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diff --git a/LLCSNAP.hs b/LLCSNAP.hs
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+module LLCSNAP where
+
+import Data.Bits
+import Data.Word
+
+import Net.PacketParsing
+
+
+-- 802.2 LLC Header                                  : SNAP extension
+-- --------------------------------------------------------------------------
+-- DSAP             : SSAP           : Control       : OUI      : Protocol ID
+-- 1 octet          : 1 octet        : 1 or 2 octets : 3 octets : 2 octets
+
+data LLCSNAP = LLCSNAP
+    { dsap    :: Word8
+    , ssap    :: Word8
+    , control :: Word16 -- 1 or 2 bytes
+    , oui     :: Word32 -- 3 bytes
+    , protoid :: Word16
+    }
+ deriving (Eq,Ord,Read,Show)
+
+instance Parse LLCSNAP where
+    parse = do
+        -- LLC
+        dsap <- word8
+        ssap <- word8
+        control <- fromIntegral <$> word8
+        -- Based on "Understanding Logical Link Control" at
+        --   https://www.cisco.com/c/en/us/support/docs/ibm-technologies/logical-link-control-llc/12247-45.html
+        --
+        -- Unless the low two bits are set, there's
+        -- another byte of the control field.
+        nr <- if 0x0003 == control .&. 0x0003
+                then return 0
+                else fromIntegral <$> word8
+        -- SNAP
+        ouilo <- fromIntegral <$> word16
+        ouihi <- fromIntegral <$> word8
+        protoid <- word16
+        return LLCSNAP
+            { dsap    = dsap
+            , ssap    = ssap
+            , control = control + 256 * nr
+            , oui     = ouilo + 65536 * ouihi
+            , protoid = protoid
+            }
+
+