diff --git a/bin/tests/system/rrchecker/tests_rrchecker.py b/bin/tests/system/rrchecker/tests_rrchecker.py
index bbe578f98b..8cc631a3da 100644
--- a/bin/tests/system/rrchecker/tests_rrchecker.py
+++ b/bin/tests/system/rrchecker/tests_rrchecker.py
@@ -49,6 +49,7 @@ pytestmark = pytest.mark.extra_artifacts(
                 "DNSKEY",
                 "DOA",
                 "DS",
+                "DSYNC",
                 "EID",
                 "EUI48",
                 "EUI64",
diff --git a/lib/dns/rdata/generic/dsync_66.c b/lib/dns/rdata/generic/dsync_66.c
new file mode 100644
index 0000000000..52867df1dc
--- /dev/null
+++ b/lib/dns/rdata/generic/dsync_66.c
@@ -0,0 +1,361 @@
+/*
+ * 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.
+ */
+
+#ifndef RDATA_GENERIC_DSYNC_66_C
+#define RDATA_GENERIC_DSYNC_66_C
+
+#include <string.h>
+
+#include <isc/net.h>
+
+#include <dns/dsync.h>
+#include <dns/fixedname.h>
+
+#define RRTYPE_DSYNC_ATTRIBUTES (0)
+
+static isc_result_t
+fromtext_dsync(ARGS_FROMTEXT) {
+	isc_token_t token;
+	isc_result_t result;
+	dns_fixedname_t fn;
+	dns_name_t *name = dns_fixedname_initname(&fn);
+	isc_buffer_t buffer;
+	dns_rdatatype_t rrtype;
+	dns_dsyncscheme_t scheme;
+	bool ok = true;
+
+	REQUIRE(type == dns_rdatatype_dsync);
+
+	UNUSED(type);
+	UNUSED(rdclass);
+	UNUSED(callbacks);
+
+	/*
+	 * RRtype
+	 */
+	RETERR(isc_lex_getmastertoken(lexer, &token, isc_tokentype_string,
+				      false));
+	result = dns_rdatatype_fromtext(&rrtype, &token.value.as_textregion);
+	if (result != ISC_R_SUCCESS && result != ISC_R_NOTIMPLEMENTED) {
+		char *e = NULL;
+		long i = strtol(DNS_AS_STR(token), &e, 10);
+		if (i < 0 || i > 65535) {
+			RETTOK(ISC_R_RANGE);
+		}
+		if (*e != 0) {
+			RETTOK(result);
+		}
+		rrtype = (dns_rdatatype_t)i;
+	}
+	RETERR(uint16_tobuffer(rrtype, target));
+
+	/*
+	 * Scheme
+	 */
+	RETERR(isc_lex_getmastertoken(lexer, &token, isc_tokentype_string,
+				      false));
+	RETERR(dns_dsyncscheme_fromtext(&scheme, &token.value.as_textregion));
+	RETERR(uint8_tobuffer(scheme, target));
+
+	/*
+	 * Port
+	 */
+	RETERR(isc_lex_getmastertoken(lexer, &token, isc_tokentype_number,
+				      false));
+	if (token.value.as_ulong > 0xffffU) {
+		RETTOK(ISC_R_RANGE);
+	}
+	RETERR(uint16_tobuffer(token.value.as_ulong, target));
+
+	/*
+	 * Target
+	 */
+	RETERR(isc_lex_getmastertoken(lexer, &token, isc_tokentype_string,
+				      false));
+
+	buffer_fromregion(&buffer, &token.value.as_region);
+	if (origin == NULL) {
+		origin = dns_rootname;
+	}
+	RETTOK(dns_name_fromtext(name, &buffer, origin, options, target));
+	if ((options & DNS_RDATA_CHECKNAMES) != 0) {
+		ok = dns_name_ishostname(name, false);
+	}
+	if (!ok && (options & DNS_RDATA_CHECKNAMESFAIL) != 0) {
+		RETTOK(DNS_R_BADNAME);
+	}
+	if (!ok && callbacks != NULL) {
+		warn_badname(name, lexer, callbacks);
+	}
+	return ISC_R_SUCCESS;
+}
+
+static isc_result_t
+totext_dsync(ARGS_TOTEXT) {
+	isc_region_t region;
+	dns_name_t name;
+	dns_name_t prefix;
+	unsigned int opts;
+	char buf[sizeof("TYPE64000")];
+	unsigned short num;
+	dns_rdatatype_t type;
+	dns_dsyncscheme_t scheme;
+
+	REQUIRE(rdata->type == dns_rdatatype_dsync);
+	REQUIRE(rdata->length != 0);
+
+	dns_name_init(&name, NULL);
+	dns_name_init(&prefix, NULL);
+
+	dns_rdata_toregion(rdata, &region);
+
+	/*
+	 * Type.
