implement handshake parsing and creation

ethcore/light/src/net/buffer_flow.rs

@@ -171,7 +171,7 @@ pub struct FlowParams {
 impl FlowParams {
 	/// Create new flow parameters from a request cost table,
 	/// buffer limit, and (minimum) rate of recharge.
-	pub fn new(costs: CostTable, limit: U256, recharge: U256) -> Self {
+	pub fn new(limit: U256, costs: CostTable, recharge: U256) -> Self {
 		FlowParams {
 			costs: costs,
 			limit: limit,
@@ -179,6 +179,15 @@ impl FlowParams {
 		}
 	}
 
+	/// Get a reference to the buffer limit.
+	pub fn limit(&self) -> &U256 { &self.limit }
+
+	/// Get a reference to the cost table.
+	pub fn cost_table(&self) -> &CostTable { &self.costs }
+
+	/// Get a reference to the recharge rate.
+	pub fn recharge_rate(&self) -> &U256 { &self.recharge }
+
 	/// Estimate the maximum cost of the request.
 	pub fn max_cost(&self, req: &Request) -> U256 {
 		let amount = match *req {
@@ -253,7 +262,7 @@ mod tests {
 		use std::thread;
 		use std::time::Duration;
 
-		let flow_params = FlowParams::new(Default::default(), 100.into(), 20.into());
+		let flow_params = FlowParams::new(100.into(), Default::default(), 20.into());
 		let mut buffer =  flow_params.create_buffer();
 
 		assert!(buffer.deduct_cost(101.into()).is_err());

ethcore/light/src/net/mod.rs

@@ -97,7 +97,7 @@ pub struct LightProtocol {
 	genesis_hash: H256,
 	mainnet: bool,
 	peers: RwLock<HashMap<PeerId, Peer>>,
-	pending_requests: RwLock<HashMap<usize, Requested>>,
+	pending_requests: RwLock<HashMap<usize, Request>>,
 	req_id: AtomicUsize,
 }
 

ethcore/light/src/net/status.rs

@@ -16,9 +16,75 @@
 
 //! Peer status and capabilities.
 
-use rlp::{RlpStream, Stream, UntrustedRlp, View};
+use rlp::{DecoderError, RlpDecodable, RlpEncodable, RlpStream, Stream, UntrustedRlp, View};
 use util::{H256, U256};
 
+use super::buffer_flow::{CostTable, FlowParams};
+
+// recognized handshake/announcement keys.
+// unknown keys are to be skipped, known keys have a defined order.
+// their string values are defined in the LES spec.
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+enum Key {
+	ProtocolVersion,
+	NetworkId,
+	HeadTD,
+	HeadHash,
+	HeadNum,
+	GenesisHash,
+	ServeHeaders,
+	ServeChainSince,
+	ServeStateSince,
+	TxRelay,
+	BufferLimit,
+	BufferCostTable,
+	BufferRechargeRate,
+}
+
+impl Key {
+	// get the string value of this key.
+	fn as_str(&self) -> &'static str {
+		match *self {
+			Key::ProtocolVersion => "protocolVersion",
+			Key::NetworkId => "networkId",
+			Key::HeadTD => "headTd",
+			Key::HeadHash => "headHash",
+			Key::HeadNum => "headNum",
+			Key::GenesisHash => "genesisHash",
+			Key::ServeHeaders => "serveHeaders",
+			Key::ServeChainSince => "serveChainSince",
+			Key::ServeStateSince => "serveStateSince",
+			Key::TxRelay => "txRelay",
+			Key::BufferLimit => "flowControl/BL",
+			Key::BufferCostTable => "flowControl/MRC",
+			Key::BufferRechargeRate => "flowControl/MRR",
+		}
+	}
+
+	fn from_str(s: &str) -> Option<Self> {
+		match s {
+			"protocolVersion" => Some(Key::ProtocolVersion),
+			"networkId" => Some(Key::NetworkId),
+			"headTd" => Some(Key::HeadTD),
+			"headHash" => Some(Key::HeadHash),
+			"headNum" => Some(Key::HeadNum),
+			"genesisHash" => Some(Key::GenesisHash),
+			"serveHeaders" => Some(Key::ServeHeaders),
+			"serveChainSince" => Some(Key::ServeChainSince),
+			"serveStateSince" => Some(Key::ServeStateSince),
+			"txRelay" => Some(Key::TxRelay),
+			"flowControl/BL" => Some(Key::BufferLimit),
+			"flowControl/MRC" => Some(Key::BufferCostTable),
+			"flowControl/MRR" => Some(Key::BufferRechargeRate),
+			_ => None
+		}
+	}
+
+	fn is_recognized(s: &str) -> bool {
+		Key::from_str(s).is_some()
+	}
+}
+
 /// Network ID structure.
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
 #[repr(u32)]
@@ -29,6 +95,66 @@ pub enum NetworkId {
 	Testnet = 0,
 }
 
