1 files changed, 289 insertions, 0 deletions
diff --git a/daemon/ffimodule.c b/daemon/ffimodule.c
new file mode 100644
index 0000000..1cb6b71
--- /dev/null
+++ b/daemon/ffimodule.c
@@ -0,0 +1,289 @@
+/*  Copyright (C) 2015-2017 CZ.NIC, z.s.p.o. <knot-dns@labs.nic.cz>
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#include <uv.h>
+
+#include "daemon/engine.h"
+#include "daemon/ffimodule.h"
+#include "daemon/bindings.h"
+#include "lib/module.h"
+#include "lib/layer.h"
+
+#if LUA_VERSION_NUM >= 502
+#define l_resume(L, argc) lua_resume((L), NULL, (argc))
+#else
+#define l_resume(L, argc) lua_resume((L), (argc))
+#endif
+
+/** @internal Slots for layer callbacks.
+  * Each slot ID corresponds to Lua reference in module API. */
+enum {
+	SLOT_begin = 0,
+	SLOT_reset,
+	SLOT_finish,
+	SLOT_consume,
+	SLOT_produce,
+	SLOT_checkout,
+	SLOT_answer_finalize,
+	SLOT_count /* dummy, must be the last */
+};
+#define SLOT_size sizeof(int)
+
+/** @internal Helper for retrieving the right function entrypoint. */
+static inline lua_State *l_ffi_preface(struct kr_module *module, const char *call) {
+	lua_State *L = module->lib;
+	lua_getglobal(L, module->name);
+	lua_getfield(L, -1, call);
+	lua_remove(L, -2);
+	if (lua_isnil(L, -1)) {
+		lua_pop(L, 1);
+		return NULL;
+	}
+	lua_pushlightuserdata(L, module);
+	return L;
+}
+
+/** @internal Continue with coroutine. */
+static void l_ffi_resume_cb(uv_idle_t *check)
+{
+	lua_State *L = check->data;
+	int status = l_resume(L, 0);
+	if (status != LUA_YIELD) {
+		uv_idle_stop(check); /* Stop coroutine */
+		uv_close((uv_handle_t *)check, (uv_close_cb)free);
+	}
+	lua_pop(L, lua_gettop(L));
+}
+
+/** @internal Schedule deferred continuation. */
+static int l_ffi_defer(lua_State *L)
+{
+	uv_idle_t *check = malloc(sizeof(*check));
+	if (!check) {
+		return kr_error(ENOMEM);
+	}
+	uv_idle_init(uv_default_loop(), check);
+	check->data = L;
+	return uv_idle_start(check, l_ffi_resume_cb);
+}
+
+/** @internal Helper for calling the entrypoint. */
+static inline int l_ffi_call(lua_State *L, int argc)
+{
+	int status = lua_pcall(L, argc, 1, 0);
+	if (status != 0) {
+		fprintf(stderr, "error: %s\n", lua_tostring(L, -1));
+		lua_pop(L, 1);
+		return kr_error(EIO);
+	}
+	if (lua_isnumber(L, -1)) { /* Return code */
+		status = lua_tonumber(L, -1);
+	} else if (lua_isthread(L, -1)) { /* Continuations */
+		status = l_ffi_defer(lua_tothread(L, -1));
+	}
+	lua_pop(L, 1);
+	return status;
+}
+
+static int l_ffi_init(struct kr_module *module)
+{
+	lua_State *L = l_ffi_preface(module, "init");
+	if (!L) {
+		return 0;
+	}
+	return l_ffi_call(L, 1);
+}
+
+static int l_ffi_deinit(struct kr_module *module)
+{
+	/* Deinit the module in Lua (if possible) */
+	int ret = 0;
+	lua_State *L = module->lib;
+	if (l_ffi_preface(module, "deinit")) {
+		ret = l_ffi_call(L, 1);
+	}
+	module->lib = NULL;
+	/* Free the layer API wrapper (unconst it) */
+	kr_layer_api_t* api = module->data;
+	if (!api) {
+		return ret;
+	}
+	/* Unregister layer callback references from registry. */
+	for (int si = 0; si < SLOT_count; ++si) {
+		if (api->cb_slots[si] > 0) {
+			luaL_unref(L, LUA_REGISTRYINDEX, api->cb_slots[si]);
+		}
+	}
+	free(api);
+	return ret;
+}
+
+/** @internal Helper for retrieving layer Lua function by name. */
+#define LAYER_FFI_CALL(ctx, slot_name) \
+	const int *cb_slot = (ctx)->api->cb_slots + SLOT_ ## slot_name; \
+	if (*cb_slot <= 0) { \
+		return ctx->state; \
+	} \
+	struct kr_module *module = (ctx)->api->data; \
+	lua_State *L = module->lib; \
+	lua_rawgeti(L, LUA_REGISTRYINDEX, *cb_slot); \
+	lua_pushnumber(L, ctx->state)
+
+static int l_ffi_layer_begin(kr_layer_t *ctx)
+{
+	LAYER_FFI_CALL(ctx, begin);
+	lua_pushlightuserdata(L, ctx->req);
+	return l_ffi_call(L, 2);
+}
+
+static int l_ffi_layer_reset(kr_layer_t *ctx)
+{
+	LAYER_FFI_CALL(ctx, reset);
+	lua_pushlightuserdata(L, ctx->req);
