pppol2tp.c

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	tunnel = pppol2tp_sock_to_tunnel(sock);
	if (tunnel == NULL)
		goto no_tunnel;

	/* UDP always verifies the packet length. */
	__skb_pull(skb, sizeof(struct udphdr));

	/* Short packet? */
	if (!pskb_may_pull(skb, 12)) {
		PRINTK(tunnel->debug, PPPOL2TP_MSG_DATA, KERN_INFO,
		       "%s: recv short packet (len=%d)\n", tunnel->name, skb->len);
		goto error;
	}

	/* Point to L2TP header */
	optr = ptr = skb->data;

	/* Get L2TP header flags */
	hdrflags = ntohs(*(__be16*)ptr);

	/* Trace packet contents, if enabled */
	if (tunnel->debug & PPPOL2TP_MSG_DATA) {
		length = min(16u, skb->len);
		if (!pskb_may_pull(skb, length))
			goto error;

		printk(KERN_DEBUG "%s: recv: ", tunnel->name);

		offset = 0;
		do {
			printk(" %02X", ptr[offset]);
		} while (++offset < length);

		printk("\n");
	}

	/* Get length of L2TP packet */
	length = skb->len;

	/* If type is control packet, it is handled by userspace. */
	if (hdrflags & L2TP_HDRFLAG_T) {
		PRINTK(tunnel->debug, PPPOL2TP_MSG_DATA, KERN_DEBUG,
		       "%s: recv control packet, len=%d\n", tunnel->name, length);
		goto error;
	}

	/* Skip flags */
	ptr += 2;

	/* If length is present, skip it */
	if (hdrflags & L2TP_HDRFLAG_L)
		ptr += 2;

	/* Extract tunnel and session ID */
	tunnel_id = ntohs(*(__be16 *) ptr);
	ptr += 2;
	session_id = ntohs(*(__be16 *) ptr);
	ptr += 2;

	/* Find the session context */
	session = pppol2tp_session_find(tunnel, session_id);
	if (!session) {
		/* Not found? Pass to userspace to deal with */
		PRINTK(tunnel->debug, PPPOL2TP_MSG_DATA, KERN_INFO,
		       "%s: no socket found (%hu/%hu). Passing up.\n",
		       tunnel->name, tunnel_id, session_id);
		goto error;
	}
	sock_hold(session->sock);

	/* The ref count on the socket was increased by the above call since
	 * we now hold a pointer to the session. Take care to do sock_put()
	 * when exiting this function from now on...
	 */

	/* Handle the optional sequence numbers.  If we are the LAC,
	 * enable/disable sequence numbers under the control of the LNS.  If
	 * no sequence numbers present but we were expecting them, discard
	 * frame.
	 */
	if (hdrflags & L2TP_HDRFLAG_S) {
		u16 ns, nr;
		ns = ntohs(*(__be16 *) ptr);
		ptr += 2;
		nr = ntohs(*(__be16 *) ptr);
		ptr += 2;

		/* Received a packet with sequence numbers. If we're the LNS,
		 * check if we sre sending sequence numbers and if not,
		 * configure it so.
		 */
		if ((!session->lns_mode) && (!session->send_seq)) {
			PRINTK(session->debug, PPPOL2TP_MSG_SEQ, KERN_INFO,
			       "%s: requested to enable seq numbers by LNS\n",
			       session->name);
			session->send_seq = -1;
		}

		/* Store L2TP info in the skb */
		PPPOL2TP_SKB_CB(skb)->ns = ns;
		PPPOL2TP_SKB_CB(skb)->nr = nr;
		PPPOL2TP_SKB_CB(skb)->has_seq = 1;

		PRINTK(session->debug, PPPOL2TP_MSG_SEQ, KERN_DEBUG,
		       "%s: recv data ns=%hu, nr=%hu, session nr=%hu\n",
		       session->name, ns, nr, session->nr);
	} else {
		/* No sequence numbers.
		 * If user has configured mandatory sequence numbers, discard.
		 */
		if (session->recv_seq) {
			PRINTK(session->debug, PPPOL2TP_MSG_SEQ, KERN_WARNING,
			       "%s: recv data has no seq numbers when required. "
			       "Discarding\n", session->name);
			session->stats.rx_seq_discards++;
			goto discard;
		}