+impl NetworkId {
+	fn from_raw(raw: u32) -> Option<Self> {
+		match raw {
+			0 => Some(NetworkId::Testnet),
+			1 => Some(NetworkId::Mainnet),
+			_ => None,
+		}
+	}
+}
+
+// helper for decoding key-value pairs in the handshake or an announcement.
+struct Parser<'a> {
+	pos: usize,
+	rlp: UntrustedRlp<'a>,
+}
+
+impl<'a> Parser<'a> {
+	// attempt to parse the next key, value pair, and decode the value to the given type.
+	fn expect<T: RlpDecodable>(&mut self, key: Key) -> Result<T, DecoderError> {
+		self.expect_raw(key).and_then(|item| item.as_val())
+	}
+
+	// attempt to parse the next key, value pair, and returns the value's RLP.
+	fn expect_raw(&mut self, key: Key) -> Result<UntrustedRlp<'a>, DecoderError> {
+		loop {
+			let pair =  try!(self.rlp.at(self.pos));
+			let k: String = try!(pair.val_at(0));
+			let k = match Key::from_str(&k) {
+				Some(k) => k,
+				None => {
+					// skip any unrecognized keys.
+					self.pos += 1;
+					continue;
+				}
+			};
+
+			if k == key {
+				self.pos += 1;
+				return pair.at(1)
+			} else {
+				return Err(DecoderError::Custom("Missing expected key"))
+			}
+		}
+	}
+}
+
+// Helper for encoding a key-value pair
+fn encode_pair<T: RlpEncodable>(key: Key, val: &T) -> Vec<u8> {
+	let mut s = RlpStream::new_list(2);
+	s.append(&key.as_str()).append(val);
+	s.out()
+}
+
+// Helper for encoding a flag.
+fn encode_flag(key: Key) -> Vec<u8> {
+	let mut s = RlpStream::new_list(2);
+	s.append(&key.as_str()).append_empty_data();
+	s.out()
+}
+
 /// A peer status message.
 #[derive(Debug, Clone, PartialEq, Eq)]
 pub struct Status {
@@ -72,26 +198,80 @@ impl Default for Capabilities {
 	}
 }
 
-impl Capabilities {
-	/// Decode capabilities from the given rlp stream, starting from the given
-	/// index.
-	fn decode_from(rlp: &UntrustedRlp, start_idx: usize) -> Result<Self, DecoderError> {
-		let mut caps = Capabilities::default();
+/// Attempt to parse a handshake message into its three parts:
+///   - chain status
+///   - serving capabilities
+///   - buffer flow parameters
+pub fn parse_handshake(rlp: UntrustedRlp) -> Result<(Status, Capabilities, FlowParams), DecoderError> {
+	let mut parser = Parser {
+		pos: 0,
+		rlp: rlp,
+	};
 
