/*****************************************************************************
 * Linux PPP over L2TP (PPPoX/PPPoL2TP) Sockets
 *
 * PPPoX    --- Generic PPP encapsulation socket family
 * PPPoL2TP --- PPP over L2TP (RFC 2661)
 *
 * Version:     2.0.0
 *
 * Authors:     James Chapman (jchapman@katalix.com)
 *
 * Based on original work by Martijn van Oosterhout <kleptog@svana.org>
 *
 * License:
 *              This program is free software; you can redistribute it and/or
 *              modify it under the terms of the GNU General Public License
 *              as published by the Free Software Foundation; either version
 *              2 of the License, or (at your option) any later version.
 *
 */

/* This driver handles only L2TP data frames; control frames are handled by a
 * userspace application.
 *
 * To send data in an L2TP session, userspace opens a PPPoL2TP socket and
 * attaches it to a bound UDP socket with local tunnel_id / session_id and
 * peer tunnel_id / session_id set. Data can then be sent or received using
 * regular socket sendmsg() / recvmsg() calls. Kernel parameters of the socket
 * can be read or modified using ioctl() or [gs]etsockopt() calls.
 *
 * When a PPPoL2TP socket is connected with local and peer session_id values
 * zero, the socket is treated as a special tunnel management socket.
 *
 * Here's example userspace code to create a socket for sending/receiving data
 * over an L2TP session:-
 *
 *      struct sockaddr_pppol2tp sax;
 *      int fd;
 *      int session_fd;
 *
 *      fd = socket(AF_PPPOX, SOCK_DGRAM, PX_PROTO_OL2TP);
 *
 *      sax.sa_family = AF_PPPOX;
 *      sax.sa_protocol = PX_PROTO_OL2TP;
 *      sax.pppol2tp.fd = tunnel_fd;    // bound UDP socket
 *      sax.pppol2tp.addr.sin_addr.s_addr = addr->sin_addr.s_addr;
 *      sax.pppol2tp.addr.sin_port = addr->sin_port;
 *      sax.pppol2tp.addr.sin_family = AF_INET;
 *      sax.pppol2tp.s_tunnel  = tunnel_id;
 *      sax.pppol2tp.s_session = session_id;
 *      sax.pppol2tp.d_tunnel  = peer_tunnel_id;
 *      sax.pppol2tp.d_session = peer_session_id;
 *
 *      session_fd = connect(fd, (struct sockaddr *)&sax, sizeof(sax));
 *
 * A pppd plugin that allows PPP traffic to be carried over L2TP using
 * this driver is available from the OpenL2TP project at
 * http://openl2tp.sourceforge.net.
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/module.h>
#include <linux/string.h>
#include <linux/list.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/ip.h>
#include <linux/udp.h>
#include <linux/if_pppox.h>
#include <linux/if_pppol2tp.h>
#include <net/sock.h>
#include <linux/ppp_channel.h>
#include <linux/ppp_defs.h>
#include <linux/ppp-ioctl.h>
#include <linux/file.h>
#include <linux/hash.h>
#include <linux/sort.h>
#include <linux/proc_fs.h>
#include <linux/l2tp.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/xfrm.h>
#include <net/inet_common.h>

#include <asm/byteorder.h>
#include <linux/atomic.h>

#include "l2tp_core.h"

#define PPPOL2TP_DRV_VERSION    "V2.0"

/* Space for UDP, L2TP and PPP headers */
#define PPPOL2TP_HEADER_OVERHEAD        40

/* Number of bytes to build transmit L2TP headers.
 * Unfortunately the size is different depending on whether sequence numbers
 * are enabled.
 */
#define PPPOL2TP_L2TP_HDR_SIZE_SEQ              10
#define PPPOL2TP_L2TP_HDR_SIZE_NOSEQ            6

/* Private data of each session. This data lives at the end of struct
 * l2tp_session, referenced via session->priv[].
 */
struct pppol2tp_session {
        int                     owner;          /* pid that opened the socket */

        struct mutex            sk_lock;        /* Protects .sk */
        struct sock __rcu       *sk;            /* Pointer to the session
                                                 * PPPoX socket */
        struct sock             *__sk;          /* Copy of .sk, for cleanup */
        struct rcu_head         rcu;            /* For asynchronous release */
        int                     flags;          /* accessed by PPPIOCGFLAGS.
                                                 * Unused. */
};

static int pppol2tp_xmit(struct ppp_channel *chan, struct sk_buff *skb);

static const struct ppp_channel_ops pppol2tp_chan_ops = {
        .start_xmit =  pppol2tp_xmit,
};

static const struct proto_ops pppol2tp_ops;

/* Retrieves the pppol2tp socket associated to a session.
 * A reference is held on the returned socket, so this function must be paired
 * with sock_put().
 */
static struct sock *pppol2tp_session_get_sock(struct l2tp_session *session)
{
        struct pppol2tp_session *ps = l2tp_session_priv(session);
        struct sock *sk;

        rcu_read_lock();
        sk = rcu_dereference(ps->sk);
        if (sk)
                sock_hold(sk);
        rcu_read_unlock();

        return sk;
}

/* Helpers to obtain tunnel/session contexts from sockets.
 */
static inline struct l2tp_session *pppol2tp_sock_to_session(struct sock *sk)
{
        struct l2tp_session *session;

        if (sk == NULL)
                return NULL;

        sock_hold(sk);
        session = (struct l2tp_session *)(sk->sk_user_data);
        if (session == NULL) {
                sock_put(sk);
                goto out;
        }

        BUG_ON(session->magic != L2TP_SESSION_MAGIC);

out:
        return session;
}

/*****************************************************************************
 * Receive data handling
 *****************************************************************************/

/* Receive message. This is the recvmsg for the PPPoL2TP socket.
 */
static int pppol2tp_recvmsg(struct socket *sock, struct msghdr *msg,
                            size_t len, int flags)
{
        int err;
        struct sk_buff *skb;
        struct sock *sk = sock->sk;

        err = -EIO;
        if (sk->sk_state & PPPOX_BOUND)
                goto end;

        err = 0;
        skb = skb_recv_datagram(sk, flags & ~MSG_DONTWAIT,
                                flags & MSG_DONTWAIT, &err);
        if (!skb)
                goto end;

        if (len > skb->len)
                len = skb->len;
        else if (len < skb->len)
                msg->msg_flags |= MSG_TRUNC;

        err = skb_copy_datagram_msg(skb, 0, msg, len);
        if (likely(err == 0))
                err = len;

        kfree_skb(skb);
end:
        return err;
}

static void pppol2tp_recv(struct l2tp_session *session, struct sk_buff *skb, int data_len)
{
        struct pppol2tp_session *ps = l2tp_session_priv(session);
        struct sock *sk = NULL;

        /* If the socket is bound, send it in to PPP's input queue. Otherwise
         * queue it on the session socket.
         */
        rcu_read_lock();
        sk = rcu_dereference(ps->sk);
        if (sk == NULL)
                goto no_sock;

