/*
 * 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 <linux/pkt_sched.h>

struct tipc_stats {
        u32 sent_info;          /* used in counting # sent packets */
        u32 recv_info;          /* used in counting # recv'd packets */
        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]
 * @keepalive_intv: link keepalive timer interval
 * @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')
 * @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;
        unsigned long keepalive_intv;
        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;

        /* 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;
        int 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,
};

/*
 * 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 void 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--;
        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;
}

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;

        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\n", l->state, l->name);
        }
        return rc;
illegal_evt:
        pr_err("Illegal FSM event %x in state %x on link %s\n",
               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
 */
/* 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 rc = 0;
        int mtyp = STATE_MSG;
        bool xmit = false;
        bool prb = false;
        u16 bc_snt = l->bc_sndlink->snd_nxt - 1;
        u16 bc_acked = l->bc_rcvlink->acked;
        bool bc_up = link_is_up(l->bc_rcvlink);

        link_profile_stats(l);

        switch (l->state) {
        case LINK_ESTABLISHED:
        case LINK_SYNCHING:
                if (!l->silent_intv_cnt) {
                        if (bc_up && (bc_acked != bc_snt))
                                xmit = true;
                } else if (l->silent_intv_cnt <= l->abort_limit) {
                        xmit = true;
                        prb = true;
                } else {
                        rc |= tipc_link_fsm_evt(l, LINK_FAILURE_EVT);
                }
                l->silent_intv_cnt++;
                break;
        case LINK_RESET:
                xmit = true;
                mtyp = RESET_MSG;
                break;
        case LINK_ESTABLISHING:
                xmit = true;
                mtyp = ACTIVATE_MSG;
                break;
        case LINK_PEER_RESET:
        case LINK_RESETTING:
        case LINK_FAILINGOVER:
                break;
        default:
                break;
        }

        if (xmit)
                tipc_link_build_proto_msg(l, mtyp, prb, 0, 0, 0, xmitq);

        return rc;
}

/**
 * link_schedule_user - schedule a message sender for wakeup after congestion
 * @link: congested link
 * @list: message that was attempted sent
 * Create pseudo msg to send back to user when congestion abates
 * Does not consume buffer list
 */
static int link_schedule_user(struct tipc_link *link, struct sk_buff_head *list)
{
        struct tipc_msg *msg = buf_msg(skb_peek(list));
        int imp = msg_importance(msg);
        u32 oport = msg_origport(msg);
        u32 addr = tipc_own_addr(link->net);
        struct sk_buff *skb;

        /* This really cannot happen...  */
        if (unlikely(imp > TIPC_CRITICAL_IMPORTANCE)) {
                pr_warn("%s<%s>, send queue full", link_rst_msg, link->name);
                return -ENOBUFS;
        }
        /* Non-blocking sender: */
        if (TIPC_SKB_CB(skb_peek(list))->wakeup_pending)
                return -ELINKCONG;

        /* Create and schedule wakeup pseudo message */
        skb = tipc_msg_create(SOCK_WAKEUP, 0, INT_H_SIZE, 0,
                              addr, addr, oport, 0, 0);
        if (!skb)
                return -ENOBUFS;
        TIPC_SKB_CB(skb)->chain_sz = skb_queue_len(list);
        TIPC_SKB_CB(skb)->chain_imp = imp;
        skb_queue_tail(&link->wakeupq, skb);
        link->stats.link_congs++;
        return -ELINKCONG;
}

/**
 * link_prepare_wakeup - prepare users for wakeup after congestion
 * @link: congested link
 * Move a number of waiting users, as permitted by available space in
 * the send queue, from link wait queue to node wait queue for wakeup
 */
void link_prepare_wakeup(struct tipc_link *l)
{
        int pnd[TIPC_SYSTEM_IMPORTANCE + 1] = {0,};
        int imp, lim;
        struct sk_buff *skb, *tmp;

        skb_queue_walk_safe(&l->wakeupq, skb, tmp) {
                imp = TIPC_SKB_CB(skb)->chain_imp;
                lim = l->window + l->backlog[imp].limit;
                pnd[imp] += TIPC_SKB_CB(skb)->chain_sz;
                if ((pnd[imp] + l->backlog[imp].len) >= lim)
                        break;
                skb_unlink(skb, &l->wakeupq);
                skb_queue_tail(l->inputq, skb);
        }
}

