keep track of the stage we're at in pairing

This avoids us responding to our own pairing messages, as well
as ignoring any out of order messages that might be received somehow.

Assistant/Threads/PairListener.hs

@@ -40,15 +40,19 @@ pairListenerThread st dstatus scanremotes urlrenderer = thread $ withSocketsDo $
 				sane <- checkSane msg
 				(pip, verified) <- verificationCheck m
 					=<< (pairingInProgress <$> getDaemonStatus dstatus)
-				case (sane, pairMsgStage m) of
-					(False, _) -> go sock cache
-					(_, PairReq) -> do
+				let wrongstage = maybe False (\p -> pairMsgStage m < inProgressPairStage p) pip
+				case (wrongstage, sane, pairMsgStage m) of
+					-- ignore our own messages, and
+					-- out of order messages
+					(True, _, _) -> go sock cache
+					(_, False, _) -> go sock cache
+					(_, _, PairReq) -> do
 						pairReqReceived verified dstatus urlrenderer m
 						go sock $ invalidateCache m cache
-					(_, PairAck) -> do
+					(_, _, PairAck) -> do
 						pairAckReceived verified pip st dstatus scanremotes m cache
 							>>= go sock
-					(_, PairDone) -> do
+					(_, _, PairDone) -> do
 						pairDoneReceived verified pip st dstatus scanremotes m
 						go sock	cache
 
@@ -132,14 +136,15 @@ pairReqReceived False dstatus urlrenderer msg = do
 
 {- When a verified PairAck is seen, a host is ready to pair with us, and has
  - already configured our ssh key. Stop sending PairReqs, finish the pairing,
- - and send a single PairDone. -}
+ - and send a single PairDone. 
+ -}
 pairAckReceived :: Bool -> Maybe PairingInProgress -> ThreadState -> DaemonStatusHandle -> ScanRemoteMap -> PairMsg -> [PairingInProgress] -> IO [PairingInProgress]
 pairAckReceived True (Just pip) st dstatus scanremotes msg cache = do
 	stopSending dstatus pip
 	setupAuthorizedKeys msg
 	finishedPairing st dstatus scanremotes msg (inProgressSshKeyPair pip)
-	startSending dstatus pip $ multicastPairMsg
-		(Just 1) (inProgressSecret pip) PairDone (inProgressPairData pip)
+	startSending dstatus pip PairDone $ multicastPairMsg
+		(Just 1) (inProgressSecret pip) (inProgressPairData pip)
 	return $ pip:(take 10 cache)
 {- A stale PairAck might also be seen, after we've finished pairing.
  - Perhaps our PairDone was not received. To handle this, we keep
@@ -149,8 +154,8 @@ pairAckReceived _ _ _ dstatus _ msg cache = do
 	let pips = filter (verifiedPairMsg msg) cache
 	unless (null pips) $
 		forM_ pips $ \pip ->
-			startSending dstatus pip $ multicastPairMsg
-				(Just 1) (inProgressSecret pip) PairDone (inProgressPairData pip)
+			startSending dstatus pip PairDone $ multicastPairMsg
+				(Just 1) (inProgressSecret pip) (inProgressPairData pip)
 	return cache
 
 {- If we get a verified PairDone, the host has accepted our PairAck, and