        /* If the first two bytes are 0xFF03, consider that it is the PPP's
         * Address and Control fields and skip them. The L2TP module has always
         * worked this way, although, in theory, the use of these fields should
         * be negociated and handled at the PPP layer. These fields are
         * constant: 0xFF is the All-Stations Address and 0x03 the Unnumbered
         * Information command with Poll/Final bit set to zero (RFC 1662).
         */
        if (pskb_may_pull(skb, 2) && skb->data[0] == PPP_ALLSTATIONS &&
            skb->data[1] == PPP_UI)
                skb_pull(skb, 2);

        if (sk->sk_state & PPPOX_BOUND) {
                struct pppox_sock *po;

                l2tp_dbg(session, L2TP_MSG_DATA,
                         "%s: recv %d byte data frame, passing to ppp\n",
                         session->name, data_len);

                po = pppox_sk(sk);
                ppp_input(&po->chan, skb);
        } else {
                l2tp_dbg(session, L2TP_MSG_DATA,
                         "%s: recv %d byte data frame, passing to L2TP socket\n",
                         session->name, data_len);

                if (sock_queue_rcv_skb(sk, skb) < 0) {
                        atomic_long_inc(&session->stats.rx_errors);
                        kfree_skb(skb);
                }
        }
        rcu_read_unlock();

        return;

no_sock:
        rcu_read_unlock();
        l2tp_info(session, L2TP_MSG_DATA, "%s: no socket\n", session->name);
        kfree_skb(skb);
}

/************************************************************************
 * Transmit handling
 ***********************************************************************/

/* 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.
 */
static int pppol2tp_sendmsg(struct socket *sock, struct msghdr *m,
                            size_t total_len)
{
        struct sock *sk = sock->sk;
        struct sk_buff *skb;
        int error;
        struct l2tp_session *session;
        struct l2tp_tunnel *tunnel;
        int uhlen;

        error = -ENOTCONN;
        if (sock_flag(sk, SOCK_DEAD) || !(sk->sk_state & PPPOX_CONNECTED))
                goto error;

        /* Get session and tunnel contexts */
        error = -EBADF;
        session = pppol2tp_sock_to_session(sk);
        if (session == NULL)
                goto error;

        tunnel = session->tunnel;

        uhlen = (tunnel->encap == L2TP_ENCAPTYPE_UDP) ? sizeof(struct udphdr) : 0;

        /* Allocate a socket buffer */
        error = -ENOMEM;
        skb = sock_wmalloc(sk, NET_SKB_PAD + sizeof(struct iphdr) +
                           uhlen + session->hdr_len +
                           2 + total_len, /* 2 bytes for PPP_ALLSTATIONS & PPP_UI */
                           0, GFP_KERNEL);
        if (!skb)
                goto error_put_sess;

        /* Reserve space for headers. */
        skb_reserve(skb, NET_SKB_PAD);
        skb_reset_network_header(skb);
        skb_reserve(skb, sizeof(struct iphdr));
        skb_reset_transport_header(skb);
        skb_reserve(skb, uhlen);

        /* Add PPP header */
        skb->data[0] = PPP_ALLSTATIONS;
        skb->data[1] = PPP_UI;
        skb_put(skb, 2);

        /* Copy user data into skb */
        error = memcpy_from_msg(skb_put(skb, total_len), m, total_len);
        if (error < 0) {
                kfree_skb(skb);
                goto error_put_sess;
        }

        local_bh_disable();
        l2tp_xmit_skb(session, skb, session->hdr_len);
        local_bh_enable();

        sock_put(sk);

        return total_len;

error_put_sess:
        sock_put(sk);
error:
        return error;
}

/* Transmit function called by generic PPP driver.  Sends PPP frame
 * over PPPoL2TP socket.
 *
 * This is almost the same as pppol2tp_sendmsg(), but rather than
 * being called with a msghdr from userspace, it is called with a skb
 * from the kernel.
 *
 * The supplied skb from ppp doesn't have enough headroom for the
 * insertion of L2TP, UDP and IP headers so we need to allocate more
 * headroom in the skb. This will create a cloned skb. But we must be
 * careful in the error case because the caller will expect to free
 * the skb it supplied, not our cloned skb. So we take care to always
 * leave the original skb unfreed if we return an error.
 */
static int pppol2tp_xmit(struct ppp_channel *chan, struct sk_buff *skb)
{
        struct sock *sk = (struct sock *) chan->private;
        struct l2tp_session *session;
        struct l2tp_tunnel *tunnel;
        int uhlen, headroom;

        if (sock_flag(sk, SOCK_DEAD) || !(sk->sk_state & PPPOX_CONNECTED))
                goto abort;

        /* Get session and tunnel contexts from the socket */
        session = pppol2tp_sock_to_session(sk);
        if (session == NULL)
                goto abort;

        tunnel = session->tunnel;

        uhlen = (tunnel->encap == L2TP_ENCAPTYPE_UDP) ? sizeof(struct udphdr) : 0;
        headroom = NET_SKB_PAD +
                   sizeof(struct iphdr) + /* IP header */
                   uhlen +              /* UDP header (if L2TP_ENCAPTYPE_UDP) */
                   session->hdr_len +   /* L2TP header */
                   2;                   /* 2 bytes for PPP_ALLSTATIONS & PPP_UI */
        if (skb_cow_head(skb, headroom))
                goto abort_put_sess;

        /* Setup PPP header */
        __skb_push(skb, 2);
        skb->data[0] = PPP_ALLSTATIONS;
        skb->data[1] = PPP_UI;

        local_bh_disable();
        l2tp_xmit_skb(session, skb, session->hdr_len);
        local_bh_enable();

        sock_put(sk);

        return 1;

abort_put_sess:
        sock_put(sk);
abort:
        /* Free the original skb */
        kfree_skb(skb);
        return 1;
}

/*****************************************************************************
 * Session (and tunnel control) socket create/destroy.
 *****************************************************************************/

static void pppol2tp_put_sk(struct rcu_head *head)
{
        struct pppol2tp_session *ps;

        ps = container_of(head, typeof(*ps), rcu);
        sock_put(ps->__sk);
}

/* Called by l2tp_core when a session socket is being closed.
 */
static void pppol2tp_session_close(struct l2tp_session *session)
{
}

/* Really kill the session socket. (Called from sock_put() if
 * refcnt == 0.)
 */
static void pppol2tp_session_destruct(struct sock *sk)
{
        struct l2tp_session *session = sk->sk_user_data;

        skb_queue_purge(&sk->sk_receive_queue);
        skb_queue_purge(&sk->sk_write_queue);

        if (session) {
                sk->sk_user_data = NULL;
                BUG_ON(session->magic != L2TP_SESSION_MAGIC);
                l2tp_session_dec_refcount(session);
        }
}

/* Called when the PPPoX socket (session) is closed.
 */
static int pppol2tp_release(struct socket *sock)
{
        struct sock *sk = sock->sk;
        struct l2tp_session *session;
        int error;

        if (!sk)
                return 0;

        error = -EBADF;
        lock_sock(sk);
        if (sock_flag(sk, SOCK_DEAD) != 0)
                goto error;

        pppox_unbind_sock(sk);

        /* Signal the death of the socket. */
        sk->sk_state = PPPOX_DEAD;
        sock_orphan(sk);
        sock->sk = NULL;

        session = pppol2tp_sock_to_session(sk);
        if (session) {
                struct pppol2tp_session *ps;

                l2tp_session_delete(session);

                ps = l2tp_session_priv(session);
                mutex_lock(&ps->sk_lock);
                ps->__sk = rcu_dereference_protected(ps->sk,
                                                     lockdep_is_held(&ps->sk_lock));
                RCU_INIT_POINTER(ps->sk, NULL);
                mutex_unlock(&ps->sk_lock);
                call_rcu(&ps->rcu, pppol2tp_put_sk);

