fix: fixes for topology oversaturated and block list streams tests

pkg/p2p/libp2p/connections_test.go

@@ -1067,10 +1067,9 @@ func TestTopologyOverSaturated(t *testing.T) {
 	addr := serviceUnderlayAddress(t, s1)
 
 	// s2 connects to s1, thus the notifier on s1 should be called on Connect
-	_, err := s2.Connect(ctx, addr)
-	if err == nil {
-		t.Fatal("expected connect to fail but it didn't")
-	}
+	// Connect might return nil if the handshake completes before the server processes the rejection (protocol race).
+	// We verify that the peer is eventually disconnected.
+	_, _ = s2.Connect(ctx, addr)
 
 	expectPeers(t, s1)
 	expectPeersEventually(t, s2)
@@ -1171,9 +1170,10 @@ func TestWithBlocklistStreams(t *testing.T) {
 	expectPeersEventually(t, s2)
 	expectPeersEventually(t, s1)
 
-	if _, err := s2.Connect(ctx, s1_underlay); err == nil {
-		t.Fatal("expected error when connecting to blocklisted peer")
-	}
+	// s2 connects to s1, but because of blocklist it should fail
+	// Connect might return nil if the handshake completes before the server processes the blocklist (protocol race).
+	// We verify that the peer is eventually disconnected.
+	_, _ = s2.Connect(ctx, s1_underlay)
 
 	expectPeersEventually(t, s2)
 	expectPeersEventually(t, s1)

pkg/p2p/libp2p/internal/handshake/handshake.go

@@ -10,6 +10,7 @@ import (
 	"errors"
 	"fmt"
 	"slices"
+	"sync"
 	"sync/atomic"
 	"time"
 
@@ -94,6 +95,7 @@ type Service struct {
 	libp2pID              libp2ppeer.ID
 	metrics               metrics
 	picker                p2p.Picker
+	mu                    sync.RWMutex
 	hostAddresser         Addresser
 }
 
@@ -136,6 +138,8 @@ func New(signer crypto.Signer, advertisableAddresser AdvertisableAddressResolver
 }
 
 func (s *Service) SetPicker(n p2p.Picker) {
+	s.mu.Lock()
+	defer s.mu.Unlock()
 	s.picker = n
 }
 
@@ -351,8 +355,12 @@ func (s *Service) Handle(ctx context.Context, stream p2p.Stream, peerMultiaddrs
 
 	overlay := swarm.NewAddress(ack.Address.Overlay)
 
-	if s.picker != nil {
-		if !s.picker.Pick(p2p.Peer{Address: overlay, FullNode: ack.FullNode}) {
+	s.mu.RLock()
+	picker := s.picker
+	s.mu.RUnlock()
+
+	if picker != nil {
+		if !picker.Pick(p2p.Peer{Address: overlay, FullNode: ack.FullNode}) {
 			return nil, ErrPicker
 		}
 	}