l2cap_core.c

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/*
   BlueZ - Bluetooth protocol stack for Linux
   Copyright (C) 2000-2001 Qualcomm Incorporated
   Copyright (C) 2009-2010 Gustavo F. Padovan <[email protected]>
   Copyright (C) 2010 Google Inc.
   Copyright (C) 2011 ProFUSION Embedded Systems
   Copyright (c) 2012 Code Aurora Forum.  All rights reserved.

   Written 2000,2001 by Maxim Krasnyansky <[email protected]>

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License version 2 as
   published by the Free Software Foundation;

   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
   OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
   FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT OF THIRD PARTY RIGHTS.
   IN NO EVENT SHALL THE COPYRIGHT HOLDER(S) AND AUTHOR(S) BE LIABLE FOR ANY
   CLAIM, OR ANY SPECIAL INDIRECT OR CONSEQUENTIAL DAMAGES, OR ANY DAMAGES
   WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
   ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
   OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.

   ALL LIABILITY, INCLUDING LIABILITY FOR INFRINGEMENT OF ANY PATENTS,
   COPYRIGHTS, TRADEMARKS OR OTHER RIGHTS, RELATING TO USE OF THIS
   SOFTWARE IS DISCLAIMED.
*/

/* Bluetooth L2CAP core. */

#include <linux/module.h>

#include <linux/debugfs.h>
#include <linux/crc16.h>

#include <net/bluetooth/bluetooth.h>
#include <net/bluetooth/hci_core.h>
#include <net/bluetooth/l2cap.h>
#include <net/bluetooth/smp.h>
#include <net/bluetooth/a2mp.h>

bool disable_ertm;

static u32 l2cap_feat_mask = L2CAP_FEAT_FIXED_CHAN;
static u8 l2cap_fixed_chan[8] = { L2CAP_FC_L2CAP, };

static LIST_HEAD(chan_list);
static DEFINE_RWLOCK(chan_list_lock);

static struct sk_buff *l2cap_build_cmd(struct l2cap_conn *conn,
                u8 code, u8 ident, u16 dlen, void *data);
static void l2cap_send_cmd(struct l2cap_conn *conn, u8 ident, u8 code, u16 len,
                                void *data);
static int l2cap_build_conf_req(struct l2cap_chan *chan, void *data);
static void l2cap_send_disconn_req(struct l2cap_conn *conn,
                   struct l2cap_chan *chan, int err);

static void l2cap_tx(struct l2cap_chan *chan, struct l2cap_ctrl *control,
            struct sk_buff_head *skbs, u8 event);

/* ---- L2CAP channels ---- */

static struct l2cap_chan *__l2cap_get_chan_by_dcid(struct l2cap_conn *conn, u16 cid)
{
    struct l2cap_chan *c;

    list_for_each_entry(c, &conn->chan_l, list) {
        if (c->dcid == cid)
            return c;
    }
    return NULL;
}

static struct l2cap_chan *__l2cap_get_chan_by_scid(struct l2cap_conn *conn, u16 cid)
{
    struct l2cap_chan *c;

    list_for_each_entry(c, &conn->chan_l, list) {
        if (c->scid == cid)
            return c;
    }
    return NULL;
}

/* Find channel with given SCID.
 * Returns locked channel. */
static struct l2cap_chan *l2cap_get_chan_by_scid(struct l2cap_conn *conn, u16 cid)
{
    struct l2cap_chan *c;

    mutex_lock(&conn->chan_lock);
    c = __l2cap_get_chan_by_scid(conn, cid);
    if (c)
        l2cap_chan_lock(c);
    mutex_unlock(&conn->chan_lock);

    return c;
}

static struct l2cap_chan *__l2cap_get_chan_by_ident(struct l2cap_conn *conn, u8 ident)
{
    struct l2cap_chan *c;

    list_for_each_entry(c, &conn->chan_l, list) {
        if (c->ident == ident)
            return c;
    }
    return NULL;
}

static struct l2cap_chan *__l2cap_global_chan_by_addr(__le16 psm, bdaddr_t *src)
{
    struct l2cap_chan *c;

    list_for_each_entry(c, &chan_list, global_l) {
        if (c->sport == psm && !bacmp(&bt_sk(c->sk)->src, src))
            return c;
    }
    return NULL;
}

int l2cap_add_psm(struct l2cap_chan *chan, bdaddr_t *src, __le16 psm)
{
    int err;

    write_lock(&chan_list_lock);

    if (psm && __l2cap_global_chan_by_addr(psm, src)) {
        err = -EADDRINUSE;
        goto done;
    }

    if (psm) {
        chan->psm = psm;
        chan->sport = psm;
        err = 0;
    } else {
        u16 p;

        err = -EINVAL;
        for (p = 0x1001; p < 0x1100; p += 2)
            if (!__l2cap_global_chan_by_addr(cpu_to_le16(p), src)) {
                chan->psm   = cpu_to_le16(p);
                chan->sport = cpu_to_le16(p);
                err = 0;
                break;
            }
    }

done:
    write_unlock(&chan_list_lock);
    return err;
}

int l2cap_add_scid(struct l2cap_chan *chan,  __u16 scid)
{
    write_lock(&chan_list_lock);

    chan->scid = scid;

    write_unlock(&chan_list_lock);

    return 0;
}

static u16 l2cap_alloc_cid(struct l2cap_conn *conn)
{
    u16 cid = L2CAP_CID_DYN_START;

    for (; cid < L2CAP_CID_DYN_END; cid++) {
        if (!__l2cap_get_chan_by_scid(conn, cid))
            return cid;
    }

    return 0;
}

static void __l2cap_state_change(struct l2cap_chan *chan, int state)
{
    BT_DBG("chan %p %s -> %s", chan, state_to_string(chan->state),
                        state_to_string(state));

    chan->state = state;
    chan->ops->state_change(chan, state);
}

static void l2cap_state_change(struct l2cap_chan *chan, int state)
{
    struct sock *sk = chan->sk;

    lock_sock(sk);
    __l2cap_state_change(chan, state);
    release_sock(sk);
}

static inline void __l2cap_chan_set_err(struct l2cap_chan *chan, int err)
{
    struct sock *sk = chan->sk;

    sk->sk_err = err;
}

static inline void l2cap_chan_set_err(struct l2cap_chan *chan, int err)
{
    struct sock *sk = chan->sk;

    lock_sock(sk);
    __l2cap_chan_set_err(chan, err);
    release_sock(sk);
}

static void __set_retrans_timer(struct l2cap_chan *chan)
{
    if (!delayed_work_pending(&chan->monitor_timer) &&
        chan->retrans_timeout) {
        l2cap_set_timer(chan, &chan->retrans_timer,
                msecs_to_jiffies(chan->retrans_timeout));
    }
}

static void __set_monitor_timer(struct l2cap_chan *chan)
{
    __clear_retrans_timer(chan);
    if (chan->monitor_timeout) {
        l2cap_set_timer(chan, &chan->monitor_timer,
                msecs_to_jiffies(chan->monitor_timeout));
    }
}

static struct sk_buff *l2cap_ertm_seq_in_queue(struct sk_buff_head *head,
                           u16 seq)
{
    struct sk_buff *skb;

    skb_queue_walk(head, skb) {
        if (bt_cb(skb)->control.txseq == seq)
            return skb;
    }

    return NULL;
}

/* ---- L2CAP sequence number lists ---- */

/* For ERTM, ordered lists of sequence numbers must be tracked for
 * SREJ requests that are received and for frames that are to be
 * retransmitted. These seq_list functions implement a singly-linked
 * list in an array, where membership in the list can also be checked
 * in constant time. Items can also be added to the tail of the list
 * and removed from the head in constant time, without further memory
 * allocs or frees.
 */

static int l2cap_seq_list_init(struct l2cap_seq_list *seq_list, u16 size)
{
    size_t alloc_size, i;

    /* Allocated size is a power of 2 to map sequence numbers
     * (which may be up to 14 bits) in to a smaller array that is
     * sized for the negotiated ERTM transmit windows.
     */
    alloc_size = roundup_pow_of_two(size);

    seq_list->list = kmalloc(sizeof(u16) * alloc_size, GFP_KERNEL);
    if (!seq_list->list)
        return -ENOMEM;

    seq_list->mask = alloc_size - 1;
    seq_list->head = L2CAP_SEQ_LIST_CLEAR;
    seq_list->tail = L2CAP_SEQ_LIST_CLEAR;
    for (i = 0; i < alloc_size; i++)
        seq_list->list[i] = L2CAP_SEQ_LIST_CLEAR;

    return 0;
}

static inline void l2cap_seq_list_free(struct l2cap_seq_list *seq_list)
{
    kfree(seq_list->list);
}

static inline bool l2cap_seq_list_contains(struct l2cap_seq_list *seq_list,
                       u16 seq)
{
    /* Constant-time check for list membership */
    return seq_list->list[seq & seq_list->mask] != L2CAP_SEQ_LIST_CLEAR;
}

static u16 l2cap_seq_list_remove(struct l2cap_seq_list *seq_list, u16 seq)
{
    u16 mask = seq_list->mask;

    if (seq_list->head == L2CAP_SEQ_LIST_CLEAR) {
        /* In case someone tries to pop the head of an empty list */
        return L2CAP_SEQ_LIST_CLEAR;
    } else if (seq_list->head == seq) {
        /* Head can be removed in constant time */
        seq_list->head = seq_list->list[seq & mask];
        seq_list->list[seq & mask] = L2CAP_SEQ_LIST_CLEAR;

        if (seq_list->head == L2CAP_SEQ_LIST_TAIL) {
            seq_list->head = L2CAP_SEQ_LIST_CLEAR;
            seq_list->tail = L2CAP_SEQ_LIST_CLEAR;
        }
    } else {
        /* Walk the list to find the sequence number */
        u16 prev = seq_list->head;
        while (seq_list->list[prev & mask] != seq) {
            prev = seq_list->list[prev & mask];
            if (prev == L2CAP_SEQ_LIST_TAIL)
                return L2CAP_SEQ_LIST_CLEAR;
        }

        /* Unlink the number from the list and clear it */
        seq_list->list[prev & mask] = seq_list->list[seq & mask];
        seq_list->list[seq & mask] = L2CAP_SEQ_LIST_CLEAR;
        if (seq_list->tail == seq)
            seq_list->tail = prev;
    }
    return seq;
}

static inline u16 l2cap_seq_list_pop(struct l2cap_seq_list *seq_list)
{
    /* Remove the head in constant time */
    return l2cap_seq_list_remove(seq_list, seq_list->head);
}

static void l2cap_seq_list_clear(struct l2cap_seq_list *seq_list)
{
    u16 i;

    if (seq_list->head == L2CAP_SEQ_LIST_CLEAR)
        return;

    for (i = 0; i <= seq_list->mask; i++)
        seq_list->list[i] = L2CAP_SEQ_LIST_CLEAR;

    seq_list->head = L2CAP_SEQ_LIST_CLEAR;
    seq_list->tail = L2CAP_SEQ_LIST_CLEAR;
}

static void l2cap_seq_list_append(struct l2cap_seq_list *seq_list, u16 seq)
{
    u16 mask = seq_list->mask;

    /* All appends happen in constant time */

    if (seq_list->list[seq & mask] != L2CAP_SEQ_LIST_CLEAR)
        return;

    if (seq_list->tail == L2CAP_SEQ_LIST_CLEAR)
        seq_list->head = seq;
    else
        seq_list->list[seq_list->tail & mask] = seq;

    seq_list->tail = seq;
    seq_list->list[seq & mask] = L2CAP_SEQ_LIST_TAIL;
}

static void l2cap_chan_timeout(struct work_struct *work)
{
    struct l2cap_chan *chan = container_of(work, struct l2cap_chan,
                            chan_timer.work);
    struct l2cap_conn *conn = chan->conn;
    int reason;

    BT_DBG("chan %p state %s", chan, state_to_string(chan->state));

    mutex_lock(&conn->chan_lock);
    l2cap_chan_lock(chan);

    if (chan->state == BT_CONNECTED || chan->state == BT_CONFIG)
        reason = ECONNREFUSED;
    else if (chan->state == BT_CONNECT &&
                    chan->sec_level != BT_SECURITY_SDP)
        reason = ECONNREFUSED;
    else
        reason = ETIMEDOUT;

    l2cap_chan_close(chan, reason);

    l2cap_chan_unlock(chan);

    chan->ops->close(chan);
    mutex_unlock(&conn->chan_lock);

    l2cap_chan_put(chan);
}

struct l2cap_chan *l2cap_chan_create(void)
{
    struct l2cap_chan *chan;

    chan = kzalloc(sizeof(*chan), GFP_ATOMIC);
    if (!chan)
        return NULL;

    mutex_init(&chan->lock);

    write_lock(&chan_list_lock);
    list_add(&chan->global_l, &chan_list);
    write_unlock(&chan_list_lock);

    INIT_DELAYED_WORK(&chan->chan_timer, l2cap_chan_timeout);

    chan->state = BT_OPEN;

    kref_init(&chan->kref);

    /* This flag is cleared in l2cap_chan_ready() */
    set_bit(CONF_NOT_COMPLETE, &chan->conf_state);

    BT_DBG("chan %p", chan);

    return chan;
}

static void l2cap_chan_destroy(struct kref *kref)
{
    struct l2cap_chan *chan = container_of(kref, struct l2cap_chan, kref);

    BT_DBG("chan %p", chan);

    write_lock(&chan_list_lock);
    list_del(&chan->global_l);
    write_unlock(&chan_list_lock);

    kfree(chan);
}

void l2cap_chan_hold(struct l2cap_chan *c)
{
    BT_DBG("chan %p orig refcnt %d", c, atomic_read(&c->kref.refcount));

    kref_get(&c->kref);
}

void l2cap_chan_put(struct l2cap_chan *c)
{
    BT_DBG("chan %p orig refcnt %d", c, atomic_read(&c->kref.refcount));

    kref_put(&c->kref, l2cap_chan_destroy);
}

void l2cap_chan_set_defaults(struct l2cap_chan *chan)
{
    chan->fcs  = L2CAP_FCS_CRC16;
    chan->max_tx = L2CAP_DEFAULT_MAX_TX;
    chan->tx_win = L2CAP_DEFAULT_TX_WINDOW;
    chan->tx_win_max = L2CAP_DEFAULT_TX_WINDOW;
    chan->ack_win = L2CAP_DEFAULT_TX_WINDOW;
    chan->sec_level = BT_SECURITY_LOW;

    set_bit(FLAG_FORCE_ACTIVE, &chan->flags);
}

static void __l2cap_chan_add(struct l2cap_conn *conn, struct l2cap_chan *chan)
{
    BT_DBG("conn %p, psm 0x%2.2x, dcid 0x%4.4x", conn,
           __le16_to_cpu(chan->psm), chan->dcid);

    conn->disc_reason = HCI_ERROR_REMOTE_USER_TERM;

    chan->conn = conn;

    switch (chan->chan_type) {
    case L2CAP_CHAN_CONN_ORIENTED:
        if (conn->hcon->type == LE_LINK) {
            /* LE connection */
            chan->omtu = L2CAP_DEFAULT_MTU;
            chan->scid = L2CAP_CID_LE_DATA;
            chan->dcid = L2CAP_CID_LE_DATA;
        } else {
            /* Alloc CID for connection-oriented socket */
            chan->scid = l2cap_alloc_cid(conn);
            chan->omtu = L2CAP_DEFAULT_MTU;
        }
        break;

    case L2CAP_CHAN_CONN_LESS:
        /* Connectionless socket */
        chan->scid = L2CAP_CID_CONN_LESS;
        chan->dcid = L2CAP_CID_CONN_LESS;
        chan->omtu = L2CAP_DEFAULT_MTU;
        break;

    case L2CAP_CHAN_CONN_FIX_A2MP:
        chan->scid = L2CAP_CID_A2MP;
        chan->dcid = L2CAP_CID_A2MP;
        chan->omtu = L2CAP_A2MP_DEFAULT_MTU;
        chan->imtu = L2CAP_A2MP_DEFAULT_MTU;
        break;

    default:
        /* Raw socket can send/recv signalling messages only */
        chan->scid = L2CAP_CID_SIGNALING;
        chan->dcid = L2CAP_CID_SIGNALING;
        chan->omtu = L2CAP_DEFAULT_MTU;
    }

    chan->local_id      = L2CAP_BESTEFFORT_ID;
    chan->local_stype   = L2CAP_SERV_BESTEFFORT;
    chan->local_msdu    = L2CAP_DEFAULT_MAX_SDU_SIZE;
    chan->local_sdu_itime   = L2CAP_DEFAULT_SDU_ITIME;
    chan->local_acc_lat = L2CAP_DEFAULT_ACC_LAT;
    chan->local_flush_to    = L2CAP_DEFAULT_FLUSH_TO;

    l2cap_chan_hold(chan);

    list_add(&chan->list, &conn->chan_l);
}

void l2cap_chan_add(struct l2cap_conn *conn, struct l2cap_chan *chan)
{
    mutex_lock(&conn->chan_lock);
    __l2cap_chan_add(conn, chan);
    mutex_unlock(&conn->chan_lock);
}

void l2cap_chan_del(struct l2cap_chan *chan, int err)
{
    struct l2cap_conn *conn = chan->conn;

    __clear_chan_timer(chan);

    BT_DBG("chan %p, conn %p, err %d", chan, conn, err);

    if (conn) {
        /* Delete from channel list */
        list_del(&chan->list);

        l2cap_chan_put(chan);

        chan->conn = NULL;

        if (chan->chan_type != L2CAP_CHAN_CONN_FIX_A2MP)
            hci_conn_put(conn->hcon);
    }

    if (chan->ops->teardown)
        chan->ops->teardown(chan, err);

    if (test_bit(CONF_NOT_COMPLETE, &chan->conf_state))
        return;

    switch(chan->mode) {
    case L2CAP_MODE_BASIC:
        break;

    case L2CAP_MODE_ERTM:
        __clear_retrans_timer(chan);
        __clear_monitor_timer(chan);
        __clear_ack_timer(chan);

        skb_queue_purge(&chan->srej_q);

        l2cap_seq_list_free(&chan->srej_list);
        l2cap_seq_list_free(&chan->retrans_list);

        /* fall through */

    case L2CAP_MODE_STREAMING:
        skb_queue_purge(&chan->tx_q);
        break;
    }

    return;
}

void l2cap_chan_close(struct l2cap_chan *chan, int reason)
{
    struct l2cap_conn *conn = chan->conn;
    struct sock *sk = chan->sk;

    BT_DBG("chan %p state %s sk %p", chan,
                    state_to_string(chan->state), sk);

    switch (chan->state) {
    case BT_LISTEN:
        if (chan->ops->teardown)
            chan->ops->teardown(chan, 0);
        break;

    case BT_CONNECTED:
    case BT_CONFIG:
        if (chan->chan_type == L2CAP_CHAN_CONN_ORIENTED &&
                    conn->hcon->type == ACL_LINK) {
            __set_chan_timer(chan, sk->sk_sndtimeo);
            l2cap_send_disconn_req(conn, chan, reason);
        } else
            l2cap_chan_del(chan, reason);
        break;

    case BT_CONNECT2:
        if (chan->chan_type == L2CAP_CHAN_CONN_ORIENTED &&
                    conn->hcon->type == ACL_LINK) {
            struct l2cap_conn_rsp rsp;
            __u16 result;

            if (test_bit(BT_SK_DEFER_SETUP, &bt_sk(sk)->flags))
                result = L2CAP_CR_SEC_BLOCK;
            else
                result = L2CAP_CR_BAD_PSM;
            l2cap_state_change(chan, BT_DISCONN);

            rsp.scid   = cpu_to_le16(chan->dcid);
            rsp.dcid   = cpu_to_le16(chan->scid);
            rsp.result = cpu_to_le16(result);
            rsp.status = __constant_cpu_to_le16(L2CAP_CS_NO_INFO);
            l2cap_send_cmd(conn, chan->ident, L2CAP_CONN_RSP,
                            sizeof(rsp), &rsp);
        }

        l2cap_chan_del(chan, reason);
        break;

    case BT_CONNECT:
    case BT_DISCONN:
        l2cap_chan_del(chan, reason);
        break;

    default:
        if (chan->ops->teardown)
            chan->ops->teardown(chan, 0);
        break;
    }
}

static inline u8 l2cap_get_auth_type(struct l2cap_chan *chan)
{
    if (chan->chan_type == L2CAP_CHAN_RAW) {
        switch (chan->sec_level) {
        case BT_SECURITY_HIGH:
            return HCI_AT_DEDICATED_BONDING_MITM;
        case BT_SECURITY_MEDIUM:
            return HCI_AT_DEDICATED_BONDING;
        default:
            return HCI_AT_NO_BONDING;
        }
    } else if (chan->psm == __constant_cpu_to_le16(L2CAP_PSM_SDP)) {
        if (chan->sec_level == BT_SECURITY_LOW)
            chan->sec_level = BT_SECURITY_SDP;

        if (chan->sec_level == BT_SECURITY_HIGH)
            return HCI_AT_NO_BONDING_MITM;
        else
            return HCI_AT_NO_BONDING;
    } else {
        switch (chan->sec_level) {
        case BT_SECURITY_HIGH:
            return HCI_AT_GENERAL_BONDING_MITM;
        case BT_SECURITY_MEDIUM:
            return HCI_AT_GENERAL_BONDING;
        default:
            return HCI_AT_NO_BONDING;
        }
    }
}

/* Service level security */
int l2cap_chan_check_security(struct l2cap_chan *chan)
{
    struct l2cap_conn *conn = chan->conn;
    __u8 auth_type;

    auth_type = l2cap_get_auth_type(chan);

    return hci_conn_security(conn->hcon, chan->sec_level, auth_type);
}

static u8 l2cap_get_ident(struct l2cap_conn *conn)
{
    u8 id;

    /* Get next available identificator.
     *    1 - 128 are used by kernel.
     *  129 - 199 are reserved.
     *  200 - 254 are used by utilities like l2ping, etc.
     */

    spin_lock(&conn->lock);

    if (++conn->tx_ident > 128)
        conn->tx_ident = 1;

    id = conn->tx_ident;

    spin_unlock(&conn->lock);

    return id;
}

static void l2cap_send_cmd(struct l2cap_conn *conn, u8 ident, u8 code, u16 len, void *data)
{
    struct sk_buff *skb = l2cap_build_cmd(conn, code, ident, len, data);
    u8 flags;

    BT_DBG("code 0x%2.2x", code);

    if (!skb)
        return;

    if (lmp_no_flush_capable(conn->hcon->hdev))
        flags = ACL_START_NO_FLUSH;
    else
        flags = ACL_START;

    bt_cb(skb)->force_active = BT_POWER_FORCE_ACTIVE_ON;
    skb->priority = HCI_PRIO_MAX;

    hci_send_acl(conn->hchan, skb, flags);
}

static void l2cap_do_send(struct l2cap_chan *chan, struct sk_buff *skb)
{
    struct hci_conn *hcon = chan->conn->hcon;
    u16 flags;

