X-Git-Url: http://git.samba.org/samba.git/?p=rsync.git;a=blobdiff_plain;f=io.c;h=004ae666c389857fd705770926d7be663364b8a3;hp=1d406490fa28efeb69d6176b02e7daeafd2b21c2;hb=3671987f4d7834dc51a6113b3d012475381e4a93;hpb=3ce0f9a653c2b6a0a4c8b3b2192ab03084213032

diff --git a/io.c b/io.c
index 1d406490..004ae666 100644
--- a/io.c
+++ b/io.c
@@ -1,29 +1,28 @@
 /* -*- c-file-style: "linux" -*-
-   
-   Copyright (C) 1996-2001 by Andrew Tridgell 
-   Copyright (C) Paul Mackerras 1996
-   Copyright (C) 2001 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.
-*/
+ *
+ * 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.
+ * Socket and pipe I/O 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
@@ -37,39 +36,109 @@
 
 #include "rsync.h"
 
-/* if no timeout is specified then use a 60 second select timeout */
+/** 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 size_t bwlimit_writemax;
 extern int verbose;
 extern int io_timeout;
+extern int am_server;
+extern int am_daemon;
+extern int am_sender;
+extern int am_generator;
+extern int eol_nulls;
+extern int csum_length;
+extern int checksum_seed;
+extern int protocol_version;
+extern char *remote_filesfrom_file;
 extern struct stats stats;
 
+const char phase_unknown[] = "unknown";
+int select_timeout = SELECT_TIMEOUT;
+int batch_fd = -1;
+int batch_gen_fd = -1;
+
+/**
+ * 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 I/O these names will be somewhat
+ * approximate; perhaps for ease of support we would rather make the
+ * buffer always flush when a single application-level I/O 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;
 
+int msg_fd_in = -1;
+int msg_fd_out = -1;
 
-static int io_error_fd = -1;
+static int io_multiplexing_out;
+static int io_multiplexing_in;
+static int sock_f_in = -1;
+static int sock_f_out = -1;
+static time_t last_io;
+static int no_flush;
+
+static int write_batch_monitor_in = -1;
+static int write_batch_monitor_out = -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);
 
+struct redo_list {
+	struct redo_list *next;
+	int num;
+};
+
+static struct redo_list *redo_list_head;
+static struct redo_list *redo_list_tail;
+
+struct msg_list {
+	struct msg_list *next;
+	char *buf;
+	int len;
+};
+
+static struct msg_list *msg_list_head;
+static struct msg_list *msg_list_tail;
+
+static void redo_list_add(int num)
+{
+	struct redo_list *rl;
+
+	if (!(rl = new(struct redo_list)))
+		exit_cleanup(RERR_MALLOC);
+	rl->next = NULL;
+	rl->num = num;
+	if (redo_list_tail)
+		redo_list_tail->next = rl;
+	else
+		redo_list_head = rl;
+	redo_list_tail = rl;
+}
+
 static void check_timeout(void)
 {
-	extern int am_server, am_daemon;
 	time_t t;
 
-	err_list_push();
-	
-	if (!io_timeout) return;
+	if (!io_timeout)
+		return;
 
 	if (!last_io) {
 		last_io = time(NULL);
@@ -78,94 +147,225 @@ static void check_timeout(void)
 
 	t = time(NULL);
 
-	if (last_io && io_timeout && (t-last_io) >= io_timeout) {
+	if (t - last_io >= io_timeout) {
 		if (!am_server && !am_daemon) {
-			rprintf(FERROR,"io timeout after %d seconds - exiting\n", 
+			rprintf(FERROR, "io timeout after %d seconds -- exiting\n",
 				(int)(t-last_io));
 		}
 		exit_cleanup(RERR_TIMEOUT);
 	}
 }
 
-/* setup the fd used to propogate errors */
-void io_set_error_fd(int fd)
+/* Note the fds used for the main socket (which might really be a pipe
+ * for a local transfer, but we can ignore that). */
+void io_set_sock_fds(int f_in, int f_out)
 {
-	io_error_fd = fd;
+	sock_f_in = f_in;
+	sock_f_out = f_out;
 }
 
