Validate DAD configs when initializing DAD state

Make sure that the initial configurations used by the DAD state is
valid.

Before this change, an invalid DAD configuration (with a zero-valued
retransmit timer) was used so the DAD state would attempt to resolve
DAD immediately.

This lead to a deadlock in TestDADResolve as when DAD resolves, the
stack notifies the NDP dispatcher which would attempt to write to an
unbuffered channel while holding a lock. The test goroutine also
attempts to obtain a stack.Route (before receiving from the channel)
which ends up attempting to take the same lock.

Test: stack_test.TestDADResolve
PiperOrigin-RevId: 373888540

1 files changed, 8 insertions, 13 deletions

diff --git a/pkg/tcpip/stack/ndp_test.go b/pkg/tcpip/stack/ndp_test.go
index d4ac9e1f8..ac2fa777e 100644
--- a/pkg/tcpip/stack/ndp_test.go
+++ b/pkg/tcpip/stack/ndp_test.go
@@ -481,13 +481,9 @@ func TestDADResolve(t *testing.T) {
 	}
 
 	for _, test := range tests {
-		test := test
-
 		t.Run(test.name, func(t *testing.T) {
-			t.Parallel()
-
 			ndpDisp := ndpDispatcher{
-				dadC: make(chan ndpDADEvent),
+				dadC: make(chan ndpDADEvent, 1),
 			}
 
 			e := channelLinkWithHeaderLength{
@@ -499,7 +495,9 @@ func TestDADResolve(t *testing.T) {
 			var secureRNG bytes.Reader
 			secureRNG.Reset(secureRNGBytes)
 
+			clock := faketime.NewManualClock()
 			s := stack.New(stack.Options{
+				Clock:     clock,
 				SecureRNG: &secureRNG,
 				NetworkProtocols: []stack.NetworkProtocolFactory{ipv6.NewProtocolWithOptions(ipv6.Options{
 					NDPDisp: &ndpDisp,
@@ -529,14 +527,10 @@ func TestDADResolve(t *testing.T) {
 				t.Fatalf("AddAddressWithPrefix(%d, %d, %s) = %s", nicID, header.IPv6ProtocolNumber, addrWithPrefix, err)
 			}
 
-			// Address should not be considered bound to the NIC yet (DAD ongoing).
-			if err := checkGetMainNICAddress(s, nicID, header.IPv6ProtocolNumber, tcpip.AddressWithPrefix{}); err != nil {
-				t.Fatal(err)
-			}
-
 			// Make sure the address does not resolve before the resolution time has
 			// passed.
-			time.Sleep(test.expectedRetransmitTimer*time.Duration(test.dupAddrDetectTransmits) - defaultAsyncNegativeEventTimeout)
+			const delta = time.Nanosecond
+			clock.Advance(test.expectedRetransmitTimer*time.Duration(test.dupAddrDetectTransmits) - delta)
 			if err := checkGetMainNICAddress(s, nicID, header.IPv6ProtocolNumber, tcpip.AddressWithPrefix{}); err != nil {
 				t.Error(err)
 			}
@@ -566,13 +560,14 @@ func TestDADResolve(t *testing.T) {
 			}
 
 			// Wait for DAD to resolve.
+			clock.Advance(delta)
 			select {
-			case <-time.After(defaultAsyncPositiveEventTimeout):
-				t.Fatal("timed out waiting for DAD resolution")
 			case e := <-ndpDisp.dadC:
 				if diff := checkDADEvent(e, nicID, addr1, &stack.DADSucceeded{}); diff != "" {
 					t.Errorf("DAD event mismatch (-want +got):\n%s", diff)
 				}
+			default:
+				t.Fatalf("expected DAD event for %s on NIC(%d)", addr1, nicID)
 			}
 			if err := checkGetMainNICAddress(s, nicID, header.IPv6ProtocolNumber, addrWithPrefix); err != nil {
 				t.Error(err)