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->stats.recv_info = 0;
        l->stale_count = 0;
        l->bc_peer_is_up = false;
        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, except when returning -ELINKCONG,
 * since the caller then may want to make more send attempts.
 * 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;
        unsigned int i, 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;

        /* Match msg importance against this and all higher backlog limits: */
        for (i = imp; i <= TIPC_SYSTEM_IMPORTANCE; i++) {
                if (unlikely(l->backlog[i].len >= l->backlog[i].limit))
                        return link_schedule_user(l, list);
        }
        if (unlikely(msg_size(hdr) > mtu)) {
                skb_queue_purge(list);
                return -EMSGSIZE;
        }

        /* 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;
                        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 0;
}

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;
                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>\n", l->name);
        link_print(l, "Resetting link ");
        pr_info("Failed msg: usr %u, typ %u, len %u, err %u\n",
                msg_user(hdr), msg_type(hdr), msg_size(hdr), msg_errcode(hdr));
        pr_info("sqno %u, prev: %x, src: %x\n",
                msg_seqno(hdr), msg_prevnode(hdr), msg_orignode(hdr));
}

int tipc_link_retrans(struct tipc_link *l, 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 (likely(l->last_retransm != buf_seqno(skb))) {
                l->last_retransm = buf_seqno(skb);
                l->stale_count = 1;
        } else if (++l->stale_count > 100) {
                link_retransmit_failure(l, skb);
                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)
{
        switch (msg_user(buf_msg(skb))) {
        case TIPC_LOW_IMPORTANCE:
        case TIPC_MEDIUM_IMPORTANCE:
        case TIPC_HIGH_IMPORTANCE:
        case TIPC_CRITICAL_IMPORTANCE:
        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\n");
                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\n");
                        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_ack_msg: prepare link acknowledge 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_ack_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;
                return TIPC_LINK_SND_BC_ACK;
        }

        /* 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;

        if (l->state == LINK_ESTABLISHING)
                mtyp = ACTIVATE_MSG;

        tipc_link_build_proto_msg(l, mtyp, 0, 0, 0, 0, xmitq);
}

/* tipc_link_build_nack_msg: prepare link nack message for transmission
 */
static void tipc_link_build_nack_msg(struct tipc_link *l,
                                     struct sk_buff_head *xmitq)
{
        u32 def_cnt = ++l->stats.deferred_recv;

        if (link_is_bc_rcvlink(l))
                return;

        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);
}

/* 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);
                        tipc_link_build_nack_msg(l, xmitq);
                        break;
                }

                /* Deliver packet */
                l->rcv_nxt++;
                l->stats.recv_info++;
                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_ack_msg(l, xmitq);
                if (unlikely(rc & ~TIPC_LINK_SND_BC_ACK))
                        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 sk_buff *skb;
        struct tipc_msg *hdr;
        struct sk_buff_head *dfq = &l->deferdq;
        bool node_up = link_is_up(l->bc_rcvlink);

        /* 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_IF_NAME, l->addr,
                              tipc_own_addr(l->net), 0, 0, 0);
        if (!skb)
                return;

        hdr = buf_msg(skb);
        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, l->bc_rcvlink->rcv_nxt - 1);
        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_size(hdr, INT_H_SIZE);
                msg_set_probe(hdr, probe);
                l->stats.sent_states++;
                l->rcv_unacked = 0;
        } else {
                /* RESET_MSG or ACTIVATE_MSG */
                msg_set_max_pkt(hdr, l->advertised_mtu);
                strcpy(msg_data(hdr), l->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\n", 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);
                if (!tnlskb) {
                        pr_warn("%sunable to send packet\n", 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;
        int mtyp = msg_type(hdr);
        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);

