cregit-Linux how code gets into the kernel

Release 4.11 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;
}


Contributors
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James Chapman76100.00%3100.00%


Total76100.00%3100.00%



/*****************************************************************************
 * 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] == PPP_ALLSTATIONS) && (skb->data[1] == PPP_UI))
		skb_pull(skb, 2);

	return 0;
}


Contributors
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James Chapman5796.61%266.67%


Gao Feng23.39%133.33%


Total59100.00%3100.00%



/* 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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James Chapman14998.68%250.00%


David S. Miller10.66%125.00%


Cyrill V. Gorcunov10.66%125.00%


Total151100.00%4100.00%






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, 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);
		}
	}

	return;

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


Contributors
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James Chapman14084.34%342.86%


Guillaume Nault1710.24%114.29%


Tom Parkin42.41%114.29%


Asbjörn Sloth Tönnesen31.81%114.29%


Joe Perches21.20%114.29%


Total166100.00%7100.00%






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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Total34100.00%2100.00%






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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James Chapman34100.00%2100.00%


Total34100.00%2100.00%



/************************************************************************
 * 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;
	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 +
			   2 + total_len, /* 2 bytes for PPP_ALLSTATIONS & PPP_UI */
			   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] = 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_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;
}


Contributors
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James Chapman30189.32%327.27%


Guillaume Nault113.26%327.27%


Jarek Poplawski113.26%19.09%


Eric Dumazet61.78%19.09%


Gao Feng41.19%19.09%


Cyrill V. Gorcunov30.89%19.09%


Al Viro10.30%19.09%


Total337100.00%11100.00%



/* 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 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 */
		   2;			/* 2 bytes for PPP_ALLSTATIONS & PPP_UI */
	if (skb_cow_head(skb, headroom))
		goto abort_put_sess_tun;

	/* 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_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;
}


Contributors
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James Chapman21079.55%457.14%


Eric Dumazet4918.56%228.57%


Gao Feng51.89%114.29%


Total264100.00%7100.00%



/*****************************************************************************
 * 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, SEND_SHUTDOWN);
		/* Don't let the session go away before our socket does */
		l2tp_session_inc_refcount(session);
	}
}


Contributors
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James Chapman5480.60%360.00%


Tom Parkin1217.91%120.00%


Gao Feng11.49%120.00%


Total67100.00%5100.00%



/* 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);
	}
}


Contributors
PersonTokensPropCommitsCommitProp
James Chapman4064.52%233.33%


Guillaume Nault1625.81%116.67%


Tom Parkin34.84%116.67%


Cyrill V. Gorcunov23.23%116.67%


Herbert Xu11.61%116.67%


Total62100.00%6100.00%



/* 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);
	}
	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;
}


Contributors
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James Chapman12590.58%240.00%


Cyrill V. Gorcunov75.07%120.00%


Tom Parkin64.35%240.00%


Total138100.00%5100.00%




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;
}


Contributors
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James Chapman40100.00%1100.00%


Total40100.00%1100.00%



/* 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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James Chapman10789.92%250.00%


Eric W. Biedermann1210.08%250.00%


Total119100.00%4100.00%



#if IS_ENABLED(CONFIG_L2TP_DEBUGFS)



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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James Chapman69100.00%1100.00%


Total69100.00%1100.00%



#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;
	bool drop_refcnt = false;
	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;

	session = l2tp_session_get(sock_net(sk), tunnel, session_id, false);
	if (session) {
		drop_refcnt = true;
		ps = l2tp_session_priv(session);

		/* Using a pre-existing session is fine as long as it hasn't
                 * been connected yet.
                 */
		if (ps->sock) {
			error = -EEXIST;
			goto end;
		}

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

		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;
		}
	}

	/* 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 IS_ENABLED(CONFIG_L2TP_DEBUGFS)
	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, L2TP_MSG_CONTROL, "%s: created\n",
		  session->name);

end:
	if (drop_refcnt)
		l2tp_session_dec_refcount(session);
	release_sock(sk);

	return error;
}


Contributors
PersonTokensPropCommitsCommitProp
James Chapman87989.97%746.67%


Guillaume Nault838.50%213.33%


Cyrill V. Gorcunov50.51%16.67%


David S. Miller40.41%16.67%


Dmitry Petukhov30.31%16.67%


Asbjörn Sloth Tönnesen10.10%16.67%


Joe Perches10.10%16.67%


Javier Martinez Canillas10.10%16.67%


Total977100.00%15100.00%



#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(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;

	/* 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 out;
	}

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

	l2tp