LXR busybox/miscutils/rx.c

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