whisper/whisperv6: implement pow/bloom exchange protocol (#15802)

This is the main feature of v6.

7 files changed, 451 insertions, 75 deletions

diff --git a/whisper/whisperv6/api.go b/whisper/whisperv6/api.go
index 3dddb6953..0e8490b41 100644
--- a/whisper/whisperv6/api.go
+++ b/whisper/whisperv6/api.go
@@ -116,12 +116,17 @@ func (api *PublicWhisperAPI) SetMaxMessageSize(ctx context.Context, size uint32)
 	return true, api.w.SetMaxMessageSize(size)
 }
 
-// SetMinPow sets the minimum PoW for a message before it is accepted.
+// SetMinPow sets the minimum PoW, and notifies the peers.
 func (api *PublicWhisperAPI) SetMinPoW(ctx context.Context, pow float64) (bool, error) {
 	return true, api.w.SetMinimumPoW(pow)
 }
 
-// MarkTrustedPeer marks a peer trusted. , which will allow it to send historic (expired) messages.
+// SetBloomFilter sets the new value of bloom filter, and notifies the peers.
+func (api *PublicWhisperAPI) SetBloomFilter(ctx context.Context, bloom hexutil.Bytes) (bool, error) {
+	return true, api.w.SetBloomFilter(bloom)
+}
+
+// MarkTrustedPeer marks a peer trusted, which will allow it to send historic (expired) messages.
 // Note: This function is not adding new nodes, the node needs to exists as a peer.
 func (api *PublicWhisperAPI) MarkTrustedPeer(ctx context.Context, enode string) (bool, error) {
 	n, err := discover.ParseNode(enode)
diff --git a/whisper/whisperv6/doc.go b/whisper/whisperv6/doc.go
index 2a4911d65..da1b4ee5b 100644
--- a/whisper/whisperv6/doc.go
+++ b/whisper/whisperv6/doc.go
@@ -35,7 +35,6 @@ import (
 )
 
 const (
-	EnvelopeVersion    = uint64(0)
 	ProtocolVersion    = uint64(6)
 	ProtocolVersionStr = "6.0"
 	ProtocolName       = "shh"
@@ -52,11 +51,14 @@ const (
 	paddingMask   = byte(3)
 	signatureFlag = byte(4)
 
-	TopicLength     = 4
-	signatureLength = 65
-	aesKeyLength    = 32
-	AESNonceLength  = 12
-	keyIdSize       = 32
+	TopicLength     = 4  // in bytes
+	signatureLength = 65 // in bytes
+	aesKeyLength    = 32 // in bytes
+	AESNonceLength  = 12 // in bytes
+	keyIdSize       = 32 // in bytes
+	bloomFilterSize = 64 // in bytes
+
+	EnvelopeHeaderLength = 20
 
 	MaxMessageSize        = uint32(10 * 1024 * 1024) // maximum accepted size of a message.
 	DefaultMaxMessageSize = uint32(1024 * 1024)
@@ -68,10 +70,8 @@ const (
 	expirationCycle   = time.Second
 	transmissionCycle = 300 * time.Millisecond
 
-	DefaultTTL     = 50 // seconds
-	SynchAllowance = 10 // seconds
-
-	EnvelopeHeaderLength = 20
+	DefaultTTL           = 50 // seconds
+	DefaultSyncAllowance = 10 // seconds
 )
 
 type unknownVersionError uint64
diff --git a/whisper/whisperv6/envelope.go b/whisper/whisperv6/envelope.go
index 676df669b..9ed712b93 100644
--- a/whisper/whisperv6/envelope.go
+++ b/whisper/whisperv6/envelope.go
@@ -42,9 +42,11 @@ type Envelope struct {
 	Data   []byte
 	Nonce  uint64
 
-	pow  float64     // Message-specific PoW as described in the Whisper specification.
-	hash common.Hash // Cached hash of the envelope to avoid rehashing every time.
-	// Don't access hash directly, use Hash() function instead.
+	pow float64 // Message-specific PoW as described in the Whisper specification.
+
+	// the following variables should not be accessed directly, use the corresponding function instead: Hash(), Bloom()
+	hash  common.Hash // Cached hash of the envelope to avoid rehashing every time.
+	bloom []byte
 }
 
