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 };
  41
  42 /* via l2tp_session_priv() */
  43 struct l2tp_eth_sess {
  44         struct net_device __rcu *dev;
  45 };
  46
  47 static int l2tp_eth_dev_init(struct net_device *dev)
  48 {
  49         eth_hw_addr_random(dev);
  50         eth_broadcast_addr(dev->broadcast);
  51         netdev_lockdep_set_classes(dev);
  52
  53         return 0;
  54 }
  55
  56 static void l2tp_eth_dev_uninit(struct net_device *dev)
  57 {
  58         struct l2tp_eth *priv = netdev_priv(dev);
  59         struct l2tp_eth_sess *spriv;
  60
  61         spriv = l2tp_session_priv(priv->session);
  62         RCU_INIT_POINTER(spriv->dev, NULL);
  63         /* No need for synchronize_net() here. We're called by
  64          * unregister_netdev*(), which does the synchronisation for us.
  65          */
  66 }
  67
  68 static netdev_tx_t l2tp_eth_dev_xmit(struct sk_buff *skb, struct net_device *dev)
  69 {
  70         struct l2tp_eth *priv = netdev_priv(dev);
  71         struct l2tp_session *session = priv->session;
  72         unsigned int len = skb->len;
  73         int ret = l2tp_xmit_skb(session, skb);
  74
  75         if (likely(ret == NET_XMIT_SUCCESS))
  76                 dev_sw_netstats_tx_add(dev, 1, len);
  77         else
  78                 DEV_STATS_INC(dev, tx_dropped);
  79
  80         return NETDEV_TX_OK;
  81 }
  82
  83 static const struct net_device_ops l2tp_eth_netdev_ops = {
  84         .ndo_init               = l2tp_eth_dev_init,
  85         .ndo_uninit             = l2tp_eth_dev_uninit,
  86         .ndo_start_xmit         = l2tp_eth_dev_xmit,
  87         .ndo_get_stats64        = dev_get_tstats64,
  88         .ndo_set_mac_address    = eth_mac_addr,
  89 };
  90
  91 static const struct device_type l2tpeth_type = {
  92         .name = "l2tpeth",
  93 };
  94
  95 static void l2tp_eth_dev_setup(struct net_device *dev)
  96 {
  97         SET_NETDEV_DEVTYPE(dev, &l2tpeth_type);
  98         ether_setup(dev);
  99         dev->priv_flags         &= ~IFF_TX_SKB_SHARING;
 100         dev->lltx               = true;
 101         dev->netdev_ops         = &l2tp_eth_netdev_ops;
 102         dev->needs_free_netdev  = true;
 103         dev->pcpu_stat_type     = NETDEV_PCPU_STAT_TSTATS;
 104 }
 105
 106 static void l2tp_eth_dev_recv(struct l2tp_session *session, struct sk_buff *skb, int data_len)
 107 {
 108         struct l2tp_eth_sess *spriv = l2tp_session_priv(session);
 109         struct net_device *dev;
 110
 111         if (!pskb_may_pull(skb, ETH_HLEN))
 112                 goto error;
 113
 114         secpath_reset(skb);
 115
 116         /* checksums verified by L2TP */
 117         skb->ip_summed = CHECKSUM_NONE;
 118
 119         /* drop outer flow-hash */
 120         skb_clear_hash(skb);
 121
 122         skb_dst_drop(skb);
 123         nf_reset_ct(skb);
 124
 125         rcu_read_lock();
 126         dev = rcu_dereference(spriv->dev);
 127         if (!dev)
 128                 goto error_rcu;
 129
 130         if (dev_forward_skb(dev, skb) == NET_RX_SUCCESS)
 131                 dev_sw_netstats_rx_add(dev, data_len);
 132         else
 133                 DEV_STATS_INC(dev, rx_errors);
 134
 135         rcu_read_unlock();
 136
 137         return;
 138
 139 error_rcu:
 140         rcu_read_unlock();
 141 error:
 142         kfree_skb(skb);
 143 }
 144
 145 static void l2tp_eth_delete(struct l2tp_session *session)
 146 {
 147         struct l2tp_eth_sess *spriv;
 148         struct net_device *dev;
 149
 150         if (session) {
 151                 spriv = l2tp_session_priv(session);
 152
 153                 rtnl_lock();
 154                 dev = rtnl_dereference(spriv->dev);
 155                 if (dev) {
 156                         unregister_netdevice(dev);
 157                         rtnl_unlock();
 158                         module_put(THIS_MODULE);
 159                 } else {
 160                         rtnl_unlock();
 161                 }
 162         }
 163 }
 164
 165 static void l2tp_eth_show(struct seq_file *m, void *arg)
 166 {
 167         struct l2tp_session *session = arg;
 168         struct l2tp_eth_sess *spriv = l2tp_session_priv(session);
 169         struct net_device *dev;
 170
 171         rcu_read_lock();
 172         dev = rcu_dereference(spriv->dev);
 173         if (!dev) {
 174                 rcu_read_unlock();
 175                 return;
 176         }
 177         dev_hold(dev);
 178         rcu_read_unlock();
 179
 180         seq_printf(m, "   interface %s\n", dev->name);
 181
 182         dev_put(dev);
 183 }
 184
 185 static void l2tp_eth_adjust_mtu(struct l2tp_tunnel *tunnel,
 186                                 struct l2tp_session *session,
 187                                 struct net_device *dev)
 188 {
 189         unsigned int overhead = 0;
 190         u32 l3_overhead = 0;
 191         u32 mtu;
 192
 193         /* if the encap is UDP, account for UDP header size */
 194         if (tunnel->encap == L2TP_ENCAPTYPE_UDP) {
 195                 overhead += sizeof(struct udphdr);
 196                 dev->needed_headroom += sizeof(struct udphdr);
 197         }
 198
 199         lock_sock(tunnel->sock);
 200         l3_overhead = kernel_sock_ip_overhead(tunnel->sock);
 201         release_sock(tunnel->sock);
 202
 203         if (l3_overhead == 0) {
 204                 /* L3 Overhead couldn't be identified, this could be
 205                  * because tunnel->sock was NULL or the socket's
 206                  * address family was not IPv4 or IPv6,
 207                  * dev mtu stays at 1500.