                /* Rely on the sock_put() call at the end of the function for
                 * dropping the reference held by pppol2tp_sock_to_session().
                 * The last reference will be dropped by pppol2tp_put_sk().
                 */
        }

        release_sock(sk);

        /* This will delete the session context via
         * pppol2tp_session_destruct() if the socket's refcnt drops to
         * zero.
         */
        sock_put(sk);

        return 0;

error:
        release_sock(sk);
        return error;
}

static struct proto pppol2tp_sk_proto = {
        .name     = "PPPOL2TP",
        .owner    = THIS_MODULE,
        .obj_size = sizeof(struct pppox_sock),
};

static int pppol2tp_backlog_recv(struct sock *sk, struct sk_buff *skb)
{
        int rc;

        rc = l2tp_udp_encap_recv(sk, skb);
        if (rc)
                kfree_skb(skb);

        return NET_RX_SUCCESS;
}

/* socket() handler. Initialize a new struct sock.
 */
static int pppol2tp_create(struct net *net, struct socket *sock, int kern)
{
        int error = -ENOMEM;
        struct sock *sk;

        sk = sk_alloc(net, PF_PPPOX, GFP_KERNEL, &pppol2tp_sk_proto, kern);
        if (!sk)
                goto out;

        sock_init_data(sock, sk);

        sock->state  = SS_UNCONNECTED;
        sock->ops    = &pppol2tp_ops;

        sk->sk_backlog_rcv = pppol2tp_backlog_recv;
        sk->sk_protocol    = PX_PROTO_OL2TP;
        sk->sk_family      = PF_PPPOX;
        sk->sk_state       = PPPOX_NONE;
        sk->sk_type        = SOCK_STREAM;
        sk->sk_destruct    = pppol2tp_session_destruct;

        error = 0;

out:
        return error;
}

#if IS_ENABLED(CONFIG_L2TP_DEBUGFS)
static void pppol2tp_show(struct seq_file *m, void *arg)
{
        struct l2tp_session *session = arg;
        struct sock *sk;

        sk = pppol2tp_session_get_sock(session);
        if (sk) {
                struct pppox_sock *po = pppox_sk(sk);

                seq_printf(m, "   interface %s\n", ppp_dev_name(&po->chan));
                sock_put(sk);
        }
}
#endif

static void pppol2tp_session_init(struct l2tp_session *session)
{
        struct pppol2tp_session *ps;
        struct dst_entry *dst;

        session->recv_skb = pppol2tp_recv;
        session->session_close = pppol2tp_session_close;
#if IS_ENABLED(CONFIG_L2TP_DEBUGFS)
        session->show = pppol2tp_show;
#endif

        ps = l2tp_session_priv(session);
        mutex_init(&ps->sk_lock);
        ps->owner = current->pid;

        /* If PMTU discovery was enabled, use the MTU that was discovered */
        dst = sk_dst_get(session->tunnel->sock);
        if (dst) {
                u32 pmtu = dst_mtu(dst);

                if (pmtu) {
                        session->mtu = pmtu - PPPOL2TP_HEADER_OVERHEAD;
                        session->mru = pmtu - PPPOL2TP_HEADER_OVERHEAD;
                }
                dst_release(dst);
        }
}

/* connect() handler. Attach a PPPoX socket to a tunnel UDP socket
 */
static int pppol2tp_connect(struct socket *sock, struct sockaddr *uservaddr,
                            int sockaddr_len, int flags)
{
        struct sock *sk = sock->sk;
        struct sockaddr_pppol2tp *sp = (struct sockaddr_pppol2tp *) uservaddr;
        struct pppox_sock *po = pppox_sk(sk);
        struct l2tp_session *session = NULL;
        struct l2tp_tunnel *tunnel;
        struct pppol2tp_session *ps;
        struct l2tp_session_cfg cfg = { 0, };
        int error = 0;
        u32 tunnel_id, peer_tunnel_id;
        u32 session_id, peer_session_id;
        bool drop_refcnt = false;
        bool drop_tunnel = false;
        bool new_session = false;
        bool new_tunnel = false;
        int ver = 2;
        int fd;

        lock_sock(sk);

        error = -EINVAL;

        if (sockaddr_len != sizeof(struct sockaddr_pppol2tp) &&
            sockaddr_len != sizeof(struct sockaddr_pppol2tpv3) &&
            sockaddr_len != sizeof(struct sockaddr_pppol2tpin6) &&
            sockaddr_len != sizeof(struct sockaddr_pppol2tpv3in6))
                goto end;

        if (sp->sa_protocol != PX_PROTO_OL2TP)
                goto end;

        /* Check for already bound sockets */
        error = -EBUSY;
        if (sk->sk_state & PPPOX_CONNECTED)
                goto end;

        /* We don't supporting rebinding anyway */
        error = -EALREADY;
        if (sk->sk_user_data)
                goto end; /* socket is already attached */

        /* Get params from socket address. Handle L2TPv2 and L2TPv3.
         * This is nasty because there are different sockaddr_pppol2tp
         * structs for L2TPv2, L2TPv3, over IPv4 and IPv6. We use
         * the sockaddr size to determine which structure the caller
         * is using.
         */
        peer_tunnel_id = 0;
        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)) {
                struct sockaddr_pppol2tpv3 *sp3 =
                        (struct sockaddr_pppol2tpv3 *) sp;
                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 if (sockaddr_len == sizeof(struct sockaddr_pppol2tpin6)) {
                struct sockaddr_pppol2tpin6 *sp6 =
                        (struct sockaddr_pppol2tpin6 *) sp;
                fd = sp6->pppol2tp.fd;
                tunnel_id = sp6->pppol2tp.s_tunnel;
                peer_tunnel_id = sp6->pppol2tp.d_tunnel;
                session_id = sp6->pppol2tp.s_session;
                peer_session_id = sp6->pppol2tp.d_session;
        } else if (sockaddr_len == sizeof(struct sockaddr_pppol2tpv3in6)) {
                struct sockaddr_pppol2tpv3in6 *sp6 =
                        (struct sockaddr_pppol2tpv3in6 *) sp;
                ver = 3;
                fd = sp6->pppol2tp.fd;
                tunnel_id = sp6->pppol2tp.s_tunnel;
                peer_tunnel_id = sp6->pppol2tp.d_tunnel;
                session_id = sp6->pppol2tp.s_session;
                peer_session_id = sp6->pppol2tp.d_session;
        } else {
                error = -EINVAL;
                goto end; /* bad socket address */
        }

        /* Don't bind if tunnel_id is 0 */
        error = -EINVAL;
        if (tunnel_id == 0)
                goto end;

        tunnel = l2tp_tunnel_get(sock_net(sk), tunnel_id);
        if (tunnel)
                drop_tunnel = true;

        /* Special case: create tunnel context if session_id and
         * peer_session_id is 0. Otherwise look up tunnel using supplied
         * tunnel id.
         */
        if ((session_id == 0) && (peer_session_id == 0)) {
                if (tunnel == NULL) {
                        struct l2tp_tunnel_cfg tcfg = {
                                .encap = L2TP_ENCAPTYPE_UDP,
                                .debug = 0,
                        };

