path: root/io.c

/* -*- c-file-style: "linux" -*-
 * 
 * Copyright (C) 1996-2001 by Andrew Tridgell 
 * Copyright (C) Paul Mackerras 1996
 * Copyright (C) 2001, 2002 by Martin Pool <mbp@samba.org>
 * 
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 * 
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

/**
 * @file io.c
 *
 * Socket and pipe IO utilities used in rsync.
 *
 * rsync provides its own multiplexing system, which is used to send
 * stderr and stdout over a single socket.  We need this because
 * stdout normally carries the binary data stream, and stderr all our
 * error messages.
 *
 * For historical reasons this is off during the start of the
 * connection, but it's switched on quite early using
 * io_start_multiplex_out() and io_start_multiplex_in().
 **/

#include "rsync.h"

/** If no timeout is specified then use a 60 second select timeout */
#define SELECT_TIMEOUT 60

static int io_multiplexing_out;
static int io_multiplexing_in;
static int multiplex_in_fd;
static int multiplex_out_fd;
static time_t last_io;
static int no_flush;

extern int bwlimit;
extern int verbose;
extern int io_timeout;
extern struct stats stats;


const char phase_unknown[] = "unknown";

/**
 * The connection might be dropped at some point; perhaps because the
 * remote instance crashed.  Just giving the offset on the stream is
 * not very helpful.  So instead we try to make io_phase_name point to
 * something useful.
 *
 * For buffered/multiplexed IO these names will be somewhat
 * approximate; perhaps for ease of support we would rather make the
 * buffer always flush when a single application-level IO finishes.
 *
 * @todo Perhaps we want some simple stack functionality, but there's
 * no need to overdo it.
 **/
const char *io_write_phase = phase_unknown;
const char *io_read_phase = phase_unknown;

/** Ignore EOF errors while reading a module listing if the remote
    version is 24 or less. */
int kludge_around_eof = False;


static int io_error_fd = -1;
static int io_filesfrom_f_in = -1;
static int io_filesfrom_f_out = -1;
static char io_filesfrom_buf[2048];
static char *io_filesfrom_bp;
static char io_filesfrom_lastchar;
static int io_filesfrom_buflen;

static void read_loop(int fd, char *buf, size_t len);

static void check_timeout(void)
{
	extern int am_server, am_daemon;
	time_t t;

	err_list_push();

	if (!io_timeout) return;

	if (!last_io) {
		last_io = time(NULL);
		return;
	}

	t = time(NULL);

	if (last_io && io_timeout && (t-last_io) >= io_timeout) {
		if (!am_server && !am_daemon) {
			rprintf(FERROR,"io timeout after %d seconds - exiting\n", 
				(int)(t-last_io));
		}
		exit_cleanup(RERR_TIMEOUT);
	}
}

/** Setup the fd used to propagate errors */
void io_set_error_fd(int fd)
{
	io_error_fd = fd;
}

/** Read some data from the error fd and write it to the write log code */
static void read_error_fd(void)
{
	char buf[200];
	size_t n;
	int fd = io_error_fd;
	int tag, len;

	/* io_error_fd is temporarily disabled -- is this meant to
	 * prevent indefinite recursion? */
	io_error_fd = -1;

	read_loop(fd, buf, 4);
	tag = IVAL(buf, 0);

	len = tag & 0xFFFFFF;
	tag = tag >> 24;
	tag -= MPLEX_BASE;

	while (len) {
		n = len;
		if (n > (sizeof buf - 1))
			n = sizeof buf - 1;
		read_loop(fd, buf, n);
		rwrite((enum logcode)tag, buf, n);
		len -= n;
	}

	io_error_fd = fd;
}

/**
 * When we're the receiver and we have a local --files-from list of names
 * that needs to be sent over the socket to the sender, we have to do two
 * things at the same time: send the sender a list of what files we're
 * processing and read the incoming file+info list from the sender.  We do
 * this by augmenting the read_timeout() function to copy this data.  It
 * uses the io_filesfrom_buf to read a block of data from f_in (when it is
 * ready, since it might be a pipe) and then blast it out f_out (when it
 * is ready to receive more data).
 */
void io_set_filesfrom_fds(int f_in, int f_out)
{
	io_filesfrom_f_in = f_in;
	io_filesfrom_f_out = f_out;
	io_filesfrom_bp = io_filesfrom_buf;
	io_filesfrom_lastchar = '\0';
	io_filesfrom_buflen = 0;
}

