Propagate announce interval, particularly for UDP

tracker/http/server/server.go

@@ -74,22 +74,23 @@ func (me Handler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 	}
 	portU64, err := strconv.ParseUint(vs.Get("port"), 0, 16)
 	addrPort := netip.AddrPortFrom(addr, uint16(portU64))
-	peers, err := me.Announce.Serve(r.Context(), tracker.AnnounceRequest{
+	res := me.Announce.Serve(r.Context(), tracker.AnnounceRequest{
 		InfoHash: infoHash,
 		PeerId:   peerId,
 		Event:    event,
 		Port:     addrPort.Port(),
 		NumWant:  -1,
-	}, addrPort, tracker.GetPeersOpts{generics.Some[uint](200)})
+	}, addrPort, tracker.GetPeersOpts{MaxCount: generics.Some[uint](200)})
+	err = res.Err
 	if err != nil {
 		log.Printf("error serving announce: %v", err)
 		http.Error(w, "error handling announce", http.StatusInternalServerError)
 		return
 	}
 	var resp httpTracker.HttpResponse
-	resp.Interval = 5 * 60
+	resp.Interval = res.Interval.UnwrapOr(5 * 60)
 	resp.Peers.Compact = true
-	for _, peer := range peers {
+	for _, peer := range res.Peers {
 		if peer.Addr().Is4() {
 			resp.Peers.List = append(resp.Peers.List, tracker.Peer{
 				IP:   peer.Addr().AsSlice(),

tracker/server.go

@@ -34,7 +34,15 @@ type AnnounceAddr = netip.AddrPort
 type AnnounceTracker interface {
 	TrackAnnounce(ctx context.Context, req udp.AnnounceRequest, addr AnnounceAddr) error
 	Scrape(ctx context.Context, infoHashes []InfoHash) ([]udp.ScrapeInfohashResult, error)
-	GetPeers(ctx context.Context, infoHash InfoHash, opts GetPeersOpts) ([]PeerInfo, error)
+	GetPeers(ctx context.Context, infoHash InfoHash, opts GetPeersOpts) ServerAnnounceResult
+}
+
+type ServerAnnounceResult struct {
+	Err      error
+	Peers    []PeerInfo
+	Interval generics.Option[int32]
+	Leechers generics.Option[int32]
+	Seeders  generics.Option[int32]
 }
 
 type AnnounceHandler struct {
@@ -91,7 +99,7 @@ var tracer = otel.Tracer("torrent.tracker.udp")
 
 func (me *AnnounceHandler) Serve(
 	ctx context.Context, req AnnounceRequest, addr AnnounceAddr, opts GetPeersOpts,
-) (peers []PeerInfo, err error) {
+) (ret ServerAnnounceResult) {
 	ctx, span := tracer.Start(
 		ctx,
 		"AnnounceHandler.Serve",
@@ -108,11 +116,11 @@ func (me *AnnounceHandler) Serve(
 	)
 	defer span.End()
 	defer func() {
-		span.SetAttributes(attribute.Int("announce.get_peers.len", len(peers)))
+		span.SetAttributes(attribute.Int("announce.get_peers.len", len(ret.Peers)))
 	}()
 
-	err = me.AnnounceTracker.TrackAnnounce(ctx, req, addr)
-	if err != nil {
+	ret.Err = me.AnnounceTracker.TrackAnnounce(ctx, req, addr)
+	if ret.Err != nil {
 		return
 	}
 	infoHash := req.InfoHash
@@ -133,15 +141,15 @@ func (me *AnnounceHandler) Serve(
 			opts.MaxCount = generics.Some(newCount)
 		}
 	}
-	peers, err = me.AnnounceTracker.GetPeers(ctx, infoHash, opts)
-	if err != nil {
+	ret = me.AnnounceTracker.GetPeers(ctx, infoHash, opts)
+	if ret.Err != nil {
 		return
 	}
 	// Take whatever peers it has ready. If it's finished, it doesn't matter if we do this inside
 	// the mutex or not.
 	if op.Ok {
 		curPeers, done := op.Value.getCurPeersAndDone()
-		addMissing(peers, curPeers)
+		addMissing(ret.Peers, curPeers)
 		if done {
 			// It doesn't get any better with this operation. Forget it.
 			op.Ok = false
@@ -152,7 +160,7 @@ func (me *AnnounceHandler) Serve(
 	// assuming the announcing peer might be that one. Really we should record a value to prevent
 	// duplicate announces. Also don't announce upstream if we got no peers because the caller asked
 	// for none.
-	if !op.Ok && len(peers) <= 1 && opts.MaxCount.UnwrapOr(1) > 0 {
+	if !op.Ok && len(ret.Peers) <= 1 && opts.MaxCount.UnwrapOr(1) > 0 {
 		op.Value, op.Ok = me.ongoingUpstreamAugmentations[infoHash]
 		if !op.Ok {
 			op.Set(me.augmentPeersFromUpstream(req.InfoHash))
@@ -170,7 +178,7 @@ func (me *AnnounceHandler) Serve(
 		case <-op.Value.doneAnnouncing:
 		}
 		cancel()
-		addMissing(peers, op.Value.getCurPeers())
+		addMissing(ret.Peers, op.Value.getCurPeers())
 	}
 	return
 }

tracker/udp/server/server.go

@@ -104,12 +104,12 @@ func (me *Server) handleAnnounce(
 	if addrFamily == udp.AddrFamilyIpv4 {
 		opts.MaxCount = generics.Some[uint](150)
 	}
-	peers, err := me.Announce.Serve(ctx, req, announceAddr, opts)
-	if err != nil {
-		return err
+	res := me.Announce.Serve(ctx, req, announceAddr, opts)
+	if res.Err != nil {
+		return res.Err
 	}
-	nodeAddrs := make([]krpc.NodeAddr, 0, len(peers))
-	for _, p := range peers {
+	nodeAddrs := make([]krpc.NodeAddr, 0, len(res.Peers))
+	for _, p := range res.Peers {
 		var ip net.IP
 		switch addrFamily {
 		default:
@@ -137,7 +137,9 @@ func (me *Server) handleAnnounce(
 	if err != nil {
 		return err
 	}
-	err = udp.Write(&buf, udp.AnnounceResponseHeader{})
+	err = udp.Write(&buf, udp.AnnounceResponseHeader{
+		Interval: res.Interval.UnwrapOr(5 * 60),
+	})
 	if err != nil {
 		return err
 	}