Merge pull request #3527 from ethcore/client-provider

LES Part 2
2016-12-07 09:31:50 +01:00 · 2016-12-07 09:31:50 +01:00 · 085b8ad553
parent 97e60a6e9c 5db93cd433
commit 085b8ad553
23 changed files with 962 additions and 142 deletions
--- a/Cargo.lock
+++ b/Cargo.lock
@ -298,6 +298,7 @@ dependencies = [
 "ethcore-ipc 1.4.0",
 "ethcore-ipc-codegen 1.4.0",
 "ethcore-ipc-nano 1.4.0",
+ "ethcore-network 1.5.0",
 "ethcore-util 1.5.0",
 "ethjson 0.1.0",
 "ethkey 0.2.0",
--- a/ethcore/light/Cargo.toml
+++ b/ethcore/light/Cargo.toml
@ -5,6 +5,10 @@ license = "GPL-3.0"
 name = "ethcore-light"
 version = "1.5.0"
 authors = ["Ethcore <admin@ethcore.io>"]
+build = "build.rs"
+
+[build-dependencies]
+"ethcore-ipc-codegen" = { path = "../../ipc/codegen" }

 [dependencies]
 log = "0.3"
@ -12,5 +16,6 @@ ethcore = { path = ".." }
 ethcore-util = { path = "../../util" }
 ethcore-network = { path = "../../util/network" }
 ethcore-io = { path = "../../util/io" }
+ethcore-ipc = { path = "../../ipc/rpc" }
 rlp = { path = "../../util/rlp" }
 time = "0.1"
--- a/ethcore/light/build.rs
+++ b/ethcore/light/build.rs
@ -0,0 +1,21 @@
+// Copyright 2015, 2016 Ethcore (UK) Ltd.
+// This file is part of Parity.
+
+// Parity is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Parity is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Parity.  If not, see <http://www.gnu.org/licenses/>.
+
+extern crate ethcore_ipc_codegen;
+
+fn main() {
+	ethcore_ipc_codegen::derive_binary("src/types/mod.rs.in").unwrap();
+}
--- a/ethcore/light/src/client.rs
+++ b/ethcore/light/src/client.rs
@ -101,7 +101,7 @@ impl Provider for Client {
 		Vec::new()
 	}

-	fn code(&self, _req: request::ContractCodes) -> Vec<Bytes> {
+	fn contract_code(&self, _req: request::ContractCodes) -> Vec<Bytes> {
 		Vec::new()
 	}

--- a/ethcore/light/src/lib.rs
+++ b/ethcore/light/src/lib.rs
@ -28,20 +28,25 @@
 //! It starts by performing a header-only sync, verifying random samples
 //! of members of the chain to varying degrees.

-// TODO: remove when integrating with parity.
+// TODO: remove when integrating with the rest of parity.
 #![allow(dead_code)]

 pub mod client;
 pub mod net;
 pub mod provider;
-pub mod request;

+mod types;
+
+pub use self::provider::Provider;
+pub use types::les_request as request;
+
+#[macro_use]
+extern crate log;
+
+extern crate ethcore;
 extern crate ethcore_util as util;
 extern crate ethcore_network as network;
 extern crate ethcore_io as io;
-extern crate ethcore;
+extern crate ethcore_ipc as ipc;
 extern crate rlp;
-extern crate time;
-
-#[macro_use]
-extern crate log;
+extern crate time;
--- a/ethcore/light/src/net/buffer_flow.rs
+++ b/ethcore/light/src/net/buffer_flow.rs
@ -206,6 +206,39 @@ impl FlowParams {
 		cost.0 + (amount * cost.1)
 	}

+	/// Compute the maximum number of costs of a specific kind which can be made 
+	/// with the given buffer.
+	/// Saturates at `usize::max()`. This is not a problem in practice because
+	/// this amount of requests is already prohibitively large.
+	pub fn max_amount(&self, buffer: &Buffer, kind: request::Kind) -> usize {
+		use util::Uint;
+		use std::usize;
+
+		let cost = match kind {
+			request::Kind::Headers => &self.costs.headers,
+			request::Kind::Bodies => &self.costs.bodies,
+			request::Kind::Receipts => &self.costs.receipts,
+			request::Kind::StateProofs => &self.costs.state_proofs,
+			request::Kind::Codes => &self.costs.contract_codes,
+			request::Kind::HeaderProofs => &self.costs.header_proofs,
+		};
+
+		let start = buffer.current();
+
+		if start <= cost.0 {
+			return 0;
+		} else if cost.1 == U256::zero() {
+			return usize::MAX;
+		}
+
+		let max = (start - cost.0) / cost.1;
+		if max >= usize::MAX.into() {
+			usize::MAX
+		} else {
+			max.as_u64() as usize
+		}
+	}
+
 	/// Create initial buffer parameter.
 	pub fn create_buffer(&self) -> Buffer {
 		Buffer {
@ -228,6 +261,16 @@ impl FlowParams {

 		buf.estimate = ::std::cmp::min(self.limit, buf.estimate + (elapsed * self.recharge));
 	}
+
+	/// Refund some buffer which was previously deducted.
+	/// Does not update the recharge timestamp.
+	pub fn refund(&self, buf: &mut Buffer, refund_amount: U256) {
+		buf.estimate = buf.estimate + refund_amount;
+
+		if buf.estimate > self.limit {
+			buf.estimate = self.limit
+		}
+	}
 }

