net: tcp: Clean up net_context lifecycle
The death of a network context was sort of a mess. There was one
function, net_context_put(), which was used both by the user as a way
to "close" the connection and by the internals to delete it and to
"clean up" a TCP connection at the end of its life.
This has led to repeated gotchas where contexts die before you are
ready for them (one example: when a user callback decides the
transation is complete and calls net_context_put() underneath the
receive callback for the EOF, which then returns and tries to inspect
the now-freed memory inside the TCP internals). I've now stepped into
this mess four times now, and it's time to fix the architecture:
Swap the solitary put() call for a more conventional reference
counting implementation. The put() call now is a pure user API (and
maybe should be renamed "close" or "shutdown"). For compatibility,
it still calls unref() where appropriate (i.e. when the context can be
synchronously deleted) and the FIN processing will still do an unref()
when the FIN packets have been both transmitted and acked. The
context will start with a refcount of 1, and all TCP callbacks made on
it will increment the refcount around the callback to prevent
premature deletion.
Note that this gives the user a "destroy" mechanism for an in-progress
connection that doesn't require a network round trip. That might be
useful in some circumstances.
Change-Id: I44cb355e42941605913b2f84eb14d4eb3c134570
Signed-off-by: Andy Ross <andrew.j.ross@intel.com>
3 files changed
