service/header: fix ExtendedHeader message duplicates on the network

CHANGELOG-PENDING.md

@@ -36,6 +36,7 @@ Month, DD, YYYY
 
 ### BUG FIXES
 
+- [service/header: fix ExtendedHeader message duplicates on the network #409](https://github.com/celestiaorg/celestia-node/pull/409) [@Wondertan](https://github.com/Wondertan)
 - [fix(header/service): #339 race](https://github.com/celestiaorg/celestia-node/pull/343) [@Wondertan](https://github.com/Wondertan)
 - [core: Properly fetch Validators from Core and two more fixes #328](https://github.com/celestiaorg/celestia-node/pull/328) [@Wondertan](https://github.com/Wondertan)
 - [header: Added missing `err` value in ErrorW logging calls](https://github.com/celestiaorg/celestia-node/pull/282) [@jbowen93](https://github.com/jbowen93)

go.mod

@@ -45,4 +45,7 @@ require (
 	go.uber.org/zap v1.20.0
 )
 
-replace github.com/tendermint/tendermint v0.34.14 => github.com/celestiaorg/celestia-core v0.34.14-celestia
+replace (
+	github.com/libp2p/go-libp2p-pubsub v0.5.7-0.20211029175501-5c90105738cf => github.com/celestiaorg/go-libp2p-pubsub v0.5.7-0.20220202152246-c33ecdf03b34
+	github.com/tendermint/tendermint v0.34.14 => github.com/celestiaorg/celestia-core v0.34.14-celestia
+)

go.sum

@@ -148,6 +148,8 @@ github.com/celestiaorg/go-leopard v0.1.0 h1:28z2EkvKJIez5J9CEaiiUEC+OxalRLtTGJJ1
 github.com/celestiaorg/go-leopard v0.1.0/go.mod h1:NtO/rjlB8dw2aq7jr06vZFKGvryQcTDXaNHelmPNOAM=
 github.com/celestiaorg/go-libp2p-messenger v0.1.0 h1:rFldTa3ZWcRRn8E2bRWS94Qp1GFYXO2a0uvqpIey1B8=
 github.com/celestiaorg/go-libp2p-messenger v0.1.0/go.mod h1:XzNksXrH0VxuNRGOnjPL9Ck4UyQlbmMpCYg9YwSBerI=
+github.com/celestiaorg/go-libp2p-pubsub v0.5.7-0.20220202152246-c33ecdf03b34 h1:NB+H2aczLNQgPUu59MHrk9ZAzCsGOkxszpHaClUGRUo=
+github.com/celestiaorg/go-libp2p-pubsub v0.5.7-0.20220202152246-c33ecdf03b34/go.mod h1:gVOzwebXVdSMDQBTfH8ACO5EJ4SQrvsHqCmYsCZpD0E=
 github.com/celestiaorg/go-verifcid v0.0.1-lazypatch h1:9TSe3w1cmJmbWlweCwCTIZkan7jV8M+KwglXpdD+UG8=
 github.com/celestiaorg/go-verifcid v0.0.1-lazypatch/go.mod h1:kXPYu0XqTNUKWA1h3M95UHjUqBzDwXVVt/RXZDjKJmQ=
 github.com/celestiaorg/merkletree v0.0.0-20210714075610-a84dc3ddbbe4 h1:CJdIpo8n5MFP2MwK0gSRcOVlDlFdQJO1p+FqdxYzmvc=
@@ -804,8 +806,6 @@ github.com/libp2p/go-libp2p-peerstore v0.3.0 h1:wp/G0+37+GLr7tu+wE+4GWNrA3uxKg6I
 github.com/libp2p/go-libp2p-peerstore v0.3.0/go.mod h1:fNX9WlOENMvdx/YD7YO/5Hkrn8+lQIk5A39BHa1HIrM=
 github.com/libp2p/go-libp2p-pnet v0.2.0 h1:J6htxttBipJujEjz1y0a5+eYoiPcFHhSYHH6na5f0/k=
 github.com/libp2p/go-libp2p-pnet v0.2.0/go.mod h1:Qqvq6JH/oMZGwqs3N1Fqhv8NVhrdYcO0BW4wssv21LA=
-github.com/libp2p/go-libp2p-pubsub v0.5.7-0.20211029175501-5c90105738cf h1:uW9m2wQ64gkTugA9nffzoiZR1ZQ0D2/xzBQfW6sgHPk=
-github.com/libp2p/go-libp2p-pubsub v0.5.7-0.20211029175501-5c90105738cf/go.mod h1:gVOzwebXVdSMDQBTfH8ACO5EJ4SQrvsHqCmYsCZpD0E=
 github.com/libp2p/go-libp2p-quic-transport v0.10.0/go.mod h1:RfJbZ8IqXIhxBRm5hqUEJqjiiY8xmEuq3HUDS993MkA=
 github.com/libp2p/go-libp2p-quic-transport v0.11.2 h1:p1YQDZRHH4Cv2LPtHubqlQ9ggz4CKng/REZuXZbZMhM=
 github.com/libp2p/go-libp2p-quic-transport v0.11.2/go.mod h1:wlanzKtIh6pHrq+0U3p3DY9PJfGqxMgPaGKaK5LifwQ=