 // size returns the size of envelope as it is sent (i.e. public fields only)
@@ -227,3 +229,30 @@ func (e *Envelope) Open(watcher *Filter) (msg *ReceivedMessage) {
 	}
 	return msg
 }
+
+// Bloom maps 4-bytes Topic into 64-byte bloom filter with 3 bits set (at most).
+func (e *Envelope) Bloom() []byte {
+	if e.bloom == nil {
+		e.bloom = TopicToBloom(e.Topic)
+	}
+	return e.bloom
+}
+
+// TopicToBloom converts the topic (4 bytes) to the bloom filter (64 bytes)
+func TopicToBloom(topic TopicType) []byte {
+	b := make([]byte, bloomFilterSize)
+	var index [3]int
+	for j := 0; j < 3; j++ {
+		index[j] = int(topic[j])
+		if (topic[3] & (1 << uint(j))) != 0 {
+			index[j] += 256
+		}
+	}
+
+	for j := 0; j < 3; j++ {
+		byteIndex := index[j] / 8
+		bitIndex := index[j] % 8
+		b[byteIndex] = (1 << uint(bitIndex))
+	}
+	return b
+}
diff --git a/whisper/whisperv6/peer.go b/whisper/whisperv6/peer.go
index 65e0c77b0..08071c0f7 100644
--- a/whisper/whisperv6/peer.go
+++ b/whisper/whisperv6/peer.go
@@ -36,6 +36,7 @@ type Peer struct {
 
 	trusted        bool
 	powRequirement float64
+	bloomFilter    []byte // may contain nil in case of full node
 
 	known *set.Set // Messages already known by the peer to avoid wasting bandwidth
 
@@ -74,8 +75,12 @@ func (p *Peer) handshake() error {
 	// Send the handshake status message asynchronously
 	errc := make(chan error, 1)
 	go func() {
-		errc <- p2p.Send(p.ws, statusCode, ProtocolVersion)
+		pow := p.host.MinPow()
+		powConverted := math.Float64bits(pow)
+		bloom := p.host.BloomFilter()
+		errc <- p2p.SendItems(p.ws, statusCode, ProtocolVersion, powConverted, bloom)
 	}()
+
 	// Fetch the remote status packet and verify protocol match
 	packet, err := p.ws.ReadMsg()
 	if err != nil {
@@ -85,14 +90,42 @@ func (p *Peer) handshake() error {
 		return fmt.Errorf("peer [%x] sent packet %x before status packet", p.ID(), packet.Code)
 	}
 	s := rlp.NewStream(packet.Payload, uint64(packet.Size))
-	peerVersion, err := s.Uint()
+	_, err = s.List()
 	if err != nil {
 		return fmt.Errorf("peer [%x] sent bad status message: %v", p.ID(), err)
 	}
+	peerVersion, err := s.Uint()
+	if err != nil {
+		return fmt.Errorf("peer [%x] sent bad status message (unable to decode version): %v", p.ID(), err)
+	}
 	if peerVersion != ProtocolVersion {
 		return fmt.Errorf("peer [%x]: protocol version mismatch %d != %d", p.ID(), peerVersion, ProtocolVersion)
 	}
-	// Wait until out own status is consumed too
+
+	// only version is mandatory, subsequent parameters are optional
+	powRaw, err := s.Uint()
+	if err == nil {
+		pow := math.Float64frombits(powRaw)
+		if math.IsInf(pow, 0) || math.IsNaN(pow) || pow < 0.0 {
+			return fmt.Errorf("peer [%x] sent bad status message: invalid pow", p.ID())
+		}
+		p.powRequirement = pow
+
+		var bloom []byte
+		err = s.Decode(&bloom)
+		if err == nil {
+			sz := len(bloom)
+			if sz != bloomFilterSize && sz != 0 {
+				return fmt.Errorf("peer [%x] sent bad status message: wrong bloom filter size %d", p.ID(), sz)
+			}
+			if isFullNode(bloom) {
+				p.bloomFilter = nil
+			} else {
+				p.bloomFilter = bloom
+			}
+		}
+	}
+
 	if err := <-errc; err != nil {
 		return fmt.Errorf("peer [%x] failed to send status packet: %v", p.ID(), err)
 	}
@@ -156,7 +189,7 @@ func (p *Peer) broadcast() error {
 	envelopes := p.host.Envelopes()
 	bundle := make([]*Envelope, 0, len(envelopes))
 	for _, envelope := range envelopes {
-		if !p.marked(envelope) && envelope.PoW() >= p.powRequirement {
+		if !p.marked(envelope) && envelope.PoW() >= p.powRequirement && p.bloomMatch(envelope) {
 			bundle = append(bundle, envelope)
 		}
 	}
@@ -186,3 +219,16 @@ func (p *Peer) notifyAboutPowRequirementChange(pow float64) error {
 	i := math.Float64bits(pow)
 	return p2p.Send(p.ws, powRequirementCode, i)
 }
+
+func (p *Peer) notifyAboutBloomFilterChange(bloom []byte) error {
+	return p2p.Send(p.ws, bloomFilterExCode, bloom)
+}
+
+func (p *Peer) bloomMatch(env *Envelope) bool {
+	if p.bloomFilter == nil {
+		// no filter - full node, accepts all envelops
+		return true
+	}
+
+	return bloomFilterMatch(p.bloomFilter, env.Bloom())
+}
diff --git a/whisper/whisperv6/peer_test.go b/whisper/whisperv6/peer_test.go
index 599a479be..8a65cb714 100644
--- a/whisper/whisperv6/peer_test.go
+++ b/whisper/whisperv6/peer_test.go
@@ -20,6 +20,7 @@ import (
 	"bytes"
 	"crypto/ecdsa"
 	"fmt"
+	mrand "math/rand"
 	"net"
 	"sync"
 	"testing"
@@ -87,6 +88,9 @@ var nodes [NumNodes]*TestNode
 var sharedKey []byte = []byte("some arbitrary data here")
 var sharedTopic TopicType = TopicType{0xF, 0x1, 0x2, 0}
 var expectedMessage []byte = []byte("per rectum ad astra")
+var masterBloomFilter []byte
+var masterPow = 0.00000001
+var round int = 1
 
