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>

1 files changed, 397 insertions, 135 deletions

diff --git a/net/l2tp/l2tp_core.c b/net/l2tp/l2tp_core.c
index 4b6da3689893..0eee1a65f1b1 100644
--- a/net/l2tp/l2tp_core.c
+++ b/net/l2tp/l2tp_core.c
@@ -65,6 +65,7 @@
 
 #define L2TP_HDR_VER_MASK  0x000F
 #define L2TP_HDR_VER_2     0x0002
+#define L2TP_HDR_VER_3     0x0003
 
 /* L2TPv3 default L2-specific sublayer */
 #define L2TP_SLFLAG_S      0x40000000
@@ -85,7 +86,7 @@
 /* Private data stored for received packets in the skb.
  */
 struct l2tp_skb_cb {
-        u16                     ns;
+        u32                     ns;
         u16                     has_seq;
         u16                     length;
         unsigned long           expires;
@@ -101,6 +102,8 @@ static unsigned int l2tp_net_id;
 struct l2tp_net {
         struct list_head l2tp_tunnel_list;
         rwlock_t l2tp_tunnel_list_lock;
+        struct hlist_head l2tp_session_hlist[L2TP_HASH_SIZE_2];
+        rwlock_t l2tp_session_hlist_lock;
 };
 
 static inline struct l2tp_net *l2tp_pernet(struct net *net)
@@ -110,6 +113,40 @@ static inline struct l2tp_net *l2tp_pernet(struct net *net)
         return net_generic(net, l2tp_net_id);
 }
 
+/* Session hash global list for L2TPv3.
+ * The session_id SHOULD be random according to RFC3931, but several
+ * L2TP implementations use incrementing session_ids.  So we do a real
+ * hash on the session_id, rather than a simple bitmask.
+ */
+static inline struct hlist_head *
+l2tp_session_id_hash_2(struct l2tp_net *pn, u32 session_id)
+{
+        return &pn->l2tp_session_hlist[hash_32(session_id, L2TP_HASH_BITS_2)];
+
+}
+
+/* Lookup a session by id in the global session list
+ */
+static struct l2tp_session *l2tp_session_find_2(struct net *net, u32 session_id)
+{
+        struct l2tp_net *pn = l2tp_pernet(net);
+        struct hlist_head *session_list =
+                l2tp_session_id_hash_2(pn, session_id);
+        struct l2tp_session *session;
+        struct hlist_node *walk;
+
+        read_lock_bh(&pn->l2tp_session_hlist_lock);
+        hlist_for_each_entry(session, walk, session_list, global_hlist) {
+                if (session->session_id == session_id) {
+                        read_unlock_bh(&pn->l2tp_session_hlist_lock);
+                        return session;
+                }
+        }
+        read_unlock_bh(&pn->l2tp_session_hlist_lock);
+
+        return NULL;
+}
+
 /* Session hash list.
  * The session_id SHOULD be random according to RFC2661, but several
  * L2TP implementations (Cisco and Microsoft) use incrementing
@@ -124,13 +161,20 @@ l2tp_session_id_hash(struct l2tp_tunnel *tunnel, u32 session_id)
 
 /* Lookup a session by id
  */
-struct l2tp_session *l2tp_session_find(struct l2tp_tunnel *tunnel, u32 session_id)
+struct l2tp_session *l2tp_session_find(struct net *net, struct l2tp_tunnel *tunnel, u32 session_id)
 {
-        struct hlist_head *session_list =
-                l2tp_session_id_hash(tunnel, session_id);
+        struct hlist_head *session_list;
         struct l2tp_session *session;
         struct hlist_node *walk;
 
+        /* In L2TPv3, session_ids are unique over all tunnels and we
+         * sometimes need to look them up before we know the
+         * tunnel.
+         */
+        if (tunnel == NULL)
+                return l2tp_session_find_2(net, session_id);
+
+        session_list = l2tp_session_id_hash(tunnel, session_id);
         read_lock_bh(&tunnel->hlist_lock);
         hlist_for_each_entry(session, walk, session_list, hlist) {
                 if (session->session_id == session_id) {
@@ -218,7 +262,7 @@ static void l2tp_recv_queue_skb(struct l2tp_session *session, struct sk_buff *sk
 {
         struct sk_buff *skbp;
         struct sk_buff *tmp;
-        u16 ns = L2TP_SKB_CB(skb)->ns;
+        u32 ns = L2TP_SKB_CB(skb)->ns;
 
