swarm/network: Cover edge case when only proxpeers and more than one farthest

swarm/network/kademlia.go

@@ -454,20 +454,32 @@ func (k *Kademlia) neighbourhoodDepth() (depth int) {
 	}
 	var size int
 	var b bool
+	var lastPo int
 	f := func(v pot.Val, i int) bool {
 		size++
+
+		// the actual depth of the farthest nn
 		if size == k.MinProxBinSize {
 			b = true
 			depth = i
 			return true
 		}
+
+		// if there are empty bins between farthest nn and current node, the depth should be the farthest of those empty bins
 		if b && i < depth {
 			depth = i + 1
+			lastPo = i
 			return false
 		}
+		lastPo = i
 		return true
 	}
 	k.conns.EachNeighbour(k.base, pof, f)
+
+	// cover edge case where more than one farthest nn and only proxpeers
+	if lastPo == depth {
+		depth = 0
+	}
 	return depth
 }
 

swarm/network/kademlia_test.go

@@ -76,7 +76,7 @@ func Register(k *Kademlia, regs ...string) {
 	}
 }
 
-func TestNeighborhoodDepth(t *testing.T) {
+func TestNeighbourhoodDepth(t *testing.T) {
 	baseAddressBytes := RandomAddr().OAddr
 	kad := NewKademlia(baseAddressBytes, NewKadParams())
 
@@ -103,7 +103,7 @@ func TestNeighborhoodDepth(t *testing.T) {
 	kad.On(midPeer)
 	depth = kad.NeighbourhoodDepth()
 	if depth != 5 {
-		t.Fatalf("expected depth 4, was %d", depth)
+		t.Fatalf("expected depth 5, was %d", depth)
 	}
 
 	kad.Off(midPeer)
@@ -119,6 +119,24 @@ func TestNeighborhoodDepth(t *testing.T) {
 	if depth != 2 {
 		t.Fatalf("expected depth 2, was %d", depth)
 	}
+
+	midSameAddress := pot.RandomAddressAt(baseAddress, 4)
+	midSamePeer := newTestDiscoveryPeer(midSameAddress, kad)
+	kad.Off(closerPeer)
+	kad.On(midPeer)
+	kad.On(midSamePeer)
+	depth = kad.NeighbourhoodDepth()
+	if depth != 2 {
+		t.Fatalf("expected depth 2, was %d", depth)
+	}
+
+	kad.Off(fartherPeer)
+	log.Trace(kad.string())
+	time.Sleep(time.Millisecond)
+	depth = kad.NeighbourhoodDepth()
+	if depth != 0 {
+		t.Fatalf("expected depth 0, was %d", depth)
+	}
 }
 
 func testSuggestPeer(k *Kademlia, expAddr string, expPo int, expWant bool) error {