-/* read some data from the error fd and write it to the write log code */
-static void read_error_fd(void)
+/* Setup the fd used to receive MSG_* messages.  Only needed during the
+ * early stages of being a local sender (up through the sending of the
+ * file list) or when we're the generator (to fetch the messages from
+ * the receiver). */
+void set_msg_fd_in(int fd)
 {
-	char buf[200];
+	msg_fd_in = fd;
+}
+
+/* Setup the fd used to send our MSG_* messages.  Only needed when
+ * we're the receiver (to send our messages to the generator). */
+void set_msg_fd_out(int fd)
+{
+	msg_fd_out = fd;
+	set_nonblocking(msg_fd_out);
+}
+
+/* Add a message to the pending MSG_* list. */
+static void msg_list_add(int code, char *buf, int len)
+{
+	struct msg_list *ml;
+
+	if (!(ml = new(struct msg_list)))
+		exit_cleanup(RERR_MALLOC);
+	ml->next = NULL;
+	if (!(ml->buf = new_array(char, len+4)))
+		exit_cleanup(RERR_MALLOC);
+	SIVAL(ml->buf, 0, ((code+MPLEX_BASE)<<24) | len);
+	memcpy(ml->buf+4, buf, len);
+	ml->len = len+4;
+	if (msg_list_tail)
+		msg_list_tail->next = ml;
+	else
+		msg_list_head = ml;
+	msg_list_tail = ml;
+}
+
+void send_msg(enum msgcode code, char *buf, int len)
+{
+	msg_list_add(code, buf, len);
+	msg_list_push(NORMAL_FLUSH);
+}
+
+/* Read a message from the MSG_* fd and handle it.  This is called either
+ * during the early stages of being a local sender (up through the sending
+ * of the file list) or when we're the generator (to fetch the messages
+ * from the receiver). */
+static void read_msg_fd(void)
+{
+	char buf[2048];
 	size_t n;
-	int fd = io_error_fd;
+	int fd = msg_fd_in;
 	int tag, len;
 
-        /* io_error_fd is temporarily disabled -- is this meant to
-         * prevent indefinite recursion? */
-	io_error_fd = -1;
+	/* Temporarily disable msg_fd_in.  This is needed to avoid looping back
+	 * to this routine from read_timeout() and writefd_unbuffered(). */
+	msg_fd_in = -1;
 
 	read_loop(fd, buf, 4);
 	tag = IVAL(buf, 0);
 
 	len = tag & 0xFFFFFF;
-	tag = tag >> 24;
-	tag -= MPLEX_BASE;
+	tag = (tag >> 24) - 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;
+	switch (tag) {
+	case MSG_DONE:
+		if (len != 0 || !am_generator) {
+			rprintf(FERROR, "invalid message %d:%d\n", tag, len);
+			exit_cleanup(RERR_STREAMIO);
+		}
+		redo_list_add(-1);
+		break;
+	case MSG_REDO:
+		if (len != 4 || !am_generator) {
+			rprintf(FERROR, "invalid message %d:%d\n", tag, len);
+			exit_cleanup(RERR_STREAMIO);
+		}
+		read_loop(fd, buf, 4);
+		redo_list_add(IVAL(buf,0));
+		break;
+	case MSG_INFO:
+	case MSG_ERROR:
+	case MSG_LOG:
+		while (len) {
+			n = len;
+			if (n >= sizeof buf)
+				n = sizeof buf - 1;
+			read_loop(fd, buf, n);
+			rwrite((enum logcode)tag, buf, n);
+			len -= n;
+		}
+		break;
+	default:
+		rprintf(FERROR, "unknown message %d:%d\n", tag, len);
+		exit_cleanup(RERR_STREAMIO);
 	}
 
-	io_error_fd = fd;
-}
-
-
-static void whine_about_eof (void)
-{
-	/**
-	   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.
-	*/
-
-	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);
+	msg_fd_in = fd;
+}
+
+/* Try to push messages off the list onto the wire.  If we leave with more
+ * to do, return 0.  On error, return -1.  If everything flushed, return 1.
+ * This is only active in the receiver. */
+int msg_list_push(int flush_it_all)
+{
+	static int written = 0;
+	struct timeval tv;
+	fd_set fds;
+
+	if (msg_fd_out < 0)
+		return -1;
+
+	while (msg_list_head) {
+		struct msg_list *ml = msg_list_head;
+		int n = write(msg_fd_out, ml->buf + written, ml->len - written);
+		if (n < 0) {
+			if (errno == EINTR)
+				continue;
+			if (errno != EWOULDBLOCK && errno != EAGAIN)
+				return -1;
+			if (!flush_it_all)
+				return 0;
+			FD_ZERO(&fds);
+			FD_SET(msg_fd_out, &fds);
+			tv.tv_sec = select_timeout;
+			tv.tv_usec = 0;
+			if (!select(msg_fd_out+1, NULL, &fds, NULL, &tv))
+				check_timeout();
+		} else if ((written += n) == ml->len) {
+			free(ml->buf);
+			msg_list_head = ml->next;
+			if (!msg_list_head)
+				msg_list_tail = NULL;
+			free(ml);
+			written = 0;
+		}
 	}
+	return 1;
+}
+
+int get_redo_num(void)
+{
+	struct redo_list *next;
+	int num;
+
+	while (!redo_list_head)
+		read_msg_fd();
+
+	num = redo_list_head->num;
+	next = redo_list_head->next;
+	free(redo_list_head);
+	redo_list_head = next;
+	if (!next)
+		redo_list_tail = NULL;
+
+	return num;
 }
 
