extmod/modlwip: Deregister all lwIP callbacks when closing a socket.

Otherwise they may be called on a socket that no longer exists.

For example, if the GC calls the finaliser on the socket and then reuses
its heap memory, the "callback" entry of the old socket may contain invalid
data.  If lwIP then calls the TCP callback the code may try to call the
user callback object which is now invalid.  The lwIP callbacks must be
deregistered during the closing of the socket, before all the pcb pointers
are set to NULL.

0 files changed, 0 insertions, 0 deletions