Added a flag to disable xattr hlink optimization.

I added a compatibility flag for protocol 31 that will let both sides
know if they should be using the xattr optimization that attempted to
avoid sending xattr info for hardlinked files.  Since this optimization
was causing some issues, this compatibility flag will ensure that both
sides know if they should be trying to use the optimization or not.

6 files changed, 25 insertions, 10 deletions

diff --git a/NEWS b/NEWS
index 9e50fe0c..22766ce6 100644
--- a/NEWS
+++ b/NEWS
@@ -56,8 +56,8 @@ Changes since 3.1.0:
     - Improve chunked xattr reading for OS X.
 
     - Removed an attempted hard-link xattr optimization that was causing a
-      transfer failure.  (If you need to interact with an rsync 3.1.0 using
-      --hard-links & --xattrs, you can specify --protocol=30.)
+      transfer failure.  This removal is flagged in the compatibility code, so
+      if a better fix can be discovered, we have a way to flip it on again.
 
     - We now generate a better error if the buffer overflows in do_mknod().
 
diff --git a/compat.c b/compat.c
index 23ed53a9..2454937f 100644
--- a/compat.c
+++ b/compat.c
@@ -26,6 +26,7 @@ int file_extra_cnt = 0; /* count of file-list extras that everyone gets */
 int inc_recurse = 0;
 int compat_flags = 0;
 int use_safe_inc_flist = 0;
+int want_xattr_optim = 0;
 
 extern int am_server;
 extern int am_sender;
@@ -76,6 +77,7 @@ int filesfrom_convert = 0;
 #define CF_SYMLINK_TIMES (1<<1)
 #define CF_SYMLINK_ICONV (1<<2)
 #define CF_SAFE_FLIST	 (1<<3)
+#define CF_AVOID_XATTR_OPTIM (1<<4)
 
 static const char *client_info;
 
@@ -267,11 +269,14 @@ void setup_protocol(int f_out,int f_in)
 #endif
 			if (local_server || strchr(client_info, 'f') != NULL)
 				compat_flags |= CF_SAFE_FLIST;
+			if (local_server || strchr(client_info, 'x') != NULL)
+				compat_flags |= CF_AVOID_XATTR_OPTIM;
 			write_byte(f_out, compat_flags);
 		} else
 			compat_flags = read_byte(f_in);
 		/* The inc_recurse var MUST be set to 0 or 1. */
 		inc_recurse = compat_flags & CF_INC_RECURSE ? 1 : 0;
+		want_xattr_optim = protocol_version >= 31 && !(compat_flags & CF_AVOID_XATTR_OPTIM);
 		if (am_sender) {
 			receiver_symlink_times = am_server
 			    ? strchr(client_info, 'L') != NULL
diff --git a/generator.c b/generator.c
index 0f7a5169..63399d3d 100644
--- a/generator.c
+++ b/generator.c
@@ -57,6 +57,7 @@ extern int update_only;
 extern int human_readable;
 extern int ignore_existing;
 extern int ignore_non_existing;
+extern int want_xattr_optim;
 extern int inplace;
 extern int append_mode;
 extern int make_backups;
@@ -553,7 +554,9 @@ void itemize(const char *fnamecmp, struct file_struct *file, int ndx, int statre
 #ifdef SUPPORT_XATTRS
 			if (preserve_xattrs && do_xfers
 			 && iflags & (ITEM_REPORT_XATTR|ITEM_TRANSFER)) {
-				int fd = iflags & ITEM_REPORT_XATTR ? sock_f_out : -1;
+				int fd = iflags & ITEM_REPORT_XATTR
+				      && !(want_xattr_optim && BITS_SET(iflags, ITEM_XNAME_FOLLOWS|ITEM_LOCAL_CHANGE))
+				       ? sock_f_out : -1;
 				send_xattr_request(NULL, file, fd);
 			}
 #endif
diff --git a/options.c b/options.c
index 0aa64bf0..5b061ade 100644
--- a/options.c
+++ b/options.c
@@ -2494,12 +2494,13 @@ void server_options(char **args, int *argc_p)
 		if (allow_inc_recurse)
 			argstr[x++] = 'i';
 #ifdef CAN_SET_SYMLINK_TIMES
-		argstr[x++] = 'L';
+		argstr[x++] = 'L'; /* symlink time-setting support */
 #endif
 #ifdef ICONV_OPTION
-		argstr[x++] = 's';
+		argstr[x++] = 's'; /* symlink iconv translation support */
 #endif
-		argstr[x++] = 'f';
+		argstr[x++] = 'f'; /* flist I/O-error safety support */
+		argstr[x++] = 'x'; /* xattr hardlink optimization not supported */
 	}
 