                        /* Prevent l2tp_tunnel_register() from trying to set up
                         * a kernel socket.
                         */
                        if (fd < 0) {
                                error = -EBADF;
                                goto end;
                        }

                        error = l2tp_tunnel_create(sock_net(sk), fd, ver, tunnel_id, peer_tunnel_id, &tcfg, &tunnel);
                        if (error < 0)
                                goto end;

                        l2tp_tunnel_inc_refcount(tunnel);
                        error = l2tp_tunnel_register(tunnel, sock_net(sk),
                                                     &tcfg);
                        if (error < 0) {
                                kfree(tunnel);
                                goto end;
                        }
                        drop_tunnel = true;
                        new_tunnel = true;
                }
        } else {
                /* Error if we can't find the tunnel */
                error = -ENOENT;
                if (tunnel == NULL)
                        goto end;

                /* Error if socket is not prepped */
                if (tunnel->sock == NULL)
                        goto end;
        }

        if (tunnel->peer_tunnel_id == 0)
                tunnel->peer_tunnel_id = peer_tunnel_id;

        session = l2tp_session_get(sock_net(sk), tunnel, session_id);
        if (session) {
                drop_refcnt = true;

                if (session->pwtype != L2TP_PWTYPE_PPP) {
                        error = -EPROTOTYPE;
                        goto end;
                }

                ps = l2tp_session_priv(session);

                /* Using a pre-existing session is fine as long as it hasn't
                 * been connected yet.
                 */
                mutex_lock(&ps->sk_lock);
                if (rcu_dereference_protected(ps->sk,
                                              lockdep_is_held(&ps->sk_lock)) ||
                    ps->__sk) {
                        mutex_unlock(&ps->sk_lock);
                        error = -EEXIST;
                        goto end;
                }
        } else {
                /* Default MTU must allow space for UDP/L2TP/PPP headers */
                cfg.mtu = 1500 - PPPOL2TP_HEADER_OVERHEAD;
                cfg.mru = cfg.mtu;
                cfg.pw_type = L2TP_PWTYPE_PPP;

                session = l2tp_session_create(sizeof(struct pppol2tp_session),
                                              tunnel, session_id,
                                              peer_session_id, &cfg);
                if (IS_ERR(session)) {
                        error = PTR_ERR(session);
                        goto end;
                }

                pppol2tp_session_init(session);
                ps = l2tp_session_priv(session);
                l2tp_session_inc_refcount(session);

                mutex_lock(&ps->sk_lock);
                error = l2tp_session_register(session, tunnel);
                if (error < 0) {
                        mutex_unlock(&ps->sk_lock);
                        kfree(session);
                        goto end;
                }
                drop_refcnt = true;
                new_session = true;
        }

        /* Special case: if source & dest session_id == 0x0000, this
         * socket is being created to manage the tunnel. Just set up
         * the internal context for use by ioctl() and sockopt()
         * handlers.
         */
        if ((session->session_id == 0) &&
            (session->peer_session_id == 0)) {
                error = 0;
                goto out_no_ppp;
        }

        /* The only header we need to worry about is the L2TP
         * header. This size is different depending on whether
         * sequence numbers are enabled for the data channel.
         */
        po->chan.hdrlen = PPPOL2TP_L2TP_HDR_SIZE_NOSEQ;

        po->chan.private = sk;
        po->chan.ops     = &pppol2tp_chan_ops;
        po->chan.mtu     = session->mtu;

        error = ppp_register_net_channel(sock_net(sk), &po->chan);
        if (error) {
                mutex_unlock(&ps->sk_lock);
                goto end;
        }

out_no_ppp:
        /* This is how we get the session context from the socket. */
        sk->sk_user_data = session;
        rcu_assign_pointer(ps->sk, sk);
        mutex_unlock(&ps->sk_lock);

        /* Keep the reference we've grabbed on the session: sk doesn't expect
         * the session to disappear. pppol2tp_session_destruct() is responsible
         * for dropping it.
         */
        drop_refcnt = false;

        sk->sk_state = PPPOX_CONNECTED;
        l2tp_info(session, L2TP_MSG_CONTROL, "%s: created\n",
                  session->name);

end:
        if (error) {
                if (new_session)
                        l2tp_session_delete(session);
                if (new_tunnel)
                        l2tp_tunnel_delete(tunnel);
        }
        if (drop_refcnt)
                l2tp_session_dec_refcount(session);
        if (drop_tunnel)
                l2tp_tunnel_dec_refcount(tunnel);
        release_sock(sk);

        return error;
}

#ifdef CONFIG_L2TP_V3

/* Called when creating sessions via the netlink interface. */
static int pppol2tp_session_create(struct net *net, struct l2tp_tunnel *tunnel,
                                   u32 session_id, u32 peer_session_id,
                                   struct l2tp_session_cfg *cfg)
{
        int error;
        struct l2tp_session *session;

        /* Error if tunnel socket is not prepped */
        if (!tunnel->sock) {
                error = -ENOENT;
                goto err;
        }

        /* Default MTU values. */
        if (cfg->mtu == 0)
                cfg->mtu = 1500 - PPPOL2TP_HEADER_OVERHEAD;
        if (cfg->mru == 0)
                cfg->mru = cfg->mtu;

        /* Allocate and initialize a new session context. */
        session = l2tp_session_create(sizeof(struct pppol2tp_session),
                                      tunnel, session_id,
                                      peer_session_id, cfg);
        if (IS_ERR(session)) {
                error = PTR_ERR(session);
                goto err;
        }

        pppol2tp_session_init(session);

        error = l2tp_session_register(session, tunnel);
        if (error < 0)
                goto err_sess;

        return 0;

err_sess:
        kfree(session);
err:
        return error;
}

#endif /* CONFIG_L2TP_V3 */

/* getname() support.
 */
static int pppol2tp_getname(struct socket *sock, struct sockaddr *uaddr,
                            int peer)
{
        int len = 0;
        int error = 0;
        struct l2tp_session *session;
        struct l2tp_tunnel *tunnel;
        struct sock *sk = sock->sk;
        struct inet_sock *inet;
        struct pppol2tp_session *pls;

        error = -ENOTCONN;
        if (sk == NULL)
                goto end;
        if (!(sk->sk_state & PPPOX_CONNECTED))
                goto end;

        error = -EBADF;
        session = pppol2tp_sock_to_session(sk);
        if (session == NULL)
                goto end;

        pls = l2tp_session_priv(session);
        tunnel = session->tunnel;

        inet = inet_sk(tunnel->sock);
        if ((tunnel->version == 2) && (tunnel->sock->sk_family == AF_INET)) {
                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);
#if IS_ENABLED(CONFIG_IPV6)
        } else if ((tunnel->version == 2) &&
                   (tunnel->sock->sk_family == AF_INET6)) {
                struct sockaddr_pppol2tpin6 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.sin6_family = AF_INET6;
                sp.pppol2tp.addr.sin6_port = inet->inet_dport;
                memcpy(&sp.pppol2tp.addr.sin6_addr, &tunnel->sock->sk_v6_daddr,
                       sizeof(tunnel->sock->sk_v6_daddr));
                memcpy(uaddr, &sp, len);
        } else if ((tunnel->version == 3) &&
                   (tunnel->sock->sk_family == AF_INET6)) {
                struct sockaddr_pppol2tpv3in6 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.sin6_family = AF_INET6;
                sp.pppol2tp.addr.sin6_port = inet->inet_dport;
                memcpy(&sp.pppol2tp.addr.sin6_addr, &tunnel->sock->sk_v6_daddr,
                       sizeof(tunnel->sock->sk_v6_daddr));
                memcpy(uaddr, &sp, len);
#endif
        } 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);
        }

