feat: add peer block filter option

This feature lets a user configure a function that will
allow / deny request for a block coming from a peer.

bitswap.go

@@ -154,8 +154,15 @@ func WithTargetMessageSize(tms int) Option {
 	}
 }
 
+func WithPeerBlockRequestFilter(pbrf PeerBlockRequestFilter) Option {
+	return func(bs *Bitswap) {
+		bs.peerBlockRequestFilter = pbrf
+	}
+}
+
 type TaskInfo = decision.TaskInfo
 type TaskComparator = decision.TaskComparator
+type PeerBlockRequestFilter = decision.PeerBlockRequestFilter
 
 // WithTaskComparator configures custom task prioritization logic.
 func WithTaskComparator(comparator TaskComparator) Option {
@@ -291,6 +298,7 @@ func New(parent context.Context, network bsnet.BitSwapNetwork,
 		activeBlocksGauge,
 		decision.WithTaskComparator(bs.taskComparator),
 		decision.WithTargetMessageSize(bs.engineTargetMessageSize),
+		decision.WithPeerBlockRequestFilter(bs.peerBlockRequestFilter),
 	)
 	bs.engine.SetSendDontHaves(bs.engineSetSendDontHaves)
 
@@ -399,6 +407,9 @@ type Bitswap struct {
 	simulateDontHavesOnTimeout bool
 
 	taskComparator TaskComparator
+
+	// an optional feature to accept / deny HAVE - DONT HAVE requests
+	peerBlockRequestFilter PeerBlockRequestFilter
 }
 
 type counters struct {

internal/decision/engine.go

@@ -180,6 +180,8 @@ type Engine struct {
 	metricUpdateCounter int
 
 	taskComparator TaskComparator
+
+	peerBlockRequestFilter PeerBlockRequestFilter
 }
 
 // TaskInfo represents the details of a request from a peer.
@@ -201,6 +203,10 @@ type TaskInfo struct {
 // It should return true if task 'ta' has higher priority than task 'tb'
 type TaskComparator func(ta, tb *TaskInfo) bool
 
+// PeerBlockRequestFilter is used to accept / deny requests for a CID coming from a PeerID
+// It should return true if the request should be fullfilled.
+type PeerBlockRequestFilter func(p peer.ID, c cid.Cid) bool
+
 type Option func(*Engine)
 
 func WithTaskComparator(comparator TaskComparator) Option {
@@ -209,6 +215,12 @@ func WithTaskComparator(comparator TaskComparator) Option {
 	}
 }
 
+func WithPeerBlockRequestFilter(pbrf PeerBlockRequestFilter) Option {
+	return func(e *Engine) {
+		e.peerBlockRequestFilter = pbrf
+	}
+}
+
 func WithTargetMessageSize(size int) Option {
 	return func(e *Engine) {
 		e.targetMessageSize = size
@@ -647,8 +659,14 @@ func (e *Engine) MessageReceived(ctx context.Context, p peer.ID, m bsmsg.BitSwap
 		// Add each want-have / want-block to the ledger
 		l.Wants(c, entry.Priority, entry.WantType)
 
-		// If the block was not found
-		if !found {
+		// Check if the peer is allowed to retrieve this block
+		passFilter := true
+		if e.peerBlockRequestFilter != nil {
+			passFilter = e.peerBlockRequestFilter(p, c)
+		}
+
+		// If the block was not found or the peer doesn't pass the policy
+		if !found || !passFilter {
 			log.Debugw("Bitswap engine: block not found", "local", e.self, "from", p, "cid", entry.Cid, "sendDontHave", entry.SendDontHave)
 
 			// Only add the task to the queue if the requester wants a DONT_HAVE

internal/decision/engine_test.go

@@ -1112,6 +1112,88 @@ func TestTaskComparator(t *testing.T) {
 	}
 }
 
+func TestPeerBlockFilter(t *testing.T) {
+	ctx, cancel := context.WithTimeout(context.Background(), 1*time.Second)
+	defer cancel()
+
+	// Generate a few keys
+	keys := []string{"a", "b", "c"}
+	cids := make(map[cid.Cid]int)
+	blks := make([]blocks.Block, 0, len(keys))
+	for i, letter := range keys {
+		block := blocks.NewBlock([]byte(letter))
+		blks = append(blks, block)
+		cids[block.Cid()] = i
+	}
+
+	// Generate a few peers
+	peerIDs := make([]peer.ID, len(keys))
+	for _, i := range cids {
+		peerID := libp2ptest.RandPeerIDFatal(t)
+		peerIDs[i] = peerID
+	}
+
+	// Setup the peer
+	fpt := &fakePeerTagger{}
+	sl := NewTestScoreLedger(shortTerm, nil, clock.New())
+	bs := blockstore.NewBlockstore(dssync.MutexWrap(ds.NewMapDatastore()))
+	if err := bs.PutMany(ctx, blks); err != nil {
+		t.Fatal(err)
+	}
+
+	// use a single task worker so that the order of outgoing messages is deterministic
+	engineTaskWorkerCount := 1
+	e := newEngineForTesting(ctx, bs, 4, engineTaskWorkerCount, defaults.BitswapMaxOutstandingBytesPerPeer, fpt, "localhost", 0, sl,
+		// if this Option is omitted, the test fails
+		WithPeerBlockRequestFilter(func(p peer.ID, c cid.Cid) bool {
+			// peer 0 has access to everything
+			if p == peerIDs[0] {
+				return true
+			}
+			// peer 1 has access to key b and c
+			if p == peerIDs[1] {
+				return blks[1].Cid().Equals(c) || blks[2].Cid().Equals(c)
+			}
+			// peer 2 and other have access to key c
+			return blks[2].Cid().Equals(c)
+		}),
+	)
+	e.StartWorkers(ctx, process.WithTeardown(func() error { return nil }))
+
+	// Create wants requests
+	for _, peerID := range peerIDs {
+		partnerWantBlocks(e, keys, peerID)
+	}
+
+	// check that outgoing messages are sent with the correct content
+	checkPeer := func(peerIndex int, expectedBlocks []blocks.Block) {
+		next := <-e.Outbox()
+		envelope := <-next
+
+		peerID := peerIDs[peerIndex]
+		responseBlocks := envelope.Message.Blocks()
+
+		if peerID != envelope.Peer {
+			t.Errorf("(Peer%v) expected message for peer ID %#v but instead got message for peer ID %#v", peerIndex, peerID, envelope.Peer)
+		}
+
+		if len(responseBlocks) != len(expectedBlocks) {
+			t.Errorf("(Peer%v) expected %v block in response but instead got %v", peerIndex, len(expectedBlocks), len(responseBlocks))
+		}
+
+		// TODO: figure out how to make this test deterministic (sort or use a set?)
+		// for i, expectedBlock := range expectedBlocks {
+		// 	if responseBlocks[i].Cid() != expectedBlock.Cid() {
+		// 		t.Errorf("(Peer%v) expected block with CID %#v but instead got block with CID %#v", peerIndex, expectedBlock.Cid(), responseBlocks[i].Cid())
+		// 	}
+		// }
+	}
+
+	checkPeer(0, blks[0:3])
+	checkPeer(1, blks[1:3])
+	checkPeer(2, blks[2:3])
+}
+
 func TestTaggingPeers(t *testing.T) {
 	ctx, cancel := context.WithTimeout(context.Background(), 1*time.Second)
 	defer cancel()