Go 1.17 switches to a register ABI on amd64 platforms.
Part of that switch is that go and defer calls use an argument-less
closure, which allocates. This means that we have an extra
alloc in some DNS work. That's unfortunate but not a showstopper,
and I don't see a clear path to fixing it.
The other performance benefits from the register ABI will all
but certainly outweigh this extra alloc.
Fixes#2545
Signed-off-by: Josh Bleecher Snyder <josh@tailscale.com>
This change (subject to some limitations) looks for the EDNS OPT record
in queries and responses, clamping the size field to fit within our DNS
receive buffer. If the size field is smaller than the DNS receive buffer
then it is left unchanged.
I think we will eventually need to transition to fully processing the
DNS queries to handle all situations, but this should cover the most
common case.
Mostly fixes#2066
Signed-off-by: Adrian Dewhurst <adrian@tailscale.com>
This raises the maximum DNS response message size from 512 to 4095. This
should be large enough for almost all situations that do not need TCP.
We still do not recognize EDNS, so we will still forward requests that
claim support for a larger response size than 4095 (that will be solved
later). For now, when a response comes back that is too large to fit in
our receive buffer, we now set the truncation flag in the DNS header,
which is an improvement from before but will prompt attempts to use TCP
which isn't supported yet.
On Windows, WSARecvFrom into a buffer that's too small returns an error
in addition to the data. On other OSes, the extra data is silently
discarded. In this case, we prefer the latter so need to catch the error
on Windows.
Partially addresses #1123
Signed-off-by: Adrian Dewhurst <adrian@tailscale.com>
The resolver still only supports a single upstream config, and
ipn/wgengine still have to split up the DNS config, but this moves
closer to unifying the DNS configs.
As a handy side-effect of the refactor, IPv6 MagicDNS records exist
now.
Signed-off-by: David Anderson <danderson@tailscale.com>
They're only used internally and in tests, and have surprising
semantics in that they only resolve MagicDNS names, not upstream
resolver queries.
Signed-off-by: David Anderson <danderson@tailscale.com>
Tor has a location-hidden service feature that enables users to host services
from inside the Tor network. Each of these gets a unique DNS name that ends with
.onion. As it stands now, if a misbehaving application somehow manages to make
a .onion DNS request to our DNS server, we will forward that to the DNS server,
which could leak that to malicious third parties. See the recent bug Brave had
with this[1] for more context.
RFC 7686 suggests that name resolution APIs and libraries MUST respond with
NXDOMAIN unless they can actually handle Tor lookups. We can't handle .onion
lookups, so we reject them.
[1]: https://twitter.com/albinowax/status/1362737949872431108Fixestailscale/corp#1351
Signed-off-by: Christine Dodrill <xe@tailscale.com>
Use tb.Cleanup to simplify both the API and the implementation.
One behavior change: When the number of goroutines shrinks, don't log.
I've never found these logs to be useful, and they frequently add noise.
Signed-off-by: Josh Bleecher Snyder <josh@tailscale.com>
This is what every other DNS resolver I could find does, so tsdns
should do it to. This also helps avoid weird error messages about
non-existent records being unimplemented, and thus fixes#848.
Signed-off-by: Smitty <me@smitop.com>
* show DNS name over hostname, removing domain's common MagicDNS suffix.
only show hostname if there's no DNS name.
but still show shared devices' MagicDNS FQDN.
* remove nerdy low-level details by default: endpoints, DERP relay,
public key. They're available in JSON mode still for those who need
them.
* only show endpoint or DERP relay when it's active with the goal of
making debugging easier. (so it's easier for users to understand
what's happening) The asterisks are gone.
* remove Tx/Rx numbers by default for idle peers; only show them when
there's traffic.
* include peers' owner login names
* add CLI option to not show peers (matching --self=true, --peers= also
defaults to true)
* sort by DNS/host name, not public key
* reorder columns
This appears to have been the intent of the previous code,
but in practice, it only returned A records.
Signed-off-by: Josh Bleecher Snyder <josh@tailscale.com>
To be honest I'm not fond of Golden Bytes tests like this, but
not so much as to want to rewrite the whole test. The DNS byte
format is essentially immutable at this point, the encoded bytes
aren't going to change. The rest of the test assumptions about
hostnames might, but we can fix that when it comes.
Signed-off-by: Denton Gentry <dgentry@tailscale.com>
Previously the client had heuristics to calculate which DNS search domains
to set, based on the peers' names. Unfortunately that prevented us from
doing some things we wanted to do server-side related to node sharing.
So, bump MapRequest.Version to 9 to signal that the client only uses the
explicitly configured DNS search domains and doesn't augment it with its own
list.
Updates tailscale/corp#1026
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
While we're here, parseQuery into a plain function.
This is helpful for fuzzing. (Which I did a bit of. Didn't find anything.)
And clean up a few minor things.
Signed-off-by: Josh Bleecher Snyder <josh@tailscale.com>
Previously, a type AAAA query would be answered with an A record
if only an IPv4 address was available. This is irrelevant for us
while we only use IPv4, but it will be a bug one day,
so it's worth being precise about semantics.
Signed-off-by: Dmytro Shynkevych <dmytro@tailscale.com>
The previous approach modifies name in-place in the request slice to avoid an allocation.
This is incorrect: the question section of a DNS request
must be copied verbatim, without any such modification.
Software may rely on it (we rely on other resolvers doing it it in tsdns/forwarder).
Signed-off-by: Dmytro Shynkevych <dmytro@tailscale.com>
This change adds to tsdns the ability to delegate lookups to upstream nameservers.
This is crucial for setting Magic DNS as the system resolver.
Signed-off-by: Dmytro Shynkevych <dmytro@tailscale.com>
Josh Bleecher Snyder
Adrian Dewhurst
Brad Fitzpatrick
David Anderson
Christine Dodrill
Smitty
Denton Gentry
Dmytro Shynkevych