X-Git-Url: https://mattmccutchen.net/rsync/rsync.git/blobdiff_plain/7b5c3eb05efb0d67348c92d81da599c64e0c03db..6aaf8d8c1041b524d985bf09b9a3f5e371cf8ac2:/io.c

diff --git a/io.c b/io.c
index 6a7b679b..1d406490 100644
--- a/io.c
+++ b/io.c
@@ -19,11 +19,22 @@
    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */
 
-/*
-  socket and pipe IO utilities used in rsync 
+/**
+ *
+ * @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().
+ **/
 
-  tridge, June 1996
-  */
 #include "rsync.h"
 
 /* if no timeout is specified then use a 60 second select timeout */
@@ -377,7 +388,8 @@ unsigned char read_byte(int f)
 	return c;
 }
 
-/* write len bytes to fd */
+/* Write len bytes to fd.  This underlies the multiplexing system,
+ * which is always called by application code.  */
 static void writefd_unbuffered(int fd,char *buf,size_t len)
 {
 	size_t total = 0;
@@ -442,8 +454,11 @@ static void writefd_unbuffered(int fd,char *buf,size_t len)
 			}
 
 			if (ret <= 0) {
-				rprintf(FERROR,
-					"error writing %d unbuffered bytes"
+				/* 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);