LXR busybox/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//config:config RX
  18//config:       bool "rx (2.9 kb)"
  19//config:       default y
  20//config:       select PLATFORM_LINUX
  21//config:       help
  22//config:       Receive files using the Xmodem protocol.
  23
  24//applet:IF_RX(APPLET(rx, BB_DIR_USR_BIN, BB_SUID_DROP))
  25
  26//kbuild:lib-$(CONFIG_RX) += rx.o
  27
  28//usage:#define rx_trivial_usage
  29//usage:       "FILE"
  30//usage:#define rx_full_usage "\n\n"
  31//usage:       "Receive a file using the xmodem protocol"
  32//usage:
  33//usage:#define rx_example_usage
  34//usage:       "$ rx /tmp/foo\n"
  35
  36#include "libbb.h"
  37
  38#define SOH 0x01
  39#define STX 0x02
  40#define EOT 0x04
  41#define ACK 0x06
  42#define NAK 0x15
  43#define BS  0x08
  44#define PAD 0x1A
  45
  46/*
  47Cf:
  48  http://www.textfiles.com/apple/xmodem
  49  http://www.phys.washington.edu/~belonis/xmodem/docxmodem.txt
  50  http://www.phys.washington.edu/~belonis/xmodem/docymodem.txt
  51  http://www.phys.washington.edu/~belonis/xmodem/modmprot.col
  52*/
  53
  54#define TIMEOUT 1
  55#define TIMEOUT_LONG 10
  56#define MAXERRORS 10
  57
  58#define read_fd  STDIN_FILENO
  59#define write_fd STDOUT_FILENO
  60
  61static int read_byte(unsigned timeout)
  62{
  63        unsigned char buf;
  64        int n;
  65
  66        alarm(timeout);
  67        /* NOT safe_read! We want ALRM to interrupt us */
  68        n = read(read_fd, &buf, 1);
  69        alarm(0);
  70        if (n == 1)
  71                return buf;
  72        return -1;
  73}
  74
  75static int receive(/*int read_fd, */int file_fd)
  76{
  77        unsigned char blockBuf[1024];
  78        unsigned blockLength = 0;
  79        unsigned errors = 0;
  80        unsigned wantBlockNo = 1;
  81        unsigned length = 0;
  82        int do_crc = 1;
  83        char reply_char;
  84        unsigned timeout = TIMEOUT_LONG;
  85
  86        /* Flush pending input */
  87        tcflush(read_fd, TCIFLUSH);
  88
  89        /* Ask for CRC; if we get errors, we will go with checksum */
  90        reply_char = 'C';
  91        full_write(write_fd, &reply_char, 1);
  92
  93        for (;;) {
  94                int blockBegin;
  95                int blockNo, blockNoOnesCompl;
  96                int cksum_or_crc;
  97                unsigned expected;
  98                int i, j;
  99
 100                blockBegin = read_byte(timeout);
 101                if (blockBegin < 0)
 102                        goto timeout;
 103
 104                /* If last block, remove padding */
 105                if (blockBegin == EOT) {
 106                        /* Data blocks can be padded with ^Z characters */
 107                        /* This code tries to detect and remove them */
 108                        if (blockLength >= 3
 109                         && blockBuf[blockLength - 1] == PAD
 110                         && blockBuf[blockLength - 2] == PAD
 111                         && blockBuf[blockLength - 3] == PAD
 112                        ) {
 113                                while (blockLength
 114                                    && blockBuf[blockLength - 1] == PAD
 115                                ) {
 116                                        blockLength--;
 117                                }
 118                        }
 119                }
 120                /* Write previously received block */
 121                errno = 0;
 122                if (full_write(file_fd, blockBuf, blockLength) != blockLength) {
 123                        bb_perror_msg(bb_msg_write_error);
 124                        goto fatal;
 125                }
 126
 127                timeout = TIMEOUT;
 128                reply_char = NAK;
 129
 130                switch (blockBegin) {
 131                case SOH:
 132                case STX:
 133                        break;
 134                case EOT:
 135                        reply_char = ACK;
 136                        full_write(write_fd, &reply_char, 1);
 137                        return length;
 138                default:
 139                        goto error;
 140                }
 141
 142                /* Block no */
 143                blockNo = read_byte(TIMEOUT);
 144                if (blockNo < 0)
 145                        goto timeout;
 146
 147                /* Block no, in one's complement form */
 148                blockNoOnesCompl = read_byte(TIMEOUT);
 149                if (blockNoOnesCompl < 0)
 150                        goto timeout;
 151
 152                if (blockNo != (255 - blockNoOnesCompl)) {
 153                        bb_error_msg("bad block ones compl");
 154                        goto error;
 155                }
 156
 157                blockLength = (blockBegin == SOH) ? 128 : 1024;
 158
 159                for (i = 0; i < blockLength; i++) {
 160                        int cc = read_byte(TIMEOUT);