         spin_lock_bh(&session->reorder_q.lock);
         skb_queue_walk_safe(&session->reorder_q, skbp, tmp) {
@@ -259,6 +303,11 @@ static void l2tp_recv_dequeue_skb(struct l2tp_session *session, struct sk_buff *
         if (L2TP_SKB_CB(skb)->has_seq) {
                 /* Bump our Nr */
                 session->nr++;
+                if (tunnel->version == L2TP_HDR_VER_2)
+                        session->nr &= 0xffff;
+                else
+                        session->nr &= 0xffffff;
+
                 PRINTK(session->debug, L2TP_MSG_SEQ, KERN_DEBUG,
                        "%s: updated nr to %hu\n", session->name, session->nr);
         }
@@ -291,8 +340,8 @@ static void l2tp_recv_dequeue(struct l2tp_session *session)
                         session->stats.rx_seq_discards++;
                         session->stats.rx_errors++;
                         PRINTK(session->debug, L2TP_MSG_SEQ, KERN_DEBUG,
-                               "%s: oos pkt %hu len %d discarded (too old), "
-                               "waiting for %hu, reorder_q_len=%d\n",
+                               "%s: oos pkt %u len %d discarded (too old), "
+                               "waiting for %u, reorder_q_len=%d\n",
                                session->name, L2TP_SKB_CB(skb)->ns,
                                L2TP_SKB_CB(skb)->length, session->nr,
                                skb_queue_len(&session->reorder_q));
@@ -306,8 +355,8 @@ static void l2tp_recv_dequeue(struct l2tp_session *session)
                 if (L2TP_SKB_CB(skb)->has_seq) {
                         if (L2TP_SKB_CB(skb)->ns != session->nr) {
                                 PRINTK(session->debug, L2TP_MSG_SEQ, KERN_DEBUG,
-                                       "%s: holding oos pkt %hu len %d, "
-                                       "waiting for %hu, reorder_q_len=%d\n",
+                                       "%s: holding oos pkt %u len %d, "
+                                       "waiting for %u, reorder_q_len=%d\n",
                                        session->name, L2TP_SKB_CB(skb)->ns,
                                        L2TP_SKB_CB(skb)->length, session->nr,
                                        skb_queue_len(&session->reorder_q));
@@ -352,100 +401,73 @@ static inline int l2tp_verify_udp_checksum(struct sock *sk,
         return __skb_checksum_complete(skb);
 }
 
