Merge tag 'mfd-for-linus-4.5' of git://git.kernel.org/pub/scm/linux/kernel/git/lee/mfd

[mirror_ubuntu-zesty-kernel.git] / net / tipc / node.c

/*
 * net/tipc/node.c: TIPC node management routines
 *
 * Copyright (c) 2000-2006, 2012-2015, Ericsson AB
 * Copyright (c) 2005-2006, 2010-2014, 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 "link.h"
#include "node.h"
#include "name_distr.h"
#include "socket.h"
#include "bcast.h"
#include "discover.h"

#define INVALID_NODE_SIG        0x10000

/* Flags used to take different actions according to flag type
 * TIPC_NOTIFY_NODE_DOWN: notify node is down
 * TIPC_NOTIFY_NODE_UP: notify node is up
 * TIPC_DISTRIBUTE_NAME: publish or withdraw link state name type
 */
enum {
        TIPC_NOTIFY_NODE_DOWN           = (1 << 3),
        TIPC_NOTIFY_NODE_UP             = (1 << 4),
        TIPC_NOTIFY_LINK_UP             = (1 << 6),
        TIPC_NOTIFY_LINK_DOWN           = (1 << 7)
};

struct tipc_link_entry {
        struct tipc_link *link;
        spinlock_t lock; /* per link */
        u32 mtu;
        struct sk_buff_head inputq;
        struct tipc_media_addr maddr;
};

struct tipc_bclink_entry {
        struct tipc_link *link;
        struct sk_buff_head inputq1;
        struct sk_buff_head arrvq;
        struct sk_buff_head inputq2;
        struct sk_buff_head namedq;
};

/**
 * struct tipc_node - TIPC node structure
 * @addr: network address of node
 * @ref: reference counter to node object
 * @lock: rwlock governing access to structure
 * @net: the applicable net namespace
 * @hash: links to adjacent nodes in unsorted hash chain
 * @inputq: pointer to input queue containing messages for msg event
 * @namedq: pointer to name table input queue with name table messages
 * @active_links: bearer ids of active links, used as index into links[] array
 * @links: array containing references to all links to node
 * @action_flags: bit mask of different types of node actions
 * @state: connectivity state vs peer node
 * @sync_point: sequence number where synch/failover is finished
 * @list: links to adjacent nodes in sorted list of cluster's nodes
 * @working_links: number of working links to node (both active and standby)
 * @link_cnt: number of links to node
 * @capabilities: bitmap, indicating peer node's functional capabilities
 * @signature: node instance identifier
 * @link_id: local and remote bearer ids of changing link, if any
 * @publ_list: list of publications
 * @rcu: rcu struct for tipc_node
 */
struct tipc_node {
        u32 addr;
        struct kref kref;
        rwlock_t lock;
        struct net *net;
        struct hlist_node hash;
        int active_links[2];
        struct tipc_link_entry links[MAX_BEARERS];
        struct tipc_bclink_entry bc_entry;
        int action_flags;
        struct list_head list;
        int state;
        u16 sync_point;
        int link_cnt;
        u16 working_links;
        u16 capabilities;
        u32 signature;
        u32 link_id;
        struct list_head publ_list;
        struct list_head conn_sks;
        unsigned long keepalive_intv;
        struct timer_list timer;
        struct rcu_head rcu;
};

/* Node FSM states and events:
 */
enum {
        SELF_DOWN_PEER_DOWN    = 0xdd,
        SELF_UP_PEER_UP        = 0xaa,
        SELF_DOWN_PEER_LEAVING = 0xd1,
        SELF_UP_PEER_COMING    = 0xac,
        SELF_COMING_PEER_UP    = 0xca,
        SELF_LEAVING_PEER_DOWN = 0x1d,
        NODE_FAILINGOVER       = 0xf0,
        NODE_SYNCHING          = 0xcc
};

enum {
        SELF_ESTABL_CONTACT_EVT = 0xece,
        SELF_LOST_CONTACT_EVT   = 0x1ce,
        PEER_ESTABL_CONTACT_EVT = 0x9ece,
        PEER_LOST_CONTACT_EVT   = 0x91ce,
        NODE_FAILOVER_BEGIN_EVT = 0xfbe,
        NODE_FAILOVER_END_EVT   = 0xfee,
        NODE_SYNCH_BEGIN_EVT    = 0xcbe,
        NODE_SYNCH_END_EVT      = 0xcee
};

static void __tipc_node_link_down(struct tipc_node *n, int *bearer_id,
                                  struct sk_buff_head *xmitq,
                                  struct tipc_media_addr **maddr);
static void tipc_node_link_down(struct tipc_node *n, int bearer_id,
                                bool delete);
static void node_lost_contact(struct tipc_node *n, struct sk_buff_head *inputq);
static void tipc_node_delete(struct tipc_node *node);
static void tipc_node_timeout(unsigned long data);
static void tipc_node_fsm_evt(struct tipc_node *n, int evt);
static struct tipc_node *tipc_node_find(struct net *net, u32 addr);
static void tipc_node_put(struct tipc_node *node);
static bool tipc_node_is_up(struct tipc_node *n);

struct tipc_sock_conn {
        u32 port;
        u32 peer_port;
        u32 peer_node;
        struct list_head list;
};

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 }
};

static const struct nla_policy tipc_nl_node_policy[TIPC_NLA_NODE_MAX + 1] = {
        [TIPC_NLA_NODE_UNSPEC]          = { .type = NLA_UNSPEC },
        [TIPC_NLA_NODE_ADDR]            = { .type = NLA_U32 },
        [TIPC_NLA_NODE_UP]              = { .type = NLA_FLAG }
};

static struct tipc_link *node_active_link(struct tipc_node *n, int sel)
{
        int bearer_id = n->active_links[sel & 1];

        if (unlikely(bearer_id == INVALID_BEARER_ID))
                return NULL;

        return n->links[bearer_id].link;
}

int tipc_node_get_mtu(struct net *net, u32 addr, u32 sel)
{
        struct tipc_node *n;
        int bearer_id;
        unsigned int mtu = MAX_MSG_SIZE;

        n = tipc_node_find(net, addr);
        if (unlikely(!n))
                return mtu;

        bearer_id = n->active_links[sel & 1];
        if (likely(bearer_id != INVALID_BEARER_ID))
                mtu = n->links[bearer_id].mtu;
        tipc_node_put(n);
        return mtu;
}
/*
 * A trivial power-of-two bitmask technique is used for speed, since this
 * operation is done for every incoming TIPC packet. The number of hash table
 * entries has been chosen so that no hash chain exceeds 8 nodes and will
 * usually be much smaller (typically only a single node).
 */
static unsigned int tipc_hashfn(u32 addr)
{
        return addr & (NODE_HTABLE_SIZE - 1);
}

static void tipc_node_kref_release(struct kref *kref)
{
        struct tipc_node *node = container_of(kref, struct tipc_node, kref);

        tipc_node_delete(node);
}

static void tipc_node_put(struct tipc_node *node)
{
        kref_put(&node->kref, tipc_node_kref_release);
}

static void tipc_node_get(struct tipc_node *node)
{
        kref_get(&node->kref);
}

