Do not perform MLD for certain multicast scopes

...as per RFC 2710 section 5 page 10.

Test: ipv6_test.TestMLDSkipProtocol
PiperOrigin-RevId: 367031126

2 files changed, 157 insertions, 1 deletions

diff --git a/pkg/tcpip/network/ipv6/mld.go b/pkg/tcpip/network/ipv6/mld.go
index dd153466d..538590baf 100644
--- a/pkg/tcpip/network/ipv6/mld.go
+++ b/pkg/tcpip/network/ipv6/mld.go
@@ -80,6 +80,25 @@ func (mld *mldState) SendLeave(groupAddress tcpip.Address) tcpip.Error {
 	return err
 }
 
+// ShouldPerformProtocol implements ip.MulticastGroupProtocol.
+func (mld *mldState) ShouldPerformProtocol(groupAddress tcpip.Address) bool {
+	// As per RFC 2710 section 5 page 10,
+	//
+	//   The link-scope all-nodes address (FF02::1) is handled as a special
+	//   case. The node starts in Idle Listener state for that address on
+	//   every interface, never transitions to another state, and never sends
+	//   a Report or Done for that address.
+	//
+	//   MLD messages are never sent for multicast addresses whose scope is 0
+	//   (reserved) or 1 (node-local).
+	if groupAddress == header.IPv6AllNodesMulticastAddress {
+		return false
+	}
+
+	scope := header.V6MulticastScope(groupAddress)
+	return scope != header.IPv6Reserved0MulticastScope && scope != header.IPv6InterfaceLocalMulticastScope
+}
+
 // init sets up an mldState struct, and is required to be called before using
 // a new mldState.
 //
@@ -91,7 +110,6 @@ func (mld *mldState) init(ep *endpoint) {
 		Clock:                     ep.protocol.stack.Clock(),
 		Protocol:                  mld,
 		MaxUnsolicitedReportDelay: UnsolicitedReportIntervalMax,
-		AllNodesAddress:           header.IPv6AllNodesMulticastAddress,
 	})
 }
 
diff --git a/pkg/tcpip/network/ipv6/mld_test.go b/pkg/tcpip/network/ipv6/mld_test.go
index 85a8f9944..1e611aca1 100644
--- a/pkg/tcpip/network/ipv6/mld_test.go
+++ b/pkg/tcpip/network/ipv6/mld_test.go
@@ -464,3 +464,141 @@ func TestMLDPacketValidation(t *testing.T) {
 		})
 	}
 }
+
+func TestMLDSkipProtocol(t *testing.T) {
+	const nicID = 1
+
+	tests := []struct {
+		name         string
+		group        tcpip.Address
+		expectReport bool
+	}{
+		{
+			name:         "Reserverd0",
+			group:        "\xff\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x11",
+			expectReport: false,
+		},
+		{
+			name:         "Interface Local",
+			group:        "\xff\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x11",
+			expectReport: false,
+		},
+		{
+			name:         "Link Local",
+			group:        "\xff\x02\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x11",
+			expectReport: true,
+		},
+		{
+			name:         "Realm Local",
+			group:        "\xff\x03\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x11",
+			expectReport: true,
+		},
+		{
+			name:         "Admin Local",
+			group:        "\xff\x04\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x11",
+			expectReport: true,
+		},
+		{
+			name:         "Site Local",
+			group:        "\xff\x05\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x11",
+			expectReport: true,
+		},
+		{
+			name:         "Unassigned(6)",
+			group:        "\xff\x06\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x11",
+			expectReport: true,
+		},
+		{
+			name:         "Unassigned(7)",
+			group:        "\xff\x07\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x11",
+			expectReport: true,
+		},
+		{
+			name:         "Organization Local",
+			group:        "\xff\x08\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x11",
+			expectReport: true,
+		},
+		{
+			name:         "Unassigned(9)",
+			group:        "\xff\x09\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x11",
+			expectReport: true,
+		},
+		{
+			name:         "Unassigned(A)",
+			group:        "\xff\x0a\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x11",
+			expectReport: true,
+		},
+		{
+			name:         "Unassigned(B)",
+			group:        "\xff\x0b\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x11",
+			expectReport: true,
+		},
+		{
+			name:         "Unassigned(C)",
+			group:        "\xff\x0c\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x11",
+			expectReport: true,
+		},
+		{
+			name:         "Unassigned(D)",
+			group:        "\xff\x0d\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x11",
+			expectReport: true,
+		},
+		{
+			name:         "Global",
+			group:        "\xff\x0e\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x11",
+			expectReport: true,
+		},
+		{
+			name:         "ReservedF",
+			group:        "\xff\x0f\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x11",
+			expectReport: true,
+		},
+	}
+
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			s := stack.New(stack.Options{
+				NetworkProtocols: []stack.NetworkProtocolFactory{ipv6.NewProtocolWithOptions(ipv6.Options{
+					MLD: ipv6.MLDOptions{
+						Enabled: true,
+					},
+				})},
+			})
+			e := channel.New(1, header.IPv6MinimumMTU, "")
+			if err := s.CreateNIC(nicID, e); err != nil {
+				t.Fatalf("CreateNIC(%d, _): %s", nicID, err)
+			}
+			if err := s.AddAddress(nicID, ipv6.ProtocolNumber, linkLocalAddr); err != nil {
+				t.Fatalf("AddAddress(%d, %d, %s) = %s", nicID, ipv6.ProtocolNumber, linkLocalAddr, err)
+			}
+			if p, ok := e.Read(); !ok {
+				t.Fatal("expected a report message to be sent")
+			} else {
+				validateMLDPacket(t, stack.PayloadSince(p.Pkt.NetworkHeader()), linkLocalAddr, linkLocalAddrSNMC, header.ICMPv6MulticastListenerReport, linkLocalAddrSNMC)
+			}
+
+			if err := s.JoinGroup(ipv6.ProtocolNumber, nicID, test.group); err != nil {
+				t.Fatalf("s.JoinGroup(%d, %d, %s): %s", ipv6.ProtocolNumber, nicID, test.group, err)
+			}
+			if isInGroup, err := s.IsInGroup(nicID, test.group); err != nil {
+				t.Fatalf("IsInGroup(%d, %s): %s", nicID, test.group, err)
+			} else if !isInGroup {
+				t.Fatalf("got IsInGroup(%d, %s) = false, want = true", nicID, test.group)
+			}
+
+			if !test.expectReport {
+				if p, ok := e.Read(); ok {
+					t.Fatalf("got e.Read() = (%#v, true), want = (_, false)", p)
+				}
+
+				return
+			}
+
+			if p, ok := e.Read(); !ok {
+				t.Fatal("expected a report message to be sent")
+			} else {
+				validateMLDPacket(t, stack.PayloadSince(p.Pkt.NetworkHeader()), linkLocalAddr, test.group, header.ICMPv6MulticastListenerReport, test.group)
+			}
+		})
+	}
+}