stack/rfcomm/rfc_ts_frames.c

/******************************************************************************
 *
 *  Copyright (C) 1999-2012 Broadcom Corporation
 *
 *  Licensed under the Apache License, Version 2.0 (the "License");
 *  you may not use this file except in compliance with the License.
 *  You may obtain a copy of the License at:
 *
 *  http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 *
 ******************************************************************************/

/******************************************************************************
 *
 *  This file contains functions to send TS 07.10 frames
 *
 ******************************************************************************/
#include "bt_target.h"
#include "gki.h"
#include "rfcdefs.h"
#include "port_api.h"
#include "l2c_api.h"
#include "port_int.h"
#include "rfc_int.h"

/*******************************************************************************
**
** Function         rfc_send_sabme
**
** Description      This function sends SABME frame.
**
*******************************************************************************/
void rfc_send_sabme (tRFC_MCB *p_mcb, UINT8 dlci)
{
    BT_HDR  *p_buf;
    UINT8   *p_data;
    UINT8   cr = RFCOMM_CR(p_mcb->is_initiator, TRUE);

    if ((p_buf = (BT_HDR *)GKI_getpoolbuf (RFCOMM_CMD_POOL_ID)) == NULL)
        return;

    p_buf->offset = L2CAP_MIN_OFFSET;
    p_data = (UINT8 *)(p_buf + 1) + L2CAP_MIN_OFFSET;

    /* SABME frame, command, PF = 1, dlci */
    *p_data++ = RFCOMM_EA | cr | (dlci << RFCOMM_SHIFT_DLCI);
    *p_data++ = RFCOMM_SABME | RFCOMM_PF;
    *p_data++ = RFCOMM_EA | 0;

    *p_data   = RFCOMM_SABME_FCS ((UINT8 *)(p_buf + 1) + L2CAP_MIN_OFFSET, cr, dlci);

    p_buf->len = 4;

    rfc_check_send_cmd(p_mcb, p_buf);
}


/*******************************************************************************
**
** Function         rfc_send_ua
**
** Description      This function sends UA frame.
**
*******************************************************************************/
void rfc_send_ua (tRFC_MCB *p_mcb, UINT8 dlci)
{
    BT_HDR  *p_buf;
    UINT8   *p_data;
    UINT8   cr = RFCOMM_CR(p_mcb->is_initiator, FALSE);

    if ((p_buf = (BT_HDR *)GKI_getpoolbuf (RFCOMM_CMD_POOL_ID)) == NULL)
        return;

    p_buf->offset = L2CAP_MIN_OFFSET;
    p_data = (UINT8 *)(p_buf + 1) + L2CAP_MIN_OFFSET;

    /* ua frame, response, PF = 1, dlci */
    *p_data++ = RFCOMM_EA | cr | (dlci << RFCOMM_SHIFT_DLCI);
    *p_data++ = RFCOMM_UA | RFCOMM_PF;
    *p_data++ = RFCOMM_EA | 0;

    *p_data   = RFCOMM_UA_FCS ((UINT8 *)(p_buf + 1) + L2CAP_MIN_OFFSET, cr, dlci);

    p_buf->len = 4;

    rfc_check_send_cmd(p_mcb, p_buf);
}


/*******************************************************************************
**
** Function         rfc_send_dm
**
** Description      This function sends DM frame.
**
*******************************************************************************/
void rfc_send_dm (tRFC_MCB *p_mcb, UINT8 dlci, BOOLEAN pf)
{
    BT_HDR  *p_buf;
    UINT8   *p_data;
    UINT8   cr = RFCOMM_CR(p_mcb->is_initiator, FALSE);

    if ((p_buf = (BT_HDR *)GKI_getpoolbuf (RFCOMM_CMD_POOL_ID)) == NULL)
        return;

    p_buf->offset = L2CAP_MIN_OFFSET;
    p_data = (UINT8 *)(p_buf + 1) + L2CAP_MIN_OFFSET;

    /* DM frame, response, PF = 1, dlci */
    *p_data++ = RFCOMM_EA | cr | (dlci << RFCOMM_SHIFT_DLCI);
    *p_data++ = RFCOMM_DM | ((pf) ? RFCOMM_PF : 0);
    *p_data++ = RFCOMM_EA | 0;

