/*
   * net/tipc/link.c: TIPC link code

   *

   * Copyright (c) 1996-2007, 2012-2016, Ericsson AB

   * Copyright (c) 2004-2007, 2010-2013, Wind River Systems

   * All rights reserved.
   *

   * Redistribution and use in source and binary forms, with or without

   * modification, are permitted provided that the following conditions are met:
   *

   * 1. Redistributions of source code must retain the above copyright
   *    notice, this list of conditions and the following disclaimer.
   * 2. Redistributions in binary form must reproduce the above copyright
   *    notice, this list of conditions and the following disclaimer in the
   *    documentation and/or other materials provided with the distribution.
   * 3. Neither the names of the copyright holders nor the names of its
   *    contributors may be used to endorse or promote products derived from
   *    this software without specific prior written permission.

   *

   * Alternatively, this software may be distributed under the terms of the
   * GNU General Public License ("GPL") version 2 as published by the Free
   * Software Foundation.
   *
   * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
   * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
   * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
   * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
   * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
   * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
   * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
   * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE

   * POSSIBILITY OF SUCH DAMAGE.
   */
  
  #include "core.h"

  #include "subscr.h"

  #include "link.h"

  #include "bcast.h"

  #include "socket.h"

  #include "name_distr.h"

  #include "discover.h"

  #include "netlink.h"

  #include "monitor.h"

  #include <linux/pkt_sched.h>

  struct tipc_stats {

  	u32 sent_pkts;
  	u32 recv_pkts;

  	u32 sent_states;
  	u32 recv_states;
  	u32 sent_probes;
  	u32 recv_probes;
  	u32 sent_nacks;
  	u32 recv_nacks;
  	u32 sent_acks;
  	u32 sent_bundled;
  	u32 sent_bundles;
  	u32 recv_bundled;
  	u32 recv_bundles;
  	u32 retransmitted;
  	u32 sent_fragmented;
  	u32 sent_fragments;
  	u32 recv_fragmented;
  	u32 recv_fragments;
  	u32 link_congs;		/* # port sends blocked by congestion */
  	u32 deferred_recv;
  	u32 duplicates;
  	u32 max_queue_sz;	/* send queue size high water mark */
  	u32 accu_queue_sz;	/* used for send queue size profiling */
  	u32 queue_sz_counts;	/* used for send queue size profiling */
  	u32 msg_length_counts;	/* used for message length profiling */
  	u32 msg_lengths_total;	/* used for message length profiling */
  	u32 msg_length_profile[7]; /* used for msg. length profiling */
  };
  
  /**
   * struct tipc_link - TIPC link data structure
   * @addr: network address of link's peer node
   * @name: link name character string
   * @media_addr: media address to use when sending messages over link
   * @timer: link timer
   * @net: pointer to namespace struct
   * @refcnt: reference counter for permanent references (owner node & timer)
   * @peer_session: link session # being used by peer end of link
   * @peer_bearer_id: bearer id used by link's peer endpoint
   * @bearer_id: local bearer id used by link
   * @tolerance: minimum link continuity loss needed to reset link [in ms]

   * @abort_limit: # of unacknowledged continuity probes needed to reset link
   * @state: current state of link FSM
   * @peer_caps: bitmap describing capabilities of peer node
   * @silent_intv_cnt: # of timer intervals without any reception from peer
   * @proto_msg: template for control messages generated by link
   * @pmsg: convenience pointer to "proto_msg" field
   * @priority: current link priority
   * @net_plane: current link network plane ('A' through 'H')

   * @mon_state: cookie with information needed by link monitor

   * @backlog_limit: backlog queue congestion thresholds (indexed by importance)
   * @exp_msg_count: # of tunnelled messages expected during link changeover
   * @reset_rcv_checkpt: seq # of last acknowledged message at time of link reset
   * @mtu: current maximum packet size for this link
   * @advertised_mtu: advertised own mtu when link is being established
   * @transmitq: queue for sent, non-acked messages
   * @backlogq: queue for messages waiting to be sent
   * @snt_nxt: next sequence number to use for outbound messages
   * @last_retransmitted: sequence number of most recently retransmitted message
   * @stale_count: # of identical retransmit requests made by peer
   * @ackers: # of peers that needs to ack each packet before it can be released
   * @acked: # last packet acked by a certain peer. Used for broadcast.
   * @rcv_nxt: next sequence number to expect for inbound messages
   * @deferred_queue: deferred queue saved OOS b'cast message received from node
   * @unacked_window: # of inbound messages rx'd without ack'ing back to peer
   * @inputq: buffer queue for messages to be delivered upwards
   * @namedq: buffer queue for name table messages to be delivered upwards
   * @next_out: ptr to first unsent outbound message in queue
   * @wakeupq: linked list of wakeup msgs waiting for link congestion to abate
   * @long_msg_seq_no: next identifier to use for outbound fragmented messages
   * @reasm_buf: head of partially reassembled inbound message fragments
   * @bc_rcvr: marks that this is a broadcast receiver link
   * @stats: collects statistics regarding link activity
   */
  struct tipc_link {
  	u32 addr;
  	char name[TIPC_MAX_LINK_NAME];

  	struct net *net;
  
  	/* Management and link supervision data */
  	u32 peer_session;

  	u32 session;

  	u32 peer_bearer_id;
  	u32 bearer_id;
  	u32 tolerance;

  	u32 abort_limit;
  	u32 state;
  	u16 peer_caps;
  	bool active;
  	u32 silent_intv_cnt;

  	char if_name[TIPC_MAX_IF_NAME];

  	u32 priority;
  	char net_plane;

  	struct tipc_mon_state mon_state;

  	u16 rst_cnt;

  
  	/* Failover/synch */
  	u16 drop_point;
  	struct sk_buff *failover_reasm_skb;
  
  	/* Max packet negotiation */
  	u16 mtu;
  	u16 advertised_mtu;
  
  	/* Sending */
  	struct sk_buff_head transmq;
  	struct sk_buff_head backlogq;
  	struct {
  		u16 len;
  		u16 limit;
  	} backlog[5];
  	u16 snd_nxt;
  	u16 last_retransm;
  	u16 window;
  	u32 stale_count;
  
  	/* Reception */
  	u16 rcv_nxt;
  	u32 rcv_unacked;
  	struct sk_buff_head deferdq;
  	struct sk_buff_head *inputq;
  	struct sk_buff_head *namedq;
  
  	/* Congestion handling */
  	struct sk_buff_head wakeupq;
  
  	/* Fragmentation/reassembly */
  	struct sk_buff *reasm_buf;
  
  	/* Broadcast */
  	u16 ackers;
  	u16 acked;
  	struct tipc_link *bc_rcvlink;
  	struct tipc_link *bc_sndlink;

  	unsigned long prev_retr;
  	u16 prev_from;
  	u16 prev_to;
  	u8 nack_state;

  	bool bc_peer_is_up;
  
  	/* Statistics */
  	struct tipc_stats stats;
  };

  /*
   * Error message prefixes
   */

  static const char *link_co_err = "Link tunneling error, ";

  static const char *link_rst_msg = "Resetting link ";

  /* Send states for broadcast NACKs
   */
  enum {
  	BC_NACK_SND_CONDITIONAL,
  	BC_NACK_SND_UNCONDITIONAL,
  	BC_NACK_SND_SUPPRESS,
  };

  #define TIPC_BC_RETR_LIMIT 10   /* [ms] */

  /*

   * Interval between NACKs when packets arrive out of order
   */
  #define TIPC_NACK_INTV (TIPC_MIN_LINK_WIN * 2)

  
  /* Wildcard value for link session numbers. When it is known that
   * peer endpoint is down, any session number must be accepted.

