If we've already connected to a certain name's IP in the past, don't
assume the problem was DNS related. That just puts unnecessarily load
on our bootstrap DNS servers during regular restarts of Tailscale
infrastructure components.
Also, if we do do a bootstrap DNS lookup and it gives the same IP(s)
that we already tried, don't try them again.
Change-Id: I743e8991a7f957381b8e4c1508b8e9d0df1782fe
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
No behavior changes (intended, at least).
This is in prep for future changes to this package, which would get
too complicated in the current style.
Change-Id: Ic260f8e34ae2f64f34819d4a56e38bee8d8ac5ce
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
A new package can also later record/report which knobs are checked and
set. It also makes the code cleaner & easier to grep for env knobs.
Change-Id: Id8a123ab7539f1fadbd27e0cbeac79c2e4f09751
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
Go 1.17 added a HandshakeContext func to take care of timeouts during
TLS handshaking, so switch from our homegrown goroutine implementation
to the standard way.
Signed-off-by: David Anderson <danderson@tailscale.com>
Cancelling the context makes the timeout goroutine race with the write that
reports a successful TLS handshake, so you can end up with a successful TLS
handshake that mysteriously reports that it timed out after ~0s in flight.
The context is always canceled and cleaned up as the function exits, which
happens mere microseconds later, so just let function exit clean up and
thereby avoid races.
Signed-off-by: David Anderson <danderson@tailscale.com>
This is enough to handle the DNS queries as generated by Go's
net package (which our HTTP/SOCKS client uses), and the responses
generated by the ExitDNS DoH server.
This isn't yet suitable for putting on 100.100.100.100 where a number
of different DNS clients would hit it, as this doesn't yet do
EDNS0. It might work, but it's untested and likely incomplete.
Likewise, this doesn't handle anything about truncation, as the
exchanges are entirely in memory between Go or DoH. That would also
need to be handled later, if/when it's hooked up to 100.100.100.100.
Updates #3507
Change-Id: I1736b0ad31eea85ea853b310c52c5e6bf65c6e2a
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
Tested manually with:
$ go test -v ./net/dnscache/ -dial-test=bogusplane.dev.tailscale.com:80
Where bogusplane has three A records, only one of which works.
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
Cache DNS results of earlier login.tailscale.com control dials, and use
them for future dials if DNS is slow or broken.
Fixes various issues with trickier setups with the domain's DNS server
behind a subnet router.
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
I started to write a full DNS caching resolver and I realized it was
overkill and wouldn't work on Windows even in Go 1.14 yet, so I'm
doing this tiny one instead for now, just for all our netcheck STUN
derp lookups, and connections to DERP servers. (This will be caching a
exactly 8 DNS entries, all ours.)
Fixes#145 (can be better later, of course)
