implement synchronous validation for locally published messages

So that locally published messages are never dropped because of full
validation queues.

pubsub.go

@@ -65,9 +65,6 @@ type PubSub struct {
 	// incoming messages from other peers
 	incoming chan *RPC
 
-	// messages we are publishing out to our peers
-	publish chan *Message
-
 	// addSub is a control channel for us to add and remove subscriptions
 	addSub chan *addSubReq
 
@@ -234,7 +231,6 @@ func NewPubSub(ctx context.Context, h host.Host, rt PubSubRouter, opts ...Option
 		signKey:               nil,
 		signPolicy:            StrictSign,
 		incoming:              make(chan *RPC, 32),
-		publish:               make(chan *Message),
 		newPeers:              make(chan peer.ID),
 		newPeerStream:         make(chan network.Stream),
 		newPeerError:          make(chan peer.ID),
@@ -589,10 +585,6 @@ func (p *PubSub) processLoop(ctx context.Context) {
 		case rpc := <-p.incoming:
 			p.handleIncomingRPC(rpc)
 
-		case msg := <-p.publish:
-			p.tracer.PublishMessage(msg)
-			p.pushMsg(msg)
-
 		case msg := <-p.sendMsg:
 			p.publishMessage(msg)
 
@@ -999,35 +991,10 @@ func (p *PubSub) pushMsg(msg *Message) {
 		return
 	}
 
-	// reject unsigned messages when strict before we even process the id
-	if p.signPolicy.mustVerify() {
-		if p.signPolicy.mustSign() {
-			if msg.Signature == nil {
-				log.Debugf("dropping unsigned message from %s", src)
-				p.tracer.RejectMessage(msg, RejectMissingSignature)
-				return
-			}
-			// Actual signature verification happens in the validation pipeline,
-			// after checking if the message was already seen or not,
-			// to avoid unnecessary signature verification processing-cost.
-		} else {
-			if msg.Signature != nil {
-				log.Debugf("dropping message with unexpected signature from %s", src)
-				p.tracer.RejectMessage(msg, RejectUnexpectedSignature)
-				return
-			}
-			// If we are expecting signed messages, and not authoring messages,
-			// then do no accept seq numbers, from data, or key data.
-			// The default msgID function still relies on Seqno and From,
-			// but is not used if we are not authoring messages ourselves.
-			if p.signID == "" {
-				if msg.Seqno != nil || msg.From != nil || msg.Key != nil {
-					log.Debugf("dropping message with unexpected auth info from %s", src)
-					p.tracer.RejectMessage(msg, RejectUnexpectedAuthInfo)
-					return
-				}
-			}
-		}
+	err := p.checkSignature(msg)
+	if err != nil {
+		log.Debugf("dropping message from %s: %s", src, err)
+		return
 	}
 
 	// reject messages claiming to be from ourselves but not locally published
@@ -1054,6 +1021,38 @@ func (p *PubSub) pushMsg(msg *Message) {
 	}
 }
 
+func (p *PubSub) checkSignature(msg *Message) error {
+	// reject unsigned messages when strict before we even process the id
+	if p.signPolicy.mustVerify() {
+		if p.signPolicy.mustSign() {
+			if msg.Signature == nil {
+				p.tracer.RejectMessage(msg, RejectMissingSignature)
+				return ValidationError{Reason: RejectMissingSignature}
+			}
+			// Actual signature verification happens in the validation pipeline,
+			// after checking if the message was already seen or not,
+			// to avoid unnecessary signature verification processing-cost.
+		} else {
+			if msg.Signature != nil {
+				p.tracer.RejectMessage(msg, RejectUnexpectedSignature)
+				return ValidationError{Reason: RejectUnexpectedSignature}
+			}
+			// If we are expecting signed messages, and not authoring messages,
+			// then do no accept seq numbers, from data, or key data.
+			// The default msgID function still relies on Seqno and From,
+			// but is not used if we are not authoring messages ourselves.
+			if p.signID == "" {
+				if msg.Seqno != nil || msg.From != nil || msg.Key != nil {
+					p.tracer.RejectMessage(msg, RejectUnexpectedAuthInfo)
+					return ValidationError{Reason: RejectUnexpectedAuthInfo}
+				}
+			}
+		}
+	}
+
+	return nil
+}
+
 func (p *PubSub) publishMessage(msg *Message) {
 	p.tracer.DeliverMessage(msg)
 	p.notifySubs(msg)

topic.go

@@ -241,13 +241,7 @@ func (t *Topic) Publish(ctx context.Context, data []byte, opts ...PubOpt) error
 		t.p.disc.Bootstrap(ctx, t.topic, pub.ready)
 	}
 
-	select {
-	case t.p.publish <- &Message{m, t.p.host.ID(), nil}:
-	case <-t.p.ctx.Done():
-		return t.p.ctx.Err()
-	}
-
-	return nil
+	return t.p.val.Publish(&Message{m, t.p.host.ID(), nil})
 }
 
 // WithReadiness returns a publishing option for only publishing when the router is ready.

validation.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"fmt"
 	"runtime"
+	"sync"
 	"time"
 
 	"github.com/libp2p/go-libp2p-core/peer"
@@ -15,6 +16,16 @@ const (
 	defaultValidateThrottle    = 8192
 )
 
