);
 141
 142         rcu_read_lock();
 143         dev = rcu_dereference(spriv->dev);
 144         if (!dev)
 145                 goto error_rcu;
 146
 147         priv = netdev_priv(dev);
 148         if (dev_forward_skb(dev, skb) == NET_RX_SUCCESS) {
 149                 atomic_long_inc(&priv->rx_packets);
 150                 atomic_long_add(data_len, &priv->rx_bytes);
 151         } else {
 152                 atomic_long_inc(&priv->rx_errors);
 153         }
 154         rcu_read_unlock();
 155
 156         return;
 157
 158 error_rcu:
 159         rcu_read_unlock();
 160 error:
 161         kfree_skb(skb);
 162 }
 163
 164 static void l2tp_eth_delete(struct l2tp_session *session)
 165 {
 166         struct l2tp_eth_sess *spriv;
 167         struct net_device *dev;
 168
 169         if (session) {
 170                 spriv = l2tp_session_priv(session);
 171
 172                 rtnl_lock();
 173                 dev = rtnl_dereference(spriv->dev);
 174                 if (dev) {
 175                         unregister_netdevice(dev);
 176                         rtnl_unlock();
 177                         module_put(THIS_MODULE);
 178                 } else {
 179                         rtnl_unlock();
 180                 }
 181         }
 182 }
 183
 184 static void l2tp_eth_show(struct seq_file *m, void *arg)
 185 {
 186         struct l2tp_session *session = arg;
 187         struct l2tp_eth_sess *spriv = l2tp_session_priv(session);
 188         struct net_device *dev;
 189
 190         rcu_read_lock();
 191         dev = rcu_dereference(spriv->dev);
 192         if (!dev) {
 193                 rcu_read_unlock();
 194                 return;
 195         }
 196         dev_hold(dev);
 197         rcu_read_unlock();
 198
 199         seq_printf(m, "   interface %s\n", dev->name);
 200
 201         dev_put(dev);
 202 }
 203
 204 static void l2tp_eth_adjust_mtu(struct l2tp_tunnel *tunnel,
 205                                 struct l2tp_session *session,
 206                                 struct net_device *dev)
 207 {
 208         unsigned int overhead = 0;
 209         u32 l3_overhead = 0;
 210         u32 mtu;
 211
 212         /* if the encap is UDP, account for UDP header size */
 213         if (tunnel->encap == L2TP_ENCAPTYPE_UDP) {
 214                 overhead += sizeof(struct udphdr);
 215                 dev->needed_headroom += sizeof(struct udphdr);
 216         }
 217
 218         lock_sock(tunnel->sock);
 219         l3_overhead = kernel_sock_ip_overhead(tunnel->sock);
 220         release_sock(tunnel->sock);
 221
 222         if (l3_overhead == 0) {
 223                 /* L3 Overhead couldn't be identified, this could be
 224                  * because tunnel->sock was NULL or the socket's
 225                  * address family was not IPv4 or IPv6,
 226                  * dev mtu stays at 1500.
 227                  */
 228                 return;
 229         }
 230         /* Adjust MTU, factor overhead - underlay L3, overlay L2 hdr
 231          * UDP overhead, if any, was already factored in above.
