kernel - Fix races created by a comedy of circumstansces (3)

[dragonfly.git] / sys / netbt / rfcomm_session.c

/* $OpenBSD: src/sys/netbt/rfcomm_session.c,v 1.3 2008/02/24 21:34:48 uwe Exp $ */
/* $NetBSD: rfcomm_session.c,v 1.12 2008/01/31 19:30:23 plunky Exp $ */

/*-
 * Copyright (c) 2006 Itronix Inc.
 * All rights reserved.
 *
 * Written by Iain Hibbert for Itronix Inc.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. The name of Itronix Inc. may not be used to endorse
 *    or promote products derived from this software without specific
 *    prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY ITRONIX INC. ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL ITRONIX INC. BE LIABLE FOR ANY
 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

#include <sys/param.h>
#include <sys/kernel.h>
#include <sys/mbuf.h>
#include <sys/proc.h>
#include <sys/systm.h>
#include <sys/types.h>
#include <sys/endian.h>

#include <net/if.h>

#include <netbt/bluetooth.h>
#include <netbt/hci.h>
#include <netbt/l2cap.h>
#include <netbt/rfcomm.h>

/******************************************************************************
 *
 * RFCOMM Multiplexer Sessions sit directly on L2CAP channels, and can
 * multiplex up to 30 incoming and 30 outgoing connections.
 * Only one Multiplexer is allowed between any two devices.
 */

static void rfcomm_session_recv_sabm(struct rfcomm_session *, int);
static void rfcomm_session_recv_disc(struct rfcomm_session *, int);
static void rfcomm_session_recv_ua(struct rfcomm_session *, int);
static void rfcomm_session_recv_dm(struct rfcomm_session *, int);
static void rfcomm_session_recv_uih(struct rfcomm_session *, int, int, struct mbuf *, int);
static void rfcomm_session_recv_mcc(struct rfcomm_session *, struct mbuf *);
static void rfcomm_session_recv_mcc_test(struct rfcomm_session *, int, struct mbuf *);
static void rfcomm_session_recv_mcc_fcon(struct rfcomm_session *, int);
static void rfcomm_session_recv_mcc_fcoff(struct rfcomm_session *, int);
static void rfcomm_session_recv_mcc_msc(struct rfcomm_session *, int, struct mbuf *);
static void rfcomm_session_recv_mcc_rpn(struct rfcomm_session *, int, struct mbuf *);
static void rfcomm_session_recv_mcc_rls(struct rfcomm_session *, int, struct mbuf *);
static void rfcomm_session_recv_mcc_pn(struct rfcomm_session *, int, struct mbuf *);
static void rfcomm_session_recv_mcc_nsc(struct rfcomm_session *, int, struct mbuf *);

/* L2CAP callbacks */
static void rfcomm_session_connecting(void *);
static void rfcomm_session_connected(void *);
static void rfcomm_session_disconnected(void *, int);
static void *rfcomm_session_newconn(void *, struct sockaddr_bt *, struct sockaddr_bt *);
static void rfcomm_session_complete(void *, int);
static void rfcomm_session_linkmode(void *, int);
static void rfcomm_session_input(void *, struct mbuf *);

static const struct btproto rfcomm_session_proto = {
        rfcomm_session_connecting,
        rfcomm_session_connected,
        rfcomm_session_disconnected,
        rfcomm_session_newconn,
        rfcomm_session_complete,
        rfcomm_session_linkmode,
        rfcomm_session_input,
};

struct rfcomm_session_list
        rfcomm_session_active = LIST_HEAD_INITIALIZER(rfcomm_session_active);

struct rfcomm_session_list
        rfcomm_session_listen = LIST_HEAD_INITIALIZER(rfcomm_session_listen);

vm_zone_t rfcomm_credit_pool;

/*
 * RFCOMM System Parameters (see section 5.3)
 */
int rfcomm_mtu_default = 127;   /* bytes */
int rfcomm_ack_timeout = 20;    /* seconds */
int rfcomm_mcc_timeout = 20;    /* seconds */

/*
 * Reversed CRC table as per TS 07.10 Annex B.3.5
 */
static const uint8_t crctable[256] = {  /* reversed, 8-bit, poly=0x07 */
        0x00, 0x91, 0xe3, 0x72, 0x07, 0x96, 0xe4, 0x75,
        0x0e, 0x9f, 0xed, 0x7c, 0x09, 0x98, 0xea, 0x7b,
        0x1c, 0x8d, 0xff, 0x6e, 0x1b, 0x8a, 0xf8, 0x69,
        0x12, 0x83, 0xf1, 0x60, 0x15, 0x84, 0xf6, 0x67,

        0x38, 0xa9, 0xdb, 0x4a, 0x3f, 0xae, 0xdc, 0x4d,
        0x36, 0xa7, 0xd5, 0x44, 0x31, 0xa0, 0xd2, 0x43,
        0x24, 0xb5, 0xc7, 0x56, 0x23, 0xb2, 0xc0, 0x51,
        0x2a, 0xbb, 0xc9, 0x58, 0x2d, 0xbc, 0xce, 0x5f,

        0x70, 0xe1, 0x93, 0x02, 0x77, 0xe6, 0x94, 0x05,
        0x7e, 0xef, 0x9d, 0x0c, 0x79, 0xe8, 0x9a, 0x0b,
        0x6c, 0xfd, 0x8f, 0x1e, 0x6b, 0xfa, 0x88, 0x19,
        0x62, 0xf3, 0x81, 0x10, 0x65, 0xf4, 0x86, 0x17,

        0x48, 0xd9, 0xab, 0x3a, 0x4f, 0xde, 0xac, 0x3d,
        0x46, 0xd7, 0xa5, 0x34, 0x41, 0xd0, 0xa2, 0x33,
        0x54, 0xc5, 0xb7, 0x26, 0x53, 0xc2, 0xb0, 0x21,
        0x5a, 0xcb, 0xb9, 0x28, 0x5d, 0xcc, 0xbe, 0x2f,

        0xe0, 0x71, 0x03, 0x92, 0xe7, 0x76, 0x04, 0x95,
        0xee, 0x7f, 0x0d, 0x9c, 0xe9, 0x78, 0x0a, 0x9b,
        0xfc, 0x6d, 0x1f, 0x8e, 0xfb, 0x6a, 0x18, 0x89,
        0xf2, 0x63, 0x11, 0x80, 0xf5, 0x64, 0x16, 0x87,

        0xd8, 0x49, 0x3b, 0xaa, 0xdf, 0x4e, 0x3c, 0xad,
        0xd6, 0x47, 0x35, 0xa4, 0xd1, 0x40, 0x32, 0xa3,
        0xc4, 0x55, 0x27, 0xb6, 0xc3, 0x52, 0x20, 0xb1,
        0xca, 0x5b, 0x29, 0xb8, 0xcd, 0x5c, 0x2e, 0xbf,

        0x90, 0x01, 0x73, 0xe2, 0x97, 0x06, 0x74, 0xe5,
        0x9e, 0x0f, 0x7d, 0xec, 0x99, 0x08, 0x7a, 0xeb,
        0x8c, 0x1d, 0x6f, 0xfe, 0x8b, 0x1a, 0x68, 0xf9,
        0x82, 0x13, 0x61, 0xf0, 0x85, 0x14, 0x66, 0xf7,

