"Too short input for last message" with the netlink library

Question

This issue is a about how to use the haskell netlink library. The casting (?) mechanism I have trouble with might be a more generic haskell problem, which is why I hope it's ok to ask here.

I previously exposed my problem here: https://github.com/Ongy/netlink-hs/issues/5 but here is summary:

I am trying to use the library netlink (https://github.com/Ongy/netlink-hs, on hackage too) to communicate with a kernel module via the netlink protocol. I receive packets through the recvOne' call (called here https://github.com/teto/netlink_pm/blob/v5/hs/daemon.hs#L502):

results <- (recvOne' simpleSock) :: IO [Either String MptcpPacket]

defined here https://github.com/Ongy/netlink-hs/blob/master/System/Linux/Netlink.hs#L395 as:

recvOne' :: (Convertable a, Eq a, Show a) => NetlinkSocket -> IO [Either String (Packet a)]
recvOne' sock = getPackets' <$> recvmsg sock bufferSize

but on launch my program stops immediately with

daemon.hs: user error (Too short input for last message =.=)

My belief is that my recvOne' call casts everything to a (big) MptcpPacket

type MptcpPacket = Packet GenlData NoDataMptcp

straightaway while the stack can send smaller Packets like ErrorMsg/DoneMsg https://github.com/Ongy/netlink-hs/blob/master/System/Linux/Netlink.hs#L115 :

data Packet a
        = Packet -- The "normal" message
    {
      packetHeader     :: Header -- ^The netlink message header
    , packetCustom     :: a -- ^The datatype for additional static data for the interface
    , packetAttributes :: Attributes -- ^The netlink attributes
    }
        | ErrorMsg -- The error message
    {
      packetHeader     :: Header -- ^The netlink message header
    , packetError      :: CInt -- ^The error ID for this error message
    , errorPacket      :: Packet a -- ^The offending message
    }
        | DoneMsg -- The done message, this should usually not be seen by a user
    {
      packetHeader     :: Header -- ^The header of the done message
    }
deriving (Eq)

My question thus becomes: - with this library, how can I retreive all packets and only afterwards distinguish between ErrorMsg / DoneMsg and the valid netlink packets. Haskell forces me to cast to something but it's weird. Should I use some kind of exception ? am I going to lose packets this way ? and so on.

As I am still a haskell beginner, any kind of example/code is welcome