   */

  #define ANY_SESSION 0x10000

  /* Link FSM states:

   */

  enum {

  	LINK_ESTABLISHED     = 0xe,
  	LINK_ESTABLISHING    = 0xe  << 4,
  	LINK_RESET           = 0x1  << 8,
  	LINK_RESETTING       = 0x2  << 12,
  	LINK_PEER_RESET      = 0xd  << 16,
  	LINK_FAILINGOVER     = 0xf  << 20,
  	LINK_SYNCHING        = 0xc  << 24

  };
  
  /* Link FSM state checking routines
   */

  static int link_is_up(struct tipc_link *l)

  {

  	return l->state & (LINK_ESTABLISHED | LINK_SYNCHING);

  }

  static int tipc_link_proto_rcv(struct tipc_link *l, struct sk_buff *skb,
  			       struct sk_buff_head *xmitq);

  static void tipc_link_build_proto_msg(struct tipc_link *l, int mtyp, bool probe,
  				      u16 rcvgap, int tolerance, int priority,
  				      struct sk_buff_head *xmitq);

  static void link_print(struct tipc_link *l, const char *str);

  static int tipc_link_build_nack_msg(struct tipc_link *l,
  				    struct sk_buff_head *xmitq);

  static void tipc_link_build_bc_init_msg(struct tipc_link *l,
  					struct sk_buff_head *xmitq);
  static bool tipc_link_release_pkts(struct tipc_link *l, u16 to);

  /*

   *  Simple non-static link routines (i.e. referenced outside this file)

   */

  bool tipc_link_is_up(struct tipc_link *l)

  {

  	return link_is_up(l);
  }

  bool tipc_link_peer_is_down(struct tipc_link *l)
  {
  	return l->state == LINK_PEER_RESET;
  }

  bool tipc_link_is_reset(struct tipc_link *l)
  {
  	return l->state & (LINK_RESET | LINK_FAILINGOVER | LINK_ESTABLISHING);
  }

  bool tipc_link_is_establishing(struct tipc_link *l)
  {
  	return l->state == LINK_ESTABLISHING;
  }

  bool tipc_link_is_synching(struct tipc_link *l)
  {
  	return l->state == LINK_SYNCHING;
  }
  
  bool tipc_link_is_failingover(struct tipc_link *l)
  {
  	return l->state == LINK_FAILINGOVER;
  }
  
  bool tipc_link_is_blocked(struct tipc_link *l)
  {
  	return l->state & (LINK_RESETTING | LINK_PEER_RESET | LINK_FAILINGOVER);

  }

  static bool link_is_bc_sndlink(struct tipc_link *l)

  {
  	return !l->bc_sndlink;
  }

  static bool link_is_bc_rcvlink(struct tipc_link *l)

  {
  	return ((l->bc_rcvlink == l) && !link_is_bc_sndlink(l));
  }

  int tipc_link_is_active(struct tipc_link *l)

  {

  	return l->active;
  }

  void tipc_link_set_active(struct tipc_link *l, bool active)
  {
  	l->active = active;

  }

  u32 tipc_link_id(struct tipc_link *l)
  {
  	return l->peer_bearer_id << 16 | l->bearer_id;
  }
  
  int tipc_link_window(struct tipc_link *l)
  {
  	return l->window;
  }
  
  int tipc_link_prio(struct tipc_link *l)
  {
  	return l->priority;
  }
  
  unsigned long tipc_link_tolerance(struct tipc_link *l)
  {
  	return l->tolerance;
  }
  
  struct sk_buff_head *tipc_link_inputq(struct tipc_link *l)
  {
  	return l->inputq;
  }
  
  char tipc_link_plane(struct tipc_link *l)
  {
  	return l->net_plane;
  }

  void tipc_link_add_bc_peer(struct tipc_link *snd_l,
  			   struct tipc_link *uc_l,
  			   struct sk_buff_head *xmitq)

  {

  	struct tipc_link *rcv_l = uc_l->bc_rcvlink;
  
  	snd_l->ackers++;
  	rcv_l->acked = snd_l->snd_nxt - 1;

  	snd_l->state = LINK_ESTABLISHED;

  	tipc_link_build_bc_init_msg(uc_l, xmitq);

  }

  void tipc_link_remove_bc_peer(struct tipc_link *snd_l,
  			      struct tipc_link *rcv_l,
  			      struct sk_buff_head *xmitq)

  {

  	u16 ack = snd_l->snd_nxt - 1;
  
  	snd_l->ackers--;

  	rcv_l->bc_peer_is_up = true;
  	rcv_l->state = LINK_ESTABLISHED;

  	tipc_link_bc_ack_rcv(rcv_l, ack, xmitq);
  	tipc_link_reset(rcv_l);
  	rcv_l->state = LINK_RESET;
  	if (!snd_l->ackers) {
  		tipc_link_reset(snd_l);

  		snd_l->state = LINK_RESET;

  		__skb_queue_purge(xmitq);
  	}

  }
  
  int tipc_link_bc_peers(struct tipc_link *l)
  {
  	return l->ackers;
  }

  u16 link_bc_rcv_gap(struct tipc_link *l)
  {
  	struct sk_buff *skb = skb_peek(&l->deferdq);
  	u16 gap = 0;
  
  	if (more(l->snd_nxt, l->rcv_nxt))
  		gap = l->snd_nxt - l->rcv_nxt;
  	if (skb)
  		gap = buf_seqno(skb) - l->rcv_nxt;
  	return gap;
  }

  void tipc_link_set_mtu(struct tipc_link *l, int mtu)
  {
  	l->mtu = mtu;
  }
  
  int tipc_link_mtu(struct tipc_link *l)
  {
  	return l->mtu;
  }

  u16 tipc_link_rcv_nxt(struct tipc_link *l)
  {
  	return l->rcv_nxt;
  }
  
  u16 tipc_link_acked(struct tipc_link *l)
  {
  	return l->acked;
  }
  
  char *tipc_link_name(struct tipc_link *l)
  {
  	return l->name;
  }

  /**

   * tipc_link_create - create a new link

   * @n: pointer to associated node

   * @if_name: associated interface name
   * @bearer_id: id (index) of associated bearer
   * @tolerance: link tolerance to be used by link
   * @net_plane: network plane (A,B,c..) this link belongs to
   * @mtu: mtu to be advertised by link
   * @priority: priority to be used by link
   * @window: send window to be used by link
   * @session: session to be used by link

   * @ownnode: identity of own node

   * @peer: node id of peer node

   * @peer_caps: bitmap describing peer node capabilities

   * @bc_sndlink: the namespace global link used for broadcast sending
   * @bc_rcvlink: the peer specific link used for broadcast reception

   * @inputq: queue to put messages ready for delivery
   * @namedq: queue to put binding table update messages ready for delivery
   * @link: return value, pointer to put the created link

   *

   * Returns true if link was created, otherwise false

   */

  bool tipc_link_create(struct net *net, char *if_name, int bearer_id,

  		      int tolerance, char net_plane, u32 mtu, int priority,
  		      int window, u32 session, u32 ownnode, u32 peer,

  		      u16 peer_caps,

  		      struct tipc_link *bc_sndlink,
  		      struct tipc_link *bc_rcvlink,
  		      struct sk_buff_head *inputq,
  		      struct sk_buff_head *namedq,

  		      struct tipc_link **link)

  {

  	struct tipc_link *l;

  	l = kzalloc(sizeof(*l), GFP_ATOMIC);
  	if (!l)
  		return false;
  	*link = l;

  	l->session = session;

  	/* Note: peer i/f name is completed by reset/activate message */

  	sprintf(l->name, "%u.%u.%u:%s-%u.%u.%u:unknown",
  		tipc_zone(ownnode), tipc_cluster(ownnode), tipc_node(ownnode),
  		if_name, tipc_zone(peer), tipc_cluster(peer), tipc_node(peer));

  	strcpy(l->if_name, if_name);

  	l->addr = peer;

  	l->peer_caps = peer_caps;

  	l->net = net;

  	l->peer_session = ANY_SESSION;

  	l->bearer_id = bearer_id;
  	l->tolerance = tolerance;
  	l->net_plane = net_plane;
  	l->advertised_mtu = mtu;
  	l->mtu = mtu;
  	l->priority = priority;
  	tipc_link_set_queue_limits(l, window);

  	l->ackers = 1;

  	l->bc_sndlink = bc_sndlink;
  	l->bc_rcvlink = bc_rcvlink;

  	l->inputq = inputq;
  	l->namedq = namedq;
  	l->state = LINK_RESETTING;

  	__skb_queue_head_init(&l->transmq);
  	__skb_queue_head_init(&l->backlogq);
  	__skb_queue_head_init(&l->deferdq);
  	skb_queue_head_init(&l->wakeupq);
  	skb_queue_head_init(l->inputq);
  	return true;

  }

  /**
   * tipc_link_bc_create - create new link to be used for broadcast
   * @n: pointer to associated node
   * @mtu: mtu to be used
   * @window: send window to be used
   * @inputq: queue to put messages ready for delivery
   * @namedq: queue to put binding table update messages ready for delivery
   * @link: return value, pointer to put the created link
   *
   * Returns true if link was created, otherwise false
   */

  bool tipc_link_bc_create(struct net *net, u32 ownnode, u32 peer,

  			 int mtu, int window, u16 peer_caps,

  			 struct sk_buff_head *inputq,
  			 struct sk_buff_head *namedq,

  			 struct tipc_link *bc_sndlink,

  			 struct tipc_link **link)
  {
  	struct tipc_link *l;

  	if (!tipc_link_create(net, "", MAX_BEARERS, 0, 'Z', mtu, 0, window,

  			      0, ownnode, peer, peer_caps, bc_sndlink,

  			      NULL, inputq, namedq, link))

  		return false;
  
  	l = *link;
  	strcpy(l->name, tipc_bclink_name);
  	tipc_link_reset(l);

  	l->state = LINK_RESET;

  	l->ackers = 0;

  	l->bc_rcvlink = l;

