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