From b2d1f57098ae12a22fe7511eb765c39158600d17 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Roman=20Smr=C5=BE?= <roman.smrz@seznam.cz>
Date: Mon, 28 Dec 2020 16:08:23 +0100
Subject: Ephemeral port option with disabled local discovery

---
 src/Main.hs    | 12 ++++++++----
 src/Network.hs | 33 ++++++++++++++++++++++++---------
 2 files changed, 32 insertions(+), 13 deletions(-)

diff --git a/src/Main.hs b/src/Main.hs
index a847bd1..8da74b1 100644
--- a/src/Main.hs
+++ b/src/Main.hs
@@ -85,10 +85,11 @@ main = do
                         BC.putStrLn . showRefDigest . refDigest . storedRef . idData =<< interactiveIdentityUpdate idt
                     | otherwise -> error "invalid identity"
 
-        [bhost] -> interactiveLoop st bhost
-        _       -> error "Expecting broadcast address"
+        [bhost] -> interactiveLoop st (Just bhost)
+        []      -> interactiveLoop st Nothing
+        _       -> error "Unrecognized options"
 
-interactiveLoop :: Storage -> String -> IO ()
+interactiveLoop :: Storage -> Maybe String -> IO ()
 interactiveLoop st bhost = runInputT defaultSettings $ do
     erebosHead <- liftIO $ loadLocalStateHead st
     outputStrLn $ T.unpack $ displayIdentity $ headLocalIdentity erebosHead
@@ -99,7 +100,10 @@ interactiveLoop st bhost = runInputT defaultSettings $ do
     let extPrintLn str = extPrint $ case reverse str of ('\n':_) -> str
                                                         _ -> str ++ "\n";
     server <- liftIO $ do
-        startServer erebosHead extPrintLn bhost
+        let sopt = defaultServerOptions
+                { serverLocalDiscovery = bhost
+                }
+        startServer sopt erebosHead extPrintLn
             [ SomeService @AttachService Proxy
             , SomeService @SyncService Proxy
             , SomeService @ContactService Proxy
diff --git a/src/Network.hs b/src/Network.hs
index 52d83bb..e09b343 100644
--- a/src/Network.hs
+++ b/src/Network.hs
@@ -2,6 +2,7 @@ module Network (
     Server,
     startServer,
     getNextPeerChange,
+    ServerOptions(..), defaultServerOptions,
 
     Peer,
     PeerAddress(..), peerAddress,
@@ -69,6 +70,15 @@ data Server = Server
 getNextPeerChange :: Server -> IO Peer
 getNextPeerChange = atomically . readTChan . serverChanPeer
 
+data ServerOptions = ServerOptions
+    { serverLocalDiscovery :: Maybe String
+    }
+
+defaultServerOptions :: ServerOptions
+defaultServerOptions = ServerOptions
+    { serverLocalDiscovery = Nothing
+    }
+
 
 data Peer = Peer
     { peerAddress :: PeerAddress
@@ -195,8 +205,8 @@ newWaitingRef pref act = do
     return wref
 
 
-startServer :: Head LocalState -> (String -> IO ()) -> String -> [SomeService] -> IO Server
-startServer origHead logd' bhost services = do
+startServer :: ServerOptions -> Head LocalState -> (String -> IO ()) -> [SomeService] -> IO Server
+startServer opt origHead logd' services = do
     let storage = refStorage $ headRef origHead
     chanPacket <- newChan
     outQueue <- newTQueueIO
@@ -244,12 +254,15 @@ startServer origHead logd' bhost services = do
             return sock
 
         loop sock = do
-            void $ forkIO $ forever $ do
-                readMVar midentity >>= \identity -> do
-                    st <- derivePartialStorage storage
-                    baddr:_ <- getAddrInfo (Just $ defaultHints { addrSocketType = Datagram }) (Just bhost) (Just discoveryPort)
-                    void $ S.sendTo sock (BL.toStrict $ serializeObject $ transportToObject $ TransportHeader [ AnnounceSelf $ partialRef st $ storedRef $ idData identity ]) (addrAddress baddr)
-                threadDelay $ announceIntervalSeconds * 1000 * 1000
+            case serverLocalDiscovery opt of
+                Just bhost -> do
+                    void $ forkIO $ forever $ do
+                        readMVar midentity >>= \identity -> do
+                            st <- derivePartialStorage storage
+                            baddr:_ <- getAddrInfo (Just $ defaultHints { addrSocketType = Datagram }) (Just bhost) (Just discoveryPort)
+                            void $ S.sendTo sock (BL.toStrict $ serializeObject $ transportToObject $ TransportHeader [ AnnounceSelf $ partialRef st $ storedRef $ idData identity ]) (addrAddress baddr)
+                        threadDelay $ announceIntervalSeconds * 1000 * 1000
+                Nothing -> return ()
 
             let announceUpdate identity = do
                     st <- derivePartialStorage storage
@@ -332,7 +345,9 @@ startServer origHead logd' bhost services = do
               { addrFlags = [AI_PASSIVE]
               , addrSocketType = Datagram
               }
-        addr:_ <- getAddrInfo (Just hints) Nothing (Just discoveryPort)
+        addr:_ <- getAddrInfo (Just hints) Nothing
+            -- use ephemeral port when local discovery is disabled
+            (Just $ if isJust (serverLocalDiscovery opt) then discoveryPort else "0")
         bracket (open addr) close loop
 
     void $ forkIO $ forever $ do
-- 
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