client: fix typo

internal/client/index.go

@@ -197,9 +197,10 @@ func (ci *Index) findByIP(ip netip.Addr) (c *Persistent, found bool) {
 		return ci.uidToClient[uid], true
 	}
 
+	ipWithoutZone := ip.WithZone("")
 	ci.subnetToUID.Range(func(pref netip.Prefix, id UID) (cont bool) {
-		// Remove zone before checking because prefixes stip zones.
-		if pref.Contains(ip.WithZone("")) {
+		// Remove zone before checking because prefixes strip zones.
+		if pref.Contains(ipWithoutZone) {
 			uid, found = id, true
 
 			return false
@@ -218,6 +219,9 @@ func (ci *Index) findByIP(ip netip.Addr) (c *Persistent, found bool) {
 // FindByIPWithoutZone finds a persistent client by IP address without zone.  It
 // strips the IPv6 zone index from the stored IP addresses before comparing,
 // because querylog entries don't have it.  See TODO on [querylog.logEntry.IP].
+//
+// Note that multiple clients can have same the IP address with different zones,
+// so result of this method is indeterminate.
 func (ci *Index) FindByIPWithoutZone(ip netip.Addr) (c *Persistent) {
 	if (ip == netip.Addr{}) {
 		return nil

internal/client/index_internal_test.go

@@ -292,13 +292,6 @@ func TestIndex_FindByIPWithoutZone(t *testing.T) {
 	for _, tc := range testCases {
 		t.Run(tc.name, func(t *testing.T) {
 			c := ci.FindByIPWithoutZone(tc.ip.WithZone(""))
-
-			if tc.want == nil {
-				require.Nil(t, c)
-
-				return
-			}
-
 			require.Equal(t, tc.want, c)
 		})
 	}