    *p_data   = RFCOMM_DM_FCS ((UINT8 *)(p_buf + 1) + L2CAP_MIN_OFFSET, cr, dlci);

    p_buf->len = 4;

    rfc_check_send_cmd(p_mcb, p_buf);
}


/*******************************************************************************
**
** Function         rfc_send_disc
**
** Description      This function sends DISC frame.
**
*******************************************************************************/
void rfc_send_disc (tRFC_MCB *p_mcb, UINT8 dlci)
{
    BT_HDR  *p_buf;
    UINT8   *p_data;
    UINT8   cr = RFCOMM_CR(p_mcb->is_initiator, TRUE);

    if ((p_buf = (BT_HDR *)GKI_getpoolbuf (RFCOMM_CMD_POOL_ID)) == NULL)
        return;

    p_buf->offset = L2CAP_MIN_OFFSET;
    p_data = (UINT8 *)(p_buf + 1) + L2CAP_MIN_OFFSET;

    /* DISC frame, command, PF = 1, dlci */
    *p_data++ = RFCOMM_EA | cr | (dlci << RFCOMM_SHIFT_DLCI);
    *p_data++ = RFCOMM_DISC | RFCOMM_PF;
    *p_data++ = RFCOMM_EA | 0;

    *p_data   = RFCOMM_DISC_FCS ((UINT8 *)(p_buf + 1) + L2CAP_MIN_OFFSET, cr, dlci);

    p_buf->len = 4;

    rfc_check_send_cmd(p_mcb, p_buf);
}


/*******************************************************************************
**
** Function         rfc_send_buf_uih
**
** Description      This function sends UIH frame.
**
*******************************************************************************/
void rfc_send_buf_uih (tRFC_MCB *p_mcb, UINT8 dlci, BT_HDR *p_buf)
{
    UINT8   *p_data;
    UINT8   cr = RFCOMM_CR(p_mcb->is_initiator, TRUE);
    UINT8   credits;

    p_buf->offset -= RFCOMM_CTRL_FRAME_LEN;
    if (p_buf->len > 127)
        p_buf->offset--;

    if (dlci)
        credits = (UINT8)p_buf->layer_specific;
    else
        credits = 0;

    if (credits)
        p_buf->offset--;

    p_data = (UINT8 *)(p_buf + 1) + p_buf->offset;

    /* UIH frame, command, PF = 0, dlci */
    *p_data++ = RFCOMM_EA | cr | (dlci << RFCOMM_SHIFT_DLCI);
    *p_data++ = RFCOMM_UIH | ((credits) ? RFCOMM_PF : 0);
    if (p_buf->len <= 127)
    {
        *p_data++   = RFCOMM_EA | (p_buf->len << 1);
        p_buf->len += 3;
    }
    else
    {
        *p_data++   = (p_buf->len & 0x7f) << 1;
        *p_data++   = p_buf->len >> RFCOMM_SHIFT_LENGTH2;
        p_buf->len += 4;
    }

    if (credits)
    {
        *p_data++ = credits;
        p_buf->len++;
    }

    p_data  = (UINT8 *)(p_buf + 1) + p_buf->offset + p_buf->len++;

    *p_data = RFCOMM_UIH_FCS ((UINT8 *)(p_buf + 1) + p_buf->offset, dlci);

    if (dlci == RFCOMM_MX_DLCI)
    {
        rfc_check_send_cmd(p_mcb, p_buf);
    }
    else
    {

        L2CA_DataWrite (p_mcb->lcid, p_buf);
    }
}


/*******************************************************************************
**
** Function         rfc_send_pn
**
** Description      This function sends DLC Parameters Negotiation Frame.
**
*******************************************************************************/
void rfc_send_pn (tRFC_MCB *p_mcb, UINT8 dlci, BOOLEAN is_command, UINT16 mtu, UINT8 cl, UINT8 k)
{
    BT_HDR   *p_buf;
    UINT8    *p_data;

    if ((p_buf = (BT_HDR *)GKI_getpoolbuf (RFCOMM_CMD_POOL_ID)) == NULL)
        return;

    p_buf->offset = L2CAP_MIN_OFFSET + RFCOMM_CTRL_FRAME_LEN;
    p_data = (UINT8 *)(p_buf + 1) + p_buf->offset;

    *p_data++ = RFCOMM_EA | RFCOMM_I_CR(is_command) | RFCOMM_MX_PN;
    *p_data++ = RFCOMM_EA | (RFCOMM_MX_PN_LEN << 1);

    *p_data++ = dlci;
    *p_data++ = RFCOMM_PN_FRAM_TYPE_UIH | cl;

    /* It appeared that we need to reply with the same priority bits as we received.
    ** We will use the fact that we reply in the same context so rx_frame can still be used.
    */
    if (is_command)
        *p_data++ = RFCOMM_PN_PRIORITY_0;
    else
        *p_data++ = rfc_cb.rfc.rx_frame.u.pn.priority;

