resolved: remove configuration knobs for mDNS until it's ready These bits were intenionally left out while mDNS is under development. Remove the exposed knobs and man page entries again until this is settled.

resolved: make MulticastDNS support configurable in resolved.conf The option is already there, but wasn't exported in the configuration file so far. Fix that.

resolved: introduce a dnssec_mode setting per scope The setting controls which kind of DNSSEC validation is done: none at all, trusting the AD bit, or client-side validation. For now, no validation is implemented, hence the setting doesn't do much yet, except of toggling the CD bit in the generated messages if full client-side validation is requested.

resolved: add a generic DnsSearchDomain concept With this change, we add a new object to resolved, "DnsSearchDomain=" which wraps a search domain. This is then used to introduce a global search domain list, in addition to the existing per-link search domain list which is reword to make use of this new object too. This is preparation for implement proper unicast DNS search domain support.

Do not advertise .d snippets over main config file For daemons which have a main configuration file, there's little reason for the administrator to use configuration snippets. They are useful for packagers which need to override settings, but we shouldn't advertise that as the main way of configuring those services. https://bugs.freedesktop.org/show_bug.cgi?id=89397

resolved: Support resolved.conf.d directories in the usual search paths

resolved: beef up DNS server configuration logic We now maintain two lists of DNS servers: system servers and fallback servers. system servers are used in combination with any per-link servers. fallback servers are only used if there are no system servers or per-link servers configured. The system server list is supposed to be populated from a foreign tool's /etc/resolv.conf (not implemented yet). Also adds a configuration switch for LLMNR, that allows configuring whether LLMNR shall be used simply for resolving or also for responding.

resolved: add daemon to manage resolv.conf Also remove the equivalent functionality from networkd.