631 lines
15 KiB
C
Executable file
631 lines
15 KiB
C
Executable file
/*
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* isdnhdlc.c -- General purpose ISDN HDLC decoder.
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*
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* Copyright (C)
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* 2009 Karsten Keil <keil@b1-systems.de>
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* 2002 Wolfgang Mües <wolfgang@iksw-muees.de>
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* 2001 Frode Isaksen <fisaksen@bewan.com>
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* 2001 Kai Germaschewski <kai.germaschewski@gmx.de>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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*/
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#include <linux/module.h>
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#include <linux/init.h>
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#include <linux/crc-ccitt.h>
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#include <linux/isdn/hdlc.h>
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#include <linux/bitrev.h>
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/*-------------------------------------------------------------------*/
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MODULE_AUTHOR("Wolfgang Mües <wolfgang@iksw-muees.de>, "
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"Frode Isaksen <fisaksen@bewan.com>, "
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"Kai Germaschewski <kai.germaschewski@gmx.de>");
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MODULE_DESCRIPTION("General purpose ISDN HDLC decoder");
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MODULE_LICENSE("GPL");
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/*-------------------------------------------------------------------*/
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enum {
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HDLC_FAST_IDLE, HDLC_GET_FLAG_B0, HDLC_GETFLAG_B1A6, HDLC_GETFLAG_B7,
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HDLC_GET_DATA, HDLC_FAST_FLAG
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};
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enum {
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HDLC_SEND_DATA, HDLC_SEND_CRC1, HDLC_SEND_FAST_FLAG,
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HDLC_SEND_FIRST_FLAG, HDLC_SEND_CRC2, HDLC_SEND_CLOSING_FLAG,
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HDLC_SEND_IDLE1, HDLC_SEND_FAST_IDLE, HDLC_SENDFLAG_B0,
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HDLC_SENDFLAG_B1A6, HDLC_SENDFLAG_B7, STOPPED, HDLC_SENDFLAG_ONE
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};
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void isdnhdlc_rcv_init(struct isdnhdlc_vars *hdlc, u32 features)
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{
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memset(hdlc, 0, sizeof(struct isdnhdlc_vars));
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hdlc->state = HDLC_GET_DATA;
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if (features & HDLC_56KBIT)
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hdlc->do_adapt56 = 1;
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if (features & HDLC_BITREVERSE)
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hdlc->do_bitreverse = 1;
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}
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EXPORT_SYMBOL(isdnhdlc_out_init);
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void isdnhdlc_out_init(struct isdnhdlc_vars *hdlc, u32 features)
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{
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memset(hdlc, 0, sizeof(struct isdnhdlc_vars));
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if (features & HDLC_DCHANNEL) {
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hdlc->dchannel = 1;
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hdlc->state = HDLC_SEND_FIRST_FLAG;
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} else {
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hdlc->dchannel = 0;
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hdlc->state = HDLC_SEND_FAST_FLAG;
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hdlc->ffvalue = 0x7e;
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}
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hdlc->cbin = 0x7e;
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if (features & HDLC_56KBIT) {
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hdlc->do_adapt56 = 1;
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hdlc->state = HDLC_SENDFLAG_B0;
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} else
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hdlc->data_bits = 8;
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if (features & HDLC_BITREVERSE)
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hdlc->do_bitreverse = 1;
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}
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EXPORT_SYMBOL(isdnhdlc_rcv_init);
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static int
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check_frame(struct isdnhdlc_vars *hdlc)
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{
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int status;
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if (hdlc->dstpos < 2) /* too small - framing error */
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status = -HDLC_FRAMING_ERROR;
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else if (hdlc->crc != 0xf0b8) /* crc error */
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status = -HDLC_CRC_ERROR;
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else {
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/* remove CRC */
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hdlc->dstpos -= 2;
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/* good frame */
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status = hdlc->dstpos;
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}
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return status;
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}
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/*
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isdnhdlc_decode - decodes HDLC frames from a transparent bit stream.