    BT_DBG("chan %p, skb %p len %d priority %u", chan, skb, skb->len,
                            skb->priority);

    if (!test_bit(FLAG_FLUSHABLE, &chan->flags) &&
                    lmp_no_flush_capable(hcon->hdev))
        flags = ACL_START_NO_FLUSH;
    else
        flags = ACL_START;

    bt_cb(skb)->force_active = test_bit(FLAG_FORCE_ACTIVE, &chan->flags);
    hci_send_acl(chan->conn->hchan, skb, flags);
}

static void __unpack_enhanced_control(u16 enh, struct l2cap_ctrl *control)
{
    control->reqseq = (enh & L2CAP_CTRL_REQSEQ) >> L2CAP_CTRL_REQSEQ_SHIFT;
    control->final = (enh & L2CAP_CTRL_FINAL) >> L2CAP_CTRL_FINAL_SHIFT;

    if (enh & L2CAP_CTRL_FRAME_TYPE) {
        /* S-Frame */
        control->sframe = 1;
        control->poll = (enh & L2CAP_CTRL_POLL) >> L2CAP_CTRL_POLL_SHIFT;
        control->super = (enh & L2CAP_CTRL_SUPERVISE) >> L2CAP_CTRL_SUPER_SHIFT;

        control->sar = 0;
        control->txseq = 0;
    } else {
        /* I-Frame */
        control->sframe = 0;
        control->sar = (enh & L2CAP_CTRL_SAR) >> L2CAP_CTRL_SAR_SHIFT;
        control->txseq = (enh & L2CAP_CTRL_TXSEQ) >> L2CAP_CTRL_TXSEQ_SHIFT;

        control->poll = 0;
        control->super = 0;
    }
}

static void __unpack_extended_control(u32 ext, struct l2cap_ctrl *control)
{
    control->reqseq = (ext & L2CAP_EXT_CTRL_REQSEQ) >> L2CAP_EXT_CTRL_REQSEQ_SHIFT;
    control->final = (ext & L2CAP_EXT_CTRL_FINAL) >> L2CAP_EXT_CTRL_FINAL_SHIFT;

    if (ext & L2CAP_EXT_CTRL_FRAME_TYPE) {
        /* S-Frame */
        control->sframe = 1;
        control->poll = (ext & L2CAP_EXT_CTRL_POLL) >> L2CAP_EXT_CTRL_POLL_SHIFT;
        control->super = (ext & L2CAP_EXT_CTRL_SUPERVISE) >> L2CAP_EXT_CTRL_SUPER_SHIFT;

        control->sar = 0;
        control->txseq = 0;
    } else {
        /* I-Frame */
        control->sframe = 0;
        control->sar = (ext & L2CAP_EXT_CTRL_SAR) >> L2CAP_EXT_CTRL_SAR_SHIFT;
        control->txseq = (ext & L2CAP_EXT_CTRL_TXSEQ) >> L2CAP_EXT_CTRL_TXSEQ_SHIFT;

        control->poll = 0;
        control->super = 0;
    }
}

static inline void __unpack_control(struct l2cap_chan *chan,
                    struct sk_buff *skb)
{
    if (test_bit(FLAG_EXT_CTRL, &chan->flags)) {
        __unpack_extended_control(get_unaligned_le32(skb->data),
                      &bt_cb(skb)->control);
        skb_pull(skb, L2CAP_EXT_CTRL_SIZE);
    } else {
        __unpack_enhanced_control(get_unaligned_le16(skb->data),
                      &bt_cb(skb)->control);
        skb_pull(skb, L2CAP_ENH_CTRL_SIZE);
    }
}

static u32 __pack_extended_control(struct l2cap_ctrl *control)
{
    u32 packed;

    packed = control->reqseq << L2CAP_EXT_CTRL_REQSEQ_SHIFT;
    packed |= control->final << L2CAP_EXT_CTRL_FINAL_SHIFT;

    if (control->sframe) {
        packed |= control->poll << L2CAP_EXT_CTRL_POLL_SHIFT;
        packed |= control->super << L2CAP_EXT_CTRL_SUPER_SHIFT;
        packed |= L2CAP_EXT_CTRL_FRAME_TYPE;
    } else {
        packed |= control->sar << L2CAP_EXT_CTRL_SAR_SHIFT;
        packed |= control->txseq << L2CAP_EXT_CTRL_TXSEQ_SHIFT;
    }

    return packed;
}

static u16 __pack_enhanced_control(struct l2cap_ctrl *control)
{
    u16 packed;

    packed = control->reqseq << L2CAP_CTRL_REQSEQ_SHIFT;
    packed |= control->final << L2CAP_CTRL_FINAL_SHIFT;

    if (control->sframe) {
        packed |= control->poll << L2CAP_CTRL_POLL_SHIFT;
        packed |= control->super << L2CAP_CTRL_SUPER_SHIFT;
        packed |= L2CAP_CTRL_FRAME_TYPE;
    } else {
        packed |= control->sar << L2CAP_CTRL_SAR_SHIFT;
        packed |= control->txseq << L2CAP_CTRL_TXSEQ_SHIFT;
    }

    return packed;
}

static inline void __pack_control(struct l2cap_chan *chan,
                  struct l2cap_ctrl *control,
                  struct sk_buff *skb)
{
    if (test_bit(FLAG_EXT_CTRL, &chan->flags)) {
        put_unaligned_le32(__pack_extended_control(control),
                   skb->data + L2CAP_HDR_SIZE);
    } else {
        put_unaligned_le16(__pack_enhanced_control(control),
                   skb->data + L2CAP_HDR_SIZE);
    }
}

static inline unsigned int __ertm_hdr_size(struct l2cap_chan *chan)
{
    if (test_bit(FLAG_EXT_CTRL, &chan->flags))
        return L2CAP_EXT_HDR_SIZE;
    else
        return L2CAP_ENH_HDR_SIZE;
}

static struct sk_buff *l2cap_create_sframe_pdu(struct l2cap_chan *chan,
                           u32 control)
{
    struct sk_buff *skb;
    struct l2cap_hdr *lh;
    int hlen = __ertm_hdr_size(chan);

    if (chan->fcs == L2CAP_FCS_CRC16)
        hlen += L2CAP_FCS_SIZE;

    skb = bt_skb_alloc(hlen, GFP_KERNEL);

    if (!skb)
        return ERR_PTR(-ENOMEM);

    lh = (struct l2cap_hdr *) skb_put(skb, L2CAP_HDR_SIZE);
    lh->len = cpu_to_le16(hlen - L2CAP_HDR_SIZE);
    lh->cid = cpu_to_le16(chan->dcid);

    if (test_bit(FLAG_EXT_CTRL, &chan->flags))
        put_unaligned_le32(control, skb_put(skb, L2CAP_EXT_CTRL_SIZE));
    else
        put_unaligned_le16(control, skb_put(skb, L2CAP_ENH_CTRL_SIZE));

    if (chan->fcs == L2CAP_FCS_CRC16) {
        u16 fcs = crc16(0, (u8 *)skb->data, skb->len);
        put_unaligned_le16(fcs, skb_put(skb, L2CAP_FCS_SIZE));
    }

    skb->priority = HCI_PRIO_MAX;
    return skb;
}

static void l2cap_send_sframe(struct l2cap_chan *chan,
                  struct l2cap_ctrl *control)
{
    struct sk_buff *skb;
    u32 control_field;

    BT_DBG("chan %p, control %p", chan, control);

    if (!control->sframe)
        return;

    if (test_and_clear_bit(CONN_SEND_FBIT, &chan->conn_state) &&
        !control->poll)
        control->final = 1;

    if (control->super == L2CAP_SUPER_RR)
        clear_bit(CONN_RNR_SENT, &chan->conn_state);
    else if (control->super == L2CAP_SUPER_RNR)
        set_bit(CONN_RNR_SENT, &chan->conn_state);

    if (control->super != L2CAP_SUPER_SREJ) {
        chan->last_acked_seq = control->reqseq;
        __clear_ack_timer(chan);
    }

    BT_DBG("reqseq %d, final %d, poll %d, super %d", control->reqseq,
           control->final, control->poll, control->super);

    if (test_bit(FLAG_EXT_CTRL, &chan->flags))
        control_field = __pack_extended_control(control);
    else
        control_field = __pack_enhanced_control(control);

    skb = l2cap_create_sframe_pdu(chan, control_field);
    if (!IS_ERR(skb))
        l2cap_do_send(chan, skb);
}

static void l2cap_send_rr_or_rnr(struct l2cap_chan *chan, bool poll)
{
    struct l2cap_ctrl control;

    BT_DBG("chan %p, poll %d", chan, poll);

    memset(&control, 0, sizeof(control));
    control.sframe = 1;
    control.poll = poll;

    if (test_bit(CONN_LOCAL_BUSY, &chan->conn_state))
        control.super = L2CAP_SUPER_RNR;
    else
        control.super = L2CAP_SUPER_RR;

    control.reqseq = chan->buffer_seq;
    l2cap_send_sframe(chan, &control);
}

static inline int __l2cap_no_conn_pending(struct l2cap_chan *chan)
{
    return !test_bit(CONF_CONNECT_PEND, &chan->conf_state);
}

static void l2cap_send_conn_req(struct l2cap_chan *chan)
{
    struct l2cap_conn *conn = chan->conn;
    struct l2cap_conn_req req;

    req.scid = cpu_to_le16(chan->scid);
    req.psm  = chan->psm;

    chan->ident = l2cap_get_ident(conn);

    set_bit(CONF_CONNECT_PEND, &chan->conf_state);

    l2cap_send_cmd(conn, chan->ident, L2CAP_CONN_REQ, sizeof(req), &req);
}

static void l2cap_chan_ready(struct l2cap_chan *chan)
{
    /* This clears all conf flags, including CONF_NOT_COMPLETE */
    chan->conf_state = 0;
    __clear_chan_timer(chan);

    chan->state = BT_CONNECTED;

    chan->ops->ready(chan);
}

static void l2cap_do_start(struct l2cap_chan *chan)
{
    struct l2cap_conn *conn = chan->conn;

    if (conn->hcon->type == LE_LINK) {
        l2cap_chan_ready(chan);
        return;
    }

    if (conn->info_state & L2CAP_INFO_FEAT_MASK_REQ_SENT) {
        if (!(conn->info_state & L2CAP_INFO_FEAT_MASK_REQ_DONE))
            return;

        if (l2cap_chan_check_security(chan) &&
                __l2cap_no_conn_pending(chan))
            l2cap_send_conn_req(chan);
    } else {
        struct l2cap_info_req req;
        req.type = __constant_cpu_to_le16(L2CAP_IT_FEAT_MASK);

        conn->info_state |= L2CAP_INFO_FEAT_MASK_REQ_SENT;
        conn->info_ident = l2cap_get_ident(conn);

        schedule_delayed_work(&conn->info_timer, L2CAP_INFO_TIMEOUT);

        l2cap_send_cmd(conn, conn->info_ident,
                    L2CAP_INFO_REQ, sizeof(req), &req);
    }
}

static inline int l2cap_mode_supported(__u8 mode, __u32 feat_mask)
{
    u32 local_feat_mask = l2cap_feat_mask;
    if (!disable_ertm)
        local_feat_mask |= L2CAP_FEAT_ERTM | L2CAP_FEAT_STREAMING;

    switch (mode) {
    case L2CAP_MODE_ERTM:
        return L2CAP_FEAT_ERTM & feat_mask & local_feat_mask;
    case L2CAP_MODE_STREAMING:
        return L2CAP_FEAT_STREAMING & feat_mask & local_feat_mask;
    default:
        return 0x00;
    }
}

static void l2cap_send_disconn_req(struct l2cap_conn *conn, struct l2cap_chan *chan, int err)
{
    struct sock *sk = chan->sk;
    struct l2cap_disconn_req req;

    if (!conn)
        return;

    if (chan->mode == L2CAP_MODE_ERTM && chan->state == BT_CONNECTED) {
        __clear_retrans_timer(chan);
        __clear_monitor_timer(chan);
        __clear_ack_timer(chan);
    }

    if (chan->chan_type == L2CAP_CHAN_CONN_FIX_A2MP) {
        __l2cap_state_change(chan, BT_DISCONN);
        return;
    }

    req.dcid = cpu_to_le16(chan->dcid);
    req.scid = cpu_to_le16(chan->scid);
    l2cap_send_cmd(conn, l2cap_get_ident(conn),
            L2CAP_DISCONN_REQ, sizeof(req), &req);

    lock_sock(sk);
    __l2cap_state_change(chan, BT_DISCONN);
    __l2cap_chan_set_err(chan, err);
    release_sock(sk);
}

/* ---- L2CAP connections ---- */
static void l2cap_conn_start(struct l2cap_conn *conn)
{
    struct l2cap_chan *chan, *tmp;

    BT_DBG("conn %p", conn);

    mutex_lock(&conn->chan_lock);

    list_for_each_entry_safe(chan, tmp, &conn->chan_l, list) {
        struct sock *sk = chan->sk;

        l2cap_chan_lock(chan);

        if (chan->chan_type != L2CAP_CHAN_CONN_ORIENTED) {
            l2cap_chan_unlock(chan);
            continue;
        }

        if (chan->state == BT_CONNECT) {
            if (!l2cap_chan_check_security(chan) ||
                    !__l2cap_no_conn_pending(chan)) {
                l2cap_chan_unlock(chan);
                continue;
            }

            if (!l2cap_mode_supported(chan->mode, conn->feat_mask)
                    && test_bit(CONF_STATE2_DEVICE,
                    &chan->conf_state)) {
                l2cap_chan_close(chan, ECONNRESET);
                l2cap_chan_unlock(chan);
                continue;
            }

            l2cap_send_conn_req(chan);

        } else if (chan->state == BT_CONNECT2) {
            struct l2cap_conn_rsp rsp;
            char buf[128];
            rsp.scid = cpu_to_le16(chan->dcid);
            rsp.dcid = cpu_to_le16(chan->scid);

            if (l2cap_chan_check_security(chan)) {
                lock_sock(sk);
                if (test_bit(BT_SK_DEFER_SETUP,
                         &bt_sk(sk)->flags)) {
                    struct sock *parent = bt_sk(sk)->parent;
                    rsp.result = __constant_cpu_to_le16(L2CAP_CR_PEND);
                    rsp.status = __constant_cpu_to_le16(L2CAP_CS_AUTHOR_PEND);
                    if (parent)
                        parent->sk_data_ready(parent, 0);

                } else {
                    __l2cap_state_change(chan, BT_CONFIG);
                    rsp.result = __constant_cpu_to_le16(L2CAP_CR_SUCCESS);
                    rsp.status = __constant_cpu_to_le16(L2CAP_CS_NO_INFO);
                }
                release_sock(sk);
            } else {
                rsp.result = __constant_cpu_to_le16(L2CAP_CR_PEND);
                rsp.status = __constant_cpu_to_le16(L2CAP_CS_AUTHEN_PEND);
            }

            l2cap_send_cmd(conn, chan->ident, L2CAP_CONN_RSP,
                            sizeof(rsp), &rsp);

            if (test_bit(CONF_REQ_SENT, &chan->conf_state) ||
                    rsp.result != L2CAP_CR_SUCCESS) {
                l2cap_chan_unlock(chan);
                continue;
            }

            set_bit(CONF_REQ_SENT, &chan->conf_state);
            l2cap_send_cmd(conn, l2cap_get_ident(conn), L2CAP_CONF_REQ,
                        l2cap_build_conf_req(chan, buf), buf);
            chan->num_conf_req++;
        }

        l2cap_chan_unlock(chan);
    }

    mutex_unlock(&conn->chan_lock);
}

/* Find socket with cid and source/destination bdaddr.
 * Returns closest match, locked.
 */
static struct l2cap_chan *l2cap_global_chan_by_scid(int state, u16 cid,
                            bdaddr_t *src,
                            bdaddr_t *dst)
{
    struct l2cap_chan *c, *c1 = NULL;

    read_lock(&chan_list_lock);

    list_for_each_entry(c, &chan_list, global_l) {
        struct sock *sk = c->sk;

        if (state && c->state != state)
            continue;

        if (c->scid == cid) {
            int src_match, dst_match;
            int src_any, dst_any;

            /* Exact match. */
            src_match = !bacmp(&bt_sk(sk)->src, src);
            dst_match = !bacmp(&bt_sk(sk)->dst, dst);
            if (src_match && dst_match) {
                read_unlock(&chan_list_lock);
                return c;
            }

            /* Closest match */
            src_any = !bacmp(&bt_sk(sk)->src, BDADDR_ANY);
            dst_any = !bacmp(&bt_sk(sk)->dst, BDADDR_ANY);
            if ((src_match && dst_any) || (src_any && dst_match) ||
                (src_any && dst_any))
                c1 = c;
        }
    }

    read_unlock(&chan_list_lock);

    return c1;
}

static void l2cap_le_conn_ready(struct l2cap_conn *conn)
{
    struct sock *parent, *sk;
    struct l2cap_chan *chan, *pchan;

    BT_DBG("");

    /* Check if we have socket listening on cid */
    pchan = l2cap_global_chan_by_scid(BT_LISTEN, L2CAP_CID_LE_DATA,
                      conn->src, conn->dst);
    if (!pchan)
        return;

    parent = pchan->sk;

    lock_sock(parent);

    chan = pchan->ops->new_connection(pchan);
    if (!chan)
        goto clean;

    sk = chan->sk;

    hci_conn_hold(conn->hcon);
    conn->hcon->disc_timeout = HCI_DISCONN_TIMEOUT;

    bacpy(&bt_sk(sk)->src, conn->src);
    bacpy(&bt_sk(sk)->dst, conn->dst);

    bt_accept_enqueue(parent, sk);

    l2cap_chan_add(conn, chan);

    l2cap_chan_ready(chan);

clean:
    release_sock(parent);
}

static void l2cap_conn_ready(struct l2cap_conn *conn)
{
    struct l2cap_chan *chan;
    struct hci_conn *hcon = conn->hcon;

    BT_DBG("conn %p", conn);

    if (!hcon->out && hcon->type == LE_LINK)
        l2cap_le_conn_ready(conn);

    if (hcon->out && hcon->type == LE_LINK)
        smp_conn_security(hcon, hcon->pending_sec_level);

    mutex_lock(&conn->chan_lock);

    list_for_each_entry(chan, &conn->chan_l, list) {

        l2cap_chan_lock(chan);

        if (chan->chan_type == L2CAP_CHAN_CONN_FIX_A2MP) {
            l2cap_chan_unlock(chan);
            continue;
        }

        if (hcon->type == LE_LINK) {
            if (smp_conn_security(hcon, chan->sec_level))
                l2cap_chan_ready(chan);

        } else if (chan->chan_type != L2CAP_CHAN_CONN_ORIENTED) {
            struct sock *sk = chan->sk;
            __clear_chan_timer(chan);
            lock_sock(sk);
            __l2cap_state_change(chan, BT_CONNECTED);
            sk->sk_state_change(sk);
            release_sock(sk);

        } else if (chan->state == BT_CONNECT)
            l2cap_do_start(chan);

        l2cap_chan_unlock(chan);
    }

    mutex_unlock(&conn->chan_lock);
}

/* Notify sockets that we cannot guaranty reliability anymore */
static void l2cap_conn_unreliable(struct l2cap_conn *conn, int err)
{
    struct l2cap_chan *chan;

    BT_DBG("conn %p", conn);

    mutex_lock(&conn->chan_lock);

    list_for_each_entry(chan, &conn->chan_l, list) {
        if (test_bit(FLAG_FORCE_RELIABLE, &chan->flags))
            __l2cap_chan_set_err(chan, err);
    }

    mutex_unlock(&conn->chan_lock);
}

static void l2cap_info_timeout(struct work_struct *work)
{
    struct l2cap_conn *conn = container_of(work, struct l2cap_conn,
                            info_timer.work);

    conn->info_state |= L2CAP_INFO_FEAT_MASK_REQ_DONE;
    conn->info_ident = 0;

    l2cap_conn_start(conn);
}

static void l2cap_conn_del(struct hci_conn *hcon, int err)
{
    struct l2cap_conn *conn = hcon->l2cap_data;
    struct l2cap_chan *chan, *l;

    if (!conn)
        return;

    BT_DBG("hcon %p conn %p, err %d", hcon, conn, err);

    kfree_skb(conn->rx_skb);

    mutex_lock(&conn->chan_lock);

    /* Kill channels */
    list_for_each_entry_safe(chan, l, &conn->chan_l, list) {
        l2cap_chan_hold(chan);
        l2cap_chan_lock(chan);

        l2cap_chan_del(chan, err);

        l2cap_chan_unlock(chan);

        chan->ops->close(chan);
        l2cap_chan_put(chan);
    }

    mutex_unlock(&conn->chan_lock);

    hci_chan_del(conn->hchan);

    if (conn->info_state & L2CAP_INFO_FEAT_MASK_REQ_SENT)
        cancel_delayed_work_sync(&conn->info_timer);

    if (test_and_clear_bit(HCI_CONN_LE_SMP_PEND, &hcon->flags)) {
        cancel_delayed_work_sync(&conn->security_timer);
        smp_chan_destroy(conn);
    }

    hcon->l2cap_data = NULL;
    kfree(conn);
}

static void security_timeout(struct work_struct *work)
{
    struct l2cap_conn *conn = container_of(work, struct l2cap_conn,
                        security_timer.work);

    BT_DBG("conn %p", conn);

    if (test_and_clear_bit(HCI_CONN_LE_SMP_PEND, &conn->hcon->flags)) {
        smp_chan_destroy(conn);
        l2cap_conn_del(conn->hcon, ETIMEDOUT);
    }
}

static struct l2cap_conn *l2cap_conn_add(struct hci_conn *hcon, u8 status)
{
    struct l2cap_conn *conn = hcon->l2cap_data;
    struct hci_chan *hchan;

    if (conn || status)
        return conn;

    hchan = hci_chan_create(hcon);
    if (!hchan)
        return NULL;

    conn = kzalloc(sizeof(struct l2cap_conn), GFP_ATOMIC);
    if (!conn) {
        hci_chan_del(hchan);
        return NULL;
    }

    hcon->l2cap_data = conn;
    conn->hcon = hcon;
    conn->hchan = hchan;

    BT_DBG("hcon %p conn %p hchan %p", hcon, conn, hchan);

    if (hcon->hdev->le_mtu && hcon->type == LE_LINK)
        conn->mtu = hcon->hdev->le_mtu;
    else
        conn->mtu = hcon->hdev->acl_mtu;

    conn->src = &hcon->hdev->bdaddr;
    conn->dst = &hcon->dst;

    conn->feat_mask = 0;

    spin_lock_init(&conn->lock);
    mutex_init(&conn->chan_lock);

    INIT_LIST_HEAD(&conn->chan_l);

    if (hcon->type == LE_LINK)
        INIT_DELAYED_WORK(&conn->security_timer, security_timeout);
    else
        INIT_DELAYED_WORK(&conn->info_timer, l2cap_info_timeout);

    conn->disc_reason = HCI_ERROR_REMOTE_USER_TERM;

    return conn;
}

/* ---- Socket interface ---- */

/* Find socket with psm and source / destination bdaddr.
 * Returns closest match.
 */
static struct l2cap_chan *l2cap_global_chan_by_psm(int state, __le16 psm,
                           bdaddr_t *src,
                           bdaddr_t *dst)
{
    struct l2cap_chan *c, *c1 = NULL;

    read_lock(&chan_list_lock);

    list_for_each_entry(c, &chan_list, global_l) {
        struct sock *sk = c->sk;

        if (state && c->state != state)
            continue;

        if (c->psm == psm) {
            int src_match, dst_match;
            int src_any, dst_any;

