Do not assume no DHCPv6 configurations

Do not assume that networks need any DHCPv6 configurations. Instead,
notify the NDP dispatcher in response to the first NDP RA's DHCPv6
flags, even if the flags indicate no DHCPv6 configurations are
available.

PiperOrigin-RevId: 310245068

1 files changed, 21 insertions, 3 deletions

diff --git a/pkg/tcpip/stack/ndp_test.go b/pkg/tcpip/stack/ndp_test.go
index 67f012840..b3d174cdd 100644
--- a/pkg/tcpip/stack/ndp_test.go
+++ b/pkg/tcpip/stack/ndp_test.go
@@ -4888,7 +4888,12 @@ func TestDHCPv6ConfigurationFromNDPDA(t *testing.T) {
 		}
 	}
 
-	// The initial DHCPv6 configuration should be stack.DHCPv6NoConfiguration.
+	// Even if the first RA reports no DHCPv6 configurations are available, the
+	// dispatcher should get an event.
+	e.InjectInbound(header.IPv6ProtocolNumber, raBufWithDHCPv6(llAddr2, false, false))
+	expectDHCPv6Event(stack.DHCPv6NoConfiguration)
+	// Receiving the same update again should not result in an event to the
+	// dispatcher.
 	e.InjectInbound(header.IPv6ProtocolNumber, raBufWithDHCPv6(llAddr2, false, false))
 	expectNoDHCPv6Event()
 
@@ -4896,8 +4901,6 @@ func TestDHCPv6ConfigurationFromNDPDA(t *testing.T) {
 	// Configurations.
 	e.InjectInbound(header.IPv6ProtocolNumber, raBufWithDHCPv6(llAddr2, false, true))
 	expectDHCPv6Event(stack.DHCPv6OtherConfigurations)
-	// Receiving the same update again should not result in an event to the
-	// NDPDispatcher.
 	e.InjectInbound(header.IPv6ProtocolNumber, raBufWithDHCPv6(llAddr2, false, true))
 	expectNoDHCPv6Event()
 
@@ -4933,6 +4936,21 @@ func TestDHCPv6ConfigurationFromNDPDA(t *testing.T) {
 	expectDHCPv6Event(stack.DHCPv6OtherConfigurations)
 	e.InjectInbound(header.IPv6ProtocolNumber, raBufWithDHCPv6(llAddr2, false, true))
 	expectNoDHCPv6Event()
+
+	// Cycling the NIC should cause the last DHCPv6 configuration to be cleared.
+	if err := s.DisableNIC(nicID); err != nil {
+		t.Fatalf("s.DisableNIC(%d): %s", nicID, err)
+	}
+	if err := s.EnableNIC(nicID); err != nil {
+		t.Fatalf("s.EnableNIC(%d): %s", nicID, err)
+	}
+
+	// Receive an RA that updates the DHCPv6 configuration to Other
+	// Configurations.
+	e.InjectInbound(header.IPv6ProtocolNumber, raBufWithDHCPv6(llAddr2, false, true))
+	expectDHCPv6Event(stack.DHCPv6OtherConfigurations)
+	e.InjectInbound(header.IPv6ProtocolNumber, raBufWithDHCPv6(llAddr2, false, true))
+	expectNoDHCPv6Event()
 }
 
 // TestRouterSolicitation tests the initial Router Solicitations that are sent