        0xa8, 0x39, 0x4b, 0xda, 0xaf, 0x3e, 0x4c, 0xdd,
        0xa6, 0x37, 0x45, 0xd4, 0xa1, 0x30, 0x42, 0xd3,
        0xb4, 0x25, 0x57, 0xc6, 0xb3, 0x22, 0x50, 0xc1,
        0xba, 0x2b, 0x59, 0xc8, 0xbd, 0x2c, 0x5e, 0xcf
};

#define FCS(f, d)       crctable[(f) ^ (d)]

/*
 * rfcomm_init()
 *
 * initialize the "credit pool".
 */
void
rfcomm_init(void)
{
        rfcomm_credit_pool = zinit("rfcomm_credit",
                                   sizeof(struct rfcomm_credit),
                                   0, 0);
}

/*
 * rfcomm_session_alloc(list, sockaddr)
 *
 * allocate a new session and fill in the blanks, then
 * attach session to front of specified list (active or listen)
 */
struct rfcomm_session *
rfcomm_session_alloc(struct rfcomm_session_list *list,
                        struct sockaddr_bt *laddr)
{
        struct rfcomm_session *rs;
        int err;

        rs = kmalloc(sizeof(*rs), M_BLUETOOTH, M_NOWAIT | M_ZERO);
        if (rs == NULL)
                return NULL;

        rs->rs_state = RFCOMM_SESSION_CLOSED;

        callout_init(&rs->rs_timeout);

        STAILQ_INIT(&rs->rs_credits);
        LIST_INIT(&rs->rs_dlcs);

        err = l2cap_attach(&rs->rs_l2cap, &rfcomm_session_proto, rs);
        if (err) {
                kfree(rs, M_BLUETOOTH);
                return NULL;
        }

        (void)l2cap_getopt(rs->rs_l2cap, SO_L2CAP_OMTU, &rs->rs_mtu);

        if (laddr->bt_psm == L2CAP_PSM_ANY)
                laddr->bt_psm = L2CAP_PSM_RFCOMM;

        (void)l2cap_bind(rs->rs_l2cap, laddr);

        LIST_INSERT_HEAD(list, rs, rs_next);

        return rs;
}

/*
 * rfcomm_session_free(rfcomm_session)
 *
 * release a session, including any cleanup
 */
void
rfcomm_session_free(struct rfcomm_session *rs)
{
        struct rfcomm_credit *credit;

        KKASSERT(rs != NULL);
        KKASSERT(LIST_EMPTY(&rs->rs_dlcs));

        rs->rs_state = RFCOMM_SESSION_CLOSED;

        /*
         * If the callout is already invoked we have no way to stop it,
         * but it will call us back right away (there are no DLC's) so
         * not to worry.
         */
        callout_stop(&rs->rs_timeout);
        if (callout_active(&rs->rs_timeout))
                return;

        /*
         * Take care that rfcomm_session_disconnected() doesnt call
         * us back either as it will do if the l2cap_channel has not
         * been closed when we detach it..
         */
        if (rs->rs_flags & RFCOMM_SESSION_FREE)
                return;

        rs->rs_flags |= RFCOMM_SESSION_FREE;

        /* throw away any remaining credit notes */
        while ((credit = STAILQ_FIRST(&rs->rs_credits)) != NULL) {
                STAILQ_REMOVE_HEAD(&rs->rs_credits, rc_next);
                zfree(rfcomm_credit_pool, credit);
        }

        KKASSERT(STAILQ_EMPTY(&rs->rs_credits));

        /* Goodbye! */
        LIST_REMOVE(rs, rs_next);
        l2cap_detach(&rs->rs_l2cap);
        kfree(rs, M_BLUETOOTH);
}

/*
 * rfcomm_session_lookup(sockaddr, sockaddr)
 *
 * Find active rfcomm session matching src and dest addresses
 * when src is BDADDR_ANY match any local address
 */
struct rfcomm_session *
rfcomm_session_lookup(struct sockaddr_bt *src, struct sockaddr_bt *dest)
{
        struct rfcomm_session *rs;
        struct sockaddr_bt addr;

        LIST_FOREACH(rs, &rfcomm_session_active, rs_next) {
                if (rs->rs_state == RFCOMM_SESSION_CLOSED)
                        continue;

                l2cap_sockaddr(rs->rs_l2cap, &addr);

                if (bdaddr_same(&src->bt_bdaddr, &addr.bt_bdaddr) == 0)
                        if (bdaddr_any(&src->bt_bdaddr) == 0)
                                continue;

                l2cap_peeraddr(rs->rs_l2cap, &addr);

                if (addr.bt_psm != dest->bt_psm)
                        continue;

                if (bdaddr_same(&dest->bt_bdaddr, &addr.bt_bdaddr))
                        break;
        }

        return rs;
}

/*
 * rfcomm_session_timeout(rfcomm_session)
 *
 * Session timeouts are scheduled when a session is left or
 * created with no DLCs, and when SABM(0) or DISC(0) are
 * sent.
 *
 * So, if it is in an open state with DLC's attached then
 * we leave it alone, otherwise the session is lost.
 */
void
rfcomm_session_timeout(void *arg)
{
        struct rfcomm_session *rs = arg;
        struct rfcomm_dlc *dlc;

        KKASSERT(rs != NULL);

        crit_enter();

        if (rs->rs_state != RFCOMM_SESSION_OPEN) {
                DPRINTF("timeout\n");
                rs->rs_state = RFCOMM_SESSION_CLOSED;

                while (!LIST_EMPTY(&rs->rs_dlcs)) {
                        dlc = LIST_FIRST(&rs->rs_dlcs);

                        rfcomm_dlc_close(dlc, ETIMEDOUT);
                }
        }

        if (LIST_EMPTY(&rs->rs_dlcs)) {
                DPRINTF("expiring\n");
                rfcomm_session_free(rs);
        }
        crit_exit();
}

/***********************************************************************
 *
 *      RFCOMM Session L2CAP protocol callbacks
 *
 */

static void
rfcomm_session_connecting(void *arg)
{
        /* struct rfcomm_session *rs = arg; */

        DPRINTF("Connecting\n");
}

static void
rfcomm_session_connected(void *arg)
{
        struct rfcomm_session *rs = arg;

        DPRINTF("Connected\n");

        /*
         * L2CAP is open.
         *
         * If we are initiator, we can send our SABM(0)
         * a timeout should be active?
         *
         * We must take note of the L2CAP MTU because currently
         * the L2CAP implementation can only do Basic Mode.
         */
        l2cap_getopt(rs->rs_l2cap, SO_L2CAP_OMTU, &rs->rs_mtu);

        rs->rs_mtu -= 6; /* (RFCOMM overhead could be this big) */
        if (rs->rs_mtu < RFCOMM_MTU_MIN) {
                rfcomm_session_disconnected(rs, EINVAL);
                return;
        }

        if (IS_INITIATOR(rs)) {
                int err;

                err = rfcomm_session_send_frame(rs, RFCOMM_FRAME_SABM, 0);
                if (err)
                        rfcomm_session_disconnected(rs, err);

                callout_reset(&rs->rs_timeout, rfcomm_ack_timeout * hz,
                    rfcomm_session_timeout, rs);
        }
}

static void
rfcomm_session_disconnected(void *arg, int err)
{
        struct rfcomm_session *rs = arg;
        struct rfcomm_dlc *dlc;

