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	Version: linux-6.0.1 spark-3.0.0 hadoop-3.2.0-src hadoop-3.3.0-src spark-2.4.7 linux-4.15.13 hadoop-2.7.4-src Revert   Change

 // SPDX-License-Identifier: GPL-2.0-only
 /* L2TP core.
  *
  * Copyright (c) 2008,2009,2010 Katalix Systems Ltd
  *
  * This file contains some code of the original L2TPv2 pppol2tp
  * driver, which has the following copyright:
  *
  * Authors: Martijn van Oosterhout <kleptog@svana.org>
  *      James Chapman (jchapman@katalix.com)
  * Contributors:
  *      Michal Ostrowski <mostrows@speakeasy.net>
  *      Arnaldo Carvalho de Melo <acme@xconectiva.com.br>
  *      David S. Miller (davem@redhat.com)
  */
 
 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
 
 #include <linux/module.h>
 #include <linux/string.h>
 #include <linux/list.h>
 #include <linux/rculist.h>
 #include <linux/uaccess.h>
 
 #include <linux/kernel.h>
 #include <linux/spinlock.h>
 #include <linux/kthread.h>
 #include <linux/sched.h>
 #include <linux/slab.h>
 #include <linux/errno.h>
 #include <linux/jiffies.h>
 
 #include <linux/netdevice.h>
 #include <linux/net.h>
 #include <linux/inetdevice.h>
 #include <linux/skbuff.h>
 #include <linux/init.h>
 #include <linux/in.h>
 #include <linux/ip.h>
 #include <linux/udp.h>
 #include <linux/l2tp.h>
 #include <linux/hash.h>
 #include <linux/sort.h>
 #include <linux/file.h>
 #include <linux/nsproxy.h>
 #include <net/net_namespace.h>
 #include <net/netns/generic.h>
 #include <net/dst.h>
 #include <net/ip.h>
 #include <net/udp.h>
 #include <net/udp_tunnel.h>
 #include <net/inet_common.h>
 #include <net/xfrm.h>
 #include <net/protocol.h>
 #include <net/inet6_connection_sock.h>
 #include <net/inet_ecn.h>
 #include <net/ip6_route.h>
 #include <net/ip6_checksum.h>
 
 #include <asm/byteorder.h>
 #include <linux/atomic.h>
 
 #include "l2tp_core.h"
 #include "trace.h"
 
 #define CREATE_TRACE_POINTS
 #include "trace.h"
 
 #define L2TP_DRV_VERSION    "V2.0"
 
 /* L2TP header constants */
 #define L2TP_HDRFLAG_T     0x8000
 #define L2TP_HDRFLAG_L     0x4000
 #define L2TP_HDRFLAG_S     0x0800
 #define L2TP_HDRFLAG_O     0x0200
 #define L2TP_HDRFLAG_P     0x0100
 
 #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
 #define L2TP_SL_SEQ_MASK   0x00ffffff
 
 #define L2TP_HDR_SIZE_MAX       14
 
 /* Default trace flags */
 #define L2TP_DEFAULT_DEBUG_FLAGS    0
 
 /* Private data stored for received packets in the skb.
  */
 struct l2tp_skb_cb {
     u32         ns;
     u16         has_seq;
     u16         length;
     unsigned long       expires;
 };
 
 #define L2TP_SKB_CB(skb)    ((struct l2tp_skb_cb *)&(skb)->cb[sizeof(struct inet_skb_parm)])
 
 static struct workqueue_struct *l2tp_wq;
 
 /* per-net private data for this module */
 static unsigned int l2tp_net_id;
 struct l2tp_net {
     struct list_head l2tp_tunnel_list;
     /* Lock for write access to l2tp_tunnel_list */
     spinlock_t l2tp_tunnel_list_lock;
     struct hlist_head l2tp_session_hlist[L2TP_HASH_SIZE_2];
     /* Lock for write access to l2tp_session_hlist */
     spinlock_t l2tp_session_hlist_lock;
 };
 
 #if IS_ENABLED(CONFIG_IPV6)
 static bool l2tp_sk_is_v6(struct sock *sk)
 {
     return sk->sk_family == PF_INET6 &&
            !ipv6_addr_v4mapped(&sk->sk_v6_daddr);
 }
 #endif
 
 static inline struct l2tp_net *l2tp_pernet(const 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)];
 }
 
 /* Session hash list.
  * The session_id SHOULD be random according to RFC2661, but several
  * L2TP implementations (Cisco and Microsoft) 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(struct l2tp_tunnel *tunnel, u32 session_id)
 {
     return &tunnel->session_hlist[hash_32(session_id, L2TP_HASH_BITS)];
 }
 
 static void l2tp_tunnel_free(struct l2tp_tunnel *tunnel)
 {
     trace_free_tunnel(tunnel);
     sock_put(tunnel->sock);
     /* the tunnel is freed in the socket destructor */
 }
 
 static void l2tp_session_free(struct l2tp_session *session)
 {
     trace_free_session(session);
     if (session->tunnel)
         l2tp_tunnel_dec_refcount(session->tunnel);
     kfree(session);
 }
 
 struct l2tp_tunnel *l2tp_sk_to_tunnel(struct sock *sk)
 {
     struct l2tp_tunnel *tunnel = sk->sk_user_data;
 
     if (tunnel)
         if (WARN_ON(tunnel->magic != L2TP_TUNNEL_MAGIC))
             return NULL;
 
     return tunnel;
 }
 EXPORT_SYMBOL_GPL(l2tp_sk_to_tunnel);
 
 void l2tp_tunnel_inc_refcount(struct l2tp_tunnel *tunnel)
 {
     refcount_inc(&tunnel->ref_count);
 }
 EXPORT_SYMBOL_GPL(l2tp_tunnel_inc_refcount);
 
 void l2tp_tunnel_dec_refcount(struct l2tp_tunnel *tunnel)
 {
     if (refcount_dec_and_test(&tunnel->ref_count))
         l2tp_tunnel_free(tunnel);
 }
 EXPORT_SYMBOL_GPL(l2tp_tunnel_dec_refcount);
 
 void l2tp_session_inc_refcount(struct l2tp_session *session)
 {
     refcount_inc(&session->ref_count);
 }
 EXPORT_SYMBOL_GPL(l2tp_session_inc_refcount);
 
 void l2tp_session_dec_refcount(struct l2tp_session *session)
 {
     if (refcount_dec_and_test(&session->ref_count))
         l2tp_session_free(session);
 }
 EXPORT_SYMBOL_GPL(l2tp_session_dec_refcount);
 
