busybox/miscutils/rx.c

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/* vi: set sw=4 ts=4: */
/*
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* Copyright: Copyright (C) 2001, Hewlett-Packard Company
* Author: Christopher Hoover <ch@hpl.hp.com>
* Description: xmodem functionality for uploading of kernels
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* and the like
* Created at: Thu Dec 20 01:58:08 PST 2001
*
* xmodem functionality for uploading of kernels and the like
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*
* Copyright (C) 2001 Hewlett-Packard Laboratories
*
* Licensed under GPLv2 or later, see file LICENSE in this source tree.
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*
* This was originally written for blob and then adapted for busybox.
*/
//config:config RX
//config: bool "rx (2.9 kb)"
//config: default y
//config: select PLATFORM_LINUX
//config: help
//config: Receive files using the Xmodem protocol.
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//applet:IF_RX(APPLET(rx, BB_DIR_USR_BIN, BB_SUID_DROP))
//kbuild:lib-$(CONFIG_RX) += rx.o
//usage:#define rx_trivial_usage
//usage: "FILE"
//usage:#define rx_full_usage "\n\n"
//usage: "Receive a file using the xmodem protocol"
//usage:
//usage:#define rx_example_usage
//usage: "$ rx /tmp/foo\n"
#include "libbb.h"
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#define SOH 0x01
#define STX 0x02
#define EOT 0x04
#define ACK 0x06
#define NAK 0x15
#define BS 0x08
#define PAD 0x1A
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/*
Cf:
http://www.textfiles.com/apple/xmodem
http://www.phys.washington.edu/~belonis/xmodem/docxmodem.txt
http://www.phys.washington.edu/~belonis/xmodem/docymodem.txt
http://www.phys.washington.edu/~belonis/xmodem/modmprot.col
*/
#define TIMEOUT 1
#define TIMEOUT_LONG 10
#define MAXERRORS 10
#define read_fd STDIN_FILENO
#define write_fd STDOUT_FILENO
static int read_byte(unsigned timeout)
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{
unsigned char buf;
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int n;
alarm(timeout);
/* NOT safe_read! We want ALRM to interrupt us */
n = read(read_fd, &buf, 1);
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alarm(0);
if (n == 1)
return buf;
return -1;
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}
static int receive(/*int read_fd, */int file_fd)
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{
unsigned char blockBuf[1024];
unsigned blockLength = 0;
unsigned errors = 0;
unsigned wantBlockNo = 1;
unsigned length = 0;
int do_crc = 1;
char reply_char;
unsigned timeout = TIMEOUT_LONG;
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/* Flush pending input */
tcflush(read_fd, TCIFLUSH);
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/* Ask for CRC; if we get errors, we will go with checksum */
reply_char = 'C';
full_write(write_fd, &reply_char, 1);
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for (;;) {
int blockBegin;
int blockNo, blockNoOnesCompl;
int cksum_or_crc;
unsigned expected;
int i, j;
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blockBegin = read_byte(timeout);
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if (blockBegin < 0)
goto timeout;
/* If last block, remove padding */
if (blockBegin == EOT) {
/* Data blocks can be padded with ^Z characters */
/* This code tries to detect and remove them */
if (blockLength >= 3
&& blockBuf[blockLength - 1] == PAD
&& blockBuf[blockLength - 2] == PAD
&& blockBuf[blockLength - 3] == PAD
) {
while (blockLength
&& blockBuf[blockLength - 1] == PAD
) {
blockLength--;
}
}
}
/* Write previously received block */
errno = 0;
if (full_write(file_fd, blockBuf, blockLength) != blockLength) {
bb_perror_msg(bb_msg_write_error);
goto fatal;
}
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timeout = TIMEOUT;
reply_char = NAK;
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switch (blockBegin) {
case SOH:
case STX:
break;
case EOT:
reply_char = ACK;
full_write(write_fd, &reply_char, 1);
return length;
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default:
goto error;
}
/* Block no */
blockNo = read_byte(TIMEOUT);
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if (blockNo < 0)
goto timeout;
/* Block no, in one's complement form */
