This patch adds the sending of the -4 or -6 option to ssh when the
-4 or -6 option was given to rsync.

To use this patch, run these commands for a successful build:

    patch -p1 <patches/ssh-4-6-options.diff
    ./configure                         (optional if already run)
    make

based-on: d73762eea3f15f2c56bb3fa9394ad1883c25c949
diff --git a/main.c b/main.c
--- a/main.c
+++ b/main.c
@@ -78,6 +78,7 @@ extern BOOL flist_receiving_enabled;
 extern BOOL shutting_down;
 extern int backup_dir_len;
 extern int basis_dir_cnt;
+extern int default_af_hint;
 extern struct stats stats;
 extern char *stdout_format;
 extern char *logfile_format;
@@ -454,6 +455,11 @@ static pid_t do_cmd(char *cmd, char *machine, char *user, char **remote_argv, in
 			*t++ = '\0';
 		}
 
+		if ((t = strrchr(cmd, '/')) != NULL)
+		    t++;
+		else
+		    t = cmd;
+
 		/* check to see if we've already been given '-l user' in
 		 * the remote-shell command */
 		for (i = 0; i < argc-1; i++) {
@@ -473,20 +479,25 @@ static pid_t do_cmd(char *cmd, char *machine, char *user, char **remote_argv, in
 			args[argc++] = "-l";
 			args[argc++] = user;
 		}
+#ifdef AF_INET
+		if (default_af_hint == AF_INET && strcmp(cmd, "ssh") == 0) {
+			/* we're using ssh so we can add a -4 option */
+			args[argc++] = "-4";
+		}
+#endif
+#ifdef AF_INET6
+		if (default_af_hint == AF_INET6 && strcmp(cmd, "ssh") == 0) {
+			/* we're using ssh so we can add a -6 option */
+			args[argc++] = "-6";
+		}
+#endif
 		args[argc++] = machine;
 #endif
 
 		args[argc++] = rsync_path;
 
-		if (blocking_io < 0) {
-			char *cp;
-			if ((cp = strrchr(cmd, '/')) != NULL)
-				cp++;
-			else
-				cp = cmd;
-			if (strcmp(cp, "rsh") == 0 || strcmp(cp, "remsh") == 0)
-				blocking_io = 1;
-		}
+		if (blocking_io < 0 && (strcmp(t, "rsh") == 0 || strcmp(t, "remsh") == 0))
+			blocking_io = 1;
 
 		server_options(args,&argc);
 
diff --git a/rsync.yo b/rsync.yo
--- a/rsync.yo
+++ b/rsync.yo
@@ -2658,14 +2658,18 @@ regardless of the remote charset you actually pass.  Thus, you may feel free to
 specify just the local charset for a daemon transfer (e.g. bf(--iconv=utf8)).
 
 dit(bf(-4, --ipv4) or bf(-6, --ipv6)) Tells rsync to prefer IPv4/IPv6
-when creating sockets.  This only affects sockets that rsync has direct
+when creating sockets.  This affects sockets that rsync has direct
 control over, such as the outgoing socket when directly contacting an
-rsync daemon.  See also these options in the bf(--daemon) mode section.
+rsync daemon, as well as forwaring the -4 or -6 option to ssh, if rsync
+deduces that ssh is being used as the remote shell.  For other remote
+shells, see the bf(--rsh) option.
 
 If rsync was complied without support for IPv6, the bf(--ipv6) option
 will have no effect.  The bf(--version) output will tell you if this
 is the case.
 
+See also these options in the bf(--daemon) mode section.
+
 dit(bf(--checksum-seed=NUM)) Set the checksum seed to the integer NUM.  This 4
 byte checksum seed is included in each block and MD4 file checksum calculation
 (the more modern MD5 file checksums don't use a seed).  By default the checksum
diff -Nurp a/rsync.1 b/rsync.1
--- a/rsync.1
+++ b/rsync.1
@@ -3008,14 +3008,18 @@ specify just the local charset for a dae
 .IP 
 .IP "\fB\-4, \-\-ipv4\fP or \fB\-6, \-\-ipv6\fP"
 Tells rsync to prefer IPv4/IPv6
-when creating sockets.  This only affects sockets that rsync has direct
+when creating sockets.  This affects sockets that rsync has direct
 control over, such as the outgoing socket when directly contacting an
-rsync daemon.  See also these options in the \fB\-\-daemon\fP mode section.
+rsync daemon, as well as forwaring the \-4 or \-6 option to ssh, if rsync
+deduces that ssh is being used as the remote shell.  For other remote
+shells, see the \fB\-\-rsh\fP option.
 .IP 
 If rsync was complied without support for IPv6, the \fB\-\-ipv6\fP option
 will have no effect.  The \fB\-\-version\fP output will tell you if this
 is the case.
 .IP 
+See also these options in the \fB\-\-daemon\fP mode section.
+.IP 
 .IP "\fB\-\-checksum\-seed=NUM\fP"
 Set the checksum seed to the integer NUM.  This 4
 byte checksum seed is included in each block and MD4 file checksum calculation