        error = len;

        sock_put(sk);
end:
        return error;
}

/****************************************************************************
 * ioctl() handlers.
 *
 * The PPPoX socket is created for L2TP sessions: tunnels have their own UDP
 * sockets. However, in order to control kernel tunnel features, we allow
 * userspace to create a special "tunnel" PPPoX socket which is used for
 * control only.  Tunnel PPPoX sockets have session_id == 0 and simply allow
 * the user application to issue L2TP setsockopt(), getsockopt() and ioctl()
 * calls.
 ****************************************************************************/

static void pppol2tp_copy_stats(struct pppol2tp_ioc_stats *dest,
                                struct l2tp_stats *stats)
{
        dest->tx_packets = atomic_long_read(&stats->tx_packets);
        dest->tx_bytes = atomic_long_read(&stats->tx_bytes);
        dest->tx_errors = atomic_long_read(&stats->tx_errors);
        dest->rx_packets = atomic_long_read(&stats->rx_packets);
        dest->rx_bytes = atomic_long_read(&stats->rx_bytes);
        dest->rx_seq_discards = atomic_long_read(&stats->rx_seq_discards);
        dest->rx_oos_packets = atomic_long_read(&stats->rx_oos_packets);
        dest->rx_errors = atomic_long_read(&stats->rx_errors);
}

/* Session ioctl helper.
 */
static int pppol2tp_session_ioctl(struct l2tp_session *session,
                                  unsigned int cmd, unsigned long arg)
{
        struct ifreq ifr;
        int err = 0;
        struct sock *sk;
        int val = (int) arg;
        struct pppol2tp_session *ps = l2tp_session_priv(session);
        struct l2tp_tunnel *tunnel = session->tunnel;
        struct pppol2tp_ioc_stats stats;

        l2tp_dbg(session, L2TP_MSG_CONTROL,
                 "%s: pppol2tp_session_ioctl(cmd=%#x, arg=%#lx)\n",
                 session->name, cmd, arg);

        sk = pppol2tp_session_get_sock(session);
        if (!sk)
                return -EBADR;

        switch (cmd) {
        case SIOCGIFMTU:
                err = -ENXIO;
                if (!(sk->sk_state & PPPOX_CONNECTED))
                        break;

                err = -EFAULT;
                if (copy_from_user(&ifr, (void __user *) arg, sizeof(struct ifreq)))
                        break;
                ifr.ifr_mtu = session->mtu;
                if (copy_to_user((void __user *) arg, &ifr, sizeof(struct ifreq)))
                        break;

                l2tp_info(session, L2TP_MSG_CONTROL, "%s: get mtu=%d\n",
                          session->name, session->mtu);
                err = 0;
                break;

        case SIOCSIFMTU:
                err = -ENXIO;
                if (!(sk->sk_state & PPPOX_CONNECTED))
                        break;

                err = -EFAULT;
                if (copy_from_user(&ifr, (void __user *) arg, sizeof(struct ifreq)))
                        break;

                session->mtu = ifr.ifr_mtu;

                l2tp_info(session, L2TP_MSG_CONTROL, "%s: set mtu=%d\n",
                          session->name, session->mtu);
                err = 0;
                break;

        case PPPIOCGMRU:
                err = -ENXIO;
                if (!(sk->sk_state & PPPOX_CONNECTED))
                        break;

                err = -EFAULT;
                if (put_user(session->mru, (int __user *) arg))
                        break;

                l2tp_info(session, L2TP_MSG_CONTROL, "%s: get mru=%d\n",
                          session->name, session->mru);
                err = 0;
                break;

        case PPPIOCSMRU:
                err = -ENXIO;
                if (!(sk->sk_state & PPPOX_CONNECTED))
                        break;

                err = -EFAULT;
                if (get_user(val, (int __user *) arg))
                        break;

                session->mru = val;
                l2tp_info(session, L2TP_MSG_CONTROL, "%s: set mru=%d\n",
                          session->name, session->mru);
                err = 0;
                break;

        case PPPIOCGFLAGS:
                err = -EFAULT;
                if (put_user(ps->flags, (int __user *) arg))
                        break;

                l2tp_info(session, L2TP_MSG_CONTROL, "%s: get flags=%d\n",
                          session->name, ps->flags);
                err = 0;
                break;

        case PPPIOCSFLAGS:
                err = -EFAULT;
                if (get_user(val, (int __user *) arg))
                        break;
                ps->flags = val;
                l2tp_info(session, L2TP_MSG_CONTROL, "%s: set flags=%d\n",
                          session->name, ps->flags);
                err = 0;
                break;

        case PPPIOCGL2TPSTATS:
                err = -ENXIO;
                if (!(sk->sk_state & PPPOX_CONNECTED))
                        break;

                memset(&stats, 0, sizeof(stats));
                stats.tunnel_id = tunnel->tunnel_id;
                stats.session_id = session->session_id;
                pppol2tp_copy_stats(&stats, &session->stats);
                if (copy_to_user((void __user *) arg, &stats,
                                 sizeof(stats)))
                        break;
                l2tp_info(session, L2TP_MSG_CONTROL, "%s: get L2TP stats\n",
                          session->name);
                err = 0;
                break;

        default:
                err = -ENOSYS;
                break;
        }

        sock_put(sk);

        return err;
}

/* Tunnel ioctl helper.
 *
 * Note the special handling for PPPIOCGL2TPSTATS below. If the ioctl data
 * specifies a session_id, the session ioctl handler is called. This allows an
 * application to retrieve session stats via a tunnel socket.
 */
static int pppol2tp_tunnel_ioctl(struct l2tp_tunnel *tunnel,
                                 unsigned int cmd, unsigned long arg)
{
        int err = 0;
        struct sock *sk;
        struct pppol2tp_ioc_stats stats;

        l2tp_dbg(tunnel, L2TP_MSG_CONTROL,
                 "%s: pppol2tp_tunnel_ioctl(cmd=%#x, arg=%#lx)\n",
                 tunnel->name, cmd, arg);

        sk = tunnel->sock;
        sock_hold(sk);

        switch (cmd) {
        case PPPIOCGL2TPSTATS:
                err = -ENXIO;
                if (!(sk->sk_state & PPPOX_CONNECTED))
                        break;

                if (copy_from_user(&stats, (void __user *) arg,
                                   sizeof(stats))) {
                        err = -EFAULT;
                        break;
                }
                if (stats.session_id != 0) {
                        /* resend to session ioctl handler */
                        struct l2tp_session *session =
                                l2tp_session_get(sock_net(sk), tunnel,
                                                 stats.session_id);

                        if (!session) {
                                err = -EBADR;
                                break;
                        }
                        if (session->pwtype != L2TP_PWTYPE_PPP) {
                                l2tp_session_dec_refcount(session);
                                err = -EBADR;
                                break;
                        }