 #[cfg(test)]
--- a/ethcore/light/src/net/error.rs
+++ b/ethcore/light/src/net/error.rs
@ -52,6 +52,8 @@ pub enum Error {
 	UnexpectedHandshake,
 	/// Peer on wrong network (wrong NetworkId or genesis hash)
 	WrongNetwork,
+	/// Unknown peer.
+	UnknownPeer,
 }

 impl Error {
@ -64,6 +66,7 @@ impl Error {
 			Error::UnrecognizedPacket(_) => Punishment::Disconnect,
 			Error::UnexpectedHandshake => Punishment::Disconnect,
 			Error::WrongNetwork => Punishment::Disable,
+			Error::UnknownPeer => Punishment::Disconnect,
 		}
 	}
 }
@ -89,6 +92,7 @@ impl fmt::Display for Error {
 			Error::UnrecognizedPacket(code) => write!(f, "Unrecognized packet: 0x{:x}", code),
 			Error::UnexpectedHandshake => write!(f, "Unexpected handshake"),
 			Error::WrongNetwork => write!(f, "Wrong network"),
+			Error::UnknownPeer => write!(f, "unknown peer"),
 		}
 	}
 }
--- a/ethcore/light/src/net/mod.rs
+++ b/ethcore/light/src/net/mod.rs
@ -19,27 +19,28 @@
 //! This uses a "Provider" to answer requests.
 //! See https://github.com/ethcore/parity/wiki/Light-Ethereum-Subprotocol-(LES)

+use ethcore::transaction::SignedTransaction;
 use io::TimerToken;
 use network::{NetworkProtocolHandler, NetworkContext, NetworkError, PeerId};
 use rlp::{RlpStream, Stream, UntrustedRlp, View};
 use util::hash::H256;
-use util::RwLock;
+use util::{Mutex, RwLock, U256};
+use time::SteadyTime;

 use std::collections::{HashMap, HashSet};
-use std::sync::atomic::AtomicUsize;
+use std::sync::atomic::{AtomicUsize, Ordering};

 use provider::Provider;
 use request::{self, Request};

 use self::buffer_flow::{Buffer, FlowParams};
 use self::error::{Error, Punishment};
-use self::status::{Status, Capabilities};

 mod buffer_flow;
 mod error;
 mod status;

-pub use self::status::Announcement;
+pub use self::status::{Status, Capabilities, Announcement, NetworkId};

 const TIMEOUT: TimerToken = 0;
 const TIMEOUT_INTERVAL_MS: u64 = 1000;
@ -86,6 +87,10 @@ mod packet {
 	pub const HEADER_PROOFS: u8 = 0x0e;
 }

+/// A request id.
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+pub struct ReqId(usize);
+
 // A pending peer: one we've sent our status to but
 // may not have received one for.
 struct PendingPeer {
@ -103,32 +108,162 @@ struct Peer {
 	sent_head: H256, // last head we've given them.
 }

+impl Peer {
+	// check the maximum cost of a request, returning an error if there's
+	// not enough buffer left.
+	// returns the calculated maximum cost.
+	fn deduct_max(&mut self, flow_params: &FlowParams, kind: request::Kind, max: usize) -> Result<U256, Error> {
+		flow_params.recharge(&mut self.local_buffer);
+
+		let max_cost = flow_params.compute_cost(kind, max);
+		try!(self.local_buffer.deduct_cost(max_cost));
+		Ok(max_cost)
+	}
+
+	// refund buffer for a request. returns new buffer amount.
+	fn refund(&mut self, flow_params: &FlowParams, amount: U256) -> U256 {
+		flow_params.refund(&mut self.local_buffer, amount);
+
+		self.local_buffer.current()
+	}
+
+	// recharge remote buffer with remote flow params.
+	fn recharge_remote(&mut self) {
+		let flow = &mut self.remote_flow;
+		flow.recharge(&mut self.remote_buffer);
+	}
+}
+
+/// An LES event handler.
+pub trait Handler: Send + Sync {
+	/// Called when a peer connects.
+	fn on_connect(&self, _id: PeerId, _status: &Status, _capabilities: &Capabilities) { }
+	/// Called when a peer disconnects
+	fn on_disconnect(&self, _id: PeerId) { }
+	/// Called when a peer makes an announcement.
+	fn on_announcement(&self, _id: PeerId, _announcement: &Announcement) { }
+	/// Called when a peer requests relay of some transactions.
+	fn on_transactions(&self, _id: PeerId, _relay: &[SignedTransaction]) { }
+}
+
+// a request and the time it was made.
+struct Requested {
+	request: Request,
+	timestamp: SteadyTime,
+}
+
+/// Protocol parameters.
+pub struct Params {
+	/// Genesis hash.
+	pub genesis_hash: H256,
+	/// Network id.
+	pub network_id: NetworkId,
+	/// Buffer flow parameters.
+	pub flow_params: FlowParams,
+	/// Initial capabilities.
+	pub capabilities: Capabilities,
+}
+
 /// This is an implementation of the light ethereum network protocol, abstracted
 /// over a `Provider` of data and a p2p network.
 ///
 /// This is simply designed for request-response purposes. Higher level uses
 /// of the protocol, such as synchronization, will function as wrappers around
 /// this system.
+// 
+// LOCK ORDER:
+//   Locks must be acquired in the order declared, and when holding a read lock 
+//   on the peers, only one peer may be held at a time.
 pub struct LightProtocol {
 	provider: Box<Provider>,
 	genesis_hash: H256,
-	network_id: status::NetworkId,
+	network_id: NetworkId,
 	pending_peers: RwLock<HashMap<PeerId, PendingPeer>>,
-	peers: RwLock<HashMap<PeerId, Peer>>,
-	pending_requests: RwLock<HashMap<usize, Request>>,
+	peers: RwLock<HashMap<PeerId, Mutex<Peer>>>,
+	pending_requests: RwLock<HashMap<usize, Requested>>,
 	capabilities: RwLock<Capabilities>,
 	flow_params: FlowParams, // assumed static and same for every peer.
+	handlers: Vec<Box<Handler>>,
 	req_id: AtomicUsize,
 }

