l2tp: Add L2TPv3 protocol support

The L2TPv3 protocol changes the layout of the L2TP packet
header. Tunnel and session ids change from 16-bit to 32-bit values,
data sequence numbers change from 16-bit to 24-bit values and PPP-specific
fields are moved into protocol-specific subheaders.

Although this patch introduces L2TPv3 protocol support, there are no
userspace interfaces to create L2TPv3 sessions yet.
Signed-off-by: James Chapman <jchapman@katalix.com>
Reviewed-by: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/l2tp/Kconfig

@@ -19,6 +19,10 @@ menuconfig L2TP
 	  connections. L2TP is also used as a VPN protocol, popular
 	  with home workers to connect to their offices.
 
+	  L2TPv3 allows other protocols as well as PPP to be carried
+	  over L2TP tunnels. L2TPv3 is defined in RFC 3931
+	  <http://www.ietf.org/rfc/rfc3931.txt>.
+
 	  The kernel component handles only L2TP data packets: a
 	  userland daemon handles L2TP the control protocol (tunnel
 	  and session setup). One such daemon is OpenL2TP
@@ -26,3 +30,24 @@ menuconfig L2TP
 
 	  If you don't need L2TP, say N. To compile all L2TP code as
 	  modules, choose M here.
+
+config L2TP_V3
+	bool "L2TPv3 support (EXPERIMENTAL)"
+	depends on EXPERIMENTAL && L2TP
+	help
+	  Layer Two Tunneling Protocol Version 3
+
+	  From RFC 3931 <http://www.ietf.org/rfc/rfc3931.txt>.
+
+	  The Layer Two Tunneling Protocol (L2TP) provides a dynamic
+	  mechanism for tunneling Layer 2 (L2) "circuits" across a
+	  packet-oriented data network (e.g., over IP).  L2TP, as
+	  originally defined in RFC 2661, is a standard method for
+	  tunneling Point-to-Point Protocol (PPP) [RFC1661] sessions.
+	  L2TP has since been adopted for tunneling a number of other
+	  L2 protocols, including ATM, Frame Relay, HDLC and even raw
+	  ethernet frames.
+
+	  If you are connecting to L2TPv3 equipment, or you want to
+	  tunnel raw ethernet frames using L2TP, say Y here. If
+	  unsure, say N.

net/l2tp/l2tp_core.h

@@ -15,9 +15,14 @@
 #define L2TP_TUNNEL_MAGIC	0x42114DDA
 #define L2TP_SESSION_MAGIC	0x0C04EB7D
 
+/* Per tunnel, session hash table size */
 #define L2TP_HASH_BITS	4
 #define L2TP_HASH_SIZE	(1 << L2TP_HASH_BITS)
 
+/* System-wide, session hash table size */
+#define L2TP_HASH_BITS_2	8
+#define L2TP_HASH_SIZE_2	(1 << L2TP_HASH_BITS_2)
+
 /* Debug message categories for the DEBUG socket option */
 enum {
 	L2TP_MSG_DEBUG		= (1 << 0),	/* verbose debug (if
@@ -28,6 +33,21 @@ enum {
 	L2TP_MSG_DATA		= (1 << 3),	/* data packets */
 };
 
+enum l2tp_pwtype {
+	L2TP_PWTYPE_NONE = 0x0000,
+	L2TP_PWTYPE_ETH_VLAN = 0x0004,
+	L2TP_PWTYPE_ETH = 0x0005,
+	L2TP_PWTYPE_PPP = 0x0007,
+	L2TP_PWTYPE_PPP_AC = 0x0008,
+	L2TP_PWTYPE_IP = 0x000b,
+	__L2TP_PWTYPE_MAX
+};
+
+enum l2tp_l2spec_type {
+	L2TP_L2SPECTYPE_NONE,
+	L2TP_L2SPECTYPE_DEFAULT,
+};
+
 struct sk_buff;
 
 struct l2tp_stats {
@@ -39,6 +59,7 @@ struct l2tp_stats {
 	u64			rx_seq_discards;
 	u64			rx_oos_packets;
 	u64			rx_errors;
+	u64			rx_cookie_discards;
 };
 
