RFC6724 defines an ipv6-centric DNS result sorting algorithm, that
takes route and source address route information for the results
given by the DNS resolution, and sorts them in order of preferability,
which defines the order they should be tried in.
If LWS_WITH_NETLINK, then lws takes care about collecting and monitoring
the interface, route and source address information, and uses it to
perform the RFC6724 sorting to re-sort the DNS before trying to make
the connections.
There's a good pattern that's encouraged by using lws_struct pieces, that
we have an lws_dll2 owner with an array of objects listed in it that exist
in an lwsac. And because it came from JSON, there is tending to be a
logical name for the objects.
This adds a typed helper and wrapper to scan the owner list looking for
a specific name (of a specified length, not NUL terminated) in a specific
member of the listed objects, which must be a NUL-terminated const char *.
Again this is a good pattern that's encouraged by use of lws_tokenize
to recover the name we're looking for.
So it leads to the helper that can cleanly search for a listed object of the
right name from an owner, and return the typed object pointer or NULL, from a
length-specified string.
By default this doesn't change any existing logging behaviour at all.
But it allows you to define cmake options to force or force-disable the
build of individual log levels using new cmake option bitfields
LWS_LOGGING_BITFIELD_SET and LWS_LOGGING_BITFIELD_CLEAR.
Eg, -DLWS_LOGGING_BITFIELD_SET="(LLL_INFO)" can force INFO log level
built even in release mode. -DLWS_LOGGING_BITFIELD_CLEAR="(LLL_NOTICE)"
will likewise remove NOTICE logging from the build regardless of
DEBUG or RELEASE mode.
There are quite a few linked-lists of things that want events after
some period. This introduces a type binding an lws_dll2 for the
list and a lws_usec_t for the duration.
The wsi timeouts, the hrtimer and the sequencer timeouts are converted
to use these, also in the common event wait calculation.
