pan: fix pathPool query path procedure + close underlay UDPConn if QU…

…IC session was not established successfully (#259)

* fix pathPool query path procedure

* refactor

* pass

pkg/pan/pool.go

@@ -67,16 +67,20 @@ func (p *pathPool) unsubscribe(dstIA IA, s pathPoolSubscriber) {
 }
 
 // paths returns paths to dstIA. This _may_ query paths, unless they have recently been queried.
-func (p *pathPool) paths(ctx context.Context, dstIA IA) ([]*Path, error) {
+func (p *pathPool) paths(ctx context.Context, dstIA IA) ([]*Path, bool, error) {
 	p.entriesMutex.RLock()
-	if entry, ok := p.entries[dstIA]; ok {
-		if time.Since(entry.lastQuery) > pathRefreshMinInterval {
-			defer p.entriesMutex.RUnlock()
-			return append([]*Path{}, entry.paths...), nil
-		}
-	}
+	entry, ok := p.entries[dstIA]
 	p.entriesMutex.RUnlock()
-	return p.queryPaths(ctx, dstIA)
+
+	if ok && !shouldQuery(time.Now(), entry.earliestExpiry, entry.lastQuery) {
+		return append([]*Path{}, entry.paths...), false, nil
+	}
+
+	paths, err := p.queryPaths(ctx, dstIA)
+	if err != nil {
+		return nil, false, err
+	}
+	return paths, true, nil
 }
 
 // queryPaths returns paths to dstIA. Unconditionally requests paths from sciond.
@@ -100,13 +104,6 @@ func (p *pathPool) cachedPaths(dst IA) []*Path {
 	return append([]*Path{}, p.entries[dst].paths...)
 }
 
-func (p *pathPool) entry(dstIA IA) (pathPoolDst, bool) {
-	p.entriesMutex.RLock()
-	defer p.entriesMutex.RUnlock()
-	e, ok := p.entries[dstIA]
-	return e, ok
-}
-
 func (e *pathPoolDst) update(paths []*Path) {
 	now := time.Now()
 	expiryDropTime := now.Add(-pathPruneLeadTime)
@@ -151,3 +148,9 @@ func earliestPathExpiry(paths []*Path) time.Time {
 	}
 	return ret
 }
+
+func shouldQuery(now, expiry, lastQuery time.Time) bool {
+	earliestAllowedRefresh := lastQuery.Add(pathRefreshMinInterval)
+	timeForRefresh := expiry.Add(-pathRefreshLeadTime)
+	return now.After(earliestAllowedRefresh) && now.After(timeForRefresh)
+}

pkg/pan/quic_dial.go

@@ -79,6 +79,8 @@ func DialQUIC(ctx context.Context,
 
 	session, err := quic.Dial(ctx, pconn, remote, tlsConf, quicConf)
 	if err != nil {
+		// Close the underlying connection if the QUIC session could not be established.
+		pconn.Close()
 		return nil, err
 	}
 	return &QUICSession{session, conn}, nil

pkg/pan/refresher.go

@@ -43,7 +43,7 @@ func makeRefresher(pool *pathPool) refresher {
 // subscribe for paths to dst.
 func (r *refresher) subscribe(ctx context.Context, dst IA, s refreshee) ([]*Path, error) {
 	// BUG: oops, this will not inform subscribers of updated paths. Need to explicily check here
-	paths, err := r.pool.paths(ctx, dst)
+	paths, _, err := r.pool.paths(ctx, dst)
 	if err != nil {
 		return nil, err
 	}
@@ -105,7 +105,6 @@ func (r *refresher) run() {
 }
 
 func (r *refresher) refresh() {
-	now := time.Now()
 	// when a refresh is triggered, we batch all
 	r.subscribersMutex.Lock()
 	refreshIAs := make([]IA, 0, len(r.subscribers))
@@ -115,32 +114,23 @@ func (r *refresher) refresh() {
 	r.subscribersMutex.Unlock()
 
 	for _, dstIA := range refreshIAs {
-		poolEntry, _ := r.pool.entry(dstIA)
-		if r.shouldRefresh(now, poolEntry.earliestExpiry, poolEntry.lastQuery) {
-			paths, err := r.pool.queryPaths(context.Background(), dstIA)
-			if err != nil {
-				// ignore errors here. The idea is that there is probably a lot of time
-				// until this manifests as an actual problem to the application (i.e.
-				// when the paths actually expire).
-				// TODO: check whether there are errors that could be handled, like try to reconnect
-				// to sciond or something like that.
-				continue
-			}
-			r.subscribersMutex.Lock()
-			for _, subscriber := range r.subscribers[dstIA] {
-				subscriber.refresh(dstIA, paths)
-			}
-			r.subscribersMutex.Unlock()
+		paths, areFresh, err := r.pool.paths(context.Background(), dstIA)
+		if err != nil || !areFresh {
+			// ignore errors here. The idea is that there is probably a lot of time
+			// until this manifests as an actual problem to the application (i.e.
+			// when the paths actually expire).
+			// TODO: check whether there are errors that could be handled, like try to reconnect
+			// to sciond or something like that.
+			continue
+		}
+		r.subscribersMutex.Lock()
+		for _, subscriber := range r.subscribers[dstIA] {
+			subscriber.refresh(dstIA, paths)
 		}
+		r.subscribersMutex.Unlock()
 	}
 }
 
-func (r *refresher) shouldRefresh(now, expiry, lastQuery time.Time) bool {
-	earliestAllowedRefresh := lastQuery.Add(pathRefreshMinInterval)
-	timeForRefresh := expiry.Add(-pathRefreshLeadTime)
-	return now.After(earliestAllowedRefresh) && now.After(timeForRefresh)
-}
-
 func (r *refresher) untilNextRefresh(prevRefresh time.Time) time.Duration {
 	return time.Until(r.nextRefresh(prevRefresh))
 }