 impl LightProtocol {
+	/// Create a new instance of the protocol manager.
+	pub fn new(provider: Box<Provider>, params: Params) -> Self {
+		LightProtocol {
+			provider: provider,
+			genesis_hash: params.genesis_hash,
+			network_id: params.network_id,
+			pending_peers: RwLock::new(HashMap::new()),
+			peers: RwLock::new(HashMap::new()),
+			pending_requests: RwLock::new(HashMap::new()),
+			capabilities: RwLock::new(params.capabilities),
+			flow_params: params.flow_params,
+			handlers: Vec::new(),
+			req_id: AtomicUsize::new(0),
+		}
+	}
+
+	/// Check the maximum amount of requests of a specific type 
+	/// which a peer would be able to serve.
+	pub fn max_requests(&self, peer: PeerId, kind: request::Kind) -> Option<usize> {
+		self.peers.read().get(&peer).map(|peer| {
+			let mut peer = peer.lock();
+			peer.recharge_remote();
+			peer.remote_flow.max_amount(&peer.remote_buffer, kind)
+		})
+	}
+
+	/// Make a request to a peer. 
+	///
+	/// Fails on: nonexistent peer, network error,
+	/// insufficient buffer. Does not check capabilities before sending.
+	/// On success, returns a request id which can later be coordinated 
+	/// with an event.
+	pub fn request_from(&self, io: &NetworkContext, peer_id: &PeerId, request: Request) -> Result<ReqId, Error> {
+		let peers = self.peers.read();
+		let peer = try!(peers.get(peer_id).ok_or_else(|| Error::UnknownPeer));
+		let mut peer = peer.lock();
+
+		peer.recharge_remote();
+
+		let max = peer.remote_flow.compute_cost(request.kind(), request.amount());
+		try!(peer.remote_buffer.deduct_cost(max));
+
+		let req_id = self.req_id.fetch_add(1, Ordering::SeqCst);
+		let packet_data = encode_request(&request, req_id);
+
+		let packet_id = match request.kind() {
+			request::Kind::Headers => packet::GET_BLOCK_HEADERS,
+			request::Kind::Bodies => packet::GET_BLOCK_BODIES,
+			request::Kind::Receipts => packet::GET_RECEIPTS,
+			request::Kind::StateProofs => packet::GET_PROOFS,
+			request::Kind::Codes => packet::GET_CONTRACT_CODES,
+			request::Kind::HeaderProofs => packet::GET_HEADER_PROOFS,
+		};
+
+		try!(io.send(*peer_id, packet_id, packet_data));
+
+		peer.current_asking.insert(req_id);
+		self.pending_requests.write().insert(req_id, Requested {
+			request: request,
+			timestamp: SteadyTime::now(),
+		});
+
+		Ok(ReqId(req_id))
+	}
+
 	/// Make an announcement of new chain head and capabilities to all peers.
 	/// The announcement is expected to be valid.
-	pub fn make_announcement(&self, mut announcement: Announcement, io: &NetworkContext) {
+	pub fn make_announcement(&self, io: &NetworkContext, mut announcement: Announcement) {
 		let mut reorgs_map = HashMap::new();

+		// update stored capabilities
+		self.capabilities.write().update_from(&announcement);
+
 		// calculate reorg info and send packets
-		for (peer_id, peer_info) in self.peers.write().iter_mut() {
+		for (peer_id, peer_info) in self.peers.read().iter() {
+			let mut peer_info = peer_info.lock();
 			let reorg_depth = reorgs_map.entry(peer_info.sent_head)
 				.or_insert_with(|| {
 					match self.provider.reorg_depth(&announcement.head_hash, &peer_info.sent_head) {
@ -151,6 +286,14 @@ impl LightProtocol {
 			}
 		}
 	}
+
+	/// Add an event handler.
+	/// Ownership will be transferred to the protocol structure,
+	/// and the handler will be kept alive as long as it is.
+	/// These are intended to be added at the beginning of the 
+	pub fn add_handler(&mut self, handler: Box<Handler>) {
+		self.handlers.push(handler);
+	}
 }

 impl LightProtocol {
@ -173,7 +316,11 @@ impl LightProtocol {
 	fn on_disconnect(&self, peer: PeerId) {
 		// TODO: reassign all requests assigned to this peer.
 		self.pending_peers.write().remove(&peer);
-		self.peers.write().remove(&peer);
+		if self.peers.write().remove(&peer).is_some() {
+			for handler in &self.handlers {
+				handler.on_disconnect(peer)
+			}	
+		}
 	}

 	// send status to a peer.
@ -219,15 +366,19 @@ impl LightProtocol {
 			return Err(Error::WrongNetwork);
 		}

-		self.peers.write().insert(*peer, Peer {
+		self.peers.write().insert(*peer, Mutex::new(Peer {
 			local_buffer: self.flow_params.create_buffer(),
 			remote_buffer: flow_params.create_buffer(),
 			current_asking: HashSet::new(),
-			status: status,
-			capabilities: capabilities,
+			status: status.clone(),
+			capabilities: capabilities.clone(),
 			remote_flow: flow_params,
 			sent_head: pending.sent_head,
-		});
+		}));
+
+		for handler in &self.handlers {
+			handler.on_connect(*peer, &status, &capabilities)
+		}

 		Ok(())
 	}
@ -240,13 +391,15 @@ impl LightProtocol {
 		}

 		let announcement = try!(status::parse_announcement(data));
-		let mut peers = self.peers.write();
+		let peers = self.peers.read();

-		let peer_info = match peers.get_mut(peer) {
+		let peer_info = match peers.get(peer) {
 			Some(info) => info,
 			None => return Ok(()),
 		};

+		let mut peer_info = peer_info.lock();
+
 		// update status.
 		{
 			// TODO: punish peer if they've moved backwards.
@ -259,15 +412,11 @@ impl LightProtocol {
 		}

 		// update capabilities.
-		{
-			let caps = &mut peer_info.capabilities;
-			caps.serve_headers = caps.serve_headers || announcement.serve_headers;
-			caps.serve_state_since = caps.serve_state_since.or(announcement.serve_state_since);
-			caps.serve_chain_since = caps.serve_chain_since.or(announcement.serve_chain_since);
-			caps.tx_relay = caps.tx_relay || announcement.tx_relay;
-		}
+		peer_info.capabilities.update_from(&announcement);

-		// TODO: notify listeners if new best block.
+		for handler in &self.handlers {
+			handler.on_announcement(*peer, &announcement);
+		}