+/**
+ * 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;
+}
 
-static void die_from_readerr (int err)
+/**
+ * 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(int fd)
 {
-	/* 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));
+	if (kludge_around_eof && fd == sock_f_in)
+		exit_cleanup(0);
+
+	rprintf(FERROR, RSYNC_NAME ": connection unexpectedly closed "
+		"(%.0f bytes received so far) [%s]\n",
+		(double)stats.total_read, who_am_i());
+
 	exit_cleanup(RERR_STREAMIO);
 }
 
 
-/*!
- * Read from a socket with IO timeout. return the number of bytes
+/**
+ * Read from a socket with I/O 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
@@ -175,80 +375,250 @@ static void die_from_readerr (int err)
  * 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)
+static int read_timeout(int fd, char *buf, size_t len)
 {
-	int n, ret=0;
+	int n, ret = 0;
 
-	io_flush();
+	io_flush(NORMAL_FLUSH);
 
 	while (ret == 0) {
 		/* until we manage to read *something* */
-		fd_set fds;
+		fd_set r_fds, w_fds;
 		struct timeval tv;
-		int fd_count = fd+1;
+		int maxfd = fd;
 		int count;
 
-		FD_ZERO(&fds);
-		FD_SET(fd, &fds);
-		if (io_error_fd != -1) {
-			FD_SET(io_error_fd, &fds);
-			if (io_error_fd > fd) fd_count = io_error_fd+1;
+		FD_ZERO(&r_fds);
+		FD_ZERO(&w_fds);
+		FD_SET(fd, &r_fds);
+		if (msg_fd_in >= 0) {
+			FD_SET(msg_fd_in, &r_fds);
+			if (msg_fd_in > maxfd)
+				maxfd = msg_fd_in;
+		} else if (msg_list_head) {
+			FD_SET(msg_fd_out, &w_fds);
+			if (msg_fd_out > maxfd)
+				maxfd = msg_fd_out;
+		}
+		if (io_filesfrom_f_out >= 0) {
+			int new_fd;
+			if (io_filesfrom_buflen == 0) {
+				if (io_filesfrom_f_in >= 0) {
+					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_SET(io_filesfrom_f_out, &w_fds);
+				new_fd = io_filesfrom_f_out;
+			}
+			if (new_fd > maxfd)
+				maxfd = new_fd;
 		}
 
-		tv.tv_sec = io_timeout?io_timeout:SELECT_TIMEOUT;
+		tv.tv_sec = select_timeout;
 		tv.tv_usec = 0;
 
 		errno = 0;
 
-		count = select(fd_count, &fds, NULL, NULL, &tv);
-
-		if (count == 0) {
-			check_timeout();
-		}
+		count = select(maxfd + 1, &r_fds, &w_fds, NULL, &tv);
 
 		if (count <= 0) {
-			if (errno == EBADF) {
+			if (errno == EBADF)
 				exit_cleanup(RERR_SOCKETIO);
-			}
+			check_timeout();
 			continue;
 		}
 
-		if (io_error_fd != -1 && FD_ISSET(io_error_fd, &fds)) {
-			read_error_fd();
+		if (msg_fd_in >= 0 && FD_ISSET(msg_fd_in, &r_fds))
+			read_msg_fd();
+		else if (msg_list_head && FD_ISSET(msg_fd_out, &w_fds))
+			msg_list_push(NORMAL_FLUSH);
+
+		if (io_filesfrom_f_out >= 0) {
+			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 >= 0) {
+				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 {
+						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, &fds)) continue;
+		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) 
+		if (n <= 0) {
+			if (n == 0)
+				whine_about_eof(fd); /* Doesn't return. */
+			if (errno == EINTR || errno == EWOULDBLOCK
+			    || errno == EAGAIN)
 				continue;
-			else
-				die_from_readerr (errno);
+
+			/* Don't write errors on a dead socket. */
+			if (fd == sock_f_in)
+				close_multiplexing_out();
+			rsyserr(FERROR, errno, "read error");
+			exit_cleanup(RERR_STREAMIO);
 		}
+
+		buf += n;
+		len -= n;
+		ret += n;
+
+		if (io_timeout && fd == sock_f_in)
+			last_io = time(NULL);
 	}
 
