l2tp: Update PPP-over-L2TP driver to work over L2TPv3

This patch makes changes to the L2TP PPP code for L2TPv3.

The existing code has some assumptions about the L2TP header which are
broken by L2TPv3. Also the sockaddr_pppol2tp structure of the original
code is too small to support the increased size of the L2TPv3 tunnel
and session id, so a new sockaddr_pppol2tpv3 structure is needed. In
the socket calls, the size of this structure is used to tell if the
operation is for L2TPv2 or L2TPv3.

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>

include/linux/if_pppol2tp.h

@@ -35,6 +35,20 @@ struct pppol2tp_addr {
 	__u16 d_tunnel, d_session;	/* For sending outgoing packets */
 };
 
+/* The L2TPv3 protocol changes tunnel and session ids from 16 to 32
+ * bits. So we need a different sockaddr structure.
+ */
+struct pppol2tpv3_addr {
+	pid_t	pid;			/* pid that owns the fd.
+					 * 0 => current */
+	int	fd;			/* FD of UDP or IP socket to use */
+
+	struct sockaddr_in addr;	/* IP address and port to send to */
+
+	__u32 s_tunnel, s_session;	/* For matching incoming packets */
+	__u32 d_tunnel, d_session;	/* For sending outgoing packets */
+};
+
 /* Socket options:
  * DEBUG	- bitmask of debug message categories
  * SENDSEQ	- 0 => don't send packets with sequence numbers

include/linux/if_pppox.h

@@ -72,6 +72,15 @@ struct sockaddr_pppol2tp {
 	struct pppol2tp_addr pppol2tp;
 }__attribute__ ((packed));
 
+/* The L2TPv3 protocol changes tunnel and session ids from 16 to 32
+ * bits. So we need a different sockaddr structure.
+ */
+struct sockaddr_pppol2tpv3 {
+	sa_family_t     sa_family;      /* address family, AF_PPPOX */
+	unsigned int    sa_protocol;    /* protocol identifier */
+	struct pppol2tpv3_addr pppol2tp;
+} __attribute__ ((packed));
+
 /*********************************************************************
  *
  * ioctl interface for defining forwarding of connections

net/l2tp/l2tp_ppp.c

@@ -291,17 +291,6 @@ static void pppol2tp_session_sock_put(struct l2tp_session *session)
  * Transmit handling
  ***********************************************************************/
 
-/* Tell how big L2TP headers are for a particular session. This
- * depends on whether sequence numbers are being used.
- */
-static inline int pppol2tp_l2tp_header_len(struct l2tp_session *session)
-{
-	if (session->send_seq)
-		return PPPOL2TP_L2TP_HDR_SIZE_SEQ;
-
-	return PPPOL2TP_L2TP_HDR_SIZE_NOSEQ;
-}
-
 /* This is the sendmsg for the PPPoL2TP pppol2tp_session socket.  We come here
  * when a user application does a sendmsg() on the session socket. L2TP and
  * PPP headers must be inserted into the user's data.
@@ -394,7 +383,6 @@ static int pppol2tp_xmit(struct ppp_channel *chan, struct sk_buff *skb)
 	static const u8 ppph[2] = { 0xff, 0x03 };
 	struct sock *sk = (struct sock *) chan->private;
 	struct sock *sk_tun;
-	int hdr_len;
 	struct l2tp_session *session;
 	struct l2tp_tunnel *tunnel;
 	struct pppol2tp_session *ps;
@@ -417,9 +405,6 @@ static int pppol2tp_xmit(struct ppp_channel *chan, struct sk_buff *skb)
 	if (tunnel == NULL)
 		goto abort_put_sess;
 
-	/* What header length is configured for this session? */
-	hdr_len = pppol2tp_l2tp_header_len(session);
-
 	old_headroom = skb_headroom(skb);
 	if (skb_cow_head(skb, sizeof(ppph)))
 		goto abort_put_sess_tun;
@@ -432,7 +417,7 @@ static int pppol2tp_xmit(struct ppp_channel *chan, struct sk_buff *skb)
 	skb->data[0] = ppph[0];
 	skb->data[1] = ppph[1];
 
