It's not safe to destroy objects inside a callback from a parent that
still has references to the object.
Formalize what the user code can indicate by its return code from the
callback functions and provide the implementations at the parents.
- LWSSSSRET_OK: no action, OK
- LWSSSSRET_DISCONNECT_ME: disconnect the underlying connection
- LWSSSSRET_DESTROY_ME: destroy the ss object
- LWSSSSRET_TX_DONT_SEND: for tx, give up the tx opportunity since nothing to send
Some streamtypes do not pass or receive payload meaningfully. Allow them
to just leave their related cb NULL. Ditto for state, although I'm not sure
how useful such a streamtype can be.
Adapt the pt sul owner list to be an array, and define two different lists,
one that acts like before and is the default for existing users, and another
that has the ability to cooperate with systemwide suspend to restrict the
interval spent suspended so that it will wake in time for the earliest
thing on this wake-suspend sul list.
Clean the api a bit and add lws_sul_cancel() that only needs the sul as the
argument.
Add a flag for client creation info to indicate that this client connection
is important enough that, eg, validity checking it to detect silently dead
connections should go on the wake-suspend sul list. That flag is exposed in
secure streams policy so it can be added to a streamtype with
"swake_validity": true
Deprecate out the old vhost timer stuff that predates sul. Add a flag
LWS_WITH_DEPRECATED_THINGS in cmake so users can get it back temporarily
before it will be removed in a v4.2.
Adapt all remaining in-tree users of it to use explicit suls.
You can disconnect the stream by returning -1 from tx(). You can
give up your chance to send anything by returning 1 from tx().
Returning 0 sends `*len` amount of the provided buffer.
Returning <0 from rx() also disconnects the stream.