 /* Lookup a tunnel. A new reference is held on the returned tunnel. */
 struct l2tp_tunnel *l2tp_tunnel_get(const struct net *net, u32 tunnel_id)
 {
     const struct l2tp_net *pn = l2tp_pernet(net);
     struct l2tp_tunnel *tunnel;
 
     rcu_read_lock_bh();
     list_for_each_entry_rcu(tunnel, &pn->l2tp_tunnel_list, list) {
         if (tunnel->tunnel_id == tunnel_id &&
             refcount_inc_not_zero(&tunnel->ref_count)) {
             rcu_read_unlock_bh();
 
             return tunnel;
         }
     }
     rcu_read_unlock_bh();
 
     return NULL;
 }
 EXPORT_SYMBOL_GPL(l2tp_tunnel_get);
 
 struct l2tp_tunnel *l2tp_tunnel_get_nth(const struct net *net, int nth)
 {
     const struct l2tp_net *pn = l2tp_pernet(net);
     struct l2tp_tunnel *tunnel;
     int count = 0;
 
     rcu_read_lock_bh();
     list_for_each_entry_rcu(tunnel, &pn->l2tp_tunnel_list, list) {
         if (++count > nth &&
             refcount_inc_not_zero(&tunnel->ref_count)) {
             rcu_read_unlock_bh();
             return tunnel;
         }
     }
     rcu_read_unlock_bh();
 
     return NULL;
 }
 EXPORT_SYMBOL_GPL(l2tp_tunnel_get_nth);
 
 struct l2tp_session *l2tp_tunnel_get_session(struct l2tp_tunnel *tunnel,
                          u32 session_id)
 {
     struct hlist_head *session_list;
     struct l2tp_session *session;
 
     session_list = l2tp_session_id_hash(tunnel, session_id);
 
     rcu_read_lock_bh();
     hlist_for_each_entry_rcu(session, session_list, hlist)
         if (session->session_id == session_id) {
             l2tp_session_inc_refcount(session);
             rcu_read_unlock_bh();
 
             return session;
         }
     rcu_read_unlock_bh();
 
     return NULL;
 }
 EXPORT_SYMBOL_GPL(l2tp_tunnel_get_session);
 
 struct l2tp_session *l2tp_session_get(const struct net *net, u32 session_id)
 {
     struct hlist_head *session_list;
     struct l2tp_session *session;
 
     session_list = l2tp_session_id_hash_2(l2tp_pernet(net), session_id);
 
     rcu_read_lock_bh();
     hlist_for_each_entry_rcu(session, session_list, global_hlist)
         if (session->session_id == session_id) {
             l2tp_session_inc_refcount(session);
             rcu_read_unlock_bh();
 
             return session;
         }
     rcu_read_unlock_bh();
 
     return NULL;
 }
 EXPORT_SYMBOL_GPL(l2tp_session_get);
 
 struct l2tp_session *l2tp_session_get_nth(struct l2tp_tunnel *tunnel, int nth)
 {
     int hash;
     struct l2tp_session *session;
     int count = 0;
 
     rcu_read_lock_bh();
     for (hash = 0; hash < L2TP_HASH_SIZE; hash++) {
         hlist_for_each_entry_rcu(session, &tunnel->session_hlist[hash], hlist) {
             if (++count > nth) {
                 l2tp_session_inc_refcount(session);
                 rcu_read_unlock_bh();
                 return session;
             }
         }
     }
 
     rcu_read_unlock_bh();
 
     return NULL;
 }
 EXPORT_SYMBOL_GPL(l2tp_session_get_nth);
 
 /* Lookup a session by interface name.
  * This is very inefficient but is only used by management interfaces.
  */
 struct l2tp_session *l2tp_session_get_by_ifname(const struct net *net,
                         const char *ifname)
 {
     struct l2tp_net *pn = l2tp_pernet(net);
     int hash;
     struct l2tp_session *session;
 
     rcu_read_lock_bh();
     for (hash = 0; hash < L2TP_HASH_SIZE_2; hash++) {
         hlist_for_each_entry_rcu(session, &pn->l2tp_session_hlist[hash], global_hlist) {
             if (!strcmp(session->ifname, ifname)) {
                 l2tp_session_inc_refcount(session);
                 rcu_read_unlock_bh();
 
                 return session;
             }
         }
     }
 
     rcu_read_unlock_bh();
 
     return NULL;
 }
 EXPORT_SYMBOL_GPL(l2tp_session_get_by_ifname);
 
 int l2tp_session_register(struct l2tp_session *session,
               struct l2tp_tunnel *tunnel)
 {
     struct l2tp_session *session_walk;
     struct hlist_head *g_head;
     struct hlist_head *head;
     struct l2tp_net *pn;
     int err;
 
     head = l2tp_session_id_hash(tunnel, session->session_id);
 
     spin_lock_bh(&tunnel->hlist_lock);
     if (!tunnel->acpt_newsess) {
         err = -ENODEV;
         goto err_tlock;
     }
 
     hlist_for_each_entry(session_walk, head, hlist)
         if (session_walk->session_id == session->session_id) {
             err = -EEXIST;
             goto err_tlock;
         }
 
     if (tunnel->version == L2TP_HDR_VER_3) {
         pn = l2tp_pernet(tunnel->l2tp_net);
         g_head = l2tp_session_id_hash_2(pn, session->session_id);
 
         spin_lock_bh(&pn->l2tp_session_hlist_lock);
 
         /* IP encap expects session IDs to be globally unique, while
          * UDP encap doesn't.
          */
         hlist_for_each_entry(session_walk, g_head, global_hlist)
             if (session_walk->session_id == session->session_id &&
                 (session_walk->tunnel->encap == L2TP_ENCAPTYPE_IP ||
                  tunnel->encap == L2TP_ENCAPTYPE_IP)) {
                 err = -EEXIST;
                 goto err_tlock_pnlock;
             }
 
         l2tp_tunnel_inc_refcount(tunnel);
         hlist_add_head_rcu(&session->global_hlist, g_head);
 
         spin_unlock_bh(&pn->l2tp_session_hlist_lock);
     } else {
         l2tp_tunnel_inc_refcount(tunnel);
     }
 
     hlist_add_head_rcu(&session->hlist, head);
     spin_unlock_bh(&tunnel->hlist_lock);
 
     trace_register_session(session);
 
     return 0;
 
 err_tlock_pnlock:
     spin_unlock_bh(&pn->l2tp_session_hlist_lock);
 err_tlock:
     spin_unlock_bh(&tunnel->hlist_lock);
 
     return err;
 }
 EXPORT_SYMBOL_GPL(l2tp_session_register);
 
 /*****************************************************************************
  * Receive data handling
  *****************************************************************************/
 
