l2tp_ppp.c

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/*****************************************************************************
 * 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 ([email protected])
 *
 * Based on original work by Martijn van Oosterhout <[email protected]>
 *
 * 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 <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 sock     *sock;      /* Pointer to the session
                         * PPPoX socket */
    struct sock     *tunnel_sock;   /* Pointer to the tunnel UDP
                         * socket */
    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;

/* 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
 *****************************************************************************/

static int pppol2tp_recv_payload_hook(struct sk_buff *skb)
{
    /* Skip PPP header, if present.  In testing, Microsoft L2TP clients
     * don't send the PPP header (PPP header compression enabled), but
     * other clients can include the header. So we cope with both cases
     * here. The PPP header is always FF03 when using L2TP.
     *
     * Note that skb->data[] isn't dereferenced from a u16 ptr here since
     * the field may be unaligned.
     */
    if (!pskb_may_pull(skb, 2))
        return 1;

    if ((skb->data[0] == 0xff) && (skb->data[1] == 0x03))
        skb_pull(skb, 2);

    return 0;
}

/* Receive message. This is the recvmsg for the PPPoL2TP socket.
 */
static int pppol2tp_recvmsg(struct kiocb *iocb, 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;

    msg->msg_namelen = 0;

    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_iovec(skb, 0, msg->msg_iov, 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.
     */
    sk = ps->sock;
    if (sk == NULL)
        goto no_sock;

    if (sk->sk_state & PPPOX_BOUND) {
        struct pppox_sock *po;
        l2tp_dbg(session, PPPOL2TP_MSG_DATA,
             "%s: recv %d byte data frame, passing to ppp\n",
             session->name, data_len);

        /* We need to forget all info related to the L2TP packet
         * gathered in the skb as we are going to reuse the same
         * skb for the inner packet.
         * Namely we need to:
         * - reset xfrm (IPSec) information as it applies to
         *   the outer L2TP packet and not to the inner one
         * - release the dst to force a route lookup on the inner
         *   IP packet since skb->dst currently points to the dst
         *   of the UDP tunnel
         * - reset netfilter information as it doesn't apply
         *   to the inner packet either
         */
        secpath_reset(skb);
        skb_dst_drop(skb);
        nf_reset(skb);

        po = pppox_sk(sk);
        ppp_input(&po->chan, skb);
    } else {
        l2tp_info(session, PPPOL2TP_MSG_DATA, "%s: socket not bound\n",
              session->name);

        /* Not bound. Nothing we can do, so discard. */
        session->stats.rx_errors++;
        kfree_skb(skb);
    }

    return;

no_sock:
    l2tp_info(session, PPPOL2TP_MSG_DATA, "%s: no socket\n", session->name);
    kfree_skb(skb);
}

static void pppol2tp_session_sock_hold(struct l2tp_session *session)
{
    struct pppol2tp_session *ps = l2tp_session_priv(session);

    if (ps->sock)
        sock_hold(ps->sock);
}

static void pppol2tp_session_sock_put(struct l2tp_session *session)
{
    struct pppol2tp_session *ps = l2tp_session_priv(session);

    if (ps->sock)
        sock_put(ps->sock);
}

/************************************************************************
 * 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 kiocb *iocb, struct socket *sock, struct msghdr *m,
                size_t total_len)
{
    static const unsigned char ppph[2] = { 0xff, 0x03 };
    struct sock *sk = sock->sk;
    struct sk_buff *skb;
    int error;
    struct l2tp_session *session;
    struct l2tp_tunnel *tunnel;
    struct pppol2tp_session *ps;
    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;

    ps = l2tp_session_priv(session);
    tunnel = l2tp_sock_to_tunnel(ps->tunnel_sock);
    if (tunnel == NULL)
        goto error_put_sess;

    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 +
               sizeof(ppph) + total_len,
               0, GFP_KERNEL);
    if (!skb)
        goto error_put_sess_tun;

    /* 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] = ppph[0];
    skb->data[1] = ppph[1];
    skb_put(skb, 2);

    /* Copy user data into skb */
    error = memcpy_fromiovec(skb->data, m->msg_iov, total_len);
    if (error < 0) {
        kfree_skb(skb);
        goto error_put_sess_tun;
    }
    skb_put(skb, total_len);