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The source buffer is scanned for valid HDLC frames looking for
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flags (01111110) to indicate the start of a frame. If the start of
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the frame is found, the bit stuffing is removed (0 after 5 1's).
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When a new flag is found, the complete frame has been received
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and the CRC is checked.
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If a valid frame is found, the function returns the frame length
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excluding the CRC with the bit HDLC_END_OF_FRAME set.
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If the beginning of a valid frame is found, the function returns
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the length.
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If a framing error is found (too many 1s and not a flag) the function
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returns the length with the bit HDLC_FRAMING_ERROR set.
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If a CRC error is found the function returns the length with the
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bit HDLC_CRC_ERROR set.
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If the frame length exceeds the destination buffer size, the function
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returns the length with the bit HDLC_LENGTH_ERROR set.
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src - source buffer
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slen - source buffer length
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count - number of bytes removed (decoded) from the source buffer
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dst _ destination buffer
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dsize - destination buffer size
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returns - number of decoded bytes in the destination buffer and status
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flag.
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*/
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int isdnhdlc_decode(struct isdnhdlc_vars *hdlc, const u8 *src, int slen,
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int *count, u8 *dst, int dsize)
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{
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int status = 0;
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static const unsigned char fast_flag[] = {
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0x00, 0x00, 0x00, 0x20, 0x30, 0x38, 0x3c, 0x3e, 0x3f
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};
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static const unsigned char fast_flag_value[] = {
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0x00, 0x7e, 0xfc, 0xf9, 0xf3, 0xe7, 0xcf, 0x9f, 0x3f
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};
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static const unsigned char fast_abort[] = {
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0x00, 0x00, 0x80, 0xc0, 0xe0, 0xf0, 0xf8, 0xfc, 0xfe, 0xff
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};
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#define handle_fast_flag(h) \
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do { \
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if (h->cbin == fast_flag[h->bit_shift]) { \
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h->ffvalue = fast_flag_value[h->bit_shift]; \
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h->state = HDLC_FAST_FLAG; \
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h->ffbit_shift = h->bit_shift; \
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h->bit_shift = 1; \
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} else { \
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h->state = HDLC_GET_DATA; \
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h->data_received = 0; \
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} \
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} while (0)
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#define handle_abort(h) \
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do { \
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h->shift_reg = fast_abort[h->ffbit_shift - 1]; \
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h->hdlc_bits1 = h->ffbit_shift - 2; \
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if (h->hdlc_bits1 < 0) \
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h->hdlc_bits1 = 0; \
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h->data_bits = h->ffbit_shift - 1; \
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h->state = HDLC_GET_DATA; \
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h->data_received = 0; \
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} while (0)
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*count = slen;
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while (slen > 0) {
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if (hdlc->bit_shift == 0) {
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/* the code is for bitreverse streams */
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if (hdlc->do_bitreverse == 0)
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hdlc->cbin = bitrev8(*src++);
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else
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hdlc->cbin = *src++;
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slen--;
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hdlc->bit_shift = 8;
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if (hdlc->do_adapt56)
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hdlc->bit_shift--;
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}
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switch (hdlc->state) {
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case STOPPED:
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return 0;
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case HDLC_FAST_IDLE:
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if (hdlc->cbin == 0xff) {
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hdlc->bit_shift = 0;
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break;
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}
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hdlc->state = HDLC_GET_FLAG_B0;
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hdlc->hdlc_bits1 = 0;
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hdlc->bit_shift = 8;
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break;
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case HDLC_GET_FLAG_B0:
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if (!(hdlc->cbin & 0x80)) {
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hdlc->state = HDLC_GETFLAG_B1A6;
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hdlc->hdlc_bits1 = 0;
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} else {
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if ((!hdlc->do_adapt56) &&
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(++hdlc->hdlc_bits1 >= 8) &&
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(hdlc->bit_shift == 1))
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hdlc->state = HDLC_FAST_IDLE;
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}
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hdlc->cbin <<= 1;
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hdlc->bit_shift--;
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break;
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case HDLC_GETFLAG_B1A6:
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if (hdlc->cbin & 0x80) {
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hdlc->hdlc_bits1++;
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if (hdlc->hdlc_bits1 == 6)
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hdlc->state = HDLC_GETFLAG_B7;
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} else