  	/* Broadcast send link is always up */
  	if (link_is_bc_sndlink(l))
  		l->state = LINK_ESTABLISHED;

  	/* Disable replicast if even a single peer doesn't support it */
  	if (link_is_bc_rcvlink(l) && !(peer_caps & TIPC_BCAST_RCAST))
  		tipc_bcast_disable_rcast(net);

  	return true;

  }

  /**

   * tipc_link_fsm_evt - link finite state machine
   * @l: pointer to link
   * @evt: state machine event to be processed

   */

  int tipc_link_fsm_evt(struct tipc_link *l, int evt)

  {

  	int rc = 0;

  
  	switch (l->state) {

  	case LINK_RESETTING:

  		switch (evt) {

  		case LINK_PEER_RESET_EVT:
  			l->state = LINK_PEER_RESET;

  			break;

  		case LINK_RESET_EVT:
  			l->state = LINK_RESET;
  			break;
  		case LINK_FAILURE_EVT:
  		case LINK_FAILOVER_BEGIN_EVT:
  		case LINK_ESTABLISH_EVT:
  		case LINK_FAILOVER_END_EVT:
  		case LINK_SYNCH_BEGIN_EVT:
  		case LINK_SYNCH_END_EVT:
  		default:
  			goto illegal_evt;
  		}
  		break;
  	case LINK_RESET:
  		switch (evt) {
  		case LINK_PEER_RESET_EVT:
  			l->state = LINK_ESTABLISHING;

  			break;

  		case LINK_FAILOVER_BEGIN_EVT:
  			l->state = LINK_FAILINGOVER;
  		case LINK_FAILURE_EVT:
  		case LINK_RESET_EVT:
  		case LINK_ESTABLISH_EVT:
  		case LINK_FAILOVER_END_EVT:

  			break;

  		case LINK_SYNCH_BEGIN_EVT:
  		case LINK_SYNCH_END_EVT:

  		default:

  			goto illegal_evt;

  		}
  		break;

  	case LINK_PEER_RESET:

  		switch (evt) {

  		case LINK_RESET_EVT:
  			l->state = LINK_ESTABLISHING;

  			break;

  		case LINK_PEER_RESET_EVT:
  		case LINK_ESTABLISH_EVT:
  		case LINK_FAILURE_EVT:

  			break;

  		case LINK_SYNCH_BEGIN_EVT:
  		case LINK_SYNCH_END_EVT:
  		case LINK_FAILOVER_BEGIN_EVT:
  		case LINK_FAILOVER_END_EVT:
  		default:
  			goto illegal_evt;
  		}
  		break;
  	case LINK_FAILINGOVER:
  		switch (evt) {
  		case LINK_FAILOVER_END_EVT:
  			l->state = LINK_RESET;

  			break;

  		case LINK_PEER_RESET_EVT:
  		case LINK_RESET_EVT:
  		case LINK_ESTABLISH_EVT:
  		case LINK_FAILURE_EVT:
  			break;
  		case LINK_FAILOVER_BEGIN_EVT:
  		case LINK_SYNCH_BEGIN_EVT:
  		case LINK_SYNCH_END_EVT:

  		default:

  			goto illegal_evt;

  		}
  		break;

  	case LINK_ESTABLISHING:

  		switch (evt) {

  		case LINK_ESTABLISH_EVT:
  			l->state = LINK_ESTABLISHED;

  			break;

  		case LINK_FAILOVER_BEGIN_EVT:
  			l->state = LINK_FAILINGOVER;
  			break;

  		case LINK_RESET_EVT:

  			l->state = LINK_RESET;
  			break;

  		case LINK_FAILURE_EVT:

  		case LINK_PEER_RESET_EVT:

  		case LINK_SYNCH_BEGIN_EVT:
  		case LINK_FAILOVER_END_EVT:
  			break;
  		case LINK_SYNCH_END_EVT:
  		default:
  			goto illegal_evt;
  		}
  		break;
  	case LINK_ESTABLISHED:
  		switch (evt) {
  		case LINK_PEER_RESET_EVT:
  			l->state = LINK_PEER_RESET;
  			rc |= TIPC_LINK_DOWN_EVT;
  			break;
  		case LINK_FAILURE_EVT:
  			l->state = LINK_RESETTING;
  			rc |= TIPC_LINK_DOWN_EVT;

  			break;

  		case LINK_RESET_EVT:
  			l->state = LINK_RESET;

  			break;

  		case LINK_ESTABLISH_EVT:

  		case LINK_SYNCH_END_EVT:

  			break;

  		case LINK_SYNCH_BEGIN_EVT:
  			l->state = LINK_SYNCHING;
  			break;

  		case LINK_FAILOVER_BEGIN_EVT:
  		case LINK_FAILOVER_END_EVT:

  		default:

  			goto illegal_evt;

  		}
  		break;

  	case LINK_SYNCHING:

  		switch (evt) {

  		case LINK_PEER_RESET_EVT:
  			l->state = LINK_PEER_RESET;
  			rc |= TIPC_LINK_DOWN_EVT;
  			break;
  		case LINK_FAILURE_EVT:
  			l->state = LINK_RESETTING;
  			rc |= TIPC_LINK_DOWN_EVT;

  			break;

  		case LINK_RESET_EVT:
  			l->state = LINK_RESET;

  			break;

  		case LINK_ESTABLISH_EVT:
  		case LINK_SYNCH_BEGIN_EVT:

  			break;

  		case LINK_SYNCH_END_EVT:
  			l->state = LINK_ESTABLISHED;
  			break;
  		case LINK_FAILOVER_BEGIN_EVT:
  		case LINK_FAILOVER_END_EVT:

  		default:

  			goto illegal_evt;

  		}
  		break;
  	default:

  		pr_err("Unknown FSM state %x in %s
  ", l->state, l->name);

  	}

  	return rc;
  illegal_evt:
  	pr_err("Illegal FSM event %x in state %x on link %s
  ",
  	       evt, l->state, l->name);

  	return rc;
  }

  /* link_profile_stats - update statistical profiling of traffic
   */
  static void link_profile_stats(struct tipc_link *l)
  {
  	struct sk_buff *skb;
  	struct tipc_msg *msg;
  	int length;
  
  	/* Update counters used in statistical profiling of send traffic */
  	l->stats.accu_queue_sz += skb_queue_len(&l->transmq);
  	l->stats.queue_sz_counts++;
  
  	skb = skb_peek(&l->transmq);
  	if (!skb)
  		return;
  	msg = buf_msg(skb);
  	length = msg_size(msg);
  
  	if (msg_user(msg) == MSG_FRAGMENTER) {
  		if (msg_type(msg) != FIRST_FRAGMENT)
  			return;
  		length = msg_size(msg_get_wrapped(msg));
  	}
  	l->stats.msg_lengths_total += length;
  	l->stats.msg_length_counts++;
  	if (length <= 64)
  		l->stats.msg_length_profile[0]++;
  	else if (length <= 256)
  		l->stats.msg_length_profile[1]++;
  	else if (length <= 1024)
  		l->stats.msg_length_profile[2]++;
  	else if (length <= 4096)
  		l->stats.msg_length_profile[3]++;
  	else if (length <= 16384)
  		l->stats.msg_length_profile[4]++;
  	else if (length <= 32768)
  		l->stats.msg_length_profile[5]++;
  	else
  		l->stats.msg_length_profile[6]++;
  }
  
  /* tipc_link_timeout - perform periodic task as instructed from node timeout
   */
  int tipc_link_timeout(struct tipc_link *l, struct sk_buff_head *xmitq)
  {

  	int mtyp = 0;
  	int rc = 0;

  	bool state = false;
  	bool probe = false;
  	bool setup = false;

  	u16 bc_snt = l->bc_sndlink->snd_nxt - 1;
  	u16 bc_acked = l->bc_rcvlink->acked;

  	struct tipc_mon_state *mstate = &l->mon_state;

  	switch (l->state) {
  	case LINK_ESTABLISHED:
  	case LINK_SYNCHING:

  		mtyp = STATE_MSG;

  		link_profile_stats(l);
  		tipc_mon_get_state(l->net, l->addr, mstate, l->bearer_id);
  		if (mstate->reset || (l->silent_intv_cnt > l->abort_limit))
  			return tipc_link_fsm_evt(l, LINK_FAILURE_EVT);

  		state = bc_acked != bc_snt;

  		state |= l->bc_rcvlink->rcv_unacked;
  		state |= l->rcv_unacked;
  		state |= !skb_queue_empty(&l->transmq);
  		state |= !skb_queue_empty(&l->deferdq);
  		probe = mstate->probing;
  		probe |= l->silent_intv_cnt;
  		if (probe || mstate->monitoring)
  			l->silent_intv_cnt++;

  		break;
  	case LINK_RESET:

  		setup = l->rst_cnt++ <= 4;
  		setup |= !(l->rst_cnt % 16);

  		mtyp = RESET_MSG;

  		break;
  	case LINK_ESTABLISHING:

  		setup = true;

  		mtyp = ACTIVATE_MSG;

  		break;

  	case LINK_PEER_RESET:

  	case LINK_RESETTING:

  	case LINK_FAILINGOVER:
  		break;
  	default:
  		break;

