Previously, we'd use a link as "default" route depending on whether
there are route-only domains defined on it or not. (If there are, it
would not be used as default route, if there aren't it would.)
Let's make this explicit and add a link variable controlling this. The
variable is not changeable from the outside yet, but subsequent commits
are supposed to add that.
Note that making this configurable adds a certain amount of redundancy,
as there are now two ways to ensure a link does not receive "default"
lookup (i.e. DNS queries matching no configured route):
1. By ensuring that at least one other link configures a route on it
(for example by add "." to its search list)
2. By setting this new boolean to false.
But this is exactly what is intended with this patch: that there is an
explicit way to configure on the link itself whether it receives
'default' traffic, rather than require this to be configured on other
links.
The variable added is a tri-state: if true, the link is suitable for
recieving "default" traffic. If false, the link is not suitable for it.
If unset (i.e. negative) the original logic of "has this route-only
routes" is used, to ensure compatibility with the status quo ante.
The function dns_server_limited_domains() was very strange as it
enumerate the domains associated with a DnsScope object to determine
whether any "route-only" domains, but did so as a function associated
with a DnsServer object.
Let's clear this up, and replace it by a function associated with a
DnsScope instead. This makes more sense philosphically and allows us to
reduce the loops through which we need to jump to determine whether a
scope is suitable for default routing a bit.
Previously, we'd return DNS_SCOPE_MAYBE for all domain lookups matching
LLMNR or mDNS. Let's upgrade this to DNS_SCOPE_YES, to make the binding
stronger.
The effect of this is that even if "local" is defined as routing domain
on some iface, we'll still lookup domains in local via mDNS — if mDNS is
turned on. This should not be limiting, as people who don't want such
lookups should turn off mDNS altogether, as it is useless if nothing is
routed to it.
This also has the nice benefit that mDNS/LLMR continue to work if people
use "~." as routing domain on some interface.
Similar for LLMNR and single label names.
Similar also for the link local IPv4 and IPv6 reverse lookups.
Fixes: #10125
This information is useful to pass back to the caller, as it tells us
where we found the answer.
(While we are at it, fix the socket level for the RECVERR logic)
Fixes: #9778
All over the place we define local variables for the various sockopts
that take a bool-like "int" value. Sometimes they are const, sometimes
static, sometimes both, sometimes neither.
Let's clean this up, introduce a common const variable "const_int_one"
(as well as one matching "const_int_zero") and use it everywhere, all
acorss the codebase.
This fixes the following valgrind warning:
```
Syscall param sendmsg(msg.msg_name) points to uninitialised byte(s)
at 0x6189CC1: sendmsg (in /usr/lib64/libpthread-2.27.so)
by 0x153082: dns_stream_writev (resolved-dns-stream.c:235)
by 0x153343: dns_stream_tls_writev (resolved-dns-stream.c:299)
by 0x5B30343: ??? (in /usr/lib64/libgnutls.so.30.20.2)
by 0x5B3158F: ??? (in /usr/lib64/libgnutls.so.30.20.2)
by 0x5B33190: ??? (in /usr/lib64/libgnutls.so.30.20.2)
by 0x5B36307: ??? (in /usr/lib64/libgnutls.so.30.20.2)
by 0x5B37D47: gnutls_handshake (in /usr/lib64/libgnutls.so.30.20.2)
by 0x154591: dns_stream_connect_tls (resolved-dns-stream.c:596)
by 0x13A889: dns_transaction_emit_tcp (resolved-dns-transaction.c:676)
by 0x13D901: dns_transaction_go (resolved-dns-transaction.c:1761)
by 0x1330C8: dns_query_candidate_go (resolved-dns-query.c:156)
Address 0xa9ac268 is 312 bytes inside a block of size 592 alloc'd
at 0x4C30B06: calloc (vg_replace_malloc.c:711)
by 0x1541F8: dns_stream_new (resolved-dns-stream.c:545)
by 0x13A662: dns_transaction_emit_tcp (resolved-dns-transaction.c:642)
by 0x13D901: dns_transaction_go (resolved-dns-transaction.c:1761)
by 0x1330C8: dns_query_candidate_go (resolved-dns-query.c:156)
by 0x134E16: dns_query_go (resolved-dns-query.c:757)
by 0x11F3FB: bus_method_resolve_hostname (resolved-bus.c:353)
by 0x4F947A7: method_callbacks_run (bus-objects.c:402)
by 0x4F97266: object_find_and_run (bus-objects.c:1260)
by 0x4F978B1: bus_process_object (bus-objects.c:1376)
by 0x4FAF82C: process_message (sd-bus.c:2661)
by 0x4FAFA1B: process_running (sd-bus.c:2703)
```
These lines are generally out-of-date, incomplete and unnecessary. With
SPDX and git repository much more accurate and fine grained information
about licensing and authorship is available, hence let's drop the
per-file copyright notice. Of course, removing copyright lines of others
is problematic, hence this commit only removes my own lines and leaves
all others untouched. It might be nicer if sooner or later those could
go away too, making git the only and accurate source of authorship
information.
This part of the copyright blurb stems from the GPL use recommendations:
https://www.gnu.org/licenses/gpl-howto.en.html
The concept appears to originate in times where version control was per
file, instead of per tree, and was a way to glue the files together.
Ultimately, we nowadays don't live in that world anymore, and this
information is entirely useless anyway, as people are very welcome to
copy these files into any projects they like, and they shouldn't have to
change bits that are part of our copyright header for that.
hence, let's just get rid of this old cruft, and shorten our codebase a
bit.
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.
Ben Boeckel