ec267aa1ea
The explict import Prelude after import Control.Applicative is a trick to avoid a warning.
113 lines
2.6 KiB
Haskell
113 lines
2.6 KiB
Haskell
{- SRV record lookup
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-
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- Uses either the ADNS Haskell library, or the standalone Haskell DNS
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- package, or the host command.
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-
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- Copyright 2012 Joey Hess <id@joeyh.name>
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-
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- License: BSD-2-clause
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-}
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{-# LANGUAGE CPP #-}
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module Utility.SRV (
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mkSRVTcp,
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mkSRV,
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lookupSRV,
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lookupSRVHost,
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HostPort,
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) where
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import Utility.Process
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import Utility.Exception
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import Utility.PartialPrelude
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import Network
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import Data.Function
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import Data.List
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import Data.Maybe
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import Control.Applicative
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import Prelude
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#ifdef WITH_ADNS
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import ADNS.Resolver
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import Data.Either
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#else
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#ifdef WITH_DNS
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import qualified Network.DNS.Lookup as DNS
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import Network.DNS.Resolver
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import qualified Data.ByteString.UTF8 as B8
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#endif
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#endif
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newtype SRV = SRV String
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deriving (Show, Eq)
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type HostPort = (HostName, PortID)
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type PriorityWeight = (Int, Int) -- sort by priority first, then weight
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mkSRV :: String -> String -> HostName -> SRV
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mkSRV transport protocol host = SRV $ concat
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["_", protocol, "._", transport, ".", host]
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mkSRVTcp :: String -> HostName -> SRV
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mkSRVTcp = mkSRV "tcp"
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{- Returns an ordered list, with highest priority hosts first.
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-
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- On error, returns an empty list. -}
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lookupSRV :: SRV -> IO [HostPort]
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#ifdef WITH_ADNS
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lookupSRV (SRV srv) = initResolver [] $ \resolver -> do
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r <- catchDefaultIO (Right []) $
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resolveSRV resolver srv
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return $ either (\_ -> []) id r
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#else
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#ifdef WITH_DNS
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lookupSRV (SRV srv) = do
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seed <- makeResolvSeed defaultResolvConf
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r <- withResolver seed $ flip DNS.lookupSRV $ B8.fromString srv
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return $
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#if MIN_VERSION_dns(1,0,0)
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either (const []) use r
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#else
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maybe [] use r
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#endif
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where
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use = orderHosts . map tohosts
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tohosts (priority, weight, port, hostname) =
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( (priority, weight)
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, (B8.toString hostname, PortNumber $ fromIntegral port)
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)
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#else
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lookupSRV = lookupSRVHost
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#endif
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#endif
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lookupSRVHost :: SRV -> IO [HostPort]
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lookupSRVHost (SRV srv) = catchDefaultIO [] $
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parseSrvHost <$> readProcessEnv "host" ["-t", "SRV", "--", srv]
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-- clear environment, to avoid LANG affecting output
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(Just [])
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parseSrvHost :: String -> [HostPort]
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parseSrvHost = orderHosts . catMaybes . map parse . lines
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where
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parse l = case words l of
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[_, _, _, _, spriority, sweight, sport, hostname] -> do
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let v =
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( readish sport :: Maybe Int
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, readish spriority :: Maybe Int
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, readish sweight :: Maybe Int
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)
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case v of
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(Just port, Just priority, Just weight) -> Just
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( (priority, weight)
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, (hostname, PortNumber $ fromIntegral port)
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)
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_ -> Nothing
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_ -> Nothing
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orderHosts :: [(PriorityWeight, HostPort)] -> [HostPort]
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orderHosts = map snd . sortBy (compare `on` fst)
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