-	l2tp_xmit_skb(session, skb, hdr_len);
+	l2tp_xmit_skb(session, skb, session->hdr_len);
 
 	sock_put(sk_tun);
 	sock_put(sk);
@@ -615,6 +600,7 @@ static int pppol2tp_connect(struct socket *sock, struct sockaddr *uservaddr,
 {
 	struct sock *sk = sock->sk;
 	struct sockaddr_pppol2tp *sp = (struct sockaddr_pppol2tp *) uservaddr;
+	struct sockaddr_pppol2tpv3 *sp3 = (struct sockaddr_pppol2tpv3 *) uservaddr;
 	struct pppox_sock *po = pppox_sk(sk);
 	struct l2tp_session *session = NULL;
 	struct l2tp_tunnel *tunnel;
@@ -622,6 +608,10 @@ static int pppol2tp_connect(struct socket *sock, struct sockaddr *uservaddr,
 	struct dst_entry *dst;
 	struct l2tp_session_cfg cfg = { 0, };
 	int error = 0;
+	u32 tunnel_id, peer_tunnel_id;
+	u32 session_id, peer_session_id;
+	int ver = 2;
+	int fd;
 
 	lock_sock(sk);
 
@@ -639,21 +629,40 @@ static int pppol2tp_connect(struct socket *sock, struct sockaddr *uservaddr,
 	if (sk->sk_user_data)
 		goto end; /* socket is already attached */
 
-	/* Don't bind if s_tunnel is 0 */
+	/* Get params from socket address. Handle L2TPv2 and L2TPv3 */
+	if (sockaddr_len == sizeof(struct sockaddr_pppol2tp)) {
+		fd = sp->pppol2tp.fd;
+		tunnel_id = sp->pppol2tp.s_tunnel;
+		peer_tunnel_id = sp->pppol2tp.d_tunnel;
+		session_id = sp->pppol2tp.s_session;
+		peer_session_id = sp->pppol2tp.d_session;
+	} else if (sockaddr_len == sizeof(struct sockaddr_pppol2tpv3)) {
+		ver = 3;
+		fd = sp3->pppol2tp.fd;
+		tunnel_id = sp3->pppol2tp.s_tunnel;
+		peer_tunnel_id = sp3->pppol2tp.d_tunnel;
+		session_id = sp3->pppol2tp.s_session;
+		peer_session_id = sp3->pppol2tp.d_session;
+	} else {
+		error = -EINVAL;
+		goto end; /* bad socket address */
+	}
+
+	/* Don't bind if tunnel_id is 0 */
 	error = -EINVAL;
-	if (sp->pppol2tp.s_tunnel == 0)
+	if (tunnel_id == 0)
 		goto end;
 
-	/* Special case: create tunnel context if s_session and
-	 * d_session is 0. Otherwise look up tunnel using supplied
+	/* Special case: create tunnel context if session_id and
+	 * peer_session_id is 0. Otherwise look up tunnel using supplied
 	 * tunnel id.
 	 */
-	if ((sp->pppol2tp.s_session == 0) && (sp->pppol2tp.d_session == 0)) {
-		error = l2tp_tunnel_create(sock_net(sk), sp->pppol2tp.fd, 2, sp->pppol2tp.s_tunnel, sp->pppol2tp.d_tunnel, NULL, &tunnel);
+	if ((session_id == 0) && (peer_session_id == 0)) {
+		error = l2tp_tunnel_create(sock_net(sk), fd, ver, tunnel_id, peer_tunnel_id, NULL, &tunnel);
 		if (error < 0)
 			goto end;
 	} else {
-		tunnel = l2tp_tunnel_find(sock_net(sk), sp->pppol2tp.s_tunnel);
+		tunnel = l2tp_tunnel_find(sock_net(sk), tunnel_id);
 
 		/* Error if we can't find the tunnel */
 		error = -ENOENT;
@@ -670,20 +679,21 @@ static int pppol2tp_connect(struct socket *sock, struct sockaddr *uservaddr,
 
 	/* Check that this session doesn't already exist */
 	error = -EEXIST;
-	session = l2tp_session_find(sock_net(sk), tunnel, sp->pppol2tp.s_session);
+	session = l2tp_session_find(sock_net(sk), tunnel, session_id);
 	if (session != NULL)
 		goto end;
 