/*
 * tipc_node_find - locate specified node object, if it exists
 */
static struct tipc_node *tipc_node_find(struct net *net, u32 addr)
{
        struct tipc_net *tn = net_generic(net, tipc_net_id);
        struct tipc_node *node;

        if (unlikely(!in_own_cluster_exact(net, addr)))
                return NULL;

        rcu_read_lock();
        hlist_for_each_entry_rcu(node, &tn->node_htable[tipc_hashfn(addr)],
                                 hash) {
                if (node->addr == addr) {
                        tipc_node_get(node);
                        rcu_read_unlock();
                        return node;
                }
        }
        rcu_read_unlock();
        return NULL;
}

static void tipc_node_read_lock(struct tipc_node *n)
{
        read_lock_bh(&n->lock);
}

static void tipc_node_read_unlock(struct tipc_node *n)
{
        read_unlock_bh(&n->lock);
}

static void tipc_node_write_lock(struct tipc_node *n)
{
        write_lock_bh(&n->lock);
}

static void tipc_node_write_unlock(struct tipc_node *n)
{
        struct net *net = n->net;
        u32 addr = 0;
        u32 flags = n->action_flags;
        u32 link_id = 0;
        struct list_head *publ_list;

        if (likely(!flags)) {
                write_unlock_bh(&n->lock);
                return;
        }

        addr = n->addr;
        link_id = n->link_id;
        publ_list = &n->publ_list;

        n->action_flags &= ~(TIPC_NOTIFY_NODE_DOWN | TIPC_NOTIFY_NODE_UP |
                             TIPC_NOTIFY_LINK_DOWN | TIPC_NOTIFY_LINK_UP);

        write_unlock_bh(&n->lock);

        if (flags & TIPC_NOTIFY_NODE_DOWN)
                tipc_publ_notify(net, publ_list, addr);

        if (flags & TIPC_NOTIFY_NODE_UP)
                tipc_named_node_up(net, addr);

        if (flags & TIPC_NOTIFY_LINK_UP)
                tipc_nametbl_publish(net, TIPC_LINK_STATE, addr, addr,
                                     TIPC_NODE_SCOPE, link_id, addr);

        if (flags & TIPC_NOTIFY_LINK_DOWN)
                tipc_nametbl_withdraw(net, TIPC_LINK_STATE, addr,
                                      link_id, addr);
}

struct tipc_node *tipc_node_create(struct net *net, u32 addr, u16 capabilities)
{
        struct tipc_net *tn = net_generic(net, tipc_net_id);
        struct tipc_node *n, *temp_node;
        int i;

        spin_lock_bh(&tn->node_list_lock);
        n = tipc_node_find(net, addr);
        if (n)
                goto exit;
        n = kzalloc(sizeof(*n), GFP_ATOMIC);
        if (!n) {
                pr_warn("Node creation failed, no memory\n");
                goto exit;
        }
        n->addr = addr;
        n->net = net;
        n->capabilities = capabilities;
        kref_init(&n->kref);
        rwlock_init(&n->lock);
        INIT_HLIST_NODE(&n->hash);
        INIT_LIST_HEAD(&n->list);
        INIT_LIST_HEAD(&n->publ_list);
        INIT_LIST_HEAD(&n->conn_sks);
        skb_queue_head_init(&n->bc_entry.namedq);
        skb_queue_head_init(&n->bc_entry.inputq1);
        __skb_queue_head_init(&n->bc_entry.arrvq);
        skb_queue_head_init(&n->bc_entry.inputq2);
        for (i = 0; i < MAX_BEARERS; i++)
                spin_lock_init(&n->links[i].lock);
        hlist_add_head_rcu(&n->hash, &tn->node_htable[tipc_hashfn(addr)]);
        list_for_each_entry_rcu(temp_node, &tn->node_list, list) {
                if (n->addr < temp_node->addr)
                        break;
        }
        list_add_tail_rcu(&n->list, &temp_node->list);
        n->state = SELF_DOWN_PEER_LEAVING;
        n->signature = INVALID_NODE_SIG;
        n->active_links[0] = INVALID_BEARER_ID;
        n->active_links[1] = INVALID_BEARER_ID;
        if (!tipc_link_bc_create(net, tipc_own_addr(net), n->addr,
                                 U16_MAX,
                                 tipc_link_window(tipc_bc_sndlink(net)),
                                 n->capabilities,
                                 &n->bc_entry.inputq1,
                                 &n->bc_entry.namedq,
                                 tipc_bc_sndlink(net),
                                 &n->bc_entry.link)) {
                pr_warn("Broadcast rcv link creation failed, no memory\n");
                kfree(n);
                n = NULL;
                goto exit;
        }
        tipc_node_get(n);
        setup_timer(&n->timer, tipc_node_timeout, (unsigned long)n);
        n->keepalive_intv = U32_MAX;
exit:
        spin_unlock_bh(&tn->node_list_lock);
        return n;
}

static void tipc_node_calculate_timer(struct tipc_node *n, struct tipc_link *l)
{
        unsigned long tol = tipc_link_tolerance(l);
        unsigned long intv = ((tol / 4) > 500) ? 500 : tol / 4;
        unsigned long keepalive_intv = msecs_to_jiffies(intv);

        /* Link with lowest tolerance determines timer interval */
        if (keepalive_intv < n->keepalive_intv)
                n->keepalive_intv = keepalive_intv;

        /* Ensure link's abort limit corresponds to current interval */
        tipc_link_set_abort_limit(l, tol / jiffies_to_msecs(n->keepalive_intv));
}

static void tipc_node_delete(struct tipc_node *node)
{
        list_del_rcu(&node->list);
        hlist_del_rcu(&node->hash);
        kfree(node->bc_entry.link);
        kfree_rcu(node, rcu);
}

void tipc_node_stop(struct net *net)
{
        struct tipc_net *tn = net_generic(net, tipc_net_id);
        struct tipc_node *node, *t_node;

        spin_lock_bh(&tn->node_list_lock);
        list_for_each_entry_safe(node, t_node, &tn->node_list, list) {
                if (del_timer(&node->timer))
                        tipc_node_put(node);
                tipc_node_put(node);
        }
        spin_unlock_bh(&tn->node_list_lock);
}

void tipc_node_subscribe(struct net *net, struct list_head *subscr, u32 addr)
{
        struct tipc_node *n;

        if (in_own_node(net, addr))
                return;

        n = tipc_node_find(net, addr);
        if (!n) {
                pr_warn("Node subscribe rejected, unknown node 0x%x\n", addr);
                return;
        }
        tipc_node_write_lock(n);
        list_add_tail(subscr, &n->publ_list);
        tipc_node_write_unlock(n);
        tipc_node_put(n);
}