-/* Internal UDP receive frame. Do the real work of receiving an L2TP data frame
- * here. The skb is not on a list when we get here.
- * Returns 0 if the packet was a data packet and was successfully passed on.
- * Returns 1 if the packet was not a good data packet and could not be
- * forwarded.  All such packets are passed up to userspace to deal with.
+/* Do receive processing of L2TP data frames. We handle both L2TPv2
+ * and L2TPv3 data frames here.
+ *
+ * L2TPv2 Data Message Header
+ *
+ *  0                   1                   2                   3
+ *  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * |T|L|x|x|S|x|O|P|x|x|x|x|  Ver  |          Length (opt)         |
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * |           Tunnel ID           |           Session ID          |
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * |             Ns (opt)          |             Nr (opt)          |
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * |      Offset Size (opt)        |    Offset pad... (opt)
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ *
+ * Data frames are marked by T=0. All other fields are the same as
+ * those in L2TP control frames.
+ *
+ * L2TPv3 Data Message Header
+ *
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * |                      L2TP Session Header                      |
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * |                      L2-Specific Sublayer                     |
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * |                        Tunnel Payload                      ...
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ *
+ * L2TPv3 Session Header Over IP
+ *
+ *  0                   1                   2                   3
+ *  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * |                           Session ID                          |
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * |               Cookie (optional, maximum 64 bits)...
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ *                                                                 |
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ *
+ * L2TPv3 L2-Specific Sublayer Format
+ *
+ *  0                   1                   2                   3
+ *  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * |x|S|x|x|x|x|x|x|              Sequence Number                  |
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ *
+ * Cookie value, sublayer format and offset (pad) are negotiated with
+ * the peer when the session is set up. Unlike L2TPv2, we do not need
+ * to parse the packet header to determine if optional fields are
+ * present.
+ *
+ * Caller must already have parsed the frame and determined that it is
+ * a data (not control) frame before coming here. Fields up to the
+ * session-id have already been parsed and ptr points to the data
+ * after the session-id.
  */
-int l2tp_udp_recv_core(struct l2tp_tunnel *tunnel, struct sk_buff *skb,
-                       int (*payload_hook)(struct sk_buff *skb))
+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))
 {
-        struct l2tp_session *session = NULL;
-        unsigned char *ptr, *optr;
-        u16 hdrflags;
-        u32 tunnel_id, session_id;
-        int length;
+        struct l2tp_tunnel *tunnel = session->tunnel;
         int offset;
-        u16 version;
-        u16 ns, nr;
-
-        if (tunnel->sock && l2tp_verify_udp_checksum(tunnel->sock, skb))
-                goto discard_bad_csum;
-
-        /* UDP always verifies the packet length. */
-        __skb_pull(skb, sizeof(struct udphdr));
-
-        /* Short packet? */
-        if (!pskb_may_pull(skb, L2TP_HDR_SIZE_SEQ)) {
-                PRINTK(tunnel->debug, L2TP_MSG_DATA, KERN_INFO,
-                       "%s: recv short packet (len=%d)\n", tunnel->name, skb->len);
-                goto error;
-        }
-
-        /* Point to L2TP header */
-        optr = ptr = skb->data;
-
-        /* Trace packet contents, if enabled */
-        if (tunnel->debug & L2TP_MSG_DATA) {
-                length = min(32u, skb->len);
-                if (!pskb_may_pull(skb, length))
-                        goto error;
-
-                printk(KERN_DEBUG "%s: recv: ", tunnel->name);
-
-                offset = 0;
-                do {
-                        printk(" %02X", ptr[offset]);
-                } while (++offset < length);
-
-                printk("\n");
-        }
-
-        /* Get L2TP header flags */
-        hdrflags = ntohs(*(__be16 *)ptr);
-
-        /* Check protocol version */
-        version = hdrflags & L2TP_HDR_VER_MASK;
-        if (version != tunnel->version) {
-                PRINTK(tunnel->debug, L2TP_MSG_DATA, KERN_INFO,
-                       "%s: recv protocol version mismatch: got %d expected %d\n",
-                       tunnel->name, version, tunnel->version);
-                goto error;
-        }
-
-        /* Get length of L2TP packet */
-        length = skb->len;
-
-        /* If type is control packet, it is handled by userspace. */
-        if (hdrflags & L2TP_HDRFLAG_T) {
-                PRINTK(tunnel->debug, L2TP_MSG_DATA, KERN_DEBUG,
-                       "%s: recv control packet, len=%d\n", tunnel->name, length);
-                goto error;
-        }
-
-        /* Skip flags */
-        ptr += 2;
-
-        /* If length is present, skip it */
-        if (hdrflags & L2TP_HDRFLAG_L)
-                ptr += 2;
-
-        /* Extract tunnel and session ID */
-        tunnel_id = ntohs(*(__be16 *) ptr);
-        ptr += 2;
-        session_id = ntohs(*(__be16 *) ptr);
-        ptr += 2;
-
-        /* Find the session context */
-        session = l2tp_session_find(tunnel, session_id);
-        if (!session) {
-                /* Not found? Pass to userspace to deal with */
-                PRINTK(tunnel->debug, L2TP_MSG_DATA, KERN_INFO,
-                       "%s: no session found (%hu/%hu). Passing up.\n",
-                       tunnel->name, tunnel_id, session_id);
-                goto error;
-        }
+        u32 ns, nr;
 
         /* The ref count is increased since we now hold a pointer to
          * the session. Take care to decrement the refcnt when exiting
@@ -455,6 +477,18 @@ int l2tp_udp_recv_core(struct l2tp_tunnel *tunnel, struct sk_buff *skb,
         if (session->ref)
                 (*session->ref)(session);
 