+// ValidationError is an error that may be signalled from message publication when the message
+// fails validation
+type ValidationError struct {
+	Reason string
+}
+
+func (e ValidationError) Error() string {
+	return e.Reason
+}
+
 // Validator is a function that validates a message with a binary decision: accept or reject.
 type Validator func(context.Context, peer.ID, *Message) bool
 
@@ -56,6 +67,8 @@ type validation struct {
 
 	tracer *pubsubTracer
 
+	// mx protects the validator map
+	mx sync.Mutex
 	// topicVals tracks per topic validators
 	topicVals map[string]*topicVal
 
@@ -123,6 +136,9 @@ func (v *validation) Start(p *PubSub) {
 
 // AddValidator adds a new validator
 func (v *validation) AddValidator(req *addValReq) {
+	v.mx.Lock()
+	defer v.mx.Unlock()
+
 	topic := req.topic
 
 	_, ok := v.topicVals[topic]
@@ -180,6 +196,9 @@ func (v *validation) AddValidator(req *addValReq) {
 
 // RemoveValidator removes an existing validator
 func (v *validation) RemoveValidator(req *rmValReq) {
+	v.mx.Lock()
+	defer v.mx.Unlock()
+
 	topic := req.topic
 
 	_, ok := v.topicVals[topic]
@@ -191,6 +210,20 @@ func (v *validation) RemoveValidator(req *rmValReq) {
 	}
 }
 
+// Publish synchronously accepts a locally published message, performs applicable
+// validations and pushes the message for propagate by the pubsub system
+func (v *validation) Publish(msg *Message) error {
+	v.p.tracer.PublishMessage(msg)
+
+	err := v.p.checkSignature(msg)
+	if err != nil {
+		return err
+	}
+
+	vals := v.getValidators(msg)
+	return v.validate(vals, msg.ReceivedFrom, msg, true)
+}
+
 // Push pushes a message into the validation pipeline.
 // It returns true if the message can be forwarded immediately without validation.
 func (v *validation) Push(src peer.ID, msg *Message) bool {
@@ -211,6 +244,9 @@ func (v *validation) Push(src peer.ID, msg *Message) bool {
 
 // getValidators returns all validators that apply to a given message
 func (v *validation) getValidators(msg *Message) []*topicVal {
+	v.mx.Lock()
+	defer v.mx.Unlock()
+
 	topic := msg.GetTopic()
 
 	val, ok := v.topicVals[topic]
@@ -226,7 +262,7 @@ func (v *validation) validateWorker() {
 	for {
 		select {
 		case req := <-v.validateQ:
-			v.validate(req.vals, req.src, req.msg)
+			v.validate(req.vals, req.src, req.msg, false)
 		case <-v.p.ctx.Done():
 			return
 		}
@@ -234,16 +270,14 @@ func (v *validation) validateWorker() {
 }
 
 // validate performs validation and only sends the message if all validators succeed
-// signature validation is performed synchronously, while user validators are invoked
-// asynchronously, throttled by the global validation throttle.
-func (v *validation) validate(vals []*topicVal, src peer.ID, msg *Message) {
+func (v *validation) validate(vals []*topicVal, src peer.ID, msg *Message, synchronous bool) error {
 	// If signature verification is enabled, but signing is disabled,
 	// the Signature is required to be nil upon receiving the message in PubSub.pushMsg.
 	if msg.Signature != nil {
 		if !v.validateSignature(msg) {
 			log.Debugf("message signature validation failed; dropping message from %s", src)
 			v.tracer.RejectMessage(msg, RejectInvalidSignature)
-			return
+			return ValidationError{Reason: RejectInvalidSignature}
 		}
 	}
 
@@ -252,14 +286,14 @@ func (v *validation) validate(vals []*topicVal, src peer.ID, msg *Message) {
 	id := v.p.msgID(msg.Message)
 	if !v.p.markSeen(id) {
 		v.tracer.DuplicateMessage(msg)
-		return
+		return nil
 	} else {
 		v.tracer.ValidateMessage(msg)
 	}
 
 	var inline, async []*topicVal
 	for _, val := range vals {
-		if val.validateInline {
+		if val.validateInline || synchronous {
 			inline = append(inline, val)
 		} else {
 			async = append(async, val)
@@ -283,7 +317,7 @@ loop:
 	if result == ValidationReject {
 		log.Debugf("message validation failed; dropping message from %s", src)
 		v.tracer.RejectMessage(msg, RejectValidationFailed)
-		return
+		return ValidationError{Reason: RejectValidationFailed}
 	}
 
 	// apply async validators
@@ -298,16 +332,21 @@ loop:
 			log.Debugf("message validation throttled; dropping message from %s", src)
 			v.tracer.RejectMessage(msg, RejectValidationThrottled)
 		}
-		return
+		return nil
 	}
 
 	if result == ValidationIgnore {
 		v.tracer.RejectMessage(msg, RejectValidationIgnored)
-		return
+		return ValidationError{Reason: RejectValidationIgnored}
 	}
 
 	// no async validators, accepted message, send it!
-	v.p.sendMsg <- msg
+	select {
+	case v.p.sendMsg <- msg:
+		return nil
+	case <-v.p.ctx.Done():
+		return v.p.ctx.Err()
+	}
 }
 
 func (v *validation) validateSignature(msg *Message) bool {