-	/* Default MTU must allow space for UDP/L2TP/PPP
-	 * headers.
-	 */
-	cfg.mtu = cfg.mru = 1500 - PPPOL2TP_HEADER_OVERHEAD;
+	/* Default MTU values. */
+	if (cfg.mtu == 0)
+		cfg.mtu = 1500 - PPPOL2TP_HEADER_OVERHEAD;
+	if (cfg.mru == 0)
+		cfg.mru = cfg.mtu;
 	cfg.debug = tunnel->debug;
 
 	/* Allocate and initialize a new session context. */
 	session = l2tp_session_create(sizeof(struct pppol2tp_session),
-				      tunnel, sp->pppol2tp.s_session,
-				      sp->pppol2tp.d_session, &cfg);
+				      tunnel, session_id,
+				      peer_session_id, &cfg);
 	if (session == NULL) {
 		error = -ENOMEM;
 		goto end;
@@ -756,8 +766,7 @@ end:
 static int pppol2tp_getname(struct socket *sock, struct sockaddr *uaddr,
 			    int *usockaddr_len, int peer)
 {
-	int len = sizeof(struct sockaddr_pppol2tp);
-	struct sockaddr_pppol2tp sp;
+	int len = 0;
 	int error = 0;
 	struct l2tp_session *session;
 	struct l2tp_tunnel *tunnel;
@@ -783,21 +792,40 @@ static int pppol2tp_getname(struct socket *sock, struct sockaddr *uaddr,
 		goto end_put_sess;
 	}
 
-	memset(&sp, 0, len);
-	sp.sa_family	= AF_PPPOX;
-	sp.sa_protocol	= PX_PROTO_OL2TP;
-	sp.pppol2tp.fd  = tunnel->fd;
-	sp.pppol2tp.pid = pls->owner;
-	sp.pppol2tp.s_tunnel = tunnel->tunnel_id;
-	sp.pppol2tp.d_tunnel = tunnel->peer_tunnel_id;
-	sp.pppol2tp.s_session = session->session_id;
-	sp.pppol2tp.d_session = session->peer_session_id;
 	inet = inet_sk(sk);
-	sp.pppol2tp.addr.sin_family = AF_INET;
-	sp.pppol2tp.addr.sin_port = inet->inet_dport;
-	sp.pppol2tp.addr.sin_addr.s_addr = inet->inet_daddr;
-
-	memcpy(uaddr, &sp, len);
+	if (tunnel->version == 2) {
+		struct sockaddr_pppol2tp sp;
+		len = sizeof(sp);
+		memset(&sp, 0, len);
+		sp.sa_family	= AF_PPPOX;
+		sp.sa_protocol	= PX_PROTO_OL2TP;
+		sp.pppol2tp.fd  = tunnel->fd;
+		sp.pppol2tp.pid = pls->owner;
+		sp.pppol2tp.s_tunnel = tunnel->tunnel_id;
+		sp.pppol2tp.d_tunnel = tunnel->peer_tunnel_id;
+		sp.pppol2tp.s_session = session->session_id;
+		sp.pppol2tp.d_session = session->peer_session_id;
+		sp.pppol2tp.addr.sin_family = AF_INET;
+		sp.pppol2tp.addr.sin_port = inet->inet_dport;
+		sp.pppol2tp.addr.sin_addr.s_addr = inet->inet_daddr;
+		memcpy(uaddr, &sp, len);
+	} else if (tunnel->version == 3) {
+		struct sockaddr_pppol2tpv3 sp;
+		len = sizeof(sp);
+		memset(&sp, 0, len);
+		sp.sa_family	= AF_PPPOX;
+		sp.sa_protocol	= PX_PROTO_OL2TP;
+		sp.pppol2tp.fd  = tunnel->fd;
+		sp.pppol2tp.pid = pls->owner;
+		sp.pppol2tp.s_tunnel = tunnel->tunnel_id;
+		sp.pppol2tp.d_tunnel = tunnel->peer_tunnel_id;
+		sp.pppol2tp.s_session = session->session_id;
+		sp.pppol2tp.d_session = session->peer_session_id;
+		sp.pppol2tp.addr.sin_family = AF_INET;
+		sp.pppol2tp.addr.sin_port = inet->inet_dport;
+		sp.pppol2tp.addr.sin_addr.s_addr = inet->inet_daddr;
+		memcpy(uaddr, &sp, len);
+	}
 
 	*usockaddr_len = len;