+        /* Parse and check optional cookie */
+        if (session->peer_cookie_len > 0) {
+                if (memcmp(ptr, &session->peer_cookie[0], session->peer_cookie_len)) {
+                        PRINTK(tunnel->debug, L2TP_MSG_DATA, KERN_INFO,
+                               "%s: cookie mismatch (%u/%u). Discarding.\n",
+                               tunnel->name, tunnel->tunnel_id, session->session_id);
+                        session->stats.rx_cookie_discards++;
+                        goto discard;
+                }
+                ptr += session->peer_cookie_len;
+        }
+
         /* Handle the optional sequence numbers. Sequence numbers are
          * in different places for L2TPv2 and L2TPv3.
          *
@@ -464,21 +498,40 @@ int l2tp_udp_recv_core(struct l2tp_tunnel *tunnel, struct sk_buff *skb,
          */
         ns = nr = 0;
         L2TP_SKB_CB(skb)->has_seq = 0;
-        if (hdrflags & L2TP_HDRFLAG_S) {
-                ns = (u16) ntohs(*(__be16 *) ptr);
-                ptr += 2;
-                nr = ntohs(*(__be16 *) ptr);
-                ptr += 2;
+        if (tunnel->version == L2TP_HDR_VER_2) {
+                if (hdrflags & L2TP_HDRFLAG_S) {
+                        ns = ntohs(*(__be16 *) ptr);
+                        ptr += 2;
+                        nr = ntohs(*(__be16 *) ptr);
+                        ptr += 2;
 
-                /* Store L2TP info in the skb */
-                L2TP_SKB_CB(skb)->ns = ns;
-                L2TP_SKB_CB(skb)->has_seq = 1;
+                        /* Store L2TP info in the skb */
+                        L2TP_SKB_CB(skb)->ns = ns;
+                        L2TP_SKB_CB(skb)->has_seq = 1;
 
-                PRINTK(session->debug, L2TP_MSG_SEQ, KERN_DEBUG,
-                       "%s: recv data ns=%hu, nr=%hu, session nr=%hu\n",
-                       session->name, ns, nr, session->nr);
+                        PRINTK(session->debug, L2TP_MSG_SEQ, KERN_DEBUG,
+                               "%s: recv data ns=%u, nr=%u, session nr=%u\n",
+                               session->name, ns, nr, session->nr);
+                }
+        } else if (session->l2specific_type == L2TP_L2SPECTYPE_DEFAULT) {
+                u32 l2h = ntohl(*(__be32 *) ptr);
+
+                if (l2h & 0x40000000) {
+                        ns = l2h & 0x00ffffff;
+
+                        /* Store L2TP info in the skb */
+                        L2TP_SKB_CB(skb)->ns = ns;
+                        L2TP_SKB_CB(skb)->has_seq = 1;
+
+                        PRINTK(session->debug, L2TP_MSG_SEQ, KERN_DEBUG,
+                               "%s: recv data ns=%u, session nr=%u\n",
+                               session->name, ns, session->nr);
+                }
         }
 
+        /* Advance past L2-specific header, if present */
+        ptr += session->l2specific_len;
+
         if (L2TP_SKB_CB(skb)->has_seq) {
                 /* Received a packet with sequence numbers. If we're the LNS,
                  * check if we sre sending sequence numbers and if not,
@@ -489,6 +542,7 @@ int l2tp_udp_recv_core(struct l2tp_tunnel *tunnel, struct sk_buff *skb,
                                "%s: requested to enable seq numbers by LNS\n",
                                session->name);
                         session->send_seq = -1;
+                        l2tp_session_set_header_len(session, tunnel->version);
                 }
         } else {
                 /* No sequence numbers.
@@ -512,6 +566,7 @@ int l2tp_udp_recv_core(struct l2tp_tunnel *tunnel, struct sk_buff *skb,
                                "%s: requested to disable seq numbers by LNS\n",
                                session->name);
                         session->send_seq = 0;
+                        l2tp_session_set_header_len(session, tunnel->version);
                 } else if (session->send_seq) {
                         PRINTK(session->debug, L2TP_MSG_SEQ, KERN_WARNING,
                                "%s: recv data has no seq numbers when required. "
@@ -521,11 +576,19 @@ int l2tp_udp_recv_core(struct l2tp_tunnel *tunnel, struct sk_buff *skb,
                 }
         }
 