            /* Exact match. */
            src_match = !bacmp(&bt_sk(sk)->src, src);
            dst_match = !bacmp(&bt_sk(sk)->dst, dst);
            if (src_match && dst_match) {
                read_unlock(&chan_list_lock);
                return c;
            }

            /* Closest match */
            src_any = !bacmp(&bt_sk(sk)->src, BDADDR_ANY);
            dst_any = !bacmp(&bt_sk(sk)->dst, BDADDR_ANY);
            if ((src_match && dst_any) || (src_any && dst_match) ||
                (src_any && dst_any))
                c1 = c;
        }
    }

    read_unlock(&chan_list_lock);

    return c1;
}

int l2cap_chan_connect(struct l2cap_chan *chan, __le16 psm, u16 cid,
               bdaddr_t *dst, u8 dst_type)
{
    struct sock *sk = chan->sk;
    bdaddr_t *src = &bt_sk(sk)->src;
    struct l2cap_conn *conn;
    struct hci_conn *hcon;
    struct hci_dev *hdev;
    __u8 auth_type;
    int err;

    BT_DBG("%s -> %s (type %u) psm 0x%2.2x", batostr(src), batostr(dst),
           dst_type, __le16_to_cpu(psm));

    hdev = hci_get_route(dst, src);
    if (!hdev)
        return -EHOSTUNREACH;

    hci_dev_lock(hdev);

    l2cap_chan_lock(chan);

    /* PSM must be odd and lsb of upper byte must be 0 */
    if ((__le16_to_cpu(psm) & 0x0101) != 0x0001 && !cid &&
                    chan->chan_type != L2CAP_CHAN_RAW) {
        err = -EINVAL;
        goto done;
    }

    if (chan->chan_type == L2CAP_CHAN_CONN_ORIENTED && !(psm || cid)) {
        err = -EINVAL;
        goto done;
    }

    switch (chan->mode) {
    case L2CAP_MODE_BASIC:
        break;
    case L2CAP_MODE_ERTM:
    case L2CAP_MODE_STREAMING:
        if (!disable_ertm)
            break;
        /* fall through */
    default:
        err = -ENOTSUPP;
        goto done;
    }

    switch (chan->state) {
    case BT_CONNECT:
    case BT_CONNECT2:
    case BT_CONFIG:
        /* Already connecting */
        err = 0;
        goto done;

    case BT_CONNECTED:
        /* Already connected */
        err = -EISCONN;
        goto done;

    case BT_OPEN:
    case BT_BOUND:
        /* Can connect */
        break;

    default:
        err = -EBADFD;
        goto done;
    }

    /* Set destination address and psm */
    lock_sock(sk);
    bacpy(&bt_sk(sk)->dst, dst);
    release_sock(sk);

    chan->psm = psm;
    chan->dcid = cid;

    auth_type = l2cap_get_auth_type(chan);

    if (chan->dcid == L2CAP_CID_LE_DATA)
        hcon = hci_connect(hdev, LE_LINK, dst, dst_type,
                   chan->sec_level, auth_type);
    else
        hcon = hci_connect(hdev, ACL_LINK, dst, dst_type,
                   chan->sec_level, auth_type);

    if (IS_ERR(hcon)) {
        err = PTR_ERR(hcon);
        goto done;
    }

    conn = l2cap_conn_add(hcon, 0);
    if (!conn) {
        hci_conn_put(hcon);
        err = -ENOMEM;
        goto done;
    }

    if (hcon->type == LE_LINK) {
        err = 0;

        if (!list_empty(&conn->chan_l)) {
            err = -EBUSY;
            hci_conn_put(hcon);
        }

        if (err)
            goto done;
    }

    /* Update source addr of the socket */
    bacpy(src, conn->src);

    l2cap_chan_unlock(chan);
    l2cap_chan_add(conn, chan);
    l2cap_chan_lock(chan);

    l2cap_state_change(chan, BT_CONNECT);
    __set_chan_timer(chan, sk->sk_sndtimeo);

    if (hcon->state == BT_CONNECTED) {
        if (chan->chan_type != L2CAP_CHAN_CONN_ORIENTED) {
            __clear_chan_timer(chan);
            if (l2cap_chan_check_security(chan))
                l2cap_state_change(chan, BT_CONNECTED);
        } else
            l2cap_do_start(chan);
    }

    err = 0;

done:
    l2cap_chan_unlock(chan);
    hci_dev_unlock(hdev);
    hci_dev_put(hdev);
    return err;
}

int __l2cap_wait_ack(struct sock *sk)
{
    struct l2cap_chan *chan = l2cap_pi(sk)->chan;
    DECLARE_WAITQUEUE(wait, current);
    int err = 0;
    int timeo = HZ/5;

    add_wait_queue(sk_sleep(sk), &wait);
    set_current_state(TASK_INTERRUPTIBLE);
    while (chan->unacked_frames > 0 && chan->conn) {
        if (!timeo)
            timeo = HZ/5;

        if (signal_pending(current)) {
            err = sock_intr_errno(timeo);
            break;
        }

        release_sock(sk);
        timeo = schedule_timeout(timeo);
        lock_sock(sk);
        set_current_state(TASK_INTERRUPTIBLE);

        err = sock_error(sk);
        if (err)
            break;
    }
    set_current_state(TASK_RUNNING);
    remove_wait_queue(sk_sleep(sk), &wait);
    return err;
}

static void l2cap_monitor_timeout(struct work_struct *work)
{
    struct l2cap_chan *chan = container_of(work, struct l2cap_chan,
                           monitor_timer.work);

    BT_DBG("chan %p", chan);

    l2cap_chan_lock(chan);

    if (!chan->conn) {
        l2cap_chan_unlock(chan);
        l2cap_chan_put(chan);
        return;
    }

    l2cap_tx(chan, NULL, NULL, L2CAP_EV_MONITOR_TO);

    l2cap_chan_unlock(chan);
    l2cap_chan_put(chan);
}

static void l2cap_retrans_timeout(struct work_struct *work)
{
    struct l2cap_chan *chan = container_of(work, struct l2cap_chan,
                           retrans_timer.work);

    BT_DBG("chan %p", chan);

    l2cap_chan_lock(chan);

    if (!chan->conn) {
        l2cap_chan_unlock(chan);
        l2cap_chan_put(chan);
        return;
    }

    l2cap_tx(chan, NULL, NULL, L2CAP_EV_RETRANS_TO);
    l2cap_chan_unlock(chan);
    l2cap_chan_put(chan);
}

static void l2cap_streaming_send(struct l2cap_chan *chan,
                 struct sk_buff_head *skbs)
{
    struct sk_buff *skb;
    struct l2cap_ctrl *control;

    BT_DBG("chan %p, skbs %p", chan, skbs);

    skb_queue_splice_tail_init(skbs, &chan->tx_q);

    while (!skb_queue_empty(&chan->tx_q)) {

        skb = skb_dequeue(&chan->tx_q);

        bt_cb(skb)->control.retries = 1;
        control = &bt_cb(skb)->control;

        control->reqseq = 0;
        control->txseq = chan->next_tx_seq;

        __pack_control(chan, control, skb);

        if (chan->fcs == L2CAP_FCS_CRC16) {
            u16 fcs = crc16(0, (u8 *) skb->data, skb->len);
            put_unaligned_le16(fcs, skb_put(skb, L2CAP_FCS_SIZE));
        }

        l2cap_do_send(chan, skb);

        BT_DBG("Sent txseq %u", control->txseq);

        chan->next_tx_seq = __next_seq(chan, chan->next_tx_seq);
        chan->frames_sent++;
    }
}

static int l2cap_ertm_send(struct l2cap_chan *chan)
{
    struct sk_buff *skb, *tx_skb;
    struct l2cap_ctrl *control;
    int sent = 0;

    BT_DBG("chan %p", chan);

    if (chan->state != BT_CONNECTED)
        return -ENOTCONN;

    if (test_bit(CONN_REMOTE_BUSY, &chan->conn_state))
        return 0;

    while (chan->tx_send_head &&
           chan->unacked_frames < chan->remote_tx_win &&
           chan->tx_state == L2CAP_TX_STATE_XMIT) {

        skb = chan->tx_send_head;

        bt_cb(skb)->control.retries = 1;
        control = &bt_cb(skb)->control;

        if (test_and_clear_bit(CONN_SEND_FBIT, &chan->conn_state))
            control->final = 1;

        control->reqseq = chan->buffer_seq;
        chan->last_acked_seq = chan->buffer_seq;
        control->txseq = chan->next_tx_seq;

        __pack_control(chan, control, skb);

        if (chan->fcs == L2CAP_FCS_CRC16) {
            u16 fcs = crc16(0, (u8 *) skb->data, skb->len);
            put_unaligned_le16(fcs, skb_put(skb, L2CAP_FCS_SIZE));
        }

        /* Clone after data has been modified. Data is assumed to be
           read-only (for locking purposes) on cloned sk_buffs.
         */
        tx_skb = skb_clone(skb, GFP_KERNEL);

        if (!tx_skb)
            break;

        __set_retrans_timer(chan);

        chan->next_tx_seq = __next_seq(chan, chan->next_tx_seq);
        chan->unacked_frames++;
        chan->frames_sent++;
        sent++;

        if (skb_queue_is_last(&chan->tx_q, skb))
            chan->tx_send_head = NULL;
        else
            chan->tx_send_head = skb_queue_next(&chan->tx_q, skb);

        l2cap_do_send(chan, tx_skb);
        BT_DBG("Sent txseq %u", control->txseq);
    }

    BT_DBG("Sent %d, %u unacked, %u in ERTM queue", sent,
           chan->unacked_frames, skb_queue_len(&chan->tx_q));

    return sent;
}

static void l2cap_ertm_resend(struct l2cap_chan *chan)
{
    struct l2cap_ctrl control;
    struct sk_buff *skb;
    struct sk_buff *tx_skb;
    u16 seq;

    BT_DBG("chan %p", chan);

    if (test_bit(CONN_REMOTE_BUSY, &chan->conn_state))
        return;

    while (chan->retrans_list.head != L2CAP_SEQ_LIST_CLEAR) {
        seq = l2cap_seq_list_pop(&chan->retrans_list);

        skb = l2cap_ertm_seq_in_queue(&chan->tx_q, seq);
        if (!skb) {
            BT_DBG("Error: Can't retransmit seq %d, frame missing",
                seq);
            continue;
        }

        bt_cb(skb)->control.retries++;
        control = bt_cb(skb)->control;

        if (chan->max_tx != 0 &&
            bt_cb(skb)->control.retries > chan->max_tx) {
            BT_DBG("Retry limit exceeded (%d)", chan->max_tx);
            l2cap_send_disconn_req(chan->conn, chan, ECONNRESET);
            l2cap_seq_list_clear(&chan->retrans_list);
            break;
        }

        control.reqseq = chan->buffer_seq;
        if (test_and_clear_bit(CONN_SEND_FBIT, &chan->conn_state))
            control.final = 1;
        else
            control.final = 0;

        if (skb_cloned(skb)) {
            /* Cloned sk_buffs are read-only, so we need a
             * writeable copy
             */
            tx_skb = skb_copy(skb, GFP_ATOMIC);
        } else {
            tx_skb = skb_clone(skb, GFP_ATOMIC);
        }

        if (!tx_skb) {
            l2cap_seq_list_clear(&chan->retrans_list);
            break;
        }

        /* Update skb contents */
        if (test_bit(FLAG_EXT_CTRL, &chan->flags)) {
            put_unaligned_le32(__pack_extended_control(&control),
                       tx_skb->data + L2CAP_HDR_SIZE);
        } else {
            put_unaligned_le16(__pack_enhanced_control(&control),
                       tx_skb->data + L2CAP_HDR_SIZE);
        }

        if (chan->fcs == L2CAP_FCS_CRC16) {
            u16 fcs = crc16(0, (u8 *) tx_skb->data, tx_skb->len);
            put_unaligned_le16(fcs, skb_put(tx_skb,
                            L2CAP_FCS_SIZE));
        }

        l2cap_do_send(chan, tx_skb);

        BT_DBG("Resent txseq %d", control.txseq);

        chan->last_acked_seq = chan->buffer_seq;
    }
}

static void l2cap_retransmit(struct l2cap_chan *chan,
                 struct l2cap_ctrl *control)
{
    BT_DBG("chan %p, control %p", chan, control);

    l2cap_seq_list_append(&chan->retrans_list, control->reqseq);
    l2cap_ertm_resend(chan);
}

static void l2cap_retransmit_all(struct l2cap_chan *chan,
                 struct l2cap_ctrl *control)
{
    struct sk_buff *skb;

    BT_DBG("chan %p, control %p", chan, control);

    if (control->poll)
        set_bit(CONN_SEND_FBIT, &chan->conn_state);

    l2cap_seq_list_clear(&chan->retrans_list);

    if (test_bit(CONN_REMOTE_BUSY, &chan->conn_state))
        return;

    if (chan->unacked_frames) {
        skb_queue_walk(&chan->tx_q, skb) {
            if (bt_cb(skb)->control.txseq == control->reqseq ||
                skb == chan->tx_send_head)
                break;
        }

        skb_queue_walk_from(&chan->tx_q, skb) {
            if (skb == chan->tx_send_head)
                break;

            l2cap_seq_list_append(&chan->retrans_list,
                          bt_cb(skb)->control.txseq);
        }

        l2cap_ertm_resend(chan);
    }
}

static void l2cap_send_ack(struct l2cap_chan *chan)
{
    struct l2cap_ctrl control;
    u16 frames_to_ack = __seq_offset(chan, chan->buffer_seq,
                     chan->last_acked_seq);
    int threshold;

    BT_DBG("chan %p last_acked_seq %d buffer_seq %d",
           chan, chan->last_acked_seq, chan->buffer_seq);

    memset(&control, 0, sizeof(control));
    control.sframe = 1;

    if (test_bit(CONN_LOCAL_BUSY, &chan->conn_state) &&
        chan->rx_state == L2CAP_RX_STATE_RECV) {
        __clear_ack_timer(chan);
        control.super = L2CAP_SUPER_RNR;
        control.reqseq = chan->buffer_seq;
        l2cap_send_sframe(chan, &control);
    } else {
        if (!test_bit(CONN_REMOTE_BUSY, &chan->conn_state)) {
            l2cap_ertm_send(chan);
            /* If any i-frames were sent, they included an ack */
            if (chan->buffer_seq == chan->last_acked_seq)
                frames_to_ack = 0;
        }

        /* Ack now if the window is 3/4ths full.
         * Calculate without mul or div
         */
        threshold = chan->ack_win;
        threshold += threshold << 1;
        threshold >>= 2;

        BT_DBG("frames_to_ack %u, threshold %d", frames_to_ack,
               threshold);

        if (frames_to_ack >= threshold) {
            __clear_ack_timer(chan);
            control.super = L2CAP_SUPER_RR;
            control.reqseq = chan->buffer_seq;
            l2cap_send_sframe(chan, &control);
            frames_to_ack = 0;
        }

        if (frames_to_ack)
            __set_ack_timer(chan);
    }
}

static inline int l2cap_skbuff_fromiovec(struct l2cap_chan *chan,
                     struct msghdr *msg, int len,
                     int count, struct sk_buff *skb)
{
    struct l2cap_conn *conn = chan->conn;
    struct sk_buff **frag;
    int sent = 0;

    if (memcpy_fromiovec(skb_put(skb, count), msg->msg_iov, count))
        return -EFAULT;

    sent += count;
    len  -= count;

    /* Continuation fragments (no L2CAP header) */
    frag = &skb_shinfo(skb)->frag_list;
    while (len) {
        struct sk_buff *tmp;

        count = min_t(unsigned int, conn->mtu, len);

        tmp = chan->ops->alloc_skb(chan, count,
                       msg->msg_flags & MSG_DONTWAIT);
        if (IS_ERR(tmp))
            return PTR_ERR(tmp);

        *frag = tmp;

        if (memcpy_fromiovec(skb_put(*frag, count), msg->msg_iov, count))
            return -EFAULT;

        (*frag)->priority = skb->priority;

        sent += count;
        len  -= count;

        skb->len += (*frag)->len;
        skb->data_len += (*frag)->len;

        frag = &(*frag)->next;
    }

    return sent;
}

static struct sk_buff *l2cap_create_connless_pdu(struct l2cap_chan *chan,
                         struct msghdr *msg, size_t len,
                         u32 priority)
{
    struct l2cap_conn *conn = chan->conn;
    struct sk_buff *skb;
    int err, count, hlen = L2CAP_HDR_SIZE + L2CAP_PSMLEN_SIZE;
    struct l2cap_hdr *lh;

    BT_DBG("chan %p len %zu priority %u", chan, len, priority);

    count = min_t(unsigned int, (conn->mtu - hlen), len);

    skb = chan->ops->alloc_skb(chan, count + hlen,
                   msg->msg_flags & MSG_DONTWAIT);
    if (IS_ERR(skb))
        return skb;

    skb->priority = priority;

    /* Create L2CAP header */
    lh = (struct l2cap_hdr *) skb_put(skb, L2CAP_HDR_SIZE);
    lh->cid = cpu_to_le16(chan->dcid);
    lh->len = cpu_to_le16(len + L2CAP_PSMLEN_SIZE);
    put_unaligned(chan->psm, skb_put(skb, L2CAP_PSMLEN_SIZE));

    err = l2cap_skbuff_fromiovec(chan, msg, len, count, skb);
    if (unlikely(err < 0)) {
        kfree_skb(skb);
        return ERR_PTR(err);
    }
    return skb;
}

static struct sk_buff *l2cap_create_basic_pdu(struct l2cap_chan *chan,
                          struct msghdr *msg, size_t len,
                          u32 priority)
{
    struct l2cap_conn *conn = chan->conn;
    struct sk_buff *skb;
    int err, count;
    struct l2cap_hdr *lh;

    BT_DBG("chan %p len %zu", chan, len);

    count = min_t(unsigned int, (conn->mtu - L2CAP_HDR_SIZE), len);

    skb = chan->ops->alloc_skb(chan, count + L2CAP_HDR_SIZE,
                   msg->msg_flags & MSG_DONTWAIT);
    if (IS_ERR(skb))
        return skb;

    skb->priority = priority;

    /* Create L2CAP header */
    lh = (struct l2cap_hdr *) skb_put(skb, L2CAP_HDR_SIZE);
    lh->cid = cpu_to_le16(chan->dcid);
    lh->len = cpu_to_le16(len);

    err = l2cap_skbuff_fromiovec(chan, msg, len, count, skb);
    if (unlikely(err < 0)) {
        kfree_skb(skb);
        return ERR_PTR(err);
    }
    return skb;
}

static struct sk_buff *l2cap_create_iframe_pdu(struct l2cap_chan *chan,
                           struct msghdr *msg, size_t len,
                           u16 sdulen)
{
    struct l2cap_conn *conn = chan->conn;
    struct sk_buff *skb;
    int err, count, hlen;
    struct l2cap_hdr *lh;

    BT_DBG("chan %p len %zu", chan, len);

    if (!conn)
        return ERR_PTR(-ENOTCONN);

    hlen = __ertm_hdr_size(chan);

    if (sdulen)
        hlen += L2CAP_SDULEN_SIZE;

    if (chan->fcs == L2CAP_FCS_CRC16)
        hlen += L2CAP_FCS_SIZE;

    count = min_t(unsigned int, (conn->mtu - hlen), len);

    skb = chan->ops->alloc_skb(chan, count + hlen,
                   msg->msg_flags & MSG_DONTWAIT);
    if (IS_ERR(skb))
        return skb;

    /* Create L2CAP header */
    lh = (struct l2cap_hdr *) skb_put(skb, L2CAP_HDR_SIZE);
    lh->cid = cpu_to_le16(chan->dcid);
    lh->len = cpu_to_le16(len + (hlen - L2CAP_HDR_SIZE));

    /* Control header is populated later */
    if (test_bit(FLAG_EXT_CTRL, &chan->flags))
        put_unaligned_le32(0, skb_put(skb, L2CAP_EXT_CTRL_SIZE));
    else
        put_unaligned_le16(0, skb_put(skb, L2CAP_ENH_CTRL_SIZE));

    if (sdulen)
        put_unaligned_le16(sdulen, skb_put(skb, L2CAP_SDULEN_SIZE));

    err = l2cap_skbuff_fromiovec(chan, msg, len, count, skb);
    if (unlikely(err < 0)) {
        kfree_skb(skb);
        return ERR_PTR(err);
    }

    bt_cb(skb)->control.fcs = chan->fcs;
    bt_cb(skb)->control.retries = 0;
    return skb;
}

static int l2cap_segment_sdu(struct l2cap_chan *chan,
                 struct sk_buff_head *seg_queue,
                 struct msghdr *msg, size_t len)
{
    struct sk_buff *skb;
    u16 sdu_len;
    size_t pdu_len;
    u8 sar;

    BT_DBG("chan %p, msg %p, len %zu", chan, msg, len);

    /* It is critical that ERTM PDUs fit in a single HCI fragment,
     * so fragmented skbs are not used.  The HCI layer's handling
     * of fragmented skbs is not compatible with ERTM's queueing.
     */

    /* PDU size is derived from the HCI MTU */
    pdu_len = chan->conn->mtu;

    pdu_len = min_t(size_t, pdu_len, L2CAP_BREDR_MAX_PAYLOAD);

    /* Adjust for largest possible L2CAP overhead. */
    if (chan->fcs)
        pdu_len -= L2CAP_FCS_SIZE;

    pdu_len -= __ertm_hdr_size(chan);

    /* Remote device may have requested smaller PDUs */
    pdu_len = min_t(size_t, pdu_len, chan->remote_mps);

    if (len <= pdu_len) {
        sar = L2CAP_SAR_UNSEGMENTED;
        sdu_len = 0;
        pdu_len = len;
    } else {
        sar = L2CAP_SAR_START;
        sdu_len = len;
        pdu_len -= L2CAP_SDULEN_SIZE;
    }

    while (len > 0) {
        skb = l2cap_create_iframe_pdu(chan, msg, pdu_len, sdu_len);

        if (IS_ERR(skb)) {
            __skb_queue_purge(seg_queue);
            return PTR_ERR(skb);
        }

        bt_cb(skb)->control.sar = sar;
        __skb_queue_tail(seg_queue, skb);

        len -= pdu_len;
        if (sdu_len) {
            sdu_len = 0;
            pdu_len += L2CAP_SDULEN_SIZE;
        }

        if (len <= pdu_len) {
            sar = L2CAP_SAR_END;
            pdu_len = len;
        } else {
            sar = L2CAP_SAR_CONTINUE;
        }
    }

    return 0;
}

int l2cap_chan_send(struct l2cap_chan *chan, struct msghdr *msg, size_t len,
                                u32 priority)
{
    struct sk_buff *skb;
    int err;
    struct sk_buff_head seg_queue;

    /* Connectionless channel */
    if (chan->chan_type == L2CAP_CHAN_CONN_LESS) {
        skb = l2cap_create_connless_pdu(chan, msg, len, priority);
        if (IS_ERR(skb))
            return PTR_ERR(skb);

        l2cap_do_send(chan, skb);
        return len;
    }

    switch (chan->mode) {
    case L2CAP_MODE_BASIC:
        /* Check outgoing MTU */
        if (len > chan->omtu)
            return -EMSGSIZE;