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

    sock_put(ps->tunnel_sock);

    return error;

error_put_sess_tun:
    sock_put(ps->tunnel_sock);
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)
{
    static const u8 ppph[2] = { 0xff, 0x03 };
    struct sock *sk = (struct sock *) chan->private;
    struct sock *sk_tun;
    struct l2tp_session *session;
    struct l2tp_tunnel *tunnel;
    struct pppol2tp_session *ps;
    int old_headroom;
    int new_headroom;
    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;

    ps = l2tp_session_priv(session);
    sk_tun = ps->tunnel_sock;
    if (sk_tun == NULL)
        goto abort_put_sess;
    tunnel = l2tp_sock_to_tunnel(sk_tun);
    if (tunnel == NULL)
        goto abort_put_sess;

    old_headroom = skb_headroom(skb);
    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 */
           sizeof(ppph);    /* PPP header */
    if (skb_cow_head(skb, headroom))
        goto abort_put_sess_tun;

    new_headroom = skb_headroom(skb);
    skb->truesize += new_headroom - old_headroom;

    /* Setup PPP header */
    __skb_push(skb, sizeof(ppph));
    skb->data[0] = ppph[0];
    skb->data[1] = ppph[1];

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

    sock_put(sk_tun);
    sock_put(sk);
    return 1;

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

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

/* Called by l2tp_core when a session socket is being closed.
 */
static void pppol2tp_session_close(struct l2tp_session *session)
{
    struct pppol2tp_session *ps = l2tp_session_priv(session);
    struct sock *sk = ps->sock;
    struct sk_buff *skb;

    BUG_ON(session->magic != L2TP_SESSION_MAGIC);

    if (session->session_id == 0)
        goto out;

    if (sk != NULL) {
        lock_sock(sk);

        if (sk->sk_state & (PPPOX_CONNECTED | PPPOX_BOUND)) {
            pppox_unbind_sock(sk);
            sk->sk_state = PPPOX_DEAD;
            sk->sk_state_change(sk);
        }

        /* Purge any queued data */
        skb_queue_purge(&sk->sk_receive_queue);
        skb_queue_purge(&sk->sk_write_queue);
        while ((skb = skb_dequeue(&session->reorder_q))) {
            kfree_skb(skb);
            sock_put(sk);
        }

        release_sock(sk);
    }

out:
    return;
}

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

    if (sk->sk_user_data != NULL) {
        session = sk->sk_user_data;
        if (session == NULL)
            goto out;

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

out:
    return;
}

/* 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);

    /* Purge any queued data */
    skb_queue_purge(&sk->sk_receive_queue);
    skb_queue_purge(&sk->sk_write_queue);
    if (session != NULL) {
        struct sk_buff *skb;
        while ((skb = skb_dequeue(&session->reorder_q))) {
            kfree_skb(skb);
            sock_put(sk);
        }
        sock_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 error = -ENOMEM;
    struct sock *sk;

    sk = sk_alloc(net, PF_PPPOX, GFP_KERNEL, &pppol2tp_sk_proto);
    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 defined(CONFIG_L2TP_DEBUGFS) || defined(CONFIG_L2TP_DEBUGFS_MODULE)
static void pppol2tp_show(struct seq_file *m, void *arg)
{
    struct l2tp_session *session = arg;
    struct pppol2tp_session *ps = l2tp_session_priv(session);

    if (ps) {
        struct pppox_sock *po = pppox_sk(ps->sock);
        if (po)
            seq_printf(m, "   interface %s\n", ppp_dev_name(&po->chan));
    }
}
#endif

/* 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 dst_entry *dst;
    struct l2tp_session_cfg cfg = { 0, };
    int error = 0;
    u32 tunnel_id, peer_tunnel_id;
    u32 session_id, peer_session_id;
    int ver = 2;
    int fd;

    lock_sock(sk);

    error = -EINVAL;
    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_find(sock_net(sk), tunnel_id);

    /* 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,
            };
            error = l2tp_tunnel_create(sock_net(sk), fd, ver, tunnel_id, peer_tunnel_id, &tcfg, &tunnel);
            if (error < 0)
                goto end;
        }
    } 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->recv_payload_hook == NULL)
        tunnel->recv_payload_hook = pppol2tp_recv_payload_hook;