    *p_data++ = RFCOMM_T1_DSEC;
    *p_data++ = mtu & 0xFF;
    *p_data++ = mtu >> 8;
    *p_data++ = RFCOMM_N2;
    *p_data   = k;

    /* Total length is sizeof PN data + mx header 2 */
    p_buf->len = RFCOMM_MX_PN_LEN + 2;

    rfc_send_buf_uih (p_mcb, RFCOMM_MX_DLCI, p_buf);
}


/*******************************************************************************
**
** Function         rfc_send_fcon
**
** Description      This function sends Flow Control On Command.
**
*******************************************************************************/
void rfc_send_fcon (tRFC_MCB *p_mcb, BOOLEAN is_command)
{
    BT_HDR  *p_buf;
    UINT8   *p_data;

    if ((p_buf = (BT_HDR *)GKI_getpoolbuf (RFCOMM_CMD_POOL_ID)) == NULL)
        return;

    p_buf->offset = L2CAP_MIN_OFFSET + RFCOMM_CTRL_FRAME_LEN;
    p_data = (UINT8 *)(p_buf + 1) + p_buf->offset;

    *p_data++ = RFCOMM_EA | RFCOMM_I_CR(is_command) | RFCOMM_MX_FCON;
    *p_data++ = RFCOMM_EA | (RFCOMM_MX_FCON_LEN << 1);

    /* Total length is sizeof FCON data + mx header 2 */
    p_buf->len = RFCOMM_MX_FCON_LEN + 2;

    rfc_send_buf_uih (p_mcb, RFCOMM_MX_DLCI, p_buf);
}


/*******************************************************************************
**
** Function         rfc_send_fcoff
**
** Description      This function sends Flow Control Off Command.
**
*******************************************************************************/
void rfc_send_fcoff (tRFC_MCB *p_mcb, BOOLEAN is_command)
{
    BT_HDR  *p_buf;
    UINT8   *p_data;

    if ((p_buf = (BT_HDR *)GKI_getpoolbuf (RFCOMM_CMD_POOL_ID)) == NULL)
        return;

    p_buf->offset = L2CAP_MIN_OFFSET + RFCOMM_CTRL_FRAME_LEN;
    p_data = (UINT8 *)(p_buf + 1) + p_buf->offset;

    *p_data++ = RFCOMM_EA | RFCOMM_I_CR(is_command) | RFCOMM_MX_FCOFF;
    *p_data++ = RFCOMM_EA | (RFCOMM_MX_FCOFF_LEN << 1);

    /* Total length is sizeof FCOFF data + mx header 2 */
    p_buf->len = RFCOMM_MX_FCOFF_LEN + 2;

    rfc_send_buf_uih (p_mcb, RFCOMM_MX_DLCI, p_buf);
}


/*******************************************************************************
**
** Function         rfc_send_msc
**
** Description      This function sends Modem Status Command Frame.
**
*******************************************************************************/
void rfc_send_msc (tRFC_MCB *p_mcb, UINT8 dlci, BOOLEAN is_command,
                   tPORT_CTRL *p_pars)
{
    BT_HDR  *p_buf;
    UINT8   *p_data;
    UINT8   signals;
    UINT8   break_duration;
    UINT8   len;

    signals        = p_pars->modem_signal;
    break_duration = p_pars->break_signal;

    if ((p_buf = (BT_HDR *)GKI_getpoolbuf (RFCOMM_CMD_POOL_ID)) == NULL)
        return;

    p_buf->offset = L2CAP_MIN_OFFSET + RFCOMM_CTRL_FRAME_LEN;
    p_data = (UINT8 *)(p_buf + 1) + p_buf->offset;

    if (break_duration)
        len = RFCOMM_MX_MSC_LEN_WITH_BREAK;
    else
        len = RFCOMM_MX_MSC_LEN_NO_BREAK;

    *p_data++ = RFCOMM_EA | RFCOMM_I_CR(is_command) | RFCOMM_MX_MSC;
    *p_data++ = RFCOMM_EA | (len << 1);

    *p_data++ = RFCOMM_EA | RFCOMM_CR_MASK | (dlci << RFCOMM_SHIFT_DLCI);
    *p_data++ = RFCOMM_EA |
                ((p_pars->fc)                    ? RFCOMM_MSC_FC : 0)  |
                ((signals & MODEM_SIGNAL_DTRDSR) ? RFCOMM_MSC_RTC : 0) |
                ((signals & MODEM_SIGNAL_RTSCTS) ? RFCOMM_MSC_RTR : 0) |
                ((signals & MODEM_SIGNAL_RI)     ? RFCOMM_MSC_IC : 0)  |
                ((signals & MODEM_SIGNAL_DCD)    ? RFCOMM_MSC_DV : 0);

    if (break_duration)
    {
        *p_data++ = RFCOMM_EA | RFCOMM_MSC_BREAK_PRESENT_MASK |
                    (break_duration << RFCOMM_MSC_SHIFT_BREAK);
    }