void tipc_node_unsubscribe(struct net *net, struct list_head *subscr, u32 addr)
{
        struct tipc_node *n;

        if (in_own_node(net, addr))
                return;

        n = tipc_node_find(net, addr);
        if (!n) {
                pr_warn("Node unsubscribe rejected, unknown node 0x%x\n", addr);
                return;
        }
        tipc_node_write_lock(n);
        list_del_init(subscr);
        tipc_node_write_unlock(n);
        tipc_node_put(n);
}

int tipc_node_add_conn(struct net *net, u32 dnode, u32 port, u32 peer_port)
{
        struct tipc_node *node;
        struct tipc_sock_conn *conn;
        int err = 0;

        if (in_own_node(net, dnode))
                return 0;

        node = tipc_node_find(net, dnode);
        if (!node) {
                pr_warn("Connecting sock to node 0x%x failed\n", dnode);
                return -EHOSTUNREACH;
        }
        conn = kmalloc(sizeof(*conn), GFP_ATOMIC);
        if (!conn) {
                err = -EHOSTUNREACH;
                goto exit;
        }
        conn->peer_node = dnode;
        conn->port = port;
        conn->peer_port = peer_port;

        tipc_node_write_lock(node);
        list_add_tail(&conn->list, &node->conn_sks);
        tipc_node_write_unlock(node);
exit:
        tipc_node_put(node);
        return err;
}

void tipc_node_remove_conn(struct net *net, u32 dnode, u32 port)
{
        struct tipc_node *node;
        struct tipc_sock_conn *conn, *safe;

        if (in_own_node(net, dnode))
                return;

        node = tipc_node_find(net, dnode);
        if (!node)
                return;

        tipc_node_write_lock(node);
        list_for_each_entry_safe(conn, safe, &node->conn_sks, list) {
                if (port != conn->port)
                        continue;
                list_del(&conn->list);
                kfree(conn);
        }
        tipc_node_write_unlock(node);
        tipc_node_put(node);
}

/* tipc_node_timeout - handle expiration of node timer
 */
static void tipc_node_timeout(unsigned long data)
{
        struct tipc_node *n = (struct tipc_node *)data;
        struct tipc_link_entry *le;
        struct sk_buff_head xmitq;
        int bearer_id;
        int rc = 0;

        __skb_queue_head_init(&xmitq);

        for (bearer_id = 0; bearer_id < MAX_BEARERS; bearer_id++) {
                tipc_node_read_lock(n);
                le = &n->links[bearer_id];
                spin_lock_bh(&le->lock);
                if (le->link) {
                        /* Link tolerance may change asynchronously: */
                        tipc_node_calculate_timer(n, le->link);
                        rc = tipc_link_timeout(le->link, &xmitq);
                }
                spin_unlock_bh(&le->lock);
                tipc_node_read_unlock(n);
                tipc_bearer_xmit(n->net, bearer_id, &xmitq, &le->maddr);
                if (rc & TIPC_LINK_DOWN_EVT)
                        tipc_node_link_down(n, bearer_id, false);
        }
        if (!mod_timer(&n->timer, jiffies + n->keepalive_intv))
                tipc_node_get(n);
        tipc_node_put(n);
}

/**
 * __tipc_node_link_up - handle addition of link
 * Node lock must be held by caller
 * Link becomes active (alone or shared) or standby, depending on its priority.
 */
static void __tipc_node_link_up(struct tipc_node *n, int bearer_id,
                                struct sk_buff_head *xmitq)
{
        int *slot0 = &n->active_links[0];
        int *slot1 = &n->active_links[1];
        struct tipc_link *ol = node_active_link(n, 0);
        struct tipc_link *nl = n->links[bearer_id].link;

        if (!nl)
                return;

        tipc_link_fsm_evt(nl, LINK_ESTABLISH_EVT);
        if (!tipc_link_is_up(nl))
                return;

        n->working_links++;
        n->action_flags |= TIPC_NOTIFY_LINK_UP;
        n->link_id = tipc_link_id(nl);

        /* Leave room for tunnel header when returning 'mtu' to users: */
        n->links[bearer_id].mtu = tipc_link_mtu(nl) - INT_H_SIZE;

        tipc_bearer_add_dest(n->net, bearer_id, n->addr);
        tipc_bcast_inc_bearer_dst_cnt(n->net, bearer_id);

        pr_debug("Established link <%s> on network plane %c\n",
                 tipc_link_name(nl), tipc_link_plane(nl));

        /* First link? => give it both slots */
        if (!ol) {
                *slot0 = bearer_id;
                *slot1 = bearer_id;
                tipc_node_fsm_evt(n, SELF_ESTABL_CONTACT_EVT);
                n->action_flags |= TIPC_NOTIFY_NODE_UP;
                tipc_bcast_add_peer(n->net, nl, xmitq);
                return;
        }

        /* Second link => redistribute slots */
        if (tipc_link_prio(nl) > tipc_link_prio(ol)) {
                pr_debug("Old link <%s> becomes standby\n", tipc_link_name(ol));
                *slot0 = bearer_id;
                *slot1 = bearer_id;
                tipc_link_set_active(nl, true);
                tipc_link_set_active(ol, false);
        } else if (tipc_link_prio(nl) == tipc_link_prio(ol)) {
                tipc_link_set_active(nl, true);
                *slot1 = bearer_id;
        } else {
                pr_debug("New link <%s> is standby\n", tipc_link_name(nl));
        }

        /* Prepare synchronization with first link */
        tipc_link_tnl_prepare(ol, nl, SYNCH_MSG, xmitq);
}

/**
 * tipc_node_link_up - handle addition of link
 *
 * Link becomes active (alone or shared) or standby, depending on its priority.
 */
static void tipc_node_link_up(struct tipc_node *n, int bearer_id,
                              struct sk_buff_head *xmitq)
{
        tipc_node_write_lock(n);
        __tipc_node_link_up(n, bearer_id, xmitq);
        tipc_node_write_unlock(n);
}

/**
 * __tipc_node_link_down - handle loss of link
 */
static void __tipc_node_link_down(struct tipc_node *n, int *bearer_id,
                                  struct sk_buff_head *xmitq,
                                  struct tipc_media_addr **maddr)
{
        struct tipc_link_entry *le = &n->links[*bearer_id];
        int *slot0 = &n->active_links[0];
        int *slot1 = &n->active_links[1];
        int i, highest = 0, prio;
        struct tipc_link *l, *_l, *tnl;

        l = n->links[*bearer_id].link;
        if (!l || tipc_link_is_reset(l))
                return;

        n->working_links--;
        n->action_flags |= TIPC_NOTIFY_LINK_DOWN;
        n->link_id = tipc_link_id(l);

        tipc_bearer_remove_dest(n->net, *bearer_id, n->addr);

        pr_debug("Lost link <%s> on network plane %c\n",
                 tipc_link_name(l), tipc_link_plane(l));