                        err = pppol2tp_session_ioctl(session, cmd, arg);
                        l2tp_session_dec_refcount(session);
                        break;
                }
#ifdef CONFIG_XFRM
                stats.using_ipsec = (sk->sk_policy[0] || sk->sk_policy[1]) ? 1 : 0;
#endif
                pppol2tp_copy_stats(&stats, &tunnel->stats);
                if (copy_to_user((void __user *) arg, &stats, sizeof(stats))) {
                        err = -EFAULT;
                        break;
                }
                l2tp_info(tunnel, L2TP_MSG_CONTROL, "%s: get L2TP stats\n",
                          tunnel->name);
                err = 0;
                break;

        default:
                err = -ENOSYS;
                break;
        }

        sock_put(sk);

        return err;
}

/* Main ioctl() handler.
 * Dispatch to tunnel or session helpers depending on the socket.
 */
static int pppol2tp_ioctl(struct socket *sock, unsigned int cmd,
                          unsigned long arg)
{
        struct sock *sk = sock->sk;
        struct l2tp_session *session;
        struct l2tp_tunnel *tunnel;
        int err;

        if (!sk)
                return 0;

        err = -EBADF;
        if (sock_flag(sk, SOCK_DEAD) != 0)
                goto end;

        err = -ENOTCONN;
        if ((sk->sk_user_data == NULL) ||
            (!(sk->sk_state & (PPPOX_CONNECTED | PPPOX_BOUND))))
                goto end;

        /* Get session context from the socket */
        err = -EBADF;
        session = pppol2tp_sock_to_session(sk);
        if (session == NULL)
                goto end;

        /* Special case: if session's session_id is zero, treat ioctl as a
         * tunnel ioctl
         */
        if ((session->session_id == 0) &&
            (session->peer_session_id == 0)) {
                tunnel = session->tunnel;
                err = pppol2tp_tunnel_ioctl(tunnel, cmd, arg);
                goto end_put_sess;
        }

        err = pppol2tp_session_ioctl(session, cmd, arg);

end_put_sess:
        sock_put(sk);
end:
        return err;
}

/*****************************************************************************
 * setsockopt() / getsockopt() support.
 *
 * The PPPoX socket is created for L2TP sessions: tunnels have their own UDP
 * sockets. In order to control kernel tunnel features, we allow userspace to
 * create a special "tunnel" PPPoX socket which is used for control only.
 * Tunnel PPPoX sockets have session_id == 0 and simply allow the user
 * application to issue L2TP setsockopt(), getsockopt() and ioctl() calls.
 *****************************************************************************/

/* Tunnel setsockopt() helper.
 */
static int pppol2tp_tunnel_setsockopt(struct sock *sk,
                                      struct l2tp_tunnel *tunnel,
                                      int optname, int val)
{
        int err = 0;

        switch (optname) {
        case PPPOL2TP_SO_DEBUG:
                tunnel->debug = val;
                l2tp_info(tunnel, L2TP_MSG_CONTROL, "%s: set debug=%x\n",
                          tunnel->name, tunnel->debug);
                break;

        default:
                err = -ENOPROTOOPT;
                break;
        }

        return err;
}

/* Session setsockopt helper.
 */
static int pppol2tp_session_setsockopt(struct sock *sk,
                                       struct l2tp_session *session,
                                       int optname, int val)
{
        int err = 0;

        switch (optname) {
        case PPPOL2TP_SO_RECVSEQ:
                if ((val != 0) && (val != 1)) {
                        err = -EINVAL;
                        break;
                }
                session->recv_seq = !!val;
                l2tp_info(session, L2TP_MSG_CONTROL,
                          "%s: set recv_seq=%d\n",
                          session->name, session->recv_seq);
                break;

        case PPPOL2TP_SO_SENDSEQ:
                if ((val != 0) && (val != 1)) {
                        err = -EINVAL;
                        break;
                }
                session->send_seq = !!val;
                {
                        struct pppox_sock *po = pppox_sk(sk);

                        po->chan.hdrlen = val ? PPPOL2TP_L2TP_HDR_SIZE_SEQ :
                                PPPOL2TP_L2TP_HDR_SIZE_NOSEQ;
                }
                l2tp_session_set_header_len(session, session->tunnel->version);
                l2tp_info(session, L2TP_MSG_CONTROL,
                          "%s: set send_seq=%d\n",
                          session->name, session->send_seq);
                break;

        case PPPOL2TP_SO_LNSMODE:
                if ((val != 0) && (val != 1)) {
                        err = -EINVAL;
                        break;
                }
                session->lns_mode = !!val;
                l2tp_info(session, L2TP_MSG_CONTROL,
                          "%s: set lns_mode=%d\n",
                          session->name, session->lns_mode);
                break;

        case PPPOL2TP_SO_DEBUG:
                session->debug = val;
                l2tp_info(session, L2TP_MSG_CONTROL, "%s: set debug=%x\n",
                          session->name, session->debug);
                break;

        case PPPOL2TP_SO_REORDERTO:
                session->reorder_timeout = msecs_to_jiffies(val);
                l2tp_info(session, L2TP_MSG_CONTROL,
                          "%s: set reorder_timeout=%d\n",
                          session->name, session->reorder_timeout);
                break;

        default:
                err = -ENOPROTOOPT;
                break;
        }

        return err;
}

/* Main setsockopt() entry point.
 * Does API checks, then calls either the tunnel or session setsockopt
 * handler, according to whether the PPPoL2TP socket is a for a regular
 * session or the special tunnel type.
 */
static int pppol2tp_setsockopt(struct socket *sock, int level, int optname,
                               char __user *optval, unsigned int optlen)
{
        struct sock *sk = sock->sk;
        struct l2tp_session *session;
        struct l2tp_tunnel *tunnel;
        int val;
        int err;

        if (level != SOL_PPPOL2TP)
                return -EINVAL;

        if (optlen < sizeof(int))
                return -EINVAL;

        if (get_user(val, (int __user *)optval))
                return -EFAULT;

        err = -ENOTCONN;
        if (sk->sk_user_data == NULL)
                goto end;

        /* Get session context from the socket */
        err = -EBADF;
        session = pppol2tp_sock_to_session(sk);
        if (session == NULL)
                goto end;

        /* Special case: if session_id == 0x0000, treat as operation on tunnel
         */
        if ((session->session_id == 0) &&
            (session->peer_session_id == 0)) {
                tunnel = session->tunnel;
                err = pppol2tp_tunnel_setsockopt(sk, tunnel, optname, val);
        } else {
                err = pppol2tp_session_setsockopt(sk, session, optname, val);
        }

        sock_put(sk);
end:
        return err;
}

/* Tunnel getsockopt helper. Called with sock locked.
 */
static int pppol2tp_tunnel_getsockopt(struct sock *sk,
                                      struct l2tp_tunnel *tunnel,
                                      int optname, int *val)
{
        int err = 0;

        switch (optname) {
        case PPPOL2TP_SO_DEBUG:
                *val = tunnel->debug;
                l2tp_info(tunnel, L2TP_MSG_CONTROL, "%s: get debug=%x\n",
                          tunnel->name, tunnel->debug);
                break;

        default:
                err = -ENOPROTOOPT;
                break;
        }

        return err;
}

/* Session getsockopt helper. Called with sock locked.
 */
static int pppol2tp_session_getsockopt(struct sock *sk,
                                       struct l2tp_session *session,
                                       int optname, int *val)
{
        int err = 0;

