Sort numeric labels by value

Records, zones and findings now order all-digit labels numerically, so
reverse zones list 2 before 101. model.CanonicalLess is replaced by
model.NameLess; other labels keep byte order.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

internal/model/blocking.go

@@ -204,7 +204,7 @@ func (s *State) SortedBlockRules() []*BlockRule {
 	sort.Slice(out, func(i, j int) bool {
 		a, b := out[i], out[j]
 		if a.Name != b.Name {
-			return CanonicalLess(a.Name+".", b.Name+".")
+			return NameLess(a.Name+".", b.Name+".")
 		}
 		if a.Exact != b.Exact {
 			return !a.Exact

internal/model/model.go

@@ -524,14 +524,14 @@ func (s *State) SortedZones() []*Zone {
 		if pi, pj := pos[out[i].ViewID], pos[out[j].ViewID]; pi != pj {
 			return pi < pj
 		}
-		return CanonicalLess(out[i].Name, out[j].Name)
+		return NameLess(out[i].Name, out[j].Name)
 	})
 	return out
 }
 
-// SortZones sorts zones by name in DNS canonical order.
+// SortZones sorts zones by name (see NameLess).
 func SortZones(zs []*Zone) {
-	sort.Slice(zs, func(i, j int) bool { return CanonicalLess(zs[i].Name, zs[j].Name) })
+	sort.Slice(zs, func(i, j int) bool { return NameLess(zs[i].Name, zs[j].Name) })
 }
 
 // FindZone finds a zone by name within a view (viewID 0 for no view).
@@ -646,7 +646,7 @@ func typeOrder(t string) string {
 }
 
 // SortRecords sorts records in zone-file order: apex first, then names in
-// DNS canonical order (so subdomains group together), then by type and
+// NameLess order (so subdomains group together), then by type and
 // data.
 func SortRecords(rs []*Record, z *Zone) {
 	apex := ""
@@ -662,7 +662,7 @@ func SortRecords(rs []*Record, z *Zone) {
 			if b.Name == apex {
 				return false
 			}
-			return CanonicalLess(a.Name, b.Name)
+			return NameLess(a.Name, b.Name)
 		}
 		if a.Type != b.Type {
 			return typeOrder(a.Type) < typeOrder(b.Type)
@@ -674,19 +674,50 @@ func SortRecords(rs []*Record, z *Zone) {
 	})
 }
 
-// CanonicalLess compares names in DNS canonical order (RFC 4034 section
-// 6.1): by label from the right.
-func CanonicalLess(a, b string) bool {
+// NameLess compares names label by label from the right, like DNS
+// canonical order (RFC 4034 section 6.1), except that two all-digit
+// labels compare as numbers, so 2.10.0.10.in-addr.arpa comes before
+// 101.10.0.10.in-addr.arpa. It orders names for people and zone files;
+// BIND does its own canonical ordering where DNSSEC needs it.
+func NameLess(a, b string) bool {
 	la := strings.Split(strings.TrimSuffix(a, "."), ".")
 	lb := strings.Split(strings.TrimSuffix(b, "."), ".")
 	for i, j := len(la)-1, len(lb)-1; i >= 0 && j >= 0; i, j = i-1, j-1 {
-		if la[i] != lb[j] {
-			return la[i] < lb[j]
+		if c := compareLabel(la[i], lb[j]); c != 0 {
+			return c < 0
 		}
 	}
 	return len(la) < len(lb)
 }
 
+func compareLabel(a, b string) int {
+	if a == b {
+		return 0
+	}
+	if allDigits(a) && allDigits(b) {
+		na, nb := strings.TrimLeft(a, "0"), strings.TrimLeft(b, "0")
+		if len(na) != len(nb) {
+			return len(na) - len(nb)
+		}
+		if c := strings.Compare(na, nb); c != 0 {
+			return c
+		}
+	}
+	return strings.Compare(a, b)
+}
+
+func allDigits(s string) bool {
+	if s == "" {
+		return false
+	}
+	for i := 0; i < len(s); i++ {
+		if s[i] < '0' || s[i] > '9' {
+			return false
+		}
+	}
+	return true
+}
+
 // RRSetKey identifies an RRset.
 type RRSetKey struct {
 	Name string

internal/model/nameorder_test.go

@@ -0,0 +1,42 @@
+package model
+
+import (
+	"slices"
+	"testing"
+)
+
+func TestNameLess(t *testing.T) {
+	want := []string{
+		"10.0.10.in-addr.arpa.",
+		"1.10.0.10.in-addr.arpa.",
+		"02.10.0.10.in-addr.arpa.",
+		"2.10.0.10.in-addr.arpa.",
+		"10.10.0.10.in-addr.arpa.",
+		"101.10.0.10.in-addr.arpa.",
+		"x.101.10.0.10.in-addr.arpa.",
+		"254.10.0.10.in-addr.arpa.",
+		"a.10.0.10.in-addr.arpa.",
+	}
+	got := slices.Clone(want)
+	slices.Reverse(got)
+	slices.SortFunc(got, func(a, b string) int {
+		if NameLess(a, b) {
+			return -1
+		}
+		if NameLess(b, a) {
+			return 1
+		}
+		return 0
+	})
+	if !slices.Equal(got, want) {
+		t.Fatalf("got %v\nwant %v", got, want)
+	}
+
+	// Non-numeric labels keep canonical (byte) order.
+	if !NameLess("host10.example.", "host2.example.") {
+		t.Error("host10 should sort before host2")
+	}
+	if !NameLess("example.", "www.example.") {
+		t.Error("parent should sort before child")
+	}
+}