 struct l2tp_tunnel;
@@ -47,6 +68,7 @@ struct l2tp_tunnel;
  * packets and transmit outgoing ones.
  */
 struct l2tp_session_cfg {
+	enum l2tp_pwtype	pw_type;
 	unsigned		data_seq:2;	/* data sequencing level
 						 * 0 => none, 1 => IP only,
 						 * 2 => all
@@ -60,12 +82,17 @@ struct l2tp_session_cfg {
 						 * control of LNS. */
 	int			debug;		/* bitmask of debug message
 						 * categories */
-	int			offset;		/* offset to payload */
+	u16			offset;		/* offset to payload */
+	u16			l2specific_len;	/* Layer 2 specific length */
+	u16			l2specific_type; /* Layer 2 specific type */
+	u8			cookie[8];	/* optional cookie */
+	int			cookie_len;	/* 0, 4 or 8 bytes */
+	u8			peer_cookie[8];	/* peer's cookie */
+	int			peer_cookie_len; /* 0, 4 or 8 bytes */
 	int			reorder_timeout; /* configured reorder timeout
 						  * (in jiffies) */
 	int			mtu;
 	int			mru;
-	int			hdr_len;
 };
 
 struct l2tp_session {
@@ -76,8 +103,17 @@ struct l2tp_session {
 						 * context */
 	u32			session_id;
 	u32			peer_session_id;
-	u16			nr;		/* session NR state (receive) */
-	u16			ns;		/* session NR state (send) */
+	u8			cookie[8];
+	int			cookie_len;
+	u8			peer_cookie[8];
+	int			peer_cookie_len;
+	u16			offset;		/* offset from end of L2TP header
+						   to beginning of data */
+	u16			l2specific_len;
+	u16			l2specific_type;
+	u16			hdr_len;
+	u32			nr;		/* session NR state (receive) */
+	u32			ns;		/* session NR state (send) */
 	struct sk_buff_head	reorder_q;	/* receive reorder queue */
 	struct hlist_node	hlist;		/* Hash list node */
 	atomic_t		ref_count;
@@ -100,9 +136,11 @@ struct l2tp_session {
 						  * (in jiffies) */
 	int			mtu;
 	int			mru;
-	int			hdr_len;
+	enum l2tp_pwtype	pwtype;
 	struct l2tp_stats	stats;
+	struct hlist_node	global_hlist;	/* Global hash list node */
 
+	int (*build_header)(struct l2tp_session *session, void *buf);
 	void (*recv_skb)(struct l2tp_session *session, struct sk_buff *skb, int data_len);
 	void (*session_close)(struct l2tp_session *session);
 	void (*ref)(struct l2tp_session *session);
@@ -132,7 +170,6 @@ struct l2tp_tunnel {
 	char			name[20];	/* for logging */
 	int			debug;		/* bitmask of debug message
 						 * categories */
-	int			hdr_len;
 	struct l2tp_stats	stats;
 
 	struct list_head	list;		/* Keep a list of all tunnels */
@@ -178,7 +215,7 @@ static inline struct l2tp_tunnel *l2tp_sock_to_tunnel(struct sock *sk)
 	return tunnel;
 }
 
-extern struct l2tp_session *l2tp_session_find(struct l2tp_tunnel *tunnel, u32 session_id);
+extern struct l2tp_session *l2tp_session_find(struct net *net, struct l2tp_tunnel *tunnel, u32 session_id);
 extern struct l2tp_session *l2tp_session_find_nth(struct l2tp_tunnel *tunnel, int nth);
 extern struct l2tp_tunnel *l2tp_tunnel_find(struct net *net, u32 tunnel_id);
 extern struct l2tp_tunnel *l2tp_tunnel_find_nth(struct net *net, int nth);
@@ -187,14 +224,15 @@ extern int l2tp_tunnel_create(struct net *net, int fd, int version, u32 tunnel_i
 extern struct l2tp_session *l2tp_session_create(int priv_size, struct l2tp_tunnel *tunnel, u32 session_id, u32 peer_session_id, struct l2tp_session_cfg *cfg);
 extern void l2tp_tunnel_free(struct l2tp_tunnel *tunnel);
 extern void l2tp_session_free(struct l2tp_session *session);
+extern void l2tp_recv_common(struct l2tp_session *session, struct sk_buff *skb, unsigned char *ptr, unsigned char *optr, u16 hdrflags, int length, int (*payload_hook)(struct sk_buff *skb));
 extern int l2tp_udp_recv_core(struct l2tp_tunnel *tunnel, struct sk_buff *skb, int (*payload_hook)(struct sk_buff *skb));
 extern int l2tp_udp_encap_recv(struct sock *sk, struct sk_buff *skb);
 
