Snapshot sync (#2047)

* PV64 sync

* Tests

* Client DB restore

* Snapshot restoration over IPC

* Upating test

* Minor tweaks

* Upating test

util/network/src/host.rs

@@ -282,6 +282,12 @@ impl<'s> NetworkContext<'s> {
 		}
 		"unknown".to_owned()
 	}
+
+	/// Returns max version for a given protocol.
+	pub fn protocol_version(&self, peer: PeerId, protocol: &str) -> Option<u8> {
+		let session = self.resolve_session(peer);
+		session.and_then(|s| s.lock().capability_version(protocol))
+	}
 }
 
 /// Shared host information

util/network/src/session.rs

@@ -243,6 +243,11 @@ impl Session {
 		self.info.capabilities.iter().any(|c| c.protocol == protocol)
 	}
 
+	/// Checks if peer supports given capability
+	pub fn capability_version(&self, protocol: &str) -> Option<u8> {
+		self.info.capabilities.iter().filter_map(|c| if c.protocol == protocol { Some(c.version) } else { None }).max()
+	}
+
 	/// Register the session socket with the event loop
 	pub fn register_socket<Host:Handler<Timeout = Token>>(&self, reg: Token, event_loop: &mut EventLoop<Host>) -> Result<(), NetworkError> {
 		if self.expired() {