  	}

  	if (state || probe || setup)
  		tipc_link_build_proto_msg(l, mtyp, probe, 0, 0, 0, xmitq);

  	return rc;
  }

  /**

   * link_schedule_user - schedule a message sender for wakeup after congestion

   * @l: congested link
   * @hdr: header of message that is being sent

   * Create pseudo msg to send back to user when congestion abates

   */

  static int link_schedule_user(struct tipc_link *l, struct tipc_msg *hdr)

  {

  	u32 dnode = tipc_own_addr(l->net);
  	u32 dport = msg_origport(hdr);

  	struct sk_buff *skb;

  	/* Create and schedule wakeup pseudo message */
  	skb = tipc_msg_create(SOCK_WAKEUP, 0, INT_H_SIZE, 0,

  			      dnode, l->addr, dport, 0, 0);

  	if (!skb)

  		return -ENOBUFS;

  	msg_set_dest_droppable(buf_msg(skb), true);
  	TIPC_SKB_CB(skb)->chain_imp = msg_importance(hdr);
  	skb_queue_tail(&l->wakeupq, skb);
  	l->stats.link_congs++;

  	return -ELINKCONG;

  }

  /**
   * link_prepare_wakeup - prepare users for wakeup after congestion

   * @l: congested link
   * Wake up a number of waiting users, as permitted by available space
   * in the send queue

   */

  void link_prepare_wakeup(struct tipc_link *l)

  {

  	struct sk_buff *skb, *tmp;

  	int imp, i = 0;

  	skb_queue_walk_safe(&l->wakeupq, skb, tmp) {
  		imp = TIPC_SKB_CB(skb)->chain_imp;

  		if (l->backlog[imp].len < l->backlog[imp].limit) {
  			skb_unlink(skb, &l->wakeupq);
  			skb_queue_tail(l->inputq, skb);
  		} else if (i++ > 10) {

  			break;

  		}

  	}

  }

  void tipc_link_reset(struct tipc_link *l)

  {

  	l->peer_session = ANY_SESSION;
  	l->session++;

  	l->mtu = l->advertised_mtu;

  	__skb_queue_purge(&l->transmq);
  	__skb_queue_purge(&l->deferdq);

  	skb_queue_splice_init(&l->wakeupq, l->inputq);

  	__skb_queue_purge(&l->backlogq);
  	l->backlog[TIPC_LOW_IMPORTANCE].len = 0;
  	l->backlog[TIPC_MEDIUM_IMPORTANCE].len = 0;
  	l->backlog[TIPC_HIGH_IMPORTANCE].len = 0;
  	l->backlog[TIPC_CRITICAL_IMPORTANCE].len = 0;
  	l->backlog[TIPC_SYSTEM_IMPORTANCE].len = 0;

  	kfree_skb(l->reasm_buf);
  	kfree_skb(l->failover_reasm_skb);
  	l->reasm_buf = NULL;
  	l->failover_reasm_skb = NULL;
  	l->rcv_unacked = 0;
  	l->snd_nxt = 1;
  	l->rcv_nxt = 1;

  	l->acked = 0;

  	l->silent_intv_cnt = 0;

  	l->rst_cnt = 0;

  	l->stale_count = 0;

  	l->bc_peer_is_up = false;

  	memset(&l->mon_state, 0, sizeof(l->mon_state));

  	tipc_link_reset_stats(l);

  }

  /**

   * tipc_link_xmit(): enqueue buffer list according to queue situation
   * @link: link to use
   * @list: chain of buffers containing message
   * @xmitq: returned list of packets to be sent by caller
   *

   * Consumes the buffer chain.

   * Returns 0 if success, or errno: -ELINKCONG, -EMSGSIZE or -ENOBUFS
   * Messages at TIPC_SYSTEM_IMPORTANCE are always accepted
   */
  int tipc_link_xmit(struct tipc_link *l, struct sk_buff_head *list,
  		   struct sk_buff_head *xmitq)
  {
  	struct tipc_msg *hdr = buf_msg(skb_peek(list));
  	unsigned int maxwin = l->window;

  	int imp = msg_importance(hdr);

  	unsigned int mtu = l->mtu;
  	u16 ack = l->rcv_nxt - 1;
  	u16 seqno = l->snd_nxt;

  	u16 bc_ack = l->bc_rcvlink->rcv_nxt - 1;

  	struct sk_buff_head *transmq = &l->transmq;
  	struct sk_buff_head *backlogq = &l->backlogq;
  	struct sk_buff *skb, *_skb, *bskb;

  	int pkt_cnt = skb_queue_len(list);

  	int rc = 0;

  	if (unlikely(msg_size(hdr) > mtu)) {
  		skb_queue_purge(list);

  		return -EMSGSIZE;

  	}

  	/* Allow oversubscription of one data msg per source at congestion */
  	if (unlikely(l->backlog[imp].len >= l->backlog[imp].limit)) {
  		if (imp == TIPC_SYSTEM_IMPORTANCE) {
  			pr_warn("%s<%s>, link overflow", link_rst_msg, l->name);
  			return -ENOBUFS;
  		}
  		rc = link_schedule_user(l, hdr);
  	}

  	if (pkt_cnt > 1) {
  		l->stats.sent_fragmented++;
  		l->stats.sent_fragments += pkt_cnt;
  	}

  	/* Prepare each packet for sending, and add to relevant queue: */
  	while (skb_queue_len(list)) {
  		skb = skb_peek(list);
  		hdr = buf_msg(skb);
  		msg_set_seqno(hdr, seqno);
  		msg_set_ack(hdr, ack);

  		msg_set_bcast_ack(hdr, bc_ack);

  
  		if (likely(skb_queue_len(transmq) < maxwin)) {
  			_skb = skb_clone(skb, GFP_ATOMIC);

  			if (!_skb) {
  				skb_queue_purge(list);

  				return -ENOBUFS;

  			}

  			__skb_dequeue(list);
  			__skb_queue_tail(transmq, skb);
  			__skb_queue_tail(xmitq, _skb);

  			TIPC_SKB_CB(skb)->ackers = l->ackers;

  			l->rcv_unacked = 0;

  			l->stats.sent_pkts++;

  			seqno++;
  			continue;
  		}
  		if (tipc_msg_bundle(skb_peek_tail(backlogq), hdr, mtu)) {
  			kfree_skb(__skb_dequeue(list));
  			l->stats.sent_bundled++;
  			continue;
  		}
  		if (tipc_msg_make_bundle(&bskb, hdr, mtu, l->addr)) {
  			kfree_skb(__skb_dequeue(list));
  			__skb_queue_tail(backlogq, bskb);
  			l->backlog[msg_importance(buf_msg(bskb))].len++;
  			l->stats.sent_bundled++;
  			l->stats.sent_bundles++;
  			continue;
  		}
  		l->backlog[imp].len += skb_queue_len(list);
  		skb_queue_splice_tail_init(list, backlogq);
  	}
  	l->snd_nxt = seqno;

  	return rc;

  }

  void tipc_link_advance_backlog(struct tipc_link *l, struct sk_buff_head *xmitq)
  {
  	struct sk_buff *skb, *_skb;
  	struct tipc_msg *hdr;
  	u16 seqno = l->snd_nxt;
  	u16 ack = l->rcv_nxt - 1;

  	u16 bc_ack = l->bc_rcvlink->rcv_nxt - 1;

  
  	while (skb_queue_len(&l->transmq) < l->window) {
  		skb = skb_peek(&l->backlogq);
  		if (!skb)
  			break;
  		_skb = skb_clone(skb, GFP_ATOMIC);
  		if (!_skb)
  			break;
  		__skb_dequeue(&l->backlogq);
  		hdr = buf_msg(skb);
  		l->backlog[msg_importance(hdr)].len--;
  		__skb_queue_tail(&l->transmq, skb);
  		__skb_queue_tail(xmitq, _skb);