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hdlc->hdlc_bits1 = 0;
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hdlc->cbin <<= 1;
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hdlc->bit_shift--;
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break;
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case HDLC_GETFLAG_B7:
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if (hdlc->cbin & 0x80) {
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hdlc->state = HDLC_GET_FLAG_B0;
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} else {
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hdlc->state = HDLC_GET_DATA;
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hdlc->crc = 0xffff;
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hdlc->shift_reg = 0;
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hdlc->hdlc_bits1 = 0;
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hdlc->data_bits = 0;
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hdlc->data_received = 0;
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}
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hdlc->cbin <<= 1;
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hdlc->bit_shift--;
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break;
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case HDLC_GET_DATA:
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if (hdlc->cbin & 0x80) {
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hdlc->hdlc_bits1++;
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switch (hdlc->hdlc_bits1) {
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case 6:
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break;
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case 7:
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if (hdlc->data_received)
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/* bad frame */
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status = -HDLC_FRAMING_ERROR;
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if (!hdlc->do_adapt56) {
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if (hdlc->cbin == fast_abort
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[hdlc->bit_shift + 1]) {
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hdlc->state =
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HDLC_FAST_IDLE;
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hdlc->bit_shift = 1;
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break;
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}
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} else
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hdlc->state = HDLC_GET_FLAG_B0;
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break;
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default:
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hdlc->shift_reg >>= 1;
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hdlc->shift_reg |= 0x80;
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hdlc->data_bits++;
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break;
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}
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} else {
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switch (hdlc->hdlc_bits1) {
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case 5:
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break;
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case 6:
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if (hdlc->data_received)
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status = check_frame(hdlc);
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hdlc->crc = 0xffff;
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hdlc->shift_reg = 0;
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hdlc->data_bits = 0;
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if (!hdlc->do_adapt56)
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handle_fast_flag(hdlc);
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else {
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hdlc->state = HDLC_GET_DATA;
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hdlc->data_received = 0;
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}
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break;
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default:
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hdlc->shift_reg >>= 1;
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hdlc->data_bits++;
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break;
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}
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hdlc->hdlc_bits1 = 0;
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}
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if (status) {
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hdlc->dstpos = 0;
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*count -= slen;
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hdlc->cbin <<= 1;
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hdlc->bit_shift--;
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return status;
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}
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if (hdlc->data_bits == 8) {
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hdlc->data_bits = 0;
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hdlc->data_received = 1;
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hdlc->crc = crc_ccitt_byte(hdlc->crc,
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hdlc->shift_reg);
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/* good byte received */
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if (hdlc->dstpos < dsize)
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dst[hdlc->dstpos++] = hdlc->shift_reg;
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else {
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/* frame too long */
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status = -HDLC_LENGTH_ERROR;
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hdlc->dstpos = 0;
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}
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}
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hdlc->cbin <<= 1;
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hdlc->bit_shift--;
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break;
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case HDLC_FAST_FLAG:
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if (hdlc->cbin == hdlc->ffvalue) {
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hdlc->bit_shift = 0;
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break;
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} else {
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if (hdlc->cbin == 0xff) {
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hdlc->state = HDLC_FAST_IDLE;
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hdlc->bit_shift = 0;
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} else if (hdlc->ffbit_shift == 8) {
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hdlc->state = HDLC_GETFLAG_B7;
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break;
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} else
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handle_abort(hdlc);
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}
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break;
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default:
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break;
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}
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}
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*count -= slen;
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return 0;
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}
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EXPORT_SYMBOL(isdnhdlc_decode);
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/*
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isdnhdlc_encode - encodes HDLC frames to a transparent bit stream.