        DPRINTF("Disconnected\n");

        rs->rs_state = RFCOMM_SESSION_CLOSED;

        while (!LIST_EMPTY(&rs->rs_dlcs)) {
                dlc = LIST_FIRST(&rs->rs_dlcs);

                rfcomm_dlc_close(dlc, err);
        }

        rfcomm_session_free(rs);
}

static void *
rfcomm_session_newconn(void *arg, struct sockaddr_bt *laddr,
                                struct sockaddr_bt *raddr)
{
        struct rfcomm_session *new, *rs = arg;

        DPRINTF("New Connection\n");

        /*
         * Incoming session connect request. We should return a new
         * session pointer if this is acceptable. The L2CAP layer
         * passes local and remote addresses, which we must check as
         * only one RFCOMM session is allowed between any two devices
         */
        new = rfcomm_session_lookup(laddr, raddr);
        if (new != NULL)
                return NULL;

        new = rfcomm_session_alloc(&rfcomm_session_active, laddr);
        if (new == NULL)
                return NULL;

        new->rs_mtu = rs->rs_mtu;
        new->rs_state = RFCOMM_SESSION_WAIT_CONNECT;

        /*
         * schedule an expiry so that if nothing comes of it we
         * can punt.
         */
        callout_reset(&rs->rs_timeout, rfcomm_mcc_timeout * hz,
            rfcomm_session_timeout, rs);

        return new->rs_l2cap;
}

static void
rfcomm_session_complete(void *arg, int count)
{
        struct rfcomm_session *rs = arg;
        struct rfcomm_credit *credit;
        struct rfcomm_dlc *dlc;

        /*
         * count L2CAP packets are 'complete', meaning that they are cleared
         * our buffers (for best effort) or arrived safe (for guaranteed) so
         * we can take it off our list and pass the message on, so that
         * eventually the data can be removed from the sockbuf
         */
        while (count-- > 0) {
                credit = STAILQ_FIRST(&rs->rs_credits);
#ifdef DIAGNOSTIC
                if (credit == NULL) {
                        kprintf("%s: too many packets completed!\n", __func__);
                        break;
                }
#endif
                dlc = credit->rc_dlc;
                if (dlc != NULL) {
                        dlc->rd_pending--;
                        (*dlc->rd_proto->complete)
                                        (dlc->rd_upper, credit->rc_len);

                        /*
                         * if not using credit flow control, we may push
                         * more data now
                         */
                        if ((rs->rs_flags & RFCOMM_SESSION_CFC) == 0
                            && dlc->rd_state == RFCOMM_DLC_OPEN) {
                                rfcomm_dlc_start(dlc);
                        }

                        /*
                         * When shutdown is indicated, we are just waiting to
                         * clear outgoing data.
                         */
                        if ((dlc->rd_flags & RFCOMM_DLC_SHUTDOWN)
                            && dlc->rd_txbuf == NULL && dlc->rd_pending == 0) {
                                dlc->rd_state = RFCOMM_DLC_WAIT_DISCONNECT;
                                rfcomm_session_send_frame(rs, RFCOMM_FRAME_DISC,
                                                            dlc->rd_dlci);
                                callout_reset(&dlc->rd_timeout,
                                    rfcomm_ack_timeout * hz,
                                    rfcomm_dlc_timeout, dlc);
                        }
                }

                STAILQ_REMOVE_HEAD(&rs->rs_credits, rc_next);
                zfree(rfcomm_credit_pool, credit);
        }

        /*
         * If session is closed, we are just waiting to clear the queue
         */
        if (rs->rs_state == RFCOMM_SESSION_CLOSED) {
                if (STAILQ_EMPTY(&rs->rs_credits))
                        l2cap_disconnect(rs->rs_l2cap, 0);
        }
}

/*
 * Link Mode changed
 *
 * This is called when a mode change is complete. Proceed with connections
 * where appropriate, or pass the new mode to any active DLCs.
 */
static void
rfcomm_session_linkmode(void *arg, int new)
{
        struct rfcomm_session *rs = arg;
        struct rfcomm_dlc *dlc, *next;
        int err, mode = 0;

        DPRINTF("auth %s, encrypt %s, secure %s\n",
                (new & L2CAP_LM_AUTH ? "on" : "off"),
                (new & L2CAP_LM_ENCRYPT ? "on" : "off"),
                (new & L2CAP_LM_SECURE ? "on" : "off"));

        if (new & L2CAP_LM_AUTH)
                mode |= RFCOMM_LM_AUTH;

        if (new & L2CAP_LM_ENCRYPT)
                mode |= RFCOMM_LM_ENCRYPT;

        if (new & L2CAP_LM_SECURE)
                mode |= RFCOMM_LM_SECURE;

        next = LIST_FIRST(&rs->rs_dlcs);
        while ((dlc = next) != NULL) {
                next = LIST_NEXT(dlc, rd_next);

                switch (dlc->rd_state) {
                case RFCOMM_DLC_WAIT_SEND_SABM: /* we are connecting */
                        if ((mode & dlc->rd_mode) != dlc->rd_mode) {
                                rfcomm_dlc_close(dlc, ECONNABORTED);
                        } else {
                                err = rfcomm_session_send_frame(rs,
                                            RFCOMM_FRAME_SABM, dlc->rd_dlci);
                                if (err) {
                                        rfcomm_dlc_close(dlc, err);
                                } else {
                                        dlc->rd_state = RFCOMM_DLC_WAIT_RECV_UA;
                                        callout_reset(&dlc->rd_timeout,
                                            rfcomm_ack_timeout * hz,
                                            rfcomm_dlc_timeout, dlc);

                                        break;
                                }
                        }

                        /*
                         * If we aborted the connection and there are no more DLCs
                         * on the session, it is our responsibility to disconnect.
                         */
                        if (!LIST_EMPTY(&rs->rs_dlcs))
                                break;

                        rs->rs_state = RFCOMM_SESSION_WAIT_DISCONNECT;
                        rfcomm_session_send_frame(rs, RFCOMM_FRAME_DISC, 0);
                        callout_reset(&rs->rs_timeout, rfcomm_ack_timeout * hz,
                            rfcomm_session_timeout, rs);
                        break;

                case RFCOMM_DLC_WAIT_SEND_UA: /* they are connecting */
                        if ((mode & dlc->rd_mode) != dlc->rd_mode) {
                                rfcomm_session_send_frame(rs,
                                            RFCOMM_FRAME_DM, dlc->rd_dlci);
                                rfcomm_dlc_close(dlc, ECONNABORTED);
                                break;
                        }

                        err = rfcomm_session_send_frame(rs,
                                            RFCOMM_FRAME_UA, dlc->rd_dlci);
                        if (err) {
                                rfcomm_session_send_frame(rs,
                                                RFCOMM_FRAME_DM, dlc->rd_dlci);
                                rfcomm_dlc_close(dlc, err);
                                break;
                        }

                        err = rfcomm_dlc_open(dlc);
                        if (err) {
                                rfcomm_session_send_frame(rs,
                                                RFCOMM_FRAME_DM, dlc->rd_dlci);
                                rfcomm_dlc_close(dlc, err);
                                break;
                        }