 /* Queue a skb in order. We come here only if the skb has an L2TP sequence
  * number.
  */
 static void l2tp_recv_queue_skb(struct l2tp_session *session, struct sk_buff *skb)
 {
     struct sk_buff *skbp;
     struct sk_buff *tmp;
     u32 ns = L2TP_SKB_CB(skb)->ns;
 
     spin_lock_bh(&session->reorder_q.lock);
     skb_queue_walk_safe(&session->reorder_q, skbp, tmp) {
         if (L2TP_SKB_CB(skbp)->ns > ns) {
             __skb_queue_before(&session->reorder_q, skbp, skb);
             atomic_long_inc(&session->stats.rx_oos_packets);
             goto out;
         }
     }
 
     __skb_queue_tail(&session->reorder_q, skb);
 
 out:
     spin_unlock_bh(&session->reorder_q.lock);
 }
 
 /* Dequeue a single skb.
  */
 static void l2tp_recv_dequeue_skb(struct l2tp_session *session, struct sk_buff *skb)
 {
     struct l2tp_tunnel *tunnel = session->tunnel;
     int length = L2TP_SKB_CB(skb)->length;
 
     /* We're about to requeue the skb, so return resources
      * to its current owner (a socket receive buffer).
      */
     skb_orphan(skb);
 
     atomic_long_inc(&tunnel->stats.rx_packets);
     atomic_long_add(length, &tunnel->stats.rx_bytes);
     atomic_long_inc(&session->stats.rx_packets);
     atomic_long_add(length, &session->stats.rx_bytes);
 
     if (L2TP_SKB_CB(skb)->has_seq) {
         /* Bump our Nr */
         session->nr++;
         session->nr &= session->nr_max;
         trace_session_seqnum_update(session);
     }
 
     /* call private receive handler */
     if (session->recv_skb)
         (*session->recv_skb)(session, skb, L2TP_SKB_CB(skb)->length);
     else
         kfree_skb(skb);
 }
 
 /* Dequeue skbs from the session's reorder_q, subject to packet order.
  * Skbs that have been in the queue for too long are simply discarded.
  */
 static void l2tp_recv_dequeue(struct l2tp_session *session)
 {
     struct sk_buff *skb;
     struct sk_buff *tmp;
 
     /* If the pkt at the head of the queue has the nr that we
      * expect to send up next, dequeue it and any other
      * in-sequence packets behind it.
      */
 start:
     spin_lock_bh(&session->reorder_q.lock);
     skb_queue_walk_safe(&session->reorder_q, skb, tmp) {
         struct l2tp_skb_cb *cb = L2TP_SKB_CB(skb);
 
         /* If the packet has been pending on the queue for too long, discard it */
         if (time_after(jiffies, cb->expires)) {
             atomic_long_inc(&session->stats.rx_seq_discards);
             atomic_long_inc(&session->stats.rx_errors);
             trace_session_pkt_expired(session, cb->ns);
             session->reorder_skip = 1;
             __skb_unlink(skb, &session->reorder_q);
             kfree_skb(skb);
             continue;
         }
 
         if (cb->has_seq) {
             if (session->reorder_skip) {
                 session->reorder_skip = 0;
                 session->nr = cb->ns;
                 trace_session_seqnum_reset(session);
             }
             if (cb->ns != session->nr)
                 goto out;
         }
         __skb_unlink(skb, &session->reorder_q);
 
         /* Process the skb. We release the queue lock while we
          * do so to let other contexts process the queue.
          */
         spin_unlock_bh(&session->reorder_q.lock);
         l2tp_recv_dequeue_skb(session, skb);
         goto start;
     }
 
 out:
     spin_unlock_bh(&session->reorder_q.lock);
 }
 
 static int l2tp_seq_check_rx_window(struct l2tp_session *session, u32 nr)
 {
     u32 nws;
 
     if (nr >= session->nr)
         nws = nr - session->nr;
     else
         nws = (session->nr_max + 1) - (session->nr - nr);
 
     return nws < session->nr_window_size;
 }
 
 /* If packet has sequence numbers, queue it if acceptable. Returns 0 if
  * acceptable, else non-zero.
  */
 static int l2tp_recv_data_seq(struct l2tp_session *session, struct sk_buff *skb)
 {
     struct l2tp_skb_cb *cb = L2TP_SKB_CB(skb);
 
     if (!l2tp_seq_check_rx_window(session, cb->ns)) {
         /* Packet sequence number is outside allowed window.
          * Discard it.
          */
         trace_session_pkt_outside_rx_window(session, cb->ns);
         goto discard;
     }
 
     if (session->reorder_timeout != 0) {
         /* Packet reordering enabled. Add skb to session's
          * reorder queue, in order of ns.
          */
         l2tp_recv_queue_skb(session, skb);
         goto out;
     }
 
     /* Packet reordering disabled. Discard out-of-sequence packets, while
      * tracking the number if in-sequence packets after the first OOS packet
      * is seen. After nr_oos_count_max in-sequence packets, reset the
      * sequence number to re-enable packet reception.
      */
     if (cb->ns == session->nr) {
         skb_queue_tail(&session->reorder_q, skb);
     } else {
         u32 nr_oos = cb->ns;
         u32 nr_next = (session->nr_oos + 1) & session->nr_max;
 
         if (nr_oos == nr_next)
             session->nr_oos_count++;
         else
             session->nr_oos_count = 0;
 
         session->nr_oos = nr_oos;
         if (session->nr_oos_count > session->nr_oos_count_max) {
             session->reorder_skip = 1;
         }
         if (!session->reorder_skip) {
             atomic_long_inc(&session->stats.rx_seq_discards);
             trace_session_pkt_oos(session, cb->ns);
             goto discard;
         }
         skb_queue_tail(&session->reorder_q, skb);
     }
 
 out:
     return 0;
 
 discard:
     return 1;
 }
 
 /* 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 and sublayer format 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.
  */
 void l2tp_recv_common(struct l2tp_session *session, struct sk_buff *skb,
               unsigned char *ptr, unsigned char *optr, u16 hdrflags,
               int length)
 {
     struct l2tp_tunnel *tunnel = session->tunnel;
     int offset;
 
     /* Parse and check optional cookie */
     if (session->peer_cookie_len > 0) {
         if (memcmp(ptr, &session->peer_cookie[0], session->peer_cookie_len)) {
             pr_debug_ratelimited("%s: cookie mismatch (%u/%u). Discarding.\n",
                          tunnel->name, tunnel->tunnel_id,
                          session->session_id);
             atomic_long_inc(&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.
      *
      * If we are the LAC, enable/disable sequence numbers under
      * the control of the LNS.  If no sequence numbers present but
      * we were expecting them, discard frame.
      */
     L2TP_SKB_CB(skb)->has_seq = 0;
     if (tunnel->version == L2TP_HDR_VER_2) {
         if (hdrflags & L2TP_HDRFLAG_S) {
             /* Store L2TP info in the skb */
             L2TP_SKB_CB(skb)->ns = ntohs(*(__be16 *)ptr);
             L2TP_SKB_CB(skb)->has_seq = 1;
             ptr += 2;
             /* Skip past nr in the header */
             ptr += 2;
 
