feat(bitswap): add option to disable Bitswap server (#911)

* add option to enable/disable server initialization
* replace serverEnabled checks with nil checks for server initialization
* add tests for BitSwap functionality with server disabled
* update NotifyNewBlocks to check for server initialization using nil check
* update changelog

Author: gystemd

CHANGELOG.md

@@ -30,6 +30,7 @@ The following emojis are used to highlight certain changes:
   - `fetcher/impl/blockservice`: new option `SkipNotFound` for the IPLD fetcher. It will skip not found nodes when traversing the DAG. This allows offline traversal of DAGs when using, for example, an offline blockservice.
   - This enables use case of providing lazy-loaded, partially local DAGs (like `ipfs files` in Kubo's MFS implementation, see [kubo#10386](https://github.com/ipfs/kubo/issues/10386))
 - `gateway`: generated HTML with UnixFS directory listings now include a button for copying CIDs of child entities [#899](https://github.com/ipfs/boxo/pull/899)
+- `bitswap/server`: Add ability to enable/disable bitswap server using `WithServerEnabled` bitswap option (#911)[https://github.com/ipfs/boxo/pull/911]
 
 ### Changed
 

bitswap/bitswap.go

@@ -51,13 +51,15 @@ type Bitswap struct {
 	*client.Client
 	*server.Server
 
-	tracer tracer.Tracer
-	net    network.BitSwapNetwork
+	tracer        tracer.Tracer
+	net           network.BitSwapNetwork
+	serverEnabled bool
 }
 
 func New(ctx context.Context, net network.BitSwapNetwork, providerFinder routing.ContentDiscovery, bstore blockstore.Blockstore, options ...Option) *Bitswap {
 	bs := &Bitswap{
-		net: net,
+		net:           net,
+		serverEnabled: true,
 	}
 
 	var serverOptions []server.Option
@@ -83,19 +85,24 @@ func New(ctx context.Context, net network.BitSwapNetwork, providerFinder routing
 	}
 
 	ctx = metrics.CtxSubScope(ctx, "bitswap")
-
-	bs.Server = server.New(ctx, net, bstore, serverOptions...)
-	bs.Client = client.New(ctx, net, providerFinder, bstore, append(clientOptions, client.WithBlockReceivedNotifier(bs.Server))...)
+	if bs.serverEnabled {
+		bs.Server = server.New(ctx, net, bstore, serverOptions...)
+		clientOptions = append(clientOptions, client.WithBlockReceivedNotifier(bs.Server))
+	}
+	bs.Client = client.New(ctx, net, providerFinder, bstore, clientOptions...)
 	net.Start(bs) // use the polyfill receiver to log received errors and trace messages only once
 
 	return bs
 }
 
 func (bs *Bitswap) NotifyNewBlocks(ctx context.Context, blks ...blocks.Block) error {
-	return multierr.Combine(
-		bs.Client.NotifyNewBlocks(ctx, blks...),
-		bs.Server.NotifyNewBlocks(ctx, blks...),
-	)
+	if bs.Server != nil {
+		return multierr.Combine(
+			bs.Client.NotifyNewBlocks(ctx, blks...),
+			bs.Server.NotifyNewBlocks(ctx, blks...),
+		)
+	}
+	return bs.Client.NotifyNewBlocks(ctx, blks...)
 }
 
 type Stat struct {
@@ -115,46 +122,63 @@ func (bs *Bitswap) Stat() (*Stat, error) {
 	if err != nil {
 		return nil, err
 	}
-	ss, err := bs.Server.Stat()
-	if err != nil {
-		return nil, err
-	}
 
