    {-# LANGUAGE CPP #-}
    -- | Only allow local connections.
    --
    module Network.Wai.Middleware.Local
        ( local
        ) where

    import Network.Wai (Middleware,remoteHost, Response)
    import Network.Socket (SockAddr(..))

    -- | This middleware rejects non-local connections with a specific response.
    --   It is useful when supporting web-based local applications, which would
    --   typically want to reject external connections.

    local :: Response -> Middleware
    local resp f r k = case remoteHost r of
                       SockAddrInet _  h | h == fromIntegral home
                                        -> f r k
    #if !defined(mingw32_HOST_OS) && !defined(_WIN32)
                       SockAddrUnix _   -> f r k
    #endif
                       _                ->  k $ resp
     where
            home :: Integer
            home = 127 + (256 * 256 * 256) * 1