         }
     } else if (session->l2specific_type == L2TP_L2SPECTYPE_DEFAULT) {
         u32 l2h = ntohl(*(__be32 *)ptr);
 
         if (l2h & 0x40000000) {
             /* Store L2TP info in the skb */
             L2TP_SKB_CB(skb)->ns = l2h & 0x00ffffff;
             L2TP_SKB_CB(skb)->has_seq = 1;
         }
         ptr += 4;
     }
 
     if (L2TP_SKB_CB(skb)->has_seq) {
         /* Received a packet with sequence numbers. If we're the LAC,
          * check if we sre sending sequence numbers and if not,
          * configure it so.
          */
         if (!session->lns_mode && !session->send_seq) {
             trace_session_seqnum_lns_enable(session);
             session->send_seq = 1;
             l2tp_session_set_header_len(session, tunnel->version);
         }
     } else {
         /* No sequence numbers.
          * If user has configured mandatory sequence numbers, discard.
          */
         if (session->recv_seq) {
             pr_debug_ratelimited("%s: recv data has no seq numbers when required. Discarding.\n",
                          session->name);
             atomic_long_inc(&session->stats.rx_seq_discards);
             goto discard;
         }
 
         /* If we're the LAC and we're sending sequence numbers, the
          * LNS has requested that we no longer send sequence numbers.
          * If we're the LNS and we're sending sequence numbers, the
          * LAC is broken. Discard the frame.
          */
         if (!session->lns_mode && session->send_seq) {
             trace_session_seqnum_lns_disable(session);
             session->send_seq = 0;
             l2tp_session_set_header_len(session, tunnel->version);
         } else if (session->send_seq) {
             pr_debug_ratelimited("%s: recv data has no seq numbers when required. Discarding.\n",
                          session->name);
             atomic_long_inc(&session->stats.rx_seq_discards);
             goto discard;
         }
     }
 
     /* Session data offset is defined only for L2TPv2 and is
      * indicated by an optional 16-bit value in the header.
      */
     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;
         }
     }
 
     offset = ptr - optr;
     if (!pskb_may_pull(skb, offset))
         goto discard;
 
     __skb_pull(skb, offset);
 
     /* Prepare skb for adding to the session's reorder_q.  Hold
      * packets for max reorder_timeout or 1 second if not
      * reordering.
      */
     L2TP_SKB_CB(skb)->length = length;
     L2TP_SKB_CB(skb)->expires = jiffies +
         (session->reorder_timeout ? session->reorder_timeout : HZ);
 
     /* Add packet to the session's receive queue. Reordering is done here, if
      * enabled. Saved L2TP protocol info is stored in skb->sb[].
      */
     if (L2TP_SKB_CB(skb)->has_seq) {
         if (l2tp_recv_data_seq(session, skb))
             goto discard;
     } else {
         /* No sequence numbers. Add the skb to the tail of the
          * reorder queue. This ensures that it will be
          * delivered after all previous sequenced skbs.
          */
         skb_queue_tail(&session->reorder_q, skb);
     }
 
     /* Try to dequeue as many skbs from reorder_q as we can. */
     l2tp_recv_dequeue(session);
 
     return;
 
 discard:
     atomic_long_inc(&session->stats.rx_errors);
     kfree_skb(skb);
 }
 EXPORT_SYMBOL_GPL(l2tp_recv_common);
 
 /* Drop skbs from the session's reorder_q
  */
 static void l2tp_session_queue_purge(struct l2tp_session *session)
 {
     struct sk_buff *skb = NULL;
 
     while ((skb = skb_dequeue(&session->reorder_q))) {
         atomic_long_inc(&session->stats.rx_errors);
         kfree_skb(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.
  */
 static int l2tp_udp_recv_core(struct l2tp_tunnel *tunnel, struct sk_buff *skb)
 {
     struct l2tp_session *session = NULL;
     unsigned char *ptr, *optr;
     u16 hdrflags;
     u32 tunnel_id, session_id;
     u16 version;
     int length;
 
     /* UDP has verified checksum */
 
     /* UDP always verifies the packet length. */
     __skb_pull(skb, sizeof(struct udphdr));
 
     /* Short packet? */
     if (!pskb_may_pull(skb, L2TP_HDR_SIZE_MAX)) {
         pr_debug_ratelimited("%s: recv short packet (len=%d)\n",
                      tunnel->name, skb->len);
         goto invalid;
     }
 
     /* Point to L2TP header */
     optr = skb->data;
     ptr = skb->data;
 
     /* Get L2TP header flags */
     hdrflags = ntohs(*(__be16 *)ptr);
 
     /* Check protocol version */
     version = hdrflags & L2TP_HDR_VER_MASK;
     if (version != tunnel->version) {
         pr_debug_ratelimited("%s: recv protocol version mismatch: got %d expected %d\n",
                      tunnel->name, version, tunnel->version);
         goto invalid;
     }
 
     /* Get length of L2TP packet */
     length = skb->len;
 
     /* If type is control packet, it is handled by userspace. */
     if (hdrflags & L2TP_HDRFLAG_T)
         goto pass;
 
     /* 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_tunnel_get_session(tunnel, session_id);
     if (!session || !session->recv_skb) {
         if (session)
             l2tp_session_dec_refcount(session);
 
         /* Not found? Pass to userspace to deal with */
         pr_debug_ratelimited("%s: no session found (%u/%u). Passing up.\n",
                      tunnel->name, tunnel_id, session_id);
         goto pass;
     }
 
     if (tunnel->version == L2TP_HDR_VER_3 &&
         l2tp_v3_ensure_opt_in_linear(session, skb, &ptr, &optr)) {
         l2tp_session_dec_refcount(session);
         goto invalid;
     }
 
     l2tp_recv_common(session, skb, ptr, optr, hdrflags, length);
     l2tp_session_dec_refcount(session);
 
     return 0;
 
 invalid:
     atomic_long_inc(&tunnel->stats.rx_invalid);
 
 pass:
     /* Put UDP header back */
     __skb_push(skb, sizeof(struct udphdr));
 
     return 1;
 }
 
 /* UDP encapsulation receive handler. See net/ipv4/udp.c.
  * Return codes:
  * 0 : success.
  * <0: error
  * >0: skb should be passed up to userspace as UDP.
  */
 int l2tp_udp_encap_recv(struct sock *sk, struct sk_buff *skb)
 {
     struct l2tp_tunnel *tunnel;
 
