1 | /* vi: set sw=4 ts=4: */
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2 | /*
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3 | * Copyright: Copyright (C) 2001, Hewlett-Packard Company
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4 | * Author: Christopher Hoover <ch@hpl.hp.com>
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5 | * Description: xmodem functionality for uploading of kernels
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6 | * and the like
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7 | * Created at: Thu Dec 20 01:58:08 PST 2001
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8 | *
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9 | * xmodem functionality for uploading of kernels and the like
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10 | *
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11 | * Copyright (C) 2001 Hewlett-Packard Laboratories
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12 | *
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13 | * Licensed under GPLv2 or later, see file LICENSE in this source tree.
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14 | *
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15 | * This was originally written for blob and then adapted for busybox.
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16 | */
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17 |
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18 | #include "libbb.h"
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19 |
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20 | #define SOH 0x01
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21 | #define STX 0x02
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22 | #define EOT 0x04
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23 | #define ACK 0x06
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24 | #define NAK 0x15
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25 | #define BS 0x08
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26 | #define PAD 0x1A
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27 |
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28 | /*
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29 | Cf:
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30 | http://www.textfiles.com/apple/xmodem
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31 | http://www.phys.washington.edu/~belonis/xmodem/docxmodem.txt
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32 | http://www.phys.washington.edu/~belonis/xmodem/docymodem.txt
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33 | http://www.phys.washington.edu/~belonis/xmodem/modmprot.col
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34 | */
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35 |
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36 | #define TIMEOUT 1
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37 | #define TIMEOUT_LONG 10
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38 | #define MAXERRORS 10
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39 |
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40 | #define read_fd STDIN_FILENO
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41 | #define write_fd STDOUT_FILENO
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42 |
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43 | static int read_byte(unsigned timeout)
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44 | {
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45 | unsigned char buf;
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46 | int n;
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47 |
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48 | alarm(timeout);
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49 | /* NOT safe_read! We want ALRM to interrupt us */
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50 | n = read(read_fd, &buf, 1);
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51 | alarm(0);
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52 | if (n == 1)
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53 | return buf;
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54 | return -1;
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55 | }
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56 |
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57 | static int receive(/*int read_fd, */int file_fd)
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58 | {
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59 | unsigned char blockBuf[1024];
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60 | unsigned blockLength = 0;
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61 | unsigned errors = 0;
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62 | unsigned wantBlockNo = 1;
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63 | unsigned length = 0;
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64 | int do_crc = 1;
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65 | char reply_char;
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66 | unsigned timeout = TIMEOUT_LONG;
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67 |
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68 | /* Flush pending input */
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69 | tcflush(read_fd, TCIFLUSH);
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70 |
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71 | /* Ask for CRC; if we get errors, we will go with checksum */
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72 | reply_char = 'C';
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73 | full_write(write_fd, &reply_char, 1);
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74 |
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75 | for (;;) {
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76 | int blockBegin;
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77 | int blockNo, blockNoOnesCompl;
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78 | int cksum_or_crc;
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79 | int expected;
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80 | int i, j;
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81 |
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82 | blockBegin = read_byte(timeout);
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83 | if (blockBegin < 0)
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84 | goto timeout;
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85 |
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86 | /* If last block, remove padding */
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87 | if (blockBegin == EOT) {
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88 | /* Data blocks can be padded with ^Z characters */
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89 | /* This code tries to detect and remove them */
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90 | if (blockLength >= 3
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91 | && blockBuf[blockLength - 1] == PAD
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92 | && blockBuf[blockLength - 2] == PAD
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93 | && blockBuf[blockLength - 3] == PAD
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94 | ) {
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95 | while (blockLength
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96 | && blockBuf[blockLength - 1] == PAD
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97 | ) {
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98 | blockLength--;
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99 | }
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100 | }
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101 | }
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102 | /* Write previously received block */
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103 | if (blockLength) {
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104 | errno = 0;
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105 | if (full_write(file_fd, blockBuf, blockLength) != blockLength) {
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106 | bb_perror_msg("can't write to file");
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107 | goto fatal;
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108 | }
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109 | }
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110 |
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111 | timeout = TIMEOUT;
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112 | reply_char = NAK;
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113 |
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114 | switch (blockBegin) {
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115 | case SOH:
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116 | case STX:
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117 | break;
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118 | case EOT:
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119 | reply_char = ACK;
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120 | full_write(write_fd, &reply_char, 1);
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121 | return length;
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122 | default:
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123 | goto error;
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124 | }
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125 |
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126 | /* Block no */
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127 | blockNo = read_byte(TIMEOUT);
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128 | if (blockNo < 0)
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129 | goto timeout;
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130 |
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131 | /* Block no, in one's complement form */
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132 | blockNoOnesCompl = read_byte(TIMEOUT);
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133 | if (blockNoOnesCompl < 0)
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134 | goto timeout;
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135 |
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136 | if (blockNo != (255 - blockNoOnesCompl)) {
