Make ipv6 test contexts consistent with ipv4

- Return by value rather than by pointer
- buildRoute takes *testing.T as its first argument

Updates #6910.

PiperOrigin-RevId: 429400727

pkg/tcpip/network/ipv6/icmp_test.go

@@ -201,13 +201,13 @@ type testContext struct {
 	s *stack.Stack
 }
 
-func newTestContext(clock tcpip.Clock) *testContext {
+func newTestContext(clock tcpip.Clock) testContext {
 	s := stack.New(stack.Options{
 		NetworkProtocols:   []stack.NetworkProtocolFactory{NewProtocol},
 		TransportProtocols: []stack.TransportProtocolFactory{icmp.NewProtocol6, udp.NewProtocol},
 		Clock:              clock,
 	})
-	return &testContext{s: s}
+	return testContext{s: s}
 }
 
 func (c *testContext) cleanup() {
@@ -409,7 +409,7 @@ func (e endpointWithResolutionCapability) Capabilities() stack.LinkEndpointCapab
 	return e.LinkEndpoint.Capabilities() | stack.CapabilityResolutionRequired
 }
 
-func newMultiStackTestContext(t *testing.T) *multiStackTestContext {
+func newMultiStackTestContext(t *testing.T) multiStackTestContext {
 	clock := faketime.NewManualClock()
 	s0 := stack.New(stack.Options{
 		NetworkProtocols:   []stack.NetworkProtocolFactory{NewProtocol},
@@ -421,7 +421,7 @@ func newMultiStackTestContext(t *testing.T) *multiStackTestContext {
 		TransportProtocols: []stack.TransportProtocolFactory{icmp.NewProtocol6},
 		Clock:              clock,
 	})
-	c := &multiStackTestContext{
+	c := multiStackTestContext{
 		s0:    s0,
 		s1:    s1,
 		clock: clock,

pkg/tcpip/network/ipv6/ipv6_test.go

@@ -2605,7 +2605,7 @@ func TestWriteStats(t *testing.T) {
 			ep := iptestutil.NewMockLinkEndpoint(header.IPv6MinimumMTU, &tcpip.ErrInvalidEndpointState{}, test.allowPackets)
 			defer ep.Close()
 
-			rt := buildRoute(c, t, ep)
+			rt := buildRoute(t, c, ep)
 			test.setup(t, rt.Stack())
 
 			nWritten := 0
@@ -2638,7 +2638,7 @@ func TestWriteStats(t *testing.T) {
 	}
 }
 
-func buildRoute(c *testContext, t *testing.T, ep stack.LinkEndpoint) *stack.Route {
+func buildRoute(t *testing.T, c testContext, ep stack.LinkEndpoint) *stack.Route {
 	s := c.s
 	if err := s.CreateNIC(1, ep); err != nil {
 		t.Fatalf("CreateNIC(1, _) failed: %s", err)
@@ -2813,7 +2813,7 @@ func TestFragmentationWritePacket(t *testing.T) {
 			ep := iptestutil.NewMockLinkEndpoint(ft.mtu, nil, math.MaxInt32)
 			defer ep.Close()
 
-			r := buildRoute(c, t, ep)
+			r := buildRoute(t, c, ep)
 			err := r.WritePacket(stack.NetworkHeaderParams{
 				Protocol: tcp.ProtocolNumber,
 				TTL:      ttl,
@@ -2915,7 +2915,7 @@ func TestFragmentationErrors(t *testing.T) {
 			ep := iptestutil.NewMockLinkEndpoint(ft.mtu, ft.mockError, ft.allowPackets)
 			defer ep.Close()
 
-			r := buildRoute(c, t, ep)
+			r := buildRoute(t, c, ep)
 			err := r.WritePacket(stack.NetworkHeaderParams{
 				Protocol: tcp.ProtocolNumber,
 				TTL:      ttl,

pkg/tcpip/network/ipv6/mld_test.go

@@ -69,7 +69,7 @@ func (c *mldTestContext) cleanup() {
 	c.s.Wait()
 }
 
-func newMLDTestContext() *mldTestContext {
+func newMLDTestContext() mldTestContext {
 	s := stack.New(stack.Options{
 		NetworkProtocols: []stack.NetworkProtocolFactory{ipv6.NewProtocolWithOptions(ipv6.Options{
 			MLD: ipv6.MLDOptions{
@@ -77,7 +77,7 @@ func newMLDTestContext() *mldTestContext {
 			},
 		})},
 	})
-	return &mldTestContext{s: s}
+	return mldTestContext{s: s}
 }
 
 func TestIPv6JoinLeaveSolicitedNodeAddressPerformsMLD(t *testing.T) {