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1 /*
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2 * SpanDSP - a series of DSP components for telephony
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3 *
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4 * v42.h
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5 *
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6 * Written by Steve Underwood <steveu@coppice.org>
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7 *
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8 * Copyright (C) 2003 Steve Underwood
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9 *
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10 * All rights reserved.
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11 *
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12 * This program is free software; you can redistribute it and/or modify
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13 * it under the terms of the GNU General Public License version 2, as
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14 * published by the Free Software Foundation.
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15 *
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16 * This program is distributed in the hope that it will be useful,
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17 * but WITHOUT ANY WARRANTY; without even the implied warranty of
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18 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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19 * GNU General Public License for more details.
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20 *
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21 * You should have received a copy of the GNU General Public License
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22 * along with this program; if not, write to the Free Software
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23 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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24 *
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25 * $Id: v42.h,v 1.17 2006/10/24 13:22:02 steveu Exp $
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26 */
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27
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28 /*! \page v42_page V.42 modem error correction
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29 \section v42_page_sec_1 What does it do?
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30 The V.42 specification defines an error correcting protocol for PSTN modems, based on
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31 HDLC and LAP. This makes it similar to an X.25 link. A special variant of LAP, known
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32 as LAP-M, is defined in the V.42 specification. A means for modems to determine if the
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33 far modem supports V.42 is also defined.
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34
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35 \section v42_page_sec_2 How does it work?
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36 */
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37
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38 #if !defined(_V42_H_)
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39 #define _V42_H_
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40
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41 enum
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42 {
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43 LAPM_DETECT = 0,
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44 LAPM_ESTABLISH = 1,
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45 LAPM_DATA = 2,
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46 LAPM_RELEASE = 3,
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47 LAPM_SIGNAL = 4,
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48 LAPM_SETPARM = 5,
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49 LAPM_TEST = 6,
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50 LAPM_UNSUPPORTED = 7
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51 };
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52
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53 typedef void (*v42_status_func_t)(void *user_data, int status);
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54 typedef void (*v42_frame_handler_t)(void *user_data, const uint8_t *pkt, int len);
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55
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56 typedef struct lapm_frame_queue_s
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57 {
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58 struct lapm_frame_queue_s *next;
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59 int len;
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60 uint8_t frame[];
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61 } lapm_frame_queue_t;
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62
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63 /*!
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64 LAP-M descriptor. This defines the working state for a single instance of LAP-M.
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65 */
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66 typedef struct
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67 {
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68 int handle;
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69 hdlc_rx_state_t hdlc_rx;
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70 hdlc_tx_state_t hdlc_tx;
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71
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72 v42_frame_handler_t iframe_receive;
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73 void *iframe_receive_user_data;
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74
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75 v42_status_func_t status_callback;
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76 void *status_callback_user_data;
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77
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78 int state;
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79 int tx_waiting;
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80 int debug;
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81 /*! TRUE if originator. FALSE if answerer */
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82 int we_are_originator;
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83 /*! Remote network type (unknown, answerer. originator) */
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84 int peer_is_originator;
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85 /*! Next N(S) for transmission */
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86 int next_tx_frame;
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87 /*! The last of our frames which the peer acknowledged */
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88 int last_frame_peer_acknowledged;
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89 /*! Next N(R) for reception */
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90 int next_expected_frame;
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91 /*! The last of the peer's frames which we acknowledged */
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92 int last_frame_we_acknowledged;
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93 /*! TRUE if we sent an I or S frame with the F-bit set */
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94 int solicit_f_bit;
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95 /*! Retransmission count */
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96 int retransmissions;
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97 /*! TRUE if peer is busy */
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98 int busy;
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99
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100 /*! Acknowledgement timer */
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101 int t401_timer;
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102 /*! Reply delay timer - optional */
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103 int t402_timer;
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104 /*! Inactivity timer - optional */
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105 int t403_timer;
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106 /*! Maximum number of octets in an information field */
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107 int n401;
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108 /*! Window size */
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109 int window_size_k;
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110
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111 lapm_frame_queue_t *txqueue;
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112 lapm_frame_queue_t *tx_next;
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113 lapm_frame_queue_t *tx_last;
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114 queue_t tx_queue;
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115
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116 span_sched_state_t sched;
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117 /*! \brief Error and flow logging control */
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118 logging_state_t logging;
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119 } lapm_state_t;
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120
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121 /*!