        /* Select new active link if any available */
        *slot0 = INVALID_BEARER_ID;
        *slot1 = INVALID_BEARER_ID;
        for (i = 0; i < MAX_BEARERS; i++) {
                _l = n->links[i].link;
                if (!_l || !tipc_link_is_up(_l))
                        continue;
                if (_l == l)
                        continue;
                prio = tipc_link_prio(_l);
                if (prio < highest)
                        continue;
                if (prio > highest) {
                        highest = prio;
                        *slot0 = i;
                        *slot1 = i;
                        continue;
                }
                *slot1 = i;
        }

        if (!tipc_node_is_up(n)) {
                if (tipc_link_peer_is_down(l))
                        tipc_node_fsm_evt(n, PEER_LOST_CONTACT_EVT);
                tipc_node_fsm_evt(n, SELF_LOST_CONTACT_EVT);
                tipc_link_fsm_evt(l, LINK_RESET_EVT);
                tipc_link_reset(l);
                tipc_link_build_reset_msg(l, xmitq);
                *maddr = &n->links[*bearer_id].maddr;
                node_lost_contact(n, &le->inputq);
                tipc_bcast_dec_bearer_dst_cnt(n->net, *bearer_id);
                return;
        }
        tipc_bcast_dec_bearer_dst_cnt(n->net, *bearer_id);

        /* There is still a working link => initiate failover */
        *bearer_id = n->active_links[0];
        tnl = n->links[*bearer_id].link;
        tipc_link_fsm_evt(tnl, LINK_SYNCH_END_EVT);
        tipc_node_fsm_evt(n, NODE_SYNCH_END_EVT);
        n->sync_point = tipc_link_rcv_nxt(tnl) + (U16_MAX / 2 - 1);
        tipc_link_tnl_prepare(l, tnl, FAILOVER_MSG, xmitq);
        tipc_link_reset(l);
        tipc_link_fsm_evt(l, LINK_RESET_EVT);
        tipc_link_fsm_evt(l, LINK_FAILOVER_BEGIN_EVT);
        tipc_node_fsm_evt(n, NODE_FAILOVER_BEGIN_EVT);
        *maddr = &n->links[*bearer_id].maddr;
}

static void tipc_node_link_down(struct tipc_node *n, int bearer_id, bool delete)
{
        struct tipc_link_entry *le = &n->links[bearer_id];
        struct tipc_link *l = le->link;
        struct tipc_media_addr *maddr;
        struct sk_buff_head xmitq;

        if (!l)
                return;

        __skb_queue_head_init(&xmitq);

        tipc_node_write_lock(n);
        if (!tipc_link_is_establishing(l)) {
                __tipc_node_link_down(n, &bearer_id, &xmitq, &maddr);
                if (delete) {
                        kfree(l);
                        le->link = NULL;
                        n->link_cnt--;
                }
        } else {
                /* Defuse pending tipc_node_link_up() */
                tipc_link_fsm_evt(l, LINK_RESET_EVT);
        }
        tipc_node_write_unlock(n);
        tipc_bearer_xmit(n->net, bearer_id, &xmitq, maddr);
        tipc_sk_rcv(n->net, &le->inputq);
}

static bool tipc_node_is_up(struct tipc_node *n)
{
        return n->active_links[0] != INVALID_BEARER_ID;
}

void tipc_node_check_dest(struct net *net, u32 onode,
                          struct tipc_bearer *b,
                          u16 capabilities, u32 signature,
                          struct tipc_media_addr *maddr,
                          bool *respond, bool *dupl_addr)
{
        struct tipc_node *n;
        struct tipc_link *l;
        struct tipc_link_entry *le;
        bool addr_match = false;
        bool sign_match = false;
        bool link_up = false;
        bool accept_addr = false;
        bool reset = true;
        char *if_name;

        *dupl_addr = false;
        *respond = false;

        n = tipc_node_create(net, onode, capabilities);
        if (!n)
                return;

        tipc_node_write_lock(n);

        le = &n->links[b->identity];

        /* Prepare to validate requesting node's signature and media address */
        l = le->link;
        link_up = l && tipc_link_is_up(l);
        addr_match = l && !memcmp(&le->maddr, maddr, sizeof(*maddr));
        sign_match = (signature == n->signature);

        /* These three flags give us eight permutations: */

        if (sign_match && addr_match && link_up) {
                /* All is fine. Do nothing. */
                reset = false;
        } else if (sign_match && addr_match && !link_up) {
                /* Respond. The link will come up in due time */
                *respond = true;
        } else if (sign_match && !addr_match && link_up) {
                /* Peer has changed i/f address without rebooting.
                 * If so, the link will reset soon, and the next
                 * discovery will be accepted. So we can ignore it.
                 * It may also be an cloned or malicious peer having
                 * chosen the same node address and signature as an
                 * existing one.
                 * Ignore requests until the link goes down, if ever.
                 */
                *dupl_addr = true;
        } else if (sign_match && !addr_match && !link_up) {
                /* Peer link has changed i/f address without rebooting.
                 * It may also be a cloned or malicious peer; we can't
                 * distinguish between the two.
                 * The signature is correct, so we must accept.
                 */
                accept_addr = true;
                *respond = true;
        } else if (!sign_match && addr_match && link_up) {
                /* Peer node rebooted. Two possibilities:
                 *  - Delayed re-discovery; this link endpoint has already
                 *    reset and re-established contact with the peer, before
                 *    receiving a discovery message from that node.
                 *    (The peer happened to receive one from this node first).
                 *  - The peer came back so fast that our side has not
                 *    discovered it yet. Probing from this side will soon
                 *    reset the link, since there can be no working link
                 *    endpoint at the peer end, and the link will re-establish.
                 *  Accept the signature, since it comes from a known peer.
                 */
                n->signature = signature;
        } else if (!sign_match && addr_match && !link_up) {
                /*  The peer node has rebooted.
                 *  Accept signature, since it is a known peer.
                 */
                n->signature = signature;
                *respond = true;
        } else if (!sign_match && !addr_match && link_up) {
                /* Peer rebooted with new address, or a new/duplicate peer.
                 * Ignore until the link goes down, if ever.
                 */
                *dupl_addr = true;
        } else if (!sign_match && !addr_match && !link_up) {
                /* Peer rebooted with new address, or it is a new peer.
                 * Accept signature and address.
                 */
                n->signature = signature;
                accept_addr = true;
                *respond = true;
        }

        if (!accept_addr)
                goto exit;