 	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;
+	int reading_remotely = remote_filesfrom_file != NULL;
+	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 = 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;
+}
+
+
+static char *iobuf_out;
+static int iobuf_out_cnt;
+
+void io_start_buffering_out(void)
+{
+	if (iobuf_out)
+		return;
+	if (!(iobuf_out = new_array(char, IO_BUFFER_SIZE)))
+		out_of_memory("io_start_buffering_out");
+	iobuf_out_cnt = 0;
+}
+
+
+static char *iobuf_in;
+static size_t iobuf_in_siz;
 
+void io_start_buffering_in(void)
+{
+	if (iobuf_in)
+		return;
+	iobuf_in_siz = 2 * IO_BUFFER_SIZE;
+	if (!(iobuf_in = new_array(char, iobuf_in_siz)))
+		out_of_memory("io_start_buffering_in");
+}
 
 
-/*! 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)
+void io_end_buffering(void)
+{
+	io_flush(NORMAL_FLUSH);
+	if (!io_multiplexing_out) {
+		free(iobuf_out);
+		iobuf_out = NULL;
+	}
+}
+
+
+/**
+ * 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);
@@ -262,76 +632,100 @@ static void read_loop (int fd, char *buf, size_t len)
 /**
  * Read from the file descriptor handling multiplexing - return number
  * of bytes read.
- * 
- * Never returns <= 0. 
+ *
+ * Never returns <= 0.
  */
-static int read_unbuffered(int fd, char *buf, size_t len)
+static int readfd_unbuffered(int fd, char *buf, size_t len)
 {
 	static size_t remaining;
+	static size_t iobuf_in_ndx;
 	int tag, ret = 0;
 	char line[1024];
 
-	if (!io_multiplexing_in || fd != multiplex_in_fd)
+	if (!iobuf_in || fd != sock_f_in)
 		return read_timeout(fd, buf, len);
 
+	if (!io_multiplexing_in && remaining == 0) {
+		remaining = read_timeout(fd, iobuf_in, iobuf_in_siz);
+		iobuf_in_ndx = 0;
+	}
+
 	while (ret == 0) {
 		if (remaining) {
 			len = MIN(len, remaining);
-			read_loop(fd, buf, len);
+			memcpy(buf, iobuf_in + iobuf_in_ndx, len);
+			iobuf_in_ndx += len;
 			remaining -= len;
 			ret = len;
-			continue;
+			break;
 		}
 
 		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 %d\n\n",
-				remaining);
+		tag = (tag >> 24) - MPLEX_BASE;
+
+		switch (tag) {
+		case MSG_DATA:
+			if (remaining > iobuf_in_siz) {
+				if (!(iobuf_in = realloc_array(iobuf_in, char,
+							       remaining)))
+					out_of_memory("readfd_unbuffered");
+				iobuf_in_siz = remaining;
+			}
+			read_loop(fd, iobuf_in, remaining);
+			iobuf_in_ndx = 0;
+			break;
+		case MSG_INFO:
+		case MSG_ERROR:
+			if (remaining >= sizeof line) {
+				rprintf(FERROR,
+					"[%s] multiplexing overflow %d:%ld\n\n",
+					who_am_i(), tag, (long)remaining);
+				exit_cleanup(RERR_STREAMIO);
+			}
+			read_loop(fd, line, remaining);
+			rwrite((enum logcode)tag, line, remaining);
+			remaining = 0;
+			break;
+		default:
+			rprintf(FERROR, "[%s] unexpected tag %d\n",
+				who_am_i(), tag);
 			exit_cleanup(RERR_STREAMIO);
 		}
-
-		read_loop(fd, line, remaining);
-		line[remaining] = 0;
-
-		rprintf((enum logcode) tag, "%s", line);
-		remaining = 0;
 	}
 
+	if (remaining == 0)
+		io_flush(NORMAL_FLUSH);
+
 	return ret;
 }
 
 
 
