1 files changed, 107 insertions, 0 deletions
diff --git a/lib/layer.h b/lib/layer.h
new file mode 100644
index 0000000..7721560
--- /dev/null
+++ b/lib/layer.h
@@ -0,0 +1,107 @@
+/*  Copyright (C) CZ.NIC, z.s.p.o. <knot-resolver@labs.nic.cz>
+ *  SPDX-License-Identifier: GPL-3.0-or-later
+ */
+
+#pragma once
+
+#include "kresconfig.h"
+#include "lib/defines.h"
+#include "lib/utils.h"
+
+/** Layer processing states.  Only one value at a time (but see TODO).
+ *
+ *  Each state represents the state machine transition,
+ *  and determines readiness for the next action.
+ *  See struct kr_layer_api for the actions.
+ *
+ *  TODO: the cookie module sometimes sets (_FAIL | _DONE) on purpose (!)
+ */
+enum kr_layer_state {
+	KR_STATE_CONSUME = 1 << 0, /*!< Consume data. */
+	KR_STATE_PRODUCE = 1 << 1, /*!< Produce data. */
+
+	/*! Finished successfully or a special case: in CONSUME phase this can
+	 * be used (by iterator) to do a transition to PRODUCE phase again,
+	 * in which case the packet wasn't accepted for some reason. */
+	KR_STATE_DONE    = 1 << 2,
+
+	KR_STATE_FAIL    = 1 << 3, /*!< Error. */
+	KR_STATE_YIELD   = 1 << 4, /*!< Paused, waiting for a sub-query. */
+};
+
+/** Check that a kr_layer_state makes sense.  We're not very strict ATM. */
+static inline bool kr_state_consistent(enum kr_layer_state s)
+{
+#ifdef __clang__
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wtautological-constant-out-of-range-compare"
+#pragma clang diagnostic ignored "-Wtautological-unsigned-enum-zero-compare"
+#endif
+	return s >= 0 && s < (1 << 5);
+#ifdef __clang__
+#pragma clang diagnostic pop
+#endif
+}
+
+/* Forward declarations. */
+struct kr_layer_api;
+
+/** Packet processing context. */
+typedef struct kr_layer {
+	int state; /*!< The current state; bitmap of enum kr_layer_state. */
+	struct kr_request *req; /*!< The corresponding request. */
+	const struct kr_layer_api *api;
+	knot_pkt_t *pkt; /*!< In glue for lua kr_layer_api it's used to pass the parameter. */
+	struct sockaddr *dst; /*!< In glue for checkout layer it's used to pass the parameter. */
+	bool is_stream;       /*!< In glue for checkout layer it's used to pass the parameter. */
+} kr_layer_t;
+
+/** Packet processing module API.  All functions return the new kr_layer_state.
+ *
+ * Lua modules are allowed to return nil/nothing, meaning the state shall not change.
+ */
+struct kr_layer_api {
+      	/** Start of processing the DNS request. */
+	int (*begin)(kr_layer_t *ctx);
+
+	int (*reset)(kr_layer_t *ctx);
+
+	/** Paired to begin, called both on successes and failures. */
+	int (*finish)(kr_layer_t *ctx);
+
+	/** Process an answer from upstream or from cache.
+	 * Lua API: call is omitted iff (state & KR_STATE_FAIL). */
+	int (*consume)(kr_layer_t *ctx, knot_pkt_t *pkt);
+
+	/** Produce either an answer to the request or a query for upstream (or fail).
+	 * Lua API: call is omitted iff (state & KR_STATE_FAIL). */
+	int (*produce)(kr_layer_t *ctx, knot_pkt_t *pkt);
+
+	/** Finalises the outbound query packet with the knowledge of the IP addresses.
+	 * The checkout layer doesn't persist the state, so canceled subrequests
+	 * don't affect the resolution or rest of the processing.
+	 * Lua API: call is omitted iff (state & KR_STATE_FAIL). */
+	int (*checkout)(kr_layer_t *ctx, knot_pkt_t *packet, struct sockaddr *dst, int type);
+
+	/** Finalises the answer.
+	 * Last chance to affect what will get into the answer, including EDNS.
+	 * Not called if the packet is being dropped. */
+	int (*answer_finalize)(kr_layer_t *ctx);
+
+	/** The C module can store anything in here. */
+	void *data;
+
+	/** Internal to ./daemon/ffimodule.c. */
+	int cb_slots[];
+};
+
+typedef struct kr_layer_api kr_layer_api_t;
+
+/** Pickled layer state (api, input, state). */
+struct kr_layer_pickle {
+    struct kr_layer_pickle *next;
+    const struct kr_layer_api *api;
+    knot_pkt_t *pkt;
+    unsigned state;
+};
+