 func TestSimulation(t *testing.T) {
 	// create a chain of whisper nodes,
@@ -104,8 +108,13 @@ func TestSimulation(t *testing.T) {
 	// check if each node have received and decrypted exactly one message
 	checkPropagation(t, true)
 
-	// send protocol-level messages (powRequirementCode) and check the new PoW requirement values
-	powReqExchange(t)
+	// check if Status message was correctly decoded
+	checkBloomFilterExchange(t)
+	checkPowExchange(t)
+
+	// send new pow and bloom exchange messages
+	resetParams(t)
+	round++
 
 	// node #1 sends one expected (decryptable) message
 	sendMsg(t, true, 1)
@@ -113,18 +122,65 @@ func TestSimulation(t *testing.T) {
 	// check if each node (except node #0) have received and decrypted exactly one message
 	checkPropagation(t, false)
 
+	for i := 1; i < NumNodes; i++ {
+		time.Sleep(20 * time.Millisecond)
+		sendMsg(t, true, i)
+	}
+
+	// check if corresponding protocol-level messages were correctly decoded
+	checkPowExchangeForNodeZero(t)
+	checkBloomFilterExchange(t)
+
 	stopServers()
 }
 
+func resetParams(t *testing.T) {
+	// change pow only for node zero
+	masterPow = 7777777.0
+	nodes[0].shh.SetMinimumPoW(masterPow)
+
+	// change bloom for all nodes
+	masterBloomFilter = TopicToBloom(sharedTopic)
+	for i := 0; i < NumNodes; i++ {
+		nodes[i].shh.SetBloomFilter(masterBloomFilter)
+	}
+}
+
+func initBloom(t *testing.T) {
+	masterBloomFilter = make([]byte, bloomFilterSize)
+	_, err := mrand.Read(masterBloomFilter)
+	if err != nil {
+		t.Fatalf("rand failed: %s.", err)
+	}
+
+	msgBloom := TopicToBloom(sharedTopic)
+	masterBloomFilter = addBloom(masterBloomFilter, msgBloom)
+	for i := 0; i < 32; i++ {
+		masterBloomFilter[i] = 0xFF
+	}
+
+	if !bloomFilterMatch(masterBloomFilter, msgBloom) {
+		t.Fatalf("bloom mismatch on initBloom.")
+	}
+}
+
 func initialize(t *testing.T) {
+	initBloom(t)
+
 	var err error
 	ip := net.IPv4(127, 0, 0, 1)
 	port0 := 30303
 