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The bit stream starts with a beginning flag (01111110). After
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that each byte is added to the bit stream with bit stuffing added
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(0 after 5 1's).
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When the last byte has been removed from the source buffer, the
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CRC (2 bytes is added) and the frame terminates with the ending flag.
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For the dchannel, the idle character (all 1's) is also added at the end.
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If this function is called with empty source buffer (slen=0), flags or
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idle character will be generated.
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src - source buffer
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slen - source buffer length
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count - number of bytes removed (encoded) from source buffer
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dst _ destination buffer
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dsize - destination buffer size
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returns - number of encoded bytes in the destination buffer
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*/
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int isdnhdlc_encode(struct isdnhdlc_vars *hdlc, const u8 *src, u16 slen,
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int *count, u8 *dst, int dsize)
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{
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static const unsigned char xfast_flag_value[] = {
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0x7e, 0x3f, 0x9f, 0xcf, 0xe7, 0xf3, 0xf9, 0xfc, 0x7e
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};
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int len = 0;
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*count = slen;
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/* special handling for one byte frames */
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if ((slen == 1) && (hdlc->state == HDLC_SEND_FAST_FLAG))
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hdlc->state = HDLC_SENDFLAG_ONE;
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while (dsize > 0) {
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if (hdlc->bit_shift == 0) {
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if (slen && !hdlc->do_closing) {
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hdlc->shift_reg = *src++;
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slen--;
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if (slen == 0)
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/* closing sequence, CRC + flag(s) */
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hdlc->do_closing = 1;
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hdlc->bit_shift = 8;
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} else {
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if (hdlc->state == HDLC_SEND_DATA) {
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if (hdlc->data_received) {
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hdlc->state = HDLC_SEND_CRC1;
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hdlc->crc ^= 0xffff;
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hdlc->bit_shift = 8;
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hdlc->shift_reg =
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hdlc->crc & 0xff;
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} else if (!hdlc->do_adapt56)
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hdlc->state =
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HDLC_SEND_FAST_FLAG;
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else
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hdlc->state =
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HDLC_SENDFLAG_B0;
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}
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}
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}
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switch (hdlc->state) {
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case STOPPED:
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while (dsize--)
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*dst++ = 0xff;
