stack/rfcomm/rfc_ts_frames.cc

/******************************************************************************
 *
 *  Copyright 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 <stddef.h>
#include "bt_common.h"
#include "bt_target.h"
#include "l2c_api.h"
#include "log/log.h"
#include "port_api.h"
#include "port_int.h"
#include "rfc_int.h"
#include "rfcdefs.h"

/*******************************************************************************
 *
 * Function         rfc_send_sabme
 *
 * Description      This function sends SABME frame.
 *
 ******************************************************************************/
void rfc_send_sabme(tRFC_MCB* p_mcb, uint8_t dlci) {
  uint8_t* p_data;
  uint8_t cr = RFCOMM_CR(p_mcb->is_initiator, true);
  BT_HDR* p_buf = (BT_HDR*)osi_malloc(RFCOMM_CMD_BUF_SIZE);

  p_buf->offset = L2CAP_MIN_OFFSET;
  p_data = (uint8_t*)(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_t*)(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_t dlci) {
  uint8_t* p_data;
  uint8_t cr = RFCOMM_CR(p_mcb->is_initiator, false);
  BT_HDR* p_buf = (BT_HDR*)osi_malloc(RFCOMM_CMD_BUF_SIZE);

  p_buf->offset = L2CAP_MIN_OFFSET;
  p_data = (uint8_t*)(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_t*)(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_t dlci, bool pf) {
  uint8_t* p_data;
  uint8_t cr = RFCOMM_CR(p_mcb->is_initiator, false);
  BT_HDR* p_buf = (BT_HDR*)osi_malloc(RFCOMM_CMD_BUF_SIZE);

  p_buf->offset = L2CAP_MIN_OFFSET;
  p_data = (uint8_t*)(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_t*)(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_t dlci) {
  uint8_t* p_data;
  uint8_t cr = RFCOMM_CR(p_mcb->is_initiator, true);
  BT_HDR* p_buf = (BT_HDR*)osi_malloc(RFCOMM_CMD_BUF_SIZE);

  p_buf->offset = L2CAP_MIN_OFFSET;
  p_data = (uint8_t*)(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_t*)(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_t dlci, BT_HDR* p_buf) {
  uint8_t* p_data;
  uint8_t cr = RFCOMM_CR(p_mcb->is_initiator, true);
  uint8_t credits;

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

  if (dlci)
    credits = (uint8_t)p_buf->layer_specific;
  else
    credits = 0;

  if (credits) p_buf->offset--;

  p_data = (uint8_t*)(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_t*)(p_buf + 1) + p_buf->offset + p_buf->len++;

  *p_data = RFCOMM_UIH_FCS((uint8_t*)(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_t dlci, bool is_command, uint16_t mtu,
                 uint8_t cl, uint8_t k) {
  uint8_t* p_data;
  BT_HDR* p_buf = (BT_HDR*)osi_malloc(RFCOMM_CMD_BUF_SIZE);

  p_buf->offset = L2CAP_MIN_OFFSET + RFCOMM_CTRL_FRAME_LEN;
  p_data = (uint8_t*)(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, bool is_command) {
  uint8_t* p_data;
  BT_HDR* p_buf = (BT_HDR*)osi_malloc(RFCOMM_CMD_BUF_SIZE);

  p_buf->offset = L2CAP_MIN_OFFSET + RFCOMM_CTRL_FRAME_LEN;
  p_data = (uint8_t*)(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, bool is_command) {
  uint8_t* p_data;
  BT_HDR* p_buf = (BT_HDR*)osi_malloc(RFCOMM_CMD_BUF_SIZE);

  p_buf->offset = L2CAP_MIN_OFFSET + RFCOMM_CTRL_FRAME_LEN;
  p_data = (uint8_t*)(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_t dlci, bool is_command,
                  tPORT_CTRL* p_pars) {
  uint8_t* p_data;
  uint8_t signals;
  uint8_t break_duration;
  uint8_t len;
  BT_HDR* p_buf = (BT_HDR*)osi_malloc(RFCOMM_CMD_BUF_SIZE);

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

  p_buf->offset = L2CAP_MIN_OFFSET + RFCOMM_CTRL_FRAME_LEN;
  p_data = (uint8_t*)(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_t dlci, bool is_command,
                  uint8_t status) {
  uint8_t* p_data;
  BT_HDR* p_buf = (BT_HDR*)osi_malloc(RFCOMM_CMD_BUF_SIZE);

  p_buf->offset = L2CAP_MIN_OFFSET + RFCOMM_CTRL_FRAME_LEN;
  p_data = (uint8_t*)(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) {
  uint8_t* p_data;
  BT_HDR* p_buf = (BT_HDR*)osi_malloc(RFCOMM_CMD_BUF_SIZE);

  p_buf->offset = L2CAP_MIN_OFFSET + RFCOMM_CTRL_FRAME_LEN;
  p_data = (uint8_t*)(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_t dlci, bool is_command,
                  tPORT_STATE* p_pars, uint16_t mask) {
  uint8_t* p_data;
  BT_HDR* p_buf = (BT_HDR*)osi_malloc(RFCOMM_CMD_BUF_SIZE);

