Add clarification on backend writer guide

For `getBeforeAndAfterNamesAbsolute()`, in case of proof of non
existence for a type (and not the name), the requested name should be
returned, **not** the name before it.

diff --git a/docs/appendices/backend-writers-guide.rst b/docs/appendices/backend-writers-guide.rst
index 6802169fad3d6a71a9f5187de376840706828d86..bd1aa293f5150eee13f44d1696b3ff804bfe05de 100644 (file)
--- a/docs/appendices/backend-writers-guide.rst
+++ b/docs/appendices/backend-writers-guide.rst
@@ -905,6 +905,7 @@ In order for a backend to support DNSSEC, quite a few number of additional opera
 .. cpp:function:: virtual bool getBeforeAndAfterNamesAbsolute(uint32_t id, const DNSName& qname, DNSName& unhashed, DNSName& before, DNSName& after)
 
   Asks the names before and after qname for NSEC and NSEC3. The qname will be hashed when using NSEC3. Care must be taken to handle wrap-around when qname is the first or last in the ordered list of zone names.
+  Please note that in case the requested name is present in the zone, it should be returned as the "before" name.
 
 .. cpp:function:: virtual bool updateDNSSECOrderNameAndAuth(uint32_t domain_id, const DNSName& qname, const DNSName& ordername, bool auth, const uint16_t qtype=QType::ANY)