        /* Now create new link if not already existing */
        if (!l) {
                if (n->link_cnt == 2) {
                        pr_warn("Cannot establish 3rd link to %x\n", n->addr);
                        goto exit;
                }
                if_name = strchr(b->name, ':') + 1;
                if (!tipc_link_create(net, if_name, b->identity, b->tolerance,
                                      b->net_plane, b->mtu, b->priority,
                                      b->window, mod(tipc_net(net)->random),
                                      tipc_own_addr(net), onode,
                                      n->capabilities,
                                      tipc_bc_sndlink(n->net), n->bc_entry.link,
                                      &le->inputq,
                                      &n->bc_entry.namedq, &l)) {
                        *respond = false;
                        goto exit;
                }
                tipc_link_reset(l);
                tipc_link_fsm_evt(l, LINK_RESET_EVT);
                if (n->state == NODE_FAILINGOVER)
                        tipc_link_fsm_evt(l, LINK_FAILOVER_BEGIN_EVT);
                le->link = l;
                n->link_cnt++;
                tipc_node_calculate_timer(n, l);
                if (n->link_cnt == 1)
                        if (!mod_timer(&n->timer, jiffies + n->keepalive_intv))
                                tipc_node_get(n);
        }
        memcpy(&le->maddr, maddr, sizeof(*maddr));
exit:
        tipc_node_write_unlock(n);
        if (reset && !tipc_link_is_reset(l))
                tipc_node_link_down(n, b->identity, false);
        tipc_node_put(n);
}

void tipc_node_delete_links(struct net *net, int bearer_id)
{
        struct tipc_net *tn = net_generic(net, tipc_net_id);
        struct tipc_node *n;

        rcu_read_lock();
        list_for_each_entry_rcu(n, &tn->node_list, list) {
                tipc_node_link_down(n, bearer_id, true);
        }
        rcu_read_unlock();
}

static void tipc_node_reset_links(struct tipc_node *n)
{
        char addr_string[16];
        int i;

        pr_warn("Resetting all links to %s\n",
                tipc_addr_string_fill(addr_string, n->addr));

        for (i = 0; i < MAX_BEARERS; i++) {
                tipc_node_link_down(n, i, false);
        }
}

/* tipc_node_fsm_evt - node finite state machine
 * Determines when contact is allowed with peer node
 */
static void tipc_node_fsm_evt(struct tipc_node *n, int evt)
{
        int state = n->state;

        switch (state) {
        case SELF_DOWN_PEER_DOWN:
                switch (evt) {
                case SELF_ESTABL_CONTACT_EVT:
                        state = SELF_UP_PEER_COMING;
                        break;
                case PEER_ESTABL_CONTACT_EVT:
                        state = SELF_COMING_PEER_UP;
                        break;
                case SELF_LOST_CONTACT_EVT:
                case PEER_LOST_CONTACT_EVT:
                        break;
                case NODE_SYNCH_END_EVT:
                case NODE_SYNCH_BEGIN_EVT:
                case NODE_FAILOVER_BEGIN_EVT:
                case NODE_FAILOVER_END_EVT:
                default:
                        goto illegal_evt;
                }
                break;
        case SELF_UP_PEER_UP:
                switch (evt) {
                case SELF_LOST_CONTACT_EVT:
                        state = SELF_DOWN_PEER_LEAVING;
                        break;
                case PEER_LOST_CONTACT_EVT:
                        state = SELF_LEAVING_PEER_DOWN;
                        break;
                case NODE_SYNCH_BEGIN_EVT:
                        state = NODE_SYNCHING;
                        break;
                case NODE_FAILOVER_BEGIN_EVT:
                        state = NODE_FAILINGOVER;
                        break;
                case SELF_ESTABL_CONTACT_EVT:
                case PEER_ESTABL_CONTACT_EVT:
                case NODE_SYNCH_END_EVT:
                case NODE_FAILOVER_END_EVT:
                        break;
                default:
                        goto illegal_evt;
                }
                break;
        case SELF_DOWN_PEER_LEAVING:
                switch (evt) {
                case PEER_LOST_CONTACT_EVT:
                        state = SELF_DOWN_PEER_DOWN;
                        break;
                case SELF_ESTABL_CONTACT_EVT:
                case PEER_ESTABL_CONTACT_EVT:
                case SELF_LOST_CONTACT_EVT:
                        break;
                case NODE_SYNCH_END_EVT:
                case NODE_SYNCH_BEGIN_EVT:
                case NODE_FAILOVER_BEGIN_EVT:
                case NODE_FAILOVER_END_EVT:
                default:
                        goto illegal_evt;
                }
                break;
        case SELF_UP_PEER_COMING:
                switch (evt) {
                case PEER_ESTABL_CONTACT_EVT:
                        state = SELF_UP_PEER_UP;
                        break;
                case SELF_LOST_CONTACT_EVT:
                        state = SELF_DOWN_PEER_LEAVING;
                        break;
                case SELF_ESTABL_CONTACT_EVT:
                case PEER_LOST_CONTACT_EVT:
                case NODE_SYNCH_END_EVT:
                case NODE_FAILOVER_BEGIN_EVT:
                        break;
                case NODE_SYNCH_BEGIN_EVT:
                case NODE_FAILOVER_END_EVT:
                default:
                        goto illegal_evt;
                }
                break;
        case SELF_COMING_PEER_UP:
                switch (evt) {
                case SELF_ESTABL_CONTACT_EVT:
                        state = SELF_UP_PEER_UP;
                        break;
                case PEER_LOST_CONTACT_EVT:
                        state = SELF_LEAVING_PEER_DOWN;
                        break;
                case SELF_LOST_CONTACT_EVT:
                case PEER_ESTABL_CONTACT_EVT:
                        break;
                case NODE_SYNCH_END_EVT:
                case NODE_SYNCH_BEGIN_EVT:
                case NODE_FAILOVER_BEGIN_EVT:
                case NODE_FAILOVER_END_EVT:
                default:
                        goto illegal_evt;
                }
                break;
        case SELF_LEAVING_PEER_DOWN:
                switch (evt) {
                case SELF_LOST_CONTACT_EVT:
                        state = SELF_DOWN_PEER_DOWN;
                        break;
                case SELF_ESTABL_CONTACT_EVT:
                case PEER_ESTABL_CONTACT_EVT:
                case PEER_LOST_CONTACT_EVT:
                        break;
                case NODE_SYNCH_END_EVT:
                case NODE_SYNCH_BEGIN_EVT:
                case NODE_FAILOVER_BEGIN_EVT:
                case NODE_FAILOVER_END_EVT:
                default:
                        goto illegal_evt;
                }
                break;
        case NODE_FAILINGOVER:
                switch (evt) {
                case SELF_LOST_CONTACT_EVT:
                        state = SELF_DOWN_PEER_LEAVING;
                        break;
                case PEER_LOST_CONTACT_EVT:
                        state = SELF_LEAVING_PEER_DOWN;
                        break;
                case NODE_FAILOVER_END_EVT:
                        state = SELF_UP_PEER_UP;
                        break;
                case NODE_FAILOVER_BEGIN_EVT:
                case SELF_ESTABL_CONTACT_EVT:
                case PEER_ESTABL_CONTACT_EVT:
                        break;
                case NODE_SYNCH_BEGIN_EVT:
                case NODE_SYNCH_END_EVT:
                default:
                        goto illegal_evt;
                }
                break;
        case NODE_SYNCHING:
                switch (evt) {
                case SELF_LOST_CONTACT_EVT:
                        state = SELF_DOWN_PEER_LEAVING;
                        break;
                case PEER_LOST_CONTACT_EVT:
                        state = SELF_LEAVING_PEER_DOWN;
                        break;
                case NODE_SYNCH_END_EVT:
                        state = SELF_UP_PEER_UP;
                        break;
                case NODE_FAILOVER_BEGIN_EVT:
                        state = NODE_FAILINGOVER;
                        break;
                case NODE_SYNCH_BEGIN_EVT:
                case SELF_ESTABL_CONTACT_EVT:
                case PEER_ESTABL_CONTACT_EVT:
                        break;
                case NODE_FAILOVER_END_EVT:
                default:
                        goto illegal_evt;
                }
                break;
        default:
                pr_err("Unknown node fsm state %x\n", state);
                break;
        }
        n->state = state;
        return;

