Merge tag 'kbuild-fixes-v6.10' of git://git.kernel.org/pub/scm/linux/kernel/git/masah...

[linux-block.git] / net / tipc / link.c

/*
 * net/tipc/link.c: TIPC link code
 *
 * Copyright (c) 1996-2007, 2012-2016, Ericsson AB
 * Copyright (c) 2004-2007, 2010-2013, Wind River Systems
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the names of the copyright holders nor the names of its
 *    contributors may be used to endorse or promote products derived from
 *    this software without specific prior written permission.
 *
 * Alternatively, this software may be distributed under the terms of the
 * GNU General Public License ("GPL") version 2 as published by the Free
 * Software Foundation.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

#include "core.h"
#include "subscr.h"
#include "link.h"
#include "bcast.h"
#include "socket.h"
#include "name_distr.h"
#include "discover.h"
#include "netlink.h"
#include "monitor.h"
#include "trace.h"
#include "crypto.h"

#include <linux/pkt_sched.h>

struct tipc_stats {
        u32 sent_pkts;
        u32 recv_pkts;
        u32 sent_states;
        u32 recv_states;
        u32 sent_probes;
        u32 recv_probes;
        u32 sent_nacks;
        u32 recv_nacks;
        u32 sent_acks;
        u32 sent_bundled;
        u32 sent_bundles;
        u32 recv_bundled;
        u32 recv_bundles;
        u32 retransmitted;
        u32 sent_fragmented;
        u32 sent_fragments;
        u32 recv_fragmented;
        u32 recv_fragments;
        u32 link_congs;         /* # port sends blocked by congestion */
        u32 deferred_recv;
        u32 duplicates;
        u32 max_queue_sz;       /* send queue size high water mark */
        u32 accu_queue_sz;      /* used for send queue size profiling */
        u32 queue_sz_counts;    /* used for send queue size profiling */
        u32 msg_length_counts;  /* used for message length profiling */
        u32 msg_lengths_total;  /* used for message length profiling */
        u32 msg_length_profile[7]; /* used for msg. length profiling */
};

/**
 * struct tipc_link - TIPC link data structure
 * @addr: network address of link's peer node
 * @name: link name character string
 * @net: pointer to namespace struct
 * @peer_session: link session # being used by peer end of link
 * @peer_bearer_id: bearer id used by link's peer endpoint
 * @bearer_id: local bearer id used by link
 * @tolerance: minimum link continuity loss needed to reset link [in ms]
 * @abort_limit: # of unacknowledged continuity probes needed to reset link
 * @state: current state of link FSM
 * @peer_caps: bitmap describing capabilities of peer node
 * @silent_intv_cnt: # of timer intervals without any reception from peer
 * @priority: current link priority
 * @net_plane: current link network plane ('A' through 'H')
 * @mon_state: cookie with information needed by link monitor
 * @mtu: current maximum packet size for this link
 * @advertised_mtu: advertised own mtu when link is being established
 * @backlogq: queue for messages waiting to be sent
 * @ackers: # of peers that needs to ack each packet before it can be released
 * @acked: # last packet acked by a certain peer. Used for broadcast.
 * @rcv_nxt: next sequence number to expect for inbound messages
 * @inputq: buffer queue for messages to be delivered upwards
 * @namedq: buffer queue for name table messages to be delivered upwards
 * @wakeupq: linked list of wakeup msgs waiting for link congestion to abate
 * @reasm_buf: head of partially reassembled inbound message fragments
 * @stats: collects statistics regarding link activity
 * @session: session to be used by link
 * @snd_nxt_state: next send seq number
 * @rcv_nxt_state: next rcv seq number
 * @in_session: have received ACTIVATE_MSG from peer
 * @active: link is active
 * @if_name: associated interface name
 * @rst_cnt: link reset counter
 * @drop_point: seq number for failover handling (FIXME)
 * @failover_reasm_skb: saved failover msg ptr (FIXME)
 * @failover_deferdq: deferred message queue for failover processing (FIXME)
 * @transmq: the link's transmit queue
 * @backlog: link's backlog by priority (importance)
 * @snd_nxt: next sequence number to be used
 * @rcv_unacked: # messages read by user, but not yet acked back to peer
 * @deferdq: deferred receive queue
 * @window: sliding window size for congestion handling
 * @min_win: minimal send window to be used by link
 * @ssthresh: slow start threshold for congestion handling
 * @max_win: maximal send window to be used by link
 * @cong_acks: congestion acks for congestion avoidance (FIXME)
 * @checkpoint: seq number for congestion window size handling
 * @reasm_tnlmsg: fragmentation/reassembly area for tunnel protocol message
 * @last_gap: last gap ack blocks for bcast (FIXME)
 * @last_ga: ptr to gap ack blocks
 * @bc_rcvlink: the peer specific link used for broadcast reception
 * @bc_sndlink: the namespace global link used for broadcast sending
 * @nack_state: bcast nack state
 * @bc_peer_is_up: peer has acked the bcast init msg
 */
struct tipc_link {
        u32 addr;
        char name[TIPC_MAX_LINK_NAME];
        struct net *net;

        /* Management and link supervision data */
        u16 peer_session;
        u16 session;
        u16 snd_nxt_state;
        u16 rcv_nxt_state;
        u32 peer_bearer_id;
        u32 bearer_id;
        u32 tolerance;
        u32 abort_limit;
        u32 state;
        u16 peer_caps;
        bool in_session;
        bool active;
        u32 silent_intv_cnt;
        char if_name[TIPC_MAX_IF_NAME];
        u32 priority;
        char net_plane;
        struct tipc_mon_state mon_state;
        u16 rst_cnt;

        /* Failover/synch */
        u16 drop_point;
        struct sk_buff *failover_reasm_skb;
        struct sk_buff_head failover_deferdq;

        /* Max packet negotiation */
        u16 mtu;
        u16 advertised_mtu;

        /* Sending */
        struct sk_buff_head transmq;
        struct sk_buff_head backlogq;
        struct {
                u16 len;
                u16 limit;
                struct sk_buff *target_bskb;
        } backlog[5];
        u16 snd_nxt;

        /* Reception */
        u16 rcv_nxt;
        u32 rcv_unacked;
        struct sk_buff_head deferdq;
        struct sk_buff_head *inputq;
        struct sk_buff_head *namedq;

        /* Congestion handling */
        struct sk_buff_head wakeupq;
        u16 window;
        u16 min_win;
        u16 ssthresh;
        u16 max_win;
        u16 cong_acks;
        u16 checkpoint;

        /* Fragmentation/reassembly */
        struct sk_buff *reasm_buf;
        struct sk_buff *reasm_tnlmsg;

        /* Broadcast */
        u16 ackers;
        u16 acked;
        u16 last_gap;
        struct tipc_gap_ack_blks *last_ga;
        struct tipc_link *bc_rcvlink;
        struct tipc_link *bc_sndlink;
        u8 nack_state;
        bool bc_peer_is_up;

        /* Statistics */
        struct tipc_stats stats;
};

/*
 * Error message prefixes
 */
static const char *link_co_err = "Link tunneling error, ";
static const char *link_rst_msg = "Resetting link ";

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

#define TIPC_BC_RETR_LIM  (jiffies + msecs_to_jiffies(10))
#define TIPC_UC_RETR_TIME (jiffies + msecs_to_jiffies(1))

/* Link FSM states:
 */
enum {
        LINK_ESTABLISHED     = 0xe,
        LINK_ESTABLISHING    = 0xe  << 4,
        LINK_RESET           = 0x1  << 8,
        LINK_RESETTING       = 0x2  << 12,
        LINK_PEER_RESET      = 0xd  << 16,
        LINK_FAILINGOVER     = 0xf  << 20,
        LINK_SYNCHING        = 0xc  << 24
};

/* Link FSM state checking routines
 */
static int link_is_up(struct tipc_link *l)
{
        return l->state & (LINK_ESTABLISHED | LINK_SYNCHING);
}

static int tipc_link_proto_rcv(struct tipc_link *l, struct sk_buff *skb,
                               struct sk_buff_head *xmitq);
static void tipc_link_build_proto_msg(struct tipc_link *l, int mtyp, bool probe,
                                      bool probe_reply, u16 rcvgap,
                                      int tolerance, int priority,
                                      struct sk_buff_head *xmitq);
static void link_print(struct tipc_link *l, const char *str);
static int tipc_link_build_nack_msg(struct tipc_link *l,
                                    struct sk_buff_head *xmitq);
static void tipc_link_build_bc_init_msg(struct tipc_link *l,
                                        struct sk_buff_head *xmitq);
static u8 __tipc_build_gap_ack_blks(struct tipc_gap_ack_blks *ga,
                                    struct tipc_link *l, u8 start_index);
static u16 tipc_build_gap_ack_blks(struct tipc_link *l, struct tipc_msg *hdr);
static int tipc_link_advance_transmq(struct tipc_link *l, struct tipc_link *r,
                                     u16 acked, u16 gap,
                                     struct tipc_gap_ack_blks *ga,
                                     struct sk_buff_head *xmitq,
                                     bool *retransmitted, int *rc);
static void tipc_link_update_cwin(struct tipc_link *l, int released,
                                  bool retransmitted);
/*
 *  Simple non-static link routines (i.e. referenced outside this file)
 */
bool tipc_link_is_up(struct tipc_link *l)
{
        return link_is_up(l);
}

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

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

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

bool tipc_link_is_synching(struct tipc_link *l)
{
        return l->state == LINK_SYNCHING;
}

bool tipc_link_is_failingover(struct tipc_link *l)
{
        return l->state == LINK_FAILINGOVER;
}

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

static bool link_is_bc_sndlink(struct tipc_link *l)
{
        return !l->bc_sndlink;
}

static bool link_is_bc_rcvlink(struct tipc_link *l)
{
        return ((l->bc_rcvlink == l) && !link_is_bc_sndlink(l));
}

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

u32 tipc_link_id(struct tipc_link *l)
{
        return l->peer_bearer_id << 16 | l->bearer_id;
}

int tipc_link_min_win(struct tipc_link *l)
{
        return l->min_win;
}

int tipc_link_max_win(struct tipc_link *l)
{
        return l->max_win;
}

int tipc_link_prio(struct tipc_link *l)
{
        return l->priority;
}

unsigned long tipc_link_tolerance(struct tipc_link *l)
{
        return l->tolerance;
}

struct sk_buff_head *tipc_link_inputq(struct tipc_link *l)
{
        return l->inputq;
}

char tipc_link_plane(struct tipc_link *l)
{
        return l->net_plane;
}

struct net *tipc_link_net(struct tipc_link *l)
{
        return l->net;
}

void tipc_link_update_caps(struct tipc_link *l, u16 capabilities)
{
        l->peer_caps = capabilities;
}

void tipc_link_add_bc_peer(struct tipc_link *snd_l,
                           struct tipc_link *uc_l,
                           struct sk_buff_head *xmitq)
{
        struct tipc_link *rcv_l = uc_l->bc_rcvlink;

        snd_l->ackers++;
        rcv_l->acked = snd_l->snd_nxt - 1;
        snd_l->state = LINK_ESTABLISHED;
        tipc_link_build_bc_init_msg(uc_l, xmitq);
}

void tipc_link_remove_bc_peer(struct tipc_link *snd_l,
                              struct tipc_link *rcv_l,
                              struct sk_buff_head *xmitq)
{
        u16 ack = snd_l->snd_nxt - 1;

        snd_l->ackers--;
        rcv_l->bc_peer_is_up = true;
        rcv_l->state = LINK_ESTABLISHED;
        tipc_link_bc_ack_rcv(rcv_l, ack, 0, NULL, xmitq, NULL);
        trace_tipc_link_reset(rcv_l, TIPC_DUMP_ALL, "bclink removed!");
        tipc_link_reset(rcv_l);
        rcv_l->state = LINK_RESET;
        if (!snd_l->ackers) {
                trace_tipc_link_reset(snd_l, TIPC_DUMP_ALL, "zero ackers!");
                tipc_link_reset(snd_l);
                snd_l->state = LINK_RESET;
                __skb_queue_purge(xmitq);
        }
}