-/* do a buffered read from fd. don't return until all N bytes
-   have been read. If all N can't be read then exit with an error */
-static void readfd (int fd, char *buffer, size_t N)
+/**
+ * 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();
+	size_t total = 0;
 
-		ret = read_unbuffered (fd, buffer + total, N-total);
+	while (total < N) {
+		ret = readfd_unbuffered(fd, buffer + total, N-total);
 		total += ret;
 	}
 
-	stats.total_read += total;
+	if (fd == write_batch_monitor_in) {
+		if ((size_t)write(batch_fd, buffer, total) != total)
+			exit_cleanup(RERR_FILEIO);
+	}
+
+	if (fd == sock_f_in)
+		stats.total_read += total;
 }
 
 
@@ -342,29 +736,26 @@ int32 read_int(int f)
 
 	readfd(f,b,4);
 	ret = IVAL(b,0);
-	if (ret == (int32)0xffffffff) return -1;
+	if (ret == (int32)0xffffffff)
+		return -1;
 	return ret;
 }
 
 int64 read_longint(int f)
 {
-	extern int remote_version;
 	int64 ret;
 	char b[8];
 	ret = read_int(f);
 
-	if ((int32)ret != (int32)0xffffffff) {
+	if ((int32)ret != (int32)0xffffffff)
 		return ret;
-	}
 
-#ifdef NO_INT64
-	rprintf(FERROR,"Integer overflow - attempted 64 bit offset\n");
+#if SIZEOF_INT64 < 8
+	rprintf(FERROR, "Integer overflow: attempted 64-bit offset\n");
 	exit_cleanup(RERR_UNSUPPORTED);
 #else
-	if (remote_version >= 16) {
-		readfd(f,b,8);
-		ret = IVAL(b,0) | (((int64)IVAL(b,4))<<32);
-	}
+	readfd(f,b,8);
+	ret = IVAL(b,0) | (((int64)IVAL(b,4))<<32);
 #endif
 
 	return ret;
@@ -377,110 +768,211 @@ void read_buf(int f,char *buf,size_t len)
 
 void read_sbuf(int f,char *buf,size_t len)
 {
-	read_buf (f,buf,len);
+	readfd(f, buf, len);
 	buf[len] = 0;
 }
 
 unsigned char read_byte(int f)
 {
 	unsigned char c;
-	read_buf (f, (char *)&c, 1);
+	readfd(f, (char *)&c, 1);
 	return c;
 }
 