illegal_evt:
        pr_err("Illegal node fsm evt %x in state %x\n", evt, state);
}

static void node_lost_contact(struct tipc_node *n,
                              struct sk_buff_head *inputq)
{
        char addr_string[16];
        struct tipc_sock_conn *conn, *safe;
        struct tipc_link *l;
        struct list_head *conns = &n->conn_sks;
        struct sk_buff *skb;
        uint i;

        pr_debug("Lost contact with %s\n",
                 tipc_addr_string_fill(addr_string, n->addr));

        /* Clean up broadcast state */
        tipc_bcast_remove_peer(n->net, n->bc_entry.link);

        /* Abort any ongoing link failover */
        for (i = 0; i < MAX_BEARERS; i++) {
                l = n->links[i].link;
                if (l)
                        tipc_link_fsm_evt(l, LINK_FAILOVER_END_EVT);
        }

        /* Notify publications from this node */
        n->action_flags |= TIPC_NOTIFY_NODE_DOWN;

        /* Notify sockets connected to node */
        list_for_each_entry_safe(conn, safe, conns, list) {
                skb = tipc_msg_create(TIPC_CRITICAL_IMPORTANCE, TIPC_CONN_MSG,
                                      SHORT_H_SIZE, 0, tipc_own_addr(n->net),
                                      conn->peer_node, conn->port,
                                      conn->peer_port, TIPC_ERR_NO_NODE);
                if (likely(skb))
                        skb_queue_tail(inputq, skb);
                list_del(&conn->list);
                kfree(conn);
        }
}

/**
 * tipc_node_get_linkname - get the name of a link
 *
 * @bearer_id: id of the bearer
 * @node: peer node address
 * @linkname: link name output buffer
 *
 * Returns 0 on success
 */
int tipc_node_get_linkname(struct net *net, u32 bearer_id, u32 addr,
                           char *linkname, size_t len)
{
        struct tipc_link *link;
        int err = -EINVAL;
        struct tipc_node *node = tipc_node_find(net, addr);

        if (!node)
                return err;

        if (bearer_id >= MAX_BEARERS)
                goto exit;

        tipc_node_read_lock(node);
        link = node->links[bearer_id].link;
        if (link) {
                strncpy(linkname, tipc_link_name(link), len);
                err = 0;
        }
exit:
        tipc_node_read_unlock(node);
        tipc_node_put(node);
        return err;
}

/* Caller should hold node lock for the passed node */
static int __tipc_nl_add_node(struct tipc_nl_msg *msg, struct tipc_node *node)
{
        void *hdr;
        struct nlattr *attrs;

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

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

        if (nla_put_u32(msg->skb, TIPC_NLA_NODE_ADDR, node->addr))
                goto attr_msg_full;
        if (tipc_node_is_up(node))
                if (nla_put_flag(msg->skb, TIPC_NLA_NODE_UP))
                        goto attr_msg_full;

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

        return 0;

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

        return -EMSGSIZE;
}

/**
 * tipc_node_xmit() is the general link level function for message sending
 * @net: the applicable net namespace
 * @list: chain of buffers containing message
 * @dnode: address of destination node
 * @selector: a number used for deterministic link selection
 * Consumes the buffer chain, except when returning -ELINKCONG
 * Returns 0 if success, otherwise errno: -ELINKCONG,-EHOSTUNREACH,-EMSGSIZE
 */
int tipc_node_xmit(struct net *net, struct sk_buff_head *list,
                   u32 dnode, int selector)
{
        struct tipc_link_entry *le = NULL;
        struct tipc_node *n;
        struct sk_buff_head xmitq;
        int bearer_id = -1;
        int rc = -EHOSTUNREACH;

        __skb_queue_head_init(&xmitq);
        n = tipc_node_find(net, dnode);
        if (likely(n)) {
                tipc_node_read_lock(n);
                bearer_id = n->active_links[selector & 1];
                if (bearer_id >= 0) {
                        le = &n->links[bearer_id];
                        spin_lock_bh(&le->lock);
                        rc = tipc_link_xmit(le->link, list, &xmitq);
                        spin_unlock_bh(&le->lock);
                }
                tipc_node_read_unlock(n);
                if (likely(!rc))
                        tipc_bearer_xmit(net, bearer_id, &xmitq, &le->maddr);
                else if (rc == -ENOBUFS)
                        tipc_node_link_down(n, bearer_id, false);
                tipc_node_put(n);
                return rc;
        }

        if (likely(in_own_node(net, dnode))) {
                tipc_sk_rcv(net, list);
                return 0;
        }
        return rc;
}

/* tipc_node_xmit_skb(): send single buffer to destination
 * Buffers sent via this functon are generally TIPC_SYSTEM_IMPORTANCE
 * messages, which will not be rejected
 * The only exception is datagram messages rerouted after secondary
 * lookup, which are rare and safe to dispose of anyway.
 * TODO: Return real return value, and let callers use
 * tipc_wait_for_sendpkt() where applicable
 */
int tipc_node_xmit_skb(struct net *net, struct sk_buff *skb, u32 dnode,
                       u32 selector)
{
        struct sk_buff_head head;
        int rc;

        skb_queue_head_init(&head);
        __skb_queue_tail(&head, skb);
        rc = tipc_node_xmit(net, &head, dnode, selector);
        if (rc == -ELINKCONG)
                kfree_skb(skb);
        return 0;
}

void tipc_node_broadcast(struct net *net, struct sk_buff *skb)
{
        struct sk_buff *txskb;
        struct tipc_node *n;
        u32 dst;

        rcu_read_lock();
        list_for_each_entry_rcu(n, tipc_nodes(net), list) {
                dst = n->addr;
                if (in_own_node(net, dst))
                        continue;
                if (!tipc_node_is_up(n))
                        continue;
                txskb = pskb_copy(skb, GFP_ATOMIC);
                if (!txskb)
                        break;
                msg_set_destnode(buf_msg(txskb), dst);
                tipc_node_xmit_skb(net, txskb, dst, 0);
        }
        rcu_read_unlock();

        kfree_skb(skb);
}

/**
 * tipc_node_bc_rcv - process TIPC broadcast packet arriving from off-node
 * @net: the applicable net namespace
 * @skb: TIPC packet
 * @bearer_id: id of bearer message arrived on
 *
 * Invoked with no locks held.
 */
static void tipc_node_bc_rcv(struct net *net, struct sk_buff *skb, int bearer_id)
{
        int rc;
        struct sk_buff_head xmitq;
        struct tipc_bclink_entry *be;
        struct tipc_link_entry *le;
        struct tipc_msg *hdr = buf_msg(skb);
        int usr = msg_user(hdr);
        u32 dnode = msg_destnode(hdr);
        struct tipc_node *n;

