compute relay address set dynamically

p2p/host/relay/autorelay.go

@@ -42,7 +42,7 @@ type AutoRelay struct {
 
 	mx     sync.Mutex
 	relays map[peer.ID]struct{}
-	addrs  []ma.Multiaddr
+	status autonat.NATStatus
 }
 
 func NewAutoRelay(ctx context.Context, bhost *basic.BasicHost, discover discovery.Discoverer, router routing.PeerRouting) *AutoRelay {
@@ -53,6 +53,7 @@ func NewAutoRelay(ctx context.Context, bhost *basic.BasicHost, discover discover
 		addrsF:     bhost.AddrsFactory,
 		relays:     make(map[peer.ID]struct{}),
 		disconnect: make(chan struct{}, 1),
+		status:     autonat.NATStatusUnknown,
 	}
 	ar.autonat = autonat.NewAutoNAT(ctx, bhost, ar.baseAddrs)
 	bhost.AddrsFactory = ar.hostAddrs
@@ -61,20 +62,14 @@ func NewAutoRelay(ctx context.Context, bhost *basic.BasicHost, discover discover
 	return ar
 }
 
-func (ar *AutoRelay) hostAddrs(addrs []ma.Multiaddr) []ma.Multiaddr {
-	ar.mx.Lock()
-	defer ar.mx.Unlock()
-	if ar.addrs != nil && ar.autonat.Status() == autonat.NATStatusPrivate {
-		return ar.addrs
-	} else {
-		return ar.addrsF(addrs)
-	}
-}
-
 func (ar *AutoRelay) baseAddrs() []ma.Multiaddr {
 	return ar.addrsF(ar.host.AllAddrs())
 }
 
+func (ar *AutoRelay) hostAddrs(addrs []ma.Multiaddr) []ma.Multiaddr {
+	return ar.relayAddrs(ar.addrsF(addrs))
+}
+
 func (ar *AutoRelay) background(ctx context.Context) {
 	select {
 	case <-time.After(autonat.AutoNATBootDelay + BootDelay):
@@ -89,37 +84,37 @@ func (ar *AutoRelay) background(ctx context.Context) {
 		wait := autonat.AutoNATRefreshInterval
 		switch ar.autonat.Status() {
 		case autonat.NATStatusUnknown:
+			ar.mx.Lock()
+			ar.status = autonat.NATStatusUnknown
+			ar.mx.Unlock()
 			wait = autonat.AutoNATRetryInterval
 
 		case autonat.NATStatusPublic:
-			// invalidate addrs
 			ar.mx.Lock()
-			if ar.addrs != nil {
-				ar.addrs = nil
+			if ar.status != autonat.NATStatusPublic {
 				push = true
 			}
+			ar.status = autonat.NATStatusPublic
 			ar.mx.Unlock()
 
-			// if we had previously announced relay addrs, push our public addrs
-			if push {
-				push = false
-				ar.host.PushIdentify()
+		case autonat.NATStatusPrivate:
+			update := ar.findRelays(ctx)
+			ar.mx.Lock()
+			if update || ar.status != autonat.NATStatusPrivate {
+				push = true
 			}
+			ar.status = autonat.NATStatusPrivate
+			ar.mx.Unlock()
+		}
 
-		case autonat.NATStatusPrivate:
-			push = false // clear, findRelays pushes as needed
-			ar.findRelays(ctx)
+		if push {
+			push = false
+			ar.host.PushIdentify()
 		}
 
 		select {
 		case <-ar.disconnect:
-			// invalidate addrs
-			ar.mx.Lock()
-			if ar.addrs != nil {
-				ar.addrs = nil
-				push = true
-			}
-			ar.mx.Unlock()
+			push = true
 		case <-time.After(wait):
 		case <-ctx.Done():
 			return
@@ -127,21 +122,13 @@ func (ar *AutoRelay) background(ctx context.Context) {
 	}
 }
 
