p2p, swarm: fix node up races by granular locking (#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: https://github.com/ethereum/go-ethereum/pull/18464
The case above was solved, but there were still intermittent/hard to
reproduce races. So let's solve the issue permanently.

resolves: ethersphere/go-ethereum#1146

* p2p/simulations: fix unmarshal of simulations.Node

Making Node.Up field private in 13292ee897
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:
https://github.com/ethersphere/go-ethereum/issues/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 85a79b3ad3,
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: https://github.com/ethersphere/go-ethereum/issues/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/network_test.go

@@ -20,6 +20,7 @@ import (
 	"context"
 	"encoding/json"
 	"fmt"
+	"reflect"
 	"strconv"
 	"strings"
 	"testing"
@@ -485,3 +486,137 @@ func benchmarkMinimalServiceTmp(b *testing.B) {
 		}
 	}
 }
+
+func TestNode_UnmarshalJSON(t *testing.T) {
+	t.Run(
+		"test unmarshal of Node up field",
+		func(t *testing.T) {
+			runNodeUnmarshalJSON(t, casesNodeUnmarshalJSONUpField())
+		},
+	)
+	t.Run(
+		"test unmarshal of Node Config field",
+		func(t *testing.T) {
+			runNodeUnmarshalJSON(t, casesNodeUnmarshalJSONConfigField())
+		},
+	)
+}
+
+func runNodeUnmarshalJSON(t *testing.T, tests []nodeUnmarshalTestCase) {
+	t.Helper()
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			var got Node
+			if err := got.UnmarshalJSON([]byte(tt.marshaled)); err != nil {
+				expectErrorMessageToContain(t, err, tt.wantErr)
+			}
+			expectNodeEquality(t, got, tt.want)
+		})
+	}
+}
+
+type nodeUnmarshalTestCase struct {
+	name      string
+	marshaled string
+	want      Node
+	wantErr   string
+}
+
+func expectErrorMessageToContain(t *testing.T, got error, want string) {
+	t.Helper()
+	if got == nil && want == "" {
+		return
+	}
+
+	if got == nil && want != "" {
+		t.Errorf("error was expected, got: nil, want: %v", want)
+		return
+	}
+
+	if !strings.Contains(got.Error(), want) {
+		t.Errorf(
+			"unexpected error message, got  %v, want: %v",
+			want,
+			got,
+		)
+	}
+}
+
+func expectNodeEquality(t *testing.T, got Node, want Node) {
+	t.Helper()
+	if !reflect.DeepEqual(got, want) {
+		t.Errorf("Node.UnmarshalJSON() = %v, want %v", got, want)
+	}
+}
+
+func casesNodeUnmarshalJSONUpField() []nodeUnmarshalTestCase {
+	return []nodeUnmarshalTestCase{
+		{
+			name:      "empty json",
+			marshaled: "{}",
+			want: Node{
+				up: false,
+			},
+		},
+		{
+			name:      "a stopped node",
+			marshaled: "{\"up\": false}",
+			want: Node{
+				up: false,
+			},
+		},
+		{
+			name:      "a running node",
+			marshaled: "{\"up\": true}",
+			want: Node{
+				up: true,
+			},
+		},
+		{
+			name:      "invalid JSON value on valid key",
+			marshaled: "{\"up\": foo}",
+			wantErr:   "invalid character",
+		},
+		{
+			name:      "invalid JSON key and value",
+			marshaled: "{foo: bar}",
+			wantErr:   "invalid character",
+		},
+		{
+			name:      "bool value expected but got something else (string)",
+			marshaled: "{\"up\": \"true\"}",
+			wantErr:   "cannot unmarshal string into Go struct",
+		},
+	}
+}
+
+func casesNodeUnmarshalJSONConfigField() []nodeUnmarshalTestCase {
+	// Don't do a big fuss around testing, as adapters.NodeConfig should
+	// handle it's own serialization. Just do a sanity check.
+	return []nodeUnmarshalTestCase{
+		{
+			name:      "Config field is omitted",
+			marshaled: "{}",
+			want: Node{
+				Config: nil,
+			},
+		},
+		{
+			name:      "Config field is nil",
+			marshaled: "{\"config\": nil}",
+			want: Node{
+				Config: nil,
+			},
+		},
+		{
+			name:      "a non default Config field",
+			marshaled: "{\"config\":{\"name\":\"node_ecdd0\",\"port\":44665}}",
+			want: Node{
+				Config: &adapters.NodeConfig{
+					Name: "node_ecdd0",
+					Port: 44665,
+				},
+			},
+		},
+	}
+}