                        break;

                case RFCOMM_DLC_WAIT_RECV_UA:
                case RFCOMM_DLC_OPEN: /* already established */
                        (*dlc->rd_proto->linkmode)(dlc->rd_upper, mode);
                        break;

                default:
                        break;
                }
        }
}

/*
 * Receive data from L2CAP layer for session. There is always exactly one
 * RFCOMM frame contained in each L2CAP frame.
 */
static void
rfcomm_session_input(void *arg, struct mbuf *m)
{
        struct rfcomm_session *rs = arg;
        int dlci, len, type, pf;
        uint8_t fcs, b;

        KKASSERT(m != NULL);
        KKASSERT(rs != NULL);

        /*
         * UIH frames: FCS is only calculated on address and control fields
         * For other frames: FCS is calculated on address, control and length
         * Length may extend to two octets
         */
        fcs = 0xff;

        if (m->m_pkthdr.len < 4) {
                DPRINTF("short frame (%d), discarded\n", m->m_pkthdr.len);
                goto done;
        }

        /* address - one octet */
        m_copydata(m, 0, 1, &b);
        m_adj(m, 1);
        fcs = FCS(fcs, b);
        dlci = RFCOMM_DLCI(b);

        /* control - one octet */
        m_copydata(m, 0, 1, &b);
        m_adj(m, 1);
        fcs = FCS(fcs, b);
        type = RFCOMM_TYPE(b);
        pf = RFCOMM_PF(b);

        /* length - may be two octets */
        m_copydata(m, 0, 1, &b);
        m_adj(m, 1);
        if (type != RFCOMM_FRAME_UIH)
                fcs = FCS(fcs, b);
        len = (b >> 1) & 0x7f;

        if (RFCOMM_EA(b) == 0) {
                if (m->m_pkthdr.len < 2) {
                        DPRINTF("short frame (%d, EA = 0), discarded\n",
                                m->m_pkthdr.len);
                        goto done;
                }

                m_copydata(m, 0, 1, &b);
                m_adj(m, 1);
                if (type != RFCOMM_FRAME_UIH)
                        fcs = FCS(fcs, b);

                len |= (b << 7);
        }

        /* FCS byte is last octet in frame */
        m_copydata(m, m->m_pkthdr.len - 1, 1, &b);
        m_adj(m, -1);
        fcs = FCS(fcs, b);

        if (fcs != 0xcf) {
                DPRINTF("Bad FCS value (%#2.2x), frame discarded\n", fcs);
                goto done;
        }

        DPRINTFN(10, "dlci %d, type %2.2x, len = %d\n", dlci, type, len);

        switch (type) {
        case RFCOMM_FRAME_SABM:
                if (pf)
                        rfcomm_session_recv_sabm(rs, dlci);
                break;

        case RFCOMM_FRAME_DISC:
                if (pf)
                        rfcomm_session_recv_disc(rs, dlci);
                break;

        case RFCOMM_FRAME_UA:
                if (pf)
                        rfcomm_session_recv_ua(rs, dlci);
                break;

        case RFCOMM_FRAME_DM:
                rfcomm_session_recv_dm(rs, dlci);
                break;

        case RFCOMM_FRAME_UIH:
                rfcomm_session_recv_uih(rs, dlci, pf, m, len);
                return; /* (no release) */

        default:
                UNKNOWN(type);
                break;
        }

done:
        m_freem(m);
}

/***********************************************************************
 *
 *      RFCOMM Session receive processing
 */

/*
 * rfcomm_session_recv_sabm(rfcomm_session, dlci)
 *
 * Set Asyncrhonous Balanced Mode - open the channel.
 */
static void
rfcomm_session_recv_sabm(struct rfcomm_session *rs, int dlci)
{
        struct rfcomm_dlc *dlc;
        int err;

        DPRINTFN(5, "SABM(%d)\n", dlci);

        if (dlci == 0) {        /* Open Session */
                rs->rs_state = RFCOMM_SESSION_OPEN;
                rfcomm_session_send_frame(rs, RFCOMM_FRAME_UA, 0);
                LIST_FOREACH(dlc, &rs->rs_dlcs, rd_next) {
                        if (dlc->rd_state == RFCOMM_DLC_WAIT_SESSION)
                                rfcomm_dlc_connect(dlc);
                }
                return;
        }

        if (rs->rs_state != RFCOMM_SESSION_OPEN) {
                DPRINTF("session was not even open!\n");
                return;
        }

        /* validate direction bit */
        if ((IS_INITIATOR(rs) && !RFCOMM_DIRECTION(dlci))
            || (!IS_INITIATOR(rs) && RFCOMM_DIRECTION(dlci))) {
                DPRINTF("Invalid direction bit on DLCI\n");
                return;
        }

        /*
         * look for our DLC - this may exist if we received PN
         * already, or we may have to fabricate a new one.
         */
        dlc = rfcomm_dlc_lookup(rs, dlci);
        if (dlc == NULL) {
                dlc = rfcomm_dlc_newconn(rs, dlci);
                if (dlc == NULL)
                        return; /* (DM is sent) */
        }

        /*
         * ..but if this DLC is not waiting to connect, they did
         * something wrong, ignore it.
         */
        if (dlc->rd_state != RFCOMM_DLC_WAIT_CONNECT)
                return;

        /* set link mode */
        err = rfcomm_dlc_setmode(dlc);
        if (err == EINPROGRESS) {
                dlc->rd_state = RFCOMM_DLC_WAIT_SEND_UA;
                (*dlc->rd_proto->connecting)(dlc->rd_upper);
                return;
        }
        if (err)
                goto close;

        err = rfcomm_session_send_frame(rs, RFCOMM_FRAME_UA, dlci);
        if (err)
                goto close;

        /* and mark it open */
        err = rfcomm_dlc_open(dlc);
        if (err)
                goto close;

        return;

close:
        rfcomm_dlc_close(dlc, err);
}

/*
 * Receive Disconnect Command
 */
static void
rfcomm_session_recv_disc(struct rfcomm_session *rs, int dlci)
{
        struct rfcomm_dlc *dlc;

        DPRINTFN(5, "DISC(%d)\n", dlci);

        if (dlci == 0) {
                /*
                 * Disconnect Session
                 *
                 * We set the session state to CLOSED so that when
                 * the UA frame is clear the session will be closed
                 * automatically. We wont bother to close any DLC's
                 * just yet as there should be none. In the unlikely
                 * event that something is left, it will get flushed
                 * out as the session goes down.
                 */
                rfcomm_session_send_frame(rs, RFCOMM_FRAME_UA, 0);
                rs->rs_state = RFCOMM_SESSION_CLOSED;
                return;
        }

        dlc = rfcomm_dlc_lookup(rs, dlci);
        if (dlc == NULL) {
                rfcomm_session_send_frame(rs, RFCOMM_FRAME_DM, dlci);
                return;
        }

        rfcomm_dlc_close(dlc, ECONNRESET);
        rfcomm_session_send_frame(rs, RFCOMM_FRAME_UA, dlci);
}

/*
 * Receive Unnumbered Acknowledgement Response
 *
 * This should be a response to a DISC or SABM frame that we
 * have previously sent. If unexpected, ignore it.
 */
static void
rfcomm_session_recv_ua(struct rfcomm_session *rs, int dlci)
{
        struct rfcomm_dlc *dlc;