 232          */
 233         overhead += session->hdr_len + ETH_HLEN + l3_overhead;
 234
 235         mtu = l2tp_tunnel_dst_mtu(tunnel) - overhead;
 236         if (mtu < dev->min_mtu || mtu > dev->max_mtu)
 237                 dev->mtu = ETH_DATA_LEN - overhead;
 238         else
 239                 dev->mtu = mtu;
 240
 241         dev->needed_headroom += session->hdr_len;
 242 }
 243
 244 static int l2tp_eth_create(struct net *net, struct l2tp_tunnel *tunnel,
 245                            u32 session_id, u32 peer_session_id,
 246                            struct l2tp_session_cfg *cfg)
 247 {
 248         unsigned char name_assign_type;
 249         struct net_device *dev;
 250         char name[IFNAMSIZ];
 251         struct l2tp_session *session;
 252         struct l2tp_eth *priv;
 253         struct l2tp_eth_sess *spriv;
 254         int rc;
 255
 256         if (cfg->ifname) {
 257                 strlcpy(name, cfg->ifname, IFNAMSIZ);
 258                 name_assign_type = NET_NAME_USER;
 259         } else {
 260                 strcpy(name, L2TP_ETH_DEV_NAME);
 261                 name_assign_type = NET_NAME_ENUM;
 262         }
 263
 264         session = l2tp_session_create(sizeof(*spriv), tunnel, session_id,
 265                                       peer_session_id, cfg);
 266         if (IS_ERR(session)) {
 267                 rc = PTR_ERR(session);
 268                 goto err;
 269         }
 270
 271         dev = alloc_netdev(sizeof(*priv), name, name_assign_type,
 272                            l2tp_eth_dev_setup);
 273         if (!dev) {
 274                 rc = -ENOMEM;
 275                 goto err_sess;
 276         }
 277
 278         dev_net_set(dev, net);
 279         dev->min_mtu = 0;
 280         dev->max_mtu = ETH_MAX_MTU;
 281         l2tp_eth_adjust_mtu(tunnel, session, dev);
 282
 283         priv = netdev_priv(dev);
 284         priv->session = session;
 285
 286         session->recv_skb = l2tp_eth_dev_recv;
 287         session->session_close = l2tp_eth_delete;
 288         if (IS_ENABLED(CONFIG_L2TP_DEBUGFS))
 289                 session->show = l2tp_eth_show;
 290
 291         spriv = l2tp_session_priv(session);
 292
 293         l2tp_session_inc_refcount(session);
 294
 295         rtnl_lock();
 296
 297         /* Register both device and session while holding the rtnl lock. This
 298          * ensures that l2tp_eth_delete() will see that there's a device to
 299          * unregister, even if it happened to run before we assign spriv->dev.
 300          */
 301         rc = l2tp_session_register(session, tunnel);
 302         if (rc < 0) {
 303                 rtnl_unlock();
 304                 goto err_sess_dev;
 305         }
 306
 307         rc = register_netdevice(dev);
 308         if (rc < 0) {
 309                 rtnl_unlock();
 310                 l2tp_session_delete(session);
 311                 l2tp_session_dec_refcount(session);
 312                 free_netdev(dev);
 313
 314                 return rc;
 315         }
 316
 317         strlcpy(session->ifname, dev->name, IFNAMSIZ);
 318         rcu_assign_pointer(spriv->dev, dev);
 319
 320         rtnl_unlock();
 321
 322         l2tp_session_dec_refcount(session);
 323
 324         __module_get(THIS_MODULE);
 325
 326         return 0;
 327
 328 err_sess_dev:
 329         l2tp_session_dec_refcount(session);
 330         free_netdev(dev);
 331 err_sess:
 332         kfree(session);
 333 err:
 334         return rc;
 335 }
 336
 337 static const struct l2tp_nl_cmd_ops l2tp_eth_nl_cmd_ops = {
 338         .session_create = l2tp_eth_create,
 339         .session_delete = l2tp_session_delete,
 340 };
 341
 342 static int __init l2tp_eth_init(void)
 343 {
 344         int err = 0;
 345
 346         err = l2tp_nl_register_ops(L2TP_PWTYPE_ETH, &l2tp_eth_nl_cmd_ops);
 347         if (err)
 348                 goto err;
 349
 350         pr_info("L2TP ethernet pseudowire support (L2TPv3)\n");
 351
 352         return 0;
 353
 354 err:
 355         return err;
 356 }
 357
 358 static void __exit l2tp_eth_exit(void)
 359 {
 360         l2tp_nl_unregister_ops(L2TP_PWTYPE_ETH);
 361 }
 362
 363 module_init(l2tp_eth_init);
 364 module_exit(l2tp_eth_exit);
 365
 366 MODULE_LICENSE("GPL");
 367 MODULE_AUTHOR("James Chapman <jchapman@katalix.com>");
 368 MODULE_DESCRIPTION("L2TP ethernet pseudowire driver");
 369 MODULE_VERSION("1.0");
 370 MODULE_ALIAS_L2TP_PWTYPE(5);