        /* Create a basic PDU */
        skb = l2cap_create_basic_pdu(chan, msg, len, priority);
        if (IS_ERR(skb))
            return PTR_ERR(skb);

        l2cap_do_send(chan, skb);
        err = len;
        break;

    case L2CAP_MODE_ERTM:
    case L2CAP_MODE_STREAMING:
        /* Check outgoing MTU */
        if (len > chan->omtu) {
            err = -EMSGSIZE;
            break;
        }

        __skb_queue_head_init(&seg_queue);

        /* Do segmentation before calling in to the state machine,
         * since it's possible to block while waiting for memory
         * allocation.
         */
        err = l2cap_segment_sdu(chan, &seg_queue, msg, len);

        /* The channel could have been closed while segmenting,
         * check that it is still connected.
         */
        if (chan->state != BT_CONNECTED) {
            __skb_queue_purge(&seg_queue);
            err = -ENOTCONN;
        }

        if (err)
            break;

        if (chan->mode == L2CAP_MODE_ERTM)
            l2cap_tx(chan, NULL, &seg_queue, L2CAP_EV_DATA_REQUEST);
        else
            l2cap_streaming_send(chan, &seg_queue);

        err = len;

        /* If the skbs were not queued for sending, they'll still be in
         * seg_queue and need to be purged.
         */
        __skb_queue_purge(&seg_queue);
        break;

    default:
        BT_DBG("bad state %1.1x", chan->mode);
        err = -EBADFD;
    }

    return err;
}

static void l2cap_send_srej(struct l2cap_chan *chan, u16 txseq)
{
    struct l2cap_ctrl control;
    u16 seq;

    BT_DBG("chan %p, txseq %u", chan, txseq);

    memset(&control, 0, sizeof(control));
    control.sframe = 1;
    control.super = L2CAP_SUPER_SREJ;

    for (seq = chan->expected_tx_seq; seq != txseq;
         seq = __next_seq(chan, seq)) {
        if (!l2cap_ertm_seq_in_queue(&chan->srej_q, seq)) {
            control.reqseq = seq;
            l2cap_send_sframe(chan, &control);
            l2cap_seq_list_append(&chan->srej_list, seq);
        }
    }

    chan->expected_tx_seq = __next_seq(chan, txseq);
}

static void l2cap_send_srej_tail(struct l2cap_chan *chan)
{
    struct l2cap_ctrl control;

    BT_DBG("chan %p", chan);

    if (chan->srej_list.tail == L2CAP_SEQ_LIST_CLEAR)
        return;

    memset(&control, 0, sizeof(control));
    control.sframe = 1;
    control.super = L2CAP_SUPER_SREJ;
    control.reqseq = chan->srej_list.tail;
    l2cap_send_sframe(chan, &control);
}

static void l2cap_send_srej_list(struct l2cap_chan *chan, u16 txseq)
{
    struct l2cap_ctrl control;
    u16 initial_head;
    u16 seq;

    BT_DBG("chan %p, txseq %u", chan, txseq);

    memset(&control, 0, sizeof(control));
    control.sframe = 1;
    control.super = L2CAP_SUPER_SREJ;

    /* Capture initial list head to allow only one pass through the list. */
    initial_head = chan->srej_list.head;

    do {
        seq = l2cap_seq_list_pop(&chan->srej_list);
        if (seq == txseq || seq == L2CAP_SEQ_LIST_CLEAR)
            break;

        control.reqseq = seq;
        l2cap_send_sframe(chan, &control);
        l2cap_seq_list_append(&chan->srej_list, seq);
    } while (chan->srej_list.head != initial_head);
}

static void l2cap_process_reqseq(struct l2cap_chan *chan, u16 reqseq)
{
    struct sk_buff *acked_skb;
    u16 ackseq;

    BT_DBG("chan %p, reqseq %u", chan, reqseq);

    if (chan->unacked_frames == 0 || reqseq == chan->expected_ack_seq)
        return;

    BT_DBG("expected_ack_seq %u, unacked_frames %u",
           chan->expected_ack_seq, chan->unacked_frames);

    for (ackseq = chan->expected_ack_seq; ackseq != reqseq;
         ackseq = __next_seq(chan, ackseq)) {

        acked_skb = l2cap_ertm_seq_in_queue(&chan->tx_q, ackseq);
        if (acked_skb) {
            skb_unlink(acked_skb, &chan->tx_q);
            kfree_skb(acked_skb);
            chan->unacked_frames--;
        }
    }

    chan->expected_ack_seq = reqseq;

    if (chan->unacked_frames == 0)
        __clear_retrans_timer(chan);

    BT_DBG("unacked_frames %u", chan->unacked_frames);
}

static void l2cap_abort_rx_srej_sent(struct l2cap_chan *chan)
{
    BT_DBG("chan %p", chan);

    chan->expected_tx_seq = chan->buffer_seq;
    l2cap_seq_list_clear(&chan->srej_list);
    skb_queue_purge(&chan->srej_q);
    chan->rx_state = L2CAP_RX_STATE_RECV;
}

static void l2cap_tx_state_xmit(struct l2cap_chan *chan,
                struct l2cap_ctrl *control,
                struct sk_buff_head *skbs, u8 event)
{
    BT_DBG("chan %p, control %p, skbs %p, event %d", chan, control, skbs,
           event);

    switch (event) {
    case L2CAP_EV_DATA_REQUEST:
        if (chan->tx_send_head == NULL)
            chan->tx_send_head = skb_peek(skbs);

        skb_queue_splice_tail_init(skbs, &chan->tx_q);
        l2cap_ertm_send(chan);
        break;
    case L2CAP_EV_LOCAL_BUSY_DETECTED:
        BT_DBG("Enter LOCAL_BUSY");
        set_bit(CONN_LOCAL_BUSY, &chan->conn_state);

        if (chan->rx_state == L2CAP_RX_STATE_SREJ_SENT) {
            /* The SREJ_SENT state must be aborted if we are to
             * enter the LOCAL_BUSY state.
             */
            l2cap_abort_rx_srej_sent(chan);
        }

        l2cap_send_ack(chan);

        break;
    case L2CAP_EV_LOCAL_BUSY_CLEAR:
        BT_DBG("Exit LOCAL_BUSY");
        clear_bit(CONN_LOCAL_BUSY, &chan->conn_state);

        if (test_bit(CONN_RNR_SENT, &chan->conn_state)) {
            struct l2cap_ctrl local_control;

            memset(&local_control, 0, sizeof(local_control));
            local_control.sframe = 1;
            local_control.super = L2CAP_SUPER_RR;
            local_control.poll = 1;
            local_control.reqseq = chan->buffer_seq;
            l2cap_send_sframe(chan, &local_control);

            chan->retry_count = 1;
            __set_monitor_timer(chan);
            chan->tx_state = L2CAP_TX_STATE_WAIT_F;
        }
        break;
    case L2CAP_EV_RECV_REQSEQ_AND_FBIT:
        l2cap_process_reqseq(chan, control->reqseq);
        break;
    case L2CAP_EV_EXPLICIT_POLL:
        l2cap_send_rr_or_rnr(chan, 1);
        chan->retry_count = 1;
        __set_monitor_timer(chan);
        __clear_ack_timer(chan);
        chan->tx_state = L2CAP_TX_STATE_WAIT_F;
        break;
    case L2CAP_EV_RETRANS_TO:
        l2cap_send_rr_or_rnr(chan, 1);
        chan->retry_count = 1;
        __set_monitor_timer(chan);
        chan->tx_state = L2CAP_TX_STATE_WAIT_F;
        break;
    case L2CAP_EV_RECV_FBIT:
        /* Nothing to process */
        break;
    default:
        break;
    }
}

static void l2cap_tx_state_wait_f(struct l2cap_chan *chan,
                  struct l2cap_ctrl *control,
                  struct sk_buff_head *skbs, u8 event)
{
    BT_DBG("chan %p, control %p, skbs %p, event %d", chan, control, skbs,
           event);

    switch (event) {
    case L2CAP_EV_DATA_REQUEST:
        if (chan->tx_send_head == NULL)
            chan->tx_send_head = skb_peek(skbs);
        /* Queue data, but don't send. */
        skb_queue_splice_tail_init(skbs, &chan->tx_q);
        break;
    case L2CAP_EV_LOCAL_BUSY_DETECTED:
        BT_DBG("Enter LOCAL_BUSY");
        set_bit(CONN_LOCAL_BUSY, &chan->conn_state);

        if (chan->rx_state == L2CAP_RX_STATE_SREJ_SENT) {
            /* The SREJ_SENT state must be aborted if we are to
             * enter the LOCAL_BUSY state.
             */
            l2cap_abort_rx_srej_sent(chan);
        }

        l2cap_send_ack(chan);

        break;
    case L2CAP_EV_LOCAL_BUSY_CLEAR:
        BT_DBG("Exit LOCAL_BUSY");
        clear_bit(CONN_LOCAL_BUSY, &chan->conn_state);

        if (test_bit(CONN_RNR_SENT, &chan->conn_state)) {
            struct l2cap_ctrl local_control;
            memset(&local_control, 0, sizeof(local_control));
            local_control.sframe = 1;
            local_control.super = L2CAP_SUPER_RR;
            local_control.poll = 1;
            local_control.reqseq = chan->buffer_seq;
            l2cap_send_sframe(chan, &local_control);

            chan->retry_count = 1;
            __set_monitor_timer(chan);
            chan->tx_state = L2CAP_TX_STATE_WAIT_F;
        }
        break;
    case L2CAP_EV_RECV_REQSEQ_AND_FBIT:
        l2cap_process_reqseq(chan, control->reqseq);

        /* Fall through */

    case L2CAP_EV_RECV_FBIT:
        if (control && control->final) {
            __clear_monitor_timer(chan);
            if (chan->unacked_frames > 0)
                __set_retrans_timer(chan);
            chan->retry_count = 0;
            chan->tx_state = L2CAP_TX_STATE_XMIT;
            BT_DBG("recv fbit tx_state 0x2.2%x", chan->tx_state);
        }
        break;
    case L2CAP_EV_EXPLICIT_POLL:
        /* Ignore */
        break;
    case L2CAP_EV_MONITOR_TO:
        if (chan->max_tx == 0 || chan->retry_count < chan->max_tx) {
            l2cap_send_rr_or_rnr(chan, 1);
            __set_monitor_timer(chan);
            chan->retry_count++;
        } else {
            l2cap_send_disconn_req(chan->conn, chan, ECONNABORTED);
        }
        break;
    default:
        break;
    }
}

static void l2cap_tx(struct l2cap_chan *chan, struct l2cap_ctrl *control,
             struct sk_buff_head *skbs, u8 event)
{
    BT_DBG("chan %p, control %p, skbs %p, event %d, state %d",
           chan, control, skbs, event, chan->tx_state);

    switch (chan->tx_state) {
    case L2CAP_TX_STATE_XMIT:
        l2cap_tx_state_xmit(chan, control, skbs, event);
        break;
    case L2CAP_TX_STATE_WAIT_F:
        l2cap_tx_state_wait_f(chan, control, skbs, event);
        break;
    default:
        /* Ignore event */
        break;
    }
}

static void l2cap_pass_to_tx(struct l2cap_chan *chan,
                 struct l2cap_ctrl *control)
{
    BT_DBG("chan %p, control %p", chan, control);
    l2cap_tx(chan, control, NULL, L2CAP_EV_RECV_REQSEQ_AND_FBIT);
}

static void l2cap_pass_to_tx_fbit(struct l2cap_chan *chan,
                  struct l2cap_ctrl *control)
{
    BT_DBG("chan %p, control %p", chan, control);
    l2cap_tx(chan, control, NULL, L2CAP_EV_RECV_FBIT);
}

/* Copy frame to all raw sockets on that connection */
static void l2cap_raw_recv(struct l2cap_conn *conn, struct sk_buff *skb)
{
    struct sk_buff *nskb;
    struct l2cap_chan *chan;

    BT_DBG("conn %p", conn);

    mutex_lock(&conn->chan_lock);

    list_for_each_entry(chan, &conn->chan_l, list) {
        struct sock *sk = chan->sk;
        if (chan->chan_type != L2CAP_CHAN_RAW)
            continue;

        /* Don't send frame to the socket it came from */
        if (skb->sk == sk)
            continue;
        nskb = skb_clone(skb, GFP_ATOMIC);
        if (!nskb)
            continue;

        if (chan->ops->recv(chan, nskb))
            kfree_skb(nskb);
    }

    mutex_unlock(&conn->chan_lock);
}

/* ---- L2CAP signalling commands ---- */
static struct sk_buff *l2cap_build_cmd(struct l2cap_conn *conn, u8 code,
                       u8 ident, u16 dlen, void *data)
{
    struct sk_buff *skb, **frag;
    struct l2cap_cmd_hdr *cmd;
    struct l2cap_hdr *lh;
    int len, count;

    BT_DBG("conn %p, code 0x%2.2x, ident 0x%2.2x, len %u",
           conn, code, ident, dlen);

    len = L2CAP_HDR_SIZE + L2CAP_CMD_HDR_SIZE + dlen;
    count = min_t(unsigned int, conn->mtu, len);

    skb = bt_skb_alloc(count, GFP_ATOMIC);
    if (!skb)
        return NULL;

    lh = (struct l2cap_hdr *) skb_put(skb, L2CAP_HDR_SIZE);
    lh->len = cpu_to_le16(L2CAP_CMD_HDR_SIZE + dlen);

    if (conn->hcon->type == LE_LINK)
        lh->cid = __constant_cpu_to_le16(L2CAP_CID_LE_SIGNALING);
    else
        lh->cid = __constant_cpu_to_le16(L2CAP_CID_SIGNALING);

    cmd = (struct l2cap_cmd_hdr *) skb_put(skb, L2CAP_CMD_HDR_SIZE);
    cmd->code  = code;
    cmd->ident = ident;
    cmd->len   = cpu_to_le16(dlen);

    if (dlen) {
        count -= L2CAP_HDR_SIZE + L2CAP_CMD_HDR_SIZE;
        memcpy(skb_put(skb, count), data, count);
        data += count;
    }

    len -= skb->len;

    /* Continuation fragments (no L2CAP header) */
    frag = &skb_shinfo(skb)->frag_list;
    while (len) {
        count = min_t(unsigned int, conn->mtu, len);

        *frag = bt_skb_alloc(count, GFP_ATOMIC);
        if (!*frag)
            goto fail;

        memcpy(skb_put(*frag, count), data, count);

        len  -= count;
        data += count;

        frag = &(*frag)->next;
    }

    return skb;

fail:
    kfree_skb(skb);
    return NULL;
}

static inline int l2cap_get_conf_opt(void **ptr, int *type, int *olen, unsigned long *val)
{
    struct l2cap_conf_opt *opt = *ptr;
    int len;

    len = L2CAP_CONF_OPT_SIZE + opt->len;
    *ptr += len;

    *type = opt->type;
    *olen = opt->len;

    switch (opt->len) {
    case 1:
        *val = *((u8 *) opt->val);
        break;

    case 2:
        *val = get_unaligned_le16(opt->val);
        break;

    case 4:
        *val = get_unaligned_le32(opt->val);
        break;

    default:
        *val = (unsigned long) opt->val;
        break;
    }

    BT_DBG("type 0x%2.2x len %u val 0x%lx", *type, opt->len, *val);
    return len;
}

static void l2cap_add_conf_opt(void **ptr, u8 type, u8 len, unsigned long val)
{
    struct l2cap_conf_opt *opt = *ptr;

    BT_DBG("type 0x%2.2x len %u val 0x%lx", type, len, val);

    opt->type = type;
    opt->len  = len;

    switch (len) {
    case 1:
        *((u8 *) opt->val)  = val;
        break;

    case 2:
        put_unaligned_le16(val, opt->val);
        break;

    case 4:
        put_unaligned_le32(val, opt->val);
        break;

    default:
        memcpy(opt->val, (void *) val, len);
        break;
    }

    *ptr += L2CAP_CONF_OPT_SIZE + len;
}

static void l2cap_add_opt_efs(void **ptr, struct l2cap_chan *chan)
{
    struct l2cap_conf_efs efs;

    switch (chan->mode) {
    case L2CAP_MODE_ERTM:
        efs.id      = chan->local_id;
        efs.stype   = chan->local_stype;
        efs.msdu    = cpu_to_le16(chan->local_msdu);
        efs.sdu_itime   = cpu_to_le32(chan->local_sdu_itime);
        efs.acc_lat = __constant_cpu_to_le32(L2CAP_DEFAULT_ACC_LAT);
        efs.flush_to    = __constant_cpu_to_le32(L2CAP_DEFAULT_FLUSH_TO);
        break;

    case L2CAP_MODE_STREAMING:
        efs.id      = 1;
        efs.stype   = L2CAP_SERV_BESTEFFORT;
        efs.msdu    = cpu_to_le16(chan->local_msdu);
        efs.sdu_itime   = cpu_to_le32(chan->local_sdu_itime);
        efs.acc_lat = 0;
        efs.flush_to    = 0;
        break;

    default:
        return;
    }

    l2cap_add_conf_opt(ptr, L2CAP_CONF_EFS, sizeof(efs),
                            (unsigned long) &efs);
}

static void l2cap_ack_timeout(struct work_struct *work)
{
    struct l2cap_chan *chan = container_of(work, struct l2cap_chan,
                           ack_timer.work);
    u16 frames_to_ack;

    BT_DBG("chan %p", chan);

    l2cap_chan_lock(chan);

    frames_to_ack = __seq_offset(chan, chan->buffer_seq,
                     chan->last_acked_seq);

    if (frames_to_ack)
        l2cap_send_rr_or_rnr(chan, 0);

    l2cap_chan_unlock(chan);
    l2cap_chan_put(chan);
}

int l2cap_ertm_init(struct l2cap_chan *chan)
{
    int err;

    chan->next_tx_seq = 0;
    chan->expected_tx_seq = 0;
    chan->expected_ack_seq = 0;
    chan->unacked_frames = 0;
    chan->buffer_seq = 0;
    chan->frames_sent = 0;
    chan->last_acked_seq = 0;
    chan->sdu = NULL;
    chan->sdu_last_frag = NULL;
    chan->sdu_len = 0;

    skb_queue_head_init(&chan->tx_q);

    if (chan->mode != L2CAP_MODE_ERTM)
        return 0;

    chan->rx_state = L2CAP_RX_STATE_RECV;
    chan->tx_state = L2CAP_TX_STATE_XMIT;

    INIT_DELAYED_WORK(&chan->retrans_timer, l2cap_retrans_timeout);
    INIT_DELAYED_WORK(&chan->monitor_timer, l2cap_monitor_timeout);
    INIT_DELAYED_WORK(&chan->ack_timer, l2cap_ack_timeout);

    skb_queue_head_init(&chan->srej_q);

    err = l2cap_seq_list_init(&chan->srej_list, chan->tx_win);
    if (err < 0)
        return err;

    err = l2cap_seq_list_init(&chan->retrans_list, chan->remote_tx_win);
    if (err < 0)
        l2cap_seq_list_free(&chan->srej_list);

    return err;
}

static inline __u8 l2cap_select_mode(__u8 mode, __u16 remote_feat_mask)
{
    switch (mode) {
    case L2CAP_MODE_STREAMING:
    case L2CAP_MODE_ERTM:
        if (l2cap_mode_supported(mode, remote_feat_mask))
            return mode;
        /* fall through */
    default:
        return L2CAP_MODE_BASIC;
    }
}

static inline bool __l2cap_ews_supported(struct l2cap_chan *chan)
{
    return enable_hs && chan->conn->feat_mask & L2CAP_FEAT_EXT_WINDOW;
}

static inline bool __l2cap_efs_supported(struct l2cap_chan *chan)
{
    return enable_hs && chan->conn->feat_mask & L2CAP_FEAT_EXT_FLOW;
}

static inline void l2cap_txwin_setup(struct l2cap_chan *chan)
{
    if (chan->tx_win > L2CAP_DEFAULT_TX_WINDOW &&
                        __l2cap_ews_supported(chan)) {
        /* use extended control field */
        set_bit(FLAG_EXT_CTRL, &chan->flags);
        chan->tx_win_max = L2CAP_DEFAULT_EXT_WINDOW;
    } else {
        chan->tx_win = min_t(u16, chan->tx_win,
                        L2CAP_DEFAULT_TX_WINDOW);
        chan->tx_win_max = L2CAP_DEFAULT_TX_WINDOW;
    }
    chan->ack_win = chan->tx_win;
}

static int l2cap_build_conf_req(struct l2cap_chan *chan, void *data)
{
    struct l2cap_conf_req *req = data;
    struct l2cap_conf_rfc rfc = { .mode = chan->mode };
    void *ptr = req->data;
    u16 size;

    BT_DBG("chan %p", chan);

    if (chan->num_conf_req || chan->num_conf_rsp)
        goto done;

    switch (chan->mode) {
    case L2CAP_MODE_STREAMING:
    case L2CAP_MODE_ERTM:
        if (test_bit(CONF_STATE2_DEVICE, &chan->conf_state))
            break;

        if (__l2cap_efs_supported(chan))
            set_bit(FLAG_EFS_ENABLE, &chan->flags);