  		TIPC_SKB_CB(skb)->ackers = l->ackers;

  		msg_set_seqno(hdr, seqno);

  		msg_set_ack(hdr, ack);
  		msg_set_bcast_ack(hdr, bc_ack);

  		l->rcv_unacked = 0;

  		l->stats.sent_pkts++;

  		seqno++;
  	}
  	l->snd_nxt = seqno;
  }

  static void link_retransmit_failure(struct tipc_link *l, struct sk_buff *skb)

  {

  	struct tipc_msg *hdr = buf_msg(skb);
  
  	pr_warn("Retransmission failure on link <%s>
  ", l->name);

  	link_print(l, "State of link ");

  	pr_info("Failed msg: usr %u, typ %u, len %u, err %u
  ",
  		msg_user(hdr), msg_type(hdr), msg_size(hdr), msg_errcode(hdr));
  	pr_info("sqno %u, prev: %x, src: %x
  ",
  		msg_seqno(hdr), msg_prevnode(hdr), msg_orignode(hdr));

  }

  int tipc_link_retrans(struct tipc_link *l, struct tipc_link *nacker,
  		      u16 from, u16 to, struct sk_buff_head *xmitq)

  {
  	struct sk_buff *_skb, *skb = skb_peek(&l->transmq);
  	struct tipc_msg *hdr;

  	u16 ack = l->rcv_nxt - 1;

  	u16 bc_ack = l->bc_rcvlink->rcv_nxt - 1;

  
  	if (!skb)
  		return 0;
  
  	/* Detect repeated retransmit failures on same packet */

  	if (nacker->last_retransm != buf_seqno(skb)) {
  		nacker->last_retransm = buf_seqno(skb);
  		nacker->stale_count = 1;
  	} else if (++nacker->stale_count > 100) {

  		link_retransmit_failure(l, skb);

  		nacker->stale_count = 0;
  		if (link_is_bc_sndlink(l))
  			return TIPC_LINK_DOWN_EVT;

  		return tipc_link_fsm_evt(l, LINK_FAILURE_EVT);

  	}

  
  	/* Move forward to where retransmission should start */

  	skb_queue_walk(&l->transmq, skb) {

  		if (!less(buf_seqno(skb), from))
  			break;
  	}
  
  	skb_queue_walk_from(&l->transmq, skb) {
  		if (more(buf_seqno(skb), to))
  			break;

  		hdr = buf_msg(skb);
  		_skb = __pskb_copy(skb, MIN_H_SIZE, GFP_ATOMIC);
  		if (!_skb)
  			return 0;
  		hdr = buf_msg(_skb);

  		msg_set_ack(hdr, ack);
  		msg_set_bcast_ack(hdr, bc_ack);

  		_skb->priority = TC_PRIO_CONTROL;
  		__skb_queue_tail(xmitq, _skb);

  		l->stats.retransmitted++;
  	}
  	return 0;
  }

  /* tipc_data_input - deliver data and name distr msgs to upper layer

   *

   * Consumes buffer if message is of right type

   * Node lock must be held
   */

  static bool tipc_data_input(struct tipc_link *l, struct sk_buff *skb,

  			    struct sk_buff_head *inputq)

  {

  	struct tipc_msg *hdr = buf_msg(skb);
  
  	switch (msg_user(hdr)) {

  	case TIPC_LOW_IMPORTANCE:
  	case TIPC_MEDIUM_IMPORTANCE:
  	case TIPC_HIGH_IMPORTANCE:
  	case TIPC_CRITICAL_IMPORTANCE:

  		if (unlikely(msg_type(hdr) == TIPC_MCAST_MSG)) {
  			skb_queue_tail(l->bc_rcvlink->inputq, skb);
  			return true;
  		}

  	case CONN_MANAGER:

  		skb_queue_tail(inputq, skb);

  		return true;

  	case NAME_DISTRIBUTOR:

  		l->bc_rcvlink->state = LINK_ESTABLISHED;
  		skb_queue_tail(l->namedq, skb);

  		return true;
  	case MSG_BUNDLER:

  	case TUNNEL_PROTOCOL:

  	case MSG_FRAGMENTER:

  	case BCAST_PROTOCOL:

  		return false;

  	default:

  		pr_warn("Dropping received illegal msg type
  ");
  		kfree_skb(skb);
  		return false;
  	};

  }

  
  /* tipc_link_input - process packet that has passed link protocol check
   *
   * Consumes buffer

   */

  static int tipc_link_input(struct tipc_link *l, struct sk_buff *skb,
  			   struct sk_buff_head *inputq)

  {

  	struct tipc_msg *hdr = buf_msg(skb);
  	struct sk_buff **reasm_skb = &l->reasm_buf;

  	struct sk_buff *iskb;

  	struct sk_buff_head tmpq;

  	int usr = msg_user(hdr);

  	int rc = 0;

  	int pos = 0;
  	int ipos = 0;

  	if (unlikely(usr == TUNNEL_PROTOCOL)) {
  		if (msg_type(hdr) == SYNCH_MSG) {
  			__skb_queue_purge(&l->deferdq);
  			goto drop;

  		}

  		if (!tipc_msg_extract(skb, &iskb, &ipos))
  			return rc;
  		kfree_skb(skb);
  		skb = iskb;
  		hdr = buf_msg(skb);
  		if (less(msg_seqno(hdr), l->drop_point))
  			goto drop;

  		if (tipc_data_input(l, skb, inputq))

  			return rc;
  		usr = msg_user(hdr);
  		reasm_skb = &l->failover_reasm_skb;
  	}

  	if (usr == MSG_BUNDLER) {

  		skb_queue_head_init(&tmpq);

  		l->stats.recv_bundles++;
  		l->stats.recv_bundled += msg_msgcnt(hdr);

  		while (tipc_msg_extract(skb, &iskb, &pos))

  			tipc_data_input(l, iskb, &tmpq);
  		tipc_skb_queue_splice_tail(&tmpq, inputq);

  		return 0;

  	} else if (usr == MSG_FRAGMENTER) {
  		l->stats.recv_fragments++;
  		if (tipc_buf_append(reasm_skb, &skb)) {
  			l->stats.recv_fragmented++;

  			tipc_data_input(l, skb, inputq);

  		} else if (!*reasm_skb && !link_is_bc_rcvlink(l)) {
  			pr_warn_ratelimited("Unable to build fragment list
  ");

  			return tipc_link_fsm_evt(l, LINK_FAILURE_EVT);

  		}

  		return 0;

  	} else if (usr == BCAST_PROTOCOL) {

  		tipc_bcast_lock(l->net);

  		tipc_link_bc_init_rcv(l->bc_rcvlink, hdr);

  		tipc_bcast_unlock(l->net);

  	}
  drop:
  	kfree_skb(skb);

  	return 0;

  }

  static bool tipc_link_release_pkts(struct tipc_link *l, u16 acked)
  {
  	bool released = false;
  	struct sk_buff *skb, *tmp;
  
  	skb_queue_walk_safe(&l->transmq, skb, tmp) {
  		if (more(buf_seqno(skb), acked))
  			break;
  		__skb_unlink(skb, &l->transmq);
  		kfree_skb(skb);
  		released = true;
  	}
  	return released;
  }

  /* tipc_link_build_state_msg: prepare link state message for transmission

   *
   * Note that sending of broadcast ack is coordinated among nodes, to reduce
   * risk of ack storms towards the sender

   */

  int tipc_link_build_state_msg(struct tipc_link *l, struct sk_buff_head *xmitq)

  {

  	if (!l)
  		return 0;
  
  	/* Broadcast ACK must be sent via a unicast link => defer to caller */
  	if (link_is_bc_rcvlink(l)) {

  		if (((l->rcv_nxt ^ tipc_own_addr(l->net)) & 0xf) != 0xf)

  			return 0;
  		l->rcv_unacked = 0;

  
  		/* Use snd_nxt to store peer's snd_nxt in broadcast rcv link */
  		l->snd_nxt = l->rcv_nxt;
  		return TIPC_LINK_SND_STATE;

  	}
  
  	/* Unicast ACK */

  	l->rcv_unacked = 0;
  	l->stats.sent_acks++;
  	tipc_link_build_proto_msg(l, STATE_MSG, 0, 0, 0, 0, xmitq);

  	return 0;

  }

  /* tipc_link_build_reset_msg: prepare link RESET or ACTIVATE message
   */
  void tipc_link_build_reset_msg(struct tipc_link *l, struct sk_buff_head *xmitq)
  {
  	int mtyp = RESET_MSG;

  	struct sk_buff *skb;

  
  	if (l->state == LINK_ESTABLISHING)
  		mtyp = ACTIVATE_MSG;
  
  	tipc_link_build_proto_msg(l, mtyp, 0, 0, 0, 0, xmitq);