 	for i := 0; i < NumNodes; i++ {
 		var node TestNode
+		b := make([]byte, bloomFilterSize)
+		copy(b, masterBloomFilter)
 		node.shh = New(&DefaultConfig)
-		node.shh.SetMinimumPowTest(0.00000001)
+		node.shh.SetMinimumPoW(masterPow)
+		node.shh.SetBloomFilter(b)
+		if !bytes.Equal(node.shh.BloomFilter(), masterBloomFilter) {
+			t.Fatalf("bloom mismatch on init.")
+		}
 		node.shh.Start(nil)
 		topics := make([]TopicType, 0)
 		topics = append(topics, sharedTopic)
@@ -206,7 +262,7 @@ func checkPropagation(t *testing.T, includingNodeZero bool) {
 		for i := first; i < NumNodes; i++ {
 			f := nodes[i].shh.GetFilter(nodes[i].filerId)
 			if f == nil {
-				t.Fatalf("failed to get filterId %s from node %d.", nodes[i].filerId, i)
+				t.Fatalf("failed to get filterId %s from node %d, round %d.", nodes[i].filerId, i, round)
 			}
 
 			mail := f.Retrieve()
@@ -332,34 +388,43 @@ func TestPeerBasic(t *testing.T) {
 	}
 }
 
-func powReqExchange(t *testing.T) {
+func checkPowExchangeForNodeZero(t *testing.T) {
+	cnt := 0
 	for i, node := range nodes {
 		for peer := range node.shh.peers {
-			if peer.powRequirement > 1000.0 {
-				t.Fatalf("node %d: one of the peers' pow requirement is too big (%f).", i, peer.powRequirement)
+			if peer.peer.ID() == discover.PubkeyID(&nodes[0].id.PublicKey) {
+				cnt++
+				if peer.powRequirement != masterPow {
+					t.Fatalf("node %d: failed to set the new pow requirement.", i)
+				}
 			}
 		}
 	}
+	if cnt == 0 {
+		t.Fatalf("no matching peers found.")
+	}
+}
 
-	const pow float64 = 7777777.0
-	nodes[0].shh.SetMinimumPoW(pow)
-
-	// wait until all the messages are delivered
-	time.Sleep(64 * time.Millisecond)
-
-	cnt := 0
+func checkPowExchange(t *testing.T) {
 	for i, node := range nodes {
 		for peer := range node.shh.peers {
-			if peer.peer.ID() == discover.PubkeyID(&nodes[0].id.PublicKey) {
-				cnt++
-				if peer.powRequirement != pow {
-					t.Fatalf("node %d: failed to set the new pow requirement.", i)
+			if peer.peer.ID() != discover.PubkeyID(&nodes[0].id.PublicKey) {
+				if peer.powRequirement != masterPow {
+					t.Fatalf("node %d: failed to exchange pow requirement in round %d; expected %f, got %f",
+						i, round, masterPow, peer.powRequirement)
 				}
 			}
 		}
 	}
+}
 
-	if cnt == 0 {
-		t.Fatalf("no matching peers found.")
+func checkBloomFilterExchange(t *testing.T) {
+	for i, node := range nodes {
+		for peer := range node.shh.peers {
+			if !bytes.Equal(peer.bloomFilter, masterBloomFilter) {
+				t.Fatalf("node %d: failed to exchange bloom filter requirement in round %d. \n%x expected \n%x got",
+					i, round, masterBloomFilter, peer.bloomFilter)
+			}
+		}
 	}
 }
diff --git a/whisper/whisperv6/whisper.go b/whisper/whisperv6/whisper.go
index 492591486..bc89aadcc 100644
--- a/whisper/whisperv6/whisper.go
+++ b/whisper/whisperv6/whisper.go
@@ -48,9 +48,12 @@ type Statistics struct {
 }
 
 const (
-	minPowIdx     = iota // Minimal PoW required by the whisper node
-	maxMsgSizeIdx = iota // Maximal message length allowed by the whisper node
-	overflowIdx   = iota // Indicator of message queue overflow
+	maxMsgSizeIdx           = iota // Maximal message length allowed by the whisper node
+	overflowIdx                    // Indicator of message queue overflow
+	minPowIdx                      // Minimal PoW required by the whisper node
+	minPowToleranceIdx             // Minimal PoW tolerated by the whisper node for a limited time
+	bloomFilterIdx                 // Bloom filter for topics of interest for this node
+	bloomFilterToleranceIdx        // Bloom filter tolerated by the whisper node for a limited time
 )
 