-	return &Stat{
+	// Initialize stat with client stats
+	stat := &Stat{
 		Wantlist:         cs.Wantlist,
 		BlocksReceived:   cs.BlocksReceived,
 		DataReceived:     cs.DataReceived,
 		DupBlksReceived:  cs.DupBlksReceived,
 		DupDataReceived:  cs.DupDataReceived,
 		MessagesReceived: cs.MessagesReceived,
-		Peers:            ss.Peers,
-		BlocksSent:       ss.BlocksSent,
-		DataSent:         ss.DataSent,
-	}, nil
+		// Server stats will be added conditionally
+	}
+
+	// Stats only available if server is enabled
+	if bs.Server != nil {
+		ss, err := bs.Server.Stat()
+		if err != nil {
+			return stat, fmt.Errorf("failed to get server stats: %w", err)
+		}
+		stat.Peers = ss.Peers
+		stat.BlocksSent = ss.BlocksSent
+		stat.DataSent = ss.DataSent
+	}
+
+	return stat, nil
 }
 
 func (bs *Bitswap) Close() error {
 	bs.net.Stop()
 	bs.Client.Close()
-	bs.Server.Close()
+	if bs.Server != nil {
+		bs.Server.Close()
+	}
 	return nil
 }
 
 func (bs *Bitswap) WantlistForPeer(p peer.ID) []cid.Cid {
 	if p == bs.net.Self() {
 		return bs.Client.GetWantlist()
 	}
-	return bs.Server.WantlistForPeer(p)
+	if bs.Server != nil {
+		return bs.Server.WantlistForPeer(p)
+	}
+	return nil
 }
 
 func (bs *Bitswap) PeerConnected(p peer.ID) {
 	bs.Client.PeerConnected(p)
-	bs.Server.PeerConnected(p)
+	if bs.Server != nil {
+		bs.Server.PeerConnected(p)
+	}
 }
 
 func (bs *Bitswap) PeerDisconnected(p peer.ID) {
 	bs.Client.PeerDisconnected(p)
-	bs.Server.PeerDisconnected(p)
+	if bs.Server != nil {
+		bs.Server.PeerDisconnected(p)
+	}
 }
 
 func (bs *Bitswap) ReceiveError(err error) {
@@ -169,5 +193,7 @@ func (bs *Bitswap) ReceiveMessage(ctx context.Context, p peer.ID, incoming messa
 	}
 
 	bs.Client.ReceiveMessage(ctx, p, incoming)
-	bs.Server.ReceiveMessage(ctx, p, incoming)
+	if bs.Server != nil {
+		bs.Server.ReceiveMessage(ctx, p, incoming)
+	}
 }

bitswap/bitswap_test.go

@@ -25,6 +25,7 @@ import (
 	tu "github.com/libp2p/go-libp2p-testing/etc"
 	p2ptestutil "github.com/libp2p/go-libp2p-testing/netutil"
 	peer "github.com/libp2p/go-libp2p/core/peer"
+	"github.com/multiformats/go-multiaddr"
 )
 