  
  	/* Inform peer that this endpoint is going down if applicable */
  	skb = skb_peek_tail(xmitq);
  	if (skb && (l->state == LINK_RESET))
  		msg_set_peer_stopping(buf_msg(skb), 1);

  }

  /* tipc_link_build_nack_msg: prepare link nack message for transmission

   * Note that sending of broadcast NACK is coordinated among nodes, to
   * reduce the risk of NACK storms towards the sender

   */

  static int tipc_link_build_nack_msg(struct tipc_link *l,
  				    struct sk_buff_head *xmitq)

  {
  	u32 def_cnt = ++l->stats.deferred_recv;

  	int match1, match2;

  	if (link_is_bc_rcvlink(l)) {
  		match1 = def_cnt & 0xf;
  		match2 = tipc_own_addr(l->net) & 0xf;
  		if (match1 == match2)
  			return TIPC_LINK_SND_STATE;
  		return 0;
  	}

  	if ((skb_queue_len(&l->deferdq) == 1) || !(def_cnt % TIPC_NACK_INTV))
  		tipc_link_build_proto_msg(l, STATE_MSG, 0, 0, 0, 0, xmitq);

  	return 0;

  }

  /* tipc_link_rcv - process TIPC packets/messages arriving from off-node

   * @l: the link that should handle the message

   * @skb: TIPC packet
   * @xmitq: queue to place packets to be sent after this call
   */
  int tipc_link_rcv(struct tipc_link *l, struct sk_buff *skb,
  		  struct sk_buff_head *xmitq)
  {

  	struct sk_buff_head *defq = &l->deferdq;

  	struct tipc_msg *hdr;

  	u16 seqno, rcv_nxt, win_lim;

  	int rc = 0;

  	do {

  		hdr = buf_msg(skb);

  		seqno = msg_seqno(hdr);
  		rcv_nxt = l->rcv_nxt;

  		win_lim = rcv_nxt + TIPC_MAX_LINK_WIN;

  
  		/* Verify and update link state */

  		if (unlikely(msg_user(hdr) == LINK_PROTOCOL))
  			return tipc_link_proto_rcv(l, skb, xmitq);

  		if (unlikely(!link_is_up(l))) {

  			if (l->state == LINK_ESTABLISHING)
  				rc = TIPC_LINK_UP_EVT;
  			goto drop;

  		}

  		/* Don't send probe at next timeout expiration */

  		l->silent_intv_cnt = 0;

  		/* Drop if outside receive window */
  		if (unlikely(less(seqno, rcv_nxt) || more(seqno, win_lim))) {
  			l->stats.duplicates++;
  			goto drop;
  		}

  		/* Forward queues and wake up waiting users */
  		if (likely(tipc_link_release_pkts(l, msg_ack(hdr)))) {
  			tipc_link_advance_backlog(l, xmitq);
  			if (unlikely(!skb_queue_empty(&l->wakeupq)))
  				link_prepare_wakeup(l);
  		}

  		/* Defer delivery if sequence gap */
  		if (unlikely(seqno != rcv_nxt)) {

  			__tipc_skb_queue_sorted(defq, seqno, skb);

  			rc |= tipc_link_build_nack_msg(l, xmitq);

  			break;

  		}

  		/* Deliver packet */

  		l->rcv_nxt++;

  		l->stats.recv_pkts++;

  		if (!tipc_data_input(l, skb, l->inputq))

  			rc |= tipc_link_input(l, skb, l->inputq);

  		if (unlikely(++l->rcv_unacked >= TIPC_MIN_LINK_WIN))

  			rc |= tipc_link_build_state_msg(l, xmitq);

  		if (unlikely(rc & ~TIPC_LINK_SND_STATE))

  			break;

  	} while ((skb = __skb_dequeue(defq)));
  
  	return rc;
  drop:
  	kfree_skb(skb);

  	return rc;
  }

  static void tipc_link_build_proto_msg(struct tipc_link *l, int mtyp, bool probe,
  				      u16 rcvgap, int tolerance, int priority,
  				      struct sk_buff_head *xmitq)
  {

  	struct tipc_link *bcl = l->bc_rcvlink;

  	struct sk_buff *skb;
  	struct tipc_msg *hdr;
  	struct sk_buff_head *dfq = &l->deferdq;

  	bool node_up = link_is_up(bcl);

  	struct tipc_mon_state *mstate = &l->mon_state;
  	int dlen = 0;
  	void *data;

  
  	/* Don't send protocol message during reset or link failover */

  	if (tipc_link_is_blocked(l))

  		return;

  	if (!tipc_link_is_up(l) && (mtyp == STATE_MSG))
  		return;
  
  	if (!skb_queue_empty(dfq))
  		rcvgap = buf_seqno(skb_peek(dfq)) - l->rcv_nxt;
  
  	skb = tipc_msg_create(LINK_PROTOCOL, mtyp, INT_H_SIZE,

  			      tipc_max_domain_size, l->addr,

  			      tipc_own_addr(l->net), 0, 0, 0);
  	if (!skb)
  		return;
  
  	hdr = buf_msg(skb);

  	data = msg_data(hdr);

  	msg_set_session(hdr, l->session);
  	msg_set_bearer_id(hdr, l->bearer_id);

  	msg_set_net_plane(hdr, l->net_plane);

  	msg_set_next_sent(hdr, l->snd_nxt);
  	msg_set_ack(hdr, l->rcv_nxt - 1);

  	msg_set_bcast_ack(hdr, bcl->rcv_nxt - 1);

  	msg_set_bc_ack_invalid(hdr, !node_up);

  	msg_set_last_bcast(hdr, l->bc_sndlink->snd_nxt - 1);

  	msg_set_link_tolerance(hdr, tolerance);
  	msg_set_linkprio(hdr, priority);
  	msg_set_redundant_link(hdr, node_up);
  	msg_set_seq_gap(hdr, 0);

  	msg_set_seqno(hdr, l->snd_nxt + U16_MAX / 2);

  
  	if (mtyp == STATE_MSG) {

  		msg_set_seq_gap(hdr, rcvgap);

  		msg_set_bc_gap(hdr, link_bc_rcv_gap(bcl));

  		msg_set_probe(hdr, probe);

  		tipc_mon_prep(l->net, data, &dlen, mstate, l->bearer_id);
  		msg_set_size(hdr, INT_H_SIZE + dlen);
  		skb_trim(skb, INT_H_SIZE + dlen);

  		l->stats.sent_states++;

  		l->rcv_unacked = 0;

  	} else {
  		/* RESET_MSG or ACTIVATE_MSG */
  		msg_set_max_pkt(hdr, l->advertised_mtu);

  		strcpy(data, l->if_name);
  		msg_set_size(hdr, INT_H_SIZE + TIPC_MAX_IF_NAME);
  		skb_trim(skb, INT_H_SIZE + TIPC_MAX_IF_NAME);

  	}

  	if (probe)
  		l->stats.sent_probes++;
  	if (rcvgap)
  		l->stats.sent_nacks++;

  	skb->priority = TC_PRIO_CONTROL;

  	__skb_queue_tail(xmitq, skb);

  }

  /* tipc_link_tnl_prepare(): prepare and return a list of tunnel packets

   * with contents of the link's transmit and backlog queues.

   */

  void tipc_link_tnl_prepare(struct tipc_link *l, struct tipc_link *tnl,
  			   int mtyp, struct sk_buff_head *xmitq)

  {

  	struct sk_buff *skb, *tnlskb;
  	struct tipc_msg *hdr, tnlhdr;
  	struct sk_buff_head *queue = &l->transmq;
  	struct sk_buff_head tmpxq, tnlq;
  	u16 pktlen, pktcnt, seqno = l->snd_nxt;

  	if (!tnl)

  		return;

  	skb_queue_head_init(&tnlq);
  	skb_queue_head_init(&tmpxq);

  	/* At least one packet required for safe algorithm => add dummy */
  	skb = tipc_msg_create(TIPC_LOW_IMPORTANCE, TIPC_DIRECT_MSG,

  			      BASIC_H_SIZE, 0, l->addr, tipc_own_addr(l->net),

  			      0, 0, TIPC_ERR_NO_PORT);
  	if (!skb) {
  		pr_warn("%sunable to create tunnel packet
  ", link_co_err);

  		return;
  	}

  	skb_queue_tail(&tnlq, skb);
  	tipc_link_xmit(l, &tnlq, &tmpxq);
  	__skb_queue_purge(&tmpxq);
  