 // Whisper represents a dark communication interface through the Ethereum
@@ -76,7 +79,7 @@ type Whisper struct {
 
 	settings syncmap.Map // holds configuration settings that can be dynamically changed
 
-	reactionAllowance int // maximum time in seconds allowed to process the whisper-related messages
+	syncAllowance int // maximum time in seconds allowed to process the whisper-related messages
 
 	statsMu sync.Mutex // guard stats
 	stats   Statistics // Statistics of whisper node
@@ -91,15 +94,15 @@ func New(cfg *Config) *Whisper {
 	}
 
 	whisper := &Whisper{
-		privateKeys:       make(map[string]*ecdsa.PrivateKey),
-		symKeys:           make(map[string][]byte),
-		envelopes:         make(map[common.Hash]*Envelope),
-		expirations:       make(map[uint32]*set.SetNonTS),
-		peers:             make(map[*Peer]struct{}),
-		messageQueue:      make(chan *Envelope, messageQueueLimit),
-		p2pMsgQueue:       make(chan *Envelope, messageQueueLimit),
-		quit:              make(chan struct{}),
-		reactionAllowance: SynchAllowance,
+		privateKeys:   make(map[string]*ecdsa.PrivateKey),
+		symKeys:       make(map[string][]byte),
+		envelopes:     make(map[common.Hash]*Envelope),
+		expirations:   make(map[uint32]*set.SetNonTS),
+		peers:         make(map[*Peer]struct{}),
+		messageQueue:  make(chan *Envelope, messageQueueLimit),
+		p2pMsgQueue:   make(chan *Envelope, messageQueueLimit),
+		quit:          make(chan struct{}),
+		syncAllowance: DefaultSyncAllowance,
 	}
 
 	whisper.filters = NewFilters(whisper)
@@ -126,11 +129,55 @@ func New(cfg *Config) *Whisper {
 	return whisper
 }
 
+// MinPow returns the PoW value required by this node.
 func (w *Whisper) MinPow() float64 {
-	val, _ := w.settings.Load(minPowIdx)
+	val, exist := w.settings.Load(minPowIdx)
+	if !exist || val == nil {
+		return DefaultMinimumPoW
+	}
+	v, ok := val.(float64)
+	if !ok {
+		log.Error("Error loading minPowIdx, using default")
+		return DefaultMinimumPoW
+	}
+	return v
+}
+
+// MinPowTolerance returns the value of minimum PoW which is tolerated for a limited
+// time after PoW was changed. If sufficient time have elapsed or no change of PoW
+// have ever occurred, the return value will be the same as return value of MinPow().
+func (w *Whisper) MinPowTolerance() float64 {
+	val, exist := w.settings.Load(minPowToleranceIdx)
+	if !exist || val == nil {
+		return DefaultMinimumPoW
+	}
 	return val.(float64)
 }
 
+// BloomFilter returns the aggregated bloom filter for all the topics of interest.
+// The nodes are required to send only messages that match the advertised bloom filter.
+// If a message does not match the bloom, it will tantamount to spam, and the peer will
+// be disconnected.
+func (w *Whisper) BloomFilter() []byte {
+	val, exist := w.settings.Load(bloomFilterIdx)
+	if !exist || val == nil {
+		return nil
+	}
+	return val.([]byte)
+}
+
+// BloomFilterTolerance returns the bloom filter which is tolerated for a limited
+// time after new bloom was advertised to the peers. If sufficient time have elapsed
+// or no change of bloom filter have ever occurred, the return value will be the same
+// as return value of BloomFilter().
+func (w *Whisper) BloomFilterTolerance() []byte {
+	val, exist := w.settings.Load(bloomFilterToleranceIdx)
+	if !exist || val == nil {
+		return nil
+	}
+	return val.([]byte)
+}
+
 // MaxMessageSize returns the maximum accepted message size.
 func (w *Whisper) MaxMessageSize() uint32 {
 	val, _ := w.settings.Load(maxMsgSizeIdx)
@@ -180,18 +227,40 @@ func (w *Whisper) SetMaxMessageSize(size uint32) error {
 	return nil
 }
 
