/*
 * net/tipc/link.c: TIPC link code
 *
 * Copyright (c) 1996-2007, 2012-2015, 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>

/*
 * Error message prefixes
 */
static const char *link_co_err = "Link tunneling error, ";
static const char *link_rst_msg = "Resetting link ";
static const char tipc_bclink_name[] = "broadcast-link";

static const struct nla_policy tipc_nl_link_policy[TIPC_NLA_LINK_MAX + 1] = {
        [TIPC_NLA_LINK_UNSPEC]          = { .type = NLA_UNSPEC },
        [TIPC_NLA_LINK_NAME] = {
                .type = NLA_STRING,
                .len = TIPC_MAX_LINK_NAME
        },
        [TIPC_NLA_LINK_MTU]             = { .type = NLA_U32 },
        [TIPC_NLA_LINK_BROADCAST]       = { .type = NLA_FLAG },
        [TIPC_NLA_LINK_UP]              = { .type = NLA_FLAG },
        [TIPC_NLA_LINK_ACTIVE]          = { .type = NLA_FLAG },
        [TIPC_NLA_LINK_PROP]            = { .type = NLA_NESTED },
        [TIPC_NLA_LINK_STATS]           = { .type = NLA_NESTED },
        [TIPC_NLA_LINK_RX]              = { .type = NLA_U32 },
        [TIPC_NLA_LINK_TX]              = { .type = NLA_U32 }
};

/* Properties valid for media, bearar and link */
static const struct nla_policy tipc_nl_prop_policy[TIPC_NLA_PROP_MAX + 1] = {
        [TIPC_NLA_PROP_UNSPEC]          = { .type = NLA_UNSPEC },
        [TIPC_NLA_PROP_PRIO]            = { .type = NLA_U32 },
        [TIPC_NLA_PROP_TOL]             = { .type = NLA_U32 },
        [TIPC_NLA_PROP_WIN]             = { .type = NLA_U32 }
};

/* 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)
/*
 * Out-of-range value for link session numbers
 */
#define WILDCARD_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_reset_statistics(struct tipc_link *l_ptr);
static void link_print(struct tipc_link *l_ptr, 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;
}

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;
}

static u32 link_own_addr(struct tipc_link *l)
{
        return msg_prevnode(l->pmsg);
}

/**
 * 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;
        struct tipc_msg *hdr;

        l = kzalloc(sizeof(*l), GFP_ATOMIC);
        if (!l)
                return false;
        *link = l;
        l->pmsg = (struct tipc_msg *)&l->proto_msg;
        hdr = l->pmsg;
        tipc_msg_init(ownnode, hdr, LINK_PROTOCOL, RESET_MSG, INT_H_SIZE, peer);
        msg_set_size(hdr, sizeof(l->proto_msg));
        msg_set_session(hdr, session);
        msg_set_bearer_id(hdr, l->bearer_id);

        /* 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((char *)msg_data(hdr), if_name);

        l->addr = peer;
        l->peer_caps = peer_caps;
        l->net = net;
        l->peer_session = WILDCARD_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 = link_own_addr(link);
        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)
{
        /* Link is down, accept any session */
        l->peer_session = WILDCARD_SESSION;

        /* If peer is up, it only accepts an incremented session number */
        msg_set_session(l->pmsg, msg_session(l->pmsg) + 1);

        /* Prepare for renewed mtu size negotiation */
        l->mtu = l->advertised_mtu;

        /* Clean up all queues and counters: */
        __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;
        link_reset_statistics(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))
                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)
                                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 ^ link_own_addr(l)) & 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;
}

/*
 * Send protocol message to the other endpoint.
 */
void tipc_link_proto_xmit(struct tipc_link *l, u32 msg_typ, int probe_msg,
                          u32 gap, u32 tolerance, u32 priority)
{
        struct sk_buff *skb = NULL;
        struct sk_buff_head xmitq;

        __skb_queue_head_init(&xmitq);
        tipc_link_build_proto_msg(l, msg_typ, probe_msg, gap,
                                  tolerance, priority, &xmitq);
        skb = __skb_dequeue(&xmitq);
        if (!skb)
                return;
        tipc_bearer_xmit_skb(l->net, l->bearer_id, skb, l->media_addr);
        l->rcv_unacked = 0;
}

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 = NULL;
        struct tipc_msg *hdr = l->pmsg;
        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;

        msg_set_type(hdr, mtyp);
        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);

        /* Compatibility: created msg must not be in sequence with pkt flow */
        msg_set_seqno(hdr, l->snd_nxt + U16_MAX / 2);

        if (mtyp == STATE_MSG) {
                if (!tipc_link_is_up(l))
                        return;