        /* fall through */
    default:
        chan->mode = l2cap_select_mode(rfc.mode, chan->conn->feat_mask);
        break;
    }

done:
    if (chan->imtu != L2CAP_DEFAULT_MTU)
        l2cap_add_conf_opt(&ptr, L2CAP_CONF_MTU, 2, chan->imtu);

    switch (chan->mode) {
    case L2CAP_MODE_BASIC:
        if (!(chan->conn->feat_mask & L2CAP_FEAT_ERTM) &&
                !(chan->conn->feat_mask & L2CAP_FEAT_STREAMING))
            break;

        rfc.mode            = L2CAP_MODE_BASIC;
        rfc.txwin_size      = 0;
        rfc.max_transmit    = 0;
        rfc.retrans_timeout = 0;
        rfc.monitor_timeout = 0;
        rfc.max_pdu_size    = 0;

        l2cap_add_conf_opt(&ptr, L2CAP_CONF_RFC, sizeof(rfc),
                            (unsigned long) &rfc);
        break;

    case L2CAP_MODE_ERTM:
        rfc.mode            = L2CAP_MODE_ERTM;
        rfc.max_transmit    = chan->max_tx;
        rfc.retrans_timeout = 0;
        rfc.monitor_timeout = 0;

        size = min_t(u16, L2CAP_DEFAULT_MAX_PDU_SIZE, chan->conn->mtu -
                        L2CAP_EXT_HDR_SIZE -
                        L2CAP_SDULEN_SIZE -
                        L2CAP_FCS_SIZE);
        rfc.max_pdu_size = cpu_to_le16(size);

        l2cap_txwin_setup(chan);

        rfc.txwin_size = min_t(u16, chan->tx_win,
                        L2CAP_DEFAULT_TX_WINDOW);

        l2cap_add_conf_opt(&ptr, L2CAP_CONF_RFC, sizeof(rfc),
                            (unsigned long) &rfc);

        if (test_bit(FLAG_EFS_ENABLE, &chan->flags))
            l2cap_add_opt_efs(&ptr, chan);

        if (!(chan->conn->feat_mask & L2CAP_FEAT_FCS))
            break;

        if (chan->fcs == L2CAP_FCS_NONE ||
                test_bit(CONF_NO_FCS_RECV, &chan->conf_state)) {
            chan->fcs = L2CAP_FCS_NONE;
            l2cap_add_conf_opt(&ptr, L2CAP_CONF_FCS, 1, chan->fcs);
        }

        if (test_bit(FLAG_EXT_CTRL, &chan->flags))
            l2cap_add_conf_opt(&ptr, L2CAP_CONF_EWS, 2,
                                chan->tx_win);
        break;

    case L2CAP_MODE_STREAMING:
        l2cap_txwin_setup(chan);
        rfc.mode            = L2CAP_MODE_STREAMING;
        rfc.txwin_size      = 0;
        rfc.max_transmit    = 0;
        rfc.retrans_timeout = 0;
        rfc.monitor_timeout = 0;

        size = min_t(u16, L2CAP_DEFAULT_MAX_PDU_SIZE, chan->conn->mtu -
                        L2CAP_EXT_HDR_SIZE -
                        L2CAP_SDULEN_SIZE -
                        L2CAP_FCS_SIZE);
        rfc.max_pdu_size = cpu_to_le16(size);

        l2cap_add_conf_opt(&ptr, L2CAP_CONF_RFC, sizeof(rfc),
                            (unsigned long) &rfc);

        if (test_bit(FLAG_EFS_ENABLE, &chan->flags))
            l2cap_add_opt_efs(&ptr, chan);

        if (!(chan->conn->feat_mask & L2CAP_FEAT_FCS))
            break;

        if (chan->fcs == L2CAP_FCS_NONE ||
                test_bit(CONF_NO_FCS_RECV, &chan->conf_state)) {
            chan->fcs = L2CAP_FCS_NONE;
            l2cap_add_conf_opt(&ptr, L2CAP_CONF_FCS, 1, chan->fcs);
        }
        break;
    }

    req->dcid  = cpu_to_le16(chan->dcid);
    req->flags = __constant_cpu_to_le16(0);

    return ptr - data;
}

static int l2cap_parse_conf_req(struct l2cap_chan *chan, void *data)
{
    struct l2cap_conf_rsp *rsp = data;
    void *ptr = rsp->data;
    void *req = chan->conf_req;
    int len = chan->conf_len;
    int type, hint, olen;
    unsigned long val;
    struct l2cap_conf_rfc rfc = { .mode = L2CAP_MODE_BASIC };
    struct l2cap_conf_efs efs;
    u8 remote_efs = 0;
    u16 mtu = L2CAP_DEFAULT_MTU;
    u16 result = L2CAP_CONF_SUCCESS;
    u16 size;

    BT_DBG("chan %p", chan);

    while (len >= L2CAP_CONF_OPT_SIZE) {
        len -= l2cap_get_conf_opt(&req, &type, &olen, &val);

        hint  = type & L2CAP_CONF_HINT;
        type &= L2CAP_CONF_MASK;

        switch (type) {
        case L2CAP_CONF_MTU:
            mtu = val;
            break;

        case L2CAP_CONF_FLUSH_TO:
            chan->flush_to = val;
            break;

        case L2CAP_CONF_QOS:
            break;

        case L2CAP_CONF_RFC:
            if (olen == sizeof(rfc))
                memcpy(&rfc, (void *) val, olen);
            break;

        case L2CAP_CONF_FCS:
            if (val == L2CAP_FCS_NONE)
                set_bit(CONF_NO_FCS_RECV, &chan->conf_state);
            break;

        case L2CAP_CONF_EFS:
            remote_efs = 1;
            if (olen == sizeof(efs))
                memcpy(&efs, (void *) val, olen);
            break;

        case L2CAP_CONF_EWS:
            if (!enable_hs)
                return -ECONNREFUSED;

            set_bit(FLAG_EXT_CTRL, &chan->flags);
            set_bit(CONF_EWS_RECV, &chan->conf_state);
            chan->tx_win_max = L2CAP_DEFAULT_EXT_WINDOW;
            chan->remote_tx_win = val;
            break;

        default:
            if (hint)
                break;

            result = L2CAP_CONF_UNKNOWN;
            *((u8 *) ptr++) = type;
            break;
        }
    }

    if (chan->num_conf_rsp || chan->num_conf_req > 1)
        goto done;

    switch (chan->mode) {
    case L2CAP_MODE_STREAMING:
    case L2CAP_MODE_ERTM:
        if (!test_bit(CONF_STATE2_DEVICE, &chan->conf_state)) {
            chan->mode = l2cap_select_mode(rfc.mode,
                    chan->conn->feat_mask);
            break;
        }

        if (remote_efs) {
            if (__l2cap_efs_supported(chan))
                set_bit(FLAG_EFS_ENABLE, &chan->flags);
            else
                return -ECONNREFUSED;
        }

        if (chan->mode != rfc.mode)
            return -ECONNREFUSED;

        break;
    }

done:
    if (chan->mode != rfc.mode) {
        result = L2CAP_CONF_UNACCEPT;
        rfc.mode = chan->mode;

        if (chan->num_conf_rsp == 1)
            return -ECONNREFUSED;

        l2cap_add_conf_opt(&ptr, L2CAP_CONF_RFC,
                    sizeof(rfc), (unsigned long) &rfc);
    }

    if (result == L2CAP_CONF_SUCCESS) {
        /* Configure output options and let the other side know
         * which ones we don't like. */

        if (mtu < L2CAP_DEFAULT_MIN_MTU)
            result = L2CAP_CONF_UNACCEPT;
        else {
            chan->omtu = mtu;
            set_bit(CONF_MTU_DONE, &chan->conf_state);
        }
        l2cap_add_conf_opt(&ptr, L2CAP_CONF_MTU, 2, chan->omtu);

        if (remote_efs) {
            if (chan->local_stype != L2CAP_SERV_NOTRAFIC &&
                    efs.stype != L2CAP_SERV_NOTRAFIC &&
                    efs.stype != chan->local_stype) {

                result = L2CAP_CONF_UNACCEPT;

                if (chan->num_conf_req >= 1)
                    return -ECONNREFUSED;

                l2cap_add_conf_opt(&ptr, L2CAP_CONF_EFS,
                            sizeof(efs),
                            (unsigned long) &efs);
            } else {
                /* Send PENDING Conf Rsp */
                result = L2CAP_CONF_PENDING;
                set_bit(CONF_LOC_CONF_PEND, &chan->conf_state);
            }
        }

        switch (rfc.mode) {
        case L2CAP_MODE_BASIC:
            chan->fcs = L2CAP_FCS_NONE;
            set_bit(CONF_MODE_DONE, &chan->conf_state);
            break;

        case L2CAP_MODE_ERTM:
            if (!test_bit(CONF_EWS_RECV, &chan->conf_state))
                chan->remote_tx_win = rfc.txwin_size;
            else
                rfc.txwin_size = L2CAP_DEFAULT_TX_WINDOW;

            chan->remote_max_tx = rfc.max_transmit;

            size = min_t(u16, le16_to_cpu(rfc.max_pdu_size),
                        chan->conn->mtu -
                        L2CAP_EXT_HDR_SIZE -
                        L2CAP_SDULEN_SIZE -
                        L2CAP_FCS_SIZE);
            rfc.max_pdu_size = cpu_to_le16(size);
            chan->remote_mps = size;

            rfc.retrans_timeout =
                __constant_cpu_to_le16(L2CAP_DEFAULT_RETRANS_TO);
            rfc.monitor_timeout =
                __constant_cpu_to_le16(L2CAP_DEFAULT_MONITOR_TO);

            set_bit(CONF_MODE_DONE, &chan->conf_state);

            l2cap_add_conf_opt(&ptr, L2CAP_CONF_RFC,
                    sizeof(rfc), (unsigned long) &rfc);

            if (test_bit(FLAG_EFS_ENABLE, &chan->flags)) {
                chan->remote_id = efs.id;
                chan->remote_stype = efs.stype;
                chan->remote_msdu = le16_to_cpu(efs.msdu);
                chan->remote_flush_to =
                        le32_to_cpu(efs.flush_to);
                chan->remote_acc_lat =
                        le32_to_cpu(efs.acc_lat);
                chan->remote_sdu_itime =
                    le32_to_cpu(efs.sdu_itime);
                l2cap_add_conf_opt(&ptr, L2CAP_CONF_EFS,
                    sizeof(efs), (unsigned long) &efs);
            }
            break;

        case L2CAP_MODE_STREAMING:
            size = min_t(u16, le16_to_cpu(rfc.max_pdu_size),
                        chan->conn->mtu -
                        L2CAP_EXT_HDR_SIZE -
                        L2CAP_SDULEN_SIZE -
                        L2CAP_FCS_SIZE);
            rfc.max_pdu_size = cpu_to_le16(size);
            chan->remote_mps = size;

            set_bit(CONF_MODE_DONE, &chan->conf_state);

            l2cap_add_conf_opt(&ptr, L2CAP_CONF_RFC,
                    sizeof(rfc), (unsigned long) &rfc);

            break;

        default:
            result = L2CAP_CONF_UNACCEPT;

            memset(&rfc, 0, sizeof(rfc));
            rfc.mode = chan->mode;
        }

        if (result == L2CAP_CONF_SUCCESS)
            set_bit(CONF_OUTPUT_DONE, &chan->conf_state);
    }
    rsp->scid   = cpu_to_le16(chan->dcid);
    rsp->result = cpu_to_le16(result);
    rsp->flags  = __constant_cpu_to_le16(0);

    return ptr - data;
}

static int l2cap_parse_conf_rsp(struct l2cap_chan *chan, void *rsp, int len, void *data, u16 *result)
{
    struct l2cap_conf_req *req = data;
    void *ptr = req->data;
    int type, olen;
    unsigned long val;
    struct l2cap_conf_rfc rfc = { .mode = L2CAP_MODE_BASIC };
    struct l2cap_conf_efs efs;

    BT_DBG("chan %p, rsp %p, len %d, req %p", chan, rsp, len, data);

    while (len >= L2CAP_CONF_OPT_SIZE) {
        len -= l2cap_get_conf_opt(&rsp, &type, &olen, &val);

        switch (type) {
        case L2CAP_CONF_MTU:
            if (val < L2CAP_DEFAULT_MIN_MTU) {
                *result = L2CAP_CONF_UNACCEPT;
                chan->imtu = L2CAP_DEFAULT_MIN_MTU;
            } else
                chan->imtu = val;
            l2cap_add_conf_opt(&ptr, L2CAP_CONF_MTU, 2, chan->imtu);
            break;

        case L2CAP_CONF_FLUSH_TO:
            chan->flush_to = val;
            l2cap_add_conf_opt(&ptr, L2CAP_CONF_FLUSH_TO,
                            2, chan->flush_to);
            break;

        case L2CAP_CONF_RFC:
            if (olen == sizeof(rfc))
                memcpy(&rfc, (void *)val, olen);

            if (test_bit(CONF_STATE2_DEVICE, &chan->conf_state) &&
                            rfc.mode != chan->mode)
                return -ECONNREFUSED;

            chan->fcs = 0;

            l2cap_add_conf_opt(&ptr, L2CAP_CONF_RFC,
                    sizeof(rfc), (unsigned long) &rfc);
            break;

        case L2CAP_CONF_EWS:
            chan->ack_win = min_t(u16, val, chan->ack_win);
            l2cap_add_conf_opt(&ptr, L2CAP_CONF_EWS, 2,
                       chan->tx_win);
            break;

        case L2CAP_CONF_EFS:
            if (olen == sizeof(efs))
                memcpy(&efs, (void *)val, olen);

            if (chan->local_stype != L2CAP_SERV_NOTRAFIC &&
                    efs.stype != L2CAP_SERV_NOTRAFIC &&
                    efs.stype != chan->local_stype)
                return -ECONNREFUSED;

            l2cap_add_conf_opt(&ptr, L2CAP_CONF_EFS,
                    sizeof(efs), (unsigned long) &efs);
            break;
        }
    }

    if (chan->mode == L2CAP_MODE_BASIC && chan->mode != rfc.mode)
        return -ECONNREFUSED;

    chan->mode = rfc.mode;

    if (*result == L2CAP_CONF_SUCCESS || *result == L2CAP_CONF_PENDING) {
        switch (rfc.mode) {
        case L2CAP_MODE_ERTM:
            chan->retrans_timeout = le16_to_cpu(rfc.retrans_timeout);
            chan->monitor_timeout = le16_to_cpu(rfc.monitor_timeout);
            chan->mps    = le16_to_cpu(rfc.max_pdu_size);
            if (!test_bit(FLAG_EXT_CTRL, &chan->flags))
                chan->ack_win = min_t(u16, chan->ack_win,
                              rfc.txwin_size);

            if (test_bit(FLAG_EFS_ENABLE, &chan->flags)) {
                chan->local_msdu = le16_to_cpu(efs.msdu);
                chan->local_sdu_itime =
                        le32_to_cpu(efs.sdu_itime);
                chan->local_acc_lat = le32_to_cpu(efs.acc_lat);
                chan->local_flush_to =
                        le32_to_cpu(efs.flush_to);
            }
            break;

        case L2CAP_MODE_STREAMING:
            chan->mps    = le16_to_cpu(rfc.max_pdu_size);
        }
    }

    req->dcid   = cpu_to_le16(chan->dcid);
    req->flags  = __constant_cpu_to_le16(0);

    return ptr - data;
}

static int l2cap_build_conf_rsp(struct l2cap_chan *chan, void *data, u16 result, u16 flags)
{
    struct l2cap_conf_rsp *rsp = data;
    void *ptr = rsp->data;

    BT_DBG("chan %p", chan);

    rsp->scid   = cpu_to_le16(chan->dcid);
    rsp->result = cpu_to_le16(result);
    rsp->flags  = cpu_to_le16(flags);

    return ptr - data;
}

void __l2cap_connect_rsp_defer(struct l2cap_chan *chan)
{
    struct l2cap_conn_rsp rsp;
    struct l2cap_conn *conn = chan->conn;
    u8 buf[128];

    rsp.scid   = cpu_to_le16(chan->dcid);
    rsp.dcid   = cpu_to_le16(chan->scid);
    rsp.result = __constant_cpu_to_le16(L2CAP_CR_SUCCESS);
    rsp.status = __constant_cpu_to_le16(L2CAP_CS_NO_INFO);
    l2cap_send_cmd(conn, chan->ident,
                L2CAP_CONN_RSP, sizeof(rsp), &rsp);

    if (test_and_set_bit(CONF_REQ_SENT, &chan->conf_state))
        return;

    l2cap_send_cmd(conn, l2cap_get_ident(conn), L2CAP_CONF_REQ,
            l2cap_build_conf_req(chan, buf), buf);
    chan->num_conf_req++;
}

static void l2cap_conf_rfc_get(struct l2cap_chan *chan, void *rsp, int len)
{
    int type, olen;
    unsigned long val;
    /* Use sane default values in case a misbehaving remote device
     * did not send an RFC or extended window size option.
     */
    u16 txwin_ext = chan->ack_win;
    struct l2cap_conf_rfc rfc = {
        .mode = chan->mode,
        .retrans_timeout = __constant_cpu_to_le16(L2CAP_DEFAULT_RETRANS_TO),
        .monitor_timeout = __constant_cpu_to_le16(L2CAP_DEFAULT_MONITOR_TO),
        .max_pdu_size = cpu_to_le16(chan->imtu),
        .txwin_size = min_t(u16, chan->ack_win, L2CAP_DEFAULT_TX_WINDOW),
    };

    BT_DBG("chan %p, rsp %p, len %d", chan, rsp, len);

    if ((chan->mode != L2CAP_MODE_ERTM) && (chan->mode != L2CAP_MODE_STREAMING))
        return;

    while (len >= L2CAP_CONF_OPT_SIZE) {
        len -= l2cap_get_conf_opt(&rsp, &type, &olen, &val);

        switch (type) {
        case L2CAP_CONF_RFC:
            if (olen == sizeof(rfc))
                memcpy(&rfc, (void *)val, olen);
            break;
        case L2CAP_CONF_EWS:
            txwin_ext = val;
            break;
        }
    }

    switch (rfc.mode) {
    case L2CAP_MODE_ERTM:
        chan->retrans_timeout = le16_to_cpu(rfc.retrans_timeout);
        chan->monitor_timeout = le16_to_cpu(rfc.monitor_timeout);
        chan->mps = le16_to_cpu(rfc.max_pdu_size);
        if (test_bit(FLAG_EXT_CTRL, &chan->flags))
            chan->ack_win = min_t(u16, chan->ack_win, txwin_ext);
        else
            chan->ack_win = min_t(u16, chan->ack_win,
                          rfc.txwin_size);
        break;
    case L2CAP_MODE_STREAMING:
        chan->mps    = le16_to_cpu(rfc.max_pdu_size);
    }
}

static inline int l2cap_command_rej(struct l2cap_conn *conn, struct l2cap_cmd_hdr *cmd, u8 *data)
{
    struct l2cap_cmd_rej_unk *rej = (struct l2cap_cmd_rej_unk *) data;

    if (rej->reason != L2CAP_REJ_NOT_UNDERSTOOD)
        return 0;

    if ((conn->info_state & L2CAP_INFO_FEAT_MASK_REQ_SENT) &&
                    cmd->ident == conn->info_ident) {
        cancel_delayed_work(&conn->info_timer);

        conn->info_state |= L2CAP_INFO_FEAT_MASK_REQ_DONE;
        conn->info_ident = 0;

        l2cap_conn_start(conn);
    }

    return 0;
}

static inline int l2cap_connect_req(struct l2cap_conn *conn, struct l2cap_cmd_hdr *cmd, u8 *data)
{
    struct l2cap_conn_req *req = (struct l2cap_conn_req *) data;
    struct l2cap_conn_rsp rsp;
    struct l2cap_chan *chan = NULL, *pchan;
    struct sock *parent, *sk = NULL;
    int result, status = L2CAP_CS_NO_INFO;

    u16 dcid = 0, scid = __le16_to_cpu(req->scid);
    __le16 psm = req->psm;

    BT_DBG("psm 0x%2.2x scid 0x%4.4x", __le16_to_cpu(psm), scid);

    /* Check if we have socket listening on psm */
    pchan = l2cap_global_chan_by_psm(BT_LISTEN, psm, conn->src, conn->dst);
    if (!pchan) {
        result = L2CAP_CR_BAD_PSM;
        goto sendresp;
    }

    parent = pchan->sk;

    mutex_lock(&conn->chan_lock);
    lock_sock(parent);

    /* Check if the ACL is secure enough (if not SDP) */
    if (psm != __constant_cpu_to_le16(L2CAP_PSM_SDP) &&
                !hci_conn_check_link_mode(conn->hcon)) {
        conn->disc_reason = HCI_ERROR_AUTH_FAILURE;
        result = L2CAP_CR_SEC_BLOCK;
        goto response;
    }

    result = L2CAP_CR_NO_MEM;

    /* Check if we already have channel with that dcid */
    if (__l2cap_get_chan_by_dcid(conn, scid))
        goto response;

    chan = pchan->ops->new_connection(pchan);
    if (!chan)
        goto response;

    sk = chan->sk;

    hci_conn_hold(conn->hcon);

    bacpy(&bt_sk(sk)->src, conn->src);
    bacpy(&bt_sk(sk)->dst, conn->dst);
    chan->psm  = psm;
    chan->dcid = scid;

    bt_accept_enqueue(parent, sk);

    __l2cap_chan_add(conn, chan);

    dcid = chan->scid;

    __set_chan_timer(chan, sk->sk_sndtimeo);

    chan->ident = cmd->ident;

    if (conn->info_state & L2CAP_INFO_FEAT_MASK_REQ_DONE) {
        if (l2cap_chan_check_security(chan)) {
            if (test_bit(BT_SK_DEFER_SETUP, &bt_sk(sk)->flags)) {
                __l2cap_state_change(chan, BT_CONNECT2);
                result = L2CAP_CR_PEND;
                status = L2CAP_CS_AUTHOR_PEND;
                parent->sk_data_ready(parent, 0);
            } else {
                __l2cap_state_change(chan, BT_CONFIG);
                result = L2CAP_CR_SUCCESS;
                status = L2CAP_CS_NO_INFO;
            }
        } else {
            __l2cap_state_change(chan, BT_CONNECT2);
            result = L2CAP_CR_PEND;
            status = L2CAP_CS_AUTHEN_PEND;
        }
    } else {
        __l2cap_state_change(chan, BT_CONNECT2);
        result = L2CAP_CR_PEND;
        status = L2CAP_CS_NO_INFO;
    }

response:
    release_sock(parent);
    mutex_unlock(&conn->chan_lock);

sendresp:
    rsp.scid   = cpu_to_le16(scid);
    rsp.dcid   = cpu_to_le16(dcid);
    rsp.result = cpu_to_le16(result);
    rsp.status = cpu_to_le16(status);
    l2cap_send_cmd(conn, cmd->ident, L2CAP_CONN_RSP, sizeof(rsp), &rsp);

    if (result == L2CAP_CR_PEND && status == L2CAP_CS_NO_INFO) {
        struct l2cap_info_req info;
        info.type = __constant_cpu_to_le16(L2CAP_IT_FEAT_MASK);

        conn->info_state |= L2CAP_INFO_FEAT_MASK_REQ_SENT;
        conn->info_ident = l2cap_get_ident(conn);

        schedule_delayed_work(&conn->info_timer, L2CAP_INFO_TIMEOUT);

        l2cap_send_cmd(conn, conn->info_ident,
                    L2CAP_INFO_REQ, sizeof(info), &info);
    }

    if (chan && !test_bit(CONF_REQ_SENT, &chan->conf_state) &&
                result == L2CAP_CR_SUCCESS) {
        u8 buf[128];
        set_bit(CONF_REQ_SENT, &chan->conf_state);
        l2cap_send_cmd(conn, l2cap_get_ident(conn), L2CAP_CONF_REQ,
                    l2cap_build_conf_req(chan, buf), buf);
        chan->num_conf_req++;
    }

    return 0;
}

static inline int l2cap_connect_rsp(struct l2cap_conn *conn, struct l2cap_cmd_hdr *cmd, u8 *data)
{
    struct l2cap_conn_rsp *rsp = (struct l2cap_conn_rsp *) data;
    u16 scid, dcid, result, status;
    struct l2cap_chan *chan;
    u8 req[128];
    int err;

    scid   = __le16_to_cpu(rsp->scid);
    dcid   = __le16_to_cpu(rsp->dcid);
    result = __le16_to_cpu(rsp->result);
    status = __le16_to_cpu(rsp->status);