+// SetBloomFilter sets the new bloom filter
+func (w *Whisper) SetBloomFilter(bloom []byte) error {
+	if len(bloom) != bloomFilterSize {
+		return fmt.Errorf("invalid bloom filter size: %d", len(bloom))
+	}
+
+	b := make([]byte, bloomFilterSize)
+	copy(b, bloom)
+
+	w.settings.Store(bloomFilterIdx, b)
+	w.notifyPeersAboutBloomFilterChange(b)
+
+	go func() {
+		// allow some time before all the peers have processed the notification
+		time.Sleep(time.Duration(w.syncAllowance) * time.Second)
+		w.settings.Store(bloomFilterToleranceIdx, b)
+	}()
+
+	return nil
+}
+
 // SetMinimumPoW sets the minimal PoW required by this node
 func (w *Whisper) SetMinimumPoW(val float64) error {
 	if val < 0.0 {
 		return fmt.Errorf("invalid PoW: %f", val)
 	}
 
+	w.settings.Store(minPowIdx, val)
 	w.notifyPeersAboutPowRequirementChange(val)
 
 	go func() {
 		// allow some time before all the peers have processed the notification
-		time.Sleep(time.Duration(w.reactionAllowance) * time.Second)
-		w.settings.Store(minPowIdx, val)
+		time.Sleep(time.Duration(w.syncAllowance) * time.Second)
+		w.settings.Store(minPowToleranceIdx, val)
 	}()
 
 	return nil
@@ -199,21 +268,13 @@ func (w *Whisper) SetMinimumPoW(val float64) error {
 
 // SetMinimumPoW sets the minimal PoW in test environment
 func (w *Whisper) SetMinimumPowTest(val float64) {
-	w.notifyPeersAboutPowRequirementChange(val)
 	w.settings.Store(minPowIdx, val)
+	w.notifyPeersAboutPowRequirementChange(val)
+	w.settings.Store(minPowToleranceIdx, val)
 }
 
 func (w *Whisper) notifyPeersAboutPowRequirementChange(pow float64) {
-	arr := make([]*Peer, len(w.peers))
-	i := 0
-
-	w.peerMu.Lock()
-	for p := range w.peers {
-		arr[i] = p
-		i++
-	}
-	w.peerMu.Unlock()
-
+	arr := w.getPeers()
 	for _, p := range arr {
 		err := p.notifyAboutPowRequirementChange(pow)
 		if err != nil {
@@ -221,11 +282,37 @@ func (w *Whisper) notifyPeersAboutPowRequirementChange(pow float64) {
 			err = p.notifyAboutPowRequirementChange(pow)
 		}
 		if err != nil {
-			log.Warn("oversized message received", "peer", p.ID(), "error", err)
+			log.Warn("failed to notify peer about new pow requirement", "peer", p.ID(), "error", err)
+		}
+	}
+}
+
+func (w *Whisper) notifyPeersAboutBloomFilterChange(bloom []byte) {
+	arr := w.getPeers()
+	for _, p := range arr {
+		err := p.notifyAboutBloomFilterChange(bloom)
+		if err != nil {
+			// allow one retry
+			err = p.notifyAboutBloomFilterChange(bloom)
+		}
+		if err != nil {
+			log.Warn("failed to notify peer about new bloom filter", "peer", p.ID(), "error", err)
 		}
 	}
 }
 