     /* Note that this is called from the encap_rcv hook inside an
      * RCU-protected region, but without the socket being locked.
      * Hence we use rcu_dereference_sk_user_data to access the
      * tunnel data structure rather the usual l2tp_sk_to_tunnel
      * accessor function.
      */
     tunnel = rcu_dereference_sk_user_data(sk);
     if (!tunnel)
         goto pass_up;
     if (WARN_ON(tunnel->magic != L2TP_TUNNEL_MAGIC))
         goto pass_up;
 
     if (l2tp_udp_recv_core(tunnel, skb))
         goto pass_up;
 
     return 0;
 
 pass_up:
     return 1;
 }
 EXPORT_SYMBOL_GPL(l2tp_udp_encap_recv);
 
 /************************************************************************
  * Transmit handling
  ***********************************************************************/
 
 /* Build an L2TP header for the session into the buffer provided.
  */
 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;
 
     if (session->send_seq)
         flags |= L2TP_HDRFLAG_S;
 
     /* Setup L2TP header. */
     *bufp++ = htons(flags);
     *bufp++ = htons(tunnel_id);
     *bufp++ = htons(session_id);
     if (session->send_seq) {
         *bufp++ = htons(session->ns);
         *bufp++ = 0;
         session->ns++;
         session->ns &= 0xffff;
         trace_session_seqnum_update(session);
     }
 
     return bufp - optr;
 }
 
 static int l2tp_build_l2tpv3_header(struct l2tp_session *session, void *buf)
 {
     struct l2tp_tunnel *tunnel = session->tunnel;
     char *bufp = buf;
     char *optr = bufp;
 
     /* Setup L2TP header. The header differs slightly for UDP and
      * IP encapsulations. For UDP, there is 4 bytes of flags.
      */
     if (tunnel->encap == L2TP_ENCAPTYPE_UDP) {
         u16 flags = L2TP_HDR_VER_3;
         *((__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_type == L2TP_L2SPECTYPE_DEFAULT) {
         u32 l2h = 0;
 
         if (session->send_seq) {
             l2h = 0x40000000 | session->ns;
             session->ns++;
             session->ns &= 0xffffff;
             trace_session_seqnum_update(session);
         }
 
         *((__be32 *)bufp) = htonl(l2h);
         bufp += 4;
     }
 
     return bufp - optr;
 }
 
 /* Queue the packet to IP for output: tunnel socket lock must be held */
 static int l2tp_xmit_queue(struct l2tp_tunnel *tunnel, struct sk_buff *skb, struct flowi *fl)
 {
     int err;
 
     skb->ignore_df = 1;
     skb_dst_drop(skb);
 #if IS_ENABLED(CONFIG_IPV6)
     if (l2tp_sk_is_v6(tunnel->sock))
         err = inet6_csk_xmit(tunnel->sock, skb, NULL);
     else
 #endif
         err = ip_queue_xmit(tunnel->sock, skb, fl);
 
     return err >= 0 ? NET_XMIT_SUCCESS : NET_XMIT_DROP;
 }
 
 static int l2tp_xmit_core(struct l2tp_session *session, struct sk_buff *skb, unsigned int *len)
 {
     struct l2tp_tunnel *tunnel = session->tunnel;
     unsigned int data_len = skb->len;
     struct sock *sk = tunnel->sock;
     int headroom, uhlen, udp_len;
     int ret = NET_XMIT_SUCCESS;
     struct inet_sock *inet;
     struct udphdr *uh;
 
     /* Check that there's enough headroom in the skb to insert IP,
      * UDP and L2TP headers. If not enough, expand it to
      * make room. Adjust truesize.
      */
     uhlen = (tunnel->encap == L2TP_ENCAPTYPE_UDP) ? sizeof(*uh) : 0;
     headroom = NET_SKB_PAD + sizeof(struct iphdr) + uhlen + session->hdr_len;
     if (skb_cow_head(skb, headroom)) {
         kfree_skb(skb);
         return NET_XMIT_DROP;
     }
 
     /* Setup L2TP header */
     if (tunnel->version == L2TP_HDR_VER_2)
         l2tp_build_l2tpv2_header(session, __skb_push(skb, session->hdr_len));
     else
         l2tp_build_l2tpv3_header(session, __skb_push(skb, session->hdr_len));
 
     /* Reset skb netfilter state */
     memset(&(IPCB(skb)->opt), 0, sizeof(IPCB(skb)->opt));
     IPCB(skb)->flags &= ~(IPSKB_XFRM_TUNNEL_SIZE | IPSKB_XFRM_TRANSFORMED | IPSKB_REROUTED);
     nf_reset_ct(skb);
 
     bh_lock_sock(sk);
     if (sock_owned_by_user(sk)) {
         kfree_skb(skb);
         ret = NET_XMIT_DROP;
         goto out_unlock;
     }
 
     /* The user-space may change the connection status for the user-space
      * provided socket at run time: we must check it under the socket lock
      */
     if (tunnel->fd >= 0 && sk->sk_state != TCP_ESTABLISHED) {
         kfree_skb(skb);
         ret = NET_XMIT_DROP;
         goto out_unlock;
     }
 
     /* Report transmitted length before we add encap header, which keeps
      * statistics consistent for both UDP and IP encap tx/rx paths.
      */
     *len = skb->len;
 
     inet = inet_sk(sk);
     switch (tunnel->encap) {
     case L2TP_ENCAPTYPE_UDP:
         /* Setup UDP header */
         __skb_push(skb, sizeof(*uh));
         skb_reset_transport_header(skb);
         uh = udp_hdr(skb);
         uh->source = inet->inet_sport;
         uh->dest = inet->inet_dport;
         udp_len = uhlen + session->hdr_len + data_len;
         uh->len = htons(udp_len);
 
         /* Calculate UDP checksum if configured to do so */
 #if IS_ENABLED(CONFIG_IPV6)
         if (l2tp_sk_is_v6(sk))
             udp6_set_csum(udp_get_no_check6_tx(sk),
                       skb, &inet6_sk(sk)->saddr,
                       &sk->sk_v6_daddr, udp_len);
         else
 #endif
             udp_set_csum(sk->sk_no_check_tx, skb, inet->inet_saddr,
                      inet->inet_daddr, udp_len);
         break;
 
     case L2TP_ENCAPTYPE_IP:
         break;
     }
 
     ret = l2tp_xmit_queue(tunnel, skb, &inet->cork.fl);
 
 out_unlock:
     bh_unlock_sock(sk);
 
     return ret;
 }
 
 /* If caller requires the skb to have a ppp header, the header must be
  * inserted in the skb data before calling this function.
  */
 int l2tp_xmit_skb(struct l2tp_session *session, struct sk_buff *skb)
 {
     unsigned int len = 0;
     int ret;
 
     ret = l2tp_xmit_core(session, skb, &len);
     if (ret == NET_XMIT_SUCCESS) {
         atomic_long_inc(&session->tunnel->stats.tx_packets);
         atomic_long_add(len, &session->tunnel->stats.tx_bytes);
         atomic_long_inc(&session->stats.tx_packets);
         atomic_long_add(len, &session->stats.tx_bytes);
     } else {
         atomic_long_inc(&session->tunnel->stats.tx_errors);
         atomic_long_inc(&session->stats.tx_errors);
     }
     return ret;
 }
 EXPORT_SYMBOL_GPL(l2tp_xmit_skb);
 