    /* Total length is sizeof MSC data + mx header 2 */
    p_buf->len = len + 2;

    rfc_send_buf_uih (p_mcb, RFCOMM_MX_DLCI, p_buf);
}


/*******************************************************************************
**
** Function         rfc_send_rls
**
** Description      This function sends Remote Line Status Command Frame.
**
*******************************************************************************/
void rfc_send_rls (tRFC_MCB *p_mcb, UINT8 dlci, BOOLEAN is_command, UINT8 status)
{
    BT_HDR  *p_buf;
    UINT8   *p_data;

    if ((p_buf = (BT_HDR *)GKI_getpoolbuf (RFCOMM_CMD_POOL_ID)) == NULL)
        return;

    p_buf->offset = L2CAP_MIN_OFFSET + RFCOMM_CTRL_FRAME_LEN;
    p_data = (UINT8 *)(p_buf + 1) + p_buf->offset;

    *p_data++ = RFCOMM_EA | RFCOMM_I_CR(is_command) | RFCOMM_MX_RLS;
    *p_data++ = RFCOMM_EA | (RFCOMM_MX_RLS_LEN << 1);

    *p_data++ = RFCOMM_EA | RFCOMM_CR_MASK | (dlci << RFCOMM_SHIFT_DLCI);
    *p_data++ = RFCOMM_RLS_ERROR | status;

    /* Total length is sizeof RLS data + mx header 2 */
    p_buf->len = RFCOMM_MX_RLS_LEN + 2;

    rfc_send_buf_uih (p_mcb, RFCOMM_MX_DLCI, p_buf);
}


/*******************************************************************************
**
** Function         rfc_send_nsc
**
** Description      This function sends Non Supported Command Response.
**
*******************************************************************************/
void rfc_send_nsc (tRFC_MCB *p_mcb)
{
    BT_HDR  *p_buf;
    UINT8   *p_data;

    if ((p_buf = (BT_HDR *)GKI_getpoolbuf (RFCOMM_CMD_POOL_ID)) == NULL)
        return;

    p_buf->offset = L2CAP_MIN_OFFSET + RFCOMM_CTRL_FRAME_LEN;
    p_data = (UINT8 *)(p_buf + 1) + p_buf->offset;

    *p_data++ = RFCOMM_EA | RFCOMM_I_CR(FALSE) | RFCOMM_MX_NSC;
    *p_data++ = RFCOMM_EA | (RFCOMM_MX_NSC_LEN << 1);

    *p_data++ =  rfc_cb.rfc.rx_frame.ea |
                (rfc_cb.rfc.rx_frame.cr << RFCOMM_SHIFT_CR) |
                 rfc_cb.rfc.rx_frame.type;

    /* Total length is sizeof NSC data + mx header 2 */
    p_buf->len = RFCOMM_MX_NSC_LEN + 2;

    rfc_send_buf_uih (p_mcb, RFCOMM_MX_DLCI, p_buf);
}


/*******************************************************************************
**
** Function         rfc_send_rpn
**
** Description      This function sends Remote Port Negotiation Command
**
*******************************************************************************/
void rfc_send_rpn (tRFC_MCB *p_mcb, UINT8 dlci, BOOLEAN is_command,
                   tPORT_STATE *p_pars, UINT16 mask)
{
    BT_HDR   *p_buf;
    UINT8    *p_data;

    if ((p_buf = (BT_HDR *)GKI_getpoolbuf (RFCOMM_CMD_POOL_ID)) == NULL)
        return;

    p_buf->offset = L2CAP_MIN_OFFSET + RFCOMM_CTRL_FRAME_LEN;
    p_data = (UINT8 *)(p_buf + 1) + p_buf->offset;

    *p_data++ = RFCOMM_EA | RFCOMM_I_CR(is_command) | RFCOMM_MX_RPN;

    if (!p_pars)
    {
        *p_data++ = RFCOMM_EA | (RFCOMM_MX_RPN_REQ_LEN << 1);

        *p_data++ = RFCOMM_EA | RFCOMM_CR_MASK | (dlci << RFCOMM_SHIFT_DLCI);

        p_buf->len = RFCOMM_MX_RPN_REQ_LEN + 2;
    }
    else
    {
        *p_data++ = RFCOMM_EA | (RFCOMM_MX_RPN_LEN << 1);