-        /* If offset bit set, skip it. */
-        if (hdrflags & L2TP_HDRFLAG_O) {
-                offset = ntohs(*(__be16 *)ptr);
-                ptr += 2 + offset;
-        }
+        /* Session data offset is handled differently for L2TPv2 and
+         * L2TPv3. For L2TPv2, there is an optional 16-bit value in
+         * the header. For L2TPv3, the offset is negotiated using AVPs
+         * in the session setup control protocol.
+         */
+        if (tunnel->version == L2TP_HDR_VER_2) {
+                /* If offset bit set, skip it. */
+                if (hdrflags & L2TP_HDRFLAG_O) {
+                        offset = ntohs(*(__be16 *)ptr);
+                        ptr += 2 + offset;
+                }
+        } else
+                ptr += session->offset;
 
         offset = ptr - optr;
         if (!pskb_may_pull(skb, offset))
@@ -564,8 +627,8 @@ int l2tp_udp_recv_core(struct l2tp_tunnel *tunnel, struct sk_buff *skb,
                         if (L2TP_SKB_CB(skb)->ns != session->nr) {
                                 session->stats.rx_seq_discards++;
                                 PRINTK(session->debug, L2TP_MSG_SEQ, KERN_DEBUG,
-                                       "%s: oos pkt %hu len %d discarded, "
-                                       "waiting for %hu, reorder_q_len=%d\n",
+                                       "%s: oos pkt %u len %d discarded, "
+                                       "waiting for %u, reorder_q_len=%d\n",
                                        session->name, L2TP_SKB_CB(skb)->ns,
                                        L2TP_SKB_CB(skb)->length, session->nr,
                                        skb_queue_len(&session->reorder_q));
@@ -586,7 +649,7 @@ int l2tp_udp_recv_core(struct l2tp_tunnel *tunnel, struct sk_buff *skb,
 
         l2tp_session_dec_refcount(session);
 
-        return 0;
+        return;
 
 discard:
         session->stats.rx_errors++;
@@ -596,6 +659,111 @@ discard:
                 (*session->deref)(session);
 
         l2tp_session_dec_refcount(session);
+}
+EXPORT_SYMBOL(l2tp_recv_common);
+
+/* Internal UDP receive frame. Do the real work of receiving an L2TP data frame
+ * here. The skb is not on a list when we get here.
+ * Returns 0 if the packet was a data packet and was successfully passed on.
+ * Returns 1 if the packet was not a good data packet and could not be
+ * forwarded.  All such packets are passed up to userspace to deal with.
+ */
+int l2tp_udp_recv_core(struct l2tp_tunnel *tunnel, struct sk_buff *skb,
+                       int (*payload_hook)(struct sk_buff *skb))
+{
+        struct l2tp_session *session = NULL;
+        unsigned char *ptr, *optr;
+        u16 hdrflags;
+        u32 tunnel_id, session_id;
+        int offset;
+        u16 version;
+        int length;
+
+        if (tunnel->sock && l2tp_verify_udp_checksum(tunnel->sock, skb))
+                goto discard_bad_csum;
+
+        /* UDP always verifies the packet length. */
+        __skb_pull(skb, sizeof(struct udphdr));
+
+        /* Short packet? */
+        if (!pskb_may_pull(skb, L2TP_HDR_SIZE_SEQ)) {
+                PRINTK(tunnel->debug, L2TP_MSG_DATA, KERN_INFO,
+                       "%s: recv short packet (len=%d)\n", tunnel->name, skb->len);
+                goto error;
+        }
+
+        /* Point to L2TP header */
+        optr = ptr = skb->data;
+
+        /* Trace packet contents, if enabled */
+        if (tunnel->debug & L2TP_MSG_DATA) {
+                length = min(32u, skb->len);
+                if (!pskb_may_pull(skb, length))
+                        goto error;
+
+                printk(KERN_DEBUG "%s: recv: ", tunnel->name);
+
+                offset = 0;
+                do {
+                        printk(" %02X", ptr[offset]);
+                } while (++offset < length);
+
+                printk("\n");
+        }
+
+        /* Get L2TP header flags */
+        hdrflags = ntohs(*(__be16 *) ptr);
+
+        /* Check protocol version */
+        version = hdrflags & L2TP_HDR_VER_MASK;
+        if (version != tunnel->version) {
+                PRINTK(tunnel->debug, L2TP_MSG_DATA, KERN_INFO,
+                       "%s: recv protocol version mismatch: got %d expected %d\n",
+                       tunnel->name, version, tunnel->version);
+                goto error;
+        }
+
+        /* Get length of L2TP packet */
+        length = skb->len;
+
+        /* If type is control packet, it is handled by userspace. */
+        if (hdrflags & L2TP_HDRFLAG_T) {
+                PRINTK(tunnel->debug, L2TP_MSG_DATA, KERN_DEBUG,
+                       "%s: recv control packet, len=%d\n", tunnel->name, length);
+                goto error;
+        }
+
+        /* Skip flags */
+        ptr += 2;
+
+        if (tunnel->version == L2TP_HDR_VER_2) {
+                /* If length is present, skip it */
+                if (hdrflags & L2TP_HDRFLAG_L)
+                        ptr += 2;
+
+                /* Extract tunnel and session ID */
+                tunnel_id = ntohs(*(__be16 *) ptr);
+                ptr += 2;
+                session_id = ntohs(*(__be16 *) ptr);
+                ptr += 2;
+        } else {
+                ptr += 2;       /* skip reserved bits */
+                tunnel_id = tunnel->tunnel_id;
+                session_id = ntohl(*(__be32 *) ptr);
+                ptr += 4;
+        }
+
+        /* Find the session context */
+        session = l2tp_session_find(tunnel->l2tp_net, tunnel, session_id);
+        if (!session) {
+                /* Not found? Pass to userspace to deal with */
+                PRINTK(tunnel->debug, L2TP_MSG_DATA, KERN_INFO,
+                       "%s: no session found (%u/%u). Passing up.\n",
+                       tunnel->name, tunnel_id, session_id);
+                goto error;
+        }
+
+        l2tp_recv_common(session, skb, ptr, optr, hdrflags, length, payload_hook);
 