        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:
                skb_linearize(skb);
                hdr = buf_msg(skb);

                /* 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, msg_data(hdr), 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 ((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;

                if (peers_prio && in_range(peers_prio, TIPC_MIN_LINK_PRI,
                                           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;
                }

                /* 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, 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;
        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;
}

/* tipc_link_bc_sync_rcv - update rcv link according to peer's send state
 */
void tipc_link_bc_sync_rcv(struct tipc_link *l, struct tipc_msg *hdr,
                           struct sk_buff_head *xmitq)
{
        u16 peers_snd_nxt = msg_bc_snd_nxt(hdr);

        if (!link_is_up(l))
                return;

        if (!msg_peer_node_is_up(hdr))
                return;

        l->bc_peer_is_up = true;

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

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

        /* 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;
        }

        /* 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;
        }

        /* 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;
}

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
 */
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, 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      = win / 2;
        l->backlog[TIPC_MEDIUM_IMPORTANCE].limit   = win;
        l->backlog[TIPC_HIGH_IMPORTANCE].limit     = win / 2 * 3;
        l->backlog[TIPC_CRITICAL_IMPORTANCE].limit = win * 2;
        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));
        if (!link_is_bc_sndlink(l)) {
                l->stats.sent_info = l->snd_nxt;
                l->stats.recv_info = l->rcv_nxt;
        }
}

static void link_print(struct tipc_link *l, const char *str)
{
        struct sk_buff *hskb = skb_peek(&l->transmq);
        u16 head = hskb ? msg_seqno(buf_msg(hskb)) : l->snd_nxt - 1;
        u16 tail = l->snd_nxt - 1;

        pr_info("%s Link <%s> state %x\n", str, l->name, l->state);
        pr_info("XMTQ: %u [%u-%u], BKLGQ: %u, SNDNX: %u, RCVNX: %u\n",
                skb_queue_len(&l->transmq), head, tail,
                skb_queue_len(&l->backlogq), l->snd_nxt, l->rcv_nxt);
}

/* Parse and validate nested (link) properties valid for media, bearer and link
 */
int tipc_nl_parse_link_prop(struct nlattr *prop, struct nlattr *props[])
{
        int err;

        err = nla_parse_nested(props, TIPC_NLA_PROP_MAX, prop,
                               tipc_nl_prop_policy);
        if (err)
                return err;

        if (props[TIPC_NLA_PROP_PRIO]) {
                u32 prio;

                prio = nla_get_u32(props[TIPC_NLA_PROP_PRIO]);
                if (prio > TIPC_MAX_LINK_PRI)
                        return -EINVAL;
        }

        if (props[TIPC_NLA_PROP_TOL]) {
                u32 tol;

                tol = nla_get_u32(props[TIPC_NLA_PROP_TOL]);
                if ((tol < TIPC_MIN_LINK_TOL) || (tol > TIPC_MAX_LINK_TOL))
                        return -EINVAL;
        }

        if (props[TIPC_NLA_PROP_WIN]) {
                u32 win;

                win = nla_get_u32(props[TIPC_NLA_PROP_WIN]);
                if ((win < TIPC_MIN_LINK_WIN) || (win > TIPC_MAX_LINK_WIN))
                        return -EINVAL;
        }

        return 0;
}

static int __tipc_nl_add_stats(struct sk_buff *skb, struct tipc_stats *s)
{
        int i;
        struct nlattr *stats;

        struct nla_map {
                u32 key;
                u32 val;
        };