 /*****************************************************************************
  * Tinnel and session create/destroy.
  *****************************************************************************/
 
 /* Tunnel socket destruct hook.
  * The tunnel context is deleted only when all session sockets have been
  * closed.
  */
 static void l2tp_tunnel_destruct(struct sock *sk)
 {
     struct l2tp_tunnel *tunnel = l2tp_sk_to_tunnel(sk);
 
     if (!tunnel)
         goto end;
 
     /* Disable udp encapsulation */
     switch (tunnel->encap) {
     case L2TP_ENCAPTYPE_UDP:
         /* No longer an encapsulation socket. See net/ipv4/udp.c */
         (udp_sk(sk))->encap_type = 0;
         (udp_sk(sk))->encap_rcv = NULL;
         (udp_sk(sk))->encap_destroy = NULL;
         break;
     case L2TP_ENCAPTYPE_IP:
         break;
     }
 
     /* Remove hooks into tunnel socket */
     sk->sk_destruct = tunnel->old_sk_destruct;
     sk->sk_user_data = NULL;
 
     /* Call the original destructor */
     if (sk->sk_destruct)
         (*sk->sk_destruct)(sk);
 
     kfree_rcu(tunnel, rcu);
 end:
     return;
 }
 
 /* Remove an l2tp session from l2tp_core's hash lists. */
 static void l2tp_session_unhash(struct l2tp_session *session)
 {
     struct l2tp_tunnel *tunnel = session->tunnel;
 
     /* Remove the session from core hashes */
     if (tunnel) {
         /* Remove from the per-tunnel hash */
         spin_lock_bh(&tunnel->hlist_lock);
         hlist_del_init_rcu(&session->hlist);
         spin_unlock_bh(&tunnel->hlist_lock);
 
         /* For L2TPv3 we have a per-net hash: remove from there, too */
         if (tunnel->version != L2TP_HDR_VER_2) {
             struct l2tp_net *pn = l2tp_pernet(tunnel->l2tp_net);
 
             spin_lock_bh(&pn->l2tp_session_hlist_lock);
             hlist_del_init_rcu(&session->global_hlist);
             spin_unlock_bh(&pn->l2tp_session_hlist_lock);
         }
 
         synchronize_rcu();
     }
 }
 
 /* When the tunnel is closed, all the attached sessions need to go too.
  */
 static void l2tp_tunnel_closeall(struct l2tp_tunnel *tunnel)
 {
     struct l2tp_session *session;
     int hash;
 
     spin_lock_bh(&tunnel->hlist_lock);
     tunnel->acpt_newsess = false;
     for (hash = 0; hash < L2TP_HASH_SIZE; hash++) {
 again:
         hlist_for_each_entry_rcu(session, &tunnel->session_hlist[hash], hlist) {
             hlist_del_init_rcu(&session->hlist);
 
             spin_unlock_bh(&tunnel->hlist_lock);
             l2tp_session_delete(session);
             spin_lock_bh(&tunnel->hlist_lock);
 
             /* Now restart from the beginning of this hash
              * chain.  We always remove a session from the
              * list so we are guaranteed to make forward
              * progress.
              */
             goto again;
         }
     }
     spin_unlock_bh(&tunnel->hlist_lock);
 }
 
 /* Tunnel socket destroy hook for UDP encapsulation */
 static void l2tp_udp_encap_destroy(struct sock *sk)
 {
     struct l2tp_tunnel *tunnel = l2tp_sk_to_tunnel(sk);
 
     if (tunnel)
         l2tp_tunnel_delete(tunnel);
 }
 
 /* Workqueue tunnel deletion function */
 static void l2tp_tunnel_del_work(struct work_struct *work)
 {
     struct l2tp_tunnel *tunnel = container_of(work, struct l2tp_tunnel,
                           del_work);
     struct sock *sk = tunnel->sock;
     struct socket *sock = sk->sk_socket;
     struct l2tp_net *pn;
 
     l2tp_tunnel_closeall(tunnel);
 
     /* If the tunnel socket was created within the kernel, use
      * the sk API to release it here.
      */
     if (tunnel->fd < 0) {
         if (sock) {
             kernel_sock_shutdown(sock, SHUT_RDWR);
             sock_release(sock);
         }
     }
 
     /* Remove the tunnel struct from the tunnel list */
     pn = l2tp_pernet(tunnel->l2tp_net);
     spin_lock_bh(&pn->l2tp_tunnel_list_lock);
     list_del_rcu(&tunnel->list);
     spin_unlock_bh(&pn->l2tp_tunnel_list_lock);
 
     /* drop initial ref */
     l2tp_tunnel_dec_refcount(tunnel);
 
     /* drop workqueue ref */
     l2tp_tunnel_dec_refcount(tunnel);
 }
 
 /* Create a socket for the tunnel, if one isn't set up by
  * userspace. This is used for static tunnels where there is no
  * managing L2TP daemon.
  *
  * Since we don't want these sockets to keep a namespace alive by
  * themselves, we drop the socket's namespace refcount after creation.
  * These sockets are freed when the namespace exits using the pernet
  * exit hook.
  */
 static int l2tp_tunnel_sock_create(struct net *net,
                    u32 tunnel_id,
                    u32 peer_tunnel_id,
                    struct l2tp_tunnel_cfg *cfg,
                    struct socket **sockp)
 {
     int err = -EINVAL;
     struct socket *sock = NULL;
     struct udp_port_cfg udp_conf;
 
     switch (cfg->encap) {
     case L2TP_ENCAPTYPE_UDP:
         memset(&udp_conf, 0, sizeof(udp_conf));
 
