encode Ping as ASN.1

Hash2Pub/FediChord.asn1

@@ -16,7 +16,8 @@ Request ::= SEQUENCE {
 		queryIDSendPayload		QueryIDSendPayload,
 		joinSendPayload			JoinSendPayload,
 		leaveSendPayload		LeaveSendPayload,
-		stabiliseSendPayload	StabiliseSendPayload
+		stabiliseSendPayload	StabiliseSendPayload,
+		pingSendPayload			PingSendPayload
 		}
 	}
 
@@ -30,7 +31,8 @@ Response ::= SEQUENCE {
 		queryIDReceivePayload	QueryIDReceivePayload,
 		joinReceivePayload		JoinReceivePayload,
 		leaveReceivePayload		LeaveReceivePayload,
-		stabiliseReceivePayload	StabiliseReceivePayload
+		stabiliseReceivePayload	StabiliseReceivePayload,
+		pingReceivePayload		PingReceivePayload
 		}
 	}
 
@@ -87,5 +89,11 @@ LeaveSendPayload ::= SEQUENCE {
 
 LeaveReceivePayload ::= NULL	-- just a confirmation
 
+PingSendPayload ::= NULL		-- do not include a node/ vserver ID, so that
+								-- the node has to respond with all active ones
+
+-- learning all active vserver IDs handled by the server at once
+PingReceivePayload ::= SEQUENCE OF NodeState
+
 
 END

Hash2Pub/src/Hash2Pub/ASN1Coding.hs

@@ -28,6 +28,8 @@ data Action =
 -- probably should be taken care of by the callers of this, as the ASN.1
 -- encoding functions are layer-4 agnostic
 
+-- ===== encoding functions =====
+
 encodeNodeState :: NodeState -> [ASN1]
 encodeNodeState ns = [
     Start Sequence
@@ -82,7 +84,7 @@ encodeQueryIDReceivePayload resp =
       FOUND _ -> []
       FORWARD entrySet ->
             Start Sequence
-          : mconcat (map encodeCacheEntry . Set.elems $ entrySet)
+          : concatMap encodeCacheEntry . Set.elems $ entrySet
           ++ [End Sequence]
   ++ [End Sequence]
 
@@ -105,7 +107,7 @@ encodeJoinReceivePayload succ' pred' ncache =
   ++ map (IntVal . getNodeID) pred'
   ++ [End Sequence
     , Start Sequence]
-  ++ mconcat (map encodeCacheEntry ncache)
+  ++ concatMap encodeCacheEntry ncache
   ++ [End Sequence
     , End Sequence]
 
@@ -131,3 +133,12 @@ encodeResponse responseTo senderID parts part action payload = [
   , IntVal part
   , Enumerated . fromIntegral . fromEnum $ action]
   ++ payload
+
+encodePingSendPayload :: [ASN1]
+encodePingSendPayload = Null
+
+encodePingReceivePayload :: [NodeState] -> [ASN1]
+encodePingReceivePayload nss =
+    Start Sequence
+  : concatMap encodeNodeState nss
+  ++ [End Sequence]