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return dsize;
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case HDLC_SEND_FAST_FLAG:
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hdlc->do_closing = 0;
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if (slen == 0) {
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/* the code is for bitreverse streams */
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if (hdlc->do_bitreverse == 0)
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*dst++ = bitrev8(hdlc->ffvalue);
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else
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*dst++ = hdlc->ffvalue;
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len++;
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dsize--;
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break;
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}
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/* fall through */
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case HDLC_SENDFLAG_ONE:
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if (hdlc->bit_shift == 8) {
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hdlc->cbin = hdlc->ffvalue >>
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(8 - hdlc->data_bits);
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hdlc->state = HDLC_SEND_DATA;
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hdlc->crc = 0xffff;
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hdlc->hdlc_bits1 = 0;
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hdlc->data_received = 1;
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}
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break;
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case HDLC_SENDFLAG_B0:
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hdlc->do_closing = 0;
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hdlc->cbin <<= 1;
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hdlc->data_bits++;
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hdlc->hdlc_bits1 = 0;
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hdlc->state = HDLC_SENDFLAG_B1A6;
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break;
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case HDLC_SENDFLAG_B1A6:
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hdlc->cbin <<= 1;
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hdlc->data_bits++;
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hdlc->cbin++;
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if (++hdlc->hdlc_bits1 == 6)
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hdlc->state = HDLC_SENDFLAG_B7;
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break;
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case HDLC_SENDFLAG_B7:
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hdlc->cbin <<= 1;
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hdlc->data_bits++;
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if (slen == 0) {
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hdlc->state = HDLC_SENDFLAG_B0;
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break;
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}
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if (hdlc->bit_shift == 8) {
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hdlc->state = HDLC_SEND_DATA;
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hdlc->crc = 0xffff;
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hdlc->hdlc_bits1 = 0;
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hdlc->data_received = 1;
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}
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break;
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case HDLC_SEND_FIRST_FLAG:
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hdlc->data_received = 1;
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if (hdlc->data_bits == 8) {
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hdlc->state = HDLC_SEND_DATA;
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hdlc->crc = 0xffff;
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hdlc->hdlc_bits1 = 0;
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break;
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}
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hdlc->cbin <<= 1;
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hdlc->data_bits++;
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if (hdlc->shift_reg & 0x01)
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hdlc->cbin++;
