tools/xenstore: add the basic framework for doing the live update

Add the main framework for executing the live update. This for now
only defines the basic execution steps with empty dummy functions.
This final step returning means failure, as in case of success the
new executable will have taken over.

Signed-off-by: Juergen Gross <jgross@suse.com>
Acked-by: Wei Liu <wl@xen.org>

tools/xenstore/xenstored_control.c

@@ -22,6 +22,7 @@ Interactive commands for Xen Store Daemon.
 #include <stdlib.h>
 #include <string.h>
 #include <syslog.h>
+#include <time.h>
 #include <sys/types.h>
 #include <sys/stat.h>
 #include <unistd.h>
@@ -44,6 +45,11 @@ struct live_update {
 #endif
 
 	char *cmdline;
+
+	/* Start parameters. */
+	bool force;
+	unsigned int timeout;
+	time_t started_at;
 };
 
 static struct live_update *lu_status;
@@ -304,6 +310,58 @@ static const char *lu_arch(const void *ctx, struct connection *conn,
 }
 #endif
 
+static bool lu_check_lu_allowed(void)
+{
+	return true;
+}
+
+static const char *lu_reject_reason(const void *ctx)
+{
+	return "BUSY";
+}
+
+static const char *lu_dump_state(const void *ctx, struct connection *conn)
+{
+	return NULL;
+}
+
+static const char *lu_activate_binary(const void *ctx)
+{
+	return "Not yet implemented.";
+}
+
+static bool do_lu_start(struct delayed_request *req)
+{
+	time_t now = time(NULL);
+	const char *ret;
+	char *resp;
+
+	if (!lu_check_lu_allowed()) {
+		if (now < lu_status->started_at + lu_status->timeout)
+			return false;
+		if (!lu_status->force) {
+			ret = lu_reject_reason(req);
+			goto out;
+		}
+	}
+
+	/* Dump out internal state, including "OK" for live update. */
+	ret = lu_dump_state(req->in, lu_status->conn);
+	if (!ret) {
+		/* Perform the activation of new binary. */
+		ret = lu_activate_binary(req->in);
+	}
+
+	/* We will reach this point only in case of failure. */
+ out:
+	talloc_free(lu_status);
+
+	resp = talloc_strdup(req->in, ret);
+	send_reply(lu_status->conn, XS_CONTROL, resp, strlen(resp) + 1);
+
+	return true;
+}
+
 static const char *lu_start(const void *ctx, struct connection *conn,
 			    bool force, unsigned int to)
 {
@@ -317,8 +375,11 @@ static const char *lu_start(const void *ctx, struct connection *conn,
 		return "Kernel not complete.";
 #endif
 
-	/* Will be replaced by real live-update later. */
-	talloc_free(lu_status);
+	lu_status->force = force;
+	lu_status->timeout = to;
+	lu_status->started_at = time(NULL);
+
+	errno = delay_request(conn, conn->in, do_lu_start, NULL);
 
 	return NULL;
 }
@@ -356,6 +417,10 @@ static int do_control_lu(void *ctx, struct connection *conn,
 				return EINVAL;
 		}
 		ret = lu_start(ctx, conn, force, to);
+		if (errno)
+			return errno;
+		if (!ret)
+			return 0;
 	} else {
 		errno = 0;
 		ret = lu_arch(ctx, conn, vec, num);