Add dns_zonemd_supported

lib/dns/include/dns/zonemd.h

@@ -22,3 +22,6 @@ dns_zonemd_buildrdata(dns_rdata_t *rdata, dns_db_t *db,
 		      dns_dbversion_t *version, uint8_t scheme,
 		      uint8_t algorithm, isc_mem_t *mctx, unsigned char *buf,
 		      size_t size);
+
+bool
+dns_zonemd_supported(dns_rdata_t *rdata);

lib/dns/zonemd.c

@@ -427,3 +427,23 @@ dns_zonemd_buildrdata(dns_rdata_t *rdata, dns_db_t *db,
 		return ISC_R_NOTIMPLEMENTED;
 	}
 }
+
+bool
+dns_zonemd_supported(dns_rdata_t *rdata) {
+	REQUIRE(rdata != NULL);
+	REQUIRE(rdata->length >= 6);
+	REQUIRE(rdata->type == dns_rdatatype_zonemd);
+
+	switch (rdata->data[4]) {
+	case DNS_ZONEMD_SCHEME_SIMPLE:
+		switch (rdata->data[5]) {
+		case DNS_ZONEMD_DIGEST_SHA384:
+		case DNS_ZONEMD_DIGEST_SHA512:
+			return true;
+		default:
+			return false;
+		}
+	default:
+		return false;
+	}
+}