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

static u16 link_bc_rcv_gap(struct tipc_link *l)
{
        struct sk_buff *skb = skb_peek(&l->deferdq);
        u16 gap = 0;

        if (more(l->snd_nxt, l->rcv_nxt))
                gap = l->snd_nxt - l->rcv_nxt;
        if (skb)
                gap = buf_seqno(skb) - l->rcv_nxt;
        return gap;
}

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

int tipc_link_mtu(struct tipc_link *l)
{
        return l->mtu;
}

int tipc_link_mss(struct tipc_link *l)
{
#ifdef CONFIG_TIPC_CRYPTO
        return l->mtu - INT_H_SIZE - EMSG_OVERHEAD;
#else
        return l->mtu - INT_H_SIZE;
#endif
}

u16 tipc_link_rcv_nxt(struct tipc_link *l)
{
        return l->rcv_nxt;
}

u16 tipc_link_acked(struct tipc_link *l)
{
        return l->acked;
}

char *tipc_link_name(struct tipc_link *l)
{
        return l->name;
}

u32 tipc_link_state(struct tipc_link *l)
{
        return l->state;
}

/**
 * tipc_link_create - create a new link
 * @net: pointer to associated network namespace
 * @if_name: associated interface name
 * @bearer_id: id (index) of associated bearer
 * @tolerance: link tolerance to be used by link
 * @net_plane: network plane (A,B,c..) this link belongs to
 * @mtu: mtu to be advertised by link
 * @priority: priority to be used by link
 * @min_win: minimal send window to be used by link
 * @max_win: maximal send window to be used by link
 * @session: session to be used by link
 * @peer: node id of peer node
 * @peer_caps: bitmap describing peer node capabilities
 * @bc_sndlink: the namespace global link used for broadcast sending
 * @bc_rcvlink: the peer specific link used for broadcast reception
 * @inputq: queue to put messages ready for delivery
 * @namedq: queue to put binding table update messages ready for delivery
 * @link: return value, pointer to put the created link
 * @self: local unicast link id
 * @peer_id: 128-bit ID of peer
 *
 * Return: true if link was created, otherwise false
 */
bool tipc_link_create(struct net *net, char *if_name, int bearer_id,
                      int tolerance, char net_plane, u32 mtu, int priority,
                      u32 min_win, u32 max_win, u32 session, u32 self,
                      u32 peer, u8 *peer_id, u16 peer_caps,
                      struct tipc_link *bc_sndlink,
                      struct tipc_link *bc_rcvlink,
                      struct sk_buff_head *inputq,
                      struct sk_buff_head *namedq,
                      struct tipc_link **link)
{
        char peer_str[NODE_ID_STR_LEN] = {0,};
        char self_str[NODE_ID_STR_LEN] = {0,};
        struct tipc_link *l;

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

        /* Set link name for unicast links only */
        if (peer_id) {
                tipc_nodeid2string(self_str, tipc_own_id(net));
                if (strlen(self_str) > 16)
                        sprintf(self_str, "%x", self);
                tipc_nodeid2string(peer_str, peer_id);
                if (strlen(peer_str) > 16)
                        sprintf(peer_str, "%x", peer);
        }
        /* Peer i/f name will be completed by reset/activate message */
        snprintf(l->name, sizeof(l->name), "%s:%s-%s:unknown",
                 self_str, if_name, peer_str);

        strcpy(l->if_name, if_name);
        l->addr = peer;
        l->peer_caps = peer_caps;
        l->net = net;
        l->in_session = false;
        l->bearer_id = bearer_id;
        l->tolerance = tolerance;
        if (bc_rcvlink)
                bc_rcvlink->tolerance = tolerance;
        l->net_plane = net_plane;
        l->advertised_mtu = mtu;
        l->mtu = mtu;
        l->priority = priority;
        tipc_link_set_queue_limits(l, min_win, max_win);
        l->ackers = 1;
        l->bc_sndlink = bc_sndlink;
        l->bc_rcvlink = bc_rcvlink;
        l->inputq = inputq;
        l->namedq = namedq;
        l->state = LINK_RESETTING;
        __skb_queue_head_init(&l->transmq);
        __skb_queue_head_init(&l->backlogq);
        __skb_queue_head_init(&l->deferdq);
        __skb_queue_head_init(&l->failover_deferdq);
        skb_queue_head_init(&l->wakeupq);
        skb_queue_head_init(l->inputq);
        return true;
}

/**
 * tipc_link_bc_create - create new link to be used for broadcast
 * @net: pointer to associated network namespace
 * @mtu: mtu to be used initially if no peers
 * @min_win: minimal send window to be used by link
 * @max_win: maximal send window to be used by link
 * @inputq: queue to put messages ready for delivery
 * @namedq: queue to put binding table update messages ready for delivery
 * @link: return value, pointer to put the created link
 * @ownnode: identity of own node
 * @peer: node id of peer node
 * @peer_id: 128-bit ID of peer
 * @peer_caps: bitmap describing peer node capabilities
 * @bc_sndlink: the namespace global link used for broadcast sending
 *
 * Return: true if link was created, otherwise false
 */
bool tipc_link_bc_create(struct net *net, u32 ownnode, u32 peer, u8 *peer_id,
                         int mtu, u32 min_win, u32 max_win, u16 peer_caps,
                         struct sk_buff_head *inputq,
                         struct sk_buff_head *namedq,
                         struct tipc_link *bc_sndlink,
                         struct tipc_link **link)
{
        struct tipc_link *l;

        if (!tipc_link_create(net, "", MAX_BEARERS, 0, 'Z', mtu, 0, min_win,
                              max_win, 0, ownnode, peer, NULL, peer_caps,
                              bc_sndlink, NULL, inputq, namedq, link))
                return false;

        l = *link;
        if (peer_id) {
                char peer_str[NODE_ID_STR_LEN] = {0,};

                tipc_nodeid2string(peer_str, peer_id);
                if (strlen(peer_str) > 16)
                        sprintf(peer_str, "%x", peer);
                /* Broadcast receiver link name: "broadcast-link:<peer>" */
                snprintf(l->name, sizeof(l->name), "%s:%s", tipc_bclink_name,
                         peer_str);
        } else {
                strcpy(l->name, tipc_bclink_name);
        }
        trace_tipc_link_reset(l, TIPC_DUMP_ALL, "bclink created!");
        tipc_link_reset(l);
        l->state = LINK_RESET;
        l->ackers = 0;
        l->bc_rcvlink = l;

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

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

        return true;
}

/**
 * tipc_link_fsm_evt - link finite state machine
 * @l: pointer to link
 * @evt: state machine event to be processed
 */
int tipc_link_fsm_evt(struct tipc_link *l, int evt)
{
        int rc = 0;
        int old_state = l->state;

        switch (l->state) {
        case LINK_RESETTING:
                switch (evt) {
                case LINK_PEER_RESET_EVT:
                        l->state = LINK_PEER_RESET;
                        break;
                case LINK_RESET_EVT:
                        l->state = LINK_RESET;
                        break;
                case LINK_FAILURE_EVT:
                case LINK_FAILOVER_BEGIN_EVT:
                case LINK_ESTABLISH_EVT:
                case LINK_FAILOVER_END_EVT:
                case LINK_SYNCH_BEGIN_EVT:
                case LINK_SYNCH_END_EVT:
                default:
                        goto illegal_evt;
                }
                break;
        case LINK_RESET:
                switch (evt) {
                case LINK_PEER_RESET_EVT:
                        l->state = LINK_ESTABLISHING;
                        break;
                case LINK_FAILOVER_BEGIN_EVT:
                        l->state = LINK_FAILINGOVER;
                        break;
                case LINK_FAILURE_EVT:
                case LINK_RESET_EVT:
                case LINK_ESTABLISH_EVT:
                case LINK_FAILOVER_END_EVT:
                        break;
                case LINK_SYNCH_BEGIN_EVT:
                case LINK_SYNCH_END_EVT:
                default:
                        goto illegal_evt;
                }
                break;
        case LINK_PEER_RESET:
                switch (evt) {
                case LINK_RESET_EVT:
                        l->state = LINK_ESTABLISHING;
                        break;
                case LINK_PEER_RESET_EVT:
                case LINK_ESTABLISH_EVT:
                case LINK_FAILURE_EVT:
                        break;
                case LINK_SYNCH_BEGIN_EVT:
                case LINK_SYNCH_END_EVT:
                case LINK_FAILOVER_BEGIN_EVT:
                case LINK_FAILOVER_END_EVT:
                default:
                        goto illegal_evt;
                }
                break;
        case LINK_FAILINGOVER:
                switch (evt) {
                case LINK_FAILOVER_END_EVT:
                        l->state = LINK_RESET;
                        break;
                case LINK_PEER_RESET_EVT:
                case LINK_RESET_EVT:
                case LINK_ESTABLISH_EVT:
                case LINK_FAILURE_EVT:
                        break;
                case LINK_FAILOVER_BEGIN_EVT:
                case LINK_SYNCH_BEGIN_EVT:
                case LINK_SYNCH_END_EVT:
                default:
                        goto illegal_evt;
                }
                break;
        case LINK_ESTABLISHING:
                switch (evt) {
                case LINK_ESTABLISH_EVT:
                        l->state = LINK_ESTABLISHED;
                        break;
                case LINK_FAILOVER_BEGIN_EVT:
                        l->state = LINK_FAILINGOVER;
                        break;
                case LINK_RESET_EVT:
                        l->state = LINK_RESET;
                        break;
                case LINK_FAILURE_EVT:
                case LINK_PEER_RESET_EVT:
                case LINK_SYNCH_BEGIN_EVT:
                case LINK_FAILOVER_END_EVT:
                        break;
                case LINK_SYNCH_END_EVT:
                default:
                        goto illegal_evt;
                }
                break;
        case LINK_ESTABLISHED:
                switch (evt) {
                case LINK_PEER_RESET_EVT:
                        l->state = LINK_PEER_RESET;
                        rc |= TIPC_LINK_DOWN_EVT;
                        break;
                case LINK_FAILURE_EVT:
                        l->state = LINK_RESETTING;
                        rc |= TIPC_LINK_DOWN_EVT;
                        break;
                case LINK_RESET_EVT:
                        l->state = LINK_RESET;
                        break;
                case LINK_ESTABLISH_EVT:
                case LINK_SYNCH_END_EVT:
                        break;
                case LINK_SYNCH_BEGIN_EVT:
                        l->state = LINK_SYNCHING;
                        break;
                case LINK_FAILOVER_BEGIN_EVT:
                case LINK_FAILOVER_END_EVT:
                default:
                        goto illegal_evt;
                }
                break;
        case LINK_SYNCHING:
                switch (evt) {
                case LINK_PEER_RESET_EVT:
                        l->state = LINK_PEER_RESET;
                        rc |= TIPC_LINK_DOWN_EVT;
                        break;
                case LINK_FAILURE_EVT:
                        l->state = LINK_RESETTING;
                        rc |= TIPC_LINK_DOWN_EVT;
                        break;
                case LINK_RESET_EVT:
                        l->state = LINK_RESET;
                        break;
                case LINK_ESTABLISH_EVT:
                case LINK_SYNCH_BEGIN_EVT:
                        break;
                case LINK_SYNCH_END_EVT:
                        l->state = LINK_ESTABLISHED;
                        break;
                case LINK_FAILOVER_BEGIN_EVT:
                case LINK_FAILOVER_END_EVT:
                default:
                        goto illegal_evt;
                }
                break;
        default:
                pr_err("Unknown FSM state %x in %s\n", l->state, l->name);
        }
        trace_tipc_link_fsm(l->name, old_state, l->state, evt);
        return rc;
illegal_evt:
        pr_err("Illegal FSM event %x in state %x on link %s\n",
               evt, l->state, l->name);
        trace_tipc_link_fsm(l->name, old_state, l->state, evt);
        return rc;
}

/* link_profile_stats - update statistical profiling of traffic
 */
static void link_profile_stats(struct tipc_link *l)
{
        struct sk_buff *skb;
        struct tipc_msg *msg;
        int length;