/**
 * It's almost always an error to get an EOF when we're trying to read
 * from the network, because the protocol is self-terminating.
 *
 * However, there is one unfortunate cases where it is not, which is
 * rsync <2.4.6 sending a list of modules on a server, since the list
 * is terminated by closing the socket. So, for the section of the
 * program where that is a problem (start_socket_client),
 * kludge_around_eof is True and we just exit.
 */
static void whine_about_eof(void)
{
	if (kludge_around_eof)
		exit_cleanup(0);
	else {
		rprintf(FERROR,
			"%s: connection unexpectedly closed "
			"(%.0f bytes read so far)\n",
			RSYNC_NAME, (double)stats.total_read);

		exit_cleanup(RERR_STREAMIO);
	}
}


static void die_from_readerr(int err)
{
	/* this prevents us trying to write errors on a dead socket */
	io_multiplexing_close();

	rprintf(FERROR, "%s: read error: %s\n",
		RSYNC_NAME, strerror(err));
	exit_cleanup(RERR_STREAMIO);
}


/**
 * Read from a socket with IO timeout. return the number of bytes
 * read. If no bytes can be read then exit, never return a number <= 0.
 *
 * TODO: If the remote shell connection fails, then current versions
 * actually report an "unexpected EOF" error here.  Since it's a
 * fairly common mistake to try to use rsh when ssh is required, we
 * should trap that: if we fail to read any data at all, we should
 * give a better explanation.  We can tell whether the connection has
 * started by looking e.g. at whether the remote version is known yet.
 */
static int read_timeout(int fd, char *buf, size_t len)
{
	int n, ret=0;

	io_flush();

	while (ret == 0) {
		/* until we manage to read *something* */
		fd_set r_fds, w_fds;
		struct timeval tv;
		int fd_count = fd+1;
		int count;

		FD_ZERO(&r_fds);
		FD_SET(fd, &r_fds);
		if (io_error_fd != -1) {
			FD_SET(io_error_fd, &r_fds);
			if (io_error_fd >= fd_count) fd_count = io_error_fd+1;
		}
		if (io_filesfrom_f_out != -1) {
			int new_fd;
			if (io_filesfrom_buflen == 0) {
				if (io_filesfrom_f_in != -1) {
					FD_SET(io_filesfrom_f_in, &r_fds);
					new_fd = io_filesfrom_f_in;
				} else {
					io_filesfrom_f_out = -1;
					new_fd = -1;
				}
			} else {
				FD_ZERO(&w_fds);
				FD_SET(io_filesfrom_f_out, &w_fds);
				new_fd = io_filesfrom_f_out;
			}
			if (new_fd >= fd_count) fd_count = new_fd+1;
		}

		tv.tv_sec = io_timeout?io_timeout:SELECT_TIMEOUT;
		tv.tv_usec = 0;

		errno = 0;

		count = select(fd_count, &r_fds,
			       io_filesfrom_buflen? &w_fds : NULL,
			       NULL, &tv);

		if (count == 0) {
			check_timeout();
		}

		if (count <= 0) {
			if (errno == EBADF) {
				exit_cleanup(RERR_SOCKETIO);
			}
			continue;
		}


		if (io_error_fd != -1 && FD_ISSET(io_error_fd, &r_fds)) {
			read_error_fd();
		}

