Quieter output and some bug fixes.

1 files changed, 16 insertions, 8 deletions

diff --git a/src/Network/QueryResponse.hs b/src/Network/QueryResponse.hs
index b757aed7..0345dd88 100644
--- a/src/Network/QueryResponse.hs
+++ b/src/Network/QueryResponse.hs
@@ -503,6 +503,17 @@ ignoreEOF def e | isEOFError e = pure def
 udpBufferSize :: Int
 udpBufferSize = 65536
 
+-- | Wrapper around 'B.sendTo' that silently ignores DoesNotExistError.
+saferSendTo :: Socket -> ByteString -> SockAddr -> IO ()
+saferSendTo sock bs saddr = void (B.sendTo sock bs saddr)
+    `catch` \e ->
+        -- sendTo: does not exist (Network is unreachable)
+        --       Occurs when IPv6 or IPv4 network is not available.
+        --       Currently, we require -threaded to prevent a forever-hang in this case.
+        if isDoesNotExistError e
+            then return ()
+            else throw e
+
 -- | A 'udpTransport' uses a UDP socket to send and receive 'ByteString's.  The
 -- argument is the listen-address for incoming packets.  This is a useful
 -- low-level 'Transport' that can be transformed for higher-level protocols
@@ -520,22 +531,19 @@ udpTransport bind_address = do
                 Just . Right <$!> B.recvFrom sock udpBufferSize
         kont $! r
     , sendMessage = case family of
-        -- TODO: sendTo: does not exist (Network is unreachable)
-        --       Occurs when IPv6 network is not available.
-        --       Currently, we require -threaded to prevent a forever-hang in this case.
         AF_INET6 -> \case
             (SockAddrInet port addr) -> \bs ->
                 -- Change IPv4 to 4mapped6 address.
-                void $ B.sendTo sock bs $ SockAddrInet6 port 0 (0,0,0x0000ffff,fromBE32 addr) 0
-            addr6 -> \bs -> void $ B.sendTo sock bs addr6
+                saferSendTo sock bs $ SockAddrInet6 port 0 (0,0,0x0000ffff,fromBE32 addr) 0
+            addr6 -> \bs -> saferSendTo sock bs addr6
         AF_INET  -> \case
             (SockAddrInet6 port 0 (0,0,0x0000ffff,raw4) 0) -> \bs -> do
                 let host4 = toBE32 raw4
                 -- Change 4mapped6 to ordinary IPv4.
                 -- hPutStrLn stderr $ "4mapped6 -> "++show (SockAddrInet port host4)
-                void $ B.sendTo sock bs (SockAddrInet port host4)
+                saferSendTo sock bs (SockAddrInet port host4)
             addr@(SockAddrInet6 {}) -> \bs -> hPutStrLn stderr ("Discarding packet to "++show addr)
-            addr4 -> \bs -> void $ B.sendTo sock bs addr4
-        _ -> \addr bs -> void $ B.sendTo sock bs addr
+            addr4 -> \bs -> saferSendTo sock bs addr4
+        _ -> \addr bs -> saferSendTo sock bs addr
     , closeTransport = close sock
     }