        /* Update counters used in statistical profiling of send traffic */
        l->stats.accu_queue_sz += skb_queue_len(&l->transmq);
        l->stats.queue_sz_counts++;

        skb = skb_peek(&l->transmq);
        if (!skb)
                return;
        msg = buf_msg(skb);
        length = msg_size(msg);

        if (msg_user(msg) == MSG_FRAGMENTER) {
                if (msg_type(msg) != FIRST_FRAGMENT)
                        return;
                length = msg_size(msg_inner_hdr(msg));
        }
        l->stats.msg_lengths_total += length;
        l->stats.msg_length_counts++;
        if (length <= 64)
                l->stats.msg_length_profile[0]++;
        else if (length <= 256)
                l->stats.msg_length_profile[1]++;
        else if (length <= 1024)
                l->stats.msg_length_profile[2]++;
        else if (length <= 4096)
                l->stats.msg_length_profile[3]++;
        else if (length <= 16384)
                l->stats.msg_length_profile[4]++;
        else if (length <= 32768)
                l->stats.msg_length_profile[5]++;
        else
                l->stats.msg_length_profile[6]++;
}

/**
 * tipc_link_too_silent - check if link is "too silent"
 * @l: tipc link to be checked
 *
 * Return: true if the link 'silent_intv_cnt' is about to reach the
 * 'abort_limit' value, otherwise false
 */
bool tipc_link_too_silent(struct tipc_link *l)
{
        return (l->silent_intv_cnt + 2 > l->abort_limit);
}

/* tipc_link_timeout - perform periodic task as instructed from node timeout
 */
int tipc_link_timeout(struct tipc_link *l, struct sk_buff_head *xmitq)
{
        int mtyp = 0;
        int rc = 0;
        bool state = false;
        bool probe = false;
        bool setup = false;
        u16 bc_snt = l->bc_sndlink->snd_nxt - 1;
        u16 bc_acked = l->bc_rcvlink->acked;
        struct tipc_mon_state *mstate = &l->mon_state;

        trace_tipc_link_timeout(l, TIPC_DUMP_NONE, " ");
        trace_tipc_link_too_silent(l, TIPC_DUMP_ALL, " ");
        switch (l->state) {
        case LINK_ESTABLISHED:
        case LINK_SYNCHING:
                mtyp = STATE_MSG;
                link_profile_stats(l);
                tipc_mon_get_state(l->net, l->addr, mstate, l->bearer_id);
                if (mstate->reset || (l->silent_intv_cnt > l->abort_limit))
                        return tipc_link_fsm_evt(l, LINK_FAILURE_EVT);
                state = bc_acked != bc_snt;
                state |= l->bc_rcvlink->rcv_unacked;
                state |= l->rcv_unacked;
                state |= !skb_queue_empty(&l->transmq);
                probe = mstate->probing;
                probe |= l->silent_intv_cnt;
                if (probe || mstate->monitoring)
                        l->silent_intv_cnt++;
                probe |= !skb_queue_empty(&l->deferdq);
                if (l->snd_nxt == l->checkpoint) {
                        tipc_link_update_cwin(l, 0, 0);
                        probe = true;
                }
                l->checkpoint = l->snd_nxt;
                break;
        case LINK_RESET:
                setup = l->rst_cnt++ <= 4;
                setup |= !(l->rst_cnt % 16);
                mtyp = RESET_MSG;
                break;
        case LINK_ESTABLISHING:
                setup = true;
                mtyp = ACTIVATE_MSG;
                break;
        case LINK_PEER_RESET:
        case LINK_RESETTING:
        case LINK_FAILINGOVER:
                break;
        default:
                break;
        }

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

        return rc;
}

/**
 * link_schedule_user - schedule a message sender for wakeup after congestion
 * @l: congested link
 * @hdr: header of message that is being sent
 * Create pseudo msg to send back to user when congestion abates
 */
static int link_schedule_user(struct tipc_link *l, struct tipc_msg *hdr)
{
        u32 dnode = tipc_own_addr(l->net);
        u32 dport = msg_origport(hdr);
        struct sk_buff *skb;

        /* Create and schedule wakeup pseudo message */
        skb = tipc_msg_create(SOCK_WAKEUP, 0, INT_H_SIZE, 0,
                              dnode, l->addr, dport, 0, 0);
        if (!skb)
                return -ENOBUFS;
        msg_set_dest_droppable(buf_msg(skb), true);
        TIPC_SKB_CB(skb)->chain_imp = msg_importance(hdr);
        skb_queue_tail(&l->wakeupq, skb);
        l->stats.link_congs++;
        trace_tipc_link_conges(l, TIPC_DUMP_ALL, "wakeup scheduled!");
        return -ELINKCONG;
}

/**
 * link_prepare_wakeup - prepare users for wakeup after congestion
 * @l: congested link
 * Wake up a number of waiting users, as permitted by available space
 * in the send queue
 */
static void link_prepare_wakeup(struct tipc_link *l)
{
        struct sk_buff_head *wakeupq = &l->wakeupq;
        struct sk_buff_head *inputq = l->inputq;
        struct sk_buff *skb, *tmp;
        struct sk_buff_head tmpq;
        int avail[5] = {0,};
        int imp = 0;

        __skb_queue_head_init(&tmpq);

        for (; imp <= TIPC_SYSTEM_IMPORTANCE; imp++)
                avail[imp] = l->backlog[imp].limit - l->backlog[imp].len;

        skb_queue_walk_safe(wakeupq, skb, tmp) {
                imp = TIPC_SKB_CB(skb)->chain_imp;
                if (avail[imp] <= 0)
                        continue;
                avail[imp]--;
                __skb_unlink(skb, wakeupq);
                __skb_queue_tail(&tmpq, skb);
        }

        spin_lock_bh(&inputq->lock);
        skb_queue_splice_tail(&tmpq, inputq);
        spin_unlock_bh(&inputq->lock);

}

/**
 * tipc_link_set_skb_retransmit_time - set the time at which retransmission of
 *                                     the given skb should be next attempted
 * @skb: skb to set a future retransmission time for
 * @l: link the skb will be transmitted on
 */
static void tipc_link_set_skb_retransmit_time(struct sk_buff *skb,
                                              struct tipc_link *l)
{
        if (link_is_bc_sndlink(l))
                TIPC_SKB_CB(skb)->nxt_retr = TIPC_BC_RETR_LIM;
        else
                TIPC_SKB_CB(skb)->nxt_retr = TIPC_UC_RETR_TIME;
}

void tipc_link_reset(struct tipc_link *l)
{
        struct sk_buff_head list;
        u32 imp;

        __skb_queue_head_init(&list);

        l->in_session = false;
        /* Force re-synch of peer session number before establishing */
        l->peer_session--;
        l->session++;
        l->mtu = l->advertised_mtu;

        spin_lock_bh(&l->wakeupq.lock);
        skb_queue_splice_init(&l->wakeupq, &list);
        spin_unlock_bh(&l->wakeupq.lock);

        spin_lock_bh(&l->inputq->lock);
        skb_queue_splice_init(&list, l->inputq);
        spin_unlock_bh(&l->inputq->lock);

        __skb_queue_purge(&l->transmq);
        __skb_queue_purge(&l->deferdq);
        __skb_queue_purge(&l->backlogq);
        __skb_queue_purge(&l->failover_deferdq);
        for (imp = 0; imp <= TIPC_SYSTEM_IMPORTANCE; imp++) {
                l->backlog[imp].len = 0;
                l->backlog[imp].target_bskb = NULL;
        }
        kfree_skb(l->reasm_buf);
        kfree_skb(l->reasm_tnlmsg);
        kfree_skb(l->failover_reasm_skb);
        l->reasm_buf = NULL;
        l->reasm_tnlmsg = NULL;
        l->failover_reasm_skb = NULL;
        l->rcv_unacked = 0;
        l->snd_nxt = 1;
        l->rcv_nxt = 1;
        l->snd_nxt_state = 1;
        l->rcv_nxt_state = 1;
        l->acked = 0;
        l->last_gap = 0;
        kfree(l->last_ga);
        l->last_ga = NULL;
        l->silent_intv_cnt = 0;
        l->rst_cnt = 0;
        l->bc_peer_is_up = false;
        memset(&l->mon_state, 0, sizeof(l->mon_state));
        tipc_link_reset_stats(l);
}

/**
 * tipc_link_xmit(): enqueue buffer list according to queue situation
 * @l: link to use
 * @list: chain of buffers containing message
 * @xmitq: returned list of packets to be sent by caller
 *
 * Consumes the buffer chain.
 * Messages at TIPC_SYSTEM_IMPORTANCE are always accepted
 * Return: 0 if success, or errno: -ELINKCONG, -EMSGSIZE or -ENOBUFS
 */
int tipc_link_xmit(struct tipc_link *l, struct sk_buff_head *list,
                   struct sk_buff_head *xmitq)
{
        struct sk_buff_head *backlogq = &l->backlogq;
        struct sk_buff_head *transmq = &l->transmq;
        struct sk_buff *skb, *_skb;
        u16 bc_ack = l->bc_rcvlink->rcv_nxt - 1;
        u16 ack = l->rcv_nxt - 1;
        u16 seqno = l->snd_nxt;
        int pkt_cnt = skb_queue_len(list);
        unsigned int mss = tipc_link_mss(l);
        unsigned int cwin = l->window;
        unsigned int mtu = l->mtu;
        struct tipc_msg *hdr;
        bool new_bundle;
        int rc = 0;
        int imp;

        if (pkt_cnt <= 0)
                return 0;

        hdr = buf_msg(skb_peek(list));
        if (unlikely(msg_size(hdr) > mtu)) {
                pr_warn("Too large msg, purging xmit list %d %d %d %d %d!\n",
                        skb_queue_len(list), msg_user(hdr),
                        msg_type(hdr), msg_size(hdr), mtu);
                __skb_queue_purge(list);
                return -EMSGSIZE;
        }

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

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

        /* Prepare each packet for sending, and add to relevant queue: */
        while ((skb = __skb_dequeue(list))) {
                if (likely(skb_queue_len(transmq) < cwin)) {
                        hdr = buf_msg(skb);
                        msg_set_seqno(hdr, seqno);
                        msg_set_ack(hdr, ack);
                        msg_set_bcast_ack(hdr, bc_ack);
                        _skb = skb_clone(skb, GFP_ATOMIC);
                        if (!_skb) {
                                kfree_skb(skb);
                                __skb_queue_purge(list);
                                return -ENOBUFS;
                        }
                        __skb_queue_tail(transmq, skb);
                        tipc_link_set_skb_retransmit_time(skb, l);
                        __skb_queue_tail(xmitq, _skb);
                        TIPC_SKB_CB(skb)->ackers = l->ackers;
                        l->rcv_unacked = 0;
                        l->stats.sent_pkts++;
                        seqno++;
                        continue;
                }
                if (tipc_msg_try_bundle(l->backlog[imp].target_bskb, &skb,
                                        mss, l->addr, &new_bundle)) {
                        if (skb) {
                                /* Keep a ref. to the skb for next try */
                                l->backlog[imp].target_bskb = skb;
                                l->backlog[imp].len++;
                                __skb_queue_tail(backlogq, skb);
                        } else {
                                if (new_bundle) {
                                        l->stats.sent_bundles++;
                                        l->stats.sent_bundled++;
                                }
                                l->stats.sent_bundled++;
                        }
                        continue;
                }
                l->backlog[imp].target_bskb = NULL;
                l->backlog[imp].len += (1 + skb_queue_len(list));
                __skb_queue_tail(backlogq, skb);
                skb_queue_splice_tail_init(list, backlogq);
        }
        l->snd_nxt = seqno;
        return rc;
}

static void tipc_link_update_cwin(struct tipc_link *l, int released,
                                  bool retransmitted)
{
        int bklog_len = skb_queue_len(&l->backlogq);
        struct sk_buff_head *txq = &l->transmq;
        int txq_len = skb_queue_len(txq);
        u16 cwin = l->window;

        /* Enter fast recovery */
        if (unlikely(retransmitted)) {
                l->ssthresh = max_t(u16, l->window / 2, 300);
                l->window = min_t(u16, l->ssthresh, l->window);
                return;
        }
        /* Enter slow start */
        if (unlikely(!released)) {
                l->ssthresh = max_t(u16, l->window / 2, 300);
                l->window = l->min_win;
                return;
        }
        /* Don't increase window if no pressure on the transmit queue */
        if (txq_len + bklog_len < cwin)
                return;