-/* Write len bytes to fd.  This underlies the multiplexing system,
- * which is always called by application code.  */
+/* Populate a sum_struct with values from the socket.  This is
+ * called by both the sender and the receiver. */
+void read_sum_head(int f, struct sum_struct *sum)
+{
+	sum->count = read_int(f);
+	sum->blength = read_int(f);
+	if (sum->blength < 0 || sum->blength > MAX_BLOCK_SIZE) {
+		rprintf(FERROR, "[%s] Invalid block length %ld\n",
+			who_am_i(), (long)sum->blength);
+		exit_cleanup(RERR_PROTOCOL);
+	}
+	sum->s2length = protocol_version < 27 ? csum_length : (int)read_int(f);
+	if (sum->s2length < 0 || sum->s2length > MD4_SUM_LENGTH) {
+		rprintf(FERROR, "[%s] Invalid checksum length %d\n",
+			who_am_i(), sum->s2length);
+		exit_cleanup(RERR_PROTOCOL);
+	}
+	sum->remainder = read_int(f);
+	if (sum->remainder < 0 || sum->remainder > sum->blength) {
+		rprintf(FERROR, "[%s] Invalid remainder length %ld\n",
+			who_am_i(), (long)sum->remainder);
+		exit_cleanup(RERR_PROTOCOL);
+	}
+}
+
+/* Send the values from a sum_struct over the socket.  Set sum to
+ * NULL if there are no checksums to send.  This is called by both
+ * the generator and the sender. */
+void write_sum_head(int f, struct sum_struct *sum)
+{
+	static struct sum_struct null_sum;
+
+	if (sum == NULL)
+		sum = &null_sum;
+
+	write_int(f, sum->count);
+	write_int(f, sum->blength);
+	if (protocol_version >= 27)
+		write_int(f, sum->s2length);
+	write_int(f, sum->remainder);
+}
+
+
+/**
+ * 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.
+ *
+ * During some phases of big transfers (file FOO is uptodate) this is
+ * called with a small bytes_written every time.  As the kernel has to
+ * round small waits up to guarantee that we actually wait at least the
+ * requested number of microseconds, this can become grossly inaccurate.
+ * We therefore keep track of the bytes we've written over time and only
+ * sleep when the accumulated delay is at least 1 tenth of a second.
+ **/
+static void sleep_for_bwlimit(int bytes_written)
+{
+	static struct timeval prior_tv;
+	static long total_written = 0; 
+	struct timeval tv, start_tv;
+	long elapsed_usec, sleep_usec;
+
+#define ONE_SEC	1000000L /* # of microseconds in a second */
+
+	if (!bwlimit)
+		return;
+
+	total_written += bytes_written; 
+
+	gettimeofday(&start_tv, NULL);
+	if (prior_tv.tv_sec) {
+		elapsed_usec = (start_tv.tv_sec - prior_tv.tv_sec) * ONE_SEC
+			     + (start_tv.tv_usec - prior_tv.tv_usec);
+		total_written -= elapsed_usec * bwlimit / (ONE_SEC/1024);
+		if (total_written < 0)
+			total_written = 0;
+	}
+
+	sleep_usec = total_written * (ONE_SEC/1024) / bwlimit;
+	if (sleep_usec < ONE_SEC / 10) {
+		prior_tv = start_tv;
+		return;
+	}
+
+	tv.tv_sec  = sleep_usec / ONE_SEC;
+	tv.tv_usec = sleep_usec % ONE_SEC;
+	select(0, NULL, NULL, NULL, &tv);
+
+	gettimeofday(&prior_tv, NULL);
+	elapsed_usec = (prior_tv.tv_sec - start_tv.tv_sec) * ONE_SEC
+		     + (prior_tv.tv_usec - start_tv.tv_usec);
+	total_written = (sleep_usec - elapsed_usec) * bwlimit / (ONE_SEC/1024);
+}
+
+
+/* Write len bytes to the file descriptor fd, looping as necessary to get
+ * the job done and also (in the generator) reading any data on msg_fd_in
+ * (to avoid deadlock).
+ *
+ * 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;
+	size_t n, total = 0;
 	fd_set w_fds, r_fds;
-	int fd_count, count;
+	int maxfd, count, ret;
 	struct timeval tv;
 
-	err_list_push();
-
 	no_flush++;
 
 	while (total < len) {
 		FD_ZERO(&w_fds);
-		FD_ZERO(&r_fds);
 		FD_SET(fd,&w_fds);
-		fd_count = fd;
+		maxfd = fd;
 
-		if (io_error_fd != -1) {
-			FD_SET(io_error_fd,&r_fds);
-			if (io_error_fd > fd_count) 
-				fd_count = io_error_fd;
+		if (msg_fd_in >= 0) {
+			FD_ZERO(&r_fds);
+			FD_SET(msg_fd_in,&r_fds);
+			if (msg_fd_in > maxfd)
+				maxfd = msg_fd_in;
+		}
+		if (fd != sock_f_out && iobuf_out_cnt && no_flush == 1) {
+			FD_SET(sock_f_out, &w_fds);
+			if (sock_f_out > maxfd)
+				maxfd = sock_f_out;
 		}
 
-		tv.tv_sec = io_timeout?io_timeout:SELECT_TIMEOUT;
+		tv.tv_sec = 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();
-		}
+		count = select(maxfd + 1, msg_fd_in >= 0 ? &r_fds : NULL,
+			       &w_fds, NULL, &tv);
 
 		if (count <= 0) {
-			if (errno == EBADF) {
+			if (count < 0 && errno == EBADF)
 				exit_cleanup(RERR_SOCKETIO);
-			}
+			check_timeout();
 			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 (msg_fd_in >= 0 && FD_ISSET(msg_fd_in, &r_fds))
+			read_msg_fd();
 
-			if (ret == -1 && errno == EINTR) {
-				continue;
+		if (!FD_ISSET(fd, &w_fds)) {
+			if (fd != sock_f_out && iobuf_out_cnt) {
+				no_flush--;
+				io_flush(NORMAL_FLUSH);
+				no_flush++;
 			}
+			continue;
+		}
 