        DPRINTFN(5, "UA(%d)\n", dlci);

        if (dlci == 0) {
                switch (rs->rs_state) {
                case RFCOMM_SESSION_WAIT_CONNECT:       /* We sent SABM */
                        callout_stop(&rs->rs_timeout);
                        rs->rs_state = RFCOMM_SESSION_OPEN;
                        LIST_FOREACH(dlc, &rs->rs_dlcs, rd_next) {
                                if (dlc->rd_state == RFCOMM_DLC_WAIT_SESSION)
                                        rfcomm_dlc_connect(dlc);
                        }
                        break;

                case RFCOMM_SESSION_WAIT_DISCONNECT:    /* We sent DISC */
                        callout_stop(&rs->rs_timeout);
                        rs->rs_state = RFCOMM_SESSION_CLOSED;
                        l2cap_disconnect(rs->rs_l2cap, 0);
                        break;

                default:
                        DPRINTF("Received spurious UA(0)!\n");
                        break;
                }

                return;
        }

        /*
         * If we have no DLC on this dlci, we may have aborted
         * without shutting down properly, so check if the session
         * needs disconnecting.
         */
        dlc = rfcomm_dlc_lookup(rs, dlci);
        if (dlc == NULL)
                goto check;

        switch (dlc->rd_state) {
        case RFCOMM_DLC_WAIT_RECV_UA:           /* We sent SABM */
                rfcomm_dlc_open(dlc);
                return;

        case RFCOMM_DLC_WAIT_DISCONNECT:        /* We sent DISC */
                rfcomm_dlc_close(dlc, 0);
                break;

        default:
                DPRINTF("Received spurious UA(%d)!\n", dlci);
                return;
        }

check:  /* last one out turns out the light */
        if (LIST_EMPTY(&rs->rs_dlcs)) {
                rs->rs_state = RFCOMM_SESSION_WAIT_DISCONNECT;
                rfcomm_session_send_frame(rs, RFCOMM_FRAME_DISC, 0);
                callout_reset(&rs->rs_timeout, rfcomm_ack_timeout*hz,rfcomm_session_timeout,rs);
        }
}

/*
 * Receive Disconnected Mode Response
 *
 * If this does not apply to a known DLC then we may ignore it.
 */
static void
rfcomm_session_recv_dm(struct rfcomm_session *rs, int dlci)
{
        struct rfcomm_dlc *dlc;

        DPRINTFN(5, "DM(%d)\n", dlci);

        dlc = rfcomm_dlc_lookup(rs, dlci);
        if (dlc == NULL)
                return;

        if (dlc->rd_state == RFCOMM_DLC_WAIT_CONNECT)
                rfcomm_dlc_close(dlc, ECONNREFUSED);
        else
                rfcomm_dlc_close(dlc, ECONNRESET);
}

/*
 * Receive Unnumbered Information with Header check (MCC or data packet)
 */
static void
rfcomm_session_recv_uih(struct rfcomm_session *rs, int dlci,
                        int pf, struct mbuf *m, int len)
{
        struct rfcomm_dlc *dlc;
        uint8_t credits = 0;

        DPRINTFN(10, "UIH(%d)\n", dlci);

        if (dlci == 0) {
                rfcomm_session_recv_mcc(rs, m);
                return;
        }

        if (m->m_pkthdr.len != len + pf) {
                DPRINTF("Bad Frame Length (%d), frame discarded\n",
                            m->m_pkthdr.len);

                goto discard;
        }

        dlc = rfcomm_dlc_lookup(rs, dlci);
        if (dlc == NULL) {
                DPRINTF("UIH received for non existent DLC, discarded\n");
                rfcomm_session_send_frame(rs, RFCOMM_FRAME_DM, dlci);
                goto discard;
        }

        if (dlc->rd_state != RFCOMM_DLC_OPEN) {
                DPRINTF("non-open DLC (state = %d), discarded\n",
                                dlc->rd_state);
                goto discard;
        }

        /* if PF is set, credits were included */
        if (rs->rs_flags & RFCOMM_SESSION_CFC) {
                if (pf != 0) {
                        if (m->m_pkthdr.len < sizeof(credits)) {
                                DPRINTF("Bad PF value, UIH discarded\n");
                                goto discard;
                        }

                        m_copydata(m, 0, sizeof(credits), &credits);
                        m_adj(m, sizeof(credits));

                        dlc->rd_txcred += credits;

                        if (credits > 0 && dlc->rd_txbuf != NULL)
                                rfcomm_dlc_start(dlc);
                }

                if (len == 0)
                        goto discard;

                if (dlc->rd_rxcred == 0) {
                        DPRINTF("Credit limit reached, UIH discarded\n");
                        goto discard;
                }

                if (len > dlc->rd_rxsize) {
                        DPRINTF("UIH frame exceeds rxsize, discarded\n");
                        goto discard;
                }

                dlc->rd_rxcred--;
                dlc->rd_rxsize -= len;
        }

        (*dlc->rd_proto->input)(dlc->rd_upper, m);
        return;

discard:
        m_freem(m);
}

/*
 * Receive Multiplexer Control Command
 */
static void
rfcomm_session_recv_mcc(struct rfcomm_session *rs, struct mbuf *m)
{
        int type, cr, len;
        uint8_t b;

        /*
         * Extract MCC header.
         *
         * Fields are variable length using extension bit = 1 to signify the
         * last octet in the sequence.
         *
         * Only single octet types are defined in TS 07.10/RFCOMM spec
         *
         * Length can realistically only use 15 bits (max RFCOMM MTU)
         */
        if (m->m_pkthdr.len < sizeof(b)) {
                DPRINTF("Short MCC header, discarded\n");
                goto release;
        }

        m_copydata(m, 0, sizeof(b), &b);
        m_adj(m, sizeof(b));

        if (RFCOMM_EA(b) == 0) {        /* verify no extensions */
                DPRINTF("MCC type EA = 0, discarded\n");
                goto release;
        }

        type = RFCOMM_MCC_TYPE(b);
        cr = RFCOMM_CR(b);

        len = 0;
        do {
                if (m->m_pkthdr.len < sizeof(b)) {
                        DPRINTF("Short MCC header, discarded\n");
                        goto release;
                }

                m_copydata(m, 0, sizeof(b), &b);
                m_adj(m, sizeof(b));

                len = (len << 7) | (b >> 1);
                len = min(len, RFCOMM_MTU_MAX);
        } while (RFCOMM_EA(b) == 0);

        if (len != m->m_pkthdr.len) {
                DPRINTF("Incorrect MCC length, discarded\n");
                goto release;
        }

        DPRINTFN(2, "MCC %s type %2.2x (%d bytes)\n",
                (cr ? "command" : "response"), type, len);

