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appc,ipn/ipnlocal: log DNS parsing errors in app connectors (#14607)

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If we fail to parse the upstream DNS response in an app connector, we
might miss new IPs for the target domain. Log parsing errors to be able
to diagnose that.

Updates #14606

Signed-off-by: Andrew Lytvynov <awly@tailscale.com>
This commit is contained in:
Andrew Lytvynov
2025-01-23 09:03:56 -08:00
committed by GitHub
parent a00623e8c4
commit f1710f4a42
5 changed files with 78 additions and 35 deletions
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6
ipn/ipnlocal/local.go
View File

@@ -7276,17 +7276,17 @@ func (b *LocalBackend) DoSelfUpdate() {
// ObserveDNSResponse passes a DNS response from the PeerAPI DNS server to the
// App Connector to enable route discovery.
func (b *LocalBackend) ObserveDNSResponse(res []byte) {
func (b *LocalBackend) ObserveDNSResponse(res []byte) error {
var appConnector *appc.AppConnector
b.mu.Lock()
if b.appConnector == nil {
b.mu.Unlock()
return
return nil
}
appConnector = b.appConnector
b.mu.Unlock()
appConnector.ObserveDNSResponse(res)
return appConnector.ObserveDNSResponse(res)
}
// ErrDisallowedAutoRoute is returned by AdvertiseRoute when a route that is not allowed is requested.

8
ipn/ipnlocal/local_test.go
View File

@@ -1372,7 +1372,9 @@ func TestObserveDNSResponse(t *testing.T) {
b := newTestBackend(t)
// ensure no error when no app connector is configured
b.ObserveDNSResponse(dnsResponse("example.com.", "192.0.0.8"))
if err := b.ObserveDNSResponse(dnsResponse("example.com.", "192.0.0.8")); err != nil {
t.Errorf("ObserveDNSResponse: %v", err)
}
rc := &appctest.RouteCollector{}
if shouldStore {
@@ -1383,7 +1385,9 @@ func TestObserveDNSResponse(t *testing.T) {
b.appConnector.UpdateDomains([]string{"example.com"})
b.appConnector.Wait(context.Background())
b.ObserveDNSResponse(dnsResponse("example.com.", "192.0.0.8"))
if err := b.ObserveDNSResponse(dnsResponse("example.com.", "192.0.0.8")); err != nil {
t.Errorf("ObserveDNSResponse: %v", err)
}
b.appConnector.Wait(context.Background())
wantRoutes := []netip.Prefix{netip.MustParsePrefix("192.0.0.8/32")}
if !slices.Equal(rc.Routes(), wantRoutes) {

6
ipn/ipnlocal/peerapi.go
View File

@@ -932,7 +932,11 @@ func (h *peerAPIHandler) handleDNSQuery(w http.ResponseWriter, r *http.Request)
// instead to avoid re-parsing the DNS response for improved performance in
// the future.
if h.ps.b.OfferingAppConnector() {
h.ps.b.ObserveDNSResponse(res)
if err := h.ps.b.ObserveDNSResponse(res); err != nil {
h.logf("ObserveDNSResponse error: %v", err)
// This is not fatal, we probably just failed to parse the upstream
// response. Return it to the caller anyway.
}
}
if pretty {