net/l2tp/l2tp_eth.c

0001 // SPDX-License-Identifier: GPL-2.0-or-later
0002 /* L2TPv3 ethernet pseudowire driver
0003  *
0004  * Copyright (c) 2008,2009,2010 Katalix Systems Ltd
0005  */
0006
0007 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
0008
0009 #include <linux/module.h>
0010 #include <linux/skbuff.h>
0011 #include <linux/socket.h>
0012 #include <linux/hash.h>
0013 #include <linux/l2tp.h>
0014 #include <linux/in.h>
0015 #include <linux/etherdevice.h>
0016 #include <linux/spinlock.h>
0017 #include <net/sock.h>
0018 #include <net/ip.h>
0019 #include <net/icmp.h>
0020 #include <net/udp.h>
0021 #include <net/inet_common.h>
0022 #include <net/inet_hashtables.h>
0023 #include <net/tcp_states.h>
0024 #include <net/protocol.h>
0025 #include <net/xfrm.h>
0026 #include <net/net_namespace.h>
0027 #include <net/netns/generic.h>
0028 #include <linux/ip.h>
0029 #include <linux/ipv6.h>
0030 #include <linux/udp.h>
0031
0032 #include "l2tp_core.h"
0033
0034 /* Default device name. May be overridden by name specified by user */
0035 #define L2TP_ETH_DEV_NAME   "l2tpeth%d"
0036
0037 /* via netdev_priv() */
0038 struct l2tp_eth {
0039     struct l2tp_session *session;
0040     atomic_long_t       tx_bytes;
0041     atomic_long_t       tx_packets;
0042     atomic_long_t       tx_dropped;
0043     atomic_long_t       rx_bytes;
0044     atomic_long_t       rx_packets;
0045     atomic_long_t       rx_errors;
0046 };
0047
0048 /* via l2tp_session_priv() */
0049 struct l2tp_eth_sess {
0050     struct net_device __rcu *dev;
0051 };
0052
0053 static int l2tp_eth_dev_init(struct net_device *dev)
0054 {
0055     eth_hw_addr_random(dev);
0056     eth_broadcast_addr(dev->broadcast);
0057     netdev_lockdep_set_classes(dev);
0058
0059     return 0;
0060 }
0061
0062 static void l2tp_eth_dev_uninit(struct net_device *dev)
0063 {
0064     struct l2tp_eth *priv = netdev_priv(dev);
0065     struct l2tp_eth_sess *spriv;
0066
0067     spriv = l2tp_session_priv(priv->session);
0068     RCU_INIT_POINTER(spriv->dev, NULL);
0069     /* No need for synchronize_net() here. We're called by
0070      * unregister_netdev*(), which does the synchronisation for us.
0071      */
0072 }
0073
0074 static netdev_tx_t l2tp_eth_dev_xmit(struct sk_buff *skb, struct net_device *dev)
0075 {
0076     struct l2tp_eth *priv = netdev_priv(dev);
0077     struct l2tp_session *session = priv->session;
0078     unsigned int len = skb->len;
0079     int ret = l2tp_xmit_skb(session, skb);
0080
0081     if (likely(ret == NET_XMIT_SUCCESS)) {
0082         atomic_long_add(len, &priv->tx_bytes);
0083         atomic_long_inc(&priv->tx_packets);
0084     } else {
0085         atomic_long_inc(&priv->tx_dropped);
0086     }
0087     return NETDEV_TX_OK;
0088 }
0089
0090 static void l2tp_eth_get_stats64(struct net_device *dev,
0091                  struct rtnl_link_stats64 *stats)
0092 {
0093     struct l2tp_eth *priv = netdev_priv(dev);
0094
0095     stats->tx_bytes   = (unsigned long)atomic_long_read(&priv->tx_bytes);
0096     stats->tx_packets = (unsigned long)atomic_long_read(&priv->tx_packets);
0097     stats->tx_dropped = (unsigned long)atomic_long_read(&priv->tx_dropped);
0098     stats->rx_bytes   = (unsigned long)atomic_long_read(&priv->rx_bytes);
0099     stats->rx_packets = (unsigned long)atomic_long_read(&priv->rx_packets);
0100     stats->rx_errors  = (unsigned long)atomic_long_read(&priv->rx_errors);
0101 }
0102
0103 static const struct net_device_ops l2tp_eth_netdev_ops = {
0104     .ndo_init       = l2tp_eth_dev_init,
0105     .ndo_uninit     = l2tp_eth_dev_uninit,
0106     .ndo_start_xmit     = l2tp_eth_dev_xmit,
0107     .ndo_get_stats64    = l2tp_eth_get_stats64,
