miscutils/rx.c

   1 /* vi: set sw=4 ts=4: */
   2 /*
   3  * Copyright:     Copyright (C) 2001, Hewlett-Packard Company
   4  * Author:        Christopher Hoover <ch@hpl.hp.com>
   5  * Description:   xmodem functionality for uploading of kernels
   6  *                and the like
   7  * Created at:    Thu Dec 20 01:58:08 PST 2001
   8  *
   9  * xmodem functionality for uploading of kernels and the like
  10  *
  11  * Copyright (C) 2001 Hewlett-Packard Laboratories
  12  *
  13  * Licensed under GPLv2 or later, see file LICENSE in this source tree.
  14  *
  15  * This was originally written for blob and then adapted for busybox.
  16  */
  17
  18 //usage:#define rx_trivial_usage
  19 //usage:       "FILE"
  20 //usage:#define rx_full_usage "\n\n"
  21 //usage:       "Receive a file using the xmodem protocol"
  22 //usage:
  23 //usage:#define rx_example_usage
  24 //usage:       "$ rx /tmp/foo\n"
  25
  26 #include "libbb.h"
  27
  28 #define SOH 0x01
  29 #define STX 0x02
  30 #define EOT 0x04
  31 #define ACK 0x06
  32 #define NAK 0x15
  33 #define BS  0x08
  34 #define PAD 0x1A
  35
  36 /*
  37 Cf:
  38   http://www.textfiles.com/apple/xmodem
  39   http://www.phys.washington.edu/~belonis/xmodem/docxmodem.txt
  40   http://www.phys.washington.edu/~belonis/xmodem/docymodem.txt
  41   http://www.phys.washington.edu/~belonis/xmodem/modmprot.col
  42 */
  43
  44 #define TIMEOUT 1
  45 #define TIMEOUT_LONG 10
  46 #define MAXERRORS 10
  47
  48 #define read_fd  STDIN_FILENO
  49 #define write_fd STDOUT_FILENO
  50
  51 static int read_byte(unsigned timeout)
  52 {
  53         unsigned char buf;
  54         int n;
  55
  56         alarm(timeout);
  57         /* NOT safe_read! We want ALRM to interrupt us */
  58         n = read(read_fd, &buf, 1);
  59         alarm(0);
  60         if (n == 1)
  61                 return buf;
  62         return -1;
  63 }
  64
  65 static int receive(/*int read_fd, */int file_fd)
  66 {
  67         unsigned char blockBuf[1024];
  68         unsigned blockLength = 0;
  69         unsigned errors = 0;
  70         unsigned wantBlockNo = 1;
  71         unsigned length = 0;
  72         int do_crc = 1;
  73         char reply_char;
  74         unsigned timeout = TIMEOUT_LONG;
  75
  76         /* Flush pending input */
  77         tcflush(read_fd, TCIFLUSH);
  78
  79         /* Ask for CRC; if we get errors, we will go with checksum */
  80         reply_char = 'C';
  81         full_write(write_fd, &reply_char, 1);
  82
  83         for (;;) {
  84                 int blockBegin;
  85                 int blockNo, blockNoOnesCompl;
  86                 int cksum_or_crc;
  87                 int expected;
  88                 int i, j;
  89
  90                 blockBegin = read_byte(timeout);
  91                 if (blockBegin < 0)
  92                         goto timeout;
  93
  94                 /* If last block, remove padding */
  95                 if (blockBegin == EOT) {
  96                         /* Data blocks can be padded with ^Z characters */
  97                         /* This code tries to detect and remove them */
  98                         if (blockLength >= 3
  99                          && blockBuf[blockLength - 1] == PAD
 100                          && blockBuf[blockLength - 2] == PAD
 101                          && blockBuf[blockLength - 3] == PAD
 102                         ) {
 103                                 while (blockLength
 104                                    && blockBuf[blockLength - 1] == PAD
 105                                 ) {
 106                                         blockLength--;
 107                                 }
 108                         }
 109                 }
 110                 /* Write previously received block */
 111                 if (blockLength) {
 112                         errno = 0;
 113                         if (full_write(file_fd, blockBuf, blockLength) != blockLength) {
 114                                 bb_perror_msg("can't write to file");
 115                                 goto fatal;
 116                         }
 117                 }
 118
 119                 timeout = TIMEOUT;
 120                 reply_char = NAK;
 121
 122                 switch (blockBegin) {
 123                 case SOH:
 124                 case STX:
 125                         break;
 126                 case EOT:
 127                         reply_char = ACK;
 128                         full_write(write_fd, &reply_char, 1);
 129                         return length;
 130                 default:
 131                         goto error;
 132                 }
 133
 134                 /* Block no */
 135                 blockNo = read_byte(TIMEOUT);
 136                 if (blockNo < 0)
 137                         goto timeout;
 138
 139                 /* Block no, in one's complement form */
 140                 blockNoOnesCompl = read_byte(TIMEOUT);
 141                 if (blockNoOnesCompl < 0)
 142                         goto timeout;
 143
 144                 if (blockNo != (255 - blockNoOnesCompl)) {
 145                         bb_error_msg("bad block ones compl");
 146                         goto error;
 147                 }
 148
 149                 blockLength = (blockBegin == SOH) ? 128 : 1024;
