version the P2P protocol

Unfortunately ReceiveMessage didn't handle unknown messages the way it
was documented to; client sending VERSION would cause the server to
return an ERROR and hang up. Fixed that, but old releases of git-annex
use the P2P protocol for tor and will still have that behavior.

So, version is not negotiated for Remote.P2P connections, only for
Remote.Git connections, which will support VERSION from their first
release. There will need to be a later flag day to change Remote.P2P;
left a commented out line that is the only thing that will need to be
changed then.

Version 1 of the P2P protocol is not implemented yet, but updated
the docs for the DATA change that will be allowed by that version.

This commit was sponsored by Jeff Goeke-Smith on Patreon.

Remote/P2P.hs

@@ -77,7 +77,7 @@ chainGen addr r u c gc = do
 	return (Just this)
 
 -- | A connection to the peer, which can be closed.
-type Connection = ClosableConnection P2PConnection
+type Connection = ClosableConnection (RunState, P2PConnection)
 
 type ConnectionPool = TVar [Connection]
 
@@ -90,8 +90,8 @@ runProto u addr connpool a = withConnection u addr connpool (runProtoConn a)
 
 runProtoConn :: P2P.Proto a -> Connection -> Annex (Connection, Maybe a)
 runProtoConn _ ClosedConnection = return (ClosedConnection, Nothing)
-runProtoConn a (OpenConnection conn) = do
-	v <- runFullProto Client conn a
+runProtoConn a c@(OpenConnection (runst, conn)) = do
+	v <- runFullProto runst conn a
 	-- When runFullProto fails, the connection is no longer usable,
 	-- so close it.
 	case v of
@@ -99,7 +99,7 @@ runProtoConn a (OpenConnection conn) = do
 			warning $ "Lost connection to peer (" ++ e ++ ")"
 			liftIO $ closeConnection conn
 			return (ClosedConnection, Nothing)
-		Right r -> return (OpenConnection conn, Just r)
+		Right r -> return (c, Just r)
 
 -- Uses an open connection if one is available in the ConnectionPool;
 -- otherwise opens a new connection.
@@ -138,11 +138,20 @@ openConnection u addr = do
 			myuuid <- getUUID
 			authtoken <- fromMaybe nullAuthToken
 				<$> loadP2PRemoteAuthToken addr
-			res <- liftIO $ runNetProto conn $
-				P2P.auth myuuid authtoken
+			let proto = P2P.auth myuuid authtoken $
+				-- Before 6.20180312, the protocol server
+				-- had a bug that made negotiating the
+				-- protocol version terminate the
+				-- connection. So, this must stay disabled
+				-- until the old version is not in use
+				-- anywhere.
+				--P2P.negotiateProtocolVersion P2P.maxProtocolVersion
+				return ()
+			runst <- liftIO $ mkRunState Client
+			res <- runFullProto runst conn proto
 			case res of
 				Right (Just theiruuid)
-					| u == theiruuid -> return (OpenConnection conn)
+					| u == theiruuid -> return (OpenConnection (runst, conn))
 					| otherwise -> do
 						liftIO $ closeConnection conn
 						warning "Remote peer uuid seems to have changed."