blockNoOnesCompl = read_byte(TIMEOUT);
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if (blockNoOnesCompl < 0)
goto timeout;
if (blockNo != (255 - blockNoOnesCompl)) {
bb_error_msg("bad block ones compl");
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goto error;
}
blockLength = (blockBegin == SOH) ? 128 : 1024;
for (i = 0; i < blockLength; i++) {
int cc = read_byte(TIMEOUT);
if (cc < 0)
goto timeout;
blockBuf[i] = cc;
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}
cksum_or_crc = read_byte(TIMEOUT);
if (cksum_or_crc < 0)
goto timeout;
if (do_crc) {
cksum_or_crc = (cksum_or_crc << 8) | read_byte(TIMEOUT);
if (cksum_or_crc < 0)
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goto timeout;
}
if (blockNo == ((wantBlockNo - 1) & 0xff)) {
/* a repeat of the last block is ok, just ignore it. */
/* this also ignores the initial block 0 which is */
/* meta data. */
blockLength = 0;
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goto next;
}
if (blockNo != (wantBlockNo & 0xff)) {
bb_error_msg("unexpected block no, 0x%08x, expecting 0x%08x", blockNo, wantBlockNo);
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goto error;
}
expected = 0;
if (do_crc) {
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for (i = 0; i < blockLength; i++) {
expected = expected ^ blockBuf[i] << 8;
for (j = 0; j < 8; j++) {
if (expected & 0x8000)
expected = (expected << 1) ^ 0x1021;
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else
expected = (expected << 1);
}
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}
expected &= 0xffff;
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} else {
for (i = 0; i < blockLength; i++)
expected += blockBuf[i];
expected &= 0xff;
}
if (cksum_or_crc != expected) {
bb_error_msg(do_crc ? "crc error, expected 0x%04x, got 0x%04x"
: "checksum error, expected 0x%02x, got 0x%02x",
expected, cksum_or_crc);
goto error;
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}
wantBlockNo++;
length += blockLength;
next:
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errors = 0;
reply_char = ACK;
full_write(write_fd, &reply_char, 1);
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continue;
error:
timeout:
blockLength = 0;
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errors++;
if (errors == MAXERRORS) {
/* Abort */
/* If were asking for crc, try again w/o crc */
if (reply_char == 'C') {
reply_char = NAK;
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errors = 0;
do_crc = 0;
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goto timeout;
}
bb_error_msg("too many errors; giving up");
fatal:
/* 5 CAN followed by 5 BS. Don't try too hard... */
safe_write(write_fd, "\030\030\030\030\030\010\010\010\010\010", 10);
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return -1;
}
/* Flush pending input */
tcflush(read_fd, TCIFLUSH);
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full_write(write_fd, &reply_char, 1);
} /* for (;;) */
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}
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static void sigalrm_handler(int UNUSED_PARAM signum)
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{
}
int rx_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int rx_main(int argc UNUSED_PARAM, char **argv)
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{
struct termios tty, orig_tty;
int termios_err;
int file_fd;
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int n;
/* Disabled by vda:
* why we can't receive from stdin? Why we *require*
* controlling tty?? */
/*read_fd = xopen(CURRENT_TTY, O_RDWR);*/
file_fd = xopen(single_argv(argv), O_RDWR|O_CREAT|O_TRUNC);
termios_err = tcgetattr(read_fd, &tty);
if (termios_err == 0) {
//TODO: use set_termios_to_raw()
orig_tty = tty;
cfmakeraw(&tty);
tcsetattr(read_fd, TCSAFLUSH, &tty);
}
/* No SA_RESTART: we want ALRM to interrupt read() */
signal_no_SA_RESTART_empty_mask(SIGALRM, sigalrm_handler);
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n = receive(file_fd);
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if (termios_err == 0)
tcsetattr(read_fd, TCSAFLUSH, &orig_tty);
if (ENABLE_FEATURE_CLEAN_UP)
close(file_fd);
fflush_stdout_and_exit(n >= 0);
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}