                /* Override rcvgap if there are packets in deferred queue */
                if (!skb_queue_empty(&l->deferdq))
                        rcvgap = buf_seqno(skb_peek(&l->deferdq)) - l->rcv_nxt;
                if (rcvgap) {
                        msg_set_seq_gap(hdr, rcvgap);
                        l->stats.sent_nacks++;
                }
                msg_set_probe(hdr, probe);
                if (probe)
                        l->stats.sent_probes++;
                l->stats.sent_states++;
                l->rcv_unacked = 0;
        } else {
                /* RESET_MSG or ACTIVATE_MSG */
                msg_set_max_pkt(hdr, l->advertised_mtu);
                msg_set_ack(hdr, l->rcv_nxt - 1);
                msg_set_next_sent(hdr, 1);
        }
        skb = tipc_buf_acquire(msg_size(hdr));
        if (!skb)
                return;
        skb_copy_to_linear_data(skb, hdr, msg_size(hdr));
        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, link_own_addr(l),
                              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(link_own_addr(l), &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 (link_own_addr(l) > 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 != WILDCARD_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, 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;

                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, link_own_addr(l), 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 == link_own_addr(l)) {
                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;
}

/* tipc_link_find_owner - locate owner node of link by link's name
 * @net: the applicable net namespace
 * @name: pointer to link name string
 * @bearer_id: pointer to index in 'node->links' array where the link was found.
 *
 * Returns pointer to node owning the link, or 0 if no matching link is found.
 */
static struct tipc_node *tipc_link_find_owner(struct net *net,
                                              const char *link_name,
                                              unsigned int *bearer_id)
{
        struct tipc_net *tn = net_generic(net, tipc_net_id);
        struct tipc_link *l_ptr;
        struct tipc_node *n_ptr;
        struct tipc_node *found_node = NULL;
        int i;

        *bearer_id = 0;
        rcu_read_lock();
        list_for_each_entry_rcu(n_ptr, &tn->node_list, list) {
                tipc_node_lock(n_ptr);
                for (i = 0; i < MAX_BEARERS; i++) {
                        l_ptr = n_ptr->links[i].link;
                        if (l_ptr && !strcmp(l_ptr->name, link_name)) {
                                *bearer_id = i;
                                found_node = n_ptr;
                                break;
                        }
                }
                tipc_node_unlock(n_ptr);
                if (found_node)
                        break;
        }
        rcu_read_unlock();

        return found_node;
}

/**
 * link_reset_statistics - reset link statistics
 * @l_ptr: pointer to link
 */
static void link_reset_statistics(struct tipc_link *l_ptr)
{
        memset(&l_ptr->stats, 0, sizeof(l_ptr->stats));
        l_ptr->stats.sent_info = l_ptr->snd_nxt;
        l_ptr->stats.recv_info = l_ptr->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;
}

int tipc_nl_link_set(struct sk_buff *skb, struct genl_info *info)
{
        int err;
        int res = 0;
        int bearer_id;
        char *name;
        struct tipc_link *link;
        struct tipc_node *node;
        struct nlattr *attrs[TIPC_NLA_LINK_MAX + 1];
        struct net *net = sock_net(skb->sk);

        if (!info->attrs[TIPC_NLA_LINK])
                return -EINVAL;

        err = nla_parse_nested(attrs, TIPC_NLA_LINK_MAX,
                               info->attrs[TIPC_NLA_LINK],
                               tipc_nl_link_policy);
        if (err)
                return err;

        if (!attrs[TIPC_NLA_LINK_NAME])
                return -EINVAL;

        name = nla_data(attrs[TIPC_NLA_LINK_NAME]);

        if (strcmp(name, tipc_bclink_name) == 0)
                return tipc_nl_bc_link_set(net, attrs);

        node = tipc_link_find_owner(net, name, &bearer_id);
        if (!node)
                return -EINVAL;

        tipc_node_lock(node);

        link = node->links[bearer_id].link;
        if (!link) {
                res = -EINVAL;
                goto out;
        }

        if (attrs[TIPC_NLA_LINK_PROP]) {
                struct nlattr *props[TIPC_NLA_PROP_MAX + 1];

                err = tipc_nl_parse_link_prop(attrs[TIPC_NLA_LINK_PROP],
                                              props);
                if (err) {
                        res = err;
                        goto out;
                }

                if (props[TIPC_NLA_PROP_TOL]) {
                        u32 tol;

                        tol = nla_get_u32(props[TIPC_NLA_PROP_TOL]);
                        link->tolerance = tol;
                        tipc_link_proto_xmit(link, STATE_MSG, 0, 0, tol, 0);
                }
                if (props[TIPC_NLA_PROP_PRIO]) {
                        u32 prio;

                        prio = nla_get_u32(props[TIPC_NLA_PROP_PRIO]);
                        link->priority = prio;
                        tipc_link_proto_xmit(link, STATE_MSG, 0, 0, 0, prio);
                }
                if (props[TIPC_NLA_PROP_WIN]) {
                        u32 win;

                        win = nla_get_u32(props[TIPC_NLA_PROP_WIN]);
                        tipc_link_set_queue_limits(link, win);
                }
        }

out:
        tipc_node_unlock(node);

        return res;
}

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 */
static 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;
}