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hdlc->shift_reg >>= 1;
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hdlc->bit_shift--;
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if (hdlc->bit_shift == 0) {
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hdlc->state = HDLC_SEND_DATA;
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hdlc->crc = 0xffff;
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hdlc->hdlc_bits1 = 0;
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}
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break;
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case HDLC_SEND_DATA:
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hdlc->cbin <<= 1;
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hdlc->data_bits++;
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if (hdlc->hdlc_bits1 == 5) {
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hdlc->hdlc_bits1 = 0;
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break;
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}
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if (hdlc->bit_shift == 8)
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hdlc->crc = crc_ccitt_byte(hdlc->crc,
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hdlc->shift_reg);
|
|
if (hdlc->shift_reg & 0x01) {
|
|
hdlc->hdlc_bits1++;
|
|
hdlc->cbin++;
|
|
hdlc->shift_reg >>= 1;
|
|
hdlc->bit_shift--;
|
|
} else {
|
|
hdlc->hdlc_bits1 = 0;
|
|
hdlc->shift_reg >>= 1;
|
|
hdlc->bit_shift--;
|
|
}
|
|
break;
|
|
case HDLC_SEND_CRC1:
|
|
hdlc->cbin <<= 1;
|
|
hdlc->data_bits++;
|
|
if (hdlc->hdlc_bits1 == 5) {
|
|
hdlc->hdlc_bits1 = 0;
|
|
break;
|
|
}
|
|
if (hdlc->shift_reg & 0x01) {
|
|
hdlc->hdlc_bits1++;
|
|
hdlc->cbin++;
|
|
hdlc->shift_reg >>= 1;
|
|
hdlc->bit_shift--;
|
|
} else {
|
|
hdlc->hdlc_bits1 = 0;
|
|
hdlc->shift_reg >>= 1;
|
|
hdlc->bit_shift--;
|
|
}
|
|
if (hdlc->bit_shift == 0) {
|
|
hdlc->shift_reg = (hdlc->crc >> 8);
|
|
hdlc->state = HDLC_SEND_CRC2;
|
|
hdlc->bit_shift = 8;
|
|
}
|
|
break;
|
|
case HDLC_SEND_CRC2:
|
|
hdlc->cbin <<= 1;
|
|
hdlc->data_bits++;
|
|
if (hdlc->hdlc_bits1 == 5) {
|
|
hdlc->hdlc_bits1 = 0;
|
|
break;
|
|
}
|
|
if (hdlc->shift_reg & 0x01) {
|
|
hdlc->hdlc_bits1++;
|
|
hdlc->cbin++;
|
|
hdlc->shift_reg >>= 1;
|
|
hdlc->bit_shift--;
|
|
} else {
|
|
hdlc->hdlc_bits1 = 0;
|
|
hdlc->shift_reg >>= 1;
|
|
hdlc->bit_shift--;
|
|
}
|
|
if (hdlc->bit_shift == 0) {
|
|
hdlc->shift_reg = 0x7e;
|
|
hdlc->state = HDLC_SEND_CLOSING_FLAG;
|
|
hdlc->bit_shift = 8;
|
|
}
|
|
break;
|
|
case HDLC_SEND_CLOSING_FLAG:
|
|
hdlc->cbin <<= 1;
|
|
hdlc->data_bits++;
|
|
if (hdlc->hdlc_bits1 == 5) {
|
|
hdlc->hdlc_bits1 = 0;
|
|
break;
|
|
}
|
|
if (hdlc->shift_reg & 0x01)
|
|
hdlc->cbin++;
|
|
hdlc->shift_reg >>= 1;
|
|
hdlc->bit_shift--;
|
|
if (hdlc->bit_shift == 0) {
|
|
hdlc->ffvalue =
|
|
xfast_flag_value[hdlc->data_bits];
|
|
if (hdlc->dchannel) {
|
|
hdlc->ffvalue = 0x7e;
|
|
hdlc->state = HDLC_SEND_IDLE1;
|
|
hdlc->bit_shift = 8-hdlc->data_bits;
|
|
if (hdlc->bit_shift == 0)
|
|
hdlc->state =
|
|
HDLC_SEND_FAST_IDLE;
|
|
} else {
|
|
if (!hdlc->do_adapt56) {
|
|
hdlc->state =
|
|
HDLC_SEND_FAST_FLAG;
|
|
hdlc->data_received = 0;
|
|
} else {
|
|
hdlc->state = HDLC_SENDFLAG_B0;
|
|
hdlc->data_received = 0;
|
|
}
|
|
/* Finished this frame, send flags */
|
|
if (dsize > 1)
|
|
dsize = 1;
|
|
}
|
|
}
|
|
break;
|
|
case HDLC_SEND_IDLE1:
|
|
hdlc->do_closing = 0;
|
|
hdlc->cbin <<= 1;
|
|
hdlc->cbin++;
|
|
hdlc->data_bits++;
|
|
hdlc->bit_shift--;
|
|
if (hdlc->bit_shift == 0) {
|
|
hdlc->state = HDLC_SEND_FAST_IDLE;
|
|
hdlc->bit_shift = 0;
|
|
}
|
|
break;
|
|
case HDLC_SEND_FAST_IDLE:
|
|
hdlc->do_closing = 0;
|
|
hdlc->cbin = 0xff;
|
|
hdlc->data_bits = 8;
|
|
if (hdlc->bit_shift == 8) {
|
|
hdlc->cbin = 0x7e;
|
|
hdlc->state = HDLC_SEND_FIRST_FLAG;
|
|
} else {
|
|
/* the code is for bitreverse streams */
|
|
if (hdlc->do_bitreverse == 0)
|
|
*dst++ = bitrev8(hdlc->cbin);
|
|
else
|
|
*dst++ = hdlc->cbin;
|
|
hdlc->bit_shift = 0;
|
|
hdlc->data_bits = 0;
|
|
len++;
|
|
dsize = 0;
|
|
}
|
|
break;
|
|
default:
|
|
break;
|
|
}
|
|
if (hdlc->do_adapt56) {
|
|
if (hdlc->data_bits == 7) {
|
|
hdlc->cbin <<= 1;
|
|
hdlc->cbin++;
|
|
hdlc->data_bits++;
|
|
}
|
|
}
|
|
if (hdlc->data_bits == 8) {
|
|
/* the code is for bitreverse streams */
|
|
if (hdlc->do_bitreverse == 0)
|
|
*dst++ = bitrev8(hdlc->cbin);
|
|
else
|
|
*dst++ = hdlc->cbin;
|
|
hdlc->data_bits = 0;
|
|
len++;
|
|
dsize--;
|
|
}
|
|
}
|
|
*count -= slen;
|
|
|
|
return len;
|
|
}
|
|
EXPORT_SYMBOL(isdnhdlc_encode);
|