		/* If we're the LAC and we're sending sequence numbers, the
		 * LNS has requested that we no longer send sequence numbers.
		 * If we're the LNS and we're sending sequence numbers, the
		 * LAC is broken. Discard the frame.
		 */
		if ((!session->lns_mode) && (session->send_seq)) {
			PRINTK(session->debug, PPPOL2TP_MSG_SEQ, KERN_INFO,
			       "%s: requested to disable seq numbers by LNS\n",
			       session->name);
			session->send_seq = 0;
		} else if (session->send_seq) {
			PRINTK(session->debug, PPPOL2TP_MSG_SEQ, KERN_WARNING,
			       "%s: recv data has no seq numbers when required. "
			       "Discarding\n", session->name);
			session->stats.rx_seq_discards++;
			goto discard;
		}

		/* Store L2TP info in the skb */
		PPPOL2TP_SKB_CB(skb)->has_seq = 0;
	}

	/* If offset bit set, skip it. */
	if (hdrflags & L2TP_HDRFLAG_O) {
		offset = ntohs(*(__be16 *)ptr);
		ptr += 2 + offset;
	}

	offset = ptr - optr;
	if (!pskb_may_pull(skb, offset))
		goto discard;

	__skb_pull(skb, offset);

	/* 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))
		goto discard;

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

	/* Prepare skb for adding to the session's reorder_q.  Hold
	 * packets for max reorder_timeout or 1 second if not
	 * reordering.
	 */
	PPPOL2TP_SKB_CB(skb)->length = length;
	PPPOL2TP_SKB_CB(skb)->expires = jiffies +
		(session->reorder_timeout ? session->reorder_timeout : HZ);

	/* Add packet to the session's receive queue. Reordering is done here, if
	 * enabled. Saved L2TP protocol info is stored in skb->sb[].
	 */
	if (PPPOL2TP_SKB_CB(skb)->has_seq) {
		if (session->reorder_timeout != 0) {
			/* Packet reordering enabled. Add skb to session's
			 * reorder queue, in order of ns.
			 */
			pppol2tp_recv_queue_skb(session, skb);
		} else {
			/* Packet reordering disabled. Discard out-of-sequence
			 * packets
			 */
			if (PPPOL2TP_SKB_CB(skb)->ns != session->nr) {
				session->stats.rx_seq_discards++;
				PRINTK(session->debug, PPPOL2TP_MSG_SEQ, KERN_DEBUG,
				       "%s: oos pkt %hu len %d discarded, "
				       "waiting for %hu, reorder_q_len=%d\n",
				       session->name, PPPOL2TP_SKB_CB(skb)->ns,
				       PPPOL2TP_SKB_CB(skb)->length, session->nr,
				       skb_queue_len(&session->reorder_q));
				goto discard;
			}
			skb_queue_tail(&session->reorder_q, skb);
		}
	} else {
		/* No sequence numbers. Add the skb to the tail of the
		 * reorder queue. This ensures that it will be
		 * delivered after all previous sequenced skbs.
		 */
		skb_queue_tail(&session->reorder_q, skb);
	}

	/* Try to dequeue as many skbs from reorder_q as we can. */
	pppol2tp_recv_dequeue(session);

	return 0;

discard:
	session->stats.rx_errors++;
	kfree_skb(skb);
	sock_put(session->sock);

	return 0;

error:
	/* Put UDP header back */
	__skb_push(skb, sizeof(struct udphdr));

no_tunnel:
	return 1;
}

/* UDP encapsulation receive handler. See net/ipv4/udp.c.
 * Return codes:
 * 0 : success.
 * <0: error
 * >0: skb should be passed up to userspace as UDP.
 */
static int pppol2tp_udp_encap_recv(struct sock *sk, struct sk_buff *skb)
{
	struct pppol2tp_tunnel *tunnel;

	tunnel = pppol2tp_sock_to_tunnel(sk);
	if (tunnel == NULL)
		goto pass_up;

	PRINTK(tunnel->debug, PPPOL2TP_MSG_DATA, KERN_DEBUG,
	       "%s: received %d bytes\n", tunnel->name, skb->len);

	if (pppol2tp_recv_core(sk, skb))
		goto pass_up;

	return 0;

pass_up:
	return 1;
}

/* 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) {
		err = memcpy_toiovec(msg->msg_iov, (unsigned char *) skb->data,
				     skb->len);
		if (err < 0)
			goto do_skb_free;
		err = skb->len;
	}
do_skb_free:
	kfree_skb(skb);
end:
	return err;
}