        __skb_queue_head_init(&xmitq);

        /* If NACK for other node, let rcv link for that node peek into it */
        if ((usr == BCAST_PROTOCOL) && (dnode != tipc_own_addr(net)))
                n = tipc_node_find(net, dnode);
        else
                n = tipc_node_find(net, msg_prevnode(hdr));
        if (!n) {
                kfree_skb(skb);
                return;
        }
        be = &n->bc_entry;
        le = &n->links[bearer_id];

        rc = tipc_bcast_rcv(net, be->link, skb);

        /* Broadcast link reset may happen at reassembly failure */
        if (rc & TIPC_LINK_DOWN_EVT)
                tipc_node_reset_links(n);

        /* Broadcast ACKs are sent on a unicast link */
        if (rc & TIPC_LINK_SND_BC_ACK) {
                tipc_node_read_lock(n);
                tipc_link_build_ack_msg(le->link, &xmitq);
                tipc_node_read_unlock(n);
        }

        if (!skb_queue_empty(&xmitq))
                tipc_bearer_xmit(net, bearer_id, &xmitq, &le->maddr);

        /* Deliver. 'arrvq' is under inputq2's lock protection */
        if (!skb_queue_empty(&be->inputq1)) {
                spin_lock_bh(&be->inputq2.lock);
                spin_lock_bh(&be->inputq1.lock);
                skb_queue_splice_tail_init(&be->inputq1, &be->arrvq);
                spin_unlock_bh(&be->inputq1.lock);
                spin_unlock_bh(&be->inputq2.lock);
                tipc_sk_mcast_rcv(net, &be->arrvq, &be->inputq2);
        }
        tipc_node_put(n);
}

/**
 * tipc_node_check_state - check and if necessary update node state
 * @skb: TIPC packet
 * @bearer_id: identity of bearer delivering the packet
 * Returns true if state is ok, otherwise consumes buffer and returns false
 */
static bool tipc_node_check_state(struct tipc_node *n, struct sk_buff *skb,
                                  int bearer_id, struct sk_buff_head *xmitq)
{
        struct tipc_msg *hdr = buf_msg(skb);
        int usr = msg_user(hdr);
        int mtyp = msg_type(hdr);
        u16 oseqno = msg_seqno(hdr);
        u16 iseqno = msg_seqno(msg_get_wrapped(hdr));
        u16 exp_pkts = msg_msgcnt(hdr);
        u16 rcv_nxt, syncpt, dlv_nxt, inputq_len;
        int state = n->state;
        struct tipc_link *l, *tnl, *pl = NULL;
        struct tipc_media_addr *maddr;
        int pb_id;

        l = n->links[bearer_id].link;
        if (!l)
                return false;
        rcv_nxt = tipc_link_rcv_nxt(l);


        if (likely((state == SELF_UP_PEER_UP) && (usr != TUNNEL_PROTOCOL)))
                return true;

        /* Find parallel link, if any */
        for (pb_id = 0; pb_id < MAX_BEARERS; pb_id++) {
                if ((pb_id != bearer_id) && n->links[pb_id].link) {
                        pl = n->links[pb_id].link;
                        break;
                }
        }

        /* Check and update node accesibility if applicable */
        if (state == SELF_UP_PEER_COMING) {
                if (!tipc_link_is_up(l))
                        return true;
                if (!msg_peer_link_is_up(hdr))
                        return true;
                tipc_node_fsm_evt(n, PEER_ESTABL_CONTACT_EVT);
        }

        if (state == SELF_DOWN_PEER_LEAVING) {
                if (msg_peer_node_is_up(hdr))
                        return false;
                tipc_node_fsm_evt(n, PEER_LOST_CONTACT_EVT);
                return true;
        }

        if (state == SELF_LEAVING_PEER_DOWN)
                return false;

        /* Ignore duplicate packets */
        if ((usr != LINK_PROTOCOL) && less(oseqno, rcv_nxt))
                return true;

        /* Initiate or update failover mode if applicable */
        if ((usr == TUNNEL_PROTOCOL) && (mtyp == FAILOVER_MSG)) {
                syncpt = oseqno + exp_pkts - 1;
                if (pl && tipc_link_is_up(pl)) {
                        __tipc_node_link_down(n, &pb_id, xmitq, &maddr);
                        tipc_skb_queue_splice_tail_init(tipc_link_inputq(pl),
                                                        tipc_link_inputq(l));
                }
                /* If pkts arrive out of order, use lowest calculated syncpt */
                if (less(syncpt, n->sync_point))
                        n->sync_point = syncpt;
        }

        /* Open parallel link when tunnel link reaches synch point */
        if ((n->state == NODE_FAILINGOVER) && tipc_link_is_up(l)) {
                if (!more(rcv_nxt, n->sync_point))
                        return true;
                tipc_node_fsm_evt(n, NODE_FAILOVER_END_EVT);
                if (pl)
                        tipc_link_fsm_evt(pl, LINK_FAILOVER_END_EVT);
                return true;
        }

        /* No synching needed if only one link */
        if (!pl || !tipc_link_is_up(pl))
                return true;

        /* Initiate synch mode if applicable */
        if ((usr == TUNNEL_PROTOCOL) && (mtyp == SYNCH_MSG) && (oseqno == 1)) {
                syncpt = iseqno + exp_pkts - 1;
                if (!tipc_link_is_up(l)) {
                        tipc_link_fsm_evt(l, LINK_ESTABLISH_EVT);
                        __tipc_node_link_up(n, bearer_id, xmitq);
                }
                if (n->state == SELF_UP_PEER_UP) {
                        n->sync_point = syncpt;
                        tipc_link_fsm_evt(l, LINK_SYNCH_BEGIN_EVT);
                        tipc_node_fsm_evt(n, NODE_SYNCH_BEGIN_EVT);
                }
        }

        /* Open tunnel link when parallel link reaches synch point */
        if (n->state == NODE_SYNCHING) {
                if (tipc_link_is_synching(l)) {
                        tnl = l;
                } else {
                        tnl = pl;
                        pl = l;
                }
                inputq_len = skb_queue_len(tipc_link_inputq(pl));
                dlv_nxt = tipc_link_rcv_nxt(pl) - inputq_len;
                if (more(dlv_nxt, n->sync_point)) {
                        tipc_link_fsm_evt(tnl, LINK_SYNCH_END_EVT);
                        tipc_node_fsm_evt(n, NODE_SYNCH_END_EVT);
                        return true;
                }
                if (l == pl)
                        return true;
                if ((usr == TUNNEL_PROTOCOL) && (mtyp == SYNCH_MSG))
                        return true;
                if (usr == LINK_PROTOCOL)
                        return true;
                return false;
        }
        return true;
}