  p_buf->offset = L2CAP_MIN_OFFSET + RFCOMM_CTRL_FRAME_LEN;
  p_data = (uint8_t*)(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, bool is_command, BT_HDR* p_buf) {
  /* Shift buffer to give space for header */
  if (p_buf->offset < (L2CAP_MIN_OFFSET + RFCOMM_MIN_OFFSET + 2)) {
    uint8_t* p_src = (uint8_t*)(p_buf + 1) + p_buf->offset + p_buf->len - 1;
    BT_HDR* p_new_buf =
        (BT_HDR*)osi_malloc(p_buf->len + (L2CAP_MIN_OFFSET + RFCOMM_MIN_OFFSET +
                                          2 + sizeof(BT_HDR) + 1));

    p_new_buf->offset = L2CAP_MIN_OFFSET + RFCOMM_MIN_OFFSET + 2;
    p_new_buf->len = p_buf->len;

    uint8_t* p_dest =
        (uint8_t*)(p_new_buf + 1) + p_new_buf->offset + p_new_buf->len - 1;

    for (uint16_t xx = 0; xx < p_buf->len; xx++) *p_dest-- = *p_src--;

    osi_free(p_buf);
    p_buf = p_new_buf;
  }

  /* Adjust offset by number of bytes we are going to fill */
  p_buf->offset -= 2;
  uint8_t* p_data = (uint8_t*)(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_t dlci, uint8_t credit) {
  uint8_t* p_data;
  uint8_t cr = RFCOMM_CR(p_mcb->is_initiator, true);
  BT_HDR* p_buf = (BT_HDR*)osi_malloc(RFCOMM_CMD_BUF_SIZE);

  p_buf->offset = L2CAP_MIN_OFFSET;
  p_data = (uint8_t*)(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_t*)(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_t rfc_parse_data(tRFC_MCB* p_mcb, MX_FRAME* p_frame, BT_HDR* p_buf) {
  uint8_t ead, eal, fcs;
  uint8_t* p_data = (uint8_t*)(p_buf + 1) + p_buf->offset;
  uint8_t* p_start = p_data;
  uint16_t 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);

  eal = *(p_data)&RFCOMM_EA;
  len = *(p_data)++ >> RFCOMM_SHIFT_LENGTH1;
  if (eal == 0 && p_buf->len > RFCOMM_CTRL_FRAME_LEN) {
    len += (*(p_data)++ << RFCOMM_SHIFT_LENGTH2);
  } else if (eal == 0) {
    RFCOMM_TRACE_ERROR("Bad Length when EAL = 0: %d", p_buf->len);
    android_errorWriteLog(0x534e4554, "78288018");
    return RFC_EVENT_BAD_FRAME;
  }

  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_t* p_data = (uint8_t*)(p_buf + 1) + p_buf->offset;
  MX_FRAME* p_rx_frame = &rfc_cb.rfc.rx_frame;
  uint16_t length = p_buf->len;
  uint8_t ea, cr, mx_len;
  bool is_command;

  if (length < 2) {
    RFCOMM_TRACE_ERROR(
        "%s: Illegal MX Frame len when reading EA, C/R. len:%d < 2", __func__,
        length);
    android_errorWriteLog(0x534e4554, "111937065");
    osi_free(p_buf);
    return;
  }
  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) {
    LOG(ERROR) << __func__
               << ": Invalid MX frame ea=" << std::to_string(p_rx_frame->ea)
               << ", len=" << length << ", bd_addr=" << p_mcb->bd_addr;
    osi_free(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) {
    if (length < 1) {
      RFCOMM_TRACE_ERROR("%s: Illegal MX Frame when EA = 0. len:%d < 1",
                         __func__, length);
      android_errorWriteLog(0x534e4554, "111937065");
      osi_free(p_buf);
      return;
    }
    mx_len += *p_data++ << RFCOMM_SHIFT_LENGTH2;
    length--;
  }

  if (mx_len != length) {
    LOG(ERROR) << __func__ << ": Bad MX frame, p_mcb=" << p_mcb
               << ", bd_addr=" << p_mcb->bd_addr;
    osi_free(p_buf);
    return;
  }

  RFCOMM_TRACE_DEBUG("%s: type=%d, p_mcb=%p", __func__, p_rx_frame->type,
                     p_mcb);
  switch (p_rx_frame->type) {
    case RFCOMM_MX_PN:
      if (length != RFCOMM_MX_PN_LEN) {
        LOG(ERROR) << __func__ << ": Invalid PN length, p_mcb=" << p_mcb
                   << ", bd_addr=" << p_mcb->bd_addr;
        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)) {
        LOG(ERROR) << __func__ << ": Bad PN frame, p_mcb=" << p_mcb
                   << ", bd_addr=" << p_mcb->bd_addr;
        break;
      }

      osi_free(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;

      osi_free(p_buf);

      rfc_process_fcon(p_mcb, is_command);
      return;

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

      osi_free(p_buf);

      rfc_process_fcoff(p_mcb, is_command);
      return;

    case RFCOMM_MX_MSC:
      if (length != RFCOMM_MX_MSC_LEN_WITH_BREAK &&
          length != RFCOMM_MX_MSC_LEN_NO_BREAK) {
        RFCOMM_TRACE_ERROR("%s: Illegal MX MSC Frame len:%d", __func__, length);
        android_errorWriteLog(0x534e4554, "111937065");
        osi_free(p_buf);
        return;
      }
      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;
      }
      osi_free(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;

      osi_free(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;
      }
      osi_free(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;
      }

      osi_free(p_buf);

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

  osi_free(p_buf);

  if (is_command) rfc_send_nsc(p_mcb);
}