-		for item in rlp.iter().skip(start_idx).take(4) {
-			let key: String = try!(item.val_at(0));
+	let status = Status {
+		protocol_version: try!(parser.expect(Key::ProtocolVersion)),
+		network_id: try!(parser.expect(Key::NetworkId)
+			.and_then(|id: u32| NetworkId::from_raw(id).ok_or(DecoderError::Custom("Invalid network ID")))),
+		head_td: try!(parser.expect(Key::HeadTD)),
+		head_hash: try!(parser.expect(Key::HeadHash)),
+		head_num: try!(parser.expect(Key::HeadNum)),
+		genesis_hash: parser.expect(Key::GenesisHash).ok(),
+		last_head: None,
+	};
 
-			match &*key {
-				"serveHeaders" => caps.serve_headers = true,
-				"serveChainSince" => caps.serve_chain_since = Some(try!(item.val_at(1))),
-				"serveStateSince" => caps.serve_state_since = Some(try!(item.val_at(1))),
-				"txRelay" => caps.tx_relay = true,
-				_ => continue,
-			}
+	let capabilities = Capabilities {
+		serve_headers: parser.expect_raw(Key::ServeHeaders).is_ok(),
+		serve_chain_since: parser.expect(Key::ServeChainSince).ok(),
+		serve_state_since: parser.expect(Key::ServeStateSince).ok(),
+		tx_relay: parser.expect_raw(Key::TxRelay).is_ok(),
+	};
+
+	let flow_params = FlowParams::new(
+		try!(parser.expect(Key::BufferLimit)),
+		try!(parser.expect(Key::BufferCostTable)),
+		try!(parser.expect(Key::BufferRechargeRate)),
+	);
+
+	Ok((status, capabilities, flow_params))
 }
 
-		Ok(caps)
+/// Write a handshake, given status, capabilities, and flow parameters.
+pub fn write_handshake(status: &Status, capabilities: &Capabilities, flow_params: &FlowParams) -> Vec<u8> {
+	let mut pairs = Vec::new();
+	pairs.push(encode_pair(Key::ProtocolVersion, &status.protocol_version));
+	pairs.push(encode_pair(Key::NetworkId, &(status.network_id as u32)));
+	pairs.push(encode_pair(Key::HeadTD, &status.head_td));
+	pairs.push(encode_pair(Key::HeadHash, &status.head_hash));
+	pairs.push(encode_pair(Key::HeadNum, &status.head_num));
+
+	if let Some(ref genesis_hash) = status.genesis_hash {
+		pairs.push(encode_pair(Key::GenesisHash, genesis_hash));
 	}
+
+	if capabilities.serve_headers {
+		pairs.push(encode_flag(Key::ServeHeaders));
+	}
+	if let Some(ref serve_chain_since) = capabilities.serve_chain_since {
+		pairs.push(encode_pair(Key::ServeChainSince, serve_chain_since));
+	}
+	if let Some(ref serve_state_since) = capabilities.serve_state_since {
+		pairs.push(encode_pair(Key::ServeStateSince, serve_state_since));
+	}
+	if capabilities.tx_relay {
+		pairs.push(encode_flag(Key::TxRelay));
+	}
+
+	pairs.push(encode_pair(Key::BufferLimit, flow_params.limit()));
+	pairs.push(encode_pair(Key::BufferCostTable, flow_params.cost_table()));
+	pairs.push(encode_pair(Key::BufferRechargeRate, flow_params.recharge_rate()));
+
+	let mut stream = RlpStream::new_list(pairs.len());
+
+	for pair in pairs {
+		stream.append_raw(&pair, 1);
+	}
+
+	stream.out()
 }
 