 const blockSize = 4
@@ -832,3 +833,121 @@ func TestWithScoreLedger(t *testing.T) {
 		t.Fatal("Expected the score ledger to be closed within 5s")
 	}
 }
+
+// TestWithServerDisabled tests that BitSwap can function properly with the server disabled.
+// In this mode, it should still be able to request and receive blocks from other peers,
+// but should not respond to requests from others.
+func TestWithServerDisabled(t *testing.T) {
+	net := tn.VirtualNetwork(delay.Fixed(kNetworkDelay))
+	block := blocks.NewBlock([]byte("block"))
+	router := mockrouting.NewServer()
+
+	// Create instance generator with default options
+	igWithServer := testinstance.NewTestInstanceGenerator(net, router, nil, nil)
+	defer igWithServer.Close()
+
+	// Create instance generator with server disabled
+	igNoServer := testinstance.NewTestInstanceGenerator(net, router, nil, []bitswap.Option{
+		bitswap.WithServerEnabled(false),
+	})
+	defer igNoServer.Close()
+
+	// Create two peers:
+	// - peerWithServer: has server enabled and has the block
+	// - peerNoServer: has server disabled
+	peerWithServer := igWithServer.Next()
+	peerNoServer := igNoServer.Next()
+
+	// We need to connect the peers so they can communicate
+	connectPeers(t, net, peerWithServer, peerNoServer)
+
+	// Add block to peerWithServer
+	addBlock(t, context.Background(), peerWithServer, block)
+
+	// Test 1: peerNoServer should be able to get a block from peerWithServer
+	ctx, cancel := context.WithTimeout(context.Background(), time.Second*5)
+	defer cancel()
+	receivedBlock, err := peerNoServer.Exchange.GetBlock(ctx, block.Cid())
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !bytes.Equal(block.RawData(), receivedBlock.RawData()) {
+		t.Fatal("Data doesn't match")
+	}
+
+	// Test 2: Now try the opposite - peerWithServer should NOT be able to get a block from peerNoServer
+	// because peerNoServer has server disabled and won't respond to requests
+	newBlock := blocks.NewBlock([]byte("newblock"))
+	addBlock(t, context.Background(), peerNoServer, newBlock)
+
+	ctx2, cancel2 := context.WithTimeout(context.Background(), 500*time.Millisecond)
+	defer cancel2()
+	_, err = peerWithServer.Exchange.GetBlock(ctx2, newBlock.Cid())
+
+	// We expect this to fail with deadline exceeded because peerNoServer won't respond
+	if err != context.DeadlineExceeded {
+		t.Fatalf("Expected DeadlineExceeded error, got: %v", err)
+	}
+
+	// Test 3: Verify that Stat() returns correct values even with server disabled
+	noServerStat, err := peerNoServer.Exchange.Stat()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// With server disabled, we should still have valid client stats
+	if noServerStat.BlocksReceived != 1 {
+		t.Errorf("Expected BlocksReceived to be 1, got %d", noServerStat.BlocksReceived)
+	}
+	if noServerStat.DataReceived != uint64(len(block.RawData())) {
+		t.Errorf("Expected DataReceived to be %d, got %d", len(block.RawData()), noServerStat.DataReceived)
+	}
+
+	// With server disabled, server stats should be zero
+	if noServerStat.BlocksSent != 0 {
+		t.Errorf("Expected BlocksSent to be 0, got %d", noServerStat.BlocksSent)
+	}
+	if noServerStat.DataSent != 0 {
+		t.Errorf("Expected DataSent to be 0, got %d", noServerStat.DataSent)
+	}
+}
+
+// Helper function to connect two peers
+func connectPeers(t *testing.T, net tn.Network, a, b testinstance.Instance) {
+	t.Helper()
+	err := a.Adapter.Connect(context.Background(), peer.AddrInfo{
+		ID:    b.Identity.ID(),
+		Addrs: []multiaddr.Multiaddr{b.Identity.Address()},
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+}
+
+// TestServerDisabledNotifyNewBlocks tests that NotifyNewBlocks works correctly
+// when the server is disabled.
+func TestServerDisabledNotifyNewBlocks(t *testing.T) {
+	net := tn.VirtualNetwork(delay.Fixed(kNetworkDelay))
+	router := mockrouting.NewServer()
+
+	// Create instance with server disabled
+	ig := testinstance.NewTestInstanceGenerator(net, router, nil, []bitswap.Option{
+		bitswap.WithServerEnabled(false),
+	})
+	defer ig.Close()
+
+	instance := ig.Next()
+	block := blocks.NewBlock([]byte("test block"))
+
+	// Add block to blockstore
+	err := instance.Blockstore.Put(context.Background(), block)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// Notify about new block - this should not cause errors even with server disabled
+	err = instance.Exchange.NotifyNewBlocks(context.Background(), block)
+	if err != nil {
+		t.Fatalf("NotifyNewBlocks failed with server disabled: %s", err)
+	}
+}

bitswap/options.go

@@ -103,6 +103,14 @@ func WithTracer(tap tracer.Tracer) Option {
 	}
 }
 
+func WithServerEnabled(enabled bool) Option {
+	return Option{
+		option(func(bs *Bitswap) {
+			bs.serverEnabled = enabled
+		}),
+	}
+}
+
 func WithClientOption(opt client.Option) Option {
 	return Option{opt}
 }