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fix: back off unroutable IPv6 DoH upstream health-check spam

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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.
This commit is contained in:
Cuong Manh Le
2026-06-30 14:47:33 +07:00
parent 8948fa402b
commit ff14fc8ac9
8 changed files with 269 additions and 27 deletions
Download Patch File Download Diff File Expand all files Collapse all files
cmd/cli/prog.go
+8 -7
View File
@@ -35,6 +35,7 @@ import (
"github.com/Control-D-Inc/ctrld/internal/controld"
"github.com/Control-D-Inc/ctrld/internal/dnscache"
"github.com/Control-D-Inc/ctrld/internal/firewall"
ctrldnet "github.com/Control-D-Inc/ctrld/internal/net"
)
const (
@@ -1311,13 +1312,14 @@ func errAddrInUse(err error) bool {
var _ = errAddrInUse
// The unreachable winsock errnos (ENETUNREACH/EHOSTUNREACH) are matched via
// ctrldnet.IsUnreachable, which owns their definitions.
//
// https://learn.microsoft.com/en-us/windows/win32/winsock/windows-sockets-error-codes-2
var (
windowsECONNREFUSED = syscall.Errno(10061)
windowsENETUNREACH = syscall.Errno(10051)
windowsEINVAL = syscall.Errno(10022)
windowsEADDRINUSE = syscall.Errno(10048)
windowsEHOSTUNREACH = syscall.Errno(10065)
)
func errUrlNetworkError(err error) bool {
@@ -1334,15 +1336,14 @@ func errNetworkError(err error) bool {
if opErr.Temporary() {
return true
}
if ctrldnet.IsUnreachable(err) {
return true
}
switch {
case errors.Is(opErr.Err, syscall.ECONNREFUSED),
errors.Is(opErr.Err, syscall.EINVAL),
errors.Is(opErr.Err, syscall.ENETUNREACH),
errors.Is(opErr.Err, syscall.EHOSTUNREACH),
errors.Is(opErr.Err, windowsENETUNREACH),
errors.Is(opErr.Err, windowsEINVAL),
errors.Is(opErr.Err, windowsECONNREFUSED),
errors.Is(opErr.Err, windowsEHOSTUNREACH):
errors.Is(opErr.Err, windowsECONNREFUSED):
return true
}
}