 /// An announcement of new chain head or capabilities made by a peer.
@@ -105,6 +285,137 @@ pub struct Announcement {
 	head_td: U256,
 	/// reorg depth to common ancestor of last announced head.
 	reorg_depth: u64,
-	/// updated capabilities.
-	new_capabilities: Capabilities,
+	/// optional new state-serving capability
+	serve_state_since: Option<u64>,
+	/// optional new chain-serving capability
+	serve_chain_since: Option<u64>,
+	// TODO: changes in buffer flow?
+}
+
+#[cfg(test)]
+mod tests {
+	use super::*;
+	use super::super::buffer_flow::FlowParams;
+	use util::{U256, H256, FixedHash};
+	use rlp::{RlpStream, Stream ,UntrustedRlp, View};
+
+	#[test]
+	fn full_handshake() {
+		let status = Status {
+			protocol_version: 1,
+			network_id: NetworkId::Mainnet,
+			head_td: U256::default(),
+			head_hash: H256::default(),
+			head_num: 10,
+			genesis_hash: Some(H256::zero()),
+			last_head: None,
+		};
+
+		let capabilities = Capabilities {
+			serve_headers: true,
+			serve_chain_since: Some(5),
+			serve_state_since: Some(8),
+			tx_relay: true,
+		};
+
+		let flow_params = FlowParams::new(
+			1_000_000.into(),
+			Default::default(),
+			1000.into(),
+		);
+
+		let handshake = write_handshake(&status, &capabilities, &flow_params);
+
+		let (read_status, read_capabilities, read_flow)
+			= parse_handshake(UntrustedRlp::new(&handshake)).unwrap();
+
+		assert_eq!(read_status, status);
+		assert_eq!(read_capabilities, capabilities);
+		assert_eq!(read_flow, flow_params);
+	}
+
+	#[test]
+	fn partial_handshake() {
+		let status = Status {
+			protocol_version: 1,
+			network_id: NetworkId::Mainnet,
+			head_td: U256::default(),
+			head_hash: H256::default(),
+			head_num: 10,
+			genesis_hash: None,
+			last_head: None,
+		};
+
+		let capabilities = Capabilities {
+			serve_headers: false,
+			serve_chain_since: Some(5),
+			serve_state_since: None,
+			tx_relay: true,
+		};
+
+		let flow_params = FlowParams::new(
+			1_000_000.into(),
+			Default::default(),
+			1000.into(),
+		);
+
+		let handshake = write_handshake(&status, &capabilities, &flow_params);
+
+		let (read_status, read_capabilities, read_flow)
+			= parse_handshake(UntrustedRlp::new(&handshake)).unwrap();
+
+		assert_eq!(read_status, status);
+		assert_eq!(read_capabilities, capabilities);
+		assert_eq!(read_flow, flow_params);
+	}
+
+	#[test]
+	fn skip_unknown_keys() {
+		let status = Status {
+			protocol_version: 1,
+			network_id: NetworkId::Mainnet,
+			head_td: U256::default(),
+			head_hash: H256::default(),
+			head_num: 10,
+			genesis_hash: None,
+			last_head: None,
+		};
+
+		let capabilities = Capabilities {
+			serve_headers: false,
+			serve_chain_since: Some(5),
+			serve_state_since: None,
+			tx_relay: true,
+		};
+
+		let flow_params = FlowParams::new(
+			1_000_000.into(),
+			Default::default(),
+			1000.into(),
+		);
+
+		let handshake = write_handshake(&status, &capabilities, &flow_params);
+		let interleaved = {
+			let handshake = UntrustedRlp::new(&handshake);
+			let mut stream = RlpStream::new_list(handshake.item_count() * 3);
+
+			for item in handshake.iter() {
+				stream.append_raw(item.as_raw(), 1);
+				let (mut s1, mut s2) = (RlpStream::new_list(2), RlpStream::new_list(2));
+				s1.append(&"foo").append_empty_data();
+				s2.append(&"bar").append_empty_data();
+				stream.append_raw(&s1.out(), 1);
+				stream.append_raw(&s2.out(), 1);
+			}
+
+			stream.out()
+		};
+
+		let (read_status, read_capabilities, read_flow)
+			= parse_handshake(UntrustedRlp::new(&interleaved)).unwrap();
+
+		assert_eq!(read_status, status);
+		assert_eq!(read_capabilities, capabilities);
+		assert_eq!(read_flow, flow_params);
+	}
 }