report: move synthetic ALIAS hop from collector to report view

checker/collect.go

@@ -400,12 +400,6 @@ func observeApex(ctx context.Context, data *AliasData, servers []string, apex st
 
 	if (hasA || hasAAAA) && !data.ApexHasCNAME {
 		data.ApexFlattening = true
-		// Synthesize a pseudo-hop so the report's chain view shows the ALIAS
-		// indirection that would otherwise be invisible from the wire.
-		data.Chain = append(data.Chain, ChainHop{
-			Owner: lowerFQDN(apex),
-			Kind:  KindALIAS,
-		})
 	}
 }
 

checker/report.go

@@ -104,7 +104,15 @@ func buildReportView(data *AliasData, states []sdk.CheckState) *reportView {
 	v.FinalAddresses = append(v.FinalAddresses, data.FinalA...)
 	v.FinalAddresses = append(v.FinalAddresses, data.FinalAAAA...)
 
-	for i, h := range data.Chain {
+	chain := data.Chain
+	if data.ApexFlattening {
+		chain = append(chain, ChainHop{
+			Owner: data.Apex,
+			Kind:  KindALIAS,
+		})
+	}
+
+	for i, h := range chain {
 		step := chainStep{
 			Index:  i + 1,
 			Owner:  h.Owner,
@@ -112,7 +120,7 @@ func buildReportView(data *AliasData, states []sdk.CheckState) *reportView {
 			Target: h.Target,
 			TTL:    h.TTL,
 			Server: h.Server,
-			IsLast: i == len(data.Chain)-1,
+			IsLast: i == len(chain)-1,
 		}
 		switch h.Kind {
 		case KindCNAME:

checker/rules_chain.go

@@ -189,24 +189,10 @@ type targetResolvableRule struct{}
 
 func (targetResolvableRule) Name() string { return "target_resolvable" }
 func (targetResolvableRule) Description() string {
-	return "Verifies that the final target of the alias chain publishes at least one A or AAAA record."
+	return "Verifies that the final target of the alias chain exists in DNS (returns NOERROR, not NXDOMAIN)."
 }
 
-func (targetResolvableRule) Options() sdk.CheckerOptionsDocumentation {
+func (targetResolvableRule) Evaluate(ctx context.Context, obs sdk.ObservationGetter, _ sdk.CheckerOptions) []sdk.CheckState {
-	return sdk.CheckerOptionsDocumentation{
-		UserOpts: []sdk.CheckerOptionDocumentation{
-			{
-				Id:          "requireResolvableTarget",
-				Type:        "bool",
-				Label:       "Require resolvable target",
-				Description: "When enabled, a chain whose final target returns no A/AAAA is reported as critical (otherwise a warning).",
-				Default:     defaultRequireResolvableTarget,
-			},
-		},
-	}
-}
-
-func (targetResolvableRule) Evaluate(ctx context.Context, obs sdk.ObservationGetter, opts sdk.CheckerOptions) []sdk.CheckState {
 	data, errState := loadAlias(ctx, obs)
 	if errState != nil {
 		return errState
@@ -217,22 +203,14 @@ func (targetResolvableRule) Evaluate(ctx context.Context, obs sdk.ObservationGet
 	if data.ChainTerminated.Reason != TermOK {
 		return skipped("chain did not terminate normally")
 	}
-	if len(data.FinalA) > 0 || len(data.FinalAAAA) > 0 {
+	if data.FinalRcode != "NXDOMAIN" {
-		return okState(data.FinalTarget, fmt.Sprintf("target %s resolves to %d address(es)", data.FinalTarget, len(data.FinalA)+len(data.FinalAAAA)))
+		return okState(data.FinalTarget, fmt.Sprintf("target %s exists in DNS", data.FinalTarget))
-	}
-	status := sdk.StatusWarn
-	if sdk.GetBoolOption(opts, "requireResolvableTarget", defaultRequireResolvableTarget) {
-		status = sdk.StatusCrit
-	}
-	rcode := data.FinalRcode
-	if rcode == "" {
-		rcode = "no A/AAAA"
 	}
 	return []sdk.CheckState{withHint(sdk.CheckState{
-		Status:  status,
+		Status:  sdk.StatusCrit,
 		Subject: data.FinalTarget,
-		Message: fmt.Sprintf("final target %s does not resolve to an address (%s)", data.FinalTarget, rcode),
+		Message: fmt.Sprintf("final target %s does not exist (NXDOMAIN)", data.FinalTarget),
-	}, "Point the alias at a name that publishes at least one A or AAAA record, or fix the upstream zone.")}
+	}, "The alias points at a name that does not exist; create the missing record or update the alias target.")}
 }
 
 type multipleRecordsRule struct{}

checker/rules_common.go

@@ -11,7 +11,6 @@ import (
 const (
 	defaultMaxChainLength = 8
 	defaultMinTargetTTL   = 60
-	defaultRequireResolvableTarget = true
 	defaultAllowApexCNAME = false
 	defaultRecognizeApexFlattening = true
 

checker/rules_test.go

@@ -290,24 +290,25 @@ func TestCnameDnssecRule(t *testing.T) {
 }
 
 func TestTargetResolvableRule(t *testing.T) {
-	t.Run("ok", func(t *testing.T) {
+	t.Run("ok when NOERROR with A record", func(t *testing.T) {
 		d := apexKnownData()
 		d.ChainTerminated.Reason = TermOK
 		d.FinalTarget = "target."
 		d.FinalA = []string{"1.2.3.4"}
 		assertSingle(t, run(targetResolvableRule{}, d, nil), sdk.StatusOK)
 	})
-	t.Run("crit by default", func(t *testing.T) {
+	t.Run("ok when NOERROR with no A/AAAA (e.g. service label)", func(t *testing.T) {
 		d := apexKnownData()
 		d.ChainTerminated.Reason = TermOK
-		d.FinalTarget = "target."
+		d.FinalTarget = "_2772._tcp.znc.example."
-		assertSingle(t, run(targetResolvableRule{}, d, nil), sdk.StatusCrit)
+		assertSingle(t, run(targetResolvableRule{}, d, nil), sdk.StatusOK)
 	})
-	t.Run("warn when requireResolvableTarget=false", func(t *testing.T) {
+	t.Run("crit when NXDOMAIN", func(t *testing.T) {
 		d := apexKnownData()
 		d.ChainTerminated.Reason = TermOK
 		d.FinalTarget = "target."
-		assertSingle(t, run(targetResolvableRule{}, d, sdk.CheckerOptions{"requireResolvableTarget": false}), sdk.StatusWarn)
+		d.FinalRcode = "NXDOMAIN"
+		assertSingle(t, run(targetResolvableRule{}, d, nil), sdk.StatusCrit)
 	})
 	t.Run("skip when chain did not terminate normally", func(t *testing.T) {
 		d := apexKnownData()