        *p_data++ = RFCOMM_EA | RFCOMM_CR_MASK | (dlci << RFCOMM_SHIFT_DLCI);
        *p_data++ = p_pars->baud_rate;
        *p_data++ =  (p_pars->byte_size << RFCOMM_RPN_BITS_SHIFT)
                   | (p_pars->stop_bits << RFCOMM_RPN_STOP_BITS_SHIFT)
                   | (p_pars->parity << RFCOMM_RPN_PARITY_SHIFT)
                   | (p_pars->parity_type << RFCOMM_RPN_PARITY_TYPE_SHIFT);
        *p_data++ = p_pars->fc_type;
        *p_data++ = p_pars->xon_char;
        *p_data++ = p_pars->xoff_char;
        *p_data++ = (mask & 0xFF);
        *p_data++ = (mask >> 8);

        /* Total length is sizeof RPN data + mx header 2 */
        p_buf->len = RFCOMM_MX_RPN_LEN + 2;
    }

    rfc_send_buf_uih (p_mcb, RFCOMM_MX_DLCI, p_buf);
}


/*******************************************************************************
**
** Function         rfc_send_test
**
** Description      This function sends Test frame.
**
*******************************************************************************/
void rfc_send_test (tRFC_MCB *p_mcb, BOOLEAN is_command, BT_HDR *p_buf)
{
    UINT8    *p_data;
    UINT16   xx;
    UINT8    *p_src, *p_dest;

    /* Shift buffer to give space for header */
    if (p_buf->offset < (L2CAP_MIN_OFFSET + RFCOMM_MIN_OFFSET + 2))
    {
        p_src  = (UINT8 *) (p_buf + 1) + p_buf->offset + p_buf->len - 1;
        p_dest = (UINT8 *) (p_buf + 1) + L2CAP_MIN_OFFSET + RFCOMM_MIN_OFFSET + 2 + p_buf->len - 1;

        for (xx = 0; xx < p_buf->len; xx++)
            *p_dest-- = *p_src--;

        p_buf->offset = L2CAP_MIN_OFFSET + RFCOMM_MIN_OFFSET + 2;
    }

    /* Adjust offset by number of bytes we are going to fill */
    p_buf->offset -= 2;
    p_data = (UINT8 *)(p_buf + 1) + p_buf->offset;

    *p_data++ = RFCOMM_EA | RFCOMM_I_CR(is_command) | RFCOMM_MX_TEST;
    *p_data++ = RFCOMM_EA | (p_buf->len << 1);

    p_buf->len += 2;

    rfc_send_buf_uih (p_mcb, RFCOMM_MX_DLCI, p_buf);
}

/*******************************************************************************
**
** Function         rfc_send_credit
**
** Description      This function sends a flow control credit in UIH frame.
**
*******************************************************************************/
void rfc_send_credit(tRFC_MCB *p_mcb, UINT8 dlci, UINT8 credit)
{
    BT_HDR   *p_buf;
    UINT8    *p_data;
    UINT8    cr = RFCOMM_CR(p_mcb->is_initiator, TRUE);

    if ((p_buf = (BT_HDR *)GKI_getpoolbuf (RFCOMM_CMD_POOL_ID)) == NULL)
        return;

    p_buf->offset = L2CAP_MIN_OFFSET;
    p_data = (UINT8 *)(p_buf + 1) + p_buf->offset;

    *p_data++ = RFCOMM_EA | cr | (dlci << RFCOMM_SHIFT_DLCI);
    *p_data++ = RFCOMM_UIH | RFCOMM_PF;
    *p_data++ = RFCOMM_EA | 0;
    *p_data++ = credit;
    *p_data   = RFCOMM_UIH_FCS ((UINT8 *)(p_buf + 1) + p_buf->offset, dlci);

    p_buf->len = 5;

    rfc_check_send_cmd(p_mcb, p_buf);
}


/*******************************************************************************
**
** Function         rfc_parse_data
**
** Description      This function processes data packet received from L2CAP
**
*******************************************************************************/
UINT8 rfc_parse_data (tRFC_MCB *p_mcb, MX_FRAME *p_frame, BT_HDR *p_buf)
{
    UINT8     ead, eal, fcs;
    UINT8     *p_data = (UINT8 *)(p_buf + 1) + p_buf->offset;
    UINT8     *p_start = p_data;
    UINT16    len;

    if (p_buf->len < RFCOMM_CTRL_FRAME_LEN)
    {
        RFCOMM_TRACE_ERROR ("Bad Length1: %d", p_buf->len);
        return (RFC_EVENT_BAD_FRAME);
    }

