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diff --git a/lib/dns/include/dns/badcache.h b/lib/dns/include/dns/badcache.h
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+++ b/lib/dns/include/dns/badcache.h
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+/*
+ * Copyright (C) Internet Systems Consortium, Inc. ("ISC")
+ *
+ * SPDX-License-Identifier: MPL-2.0
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, you can obtain one at https://mozilla.org/MPL/2.0/.
+ *
+ * See the COPYRIGHT file distributed with this work for additional
+ * information regarding copyright ownership.
+ */
+
+#pragma once
+
+/*****
+***** Module Info
+*****/
+
+/*! \file dns/badcache.h
+ * \brief
+ * Defines dns_badcache_t, the "bad cache" object.
+ *
+ * Notes:
+ *\li 	A bad cache object is a hash table of name/type tuples,
+ *	indicating whether a given tuple known to be "bad" in some
+ *	sense (e.g., queries for that name and type have been
+ *	returning SERVFAIL). This is used for both the "bad server
+ *	cache" in the resolver and for the "servfail cache" in
+ *	the view.
+ *
+ * Reliability:
+ *
+ * Resources:
+ *
+ * Security:
+ *
+ * Standards:
+ */
+
+/***
+ ***	Imports
+ ***/
+
+#include <inttypes.h>
+#include <stdbool.h>
+
+#include <dns/types.h>
+
+ISC_LANG_BEGINDECLS
+
+/***
+ ***	Functions
+ ***/
+
+isc_result_t
+dns_badcache_init(isc_mem_t *mctx, unsigned int size, dns_badcache_t **bcp);
+/*%
+ * Allocate and initialize a badcache and store it in '*bcp'.
+ *
+ * Requires:
+ * \li	mctx != NULL
+ * \li	bcp != NULL
+ * \li	*bcp == NULL
+ */
+
+void
+dns_badcache_destroy(dns_badcache_t **bcp);
+/*%
+ * Flush and then free badcache in 'bcp'. '*bcp' is set to NULL on return.
+ *
+ * Requires:
+ * \li	'*bcp' to be a valid badcache
+ */
+
+void
+dns_badcache_add(dns_badcache_t *bc, const dns_name_t *name,
+		 dns_rdatatype_t type, bool update, uint32_t flags,
+		 isc_time_t *expire);
+/*%
+ * Adds a badcache entry to the badcache 'bc' for name 'name' and
+ * type 'type'.  If an entry already exists, then it will be updated if
+ * 'update' is true.  The entry will be stored with flags 'flags'
+ * and expiration date 'expire'.
+ *
+ * Requires:
+ * \li	bc to be a valid badcache.
+ * \li	name != NULL
+ * \li	expire != NULL
+ */
+
+bool
+dns_badcache_find(dns_badcache_t *bc, const dns_name_t *name,
+		  dns_rdatatype_t type, uint32_t *flagp, isc_time_t *now);
+/*%
+ * Returns true if a record is found in the badcache 'bc' matching
+ * 'name' and 'type', with an expiration date later than 'now'.
+ * If 'flagp' is not NULL, then '*flagp' is updated to the flags
+ * that were stored in the badcache entry.  Returns false if
+ * no matching record is found.
+ *
+ * Requires:
+ * \li	bc to be a valid badcache.
+ * \li	name != NULL
+ * \li	now != NULL
+ */
+
+void
+dns_badcache_flush(dns_badcache_t *bc);
+/*%
+ * Flush the entire bad cache.
+ *
+ * Requires:
+ * \li	bc to be a valid badcache
+ */
+
+void
+dns_badcache_flushname(dns_badcache_t *bc, const dns_name_t *name);
+/*%
+ * Flush the bad cache of all entries at 'name'.
+ *
+ * Requires:
+ * \li	bc to be a valid badcache
+ * \li	name != NULL
+ */
+
+void
+dns_badcache_flushtree(dns_badcache_t *bc, const dns_name_t *name);
+/*%
+ * Flush the bad cache of all entries at or below 'name'.
+ *
+ * Requires:
+ * \li	bc to be a valid badcache
+ * \li	name != NULL
+ */
+
+void
+dns_badcache_print(dns_badcache_t *bc, const char *cachename, FILE *fp);
+/*%
+ * Print the contents of badcache 'bc' (headed by the title 'cachename')
+ * to file pointer 'fp'.
+ *
+ * Requires:
+ * \li	bc to be a valid badcache
+ * \li	cachename != NULL
+ * \li	fp != NULL
+ */
+
+ISC_LANG_ENDDECLS