[PATCH v3 10/12] l2tp: Add L2TP ethernet pseudowire support

[James Chapman <jchapman@katalix.com>]

This driver presents a regular net_device for each L2TP ethernet
pseudowire instance. These interfaces are named l2tpethN by default,
though userspace can specify an alternative name when the L2TP
session is created, if preferred. When the pseudowire is established,
regular Linux networking utilities may be used to configure the
interface, i.e. give it IP address info or add it to a bridge. Any
data passed over the interface is carried over an L2TP tunnel.

Signed-off-by: James Chapman <jchapman@katalix.com>
Reviewed-by: Randy Dunlap <randy.dunlap@oracle.com>
---
 net/l2tp/Kconfig    |   24 +++
 net/l2tp/Makefile   |    1 
 net/l2tp/l2tp_eth.c |  371 +++++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 396 insertions(+), 0 deletions(-)
 create mode 100644 net/l2tp/l2tp_eth.c

diff --git a/net/l2tp/Kconfig b/net/l2tp/Kconfig
index 0a11ccf..a292270 100644
--- a/net/l2tp/Kconfig
+++ b/net/l2tp/Kconfig
@@ -68,3 +68,27 @@ config L2TP_IP
 
 	  To compile this driver as a module, choose M here. The module
 	  will be called l2tp_ip.
+
+config L2TP_ETH
+	tristate "L2TP ethernet pseudowire support for L2TPv3"
+	depends on L2TP_V3
+	help
+	  Support for carrying raw ethernet frames over L2TPv3.
+
+	  From RFC 4719 <http://www.ietf.org/rfc/rfc4719.txt>.
+
+	  The Layer 2 Tunneling Protocol, Version 3 (L2TPv3) can be
+	  used as a control protocol and for data encapsulation to set
+	  up Pseudowires for transporting layer 2 Packet Data Units
+	  across an IP network [RFC3931].
+
+	  This driver provides an ethernet virtual interface for each
+	  L2TP ethernet pseudowire instance. Standard Linux tools may
+	  be used to assign an IP address to the local virtual
+	  interface, or add the interface to a bridge.
+
+	  If you are using L2TPv3, you will almost certainly want to
+	  enable this option.
+
+	  To compile this driver as a module, choose M here. The module
+	  will be called l2tp_eth.
diff --git a/net/l2tp/Makefile b/net/l2tp/Makefile
index 2c4a14b..bddbf04 100644
--- a/net/l2tp/Makefile
+++ b/net/l2tp/Makefile
@@ -8,3 +8,4 @@ obj-$(CONFIG_L2TP) += l2tp_core.o
 obj-$(subst y,$(CONFIG_L2TP),$(CONFIG_PPPOL2TP)) += l2tp_ppp.o
 obj-$(subst y,$(CONFIG_L2TP),$(CONFIG_L2TP_IP)) += l2tp_ip.o
 obj-$(subst y,$(CONFIG_L2TP),$(CONFIG_L2TP_V3)) += l2tp_netlink.o
+obj-$(subst y,$(CONFIG_L2TP),$(CONFIG_L2TP_ETH)) += l2tp_eth.o
diff --git a/net/l2tp/l2tp_eth.c b/net/l2tp/l2tp_eth.c
new file mode 100644
index 0000000..3c4f254
--- /dev/null
+++ b/net/l2tp/l2tp_eth.c
@@ -0,0 +1,371 @@
+/*
+ * L2TPv3 ethernet pseudowire driver
+ *
+ * Copyright (c) 2008,2009,2010 Katalix Systems Ltd
+ *
+ *	This program is free software; you can redistribute it and/or
+ *	modify it under the terms of the GNU General Public License
+ *	as published by the Free Software Foundation; either version
+ *	2 of the License, or (at your option) any later version.
+ */
+
+#include <linux/module.h>
+#include <linux/skbuff.h>
+#include <linux/socket.h>
+#include <linux/hash.h>
+#include <linux/l2tp.h>
+#include <linux/in.h>
+#include <linux/etherdevice.h>
+#include <net/sock.h>
+#include <net/ip.h>
+#include <net/icmp.h>
+#include <net/udp.h>
+#include <net/inet_common.h>
+#include <net/inet_hashtables.h>
+#include <net/tcp_states.h>
+#include <net/protocol.h>
+#include <net/xfrm.h>
+#include <net/net_namespace.h>
+#include <net/netns/generic.h>
+
+#include "l2tp_core.h"
+
+/* Default device name. May be overridden by name specified by user */
+#define L2TP_ETH_DEV_NAME	"l2tpeth%d"
+
+/* via netdev_priv() */
+struct l2tp_eth {
+	struct net_device	*dev;