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

    /* Create session if it doesn't already exist. We handle the
     * case where a session was previously created by the netlink
     * interface by checking that the session doesn't already have
     * a socket and its tunnel socket are what we expect. If any
     * of those checks fail, return EEXIST to the caller.
     */
    session = l2tp_session_find(sock_net(sk), tunnel, session_id);
    if (session == NULL) {
        /* Default MTU must allow space for UDP/L2TP/PPP
         * headers.
         */
        cfg.mtu = cfg.mru = 1500 - PPPOL2TP_HEADER_OVERHEAD;

        /* Allocate and initialize a new session context. */
        session = l2tp_session_create(sizeof(struct pppol2tp_session),
                          tunnel, session_id,
                          peer_session_id, &cfg);
        if (session == NULL) {
            error = -ENOMEM;
            goto end;
        }
    } else {
        ps = l2tp_session_priv(session);
        error = -EEXIST;
        if (ps->sock != NULL)
            goto end;

        /* consistency checks */
        if (ps->tunnel_sock != tunnel->sock)
            goto end;
    }

    /* Associate session with its PPPoL2TP socket */
    ps = l2tp_session_priv(session);
    ps->owner        = current->pid;
    ps->sock         = sk;
    ps->tunnel_sock = tunnel->sock;

    session->recv_skb   = pppol2tp_recv;
    session->session_close  = pppol2tp_session_close;
#if defined(CONFIG_L2TP_DEBUGFS) || defined(CONFIG_L2TP_DEBUGFS_MODULE)
    session->show       = pppol2tp_show;
#endif

    /* We need to know each time a skb is dropped from the reorder
     * queue.
     */
    session->ref = pppol2tp_session_sock_hold;
    session->deref = pppol2tp_session_sock_put;

    /* If PMTU discovery was enabled, use the MTU that was discovered */
    dst = sk_dst_get(sk);
    if (dst != NULL) {
        u32 pmtu = dst_mtu(__sk_dst_get(sk));
        if (pmtu != 0)
            session->mtu = session->mru = pmtu -
                PPPOL2TP_HEADER_OVERHEAD;
        dst_release(dst);
    }

    /* 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)
        goto end;

out_no_ppp:
    /* This is how we get the session context from the socket. */
    sk->sk_user_data = session;
    sk->sk_state = PPPOX_CONNECTED;
    l2tp_info(session, PPPOL2TP_MSG_CONTROL, "%s: created\n",
          session->name);

end:
    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, u32 tunnel_id, u32 session_id, u32 peer_session_id, struct l2tp_session_cfg *cfg)
{
    int error;
    struct l2tp_tunnel *tunnel;
    struct l2tp_session *session;
    struct pppol2tp_session *ps;

    tunnel = l2tp_tunnel_find(net, tunnel_id);

    /* Error if we can't find the tunnel */
    error = -ENOENT;
    if (tunnel == NULL)
        goto out;

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

    /* Check that this session doesn't already exist */
    error = -EEXIST;
    session = l2tp_session_find(net, tunnel, session_id);
    if (session != NULL)
        goto out;

    /* 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. */
    error = -ENOMEM;
    session = l2tp_session_create(sizeof(struct pppol2tp_session),
                      tunnel, session_id,
                      peer_session_id, cfg);
    if (session == NULL)
        goto out;

    ps = l2tp_session_priv(session);
    ps->tunnel_sock = tunnel->sock;

    l2tp_info(session, PPPOL2TP_MSG_CONTROL, "%s: created\n",
          session->name);

    error = 0;

out:
    return error;
}

/* Called when deleting sessions via the netlink interface.
 */
static int pppol2tp_session_delete(struct l2tp_session *session)
{
    struct pppol2tp_session *ps = l2tp_session_priv(session);

    if (ps->sock == NULL)
        l2tp_session_dec_refcount(session);

    return 0;
}

#endif /* CONFIG_L2TP_V3 */

/* getname() support.
 */
static int pppol2tp_getname(struct socket *sock, struct sockaddr *uaddr,
                int *usockaddr_len, 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 = l2tp_sock_to_tunnel(pls->tunnel_sock);
    if (tunnel == NULL) {
        error = -EBADF;
        goto end_put_sess;
    }

    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 ipv6_pinfo *np = inet6_sk(tunnel->sock);
        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, &np->daddr,
               sizeof(np->daddr));
        memcpy(uaddr, &sp, len);
    } else if ((tunnel->version == 3) &&
           (tunnel->sock->sk_family == AF_INET6)) {
        struct ipv6_pinfo *np = inet6_sk(tunnel->sock);
        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, &np->daddr,
               sizeof(np->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);
    }