0108     .ndo_set_mac_address    = eth_mac_addr,
0109 };
0110
0111 static struct device_type l2tpeth_type = {
0112     .name = "l2tpeth",
0113 };
0114
0115 static void l2tp_eth_dev_setup(struct net_device *dev)
0116 {
0117     SET_NETDEV_DEVTYPE(dev, &l2tpeth_type);
0118     ether_setup(dev);
0119     dev->priv_flags     &= ~IFF_TX_SKB_SHARING;
0120     dev->features       |= NETIF_F_LLTX;
0121     dev->netdev_ops     = &l2tp_eth_netdev_ops;
0122     dev->needs_free_netdev  = true;
0123 }
0124
0125 static void l2tp_eth_dev_recv(struct l2tp_session *session, struct sk_buff *skb, int data_len)
0126 {
0127     struct l2tp_eth_sess *spriv = l2tp_session_priv(session);
0128     struct net_device *dev;
0129     struct l2tp_eth *priv;
0130
0131     if (!pskb_may_pull(skb, ETH_HLEN))
0132         goto error;
0133
0134     secpath_reset(skb);
0135
0136     /* checksums verified by L2TP */
0137     skb->ip_summed = CHECKSUM_NONE;
0138
0139     skb_dst_drop(skb);
0140     nf_reset_ct(skb);
0141
0142     rcu_read_lock();
0143     dev = rcu_dereference(spriv->dev);
0144     if (!dev)
0145         goto error_rcu;
0146
0147     priv = netdev_priv(dev);
0148     if (dev_forward_skb(dev, skb) == NET_RX_SUCCESS) {
0149         atomic_long_inc(&priv->rx_packets);
0150         atomic_long_add(data_len, &priv->rx_bytes);
0151     } else {
0152         atomic_long_inc(&priv->rx_errors);
0153     }
0154     rcu_read_unlock();
0155
0156     return;
0157
0158 error_rcu:
0159     rcu_read_unlock();
0160 error:
0161     kfree_skb(skb);
0162 }
0163
0164 static void l2tp_eth_delete(struct l2tp_session *session)
0165 {
0166     struct l2tp_eth_sess *spriv;
0167     struct net_device *dev;
0168
0169     if (session) {
0170         spriv = l2tp_session_priv(session);
0171
0172         rtnl_lock();
0173         dev = rtnl_dereference(spriv->dev);
0174         if (dev) {
0175             unregister_netdevice(dev);
0176             rtnl_unlock();
0177             module_put(THIS_MODULE);
0178         } else {
0179             rtnl_unlock();
0180         }
0181     }
0182 }
0183
0184 static void l2tp_eth_show(struct seq_file *m, void *arg)
0185 {
0186     struct l2tp_session *session = arg;
0187     struct l2tp_eth_sess *spriv = l2tp_session_priv(session);
0188     struct net_device *dev;
0189
0190     rcu_read_lock();
0191     dev = rcu_dereference(spriv->dev);
0192     if (!dev) {
0193         rcu_read_unlock();
0194         return;
0195     }
0196     dev_hold(dev);
0197     rcu_read_unlock();
0198
0199     seq_printf(m, "   interface %s\n", dev->name);
0200
0201     dev_put(dev);
0202 }
0203
0204 static void l2tp_eth_adjust_mtu(struct l2tp_tunnel *tunnel,
0205                 struct l2tp_session *session,
0206                 struct net_device *dev)
0207 {
0208     unsigned int overhead = 0;
0209     u32 l3_overhead = 0;
0210     u32 mtu;
0211
0212     /* if the encap is UDP, account for UDP header size */
0213     if (tunnel->encap == L2TP_ENCAPTYPE_UDP) {
0214         overhead += sizeof(struct udphdr);
0215         dev->needed_headroom += sizeof(struct udphdr);
0216     }
0217
0218     lock_sock(tunnel->sock);
0219     l3_overhead = kernel_sock_ip_overhead(tunnel->sock);
0220     release_sock(tunnel->sock);
0221
0222     if (l3_overhead == 0) {
0223         /* L3 Overhead couldn't be identified, this could be
0224          * because tunnel->sock was NULL or the socket's
0225          * address family was not IPv4 or IPv6,
0226          * dev mtu stays at 1500.
0227          */
0228         return;
0229     }
0230     /* Adjust MTU, factor overhead - underlay L3, overlay L2 hdr
0231      * UDP overhead, if any, was already factored in above.