+	struct sock		*tunnel_sock;
+	struct l2tp_session	*session;
+	struct list_head	list;
+};
+
+/* via l2tp_session_priv() */
+struct l2tp_eth_sess {
+	struct net_device	*dev;
+};
+
+/* per-net private data for this module */
+static unsigned int l2tp_eth_net_id;
+struct l2tp_eth_net {
+	struct list_head l2tp_eth_dev_list;
+	rwlock_t l2tp_eth_lock;
+};
+
+static inline struct l2tp_eth_net *l2tp_eth_pernet(struct net *net)
+{
+	BUG_ON(!net);
+
+	return net_generic(net, l2tp_eth_net_id);
+}
+
+static int l2tp_eth_dev_init(struct net_device *dev)
+{
+	struct l2tp_eth *priv = netdev_priv(dev);
+	struct l2tp_session *session = priv->session;
+	__be32 sid = htonl(session->session_id);
+
+	priv->dev = dev;
+
+	/* Derive a MAC address for the new interface. We use the L2TP
+	 * session's session-id to guarantee a system-wide unique
+	 * address. This MAC is only visible within the L2TP session.
+	 */
+	dev->dev_addr[0] = 0x02; /* IEEE 802 local */
+	dev->dev_addr[1] = 'L';
+	memcpy(&dev->dev_addr[2], &sid, 4);
+	memset(&dev->broadcast[0], 0xff, 6);
+
+	return 0;
+}
+
+static void l2tp_eth_dev_uninit(struct net_device *dev)
+{
+	struct l2tp_eth *priv = netdev_priv(dev);
+	struct l2tp_eth_net *pn = l2tp_eth_pernet(dev_net(dev));
+
+	write_lock(&pn->l2tp_eth_lock);
+	list_del_init(&priv->list);
+	write_unlock(&pn->l2tp_eth_lock);
+	dev_put(dev);
+}
+
+static int l2tp_eth_dev_xmit(struct sk_buff *skb, struct net_device *dev)
+{
+	struct l2tp_eth *priv = netdev_priv(dev);
+	struct l2tp_session *session = priv->session;
+
+	l2tp_xmit_skb(session, skb, session->hdr_len);
+
+	dev->stats.tx_bytes += skb->len;
+	dev->stats.tx_packets++;
+
+	return 0;
+}
+
+static struct net_device_ops l2tp_eth_netdev_ops = {
+	.ndo_init		= l2tp_eth_dev_init,
+	.ndo_uninit		= l2tp_eth_dev_uninit,
+	.ndo_start_xmit		= l2tp_eth_dev_xmit,
+};
+
+static void l2tp_eth_dev_setup(struct net_device *dev)
+{
+	ether_setup(dev);
+
+	dev->netdev_ops		= &l2tp_eth_netdev_ops;
+	dev->destructor		= free_netdev;
+}
+
+static void l2tp_eth_dev_recv(struct l2tp_session *session, struct sk_buff *skb, int data_len)
+{
+	struct l2tp_eth_sess *spriv = l2tp_session_priv(session);
+	struct net_device *dev = spriv->dev;
+
+	if (session->debug & L2TP_MSG_DATA) {
+		unsigned int length;
+		int offset;
+		u8 *ptr = skb->data;
+
+		length = min(32u, skb->len);
+		if (!pskb_may_pull(skb, length))
+			goto error;
+
+		printk(KERN_DEBUG "%s: eth recv: ", session->name);
+
+		offset = 0;
+		do {
+			printk(" %02X", ptr[offset]);
+		} while (++offset < length);
+
+		printk("\n");
+	}
+
+	if (data_len < ETH_HLEN)
+		goto error;
+
+	secpath_reset(skb);
+
+	/* checksums verified by L2TP */
+	skb->ip_summed = CHECKSUM_NONE;
+
+	skb_dst_drop(skb);
+	nf_reset(skb);
+
+	if (dev_forward_skb(dev, skb) == NET_RX_SUCCESS) {
+		dev->last_rx = jiffies;
+		dev->stats.rx_packets++;
+		dev->stats.rx_bytes += data_len;
+	} else
+		dev->stats.rx_errors++;
+
+	return;
+
+error:
+	dev->stats.rx_errors++;
+	kfree_skb(skb);
+}
+
+static void l2tp_eth_delete(struct l2tp_session *session)
+{
+	struct l2tp_eth_sess *spriv;
+	struct net_device *dev;
+
+	if (session) {
+		spriv = l2tp_session_priv(session);
+		dev = spriv->dev;
+		if (dev) {
+			unregister_netdev(dev);
+			spriv->dev = NULL;
+		}
+	}
+}
+
+#ifdef CONFIG_PROC_FS
+static void l2tp_eth_show(struct seq_file *m, void *arg)
+{
+	struct l2tp_session *session = arg;
+	struct l2tp_eth_sess *spriv = l2tp_session_priv(session);
+	struct net_device *dev = spriv->dev;
+
+	seq_printf(m, "   interface %s\n", dev->name);
+}
+#endif
+
+static int l2tp_eth_create(struct net *net, u32 tunnel_id, u32 session_id, u32 peer_session_id, struct l2tp_session_cfg *cfg)
+{