    BT_DBG("dcid 0x%4.4x scid 0x%4.4x result 0x%2.2x status 0x%2.2x",
                        dcid, scid, result, status);

    mutex_lock(&conn->chan_lock);

    if (scid) {
        chan = __l2cap_get_chan_by_scid(conn, scid);
        if (!chan) {
            err = -EFAULT;
            goto unlock;
        }
    } else {
        chan = __l2cap_get_chan_by_ident(conn, cmd->ident);
        if (!chan) {
            err = -EFAULT;
            goto unlock;
        }
    }

    err = 0;

    l2cap_chan_lock(chan);

    switch (result) {
    case L2CAP_CR_SUCCESS:
        l2cap_state_change(chan, BT_CONFIG);
        chan->ident = 0;
        chan->dcid = dcid;
        clear_bit(CONF_CONNECT_PEND, &chan->conf_state);

        if (test_and_set_bit(CONF_REQ_SENT, &chan->conf_state))
            break;

        l2cap_send_cmd(conn, l2cap_get_ident(conn), L2CAP_CONF_REQ,
                    l2cap_build_conf_req(chan, req), req);
        chan->num_conf_req++;
        break;

    case L2CAP_CR_PEND:
        set_bit(CONF_CONNECT_PEND, &chan->conf_state);
        break;

    default:
        l2cap_chan_del(chan, ECONNREFUSED);
        break;
    }

    l2cap_chan_unlock(chan);

unlock:
    mutex_unlock(&conn->chan_lock);

    return err;
}

static inline void set_default_fcs(struct l2cap_chan *chan)
{
    /* FCS is enabled only in ERTM or streaming mode, if one or both
     * sides request it.
     */
    if (chan->mode != L2CAP_MODE_ERTM && chan->mode != L2CAP_MODE_STREAMING)
        chan->fcs = L2CAP_FCS_NONE;
    else if (!test_bit(CONF_NO_FCS_RECV, &chan->conf_state))
        chan->fcs = L2CAP_FCS_CRC16;
}

static inline int l2cap_config_req(struct l2cap_conn *conn, struct l2cap_cmd_hdr *cmd, u16 cmd_len, u8 *data)
{
    struct l2cap_conf_req *req = (struct l2cap_conf_req *) data;
    u16 dcid, flags;
    u8 rsp[64];
    struct l2cap_chan *chan;
    int len, err = 0;

    dcid  = __le16_to_cpu(req->dcid);
    flags = __le16_to_cpu(req->flags);

    BT_DBG("dcid 0x%4.4x flags 0x%2.2x", dcid, flags);

    chan = l2cap_get_chan_by_scid(conn, dcid);
    if (!chan)
        return -ENOENT;

    if (chan->state != BT_CONFIG && chan->state != BT_CONNECT2) {
        struct l2cap_cmd_rej_cid rej;

        rej.reason = __constant_cpu_to_le16(L2CAP_REJ_INVALID_CID);
        rej.scid = cpu_to_le16(chan->scid);
        rej.dcid = cpu_to_le16(chan->dcid);

        l2cap_send_cmd(conn, cmd->ident, L2CAP_COMMAND_REJ,
                sizeof(rej), &rej);
        goto unlock;
    }

    /* Reject if config buffer is too small. */
    len = cmd_len - sizeof(*req);
    if (len < 0 || chan->conf_len + len > sizeof(chan->conf_req)) {
        l2cap_send_cmd(conn, cmd->ident, L2CAP_CONF_RSP,
                l2cap_build_conf_rsp(chan, rsp,
                    L2CAP_CONF_REJECT, flags), rsp);
        goto unlock;
    }

    /* Store config. */
    memcpy(chan->conf_req + chan->conf_len, req->data, len);
    chan->conf_len += len;

    if (flags & L2CAP_CONF_FLAG_CONTINUATION) {
        /* Incomplete config. Send empty response. */
        l2cap_send_cmd(conn, cmd->ident, L2CAP_CONF_RSP,
                l2cap_build_conf_rsp(chan, rsp,
                    L2CAP_CONF_SUCCESS, flags), rsp);
        goto unlock;
    }

    /* Complete config. */
    len = l2cap_parse_conf_req(chan, rsp);
    if (len < 0) {
        l2cap_send_disconn_req(conn, chan, ECONNRESET);
        goto unlock;
    }

    l2cap_send_cmd(conn, cmd->ident, L2CAP_CONF_RSP, len, rsp);
    chan->num_conf_rsp++;

    /* Reset config buffer. */
    chan->conf_len = 0;

    if (!test_bit(CONF_OUTPUT_DONE, &chan->conf_state))
        goto unlock;

    if (test_bit(CONF_INPUT_DONE, &chan->conf_state)) {
        set_default_fcs(chan);

        if (chan->mode == L2CAP_MODE_ERTM ||
            chan->mode == L2CAP_MODE_STREAMING)
            err = l2cap_ertm_init(chan);

        if (err < 0)
            l2cap_send_disconn_req(chan->conn, chan, -err);
        else
            l2cap_chan_ready(chan);

        goto unlock;
    }

    if (!test_and_set_bit(CONF_REQ_SENT, &chan->conf_state)) {
        u8 buf[64];
        l2cap_send_cmd(conn, l2cap_get_ident(conn), L2CAP_CONF_REQ,
                    l2cap_build_conf_req(chan, buf), buf);
        chan->num_conf_req++;
    }

    /* Got Conf Rsp PENDING from remote side and asume we sent
       Conf Rsp PENDING in the code above */
    if (test_bit(CONF_REM_CONF_PEND, &chan->conf_state) &&
            test_bit(CONF_LOC_CONF_PEND, &chan->conf_state)) {

        /* check compatibility */

        clear_bit(CONF_LOC_CONF_PEND, &chan->conf_state);
        set_bit(CONF_OUTPUT_DONE, &chan->conf_state);

        l2cap_send_cmd(conn, cmd->ident, L2CAP_CONF_RSP,
                    l2cap_build_conf_rsp(chan, rsp,
                    L2CAP_CONF_SUCCESS, flags), rsp);
    }

unlock:
    l2cap_chan_unlock(chan);
    return err;
}

static inline int l2cap_config_rsp(struct l2cap_conn *conn, struct l2cap_cmd_hdr *cmd, u8 *data)
{
    struct l2cap_conf_rsp *rsp = (struct l2cap_conf_rsp *)data;
    u16 scid, flags, result;
    struct l2cap_chan *chan;
    int len = le16_to_cpu(cmd->len) - sizeof(*rsp);
    int err = 0;

    scid   = __le16_to_cpu(rsp->scid);
    flags  = __le16_to_cpu(rsp->flags);
    result = __le16_to_cpu(rsp->result);

    BT_DBG("scid 0x%4.4x flags 0x%2.2x result 0x%2.2x len %d", scid, flags,
           result, len);

    chan = l2cap_get_chan_by_scid(conn, scid);
    if (!chan)
        return 0;

    switch (result) {
    case L2CAP_CONF_SUCCESS:
        l2cap_conf_rfc_get(chan, rsp->data, len);
        clear_bit(CONF_REM_CONF_PEND, &chan->conf_state);
        break;

    case L2CAP_CONF_PENDING:
        set_bit(CONF_REM_CONF_PEND, &chan->conf_state);

        if (test_bit(CONF_LOC_CONF_PEND, &chan->conf_state)) {
            char buf[64];

            len = l2cap_parse_conf_rsp(chan, rsp->data, len,
                                buf, &result);
            if (len < 0) {
                l2cap_send_disconn_req(conn, chan, ECONNRESET);
                goto done;
            }

            /* check compatibility */

            clear_bit(CONF_LOC_CONF_PEND, &chan->conf_state);
            set_bit(CONF_OUTPUT_DONE, &chan->conf_state);

            l2cap_send_cmd(conn, cmd->ident, L2CAP_CONF_RSP,
                        l2cap_build_conf_rsp(chan, buf,
                        L2CAP_CONF_SUCCESS, 0x0000), buf);
        }
        goto done;

    case L2CAP_CONF_UNACCEPT:
        if (chan->num_conf_rsp <= L2CAP_CONF_MAX_CONF_RSP) {
            char req[64];

            if (len > sizeof(req) - sizeof(struct l2cap_conf_req)) {
                l2cap_send_disconn_req(conn, chan, ECONNRESET);
                goto done;
            }

            /* throw out any old stored conf requests */
            result = L2CAP_CONF_SUCCESS;
            len = l2cap_parse_conf_rsp(chan, rsp->data, len,
                                req, &result);
            if (len < 0) {
                l2cap_send_disconn_req(conn, chan, ECONNRESET);
                goto done;
            }

            l2cap_send_cmd(conn, l2cap_get_ident(conn),
                        L2CAP_CONF_REQ, len, req);
            chan->num_conf_req++;
            if (result != L2CAP_CONF_SUCCESS)
                goto done;
            break;
        }

    default:
        l2cap_chan_set_err(chan, ECONNRESET);

        __set_chan_timer(chan, L2CAP_DISC_REJ_TIMEOUT);
        l2cap_send_disconn_req(conn, chan, ECONNRESET);
        goto done;
    }

    if (flags & L2CAP_CONF_FLAG_CONTINUATION)
        goto done;

    set_bit(CONF_INPUT_DONE, &chan->conf_state);

    if (test_bit(CONF_OUTPUT_DONE, &chan->conf_state)) {
        set_default_fcs(chan);

        if (chan->mode == L2CAP_MODE_ERTM ||
            chan->mode == L2CAP_MODE_STREAMING)
            err = l2cap_ertm_init(chan);

        if (err < 0)
            l2cap_send_disconn_req(chan->conn, chan, -err);
        else
            l2cap_chan_ready(chan);
    }

done:
    l2cap_chan_unlock(chan);
    return err;
}

static inline int l2cap_disconnect_req(struct l2cap_conn *conn, struct l2cap_cmd_hdr *cmd, u8 *data)
{
    struct l2cap_disconn_req *req = (struct l2cap_disconn_req *) data;
    struct l2cap_disconn_rsp rsp;
    u16 dcid, scid;
    struct l2cap_chan *chan;
    struct sock *sk;

    scid = __le16_to_cpu(req->scid);
    dcid = __le16_to_cpu(req->dcid);

    BT_DBG("scid 0x%4.4x dcid 0x%4.4x", scid, dcid);

    mutex_lock(&conn->chan_lock);

    chan = __l2cap_get_chan_by_scid(conn, dcid);
    if (!chan) {
        mutex_unlock(&conn->chan_lock);
        return 0;
    }

    l2cap_chan_lock(chan);

    sk = chan->sk;

    rsp.dcid = cpu_to_le16(chan->scid);
    rsp.scid = cpu_to_le16(chan->dcid);
    l2cap_send_cmd(conn, cmd->ident, L2CAP_DISCONN_RSP, sizeof(rsp), &rsp);

    lock_sock(sk);
    sk->sk_shutdown = SHUTDOWN_MASK;
    release_sock(sk);

    l2cap_chan_hold(chan);
    l2cap_chan_del(chan, ECONNRESET);

    l2cap_chan_unlock(chan);

    chan->ops->close(chan);
    l2cap_chan_put(chan);

    mutex_unlock(&conn->chan_lock);

    return 0;
}

static inline int l2cap_disconnect_rsp(struct l2cap_conn *conn, struct l2cap_cmd_hdr *cmd, u8 *data)
{
    struct l2cap_disconn_rsp *rsp = (struct l2cap_disconn_rsp *) data;
    u16 dcid, scid;
    struct l2cap_chan *chan;

    scid = __le16_to_cpu(rsp->scid);
    dcid = __le16_to_cpu(rsp->dcid);

    BT_DBG("dcid 0x%4.4x scid 0x%4.4x", dcid, scid);

    mutex_lock(&conn->chan_lock);

    chan = __l2cap_get_chan_by_scid(conn, scid);
    if (!chan) {
        mutex_unlock(&conn->chan_lock);
        return 0;
    }

    l2cap_chan_lock(chan);

    l2cap_chan_hold(chan);
    l2cap_chan_del(chan, 0);

    l2cap_chan_unlock(chan);

    chan->ops->close(chan);
    l2cap_chan_put(chan);

    mutex_unlock(&conn->chan_lock);

    return 0;
}

static inline int l2cap_information_req(struct l2cap_conn *conn, struct l2cap_cmd_hdr *cmd, u8 *data)
{
    struct l2cap_info_req *req = (struct l2cap_info_req *) data;
    u16 type;

    type = __le16_to_cpu(req->type);

    BT_DBG("type 0x%4.4x", type);

    if (type == L2CAP_IT_FEAT_MASK) {
        u8 buf[8];
        u32 feat_mask = l2cap_feat_mask;
        struct l2cap_info_rsp *rsp = (struct l2cap_info_rsp *) buf;
        rsp->type   = __constant_cpu_to_le16(L2CAP_IT_FEAT_MASK);
        rsp->result = __constant_cpu_to_le16(L2CAP_IR_SUCCESS);
        if (!disable_ertm)
            feat_mask |= L2CAP_FEAT_ERTM | L2CAP_FEAT_STREAMING
                             | L2CAP_FEAT_FCS;
        if (enable_hs)
            feat_mask |= L2CAP_FEAT_EXT_FLOW
                        | L2CAP_FEAT_EXT_WINDOW;

        put_unaligned_le32(feat_mask, rsp->data);
        l2cap_send_cmd(conn, cmd->ident,
                    L2CAP_INFO_RSP, sizeof(buf), buf);
    } else if (type == L2CAP_IT_FIXED_CHAN) {
        u8 buf[12];
        struct l2cap_info_rsp *rsp = (struct l2cap_info_rsp *) buf;

        if (enable_hs)
            l2cap_fixed_chan[0] |= L2CAP_FC_A2MP;
        else
            l2cap_fixed_chan[0] &= ~L2CAP_FC_A2MP;

        rsp->type   = __constant_cpu_to_le16(L2CAP_IT_FIXED_CHAN);
        rsp->result = __constant_cpu_to_le16(L2CAP_IR_SUCCESS);
        memcpy(rsp->data, l2cap_fixed_chan, sizeof(l2cap_fixed_chan));
        l2cap_send_cmd(conn, cmd->ident,
                    L2CAP_INFO_RSP, sizeof(buf), buf);
    } else {
        struct l2cap_info_rsp rsp;
        rsp.type   = cpu_to_le16(type);
        rsp.result = __constant_cpu_to_le16(L2CAP_IR_NOTSUPP);
        l2cap_send_cmd(conn, cmd->ident,
                    L2CAP_INFO_RSP, sizeof(rsp), &rsp);
    }

    return 0;
}

static inline int l2cap_information_rsp(struct l2cap_conn *conn, struct l2cap_cmd_hdr *cmd, u8 *data)
{
    struct l2cap_info_rsp *rsp = (struct l2cap_info_rsp *) data;
    u16 type, result;

    type   = __le16_to_cpu(rsp->type);
    result = __le16_to_cpu(rsp->result);

    BT_DBG("type 0x%4.4x result 0x%2.2x", type, result);

    /* L2CAP Info req/rsp are unbound to channels, add extra checks */
    if (cmd->ident != conn->info_ident ||
            conn->info_state & L2CAP_INFO_FEAT_MASK_REQ_DONE)
        return 0;

    cancel_delayed_work(&conn->info_timer);

    if (result != L2CAP_IR_SUCCESS) {
        conn->info_state |= L2CAP_INFO_FEAT_MASK_REQ_DONE;
        conn->info_ident = 0;

        l2cap_conn_start(conn);

        return 0;
    }

    switch (type) {
    case L2CAP_IT_FEAT_MASK:
        conn->feat_mask = get_unaligned_le32(rsp->data);

        if (conn->feat_mask & L2CAP_FEAT_FIXED_CHAN) {
            struct l2cap_info_req req;
            req.type = __constant_cpu_to_le16(L2CAP_IT_FIXED_CHAN);

            conn->info_ident = l2cap_get_ident(conn);

            l2cap_send_cmd(conn, conn->info_ident,
                    L2CAP_INFO_REQ, sizeof(req), &req);
        } else {
            conn->info_state |= L2CAP_INFO_FEAT_MASK_REQ_DONE;
            conn->info_ident = 0;

            l2cap_conn_start(conn);
        }
        break;

    case L2CAP_IT_FIXED_CHAN:
        conn->fixed_chan_mask = rsp->data[0];
        conn->info_state |= L2CAP_INFO_FEAT_MASK_REQ_DONE;
        conn->info_ident = 0;

        l2cap_conn_start(conn);
        break;
    }

    return 0;
}

static inline int l2cap_create_channel_req(struct l2cap_conn *conn,
                    struct l2cap_cmd_hdr *cmd, u16 cmd_len,
                    void *data)
{
    struct l2cap_create_chan_req *req = data;
    struct l2cap_create_chan_rsp rsp;
    u16 psm, scid;

    if (cmd_len != sizeof(*req))
        return -EPROTO;

    if (!enable_hs)
        return -EINVAL;

    psm = le16_to_cpu(req->psm);
    scid = le16_to_cpu(req->scid);

    BT_DBG("psm 0x%2.2x, scid 0x%4.4x, amp_id %d", psm, scid, req->amp_id);

    /* Placeholder: Always reject */
    rsp.dcid = 0;
    rsp.scid = cpu_to_le16(scid);
    rsp.result = __constant_cpu_to_le16(L2CAP_CR_NO_MEM);
    rsp.status = __constant_cpu_to_le16(L2CAP_CS_NO_INFO);

    l2cap_send_cmd(conn, cmd->ident, L2CAP_CREATE_CHAN_RSP,
               sizeof(rsp), &rsp);

    return 0;
}

static inline int l2cap_create_channel_rsp(struct l2cap_conn *conn,
                    struct l2cap_cmd_hdr *cmd, void *data)
{
    BT_DBG("conn %p", conn);

    return l2cap_connect_rsp(conn, cmd, data);
}

static void l2cap_send_move_chan_rsp(struct l2cap_conn *conn, u8 ident,
                     u16 icid, u16 result)
{
    struct l2cap_move_chan_rsp rsp;

    BT_DBG("icid 0x%4.4x, result 0x%4.4x", icid, result);

    rsp.icid = cpu_to_le16(icid);
    rsp.result = cpu_to_le16(result);

    l2cap_send_cmd(conn, ident, L2CAP_MOVE_CHAN_RSP, sizeof(rsp), &rsp);
}

static void l2cap_send_move_chan_cfm(struct l2cap_conn *conn,
                     struct l2cap_chan *chan,
                     u16 icid, u16 result)
{
    struct l2cap_move_chan_cfm cfm;
    u8 ident;

    BT_DBG("icid 0x%4.4x, result 0x%4.4x", icid, result);

    ident = l2cap_get_ident(conn);
    if (chan)
        chan->ident = ident;

    cfm.icid = cpu_to_le16(icid);
    cfm.result = cpu_to_le16(result);

    l2cap_send_cmd(conn, ident, L2CAP_MOVE_CHAN_CFM, sizeof(cfm), &cfm);
}

static void l2cap_send_move_chan_cfm_rsp(struct l2cap_conn *conn, u8 ident,
                     u16 icid)
{
    struct l2cap_move_chan_cfm_rsp rsp;

    BT_DBG("icid 0x%4.4x", icid);

    rsp.icid = cpu_to_le16(icid);
    l2cap_send_cmd(conn, ident, L2CAP_MOVE_CHAN_CFM_RSP, sizeof(rsp), &rsp);
}

static inline int l2cap_move_channel_req(struct l2cap_conn *conn,
                     struct l2cap_cmd_hdr *cmd,
                     u16 cmd_len, void *data)
{
    struct l2cap_move_chan_req *req = data;
    u16 icid = 0;
    u16 result = L2CAP_MR_NOT_ALLOWED;

    if (cmd_len != sizeof(*req))
        return -EPROTO;

    icid = le16_to_cpu(req->icid);

    BT_DBG("icid 0x%4.4x, dest_amp_id %d", icid, req->dest_amp_id);

    if (!enable_hs)
        return -EINVAL;

    /* Placeholder: Always refuse */
    l2cap_send_move_chan_rsp(conn, cmd->ident, icid, result);

    return 0;
}

static inline int l2cap_move_channel_rsp(struct l2cap_conn *conn,
                     struct l2cap_cmd_hdr *cmd,
                     u16 cmd_len, void *data)
{
    struct l2cap_move_chan_rsp *rsp = data;
    u16 icid, result;

    if (cmd_len != sizeof(*rsp))
        return -EPROTO;

    icid = le16_to_cpu(rsp->icid);
    result = le16_to_cpu(rsp->result);

    BT_DBG("icid 0x%4.4x, result 0x%4.4x", icid, result);

    /* Placeholder: Always unconfirmed */
    l2cap_send_move_chan_cfm(conn, NULL, icid, L2CAP_MC_UNCONFIRMED);

    return 0;
}

static inline int l2cap_move_channel_confirm(struct l2cap_conn *conn,
                         struct l2cap_cmd_hdr *cmd,
                         u16 cmd_len, void *data)
{
    struct l2cap_move_chan_cfm *cfm = data;
    u16 icid, result;

    if (cmd_len != sizeof(*cfm))
        return -EPROTO;

    icid = le16_to_cpu(cfm->icid);
    result = le16_to_cpu(cfm->result);

    BT_DBG("icid 0x%4.4x, result 0x%4.4x", icid, result);

    l2cap_send_move_chan_cfm_rsp(conn, cmd->ident, icid);

    return 0;
}

static inline int l2cap_move_channel_confirm_rsp(struct l2cap_conn *conn,
                         struct l2cap_cmd_hdr *cmd,
                         u16 cmd_len, void *data)
{
    struct l2cap_move_chan_cfm_rsp *rsp = data;
    u16 icid;

    if (cmd_len != sizeof(*rsp))
        return -EPROTO;

    icid = le16_to_cpu(rsp->icid);

    BT_DBG("icid 0x%4.4x", icid);

    return 0;
}

static inline int l2cap_check_conn_param(u16 min, u16 max, u16 latency,
                            u16 to_multiplier)
{
    u16 max_latency;

    if (min > max || min < 6 || max > 3200)
        return -EINVAL;

    if (to_multiplier < 10 || to_multiplier > 3200)
        return -EINVAL;

    if (max >= to_multiplier * 8)
        return -EINVAL;

    max_latency = (to_multiplier * 8 / max) - 1;
    if (latency > 499 || latency > max_latency)
        return -EINVAL;

    return 0;
}

static inline int l2cap_conn_param_update_req(struct l2cap_conn *conn,
                    struct l2cap_cmd_hdr *cmd, u8 *data)
{
    struct hci_conn *hcon = conn->hcon;
    struct l2cap_conn_param_update_req *req;
    struct l2cap_conn_param_update_rsp rsp;
    u16 min, max, latency, to_multiplier, cmd_len;
    int err;

    if (!(hcon->link_mode & HCI_LM_MASTER))
        return -EINVAL;

    cmd_len = __le16_to_cpu(cmd->len);
    if (cmd_len != sizeof(struct l2cap_conn_param_update_req))
        return -EPROTO;

    req = (struct l2cap_conn_param_update_req *) data;
    min     = __le16_to_cpu(req->min);
    max     = __le16_to_cpu(req->max);
    latency     = __le16_to_cpu(req->latency);
    to_multiplier   = __le16_to_cpu(req->to_multiplier);