service/header/p2p_subscriber.go

@@ -6,6 +6,8 @@ import (
 
 	"github.com/libp2p/go-libp2p-core/peer"
 	pubsub "github.com/libp2p/go-libp2p-pubsub"
+	pb "github.com/libp2p/go-libp2p-pubsub/pb"
+	"github.com/minio/blake2b-simd"
 )
 
 // PubSubTopic hardcodes the name of the ExtendedHeader
@@ -30,7 +32,7 @@ func NewP2PSubscriber(ps *pubsub.PubSub) *P2PSubscriber {
 // Start starts the P2PSubscriber, registering a topic validator for the "header-sub"
 // topic and joining it.
 func (p *P2PSubscriber) Start(context.Context) (err error) {
-	p.topic, err = p.pubsub.Join(PubSubTopic)
+	p.topic, err = p.pubsub.Join(PubSubTopic, pubsub.WithTopicMessageIdFn(msgID))
 	return err
 }
 
@@ -78,3 +80,38 @@ func (p *P2PSubscriber) Broadcast(ctx context.Context, header *ExtendedHeader) e
 	}
 	return p.topic.Publish(ctx, bin)
 }
+
+// msgID computes an id for a pubsub message
+// TODO(@Wondertan): This cause additional allocations per each recvd message in the topic. Find a way to avoid those.
+func msgID(pmsg *pb.Message) string {
+	msgID := func(data []byte) string {
+		hash := blake2b.Sum256(data)
+		return string(hash[:])
+	}
+
+	h, err := UnmarshalExtendedHeader(pmsg.Data)
+	if err != nil {
+		// There is nothing we can do about the error, and it will be anyway caught during validation.
+		// We also *have* to return some ID for the msg, so give the hash of even faulty msg
+		return msgID(pmsg.Data)
+	}
+
+	// IMPORTANT NOTE:
+	// Due to the nature of the Tendermint consensus, validators don't necessarily collect commit signatures from the
+	// entire validator set, but only the minimum required amount of them (>2/3 of voting power). In addition,
+	// signatures are collected asynchronously. Therefore, each validator may have a different set of signatures that
+	// pass the minimum required voting power threshold, causing nondeterminism in the header message gossiped over the
+	// network. Subsequently, this causes message duplicates as each Bridge Node, connected to a personal validator,
+	// sends the validator's own view of commits of effectively the same header.
+	//
+	// To solve the problem above, we exclude nondeterministic value from message id calculation
+	h.Commit.Signatures = nil
+
+	data, err := MarshalExtendedHeader(h)
+	if err != nil {
+		// See the note under unmarshalling step
+		return msgID(pmsg.Data)
+	}
+
+	return msgID(data)
+}

service/header/sync.go

@@ -221,9 +221,6 @@ func (s *Syncer) processIncoming(ctx context.Context, maybeHead *ExtendedHeader)
 		log.Warnw("received known header",
 			"height", maybeHead.Height,
 			"hash", maybeHead.Hash())
-
-		// TODO(@Wondertan): Remove once duplicates are fully fixed
-		log.Warnf("Ignore the warn above - there is a known issue with duplicate headers on the network.")
 		return pubsub.ValidationIgnore // we don't know if header is invalid so ignore
 	}