+	struct net_device *dev;
+	char name[IFNAMSIZ];
+	struct l2tp_tunnel *tunnel;
+	struct l2tp_session *session;
+	struct l2tp_eth *priv;
+	struct l2tp_eth_sess *spriv;
+	int rc;
+	struct l2tp_eth_net *pn;
+
+	tunnel = l2tp_tunnel_find(net, tunnel_id);
+	if (!tunnel) {
+		rc = -ENODEV;
+		goto out;
+	}
+
+	session = l2tp_session_find(net, tunnel, session_id);
+	if (session) {
+		rc = -EEXIST;
+		goto out;
+	}
+
+	if (cfg->ifname) {
+		dev = dev_get_by_name(net, cfg->ifname);
+		if (dev) {
+			dev_put(dev);
+			rc = -EEXIST;
+			goto out;
+		}
+		strlcpy(name, cfg->ifname, IFNAMSIZ);
+	} else
+		strcpy(name, L2TP_ETH_DEV_NAME);
+
+	session = l2tp_session_create(sizeof(*spriv), tunnel, session_id,
+				      peer_session_id, cfg);
+	if (!session) {
+		rc = -ENOMEM;
+		goto out;
+	}
+
+	dev = alloc_netdev(sizeof(*priv), name, l2tp_eth_dev_setup);
+	if (!dev) {
+		rc = -ENOMEM;
+		goto out_del_session;
+	}
+
+	dev_net_set(dev, net);
+	if (session->mtu == 0)
+		session->mtu = dev->mtu - session->hdr_len;
+	dev->mtu = session->mtu;
+	dev->needed_headroom += session->hdr_len;
+
+	priv = netdev_priv(dev);
+	priv->dev = dev;
+	priv->session = session;
+	INIT_LIST_HEAD(&priv->list);
+
+	priv->tunnel_sock = tunnel->sock;
+	session->recv_skb = l2tp_eth_dev_recv;
+	session->session_close = l2tp_eth_delete;
+#ifdef CONFIG_PROC_FS
+	session->show = l2tp_eth_show;
+#endif
+
+	spriv = l2tp_session_priv(session);
+	spriv->dev = dev;
+
+	rc = register_netdev(dev);
+	if (rc < 0)
+		goto out_del_dev;
+
+	/* Must be done after register_netdev() */
+	strlcpy(session->ifname, dev->name, IFNAMSIZ);
+
+	dev_hold(dev);
+	pn = l2tp_eth_pernet(dev_net(dev));
+	write_lock(&pn->l2tp_eth_lock);
+	list_add(&priv->list, &pn->l2tp_eth_dev_list);
+	write_unlock(&pn->l2tp_eth_lock);
+
+	return 0;
+
+out_del_dev:
+	free_netdev(dev);
+out_del_session:
+	l2tp_session_delete(session);
+out:
+	return rc;
+}
+
+static __net_init int l2tp_eth_init_net(struct net *net)
+{
+	struct l2tp_eth_net *pn;
+	int err;
+
+	pn = kzalloc(sizeof(*pn), GFP_KERNEL);
+	if (!pn)
+		return -ENOMEM;
+
+	INIT_LIST_HEAD(&pn->l2tp_eth_dev_list);
+	rwlock_init(&pn->l2tp_eth_lock);
+
+	err = net_assign_generic(net, l2tp_eth_net_id, pn);
+	if (err)
+		goto out;
+
+	return 0;
+
+out:
+	kfree(pn);
+	return err;
+}
+
+static __net_exit void l2tp_eth_exit_net(struct net *net)
+{
+	struct l2tp_eth_net *pn;
+
+	pn = net_generic(net, l2tp_eth_net_id);
+	/*
+	 * if someone has cached our net then
+	 * further net_generic call will return NULL
+	 */
+	net_assign_generic(net, l2tp_eth_net_id, NULL);
+	kfree(pn);
+}
+
+static __net_initdata struct pernet_operations l2tp_eth_net_ops = {
+	.init = l2tp_eth_init_net,
+	.exit = l2tp_eth_exit_net,
+	.id   = &l2tp_eth_net_id,
+	.size = sizeof(struct l2tp_eth_net),
+};
+
+
+static const struct l2tp_nl_cmd_ops l2tp_eth_nl_cmd_ops = {
+	.session_create	= l2tp_eth_create,
+	.session_delete	= l2tp_session_delete,
+};
+
+
+static int __init l2tp_eth_init(void)
+{
+	int err = 0;
+
+	err = l2tp_nl_register_ops(L2TP_PWTYPE_ETH, &l2tp_eth_nl_cmd_ops);
+	if (err)
+		goto out;
+
+	err = register_pernet_device(&l2tp_eth_net_ops);
+	if (err)
+		goto out_unreg;
+
+	printk(KERN_INFO "L2TP ethernet pseudowire support (L2TPv3)\n");
+
+	return 0;
+
+out_unreg:
+	l2tp_nl_unregister_ops(L2TP_PWTYPE_ETH);
+out:
+	return err;
+}
+
+static void __exit l2tp_eth_exit(void)
+{
+	unregister_pernet_device(&l2tp_eth_net_ops);
+	l2tp_nl_unregister_ops(L2TP_PWTYPE_ETH);
+}
+
+module_init(l2tp_eth_init);
+module_exit(l2tp_eth_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("James Chapman <jchapman@katalix.com>");
+MODULE_DESCRIPTION("L2TP ethernet pseudowire driver");
+MODULE_VERSION("1.0");