/* Caller should hold node lock  */
static int __tipc_nl_add_node_links(struct net *net, struct tipc_nl_msg *msg,
                                    struct tipc_node *node, u32 *prev_link)
{
        u32 i;
        int err;

        for (i = *prev_link; i < MAX_BEARERS; i++) {
                *prev_link = i;

                if (!node->links[i].link)
                        continue;

                err = __tipc_nl_add_link(net, msg,
                                         node->links[i].link, NLM_F_MULTI);
                if (err)
                        return err;
        }
        *prev_link = 0;

        return 0;
}

int tipc_nl_link_dump(struct sk_buff *skb, struct netlink_callback *cb)
{
        struct net *net = sock_net(skb->sk);
        struct tipc_net *tn = net_generic(net, tipc_net_id);
        struct tipc_node *node;
        struct tipc_nl_msg msg;
        u32 prev_node = cb->args[0];
        u32 prev_link = cb->args[1];
        int done = cb->args[2];
        int err;

        if (done)
                return 0;

        msg.skb = skb;
        msg.portid = NETLINK_CB(cb->skb).portid;
        msg.seq = cb->nlh->nlmsg_seq;

        rcu_read_lock();
        if (prev_node) {
                node = tipc_node_find(net, prev_node);
                if (!node) {
                        /* We never set seq or call nl_dump_check_consistent()
                         * this means that setting prev_seq here will cause the
                         * consistence check to fail in the netlink callback
                         * handler. Resulting in the last NLMSG_DONE message
                         * having the NLM_F_DUMP_INTR flag set.
                         */
                        cb->prev_seq = 1;
                        goto out;
                }
                tipc_node_put(node);

                list_for_each_entry_continue_rcu(node, &tn->node_list,
                                                 list) {
                        tipc_node_lock(node);
                        err = __tipc_nl_add_node_links(net, &msg, node,
                                                       &prev_link);
                        tipc_node_unlock(node);
                        if (err)
                                goto out;

                        prev_node = node->addr;
                }
        } else {
                err = tipc_nl_add_bc_link(net, &msg);
                if (err)
                        goto out;

                list_for_each_entry_rcu(node, &tn->node_list, list) {
                        tipc_node_lock(node);
                        err = __tipc_nl_add_node_links(net, &msg, node,
                                                       &prev_link);
                        tipc_node_unlock(node);
                        if (err)
                                goto out;

                        prev_node = node->addr;
                }
        }
        done = 1;
out:
        rcu_read_unlock();

        cb->args[0] = prev_node;
        cb->args[1] = prev_link;
        cb->args[2] = done;

        return skb->len;
}

int tipc_nl_link_get(struct sk_buff *skb, struct genl_info *info)
{
        struct net *net = genl_info_net(info);
        struct tipc_nl_msg msg;
        char *name;
        int err;

        msg.portid = info->snd_portid;
        msg.seq = info->snd_seq;

        if (!info->attrs[TIPC_NLA_LINK_NAME])
                return -EINVAL;
        name = nla_data(info->attrs[TIPC_NLA_LINK_NAME]);

        msg.skb = nlmsg_new(NLMSG_GOODSIZE, GFP_KERNEL);
        if (!msg.skb)
                return -ENOMEM;

        if (strcmp(name, tipc_bclink_name) == 0) {
                err = tipc_nl_add_bc_link(net, &msg);
                if (err) {
                        nlmsg_free(msg.skb);
                        return err;
                }
        } else {
                int bearer_id;
                struct tipc_node *node;
                struct tipc_link *link;

                node = tipc_link_find_owner(net, name, &bearer_id);
                if (!node)
                        return -EINVAL;

                tipc_node_lock(node);
                link = node->links[bearer_id].link;
                if (!link) {
                        tipc_node_unlock(node);
                        nlmsg_free(msg.skb);
                        return -EINVAL;
                }

                err = __tipc_nl_add_link(net, &msg, link, 0);
                tipc_node_unlock(node);
                if (err) {
                        nlmsg_free(msg.skb);
                        return err;
                }
        }

        return genlmsg_reply(msg.skb, info);
}

int tipc_nl_link_reset_stats(struct sk_buff *skb, struct genl_info *info)
{
        int err;
        char *link_name;
        unsigned int bearer_id;
        struct tipc_link *link;
        struct tipc_node *node;
        struct nlattr *attrs[TIPC_NLA_LINK_MAX + 1];
        struct net *net = sock_net(skb->sk);

        if (!info->attrs[TIPC_NLA_LINK])
                return -EINVAL;

        err = nla_parse_nested(attrs, TIPC_NLA_LINK_MAX,
                               info->attrs[TIPC_NLA_LINK],
                               tipc_nl_link_policy);
        if (err)
                return err;

        if (!attrs[TIPC_NLA_LINK_NAME])
                return -EINVAL;

        link_name = nla_data(attrs[TIPC_NLA_LINK_NAME]);

        if (strcmp(link_name, tipc_bclink_name) == 0) {
                err = tipc_bclink_reset_stats(net);
                if (err)
                        return err;
                return 0;
        }

        node = tipc_link_find_owner(net, link_name, &bearer_id);
        if (!node)
                return -EINVAL;

        tipc_node_lock(node);

        link = node->links[bearer_id].link;
        if (!link) {
                tipc_node_unlock(node);
                return -EINVAL;
        }

        link_reset_statistics(link);

        tipc_node_unlock(node);

        return 0;
}