-			if (ret == -1 && 
-			    (errno == EWOULDBLOCK || errno == EAGAIN)) {
-				msleep(1);
-				continue;
+		n = len - total;
+		if (bwlimit && n > bwlimit_writemax)
+			n = bwlimit_writemax;
+		ret = write(fd, buf + total, n);
+
+		if (ret <= 0) {
+			if (ret < 0) {
+				if (errno == EINTR)
+					continue;
+				if (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
-					": error writing %d unbuffered bytes"
-					" - exiting: %s\n", len,
-					strerror(errno));
-				exit_cleanup(RERR_STREAMIO);
+			/* Don't try to write errors back across the stream. */
+			if (fd == sock_f_out)
+				close_multiplexing_out();
+			rsyserr(FERROR, errno,
+				"writefd_unbuffered failed to write %ld bytes: phase \"%s\" [%s]",
+				(long)len, io_write_phase, who_am_i());
+			/* If the other side is sending us error messages, try
+			 * to grab any messages they sent before they died. */
+			while (fd == sock_f_out && io_multiplexing_in) {
+				io_timeout = select_timeout = 30;
+				readfd_unbuffered(sock_f_in, io_filesfrom_buf,
+						  sizeof io_filesfrom_buf);
 			}
+			exit_cleanup(RERR_STREAMIO);
+		}
 
-			/* Sleep after writing to limit I/O bandwidth */
-			if (bwlimit)
-			{
-			    tv.tv_sec = 0;
-			    tv.tv_usec = ret * 1000 / bwlimit;
-			    while (tv.tv_usec > 1000000)
-			    {
-				tv.tv_sec++;
-				tv.tv_usec -= 1000000;
-			    }
-			    select(0, NULL, NULL, NULL, &tv);
- 			}
- 
-			total += ret;
+		total += ret;
 
+		if (fd == sock_f_out) {
 			if (io_timeout)
 				last_io = time(NULL);
+			sleep_for_bwlimit(ret);
 		}
 	}
 
@@ -488,90 +980,77 @@ static void writefd_unbuffered(int fd,char *buf,size_t len)
 }
 
 
-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)
+/**
+ * Write an message to a multiplexed stream. If this fails then rsync
+ * exits.
+ **/
+static void mplex_write(enum msgcode 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;
-	}
+	if (n > sizeof buffer - 4)
+		n = sizeof buffer - 4;
 
 	memcpy(&buffer[4], buf, n);
-	writefd_unbuffered(fd, buffer, n+4);
+	writefd_unbuffered(sock_f_out, buffer, n+4);
 
 	len -= n;
 	buf += n;
 
-	if (len) {
-		writefd_unbuffered(fd, buf, len);
-	}
+	if (len)
+		writefd_unbuffered(sock_f_out, buf, len);
 }
 
 
-void io_flush(void)
+void io_flush(int flush_it_all)
 {
-	int fd = multiplex_out_fd;
-
-	err_list_push();
+	msg_list_push(flush_it_all);
 
-	if (!io_buffer_count || no_flush) return;
+	if (!iobuf_out_cnt || 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;
+	if (io_multiplexing_out)
+		mplex_write(MSG_DATA, iobuf_out, iobuf_out_cnt);
+	else
+		writefd_unbuffered(sock_f_out, iobuf_out, iobuf_out_cnt);
+	iobuf_out_cnt = 0;
 }
 
 
-void io_end_buffering(void)
+static void writefd(int fd,char *buf,size_t len)
 {
-	io_flush();
-	if (!io_multiplexing_out) {
-		free(io_buffer);
-		io_buffer = NULL;
+	if (fd == msg_fd_out) {
+		rprintf(FERROR, "Internal error: wrong write used in receiver.\n");
+		exit_cleanup(RERR_PROTOCOL);
 	}
-}
 
-static void writefd(int fd,char *buf,size_t len)
-{
-	stats.total_written += len;
+	if (fd == sock_f_out)
+		stats.total_written += len;
 
-	err_list_push();
+	if (fd == write_batch_monitor_out) {
+		if ((size_t)write(batch_fd, buf, len) != len)
+			exit_cleanup(RERR_FILEIO);
+	}
 
-	if (!io_buffer || fd != multiplex_out_fd) {
+	if (!iobuf_out || fd != sock_f_out) {
 		writefd_unbuffered(fd, buf, len);
 		return;
 	}
 
 	while (len) {
-		int n = MIN((int) len, IO_BUFFER_SIZE-io_buffer_count);
+		int n = MIN((int)len, IO_BUFFER_SIZE - iobuf_out_cnt);
 		if (n > 0) {
-			memcpy(io_buffer+io_buffer_count, buf, n);
+			memcpy(iobuf_out+iobuf_out_cnt, buf, n);
 			buf += n;
 			len -= n;
-			io_buffer_count += n;
+			iobuf_out_cnt += n;
 		}
-		
-		if (io_buffer_count == IO_BUFFER_SIZE) io_flush();
+
+		if (iobuf_out_cnt == IO_BUFFER_SIZE)
+			io_flush(NORMAL_FLUSH);
 	}
 }
 