 		Ok(())
 	}
@ -276,45 +425,39 @@ impl LightProtocol {
 	fn get_block_headers(&self, peer: &PeerId, io: &NetworkContext, data: UntrustedRlp) -> Result<(), Error> {
 		const MAX_HEADERS: usize = 512;

-		let mut present_buffer = match self.peers.read().get(peer) {
-			Some(peer) => peer.local_buffer.clone(),
+		let peers = self.peers.read();
+		let peer = match peers.get(peer) {
+			Some(peer) => peer,
 			None => {
-				debug!(target: "les", "Ignoring announcement from unknown peer");
+				debug!(target: "les", "Ignoring request from unknown peer");
 				return Ok(())
 			}
 		};

-		self.flow_params.recharge(&mut present_buffer);
+		let mut peer = peer.lock();
+
 		let req_id: u64 = try!(data.val_at(0));

+		let block = {
+			let rlp = try!(data.at(1));
+			(try!(rlp.val_at(0)), try!(rlp.val_at(1)))
+		};
+
 		let req = request::Headers {
-			block: {
-				let rlp = try!(data.at(1));
-				(try!(rlp.val_at(0)), try!(rlp.val_at(1)))
-			},
+			block_num: block.0,
+			block_hash: block.1,
 			max: ::std::cmp::min(MAX_HEADERS, try!(data.val_at(2))),
 			skip: try!(data.val_at(3)),
 			reverse: try!(data.val_at(4)),
 		};

-		let max_cost = self.flow_params.compute_cost(request::Kind::Headers, req.max);
-		try!(present_buffer.deduct_cost(max_cost));
+		let max_cost = try!(peer.deduct_max(&self.flow_params, request::Kind::Headers, req.max));

 		let response = self.provider.block_headers(req);
 		let actual_cost = self.flow_params.compute_cost(request::Kind::Headers, response.len());
+		assert!(max_cost >= actual_cost, "Actual cost exceeded maximum computed cost.");

-		let cur_buffer = match self.peers.write().get_mut(peer) {
-			Some(peer) => {
-				self.flow_params.recharge(&mut peer.local_buffer);
-				try!(peer.local_buffer.deduct_cost(actual_cost));
-				peer.local_buffer.current()
-			}
-			None => {
-				debug!(target: "les", "peer disconnected during serving of request.");
-				return Ok(())
-			}
-		};
-
+		let cur_buffer = peer.refund(&self.flow_params, max_cost - actual_cost);
 		io.respond(packet::BLOCK_HEADERS, {
 			let mut stream = RlpStream::new_list(response.len() + 2);
 			stream.append(&req_id).append(&cur_buffer);
@ -336,39 +479,30 @@ impl LightProtocol {
 	fn get_block_bodies(&self, peer: &PeerId, io: &NetworkContext, data: UntrustedRlp) -> Result<(), Error> {
 		const MAX_BODIES: usize = 256;

-		let mut present_buffer = match self.peers.read().get(peer) {
-			Some(peer) => peer.local_buffer.clone(),
+		let peers = self.peers.read();
+		let peer = match peers.get(peer) {
+			Some(peer) => peer,
 			None => {
-				debug!(target: "les", "Ignoring announcement from unknown peer");
+				debug!(target: "les", "Ignoring request from unknown peer");
 				return Ok(())
 			}
 		};
+		let mut peer = peer.lock();

-		self.flow_params.recharge(&mut present_buffer);
 		let req_id: u64 = try!(data.val_at(0));

 		let req = request::Bodies {
 			block_hashes: try!(data.iter().skip(1).take(MAX_BODIES).map(|x| x.as_val()).collect())
 		};

-		let max_cost = self.flow_params.compute_cost(request::Kind::Bodies, req.block_hashes.len());
-		try!(present_buffer.deduct_cost(max_cost));
+		let max_cost = try!(peer.deduct_max(&self.flow_params, request::Kind::Bodies, req.block_hashes.len()));

 		let response = self.provider.block_bodies(req);
 		let response_len = response.iter().filter(|x| &x[..] != &::rlp::EMPTY_LIST_RLP).count();
 		let actual_cost = self.flow_params.compute_cost(request::Kind::Bodies, response_len);
+		assert!(max_cost >= actual_cost, "Actual cost exceeded maximum computed cost.");

-		let cur_buffer = match self.peers.write().get_mut(peer) {
-			Some(peer) => {
-				self.flow_params.recharge(&mut peer.local_buffer);
-				try!(peer.local_buffer.deduct_cost(actual_cost));
-				peer.local_buffer.current()
-			}
-			None => {
-				debug!(target: "les", "peer disconnected during serving of request.");
-				return Ok(())
-			}
-		};
+		let cur_buffer = peer.refund(&self.flow_params, max_cost - actual_cost);

 		io.respond(packet::BLOCK_BODIES, {
 			let mut stream = RlpStream::new_list(response.len() + 2);
@ -388,8 +522,44 @@ impl LightProtocol {
 	}

 	// Handle a request for receipts.
-	fn get_receipts(&self, _: &PeerId, _: &NetworkContext, _: UntrustedRlp) -> Result<(), Error> {
-		unimplemented!()
+	fn get_receipts(&self, peer: &PeerId, io: &NetworkContext, data: UntrustedRlp) -> Result<(), Error> {
+		const MAX_RECEIPTS: usize = 256;
+
+		let peers = self.peers.read();
+		let peer = match peers.get(peer) {
+			Some(peer) => peer,
+			None => {
+				debug!(target: "les", "Ignoring request from unknown peer");
+				return Ok(())
+			}
+		};
+		let mut peer = peer.lock();
+
+		let req_id: u64 = try!(data.val_at(0));
+
+		let req = request::Receipts {
+			block_hashes: try!(data.iter().skip(1).take(MAX_RECEIPTS).map(|x| x.as_val()).collect())
+		};
+
+		let max_cost = try!(peer.deduct_max(&self.flow_params, request::Kind::Receipts, req.block_hashes.len()));
+
+		let response = self.provider.receipts(req);
+		let response_len = response.iter().filter(|x| &x[..] != &::rlp::EMPTY_LIST_RLP).count();
+		let actual_cost = self.flow_params.compute_cost(request::Kind::Receipts, response_len);
+		assert!(max_cost >= actual_cost, "Actual cost exceeded maximum computed cost.");
+
+		let cur_buffer = peer.refund(&self.flow_params, max_cost - actual_cost);
+
+		io.respond(packet::RECEIPTS, {
+			let mut stream = RlpStream::new_list(response.len() + 2);
+			stream.append(&req_id).append(&cur_buffer);
+
+			for receipts in response {
+				stream.append_raw(&receipts, 1);
+			}
+
+			stream.out()
+		}).map_err(Into::into)
 	}

