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+/* Copyright (C) CZ.NIC, z.s.p.o. <knot-resolver@labs.nic.cz>
+ * SPDX-License-Identifier: GPL-3.0-or-later
+ */
+
+#pragma once
+
+#include <sys/time.h>
+#include <libknot/dname.h>
+#include <libknot/codes.h>
+
+#include "lib/selection.h"
+#include "lib/zonecut.h"
+
+/** Query flags */
+struct kr_qflags {
+ bool NO_MINIMIZE : 1; /**< Don't minimize QNAME. */
+ bool NO_IPV6 : 1; /**< Disable IPv6 */
+ bool NO_IPV4 : 1; /**< Disable IPv4 */
+ bool TCP : 1; /**< Use TCP (or TLS) for this query. */
+ bool NO_ANSWER : 1; /**< Do not send any answer to the client.
+ * Request state should be set to `KR_STATE_FAIL`
+ * when this flag is set. */
+ bool RESOLVED : 1; /**< Query is resolved. Note that kr_query gets
+ * RESOLVED before following a CNAME chain; see .CNAME. */
+ bool AWAIT_IPV4 : 1; /**< Query is waiting for A address. */
+ bool AWAIT_IPV6 : 1; /**< Query is waiting for AAAA address. */
+ bool AWAIT_CUT : 1; /**< Query is waiting for zone cut lookup */
+ bool NO_EDNS : 1; /**< Don't use EDNS. */
+ bool CACHED : 1; /**< Query response is cached. */
+ bool NO_CACHE : 1; /**< No cache for lookup; exception: finding NSs and subqueries. */
+ bool EXPIRING : 1; /**< Query response is cached but expiring. See is_expiring(). */
+ bool ALLOW_LOCAL : 1; /**< Allow queries to local or private address ranges. */
+ bool DNSSEC_WANT : 1; /**< Want DNSSEC secured answer; exception: +cd,
+ * i.e. knot_wire_get_cd(request->qsource.packet->wire) */
+ bool DNSSEC_BOGUS : 1; /**< Query response is DNSSEC bogus. */
+ bool DNSSEC_INSECURE : 1;/**< Query response is DNSSEC insecure. */
+ bool DNSSEC_CD : 1; /**< Instruction to set CD bit in request. */
+ bool STUB : 1; /**< Stub resolution, accept received answer as solved. */
+ bool ALWAYS_CUT : 1; /**< Always recover zone cut (even if cached). */
+ bool DNSSEC_WEXPAND : 1; /**< Query response has wildcard expansion. */
+ bool PERMISSIVE : 1; /**< Permissive resolver mode. */
+ bool STRICT : 1; /**< Strict resolver mode. */
+ bool BADCOOKIE_AGAIN : 1;/**< Query again because bad cookie returned. */
+ bool CNAME : 1; /**< Query response contains CNAME in answer section. */
+ bool REORDER_RR : 1; /**< Reorder cached RRs. */
+ bool TRACE : 1; /**< Also log answers on debug level. */
+ bool NO_0X20 : 1; /**< Disable query case randomization . */
+ bool DNSSEC_NODS : 1; /**< DS non-existence is proven */
+ bool DNSSEC_OPTOUT : 1; /**< Closest encloser proof has optout */
+ bool NONAUTH : 1; /**< Non-authoritative in-bailiwick records are enough.
+ * TODO: utilize this also outside cache. */
+ bool FORWARD : 1; /**< Forward all queries to upstream; validate answers. */
+ bool DNS64_MARK : 1; /**< Internal mark for dns64 module. */
+ bool CACHE_TRIED : 1; /**< Internal to cache module. */
+ bool NO_NS_FOUND : 1; /**< No valid NS found during last PRODUCE stage. */
+ bool PKT_IS_SANE : 1; /**< Set by iterator in consume phase to indicate whether
+ * some basic aspects of the packet are OK, e.g. QNAME. */
+ bool DNS64_DISABLE : 1; /**< Don't do any DNS64 stuff (meant for view:addr). */
+};
+
+/** Combine flags together. This means set union for simple flags. */
+KR_EXPORT
+void kr_qflags_set(struct kr_qflags *fl1, struct kr_qflags fl2);
+
+/** Remove flags. This means set-theoretic difference. */
+KR_EXPORT
+void kr_qflags_clear(struct kr_qflags *fl1, struct kr_qflags fl2);
+
+/** Callback for serve-stale decisions.
+ * @param ttl the expired TTL (i.e. it's < 0)
+ * @return the adjusted TTL (typically 1) or < 0.
+ */
+typedef int32_t (*kr_stale_cb)(int32_t ttl, const knot_dname_t *owner, uint16_t type,
+ const struct kr_query *qry);
+
+/**
+ * Single query representation.
+ */
+struct kr_query {
+ struct kr_query *parent;
+ knot_dname_t *sname; /**< The name to resolve - lower-cased, uncompressed. */
+ uint16_t stype;
+ uint16_t sclass;
+ uint16_t id;
+ uint16_t reorder; /**< Seed to reorder (cached) RRs in answer or zero. */
+ struct kr_qflags flags;
+ struct kr_qflags forward_flags;
+ uint32_t secret;
+ uint32_t uid; /**< Query iteration number, unique within the kr_rplan. */
+ uint64_t creation_time_mono; /* The time of query's creation (milliseconds).