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137 | bb_error_msg("bad block ones compl");
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138 | goto error;
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139 | }
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140 |
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141 | blockLength = (blockBegin == SOH) ? 128 : 1024;
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142 |
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143 | for (i = 0; i < blockLength; i++) {
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144 | int cc = read_byte(TIMEOUT);
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145 | if (cc < 0)
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146 | goto timeout;
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147 | blockBuf[i] = cc;
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148 | }
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149 |
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150 | if (do_crc) {
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151 | cksum_or_crc = read_byte(TIMEOUT);
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152 | if (cksum_or_crc < 0)
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153 | goto timeout;
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154 | cksum_or_crc = (cksum_or_crc << 8) | read_byte(TIMEOUT);
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155 | if (cksum_or_crc < 0)
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156 | goto timeout;
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157 | } else {
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158 | cksum_or_crc = read_byte(TIMEOUT);
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159 | if (cksum_or_crc < 0)
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160 | goto timeout;
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161 | }
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162 |
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163 | if (blockNo == ((wantBlockNo - 1) & 0xff)) {
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164 | /* a repeat of the last block is ok, just ignore it. */
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165 | /* this also ignores the initial block 0 which is */
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166 | /* meta data. */
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167 | goto next;
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168 | }
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169 | if (blockNo != (wantBlockNo & 0xff)) {
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170 | bb_error_msg("unexpected block no, 0x%08x, expecting 0x%08x", blockNo, wantBlockNo);
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171 | goto error;
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172 | }
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173 |
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174 | expected = 0;
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175 | if (do_crc) {
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176 | for (i = 0; i < blockLength; i++) {
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177 | expected = expected ^ blockBuf[i] << 8;
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178 | for (j = 0; j < 8; j++) {
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179 | if (expected & 0x8000)
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180 | expected = (expected << 1) ^ 0x1021;
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181 | else
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182 | expected = (expected << 1);
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183 | }
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184 | }
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185 | expected &= 0xffff;
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186 | } else {
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187 | for (i = 0; i < blockLength; i++)
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188 | expected += blockBuf[i];
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189 | expected &= 0xff;
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190 | }
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191 | if (cksum_or_crc != expected) {
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192 | bb_error_msg(do_crc ? "crc error, expected 0x%04x, got 0x%04x"
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193 | : "checksum error, expected 0x%02x, got 0x%02x",
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194 | expected, cksum_or_crc);
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195 | goto error;
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196 | }
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197 |
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198 | wantBlockNo++;
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199 | length += blockLength;
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200 | next:
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201 | errors = 0;
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202 | reply_char = ACK;
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203 | full_write(write_fd, &reply_char, 1);
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204 | continue;
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205 | error:
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206 | timeout:
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207 | errors++;
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208 | if (errors == MAXERRORS) {
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209 | /* Abort */
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210 |
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211 | /* If were asking for crc, try again w/o crc */
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212 | if (reply_char == 'C') {
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213 | reply_char = NAK;
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214 | errors = 0;
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215 | do_crc = 0;
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216 | goto timeout;
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217 | }
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218 | bb_error_msg("too many errors; giving up");
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219 | fatal:
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220 | /* 5 CAN followed by 5 BS. Don't try too hard... */
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221 | safe_write(write_fd, "\030\030\030\030\030\010\010\010\010\010", 10);
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222 | return -1;
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223 | }
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224 |
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225 | /* Flush pending input */
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226 | tcflush(read_fd, TCIFLUSH);
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227 |
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228 | full_write(write_fd, &reply_char, 1);
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229 | } /* for (;;) */
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230 | }
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231 |
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232 | static void sigalrm_handler(int UNUSED_PARAM signum)
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233 | {
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234 | }
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235 |
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236 | int rx_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
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237 | int rx_main(int argc UNUSED_PARAM, char **argv)
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238 | {
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239 | struct termios tty, orig_tty;
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240 | int termios_err;
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241 | int file_fd;
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242 | int n;
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243 |
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244 | /* Disabled by vda:
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245 | * why we can't receive from stdin? Why we *require*
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246 | * controlling tty?? */
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247 | /*read_fd = xopen(CURRENT_TTY, O_RDWR);*/
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248 | file_fd = xopen(single_argv(argv), O_RDWR|O_CREAT|O_TRUNC);
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249 |
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250 | termios_err = tcgetattr(read_fd, &tty);
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251 | if (termios_err == 0) {
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252 | orig_tty = tty;
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253 | cfmakeraw(&tty);
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254 | tcsetattr(read_fd, TCSAFLUSH, &tty);
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255 | }
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256 |
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257 | /* No SA_RESTART: we want ALRM to interrupt read() */
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258 | signal_no_SA_RESTART_empty_mask(SIGALRM, sigalrm_handler);
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259 |
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260 | n = receive(file_fd);
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261 |
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262 | if (termios_err == 0)
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263 | tcsetattr(read_fd, TCSAFLUSH, &orig_tty);
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264 | if (ENABLE_FEATURE_CLEAN_UP)
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265 | close(file_fd);
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266 | fflush_stdout_and_exit(n >= 0);
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267 | }
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