@@ -584,25 +1063,37 @@ void write_int(int f,int32 x)
 }
 
 
+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)
 {
-	extern int remote_version;
 	char b[8];
 
-	if (remote_version < 16 || x <= 0x7FFFFFFF) {
+	if (x <= 0x7FFFFFFF) {
 		write_int(f, (int)x);
 		return;
 	}
 
+#if SIZEOF_INT64 < 8
+	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)
@@ -610,91 +1101,121 @@ 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 a string to the connection */
+void write_sbuf(int f, char *buf)
 {
-	write_buf(f, buf, strlen(buf));
+	writefd(f, buf, strlen(buf));
 }
 
-
 void write_byte(int f,unsigned char c)
 {
-	write_buf(f,(char *)&c,1);
+	writefd(f, (char *)&c, 1);
 }
 
 
 
+/**
+ * Read a line of up to @p maxlen characters into @p buf (not counting
+ * the trailing null).  Strips the (required) trailing newline and all
+ * carriage returns.
+ *
+ * @return 1 for success; 0 for I/O 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;
+		if (buf[0] == 0)
+			return 0;
+		if (buf[0] == '\n')
 			break;
-		}
 		if (buf[0] != '\r') {
 			buf++;
 			maxlen--;
 		}
 	}
-	if (maxlen == 0) {
-		*buf = 0;
-		return 0;
-	}
-
-	return 1;
+	*buf = '\0';
+	return maxlen > 0;
 }
 
 
 void io_printf(int fd, const char *format, ...)
 {
-	va_list ap;  
+	va_list ap;
 	char buf[1024];
 	int len;
-	
+
 	va_start(ap, format);
-	len = vsnprintf(buf, sizeof(buf), format, ap);
+	len = vsnprintf(buf, sizeof buf, format, ap);
 	va_end(ap);
 
-	if (len < 0) exit_cleanup(RERR_STREAMIO);
+	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)
+/** Setup for multiplexing a MSG_* stream with the data stream. */
+void io_start_multiplex_out(void)
 {
-	multiplex_out_fd = fd;
-	io_flush();
-	io_start_buffering(fd);
+	io_flush(NORMAL_FLUSH);
+	io_start_buffering_out();
 	io_multiplexing_out = 1;
 }
 
-/* setup for multiplexing an error stream with the data stream */
-void io_start_multiplex_in(int fd)
+/** Setup for multiplexing a MSG_* stream with the data stream. */
+void io_start_multiplex_in(void)
 {
-	multiplex_in_fd = fd;
-	io_flush();
+	io_flush(NORMAL_FLUSH);
+	io_start_buffering_in();
 	io_multiplexing_in = 1;
 }
 
-/* write an message to the multiplexed error stream */
-int io_multiplex_write(enum logcode code, char *buf, size_t len)
+/** Write an message to the multiplexed data stream. */
+int io_multiplex_write(enum msgcode code, char *buf, size_t len)
 {
-	if (!io_multiplexing_out) return 0;
+	if (!io_multiplexing_out)
+		return 0;
 
-	io_flush();
+	io_flush(NORMAL_FLUSH);
 	stats.total_written += (len+4);
-	mplex_write(multiplex_out_fd, code, buf, len);
+	mplex_write(code, buf, len);
 	return 1;
 }
 
-/* stop output multiplexing */
-void io_multiplexing_close(void)
+void close_multiplexing_in(void)
+{
+	io_multiplexing_in = 0;
+}
+
+/** Stop output multiplexing. */
+void close_multiplexing_out(void)
 {
 	io_multiplexing_out = 0;
 }
 
+void start_write_batch(int fd)
+{
+	write_stream_flags(batch_fd);
+
+	/* Some communication has already taken place, but we don't
+	 * enable batch writing until here so that we can write a
+	 * canonical record of the communication even though the
+	 * actual communication so far depends on whether a daemon
+	 * is involved. */
+	write_int(batch_fd, protocol_version);
+	write_int(batch_fd, checksum_seed);
+
+	if (am_sender)
+		write_batch_monitor_out = fd;
+	else
+		write_batch_monitor_in = fd;
+}
+
+void stop_write_batch(void)
+{
+	write_batch_monitor_out = -1;
+	write_batch_monitor_in = -1;
+}