 #if IS_ENABLED(CONFIG_IPV6)
         if (cfg->local_ip6 && cfg->peer_ip6) {
             udp_conf.family = AF_INET6;
             memcpy(&udp_conf.local_ip6, cfg->local_ip6,
                    sizeof(udp_conf.local_ip6));
             memcpy(&udp_conf.peer_ip6, cfg->peer_ip6,
                    sizeof(udp_conf.peer_ip6));
             udp_conf.use_udp6_tx_checksums =
               !cfg->udp6_zero_tx_checksums;
             udp_conf.use_udp6_rx_checksums =
               !cfg->udp6_zero_rx_checksums;
         } else
 #endif
         {
             udp_conf.family = AF_INET;
             udp_conf.local_ip = cfg->local_ip;
             udp_conf.peer_ip = cfg->peer_ip;
             udp_conf.use_udp_checksums = cfg->use_udp_checksums;
         }
 
         udp_conf.local_udp_port = htons(cfg->local_udp_port);
         udp_conf.peer_udp_port = htons(cfg->peer_udp_port);
 
         err = udp_sock_create(net, &udp_conf, &sock);
         if (err < 0)
             goto out;
 
         break;
 
     case L2TP_ENCAPTYPE_IP:
 #if IS_ENABLED(CONFIG_IPV6)
         if (cfg->local_ip6 && cfg->peer_ip6) {
             struct sockaddr_l2tpip6 ip6_addr = {0};
 
             err = sock_create_kern(net, AF_INET6, SOCK_DGRAM,
                            IPPROTO_L2TP, &sock);
             if (err < 0)
                 goto out;
 
             ip6_addr.l2tp_family = AF_INET6;
             memcpy(&ip6_addr.l2tp_addr, cfg->local_ip6,
                    sizeof(ip6_addr.l2tp_addr));
             ip6_addr.l2tp_conn_id = tunnel_id;
             err = kernel_bind(sock, (struct sockaddr *)&ip6_addr,
                       sizeof(ip6_addr));
             if (err < 0)
                 goto out;
 
             ip6_addr.l2tp_family = AF_INET6;
             memcpy(&ip6_addr.l2tp_addr, cfg->peer_ip6,
                    sizeof(ip6_addr.l2tp_addr));
             ip6_addr.l2tp_conn_id = peer_tunnel_id;
             err = kernel_connect(sock,
                          (struct sockaddr *)&ip6_addr,
                          sizeof(ip6_addr), 0);
             if (err < 0)
                 goto out;
         } else
 #endif
         {
             struct sockaddr_l2tpip ip_addr = {0};
 
             err = sock_create_kern(net, AF_INET, SOCK_DGRAM,
                            IPPROTO_L2TP, &sock);
             if (err < 0)
                 goto out;
 
             ip_addr.l2tp_family = AF_INET;
             ip_addr.l2tp_addr = cfg->local_ip;
             ip_addr.l2tp_conn_id = tunnel_id;
             err = kernel_bind(sock, (struct sockaddr *)&ip_addr,
                       sizeof(ip_addr));
             if (err < 0)
                 goto out;
 
             ip_addr.l2tp_family = AF_INET;
             ip_addr.l2tp_addr = cfg->peer_ip;
             ip_addr.l2tp_conn_id = peer_tunnel_id;
             err = kernel_connect(sock, (struct sockaddr *)&ip_addr,
                          sizeof(ip_addr), 0);
             if (err < 0)
                 goto out;
         }
         break;
 
     default:
         goto out;
     }
 
 out:
     *sockp = sock;
     if (err < 0 && sock) {
         kernel_sock_shutdown(sock, SHUT_RDWR);
         sock_release(sock);
         *sockp = NULL;
     }
 
     return err;
 }
 
 static struct lock_class_key l2tp_socket_class;
 
 int l2tp_tunnel_create(int fd, int version, u32 tunnel_id, u32 peer_tunnel_id,
                struct l2tp_tunnel_cfg *cfg, struct l2tp_tunnel **tunnelp)
 {
     struct l2tp_tunnel *tunnel = NULL;
     int err;
     enum l2tp_encap_type encap = L2TP_ENCAPTYPE_UDP;
 
     if (cfg)
         encap = cfg->encap;
 
     tunnel = kzalloc(sizeof(*tunnel), GFP_KERNEL);
     if (!tunnel) {
         err = -ENOMEM;
         goto err;
     }
 
     tunnel->version = version;
     tunnel->tunnel_id = tunnel_id;
     tunnel->peer_tunnel_id = peer_tunnel_id;
 
     tunnel->magic = L2TP_TUNNEL_MAGIC;
     sprintf(&tunnel->name[0], "tunl %u", tunnel_id);
     spin_lock_init(&tunnel->hlist_lock);
     tunnel->acpt_newsess = true;
 
     tunnel->encap = encap;
 
     refcount_set(&tunnel->ref_count, 1);
     tunnel->fd = fd;
 
     /* Init delete workqueue struct */
     INIT_WORK(&tunnel->del_work, l2tp_tunnel_del_work);
 
     INIT_LIST_HEAD(&tunnel->list);
 
     err = 0;
 err:
     if (tunnelp)
         *tunnelp = tunnel;
 
     return err;
 }
 EXPORT_SYMBOL_GPL(l2tp_tunnel_create);
 
 static int l2tp_validate_socket(const struct sock *sk, const struct net *net,
                 enum l2tp_encap_type encap)
 {
     if (!net_eq(sock_net(sk), net))
         return -EINVAL;
 
     if (sk->sk_type != SOCK_DGRAM)
         return -EPROTONOSUPPORT;
 
     if (sk->sk_family != PF_INET && sk->sk_family != PF_INET6)
         return -EPROTONOSUPPORT;
 
     if ((encap == L2TP_ENCAPTYPE_UDP && sk->sk_protocol != IPPROTO_UDP) ||
         (encap == L2TP_ENCAPTYPE_IP && sk->sk_protocol != IPPROTO_L2TP))
         return -EPROTONOSUPPORT;
 
     if (sk->sk_user_data)
         return -EBUSY;
 
     return 0;
 }
 
 int l2tp_tunnel_register(struct l2tp_tunnel *tunnel, struct net *net,
              struct l2tp_tunnel_cfg *cfg)
 {
     struct l2tp_tunnel *tunnel_walk;
     struct l2tp_net *pn;
     struct socket *sock;
     struct sock *sk;
     int ret;
 
     if (tunnel->fd < 0) {
         ret = l2tp_tunnel_sock_create(net, tunnel->tunnel_id,
                           tunnel->peer_tunnel_id, cfg,
                           &sock);
         if (ret < 0)
             goto err;
     } else {
         sock = sockfd_lookup(tunnel->fd, &ret);
         if (!sock)
             goto err;
 
         ret = l2tp_validate_socket(sock->sk, net, tunnel->encap);
         if (ret < 0)
             goto err_sock;
     }
 
     tunnel->l2tp_net = net;
     pn = l2tp_pernet(net);
 
     sk = sock->sk;
     sock_hold(sk);
     tunnel->sock = sk;
 
     spin_lock_bh(&pn->l2tp_tunnel_list_lock);
     list_for_each_entry(tunnel_walk, &pn->l2tp_tunnel_list, list) {
         if (tunnel_walk->tunnel_id == tunnel->tunnel_id) {
             spin_unlock_bh(&pn->l2tp_tunnel_list_lock);
             sock_put(sk);
             ret = -EEXIST;
             goto err_sock;
         }
     }
     list_add_rcu(&tunnel->list, &pn->l2tp_tunnel_list);
     spin_unlock_bh(&pn->l2tp_tunnel_list_lock);
 
