Don't ignore override if it is longer than layerStates

PiperOrigin-RevId: 307708653

test/packetimpact/testbench/connections.go

@@ -363,16 +363,33 @@ type Connection struct {
 // reverse is never a match. override overrides the default matchers for each
 // Layer.
 func (conn *Connection) match(override, received Layers) bool {
-	if len(received) < len(conn.layerStates) {
+	var layersToMatch int
+	if len(override) < len(conn.layerStates) {
+		layersToMatch = len(conn.layerStates)
+	} else {
+		layersToMatch = len(override)
+	}
+	if len(received) < layersToMatch {
 		return false
 	}
-	for i, s := range conn.layerStates {
-		toMatch := s.incoming(received[i])
-		if toMatch == nil {
-			return false
-		}
-		if i < len(override) {
-			toMatch.merge(override[i])
+	for i := 0; i < layersToMatch; i++ {
+		var toMatch Layer
+		if i < len(conn.layerStates) {
+			s := conn.layerStates[i]
+			toMatch = s.incoming(received[i])
+			if toMatch == nil {
+				return false
+			}
+			if i < len(override) {
+				if err := toMatch.merge(override[i]); err != nil {
+					conn.t.Fatalf("failed to merge: %s", err)
+				}
+			}
+		} else {
+			toMatch = override[i]
+			if toMatch == nil {
+				conn.t.Fatalf("expect the overriding layers to be non-nil")
+			}
 		}
 		if !toMatch.match(received[i]) {
 			return false

test/packetimpact/testbench/layers_test.go

@@ -154,3 +154,53 @@ func TestLayerStringFormat(t *testing.T) {
 		})
 	}
 }
+
+func TestConnectionMatch(t *testing.T) {
+	conn := Connection{
+		layerStates: []layerState{&etherState{}},
+	}
+	protoNum0 := tcpip.NetworkProtocolNumber(0)
+	protoNum1 := tcpip.NetworkProtocolNumber(1)
+	for _, tt := range []struct {
+		description        string
+		override, received Layers
+		wantMatch          bool
+	}{
+		{
+			description: "shorter override",
+			override:    []Layer{&Ether{}},
+			received:    []Layer{&Ether{}, &Payload{Bytes: []byte("hello")}},
+			wantMatch:   true,
+		},
+		{
+			description: "longer override",
+			override:    []Layer{&Ether{}, &Payload{Bytes: []byte("hello")}},
+			received:    []Layer{&Ether{}},
+			wantMatch:   false,
+		},
+		{
+			description: "ether layer mismatch",
+			override:    []Layer{&Ether{Type: &protoNum0}},
+			received:    []Layer{&Ether{Type: &protoNum1}},
+			wantMatch:   false,
+		},
+		{
+			description: "both nil",
+			override:    nil,
+			received:    nil,
+			wantMatch:   false,
+		},
+		{
+			description: "nil override",
+			override:    nil,
+			received:    []Layer{&Ether{}},
+			wantMatch:   true,
+		},
+	} {
+		t.Run(tt.description, func(t *testing.T) {
+			if gotMatch := conn.match(tt.override, tt.received); gotMatch != tt.wantMatch {
+				t.Fatalf("conn.match(%s, %s) = %t, want %t", tt.override, tt.received, gotMatch, tt.wantMatch)
+			}
+		})
+	}
+}