-func (ar *AutoRelay) findRelays(ctx context.Context) {
+func (ar *AutoRelay) findRelays(ctx context.Context) bool {
 again:
 	ar.mx.Lock()
 	haveRelays := len(ar.relays)
 	if haveRelays >= DesiredRelays {
 		ar.mx.Unlock()
-		// this dance is necessary to cover the Private->Public->Private transition
-		// where we were already connected to enough relays while private and dropped
-		// the addrs while public.
-		// Note tht we don't need the lock for reading addrs, as the only writer is
-		// the current goroutine.
-		if ar.addrs == nil {
-			ar.updateAddrs()
-		}
-		return
+		return false
 	}
 	need := DesiredRelays - len(ar.relays)
 	ar.mx.Unlock()
@@ -153,7 +140,16 @@ again:
 	cancel()
 	if err != nil {
 		log.Debugf("error discovering relays: %s", err.Error())
-		return
+
+		if haveRelays == 0 {
+			log.Debug("no relays connected; retrying in 30s")
+			select {
+			case <-time.After(30 * time.Second):
+				goto again
+			case <-ctx.Done():
+				return false
+			}
+		}
 	}
 
 	log.Debugf("discovered %d relays", len(pis))
@@ -201,13 +197,11 @@ again:
 		case <-time.After(30 * time.Second):
 			goto again
 		case <-ctx.Done():
-			return
+			return false
 		}
 	}
 
-	if update > 0 || ar.addrs == nil {
-		ar.updateAddrs()
-	}
+	return update > 0
 }
 
 func (ar *AutoRelay) selectRelays(ctx context.Context, pis []pstore.PeerInfo, count, maxq int) []pstore.PeerInfo {
@@ -273,33 +267,28 @@ func (ar *AutoRelay) selectRelays(ctx context.Context, pis []pstore.PeerInfo, co
 	return result
 }
 
-func (ar *AutoRelay) updateAddrs() {
-	ar.doUpdateAddrs()
-	ar.host.PushIdentify()
-}
-
-// This function updates our NATed advertised addrs (ar.addrs)
-// The public addrs are rewritten so that they only retain the public IP part; they
-// become undialable but are useful as a hint to the dialer to determine whether or not
-// to dial private addrs.
-// The non-public addrs are included verbatim so that peers behind the same NAT/firewall
-// can still dial us directly.
-// On top of those, we add the relay-specific addrs for the relays to which we are
-// connected. For each non-private relay addr, we encapsulate the p2p-circuit addr
-// through which we can be dialed.
-func (ar *AutoRelay) doUpdateAddrs() {
+// This function is computes the NATed relay addrs when our status is private:
+// - The public addrs are removed from the address set.
+// - The non-public addrs are included verbatim so that peers behind the same NAT/firewall
+//   can still dial us directly.
+// - On top of those, we add the relay-specific addrs for the relays to which we are
+//   connected. For each non-private relay addr, we encapsulate the p2p-circuit addr
+//   through which we can be dialed.
+func (ar *AutoRelay) relayAddrs(addrs []ma.Multiaddr) []ma.Multiaddr {
 	ar.mx.Lock()
 	defer ar.mx.Unlock()
 
-	addrs := ar.baseAddrs()
+	if ar.status != autonat.NATStatusPrivate {
+		return addrs
+	}
+
 	raddrs := make([]ma.Multiaddr, 0, len(addrs)+len(ar.relays))
 
-	// remove our public addresses from the list
+	// only keep private addrs from the original addr set
 	for _, addr := range addrs {
-		if manet.IsPublicAddr(addr) {
-			continue
+		if manet.IsPrivateAddr(addr) {
+			raddrs = append(raddrs, addr)
 		}
-		raddrs = append(raddrs, addr)
 	}
 
 	// add relay specific addrs to the list
@@ -317,7 +306,7 @@ func (ar *AutoRelay) doUpdateAddrs() {
 		}
 	}
 
-	ar.addrs = raddrs
+	return raddrs
 }
 
 func shuffleRelays(pis []pstore.PeerInfo) {