Currently we always reserve a fakewsi per pt so events that don't have a related actual
wsi, like vhost-protocol-init or vhost cert init via protocol callback can make callbacks
that look reasonable to user protocol handler code expecting a valid wsi every time.
This patch splits out stuff that user callbacks often unconditionally expect to be in
a wsi, like context pointer, vhost pointer etc into a substructure, which is composed
into struct lws at the top of it. Internal references (struct lws is opaque, so there
are only internal references) are all updated to go via the substructre, the compiler
should make that a NOP.
Helpers are added when fakewsi is used and referenced.
If not PLAT_FREERTOS, we continue to provide a full fakewsi in the pt as before,
although the helpers improve consistency by zeroing down the substructure. There is
a huge amount of user code out there over the last 10 years that did not always have
the minimal examples to follow, some of it does some unexpected things.
If it is PLAT_FREERTOS, that is a newer thing in lws and users have the benefit of
being able to follow the minimal examples' approach. For PLAT_FREERTOS we don't
reserve the fakewsi in the pt any more, saving around 800 bytes. The helpers then
create a struct lws_a (the substructure) on the stack, zero it down (but it is only
like 4 pointers) and prepare it with whatever we know like the context.
Then we cast it to a struct lws * and use it in the user protocol handler call.
In this case, the remainder of the struct lws is undefined. However the amount of
old protocol handlers that might touch things outside of the substructure in
PLAT_FREERTOS is very limited compared to legacy lws user code and the saving is
significant on constrained devices.
User handlers should not be touching everything in a wsi every time anyway, there
are several cases where there is no valid wsi to do the call with. Dereference of
things outside the substructure should only happen when the callback reason shows
there is a valid wsi bound to the activity (as in all the minimal examples).
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.
Secure Streams is an optional layer on top of lws that separates policy
like endpoint selection and tls cert validation into a device JSON
policy document.
Code that wants to open a client connection just specifies a streamtype name,
and no longer deals with details like the endpoint, the protocol (!) or anything
else other than payloads and optionally generic metadata; the JSON policy
contains all the details for each streamtype. h1, h2, ws and mqtt client
connections are supported.
Logical secure streams outlive any particular connection and supports "nailed-up"
connectivity regardless of underlying connection stability.
Adds client support for MQTT QoS0 and QoS1, compatible with AWS IoT
Supports stream binding where independent client connections to the
same endpoint can mux on a single tcp + tls connection with topic
routing managed internally.