 208                  */
 209                 return;
 210         }
 211         /* Adjust MTU, factor overhead - underlay L3, overlay L2 hdr
 212          * UDP overhead, if any, was already factored in above.
 213          */
 214         overhead += session->hdr_len + ETH_HLEN + l3_overhead;
 215
 216         mtu = l2tp_tunnel_dst_mtu(tunnel) - overhead;
 217         if (mtu < dev->min_mtu || mtu > dev->max_mtu)
 218                 dev->mtu = ETH_DATA_LEN - overhead;
 219         else
 220                 dev->mtu = mtu;
 221
 222         dev->needed_headroom += session->hdr_len;
 223 }
 224
 225 static int l2tp_eth_create(struct net *net, struct l2tp_tunnel *tunnel,
 226                            u32 session_id, u32 peer_session_id,
 227                            struct l2tp_session_cfg *cfg)
 228 {
 229         unsigned char name_assign_type;
 230         struct net_device *dev;
 231         char name[IFNAMSIZ];
 232         struct l2tp_session *session;
 233         struct l2tp_eth *priv;
 234         struct l2tp_eth_sess *spriv;
 235         int rc;
 236
 237         if (cfg->ifname) {
 238                 strscpy(name, cfg->ifname, IFNAMSIZ);
 239                 name_assign_type = NET_NAME_USER;
 240         } else {
 241                 strcpy(name, L2TP_ETH_DEV_NAME);
 242                 name_assign_type = NET_NAME_ENUM;
 243         }
 244
 245         session = l2tp_session_create(sizeof(*spriv), tunnel, session_id,
 246                                       peer_session_id, cfg);
 247         if (IS_ERR(session)) {
 248                 rc = PTR_ERR(session);
 249                 goto err;
 250         }
 251
 252         dev = alloc_netdev(sizeof(*priv), name, name_assign_type,
 253                            l2tp_eth_dev_setup);
 254         if (!dev) {
 255                 rc = -ENOMEM;
 256                 goto err_sess;
 257         }
 258
 259         dev_net_set(dev, net);
 260         dev->min_mtu = 0;
 261         dev->max_mtu = ETH_MAX_MTU;
 262         l2tp_eth_adjust_mtu(tunnel, session, dev);
 263
 264         priv = netdev_priv(dev);
 265         priv->session = session;
 266
 267         session->recv_skb = l2tp_eth_dev_recv;
 268         session->session_close = l2tp_eth_delete;
 269         if (IS_ENABLED(CONFIG_L2TP_DEBUGFS))
 270                 session->show = l2tp_eth_show;
 271
 272         spriv = l2tp_session_priv(session);
 273
 274         refcount_inc(&session->ref_count);
 275
 276         rtnl_lock();
 277
 278         /* Register both device and session while holding the rtnl lock. This
 279          * ensures that l2tp_eth_delete() will see that there's a device to
 280          * unregister, even if it happened to run before we assign spriv->dev.
 281          */
 282         rc = l2tp_session_register(session, tunnel);
 283         if (rc < 0) {
 284                 rtnl_unlock();
 285                 goto err_sess_dev;
 286         }
 287
 288         rc = register_netdevice(dev);
 289         if (rc < 0) {
 290                 rtnl_unlock();
 291                 l2tp_session_delete(session);
 292                 l2tp_session_put(session);
 293                 free_netdev(dev);
 294
 295                 return rc;
 296         }
 297
 298         strscpy(session->ifname, dev->name, IFNAMSIZ);
 299         rcu_assign_pointer(spriv->dev, dev);
 300
 301         rtnl_unlock();
 302
 303         l2tp_session_put(session);
 304
 305         __module_get(THIS_MODULE);
 306
 307         return 0;
 308
 309 err_sess_dev:
 310         l2tp_session_put(session);
 311         free_netdev(dev);
 312 err_sess:
 313         l2tp_session_put(session);
 314 err:
 315         return rc;
 316 }
 317
 318 static const struct l2tp_nl_cmd_ops l2tp_eth_nl_cmd_ops = {
 319         .session_create = l2tp_eth_create,
 320         .session_delete = l2tp_session_delete,
 321 };
 322
 323 static int __init l2tp_eth_init(void)
 324 {
 325         int err = 0;
 326
 327         err = l2tp_nl_register_ops(L2TP_PWTYPE_ETH, &l2tp_eth_nl_cmd_ops);
 328         if (err)
 329                 goto err;
 330
 331         pr_info("L2TP ethernet pseudowire support (L2TPv3)\n");
 332
 333         return 0;
 334
 335 err:
 336         return err;
 337 }
 338
 339 static void __exit l2tp_eth_exit(void)
 340 {
 341         l2tp_nl_unregister_ops(L2TP_PWTYPE_ETH);
 342 }
 343
 344 module_init(l2tp_eth_init);
 345 module_exit(l2tp_eth_exit);
 346
 347 MODULE_LICENSE("GPL");
 348 MODULE_AUTHOR("James Chapman <jchapman@katalix.com>");
 349 MODULE_DESCRIPTION("L2TP ethernet pseudowire driver");
 350 MODULE_VERSION("1.0");
 351 MODULE_ALIAS_L2TP_PWTYPE(5);