		if (io_filesfrom_f_out != -1) {
			if (io_filesfrom_buflen) {
				if (FD_ISSET(io_filesfrom_f_out, &w_fds)) {
					int l = write(io_filesfrom_f_out,
						      io_filesfrom_bp,
						      io_filesfrom_buflen);
					if (l > 0) {
						if (!(io_filesfrom_buflen -= l))
							io_filesfrom_bp = io_filesfrom_buf;
						else
							io_filesfrom_bp += l;
					} else {
						/* XXX should we complain? */
						io_filesfrom_f_out = -1;
					}
				}
			} else if (io_filesfrom_f_in != -1) {
				if (FD_ISSET(io_filesfrom_f_in, &r_fds)) {
					int l = read(io_filesfrom_f_in,
						     io_filesfrom_buf,
						     sizeof io_filesfrom_buf);
					if (l <= 0) {
						/* Send end-of-file marker */
						io_filesfrom_buf[0] = '\0';
						io_filesfrom_buf[1] = '\0';
						io_filesfrom_buflen = io_filesfrom_lastchar? 2 : 1;
						io_filesfrom_f_in = -1;
					} else {
						extern int eol_nulls;
						if (!eol_nulls) {
							char *s = io_filesfrom_buf + l;
							/* Transform CR and/or LF into '\0' */
							while (s-- > io_filesfrom_buf) {
								if (*s == '\n' || *s == '\r')
									*s = '\0';
							}
						}
						if (!io_filesfrom_lastchar) {
							/* Last buf ended with a '\0', so don't
							 * let this buf start with one. */
							while (l && !*io_filesfrom_bp)
								io_filesfrom_bp++, l--;
						}
						if (!l)
							io_filesfrom_bp = io_filesfrom_buf;
						else {
							char *f = io_filesfrom_bp;
							char *t = f;
							char *eob = f + l;
							/* Eliminate any multi-'\0' runs. */
							while (f != eob) {
								if (!(*t++ = *f++)) {
									while (f != eob && !*f)
										f++, l--;
								}
							}
							io_filesfrom_lastchar = f[-1];
						}
						io_filesfrom_buflen = l;
					}
				}
			}
		}

		if (!FD_ISSET(fd, &r_fds)) continue;

		n = read(fd, buf, len);

		if (n > 0) {
			buf += n;
			len -= n;
			ret += n;
			if (io_timeout)
				last_io = time(NULL);
			continue;
		} else if (n == 0) {
			whine_about_eof();
			return -1; /* doesn't return */
		} else if (n == -1) {
			if (errno == EINTR || errno == EWOULDBLOCK ||
			    errno == EAGAIN) 
				continue;
			die_from_readerr(errno);
		}
	}

	return ret;
}

/**
 * Read a line into the "fname" buffer (which must be at least MAXPATHLEN
 * characters long).
 */
int read_filesfrom_line(int fd, char *fname)
{
	char ch, *s, *eob = fname + MAXPATHLEN - 1;
	int cnt;
	extern int io_timeout;
	extern int eol_nulls;
	extern char *remote_filesfrom_file;
	extern int am_server;
	int reading_remotely = remote_filesfrom_file || (am_server && fd == 0);
	int nulls = eol_nulls || reading_remotely;

  start:
	s = fname;
	while (1) {
		cnt = read(fd, &ch, 1);
		if (cnt < 0 && (errno == EWOULDBLOCK
		  || errno == EINTR || errno == EAGAIN)) {
			struct timeval tv;
			fd_set fds;
			FD_ZERO(&fds);
			FD_SET(fd, &fds);
			tv.tv_sec = io_timeout? io_timeout : SELECT_TIMEOUT;
			tv.tv_usec = 0;
			if (!select(fd+1, &fds, NULL, NULL, &tv))
				check_timeout();
			continue;
		}
		if (cnt != 1)
			break;
		if (nulls? !ch : (ch == '\r' || ch == '\n')) {
			/* Skip empty lines if reading locally. */
			if (!reading_remotely && s == fname)
				continue;
			break;
		}
		if (s < eob)
			*s++ = ch;
	}
	*s = '\0';