     if (tunnel->encap == L2TP_ENCAPTYPE_UDP) {
         struct udp_tunnel_sock_cfg udp_cfg = {
             .sk_user_data = tunnel,
             .encap_type = UDP_ENCAP_L2TPINUDP,
             .encap_rcv = l2tp_udp_encap_recv,
             .encap_destroy = l2tp_udp_encap_destroy,
         };
 
         setup_udp_tunnel_sock(net, sock, &udp_cfg);
     } else {
         sk->sk_user_data = tunnel;
     }
 
     tunnel->old_sk_destruct = sk->sk_destruct;
     sk->sk_destruct = &l2tp_tunnel_destruct;
     lockdep_set_class_and_name(&sk->sk_lock.slock, &l2tp_socket_class,
                    "l2tp_sock");
     sk->sk_allocation = GFP_ATOMIC;
 
     trace_register_tunnel(tunnel);
 
     if (tunnel->fd >= 0)
         sockfd_put(sock);
 
     return 0;
 
 err_sock:
     if (tunnel->fd < 0)
         sock_release(sock);
     else
         sockfd_put(sock);
 err:
     return ret;
 }
 EXPORT_SYMBOL_GPL(l2tp_tunnel_register);
 
 /* This function is used by the netlink TUNNEL_DELETE command.
  */
 void l2tp_tunnel_delete(struct l2tp_tunnel *tunnel)
 {
     if (!test_and_set_bit(0, &tunnel->dead)) {
         trace_delete_tunnel(tunnel);
         l2tp_tunnel_inc_refcount(tunnel);
         queue_work(l2tp_wq, &tunnel->del_work);
     }
 }
 EXPORT_SYMBOL_GPL(l2tp_tunnel_delete);
 
 void l2tp_session_delete(struct l2tp_session *session)
 {
     if (test_and_set_bit(0, &session->dead))
         return;
 
     trace_delete_session(session);
     l2tp_session_unhash(session);
     l2tp_session_queue_purge(session);
     if (session->session_close)
         (*session->session_close)(session);
 
     l2tp_session_dec_refcount(session);
 }
 EXPORT_SYMBOL_GPL(l2tp_session_delete);
 
 /* We come here whenever a session's send_seq, cookie_len or
  * l2specific_type 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 = 4 + session->cookie_len;
         session->hdr_len += l2tp_get_l2specific_len(session);
         if (session->tunnel->encap == L2TP_ENCAPTYPE_UDP)
             session->hdr_len += 4;
     }
 }
 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;
 
     session = kzalloc(sizeof(*session) + priv_size, GFP_KERNEL);
     if (session) {
         session->magic = L2TP_SESSION_MAGIC;
         session->tunnel = tunnel;
 
         session->session_id = session_id;
         session->peer_session_id = peer_session_id;
         session->nr = 0;
         if (tunnel->version == L2TP_HDR_VER_2)
             session->nr_max = 0xffff;
         else
             session->nr_max = 0xffffff;
         session->nr_window_size = session->nr_max / 2;
         session->nr_oos_count_max = 4;
 
         /* Use NR of first received packet */
         session->reorder_skip = 1;
 
         sprintf(&session->name[0], "sess %u/%u",
             tunnel->tunnel_id, session->session_id);
 
         skb_queue_head_init(&session->reorder_q);
 
         INIT_HLIST_NODE(&session->hlist);
         INIT_HLIST_NODE(&session->global_hlist);
 
         if (cfg) {
             session->pwtype = cfg->pw_type;
             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->l2specific_type = cfg->l2specific_type;
             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);
         }
 
         l2tp_session_set_header_len(session, tunnel->version);
 
         refcount_set(&session->ref_count, 1);
 
         return session;
     }
 
     return ERR_PTR(-ENOMEM);
 }
 EXPORT_SYMBOL_GPL(l2tp_session_create);
 
 /*****************************************************************************
  * Init and cleanup
  *****************************************************************************/
 
 static __net_init int l2tp_init_net(struct net *net)
 {
     struct l2tp_net *pn = net_generic(net, l2tp_net_id);
     int hash;
 
     INIT_LIST_HEAD(&pn->l2tp_tunnel_list);
     spin_lock_init(&pn->l2tp_tunnel_list_lock);
 
     for (hash = 0; hash < L2TP_HASH_SIZE_2; hash++)
         INIT_HLIST_HEAD(&pn->l2tp_session_hlist[hash]);
 
     spin_lock_init(&pn->l2tp_session_hlist_lock);
 
     return 0;
 }
 
 static __net_exit void l2tp_exit_net(struct net *net)
 {
     struct l2tp_net *pn = l2tp_pernet(net);
     struct l2tp_tunnel *tunnel = NULL;
     int hash;
 
     rcu_read_lock_bh();
     list_for_each_entry_rcu(tunnel, &pn->l2tp_tunnel_list, list) {
         l2tp_tunnel_delete(tunnel);
     }
     rcu_read_unlock_bh();
 
     if (l2tp_wq)
         flush_workqueue(l2tp_wq);
     rcu_barrier();
 
     for (hash = 0; hash < L2TP_HASH_SIZE_2; hash++)
         WARN_ON_ONCE(!hlist_empty(&pn->l2tp_session_hlist[hash]));
 }
 
 static struct pernet_operations l2tp_net_ops = {
     .init = l2tp_init_net,
     .exit = l2tp_exit_net,
     .id   = &l2tp_net_id,
     .size = sizeof(struct l2tp_net),
 };
 
 static int __init l2tp_init(void)
 {
     int rc = 0;
 
     rc = register_pernet_device(&l2tp_net_ops);
     if (rc)
         goto out;
 
     l2tp_wq = alloc_workqueue("l2tp", WQ_UNBOUND, 0);
     if (!l2tp_wq) {
         pr_err("alloc_workqueue failed\n");
         unregister_pernet_device(&l2tp_net_ops);
         rc = -ENOMEM;
         goto out;
     }
 
     pr_info("L2TP core driver, %s\n", L2TP_DRV_VERSION);
 
 out:
     return rc;
 }
 
 static void __exit l2tp_exit(void)
 {
     unregister_pernet_device(&l2tp_net_ops);
     if (l2tp_wq) {
         destroy_workqueue(l2tp_wq);
         l2tp_wq = NULL;
     }
 }
 
 module_init(l2tp_init);
 module_exit(l2tp_exit);
 
 MODULE_AUTHOR("James Chapman <jchapman@katalix.com>");
 MODULE_DESCRIPTION("L2TP core");
 MODULE_LICENSE("GPL");
 MODULE_VERSION(L2TP_DRV_VERSION);

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