        /*
         * pass to command handler
         */
        switch(type) {
        case RFCOMM_MCC_TEST:   /* Test */
                rfcomm_session_recv_mcc_test(rs, cr, m);
                break;

        case RFCOMM_MCC_FCON:   /* Flow Control On */
                rfcomm_session_recv_mcc_fcon(rs, cr);
                break;

        case RFCOMM_MCC_FCOFF:  /* Flow Control Off */
                rfcomm_session_recv_mcc_fcoff(rs, cr);
                break;

        case RFCOMM_MCC_MSC:    /* Modem Status Command */
                rfcomm_session_recv_mcc_msc(rs, cr, m);
                break;

        case RFCOMM_MCC_RPN:    /* Remote Port Negotiation */
                rfcomm_session_recv_mcc_rpn(rs, cr, m);
                break;

        case RFCOMM_MCC_RLS:    /* Remote Line Status */
                rfcomm_session_recv_mcc_rls(rs, cr, m);
                break;

        case RFCOMM_MCC_PN:     /* Parameter Negotiation */
                rfcomm_session_recv_mcc_pn(rs, cr, m);
                break;

        case RFCOMM_MCC_NSC:    /* Non Supported Command */
                rfcomm_session_recv_mcc_nsc(rs, cr, m);
                break;

        default:
                b = RFCOMM_MKMCC_TYPE(cr, type);
                rfcomm_session_send_mcc(rs, 0, RFCOMM_MCC_NSC, &b, sizeof(b));
        }

release:
        m_freem(m);
}

/*
 * process TEST command/response
 */
static void
rfcomm_session_recv_mcc_test(struct rfcomm_session *rs, int cr, struct mbuf *m)
{
        void *data;
        int len;

        if (cr == 0)    /* ignore ack */
                return;

        /*
         * we must send all the data they included back as is
         */

        len = m->m_pkthdr.len;
        if (len > RFCOMM_MTU_MAX)
                return;

        data = kmalloc(len, M_BLUETOOTH, M_NOWAIT);
        if (data == NULL)
                return;

        m_copydata(m, 0, len, data);
        rfcomm_session_send_mcc(rs, 0, RFCOMM_MCC_TEST, data, len);
        kfree(data, M_BLUETOOTH);
}

/*
 * process Flow Control ON command/response
 */
static void
rfcomm_session_recv_mcc_fcon(struct rfcomm_session *rs, int cr)
{

        if (cr == 0)    /* ignore ack */
                return;

        rs->rs_flags |= RFCOMM_SESSION_RFC;
        rfcomm_session_send_mcc(rs, 0, RFCOMM_MCC_FCON, NULL, 0);
}

/*
 * process Flow Control OFF command/response
 */
static void
rfcomm_session_recv_mcc_fcoff(struct rfcomm_session *rs, int cr)
{
        if (cr == 0)    /* ignore ack */
                return;

        rs->rs_flags &= ~RFCOMM_SESSION_RFC;
        rfcomm_session_send_mcc(rs, 0, RFCOMM_MCC_FCOFF, NULL, 0);
}

/*
 * process Modem Status Command command/response
 */
static void
rfcomm_session_recv_mcc_msc(struct rfcomm_session *rs, int cr, struct mbuf *m)
{
        struct rfcomm_mcc_msc msc;      /* (3 octets) */
        struct rfcomm_dlc *dlc;
        int len = 0;

        /* [ADDRESS] */
        if (m->m_pkthdr.len < sizeof(msc.address))
                return;

        m_copydata(m, 0, sizeof(msc.address), &msc.address);
        m_adj(m, sizeof(msc.address));
        len += sizeof(msc.address);

        dlc = rfcomm_dlc_lookup(rs, RFCOMM_DLCI(msc.address));

        if (cr == 0) {  /* ignore acks */
                if (dlc != NULL)
                        callout_stop(&dlc->rd_timeout);

                return;
        }

        if (dlc == NULL) {
                rfcomm_session_send_frame(rs, RFCOMM_FRAME_DM,
                                                RFCOMM_DLCI(msc.address));
                return;
        }

        /* [SIGNALS] */
        if (m->m_pkthdr.len < sizeof(msc.modem))
                return;

        m_copydata(m, 0, sizeof(msc.modem), &msc.modem);
        m_adj(m, sizeof(msc.modem));
        len += sizeof(msc.modem);

        dlc->rd_rmodem = msc.modem;
        /* XXX how do we signal this upstream? */

        if (RFCOMM_EA(msc.modem) == 0) {
                if (m->m_pkthdr.len < sizeof(msc.brk))
                        return;

                m_copydata(m, 0, sizeof(msc.brk), &msc.brk);
                m_adj(m, sizeof(msc.brk));
                len += sizeof(msc.brk);

                /* XXX how do we signal this upstream? */
        }

        rfcomm_session_send_mcc(rs, 0, RFCOMM_MCC_MSC, &msc, len);
}

/*
 * process Remote Port Negotiation command/response
 */
static void
rfcomm_session_recv_mcc_rpn(struct rfcomm_session *rs, int cr, struct mbuf *m)
{
        struct rfcomm_mcc_rpn rpn;
        uint16_t mask;

        if (cr == 0)    /* ignore ack */
                return;

        /* default values */
        rpn.bit_rate = RFCOMM_RPN_BR_9600;
        rpn.line_settings = RFCOMM_RPN_8_N_1;
        rpn.flow_control = RFCOMM_RPN_FLOW_NONE;
        rpn.xon_char = RFCOMM_RPN_XON_CHAR;
        rpn.xoff_char = RFCOMM_RPN_XOFF_CHAR;

        if (m->m_pkthdr.len == sizeof(rpn)) {
                m_copydata(m, 0, sizeof(rpn), (caddr_t)&rpn);
                rpn.param_mask = RFCOMM_RPN_PM_ALL;
        } else if (m->m_pkthdr.len == 1) {
                m_copydata(m, 0, 1, (caddr_t)&rpn);
                rpn.param_mask = letoh16(rpn.param_mask);
        } else {
                DPRINTF("Bad RPN length (%d)\n", m->m_pkthdr.len);
                return;
        }

        mask = 0;

        if (rpn.param_mask & RFCOMM_RPN_PM_RATE)
                mask |= RFCOMM_RPN_PM_RATE;

        if (rpn.param_mask & RFCOMM_RPN_PM_DATA
            && RFCOMM_RPN_DATA_BITS(rpn.line_settings) == RFCOMM_RPN_DATA_8)
                mask |= RFCOMM_RPN_PM_DATA;

        if (rpn.param_mask & RFCOMM_RPN_PM_STOP
            && RFCOMM_RPN_STOP_BITS(rpn.line_settings) == RFCOMM_RPN_STOP_1)
                mask |= RFCOMM_RPN_PM_STOP;

        if (rpn.param_mask & RFCOMM_RPN_PM_PARITY
            && RFCOMM_RPN_PARITY(rpn.line_settings) == RFCOMM_RPN_PARITY_NONE)
                mask |= RFCOMM_RPN_PM_PARITY;

        if (rpn.param_mask & RFCOMM_RPN_PM_XON
            && rpn.xon_char == RFCOMM_RPN_XON_CHAR)
                mask |= RFCOMM_RPN_PM_XON;

        if (rpn.param_mask & RFCOMM_RPN_PM_XOFF
            && rpn.xoff_char == RFCOMM_RPN_XOFF_CHAR)
                mask |= RFCOMM_RPN_PM_XOFF;

        if (rpn.param_mask & RFCOMM_RPN_PM_FLOW
            && rpn.flow_control == RFCOMM_RPN_FLOW_NONE)
                mask |= RFCOMM_RPN_PM_FLOW;

        rpn.param_mask = htole16(mask);

        rfcomm_session_send_mcc(rs, 0, RFCOMM_MCC_RPN, &rpn, sizeof(rpn));
}

/*
 * process Remote Line Status command/response
 */
static void
rfcomm_session_recv_mcc_rls(struct rfcomm_session *rs, int cr, struct mbuf *m)
{
        struct rfcomm_mcc_rls rls;

        if (cr == 0)    /* ignore ack */
                return;

        if (m->m_pkthdr.len != sizeof(rls)) {
                DPRINTF("Bad RLS length %d\n", m->m_pkthdr.len);
                return;
        }

        m_copydata(m, 0, sizeof(rls), (caddr_t)&rls);