        struct nla_map map[] = {
                {TIPC_NLA_STATS_RX_INFO, s->recv_info},
                {TIPC_NLA_STATS_RX_FRAGMENTS, s->recv_fragments},
                {TIPC_NLA_STATS_RX_FRAGMENTED, s->recv_fragmented},
                {TIPC_NLA_STATS_RX_BUNDLES, s->recv_bundles},
                {TIPC_NLA_STATS_RX_BUNDLED, s->recv_bundled},
                {TIPC_NLA_STATS_TX_INFO, s->sent_info},
                {TIPC_NLA_STATS_TX_FRAGMENTS, s->sent_fragments},
                {TIPC_NLA_STATS_TX_FRAGMENTED, s->sent_fragmented},
                {TIPC_NLA_STATS_TX_BUNDLES, s->sent_bundles},
                {TIPC_NLA_STATS_TX_BUNDLED, s->sent_bundled},
                {TIPC_NLA_STATS_MSG_PROF_TOT, (s->msg_length_counts) ?
                        s->msg_length_counts : 1},
                {TIPC_NLA_STATS_MSG_LEN_CNT, s->msg_length_counts},
                {TIPC_NLA_STATS_MSG_LEN_TOT, s->msg_lengths_total},
                {TIPC_NLA_STATS_MSG_LEN_P0, s->msg_length_profile[0]},
                {TIPC_NLA_STATS_MSG_LEN_P1, s->msg_length_profile[1]},
                {TIPC_NLA_STATS_MSG_LEN_P2, s->msg_length_profile[2]},
                {TIPC_NLA_STATS_MSG_LEN_P3, s->msg_length_profile[3]},
                {TIPC_NLA_STATS_MSG_LEN_P4, s->msg_length_profile[4]},
                {TIPC_NLA_STATS_MSG_LEN_P5, s->msg_length_profile[5]},
                {TIPC_NLA_STATS_MSG_LEN_P6, s->msg_length_profile[6]},
                {TIPC_NLA_STATS_RX_STATES, s->recv_states},
                {TIPC_NLA_STATS_RX_PROBES, s->recv_probes},
                {TIPC_NLA_STATS_RX_NACKS, s->recv_nacks},
                {TIPC_NLA_STATS_RX_DEFERRED, s->deferred_recv},
                {TIPC_NLA_STATS_TX_STATES, s->sent_states},
                {TIPC_NLA_STATS_TX_PROBES, s->sent_probes},
                {TIPC_NLA_STATS_TX_NACKS, s->sent_nacks},
                {TIPC_NLA_STATS_TX_ACKS, s->sent_acks},
                {TIPC_NLA_STATS_RETRANSMITTED, s->retransmitted},
                {TIPC_NLA_STATS_DUPLICATES, s->duplicates},
                {TIPC_NLA_STATS_LINK_CONGS, s->link_congs},
                {TIPC_NLA_STATS_MAX_QUEUE, s->max_queue_sz},
                {TIPC_NLA_STATS_AVG_QUEUE, s->queue_sz_counts ?
                        (s->accu_queue_sz / s->queue_sz_counts) : 0}
        };

        stats = nla_nest_start(skb, TIPC_NLA_LINK_STATS);
        if (!stats)
                return -EMSGSIZE;

        for (i = 0; i <  ARRAY_SIZE(map); i++)
                if (nla_put_u32(skb, map[i].key, map[i].val))
                        goto msg_full;

        nla_nest_end(skb, stats);

        return 0;
msg_full:
        nla_nest_cancel(skb, stats);

        return -EMSGSIZE;
}

/* Caller should hold appropriate locks to protect the link */
int __tipc_nl_add_link(struct net *net, struct tipc_nl_msg *msg,
                       struct tipc_link *link, int nlflags)
{
        int err;
        void *hdr;
        struct nlattr *attrs;
        struct nlattr *prop;
        struct tipc_net *tn = net_generic(net, tipc_net_id);

        hdr = genlmsg_put(msg->skb, msg->portid, msg->seq, &tipc_genl_family,
                          nlflags, TIPC_NL_LINK_GET);
        if (!hdr)
                return -EMSGSIZE;

        attrs = nla_nest_start(msg->skb, TIPC_NLA_LINK);
        if (!attrs)
                goto msg_full;

