When I see "test", I have to think three times what the return value
means. With "below" this is immediately clear. ratelimit_below(&limit)
sounds almost like English and is imho immediately obvious.
(I also considered ratelimit_ok, but this strongly implies that being under the
limit is somehow better. Most of the times this is true, but then we use the
ratelimit to detect triple-c-a-d, and "ok" doesn't fit so well there.)
C.f. a1bcaa07.
Files which are installed as-is (any .service and other unit files, .conf
files, .policy files, etc), are left as is. My assumption is that SPDX
identifiers are not yet that well known, so it's better to retain the
extended header to avoid any doubt.
I also kept any copyright lines. We can probably remove them, but it'd nice to
obtain explicit acks from all involved authors before doing that.
This is similar to TAKE_PTR() but operates on file descriptors, and thus
assigns -1 to the fd parameter after returning it.
Removes 60 lines from our codebase. Pretty good too I think.
Enumerating DNS-SD PTR resource records are a special case and
are supposed to have non-unique keys pointing to services of the
same type running on different hosts. There's no need for them
to be checked for conflicts.
Thus don't check for conflicts such RRs.
Refcounting for a RR's key is done separately from refcounting
for the RR itself, but in dns_scope_notify_conflict() we don't
do that. This may lead to a situation when a RR key put in the
conflict_queue hash as a value's key gets freed upon
cache reduction when it's still referenced by the hash.
Thus increase refcount for the key when putting it into the hash
and unreference it upon removing from the hash.
Closes#6456
Currently, we accept SERVFAIL after downgrading fully, cache it and move
on. Let's extend this a bit: after downgrading fully, if the SERVFAIL
logic continues to be an issue, then use a different DNS server if there
are any.
Fixes: #7147
This makes sure that a classic DNS scope that has no DNS servers
assigned is never considered for routing requests to even if it has
matching search/routing domains associated.
This is inspired by #7544, where lookup requests are refused since a
scope with no DNS server is configured. This change does not deliver
what the reporter intended, but is generally useful in general, as it
makes us mor robust to misconfiguration.
It might happen that a DNS-SD service doesn't include local host's
name in its RR keys and still conflicts with a remote service.
In this case try to resolve the conflict by changing name for
this particular service.
When we a reply message gets longer than the client supports we need to
truncate the response and set the TC bit, and we already do that.
However, we are not supposed to send incomplete RRs in that case, but
instead truncate right at a record boundary. Do that.
This fixes the "Message parser reports malformed message packet."
warning the venerable "host" tool outputs when a very large response is
requested.
See: #6520
The array doesn't grow dynamically, hence pick the right size at the
moment of allocation. Let's simply multiply the number of addresses of
this link by 2, as that's how many RRs we maintain for it.
We don't actually make use of the return value for now, but it matches
our coding style elsewhere, and it actually shortens our code quite a
bit.
Also, add a missing OOM check after dns_answer_new().
This reverts a part of 53fda2bb933694c9bdb1bbf1f5583e39673b74b2:
On classic DNS and LLMNR ANY requests may be replied to with any kind of
RR, and the reply does not have to be comprehensive: these protocols
simply define that if there's an RRset that can answer the question,
then at least one should be sent as reply, but not necessarily all. This
means it's not safe to "merge" transactions for arbitrary RR types into
ANY requests, as the reply might not answer the specific question.
As the merging is primarily an optimization, let's undo this for now.
This logic may be readded later, in a way that only applies to mDNS.
Also, there's an OOM problem with this chunk: dns_resource_key_new()
might fail due to OOM and this is not handled. (This is easily removed
though, by using DNS_RESOURCE_KEY_CONST()).
DNS servers which have route-only domains should only be used for
the specified domains. Routing queries about other domains there is a privacy
violation, prone to fail (as that DNS server was not meant to be used for other
domains), and puts unnecessary load onto that server.
Introduce a new helper function dns_server_limited_domains() that checks if the
DNS server should only be used for some selected domains, i. e. has some
route-only domains without "~.". Use that when determining whether to query it
in the scope, and when writing resolv.conf.
Extend the test_route_only_dns() case to ensure that the DNS server limited to
~company does not appear in resolv.conf. Add test_route_only_dns_all_domains()
to ensure that a server that also has ~. does appear in resolv.conf as global
name server. These reproduce #3420.
Add a new test_resolved_domain_restricted_dns() test case that verifies that
domain-limited DNS servers are only being used for those domains. This
reproduces #3421.
Clarify what a "routing domain" is in the manpage.
Fixes#3420Fixes#3421
In order to improve compatibility with local clients that speak DNS directly
(and do not use NSS or our bus API) listen locally on 127.0.0.53:53 and process
any queries made that way.