+ * Or time of creation of an oldest
+ * ancestor if it is a subquery. */
+ uint64_t timestamp_mono; /**< Time of query created or time of
+ * query to upstream resolver (milliseconds). */
+ struct timeval timestamp; /**< Real time for TTL+DNSSEC checks (.tv_sec only). */
+ struct kr_zonecut zone_cut;
+ struct kr_layer_pickle *deferred;
+
+ /** Current xNAME depth, set by iterator. 0 = uninitialized, 1 = no CNAME, ...
+ * See also KR_CNAME_CHAIN_LIMIT. */
+ int8_t cname_depth;
+ /** Pointer to the query that originated this one because of following a CNAME (or NULL). */
+ struct kr_query *cname_parent;
+ struct kr_request *request; /**< Parent resolution request. */
+ kr_stale_cb stale_cb; /**< See the type */
+ struct kr_server_selection server_selection;
+};
+
+/** @cond internal Array of queries. */
+typedef array_t(struct kr_query *) kr_qarray_t;
+/* @endcond */
+
+/**
+ * Query resolution plan structure.
+ *
+ * The structure most importantly holds the original query, answer and the
+ * list of pending queries required to resolve the original query.
+ * It also keeps a notion of current zone cut.
+ */
+struct kr_rplan {
+ kr_qarray_t pending; /**< List of pending queries.
+ Beware: order is significant ATM,
+ as the last is the next one to solve,
+ and they may be inter-dependent. */
+ kr_qarray_t resolved; /**< List of resolved queries. */
+ struct kr_query *initial; /**< The initial query (also in pending or resolved). */
+
+ struct kr_request *request; /**< Parent resolution request. */
+ knot_mm_t *pool; /**< Temporary memory pool. */
+ uint32_t next_uid; /**< Next value for kr_query::uid (incremental). */
+};
+
+/**
+ * Initialize resolution plan (empty).
+ * @param rplan plan instance
+ * @param request resolution request
+ * @param pool ephemeral memory pool for whole resolution
+ */
+KR_EXPORT
+int kr_rplan_init(struct kr_rplan *rplan, struct kr_request *request, knot_mm_t *pool);
+
+/**
+ * Deinitialize resolution plan, aborting any uncommitted transactions.
+ * @param rplan plan instance
+ */
+KR_EXPORT
+void kr_rplan_deinit(struct kr_rplan *rplan);
+
+/**
+ * Return true if the resolution plan is empty (i.e. finished or initialized)
+ * @param rplan plan instance
+ * @return true or false
+ */
+KR_EXPORT KR_PURE
+bool kr_rplan_empty(struct kr_rplan *rplan);
+
+/**
+ * Push empty query to the top of the resolution plan.
+ * @note This query serves as a cookie query only.
+ * @param rplan plan instance
+ * @param parent query parent (or NULL)
+ * @return query instance or NULL
+ */
+KR_EXPORT
+struct kr_query *kr_rplan_push_empty(struct kr_rplan *rplan,
+ struct kr_query *parent);
+
+/**
+ * Push a query to the top of the resolution plan.
+ * @note This means that this query takes precedence before all pending queries.
+ * @param rplan plan instance
+ * @param parent query parent (or NULL)
+ * @param name resolved name
+ * @param cls resolved class
+ * @param type resolved type
+ * @return query instance or NULL
+ */
+KR_EXPORT
+struct kr_query *kr_rplan_push(struct kr_rplan *rplan, struct kr_query *parent,
+ const knot_dname_t *name, uint16_t cls, uint16_t type);
+
+/**
+ * Pop existing query from the resolution plan.
+ * @note Popped queries are not discarded, but moved to the resolved list.
+ * @param rplan plan instance
+ * @param qry resolved query
+ * @return 0 or an error
+ */
+KR_EXPORT
+int kr_rplan_pop(struct kr_rplan *rplan, struct kr_query *qry);
+
+/**
+ * Return true if resolution chain satisfies given query.
+ */
+KR_EXPORT KR_PURE
+bool kr_rplan_satisfies(struct kr_query *closure, const knot_dname_t *name, uint16_t cls, uint16_t type);
+
+/** Return last resolved query. */
+KR_EXPORT KR_PURE
+struct kr_query *kr_rplan_resolved(struct kr_rplan *rplan);
+
+/**
+ * Return last query (either currently being solved or last resolved).
+ * This is necessary to retrieve the last query in case of resolution failures (e.g. time limit reached).
+ */
+KR_EXPORT KR_PURE
+struct kr_query *kr_rplan_last(struct kr_rplan *rplan);
+
+
+/**
+ * Check if a given query already resolved.
+ * @param rplan plan instance
+ * @param parent query parent (or NULL)
+ * @param name resolved name
+ * @param cls resolved class
+ * @param type resolved type
+ * @return query instance or NULL
+ */
+KR_EXPORT KR_PURE
+struct kr_query *kr_rplan_find_resolved(struct kr_rplan *rplan, struct kr_query *parent,
+ const knot_dname_t *name, uint16_t cls, uint16_t type);