p2p, swarm: fix node up races by granular locking (ethereum#18976)

* swarm/network: DRY out repeated giga comment

I not necessarily agree with the way we wait for event propagation.
But I truly disagree with having duplicated giga comments.

* p2p/simulations: encapsulate Node.Up field so we avoid data races

The Node.Up field was accessed concurrently without "proper" locking.
There was a lock on Network and that was used sometimes to access
the  field. Other times the locking was missed and we had
a data race.

For example: ethereum#18464
The case above was solved, but there were still intermittent/hard to
reproduce races. So let's solve the issue permanently.

resolves: ethersphere/swarm#1146

* p2p/simulations: fix unmarshal of simulations.Node

Making Node.Up field private in 13292ee
broke TestHTTPNetwork and TestHTTPSnapshot. Because the default
UnmarshalJSON does not handle unexported fields.

Important: The fix is partial and not proper to my taste. But I cut
scope as I think the fix may require a change to the current
serialization format. New ticket:
ethersphere/swarm#1177

* p2p/simulations: Add a sanity test case for Node.Config UnmarshalJSON

* p2p/simulations: revert back to defer Unlock() pattern for Network

It's a good patten to call `defer Unlock()` right after `Lock()` so
(new) error cases won't miss to unlock. Let's get back to that pattern.

The patten was abandoned in 85a79b3,
while fixing a data race. That data race does not exist anymore,
since the Node.Up field got hidden behind its own lock.

* p2p/simulations: consistent naming for test providers Node.UnmarshalJSON

* p2p/simulations: remove JSON annotation from private fields of Node

As unexported fields are not serialized.

* p2p/simulations: fix deadlock in Network.GetRandomDownNode()

Problem: GetRandomDownNode() locks -> getDownNodeIDs() ->
GetNodes() tries to lock -> deadlock

On Network type, unexported functions must assume that `net.lock`
is already acquired and should not call exported functions which
might try to lock again.

* p2p/simulations: ensure method conformity for Network

Connect* methods were moved to p2p/simulations.Network from
swarm/network/simulation. However these new methods did not follow
the pattern of Network methods, i.e., all exported method locks
the whole Network either for read or write.

* p2p/simulations: fix deadlock during network shutdown

`TestDiscoveryPersistenceSimulationSimAdapter` often got into deadlock.
The execution was stuck on two locks, i.e, `Kademlia.lock` and
`p2p/simulations.Network.lock`. Usually the test got stuck once in each
20 executions with high confidence.

`Kademlia` was stuck in `Kademlia.EachAddr()` and `Network` in
`Network.Stop()`.

Solution: in `Network.Stop()` `net.lock` must be released before
calling `node.Stop()` as stopping a node (somehow - I did not find
the exact code path) causes `Network.InitConn()` to be called from
`Kademlia.SuggestPeer()` and that blocks on `net.lock`.

Related ticket: ethersphere/swarm#1223

* swarm/state: simplify if statement in DBStore.Put()

* p2p/simulations: remove faulty godoc from private function

The comment started with the wrong method name.

The method is simple and self explanatory. Also, it's private.
=> Let's just remove the comment.

p2p/simulations/connect.go

@@ -32,6 +32,9 @@ var (
 // It is useful when constructing a chain network topology
 // when Network adds and removes nodes dynamically.
 func (net *Network) ConnectToLastNode(id enode.ID) (err error) {
+	net.lock.Lock()
+	defer net.lock.Unlock()
+
 	ids := net.getUpNodeIDs()
 	l := len(ids)
 	if l < 2 {
@@ -41,29 +44,35 @@ func (net *Network) ConnectToLastNode(id enode.ID) (err error) {
 	if last == id {
 		last = ids[l-2]
 	}
-	return net.connect(last, id)
+	return net.connectNotConnected(last, id)
 }
 
 // ConnectToRandomNode connects the node with provided NodeID
 // to a random node that is up.
 func (net *Network) ConnectToRandomNode(id enode.ID) (err error) {
-	selected := net.GetRandomUpNode(id)
+	net.lock.Lock()
+	defer net.lock.Unlock()
+
+	selected := net.getRandomUpNode(id)
 	if selected == nil {
 		return ErrNodeNotFound
 	}
-	return net.connect(selected.ID(), id)
+	return net.connectNotConnected(selected.ID(), id)
 }
 
