/*
 * 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"

/* 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);

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

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 }
};

/*
 * 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);
}

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
 */
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;
}

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_ptr, *temp_node;

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

static void tipc_node_calculate_timer(struct tipc_node *n, struct tipc_link *l)
{
        unsigned long tol = l->tolerance;
        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 */
        l->abort_limit = l->tolerance / 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);
}

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_lock(node);
        list_add_tail(&conn->list, &node->conn_sks);
        tipc_node_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_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_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_lock(n);
                le = &n->links[bearer_id];
                if (le->link) {
                        /* Link tolerance may change asynchronously: */
                        tipc_node_calculate_timer(n, le->link);
                        rc = tipc_link_timeout(le->link, &xmitq);
                }
                tipc_node_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 = nl->peer_bearer_id << 16 | bearer_id;

        /* Leave room for tunnel header when returning 'mtu' to users: */
        n->links[bearer_id].mtu = nl->mtu - 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",
                 nl->name, nl->net_plane);

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

        /* 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_lock(n);
        __tipc_node_link_up(n, bearer_id, xmitq);
        tipc_node_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;
        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 = l->peer_bearer_id << 16 | *bearer_id;

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

        pr_debug("Lost link <%s> on network plane %c\n",
                 l->name, l->net_plane);

        /* 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;
                if (_l->priority < highest)
                        continue;
                if (_l->priority > highest) {
                        highest = _l->priority;
                        *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 */
        tnl = node_active_link(n, 0);
        tipc_link_fsm_evt(tnl, LINK_SYNCH_END_EVT);
        tipc_node_fsm_evt(n, NODE_SYNCH_END_EVT);
        n->sync_point = tnl->rcv_nxt + (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[tnl->bearer_id].maddr;
        *bearer_id = tnl->bearer_id;
}

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_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_unlock(n);
        tipc_bearer_xmit(n->net, bearer_id, &xmitq, maddr);
        tipc_sk_rcv(n->net, &le->inputq);
}

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_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_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);
}

bool tipc_node_filter_pkt(struct tipc_node *n, struct tipc_msg *hdr)
{
        int state = n->state;

        if (likely(state == SELF_UP_PEER_UP))
                return true;

        if (state == SELF_LEAVING_PEER_DOWN)
                return false;

        if (state == SELF_DOWN_PEER_LEAVING) {
                if (msg_peer_node_is_up(hdr))
                        return false;
        }

        return true;
}

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

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

        if (likely(!flags)) {
                spin_unlock_bh(&node->lock);
                return;
        }

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

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

        spin_unlock_bh(&node->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);

}

/* 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;
}

static struct tipc_link *tipc_node_select_link(struct tipc_node *n, int sel,

                                               int *bearer_id,
                                               struct tipc_media_addr **maddr)
{
        int id = n->active_links[sel & 1];

        if (unlikely(id < 0))
                return NULL;

        *bearer_id = id;
        *maddr = &n->links[id].maddr;
        return n->links[id].link;
}

/**
 * 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 *l = NULL;
        struct tipc_node *n;
        struct sk_buff_head xmitq;
        struct tipc_media_addr *maddr;
        int bearer_id;
        int rc = -EHOSTUNREACH;

        __skb_queue_head_init(&xmitq);
        n = tipc_node_find(net, dnode);
        if (likely(n)) {
                tipc_node_lock(n);
                l = tipc_node_select_link(n, selector, &bearer_id, &maddr);
                if (likely(l))
                        rc = tipc_link_xmit(l, list, &xmitq);
                tipc_node_unlock(n);
                if (unlikely(rc == -ENOBUFS))
                        tipc_node_link_down(n, bearer_id, false);
                tipc_node_put(n);
        }
        if (likely(!rc)) {
                tipc_bearer_xmit(net, bearer_id, &xmitq, maddr);
                return 0;
        }
        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;
}

/**
 * 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_lock(n);
                tipc_link_build_ack_msg(le->link, &xmitq);
                tipc_node_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;
        int state = n->state;
        struct tipc_link *l, *tnl, *pl = NULL;
        struct tipc_media_addr *maddr;
        int i, pb_id;

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


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

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

        /* 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);
        }

        /* 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)) {
                        pb_id = pl->bearer_id;
                        __tipc_node_link_down(n, &pb_id, xmitq, &maddr);
                        tipc_skb_queue_splice_tail_init(pl->inputq, l->inputq);
                }
                /* 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);
                }
                if (less(syncpt, n->sync_point))
                        n->sync_point = syncpt;
        }

        /* Open tunnel link when parallel link reaches synch point */
        if ((n->state == NODE_SYNCHING) && tipc_link_is_synching(l)) {
                if (tipc_link_is_synching(l)) {
                        tnl = l;
                } else {
                        tnl = pl;
                        pl = l;
                }
                dlv_nxt = pl->rcv_nxt - mod(skb_queue_len(pl->inputq));
                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(n->bc_entry.link->acked != bc_ack))
                tipc_bcast_ack_rcv(net, n->bc_entry.link, bc_ack);

        tipc_node_lock(n);

        /* Is reception permitted at the moment ? */
        if (!tipc_node_filter_pkt(n, hdr))
                goto unlock;

        /* Check and if necessary update node state */
        if (likely(tipc_node_check_state(n, skb, bearer_id, &xmitq))) {
                rc = tipc_link_rcv(le->link, skb, &xmitq);
                skb = NULL;
        }
unlock:
        tipc_node_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_lock(node);
                err = __tipc_nl_add_node(&msg, node);
                if (err) {
                        last_addr = node->addr;
                        tipc_node_unlock(node);
                        goto out;
                }

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

        return skb->len;
}