 	// Receive a response for receipts.
@ -398,8 +568,55 @@ impl LightProtocol {
 	}

 	// Handle a request for proofs.
-	fn get_proofs(&self, _: &PeerId, _: &NetworkContext, _: UntrustedRlp) -> Result<(), Error> {
-		unimplemented!()
+	fn get_proofs(&self, peer: &PeerId, io: &NetworkContext, data: UntrustedRlp) -> Result<(), Error> {
+		const MAX_PROOFS: usize = 128;
+
+		let peers = self.peers.read();
+		let peer = match peers.get(peer) {
+			Some(peer) => peer,
+			None => {
+				debug!(target: "les", "Ignoring request from unknown peer");
+				return Ok(())
+			}
+		};
+		let mut peer = peer.lock();
+
+		let req_id: u64 = try!(data.val_at(0));
+
+		let req = {
+			let requests: Result<Vec<_>, Error> = data.iter().skip(1).take(MAX_PROOFS).map(|x| {
+				Ok(request::StateProof {
+					block: try!(x.val_at(0)),
+					key1: try!(x.val_at(1)),
+					key2: if try!(x.at(2)).is_empty() { None } else { Some(try!(x.val_at(2))) },
+					from_level: try!(x.val_at(3)),
+				})
+			}).collect();
+
+			request::StateProofs {
+				requests: try!(requests),
+			}
+		};
+
+		let max_cost = try!(peer.deduct_max(&self.flow_params, request::Kind::StateProofs, req.requests.len()));
+
+		let response = self.provider.proofs(req);
+		let response_len = response.iter().filter(|x| &x[..] != &::rlp::EMPTY_LIST_RLP).count();
+		let actual_cost = self.flow_params.compute_cost(request::Kind::StateProofs, response_len);
+		assert!(max_cost >= actual_cost, "Actual cost exceeded maximum computed cost.");
+
+		let cur_buffer = peer.refund(&self.flow_params, max_cost - actual_cost);
+
+		io.respond(packet::PROOFS, {
+			let mut stream = RlpStream::new_list(response.len() + 2);
+			stream.append(&req_id).append(&cur_buffer);
+
+			for proof in response {
+				stream.append_raw(&proof, 1);
+			}
+
+			stream.out()
+		}).map_err(Into::into)
 	}

 	// Receive a response for proofs.
@ -408,8 +625,53 @@ impl LightProtocol {
 	}

 	// Handle a request for contract code.
-	fn get_contract_code(&self, _: &PeerId, _: &NetworkContext, _: UntrustedRlp) -> Result<(), Error> {
-		unimplemented!()
+	fn get_contract_code(&self, peer: &PeerId, io: &NetworkContext, data: UntrustedRlp) -> Result<(), Error> {
+		const MAX_CODES: usize = 256;
+
+		let peers = self.peers.read();
+		let peer = match peers.get(peer) {
+			Some(peer) => peer,
+			None => {
+				debug!(target: "les", "Ignoring request from unknown peer");
+				return Ok(())
+			}
+		};
+		let mut peer = peer.lock();
+
+		let req_id: u64 = try!(data.val_at(0));
+
+		let req = {
+			let requests: Result<Vec<_>, Error> = data.iter().skip(1).take(MAX_CODES).map(|x| {
+				Ok(request::ContractCode {
+					block_hash: try!(x.val_at(0)),
+					account_key: try!(x.val_at(1)),
+				})
+			}).collect();
+
+			request::ContractCodes {
+				code_requests: try!(requests),
+			}
+		};
+
+		let max_cost = try!(peer.deduct_max(&self.flow_params, request::Kind::Codes, req.code_requests.len()));
+
+		let response = self.provider.contract_code(req);
+		let response_len = response.iter().filter(|x| !x.is_empty()).count();
+		let actual_cost = self.flow_params.compute_cost(request::Kind::Codes, response_len);
+		assert!(max_cost >= actual_cost, "Actual cost exceeded maximum computed cost.");
+
+		let cur_buffer = peer.refund(&self.flow_params, max_cost - actual_cost);
+
+		io.respond(packet::CONTRACT_CODES, {
+			let mut stream = RlpStream::new_list(response.len() + 2);
+			stream.append(&req_id).append(&cur_buffer);
+
+			for code in response {
+				stream.append_raw(&code, 1);
+			}
+
+			stream.out()
+		}).map_err(Into::into)
 	}

 	// Receive a response for contract code.
@ -418,8 +680,54 @@ impl LightProtocol {
 	}