    RFCOMM_PARSE_CTRL_FIELD (ead, p_frame->cr, p_frame->dlci, p_data);
    if( !ead )
    {
        RFCOMM_TRACE_ERROR ("Bad Address(EA must be 1)");
        return (RFC_EVENT_BAD_FRAME);
    }
    RFCOMM_PARSE_TYPE_FIELD (p_frame->type, p_frame->pf, p_data);
    RFCOMM_PARSE_LEN_FIELD (eal, len, p_data);

    p_buf->len      -= (3 + !ead + !eal + 1);  /* Additional 1 for FCS */
    p_buf->offset   += (3 + !ead + !eal);

    /* handle credit if credit based flow control */
    if ((p_mcb->flow == PORT_FC_CREDIT) && (p_frame->type == RFCOMM_UIH) &&
        (p_frame->dlci != RFCOMM_MX_DLCI) && (p_frame->pf == 1))
    {
        p_frame->credit = *p_data++;
        p_buf->len--;
        p_buf->offset++;
    }
    else
        p_frame->credit = 0;

    if (p_buf->len != len)
    {
        RFCOMM_TRACE_ERROR ("Bad Length2 %d %d", p_buf->len, len);
        return (RFC_EVENT_BAD_FRAME);
    }

    fcs = *(p_data + len);

    /* All control frames that we are sending are sent with P=1, expect */
    /* reply with F=1 */
    /* According to TS 07.10 spec ivalid frames are discarded without */
    /* notification to the sender */
    switch (p_frame->type)
    {
    case RFCOMM_SABME:
        if (RFCOMM_FRAME_IS_RSP(p_mcb->is_initiator, p_frame->cr)
         || !p_frame->pf || len || !RFCOMM_VALID_DLCI (p_frame->dlci)
         || !rfc_check_fcs (RFCOMM_CTRL_FRAME_LEN, p_start, fcs))
        {
            RFCOMM_TRACE_ERROR ("Bad SABME");
            return (RFC_EVENT_BAD_FRAME);
        }
        else
            return (RFC_EVENT_SABME);

    case RFCOMM_UA:
        if (RFCOMM_FRAME_IS_CMD(p_mcb->is_initiator, p_frame->cr)
          || !p_frame->pf || len || !RFCOMM_VALID_DLCI (p_frame->dlci)
          || !rfc_check_fcs (RFCOMM_CTRL_FRAME_LEN, p_start, fcs))
        {
            RFCOMM_TRACE_ERROR ("Bad UA");
            return (RFC_EVENT_BAD_FRAME);
        }
        else
            return (RFC_EVENT_UA);

    case RFCOMM_DM:
        if (RFCOMM_FRAME_IS_CMD(p_mcb->is_initiator, p_frame->cr)
         || len || !RFCOMM_VALID_DLCI(p_frame->dlci)
         || !rfc_check_fcs (RFCOMM_CTRL_FRAME_LEN, p_start, fcs))
        {
            RFCOMM_TRACE_ERROR ("Bad DM");
            return (RFC_EVENT_BAD_FRAME);
        }
        else
            return (RFC_EVENT_DM);

    case RFCOMM_DISC:
        if (RFCOMM_FRAME_IS_RSP(p_mcb->is_initiator, p_frame->cr)
          || !p_frame->pf || len || !RFCOMM_VALID_DLCI(p_frame->dlci)
          || !rfc_check_fcs (RFCOMM_CTRL_FRAME_LEN, p_start, fcs))
        {
            RFCOMM_TRACE_ERROR ("Bad DISC");
            return (RFC_EVENT_BAD_FRAME);
        }
        else
            return (RFC_EVENT_DISC);

    case RFCOMM_UIH:
        if (!RFCOMM_VALID_DLCI(p_frame->dlci))
        {
            RFCOMM_TRACE_ERROR ("Bad UIH - invalid DLCI");
            return (RFC_EVENT_BAD_FRAME);
        }
        else if (!rfc_check_fcs (2, p_start, fcs))
        {
            RFCOMM_TRACE_ERROR ("Bad UIH - FCS");
            return (RFC_EVENT_BAD_FRAME);
        }
        else if (RFCOMM_FRAME_IS_RSP(p_mcb->is_initiator, p_frame->cr))
        {
            /* we assume that this is ok to allow bad implementations to work */
            RFCOMM_TRACE_ERROR ("Bad UIH - response");
            return (RFC_EVENT_UIH);
        }
        else
            return (RFC_EVENT_UIH);
    }

