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chore(kad): stricter closest peer #5688

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16bbbc6
chore: stricter closest peer
acud Nov 5, 2026
30c26c4
chore: add missing test vectors
acud Nov 10, 2026
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8 changes: 1 addition & 7 deletions pkg/topology/kademlia/kademlia.go
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Original file line number Diff line number Diff line change
Expand Up @@ -1356,22 +1356,16 @@ func (k *Kad) ClosestPeer(addr swarm.Address, includeSelf bool, filter topology.

closest := swarm.ZeroAddress

if includeSelf && k.reachability == p2p.ReachabilityStatusPublic {
if includeSelf {
closest = k.base
}

prox := swarm.Proximity(k.base.Bytes(), addr.Bytes())

// iterate starting from bin 0 to the maximum bin
err := k.EachConnectedPeerRev(func(peer swarm.Address, bin uint8) (bool, bool, error) {
if swarm.ContainsAddress(skipPeers, peer) {
return false, false, nil
}

if bin > prox && !closest.IsZero() {
return true, false, nil
}

if closest.IsZero() {
closest = peer
return false, false, nil
Expand Down
40 changes: 37 additions & 3 deletions pkg/topology/kademlia/kademlia_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -973,6 +973,12 @@ func TestClosestPeer(t *testing.T) {
{
Address: swarm.MustParseHexAddress("6000000000000000000000000000000000000000000000000000000000000000"), // binary 0110 -> po 1 to base
},
{
Address: swarm.MustParseHexAddress("1000000000000000000000000000000000000000000000000000000000000000"), // binary 0001 -> po 3 to base
},
{
Address: swarm.MustParseHexAddress("0800000000000000000000000000000000000000000000000000000000000000"), // binary 0000 1 -> po 4 to base
},
}

disc := mock.NewDiscovery()
Expand Down Expand Up @@ -1002,7 +1008,7 @@ func TestClosestPeer(t *testing.T) {
addOne(t, beeCrypto.NewDefaultSigner(pk), kad, ab, v.Address)
}

waitPeers(t, kad, 3)
waitPeers(t, kad, 5)

// ClosestPeer only considers self when the node is publicly reachable.
kad.UpdateReachability(p2p.ReachabilityStatusPublic)
Expand All @@ -1011,8 +1017,10 @@ func TestClosestPeer(t *testing.T) {
chunkAddress swarm.Address // chunk address to test
expectedPeer int // points to the index of the connectedPeers slice. -1 means self (baseOverlay)
includeSelf bool
skipPeers []int // indexes of connectedPeers to skip
}{
{
// po(base, chunk) = 1, the peer in the deeper bin 3 must not stop the search
chunkAddress: swarm.MustParseHexAddress("7000000000000000000000000000000000000000000000000000000000000000"), // 0111, wants peer 2
expectedPeer: 2,
includeSelf: true,
Expand Down Expand Up @@ -1047,13 +1055,39 @@ func TestClosestPeer(t *testing.T) {
expectedPeer: -1,
includeSelf: true,
},
{
chunkAddress: swarm.MustParseHexAddress("0000001000000000000000000000000000000000000000000000000000000000"), // 1000 want peer 4
expectedPeer: 4,
includeSelf: false,
},
{
chunkAddress: swarm.MustParseHexAddress("0000001000000000000000000000000000000000000000000000000000000000"), // 1000 want peer 1
expectedPeer: 1, // smallest distance: 2894...
expectedPeer: 1, // smallest distance once peers 3 and 4 are skipped
includeSelf: false,
skipPeers: []int{3, 4},
},
{
// po(base, chunk) = 2, the peers in the deeper bins 3 and 4 are skipped
chunkAddress: swarm.MustParseHexAddress("3000000000000000000000000000000000000000000000000000000000000000"), // 0011, want peer 2
expectedPeer: 2,
includeSelf: false,
skipPeers: []int{3, 4},
},
{
// po(base, chunk) = 2, the peers in bins 0-1 are skipped, so only peers in bins
// deeper than po(base, chunk) are left. The peer in bin 4 is closer than the one
// in bin 3, so the search must not stop after the first deeper bin.
chunkAddress: swarm.MustParseHexAddress("2000000000000000000000000000000000000000000000000000000000000000"), // 0010, want peer 4
expectedPeer: 4,
includeSelf: false,
skipPeers: []int{0, 1, 2},
},
} {
peer, err := kad.ClosestPeer(tc.chunkAddress, tc.includeSelf, topology.Select{})
var skip []swarm.Address
for _, i := range tc.skipPeers {
skip = append(skip, connectedPeers[i].Address)
}
peer, err := kad.ClosestPeer(tc.chunkAddress, tc.includeSelf, topology.Select{}, skip...)
if tc.expectedPeer == -1 {
if !errors.Is(err, topology.ErrWantSelf) {
t.Fatalf("wanted %v but got %v", topology.ErrWantSelf, err)
Expand Down
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