        /*
         * So far as I can tell, we just send back what
         * they sent us. This signifies errors that seem
         * irrelevent for RFCOMM over L2CAP.
         */
        rls.address |= 0x03;    /* EA = 1, CR = 1 */
        rls.status &= 0x0f;     /* only 4 bits valid */

        rfcomm_session_send_mcc(rs, 0, RFCOMM_MCC_RLS, &rls, sizeof(rls));
}

/*
 * process Parameter Negotiation command/response
 */
static void
rfcomm_session_recv_mcc_pn(struct rfcomm_session *rs, int cr, struct mbuf *m)
{
        struct rfcomm_dlc *dlc;
        struct rfcomm_mcc_pn pn;
        int err;

        if (m->m_pkthdr.len != sizeof(pn)) {
                DPRINTF("Bad PN length %d\n", m->m_pkthdr.len);
                return;
        }

        m_copydata(m, 0, sizeof(pn), (caddr_t)&pn);

        pn.dlci &= 0x3f;
        pn.mtu = letoh16(pn.mtu);

        dlc = rfcomm_dlc_lookup(rs, pn.dlci);
        if (cr) {       /* Command */
                /*
                 * If there is no DLC present, this is a new
                 * connection so attempt to make one
                 */
                if (dlc == NULL) {
                        dlc = rfcomm_dlc_newconn(rs, pn.dlci);
                        if (dlc == NULL)
                                return; /* (DM is sent) */
                }

                /* accept any valid MTU, and offer it back */
                pn.mtu = min(pn.mtu, RFCOMM_MTU_MAX);
                pn.mtu = min(pn.mtu, rs->rs_mtu);
                pn.mtu = max(pn.mtu, RFCOMM_MTU_MIN);
                dlc->rd_mtu = pn.mtu;
                pn.mtu = htole16(pn.mtu);

                /* credits are only set before DLC is open */
                if (dlc->rd_state == RFCOMM_DLC_WAIT_CONNECT
                    && (pn.flow_control & 0xf0) == 0xf0) {
                        rs->rs_flags |= RFCOMM_SESSION_CFC;
                        dlc->rd_txcred = pn.credits & 0x07;

                        dlc->rd_rxcred = (dlc->rd_rxsize / dlc->rd_mtu);
                        dlc->rd_rxcred = min(dlc->rd_rxcred,
                                                RFCOMM_CREDITS_DEFAULT);

                        pn.flow_control = 0xe0;
                        pn.credits = dlc->rd_rxcred;
                } else {
                        pn.flow_control = 0x00;
                        pn.credits = 0x00;
                }

                /* unused fields must be ignored and set to zero */
                pn.ack_timer = 0;
                pn.max_retrans = 0;

                /* send our response */
                err = rfcomm_session_send_mcc(rs, 0,
                                        RFCOMM_MCC_PN, &pn, sizeof(pn));
                if (err)
                        goto close;

        } else {        /* Response */
                /* ignore responses with no matching DLC */
                if (dlc == NULL)
                        return;

                callout_stop(&dlc->rd_timeout);

                if (pn.mtu > RFCOMM_MTU_MAX || pn.mtu > dlc->rd_mtu) {
                        dlc->rd_state = RFCOMM_DLC_WAIT_DISCONNECT;
                        err = rfcomm_session_send_frame(rs, RFCOMM_FRAME_DISC,
                                                        pn.dlci);
                        if (err)
                                goto close;

                        callout_reset(&dlc->rd_timeout, rfcomm_ack_timeout * hz,
                                    rfcomm_dlc_timeout, dlc);
                        return;
                }
                dlc->rd_mtu = pn.mtu;

                /* if DLC is not waiting to connect, we are done */
                if (dlc->rd_state != RFCOMM_DLC_WAIT_CONNECT)
                        return;

                /* set initial credits according to RFCOMM spec */
                if ((pn.flow_control & 0xf0) == 0xe0) {
                        rs->rs_flags |= RFCOMM_SESSION_CFC;
                        dlc->rd_txcred = (pn.credits & 0x07);
                }

                callout_reset(&dlc->rd_timeout, rfcomm_ack_timeout * hz,
                                    rfcomm_dlc_timeout, dlc);

                /* set link mode */
                err = rfcomm_dlc_setmode(dlc);
                if (err == EINPROGRESS) {
                        dlc->rd_state = RFCOMM_DLC_WAIT_SEND_SABM;
                        (*dlc->rd_proto->connecting)(dlc->rd_upper);
                        return;
                }
                if (err)
                        goto close;

                /* we can proceed now */
                err = rfcomm_session_send_frame(rs, RFCOMM_FRAME_SABM, pn.dlci);
                if (err)
                        goto close;

                dlc->rd_state = RFCOMM_DLC_WAIT_RECV_UA;
        }
        return;

close:
        rfcomm_dlc_close(dlc, err);
}

/*
 * process Non Supported Command command/response
 */
static void
rfcomm_session_recv_mcc_nsc(struct rfcomm_session *rs,
    int cr, struct mbuf *m)
{
        struct rfcomm_dlc *dlc, *next;

        /*
         * Since we did nothing that is not mandatory,
         * we just abort the whole session..
         */

        next = LIST_FIRST(&rs->rs_dlcs);
        while ((dlc = next) != NULL) {
                next = LIST_NEXT(dlc, rd_next);
                rfcomm_dlc_close(dlc, ECONNABORTED);
        }

        rfcomm_session_free(rs);
}

/***********************************************************************
 *
 *      RFCOMM Session outward frame/uih/mcc building
 */

/*
 * SABM/DISC/DM/UA frames are all minimal and mostly identical.
 */
int
rfcomm_session_send_frame(struct rfcomm_session *rs, int type, int dlci)
{
        struct rfcomm_cmd_hdr *hdr;
        struct rfcomm_credit *credit;
        struct mbuf *m;
        uint8_t fcs, cr;

        credit = zalloc(rfcomm_credit_pool);
        if (credit == NULL)
                return ENOMEM;

        m = m_gethdr(M_NOWAIT, MT_DATA);
        if (m == NULL) {
                zfree(rfcomm_credit_pool, credit);
                return ENOMEM;
        }

        /*
         * The CR (command/response) bit identifies the frame either as a
         * commmand or a response and is used along with the DLCI to form
         * the address. Commands contain the non-initiator address, whereas
         * responses contain the initiator address, so the CR value is
         * also dependent on the session direction.
         */
        if (type == RFCOMM_FRAME_UA || type == RFCOMM_FRAME_DM)
                cr = IS_INITIATOR(rs) ? 0 : 1;
        else
                cr = IS_INITIATOR(rs) ? 1 : 0;

        hdr = mtod(m, struct rfcomm_cmd_hdr *);
        hdr->address = RFCOMM_MKADDRESS(cr, dlci);
        hdr->control = RFCOMM_MKCONTROL(type, 1);   /* PF = 1 */
        hdr->length = (0x00 << 1) | 0x01;           /* len = 0x00, EA = 1 */

        fcs = 0xff;
        fcs = FCS(fcs, hdr->address);
        fcs = FCS(fcs, hdr->control);
        fcs = FCS(fcs, hdr->length);
        fcs = 0xff - fcs;       /* ones complement */
        hdr->fcs = fcs;

        m->m_pkthdr.len = m->m_len = sizeof(struct rfcomm_cmd_hdr);