+	 */
+	type = uint16_fromregion(&region);
+	isc_region_consume(&region, 2);
+	/*
+	 * XXXAG We should have something like dns_rdatatype_isknown()
+	 * that does the right thing with type 0.
+	 */
+	if (dns_rdatatype_isknown(type) && type != 0) {
+		RETERR(dns_rdatatype_totext(type, target));
+	} else {
+		snprintf(buf, sizeof(buf), "TYPE%u", type);
+		RETERR(str_totext(buf, target));
+	}
+	RETERR(str_totext(" ", target));
+
+	/*
+	 * Scheme.
+	 */
+	scheme = uint8_fromregion(&region);
+	isc_region_consume(&region, 1);
+	RETERR(dns_dsyncscheme_totext(scheme, target));
+
+	RETERR(str_totext(" ", target));
+
+	/*
+	 * Port
+	 */
+	num = uint16_fromregion(&region);
+	isc_region_consume(&region, 2);
+	snprintf(buf, sizeof(buf), "%u", num);
+	RETERR(str_totext(buf, target));
+
+	RETERR(str_totext(" ", target));
+
+	/*
+	 * Target
+	 */
+	dns_name_fromregion(&name, &region);
+	opts = name_prefix(&name, tctx->origin, &prefix) ? DNS_NAME_OMITFINALDOT
+							 : 0;
+	return dns_name_totext(&prefix, opts, target);
+}
+
+static isc_result_t
+fromwire_dsync(ARGS_FROMWIRE) {
+	dns_name_t name;
+	isc_region_t sregion;
+
+	REQUIRE(type == dns_rdatatype_dsync);
+
+	UNUSED(type);
+	UNUSED(rdclass);
+
+	dns_decompress_setmethods(dctx, DNS_COMPRESS_NONE);
+
+	dns_name_init(&name, NULL);
+
+	isc_buffer_activeregion(source, &sregion);
+	if (sregion.length < 5) {
+		return ISC_R_UNEXPECTEDEND;
+	}
+	RETERR(mem_tobuffer(target, sregion.base, 5));
+	isc_buffer_forward(source, 5);
+	return dns_name_fromwire(&name, source, dctx, options, target);
+}
+
+static isc_result_t
+towire_dsync(ARGS_TOWIRE) {
+	dns_name_t name;
+	isc_region_t region;
+
+	REQUIRE(rdata->type == dns_rdatatype_dsync);
+	REQUIRE(rdata->length != 0);
+
+	dns_compress_setmethods(cctx, DNS_COMPRESS_NONE);
+
+	dns_rdata_toregion(rdata, &region);
+	RETERR(mem_tobuffer(target, region.base, 5));
+	isc_region_consume(&region, 5);
+
+	dns_name_init(&name, NULL);
+	dns_name_fromregion(&name, &region);
+
+	return dns_name_towire(&name, cctx, target);
+}
+
+static int
+compare_dsync(ARGS_COMPARE) {
+	isc_region_t region1;
+	isc_region_t region2;
+
+	REQUIRE(rdata1->type == rdata2->type);
+	REQUIRE(rdata1->rdclass == rdata2->rdclass);
+	REQUIRE(rdata1->type == dns_rdatatype_dsync);
+	REQUIRE(rdata1->length != 0);
+	REQUIRE(rdata2->length != 0);
+
+	dns_rdata_toregion(rdata1, &region1);
+	dns_rdata_toregion(rdata2, &region2);
+	return isc_region_compare(&region1, &region2);
+}
+
+static isc_result_t
+fromstruct_dsync(ARGS_FROMSTRUCT) {
+	dns_rdata_dsync_t *dsync = source;
+	isc_region_t region;
+
+	REQUIRE(type == dns_rdatatype_dsync);
+	REQUIRE(dsync != NULL);
+	REQUIRE(dsync->common.rdtype == type);
+	REQUIRE(dsync->common.rdclass == rdclass);
+
+	UNUSED(type);
+	UNUSED(rdclass);
+
+	RETERR(uint16_tobuffer(dsync->type, target));
+	RETERR(uint16_tobuffer(dsync->scheme, target));
+	RETERR(uint16_tobuffer(dsync->port, target));
+	dns_name_toregion(&dsync->target, &region);
+	return isc_buffer_copyregion(target, &region);