 	if (x >= (int)sizeof argstr) { /* Not possible... */
diff --git a/receiver.c b/receiver.c
index 39f66274..571b7da6 100644
--- a/receiver.c
+++ b/receiver.c
@@ -30,6 +30,7 @@ extern int inc_recurse;
 extern int log_before_transfer;
 extern int stdout_format_has_i;
 extern int logfile_format_has_i;
+extern int want_xattr_optim;
 extern int csum_length;
 extern int read_batch;
 extern int write_batch;
@@ -583,14 +584,16 @@ int recv_files(int f_in, int f_out, char *local_name)
 			rprintf(FINFO, "recv_files(%s)\n", fname);
 
 #ifdef SUPPORT_XATTRS
-		if (preserve_xattrs && iflags & ITEM_REPORT_XATTR && do_xfers)
+		if (preserve_xattrs && iflags & ITEM_REPORT_XATTR && do_xfers
+		 && !(want_xattr_optim && BITS_SET(iflags, ITEM_XNAME_FOLLOWS|ITEM_LOCAL_CHANGE)))
 			recv_xattr_request(file, f_in);
 #endif
 
 		if (!(iflags & ITEM_TRANSFER)) {
 			maybe_log_item(file, iflags, itemizing, xname);
 #ifdef SUPPORT_XATTRS
-			if (preserve_xattrs && iflags & ITEM_REPORT_XATTR && do_xfers)
+			if (preserve_xattrs && iflags & ITEM_REPORT_XATTR && do_xfers
+			 && !BITS_SET(iflags, ITEM_XNAME_FOLLOWS|ITEM_LOCAL_CHANGE))
 				set_file_attrs(fname, file, NULL, fname, 0);
 #endif
 			if (iflags & ITEM_IS_NEW) {
diff --git a/sender.c b/sender.c
index 38743447..5adc2fd8 100644
--- a/sender.c
+++ b/sender.c
@@ -29,6 +29,7 @@ extern int inc_recurse;
 extern int log_before_transfer;
 extern int stdout_format_has_i;
 extern int logfile_format_has_i;
+extern int want_xattr_optim;
 extern int csum_length;
 extern int append_mode;
 extern int io_error;
@@ -177,7 +178,8 @@ static void write_ndx_and_attrs(int f_out, int ndx, int iflags,
 	if (iflags & ITEM_XNAME_FOLLOWS)
 		write_vstring(f_out, buf, len);
 #ifdef SUPPORT_XATTRS
-	if (preserve_xattrs && iflags & ITEM_REPORT_XATTR && do_xfers)
+	if (preserve_xattrs && iflags & ITEM_REPORT_XATTR && do_xfers
+	 && !(want_xattr_optim && BITS_SET(iflags, ITEM_XNAME_FOLLOWS|ITEM_LOCAL_CHANGE)))
 		send_xattr_request(fname, file, f_out);
 #endif
 }
@@ -258,7 +260,8 @@ void send_files(int f_in, int f_out)
 			rprintf(FINFO, "send_files(%d, %s%s%s)\n", ndx, path,slash,fname);
 
 #ifdef SUPPORT_XATTRS
-		if (preserve_xattrs && iflags & ITEM_REPORT_XATTR && do_xfers)
+		if (preserve_xattrs && iflags & ITEM_REPORT_XATTR && do_xfers
+		 && !(want_xattr_optim && BITS_SET(iflags, ITEM_XNAME_FOLLOWS|ITEM_LOCAL_CHANGE)))
 			recv_xattr_request(file, f_in);
 #endif