This ensures that each DERP server is probed individually (TLS and STUN)
and also manages per-region mesh probing. Actual probing code has been
copied from cmd/derpprobe.
Signed-off-by: Anton Tolchanov <anton@tailscale.com>
Instead of treating any interface with a non-ifscope route as a
potential default gateway, now verify that a given route is
actually a default route (0.0.0.0/0 or ::/0).
Fixes#5879
Signed-off-by: Anton Tolchanov <anton@tailscale.com>
TLS prober now checks validity period for all server certificates
and verifies OCSP revocation status for the leaf cert.
Signed-off-by: Anton Tolchanov <anton@tailscale.com>