 161                        if (cc < 0)
 162                                goto timeout;
 163                        blockBuf[i] = cc;
 164                }
 165
 166                cksum_or_crc = read_byte(TIMEOUT);
 167                if (cksum_or_crc < 0)
 168                        goto timeout;
 169                if (do_crc) {
 170                        cksum_or_crc = (cksum_or_crc << 8) | read_byte(TIMEOUT);
 171                        if (cksum_or_crc < 0)
 172                                goto timeout;
 173                }
 174
 175                if (blockNo == ((wantBlockNo - 1) & 0xff)) {
 176                        /* a repeat of the last block is ok, just ignore it. */
 177                        /* this also ignores the initial block 0 which is */
 178                        /* meta data. */
 179                        blockLength = 0;
 180                        goto next;
 181                }
 182                if (blockNo != (wantBlockNo & 0xff)) {
 183                        bb_error_msg("unexpected block no, 0x%08x, expecting 0x%08x", blockNo, wantBlockNo);
 184                        goto error;
 185                }
 186
 187                expected = 0;
 188                if (do_crc) {
 189                        for (i = 0; i < blockLength; i++) {
 190                                expected = expected ^ blockBuf[i] << 8;
 191                                for (j = 0; j < 8; j++) {
 192                                        if (expected & 0x8000)
 193                                                expected = (expected << 1) ^ 0x1021;
 194                                        else
 195                                                expected = (expected << 1);
 196                                }
 197                        }
 198                        expected &= 0xffff;
 199                } else {
 200                        for (i = 0; i < blockLength; i++)
 201                                expected += blockBuf[i];
 202                        expected &= 0xff;
 203                }
 204                if (cksum_or_crc != expected) {
 205                        bb_error_msg(do_crc ? "crc error, expected 0x%04x, got 0x%04x"
 206                                        : "checksum error, expected 0x%02x, got 0x%02x",
 207                                expected, cksum_or_crc);
 208                        goto error;
 209                }
 210
 211                wantBlockNo++;
 212                length += blockLength;
 213 next:
 214                errors = 0;
 215                reply_char = ACK;
 216                full_write(write_fd, &reply_char, 1);
 217                continue;
 218 error:
 219 timeout:
 220                blockLength = 0;
 221                errors++;
 222                if (errors == MAXERRORS) {
 223                        /* Abort */
 224
 225                        /* If were asking for crc, try again w/o crc */
 226                        if (reply_char == 'C') {
 227                                reply_char = NAK;
 228                                errors = 0;
 229                                do_crc = 0;
 230                                goto timeout;
 231                        }
 232                        bb_error_msg("too many errors; giving up");
 233 fatal:
 234                        /* 5 CAN followed by 5 BS. Don't try too hard... */
 235                        safe_write(write_fd, "\030\030\030\030\030\010\010\010\010\010", 10);
 236                        return -1;
 237                }
 238
 239                /* Flush pending input */
 240                tcflush(read_fd, TCIFLUSH);
 241
 242                full_write(write_fd, &reply_char, 1);
 243        } /* for (;;) */
 244}
 245
 246static void sigalrm_handler(int UNUSED_PARAM signum)
 247{
 248}
 249
 250int rx_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 251int rx_main(int argc UNUSED_PARAM, char **argv)
 252{
 253        struct termios tty, orig_tty;
 254        int termios_err;
 255        int file_fd;
 256        int n;
 257
 258        /* Disabled by vda:
 259         * why we can't receive from stdin? Why we *require*
 260         * controlling tty?? */
 261        /*read_fd = xopen(CURRENT_TTY, O_RDWR);*/
 262        file_fd = xopen(single_argv(argv), O_RDWR|O_CREAT|O_TRUNC);
 263
 264        termios_err = tcgetattr(read_fd, &tty);
 265        if (termios_err == 0) {
 266//TODO: use set_termios_to_raw()
 267                orig_tty = tty;
 268                cfmakeraw(&tty);
 269                tcsetattr(read_fd, TCSAFLUSH, &tty);
 270        }
 271
 272        /* No SA_RESTART: we want ALRM to interrupt read() */
 273        signal_no_SA_RESTART_empty_mask(SIGALRM, sigalrm_handler);
 274
 275        n = receive(file_fd);
 276
 277        if (termios_err == 0)
 278                tcsetattr(read_fd, TCSAFLUSH, &orig_tty);
 279        if (ENABLE_FEATURE_CLEAN_UP)
 280                close(file_fd);
 281        fflush_stdout_and_exit(n >= 0);
 282}
 283