i made this script-like code

.gitignore

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+*.hi
+*.o
+input

README.md

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+VERY dumb and simple attempt to catch some computers online if they're connected to you through the Yggdrasil and you're the peer to them.
+
+Use with command
+
+```
+sudo journalctl -xeu yggdrasil --no-pager -o json-pretty  | jq ".MESSAGE" -r | cut -f3- -d' ' | sed 's/inbound:/Inbound/; s/outbound:/Outbound/' | cut -f1 -d@ | sed 's/$/"/;' | ./yggscraper
+```

shell.nix

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+{ pkgs ? import <nixpkgs> {} }:
+
+pkgs.mkShell {
+  buildInputs = [
+    pkgs.jq
+    (pkgs.haskellPackages.ghcWithPackages (p: with p; [
+      ip
+      haskell-language-server
+    ]))
+  ];
+}
+

yggscraper.hs

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+module Main where
+
+import Net.IP ( IP ) 
+import qualified Net.IP as IP
+import qualified  Net.IPv4 as NIPv4 
+import qualified  Net.IPv6 as NIPv6
+import qualified Data.Text as T
+
+import System.Directory
+    ( doesFileExist, getXdgDirectory, XdgDirectory(XdgConfig) )
+import System.FilePath ((</>))
+
+import Data.Set (empty, Set, insert, delete, toList)
+import Data.String ( IsString(fromString) )
+import Data.Maybe (catMaybes)
+
+data Bound
+  = Inbound
+  | Outbound
+  deriving (Show, Eq, Ord)
+
+data LogRecord
+  = Connected Bound IP
+  | Disconnected Bound IP
+  deriving (Show, Eq)
+
+parseBound :: String -> Maybe Bound
+parseBound "Inbound" = Just Inbound
+parseBound "Outbound" = Just Outbound
+parseBound _ = Nothing
+
+parseLogRecord :: String -> Maybe LogRecord
+parseLogRecord s =
+  case words s of
+    ["Connected", b, ipTxt] -> do
+      bound <- parseBound b
+      ip <- IP.decode . fromString $ ipTxt
+      pure (Connected bound ip)
+    ["Disconnected", b, ipTxt] -> do
+      bound <- parseBound b
+      ip <- IP.decode . fromString $ ipTxt
+      pure (Disconnected bound ip)
+    _ -> Nothing
+
+type Connection = (Bound, IP)
+
+data SuperIP
+  = Address IP
+  | Range4 NIPv4.IPv4Range
+  | Range6 NIPv6.IPv6Range
+
+inSuper :: SuperIP -> IP -> Bool
+inSuper (Address i0) i1 = i0 == i1
+inSuper (Range4 r4) ip =
+  IP.case_
+    (\ip4 -> NIPv4.member ip4 r4)
+    (\_   -> False)
+    ip
+inSuper (Range6 r6) ip =
+  IP.case_
+    (\_   -> False)
+    (\ip6 -> NIPv6.member ip6 r6)
+    ip
+
+instance Read SuperIP where
+  readsPrec :: Int -> ReadS SuperIP
+  readsPrec _ c
+    | Just i  <- IP.decode s       = [(Address i, "")]
+    | Just r4 <- NIPv4.decodeRange s   = [(Range4 r4, "")]
+    | Just r6 <- NIPv6.decodeRange s   = [(Range6 r6, "")]
+    | otherwise                       = []
+    where
+      s = fromString c
+
+instance Show SuperIP where
+  show (Address ip) = show ip
+  show (Range4 r)   = show r
+  show (Range6 r)   = show r
+
+f :: Set Connection -> LogRecord -> Set Connection
+f s (Connected b ip) = insert (b, ip) s
+f s (Disconnected b ip) = delete (b, ip) s
+
+main :: IO ()
+main = do
+  dir <- getXdgDirectory XdgConfig "yggscraper"
+  let path = dir </> "blacklist"
+  exists <- doesFileExist path
+  blacklist <- if exists
+      then do
+        blacklistFile <- readFile (dir </> "blacklist")
+        return . map (\x -> read x :: SuperIP) . lines $ blacklistFile
+      else
+        return []
+  
+  strs <- getContents
+  let xs = catMaybes . map parseLogRecord . lines $ strs
+      online = toList $ foldl' f empty xs
+      finder (_, ip) = any (\x -> inSuper x ip)
+      notBlacklisted = [x | x <- online, not $ finder x blacklist]
+  putStrLn . T.unpack . T.unlines . map (IP.encode . snd) $ notBlacklisted