tree-wide: remove Emacs lines from all files This should be handled fine now by .dir-locals.el, so need to carry that stuff in every file.

resolved: never consider following a CNAME/DNAME chain for a CNAME/DNAME lookup Let's avoid thinking that a CNAME/DNAME chain traversal could be a good idea if QTYPE is already CNAME/DNAME. (Also, let's bail out early when trying to see if some RR is a suitable CNAME/DNAME for some other RR).

resolved: rework IDNA logic Move IDNA logic out of the normal domain name processing, and into the bus frontend calls. Previously whenever comparing two domain names we'd implicitly do IDNA conversion so that "pöttering.de" and "xn--pttering-n4a.de" would be considered equal. This is problematic not only for DNSSEC, but actually also against he IDNA specs. Moreover it creates problems when encoding DNS-SD services in classic DNS. There, the specification suggests using UTF8 encoding for the actual service name, but apply IDNA encoding to the domain suffix. With this change IDNA conversion is done only: - When the user passes a non-ASCII hostname when resolving a host name using ResolveHostname() - When the user passes a non-ASCII domain suffix when resolving a service using ResolveService() No IDNA encoding is done anymore: - When the user does raw ResolveRecord() RR resolving - On the service part of a DNS-SD service name Previously, IDNA encoding was done when serializing names into packets, at a point where information whether something is a label that needs IDNA encoding or not was not available, but at a point whether it was known whether to generate a classic DNS packet (where IDNA applies), or an mDNS/LLMNR packet (where IDNA does not apply, and UTF8 is used instead for all host names). With this change each DnsQuery object will now maintain two copies of the DnsQuestion to ask: one encoded in IDNA for use with classic DNS, and one encoded in UTF8 for use with LLMNR and MulticastDNS.

resolved: minor optimization for dns_question_is_equal() If the poinetrs are equal, we don't have to do a deep comparison. This is similar to a similar optimization we already have in place for RRs and keys.

resolved: be slightly stricter when validating DnsQuestion Also verify whether the DNS RR types are actually suitable for a question.

resolved: make key argument of dns_question_contains() const

resolved: cache - do negative caching only on the canonical name Apart from dropping redundant information, this fixes an issue where, due to broken DNS servers, we can only be certain of whether an apparent NODATA response is in fact an NXDOMAIN response after explicitly resolving the canonical name. This issue is outlined in RFC2308. Moreover, by caching NXDOMAIN for an existing name, we would mistakenly return NXDOMAIN for types which should not be redirected. I.e., a query for AAAA on test-nx-1.jklm.no correctly returns NXDOMAIN, but a query for CNAME should return the record and a query for DNAME should return NODATA. Note that this means we will not cache an NXDOMAIN response in the presence of redirection, meaning one redundant roundtrip in case the name is queried again.

resolved: fully support DNS search domains This adds support for searching single-label hostnames in a set of configured search domains. A new object DnsQueryCandidate is added that links queries to scopes. It keeps track of the search domain last used for a query on a specific link. Whenever a host name was unsuccessfuly resolved on a scope all its transactions are flushed out and replaced by a new set, with the next search domain appended. This also adds a new flag SD_RESOLVED_NO_SEARCH to disable search domain behaviour. The "systemd-resolve-host" tool is updated to make this configurable via --search=. Fixes #1697

resolved: don't claim DnsQuestion have to have the same names Wen DnsQuestion objects are used for DnsQuery objects all contained keys have to share the same name, but otherwise they generally don't have to, and this can actually happen in real-life because DnsPacket objects for mDNS use DnsQuestion for the question section. Hence, rename: dns_question_is_valid() to dns_question_is_valid_for_query(), since the name uniqueness check it does is only relevant when used for a query. Similar, rename dns_question_name() to dns_question_first_name(), to be more accurate, as this difference matters if we keys don#t have to share the same name.

resolved: implement client-side DNAME resolution Most servers apparently always implicitly convert DNAME to CNAME, but some servers don't, hence implement this properly, as this is required by edns0.

question: drop dns_question_is_superset() which we don't use anymore

resolved: add ResolveService() bus call for resolving SRV and DNS-SD services This also adds client-side support for this to systemd-resolve-host. Note that the ResolveService() API can deal both with DNS-SD service (consisting of service name, type and domain), as well as classic SRV services (consisting just of a type and a domain), all exposed in the same call. This patch also reworks CNAME handling in order to reuse it between hostname, RR and service lookups. In contrast to Avahi and Bonjour, this new API will actually reolve the A/AAAA RRs the SRV RRs point to in one go (unless this is explicitly disabled). This normally comes for free, as these RRs are sent along the SRV responses anyway, hence let's make use of that. This makes the API considerably easier to use, as a single ResolveService() invocation will return all necessary data to pick a server and connect() to it. Note that this only implements the DNS-SD resolving step, it does not implement DNS-SD browsing, as that makes sense primarily on mDNS, due to its continuous nature.

util-lib: split out allocation calls into alloc-util.[ch]

resolved: rr - introduce dns_resource_key_new_redirect() Takes a key and CNAME RR and returns the canonical RR of the right type. Make use of this in dns_question_redirect().

resolved: only maintain one question RR key per transaction Let's simplify things and only maintain a single RR key per transaction object, instead of a full DnsQuestion. Unicast DNS and LLMNR don't support multiple questions per packet anway, and Multicast DNS suggests coalescing questions beyond a single dns query, across the whole system.

resolved: make DnsQuestion logic handle NULL arrays as empty arrays Following our usual logic of treating NULL arrays as empty arrays (for example, see strv.c) do the same for questions too.

resolved: compare dns question arrays properly Let's optimize things a bit and properly compare DNS question arrays, instead of checking if they are mutual supersets. This also makes ANY query handling more accurate.

resolve: move dns routines into shared

resolved: fix cname handling

resolved: when resolving an address PTR record via llmnr, make a tcp connection by default

resolved: implement negative caching

resolved: rework logic so that we can share transactions between queries of different clients