+func (w *Whisper) getPeers() []*Peer {
+	arr := make([]*Peer, len(w.peers))
+	i := 0
+	w.peerMu.Lock()
+	for p := range w.peers {
+		arr[i] = p
+		i++
+	}
+	w.peerMu.Unlock()
+	return arr
+}
+
 // getPeer retrieves peer by ID
 func (w *Whisper) getPeer(peerID []byte) (*Peer, error) {
 	w.peerMu.Lock()
@@ -459,7 +546,28 @@ func (w *Whisper) GetSymKey(id string) ([]byte, error) {
 // Subscribe installs a new message handler used for filtering, decrypting
 // and subsequent storing of incoming messages.
 func (w *Whisper) Subscribe(f *Filter) (string, error) {
-	return w.filters.Install(f)
+	s, err := w.filters.Install(f)
+	if err == nil {
+		w.updateBloomFilter(f)
+	}
+	return s, err
+}
+
+// updateBloomFilter recalculates the new value of bloom filter,
+// and informs the peers if necessary.
+func (w *Whisper) updateBloomFilter(f *Filter) {
+	aggregate := make([]byte, bloomFilterSize)
+	for _, t := range f.Topics {
+		top := BytesToTopic(t)
+		b := TopicToBloom(top)
+		aggregate = addBloom(aggregate, b)
+	}
+
+	if !bloomFilterMatch(w.BloomFilter(), aggregate) {
+		// existing bloom filter must be updated
+		aggregate = addBloom(w.BloomFilter(), aggregate)
+		w.SetBloomFilter(aggregate)
+	}
 }
 
 // GetFilter returns the filter by id.
@@ -592,7 +700,21 @@ func (wh *Whisper) runMessageLoop(p *Peer, rw p2p.MsgReadWriter) error {
 			}
 			p.powRequirement = f
 		case bloomFilterExCode:
-			// to be implemented
+			var bloom []byte
+			err := packet.Decode(&bloom)
+			if err == nil && len(bloom) != bloomFilterSize {
+				err = fmt.Errorf("wrong bloom filter size %d", len(bloom))
+			}
+
+			if err != nil {
+				log.Warn("failed to decode bloom filter exchange message, peer will be disconnected", "peer", p.peer.ID(), "err", err)
+				return errors.New("invalid bloom filter exchange message")
+			}
+			if isFullNode(bloom) {
+				p.bloomFilter = nil
+			} else {
+				p.bloomFilter = bloom
+			}
 		case p2pMessageCode:
 			// peer-to-peer message, sent directly to peer bypassing PoW checks, etc.
 			// this message is not supposed to be forwarded to other peers, and
@@ -633,7 +755,7 @@ func (wh *Whisper) add(envelope *Envelope) (bool, error) {
 	sent := envelope.Expiry - envelope.TTL
 
 	if sent > now {
-		if sent-SynchAllowance > now {
+		if sent-DefaultSyncAllowance > now {
 			return false, fmt.Errorf("envelope created in the future [%x]", envelope.Hash())
 		} else {
 			// recalculate PoW, adjusted for the time difference, plus one second for latency
@@ -642,7 +764,7 @@ func (wh *Whisper) add(envelope *Envelope) (bool, error) {
 	}
 
 	if envelope.Expiry < now {
-		if envelope.Expiry+SynchAllowance*2 < now {
+		if envelope.Expiry+DefaultSyncAllowance*2 < now {
 			return false, fmt.Errorf("very old message")
 		} else {
 			log.Debug("expired envelope dropped", "hash", envelope.Hash().Hex())
@@ -655,11 +777,22 @@ func (wh *Whisper) add(envelope *Envelope) (bool, error) {
 	}
 
 	if envelope.PoW() < wh.MinPow() {
-		log.Debug("envelope with low PoW dropped", "PoW", envelope.PoW(), "hash", envelope.Hash().Hex())
-		return false, nil // drop envelope without error for now
+		// maybe the value was recently changed, and the peers did not adjust yet.
+		// in this case the previous value is retrieved by MinPowTolerance()
+		// for a short period of peer synchronization.
+		if envelope.PoW() < wh.MinPowTolerance() {
+			return false, fmt.Errorf("envelope with low PoW received: PoW=%f, hash=[%v]", envelope.PoW(), envelope.Hash().Hex())
+		}
+	}
 