         return 0;
 
@@ -651,11 +819,11 @@ EXPORT_SYMBOL_GPL(l2tp_udp_encap_recv);
 
 /* Build an L2TP header for the session into the buffer provided.
  */
-static void l2tp_build_l2tpv2_header(struct l2tp_tunnel *tunnel,
-                                     struct l2tp_session *session,
-                                     void *buf)
+static int l2tp_build_l2tpv2_header(struct l2tp_session *session, void *buf)
 {
+        struct l2tp_tunnel *tunnel = session->tunnel;
         __be16 *bufp = buf;
+        __be16 *optr = buf;
         u16 flags = L2TP_HDR_VER_2;
         u32 tunnel_id = tunnel->peer_tunnel_id;
         u32 session_id = session->peer_session_id;
@@ -671,19 +839,51 @@ static void l2tp_build_l2tpv2_header(struct l2tp_tunnel *tunnel,
                 *bufp++ = htons(session->ns);
                 *bufp++ = 0;
                 session->ns++;
+                session->ns &= 0xffff;
                 PRINTK(session->debug, L2TP_MSG_SEQ, KERN_DEBUG,
-                       "%s: updated ns to %hu\n", session->name, session->ns);
+                       "%s: updated ns to %u\n", session->name, session->ns);
         }
+
+        return bufp - optr;
 }
 
-void l2tp_build_l2tp_header(struct l2tp_session *session, void *buf)
+static int l2tp_build_l2tpv3_header(struct l2tp_session *session, void *buf)
 {
-        struct l2tp_tunnel *tunnel = session->tunnel;
+        char *bufp = buf;
+        char *optr = bufp;
+        u16 flags = L2TP_HDR_VER_3;
+
+        /* Setup L2TP header. */
+        *((__be16 *) bufp) = htons(flags);
+        bufp += 2;
+        *((__be16 *) bufp) = 0;
+        bufp += 2;
+        *((__be32 *) bufp) = htonl(session->peer_session_id);
+        bufp += 4;
+        if (session->cookie_len) {
+                memcpy(bufp, &session->cookie[0], session->cookie_len);
+                bufp += session->cookie_len;
+        }
+        if (session->l2specific_len) {
+                if (session->l2specific_type == L2TP_L2SPECTYPE_DEFAULT) {
+                        u32 l2h = 0;
+                        if (session->send_seq) {
+                                l2h = 0x40000000 | session->ns;
+                                session->ns++;
+                                session->ns &= 0xffffff;
+                                PRINTK(session->debug, L2TP_MSG_SEQ, KERN_DEBUG,
+                                       "%s: updated ns to %u\n", session->name, session->ns);
+                        }
+
+                        *((__be32 *) bufp) = htonl(l2h);
+                }
+                bufp += session->l2specific_len;
+        }
+        if (session->offset)
+                bufp += session->offset;
 