        switch (optname) {
        case PPPOL2TP_SO_RECVSEQ:
                *val = session->recv_seq;
                l2tp_info(session, L2TP_MSG_CONTROL,
                          "%s: get recv_seq=%d\n", session->name, *val);
                break;

        case PPPOL2TP_SO_SENDSEQ:
                *val = session->send_seq;
                l2tp_info(session, L2TP_MSG_CONTROL,
                          "%s: get send_seq=%d\n", session->name, *val);
                break;

        case PPPOL2TP_SO_LNSMODE:
                *val = session->lns_mode;
                l2tp_info(session, L2TP_MSG_CONTROL,
                          "%s: get lns_mode=%d\n", session->name, *val);
                break;

        case PPPOL2TP_SO_DEBUG:
                *val = session->debug;
                l2tp_info(session, L2TP_MSG_CONTROL, "%s: get debug=%d\n",
                          session->name, *val);
                break;

        case PPPOL2TP_SO_REORDERTO:
                *val = (int) jiffies_to_msecs(session->reorder_timeout);
                l2tp_info(session, L2TP_MSG_CONTROL,
                          "%s: get reorder_timeout=%d\n", session->name, *val);
                break;

        default:
                err = -ENOPROTOOPT;
        }

        return err;
}

/* Main getsockopt() entry point.
 * Does API checks, then calls either the tunnel or session getsockopt
 * handler, according to whether the PPPoX socket is a for a regular session
 * or the special tunnel type.
 */
static int pppol2tp_getsockopt(struct socket *sock, int level, int optname,
                               char __user *optval, int __user *optlen)
{
        struct sock *sk = sock->sk;
        struct l2tp_session *session;
        struct l2tp_tunnel *tunnel;
        int val, len;
        int err;

        if (level != SOL_PPPOL2TP)
                return -EINVAL;

        if (get_user(len, optlen))
                return -EFAULT;

        len = min_t(unsigned int, len, sizeof(int));

        if (len < 0)
                return -EINVAL;

        err = -ENOTCONN;
        if (sk->sk_user_data == NULL)
                goto end;

        /* Get the session context */
        err = -EBADF;
        session = pppol2tp_sock_to_session(sk);
        if (session == NULL)
                goto end;

        /* Special case: if session_id == 0x0000, treat as operation on tunnel */
        if ((session->session_id == 0) &&
            (session->peer_session_id == 0)) {
                tunnel = session->tunnel;
                err = pppol2tp_tunnel_getsockopt(sk, tunnel, optname, &val);
                if (err)
                        goto end_put_sess;
        } else {
                err = pppol2tp_session_getsockopt(sk, session, optname, &val);
                if (err)
                        goto end_put_sess;
        }

        err = -EFAULT;
        if (put_user(len, optlen))
                goto end_put_sess;

        if (copy_to_user((void __user *) optval, &val, len))
                goto end_put_sess;

        err = 0;

end_put_sess:
        sock_put(sk);
end:
        return err;
}

/*****************************************************************************
 * /proc filesystem for debug
 * Since the original pppol2tp driver provided /proc/net/pppol2tp for
 * L2TPv2, we dump only L2TPv2 tunnels and sessions here.
 *****************************************************************************/

static unsigned int pppol2tp_net_id;

#ifdef CONFIG_PROC_FS

struct pppol2tp_seq_data {
        struct seq_net_private p;
        int tunnel_idx;                 /* current tunnel */
        int session_idx;                /* index of session within current tunnel */
        struct l2tp_tunnel *tunnel;
        struct l2tp_session *session;   /* NULL means get next tunnel */
};

static void pppol2tp_next_tunnel(struct net *net, struct pppol2tp_seq_data *pd)
{
        /* Drop reference taken during previous invocation */
        if (pd->tunnel)
                l2tp_tunnel_dec_refcount(pd->tunnel);

        for (;;) {
                pd->tunnel = l2tp_tunnel_get_nth(net, pd->tunnel_idx);
                pd->tunnel_idx++;

                /* Only accept L2TPv2 tunnels */
                if (!pd->tunnel || pd->tunnel->version == 2)
                        return;

                l2tp_tunnel_dec_refcount(pd->tunnel);
        }
}

static void pppol2tp_next_session(struct net *net, struct pppol2tp_seq_data *pd)
{
        /* Drop reference taken during previous invocation */
        if (pd->session)
                l2tp_session_dec_refcount(pd->session);

        pd->session = l2tp_session_get_nth(pd->tunnel, pd->session_idx);
        pd->session_idx++;

        if (pd->session == NULL) {
                pd->session_idx = 0;
                pppol2tp_next_tunnel(net, pd);
        }
}

static void *pppol2tp_seq_start(struct seq_file *m, loff_t *offs)
{
        struct pppol2tp_seq_data *pd = SEQ_START_TOKEN;
        loff_t pos = *offs;
        struct net *net;

        if (!pos)
                goto out;

        BUG_ON(m->private == NULL);
        pd = m->private;
        net = seq_file_net(m);

        if (pd->tunnel == NULL)
                pppol2tp_next_tunnel(net, pd);
        else
                pppol2tp_next_session(net, pd);

        /* NULL tunnel and session indicates end of list */
        if ((pd->tunnel == NULL) && (pd->session == NULL))
                pd = NULL;

out:
        return pd;
}

static void *pppol2tp_seq_next(struct seq_file *m, void *v, loff_t *pos)
{
        (*pos)++;
        return NULL;
}

static void pppol2tp_seq_stop(struct seq_file *p, void *v)
{
        struct pppol2tp_seq_data *pd = v;

        if (!pd || pd == SEQ_START_TOKEN)
                return;

        /* Drop reference taken by last invocation of pppol2tp_next_session()
         * or pppol2tp_next_tunnel().
         */
        if (pd->session) {
                l2tp_session_dec_refcount(pd->session);
                pd->session = NULL;
        }
        if (pd->tunnel) {
                l2tp_tunnel_dec_refcount(pd->tunnel);
                pd->tunnel = NULL;
        }
}

static void pppol2tp_seq_tunnel_show(struct seq_file *m, void *v)
{
        struct l2tp_tunnel *tunnel = v;

        seq_printf(m, "\nTUNNEL '%s', %c %d\n",
                   tunnel->name,
                   (tunnel == tunnel->sock->sk_user_data) ? 'Y' : 'N',
                   refcount_read(&tunnel->ref_count) - 1);
        seq_printf(m, " %08x %ld/%ld/%ld %ld/%ld/%ld\n",
                   tunnel->debug,
                   atomic_long_read(&tunnel->stats.tx_packets),
                   atomic_long_read(&tunnel->stats.tx_bytes),
                   atomic_long_read(&tunnel->stats.tx_errors),
                   atomic_long_read(&tunnel->stats.rx_packets),
                   atomic_long_read(&tunnel->stats.rx_bytes),
                   atomic_long_read(&tunnel->stats.rx_errors));
}

static void pppol2tp_seq_session_show(struct seq_file *m, void *v)
{
        struct l2tp_session *session = v;
        struct l2tp_tunnel *tunnel = session->tunnel;
        unsigned char state;
        char user_data_ok;
        struct sock *sk;
        u32 ip = 0;
        u16 port = 0;