    *usockaddr_len = len;

    sock_put(pls->tunnel_sock);
end_put_sess:
    sock_put(sk);
    error = 0;

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 = stats->tx_packets;
    dest->tx_bytes = stats->tx_bytes;
    dest->tx_errors = stats->tx_errors;
    dest->rx_packets = stats->rx_packets;
    dest->rx_bytes = stats->rx_bytes;
    dest->rx_seq_discards = stats->rx_seq_discards;
    dest->rx_oos_packets = stats->rx_oos_packets;
    dest->rx_errors = 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, PPPOL2TP_MSG_CONTROL,
         "%s: pppol2tp_session_ioctl(cmd=%#x, arg=%#lx)\n",
         session->name, cmd, arg);

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

    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, PPPOL2TP_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, PPPOL2TP_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, PPPOL2TP_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, PPPOL2TP_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, PPPOL2TP_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, PPPOL2TP_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, PPPOL2TP_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, PPPOL2TP_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_find(sock_net(sk), tunnel, stats.session_id);
            if (session != NULL)
                err = pppol2tp_session_ioctl(session, cmd, arg);
            else
                err = -EBADR;
            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, PPPOL2TP_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;
    struct pppol2tp_session *ps;
    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
     */
    ps = l2tp_session_priv(session);
    if ((session->session_id == 0) &&
        (session->peer_session_id == 0)) {
        err = -EBADF;
        tunnel = l2tp_sock_to_tunnel(ps->tunnel_sock);
        if (tunnel == NULL)
            goto end_put_sess;

        err = pppol2tp_tunnel_ioctl(tunnel, cmd, arg);
        sock_put(ps->tunnel_sock);
        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, PPPOL2TP_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;
    struct pppol2tp_session *ps = l2tp_session_priv(session);

    switch (optname) {
    case PPPOL2TP_SO_RECVSEQ:
        if ((val != 0) && (val != 1)) {
            err = -EINVAL;
            break;
        }
        session->recv_seq = val ? -1 : 0;
        l2tp_info(session, PPPOL2TP_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 ? -1 : 0;
        {
            struct sock *ssk      = ps->sock;
            struct pppox_sock *po = pppox_sk(ssk);
            po->chan.hdrlen = val ? PPPOL2TP_L2TP_HDR_SIZE_SEQ :
                PPPOL2TP_L2TP_HDR_SIZE_NOSEQ;
        }
        l2tp_info(session, PPPOL2TP_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 ? -1 : 0;
        l2tp_info(session, PPPOL2TP_MSG_CONTROL,
              "%s: set lns_mode=%d\n",
              session->name, session->lns_mode);
        break;

    case PPPOL2TP_SO_DEBUG:
        session->debug = val;
        l2tp_info(session, PPPOL2TP_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, PPPOL2TP_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;
    struct pppol2tp_session *ps;
    int val;
    int err;

    if (level != SOL_PPPOL2TP)
        return udp_prot.setsockopt(sk, level, optname, optval, optlen);

    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
     */
    ps = l2tp_session_priv(session);
    if ((session->session_id == 0) &&
        (session->peer_session_id == 0)) {
        err = -EBADF;
        tunnel = l2tp_sock_to_tunnel(ps->tunnel_sock);
        if (tunnel == NULL)
            goto end_put_sess;

        err = pppol2tp_tunnel_setsockopt(sk, tunnel, optname, val);
        sock_put(ps->tunnel_sock);
    } else
        err = pppol2tp_session_setsockopt(sk, session, optname, val);

    err = 0;

end_put_sess:
    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, PPPOL2TP_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, PPPOL2TP_MSG_CONTROL,
              "%s: get recv_seq=%d\n", session->name, *val);
        break;

    case PPPOL2TP_SO_SENDSEQ:
        *val = session->send_seq;
        l2tp_info(session, PPPOL2TP_MSG_CONTROL,
              "%s: get send_seq=%d\n", session->name, *val);
        break;

    case PPPOL2TP_SO_LNSMODE:
        *val = session->lns_mode;
        l2tp_info(session, PPPOL2TP_MSG_CONTROL,
              "%s: get lns_mode=%d\n", session->name, *val);
        break;

    case PPPOL2TP_SO_DEBUG:
        *val = session->debug;
        l2tp_info(session, PPPOL2TP_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, PPPOL2TP_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;
    struct pppol2tp_session *ps;

    if (level != SOL_PPPOL2TP)
        return udp_prot.getsockopt(sk, level, optname, optval, optlen);

