Inform NDPDispatcher when Stack learns about available configurations via DHCPv6

Inform the Stack's NDPDispatcher when it receives an NDP Router Advertisement
that updates the available configurations via DHCPv6. The Stack makes sure that
its NDPDispatcher isn't informed unless the avaiable configurations via DHCPv6
for a NIC is updated.

Tests: Test that a Stack's NDPDispatcher is informed when it receives an NDP
Router Advertisement that informs it of new configurations available via DHCPv6.
PiperOrigin-RevId: 289001283

1 files changed, 150 insertions, 15 deletions

diff --git a/pkg/tcpip/stack/ndp_test.go b/pkg/tcpip/stack/ndp_test.go
index fa84c94a6..108762b6e 100644
--- a/pkg/tcpip/stack/ndp_test.go
+++ b/pkg/tcpip/stack/ndp_test.go
@@ -162,18 +162,24 @@ type ndpRDNSSEvent struct {
 	rdnss ndpRDNSS
 }
 
+type ndpDHCPv6Event struct {
+	nicID         tcpip.NICID
+	configuration stack.DHCPv6ConfigurationFromNDPRA
+}
+
 var _ stack.NDPDispatcher = (*ndpDispatcher)(nil)
 
 // ndpDispatcher implements NDPDispatcher so tests can know when various NDP
 // related events happen for test purposes.
 type ndpDispatcher struct {
-	dadC           chan ndpDADEvent
-	routerC        chan ndpRouterEvent
-	rememberRouter bool
-	prefixC        chan ndpPrefixEvent
-	rememberPrefix bool
-	autoGenAddrC   chan ndpAutoGenAddrEvent
-	rdnssC         chan ndpRDNSSEvent
+	dadC                 chan ndpDADEvent
+	routerC              chan ndpRouterEvent
+	rememberRouter       bool
+	prefixC              chan ndpPrefixEvent
+	rememberPrefix       bool
+	autoGenAddrC         chan ndpAutoGenAddrEvent
+	rdnssC               chan ndpRDNSSEvent
+	dhcpv6ConfigurationC chan ndpDHCPv6Event
 }
 
 // Implements stack.NDPDispatcher.OnDuplicateAddressDetectionStatus.
@@ -280,6 +286,16 @@ func (n *ndpDispatcher) OnRecursiveDNSServerOption(nicID tcpip.NICID, addrs []tc
 	}
 }
 
+// Implements stack.NDPDispatcher.OnDHCPv6Configuration.
+func (n *ndpDispatcher) OnDHCPv6Configuration(nicID tcpip.NICID, configuration stack.DHCPv6ConfigurationFromNDPRA) {
+	if c := n.dhcpv6ConfigurationC; c != nil {
+		c <- ndpDHCPv6Event{
+			nicID,
+			configuration,
+		}
+	}
+}
+
 // TestDADResolve tests that an address successfully resolves after performing
 // DAD for various values of DupAddrDetectTransmits and RetransmitTimer.
 // Included in the subtests is a test to make sure that an invalid
@@ -870,21 +886,32 @@ func TestSetNDPConfigurations(t *testing.T) {
 	}
 }
 
-// raBufWithOpts returns a valid NDP Router Advertisement with options.
-//
-// Note, raBufWithOpts does not populate any of the RA fields other than the
-// Router Lifetime.
-func raBufWithOpts(ip tcpip.Address, rl uint16, optSer header.NDPOptionsSerializer) tcpip.PacketBuffer {
+// raBufWithOptsAndDHCPv6 returns a valid NDP Router Advertisement with options
+// and DHCPv6 configurations specified.
+func raBufWithOptsAndDHCPv6(ip tcpip.Address, rl uint16, managedAddress, otherConfigurations bool, optSer header.NDPOptionsSerializer) tcpip.PacketBuffer {
 	icmpSize := header.ICMPv6HeaderSize + header.NDPRAMinimumSize + int(optSer.Length())
 	hdr := buffer.NewPrependable(header.IPv6MinimumSize + icmpSize)
 	pkt := header.ICMPv6(hdr.Prepend(icmpSize))
 	pkt.SetType(header.ICMPv6RouterAdvert)
 	pkt.SetCode(0)
-	ra := header.NDPRouterAdvert(pkt.NDPPayload())
+	raPayload := pkt.NDPPayload()
+	ra := header.NDPRouterAdvert(raPayload)
+	// Populate the Router Lifetime.
+	binary.BigEndian.PutUint16(raPayload[2:], rl)
+	// Populate the Managed Address flag field.
+	if managedAddress {
+		// The Managed Addresses flag field is the 7th bit of byte #1 (0-indexing)
+		// of the RA payload.
+		raPayload[1] |= (1 << 7)
+	}
+	// Populate the Other Configurations flag field.
+	if otherConfigurations {
+		// The Other Configurations flag field is the 6th bit of byte #1
+		// (0-indexing) of the RA payload.
+		raPayload[1] |= (1 << 6)
+	}
 	opts := ra.Options()
 	opts.Serialize(optSer)
-	// Populate the Router Lifetime.
-	binary.BigEndian.PutUint16(pkt.NDPPayload()[2:], rl)
 	pkt.SetChecksum(header.ICMPv6Checksum(pkt, ip, header.IPv6AllNodesMulticastAddress, buffer.VectorisedView{}))
 	payloadLength := hdr.UsedLength()
 	iph := header.IPv6(hdr.Prepend(header.IPv6MinimumSize))
@@ -899,6 +926,23 @@ func raBufWithOpts(ip tcpip.Address, rl uint16, optSer header.NDPOptionsSerializ
 	return tcpip.PacketBuffer{Data: hdr.View().ToVectorisedView()}
 }
 