    BT_DBG("min 0x%4.4x max 0x%4.4x latency: 0x%4.4x Timeout: 0x%4.4x",
                        min, max, latency, to_multiplier);

    memset(&rsp, 0, sizeof(rsp));

    err = l2cap_check_conn_param(min, max, latency, to_multiplier);
    if (err)
        rsp.result = __constant_cpu_to_le16(L2CAP_CONN_PARAM_REJECTED);
    else
        rsp.result = __constant_cpu_to_le16(L2CAP_CONN_PARAM_ACCEPTED);

    l2cap_send_cmd(conn, cmd->ident, L2CAP_CONN_PARAM_UPDATE_RSP,
                            sizeof(rsp), &rsp);

    if (!err)
        hci_le_conn_update(hcon, min, max, latency, to_multiplier);

    return 0;
}

static inline int l2cap_bredr_sig_cmd(struct l2cap_conn *conn,
            struct l2cap_cmd_hdr *cmd, u16 cmd_len, u8 *data)
{
    int err = 0;

    switch (cmd->code) {
    case L2CAP_COMMAND_REJ:
        l2cap_command_rej(conn, cmd, data);
        break;

    case L2CAP_CONN_REQ:
        err = l2cap_connect_req(conn, cmd, data);
        break;

    case L2CAP_CONN_RSP:
        err = l2cap_connect_rsp(conn, cmd, data);
        break;

    case L2CAP_CONF_REQ:
        err = l2cap_config_req(conn, cmd, cmd_len, data);
        break;

    case L2CAP_CONF_RSP:
        err = l2cap_config_rsp(conn, cmd, data);
        break;

    case L2CAP_DISCONN_REQ:
        err = l2cap_disconnect_req(conn, cmd, data);
        break;

    case L2CAP_DISCONN_RSP:
        err = l2cap_disconnect_rsp(conn, cmd, data);
        break;

    case L2CAP_ECHO_REQ:
        l2cap_send_cmd(conn, cmd->ident, L2CAP_ECHO_RSP, cmd_len, data);
        break;

    case L2CAP_ECHO_RSP:
        break;

    case L2CAP_INFO_REQ:
        err = l2cap_information_req(conn, cmd, data);
        break;

    case L2CAP_INFO_RSP:
        err = l2cap_information_rsp(conn, cmd, data);
        break;

    case L2CAP_CREATE_CHAN_REQ:
        err = l2cap_create_channel_req(conn, cmd, cmd_len, data);
        break;

    case L2CAP_CREATE_CHAN_RSP:
        err = l2cap_create_channel_rsp(conn, cmd, data);
        break;

    case L2CAP_MOVE_CHAN_REQ:
        err = l2cap_move_channel_req(conn, cmd, cmd_len, data);
        break;

    case L2CAP_MOVE_CHAN_RSP:
        err = l2cap_move_channel_rsp(conn, cmd, cmd_len, data);
        break;

    case L2CAP_MOVE_CHAN_CFM:
        err = l2cap_move_channel_confirm(conn, cmd, cmd_len, data);
        break;

    case L2CAP_MOVE_CHAN_CFM_RSP:
        err = l2cap_move_channel_confirm_rsp(conn, cmd, cmd_len, data);
        break;

    default:
        BT_ERR("Unknown BR/EDR signaling command 0x%2.2x", cmd->code);
        err = -EINVAL;
        break;
    }

    return err;
}

static inline int l2cap_le_sig_cmd(struct l2cap_conn *conn,
                    struct l2cap_cmd_hdr *cmd, u8 *data)
{
    switch (cmd->code) {
    case L2CAP_COMMAND_REJ:
        return 0;

    case L2CAP_CONN_PARAM_UPDATE_REQ:
        return l2cap_conn_param_update_req(conn, cmd, data);

    case L2CAP_CONN_PARAM_UPDATE_RSP:
        return 0;

    default:
        BT_ERR("Unknown LE signaling command 0x%2.2x", cmd->code);
        return -EINVAL;
    }
}

static inline void l2cap_sig_channel(struct l2cap_conn *conn,
                            struct sk_buff *skb)
{
    u8 *data = skb->data;
    int len = skb->len;
    struct l2cap_cmd_hdr cmd;
    int err;

    l2cap_raw_recv(conn, skb);

    while (len >= L2CAP_CMD_HDR_SIZE) {
        u16 cmd_len;
        memcpy(&cmd, data, L2CAP_CMD_HDR_SIZE);
        data += L2CAP_CMD_HDR_SIZE;
        len  -= L2CAP_CMD_HDR_SIZE;

        cmd_len = le16_to_cpu(cmd.len);

        BT_DBG("code 0x%2.2x len %d id 0x%2.2x", cmd.code, cmd_len, cmd.ident);

        if (cmd_len > len || !cmd.ident) {
            BT_DBG("corrupted command");
            break;
        }

        if (conn->hcon->type == LE_LINK)
            err = l2cap_le_sig_cmd(conn, &cmd, data);
        else
            err = l2cap_bredr_sig_cmd(conn, &cmd, cmd_len, data);

        if (err) {
            struct l2cap_cmd_rej_unk rej;

            BT_ERR("Wrong link type (%d)", err);

            /* FIXME: Map err to a valid reason */
            rej.reason = __constant_cpu_to_le16(L2CAP_REJ_NOT_UNDERSTOOD);
            l2cap_send_cmd(conn, cmd.ident, L2CAP_COMMAND_REJ, sizeof(rej), &rej);
        }

        data += cmd_len;
        len  -= cmd_len;
    }

    kfree_skb(skb);
}

static int l2cap_check_fcs(struct l2cap_chan *chan,  struct sk_buff *skb)
{
    u16 our_fcs, rcv_fcs;
    int hdr_size;

    if (test_bit(FLAG_EXT_CTRL, &chan->flags))
        hdr_size = L2CAP_EXT_HDR_SIZE;
    else
        hdr_size = L2CAP_ENH_HDR_SIZE;

    if (chan->fcs == L2CAP_FCS_CRC16) {
        skb_trim(skb, skb->len - L2CAP_FCS_SIZE);
        rcv_fcs = get_unaligned_le16(skb->data + skb->len);
        our_fcs = crc16(0, skb->data - hdr_size, skb->len + hdr_size);

        if (our_fcs != rcv_fcs)
            return -EBADMSG;
    }
    return 0;
}

static void l2cap_send_i_or_rr_or_rnr(struct l2cap_chan *chan)
{
    struct l2cap_ctrl control;

    BT_DBG("chan %p", chan);

    memset(&control, 0, sizeof(control));
    control.sframe = 1;
    control.final = 1;
    control.reqseq = chan->buffer_seq;
    set_bit(CONN_SEND_FBIT, &chan->conn_state);

    if (test_bit(CONN_LOCAL_BUSY, &chan->conn_state)) {
        control.super = L2CAP_SUPER_RNR;
        l2cap_send_sframe(chan, &control);
    }

    if (test_and_clear_bit(CONN_REMOTE_BUSY, &chan->conn_state) &&
        chan->unacked_frames > 0)
        __set_retrans_timer(chan);

    /* Send pending iframes */
    l2cap_ertm_send(chan);

    if (!test_bit(CONN_LOCAL_BUSY, &chan->conn_state) &&
        test_bit(CONN_SEND_FBIT, &chan->conn_state)) {
        /* F-bit wasn't sent in an s-frame or i-frame yet, so
         * send it now.
         */
        control.super = L2CAP_SUPER_RR;
        l2cap_send_sframe(chan, &control);
    }
}

static void append_skb_frag(struct sk_buff *skb,
            struct sk_buff *new_frag, struct sk_buff **last_frag)
{
    /* skb->len reflects data in skb as well as all fragments
     * skb->data_len reflects only data in fragments
     */
    if (!skb_has_frag_list(skb))
        skb_shinfo(skb)->frag_list = new_frag;

    new_frag->next = NULL;

    (*last_frag)->next = new_frag;
    *last_frag = new_frag;

    skb->len += new_frag->len;
    skb->data_len += new_frag->len;
    skb->truesize += new_frag->truesize;
}

static int l2cap_reassemble_sdu(struct l2cap_chan *chan, struct sk_buff *skb,
                struct l2cap_ctrl *control)
{
    int err = -EINVAL;

    switch (control->sar) {
    case L2CAP_SAR_UNSEGMENTED:
        if (chan->sdu)
            break;

        err = chan->ops->recv(chan, skb);
        break;

    case L2CAP_SAR_START:
        if (chan->sdu)
            break;

        chan->sdu_len = get_unaligned_le16(skb->data);
        skb_pull(skb, L2CAP_SDULEN_SIZE);

        if (chan->sdu_len > chan->imtu) {
            err = -EMSGSIZE;
            break;
        }

        if (skb->len >= chan->sdu_len)
            break;

        chan->sdu = skb;
        chan->sdu_last_frag = skb;

        skb = NULL;
        err = 0;
        break;

    case L2CAP_SAR_CONTINUE:
        if (!chan->sdu)
            break;

        append_skb_frag(chan->sdu, skb,
                &chan->sdu_last_frag);
        skb = NULL;

        if (chan->sdu->len >= chan->sdu_len)
            break;

        err = 0;
        break;

    case L2CAP_SAR_END:
        if (!chan->sdu)
            break;

        append_skb_frag(chan->sdu, skb,
                &chan->sdu_last_frag);
        skb = NULL;

        if (chan->sdu->len != chan->sdu_len)
            break;

        err = chan->ops->recv(chan, chan->sdu);

        if (!err) {
            /* Reassembly complete */
            chan->sdu = NULL;
            chan->sdu_last_frag = NULL;
            chan->sdu_len = 0;
        }
        break;
    }

    if (err) {
        kfree_skb(skb);
        kfree_skb(chan->sdu);
        chan->sdu = NULL;
        chan->sdu_last_frag = NULL;
        chan->sdu_len = 0;
    }

    return err;
}

void l2cap_chan_busy(struct l2cap_chan *chan, int busy)
{
    u8 event;

    if (chan->mode != L2CAP_MODE_ERTM)
        return;

    event = busy ? L2CAP_EV_LOCAL_BUSY_DETECTED : L2CAP_EV_LOCAL_BUSY_CLEAR;
    l2cap_tx(chan, NULL, NULL, event);
}

static int l2cap_rx_queued_iframes(struct l2cap_chan *chan)
{
    int err = 0;
    /* Pass sequential frames to l2cap_reassemble_sdu()
     * until a gap is encountered.
     */

    BT_DBG("chan %p", chan);

    while (!test_bit(CONN_LOCAL_BUSY, &chan->conn_state)) {
        struct sk_buff *skb;
        BT_DBG("Searching for skb with txseq %d (queue len %d)",
               chan->buffer_seq, skb_queue_len(&chan->srej_q));

        skb = l2cap_ertm_seq_in_queue(&chan->srej_q, chan->buffer_seq);

        if (!skb)
            break;

        skb_unlink(skb, &chan->srej_q);
        chan->buffer_seq = __next_seq(chan, chan->buffer_seq);
        err = l2cap_reassemble_sdu(chan, skb, &bt_cb(skb)->control);
        if (err)
            break;
    }

    if (skb_queue_empty(&chan->srej_q)) {
        chan->rx_state = L2CAP_RX_STATE_RECV;
        l2cap_send_ack(chan);
    }

    return err;
}

static void l2cap_handle_srej(struct l2cap_chan *chan,
                  struct l2cap_ctrl *control)
{
    struct sk_buff *skb;

    BT_DBG("chan %p, control %p", chan, control);

    if (control->reqseq == chan->next_tx_seq) {
        BT_DBG("Invalid reqseq %d, disconnecting", control->reqseq);
        l2cap_send_disconn_req(chan->conn, chan, ECONNRESET);
        return;
    }

    skb = l2cap_ertm_seq_in_queue(&chan->tx_q, control->reqseq);

    if (skb == NULL) {
        BT_DBG("Seq %d not available for retransmission",
               control->reqseq);
        return;
    }

    if (chan->max_tx != 0 && bt_cb(skb)->control.retries >= chan->max_tx) {
        BT_DBG("Retry limit exceeded (%d)", chan->max_tx);
        l2cap_send_disconn_req(chan->conn, chan, ECONNRESET);
        return;
    }

    clear_bit(CONN_REMOTE_BUSY, &chan->conn_state);

    if (control->poll) {
        l2cap_pass_to_tx(chan, control);

        set_bit(CONN_SEND_FBIT, &chan->conn_state);
        l2cap_retransmit(chan, control);
        l2cap_ertm_send(chan);

        if (chan->tx_state == L2CAP_TX_STATE_WAIT_F) {
            set_bit(CONN_SREJ_ACT, &chan->conn_state);
            chan->srej_save_reqseq = control->reqseq;
        }
    } else {
        l2cap_pass_to_tx_fbit(chan, control);

        if (control->final) {
            if (chan->srej_save_reqseq != control->reqseq ||
                !test_and_clear_bit(CONN_SREJ_ACT,
                        &chan->conn_state))
                l2cap_retransmit(chan, control);
        } else {
            l2cap_retransmit(chan, control);
            if (chan->tx_state == L2CAP_TX_STATE_WAIT_F) {
                set_bit(CONN_SREJ_ACT, &chan->conn_state);
                chan->srej_save_reqseq = control->reqseq;
            }
        }
    }
}

static void l2cap_handle_rej(struct l2cap_chan *chan,
                 struct l2cap_ctrl *control)
{
    struct sk_buff *skb;

    BT_DBG("chan %p, control %p", chan, control);

    if (control->reqseq == chan->next_tx_seq) {
        BT_DBG("Invalid reqseq %d, disconnecting", control->reqseq);
        l2cap_send_disconn_req(chan->conn, chan, ECONNRESET);
        return;
    }

    skb = l2cap_ertm_seq_in_queue(&chan->tx_q, control->reqseq);

    if (chan->max_tx && skb &&
        bt_cb(skb)->control.retries >= chan->max_tx) {
        BT_DBG("Retry limit exceeded (%d)", chan->max_tx);
        l2cap_send_disconn_req(chan->conn, chan, ECONNRESET);
        return;
    }

    clear_bit(CONN_REMOTE_BUSY, &chan->conn_state);

    l2cap_pass_to_tx(chan, control);

    if (control->final) {
        if (!test_and_clear_bit(CONN_REJ_ACT, &chan->conn_state))
            l2cap_retransmit_all(chan, control);
    } else {
        l2cap_retransmit_all(chan, control);
        l2cap_ertm_send(chan);
        if (chan->tx_state == L2CAP_TX_STATE_WAIT_F)
            set_bit(CONN_REJ_ACT, &chan->conn_state);
    }
}

static u8 l2cap_classify_txseq(struct l2cap_chan *chan, u16 txseq)
{
    BT_DBG("chan %p, txseq %d", chan, txseq);

    BT_DBG("last_acked_seq %d, expected_tx_seq %d", chan->last_acked_seq,
           chan->expected_tx_seq);

    if (chan->rx_state == L2CAP_RX_STATE_SREJ_SENT) {
        if (__seq_offset(chan, txseq, chan->last_acked_seq) >=
                                chan->tx_win) {
            /* See notes below regarding "double poll" and
             * invalid packets.
             */
            if (chan->tx_win <= ((chan->tx_win_max + 1) >> 1)) {
                BT_DBG("Invalid/Ignore - after SREJ");
                return L2CAP_TXSEQ_INVALID_IGNORE;
            } else {
                BT_DBG("Invalid - in window after SREJ sent");
                return L2CAP_TXSEQ_INVALID;
            }
        }

        if (chan->srej_list.head == txseq) {
            BT_DBG("Expected SREJ");
            return L2CAP_TXSEQ_EXPECTED_SREJ;
        }

        if (l2cap_ertm_seq_in_queue(&chan->srej_q, txseq)) {
            BT_DBG("Duplicate SREJ - txseq already stored");
            return L2CAP_TXSEQ_DUPLICATE_SREJ;
        }

        if (l2cap_seq_list_contains(&chan->srej_list, txseq)) {
            BT_DBG("Unexpected SREJ - not requested");
            return L2CAP_TXSEQ_UNEXPECTED_SREJ;
        }
    }

    if (chan->expected_tx_seq == txseq) {
        if (__seq_offset(chan, txseq, chan->last_acked_seq) >=
            chan->tx_win) {
            BT_DBG("Invalid - txseq outside tx window");
            return L2CAP_TXSEQ_INVALID;
        } else {
            BT_DBG("Expected");
            return L2CAP_TXSEQ_EXPECTED;
        }
    }

    if (__seq_offset(chan, txseq, chan->last_acked_seq) <
        __seq_offset(chan, chan->expected_tx_seq,
                 chan->last_acked_seq)){
        BT_DBG("Duplicate - expected_tx_seq later than txseq");
        return L2CAP_TXSEQ_DUPLICATE;
    }

    if (__seq_offset(chan, txseq, chan->last_acked_seq) >= chan->tx_win) {
        /* A source of invalid packets is a "double poll" condition,
         * where delays cause us to send multiple poll packets.  If
         * the remote stack receives and processes both polls,
         * sequence numbers can wrap around in such a way that a
         * resent frame has a sequence number that looks like new data
         * with a sequence gap.  This would trigger an erroneous SREJ
         * request.
         *
         * Fortunately, this is impossible with a tx window that's
         * less than half of the maximum sequence number, which allows
         * invalid frames to be safely ignored.
         *
         * With tx window sizes greater than half of the tx window
         * maximum, the frame is invalid and cannot be ignored.  This
         * causes a disconnect.
         */

        if (chan->tx_win <= ((chan->tx_win_max + 1) >> 1)) {
            BT_DBG("Invalid/Ignore - txseq outside tx window");
            return L2CAP_TXSEQ_INVALID_IGNORE;
        } else {
            BT_DBG("Invalid - txseq outside tx window");
            return L2CAP_TXSEQ_INVALID;
        }
    } else {
        BT_DBG("Unexpected - txseq indicates missing frames");
        return L2CAP_TXSEQ_UNEXPECTED;
    }
}

static int l2cap_rx_state_recv(struct l2cap_chan *chan,
                   struct l2cap_ctrl *control,
                   struct sk_buff *skb, u8 event)
{
    int err = 0;
    bool skb_in_use = 0;

    BT_DBG("chan %p, control %p, skb %p, event %d", chan, control, skb,
           event);

    switch (event) {
    case L2CAP_EV_RECV_IFRAME:
        switch (l2cap_classify_txseq(chan, control->txseq)) {
        case L2CAP_TXSEQ_EXPECTED:
            l2cap_pass_to_tx(chan, control);

            if (test_bit(CONN_LOCAL_BUSY, &chan->conn_state)) {
                BT_DBG("Busy, discarding expected seq %d",
                       control->txseq);
                break;
            }

            chan->expected_tx_seq = __next_seq(chan,
                               control->txseq);

            chan->buffer_seq = chan->expected_tx_seq;
            skb_in_use = 1;

            err = l2cap_reassemble_sdu(chan, skb, control);
            if (err)
                break;

            if (control->final) {
                if (!test_and_clear_bit(CONN_REJ_ACT,
                            &chan->conn_state)) {
                    control->final = 0;
                    l2cap_retransmit_all(chan, control);
                    l2cap_ertm_send(chan);
                }
            }

            if (!test_bit(CONN_LOCAL_BUSY, &chan->conn_state))
                l2cap_send_ack(chan);
            break;
        case L2CAP_TXSEQ_UNEXPECTED:
            l2cap_pass_to_tx(chan, control);

            /* Can't issue SREJ frames in the local busy state.
             * Drop this frame, it will be seen as missing
             * when local busy is exited.
             */
            if (test_bit(CONN_LOCAL_BUSY, &chan->conn_state)) {
                BT_DBG("Busy, discarding unexpected seq %d",
                       control->txseq);
                break;
            }

            /* There was a gap in the sequence, so an SREJ
             * must be sent for each missing frame.  The
             * current frame is stored for later use.
             */
            skb_queue_tail(&chan->srej_q, skb);
            skb_in_use = 1;
            BT_DBG("Queued %p (queue len %d)", skb,
                   skb_queue_len(&chan->srej_q));

            clear_bit(CONN_SREJ_ACT, &chan->conn_state);
            l2cap_seq_list_clear(&chan->srej_list);
            l2cap_send_srej(chan, control->txseq);

            chan->rx_state = L2CAP_RX_STATE_SREJ_SENT;
            break;
        case L2CAP_TXSEQ_DUPLICATE:
            l2cap_pass_to_tx(chan, control);
            break;
        case L2CAP_TXSEQ_INVALID_IGNORE:
            break;
        case L2CAP_TXSEQ_INVALID:
        default:
            l2cap_send_disconn_req(chan->conn, chan,
                           ECONNRESET);
            break;
        }
        break;
    case L2CAP_EV_RECV_RR:
        l2cap_pass_to_tx(chan, control);
        if (control->final) {
            clear_bit(CONN_REMOTE_BUSY, &chan->conn_state);

            if (!test_and_clear_bit(CONN_REJ_ACT,
                        &chan->conn_state)) {
                control->final = 0;
                l2cap_retransmit_all(chan, control);
            }

            l2cap_ertm_send(chan);
        } else if (control->poll) {
            l2cap_send_i_or_rr_or_rnr(chan);
        } else {
            if (test_and_clear_bit(CONN_REMOTE_BUSY,
                           &chan->conn_state) &&
                chan->unacked_frames)
                __set_retrans_timer(chan);

            l2cap_ertm_send(chan);
        }
        break;
    case L2CAP_EV_RECV_RNR:
        set_bit(CONN_REMOTE_BUSY, &chan->conn_state);
        l2cap_pass_to_tx(chan, control);
        if (control && control->poll) {
            set_bit(CONN_SEND_FBIT, &chan->conn_state);
            l2cap_send_rr_or_rnr(chan, 0);
        }
        __clear_retrans_timer(chan);
        l2cap_seq_list_clear(&chan->retrans_list);
        break;
    case L2CAP_EV_RECV_REJ:
        l2cap_handle_rej(chan, control);
        break;
    case L2CAP_EV_RECV_SREJ:
        l2cap_handle_srej(chan, control);
        break;
    default:
        break;
    }

    if (skb && !skb_in_use) {
        BT_DBG("Freeing %p", skb);
        kfree_skb(skb);
    }

    return err;
}

static int l2cap_rx_state_srej_sent(struct l2cap_chan *chan,
                    struct l2cap_ctrl *control,
                    struct sk_buff *skb, u8 event)
{
    int err = 0;
    u16 txseq = control->txseq;
    bool skb_in_use = 0;