0232      */
0233     overhead += session->hdr_len + ETH_HLEN + l3_overhead;
0234
0235     mtu = l2tp_tunnel_dst_mtu(tunnel) - overhead;
0236     if (mtu < dev->min_mtu || mtu > dev->max_mtu)
0237         dev->mtu = ETH_DATA_LEN - overhead;
0238     else
0239         dev->mtu = mtu;
0240
0241     dev->needed_headroom += session->hdr_len;
0242 }
0243
0244 static int l2tp_eth_create(struct net *net, struct l2tp_tunnel *tunnel,
0245                u32 session_id, u32 peer_session_id,
0246                struct l2tp_session_cfg *cfg)
0247 {
0248     unsigned char name_assign_type;
0249     struct net_device *dev;
0250     char name[IFNAMSIZ];
0251     struct l2tp_session *session;
0252     struct l2tp_eth *priv;
0253     struct l2tp_eth_sess *spriv;
0254     int rc;
0255
0256     if (cfg->ifname) {
0257         strlcpy(name, cfg->ifname, IFNAMSIZ);
0258         name_assign_type = NET_NAME_USER;
0259     } else {
0260         strcpy(name, L2TP_ETH_DEV_NAME);
0261         name_assign_type = NET_NAME_ENUM;
0262     }
0263
0264     session = l2tp_session_create(sizeof(*spriv), tunnel, session_id,
0265                       peer_session_id, cfg);
0266     if (IS_ERR(session)) {
0267         rc = PTR_ERR(session);
0268         goto err;
0269     }
0270
0271     dev = alloc_netdev(sizeof(*priv), name, name_assign_type,
0272                l2tp_eth_dev_setup);
0273     if (!dev) {
0274         rc = -ENOMEM;
0275         goto err_sess;
0276     }
0277
0278     dev_net_set(dev, net);
0279     dev->min_mtu = 0;
0280     dev->max_mtu = ETH_MAX_MTU;
0281     l2tp_eth_adjust_mtu(tunnel, session, dev);
0282
0283     priv = netdev_priv(dev);
0284     priv->session = session;
0285
0286     session->recv_skb = l2tp_eth_dev_recv;
0287     session->session_close = l2tp_eth_delete;
0288     if (IS_ENABLED(CONFIG_L2TP_DEBUGFS))
0289         session->show = l2tp_eth_show;
0290
0291     spriv = l2tp_session_priv(session);
0292
0293     l2tp_session_inc_refcount(session);
0294
0295     rtnl_lock();
0296
0297     /* Register both device and session while holding the rtnl lock. This
0298      * ensures that l2tp_eth_delete() will see that there's a device to
0299      * unregister, even if it happened to run before we assign spriv->dev.
0300      */
0301     rc = l2tp_session_register(session, tunnel);
0302     if (rc < 0) {
0303         rtnl_unlock();
0304         goto err_sess_dev;
0305     }
0306
0307     rc = register_netdevice(dev);
0308     if (rc < 0) {
0309         rtnl_unlock();
0310         l2tp_session_delete(session);
0311         l2tp_session_dec_refcount(session);
0312         free_netdev(dev);
0313
0314         return rc;
0315     }
0316
0317     strlcpy(session->ifname, dev->name, IFNAMSIZ);
0318     rcu_assign_pointer(spriv->dev, dev);
0319
0320     rtnl_unlock();
0321
0322     l2tp_session_dec_refcount(session);
0323
0324     __module_get(THIS_MODULE);
0325
0326     return 0;
0327
0328 err_sess_dev:
0329     l2tp_session_dec_refcount(session);
0330     free_netdev(dev);
0331 err_sess:
0332     kfree(session);
0333 err:
0334     return rc;
0335 }
0336
0337 static const struct l2tp_nl_cmd_ops l2tp_eth_nl_cmd_ops = {
0338     .session_create = l2tp_eth_create,
0339     .session_delete = l2tp_session_delete,
0340 };
0341
0342 static int __init l2tp_eth_init(void)
0343 {
0344     int err = 0;
0345
0346     err = l2tp_nl_register_ops(L2TP_PWTYPE_ETH, &l2tp_eth_nl_cmd_ops);
0347     if (err)
0348         goto err;
0349
0350     pr_info("L2TP ethernet pseudowire support (L2TPv3)\n");
0351
0352     return 0;
0353
0354 err:
0355     return err;
0356 }
0357
0358 static void __exit l2tp_eth_exit(void)
0359 {
0360     l2tp_nl_unregister_ops(L2TP_PWTYPE_ETH);
0361 }
0362
0363 module_init(l2tp_eth_init);
0364 module_exit(l2tp_eth_exit);
0365
0366 MODULE_LICENSE("GPL");
0367 MODULE_AUTHOR("James Chapman <jchapman@katalix.com>");
0368 MODULE_DESCRIPTION("L2TP ethernet pseudowire driver");
0369 MODULE_VERSION("1.0");
0370 MODULE_ALIAS_L2TP_PWTYPE(5);