+}
+
+static isc_result_t
+tostruct_dsync(ARGS_TOSTRUCT) {
+	isc_region_t region;
+	dns_rdata_dsync_t *dsync = target;
+	dns_name_t name;
+
+	REQUIRE(rdata->type == dns_rdatatype_dsync);
+	REQUIRE(dsync != NULL);
+	REQUIRE(rdata->length != 0);
+
+	dsync->common.rdclass = rdata->rdclass;
+	dsync->common.rdtype = rdata->type;
+	ISC_LINK_INIT(&dsync->common, link);
+
+	dns_name_init(&name, NULL);
+	dns_rdata_toregion(rdata, &region);
+	dsync->type = uint16_fromregion(&region);
+	isc_region_consume(&region, 2);
+	dsync->scheme = uint8_fromregion(&region);
+	isc_region_consume(&region, 1);
+	dsync->port = uint16_fromregion(&region);
+	isc_region_consume(&region, 2);
+	dns_name_fromregion(&name, &region);
+	dns_name_init(&dsync->target, NULL);
+	name_duporclone(&name, mctx, &dsync->target);
+	dsync->mctx = mctx;
+	return ISC_R_SUCCESS;
+}
+
+static void
+freestruct_dsync(ARGS_FREESTRUCT) {
+	dns_rdata_dsync_t *dsync = source;
+
+	REQUIRE(dsync != NULL);
+	REQUIRE(dsync->common.rdtype == dns_rdatatype_dsync);
+
+	if (dsync->mctx == NULL) {
+		return;
+	}
+
+	dns_name_free(&dsync->target, dsync->mctx);
+	dsync->mctx = NULL;
+}
+
+static isc_result_t
+additionaldata_dsync(ARGS_ADDLDATA) {
+	dns_name_t name;
+	isc_region_t region;
+
+	REQUIRE(rdata->type == dns_rdatatype_dsync);
+
+	UNUSED(owner);
+
+	dns_name_init(&name, NULL);
+	dns_rdata_toregion(rdata, &region);
+	isc_region_consume(&region, 5);
+	dns_name_fromregion(&name, &region);
+
+	if (dns_name_equal(&name, dns_rootname)) {
+		return ISC_R_SUCCESS;
+	}
+
+	return (add)(arg, &name, dns_rdatatype_a, NULL);
+}
+
+static isc_result_t
+digest_dsync(ARGS_DIGEST) {
+	isc_region_t r1;
+
+	REQUIRE(rdata->type == dns_rdatatype_dsync);
+
+	dns_rdata_toregion(rdata, &r1);
+	return (digest)(arg, &r1);
+}
+
+static bool
+checkowner_dsync(ARGS_CHECKOWNER) {
+	REQUIRE(type == dns_rdatatype_dsync);
+
+	UNUSED(name);
+	UNUSED(rdclass);
+	UNUSED(type);
+	UNUSED(wildcard);
+
+	return true;
+}
+
+static bool
+checknames_dsync(ARGS_CHECKNAMES) {
+	isc_region_t region;
+	dns_name_t name;
+
+	REQUIRE(rdata->type == dns_rdatatype_dsync);
+	REQUIRE(rdata->length > 5);
+
+	UNUSED(owner);
+
+	dns_rdata_toregion(rdata, &region);
+	isc_region_consume(&region, 5);
+	dns_name_init(&name, NULL);
+	dns_name_fromregion(&name, &region);
+	if (!dns_name_ishostname(&name, false)) {
+		if (bad != NULL) {
+			dns_name_clone(&name, bad);
+		}
+		return false;
+	}
+	return true;
+}
+
+static int
+casecompare_dsync(ARGS_COMPARE) {
+	return compare_dsync(rdata1, rdata2);
+}
+
+#endif /* RDATA_GENERIC_DSYNC_66_C */
diff --git a/lib/dns/rdata/generic/dsync_66.h b/lib/dns/rdata/generic/dsync_66.h
new file mode 100644
index 0000000000..4ec9eec2ab
--- /dev/null
+++ b/lib/dns/rdata/generic/dsync_66.h
@@ -0,0 +1,24 @@
+/*
+ * 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
+
+typedef struct dns_rdata_dsync {
+	dns_rdatacommon_t common;
+	isc_mem_t *mctx;
+	uint16_t type;
+	uint8_t scheme;
+	uint16_t port;
+	dns_name_t target;
+} dns_rdata_dsync_t;