Reuse the market process PubSub instance in index provider engine

The markets process instantiates its own `PubSub` instance with all
validators, peer scoring, etc. set up. Use that instane to join the
indexing topic, otherwise the default topic instantiated by
index-provider internally (via go-legs) has no validators.

node/modules/storageminer_idxprov.go

@@ -9,6 +9,7 @@ import (
 	"github.com/ipfs/go-datastore"
 	"github.com/ipfs/go-datastore/namespace"
 	"github.com/libp2p/go-libp2p-core/host"
+	pubsub "github.com/libp2p/go-libp2p-pubsub"
 	"go.uber.org/fx"
 	"golang.org/x/xerrors"
 
@@ -23,8 +24,8 @@ type IdxProv struct {
 	Datastore dtypes.MetadataDS
 }
 
-func IndexProvider(cfg config.IndexProviderConfig) func(params IdxProv, marketHost host.Host, dt dtypes.ProviderDataTransfer, maddr dtypes.MinerAddress) (provider.Interface, error) {
+func IndexProvider(cfg config.IndexProviderConfig) func(params IdxProv, marketHost host.Host, dt dtypes.ProviderDataTransfer, maddr dtypes.MinerAddress, ps *pubsub.PubSub) (provider.Interface, error) {
-	return func(args IdxProv, marketHost host.Host, dt dtypes.ProviderDataTransfer, maddr dtypes.MinerAddress) (provider.Interface, error) {
+	return func(args IdxProv, marketHost host.Host, dt dtypes.ProviderDataTransfer, maddr dtypes.MinerAddress, ps *pubsub.PubSub) (provider.Interface, error) {
 		ipds := namespace.Wrap(args.Datastore, datastore.NewKey("/index-provider"))
 		var opts = []engine.Option{
 			engine.WithDatastore(ipds),
@@ -36,16 +37,31 @@ func IndexProvider(cfg config.IndexProviderConfig) func(params IdxProv, marketHo
 			engine.WithPurgeCacheOnStart(cfg.PurgeCacheOnStart),
 		}
 
-		llog := log.With("idxProvEnabled", cfg.Enable, "pid", marketHost.ID(), "retAddrs", marketHost.Addrs())
+		llog := log.With(
+			"idxProvEnabled", cfg.Enable,
+			"pid", marketHost.ID(),
+			"topic", cfg.TopicName,
+			"retAddrs", marketHost.Addrs())
 		// If announcements to the network are enabled, then set options for datatransfer publisher.
 		if cfg.Enable {
+			// Join the indexer topic using the market's pubsub instance. Otherwise, the provider
+			// engine would create its own instance of pubsub down the line in go-legs, which has
+			// no validators by default.
+			t, err := ps.Join(cfg.TopicName)
+			if err != nil {
+				llog.Errorw("Failed to join indexer topic", "err", err)
+				return nil, xerrors.Errorf("joining indexer topic %s: %w", cfg.TopicName, err)
+			}
+
 			// Get the miner ID and set as extra gossip data.
 			// The extra data is required by the lotus-specific index-provider gossip message validators.
 			ma := address.Address(maddr)
 			opts = append(opts,
 				engine.WithPublisherKind(engine.DataTransferPublisher),
 				engine.WithDataTransfer(dt),
-				engine.WithExtraGossipData(ma.Bytes()))
+				engine.WithExtraGossipData(ma.Bytes()),
+				engine.WithTopic(t),
+			)
 			llog = llog.With("extraGossipData", ma)
 		} else {
 			opts = append(opts, engine.WithPublisherKind(engine.NoPublisher))