From 0ef0bfedc65cc67cbe8ad66ab9ae2fb9ae20b7f3 Mon Sep 17 00:00:00 2001
From: joe <joe@jerkface.net>
Date: Sat, 29 Jul 2017 03:13:26 -0400
Subject: Refactoring for tox/mainline code-sharing.

---
 src/Network/Address.hs | 37 +++++++++++++++++++++++++++++++++++++
 1 file changed, 37 insertions(+)

(limited to 'src/Network')

diff --git a/src/Network/Address.hs b/src/Network/Address.hs
index 8715a82d..cc06ac0d 100644
--- a/src/Network/Address.hs
+++ b/src/Network/Address.hs
@@ -35,6 +35,11 @@ module Network.Address
        , IPv4
        , IPv6
        , IP (..)
+       , un4map
+       , WantIP (..)
+       , ipFamily
+       , is4mapped
+       , either4or6
 
          -- * PeerId
          -- $peer-id
@@ -1180,3 +1185,35 @@ getBindAddress listenPortString enabled6 = do
                   else SockAddrInet (parsePort listenPortString) iNADDR_ANY
                     where parsePort s = fromMaybe 0 $ readMaybe s
     return listenAddr
+
+-- | True if the argument is an IPv4-mapped address with prefix ::FFFF:0:0/96
+-- as defined in RFC 4291.
+is4mapped :: IPv6 -> Bool
+is4mapped ip
+    | [0,0,0,0,0,0xffff,_,_] <- fromIPv6 ip
+                = True
+    | otherwise = False
+
+un4map :: IPv6 -> Maybe IPv4
+un4map ip
+    | [0,0,0,0,0,0xffff,x,y] <- fromIPv6 ip
+                = Just $ toIPv4
+                       $ L.map (.&. 0xFF)
+                               [x `shiftR` 8, x, y `shiftR` 8, y ]
+    | otherwise = Nothing
+
+ipFamily :: IP -> WantIP
+ipFamily ip = case ip of
+    IPv4 _               -> Want_IP4
+    IPv6 a | is4mapped a -> Want_IP4
+           | otherwise   -> Want_IP6
+
+either4or6 :: SockAddr -> Either SockAddr SockAddr
+either4or6 a4@(SockAddrInet port addr)         = Left a4
+either4or6 a6@(SockAddrInet6 port _ addr _)
+    | Just ip4 <- (fromSockAddr a6 >>= un4map) = Left (setPort port $ toSockAddr ip4)
+    | otherwise                                = Right a6
+
+data WantIP = Want_IP4 | Want_IP6 | Want_Both
+ deriving (Eq, Enum, Ord, Show)
+
-- 
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