When IPv6 is available locally but the selected IPv6 DoH endpoint is
unroutable (e.g. dialing [2606:1a40::22]:443 returns "no route to host"
while IPv4 stays usable), ctrld re-bootstrapped and re-dialed the endpoint
every ~2s. A weekend soak produced ~46.7k "no route to host" lines, with
the dial/health-check loop dominating the log during bad windows.
Add bounded backoff/suppression for network-unreachable endpoints at two
levels:
- ParallelDialer (internal/net): track dial addresses that fail with
ENETUNREACH/EHOSTUNREACH and skip them for an exponentially growing,
bounded window (5s -> 60s). A successful dial clears the entry
immediately, so recovery is preserved when the route returns. When every
candidate is suppressed the dial fails fast and quietly instead of
hammering known-unroutable addresses.
- Upstream recovery loop (cmd/cli): demote unreachable check failures to
debug and back off the retry cadence (2s -> 60s) for an unreachable
streak; any other failure resets to the base cadence.
The new IsUnreachable classifier lives in internal/net and is reused by
cmd/cli's errNetworkError, so the unreachable-errno matching has a single
definition. Note the explicit winsock constants (10051/10065) are required
on Windows: syscall.ENETUNREACH/EHOSTUNREACH are Go's portable "invented"
values and never equal the raw WSA codes a failing connect surfaces.
Suppression and backoff are always bounded, so IPv6 is never disabled until
restart and recovers on its own once the route is back. Split-stack
selection and the #549 macOS intercept recovery work are untouched.
Adds unit tests for the classifier, the dialer's suppression tracker, and
the recovery backoff schedule.
Changed the IPv6 support detection to try multiple common ports (HTTP/HTTPS) instead of
just testing against a DNS port. The function now returns both the IPv6 support status
and the successful port that confirmed the connectivity. This makes the IPv6 detection
more reliable by not depending solely on DNS port availability.
Previously, the function only tested connectivity to a DNS port (53) over IPv6.
Now it tries to connect to commonly available ports like HTTP (80) and HTTPS (443)
until it finds a working one, making the detection more robust in environments where
certain ports might be blocked.
On Windows host with StarLink network, ctrld hangs on startup for ~30s
before continue running. This dues to IPv6 is configured but no external
IPv6 can be reached. When probing stack, ctrld is dialing using ipv6
without any timeout set, so the dialing timeout is enforced by OS.
This commit adds a timeout for probing dialer, so we ensure the probing
process will fail fast.
Cuong Manh Le