Ensure sent event is received from a mailserver (#1304)

In previous change i used same filtering for a handler that processes confirmations.
But if we are connected with peers that do not support confirmations on whisper level,
whisper may send "Sent" event when envelope is written to a socket. This is our old behaviour.

So, this PR allows to use confirmations from a mail servers and ensure that transition between
multiple version of peers will be smooth.

node/node.go

@@ -333,6 +333,7 @@ func activateShhService(stack *node.Node, config *params.NodeConfig, db *leveldb
 			InstallationID:          config.InstallationID,
 			Debug:                   config.DebugAPIEnabled,
 			PFSEnabled:              config.PFSEnabled,
+			MailServerConfirmations: config.MailServerConfirmations,
 		}
 
 		svc := shhext.New(whisper, shhext.EnvelopeSignalHandler{}, db, config)

params/config.go

@@ -303,6 +303,9 @@ type NodeConfig struct {
 
 	// MailServerRegistryAddress is the MailServerRegistry contract address
 	MailServerRegistryAddress string
+
+	// MailServerConfirmations should be true if client wants to receive confirmatons only from a selected mail servers.
+	MailServerConfirmations bool
 }
 
 // Option is an additional setting when creating a NodeConfig

services/shhext/tracker.go

@@ -107,6 +107,12 @@ func (t *tracker) handleEvent(event whisper.EnvelopeEvent) {
 }
 
 func (t *tracker) handleEventEnvelopeSent(event whisper.EnvelopeEvent) {
+	if t.mailServerConfirmation {
+		if !t.isMailserver(event.Peer) {
+			return
+		}
+	}
+
 	t.mu.Lock()
 	defer t.mu.Unlock()
 

services/shhext/tracker_test.go

@@ -32,7 +32,6 @@ func (s *TrackerSuite) SetupTest() {
 		cache:     map[common.Hash]EnvelopeState{},
 		batches:   map[common.Hash]map[common.Hash]struct{}{},
 		mailPeers: mailservers.NewPeerStore(),
-		mailServerConfirmation: true,
 	}
 }
 
@@ -142,3 +141,15 @@ func (s *TrackerSuite) TestRequestExpiration() {
 		s.Fail("timed out while waiting for request expiration")
 	}
 }
+
+func (s *TrackerSuite) TestIgnoreNotFromMailserver() {
+	// enables filter in the tracker to drop confirmations from non-mailserver peers
+	s.tracker.mailServerConfirmation = true
+	s.tracker.Add(testHash)
+	s.tracker.handleEvent(whisper.EnvelopeEvent{
+		Event: whisper.EventEnvelopeSent,
+		Hash:  testHash,
+		Peer:  enode.ID{1}, // could be empty, doesn't impact test behaviour
+	})
+	s.Require().Equal(EnvelopePosted, s.tracker.GetState(testHash))
+}