    return (RFC_EVENT_BAD_FRAME);
}


/*******************************************************************************
**
** Function         rfc_process_mx_message
**
** Description      This function processes UIH frames received on the
**                  multiplexer control channel.
**
*******************************************************************************/
void rfc_process_mx_message (tRFC_MCB *p_mcb, BT_HDR *p_buf)
{
    UINT8       *p_data = (UINT8 *)(p_buf + 1) + p_buf->offset;
    MX_FRAME    *p_rx_frame = &rfc_cb.rfc.rx_frame;
    UINT16       length  = p_buf->len;
    UINT8        ea, cr, mx_len;
    BOOLEAN      is_command;

    p_rx_frame->ea   = *p_data & RFCOMM_EA;
    p_rx_frame->cr   = (*p_data & RFCOMM_CR_MASK) >> RFCOMM_SHIFT_CR;
    p_rx_frame->type = *p_data++ & ~(RFCOMM_CR_MASK | RFCOMM_EA_MASK);

    if (!p_rx_frame->ea || !length)
    {
        RFCOMM_TRACE_ERROR ("Illegal MX Frame ea:%d len:%d", p_rx_frame->ea, length);
        GKI_freebuf (p_buf);
        return;
    }

    length--;

    is_command = p_rx_frame->cr;

    ea = *p_data & RFCOMM_EA;

    mx_len = *p_data++ >> RFCOMM_SHIFT_LENGTH1;
    length--;

    if (!ea)
    {
        mx_len += *p_data++ << RFCOMM_SHIFT_LENGTH2;
        length --;
    }

    if (mx_len != length)
    {
        RFCOMM_TRACE_ERROR ("Bad MX frame");
        GKI_freebuf (p_buf);
        return;
    }

    switch (p_rx_frame->type)
    {
    case RFCOMM_MX_PN:
        if (length != RFCOMM_MX_PN_LEN)
            break;

        p_rx_frame->dlci            = *p_data++ & RFCOMM_PN_DLCI_MASK;
        p_rx_frame->u.pn.frame_type = *p_data & RFCOMM_PN_FRAME_TYPE_MASK;
        p_rx_frame->u.pn.conv_layer = *p_data++ & RFCOMM_PN_CONV_LAYER_MASK;
        p_rx_frame->u.pn.priority   = *p_data++ & RFCOMM_PN_PRIORITY_MASK;
        p_rx_frame->u.pn.t1         = *p_data++;
        p_rx_frame->u.pn.mtu        = *p_data + (*(p_data + 1) << 8);
        p_data += 2;
        p_rx_frame->u.pn.n2         = *p_data++;
        p_rx_frame->u.pn.k          = *p_data++ & RFCOMM_PN_K_MASK;

        if (!p_rx_frame->dlci
         || !RFCOMM_VALID_DLCI (p_rx_frame->dlci)
         || (p_rx_frame->u.pn.mtu < RFCOMM_MIN_MTU)
         || (p_rx_frame->u.pn.mtu > RFCOMM_MAX_MTU))
        {
            RFCOMM_TRACE_ERROR ("Bad PN frame");
            break;
        }

        GKI_freebuf (p_buf);

        rfc_process_pn (p_mcb, is_command, p_rx_frame);
        return;

    case RFCOMM_MX_TEST:
        if (!length)
            break;

        p_rx_frame->u.test.p_data   = p_data;
        p_rx_frame->u.test.data_len = length;

        p_buf->offset += 2;
        p_buf->len    -= 2;

        if (is_command)
            rfc_send_test (p_mcb, FALSE, p_buf);
        else
            rfc_process_test_rsp (p_mcb, p_buf);
        return;

    case RFCOMM_MX_FCON:
        if (length != RFCOMM_MX_FCON_LEN)
            break;

        GKI_freebuf (p_buf);

        rfc_process_fcon (p_mcb, is_command);
        return;

    case RFCOMM_MX_FCOFF:
        if (length != RFCOMM_MX_FCOFF_LEN)
            break;

