p2p/discover: fix TestUDPv4_findnode data race with revalidation ping

Author: hero5512

p2p/discover/v4_udp_test.go

@@ -282,20 +282,46 @@ func TestUDPv4_findnode(t *testing.T) {
 	expected := test.table.findnodeByID(testTarget.ID(), bucketSize, true)
 	test.packetIn(nil, &v4wire.Findnode{Target: testTarget, Expiration: futureExp})
 	waitNeighbors := func(want []*enode.Node) {
-		test.waitPacketOut(func(p *v4wire.Neighbors, to netip.AddrPort, hash []byte) {
-			if len(p.Nodes) != len(want) {
-				t.Errorf("wrong number of results: got %d, want %d", len(p.Nodes), len(want))
+		timeout := time.After(1 * time.Minute)
+		for {
+			select {
+			case <-timeout:
+				t.Fatal("timeout waiting for neighbors response")
+			default:
+			}
+			dgram, err := test.pipe.receive()
+			if err == errClosed {
+				t.Fatal("socket closed before receiving neighbors")
+			} else if err != nil {
+				t.Fatal("packet receive error:", err)
+			}
+			p, _, _, err := v4wire.Decode(dgram.data)
+			if err != nil {
+				t.Fatalf("sent packet decode error: %v", err)
+			}
+			// Skip any PING packets from revalidation
+			if _, ok := p.(*v4wire.Ping); ok {
+				continue
+			}
+			// Check we got NEIGHBORS
+			neighbors, ok := p.(*v4wire.Neighbors)
+			if !ok {
+				t.Fatalf("sent packet type mismatch, got: %T, want: *v4wire.Neighbors", p)
+			}
+			if len(neighbors.Nodes) != len(want) {
+				t.Errorf("wrong number of results: got %d, want %d", len(neighbors.Nodes), len(want))
 				return
 			}
-			for i, n := range p.Nodes {
+			for i, n := range neighbors.Nodes {
 				if n.ID.ID() != want[i].ID() {
 					t.Errorf("result mismatch at %d:\n  got: %v\n  want: %v", i, n, expected.entries[i])
 				}
 				if !live[n.ID.ID()] {
 					t.Errorf("result includes dead node %v", n.ID.ID())
 				}
 			}
-		})
+			return
+		}
 	}
 	// Receive replies.
 	want := expected.entries