/**
 * tipc_rcv - process TIPC packets/messages arriving from off-node
 * @net: the applicable net namespace
 * @skb: TIPC packet
 * @bearer: pointer to bearer message arrived on
 *
 * Invoked with no locks held. Bearer pointer must point to a valid bearer
 * structure (i.e. cannot be NULL), but bearer can be inactive.
 */
void tipc_rcv(struct net *net, struct sk_buff *skb, struct tipc_bearer *b)
{
        struct sk_buff_head xmitq;
        struct tipc_node *n;
        struct tipc_msg *hdr = buf_msg(skb);
        int usr = msg_user(hdr);
        int bearer_id = b->identity;
        struct tipc_link_entry *le;
        u16 bc_ack = msg_bcast_ack(hdr);
        int rc = 0;

        __skb_queue_head_init(&xmitq);

        /* Ensure message is well-formed */
        if (unlikely(!tipc_msg_validate(skb)))
                goto discard;

        /* Handle arrival of discovery or broadcast packet */
        if (unlikely(msg_non_seq(hdr))) {
                if (unlikely(usr == LINK_CONFIG))
                        return tipc_disc_rcv(net, skb, b);
                else
                        return tipc_node_bc_rcv(net, skb, bearer_id);
        }

        /* Locate neighboring node that sent packet */
        n = tipc_node_find(net, msg_prevnode(hdr));
        if (unlikely(!n))
                goto discard;
        le = &n->links[bearer_id];

        /* Ensure broadcast reception is in synch with peer's send state */
        if (unlikely(usr == LINK_PROTOCOL))
                tipc_bcast_sync_rcv(net, n->bc_entry.link, hdr);
        else if (unlikely(tipc_link_acked(n->bc_entry.link) != bc_ack))
                tipc_bcast_ack_rcv(net, n->bc_entry.link, bc_ack);

        /* Receive packet directly if conditions permit */
        tipc_node_read_lock(n);
        if (likely((n->state == SELF_UP_PEER_UP) && (usr != TUNNEL_PROTOCOL))) {
                spin_lock_bh(&le->lock);
                if (le->link) {
                        rc = tipc_link_rcv(le->link, skb, &xmitq);
                        skb = NULL;
                }
                spin_unlock_bh(&le->lock);
        }
        tipc_node_read_unlock(n);

        /* Check/update node state before receiving */
        if (unlikely(skb)) {
                tipc_node_write_lock(n);
                if (tipc_node_check_state(n, skb, bearer_id, &xmitq)) {
                        if (le->link) {
                                rc = tipc_link_rcv(le->link, skb, &xmitq);
                                skb = NULL;
                        }
                }
                tipc_node_write_unlock(n);
        }

        if (unlikely(rc & TIPC_LINK_UP_EVT))
                tipc_node_link_up(n, bearer_id, &xmitq);

        if (unlikely(rc & TIPC_LINK_DOWN_EVT))
                tipc_node_link_down(n, bearer_id, false);

        if (unlikely(!skb_queue_empty(&n->bc_entry.namedq)))
                tipc_named_rcv(net, &n->bc_entry.namedq);

        if (!skb_queue_empty(&le->inputq))
                tipc_sk_rcv(net, &le->inputq);

        if (!skb_queue_empty(&xmitq))
                tipc_bearer_xmit(net, bearer_id, &xmitq, &le->maddr);

        tipc_node_put(n);
discard:
        kfree_skb(skb);
}

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

        if (done)
                return 0;

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

        rcu_read_lock();
        if (last_addr) {
                node = tipc_node_find(net, last_addr);
                if (!node) {
                        rcu_read_unlock();
                        /* 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 NLMSG_DONE message having
                         * the NLM_F_DUMP_INTR flag set if the node state
                         * changed while we released the lock.
                         */
                        cb->prev_seq = 1;
                        return -EPIPE;
                }
                tipc_node_put(node);
        }

        list_for_each_entry_rcu(node, &tn->node_list, list) {
                if (last_addr) {
                        if (node->addr == last_addr)
                                last_addr = 0;
                        else
                                continue;
                }

                tipc_node_read_lock(node);
                err = __tipc_nl_add_node(&msg, node);
                if (err) {
                        last_addr = node->addr;
                        tipc_node_read_unlock(node);
                        goto out;
                }

                tipc_node_read_unlock(node);
        }
        done = 1;
out:
        cb->args[0] = done;
        cb->args[1] = last_addr;
        rcu_read_unlock();

        return skb->len;
}

/* tipc_node_find_by_name - 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_node_find_by_name(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;
        struct tipc_node *n;
        struct tipc_node *found_node = NULL;
        int i;

        *bearer_id = 0;
        rcu_read_lock();
        list_for_each_entry_rcu(n, &tn->node_list, list) {
                tipc_node_read_lock(n);
                for (i = 0; i < MAX_BEARERS; i++) {
                        l = n->links[i].link;
                        if (l && !strcmp(tipc_link_name(l), link_name)) {
                                *bearer_id = i;
                                found_node = n;
                                break;
                        }
                }
                tipc_node_read_unlock(n);
                if (found_node)
                        break;
        }
        rcu_read_unlock();

        return found_node;
}

int tipc_nl_node_set_link(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_node_find_by_name(net, name, &bearer_id);
        if (!node)
                return -EINVAL;

        tipc_node_read_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]);
                        tipc_link_set_tolerance(link, tol);
                }
                if (props[TIPC_NLA_PROP_PRIO]) {
                        u32 prio;

                        prio = nla_get_u32(props[TIPC_NLA_PROP_PRIO]);
                        tipc_link_set_prio(link, 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_read_unlock(node);

        return res;
}

int tipc_nl_node_get_link(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_node_find_by_name(net, name, &bearer_id);
                if (!node)
                        return -EINVAL;

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

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

        return genlmsg_reply(msg.skb, info);
}

int tipc_nl_node_reset_link_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);
        struct tipc_link_entry *le;

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

        le = &node->links[bearer_id];
        tipc_node_read_lock(node);
        spin_lock_bh(&le->lock);
        link = node->links[bearer_id].link;
        if (!link) {
                spin_unlock_bh(&le->lock);
                tipc_node_read_unlock(node);
                return -EINVAL;
        }
        tipc_link_reset_stats(link);
        spin_unlock_bh(&le->lock);
        tipc_node_read_unlock(node);
        return 0;
}

/* 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_node_dump_link(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_read_lock(node);
                        err = __tipc_nl_add_node_links(net, &msg, node,
                                                       &prev_link);
                        tipc_node_read_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_read_lock(node);
                        err = __tipc_nl_add_node_links(net, &msg, node,
                                                       &prev_link);
                        tipc_node_read_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;
}