        if (nla_put_string(msg->skb, TIPC_NLA_LINK_NAME, link->name))
                goto attr_msg_full;
        if (nla_put_u32(msg->skb, TIPC_NLA_LINK_DEST,
                        tipc_cluster_mask(tn->own_addr)))
                goto attr_msg_full;
        if (nla_put_u32(msg->skb, TIPC_NLA_LINK_MTU, link->mtu))
                goto attr_msg_full;
        if (nla_put_u32(msg->skb, TIPC_NLA_LINK_RX, link->rcv_nxt))
                goto attr_msg_full;
        if (nla_put_u32(msg->skb, TIPC_NLA_LINK_TX, link->snd_nxt))
                goto attr_msg_full;

        if (tipc_link_is_up(link))
                if (nla_put_flag(msg->skb, TIPC_NLA_LINK_UP))
                        goto attr_msg_full;
        if (link->active)
                if (nla_put_flag(msg->skb, TIPC_NLA_LINK_ACTIVE))
                        goto attr_msg_full;

        prop = nla_nest_start(msg->skb, TIPC_NLA_LINK_PROP);
        if (!prop)
                goto attr_msg_full;
        if (nla_put_u32(msg->skb, TIPC_NLA_PROP_PRIO, link->priority))
                goto prop_msg_full;
        if (nla_put_u32(msg->skb, TIPC_NLA_PROP_TOL, link->tolerance))
                goto prop_msg_full;
        if (nla_put_u32(msg->skb, TIPC_NLA_PROP_WIN,
                        link->window))
                goto prop_msg_full;
        if (nla_put_u32(msg->skb, TIPC_NLA_PROP_PRIO, link->priority))
                goto prop_msg_full;
        nla_nest_end(msg->skb, prop);

        err = __tipc_nl_add_stats(msg->skb, &link->stats);
        if (err)
                goto attr_msg_full;

        nla_nest_end(msg->skb, attrs);
        genlmsg_end(msg->skb, hdr);

        return 0;

prop_msg_full:
        nla_nest_cancel(msg->skb, prop);
attr_msg_full:
        nla_nest_cancel(msg->skb, attrs);
msg_full:
        genlmsg_cancel(msg->skb, hdr);

        return -EMSGSIZE;
}

static int __tipc_nl_add_bc_link_stat(struct sk_buff *skb,
                                      struct tipc_stats *stats)
{
        int i;
        struct nlattr *nest;

        struct nla_map {
                __u32 key;
                __u32 val;
        };

        struct nla_map map[] = {
                {TIPC_NLA_STATS_RX_INFO, stats->recv_info},
                {TIPC_NLA_STATS_RX_FRAGMENTS, stats->recv_fragments},
                {TIPC_NLA_STATS_RX_FRAGMENTED, stats->recv_fragmented},
                {TIPC_NLA_STATS_RX_BUNDLES, stats->recv_bundles},
                {TIPC_NLA_STATS_RX_BUNDLED, stats->recv_bundled},
                {TIPC_NLA_STATS_TX_INFO, stats->sent_info},
                {TIPC_NLA_STATS_TX_FRAGMENTS, stats->sent_fragments},
                {TIPC_NLA_STATS_TX_FRAGMENTED, stats->sent_fragmented},
                {TIPC_NLA_STATS_TX_BUNDLES, stats->sent_bundles},
                {TIPC_NLA_STATS_TX_BUNDLED, stats->sent_bundled},
                {TIPC_NLA_STATS_RX_NACKS, stats->recv_nacks},
                {TIPC_NLA_STATS_RX_DEFERRED, stats->deferred_recv},
                {TIPC_NLA_STATS_TX_NACKS, stats->sent_nacks},
                {TIPC_NLA_STATS_TX_ACKS, stats->sent_acks},
                {TIPC_NLA_STATS_RETRANSMITTED, stats->retransmitted},
                {TIPC_NLA_STATS_DUPLICATES, stats->duplicates},
                {TIPC_NLA_STATS_LINK_CONGS, stats->link_congs},
                {TIPC_NLA_STATS_MAX_QUEUE, stats->max_queue_sz},
                {TIPC_NLA_STATS_AVG_QUEUE, stats->queue_sz_counts ?
                        (stats->accu_queue_sz / stats->queue_sz_counts) : 0}
        };