    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 */
    ps = l2tp_session_priv(session);
    if ((session->session_id == 0) &&
        (session->peer_session_id == 0)) {
        err = -EBADF;
        tunnel = l2tp_sock_to_tunnel(ps->tunnel_sock);
        if (tunnel == NULL)
            goto end_put_sess;

        err = pppol2tp_tunnel_getsockopt(sk, tunnel, optname, &val);
        sock_put(ps->tunnel_sock);
    } else
        err = pppol2tp_session_getsockopt(sk, session, optname, &val);

    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)
{
    for (;;) {
        pd->tunnel = l2tp_tunnel_find_nth(net, pd->tunnel_idx);
        pd->tunnel_idx++;

        if (pd->tunnel == NULL)
            break;

        /* Ignore L2TPv3 tunnels */
        if (pd->tunnel->version < 3)
            break;
    }
}

static void pppol2tp_next_session(struct net *net, struct pppol2tp_seq_data *pd)
{
    pd->session = l2tp_session_find_nth(pd->tunnel, pd->session_idx);
    pd->session_idx++;

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

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)
{
    /* nothing to do */
}

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',
           atomic_read(&tunnel->ref_count) - 1);
    seq_printf(m, " %08x %llu/%llu/%llu %llu/%llu/%llu\n",
           tunnel->debug,
           (unsigned long long)tunnel->stats.tx_packets,
           (unsigned long long)tunnel->stats.tx_bytes,
           (unsigned long long)tunnel->stats.tx_errors,
           (unsigned long long)tunnel->stats.rx_packets,
           (unsigned long long)tunnel->stats.rx_bytes,
           (unsigned long long)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;
    struct pppol2tp_session *ps = l2tp_session_priv(session);
    struct pppox_sock *po = pppox_sk(ps->sock);
    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);
    }

    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,
           ps->sock->sk_state,
           (session == ps->sock->sk_user_data) ?
           'Y' : 'N');
    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 %llu/%llu/%llu %llu/%llu/%llu\n",
           session->nr, session->ns,
           (unsigned long long)session->stats.tx_packets,
           (unsigned long long)session->stats.tx_bytes,
           (unsigned long long)session->stats.tx_errors,
           (unsigned long long)session->stats.rx_packets,
           (unsigned long long)session->stats.rx_bytes,
           (unsigned long long)session->stats.rx_errors);

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

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;
    }

    /* Show the tunnel or session context.
     */
    if (pd->session == NULL)
        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,
};

/* Called when our /proc file is opened. We allocate data for use when
 * iterating our tunnel / session contexts and store it in the private
 * data of the seq_file.
 */
static int pppol2tp_proc_open(struct inode *inode, struct file *file)
{
    return seq_open_net(inode, file, &pppol2tp_seq_ops,
                sizeof(struct pppol2tp_seq_data));
}

static const struct file_operations pppol2tp_proc_fops = {
    .owner      = THIS_MODULE,
    .open       = pppol2tp_proc_open,
    .read       = seq_read,
    .llseek     = seq_lseek,
    .release    = seq_release_net,
};

#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_net_fops_create(net, "pppol2tp", S_IRUGO, &pppol2tp_proc_fops);
    if (!pde) {
        err = -ENOMEM;
        goto out;
    }

out:
    return err;
}

static __net_exit void pppol2tp_exit_net(struct net *net)
{
    proc_net_remove(net, "pppol2tp");
}

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
};

#ifdef CONFIG_L2TP_V3

static const struct l2tp_nl_cmd_ops pppol2tp_nl_cmd_ops = {
    .session_create = pppol2tp_session_create,
    .session_delete = pppol2tp_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 <[email protected]>");
MODULE_DESCRIPTION("PPP over L2TP over UDP");
MODULE_LICENSE("GPL");
MODULE_VERSION(PPPOL2TP_DRV_VERSION);
MODULE_ALIAS("pppox-proto-" __stringify(PX_PROTO_OL2TP));