	/* Dump comments. */
	if (*fname == '#' || *fname == ';')
		goto start;

	return s - fname;
}


/**
 * Continue trying to read len bytes - don't return until len has been
 * read.
 **/
static void read_loop(int fd, char *buf, size_t len)
{
	while (len) {
		int n = read_timeout(fd, buf, len);

		buf += n;
		len -= n;
	}
}


/**
 * Read from the file descriptor handling multiplexing - return number
 * of bytes read.
 * 
 * Never returns <= 0. 
 */
static int read_unbuffered(int fd, char *buf, size_t len)
{
	static size_t remaining;
	int tag, ret = 0;
	char line[1024];

	if (!io_multiplexing_in || fd != multiplex_in_fd)
		return read_timeout(fd, buf, len);

	while (ret == 0) {
		if (remaining) {
			len = MIN(len, remaining);
			read_loop(fd, buf, len);
			remaining -= len;
			ret = len;
			continue;
		}

		read_loop(fd, line, 4);
		tag = IVAL(line, 0);

		remaining = tag & 0xFFFFFF;
		tag = tag >> 24;

		if (tag == MPLEX_BASE)
			continue;

		tag -= MPLEX_BASE;

		if (tag != FERROR && tag != FINFO) {
			rprintf(FERROR, "unexpected tag %d\n", tag);
			exit_cleanup(RERR_STREAMIO);
		}

		if (remaining > sizeof line - 1) {
			rprintf(FERROR, "multiplexing overflow %ld\n\n",
				(long)remaining);
			exit_cleanup(RERR_STREAMIO);
		}

		read_loop(fd, line, remaining);
		line[remaining] = 0;

		rprintf((enum logcode) tag, "%s", line);
		remaining = 0;
	}

	return ret;
}



/**
 * Do a buffered read from @p fd.  Don't return until all @p n bytes
 * have been read.  If all @p n can't be read then exit with an
 * error.
 **/
static void readfd(int fd, char *buffer, size_t N)
{
	int  ret;
	size_t total=0;  

	while (total < N) {
		io_flush();

		ret = read_unbuffered(fd, buffer + total, N-total);
		total += ret;
	}

	stats.total_read += total;
}


int32 read_int(int f)
{
	char b[4];
	int32 ret;

	readfd(f,b,4);
	ret = IVAL(b,0);
	if (ret == (int32)0xffffffff) return -1;
	return ret;
}

int64 read_longint(int f)
{
	int64 ret;
	char b[8];
	ret = read_int(f);

	if ((int32)ret != (int32)0xffffffff) {
		return ret;
	}

#ifdef NO_INT64
	rprintf(FERROR,"Integer overflow - attempted 64 bit offset\n");
	exit_cleanup(RERR_UNSUPPORTED);
#else
	readfd(f,b,8);
	ret = IVAL(b,0) | (((int64)IVAL(b,4))<<32);
#endif

	return ret;
}

void read_buf(int f,char *buf,size_t len)
{
	readfd(f,buf,len);
}

void read_sbuf(int f,char *buf,size_t len)
{
	read_buf(f,buf,len);
	buf[len] = 0;
}

unsigned char read_byte(int f)
{
	unsigned char c;
	read_buf(f, (char *)&c, 1);
	return c;
}