  	/* Initialize reusable tunnel packet header */

  	tipc_msg_init(tipc_own_addr(l->net), &tnlhdr, TUNNEL_PROTOCOL,

  		      mtyp, INT_H_SIZE, l->addr);
  	pktcnt = skb_queue_len(&l->transmq) + skb_queue_len(&l->backlogq);
  	msg_set_msgcnt(&tnlhdr, pktcnt);
  	msg_set_bearer_id(&tnlhdr, l->peer_bearer_id);
  tnl:
  	/* Wrap each packet into a tunnel packet */

  	skb_queue_walk(queue, skb) {

  		hdr = buf_msg(skb);
  		if (queue == &l->backlogq)
  			msg_set_seqno(hdr, seqno++);
  		pktlen = msg_size(hdr);
  		msg_set_size(&tnlhdr, pktlen + INT_H_SIZE);

  		tnlskb = tipc_buf_acquire(pktlen + INT_H_SIZE, GFP_ATOMIC);

  		if (!tnlskb) {
  			pr_warn("%sunable to send packet
  ", link_co_err);

  			return;
  		}

  		skb_copy_to_linear_data(tnlskb, &tnlhdr, INT_H_SIZE);
  		skb_copy_to_linear_data_offset(tnlskb, INT_H_SIZE, hdr, pktlen);
  		__skb_queue_tail(&tnlq, tnlskb);

  	}

  	if (queue != &l->backlogq) {
  		queue = &l->backlogq;
  		goto tnl;

  	}

  	tipc_link_xmit(tnl, &tnlq, xmitq);

  	if (mtyp == FAILOVER_MSG) {
  		tnl->drop_point = l->rcv_nxt;
  		tnl->failover_reasm_skb = l->reasm_buf;
  		l->reasm_buf = NULL;

  	}

  }

  /* tipc_link_proto_rcv(): receive link level protocol message :
   * Note that network plane id propagates through the network, and may
   * change at any time. The node with lowest numerical id determines
   * network plane
   */
  static int tipc_link_proto_rcv(struct tipc_link *l, struct sk_buff *skb,
  			       struct sk_buff_head *xmitq)
  {
  	struct tipc_msg *hdr = buf_msg(skb);
  	u16 rcvgap = 0;

  	u16 ack = msg_ack(hdr);
  	u16 gap = msg_seq_gap(hdr);

  	u16 peers_snd_nxt =  msg_next_sent(hdr);
  	u16 peers_tol = msg_link_tolerance(hdr);
  	u16 peers_prio = msg_linkprio(hdr);

  	u16 rcv_nxt = l->rcv_nxt;

  	u16 dlen = msg_data_sz(hdr);

  	int mtyp = msg_type(hdr);

  	void *data;

  	char *if_name;
  	int rc = 0;

  	if (tipc_link_is_blocked(l) || !xmitq)

  		goto exit;

  	if (tipc_own_addr(l->net) > msg_prevnode(hdr))

  		l->net_plane = msg_net_plane(hdr);

  	skb_linearize(skb);
  	hdr = buf_msg(skb);
  	data = msg_data(hdr);

  	switch (mtyp) {

  	case RESET_MSG:
  
  		/* Ignore duplicate RESET with old session number */
  		if ((less_eq(msg_session(hdr), l->peer_session)) &&

  		    (l->peer_session != ANY_SESSION))

  			break;
  		/* fall thru' */

  	case ACTIVATE_MSG:
  
  		/* Complete own link name with peer's interface name */
  		if_name =  strrchr(l->name, ':') + 1;
  		if (sizeof(l->name) - (if_name - l->name) <= TIPC_MAX_IF_NAME)
  			break;
  		if (msg_data_sz(hdr) < TIPC_MAX_IF_NAME)
  			break;

  		strncpy(if_name, data, TIPC_MAX_IF_NAME);

  
  		/* Update own tolerance if peer indicates a non-zero value */
  		if (in_range(peers_tol, TIPC_MIN_LINK_TOL, TIPC_MAX_LINK_TOL))
  			l->tolerance = peers_tol;
  
  		/* Update own priority if peer's priority is higher */
  		if (in_range(peers_prio, l->priority + 1, TIPC_MAX_LINK_PRI))
  			l->priority = peers_prio;

  		/* ACTIVATE_MSG serves as PEER_RESET if link is already down */

  		if (msg_peer_stopping(hdr))
  			rc = tipc_link_fsm_evt(l, LINK_FAILURE_EVT);
  		else if ((mtyp == RESET_MSG) || !link_is_up(l))

  			rc = tipc_link_fsm_evt(l, LINK_PEER_RESET_EVT);
  
  		/* ACTIVATE_MSG takes up link if it was already locally reset */
  		if ((mtyp == ACTIVATE_MSG) && (l->state == LINK_ESTABLISHING))
  			rc = TIPC_LINK_UP_EVT;

  		l->peer_session = msg_session(hdr);
  		l->peer_bearer_id = msg_bearer_id(hdr);

  		if (l->mtu > msg_max_pkt(hdr))
  			l->mtu = msg_max_pkt(hdr);
  		break;

  	case STATE_MSG:

  		/* Update own tolerance if peer indicates a non-zero value */
  		if (in_range(peers_tol, TIPC_MIN_LINK_TOL, TIPC_MAX_LINK_TOL))
  			l->tolerance = peers_tol;

  		/* Update own prio if peer indicates a different value */
  		if ((peers_prio != l->priority) &&
  		    in_range(peers_prio, 1, TIPC_MAX_LINK_PRI)) {

  			l->priority = peers_prio;
  			rc = tipc_link_fsm_evt(l, LINK_FAILURE_EVT);
  		}

  		l->silent_intv_cnt = 0;
  		l->stats.recv_states++;
  		if (msg_probe(hdr))
  			l->stats.recv_probes++;

  
  		if (!link_is_up(l)) {
  			if (l->state == LINK_ESTABLISHING)
  				rc = TIPC_LINK_UP_EVT;

  			break;

  		}

  		tipc_mon_rcv(l->net, data, dlen, l->addr,
  			     &l->mon_state, l->bearer_id);

  		/* Send NACK if peer has sent pkts we haven't received yet */

  		if (more(peers_snd_nxt, rcv_nxt) && !tipc_link_is_synching(l))

  			rcvgap = peers_snd_nxt - l->rcv_nxt;
  		if (rcvgap || (msg_probe(hdr)))
  			tipc_link_build_proto_msg(l, STATE_MSG, 0, rcvgap,

  						  0, 0, xmitq);

  		tipc_link_release_pkts(l, ack);

  
  		/* If NACK, retransmit will now start at right position */

  		if (gap) {

  			rc = tipc_link_retrans(l, l, ack + 1, ack + gap, xmitq);

  			l->stats.recv_nacks++;
  		}

  		tipc_link_advance_backlog(l, xmitq);
  		if (unlikely(!skb_queue_empty(&l->wakeupq)))
  			link_prepare_wakeup(l);
  	}
  exit:
  	kfree_skb(skb);
  	return rc;
  }

  /* tipc_link_build_bc_proto_msg() - create broadcast protocol message
   */
  static bool tipc_link_build_bc_proto_msg(struct tipc_link *l, bool bcast,
  					 u16 peers_snd_nxt,
  					 struct sk_buff_head *xmitq)
  {
  	struct sk_buff *skb;
  	struct tipc_msg *hdr;
  	struct sk_buff *dfrd_skb = skb_peek(&l->deferdq);
  	u16 ack = l->rcv_nxt - 1;
  	u16 gap_to = peers_snd_nxt - 1;
  
  	skb = tipc_msg_create(BCAST_PROTOCOL, STATE_MSG, INT_H_SIZE,

  			      0, l->addr, tipc_own_addr(l->net), 0, 0, 0);

  	if (!skb)
  		return false;
  	hdr = buf_msg(skb);
  	msg_set_last_bcast(hdr, l->bc_sndlink->snd_nxt - 1);
  	msg_set_bcast_ack(hdr, ack);
  	msg_set_bcgap_after(hdr, ack);
  	if (dfrd_skb)
  		gap_to = buf_seqno(dfrd_skb) - 1;
  	msg_set_bcgap_to(hdr, gap_to);
  	msg_set_non_seq(hdr, bcast);
  	__skb_queue_tail(xmitq, skb);
  	return true;
  }
  
  /* tipc_link_build_bc_init_msg() - synchronize broadcast link endpoints.
   *
   * Give a newly added peer node the sequence number where it should
   * start receiving and acking broadcast packets.
   */

  static void tipc_link_build_bc_init_msg(struct tipc_link *l,
  					struct sk_buff_head *xmitq)

  {
  	struct sk_buff_head list;
  
