The ResolvConfMode property is documented to return how systemd-resolved
is currently managing /etc/resolv.conf. Include that information in the
debug line, when available, to assist in debugging DNS issues.
Signed-off-by: Andrew Dunham <andrew@du.nham.ca>
Change-Id: I1ae3a257df1d318d0193a8c7f135c458ec45093e
The Lufthansa in-flight wifi generates a synthetic 204 response to the
DERP server's /generate_204 endpoint. This PR adds a basic
challenge/response to the endpoint; something sufficiently complicated
that it's unlikely to be implemented by a captive portal. We can then
check for the expected response to verify whether we're being MITM'd.
Follow-up to #5601
Signed-off-by: Andrew Dunham <andrew@du.nham.ca>
Change-Id: I94a68c9a16a7be7290200eea6a549b64f02ff48f
This is especially helpful as we launch newer DERPs over time, and older
clients have progressively out-of-date static DERP maps baked in. After
this, as long as the client has successfully connected once, it'll cache
the most recent DERP map it knows about.
Resolves an in-code comment from @bradfitz
Signed-off-by: Andrew Dunham <andrew@du.nham.ca>
This is entirely optional (i.e. failing in this code is non-fatal) and
only enabled on Linux for now. Additionally, this new behaviour can be
disabled by setting the TS_DEBUG_DISABLE_AF_PACKET environment variable.
Updates #3824
Replaces #5474
Co-authored-by: Andrew Dunham <andrew@du.nham.ca>
Signed-off-by: David Anderson <danderson@tailscale.com>
On sufficiently large tailnets, even writing the peer header (~95 bytes)
can result in a large amount of data that needs to be serialized and
deserialized. Only write headers for peers that need to have their
configuration changed.
Signed-off-by: Andrew Dunham <andrew@tailscale.com>
I was working on my "dump iptables rules using only syscalls" branch and
had a bunch of C structure decoding to do. Rather than manually
calculating the padding or using unsafe trickery to actually cast
variable-length structures to Go types, I'd rather use a helper package
that deals with padding for me.
Padding rules were taken from the following article:
http://www.catb.org/esr/structure-packing/
Signed-off-by: Andrew Dunham <andrew@du.nham.ca>
Andrew Dunham