/**
 * Sleep after writing to limit I/O bandwidth usage.
 *
 * @todo Rather than sleeping after each write, it might be better to
 * use some kind of averaging.  The current algorithm seems to always
 * use a bit less bandwidth than specified, because it doesn't make up
 * for slow periods.  But arguably this is a feature.  In addition, we
 * ought to take the time used to write the data into account.
 **/
static void sleep_for_bwlimit(int bytes_written)
{
	struct timeval tv;

	if (!bwlimit)
		return;

	assert(bytes_written > 0);
	assert(bwlimit > 0);

	tv.tv_usec = bytes_written * 1000 / bwlimit;
	tv.tv_sec  = tv.tv_usec / 1000000;
	tv.tv_usec = tv.tv_usec % 1000000;

	select(0, NULL, NULL, NULL, &tv);
}


/**
 * Write len bytes to the file descriptor @p fd.
 *
 * This function underlies the multiplexing system.  The body of the
 * application never calls this function directly.
 **/
static void writefd_unbuffered(int fd,char *buf,size_t len)
{
	size_t total = 0;
	fd_set w_fds, r_fds;
	int fd_count, count;
	struct timeval tv;

	err_list_push();

	no_flush++;

	while (total < len) {
		FD_ZERO(&w_fds);
		FD_SET(fd,&w_fds);
		fd_count = fd;

		if (io_error_fd != -1) {
			FD_ZERO(&r_fds);
			FD_SET(io_error_fd,&r_fds);
			if (io_error_fd > fd_count) 
				fd_count = io_error_fd;
		}

		tv.tv_sec = io_timeout?io_timeout:SELECT_TIMEOUT;
		tv.tv_usec = 0;

		errno = 0;

		count = select(fd_count+1,
			       io_error_fd != -1?&r_fds:NULL,
			       &w_fds,NULL,
			       &tv);

		if (count == 0) {
			check_timeout();
		}

		if (count <= 0) {
			if (errno == EBADF) {
				exit_cleanup(RERR_SOCKETIO);
			}
			continue;
		}

		if (io_error_fd != -1 && FD_ISSET(io_error_fd, &r_fds)) {
			read_error_fd();
		}

		if (FD_ISSET(fd, &w_fds)) {
			int ret;
			size_t n = len-total;
			ret = write(fd,buf+total,n);

			if (ret == -1 && errno == EINTR) {
				continue;
			}

			if (ret == -1 && 
			    (errno == EWOULDBLOCK || errno == EAGAIN)) {
				msleep(1);
				continue;
			}

			if (ret <= 0) {
				/* Don't try to write errors back
				 * across the stream */
				io_multiplexing_close();
				rprintf(FERROR, RSYNC_NAME
					": writefd_unbuffered failed to write %ld bytes: phase \"%s\": %s\n",
					(long) len, io_write_phase, 
					strerror(errno));
				exit_cleanup(RERR_STREAMIO);
			}

			sleep_for_bwlimit(ret);
 
			total += ret;

			if (io_timeout)
				last_io = time(NULL);
		}
	}

	no_flush--;
}


static char *io_buffer;
static int io_buffer_count;

void io_start_buffering(int fd)
{
	if (io_buffer) return;
	multiplex_out_fd = fd;
	io_buffer = (char *)malloc(IO_BUFFER_SIZE);
	if (!io_buffer) out_of_memory("writefd");
	io_buffer_count = 0;
}

/**
 * Write an message to a multiplexed stream. If this fails then rsync
 * exits.
 **/
static void mplex_write(int fd, enum logcode code, char *buf, size_t len)
{
	char buffer[4096];
	size_t n = len;

	SIVAL(buffer, 0, ((MPLEX_BASE + (int)code)<<24) + len);

	if (n > (sizeof buffer - 4)) {
		n = sizeof buffer - 4;
	}

	memcpy(&buffer[4], buf, n);
	writefd_unbuffered(fd, buffer, n+4);

	len -= n;
	buf += n;

	if (len) {
		writefd_unbuffered(fd, buf, len);
	}
}


void io_flush(void)
{
	int fd = multiplex_out_fd;

	err_list_push();

	if (!io_buffer_count || no_flush) return;

	if (io_multiplexing_out) {
		mplex_write(fd, FNONE, io_buffer, io_buffer_count);
	} else {
		writefd_unbuffered(fd, io_buffer, io_buffer_count);
	}
	io_buffer_count = 0;
}