  	__skb_queue_head_init(&list);
  	if (!tipc_link_build_bc_proto_msg(l->bc_rcvlink, false, 0, &list))
  		return;

  	msg_set_bc_ack_invalid(buf_msg(skb_peek(&list)), true);

  	tipc_link_xmit(l, &list, xmitq);
  }
  
  /* tipc_link_bc_init_rcv - receive initial broadcast synch data from peer
   */
  void tipc_link_bc_init_rcv(struct tipc_link *l, struct tipc_msg *hdr)
  {
  	int mtyp = msg_type(hdr);
  	u16 peers_snd_nxt = msg_bc_snd_nxt(hdr);
  
  	if (link_is_up(l))
  		return;
  
  	if (msg_user(hdr) == BCAST_PROTOCOL) {
  		l->rcv_nxt = peers_snd_nxt;
  		l->state = LINK_ESTABLISHED;
  		return;
  	}
  
  	if (l->peer_caps & TIPC_BCAST_SYNCH)
  		return;
  
  	if (msg_peer_node_is_up(hdr))
  		return;
  
  	/* Compatibility: accept older, less safe initial synch data */
  	if ((mtyp == RESET_MSG) || (mtyp == ACTIVATE_MSG))
  		l->rcv_nxt = peers_snd_nxt;
  }

  /* link_bc_retr eval()- check if the indicated range can be retransmitted now
   * - Adjust permitted range if there is overlap with previous retransmission
   */
  static bool link_bc_retr_eval(struct tipc_link *l, u16 *from, u16 *to)
  {
  	unsigned long elapsed = jiffies_to_msecs(jiffies - l->prev_retr);
  
  	if (less(*to, *from))
  		return false;
  
  	/* New retransmission request */
  	if ((elapsed > TIPC_BC_RETR_LIMIT) ||
  	    less(*to, l->prev_from) || more(*from, l->prev_to)) {
  		l->prev_from = *from;
  		l->prev_to = *to;
  		l->prev_retr = jiffies;
  		return true;
  	}
  
  	/* Inside range of previous retransmit */
  	if (!less(*from, l->prev_from) && !more(*to, l->prev_to))
  		return false;
  
  	/* Fully or partially outside previous range => exclude overlap */
  	if (less(*from, l->prev_from)) {
  		*to = l->prev_from - 1;
  		l->prev_from = *from;
  	}
  	if (more(*to, l->prev_to)) {
  		*from = l->prev_to + 1;
  		l->prev_to = *to;
  	}
  	l->prev_retr = jiffies;
  	return true;
  }

  /* tipc_link_bc_sync_rcv - update rcv link according to peer's send state
   */

  int tipc_link_bc_sync_rcv(struct tipc_link *l, struct tipc_msg *hdr,
  			  struct sk_buff_head *xmitq)

  {

  	struct tipc_link *snd_l = l->bc_sndlink;

  	u16 peers_snd_nxt = msg_bc_snd_nxt(hdr);

  	u16 from = msg_bcast_ack(hdr) + 1;
  	u16 to = from + msg_bc_gap(hdr) - 1;
  	int rc = 0;

  
  	if (!link_is_up(l))

  		return rc;

  
  	if (!msg_peer_node_is_up(hdr))

  		return rc;

  	/* Open when peer ackowledges our bcast init msg (pkt #1) */
  	if (msg_ack(hdr))
  		l->bc_peer_is_up = true;
  
  	if (!l->bc_peer_is_up)

  		return rc;

  	l->stats.recv_nacks++;

  	/* Ignore if peers_snd_nxt goes beyond receive window */
  	if (more(peers_snd_nxt, l->rcv_nxt + l->window))

  		return rc;

  	if (link_bc_retr_eval(snd_l, &from, &to))

  		rc = tipc_link_retrans(snd_l, l, from, to, xmitq);

  
  	l->snd_nxt = peers_snd_nxt;
  	if (link_bc_rcv_gap(l))
  		rc |= TIPC_LINK_SND_STATE;
  
  	/* Return now if sender supports nack via STATE messages */
  	if (l->peer_caps & TIPC_BCAST_STATE_NACK)
  		return rc;
  
  	/* Otherwise, be backwards compatible */

  
  	if (!more(peers_snd_nxt, l->rcv_nxt)) {
  		l->nack_state = BC_NACK_SND_CONDITIONAL;

  		return 0;

  	}
  
  	/* Don't NACK if one was recently sent or peeked */
  	if (l->nack_state == BC_NACK_SND_SUPPRESS) {
  		l->nack_state = BC_NACK_SND_UNCONDITIONAL;

  		return 0;

  	}
  
  	/* Conditionally delay NACK sending until next synch rcv */
  	if (l->nack_state == BC_NACK_SND_CONDITIONAL) {
  		l->nack_state = BC_NACK_SND_UNCONDITIONAL;
  		if ((peers_snd_nxt - l->rcv_nxt) < TIPC_MIN_LINK_WIN)

  			return 0;

  	}
  
  	/* Send NACK now but suppress next one */
  	tipc_link_build_bc_proto_msg(l, true, peers_snd_nxt, xmitq);
  	l->nack_state = BC_NACK_SND_SUPPRESS;

  	return 0;

  }
  
  void tipc_link_bc_ack_rcv(struct tipc_link *l, u16 acked,
  			  struct sk_buff_head *xmitq)
  {
  	struct sk_buff *skb, *tmp;
  	struct tipc_link *snd_l = l->bc_sndlink;
  
  	if (!link_is_up(l) || !l->bc_peer_is_up)
  		return;
  
  	if (!more(acked, l->acked))
  		return;
  
  	/* Skip over packets peer has already acked */
  	skb_queue_walk(&snd_l->transmq, skb) {
  		if (more(buf_seqno(skb), l->acked))
  			break;
  	}
  
  	/* Update/release the packets peer is acking now */
  	skb_queue_walk_from_safe(&snd_l->transmq, skb, tmp) {
  		if (more(buf_seqno(skb), acked))
  			break;
  		if (!--TIPC_SKB_CB(skb)->ackers) {
  			__skb_unlink(skb, &snd_l->transmq);
  			kfree_skb(skb);
  		}
  	}
  	l->acked = acked;
  	tipc_link_advance_backlog(snd_l, xmitq);
  	if (unlikely(!skb_queue_empty(&snd_l->wakeupq)))
  		link_prepare_wakeup(snd_l);
  }
  
  /* tipc_link_bc_nack_rcv(): receive broadcast nack message

   * This function is here for backwards compatibility, since
   * no BCAST_PROTOCOL/STATE messages occur from TIPC v2.5.

   */
  int tipc_link_bc_nack_rcv(struct tipc_link *l, struct sk_buff *skb,
  			  struct sk_buff_head *xmitq)
  {
  	struct tipc_msg *hdr = buf_msg(skb);
  	u32 dnode = msg_destnode(hdr);
  	int mtyp = msg_type(hdr);
  	u16 acked = msg_bcast_ack(hdr);
  	u16 from = acked + 1;
  	u16 to = msg_bcgap_to(hdr);
  	u16 peers_snd_nxt = to + 1;
  	int rc = 0;
  
  	kfree_skb(skb);
  
  	if (!tipc_link_is_up(l) || !l->bc_peer_is_up)
  		return 0;
  
  	if (mtyp != STATE_MSG)
  		return 0;

  	if (dnode == tipc_own_addr(l->net)) {

  		tipc_link_bc_ack_rcv(l, acked, xmitq);

  		rc = tipc_link_retrans(l->bc_sndlink, l, from, to, xmitq);

  		l->stats.recv_nacks++;
  		return rc;
  	}
  
  	/* Msg for other node => suppress own NACK at next sync if applicable */
  	if (more(peers_snd_nxt, l->rcv_nxt) && !less(l->rcv_nxt, from))
  		l->nack_state = BC_NACK_SND_SUPPRESS;
  
  	return 0;
  }

  void tipc_link_set_queue_limits(struct tipc_link *l, u32 win)

  {

  	int max_bulk = TIPC_MAX_PUBLICATIONS / (l->mtu / ITEM_SIZE);

  
  	l->window = win;

  	l->backlog[TIPC_LOW_IMPORTANCE].limit      = max_t(u16, 50, win);
  	l->backlog[TIPC_MEDIUM_IMPORTANCE].limit   = max_t(u16, 100, win * 2);
  	l->backlog[TIPC_HIGH_IMPORTANCE].limit     = max_t(u16, 150, win * 3);
  	l->backlog[TIPC_CRITICAL_IMPORTANCE].limit = max_t(u16, 200, win * 4);

  	l->backlog[TIPC_SYSTEM_IMPORTANCE].limit   = max_bulk;

  }

  /**

   * link_reset_stats - reset link statistics

   * @l: pointer to link

   */

  void tipc_link_reset_stats(struct tipc_link *l)

  {

  	memset(&l->stats, 0, sizeof(l->stats));

  }