        GKI_freebuf (p_buf);

        rfc_process_fcoff (p_mcb, is_command);
        return;

    case RFCOMM_MX_MSC:

        ea                   = *p_data & RFCOMM_EA;
        cr                   = (*p_data & RFCOMM_CR_MASK) >> RFCOMM_SHIFT_CR;
        p_rx_frame->dlci = *p_data++ >> RFCOMM_SHIFT_DLCI;

        if (!ea || !cr || !p_rx_frame->dlci
         || !RFCOMM_VALID_DLCI (p_rx_frame->dlci))
        {
            RFCOMM_TRACE_ERROR ("Bad MSC frame");
            break;
        }

        p_rx_frame->u.msc.signals        = *p_data++;

        if (mx_len == RFCOMM_MX_MSC_LEN_WITH_BREAK)
        {
            p_rx_frame->u.msc.break_present  = *p_data & RFCOMM_MSC_BREAK_PRESENT_MASK;
            p_rx_frame->u.msc.break_duration = (*p_data & RFCOMM_MSC_BREAK_MASK) >> RFCOMM_MSC_SHIFT_BREAK;
        }
        else
        {
            p_rx_frame->u.msc.break_present  = FALSE;
            p_rx_frame->u.msc.break_duration = 0;
        }
        GKI_freebuf (p_buf);

        rfc_process_msc (p_mcb, is_command, p_rx_frame);
        return;

    case RFCOMM_MX_NSC:
        if ((length != RFCOMM_MX_NSC_LEN) || !is_command)
            break;

        p_rx_frame->u.nsc.ea   = *p_data & RFCOMM_EA;
        p_rx_frame->u.nsc.cr   = (*p_data & RFCOMM_CR_MASK) >> RFCOMM_SHIFT_CR;
        p_rx_frame->u.nsc.type = *p_data++ >> RFCOMM_SHIFT_DLCI;

        GKI_freebuf (p_buf);

        rfc_process_nsc (p_mcb, p_rx_frame);
        return;

    case RFCOMM_MX_RPN:
        if ((length != RFCOMM_MX_RPN_REQ_LEN) && (length != RFCOMM_MX_RPN_LEN))
            break;

        ea                   = *p_data & RFCOMM_EA;
        cr                   = (*p_data & RFCOMM_CR_MASK) >> RFCOMM_SHIFT_CR;
        p_rx_frame->dlci = *p_data++ >> RFCOMM_SHIFT_DLCI;

        if (!ea || !cr || !p_rx_frame->dlci
         || !RFCOMM_VALID_DLCI (p_rx_frame->dlci))
        {
            RFCOMM_TRACE_ERROR ("Bad RPN frame");
            break;
        }

        p_rx_frame->u.rpn.is_request  = (length == RFCOMM_MX_RPN_REQ_LEN);

        if (!p_rx_frame->u.rpn.is_request)
        {
            p_rx_frame->u.rpn.baud_rate   = *p_data++;
            p_rx_frame->u.rpn.byte_size   = (*p_data >> RFCOMM_RPN_BITS_SHIFT) & RFCOMM_RPN_BITS_MASK;
            p_rx_frame->u.rpn.stop_bits   = (*p_data >> RFCOMM_RPN_STOP_BITS_SHIFT) & RFCOMM_RPN_STOP_BITS_MASK;
            p_rx_frame->u.rpn.parity      = (*p_data >> RFCOMM_RPN_PARITY_SHIFT) & RFCOMM_RPN_PARITY_MASK;
            p_rx_frame->u.rpn.parity_type = (*p_data++ >> RFCOMM_RPN_PARITY_TYPE_SHIFT) & RFCOMM_RPN_PARITY_TYPE_MASK;

            p_rx_frame->u.rpn.fc_type     = *p_data++ & RFCOMM_FC_MASK;
            p_rx_frame->u.rpn.xon_char    = *p_data++;
            p_rx_frame->u.rpn.xoff_char   = *p_data++;
            p_rx_frame->u.rpn.param_mask  = (*p_data + (*(p_data + 1) << 8)) & RFCOMM_RPN_PM_MASK;
        }
        GKI_freebuf (p_buf);

        rfc_process_rpn (p_mcb, is_command, p_rx_frame->u.rpn.is_request, p_rx_frame);
        return;

    case RFCOMM_MX_RLS:
        if (length != RFCOMM_MX_RLS_LEN)
            break;

        ea = *p_data & RFCOMM_EA;
        cr = (*p_data & RFCOMM_CR_MASK) >> RFCOMM_SHIFT_CR;

        p_rx_frame->dlci              = *p_data++ >> RFCOMM_SHIFT_DLCI;
        p_rx_frame->u.rls.line_status = (*p_data & ~0x01);

        if (!ea || !cr || !p_rx_frame->dlci
         || !RFCOMM_VALID_DLCI (p_rx_frame->dlci))
        {
            RFCOMM_TRACE_ERROR ("Bad RPN frame");
            break;
        }

        GKI_freebuf (p_buf);

        rfc_process_rls (p_mcb, is_command, p_rx_frame);
        return;
    }

    GKI_freebuf (p_buf);

    if (is_command)
        rfc_send_nsc (p_mcb);
}