 // ConnectNodesFull connects all nodes one to another.
 // It provides a complete connectivity in the network
 // which should be rarely needed.
 func (net *Network) ConnectNodesFull(ids []enode.ID) (err error) {
+	net.lock.Lock()
+	defer net.lock.Unlock()
+
 	if ids == nil {
 		ids = net.getUpNodeIDs()
 	}
 	for i, lid := range ids {
 		for _, rid := range ids[i+1:] {
-			if err = net.connect(lid, rid); err != nil {
+			if err = net.connectNotConnected(lid, rid); err != nil {
 				return err
 			}
 		}
@@ -74,12 +83,19 @@ func (net *Network) ConnectNodesFull(ids []enode.ID) (err error) {
 // ConnectNodesChain connects all nodes in a chain topology.
 // If ids argument is nil, all nodes that are up will be connected.
 func (net *Network) ConnectNodesChain(ids []enode.ID) (err error) {
+	net.lock.Lock()
+	defer net.lock.Unlock()
+
+	return net.connectNodesChain(ids)
+}
+
+func (net *Network) connectNodesChain(ids []enode.ID) (err error) {
 	if ids == nil {
 		ids = net.getUpNodeIDs()
 	}
 	l := len(ids)
 	for i := 0; i < l-1; i++ {
-		if err := net.connect(ids[i], ids[i+1]); err != nil {
+		if err := net.connectNotConnected(ids[i], ids[i+1]); err != nil {
 			return err
 		}
 	}
@@ -89,39 +105,44 @@ func (net *Network) ConnectNodesChain(ids []enode.ID) (err error) {
 // ConnectNodesRing connects all nodes in a ring topology.
 // If ids argument is nil, all nodes that are up will be connected.
 func (net *Network) ConnectNodesRing(ids []enode.ID) (err error) {
+	net.lock.Lock()
+	defer net.lock.Unlock()
+
 	if ids == nil {
 		ids = net.getUpNodeIDs()
 	}
 	l := len(ids)
 	if l < 2 {
 		return nil
 	}
-	if err := net.ConnectNodesChain(ids); err != nil {
+	if err := net.connectNodesChain(ids); err != nil {
 		return err
 	}
-	return net.connect(ids[l-1], ids[0])
+	return net.connectNotConnected(ids[l-1], ids[0])
 }
 
 // ConnectNodesStar connects all nodes into a star topology
 // If ids argument is nil, all nodes that are up will be connected.
 func (net *Network) ConnectNodesStar(ids []enode.ID, center enode.ID) (err error) {
+	net.lock.Lock()
+	defer net.lock.Unlock()
+
 	if ids == nil {
 		ids = net.getUpNodeIDs()
 	}
 	for _, id := range ids {
 		if center == id {
 			continue
 		}
-		if err := net.connect(center, id); err != nil {
+		if err := net.connectNotConnected(center, id); err != nil {
 			return err
 		}
 	}
 	return nil
 }
 
-// connect connects two nodes but ignores already connected error.
-func (net *Network) connect(oneID, otherID enode.ID) error {
-	return ignoreAlreadyConnectedErr(net.Connect(oneID, otherID))
+func (net *Network) connectNotConnected(oneID, otherID enode.ID) error {
+	return ignoreAlreadyConnectedErr(net.connect(oneID, otherID))
 }
 
 func ignoreAlreadyConnectedErr(err error) error {

p2p/simulations/events.go

@@ -100,7 +100,7 @@ func ControlEvent(v interface{}) *Event {
 func (e *Event) String() string {
 	switch e.Type {
 	case EventTypeNode:
-		return fmt.Sprintf("<node-event> id: %s up: %t", e.Node.ID().TerminalString(), e.Node.Up)
+		return fmt.Sprintf("<node-event> id: %s up: %t", e.Node.ID().TerminalString(), e.Node.Up())
 	case EventTypeConn:
 		return fmt.Sprintf("<conn-event> nodes: %s->%s up: %t", e.Conn.One.TerminalString(), e.Conn.Other.TerminalString(), e.Conn.Up)
 	case EventTypeMsg:

p2p/simulations/http_test.go

@@ -421,14 +421,15 @@ type expectEvents struct {
 }
 
 func (t *expectEvents) nodeEvent(id string, up bool) *Event {
+	node := Node{
+		Config: &adapters.NodeConfig{
+			ID: enode.HexID(id),
+		},
+		up: up,
+	}
 	return &Event{
 		Type: EventTypeNode,
-		Node: &Node{
-			Config: &adapters.NodeConfig{
-				ID: enode.HexID(id),
-			},
-			Up: up,
-		},
+		Node: &node,
 	}
 }
 
@@ -480,6 +481,7 @@ loop:
 }
 
 func (t *expectEvents) expect(events ...*Event) {
+	t.Helper()
 	timeout := time.After(10 * time.Second)
 	i := 0
 	for {
@@ -501,8 +503,8 @@ func (t *expectEvents) expect(events ...*Event) {
 				if event.Node.ID() != expected.Node.ID() {
 					t.Fatalf("expected node event %d to have id %q, got %q", i, expected.Node.ID().TerminalString(), event.Node.ID().TerminalString())
 				}
-				if event.Node.Up != expected.Node.Up {
-					t.Fatalf("expected node event %d to have up=%t, got up=%t", i, expected.Node.Up, event.Node.Up)
+				if event.Node.Up() != expected.Node.Up() {
+					t.Fatalf("expected node event %d to have up=%t, got up=%t", i, expected.Node.Up(), event.Node.Up())
 				}
 
 			case EventTypeConn:

p2p/simulations/mocker_test.go

@@ -90,15 +90,12 @@ func TestMocker(t *testing.T) {
 		for {
 			select {
 			case event := <-events:
-				//if the event is a node Up event only
-				if event.Node != nil && event.Node.Up {
+				if isNodeUp(event) {
 					//add the correspondent node ID to the map
 					nodemap[event.Node.Config.ID] = true
 					//this means all nodes got a nodeUp event, so we can continue the test
 					if len(nodemap) == nodeCount {
 						nodesComplete = true
-						//wait for 3s as the mocker will need time to connect the nodes
-						//time.Sleep( 3 *time.Second)
 					}
 				} else if event.Conn != nil && nodesComplete {
 					connCount += 1
@@ -169,3 +166,7 @@ func TestMocker(t *testing.T) {
 		t.Fatalf("Expected empty list of nodes, got: %d", len(nodesInfo))
 	}
 }
+
+func isNodeUp(event *Event) bool {
+	return event.Node != nil && event.Node.Up()
+}