[1758] Interface for getting previous name

diff --git a/src/lib/datasrc/database.h b/src/lib/datasrc/database.h
index ba7b0e0b1842b48d634d9d1443ca09476ad2a6c4..d9d6dfadde1c0a7b81c433ede0b34b6a13ea537e 100644 (file)
--- a/src/lib/datasrc/database.h
+++ b/src/lib/datasrc/database.h
@@ -253,6 +253,9 @@ public:
     /// The iterator might be empty (containing no RRs) in case the zone is not
     /// signed by NSEC3.
     ///
+    /// \note In case there are multiple NSEC3 chains and they collide
+    ///     (unlikely, but it can happen), this can return multiple NSEC3
+    ///     records.
     /// \exception any Since any implementaion can be used, the caller should
     ///     expect any exception to be thrown.
     /// \exception isc::NotImplemented in case the database does not support
@@ -675,6 +678,34 @@ public:
     ///     apex of the zone).
     virtual std::string findPreviousName(int zone_id,
                                          const std::string& rname) const = 0;
+
+    /// \brief It returns the previous hash in the NSEC3 chain.
+    ///
+    /// This is used to find previous NSEC3 hashes, to find covering NSEC3 in
+    /// case none match exactly.
+    ///
+    /// In case a hash before before the lowest or the lowest is provided,
+    /// this should return the largest one in the zone (NSEC3 needs a
+    /// wrap-around semantics).
+    ///
+    /// \param zone_id Specifies the zone to look into, as returned by getZone.
+    /// \param hash The hash to look before.
+    /// \return The nearest smaller hash than the provided one, or the largest
+    ///     hash in the zone if something smaller or equal to the lowest one
+    ///     is provided.
+    /// \note If the zone contains multiple NSEC3 chains, you should check that
+    ///     the returned result contains the NSEC3 for correct parameters. If
+    ///     not, query again and get something smaller - this will eventually
+    ///     get to the correct one. This interface and semantics might change
+    ///     in future.
+    ///
+    /// \throw DataSourceError if there's a problem with the database or if
+    ///     this zone is not signed with NSEC3.
+    /// \throw NotImplemented if this database doesn't support NSEC3.
+    /// \throw anything else, as this might be any implementation.
+    virtual std::string findPreviousNSEC3Hash(int zone_id,
+                                              const std::string& hash)
+        const = 0;
 };
 
 /// \brief Concrete data source client oriented at database backends.