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diff --git a/lib/cookies/helper.h b/lib/cookies/helper.h
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+/*  Copyright (C) 2016-2017 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/>.
+ */
+
+#pragma once
+
+#include <libknot/packet/pkt.h>
+
+#include "lib/cookies/alg_containers.h"
+#include "lib/cookies/control.h"
+#include "lib/cookies/lru_cache.h"
+#include "lib/cookies/nonce.h"
+#include "lib/defines.h"
+#include "lib/resolve.h"
+
+/**
+ * @brief Updates DNS cookie in the request EDNS options.
+ * @note This function must be called before the request packet is finalised.
+ * @param clnt_comp    client cookie control structure
+ * @param cookie_cache cookie cache
+ * @param clnt_sa      client socket address
+ * @param srvr_sa      server socket address
+ * @param req          name resolution request
+ * @return kr_ok() or error code
+ */
+KR_EXPORT
+int kr_request_put_cookie(const struct kr_cookie_comp *clnt_comp,
+                          kr_cookie_lru_t *cookie_cache,
+                          const struct sockaddr *clnt_sa,
+                          const struct sockaddr *srvr_sa,
+                          struct kr_request *req);
+
+/**
+ * @brief Inserts a cookie option into the OPT RR. It does not write any
+ *        wire data.
+ * @note The content of @a sc_input is modified. Any pre-set nonce value is
+ *       ignored. After retuning its nonce value will be null.
+ * @param sc_input  data needed to compute server cookie, nonce is ignored
+ * @param nonce     nonce value that is actually used
+ * @param alg       hash algorithm
+ * @param pkt       DNS response packet
+ */
+KR_EXPORT
+int kr_answer_write_cookie(struct knot_sc_input *sc_input,
+                           const struct kr_nonce_input *nonce,
+                           const struct knot_sc_alg *alg, knot_pkt_t *pkt);
+
+/**
+ * @brief Set RCODE and extended RCODE.
+ * @param pkt DNS packet
+ * @param whole_rcode RCODE value
+ * @return kr_ok() or error code
+ */
+KR_EXPORT
+int kr_pkt_set_ext_rcode(knot_pkt_t *pkt, uint16_t whole_rcode);
+
+/**
+ * @brief Check whether packet is a server cookie request according to
+ *        RFC7873 5.4.
+ * @param pkt Packet to be examined.
+ * @return Pointer to entire cookie option if is a server cookie query, NULL on
+ *         errors or if packet doesn't contain cookies or if QDCOUNT > 0.
+ */
+KR_EXPORT
+uint8_t *kr_no_question_cookie_query(const knot_pkt_t *pkt);
+
+/**
+ * @brief Parse cookies from cookie option.
+ * @param cookie_opt Cookie option.
+ * @param cookies    Cookie structure to be set.
+ * @return kr_ok() on success, error if cookies are malformed.
+ */
+KR_EXPORT
+int kr_parse_cookie_opt(uint8_t *cookie_opt, struct knot_dns_cookies *cookies);