Remove NICs before closing their link endpoints

...in IPv6 ICMP tests.

A channel link endpoint's channel is closed when the link endpoint is
closed.

When the stack tries to send packets through a NIC with a closed channel
endpoint, a panic will occur when attempting to write to a closed
channel (https://golang.org/ref/spec#Close). To make sure the stack does
not try to send packets through a NIC, we remove it.

PiperOrigin-RevId: 354822085

pkg/tcpip/network/ipv6/icmp_test.go

@@ -492,6 +492,8 @@ func visitStats(v reflect.Value, f func(string, *tcpip.StatCounter)) {
 }
 
 type testContext struct {
+	t *testing.T
+
 	s0 *stack.Stack
 	s1 *stack.Stack
 
@@ -509,6 +511,8 @@ func (e endpointWithResolutionCapability) Capabilities() stack.LinkEndpointCapab
 
 func newTestContext(t *testing.T) *testContext {
 	c := &testContext{
+		t: t,
+
 		s0: stack.New(stack.Options{
 			NetworkProtocols:   []stack.NetworkProtocolFactory{NewProtocol},
 			TransportProtocols: []stack.TransportProtocolFactory{icmp.NewProtocol6},
@@ -562,10 +566,19 @@ func newTestContext(t *testing.T) *testContext {
 		}},
 	)
 
+	t.Cleanup(c.cleanup)
+
 	return c
 }
 
 func (c *testContext) cleanup() {
+	if err := c.s0.RemoveNIC(nicID); err != nil {
+		c.t.Errorf("c.s0.RemoveNIC(%d): %s", nicID, err)
+	}
+	if err := c.s1.RemoveNIC(nicID); err != nil {
+		c.t.Errorf("c.s1.RemoveNIC(%d): %s", nicID, err)
+	}
+
 	c.linkEP0.Close()
 	c.linkEP1.Close()
 }
@@ -617,7 +630,6 @@ func routeICMPv6Packet(t *testing.T, args routeArgs, fn func(*testing.T, header.
 
 func TestLinkResolution(t *testing.T) {
 	c := newTestContext(t)
-	defer c.cleanup()
 
 	r, err := c.s0.FindRoute(nicID, lladdr0, lladdr1, ProtocolNumber, false /* multicastLoop */)
 	if err != nil {