+	return l_ffi_call(L, 2);
+}
+
+static int l_ffi_layer_finish(kr_layer_t *ctx)
+{
+	struct kr_request *req = ctx->req;
+	LAYER_FFI_CALL(ctx, finish);
+	lua_pushlightuserdata(L, req);
+	lua_pushlightuserdata(L, req->answer);
+	return l_ffi_call(L, 3);
+}
+
+static int l_ffi_layer_consume(kr_layer_t *ctx, knot_pkt_t *pkt)
+{
+	if (ctx->state & KR_STATE_FAIL) {
+		return ctx->state; /* Already failed, skip */
+	}
+	LAYER_FFI_CALL(ctx, consume);
+	lua_pushlightuserdata(L, ctx->req);
+	lua_pushlightuserdata(L, pkt);
+	return l_ffi_call(L, 3);
+}
+
+static int l_ffi_layer_produce(kr_layer_t *ctx, knot_pkt_t *pkt)
+{
+	if (ctx->state & (KR_STATE_FAIL)) {
+		return ctx->state; /* Already failed or done, skip */
+	}
+	LAYER_FFI_CALL(ctx, produce);
+	lua_pushlightuserdata(L, ctx->req);
+	lua_pushlightuserdata(L, pkt);
+	return l_ffi_call(L, 3);
+}
+
+static int l_ffi_layer_checkout(kr_layer_t *ctx, knot_pkt_t *pkt, struct sockaddr *dst, int type)
+{
+	if (ctx->state & (KR_STATE_FAIL)) {
+		return ctx->state; /* Already failed or done, skip */
+	}
+	LAYER_FFI_CALL(ctx, checkout);
+	lua_pushlightuserdata(L, ctx->req);
+	lua_pushlightuserdata(L, pkt);
+	lua_pushlightuserdata(L, dst);
+	lua_pushboolean(L, type == SOCK_STREAM);
+	return l_ffi_call(L, 5);
+}
+
+static int l_ffi_layer_answer_finalize(kr_layer_t *ctx)
+{
+	LAYER_FFI_CALL(ctx, answer_finalize);
+	lua_pushlightuserdata(L, ctx->req);
+	return l_ffi_call(L, 2);
+}
+#undef LAYER_FFI_CALL
+
+/** @internal Conditionally register layer trampoline
+  * @warning Expects 'module.layer' to be on top of Lua stack. */
+#define LAYER_REGISTER(L, api, name) do { \
+	int *cb_slot = (api)->cb_slots + SLOT_ ## name; \
+	lua_getfield((L), -1, #name); \
+	if (!lua_isnil((L), -1)) { \
+		(api)->name = l_ffi_layer_ ## name; \
+		*cb_slot = luaL_ref((L), LUA_REGISTRYINDEX); \
+	} else { \
+		lua_pop((L), 1); \
+	} \
+} while(0)
+
+/** @internal Create C layer api wrapper. */
+static kr_layer_api_t *l_ffi_layer_create(lua_State *L, struct kr_module *module)
+{
+	/* Fabricate layer API wrapping the Lua functions
+	 * reserve slots after it for references to Lua callbacks. */
+	const size_t api_length = offsetof(kr_layer_api_t, cb_slots)
+				+ (SLOT_count * SLOT_size);
+	kr_layer_api_t *api = malloc(api_length);
+	if (api) {
+		memset(api, 0, api_length);
+		LAYER_REGISTER(L, api, begin);
+		LAYER_REGISTER(L, api, finish);
+		LAYER_REGISTER(L, api, consume);
+		LAYER_REGISTER(L, api, produce);
+		LAYER_REGISTER(L, api, checkout);
+		LAYER_REGISTER(L, api, answer_finalize);
+		LAYER_REGISTER(L, api, reset);
+		/* Begin is always set, as it initializes layer baton. */
+		api->begin = l_ffi_layer_begin;
+		api->data = module;
+	}
+	return api;
+}
+
+/** @internal Retrieve C layer api wrapper. */
+static const kr_layer_api_t *l_ffi_layer(struct kr_module *module)
+{
+	if (module) {
+		return (const kr_layer_api_t *)module->data;
+	}
+	return NULL;
+}
+#undef LAYER_REGISTER
+
+int ffimodule_register_lua(struct engine *engine, struct kr_module *module, const char *name)
+{
+	/* Register module in Lua */
+	lua_State *L = engine->L;
+	lua_getglobal(L, "require");
+	lua_pushstring(L, name);
+	if (lua_pcall(L, 1, LUA_MULTRET, 0) != 0) {
+		fprintf(stderr, "error: %s\n", lua_tostring(L, -1));
+		lua_pop(L, 1);
+		return kr_error(ENOENT);
+	}
+	lua_setglobal(L, name);
+	lua_getglobal(L, name);
+
+	/* Create FFI module with trampolined functions. */
+	memset(module, 0, sizeof(*module));
+	module->name = strdup(name);
+	module->init = &l_ffi_init;
+	module->deinit = &l_ffi_deinit;
+	/* Bake layer API if defined in module */
+	lua_getfield(L, -1, "layer");
+	if (!lua_isnil(L, -1)) {
+		module->layer = &l_ffi_layer;
+		module->data = l_ffi_layer_create(L, module);
+	}
+	module->lib = L;
+	lua_pop(L, 2); /* Clear the layer + module global */
+	if (module->init) {
+		return module->init(module);
+	}
+	return kr_ok();
+}