Send a status message on block announce handshake (#5726)

* Send a status message on block announce handshake

* Make sure to send the handshake to all handlers

substrate/client/network/src/protocol/generic_proto/behaviour.rs

@@ -201,7 +201,21 @@ enum PeerState {
 }
 
 impl PeerState {
-	/// True if there exists an established connection to tbe peer
+	/// True if there exists any established connection to the peer.
+	fn is_connected(&self) -> bool {
+		match self {
+			PeerState::Disabled { .. } |
+			PeerState::DisabledPendingEnable { .. } |
+			PeerState::Enabled { .. } |
+			PeerState::PendingRequest { .. } |
+			PeerState::Requested |
+			PeerState::Incoming { .. } => true,
+			PeerState::Poisoned |
+			PeerState::Banned { .. } => false,
+		}
+	}
+
+	/// True if there exists an established connection to the peer
 	/// that is open for custom protocol traffic.
 	fn is_open(&self) -> bool {
 		self.get_open().is_some()
@@ -338,6 +352,34 @@ impl GenericProto {
 		self.notif_protocols.push((protocol_name.into(), handshake_msg.into()));
 	}
 
+	/// Modifies the handshake of the given notifications protocol.
+	///
+	/// Has no effect if the protocol is unknown.
+	pub fn set_notif_protocol_handshake(
+		&mut self,
+		protocol_name: &[u8],
+		handshake_message: impl Into<Vec<u8>>
+	) {
+		let handshake_message = handshake_message.into();
+		if let Some(protocol) = self.notif_protocols.iter_mut().find(|(name, _)| name == &protocol_name) {
+			protocol.1 = handshake_message.clone();
+		} else {
+			return;
+		}
+
+		// Send an event to all the peers we're connected to, updating the handshake message.
+		for (peer_id, _) in self.peers.iter().filter(|(_, state)| state.is_connected()) {
+			self.events.push(NetworkBehaviourAction::NotifyHandler {
+				peer_id: peer_id.clone(),
+				handler: NotifyHandler::All,
+				event: NotifsHandlerIn::UpdateHandshake {
+					protocol_name: Cow::Owned(protocol_name.to_owned()),
+					handshake_message: handshake_message.clone(),
+				},
+			});
+		}
+	}
+
 	/// Returns the number of discovered nodes that we keep in memory.
 	pub fn num_discovered_peers(&self) -> usize {
 		self.peerset.num_discovered_peers()

substrate/client/network/src/protocol/generic_proto/handler/group.rs

@@ -161,6 +161,18 @@ pub enum NotifsHandlerIn {
 		message: Vec<u8>,
 	},
 
+	/// Modifies the handshake message of a notifications protocol.
+	UpdateHandshake {
+		/// Name of the protocol for the message.
+		///
+		/// Must match one of the registered protocols.
+		protocol_name: Cow<'static, [u8]>,
+
+		/// The new handshake message to send if we open a substream or if the remote opens a
+		/// substream towards us.
+		handshake_message: Vec<u8>,
+	},
+
 	/// Sends a notifications message.
 	SendNotification {
 		/// Name of the protocol for the message.
@@ -363,6 +375,18 @@ impl ProtocolsHandler for NotifsHandler {
 			},
 			NotifsHandlerIn::SendLegacy { message } =>
 				self.legacy.inject_event(LegacyProtoHandlerIn::SendCustomMessage { message }),
+			NotifsHandlerIn::UpdateHandshake { protocol_name, handshake_message } => {
+				for (handler, current_handshake) in &mut self.in_handlers {
+					if handler.protocol_name() == &*protocol_name {
+						*current_handshake = handshake_message.clone();
+					}
+				}
+				for (handler, current_handshake) in &mut self.out_handlers {
+					if handler.protocol_name() == &*protocol_name {
+						*current_handshake = handshake_message.clone();
+					}
+				}
+			}
 			NotifsHandlerIn::SendNotification { message, encoded_fallback_message, protocol_name } => {
 				for (handler, _) in &mut self.out_handlers {
 					if handler.protocol_name() != &protocol_name[..] {