Fix not setting AddressDispatcher on promotion

AddressDispatcher was being set when adding an address only for new
addresses, resulting in cases such as when an expired addresses is
re-added to lose the AddressDispatcher that is passed.

Added a regression test.

PiperOrigin-RevId: 494220872

pkg/tcpip/stack/addressable_endpoint_state.go

@@ -271,7 +271,6 @@ func (a *AddressableEndpointState) addAndAcquireAddressLocked(addr tcpip.Address
 		// We never promote an address to temporary - it can only be added as such.
 		// If we are actually adding a permanent address, it is promoted below.
 		addrState.kind = Temporary
-		addrState.disp = properties.Disp
 	}
 
 	// At this point we have an address we are either promoting from an expired or
@@ -295,6 +294,7 @@ func (a *AddressableEndpointState) addAndAcquireAddressLocked(addr tcpip.Address
 	lifetimes := properties.Lifetimes
 	lifetimes.sanitize()
 	addrState.lifetimes = lifetimes
+	addrState.disp = properties.Disp
 
 	if attemptAddToPrimary {
 		switch properties.PEB {

pkg/tcpip/stack/addressable_endpoint_state_test.go

@@ -60,3 +60,47 @@ func TestAddressableEndpointStateCleanup(t *testing.T) {
 		t.Fatalf("got s.AcquireAssignedAddress(%s, false, NeverPrimaryEndpoint) = %s, want = nil", addr.Address, ep.AddressWithPrefix())
 	}
 }
+
+func TestAddressDispatcherExpiredToAssigned(t *testing.T) {
+	var networkEp fakeNetworkEndpoint
+	if err := networkEp.Enable(); err != nil {
+		t.Fatalf("ep.Enable(): %s", err)
+	}
+
+	var s stack.AddressableEndpointState
+	s.Init(&networkEp, stack.AddressableEndpointStateOptions{HiddenWhileDisabled: false})
+
+	addr := tcpip.AddressWithPrefix{
+		Address:   "\x01",
+		PrefixLen: 8,
+	}
+
+	ep, err := s.AddAndAcquirePermanentAddress(addr, stack.AddressProperties{})
+	if err != nil {
+		t.Fatalf("s.AddAndAcquirePermanentAddress(%s, {}): %s", addr, err)
+	}
+	defer ep.DecRef()
+	if !ep.IncRef() {
+		t.Fatalf("failed to increase ref count of address endpoint")
+	}
+
+	if err := s.RemovePermanentEndpoint(ep, stack.AddressRemovalManualAction); err != nil {
+		ep.DecRef()
+		t.Fatalf("s.RemovePermanentEndpoint(ep, stack.AddressRemovalManualAction): %s", err)
+	}
+
+	addrDisp := &addressDispatcher{
+		changedCh: make(chan addressChangedEvent, 1),
+		removedCh: make(chan stack.AddressRemovalReason, 1),
+		addr:      addr,
+	}
+	properties := stack.AddressProperties{Disp: addrDisp}
+	readdedEp, err := s.AddAndAcquirePermanentAddress(addr, properties)
+	if err != nil {
+		t.Fatalf("s.AddAndAcquirePermanentAddress(%s, %+v): %s", addr, properties, err)
+	}
+	defer readdedEp.DecRef()
+	if err := addrDisp.expectChanged(stack.AddressLifetimes{}, stack.AddressAssigned); err != nil {
+		t.Fatalf("expect to observe address added: %s", err)
+	}
+}