Added a message queue for the receiver->generator messages to handle the case

where the message pipe is being used to forward the file-list data.

io.c

@@ -133,7 +133,7 @@ struct msg_list {
 	struct msg_list_item *head, *tail;
 };
 
-static struct msg_list msg2sndr;
+static struct msg_list msg_queue;
 
 static void flist_ndx_push(struct flist_ndx_list *lp, int ndx)
 {
@@ -247,17 +247,29 @@ static void msg_list_add(struct msg_list *lst, int code, const char *buf, int le
 	lst->tail = m;
 }
 
-static void msg2sndr_flush(void)
+static void msg_flush(void)
 {
-	while (msg2sndr.head && io_multiplexing_out) {
-		struct msg_list_item *m = msg2sndr.head;
-		if (!(msg2sndr.head = m->next))
-			msg2sndr.tail = NULL;
-		stats.total_written += m->len;
-		defer_forwarding_messages = 1;
-		writefd_unbuffered(sock_f_out, m->buf, m->len);
-		defer_forwarding_messages = 0;
-		free(m);
+	if (am_generator) {
+		while (msg_queue.head && io_multiplexing_out) {
+			struct msg_list_item *m = msg_queue.head;
+			if (!(msg_queue.head = m->next))
+				msg_queue.tail = NULL;
+			stats.total_written += m->len;
+			defer_forwarding_messages++;
+			writefd_unbuffered(sock_f_out, m->buf, m->len);
+			defer_forwarding_messages--;
+			free(m);
+		}
+	} else {
+		while (msg_queue.head) {
+			struct msg_list_item *m = msg_queue.head;
+			if (!(msg_queue.head = m->next))
+				msg_queue.tail = NULL;
+			defer_forwarding_messages++;
+			writefd_unbuffered(msg_fd_out, m->buf, m->len);
+			defer_forwarding_messages--;
+			free(m);
+		}
 	}
 }
 
@@ -379,7 +391,7 @@ static void read_msg_fd(void)
 	no_flush--;
 	msg_fd_in = fd;
 	if (!--defer_forwarding_messages)
-		msg2sndr_flush();
+		msg_flush();
 }
 
 /* This is used by the generator to limit how many file transfers can
@@ -456,7 +468,7 @@ static void mplex_write(int fd, enum msgcode code, const char *buf, size_t len)
 		defer_forwarding_messages++;
 		writefd_unbuffered(fd, buf, len);
 		if (!--defer_forwarding_messages)
-			msg2sndr_flush();
+			msg_flush();
 	}
 }
 
@@ -467,10 +479,13 @@ int send_msg(enum msgcode code, const char *buf, int len)
 			return io_multiplex_write(code, buf, len);
 		if (!io_multiplexing_out)
 			return 0;
-		msg_list_add(&msg2sndr, code, buf, len);
+		msg_list_add(&msg_queue, code, buf, len);
 		return 1;
 	}
-	mplex_write(msg_fd_out, code, buf, len);
+	if (flist_forward_from >= 0)
+		msg_list_add(&msg_queue, code, buf, len);
+	else
+		mplex_write(msg_fd_out, code, buf, len);
 	return 1;
 }
 
@@ -1254,11 +1269,11 @@ static void writefd_unbuffered(int fd, const char *buf, size_t len)
 	size_t n, total = 0;
 	fd_set w_fds, r_fds, e_fds;
 	int maxfd, count, cnt, using_r_fds;
-	int defer_save = defer_forwarding_messages;
+	int defer_inc = 0;
 	struct timeval tv;
 
 	if (no_flush++)
-		defer_forwarding_messages = 1;
+		defer_forwarding_messages++, defer_inc++;
 
 	while (total < len) {
 		FD_ZERO(&w_fds);
@@ -1337,7 +1352,7 @@ static void writefd_unbuffered(int fd, const char *buf, size_t len)
 		}
 
 		total += cnt;
-		defer_forwarding_messages = 1;
+		defer_forwarding_messages++, defer_inc++;
 
 		if (fd == sock_f_out) {
 			if (io_timeout || am_generator)
@@ -1347,15 +1362,12 @@ static void writefd_unbuffered(int fd, const char *buf, size_t len)
 	}
 
 	no_flush--;
-	if (!(defer_forwarding_messages = defer_save))
-		msg2sndr_flush();
+	if (!(defer_forwarding_messages -= defer_inc))
+		msg_flush();
 }
 
 void io_flush(int flush_it_all)
 {
-	if (flush_it_all && !defer_forwarding_messages)
-		msg2sndr_flush();
-
 	if (!iobuf_out_cnt || no_flush)
 		return;
 
@@ -1364,6 +1376,9 @@ void io_flush(int flush_it_all)
 	else
 		writefd_unbuffered(iobuf_f_out, iobuf_out, iobuf_out_cnt);
 	iobuf_out_cnt = 0;
+
+	if (flush_it_all && !defer_forwarding_messages)
+		msg_flush();
 }
 
 static void writefd(int fd, const char *buf, size_t len)