-		// once the status message includes the PoW requirement, an error should be returned here:
-		//return false, fmt.Errorf("envelope with low PoW dropped: PoW=%f, hash=[%v]", envelope.PoW(), envelope.Hash().Hex())
+	if !bloomFilterMatch(wh.BloomFilter(), envelope.Bloom()) {
+		// maybe the value was recently changed, and the peers did not adjust yet.
+		// in this case the previous value is retrieved by BloomFilterTolerance()
+		// for a short period of peer synchronization.
+		if !bloomFilterMatch(wh.BloomFilterTolerance(), envelope.Bloom()) {
+			return false, fmt.Errorf("envelope does not match bloom filter, hash=[%v], bloom: \n%x \n%x \n%x",
+				envelope.Hash().Hex(), wh.BloomFilter(), envelope.Bloom(), envelope.Topic)
+		}
 	}
 
 	hash := envelope.Hash()
@@ -897,3 +1030,40 @@ func GenerateRandomID() (id string, err error) {
 	id = common.Bytes2Hex(buf)
 	return id, err
 }
+
+func isFullNode(bloom []byte) bool {
+	if bloom == nil {
+		return true
+	}
+	for _, b := range bloom {
+		if b != 255 {
+			return false
+		}
+	}
+	return true
+}
+
+func bloomFilterMatch(filter, sample []byte) bool {
+	if filter == nil {
+		// full node, accepts all messages
+		return true
+	}
+
+	for i := 0; i < bloomFilterSize; i++ {
+		f := filter[i]
+		s := sample[i]
+		if (f | s) != f {
+			return false
+		}
+	}
+
+	return true
+}
+
+func addBloom(a, b []byte) []byte {
+	c := make([]byte, bloomFilterSize)
+	for i := 0; i < bloomFilterSize; i++ {
+		c[i] = a[i] | b[i]
+	}
+	return c
+}
diff --git a/whisper/whisperv6/whisper_test.go b/whisper/whisperv6/whisper_test.go
index b391a1161..fa14acb1b 100644
--- a/whisper/whisperv6/whisper_test.go
+++ b/whisper/whisperv6/whisper_test.go
@@ -843,3 +843,64 @@ func TestSymmetricSendKeyMismatch(t *testing.T) {
 		t.Fatalf("received a message when keys weren't matching")
 	}
 }
+
+func TestBloom(t *testing.T) {
+	topic := TopicType{0, 0, 255, 6}
+	b := TopicToBloom(topic)
+	x := make([]byte, bloomFilterSize)
+	x[0] = byte(1)
+	x[32] = byte(1)
+	x[bloomFilterSize-1] = byte(128)
+	if !bloomFilterMatch(x, b) || !bloomFilterMatch(b, x) {
+		t.Fatalf("bloom filter does not match the mask")
+	}
+
+	_, err := mrand.Read(b)
+	if err != nil {
+		t.Fatalf("math rand error")
+	}
+	_, err = mrand.Read(x)
+	if err != nil {
+		t.Fatalf("math rand error")
+	}
+	if !bloomFilterMatch(b, b) {
+		t.Fatalf("bloom filter does not match self")
+	}
+	x = addBloom(x, b)
+	if !bloomFilterMatch(x, b) {
+		t.Fatalf("bloom filter does not match combined bloom")
+	}
+	if !isFullNode(nil) {
+		t.Fatalf("isFullNode did not recognize nil as full node")
+	}
+	x[17] = 254
+	if isFullNode(x) {
+		t.Fatalf("isFullNode false positive")
+	}
+	for i := 0; i < bloomFilterSize; i++ {
+		b[i] = byte(255)
+	}
+	if !isFullNode(b) {
+		t.Fatalf("isFullNode false negative")
+	}
+	if bloomFilterMatch(x, b) {
+		t.Fatalf("bloomFilterMatch false positive")
+	}
+	if !bloomFilterMatch(b, x) {
+		t.Fatalf("bloomFilterMatch false negative")
+	}
+
+	w := New(&DefaultConfig)
+	f := w.BloomFilter()
+	if f != nil {
+		t.Fatalf("wrong bloom on creation")
+	}
+	err = w.SetBloomFilter(x)
+	if err != nil {
+		t.Fatalf("failed to set bloom filter: %s", err)
+	}
+	f = w.BloomFilter()
+	if !bloomFilterMatch(f, x) || !bloomFilterMatch(x, f) {
+		t.Fatalf("retireved wrong bloom filter")
+	}
+}