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

/* Tell how big L2TP headers are for a particular session. This
 * depends on whether sequence numbers are being used.
 */
static inline int pppol2tp_l2tp_header_len(struct pppol2tp_session *session)
{
	if (session->send_seq)
		return PPPOL2TP_L2TP_HDR_SIZE_SEQ;

	return PPPOL2TP_L2TP_HDR_SIZE_NOSEQ;
}

/* Build an L2TP header for the session into the buffer provided.
 */
static void pppol2tp_build_l2tp_header(struct pppol2tp_session *session,
				       void *buf)
{
	__be16 *bufp = buf;
	u16 flags = L2TP_HDR_VER;

	if (session->send_seq)
		flags |= L2TP_HDRFLAG_S;

	/* Setup L2TP header.
	 * FIXME: Can this ever be unaligned? Is direct dereferencing of
	 * 16-bit header fields safe here for all architectures?
	 */
	*bufp++ = htons(flags);
	*bufp++ = htons(session->tunnel_addr.d_tunnel);
	*bufp++ = htons(session->tunnel_addr.d_session);
	if (session->send_seq) {
		*bufp++ = htons(session->ns);
		*bufp++ = 0;
		session->ns++;
		PRINTK(session->debug, PPPOL2TP_MSG_SEQ, KERN_DEBUG,
		       "%s: updated ns to %hu\n", session->name, session->ns);
	}
}

/* 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 inet_sock *inet;
	__wsum csum = 0;
	struct sk_buff *skb;
	int error;
	int hdr_len;
	struct pppol2tp_session *session;
	struct pppol2tp_tunnel *tunnel;
	struct udphdr *uh;
	unsigned int len;

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

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

	tunnel = pppol2tp_sock_to_tunnel(session->tunnel_sock);
	if (tunnel == NULL)
		goto error;

	/* What header length is configured for this session? */
	hdr_len = pppol2tp_l2tp_header_len(session);

	/* Allocate a socket buffer */
	error = -ENOMEM;
	skb = sock_wmalloc(sk, NET_SKB_PAD + sizeof(struct iphdr) +
			   sizeof(struct udphdr) + hdr_len +
			   sizeof(ppph) + total_len,
			   0, GFP_KERNEL);
	if (!skb)
		goto error;

	/* 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);

	/* Build UDP header */
	inet = inet_sk(session->tunnel_sock);
	uh = (struct udphdr *) skb->data;
	uh->source = inet->sport;
	uh->dest = inet->dport;
	uh->len = htons(hdr_len + sizeof(ppph) + total_len);
	uh->check = 0;
	skb_put(skb, sizeof(struct udphdr));

	/* Build L2TP header */
	pppol2tp_build_l2tp_header(session, skb->data);
	skb_put(skb, hdr_len);

	/* 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;
	}
	skb_put(skb, total_len);

	/* Calculate UDP checksum if configured to do so */
	if (session->tunnel_sock->sk_no_check != UDP_CSUM_NOXMIT)
		csum = udp_csum_outgoing(sk, skb);

	/* Debug */
	if (session->send_seq)
		PRINTK(session->debug, PPPOL2TP_MSG_DATA, KERN_DEBUG,
		       "%s: send %Zd bytes, ns=%hu\n", session->name,
		       total_len, session->ns - 1);
	else
		PRINTK(session->debug, PPPOL2TP_MSG_DATA, KERN_DEBUG,
		       "%s: send %Zd bytes\n", session->name, total_len);

	if (session->debug & PPPOL2TP_MSG_DATA) {
		int i;
		unsigned char *datap = skb->data;

		printk(KERN_DEBUG "%s: xmit:", session->name);
		for (i = 0; i < total_len; i++) {
			printk(" %02X", *datap++);
			if (i == 15) {
				printk(" ...");
				break;
			}
		}
		printk("\n");
	}

	/* Queue the packet to IP for output */
	len = skb->len;
	error = ip_queue_xmit(skb, 1);

	/* Update stats */
	if (error >= 0) {
		tunnel->stats.tx_packets++;
		tunnel->stats.tx_bytes += len;
		session->stats.tx_packets++;
		session->stats.tx_bytes += len;
	} else {
		tunnel->stats.tx_errors++;
		session->stats.tx_errors++;
	}

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;
	int hdr_len;
	struct pppol2tp_session *session;
	struct pppol2tp_tunnel *tunnel;
	int rc;
	int headroom;
	int data_len = skb->len;
	struct inet_sock *inet;
	__wsum csum = 0;
	struct udphdr *uh;
	unsigned int len;

	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;

	sk_tun = session->tunnel_sock;
	if (sk_tun == NULL)
		goto abort;
	tunnel = pppol2tp_sock_to_tunnel(sk_tun);
	if (tunnel == NULL)