        /* empty credit note */
        credit->rc_dlc = NULL;
        credit->rc_len = m->m_pkthdr.len;
        STAILQ_INSERT_TAIL(&rs->rs_credits, credit, rc_next);

        DPRINTFN(5, "dlci %d type %2.2x (%d bytes, fcs=%#2.2x)\n",
                dlci, type, m->m_pkthdr.len, fcs);

        return l2cap_send(rs->rs_l2cap, m);
}

/*
 * rfcomm_session_send_uih(rfcomm_session, rfcomm_dlc, credits, mbuf)
 *
 * UIH frame is per DLC data or Multiplexer Control Commands
 * when no DLC is given. Data mbuf is optional (just credits
 * will be sent in that case)
 */
int
rfcomm_session_send_uih(struct rfcomm_session *rs, struct rfcomm_dlc *dlc,
                        int credits, struct mbuf *m)
{
        struct rfcomm_credit *credit;
        struct mbuf *m0 = NULL;
        int err, len;
        uint8_t fcs, *hdr;

        KKASSERT(rs != NULL);

        len = (m == NULL) ? 0 : m->m_pkthdr.len;
        KKASSERT(!(credits == 0 && len == 0));

        /*
         * Make a credit note for the completion notification
         */
        credit = zalloc(rfcomm_credit_pool);
        if (credit == NULL)
                goto nomem;

        credit->rc_len = len;
        credit->rc_dlc = dlc;

        /*
         * Wrap UIH frame information around payload.
         *
         * [ADDRESS] [CONTROL] [LENGTH] [CREDITS] [...] [FCS]
         *
         * Address is one octet.
         * Control is one octet.
         * Length is one or two octets.
         * Credits may be one octet.
         *
         * FCS is one octet and calculated on address and
         *      control octets only.
         *
         * If there are credits to be sent, we will set the PF
         * flag and include them in the frame.
         */
        m0 = m_gethdr(M_NOWAIT, MT_DATA);
        if (m0 == NULL)
                goto nomem;

        MH_ALIGN(m0, 5);        /* (max 5 header octets) */
        hdr = mtod(m0, uint8_t *);

        /* CR bit is set according to the initiator of the session */
        *hdr = RFCOMM_MKADDRESS((IS_INITIATOR(rs) ? 1 : 0),
                                (dlc ? dlc->rd_dlci : 0));
        fcs = FCS(0xff, *hdr);
        hdr++;

        /* PF bit is set if credits are being sent */
        *hdr = RFCOMM_MKCONTROL(RFCOMM_FRAME_UIH, (credits > 0 ? 1 : 0));
        fcs = FCS(fcs, *hdr);
        hdr++;

        if (len < (1 << 7)) {
                *hdr++ = ((len << 1) & 0xfe) | 0x01;    /* 7 bits, EA = 1 */
        } else {
                *hdr++ = ((len << 1) & 0xfe);           /* 7 bits, EA = 0 */
                *hdr++ = ((len >> 7) & 0xff);           /* 8 bits, no EA */
        }

        if (credits > 0)
                *hdr++ = (uint8_t)credits;

        m0->m_len = hdr - mtod(m0, uint8_t *);

        /* Append payload */
        m0->m_next = m;
        m = NULL;

        m0->m_pkthdr.len = m0->m_len + len;

        /* Append FCS */
        fcs = 0xff - fcs;       /* ones complement */
        len = m0->m_pkthdr.len;
        m_copyback(m0, len, sizeof(fcs), &fcs);
        if (m0->m_pkthdr.len != len + sizeof(fcs))
                goto nomem;

        DPRINTFN(10, "dlci %d, pktlen %d (%d data, %d credits), fcs=%#2.2x\n",
                dlc ? dlc->rd_dlci : 0, m0->m_pkthdr.len, credit->rc_len,
                credits, fcs);

        /*
         * UIH frame ready to go..
         */
        err = l2cap_send(rs->rs_l2cap, m0);
        if (err)
                goto fail;

        STAILQ_INSERT_TAIL(&rs->rs_credits, credit, rc_next);
        return 0;

nomem:
        err = ENOMEM;

        if (m0 != NULL)
                m_freem(m0);

        if (m != NULL)
                m_freem(m);

fail:
        if (credit != NULL)
                zfree(rfcomm_credit_pool, credit);

        return err;
}

/*
 * send Multiplexer Control Command (or Response) on session
 */
int
rfcomm_session_send_mcc(struct rfcomm_session *rs, int cr,
                        uint8_t type, void *data, int len)
{
        struct mbuf *m;
        uint8_t *hdr;
        int hlen;

        m = m_gethdr(M_NOWAIT, MT_DATA);
        if (m == NULL)
                return ENOMEM;

        hdr = mtod(m, uint8_t *);

        /*
         * Technically the type field can extend past one octet, but none
         * currently defined will do that.
         */
        *hdr++ = RFCOMM_MKMCC_TYPE(cr, type);

        /*
         * In the frame, the max length size is 2 octets (15 bits) whereas
         * no max length size is specified for MCC commands. We must allow
         * for 3 octets since for MCC frames we use 7 bits + EA in each.
         *
         * Only test data can possibly be that big.
         *
         * XXX Should we check this against the MTU?
         */
        if (len < (1 << 7)) {
                *hdr++ = ((len << 1) & 0xfe) | 0x01;    /* 7 bits, EA = 1 */
        } else if (len < (1 << 14)) {
                *hdr++ = ((len << 1) & 0xfe);           /* 7 bits, EA = 0 */
                *hdr++ = ((len >> 6) & 0xfe) | 0x01;    /* 7 bits, EA = 1 */
        } else if (len < (1 << 15)) {
                *hdr++ = ((len << 1) & 0xfe);           /* 7 bits, EA = 0 */
                *hdr++ = ((len >> 6) & 0xfe);           /* 7 bits, EA = 0 */
                *hdr++ = ((len >> 13) & 0x02) | 0x01;   /* 1 bit,  EA = 1 */
        } else {
                DPRINTF("incredible length! (%d)\n", len);
                m_freem(m);
                return EMSGSIZE;
        }

        /*
         * add command data (to same mbuf if possible)
         */
        hlen = hdr - mtod(m, uint8_t *);

        if (len > 0) {
                m->m_pkthdr.len = m->m_len = MHLEN;
                m_copyback(m, hlen, len, data);
                if (m->m_pkthdr.len != max(MHLEN, hlen + len)) {
                        m_freem(m);
                        return ENOMEM;
                }
        }

        m->m_pkthdr.len = hlen + len;
        m->m_len = min(MHLEN, m->m_pkthdr.len);

        DPRINTFN(5, "%s type %2.2x len %d\n",
                (cr ? "command" : "response"), type, m->m_pkthdr.len);

        return rfcomm_session_send_uih(rs, NULL, 0, m);
}