Note that resolved does not implement a full DNS server on this port, but
simply enough to allow normal, local clients to resolve RRs through resolved.
Specifically it does not implement queries without the RD bit set (these are
requests where recursive lookups are explicitly disabled), and neither queries
with DNSSEC DO set in combination with DNSSEC CD (i.e. DNSSEC lookups with
validation turned off). It also refuses zone transfers and obsolete RR types.
All lookups done this way will be rejected with a clean error code, so that the
client side can repeat the query with a reduced feature set.
The code will set the DNSSEC AD flag however, depending on whether the data
resolved has been validated (or comes from a local, trusted source).
Lookups made via this mechanisms are propagated to LLMNR and mDNS as necessary,
but this is only partially useful as DNS packets cannot carry IP scope data
(i.e. the ifindex), and hence link-local addresses returned cannot be used
properly (and given that LLMNR/mDNS are mostly about link-local communication
this is quite a limitation). Also, given that DNS tends to use IDNA for
non-ASCII names, while LLMNR/mDNS uses UTF-8 lookups cannot be mapped 1:1.
In general this should improve compatibility with clients bypassing NSS but
it is highly recommended for clients to instead use NSS or our native bus API.
This patch also beefs up the DnsStream logic, as it reuses the code for local
TCP listening. DnsStream now provides proper reference counting for its
objects.
In order to avoid feedback loops resolved will no silently ignore 127.0.0.53
specified as DNS server when reading configuration.
resolved listens on 127.0.0.53:53 instead of 127.0.0.1:53 in order to leave
the latter free for local, external DNS servers or forwarders.
This also changes the "etc.conf" tmpfiles snippet to create a symlink from
/etc/resolv.conf to /usr/lib/systemd/resolv.conf by default, thus making this
stub the default mode of operation if /etc is not populated.
Make sure we can parse DNS server addresses that use the "zone id" syntax for
local link addresses, i.e. "fe80::c256:27ff:febb:12f%wlp3s0", when reading
/etc/resolv.conf.
Also make sure we spit this out correctly again when writing /etc/resolv.conf
and via the bus.
Fixes: #3359
Previously, if a hostanem is resolved with AF_UNSPEC specified, this would be used as indication to resolve both an
AF_INET and an AF_INET6 address. With this change this logic is altered: an AF_INET address is only resolved if there's
actually a routable IPv4 address on the specific interface, and similar an AF_INET6 address is only resolved if there's
a routable IPv6 address. With this in place, it's ensured that the returned data is actually connectable by
applications. This logic mimics glibc's resolver behaviour.
Note that if the client asks explicitly for AF_INET or AF_INET6 it will get what it asked for.
This also simplifies the logic how it is determined whether a specific lookup shall take place on a scope.
Specifically, the checks with dns_scope_good_key() are now moved out of the transaction code and into the query code,
so that we don't even create a transaction object on a specific scope if we cannot execute the resolution on it anyway.
Not only report whether the server actually supports DNSSEC, but also first check whether DNSSEC is actually enabled
for it in our local configuration.
Also, export a per-link DNSSECSupported property in addition to the existing manager-wide property.
This moves management of the OPT RR out of the scope management and into
the server and packet management. There are now explicit calls for
appending and truncating the OPT RR from a packet
(dns_packet_append_opt() and dns_packet_truncate_opt()) as well as a
call to do the right thing depending on a DnsServer's feature level
(dns_server_adjust_opt()).
This also unifies the code to pick a server between the TCP and UDP code
paths, and makes sure the feature level used for the transaction is
selected at the time the server is picked, and not changed until the
next time we pick a server. The server selction code is now unified in
dns_transaction_pick_server().
This all fixes problems when changing between UDP and TCP communication
for the same server, and makes sure the UDP and TCP codepaths are more
alike. It also makes sure we never keep the UDP port open when switchung
to TCP, so that we don't have to handle incoming datagrams on the latter
we don't expect.
As the new code picks the DNS server at the time we make a connection,
we don't need to invalidate the DNS server anymore when changing to the
next one, thus dns_transaction_next_dns_server() has been removed.
Previously the calls for emitting DNS UDP packets were just called
dns_{transacion|scope}_emit(), but the one to establish a DNS TCP
connection was called dns_transaction_open_tcp(). Clean this up, and
rename them dns_{transaction|scope}_emit_udp() and
dns_transaction_open_tcp().
We have many types of failure for a transaction, and
DNS_TRANSACTION_FAILURE was just one specific one of them, if the server
responded with a non-zero RCODE. Hence let's rename this, to indicate
which kind of failure this actually refers to.
