Do Duplicate Address Detection on permanent IPv6 addresses.

This change adds support for Duplicate Address Detection on IPv6 addresses
as defined by RFC 4862 section 5.4.

Note, this change will not break existing uses of netstack as the default
configuration for the stack options is set in such a way that DAD will not be
performed. See `stack.Options` and `stack.NDPConfigurations` for more details.

Tests: Tests to make sure that the DAD process properly resolves or fails.
That is, tests make sure that DAD resolves only if:
  - No other node is performing DAD for the same address
  - No other node owns the same address
PiperOrigin-RevId: 275189471

1 files changed, 61 insertions, 0 deletions

diff --git a/pkg/tcpip/checker/checker.go b/pkg/tcpip/checker/checker.go
index 096ad71ab..02137e1c9 100644
--- a/pkg/tcpip/checker/checker.go
+++ b/pkg/tcpip/checker/checker.go
@@ -686,3 +686,64 @@ func ICMPv6Code(want byte) TransportChecker {
 		}
 	}
 }
+
+// NDP creates a checker that checks that the packet contains a valid NDP
+// message for type of ty, with potentially additional checks specified by
+// checkers.
+//
+// checkers may assume that a valid ICMPv6 is passed to it containing a valid
+// NDP message as far as the size of the message (minSize) is concerned. The
+// values within the message are up to checkers to validate.
+func NDP(msgType header.ICMPv6Type, minSize int, checkers ...TransportChecker) NetworkChecker {
+	return func(t *testing.T, h []header.Network) {
+		t.Helper()
+
+		// Check normal ICMPv6 first.
+		ICMPv6(
+			ICMPv6Type(msgType),
+			ICMPv6Code(0))(t, h)
+
+		last := h[len(h)-1]
+
+		icmp := header.ICMPv6(last.Payload())
+		if got := len(icmp.NDPPayload()); got < minSize {
+			t.Fatalf("ICMPv6 NDP (type = %d) payload size of %d is less than the minimum size of %d", msgType, got, minSize)
+		}
+
+		for _, f := range checkers {
+			f(t, icmp)
+		}
+		if t.Failed() {
+			t.FailNow()
+		}
+	}
+}
+
+// NDPNS creates a checker that checks that the packet contains a valid NDP
+// Neighbor Solicitation message (as per the raw wire format), with potentially
+// additional checks specified by checkers.
+//
+// checkers may assume that a valid ICMPv6 is passed to it containing a valid
+// NDPNS message as far as the size of the messages concerned. The values within
+// the message are up to checkers to validate.
+func NDPNS(checkers ...TransportChecker) NetworkChecker {
+	return NDP(header.ICMPv6NeighborSolicit, header.NDPNSMinimumSize, checkers...)
+}
+
+// NDPNSTargetAddress creates a checker that checks the Target Address field of
+// a header.NDPNeighborSolicit.
+//
+// The returned TransportChecker assumes that a valid ICMPv6 is passed to it
+// containing a valid NDPNS message as far as the size is concerned.
+func NDPNSTargetAddress(want tcpip.Address) TransportChecker {
+	return func(t *testing.T, h header.Transport) {
+		t.Helper()
+
+		icmp := h.(header.ICMPv6)
+		ns := header.NDPNeighborSolicit(icmp.NDPPayload())
+
+		if got := ns.TargetAddress(); got != want {
+			t.Fatalf("got %T.TargetAddress = %s, want = %s", ns, got, want)
+		}
+	}
+}