-        BUG_ON(tunnel->version != L2TP_HDR_VER_2);
-        l2tp_build_l2tpv2_header(tunnel, session, buf);
+        return bufp - optr;
 }
-EXPORT_SYMBOL_GPL(l2tp_build_l2tp_header);
 
 int l2tp_xmit_core(struct l2tp_session *session, struct sk_buff *skb, size_t data_len)
 {
@@ -694,7 +894,7 @@ int l2tp_xmit_core(struct l2tp_session *session, struct sk_buff *skb, size_t dat
         /* Debug */
         if (session->send_seq)
                 PRINTK(session->debug, L2TP_MSG_DATA, KERN_DEBUG,
-                       "%s: send %Zd bytes, ns=%hu\n", session->name,
+                       "%s: send %Zd bytes, ns=%u\n", session->name,
                        data_len, session->ns - 1);
         else
                 PRINTK(session->debug, L2TP_MSG_DATA, KERN_DEBUG,
@@ -780,7 +980,7 @@ int l2tp_xmit_skb(struct l2tp_session *session, struct sk_buff *skb, int hdr_len
         skb->truesize += new_headroom - old_headroom;
 
         /* Setup L2TP header */
-        l2tp_build_l2tp_header(session, __skb_push(skb, hdr_len));
+        session->build_header(session, __skb_push(skb, hdr_len));
         udp_len = sizeof(struct udphdr) + hdr_len + data_len;
 
         /* Setup UDP header */
@@ -791,7 +991,6 @@ int l2tp_xmit_skb(struct l2tp_session *session, struct sk_buff *skb, int hdr_len
         uh->source = inet->inet_sport;
         uh->dest = inet->inet_dport;
         uh->len = htons(udp_len);
-
         uh->check = 0;
 
         memset(&(IPCB(skb)->opt), 0, sizeof(IPCB(skb)->opt));
@@ -911,6 +1110,14 @@ again:
 
                         write_unlock_bh(&tunnel->hlist_lock);
 
+                        if (tunnel->version != L2TP_HDR_VER_2) {
+                                struct l2tp_net *pn = l2tp_pernet(tunnel->l2tp_net);
+
+                                write_lock_bh(&pn->l2tp_session_hlist_lock);
+                                hlist_del_init(&session->global_hlist);
+                                write_unlock_bh(&pn->l2tp_session_hlist_lock);
+                        }
+
                         if (session->session_close != NULL)
                                 (*session->session_close)(session);
 
@@ -997,9 +1204,6 @@ int l2tp_tunnel_create(struct net *net, int fd, int version, u32 tunnel_id, u32
                 goto err;
         }
 
-        if (version != L2TP_HDR_VER_2)
-                goto err;
-
         tunnel = kzalloc(sizeof(struct l2tp_tunnel), GFP_KERNEL);
         if (tunnel == NULL) {
                 err = -ENOMEM;
@@ -1077,6 +1281,15 @@ void l2tp_session_free(struct l2tp_session *session)
                 hlist_del_init(&session->hlist);
                 write_unlock_bh(&tunnel->hlist_lock);
 
+                /* Unlink from the global hash if not L2TPv2 */
+                if (tunnel->version != L2TP_HDR_VER_2) {
+                        struct l2tp_net *pn = l2tp_pernet(tunnel->l2tp_net);
+
+                        write_lock_bh(&pn->l2tp_session_hlist_lock);
+                        hlist_del_init(&session->global_hlist);
+                        write_unlock_bh(&pn->l2tp_session_hlist_lock);
+                }
+
                 if (session->session_id != 0)
                         atomic_dec(&l2tp_session_count);
 
@@ -1095,6 +1308,22 @@ void l2tp_session_free(struct l2tp_session *session)
 }
 EXPORT_SYMBOL_GPL(l2tp_session_free);
 