        /* Don't increase window if there are holes the transmit queue */
        if (txq_len && l->snd_nxt - buf_seqno(skb_peek(txq)) != txq_len)
                return;

        l->cong_acks += released;

        /* Slow start  */
        if (cwin <= l->ssthresh) {
                l->window = min_t(u16, cwin + released, l->max_win);
                return;
        }
        /* Congestion avoidance */
        if (l->cong_acks < cwin)
                return;
        l->window = min_t(u16, ++cwin, l->max_win);
        l->cong_acks = 0;
}

static void tipc_link_advance_backlog(struct tipc_link *l,
                                      struct sk_buff_head *xmitq)
{
        u16 bc_ack = l->bc_rcvlink->rcv_nxt - 1;
        struct sk_buff_head *txq = &l->transmq;
        struct sk_buff *skb, *_skb;
        u16 ack = l->rcv_nxt - 1;
        u16 seqno = l->snd_nxt;
        struct tipc_msg *hdr;
        u16 cwin = l->window;
        u32 imp;

        while (skb_queue_len(txq) < cwin) {
                skb = skb_peek(&l->backlogq);
                if (!skb)
                        break;
                _skb = skb_clone(skb, GFP_ATOMIC);
                if (!_skb)
                        break;
                __skb_dequeue(&l->backlogq);
                hdr = buf_msg(skb);
                imp = msg_importance(hdr);
                l->backlog[imp].len--;
                if (unlikely(skb == l->backlog[imp].target_bskb))
                        l->backlog[imp].target_bskb = NULL;
                __skb_queue_tail(&l->transmq, skb);
                tipc_link_set_skb_retransmit_time(skb, l);

                __skb_queue_tail(xmitq, _skb);
                TIPC_SKB_CB(skb)->ackers = l->ackers;
                msg_set_seqno(hdr, seqno);
                msg_set_ack(hdr, ack);
                msg_set_bcast_ack(hdr, bc_ack);
                l->rcv_unacked = 0;
                l->stats.sent_pkts++;
                seqno++;
        }
        l->snd_nxt = seqno;
}

/**
 * link_retransmit_failure() - Detect repeated retransmit failures
 * @l: tipc link sender
 * @r: tipc link receiver (= l in case of unicast)
 * @rc: returned code
 *
 * Return: true if the repeated retransmit failures happens, otherwise
 * false
 */
static bool link_retransmit_failure(struct tipc_link *l, struct tipc_link *r,
                                    int *rc)
{
        struct sk_buff *skb = skb_peek(&l->transmq);
        struct tipc_msg *hdr;

        if (!skb)
                return false;

        if (!TIPC_SKB_CB(skb)->retr_cnt)
                return false;

        if (!time_after(jiffies, TIPC_SKB_CB(skb)->retr_stamp +
                        msecs_to_jiffies(r->tolerance * 10)))
                return false;

        hdr = buf_msg(skb);
        if (link_is_bc_sndlink(l) && !less(r->acked, msg_seqno(hdr)))
                return false;

        pr_warn("Retransmission failure on link <%s>\n", l->name);
        link_print(l, "State of link ");
        pr_info("Failed msg: usr %u, typ %u, len %u, err %u\n",
                msg_user(hdr), msg_type(hdr), msg_size(hdr), msg_errcode(hdr));
        pr_info("sqno %u, prev: %x, dest: %x\n",
                msg_seqno(hdr), msg_prevnode(hdr), msg_destnode(hdr));
        pr_info("retr_stamp %d, retr_cnt %d\n",
                jiffies_to_msecs(TIPC_SKB_CB(skb)->retr_stamp),
                TIPC_SKB_CB(skb)->retr_cnt);

        trace_tipc_list_dump(&l->transmq, true, "retrans failure!");
        trace_tipc_link_dump(l, TIPC_DUMP_NONE, "retrans failure!");
        trace_tipc_link_dump(r, TIPC_DUMP_NONE, "retrans failure!");

        if (link_is_bc_sndlink(l)) {
                r->state = LINK_RESET;
                *rc |= TIPC_LINK_DOWN_EVT;
        } else {
                *rc |= tipc_link_fsm_evt(l, LINK_FAILURE_EVT);
        }

        return true;
}

/* tipc_data_input - deliver data and name distr msgs to upper layer
 *
 * Consumes buffer if message is of right type
 * Node lock must be held
 */
static bool tipc_data_input(struct tipc_link *l, struct sk_buff *skb,
                            struct sk_buff_head *inputq)
{
        struct sk_buff_head *mc_inputq = l->bc_rcvlink->inputq;
        struct tipc_msg *hdr = buf_msg(skb);

        switch (msg_user(hdr)) {
        case TIPC_LOW_IMPORTANCE:
        case TIPC_MEDIUM_IMPORTANCE:
        case TIPC_HIGH_IMPORTANCE:
        case TIPC_CRITICAL_IMPORTANCE:
                if (unlikely(msg_in_group(hdr) || msg_mcast(hdr))) {
                        skb_queue_tail(mc_inputq, skb);
                        return true;
                }
                fallthrough;
        case CONN_MANAGER:
                skb_queue_tail(inputq, skb);
                return true;
        case GROUP_PROTOCOL:
                skb_queue_tail(mc_inputq, skb);
                return true;
        case NAME_DISTRIBUTOR:
                l->bc_rcvlink->state = LINK_ESTABLISHED;
                skb_queue_tail(l->namedq, skb);
                return true;
        case MSG_BUNDLER:
        case TUNNEL_PROTOCOL:
        case MSG_FRAGMENTER:
        case BCAST_PROTOCOL:
                return false;
#ifdef CONFIG_TIPC_CRYPTO
        case MSG_CRYPTO:
                if (sysctl_tipc_key_exchange_enabled &&
                    TIPC_SKB_CB(skb)->decrypted) {
                        tipc_crypto_msg_rcv(l->net, skb);
                        return true;
                }
                fallthrough;
#endif
        default:
                pr_warn("Dropping received illegal msg type\n");
                kfree_skb(skb);
                return true;
        }
}

/* tipc_link_input - process packet that has passed link protocol check
 *
 * Consumes buffer
 */
static int tipc_link_input(struct tipc_link *l, struct sk_buff *skb,
                           struct sk_buff_head *inputq,
                           struct sk_buff **reasm_skb)
{
        struct tipc_msg *hdr = buf_msg(skb);
        struct sk_buff *iskb;
        struct sk_buff_head tmpq;
        int usr = msg_user(hdr);
        int pos = 0;

        if (usr == MSG_BUNDLER) {
                skb_queue_head_init(&tmpq);
                l->stats.recv_bundles++;
                l->stats.recv_bundled += msg_msgcnt(hdr);
                while (tipc_msg_extract(skb, &iskb, &pos))
                        tipc_data_input(l, iskb, &tmpq);
                tipc_skb_queue_splice_tail(&tmpq, inputq);
                return 0;
        } else if (usr == MSG_FRAGMENTER) {
                l->stats.recv_fragments++;
                if (tipc_buf_append(reasm_skb, &skb)) {
                        l->stats.recv_fragmented++;
                        tipc_data_input(l, skb, inputq);
                } else if (!*reasm_skb && !link_is_bc_rcvlink(l)) {
                        pr_warn_ratelimited("Unable to build fragment list\n");
                        return tipc_link_fsm_evt(l, LINK_FAILURE_EVT);
                }
                return 0;
        } else if (usr == BCAST_PROTOCOL) {
                tipc_bcast_lock(l->net);
                tipc_link_bc_init_rcv(l->bc_rcvlink, hdr);
                tipc_bcast_unlock(l->net);
        }

        kfree_skb(skb);
        return 0;
}

/* tipc_link_tnl_rcv() - receive TUNNEL_PROTOCOL message, drop or process the
 *                       inner message along with the ones in the old link's
 *                       deferdq
 * @l: tunnel link
 * @skb: TUNNEL_PROTOCOL message
 * @inputq: queue to put messages ready for delivery
 */
static int tipc_link_tnl_rcv(struct tipc_link *l, struct sk_buff *skb,
                             struct sk_buff_head *inputq)
{
        struct sk_buff **reasm_skb = &l->failover_reasm_skb;
        struct sk_buff **reasm_tnlmsg = &l->reasm_tnlmsg;
        struct sk_buff_head *fdefq = &l->failover_deferdq;
        struct tipc_msg *hdr = buf_msg(skb);
        struct sk_buff *iskb;
        int ipos = 0;
        int rc = 0;
        u16 seqno;

        if (msg_type(hdr) == SYNCH_MSG) {
                kfree_skb(skb);
                return 0;
        }

        /* Not a fragment? */
        if (likely(!msg_nof_fragms(hdr))) {
                if (unlikely(!tipc_msg_extract(skb, &iskb, &ipos))) {
                        pr_warn_ratelimited("Unable to extract msg, defq: %d\n",
                                            skb_queue_len(fdefq));
                        return 0;
                }
                kfree_skb(skb);
        } else {
                /* Set fragment type for buf_append */
                if (msg_fragm_no(hdr) == 1)
                        msg_set_type(hdr, FIRST_FRAGMENT);
                else if (msg_fragm_no(hdr) < msg_nof_fragms(hdr))
                        msg_set_type(hdr, FRAGMENT);
                else
                        msg_set_type(hdr, LAST_FRAGMENT);

                if (!tipc_buf_append(reasm_tnlmsg, &skb)) {
                        /* Successful but non-complete reassembly? */
                        if (*reasm_tnlmsg || link_is_bc_rcvlink(l))
                                return 0;
                        pr_warn_ratelimited("Unable to reassemble tunnel msg\n");
                        return tipc_link_fsm_evt(l, LINK_FAILURE_EVT);
                }
                iskb = skb;
        }

        do {
                seqno = buf_seqno(iskb);
                if (unlikely(less(seqno, l->drop_point))) {
                        kfree_skb(iskb);
                        continue;
                }
                if (unlikely(seqno != l->drop_point)) {
                        __tipc_skb_queue_sorted(fdefq, seqno, iskb);
                        continue;
                }

                l->drop_point++;
                if (!tipc_data_input(l, iskb, inputq))
                        rc |= tipc_link_input(l, iskb, inputq, reasm_skb);
                if (unlikely(rc))
                        break;
        } while ((iskb = __tipc_skb_dequeue(fdefq, l->drop_point)));

        return rc;
}

/**
 * tipc_get_gap_ack_blks - get Gap ACK blocks from PROTOCOL/STATE_MSG
 * @ga: returned pointer to the Gap ACK blocks if any
 * @l: the tipc link
 * @hdr: the PROTOCOL/STATE_MSG header
 * @uc: desired Gap ACK blocks type, i.e. unicast (= 1) or broadcast (= 0)
 *
 * Return: the total Gap ACK blocks size
 */
u16 tipc_get_gap_ack_blks(struct tipc_gap_ack_blks **ga, struct tipc_link *l,
                          struct tipc_msg *hdr, bool uc)
{
        struct tipc_gap_ack_blks *p;
        u16 sz = 0;

        /* Does peer support the Gap ACK blocks feature? */
        if (l->peer_caps & TIPC_GAP_ACK_BLOCK) {
                p = (struct tipc_gap_ack_blks *)msg_data(hdr);
                sz = ntohs(p->len);
                /* Sanity check */
                if (sz == struct_size(p, gacks, size_add(p->ugack_cnt, p->bgack_cnt))) {
                        /* Good, check if the desired type exists */
                        if ((uc && p->ugack_cnt) || (!uc && p->bgack_cnt))
                                goto ok;
                /* Backward compatible: peer might not support bc, but uc? */
                } else if (uc && sz == struct_size(p, gacks, p->ugack_cnt)) {
                        if (p->ugack_cnt) {
                                p->bgack_cnt = 0;
                                goto ok;
                        }
                }
        }
        /* Other cases: ignore! */
        p = NULL;

ok:
        *ga = p;
        return sz;
}

static u8 __tipc_build_gap_ack_blks(struct tipc_gap_ack_blks *ga,
                                    struct tipc_link *l, u8 start_index)
{
        struct tipc_gap_ack *gacks = &ga->gacks[start_index];
        struct sk_buff *skb = skb_peek(&l->deferdq);
        u16 expect, seqno = 0;
        u8 n = 0;

        if (!skb)
                return 0;

        expect = buf_seqno(skb);
        skb_queue_walk(&l->deferdq, skb) {
                seqno = buf_seqno(skb);
                if (unlikely(more(seqno, expect))) {
                        gacks[n].ack = htons(expect - 1);
                        gacks[n].gap = htons(seqno - expect);
                        if (++n >= MAX_GAP_ACK_BLKS / 2) {
                                pr_info_ratelimited("Gacks on %s: %d, ql: %d!\n",
                                                    l->name, n,
                                                    skb_queue_len(&l->deferdq));
                                return n;
                        }
                } else if (unlikely(less(seqno, expect))) {
                        pr_warn("Unexpected skb in deferdq!\n");
                        continue;
                }
                expect = seqno + 1;
        }