 	// Handle a request for header proofs
-	fn get_header_proofs(&self, _: &PeerId, _: &NetworkContext, _: UntrustedRlp) -> Result<(), Error> {
-		unimplemented!()
+	fn get_header_proofs(&self, peer: &PeerId, io: &NetworkContext, data: UntrustedRlp) -> Result<(), Error> {
+		const MAX_PROOFS: usize = 256;
+
+		let peers = self.peers.read();
+		let peer = match peers.get(peer) {
+			Some(peer) => peer,
+			None => {
+				debug!(target: "les", "Ignoring request from unknown peer");
+				return Ok(())
+			}
+		};
+		let mut peer = peer.lock();
+
+		let req_id: u64 = try!(data.val_at(0));
+
+		let req = {
+			let requests: Result<Vec<_>, Error> = data.iter().skip(1).take(MAX_PROOFS).map(|x| {
+				Ok(request::HeaderProof {
+					cht_number: try!(x.val_at(0)),
+					block_number: try!(x.val_at(1)),
+					from_level: try!(x.val_at(2)),
+				})
+			}).collect();
+
+			request::HeaderProofs {
+				requests: try!(requests),
+			}
+		};
+
+		let max_cost = try!(peer.deduct_max(&self.flow_params, request::Kind::HeaderProofs, req.requests.len()));
+
+		let response = self.provider.header_proofs(req);
+		let response_len = response.iter().filter(|x| &x[..] != ::rlp::EMPTY_LIST_RLP).count();
+		let actual_cost = self.flow_params.compute_cost(request::Kind::HeaderProofs, response_len);
+		assert!(max_cost >= actual_cost, "Actual cost exceeded maximum computed cost.");
+
+		let cur_buffer = peer.refund(&self.flow_params, max_cost - actual_cost);
+
+		io.respond(packet::HEADER_PROOFS, {
+			let mut stream = RlpStream::new_list(response.len() + 2);
+			stream.append(&req_id).append(&cur_buffer);
+
+			for proof in response {
+				stream.append_raw(&proof, 1);
+			}
+
+			stream.out()
+		}).map_err(Into::into)
 	}

 	// Receive a response for header proofs
@ -428,8 +736,18 @@ impl LightProtocol {
 	}

 	// Receive a set of transactions to relay.
-	fn relay_transactions(&self, _: &PeerId, _: &NetworkContext, _: UntrustedRlp) -> Result<(), Error> {
-		unimplemented!()
+	fn relay_transactions(&self, peer: &PeerId, data: UntrustedRlp) -> Result<(), Error> {
+		const MAX_TRANSACTIONS: usize = 256;
+
+		let txs: Vec<_> = try!(data.iter().take(MAX_TRANSACTIONS).map(|x| x.as_val::<SignedTransaction>()).collect());
+
+		debug!(target: "les", "Received {} transactions to relay from peer {}", txs.len(), peer);
+
+		for handler in &self.handlers {
+			handler.on_transactions(*peer, &txs);
+		}
+
+		Ok(())
 	}
 }

@ -464,7 +782,7 @@ impl NetworkProtocolHandler for LightProtocol {
 			packet::GET_HEADER_PROOFS => self.get_header_proofs(peer, io, rlp),
 			packet::HEADER_PROOFS => self.header_proofs(peer, io, rlp),

-			packet::SEND_TRANSACTIONS => self.relay_transactions(peer, io, rlp),
+			packet::SEND_TRANSACTIONS => self.relay_transactions(peer, rlp),

 			other => {
 				Err(Error::UnrecognizedPacket(other))
@ -503,4 +821,86 @@ impl NetworkProtocolHandler for LightProtocol {
 			_ => warn!(target: "les", "received timeout on unknown token {}", timer),
 		}
 	}
+}
+
+// Helper for encoding the request to RLP with the given ID.
+fn encode_request(req: &Request, req_id: usize) -> Vec<u8> {
+	match *req {
+		Request::Headers(ref headers) => {
+			let mut stream = RlpStream::new_list(5);
+			stream
+				.append(&req_id)
+				.begin_list(2)
+					.append(&headers.block_num)
+					.append(&headers.block_hash)
+				.append(&headers.max)
+				.append(&headers.skip)
+				.append(&headers.reverse);
+			stream.out()
+		}
+		Request::Bodies(ref request) => {
+			let mut stream = RlpStream::new_list(request.block_hashes.len() + 1);
+			stream.append(&req_id);
+
+			for hash in &request.block_hashes {
+				stream.append(hash);
+			}
+
+			stream.out()
+		}
+		Request::Receipts(ref request) => {
+			let mut stream = RlpStream::new_list(request.block_hashes.len() + 1);
+			stream.append(&req_id);
+
+			for hash in &request.block_hashes {
+				stream.append(hash);
+			}
+
+			stream.out()
+		}
+		Request::StateProofs(ref request) => {
+			let mut stream = RlpStream::new_list(request.requests.len() + 1);
+			stream.append(&req_id);
+
+			for proof_req in &request.requests {
+				stream.begin_list(4)
+					.append(&proof_req.block)
+					.append(&proof_req.key1);
+
+				match proof_req.key2 {
+					Some(ref key2) => stream.append(key2),
+					None => stream.append_empty_data(),
+				};
+
+				stream.append(&proof_req.from_level);
+			}
+
+			stream.out()
+		}
+		Request::Codes(ref request) => {
+			let mut stream = RlpStream::new_list(request.code_requests.len() + 1);
+			stream.append(&req_id);
+
+			for code_req in &request.code_requests {
+				stream.begin_list(2)
+					.append(&code_req.block_hash)
+					.append(&code_req.account_key);
+			}
+
+			stream.out()
+		}
+		Request::HeaderProofs(ref request) => {
+			let mut stream = RlpStream::new_list(request.requests.len() + 1);
+			stream.append(&req_id);
+
+			for proof_req in &request.requests {
+				stream.begin_list(3)
+					.append(&proof_req.cht_number)
+					.append(&proof_req.block_number)
+					.append(&proof_req.from_level);
+			}
+
+			stream.out()
+		}
+	}
 }
--- a/ethcore/light/src/net/status.rs
+++ b/ethcore/light/src/net/status.rs
@ -183,8 +183,10 @@ pub struct Capabilities {
 	/// Whether this peer can serve headers
 	pub serve_headers: bool,
 	/// Earliest block number it can serve block/receipt requests for.
+	/// `None` means no requests will be servable.
 	pub serve_chain_since: Option<u64>,
 	/// Earliest block number it can serve state requests for.
+	/// `None` means no requests will be servable.
 	pub serve_state_since: Option<u64>,
 	/// Whether it can relay transactions to the eth network.
 	pub tx_relay: bool,
@ -201,6 +203,16 @@ impl Default for Capabilities {
 	}
 }

+impl Capabilities {
+	/// Update the capabilities from an announcement.
+	pub fn update_from(&mut self, announcement: &Announcement) {
+		self.serve_headers = self.serve_headers || announcement.serve_headers;
+		self.serve_state_since = self.serve_state_since.or(announcement.serve_state_since);
+		self.serve_chain_since = self.serve_chain_since.or(announcement.serve_chain_since);
+		self.tx_relay = self.tx_relay || announcement.tx_relay;
+	}
+}
+
 /// Attempt to parse a handshake message into its three parts:
 ///   - chain status
 ///   - serving capabilities
--- a/ethcore/light/src/provider.rs
+++ b/ethcore/light/src/provider.rs
@ -17,8 +17,11 @@
 //! A provider for the LES protocol. This is typically a full node, who can
 //! give as much data as necessary to its peers.