+// raBufWithOpts returns a valid NDP Router Advertisement with options.
+//
+// Note, raBufWithOpts does not populate any of the RA fields other than the
+// Router Lifetime.
+func raBufWithOpts(ip tcpip.Address, rl uint16, optSer header.NDPOptionsSerializer) tcpip.PacketBuffer {
+	return raBufWithOptsAndDHCPv6(ip, rl, false, false, optSer)
+}
+
+// raBufWithDHCPv6 returns a valid NDP Router Advertisement with DHCPv6 related
+// fields set.
+//
+// Note, raBufWithDHCPv6 does not populate any of the RA fields other than the
+// DHCPv6 related ones.
+func raBufWithDHCPv6(ip tcpip.Address, managedAddresses, otherConfiguratiosns bool) tcpip.PacketBuffer {
+	return raBufWithOptsAndDHCPv6(ip, 0, managedAddresses, otherConfiguratiosns, header.NDPOptionsSerializer{})
+}
+
 // raBuf returns a valid NDP Router Advertisement.
 //
 // Note, raBuf does not populate any of the RA fields other than the
@@ -3024,3 +3068,94 @@ func TestCleanupHostOnlyStateOnBecomingRouter(t *testing.T) {
 	default:
 	}
 }
+
+// TestDHCPv6ConfigurationFromNDPDA tests that the NDPDispatcher is properly
+// informed when new information about what configurations are available via
+// DHCPv6 is learned.
+func TestDHCPv6ConfigurationFromNDPDA(t *testing.T) {
+	const nicID = 1
+
+	ndpDisp := ndpDispatcher{
+		dhcpv6ConfigurationC: make(chan ndpDHCPv6Event, 1),
+		rememberRouter:       true,
+	}
+	e := channel.New(0, 1280, linkAddr1)
+	s := stack.New(stack.Options{
+		NetworkProtocols: []stack.NetworkProtocol{ipv6.NewProtocol()},
+		NDPConfigs: stack.NDPConfigurations{
+			HandleRAs: true,
+		},
+		NDPDisp: &ndpDisp,
+	})
+
+	if err := s.CreateNIC(nicID, e); err != nil {
+		t.Fatalf("CreateNIC(%d, _) = %s", nicID, err)
+	}
+
+	expectDHCPv6Event := func(configuration stack.DHCPv6ConfigurationFromNDPRA) {
+		t.Helper()
+		select {
+		case e := <-ndpDisp.dhcpv6ConfigurationC:
+			if diff := cmp.Diff(ndpDHCPv6Event{nicID: nicID, configuration: configuration}, e, cmp.AllowUnexported(e)); diff != "" {
+				t.Errorf("dhcpv6 event mismatch (-want +got):\n%s", diff)
+			}
+		default:
+			t.Fatal("expected DHCPv6 configuration event")
+		}
+	}
+
+	expectNoDHCPv6Event := func() {
+		t.Helper()
+		select {
+		case <-ndpDisp.dhcpv6ConfigurationC:
+			t.Fatal("unexpected DHCPv6 configuration event")
+		default:
+		}
+	}
+
+	// The initial DHCPv6 configuration should be stack.DHCPv6NoConfiguration.
+	e.InjectInbound(header.IPv6ProtocolNumber, raBufWithDHCPv6(llAddr2, false, false))
+	expectNoDHCPv6Event()
+
+	// Receive an RA that updates the DHCPv6 configuration to Other
+	// 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()
+
+	// Receive an RA that updates the DHCPv6 configuration to Managed Address.
+	e.InjectInbound(header.IPv6ProtocolNumber, raBufWithDHCPv6(llAddr2, true, false))
+	expectDHCPv6Event(stack.DHCPv6ManagedAddress)
+	e.InjectInbound(header.IPv6ProtocolNumber, raBufWithDHCPv6(llAddr2, true, false))
+	expectNoDHCPv6Event()
+
+	// Receive an RA that updates the DHCPv6 configuration to none.
+	e.InjectInbound(header.IPv6ProtocolNumber, raBufWithDHCPv6(llAddr2, false, false))
+	expectDHCPv6Event(stack.DHCPv6NoConfiguration)
+	e.InjectInbound(header.IPv6ProtocolNumber, raBufWithDHCPv6(llAddr2, false, false))
+	expectNoDHCPv6Event()
+
+	// Receive an RA that updates the DHCPv6 configuration to Managed Address.
+	//
+	// Note, when the M flag is set, the O flag is redundant.
+	e.InjectInbound(header.IPv6ProtocolNumber, raBufWithDHCPv6(llAddr2, true, true))
+	expectDHCPv6Event(stack.DHCPv6ManagedAddress)
+	e.InjectInbound(header.IPv6ProtocolNumber, raBufWithDHCPv6(llAddr2, true, true))
+	expectNoDHCPv6Event()
+	// Even though the DHCPv6 flags are different, the effective configuration is
+	// the same so we should not receive a new event.
+	e.InjectInbound(header.IPv6ProtocolNumber, raBufWithDHCPv6(llAddr2, true, false))
+	expectNoDHCPv6Event()
+	e.InjectInbound(header.IPv6ProtocolNumber, raBufWithDHCPv6(llAddr2, true, true))
+	expectNoDHCPv6Event()
+
+	// 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()
+}