void io_end_buffering(void)
{
	io_flush();
	if (!io_multiplexing_out) {
		free(io_buffer);
		io_buffer = NULL;
	}
}

static void writefd(int fd,char *buf,size_t len)
{
	stats.total_written += len;

	err_list_push();

	if (!io_buffer || fd != multiplex_out_fd) {
		writefd_unbuffered(fd, buf, len);
		return;
	}

	while (len) {
		int n = MIN((int) len, IO_BUFFER_SIZE-io_buffer_count);
		if (n > 0) {
			memcpy(io_buffer+io_buffer_count, buf, n);
			buf += n;
			len -= n;
			io_buffer_count += n;
		}

		if (io_buffer_count == IO_BUFFER_SIZE) io_flush();
	}
}


void write_int(int f,int32 x)
{
	char b[4];
	SIVAL(b,0,x);
	writefd(f,b,4);
}


void write_int_named(int f, int32 x, const char *phase)
{
	io_write_phase = phase;
	write_int(f, x);
	io_write_phase = phase_unknown;
}


/*
 * Note: int64 may actually be a 32-bit type if ./configure couldn't find any
 * 64-bit types on this platform.
 */
void write_longint(int f, int64 x)
{
	char b[8];

	if (x <= 0x7FFFFFFF) {
		write_int(f, (int)x);
		return;
	}

#ifdef NO_INT64
	rprintf(FERROR,"Integer overflow - attempted 64 bit offset\n");
	exit_cleanup(RERR_UNSUPPORTED);
#else
	write_int(f, (int32)0xFFFFFFFF);
	SIVAL(b,0,(x&0xFFFFFFFF));
	SIVAL(b,4,((x>>32)&0xFFFFFFFF));

	writefd(f,b,8);
#endif
}

void write_buf(int f,char *buf,size_t len)
{
	writefd(f,buf,len);
}

/** Write a string to the connection */
static void write_sbuf(int f,char *buf)
{
	write_buf(f, buf, strlen(buf));
}


void write_byte(int f,unsigned char c)
{
	write_buf(f,(char *)&c,1);
}



/**
 * Read a line of up to @p maxlen characters into @p buf.  Does not
 * contain a trailing newline or carriage return.
 *
 * @return 1 for success; 0 for io error or truncation.
 **/
int read_line(int f, char *buf, size_t maxlen)
{
	while (maxlen) {
		buf[0] = 0;
		read_buf(f, buf, 1);
		if (buf[0] == 0)
			return 0;
		if (buf[0] == '\n') {
			buf[0] = 0;
			break;
		}
		if (buf[0] != '\r') {
			buf++;
			maxlen--;
		}
	}
	if (maxlen == 0) {
		*buf = 0;
		return 0;
	}

	return 1;
}


void io_printf(int fd, const char *format, ...)
{
	va_list ap;  
	char buf[1024];
	int len;

	va_start(ap, format);
	len = vsnprintf(buf, sizeof buf, format, ap);
	va_end(ap);

	if (len < 0) exit_cleanup(RERR_STREAMIO);

	write_sbuf(fd, buf);
}


/** Setup for multiplexing an error stream with the data stream */
void io_start_multiplex_out(int fd)
{
	multiplex_out_fd = fd;
	io_flush();
	io_start_buffering(fd);
	io_multiplexing_out = 1;
}

/** Setup for multiplexing an error stream with the data stream */
void io_start_multiplex_in(int fd)
{
	multiplex_in_fd = fd;
	io_flush();
	io_multiplexing_in = 1;
}

/** Write an message to the multiplexed error stream */
int io_multiplex_write(enum logcode code, char *buf, size_t len)
{
	if (!io_multiplexing_out) return 0;

	io_flush();
	stats.total_written += (len+4);
	mplex_write(multiplex_out_fd, code, buf, len);
	return 1;
}

/** Stop output multiplexing */
void io_multiplexing_close(void)
{
	io_multiplexing_out = 0;
}