-use ethcore::transaction::SignedTransaction;
 use ethcore::blockchain_info::BlockChainInfo;
+use ethcore::client::{BlockChainClient, ProvingBlockChainClient};
+use ethcore::transaction::SignedTransaction;
+use ethcore::ids::BlockID;
+
 use util::{Bytes, H256};

 use request;
@ -26,7 +29,8 @@ use request;
 /// Defines the operations that a provider for `LES` must fulfill.
 ///
 /// These are defined at [1], but may be subject to change.
-/// Requests which can't be fulfilled should return an empty RLP list.
+/// Requests which can't be fulfilled should return either an empty RLP list
+/// or empty vector where appropriate.
 ///
 /// [1]: https://github.com/ethcore/parity/wiki/Light-Ethereum-Subprotocol-(LES)
 pub trait Provider: Send + Sync {
@ -34,9 +38,12 @@ pub trait Provider: Send + Sync {
 	fn chain_info(&self) -> BlockChainInfo;

 	/// Find the depth of a common ancestor between two blocks.
+	/// If either block is unknown or an ancestor can't be found
+	/// then return `None`.
 	fn reorg_depth(&self, a: &H256, b: &H256) -> Option<u64>;

-	/// Earliest state.
+	/// Earliest block where state queries are available.
+	/// If `None`, no state queries are servable.
 	fn earliest_state(&self) -> Option<u64>;

 	/// Provide a list of headers starting at the requested block,
@ -57,15 +64,105 @@ pub trait Provider: Send + Sync {
 	/// Provide a set of merkle proofs, as requested. Each request is a
 	/// block hash and request parameters.
 	///
-	/// Returns a vector to RLP-encoded lists satisfying the requests.
+	/// Returns a vector of RLP-encoded lists satisfying the requests.
 	fn proofs(&self, req: request::StateProofs) -> Vec<Bytes>;

 	/// Provide contract code for the specified (block_hash, account_hash) pairs.
-	fn code(&self, req: request::ContractCodes) -> Vec<Bytes>;
+	/// Each item in the resulting vector is either the raw bytecode or empty.
+	fn contract_code(&self, req: request::ContractCodes) -> Vec<Bytes>;

 	/// Provide header proofs from the Canonical Hash Tries.
 	fn header_proofs(&self, req: request::HeaderProofs) -> Vec<Bytes>;

 	/// Provide pending transactions.
 	fn pending_transactions(&self) -> Vec<SignedTransaction>;
+}
+
+// Implementation of a light client data provider for a client.
+impl<T: ProvingBlockChainClient + ?Sized> Provider for T {
+	fn chain_info(&self) -> BlockChainInfo {
+		BlockChainClient::chain_info(self)
+	}
+
+	fn reorg_depth(&self, a: &H256, b: &H256) -> Option<u64> {
+		self.tree_route(a, b).map(|route| route.index as u64)
+	}
+
+	fn earliest_state(&self) -> Option<u64> {
+		Some(self.pruning_info().earliest_state)
+	}
+
+	fn block_headers(&self, req: request::Headers) -> Vec<Bytes> {
+		let best_num = self.chain_info().best_block_number;
+		let start_num = req.block_num;
+
+		match self.block_hash(BlockID::Number(req.block_num)) {
+			Some(hash) if hash == req.block_hash => {}
+			_=> {
+				trace!(target: "les_provider", "unknown/non-canonical start block in header request: {:?}", (req.block_num, req.block_hash));
+				return vec![]
+			}
+		}
+
+		(0u64..req.max as u64)
+			.map(|x: u64| x.saturating_mul(req.skip))
+			.take_while(|x| if req.reverse { x < &start_num } else { best_num - start_num < *x })
+			.map(|x| if req.reverse { start_num - x } else { start_num + x })
+			.map(|x| self.block_header(BlockID::Number(x)))
+			.take_while(|x| x.is_some())
+			.flat_map(|x| x)
+			.collect()
+	}
+
+	fn block_bodies(&self, req: request::Bodies) -> Vec<Bytes> {
+		req.block_hashes.into_iter()
+			.map(|hash| self.block_body(BlockID::Hash(hash)))
+			.map(|body| body.unwrap_or_else(|| ::rlp::EMPTY_LIST_RLP.to_vec()))
+			.collect()
+	}
+
+	fn receipts(&self, req: request::Receipts) -> Vec<Bytes> {
+		req.block_hashes.into_iter()
+			.map(|hash| self.block_receipts(&hash))
+			.map(|receipts| receipts.unwrap_or_else(|| ::rlp::EMPTY_LIST_RLP.to_vec()))
+			.collect()
+	}
+
+	fn proofs(&self, req: request::StateProofs) -> Vec<Bytes> {
+		use rlp::{RlpStream, Stream};
+
+		let mut results = Vec::with_capacity(req.requests.len());
+
+		for request in req.requests {
+			let proof = match request.key2 {
+				Some(key2) => self.prove_storage(request.key1, key2, request.from_level, BlockID::Hash(request.block)),
+				None => self.prove_account(request.key1, request.from_level, BlockID::Hash(request.block)),
+			};
+
+			let mut stream = RlpStream::new_list(proof.len());
+			for node in proof {
+				stream.append_raw(&node, 1);
+			}
+
+			results.push(stream.out());
+		}
+
+		results
+	}
+
+	fn contract_code(&self, req: request::ContractCodes) -> Vec<Bytes> {
+		req.code_requests.into_iter()
+			.map(|req| {
+				self.code_by_hash(req.account_key, BlockID::Hash(req.block_hash))
+			})
+			.collect()
+	}
+
+	fn header_proofs(&self, req: request::HeaderProofs) -> Vec<Bytes> {
+		req.requests.into_iter().map(|_| ::rlp::EMPTY_LIST_RLP.to_vec()).collect()
+	}
+
+	fn pending_transactions(&self) -> Vec<SignedTransaction> {
+		BlockChainClient::pending_transactions(self)
+	}
 }
--- a/ethcore/light/src/types/les_request.rs
+++ b/ethcore/light/src/types/les_request.rs
@ -16,25 +16,26 @@

 //! LES request types.

