network: don't send VP in MOI messages if unsupported by remote peer

network/wsNetwork.go

@@ -1191,7 +1191,17 @@ func (wn *WebsocketNetwork) maybeSendMessagesOfInterest(peer *wsPeer, messagesOf
 			messagesOfInterestEnc = wn.messagesOfInterestEnc
 			wn.messagesOfInterestMu.Unlock()
 		}
+
 		if messagesOfInterestEnc != nil {
+			// Filter VP tag for peers lacking stateful compression support
+			// older nodes (<= v4.3) treat unknown tags as protocol violations and disconnect.
+			if !peer.vpackStatefulCompressionSupported() {
+				tags, err := unmarshallMessageOfInterest(messagesOfInterestEnc)
+				if err == nil && tags[protocol.VotePackedTag] {
+					delete(tags, protocol.VotePackedTag)
+					messagesOfInterestEnc = marshallMessageOfInterestMap(tags)
+				}
+			}
 			peer.sendMessagesOfInterest(messagesOfInterestGeneration, messagesOfInterestEnc)
 		} else {
 			wn.log.Infof("msgOfInterest Enc=nil, MOIGen=%d", messagesOfInterestGeneration)

network/wsNetwork_test.go

@@ -24,6 +24,7 @@ import (
 	"encoding/json"
 	"fmt"
 	"io"
+	"maps"
 	"math/rand"
 	"net"
 	"net/http"
@@ -4773,3 +4774,125 @@ func TestPeerComparisonInBroadcast(t *testing.T) {
 	require.Equal(t, 1, len(testPeer.sendBufferBulk))
 	require.Equal(t, 0, len(exceptPeer.sendBufferBulk))
 }
+
+func TestMaybeSendMessagesOfInterestLegacyPeer(t *testing.T) {
+	partitiontest.PartitionTest(t)
+	t.Parallel()
+
+	makePeer := func(wn *WebsocketNetwork, features peerFeatureFlag) (*wsPeer, chan sendMessage) {
+		ch := make(chan sendMessage, 1)
+		return &wsPeer{
+			wsPeerCore:         makePeerCore(wn.ctx, wn, wn.log, nil, "test-addr", nil, ""),
+			features:           features,
+			sendBufferHighPrio: ch,
+			sendBufferBulk:     make(chan sendMessage, 1),
+			closing:            make(chan struct{}),
+			processed:          make(chan struct{}, 1),
+		}, ch
+	}
+
+	newTestNetwork := func(tags map[protocol.Tag]bool) *WebsocketNetwork {
+		wn := &WebsocketNetwork{
+			log: logging.TestingLog(t),
+		}
+		wn.ctx = context.Background()
+		cloned := maps.Clone(tags)
+		wn.messagesOfInterest = cloned
+		wn.messagesOfInterestEnc = marshallMessageOfInterestMap(cloned)
+		wn.messagesOfInterestGeneration.Store(1)
+		return wn
+	}
+
+	t.Run("filters VP for peers without stateful support", func(t *testing.T) {
+		wn := newTestNetwork(map[protocol.Tag]bool{
+			protocol.AgreementVoteTag: true,
+			protocol.VotePackedTag:    true,
+		})
+
+		peer, ch := makePeer(wn, pfCompressedProposal|pfCompressedVoteVpack)
+		wn.maybeSendMessagesOfInterest(peer, nil)
+
+		select {
+		case msg := <-ch:
+			require.Equal(t, protocol.MsgOfInterestTag, protocol.Tag(msg.data[:2]))
+
+			decoded, err := unmarshallMessageOfInterest(msg.data[2:])
+			require.NoError(t, err)
+
+			require.Contains(t, decoded, protocol.AgreementVoteTag)
+			require.True(t, decoded[protocol.AgreementVoteTag])
+			_, hasVP := decoded[protocol.VotePackedTag]
+			require.False(t, hasVP, "VP tag should be filtered for legacy peers")
+		default:
+			t.Fatal("expected MOI message for legacy peer")
+		}
+	})
+
+	t.Run("retains VP for peers with stateful support", func(t *testing.T) {
+		wn := newTestNetwork(map[protocol.Tag]bool{
+			protocol.AgreementVoteTag: true,
+			protocol.VotePackedTag:    true,
+		})
+
+		peer, ch := makePeer(wn, pfCompressedProposal|pfCompressedVoteVpack|pfCompressedVoteVpackStateful256)
+
+		wn.maybeSendMessagesOfInterest(peer, nil)
+
+		select {
+		case msg := <-ch:
+			require.Equal(t, protocol.MsgOfInterestTag, protocol.Tag(msg.data[:2]))
+
+			decoded, err := unmarshallMessageOfInterest(msg.data[2:])
+			require.NoError(t, err)
+
+			require.Contains(t, decoded, protocol.AgreementVoteTag)
+			require.True(t, decoded[protocol.AgreementVoteTag])
+			require.Contains(t, decoded, protocol.VotePackedTag)
+			require.True(t, decoded[protocol.VotePackedTag], "expected VP tag for peer with stateful support")
+		default:
+			t.Fatal("expected MOI message for stateful peer")
+		}
+	})
+
+	t.Run("gracefully handles configuration without VP tag", func(t *testing.T) {
+		wn := newTestNetwork(map[protocol.Tag]bool{
+			protocol.AgreementVoteTag: true,
+		})
+
+		peer, ch := makePeer(wn, pfCompressedProposal|pfCompressedVoteVpack)
+		wn.maybeSendMessagesOfInterest(peer, nil)
+
+		select {
+		case msg := <-ch:
+			require.Equal(t, protocol.MsgOfInterestTag, protocol.Tag(msg.data[:2]))
+
+			decoded, err := unmarshallMessageOfInterest(msg.data[2:])
+			require.NoError(t, err)
+
+			require.Contains(t, decoded, protocol.AgreementVoteTag)
+			require.True(t, decoded[protocol.AgreementVoteTag])
+			_, hasVP := decoded[protocol.VotePackedTag]
+			require.False(t, hasVP)
+		default:
+			t.Fatal("expected MOI message when VP is absent from configuration")
+		}
+	})
+
+	t.Run("skips sending when peer generation matches", func(t *testing.T) {
+		wn := newTestNetwork(map[protocol.Tag]bool{
+			protocol.AgreementVoteTag: true,
+			protocol.VotePackedTag:    true,
+		})
+
+		peer, ch := makePeer(wn, pfCompressedProposal|pfCompressedVoteVpack)
+		peer.messagesOfInterestGeneration.Store(wn.messagesOfInterestGeneration.Load())
+
+		wn.maybeSendMessagesOfInterest(peer, nil)
+
+		select {
+		case <-ch:
+			t.Fatal("did not expect MOI message when generations already match")
+		default:
+		}
+	})
+}