cregit-Linux how code gets into the kernel

Release 4.8 net/l2tp/l2tp_ppp.c

Directory: net/l2tp
/*****************************************************************************
 * 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 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; }

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/***************************************************************************** * 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; }

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/* 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; }

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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); po = pppox_sk(sk); ppp_input(&po->chan, skb); } else { l2tp_dbg(session, PPPOL2TP_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); } } return; no_sock: l2tp_info(session, PPPOL2TP_MSG_DATA, "%s: no socket\n", session->name); kfree_skb(skb); }

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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); }

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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); }

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/************************************************************************ * 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) { 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_from_msg(skb_put(skb, total_len), m, total_len); if (error < 0) { kfree_skb(skb); goto error_put_sess_tun; } local_bh_disable(); l2tp_xmit_skb(session, skb, session->hdr_len); local_bh_enable(); sock_put(ps->tunnel_sock); sock_put(sk); return total_len; error_put_sess_tun: sock_put(ps->tunnel_sock); error_put_sess: sock_put(sk); error: return error; }

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/* 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 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; 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; /* Setup PPP header */ __skb_push(skb, sizeof(ppph)); skb->data[0] = ppph[0]; skb->data[1] = ppph[1]; local_bh_disable(); l2tp_xmit_skb(session, skb, session->hdr_len); local_bh_enable(); 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; }

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/***************************************************************************** * 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 socket *sock = sk->sk_socket; BUG_ON(session->magic != L2TP_SESSION_MAGIC); if (sock) { inet_shutdown(sock, 2); /* Don't let the session go away before our socket does */ l2tp_session_inc_refcount(session); } }

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

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/* 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 */ if (session != NULL) { __l2tp_session_unhash(session); l2tp_session_queue_purge(session); sock_put(sk); } skb_queue_purge(&sk->sk_receive_queue); skb_queue_purge(&sk->sk_write_queue); 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; }

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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; }

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/* 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; }

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#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)); } }

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#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(tunnel->sock); if (dst != NULL) { u32 pmtu = dst_mtu(dst); 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; }

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james chapmanjames chapman93197.90%758.33%
david s. millerdavid s. miller101.05%18.33%
cyrill gorcunovcyrill gorcunov50.53%18.33%
dmitry petukhovdmitry petukhov30.32%18.33%
guillaume naultguillaume nault10.11%18.33%
joe perchesjoe perches10.11%18.33%
Total951100.00%12100.00%

#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