 150
 151                 for (i = 0; i < blockLength; i++) {
 152                         int cc = read_byte(TIMEOUT);
 153                         if (cc < 0)
 154                                 goto timeout;
 155                         blockBuf[i] = cc;
 156                 }
 157
 158                 if (do_crc) {
 159                         cksum_or_crc = read_byte(TIMEOUT);
 160                         if (cksum_or_crc < 0)
 161                                 goto timeout;
 162                         cksum_or_crc = (cksum_or_crc << 8) | read_byte(TIMEOUT);
 163                         if (cksum_or_crc < 0)
 164                                 goto timeout;
 165                 } else {
 166                         cksum_or_crc = read_byte(TIMEOUT);
 167                         if (cksum_or_crc < 0)
 168                                 goto timeout;
 169                 }
 170
 171                 if (blockNo == ((wantBlockNo - 1) & 0xff)) {
 172                         /* a repeat of the last block is ok, just ignore it. */
 173                         /* this also ignores the initial block 0 which is */
 174                         /* meta data. */
 175                         goto next;
 176                 }
 177                 if (blockNo != (wantBlockNo & 0xff)) {
 178                         bb_error_msg("unexpected block no, 0x%08x, expecting 0x%08x", blockNo, wantBlockNo);
 179                         goto error;
 180                 }
 181
 182                 expected = 0;
 183                 if (do_crc) {
 184                         for (i = 0; i < blockLength; i++) {
 185                                 expected = expected ^ blockBuf[i] << 8;
 186                                 for (j = 0; j < 8; j++) {
 187                                         if (expected & 0x8000)
 188                                                 expected = (expected << 1) ^ 0x1021;
 189                                         else
 190                                                 expected = (expected << 1);
 191                                 }
 192                         }
 193                         expected &= 0xffff;
 194                 } else {
 195                         for (i = 0; i < blockLength; i++)
 196                                 expected += blockBuf[i];
 197                         expected &= 0xff;
 198                 }
 199                 if (cksum_or_crc != expected) {
 200                         bb_error_msg(do_crc ? "crc error, expected 0x%04x, got 0x%04x"
 201                                            : "checksum error, expected 0x%02x, got 0x%02x",
 202                                         expected, cksum_or_crc);
 203                         goto error;
 204                 }
 205
 206                 wantBlockNo++;
 207                 length += blockLength;
 208  next:
 209                 errors = 0;
 210                 reply_char = ACK;
 211                 full_write(write_fd, &reply_char, 1);
 212                 continue;
 213  error:
 214  timeout:
 215                 errors++;
 216                 if (errors == MAXERRORS) {
 217                         /* Abort */
 218
 219                         /* If were asking for crc, try again w/o crc */
 220                         if (reply_char == 'C') {
 221                                 reply_char = NAK;
 222                                 errors = 0;
 223                                 do_crc = 0;
 224                                 goto timeout;
 225                         }
 226                         bb_error_msg("too many errors; giving up");
 227  fatal:
 228                         /* 5 CAN followed by 5 BS. Don't try too hard... */
 229                         safe_write(write_fd, "\030\030\030\030\030\010\010\010\010\010", 10);
 230                         return -1;
 231                 }
 232
 233                 /* Flush pending input */
 234                 tcflush(read_fd, TCIFLUSH);
 235
 236                 full_write(write_fd, &reply_char, 1);
 237         } /* for (;;) */
 238 }
 239
 240 static void sigalrm_handler(int UNUSED_PARAM signum)
 241 {
 242 }
 243
 244 int rx_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 245 int rx_main(int argc UNUSED_PARAM, char **argv)
 246 {
 247         struct termios tty, orig_tty;
 248         int termios_err;
 249         int file_fd;
 250         int n;
 251
 252         /* Disabled by vda:
 253          * why we can't receive from stdin? Why we *require*
 254          * controlling tty?? */
 255         /*read_fd = xopen(CURRENT_TTY, O_RDWR);*/
 256         file_fd = xopen(single_argv(argv), O_RDWR|O_CREAT|O_TRUNC);
 257
 258         termios_err = tcgetattr(read_fd, &tty);
 259         if (termios_err == 0) {
 260                 orig_tty = tty;
 261                 cfmakeraw(&tty);
 262                 tcsetattr(read_fd, TCSAFLUSH, &tty);
 263         }
 264
 265         /* No SA_RESTART: we want ALRM to interrupt read() */
 266         signal_no_SA_RESTART_empty_mask(SIGALRM, sigalrm_handler);
 267
 268         n = receive(file_fd);
 269
 270         if (termios_err == 0)
 271                 tcsetattr(read_fd, TCSAFLUSH, &orig_tty);
 272         if (ENABLE_FEATURE_CLEAN_UP)
 273                 close(file_fd);
 274         fflush_stdout_and_exit(n >= 0);
 275 }