        nest = nla_nest_start(skb, TIPC_NLA_LINK_STATS);
        if (!nest)
                return -EMSGSIZE;

        for (i = 0; i <  ARRAY_SIZE(map); i++)
                if (nla_put_u32(skb, map[i].key, map[i].val))
                        goto msg_full;

        nla_nest_end(skb, nest);

        return 0;
msg_full:
        nla_nest_cancel(skb, nest);

        return -EMSGSIZE;
}

int tipc_nl_add_bc_link(struct net *net, struct tipc_nl_msg *msg)
{
        int err;
        void *hdr;
        struct nlattr *attrs;
        struct nlattr *prop;
        struct tipc_net *tn = net_generic(net, tipc_net_id);
        struct tipc_link *bcl = tn->bcl;

        if (!bcl)
                return 0;

        tipc_bcast_lock(net);

        hdr = genlmsg_put(msg->skb, msg->portid, msg->seq, &tipc_genl_family,
                          NLM_F_MULTI, TIPC_NL_LINK_GET);
        if (!hdr) {
                tipc_bcast_unlock(net);
                return -EMSGSIZE;
        }

        attrs = nla_nest_start(msg->skb, TIPC_NLA_LINK);
        if (!attrs)
                goto msg_full;

        /* The broadcast link is always up */
        if (nla_put_flag(msg->skb, TIPC_NLA_LINK_UP))
                goto attr_msg_full;

        if (nla_put_flag(msg->skb, TIPC_NLA_LINK_BROADCAST))
                goto attr_msg_full;
        if (nla_put_string(msg->skb, TIPC_NLA_LINK_NAME, bcl->name))
                goto attr_msg_full;
        if (nla_put_u32(msg->skb, TIPC_NLA_LINK_RX, bcl->rcv_nxt))
                goto attr_msg_full;
        if (nla_put_u32(msg->skb, TIPC_NLA_LINK_TX, bcl->snd_nxt))
                goto attr_msg_full;

        prop = nla_nest_start(msg->skb, TIPC_NLA_LINK_PROP);
        if (!prop)
                goto attr_msg_full;
        if (nla_put_u32(msg->skb, TIPC_NLA_PROP_WIN, bcl->window))
                goto prop_msg_full;
        nla_nest_end(msg->skb, prop);

        err = __tipc_nl_add_bc_link_stat(msg->skb, &bcl->stats);
        if (err)
                goto attr_msg_full;

        tipc_bcast_unlock(net);
        nla_nest_end(msg->skb, attrs);
        genlmsg_end(msg->skb, hdr);

        return 0;

prop_msg_full:
        nla_nest_cancel(msg->skb, prop);
attr_msg_full:
        nla_nest_cancel(msg->skb, attrs);
msg_full:
        tipc_bcast_unlock(net);
        genlmsg_cancel(msg->skb, hdr);

        return -EMSGSIZE;
}

void tipc_link_set_tolerance(struct tipc_link *l, u32 tol,
                             struct sk_buff_head *xmitq)
{
        l->tolerance = tol;
        tipc_link_build_proto_msg(l, STATE_MSG, 0, 0, tol, 0, xmitq);
}

void tipc_link_set_prio(struct tipc_link *l, u32 prio,
                        struct sk_buff_head *xmitq)
{
        l->priority = prio;
        tipc_link_build_proto_msg(l, STATE_MSG, 0, 0, 0, prio, xmitq);
}

void tipc_link_set_abort_limit(struct tipc_link *l, u32 limit)
{
        l->abort_limit = limit;
}