        /* last block */
        gacks[n].ack = htons(seqno);
        gacks[n].gap = 0;
        n++;
        return n;
}

/* tipc_build_gap_ack_blks - build Gap ACK blocks
 * @l: tipc unicast link
 * @hdr: the tipc message buffer to store the Gap ACK blocks after built
 *
 * The function builds Gap ACK blocks for both the unicast & broadcast receiver
 * links of a certain peer, the buffer after built has the network data format
 * as found at the struct tipc_gap_ack_blks definition.
 *
 * returns the actual allocated memory size
 */
static u16 tipc_build_gap_ack_blks(struct tipc_link *l, struct tipc_msg *hdr)
{
        struct tipc_link *bcl = l->bc_rcvlink;
        struct tipc_gap_ack_blks *ga;
        u16 len;

        ga = (struct tipc_gap_ack_blks *)msg_data(hdr);

        /* Start with broadcast link first */
        tipc_bcast_lock(bcl->net);
        msg_set_bcast_ack(hdr, bcl->rcv_nxt - 1);
        msg_set_bc_gap(hdr, link_bc_rcv_gap(bcl));
        ga->bgack_cnt = __tipc_build_gap_ack_blks(ga, bcl, 0);
        tipc_bcast_unlock(bcl->net);

        /* Now for unicast link, but an explicit NACK only (???) */
        ga->ugack_cnt = (msg_seq_gap(hdr)) ?
                        __tipc_build_gap_ack_blks(ga, l, ga->bgack_cnt) : 0;

        /* Total len */
        len = struct_size(ga, gacks, size_add(ga->bgack_cnt, ga->ugack_cnt));
        ga->len = htons(len);
        return len;
}

/* tipc_link_advance_transmq - advance TIPC link transmq queue by releasing
 *                             acked packets, also doing retransmissions if
 *                             gaps found
 * @l: tipc link with transmq queue to be advanced
 * @r: tipc link "receiver" i.e. in case of broadcast (= "l" if unicast)
 * @acked: seqno of last packet acked by peer without any gaps before
 * @gap: # of gap packets
 * @ga: buffer pointer to Gap ACK blocks from peer
 * @xmitq: queue for accumulating the retransmitted packets if any
 * @retransmitted: returned boolean value if a retransmission is really issued
 * @rc: returned code e.g. TIPC_LINK_DOWN_EVT if a repeated retransmit failures
 *      happens (- unlikely case)
 *
 * Return: the number of packets released from the link transmq
 */
static int tipc_link_advance_transmq(struct tipc_link *l, struct tipc_link *r,
                                     u16 acked, u16 gap,
                                     struct tipc_gap_ack_blks *ga,
                                     struct sk_buff_head *xmitq,
                                     bool *retransmitted, int *rc)
{
        struct tipc_gap_ack_blks *last_ga = r->last_ga, *this_ga = NULL;
        struct tipc_gap_ack *gacks = NULL;
        struct sk_buff *skb, *_skb, *tmp;
        struct tipc_msg *hdr;
        u32 qlen = skb_queue_len(&l->transmq);
        u16 nacked = acked, ngap = gap, gack_cnt = 0;
        u16 bc_ack = l->bc_rcvlink->rcv_nxt - 1;
        u16 ack = l->rcv_nxt - 1;
        u16 seqno, n = 0;
        u16 end = r->acked, start = end, offset = r->last_gap;
        u16 si = (last_ga) ? last_ga->start_index : 0;
        bool is_uc = !link_is_bc_sndlink(l);
        bool bc_has_acked = false;

        trace_tipc_link_retrans(r, acked + 1, acked + gap, &l->transmq);

        /* Determine Gap ACK blocks if any for the particular link */
        if (ga && is_uc) {
                /* Get the Gap ACKs, uc part */
                gack_cnt = ga->ugack_cnt;
                gacks = &ga->gacks[ga->bgack_cnt];
        } else if (ga) {
                /* Copy the Gap ACKs, bc part, for later renewal if needed */
                this_ga = kmemdup(ga, struct_size(ga, gacks, ga->bgack_cnt),
                                  GFP_ATOMIC);
                if (likely(this_ga)) {
                        this_ga->start_index = 0;
                        /* Start with the bc Gap ACKs */
                        gack_cnt = this_ga->bgack_cnt;
                        gacks = &this_ga->gacks[0];
                } else {
                        /* Hmm, we can get in trouble..., simply ignore it */
                        pr_warn_ratelimited("Ignoring bc Gap ACKs, no memory\n");
                }
        }

        /* Advance the link transmq */
        skb_queue_walk_safe(&l->transmq, skb, tmp) {
                seqno = buf_seqno(skb);

next_gap_ack:
                if (less_eq(seqno, nacked)) {
                        if (is_uc)
                                goto release;
                        /* Skip packets peer has already acked */
                        if (!more(seqno, r->acked))
                                continue;
                        /* Get the next of last Gap ACK blocks */
                        while (more(seqno, end)) {
                                if (!last_ga || si >= last_ga->bgack_cnt)
                                        break;
                                start = end + offset + 1;
                                end = ntohs(last_ga->gacks[si].ack);
                                offset = ntohs(last_ga->gacks[si].gap);
                                si++;
                                WARN_ONCE(more(start, end) ||
                                          (!offset &&
                                           si < last_ga->bgack_cnt) ||
                                          si > MAX_GAP_ACK_BLKS,
                                          "Corrupted Gap ACK: %d %d %d %d %d\n",
                                          start, end, offset, si,
                                          last_ga->bgack_cnt);
                        }
                        /* Check against the last Gap ACK block */
                        if (tipc_in_range(seqno, start, end))
                                continue;
                        /* Update/release the packet peer is acking */
                        bc_has_acked = true;
                        if (--TIPC_SKB_CB(skb)->ackers)
                                continue;
release:
                        /* release skb */
                        __skb_unlink(skb, &l->transmq);
                        kfree_skb(skb);
                } else if (less_eq(seqno, nacked + ngap)) {
                        /* First gap: check if repeated retrans failures? */
                        if (unlikely(seqno == acked + 1 &&
                                     link_retransmit_failure(l, r, rc))) {
                                /* Ignore this bc Gap ACKs if any */
                                kfree(this_ga);
                                this_ga = NULL;
                                break;
                        }
                        /* retransmit skb if unrestricted*/
                        if (time_before(jiffies, TIPC_SKB_CB(skb)->nxt_retr))
                                continue;
                        tipc_link_set_skb_retransmit_time(skb, l);
                        _skb = pskb_copy(skb, GFP_ATOMIC);
                        if (!_skb)
                                continue;
                        hdr = buf_msg(_skb);
                        msg_set_ack(hdr, ack);
                        msg_set_bcast_ack(hdr, bc_ack);
                        _skb->priority = TC_PRIO_CONTROL;
                        __skb_queue_tail(xmitq, _skb);
                        l->stats.retransmitted++;
                        if (!is_uc)
                                r->stats.retransmitted++;
                        *retransmitted = true;
                        /* Increase actual retrans counter & mark first time */
                        if (!TIPC_SKB_CB(skb)->retr_cnt++)
                                TIPC_SKB_CB(skb)->retr_stamp = jiffies;
                } else {
                        /* retry with Gap ACK blocks if any */
                        if (n >= gack_cnt)
                                break;
                        nacked = ntohs(gacks[n].ack);
                        ngap = ntohs(gacks[n].gap);
                        n++;
                        goto next_gap_ack;
                }
        }

        /* Renew last Gap ACK blocks for bc if needed */
        if (bc_has_acked) {
                if (this_ga) {
                        kfree(last_ga);
                        r->last_ga = this_ga;
                        r->last_gap = gap;
                } else if (last_ga) {
                        if (less(acked, start)) {
                                si--;
                                offset = start - acked - 1;
                        } else if (less(acked, end)) {
                                acked = end;
                        }
                        if (si < last_ga->bgack_cnt) {
                                last_ga->start_index = si;
                                r->last_gap = offset;
                        } else {
                                kfree(last_ga);
                                r->last_ga = NULL;
                                r->last_gap = 0;
                        }
                } else {
                        r->last_gap = 0;
                }
                r->acked = acked;
        } else {
                kfree(this_ga);
        }

        return qlen - skb_queue_len(&l->transmq);
}

/* tipc_link_build_state_msg: prepare link state message for transmission
 *
 * Note that sending of broadcast ack is coordinated among nodes, to reduce
 * risk of ack storms towards the sender
 */
int tipc_link_build_state_msg(struct tipc_link *l, struct sk_buff_head *xmitq)
{
        if (!l)
                return 0;

        /* Broadcast ACK must be sent via a unicast link => defer to caller */
        if (link_is_bc_rcvlink(l)) {
                if (((l->rcv_nxt ^ tipc_own_addr(l->net)) & 0xf) != 0xf)
                        return 0;
                l->rcv_unacked = 0;

                /* Use snd_nxt to store peer's snd_nxt in broadcast rcv link */
                l->snd_nxt = l->rcv_nxt;
                return TIPC_LINK_SND_STATE;
        }
        /* Unicast ACK */
        l->rcv_unacked = 0;
        l->stats.sent_acks++;
        tipc_link_build_proto_msg(l, STATE_MSG, 0, 0, 0, 0, 0, xmitq);
        return 0;
}

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

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

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

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

/* tipc_link_build_nack_msg: prepare link nack message for transmission
 * Note that sending of broadcast NACK is coordinated among nodes, to
 * reduce the risk of NACK storms towards the sender
 */
static int tipc_link_build_nack_msg(struct tipc_link *l,
                                    struct sk_buff_head *xmitq)
{
        u32 def_cnt = ++l->stats.deferred_recv;
        struct sk_buff_head *dfq = &l->deferdq;
        u32 defq_len = skb_queue_len(dfq);
        int match1, match2;

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

        if (defq_len >= 3 && !((defq_len - 3) % 16)) {
                u16 rcvgap = buf_seqno(skb_peek(dfq)) - l->rcv_nxt;

                tipc_link_build_proto_msg(l, STATE_MSG, 0, 0,
                                          rcvgap, 0, 0, xmitq);
        }
        return 0;
}

/* tipc_link_rcv - process TIPC packets/messages arriving from off-node
 * @l: the link that should handle the message
 * @skb: TIPC packet
 * @xmitq: queue to place packets to be sent after this call
 */
int tipc_link_rcv(struct tipc_link *l, struct sk_buff *skb,
                  struct sk_buff_head *xmitq)
{
        struct sk_buff_head *defq = &l->deferdq;
        struct tipc_msg *hdr = buf_msg(skb);
        u16 seqno, rcv_nxt, win_lim;
        int released = 0;
        int rc = 0;

        /* Verify and update link state */
        if (unlikely(msg_user(hdr) == LINK_PROTOCOL))
                return tipc_link_proto_rcv(l, skb, xmitq);

        /* Don't send probe at next timeout expiration */
        l->silent_intv_cnt = 0;

        do {
                hdr = buf_msg(skb);
                seqno = msg_seqno(hdr);
                rcv_nxt = l->rcv_nxt;
                win_lim = rcv_nxt + TIPC_MAX_LINK_WIN;

                if (unlikely(!link_is_up(l))) {
                        if (l->state == LINK_ESTABLISHING)
                                rc = TIPC_LINK_UP_EVT;
                        kfree_skb(skb);
                        break;
                }

