fix probable race in use of restoreHashes

I think there was a race where a SessionKey message had been drained
from the TChan, but not yet added to the developer state, which was
resonsible for recent instability at startup.

It manifested as protocol errors where the prevActivity hash was wrongly
Nothing.

Fixed by adding a MissingHashes type to tag things whose hashes have
been stripped, and adding back the hashes when needed, which always
happens inside atomically blocks, so won't have such a race.

1 files changed, 2 insertions, 3 deletions

diff --git a/Server.hs b/Server.hs
index b9f46dd..deafe41 100644
--- a/Server.hs
+++ b/Server.hs
@@ -7,7 +7,6 @@ import CmdLine
 import WebSockets
 import SessionID
 import Log
-import PrevActivity
 
 import Network.Wai
 import Network.Wai.Handler.Warp
@@ -145,7 +144,7 @@ user o ssv conn = withSessionID (serverDirectory o) $ \(loghv, sid) -> do
 	-- (The user is allowed to send Developer messages too.. perhaps
 	-- they got them from a developer connected to them some other
 	-- way.)
-	relayfromuser mytid session = relayFromSocket conn noRecentActivity (return ()) $ \msg -> do
+	relayfromuser mytid session = relayFromSocket conn $ \msg -> do
 		l <- mkLog msg <$> getPOSIXTime
 		writeSession mytid session l
 	
@@ -184,7 +183,7 @@ developer o ssv sid conn = bracket setup cleanup go
 	
 	-- Relay all Developer amessages from the developer's websocket
 	-- to the broadcast channel.
-	relayfromdeveloper mytid session = relayFromSocket conn noRecentActivity (return ())
+	relayfromdeveloper mytid session = relayFromSocket conn
 		$ \msg -> case msg of
 			Developer _ -> do
 				l <- mkLog msg <$> getPOSIXTime