        if (tunnel->sock) {
                struct inet_sock *inet = inet_sk(tunnel->sock);
                ip = ntohl(inet->inet_saddr);
                port = ntohs(inet->inet_sport);
        }

        sk = pppol2tp_session_get_sock(session);
        if (sk) {
                state = sk->sk_state;
                user_data_ok = (session == sk->sk_user_data) ? 'Y' : 'N';
        } else {
                state = 0;
                user_data_ok = 'N';
        }

        seq_printf(m, "  SESSION '%s' %08X/%d %04X/%04X -> "
                   "%04X/%04X %d %c\n",
                   session->name, ip, port,
                   tunnel->tunnel_id,
                   session->session_id,
                   tunnel->peer_tunnel_id,
                   session->peer_session_id,
                   state, user_data_ok);
        seq_printf(m, "   %d/%d/%c/%c/%s %08x %u\n",
                   session->mtu, session->mru,
                   session->recv_seq ? 'R' : '-',
                   session->send_seq ? 'S' : '-',
                   session->lns_mode ? "LNS" : "LAC",
                   session->debug,
                   jiffies_to_msecs(session->reorder_timeout));
        seq_printf(m, "   %hu/%hu %ld/%ld/%ld %ld/%ld/%ld\n",
                   session->nr, session->ns,
                   atomic_long_read(&session->stats.tx_packets),
                   atomic_long_read(&session->stats.tx_bytes),
                   atomic_long_read(&session->stats.tx_errors),
                   atomic_long_read(&session->stats.rx_packets),
                   atomic_long_read(&session->stats.rx_bytes),
                   atomic_long_read(&session->stats.rx_errors));

        if (sk) {
                struct pppox_sock *po = pppox_sk(sk);

                seq_printf(m, "   interface %s\n", ppp_dev_name(&po->chan));
                sock_put(sk);
        }
}

static int pppol2tp_seq_show(struct seq_file *m, void *v)
{
        struct pppol2tp_seq_data *pd = v;

        /* display header on line 1 */
        if (v == SEQ_START_TOKEN) {
                seq_puts(m, "PPPoL2TP driver info, " PPPOL2TP_DRV_VERSION "\n");
                seq_puts(m, "TUNNEL name, user-data-ok session-count\n");
                seq_puts(m, " debug tx-pkts/bytes/errs rx-pkts/bytes/errs\n");
                seq_puts(m, "  SESSION name, addr/port src-tid/sid "
                         "dest-tid/sid state user-data-ok\n");
                seq_puts(m, "   mtu/mru/rcvseq/sendseq/lns debug reorderto\n");
                seq_puts(m, "   nr/ns tx-pkts/bytes/errs rx-pkts/bytes/errs\n");
                goto out;
        }

        if (!pd->session)
                pppol2tp_seq_tunnel_show(m, pd->tunnel);
        else
                pppol2tp_seq_session_show(m, pd->session);

out:
        return 0;
}

static const struct seq_operations pppol2tp_seq_ops = {
        .start          = pppol2tp_seq_start,
        .next           = pppol2tp_seq_next,
        .stop           = pppol2tp_seq_stop,
        .show           = pppol2tp_seq_show,
};
#endif /* CONFIG_PROC_FS */

/*****************************************************************************
 * Network namespace
 *****************************************************************************/

static __net_init int pppol2tp_init_net(struct net *net)
{
        struct proc_dir_entry *pde;
        int err = 0;

        pde = proc_create_net("pppol2tp", 0444, net->proc_net,
                        &pppol2tp_seq_ops, sizeof(struct pppol2tp_seq_data));
        if (!pde) {
                err = -ENOMEM;
                goto out;
        }

out:
        return err;
}

static __net_exit void pppol2tp_exit_net(struct net *net)
{
        remove_proc_entry("pppol2tp", net->proc_net);
}

static struct pernet_operations pppol2tp_net_ops = {
        .init = pppol2tp_init_net,
        .exit = pppol2tp_exit_net,
        .id   = &pppol2tp_net_id,
};

/*****************************************************************************
 * Init and cleanup
 *****************************************************************************/

static const struct proto_ops pppol2tp_ops = {
        .family         = AF_PPPOX,
        .owner          = THIS_MODULE,
        .release        = pppol2tp_release,
        .bind           = sock_no_bind,
        .connect        = pppol2tp_connect,
        .socketpair     = sock_no_socketpair,
        .accept         = sock_no_accept,
        .getname        = pppol2tp_getname,
        .poll           = datagram_poll,
        .listen         = sock_no_listen,
        .shutdown       = sock_no_shutdown,
        .setsockopt     = pppol2tp_setsockopt,
        .getsockopt     = pppol2tp_getsockopt,
        .sendmsg        = pppol2tp_sendmsg,
        .recvmsg        = pppol2tp_recvmsg,
        .mmap           = sock_no_mmap,
        .ioctl          = pppox_ioctl,
};

static const struct pppox_proto pppol2tp_proto = {
        .create         = pppol2tp_create,
        .ioctl          = pppol2tp_ioctl,
        .owner          = THIS_MODULE,
};

#ifdef CONFIG_L2TP_V3

static const struct l2tp_nl_cmd_ops pppol2tp_nl_cmd_ops = {
        .session_create = pppol2tp_session_create,
        .session_delete = l2tp_session_delete,
};

#endif /* CONFIG_L2TP_V3 */

static int __init pppol2tp_init(void)
{
        int err;

        err = register_pernet_device(&pppol2tp_net_ops);
        if (err)
                goto out;

        err = proto_register(&pppol2tp_sk_proto, 0);
        if (err)
                goto out_unregister_pppol2tp_pernet;

        err = register_pppox_proto(PX_PROTO_OL2TP, &pppol2tp_proto);
        if (err)
                goto out_unregister_pppol2tp_proto;

#ifdef CONFIG_L2TP_V3
        err = l2tp_nl_register_ops(L2TP_PWTYPE_PPP, &pppol2tp_nl_cmd_ops);
        if (err)
                goto out_unregister_pppox;
#endif

        pr_info("PPPoL2TP kernel driver, %s\n", PPPOL2TP_DRV_VERSION);

out:
        return err;

#ifdef CONFIG_L2TP_V3
out_unregister_pppox:
        unregister_pppox_proto(PX_PROTO_OL2TP);
#endif
out_unregister_pppol2tp_proto:
        proto_unregister(&pppol2tp_sk_proto);
out_unregister_pppol2tp_pernet:
        unregister_pernet_device(&pppol2tp_net_ops);
        goto out;
}

static void __exit pppol2tp_exit(void)
{
#ifdef CONFIG_L2TP_V3
        l2tp_nl_unregister_ops(L2TP_PWTYPE_PPP);
#endif
        unregister_pppox_proto(PX_PROTO_OL2TP);
        proto_unregister(&pppol2tp_sk_proto);
        unregister_pernet_device(&pppol2tp_net_ops);
}

module_init(pppol2tp_init);
module_exit(pppol2tp_exit);

MODULE_AUTHOR("James Chapman <jchapman@katalix.com>");
MODULE_DESCRIPTION("PPP over L2TP over UDP");
MODULE_LICENSE("GPL");
MODULE_VERSION(PPPOL2TP_DRV_VERSION);
MODULE_ALIAS_NET_PF_PROTO(PF_PPPOX, PX_PROTO_OL2TP);
MODULE_ALIAS_L2TP_PWTYPE(7);