tools/xenstored: add depth handling to XS_WATCH

In case XENSTORE_SERVER_FEATURE_WATCHDEPTH is set, allow XS_WATCH to
have "depth" as 3rd parameter.

Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Jason Andryuk <jason.andryuk@amd.com>

tools/xenstored/domain.c

@@ -390,6 +390,14 @@ void wrl_apply_debit_trans_commit(struct connection *conn)
 	wrl_apply_debit_actual(conn->domain);
 }
 
+bool feature_available(const struct connection *conn, unsigned int feature)
+{
+	if (!conn->domain)
+		return XENSTORE_FEATURES & feature;
+
+	return conn->domain->features & feature;
+}
+
 static unsigned int domain_get_soft_quota(struct domain *d, enum accitem what)
 {
 	if (d && d->acc[what].val[Q_IDX_SOFT] != Q_VAL_DISABLED)

tools/xenstored/domain.h

@@ -188,4 +188,6 @@ struct hashtable *domain_check_acc_init(void);
 void domain_check_acc_add(const struct node *node, struct hashtable *domains);
 void domain_check_acc(struct hashtable *domains);
 
+bool feature_available(const struct connection *conn, unsigned int feature);
+
 #endif /* _XENSTORED_DOMAIN_H */

tools/xenstored/watch.c

@@ -213,11 +213,18 @@ static struct watch *add_watch(struct connection *conn, const char *path,
 int do_watch(const void *ctx, struct connection *conn, struct buffered_data *in)
 {
 	struct watch *watch;
-	const char *vec[2];
+	const char *vec[3];
+	unsigned int n_pars;
 	int depth = -1;
 	bool relative;
 
-	if (get_strings(in, vec, ARRAY_SIZE(vec)) != ARRAY_SIZE(vec))
+	n_pars = get_strings(in, vec, ARRAY_SIZE(vec));
+	if (n_pars == 3 &&
+	    feature_available(conn, XENSTORE_SERVER_FEATURE_WATCHDEPTH)) {
+		depth = atoi(vec[2]);
+		if (depth < 0)
+			return EINVAL;
+	} else if (n_pars != 2)
 		return EINVAL;
 
 	errno = check_watch_path(conn, ctx, &(vec[0]), &relative);