We have an option to set the fallback list, so we don't know what the contents
are. It may in fact be empty. Let's add some examples to make it easy for a user
stranded without any DNS to fill in something that would work. As a bonus, this
also gives names to the entries we provide by default.
(I added google and cloudflare because that's what we have currently, and quad9
because it seems to be a good privacy-concious and fast choice and was requested
in #12499. As a minimum, things we should include should be well-known global
services with a documented privacy policy and both IPv4 and IPv6 support and
decent response times.)
RFC7766 section 4 states that in the absence of EDNS0, a response that
is too large for a 512-byte UDP packet will have the 'truncated' bit
set. The client is expected to retry the query over TCP.
Fixes#10264.
In some cases, caching DNS results locally is not desirable, a it makes DNS
cache poisoning attacks a tad easier and also allows users on the system to
determine whether or not a particular domain got visited by another user. Thus
provide a new "Cache" resolved.conf option to disable it.
Let's make sure DNSSEC gets more testing, by defaulting DNSSEC to
"allow-downgrade" mode. Since distros should probably not ship DNSSEC enabled
by default add a configure switch to disable this again.
DNSSEC in "allow-downgrade" mode should mostly work without affecting user
experience. There's one exception: some captive portal systems rewrite DNS in
order to redirect HTTP traffic to the captive portal. If these systems
implement DNS servers that are otherwise DNSSEC-capable (which in fact is
pretty unlikely, but still...), then this will result in the captive portal
being inaccessible. To fix this support in NetworkManager (or any other network
management solution that does captive portal detection) is required, which
simply turns off DNSSEC during the captive portal detection, and resets it back
to the default (i.e. on) after captive portal authentication is complete.
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.
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.
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
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.
Zbigniew Jędrzejewski-Szmek