1 files changed, 112 insertions, 0 deletions
diff --git a/lib/module.h b/lib/module.h
new file mode 100644
index 0000000..507b2df
--- /dev/null
+++ b/lib/module.h
@@ -0,0 +1,112 @@
+/*  Copyright (C) CZ.NIC, z.s.p.o. <knot-resolver@labs.nic.cz>
+ *  SPDX-License-Identifier: GPL-3.0-or-later
+ */
+
+/** @file
+ * Module API definition and functions for (un)loading modules.
+ */
+
+#pragma once
+
+#include "lib/defines.h"
+#include "lib/utils.h"
+#include "lib/layer.h"
+
+struct kr_module;
+struct kr_prop;
+
+
+/**
+ * Export module API version (place this at the end of your module).
+ *
+ * @param module module name (e.g. policy)
+ */
+#define KR_MODULE_EXPORT(module) \
+    KR_EXPORT uint32_t module ## _api(void) { return KR_MODULE_API; }
+#define KR_MODULE_API ((uint32_t) 0x20210125)
+
+typedef uint32_t (module_api_cb)(void);
+
+
+/**
+ * Module representation.
+ *
+ * The five symbols (init, ...) may be defined by the module as name_init(), etc;
+ * all are optional and missing symbols are represented as NULLs;
+ */
+struct kr_module {
+	char *name;
+
+	/** Constructor.  Called after loading the module.  @return error code.
+	 * Lua modules: not populated, called via lua directly. */
+	int (*init)(struct kr_module *self);
+
+	/** Destructor.  Called before unloading the module.  @return error code. */
+	int (*deinit)(struct kr_module *self);
+
+	/** Configure with encoded JSON (NULL if missing).  @return error code.
+	 * Lua modules: not used and not useful from C.
+	 * When called from lua, input is JSON, like for kr_prop_cb. */
+	int (*config)(struct kr_module *self, const char *input);
+
+	/** Packet processing API specs.  May be NULL.  See docs on that type.
+	 * Owned by the module code. */
+	const kr_layer_api_t *layer;
+
+	/** List of properties.  May be NULL.  Terminated by { NULL, NULL, NULL }.
+	 * Lua modules: not used and not useful. */
+	const struct kr_prop *props;
+
+	/** dlopen() handle; RTLD_DEFAULT for embedded modules; NULL for lua modules. */
+	void *lib;
+	void *data; /**< Custom data context. */
+};
+
+/**
+ * Module property callback.  Input and output is passed via a JSON encoded in a string.
+ *
+ * @param env pointer to the lua engine, i.e. struct engine *env (TODO: explicit type)
+ * @param input parameter (NULL if missing/nil on lua level)
+ * @return a free-form JSON output (malloc-ated)
+ * @note see modules_create_table_for_c() implementation for details
+ *       about the input/output conversion.
+ */
+typedef char *(kr_prop_cb)(void *env, struct kr_module *self, const char *input);
+
+/**
+ * Module property (named callable).
+ */
+struct kr_prop {
+	kr_prop_cb *cb;
+	const char *name;
+	const char *info;
+};
+
+
+/**
+ * Load a C module instance into memory.  And call its init().
+ *
+ * @param module module structure.  Will be overwritten except for ->data on success.
+ * @param name module name
+ * @param path module search path
+ * @return 0 or an error
+ */
+KR_EXPORT
+int kr_module_load(struct kr_module *module, const char *name, const char *path);
+
+/**
+ * Unload module instance.
+ *
+ * @param module module structure
+ * @note currently used even for lua modules
+ */
+KR_EXPORT
+void kr_module_unload(struct kr_module *module);
+
+typedef int (*kr_module_init_cb)(struct kr_module *);
+/**
+ * Get embedded module's init function by name (or NULL).
+ */
+KR_EXPORT
+kr_module_init_cb kr_module_get_embedded(const char *name);
+