    BT_DBG("chan %p, control %p, skb %p, event %d", chan, control, skb,
           event);

    switch (event) {
    case L2CAP_EV_RECV_IFRAME:
        switch (l2cap_classify_txseq(chan, txseq)) {
        case L2CAP_TXSEQ_EXPECTED:
            /* Keep frame for reassembly later */
            l2cap_pass_to_tx(chan, control);
            skb_queue_tail(&chan->srej_q, skb);
            skb_in_use = 1;
            BT_DBG("Queued %p (queue len %d)", skb,
                   skb_queue_len(&chan->srej_q));

            chan->expected_tx_seq = __next_seq(chan, txseq);
            break;
        case L2CAP_TXSEQ_EXPECTED_SREJ:
            l2cap_seq_list_pop(&chan->srej_list);

            l2cap_pass_to_tx(chan, control);
            skb_queue_tail(&chan->srej_q, skb);
            skb_in_use = 1;
            BT_DBG("Queued %p (queue len %d)", skb,
                   skb_queue_len(&chan->srej_q));

            err = l2cap_rx_queued_iframes(chan);
            if (err)
                break;

            break;
        case L2CAP_TXSEQ_UNEXPECTED:
            /* Got a frame that can't be reassembled yet.
             * Save it for later, and send SREJs to cover
             * the missing frames.
             */
            skb_queue_tail(&chan->srej_q, skb);
            skb_in_use = 1;
            BT_DBG("Queued %p (queue len %d)", skb,
                   skb_queue_len(&chan->srej_q));

            l2cap_pass_to_tx(chan, control);
            l2cap_send_srej(chan, control->txseq);
            break;
        case L2CAP_TXSEQ_UNEXPECTED_SREJ:
            /* This frame was requested with an SREJ, but
             * some expected retransmitted frames are
             * missing.  Request retransmission of missing
             * SREJ'd frames.
             */
            skb_queue_tail(&chan->srej_q, skb);
            skb_in_use = 1;
            BT_DBG("Queued %p (queue len %d)", skb,
                   skb_queue_len(&chan->srej_q));

            l2cap_pass_to_tx(chan, control);
            l2cap_send_srej_list(chan, control->txseq);
            break;
        case L2CAP_TXSEQ_DUPLICATE_SREJ:
            /* We've already queued this frame.  Drop this copy. */
            l2cap_pass_to_tx(chan, control);
            break;
        case L2CAP_TXSEQ_DUPLICATE:
            /* Expecting a later sequence number, so this frame
             * was already received.  Ignore it completely.
             */
            break;
        case L2CAP_TXSEQ_INVALID_IGNORE:
            break;
        case L2CAP_TXSEQ_INVALID:
        default:
            l2cap_send_disconn_req(chan->conn, chan,
                           ECONNRESET);
            break;
        }
        break;
    case L2CAP_EV_RECV_RR:
        l2cap_pass_to_tx(chan, control);
        if (control->final) {
            clear_bit(CONN_REMOTE_BUSY, &chan->conn_state);

            if (!test_and_clear_bit(CONN_REJ_ACT,
                        &chan->conn_state)) {
                control->final = 0;
                l2cap_retransmit_all(chan, control);
            }

            l2cap_ertm_send(chan);
        } else if (control->poll) {
            if (test_and_clear_bit(CONN_REMOTE_BUSY,
                           &chan->conn_state) &&
                chan->unacked_frames) {
                __set_retrans_timer(chan);
            }

            set_bit(CONN_SEND_FBIT, &chan->conn_state);
            l2cap_send_srej_tail(chan);
        } else {
            if (test_and_clear_bit(CONN_REMOTE_BUSY,
                           &chan->conn_state) &&
                chan->unacked_frames)
                __set_retrans_timer(chan);

            l2cap_send_ack(chan);
        }
        break;
    case L2CAP_EV_RECV_RNR:
        set_bit(CONN_REMOTE_BUSY, &chan->conn_state);
        l2cap_pass_to_tx(chan, control);
        if (control->poll) {
            l2cap_send_srej_tail(chan);
        } else {
            struct l2cap_ctrl rr_control;
            memset(&rr_control, 0, sizeof(rr_control));
            rr_control.sframe = 1;
            rr_control.super = L2CAP_SUPER_RR;
            rr_control.reqseq = chan->buffer_seq;
            l2cap_send_sframe(chan, &rr_control);
        }

        break;
    case L2CAP_EV_RECV_REJ:
        l2cap_handle_rej(chan, control);
        break;
    case L2CAP_EV_RECV_SREJ:
        l2cap_handle_srej(chan, control);
        break;
    }

    if (skb && !skb_in_use) {
        BT_DBG("Freeing %p", skb);
        kfree_skb(skb);
    }

    return err;
}

static bool __valid_reqseq(struct l2cap_chan *chan, u16 reqseq)
{
    /* Make sure reqseq is for a packet that has been sent but not acked */
    u16 unacked;

    unacked = __seq_offset(chan, chan->next_tx_seq, chan->expected_ack_seq);
    return __seq_offset(chan, chan->next_tx_seq, reqseq) <= unacked;
}

static int l2cap_rx(struct l2cap_chan *chan, struct l2cap_ctrl *control,
            struct sk_buff *skb, u8 event)
{
    int err = 0;

    BT_DBG("chan %p, control %p, skb %p, event %d, state %d", chan,
           control, skb, event, chan->rx_state);

    if (__valid_reqseq(chan, control->reqseq)) {
        switch (chan->rx_state) {
        case L2CAP_RX_STATE_RECV:
            err = l2cap_rx_state_recv(chan, control, skb, event);
            break;
        case L2CAP_RX_STATE_SREJ_SENT:
            err = l2cap_rx_state_srej_sent(chan, control, skb,
                               event);
            break;
        default:
            /* shut it down */
            break;
        }
    } else {
        BT_DBG("Invalid reqseq %d (next_tx_seq %d, expected_ack_seq %d",
               control->reqseq, chan->next_tx_seq,
               chan->expected_ack_seq);
        l2cap_send_disconn_req(chan->conn, chan, ECONNRESET);
    }

    return err;
}

static int l2cap_stream_rx(struct l2cap_chan *chan, struct l2cap_ctrl *control,
               struct sk_buff *skb)
{
    int err = 0;

    BT_DBG("chan %p, control %p, skb %p, state %d", chan, control, skb,
           chan->rx_state);

    if (l2cap_classify_txseq(chan, control->txseq) ==
        L2CAP_TXSEQ_EXPECTED) {
        l2cap_pass_to_tx(chan, control);

        BT_DBG("buffer_seq %d->%d", chan->buffer_seq,
               __next_seq(chan, chan->buffer_seq));

        chan->buffer_seq = __next_seq(chan, chan->buffer_seq);

        l2cap_reassemble_sdu(chan, skb, control);
    } else {
        if (chan->sdu) {
            kfree_skb(chan->sdu);
            chan->sdu = NULL;
        }
        chan->sdu_last_frag = NULL;
        chan->sdu_len = 0;

        if (skb) {
            BT_DBG("Freeing %p", skb);
            kfree_skb(skb);
        }
    }

    chan->last_acked_seq = control->txseq;
    chan->expected_tx_seq = __next_seq(chan, control->txseq);

    return err;
}

static int l2cap_data_rcv(struct l2cap_chan *chan, struct sk_buff *skb)
{
    struct l2cap_ctrl *control = &bt_cb(skb)->control;
    u16 len;
    u8 event;

    __unpack_control(chan, skb);

    len = skb->len;

    /*
     * We can just drop the corrupted I-frame here.
     * Receiver will miss it and start proper recovery
     * procedures and ask for retransmission.
     */
    if (l2cap_check_fcs(chan, skb))
        goto drop;

    if (!control->sframe && control->sar == L2CAP_SAR_START)
        len -= L2CAP_SDULEN_SIZE;

    if (chan->fcs == L2CAP_FCS_CRC16)
        len -= L2CAP_FCS_SIZE;

    if (len > chan->mps) {
        l2cap_send_disconn_req(chan->conn, chan, ECONNRESET);
        goto drop;
    }

    if (!control->sframe) {
        int err;

        BT_DBG("iframe sar %d, reqseq %d, final %d, txseq %d",
               control->sar, control->reqseq, control->final,
               control->txseq);

        /* Validate F-bit - F=0 always valid, F=1 only
         * valid in TX WAIT_F
         */
        if (control->final && chan->tx_state != L2CAP_TX_STATE_WAIT_F)
            goto drop;

        if (chan->mode != L2CAP_MODE_STREAMING) {
            event = L2CAP_EV_RECV_IFRAME;
            err = l2cap_rx(chan, control, skb, event);
        } else {
            err = l2cap_stream_rx(chan, control, skb);
        }

        if (err)
            l2cap_send_disconn_req(chan->conn, chan,
                           ECONNRESET);
    } else {
        const u8 rx_func_to_event[4] = {
            L2CAP_EV_RECV_RR, L2CAP_EV_RECV_REJ,
            L2CAP_EV_RECV_RNR, L2CAP_EV_RECV_SREJ
        };

        /* Only I-frames are expected in streaming mode */
        if (chan->mode == L2CAP_MODE_STREAMING)
            goto drop;

        BT_DBG("sframe reqseq %d, final %d, poll %d, super %d",
               control->reqseq, control->final, control->poll,
               control->super);

        if (len != 0) {
            BT_ERR("%d", len);
            l2cap_send_disconn_req(chan->conn, chan, ECONNRESET);
            goto drop;
        }

        /* Validate F and P bits */
        if (control->final && (control->poll ||
                       chan->tx_state != L2CAP_TX_STATE_WAIT_F))
            goto drop;

        event = rx_func_to_event[control->super];
        if (l2cap_rx(chan, control, skb, event))
            l2cap_send_disconn_req(chan->conn, chan, ECONNRESET);
    }

    return 0;

drop:
    kfree_skb(skb);
    return 0;
}

static void l2cap_data_channel(struct l2cap_conn *conn, u16 cid,
                   struct sk_buff *skb)
{
    struct l2cap_chan *chan;

    chan = l2cap_get_chan_by_scid(conn, cid);
    if (!chan) {
        if (cid == L2CAP_CID_A2MP) {
            chan = a2mp_channel_create(conn, skb);
            if (!chan) {
                kfree_skb(skb);
                return;
            }

            l2cap_chan_lock(chan);
        } else {
            BT_DBG("unknown cid 0x%4.4x", cid);
            /* Drop packet and return */
            kfree_skb(skb);
            return;
        }
    }

    BT_DBG("chan %p, len %d", chan, skb->len);

    if (chan->state != BT_CONNECTED)
        goto drop;

    switch (chan->mode) {
    case L2CAP_MODE_BASIC:
        /* If socket recv buffers overflows we drop data here
         * which is *bad* because L2CAP has to be reliable.
         * But we don't have any other choice. L2CAP doesn't
         * provide flow control mechanism. */

        if (chan->imtu < skb->len)
            goto drop;

        if (!chan->ops->recv(chan, skb))
            goto done;
        break;

    case L2CAP_MODE_ERTM:
    case L2CAP_MODE_STREAMING:
        l2cap_data_rcv(chan, skb);
        goto done;

    default:
        BT_DBG("chan %p: bad mode 0x%2.2x", chan, chan->mode);
        break;
    }

drop:
    kfree_skb(skb);

done:
    l2cap_chan_unlock(chan);
}

static void l2cap_conless_channel(struct l2cap_conn *conn, __le16 psm,
                  struct sk_buff *skb)
{
    struct l2cap_chan *chan;

    chan = l2cap_global_chan_by_psm(0, psm, conn->src, conn->dst);
    if (!chan)
        goto drop;

    BT_DBG("chan %p, len %d", chan, skb->len);

    if (chan->state != BT_BOUND && chan->state != BT_CONNECTED)
        goto drop;

    if (chan->imtu < skb->len)
        goto drop;

    if (!chan->ops->recv(chan, skb))
        return;

drop:
    kfree_skb(skb);
}

static void l2cap_att_channel(struct l2cap_conn *conn, u16 cid,
                  struct sk_buff *skb)
{
    struct l2cap_chan *chan;

    chan = l2cap_global_chan_by_scid(0, cid, conn->src, conn->dst);
    if (!chan)
        goto drop;

    BT_DBG("chan %p, len %d", chan, skb->len);

    if (chan->state != BT_BOUND && chan->state != BT_CONNECTED)
        goto drop;

    if (chan->imtu < skb->len)
        goto drop;

    if (!chan->ops->recv(chan, skb))
        return;

drop:
    kfree_skb(skb);
}

static void l2cap_recv_frame(struct l2cap_conn *conn, struct sk_buff *skb)
{
    struct l2cap_hdr *lh = (void *) skb->data;
    u16 cid, len;
    __le16 psm;

    skb_pull(skb, L2CAP_HDR_SIZE);
    cid = __le16_to_cpu(lh->cid);
    len = __le16_to_cpu(lh->len);

    if (len != skb->len) {
        kfree_skb(skb);
        return;
    }

    BT_DBG("len %d, cid 0x%4.4x", len, cid);

    switch (cid) {
    case L2CAP_CID_LE_SIGNALING:
    case L2CAP_CID_SIGNALING:
        l2cap_sig_channel(conn, skb);
        break;

    case L2CAP_CID_CONN_LESS:
        psm = get_unaligned((__le16 *) skb->data);
        skb_pull(skb, L2CAP_PSMLEN_SIZE);
        l2cap_conless_channel(conn, psm, skb);
        break;

    case L2CAP_CID_LE_DATA:
        l2cap_att_channel(conn, cid, skb);
        break;

    case L2CAP_CID_SMP:
        if (smp_sig_channel(conn, skb))
            l2cap_conn_del(conn->hcon, EACCES);
        break;

    default:
        l2cap_data_channel(conn, cid, skb);
        break;
    }
}

/* ---- L2CAP interface with lower layer (HCI) ---- */

int l2cap_connect_ind(struct hci_dev *hdev, bdaddr_t *bdaddr)
{
    int exact = 0, lm1 = 0, lm2 = 0;
    struct l2cap_chan *c;

    BT_DBG("hdev %s, bdaddr %s", hdev->name, batostr(bdaddr));

    /* Find listening sockets and check their link_mode */
    read_lock(&chan_list_lock);
    list_for_each_entry(c, &chan_list, global_l) {
        struct sock *sk = c->sk;

        if (c->state != BT_LISTEN)
            continue;

        if (!bacmp(&bt_sk(sk)->src, &hdev->bdaddr)) {
            lm1 |= HCI_LM_ACCEPT;
            if (test_bit(FLAG_ROLE_SWITCH, &c->flags))
                lm1 |= HCI_LM_MASTER;
            exact++;
        } else if (!bacmp(&bt_sk(sk)->src, BDADDR_ANY)) {
            lm2 |= HCI_LM_ACCEPT;
            if (test_bit(FLAG_ROLE_SWITCH, &c->flags))
                lm2 |= HCI_LM_MASTER;
        }
    }
    read_unlock(&chan_list_lock);

    return exact ? lm1 : lm2;
}

void l2cap_connect_cfm(struct hci_conn *hcon, u8 status)
{
    struct l2cap_conn *conn;

    BT_DBG("hcon %p bdaddr %s status %d", hcon, batostr(&hcon->dst), status);

    if (!status) {
        conn = l2cap_conn_add(hcon, status);
        if (conn)
            l2cap_conn_ready(conn);
    } else
        l2cap_conn_del(hcon, bt_to_errno(status));

}

int l2cap_disconn_ind(struct hci_conn *hcon)
{
    struct l2cap_conn *conn = hcon->l2cap_data;

    BT_DBG("hcon %p", hcon);

    if (!conn)
        return HCI_ERROR_REMOTE_USER_TERM;
    return conn->disc_reason;
}

void l2cap_disconn_cfm(struct hci_conn *hcon, u8 reason)
{
    BT_DBG("hcon %p reason %d", hcon, reason);

    l2cap_conn_del(hcon, bt_to_errno(reason));
}

static inline void l2cap_check_encryption(struct l2cap_chan *chan, u8 encrypt)
{
    if (chan->chan_type != L2CAP_CHAN_CONN_ORIENTED)
        return;

    if (encrypt == 0x00) {
        if (chan->sec_level == BT_SECURITY_MEDIUM) {
            __set_chan_timer(chan, L2CAP_ENC_TIMEOUT);
        } else if (chan->sec_level == BT_SECURITY_HIGH)
            l2cap_chan_close(chan, ECONNREFUSED);
    } else {
        if (chan->sec_level == BT_SECURITY_MEDIUM)
            __clear_chan_timer(chan);
    }
}

int l2cap_security_cfm(struct hci_conn *hcon, u8 status, u8 encrypt)
{
    struct l2cap_conn *conn = hcon->l2cap_data;
    struct l2cap_chan *chan;

    if (!conn)
        return 0;

    BT_DBG("conn %p status 0x%2.2x encrypt %u", conn, status, encrypt);

    if (hcon->type == LE_LINK) {
        if (!status && encrypt)
            smp_distribute_keys(conn, 0);
        cancel_delayed_work(&conn->security_timer);
    }

    mutex_lock(&conn->chan_lock);

    list_for_each_entry(chan, &conn->chan_l, list) {
        l2cap_chan_lock(chan);

        BT_DBG("chan %p scid 0x%4.4x state %s", chan, chan->scid,
               state_to_string(chan->state));

        if (chan->chan_type == L2CAP_CHAN_CONN_FIX_A2MP) {
            l2cap_chan_unlock(chan);
            continue;
        }

        if (chan->scid == L2CAP_CID_LE_DATA) {
            if (!status && encrypt) {
                chan->sec_level = hcon->sec_level;
                l2cap_chan_ready(chan);
            }

            l2cap_chan_unlock(chan);
            continue;
        }

        if (test_bit(CONF_CONNECT_PEND, &chan->conf_state)) {
            l2cap_chan_unlock(chan);
            continue;
        }

        if (!status && (chan->state == BT_CONNECTED ||
                        chan->state == BT_CONFIG)) {
            struct sock *sk = chan->sk;

            clear_bit(BT_SK_SUSPEND, &bt_sk(sk)->flags);
            sk->sk_state_change(sk);

            l2cap_check_encryption(chan, encrypt);
            l2cap_chan_unlock(chan);
            continue;
        }

        if (chan->state == BT_CONNECT) {
            if (!status) {
                l2cap_send_conn_req(chan);
            } else {
                __set_chan_timer(chan, L2CAP_DISC_TIMEOUT);
            }
        } else if (chan->state == BT_CONNECT2) {
            struct sock *sk = chan->sk;
            struct l2cap_conn_rsp rsp;
            __u16 res, stat;

            lock_sock(sk);

            if (!status) {
                if (test_bit(BT_SK_DEFER_SETUP,
                         &bt_sk(sk)->flags)) {
                    struct sock *parent = bt_sk(sk)->parent;
                    res = L2CAP_CR_PEND;
                    stat = L2CAP_CS_AUTHOR_PEND;
                    if (parent)
                        parent->sk_data_ready(parent, 0);
                } else {
                    __l2cap_state_change(chan, BT_CONFIG);
                    res = L2CAP_CR_SUCCESS;
                    stat = L2CAP_CS_NO_INFO;
                }
            } else {
                __l2cap_state_change(chan, BT_DISCONN);
                __set_chan_timer(chan, L2CAP_DISC_TIMEOUT);
                res = L2CAP_CR_SEC_BLOCK;
                stat = L2CAP_CS_NO_INFO;
            }

            release_sock(sk);

            rsp.scid   = cpu_to_le16(chan->dcid);
            rsp.dcid   = cpu_to_le16(chan->scid);
            rsp.result = cpu_to_le16(res);
            rsp.status = cpu_to_le16(stat);
            l2cap_send_cmd(conn, chan->ident, L2CAP_CONN_RSP,
                            sizeof(rsp), &rsp);

            if (!test_bit(CONF_REQ_SENT, &chan->conf_state) &&
                res == L2CAP_CR_SUCCESS) {
                char buf[128];
                set_bit(CONF_REQ_SENT, &chan->conf_state);
                l2cap_send_cmd(conn, l2cap_get_ident(conn),
                           L2CAP_CONF_REQ,
                           l2cap_build_conf_req(chan, buf),
                           buf);
                chan->num_conf_req++;
            }
        }

        l2cap_chan_unlock(chan);
    }

    mutex_unlock(&conn->chan_lock);

    return 0;
}

int l2cap_recv_acldata(struct hci_conn *hcon, struct sk_buff *skb, u16 flags)
{
    struct l2cap_conn *conn = hcon->l2cap_data;

    if (!conn)
        conn = l2cap_conn_add(hcon, 0);

    if (!conn)
        goto drop;

    BT_DBG("conn %p len %d flags 0x%x", conn, skb->len, flags);

    if (!(flags & ACL_CONT)) {
        struct l2cap_hdr *hdr;
        int len;

        if (conn->rx_len) {
            BT_ERR("Unexpected start frame (len %d)", skb->len);
            kfree_skb(conn->rx_skb);
            conn->rx_skb = NULL;
            conn->rx_len = 0;
            l2cap_conn_unreliable(conn, ECOMM);
        }

        /* Start fragment always begin with Basic L2CAP header */
        if (skb->len < L2CAP_HDR_SIZE) {
            BT_ERR("Frame is too short (len %d)", skb->len);
            l2cap_conn_unreliable(conn, ECOMM);
            goto drop;
        }

        hdr = (struct l2cap_hdr *) skb->data;
        len = __le16_to_cpu(hdr->len) + L2CAP_HDR_SIZE;

        if (len == skb->len) {
            /* Complete frame received */
            l2cap_recv_frame(conn, skb);
            return 0;
        }

        BT_DBG("Start: total len %d, frag len %d", len, skb->len);

        if (skb->len > len) {
            BT_ERR("Frame is too long (len %d, expected len %d)",
                skb->len, len);
            l2cap_conn_unreliable(conn, ECOMM);
            goto drop;
        }

        /* Allocate skb for the complete frame (with header) */
        conn->rx_skb = bt_skb_alloc(len, GFP_ATOMIC);
        if (!conn->rx_skb)
            goto drop;

        skb_copy_from_linear_data(skb, skb_put(conn->rx_skb, skb->len),
                                skb->len);
        conn->rx_len = len - skb->len;
    } else {
        BT_DBG("Cont: frag len %d (expecting %d)", skb->len, conn->rx_len);

        if (!conn->rx_len) {
            BT_ERR("Unexpected continuation frame (len %d)", skb->len);
            l2cap_conn_unreliable(conn, ECOMM);
            goto drop;
        }

        if (skb->len > conn->rx_len) {
            BT_ERR("Fragment is too long (len %d, expected %d)",
                    skb->len, conn->rx_len);
            kfree_skb(conn->rx_skb);
            conn->rx_skb = NULL;
            conn->rx_len = 0;
            l2cap_conn_unreliable(conn, ECOMM);
            goto drop;
        }

        skb_copy_from_linear_data(skb, skb_put(conn->rx_skb, skb->len),
                                skb->len);
        conn->rx_len -= skb->len;

        if (!conn->rx_len) {
            /* Complete frame received */
            l2cap_recv_frame(conn, conn->rx_skb);
            conn->rx_skb = NULL;
        }
    }

drop:
    kfree_skb(skb);
    return 0;
}

static int l2cap_debugfs_show(struct seq_file *f, void *p)
{
    struct l2cap_chan *c;

    read_lock(&chan_list_lock);

    list_for_each_entry(c, &chan_list, global_l) {
        struct sock *sk = c->sk;

        seq_printf(f, "%s %s %d %d 0x%4.4x 0x%4.4x %d %d %d %d\n",
                    batostr(&bt_sk(sk)->src),
                    batostr(&bt_sk(sk)->dst),
                    c->state, __le16_to_cpu(c->psm),
                    c->scid, c->dcid, c->imtu, c->omtu,
                    c->sec_level, c->mode);
    }

    read_unlock(&chan_list_lock);

    return 0;
}

static int l2cap_debugfs_open(struct inode *inode, struct file *file)
{
    return single_open(file, l2cap_debugfs_show, inode->i_private);
}

static const struct file_operations l2cap_debugfs_fops = {
    .open       = l2cap_debugfs_open,
    .read       = seq_read,
    .llseek     = seq_lseek,
    .release    = single_release,
};

static struct dentry *l2cap_debugfs;

int __init l2cap_init(void)
{
    int err;

    err = l2cap_init_sockets();
    if (err < 0)
        return err;

    if (bt_debugfs) {
        l2cap_debugfs = debugfs_create_file("l2cap", 0444,
                    bt_debugfs, NULL, &l2cap_debugfs_fops);
        if (!l2cap_debugfs)
            BT_ERR("Failed to create L2CAP debug file");
    }

    return 0;
}

void l2cap_exit(void)
{
    debugfs_remove(l2cap_debugfs);
    l2cap_cleanup_sockets();
}

module_param(disable_ertm, bool, 0644);
MODULE_PARM_DESC(disable_ertm, "Disable enhanced retransmission mode");