                /* Drop if outside receive window */
                if (unlikely(less(seqno, rcv_nxt) || more(seqno, win_lim))) {
                        l->stats.duplicates++;
                        kfree_skb(skb);
                        break;
                }
                released += tipc_link_advance_transmq(l, l, msg_ack(hdr), 0,
                                                      NULL, NULL, NULL, NULL);

                /* Defer delivery if sequence gap */
                if (unlikely(seqno != rcv_nxt)) {
                        if (!__tipc_skb_queue_sorted(defq, seqno, skb))
                                l->stats.duplicates++;
                        rc |= tipc_link_build_nack_msg(l, xmitq);
                        break;
                }

                /* Deliver packet */
                l->rcv_nxt++;
                l->stats.recv_pkts++;

                if (unlikely(msg_user(hdr) == TUNNEL_PROTOCOL))
                        rc |= tipc_link_tnl_rcv(l, skb, l->inputq);
                else if (!tipc_data_input(l, skb, l->inputq))
                        rc |= tipc_link_input(l, skb, l->inputq, &l->reasm_buf);
                if (unlikely(++l->rcv_unacked >= TIPC_MIN_LINK_WIN))
                        rc |= tipc_link_build_state_msg(l, xmitq);
                if (unlikely(rc & ~TIPC_LINK_SND_STATE))
                        break;
        } while ((skb = __tipc_skb_dequeue(defq, l->rcv_nxt)));

        /* Forward queues and wake up waiting users */
        if (released) {
                tipc_link_update_cwin(l, released, 0);
                tipc_link_advance_backlog(l, xmitq);
                if (unlikely(!skb_queue_empty(&l->wakeupq)))
                        link_prepare_wakeup(l);
        }
        return rc;
}

static void tipc_link_build_proto_msg(struct tipc_link *l, int mtyp, bool probe,
                                      bool probe_reply, u16 rcvgap,
                                      int tolerance, int priority,
                                      struct sk_buff_head *xmitq)
{
        struct tipc_mon_state *mstate = &l->mon_state;
        struct sk_buff_head *dfq = &l->deferdq;
        struct tipc_link *bcl = l->bc_rcvlink;
        struct tipc_msg *hdr;
        struct sk_buff *skb;
        bool node_up = link_is_up(bcl);
        u16 glen = 0, bc_rcvgap = 0;
        int dlen = 0;
        void *data;

        /* Don't send protocol message during reset or link failover */
        if (tipc_link_is_blocked(l))
                return;

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

        if ((probe || probe_reply) && !skb_queue_empty(dfq))
                rcvgap = buf_seqno(skb_peek(dfq)) - l->rcv_nxt;

        skb = tipc_msg_create(LINK_PROTOCOL, mtyp, INT_H_SIZE,
                              tipc_max_domain_size + MAX_GAP_ACK_BLKS_SZ,
                              l->addr, tipc_own_addr(l->net), 0, 0, 0);
        if (!skb)
                return;

        hdr = buf_msg(skb);
        data = msg_data(hdr);
        msg_set_session(hdr, l->session);
        msg_set_bearer_id(hdr, l->bearer_id);
        msg_set_net_plane(hdr, l->net_plane);
        msg_set_next_sent(hdr, l->snd_nxt);
        msg_set_ack(hdr, l->rcv_nxt - 1);
        msg_set_bcast_ack(hdr, bcl->rcv_nxt - 1);
        msg_set_bc_ack_invalid(hdr, !node_up);
        msg_set_last_bcast(hdr, l->bc_sndlink->snd_nxt - 1);
        msg_set_link_tolerance(hdr, tolerance);
        msg_set_linkprio(hdr, priority);
        msg_set_redundant_link(hdr, node_up);
        msg_set_seq_gap(hdr, 0);
        msg_set_seqno(hdr, l->snd_nxt + U16_MAX / 2);

        if (mtyp == STATE_MSG) {
                if (l->peer_caps & TIPC_LINK_PROTO_SEQNO)
                        msg_set_seqno(hdr, l->snd_nxt_state++);
                msg_set_seq_gap(hdr, rcvgap);
                bc_rcvgap = link_bc_rcv_gap(bcl);
                msg_set_bc_gap(hdr, bc_rcvgap);
                msg_set_probe(hdr, probe);
                msg_set_is_keepalive(hdr, probe || probe_reply);
                if (l->peer_caps & TIPC_GAP_ACK_BLOCK)
                        glen = tipc_build_gap_ack_blks(l, hdr);
                tipc_mon_prep(l->net, data + glen, &dlen, mstate, l->bearer_id);
                msg_set_size(hdr, INT_H_SIZE + glen + dlen);
                skb_trim(skb, INT_H_SIZE + glen + dlen);
                l->stats.sent_states++;
                l->rcv_unacked = 0;
        } else {
                /* RESET_MSG or ACTIVATE_MSG */
                if (mtyp == ACTIVATE_MSG) {
                        msg_set_dest_session_valid(hdr, 1);
                        msg_set_dest_session(hdr, l->peer_session);
                }
                msg_set_max_pkt(hdr, l->advertised_mtu);
                strcpy(data, l->if_name);
                msg_set_size(hdr, INT_H_SIZE + TIPC_MAX_IF_NAME);
                skb_trim(skb, INT_H_SIZE + TIPC_MAX_IF_NAME);
        }
        if (probe)
                l->stats.sent_probes++;
        if (rcvgap)
                l->stats.sent_nacks++;
        if (bc_rcvgap)
                bcl->stats.sent_nacks++;
        skb->priority = TC_PRIO_CONTROL;
        __skb_queue_tail(xmitq, skb);
        trace_tipc_proto_build(skb, false, l->name);
}

void tipc_link_create_dummy_tnl_msg(struct tipc_link *l,
                                    struct sk_buff_head *xmitq)
{
        u32 onode = tipc_own_addr(l->net);
        struct tipc_msg *hdr, *ihdr;
        struct sk_buff_head tnlq;
        struct sk_buff *skb;
        u32 dnode = l->addr;

        __skb_queue_head_init(&tnlq);
        skb = tipc_msg_create(TUNNEL_PROTOCOL, FAILOVER_MSG,
                              INT_H_SIZE, BASIC_H_SIZE,
                              dnode, onode, 0, 0, 0);
        if (!skb) {
                pr_warn("%sunable to create tunnel packet\n", link_co_err);
                return;
        }

        hdr = buf_msg(skb);
        msg_set_msgcnt(hdr, 1);
        msg_set_bearer_id(hdr, l->peer_bearer_id);

        ihdr = (struct tipc_msg *)msg_data(hdr);
        tipc_msg_init(onode, ihdr, TIPC_LOW_IMPORTANCE, TIPC_DIRECT_MSG,
                      BASIC_H_SIZE, dnode);
        msg_set_errcode(ihdr, TIPC_ERR_NO_PORT);
        __skb_queue_tail(&tnlq, skb);
        tipc_link_xmit(l, &tnlq, xmitq);
}

/* tipc_link_tnl_prepare(): prepare and return a list of tunnel packets
 * with contents of the link's transmit and backlog queues.
 */
void tipc_link_tnl_prepare(struct tipc_link *l, struct tipc_link *tnl,
                           int mtyp, struct sk_buff_head *xmitq)
{
        struct sk_buff_head *fdefq = &tnl->failover_deferdq;
        struct sk_buff *skb, *tnlskb;
        struct tipc_msg *hdr, tnlhdr;
        struct sk_buff_head *queue = &l->transmq;
        struct sk_buff_head tmpxq, tnlq, frags;
        u16 pktlen, pktcnt, seqno = l->snd_nxt;
        bool pktcnt_need_update = false;
        u16 syncpt;
        int rc;

        if (!tnl)
                return;

        __skb_queue_head_init(&tnlq);
        /* Link Synching:
         * From now on, send only one single ("dummy") SYNCH message
         * to peer. The SYNCH message does not contain any data, just
         * a header conveying the synch point to the peer.
         */
        if (mtyp == SYNCH_MSG && (tnl->peer_caps & TIPC_TUNNEL_ENHANCED)) {
                tnlskb = tipc_msg_create(TUNNEL_PROTOCOL, SYNCH_MSG,
                                         INT_H_SIZE, 0, l->addr,
                                         tipc_own_addr(l->net),
                                         0, 0, 0);
                if (!tnlskb) {
                        pr_warn("%sunable to create dummy SYNCH_MSG\n",
                                link_co_err);
                        return;
                }

                hdr = buf_msg(tnlskb);
                syncpt = l->snd_nxt + skb_queue_len(&l->backlogq) - 1;
                msg_set_syncpt(hdr, syncpt);
                msg_set_bearer_id(hdr, l->peer_bearer_id);
                __skb_queue_tail(&tnlq, tnlskb);
                tipc_link_xmit(tnl, &tnlq, xmitq);
                return;
        }

        __skb_queue_head_init(&tmpxq);
        __skb_queue_head_init(&frags);
        /* At least one packet required for safe algorithm => add dummy */
        skb = tipc_msg_create(TIPC_LOW_IMPORTANCE, TIPC_DIRECT_MSG,
                              BASIC_H_SIZE, 0, l->addr, tipc_own_addr(l->net),
                              0, 0, TIPC_ERR_NO_PORT);
        if (!skb) {
                pr_warn("%sunable to create tunnel packet\n", link_co_err);
                return;
        }
        __skb_queue_tail(&tnlq, skb);
        tipc_link_xmit(l, &tnlq, &tmpxq);
        __skb_queue_purge(&tmpxq);

        /* Initialize reusable tunnel packet header */
        tipc_msg_init(tipc_own_addr(l->net), &tnlhdr, TUNNEL_PROTOCOL,
                      mtyp, INT_H_SIZE, l->addr);
        if (mtyp == SYNCH_MSG)
                pktcnt = l->snd_nxt - buf_seqno(skb_peek(&l->transmq));
        else
                pktcnt = skb_queue_len(&l->transmq);
        pktcnt += skb_queue_len(&l->backlogq);
        msg_set_msgcnt(&tnlhdr, pktcnt);
        msg_set_bearer_id(&tnlhdr, l->peer_bearer_id);
tnl:
        /* Wrap each packet into a tunnel packet */
        skb_queue_walk(queue, skb) {
                hdr = buf_msg(skb);
                if (queue == &l->backlogq)
                        msg_set_seqno(hdr, seqno++);
                pktlen = msg_size(hdr);

                /* Tunnel link MTU is not large enough? This could be
                 * due to:
                 * 1) Link MTU has just changed or set differently;
                 * 2) Or FAILOVER on the top of a SYNCH message
                 *
                 * The 2nd case should not happen if peer supports
                 * TIPC_TUNNEL_ENHANCED
                 */
                if (pktlen > tnl->mtu - INT_H_SIZE) {
                        if (mtyp == FAILOVER_MSG &&
                            (tnl->peer_caps & TIPC_TUNNEL_ENHANCED)) {
                                rc = tipc_msg_fragment(skb, &tnlhdr, tnl->mtu,
                                                       &frags);
                                if (rc) {
                                        pr_warn("%sunable to frag msg: rc %d\n",
                                                link_co_err, rc);
                                        return;
                                }
                                pktcnt += skb_queue_len(&frags) - 1;
                                pktcnt_need_update = true;
                                skb_queue_splice_tail_init(&frags, &tnlq);
                                continue;
                        }
                        /* Unluckily, peer doesn't have TIPC_TUNNEL_ENHANCED
                         * => Just warn it and return!
                         */
                        pr_warn_ratelimited("%stoo large msg <%d, %d>: %d!\n",
                                            link_co_err, msg_user(hdr),
                                            msg_type(hdr), msg_size(hdr));
                        return;
                }

                msg_set_size(&tnlhdr, pktlen + INT_H_SIZE);
                tnlskb = tipc_buf_acquire(pktlen + INT_H_SIZE, GFP_ATOMIC);
                if (!tnlskb) {
                        pr_warn("%sunable to send packet\n", link_co_err);
                        return;
                }
                skb_copy_to_linear_data(tnlskb, &tnlhdr, INT_H_SIZE);
                skb_copy_to_linear_data_offset(tnlskb, INT_H_SIZE, hdr, pktlen);
                __skb_queue_tail(&tnlq, tnlskb);
        }
        if (queue != &l->backlogq) {
                queue = &l->backlogq;
                goto tnl;
        }

        if (pktcnt_need_update)
                skb_queue_walk(&tnlq, skb) {
                        hdr = buf_msg(skb);
                        msg_set_msgcnt(hdr, pktcnt);
                }

        tipc_link_xmit(tnl, &tnlq, xmitq);