+/* We come here whenever a session's send_seq, cookie_len or
+ * l2specific_len parameters are set.
+ */
+void l2tp_session_set_header_len(struct l2tp_session *session, int version)
+{
+        if (version == L2TP_HDR_VER_2) {
+                session->hdr_len = 6;
+                if (session->send_seq)
+                        session->hdr_len += 4;
+        } else {
+                session->hdr_len = 8 + session->cookie_len + session->l2specific_len + session->offset;
+        }
+
+}
+EXPORT_SYMBOL_GPL(l2tp_session_set_header_len);
+
 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)
 {
         struct l2tp_session *session;
@@ -1106,6 +1335,7 @@ struct l2tp_session *l2tp_session_create(int priv_size, struct l2tp_tunnel *tunn
 
                 session->session_id = session_id;
                 session->peer_session_id = peer_session_id;
+                session->nr = 1;
 
                 sprintf(&session->name[0], "sess %u/%u",
                         tunnel->tunnel_id, session->session_id);
@@ -1113,20 +1343,36 @@ struct l2tp_session *l2tp_session_create(int priv_size, struct l2tp_tunnel *tunn
                 skb_queue_head_init(&session->reorder_q);
 
                 INIT_HLIST_NODE(&session->hlist);
+                INIT_HLIST_NODE(&session->global_hlist);
 
                 /* Inherit debug options from tunnel */
                 session->debug = tunnel->debug;
 
                 if (cfg) {
+                        session->pwtype = cfg->pw_type;
                         session->debug = cfg->debug;
-                        session->hdr_len = cfg->hdr_len;
                         session->mtu = cfg->mtu;
                         session->mru = cfg->mru;
                         session->send_seq = cfg->send_seq;
                         session->recv_seq = cfg->recv_seq;
                         session->lns_mode = cfg->lns_mode;
+                        session->reorder_timeout = cfg->reorder_timeout;
+                        session->offset = cfg->offset;
+                        session->l2specific_type = cfg->l2specific_type;
+                        session->l2specific_len = cfg->l2specific_len;
+                        session->cookie_len = cfg->cookie_len;
+                        memcpy(&session->cookie[0], &cfg->cookie[0], cfg->cookie_len);
+                        session->peer_cookie_len = cfg->peer_cookie_len;
+                        memcpy(&session->peer_cookie[0], &cfg->peer_cookie[0], cfg->peer_cookie_len);
                 }
 
+                if (tunnel->version == L2TP_HDR_VER_2)
+                        session->build_header = l2tp_build_l2tpv2_header;
+                else
+                        session->build_header = l2tp_build_l2tpv3_header;
+
+                l2tp_session_set_header_len(session, tunnel->version);
+
                 /* Bump the reference count. The session context is deleted
                  * only when this drops to zero.
                  */
@@ -1142,6 +1388,16 @@ struct l2tp_session *l2tp_session_create(int priv_size, struct l2tp_tunnel *tunn
                                l2tp_session_id_hash(tunnel, session_id));
                 write_unlock_bh(&tunnel->hlist_lock);
 
+                /* And to the global session list if L2TPv3 */
+                if (tunnel->version != L2TP_HDR_VER_2) {
+                        struct l2tp_net *pn = l2tp_pernet(tunnel->l2tp_net);
+
+                        write_lock_bh(&pn->l2tp_session_hlist_lock);
+                        hlist_add_head(&session->global_hlist,
+                                       l2tp_session_id_hash_2(pn, session_id));
+                        write_unlock_bh(&pn->l2tp_session_hlist_lock);
+                }
+
                 /* Ignore management session in session count value */
                 if (session->session_id != 0)
                         atomic_inc(&l2tp_session_count);
@@ -1159,6 +1415,7 @@ static __net_init int l2tp_init_net(struct net *net)
 {
         struct l2tp_net *pn;
         int err;
+        int hash;
 
         pn = kzalloc(sizeof(*pn), GFP_KERNEL);
         if (!pn)
@@ -1167,6 +1424,11 @@ static __net_init int l2tp_init_net(struct net *net)
         INIT_LIST_HEAD(&pn->l2tp_tunnel_list);
         rwlock_init(&pn->l2tp_tunnel_list_lock);
 
+        for (hash = 0; hash < L2TP_HASH_SIZE_2; hash++)
+                INIT_HLIST_HEAD(&pn->l2tp_session_hlist[hash]);
+
+        rwlock_init(&pn->l2tp_session_hlist_lock);
+
         err = net_assign_generic(net, l2tp_net_id, pn);
         if (err)
                 goto out;