king: Add CLI options for NAT traversal.

(Not yet hooked up to anything.)

pkg/hs/urbit-king/lib/Urbit/King/CLI.hs

@@ -13,11 +13,15 @@ import Options.Applicative.Help.Pretty
 import Data.Word          (Word16)
 import System.Environment (getProgName)
 
+import Data.IP
+import Network.Socket
+
 --------------------------------------------------------------------------------
 
 data KingOpts = KingOpts
   { koSharedHttpPort  :: Maybe Word16
   , koSharedHttpsPort :: Maybe Word16
+  , koIPSource        :: Maybe IPSource
   }
  deriving (Show)
 
@@ -55,6 +59,11 @@ data PillSource
   | PillSourceURL String
   deriving (Show)
 
+data IPSource
+  = IPSourceManual HostAddress
+  | IPSourceNAT
+  deriving (Show)
+
 data New = New
     { nPillSource :: PillSource
     , nPierPath   :: Maybe FilePath -- Derived from ship name if not specified.
@@ -195,6 +204,23 @@ pillFromURL = PillSourceURL <$> strOption
                     <> value defaultPillURL
                     <> help "URL to pill file")
 
+ipFromNAT :: Parser IPSource
+ipFromNAT = flag' IPSourceNAT
+                     ( long "ip-from-nat"
+                    <> help "Try to fetch the local IP from the NAT gateway")
+
+ipReader :: ReadM HostAddress
+ipReader = eitherReader $ \arg ->
+  case readMay arg :: Maybe IPv4 of
+    Nothing -> Left ("Cannot parse ipv4 address: " ++ arg)
+    Just ipv4 -> Right $ toHostAddress ipv4
+
+ipFromManual :: Parser IPSource
+ipFromManual = IPSourceManual <$> option ipReader
+                     ( long "ip-manual"
+                    <> metavar "IPv4"
+                    <> help "Manually specify the external IP")
+
 pierPath :: Parser FilePath
 pierPath = strArgument (metavar "PIER" <> help "Path to pier")
 
@@ -347,6 +373,8 @@ runOneShip = (,,) <$> fmap Run pierPath <*> opts <*> df
 
 kingOpts :: Parser KingOpts
 kingOpts = do
+  koIPSource <- optional (ipFromManual <|> ipFromNAT)
+
   koSharedHttpPort <-
     optional
     $  option auto