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

                /* Failover the link's deferdq */
                if (unlikely(!skb_queue_empty(fdefq))) {
                        pr_warn("Link failover deferdq not empty: %d!\n",
                                skb_queue_len(fdefq));
                        __skb_queue_purge(fdefq);
                }
                skb_queue_splice_init(&l->deferdq, fdefq);
        }
}

/**
 * tipc_link_failover_prepare() - prepare tnl for link failover
 *
 * This is a special version of the precursor - tipc_link_tnl_prepare(),
 * see the tipc_node_link_failover() for details
 *
 * @l: failover link
 * @tnl: tunnel link
 * @xmitq: queue for messages to be xmited
 */
void tipc_link_failover_prepare(struct tipc_link *l, struct tipc_link *tnl,
                                struct sk_buff_head *xmitq)
{
        struct sk_buff_head *fdefq = &tnl->failover_deferdq;

        tipc_link_create_dummy_tnl_msg(tnl, xmitq);

        /* This failover link endpoint was never established before,
         * so it has not received anything from peer.
         * Otherwise, it must be a normal failover situation or the
         * node has entered SELF_DOWN_PEER_LEAVING and both peer nodes
         * would have to start over from scratch instead.
         */
        tnl->drop_point = 1;
        tnl->failover_reasm_skb = NULL;

        /* Initiate the link's failover deferdq */
        if (unlikely(!skb_queue_empty(fdefq))) {
                pr_warn("Link failover deferdq not empty: %d!\n",
                        skb_queue_len(fdefq));
                __skb_queue_purge(fdefq);
        }
}

/* tipc_link_validate_msg(): validate message against current link state
 * Returns true if message should be accepted, otherwise false
 */
bool tipc_link_validate_msg(struct tipc_link *l, struct tipc_msg *hdr)
{
        u16 curr_session = l->peer_session;
        u16 session = msg_session(hdr);
        int mtyp = msg_type(hdr);

        if (msg_user(hdr) != LINK_PROTOCOL)
                return true;

        switch (mtyp) {
        case RESET_MSG:
                if (!l->in_session)
                        return true;
                /* Accept only RESET with new session number */
                return more(session, curr_session);
        case ACTIVATE_MSG:
                if (!l->in_session)
                        return true;
                /* Accept only ACTIVATE with new or current session number */
                return !less(session, curr_session);
        case STATE_MSG:
                /* Accept only STATE with current session number */
                if (!l->in_session)
                        return false;
                if (session != curr_session)
                        return false;
                /* Extra sanity check */
                if (!link_is_up(l) && msg_ack(hdr))
                        return false;
                if (!(l->peer_caps & TIPC_LINK_PROTO_SEQNO))
                        return true;
                /* Accept only STATE with new sequence number */
                return !less(msg_seqno(hdr), l->rcv_nxt_state);
        default:
                return false;
        }
}

/* tipc_link_proto_rcv(): receive link level protocol message :
 * Note that network plane id propagates through the network, and may
 * change at any time. The node with lowest numerical id determines
 * network plane
 */
static int tipc_link_proto_rcv(struct tipc_link *l, struct sk_buff *skb,
                               struct sk_buff_head *xmitq)
{
        struct tipc_msg *hdr = buf_msg(skb);
        struct tipc_gap_ack_blks *ga = NULL;
        bool reply = msg_probe(hdr), retransmitted = false;
        u32 dlen = msg_data_sz(hdr), glen = 0, msg_max;
        u16 peers_snd_nxt =  msg_next_sent(hdr);
        u16 peers_tol = msg_link_tolerance(hdr);
        u16 peers_prio = msg_linkprio(hdr);
        u16 gap = msg_seq_gap(hdr);
        u16 ack = msg_ack(hdr);
        u16 rcv_nxt = l->rcv_nxt;
        u16 rcvgap = 0;
        int mtyp = msg_type(hdr);
        int rc = 0, released;
        char *if_name;
        void *data;

        trace_tipc_proto_rcv(skb, false, l->name);

        if (dlen > U16_MAX)
                goto exit;

        if (tipc_link_is_blocked(l) || !xmitq)
                goto exit;

        if (tipc_own_addr(l->net) > msg_prevnode(hdr))
                l->net_plane = msg_net_plane(hdr);

        if (skb_linearize(skb))
                goto exit;

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

        if (!tipc_link_validate_msg(l, hdr)) {
                trace_tipc_skb_dump(skb, false, "PROTO invalid (1)!");
                trace_tipc_link_dump(l, TIPC_DUMP_NONE, "PROTO invalid (1)!");
                goto exit;
        }

        switch (mtyp) {
        case RESET_MSG:
        case ACTIVATE_MSG:
                msg_max = msg_max_pkt(hdr);
                if (msg_max < tipc_bearer_min_mtu(l->net, l->bearer_id))
                        break;
                /* Complete own link name with peer's interface name */
                if_name =  strrchr(l->name, ':') + 1;
                if (sizeof(l->name) - (if_name - l->name) <= TIPC_MAX_IF_NAME)
                        break;
                if (msg_data_sz(hdr) < TIPC_MAX_IF_NAME)
                        break;
                strncpy(if_name, data, TIPC_MAX_IF_NAME);

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

                /* If peer is going down we want full re-establish cycle */
                if (msg_peer_stopping(hdr)) {
                        rc = tipc_link_fsm_evt(l, LINK_FAILURE_EVT);
                        break;
                }

                /* If this endpoint was re-created while peer was ESTABLISHING
                 * it doesn't know current session number. Force re-synch.
                 */
                if (mtyp == ACTIVATE_MSG && msg_dest_session_valid(hdr) &&
                    l->session != msg_dest_session(hdr)) {
                        if (less(l->session, msg_dest_session(hdr)))
                                l->session = msg_dest_session(hdr) + 1;
                        break;
                }

                /* ACTIVATE_MSG serves as PEER_RESET if link is already down */
                if (mtyp == RESET_MSG || !link_is_up(l))
                        rc = tipc_link_fsm_evt(l, LINK_PEER_RESET_EVT);

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

                l->peer_session = msg_session(hdr);
                l->in_session = true;
                l->peer_bearer_id = msg_bearer_id(hdr);
                if (l->mtu > msg_max)
                        l->mtu = msg_max;
                break;

        case STATE_MSG:
                /* Validate Gap ACK blocks, drop if invalid */
                glen = tipc_get_gap_ack_blks(&ga, l, hdr, true);
                if (glen > dlen)
                        break;

                l->rcv_nxt_state = msg_seqno(hdr) + 1;

                /* Update own tolerance if peer indicates a non-zero value */
                if (tipc_in_range(peers_tol, TIPC_MIN_LINK_TOL, TIPC_MAX_LINK_TOL)) {
                        l->tolerance = peers_tol;
                        l->bc_rcvlink->tolerance = peers_tol;
                }
                /* Update own prio if peer indicates a different value */
                if ((peers_prio != l->priority) &&
                    tipc_in_range(peers_prio, 1, TIPC_MAX_LINK_PRI)) {
                        l->priority = peers_prio;
                        rc = tipc_link_fsm_evt(l, LINK_FAILURE_EVT);
                }

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

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

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

                /* Send NACK if peer has sent pkts we haven't received yet */
                if ((reply || msg_is_keepalive(hdr)) &&
                    more(peers_snd_nxt, rcv_nxt) &&
                    !tipc_link_is_synching(l) &&
                    skb_queue_empty(&l->deferdq))
                        rcvgap = peers_snd_nxt - l->rcv_nxt;
                if (rcvgap || reply)
                        tipc_link_build_proto_msg(l, STATE_MSG, 0, reply,
                                                  rcvgap, 0, 0, xmitq);

                released = tipc_link_advance_transmq(l, l, ack, gap, ga, xmitq,
                                                     &retransmitted, &rc);
                if (gap)
                        l->stats.recv_nacks++;
                if (released || retransmitted)
                        tipc_link_update_cwin(l, released, retransmitted);
                if (released)
                        tipc_link_advance_backlog(l, xmitq);
                if (unlikely(!skb_queue_empty(&l->wakeupq)))
                        link_prepare_wakeup(l);
        }
exit:
        kfree_skb(skb);
        return rc;
}

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

        skb = tipc_msg_create(BCAST_PROTOCOL, STATE_MSG, INT_H_SIZE,
                              0, l->addr, tipc_own_addr(l->net), 0, 0, 0);
        if (!skb)
                return false;
        hdr = buf_msg(skb);
        msg_set_last_bcast(hdr, l->bc_sndlink->snd_nxt - 1);
        msg_set_bcast_ack(hdr, ack);
        msg_set_bcgap_after(hdr, ack);
        if (dfrd_skb)
                gap_to = buf_seqno(dfrd_skb) - 1;
        msg_set_bcgap_to(hdr, gap_to);
        msg_set_non_seq(hdr, bcast);
        __skb_queue_tail(xmitq, skb);
        return true;
}

/* tipc_link_build_bc_init_msg() - synchronize broadcast link endpoints.
 *
 * Give a newly added peer node the sequence number where it should
 * start receiving and acking broadcast packets.
 */
static void tipc_link_build_bc_init_msg(struct tipc_link *l,
                                        struct sk_buff_head *xmitq)
{
        struct sk_buff_head list;

        __skb_queue_head_init(&list);
        if (!tipc_link_build_bc_proto_msg(l->bc_rcvlink, false, 0, &list))
                return;
        msg_set_bc_ack_invalid(buf_msg(skb_peek(&list)), true);
        tipc_link_xmit(l, &list, xmitq);
}

/* tipc_link_bc_init_rcv - receive initial broadcast synch data from peer
 */
void tipc_link_bc_init_rcv(struct tipc_link *l, struct tipc_msg *hdr)
{
        int mtyp = msg_type(hdr);
        u16 peers_snd_nxt = msg_bc_snd_nxt(hdr);

        if (link_is_up(l))
                return;

        if (msg_user(hdr) == BCAST_PROTOCOL) {
                l->rcv_nxt = peers_snd_nxt;
                l->state = LINK_ESTABLISHED;
                return;
        }

        if (l->peer_caps & TIPC_BCAST_SYNCH)
                return;

        if (msg_peer_node_is_up(hdr))
                return;

        /* Compatibility: accept older, less safe initial synch data */
        if ((mtyp == RESET_MSG) || (mtyp == ACTIVATE_MSG))
                l->rcv_nxt = peers_snd_nxt;
}

/* tipc_link_bc_sync_rcv - update rcv link according to peer's send state
 */
int tipc_link_bc_sync_rcv(struct tipc_link *l, struct tipc_msg *hdr,
                          struct sk_buff_head *xmitq)
{
        u16 peers_snd_nxt = msg_bc_snd_nxt(hdr);
        int rc = 0;

        if (!link_is_up(l))
                return rc;

        if (!msg_peer_node_is_up(hdr))
                return rc;

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

        if (!l->bc_peer_is_up)
                return rc;

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

        l->snd_nxt = peers_snd_nxt;
        if (link_bc_rcv_gap(l))
                rc |= TIPC_LINK_SND_STATE;

        /* Return now if sender supports nack via STATE messages */
        if (l->peer_caps & TIPC_BCAST_STATE_NACK)
                return rc;

        /* Otherwise, be backwards compatible */

        if (!more(peers_snd_nxt, l->rcv_nxt)) {
                l->nack_state = BC_NACK_SND_CONDITIONAL;
                return 0;
        }

        /* Don't NACK if one was recently sent or peeked */
        if (l->nack_state == BC_NACK_SND_SUPPRESS) {
                l->nack_state = BC_NACK_SND_UNCONDITIONAL;
                return 0;
        }

        /* Conditionally delay NACK sending until next synch rcv */
        if (l->nack_state == BC_NACK_SND_CONDITIONAL) {
                l->nack_state = BC_NACK_SND_UNCONDITIONAL;
                if ((peers_snd_nxt - l->rcv_nxt) < TIPC_MIN_LINK_WIN)
                        return 0;
        }

