From 54625d0274dee7072ae660a631f4d4d9d0f5ce49 Mon Sep 17 00:00:00 2001
From: Kazu Yamamoto <kazu@iij.ad.jp>
Date: Thu, 18 Mar 2010 13:42:30 +0900
Subject: adding Resolver.hs

---
 Network/DNS/Resolver.hs | 114 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 114 insertions(+)
 create mode 100644 Network/DNS/Resolver.hs

(limited to 'Network')

diff --git a/Network/DNS/Resolver.hs b/Network/DNS/Resolver.hs
new file mode 100644
index 0000000..6ae7d50
--- /dev/null
+++ b/Network/DNS/Resolver.hs
@@ -0,0 +1,114 @@
+{-|
+  APIs of DNS Resolver.
+-}
+
+module Network.DNS.Resolver (
+    Resolver, makeResolver, makeDefaultResolver
+  , lookup, lookupRaw
+  ) where
+
+import Control.Applicative
+import Data.List hiding (find, lookup)
+import Data.Int
+import Network.DNS.Types
+import Network.DNS.Query
+import Network.DNS.Response
+import Random
+import Network.BSD
+import Network.Socket hiding (send, sendTo, recv, recvFrom)
+import Network.Socket.ByteString.Lazy
+import Prelude hiding (lookup)
+
+----------------------------------------------------------------
+
+{-|
+  Abstract data type of DNS Resolver
+-}
+data Resolver = Resolver {
+    genId    :: IO Int
+  , addrInfo :: AddrInfo
+}
+
+----------------------------------------------------------------
+
+resolvConf :: String
+resolvConf = "/etc/resolv.conf"
+
+dnsBufferSize :: Int64
+dnsBufferSize = 512
+
+----------------------------------------------------------------
+
+{-|
+  Making Resolver from an IP address of a DNS cache server.
+-}
+makeResolver :: HostName -> IO Resolver
+makeResolver addr = do
+    ai <- makeAddrInfo addr
+    return $ Resolver { genId = getRandom, addrInfo = ai }
+
+{-|
+  Making Resolver from \"/etc/resolv.conf\".
+-}
+makeDefaultResolver :: IO Resolver
+makeDefaultResolver = do
+  cs <- readFile resolvConf
+  let l:_ = filter ("nameserver" `isPrefixOf`) $ lines cs
+  makeResolver $ drop 11 l
+
+----------------------------------------------------------------
+
+getRandom :: IO Int
+getRandom = getStdRandom (randomR (0,65535))
+
+makeAddrInfo :: HostName -> IO AddrInfo
+makeAddrInfo addr = do
+    proto <- getProtocolNumber "udp"
+    let hints = defaultHints {
+            addrFlags = [AI_ADDRCONFIG, AI_NUMERICHOST, AI_PASSIVE]
+          , addrSocketType = Datagram
+          , addrProtocol = proto
+          }
+    a:_ <- getAddrInfo (Just hints) (Just addr) (Just "domain")
+    return a
+
+----------------------------------------------------------------
+
+{-|
+  Looking up resource records of a domain.
+-}
+lookup :: Domain -> TYPE -> Resolver -> IO (Maybe [RDATA])
+lookup dom typ rlv = do
+    idnt <- genId rlv
+    res <- lookupRaw' dom typ rlv idnt
+    let hdr = header res
+    if identifier hdr == idnt && anCount hdr /= 0
+       then return . listToMaybe . map rdata . filter correct $ answer res
+       else return Nothing
+  where
+    {- CNAME hack
+    dom' = if "." `isSuffixOf` dom
+           then dom
+           else dom ++ "."
+    correct r = rrname r == dom' && rrtype r == typ
+    -}
+    correct r = rrtype r == typ
+    listToMaybe [] = Nothing
+    listToMaybe xs = Just xs
+
+{-|
+  Looking up a domain and returning an entire DNS Response.
+-}
+lookupRaw :: Domain -> TYPE -> Resolver -> IO DNSFormat
+lookupRaw dom typ rlv = genId rlv >>= lookupRaw' dom typ rlv
+
+lookupRaw' :: Domain -> TYPE -> Resolver -> Int -> IO DNSFormat
+lookupRaw' dom typ rlv idnt = do
+  let ai = addrInfo rlv
+      q = makeQuestion dom typ
+  sock <- socket (addrFamily ai) (addrSocketType ai) (addrProtocol ai)
+  connect sock (addrAddress ai)
+  sendAll sock (composeQuery idnt [q])
+  fmt <- parseResponse <$> recv sock dnsBufferSize
+  sClose sock
+  return fmt
-- 
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