-extern void l2tp_build_l2tp_header(struct l2tp_session *session, void *buf);
 extern int l2tp_xmit_core(struct l2tp_session *session, struct sk_buff *skb, size_t data_len);
 extern int l2tp_xmit_skb(struct l2tp_session *session, struct sk_buff *skb, int hdr_len);
 extern void l2tp_tunnel_destruct(struct sock *sk);
 extern void l2tp_tunnel_closeall(struct l2tp_tunnel *tunnel);
+extern void l2tp_session_set_header_len(struct l2tp_session *session, int version);
 
 /* Tunnel reference counts. Incremented per session that is added to
  * the tunnel.

net/l2tp/l2tp_ppp.c

@@ -670,7 +670,7 @@ static int pppol2tp_connect(struct socket *sock, struct sockaddr *uservaddr,
 
 	/* Check that this session doesn't already exist */
 	error = -EEXIST;
-	session = l2tp_session_find(tunnel, sp->pppol2tp.s_session);
+	session = l2tp_session_find(sock_net(sk), tunnel, sp->pppol2tp.s_session);
 	if (session != NULL)
 		goto end;
 
@@ -678,7 +678,6 @@ static int pppol2tp_connect(struct socket *sock, struct sockaddr *uservaddr,
 	 * headers.
 	 */
 	cfg.mtu = cfg.mru = 1500 - PPPOL2TP_HEADER_OVERHEAD;
-	cfg.hdr_len = PPPOL2TP_L2TP_HDR_SIZE_NOSEQ;
 	cfg.debug = tunnel->debug;
 
 	/* Allocate and initialize a new session context. */
@@ -999,7 +998,7 @@ static int pppol2tp_tunnel_ioctl(struct l2tp_tunnel *tunnel,
 		if (stats.session_id != 0) {
 			/* resend to session ioctl handler */
 			struct l2tp_session *session =
-				l2tp_session_find(tunnel, stats.session_id);
+				l2tp_session_find(sock_net(sk), tunnel, stats.session_id);
 			if (session != NULL)
 				err = pppol2tp_session_ioctl(session, cmd, arg);
 			else
@@ -1375,6 +1374,8 @@ static int pppol2tp_getsockopt(struct socket *sock, int level,
 
 /*****************************************************************************
  * /proc filesystem for debug
+ * Since the original pppol2tp driver provided /proc/net/pppol2tp for
+ * L2TPv2, we dump only L2TPv2 tunnels and sessions here.
  *****************************************************************************/
 
 static unsigned int pppol2tp_net_id;
@@ -1391,14 +1392,24 @@ struct pppol2tp_seq_data {
 
 static void pppol2tp_next_tunnel(struct net *net, struct pppol2tp_seq_data *pd)
 {
-	pd->tunnel = l2tp_tunnel_find_nth(net, pd->tunnel_idx);
-	pd->tunnel_idx++;
+	for (;;) {
+		pd->tunnel = l2tp_tunnel_find_nth(net, pd->tunnel_idx);
+		pd->tunnel_idx++;
+
+		if (pd->tunnel == NULL)
+			break;
+
+		/* Ignore L2TPv3 tunnels */
+		if (pd->tunnel->version < 3)
+			break;
+	}
 }
 
 static void pppol2tp_next_session(struct net *net, struct pppol2tp_seq_data *pd)
 {
 	pd->session = l2tp_session_find_nth(pd->tunnel, pd->session_idx);
 	pd->session_idx++;
+
 	if (pd->session == NULL) {
 		pd->session_idx = 0;
 		pppol2tp_next_tunnel(net, pd);