        /* Send NACK now but suppress next one */
        tipc_link_build_bc_proto_msg(l, true, peers_snd_nxt, xmitq);
        l->nack_state = BC_NACK_SND_SUPPRESS;
        return 0;
}

int tipc_link_bc_ack_rcv(struct tipc_link *r, u16 acked, u16 gap,
                         struct tipc_gap_ack_blks *ga,
                         struct sk_buff_head *xmitq,
                         struct sk_buff_head *retrq)
{
        struct tipc_link *l = r->bc_sndlink;
        bool unused = false;
        int rc = 0;

        if (!link_is_up(r) || !r->bc_peer_is_up)
                return 0;

        if (gap) {
                l->stats.recv_nacks++;
                r->stats.recv_nacks++;
        }

        if (less(acked, r->acked) || (acked == r->acked && !gap && !ga))
                return 0;

        trace_tipc_link_bc_ack(r, acked, gap, &l->transmq);
        tipc_link_advance_transmq(l, r, acked, gap, ga, retrq, &unused, &rc);

        tipc_link_advance_backlog(l, xmitq);
        if (unlikely(!skb_queue_empty(&l->wakeupq)))
                link_prepare_wakeup(l);

        return rc;
}

/* tipc_link_bc_nack_rcv(): receive broadcast nack message
 * This function is here for backwards compatibility, since
 * no BCAST_PROTOCOL/STATE messages occur from TIPC v2.5.
 */
int tipc_link_bc_nack_rcv(struct tipc_link *l, struct sk_buff *skb,
                          struct sk_buff_head *xmitq)
{
        struct tipc_msg *hdr = buf_msg(skb);
        u32 dnode = msg_destnode(hdr);
        int mtyp = msg_type(hdr);
        u16 acked = msg_bcast_ack(hdr);
        u16 from = acked + 1;
        u16 to = msg_bcgap_to(hdr);
        u16 peers_snd_nxt = to + 1;
        int rc = 0;

        kfree_skb(skb);

        if (!tipc_link_is_up(l) || !l->bc_peer_is_up)
                return 0;

        if (mtyp != STATE_MSG)
                return 0;

        if (dnode == tipc_own_addr(l->net)) {
                rc = tipc_link_bc_ack_rcv(l, acked, to - acked, NULL, xmitq,
                                          xmitq);
                l->stats.recv_nacks++;
                return rc;
        }

        /* Msg for other node => suppress own NACK at next sync if applicable */
        if (more(peers_snd_nxt, l->rcv_nxt) && !less(l->rcv_nxt, from))
                l->nack_state = BC_NACK_SND_SUPPRESS;

        return 0;
}

void tipc_link_set_queue_limits(struct tipc_link *l, u32 min_win, u32 max_win)
{
        int max_bulk = TIPC_MAX_PUBL / (l->mtu / ITEM_SIZE);

        l->min_win = min_win;
        l->ssthresh = max_win;
        l->max_win = max_win;
        l->window = min_win;
        l->backlog[TIPC_LOW_IMPORTANCE].limit      = min_win * 2;
        l->backlog[TIPC_MEDIUM_IMPORTANCE].limit   = min_win * 4;
        l->backlog[TIPC_HIGH_IMPORTANCE].limit     = min_win * 6;
        l->backlog[TIPC_CRITICAL_IMPORTANCE].limit = min_win * 8;
        l->backlog[TIPC_SYSTEM_IMPORTANCE].limit   = max_bulk;
}

/**
 * tipc_link_reset_stats - reset link statistics
 * @l: pointer to link
 */
void tipc_link_reset_stats(struct tipc_link *l)
{
        memset(&l->stats, 0, sizeof(l->stats));
}

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

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

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

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

        if (props[TIPC_NLA_PROP_PRIO]) {
                u32 prio;

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

        if (props[TIPC_NLA_PROP_TOL]) {
                u32 tol;

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

        if (props[TIPC_NLA_PROP_WIN]) {
                u32 max_win;

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

        return 0;
}

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

        struct nla_map {
                u32 key;
                u32 val;
        };

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

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

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

        nla_nest_end(skb, stats);

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

        return -EMSGSIZE;
}

/* Caller should hold appropriate locks to protect the link */
int __tipc_nl_add_link(struct net *net, struct tipc_nl_msg *msg,
                       struct tipc_link *link, int nlflags)
{
        u32 self = tipc_own_addr(net);
        struct nlattr *attrs;
        struct nlattr *prop;
        void *hdr;
        int err;

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

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

        if (nla_put_string(msg->skb, TIPC_NLA_LINK_NAME, link->name))
                goto attr_msg_full;
        if (nla_put_u32(msg->skb, TIPC_NLA_LINK_DEST, tipc_cluster_mask(self)))
                goto attr_msg_full;
        if (nla_put_u32(msg->skb, TIPC_NLA_LINK_MTU, link->mtu))
                goto attr_msg_full;
        if (nla_put_u32(msg->skb, TIPC_NLA_LINK_RX, link->stats.recv_pkts))
                goto attr_msg_full;
        if (nla_put_u32(msg->skb, TIPC_NLA_LINK_TX, link->stats.sent_pkts))
                goto attr_msg_full;

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

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

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

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

        return 0;

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

        return -EMSGSIZE;
}

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

        struct nla_map {
                __u32 key;
                __u32 val;
        };

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

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

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

        nla_nest_end(skb, nest);

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

        return -EMSGSIZE;
}

int tipc_nl_add_bc_link(struct net *net, struct tipc_nl_msg *msg,
                        struct tipc_link *bcl)
{
        int err;
        void *hdr;
        struct nlattr *attrs;
        struct nlattr *prop;
        u32 bc_mode = tipc_bcast_get_mode(net);
        u32 bc_ratio = tipc_bcast_get_broadcast_ratio(net);

        if (!bcl)
                return 0;

        tipc_bcast_lock(net);

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

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

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

        if (nla_put_flag(msg->skb, TIPC_NLA_LINK_BROADCAST))
                goto attr_msg_full;
        if (nla_put_string(msg->skb, TIPC_NLA_LINK_NAME, bcl->name))
                goto attr_msg_full;
        if (nla_put_u32(msg->skb, TIPC_NLA_LINK_RX, 0))
                goto attr_msg_full;
        if (nla_put_u32(msg->skb, TIPC_NLA_LINK_TX, 0))
                goto attr_msg_full;

        prop = nla_nest_start_noflag(msg->skb, TIPC_NLA_LINK_PROP);
        if (!prop)
                goto attr_msg_full;
        if (nla_put_u32(msg->skb, TIPC_NLA_PROP_WIN, bcl->max_win))
                goto prop_msg_full;
        if (nla_put_u32(msg->skb, TIPC_NLA_PROP_BROADCAST, bc_mode))
                goto prop_msg_full;
        if (bc_mode & BCLINK_MODE_SEL)
                if (nla_put_u32(msg->skb, TIPC_NLA_PROP_BROADCAST_RATIO,
                                bc_ratio))
                        goto prop_msg_full;
        nla_nest_end(msg->skb, prop);

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

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

        return 0;

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

        return -EMSGSIZE;
}

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

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

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

/**
 * tipc_link_dump - dump TIPC link data
 * @l: tipc link to be dumped
 * @dqueues: bitmask to decide if any link queue to be dumped?
 *           - TIPC_DUMP_NONE: don't dump link queues
 *           - TIPC_DUMP_TRANSMQ: dump link transmq queue
 *           - TIPC_DUMP_BACKLOGQ: dump link backlog queue
 *           - TIPC_DUMP_DEFERDQ: dump link deferd queue
 *           - TIPC_DUMP_INPUTQ: dump link input queue
 *           - TIPC_DUMP_WAKEUP: dump link wakeup queue
 *           - TIPC_DUMP_ALL: dump all the link queues above
 * @buf: returned buffer of dump data in format
 */
int tipc_link_dump(struct tipc_link *l, u16 dqueues, char *buf)
{
        int i = 0;
        size_t sz = (dqueues) ? LINK_LMAX : LINK_LMIN;
        struct sk_buff_head *list;
        struct sk_buff *hskb, *tskb;
        u32 len;

        if (!l) {
                i += scnprintf(buf, sz, "link data: (null)\n");
                return i;
        }

        i += scnprintf(buf, sz, "link data: %x", l->addr);
        i += scnprintf(buf + i, sz - i, " %x", l->state);
        i += scnprintf(buf + i, sz - i, " %u", l->in_session);
        i += scnprintf(buf + i, sz - i, " %u", l->session);
        i += scnprintf(buf + i, sz - i, " %u", l->peer_session);
        i += scnprintf(buf + i, sz - i, " %u", l->snd_nxt);
        i += scnprintf(buf + i, sz - i, " %u", l->rcv_nxt);
        i += scnprintf(buf + i, sz - i, " %u", l->snd_nxt_state);
        i += scnprintf(buf + i, sz - i, " %u", l->rcv_nxt_state);
        i += scnprintf(buf + i, sz - i, " %x", l->peer_caps);
        i += scnprintf(buf + i, sz - i, " %u", l->silent_intv_cnt);
        i += scnprintf(buf + i, sz - i, " %u", l->rst_cnt);
        i += scnprintf(buf + i, sz - i, " %u", 0);
        i += scnprintf(buf + i, sz - i, " %u", 0);
        i += scnprintf(buf + i, sz - i, " %u", l->acked);

        list = &l->transmq;
        len = skb_queue_len(list);
        hskb = skb_peek(list);
        tskb = skb_peek_tail(list);
        i += scnprintf(buf + i, sz - i, " | %u %u %u", len,
                       (hskb) ? msg_seqno(buf_msg(hskb)) : 0,
                       (tskb) ? msg_seqno(buf_msg(tskb)) : 0);

        list = &l->deferdq;
        len = skb_queue_len(list);
        hskb = skb_peek(list);
        tskb = skb_peek_tail(list);
        i += scnprintf(buf + i, sz - i, " | %u %u %u", len,
                       (hskb) ? msg_seqno(buf_msg(hskb)) : 0,
                       (tskb) ? msg_seqno(buf_msg(tskb)) : 0);

        list = &l->backlogq;
        len = skb_queue_len(list);
        hskb = skb_peek(list);
        tskb = skb_peek_tail(list);
        i += scnprintf(buf + i, sz - i, " | %u %u %u", len,
                       (hskb) ? msg_seqno(buf_msg(hskb)) : 0,
                       (tskb) ? msg_seqno(buf_msg(tskb)) : 0);

        list = l->inputq;
        len = skb_queue_len(list);
        hskb = skb_peek(list);
        tskb = skb_peek_tail(list);
        i += scnprintf(buf + i, sz - i, " | %u %u %u\n", len,
                       (hskb) ? msg_seqno(buf_msg(hskb)) : 0,
                       (tskb) ? msg_seqno(buf_msg(tskb)) : 0);

        if (dqueues & TIPC_DUMP_TRANSMQ) {
                i += scnprintf(buf + i, sz - i, "transmq: ");
                i += tipc_list_dump(&l->transmq, false, buf + i);
        }
        if (dqueues & TIPC_DUMP_BACKLOGQ) {
                i += scnprintf(buf + i, sz - i,
                               "backlogq: <%u %u %u %u %u>, ",
                               l->backlog[TIPC_LOW_IMPORTANCE].len,
                               l->backlog[TIPC_MEDIUM_IMPORTANCE].len,
                               l->backlog[TIPC_HIGH_IMPORTANCE].len,
                               l->backlog[TIPC_CRITICAL_IMPORTANCE].len,
                               l->backlog[TIPC_SYSTEM_IMPORTANCE].len);
                i += tipc_list_dump(&l->backlogq, false, buf + i);
        }
        if (dqueues & TIPC_DUMP_DEFERDQ) {
                i += scnprintf(buf + i, sz - i, "deferdq: ");
                i += tipc_list_dump(&l->deferdq, false, buf + i);
        }
        if (dqueues & TIPC_DUMP_INPUTQ) {
                i += scnprintf(buf + i, sz - i, "inputq: ");
                i += tipc_list_dump(l->inputq, false, buf + i);
        }
        if (dqueues & TIPC_DUMP_WAKEUP) {
                i += scnprintf(buf + i, sz - i, "wakeup: ");
                i += tipc_list_dump(&l->wakeupq, false, buf + i);
        }

        return i;
}