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122 V.42 descriptor. This defines the working state for a single instance of V.42.
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123 */
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124 typedef struct
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125 {
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126 /*! TRUE if we are the calling party, otherwise FALSE */
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127 int caller;
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128 /*! TRUE if we should detect whether the far end is V.42 capable. FALSE if we go
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129 directly to protocol establishment */
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130 int detect;
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131
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132 /*! Stage in negotiating V.42 support */
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133 int rx_negotiation_step;
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134 int rxbits;
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135 int rxstream;
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136 int rxoks;
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137 int odp_seen;
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138 int txbits;
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139 int txstream;
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140 int txadps;
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141 /*! The LAP.M context */
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142 lapm_state_t lapm;
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143
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144 /*! V.42 support detection timer */
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145 int t400_timer;
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146 /*! \brief Error and flow logging control */
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147 logging_state_t logging;
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148 } v42_state_t;
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149
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150 /*! Log the raw HDLC frames */
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151 #define LAPM_DEBUG_LAPM_RAW (1 << 0)
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152 /*! Log the interpreted frames */
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153 #define LAPM_DEBUG_LAPM_DUMP (1 << 1)
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154 /*! Log state machine changes */
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155 #define LAPM_DEBUG_LAPM_STATE (1 << 2)
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156
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157 #ifdef __cplusplus
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158 extern "C" {
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159 #endif
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160
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161 const char *lapm_status_to_str(int status);
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162
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163 /*! Dump LAP.M frames in a raw and/or decoded forms
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164 \param frame The frame itself
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165 \param len The length of the frame, in octets
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166 \param showraw TRUE if the raw octets should be dumped
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167 \param txrx TRUE if tx, FALSE if rx. Used to highlight the packet's direction.
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168 */
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169 void lapm_dump(lapm_state_t *s, const uint8_t *frame, int len, int showraw, int txrx);
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170
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171 /*! Accept an HDLC packet
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172 */
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173 void lapm_receive(void *user_data, int ok, const uint8_t *buf, int len);
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174
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175 /*! Transmit a LAP.M frame
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176 */
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177 int lapm_tx(lapm_state_t *s, const void *buf, int len);
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178
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179 /*! Transmit a LAP.M information frame
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180 */
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181 int lapm_tx_iframe(lapm_state_t *s, const void *buf, int len, int cr);
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182
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183 /*! Send a break over a LAP.M connection
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184 */
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185 int lapm_break(lapm_state_t *s, int enable);
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186
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187 /*! Initiate an orderly release of a LAP.M connection
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188 */
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189 int lapm_release(lapm_state_t *s);
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190
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191 /*! Enable or disable loopback of a LAP.M connection
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192 */
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193 int lapm_loopback(lapm_state_t *s, int enable);
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194
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195 /*! Assign or remove a callback routine used to deal with V.42 status changes.
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196 */
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197 void v42_set_status_callback(v42_state_t *s, v42_status_func_t callback, void *user_data);
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198
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199 /*! Process a newly received bit for a V.42 context.
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200 */
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201 void v42_rx_bit(void *user_data, int bit);
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202
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203 /*! Get the next transmit bit for a V.42 context.
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204 */
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205 int v42_tx_bit(void *user_data);
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206
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207 /*! Initialise a V.42 context.
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208 \param s The V.42 context.
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209 \param caller TRUE if caller mode, else answerer mode.
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210 \param frame_handler A callback function to handle received frames of data.
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211 \param user_data An opaque pointer passed to the frame handler routine.
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212 \return ???
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213 */
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214 v42_state_t *v42_init(v42_state_t *s, int caller, int detect, v42_frame_handler_t frame_handler, void *user_data);
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215
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216 /*! Restart a V.42 context.
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217 \param s The V.42 context.
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218 */
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219 void v42_restart(v42_state_t *s);
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220
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221 /*! Release a V.42 context.
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222 \param s The V.42 context.
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223 \return 0 if OK */
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224 int v42_release(v42_state_t *s);
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225
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226 #ifdef __cplusplus
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227 }
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228 #endif
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229
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230 #endif
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231 /*- End of file ------------------------------------------------------------*/
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