-// TODO: make IPC compatible.
-
 use util::H256;

 /// A request for block headers.
-#[derive(Debug, Clone, PartialEq, Eq)]
+#[derive(Debug, Clone, PartialEq, Eq, Binary)]
 pub struct Headers {
-	/// Block information for the request being made.
-	pub block: (u64, H256),
+	/// Starting block number
+	pub block_num: u64,
+	/// Starting block hash. This and number could be combined but IPC codegen is
+	/// not robust enough to support it.
+	pub block_hash: H256,
 	/// The maximum amount of headers which can be returned.
 	pub max: usize,
 	/// The amount of headers to skip between each response entry.
-	pub skip: usize,
+	pub skip: u64,
 	/// Whether the headers should proceed in falling number from the initial block.
 	pub reverse: bool,
 }

 /// A request for specific block bodies.
-#[derive(Debug, Clone, PartialEq, Eq)]
+#[derive(Debug, Clone, PartialEq, Eq, Binary)]
 pub struct Bodies {
 	/// Hashes which bodies are being requested for.
 	pub block_hashes: Vec<H256>
@ -44,14 +45,14 @@ pub struct Bodies {
 ///
 /// This request is answered with a list of transaction receipts for each block
 /// requested.
-#[derive(Debug, Clone, PartialEq, Eq)]
+#[derive(Debug, Clone, PartialEq, Eq, Binary)]
 pub struct Receipts {
 	/// Block hashes to return receipts for.
 	pub block_hashes: Vec<H256>,
 }

 /// A request for a state proof
-#[derive(Debug, Clone, PartialEq, Eq)]
+#[derive(Debug, Clone, PartialEq, Eq, Binary)]
 pub struct StateProof {
 	/// Block hash to query state from.
 	pub block: H256,
@ -65,21 +66,30 @@ pub struct StateProof {
 }

 /// A request for state proofs.
-#[derive(Debug, Clone, PartialEq, Eq)]
+#[derive(Debug, Clone, PartialEq, Eq, Binary)]
 pub struct StateProofs {
 	/// All the proof requests.
 	pub requests: Vec<StateProof>,
 }

 /// A request for contract code.
-#[derive(Debug, Clone, PartialEq, Eq)]
+#[derive(Debug, Clone, PartialEq, Eq, Binary)]
+pub struct ContractCode {
+	/// Block hash
+	pub block_hash: H256,
+	/// Account key (== sha3(address))
+	pub account_key: H256,
+}
+
+/// A request for contract code.
+#[derive(Debug, Clone, PartialEq, Eq, Binary)]
 pub struct ContractCodes {
 	/// Block hash and account key (== sha3(address)) pairs to fetch code for.
-	pub code_requests: Vec<(H256, H256)>,
+	pub code_requests: Vec<ContractCode>,
 }

 /// A request for a header proof from the Canonical Hash Trie.
-#[derive(Debug, Clone, PartialEq, Eq)]
+#[derive(Debug, Clone, PartialEq, Eq, Binary)]
 pub struct HeaderProof {
 	/// Number of the CHT.
 	pub cht_number: u64,
@ -90,14 +100,14 @@ pub struct HeaderProof {
 }

 /// A request for header proofs from the CHT.
-#[derive(Debug, Clone, PartialEq, Eq)]
+#[derive(Debug, Clone, PartialEq, Eq, Binary)]
 pub struct HeaderProofs {
 	/// All the proof requests.
-	pub requests: Vec<HeaderProofs>,
+	pub requests: Vec<HeaderProof>,
 }

 /// Kinds of requests.
-#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Binary)]
 pub enum Kind {
 	/// Requesting headers.
 	Headers,
@ -114,7 +124,7 @@ pub enum Kind {
 }

 /// Encompasses all possible types of requests in a single structure.
-#[derive(Debug, Clone, PartialEq, Eq)]
+#[derive(Debug, Clone, PartialEq, Eq, Binary)]
 pub enum Request {
 	/// Requesting headers.
 	Headers(Headers),
@ -142,4 +152,16 @@ impl Request {
 			Request::HeaderProofs(_) => Kind::HeaderProofs,
 		}
 	}
+
+	/// Get the amount of requests being made.
+	pub fn amount(&self) -> usize {
+		match *self {
+			Request::Headers(ref req) => req.max,
+			Request::Bodies(ref req) => req.block_hashes.len(),
+			Request::Receipts(ref req) => req.block_hashes.len(),
+			Request::StateProofs(ref req) => req.requests.len(),
+			Request::Codes(ref req) => req.code_requests.len(),
+			Request::HeaderProofs(ref req) => req.requests.len(),
+		}
+	}
 }
--- a/ethcore/light/src/types/mod.rs
+++ b/ethcore/light/src/types/mod.rs
@ -0,0 +1,20 @@
+// Copyright 2015, 2016 Ethcore (UK) Ltd.
+// This file is part of Parity.
+
+// Parity is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Parity is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Parity.  If not, see <http://www.gnu.org/licenses/>.
+
+//! Types used in the public (IPC) api which require custom code generation.
+
+#![allow(dead_code, unused_assignments, unused_variables)] // codegen issues
+include!(concat!(env!("OUT_DIR"), "/mod.rs.in"));
--- a/ethcore/light/src/types/mod.rs.in
+++ b/ethcore/light/src/types/mod.rs.in
@ -0,0 +1,17 @@
+// Copyright 2015, 2016 Ethcore (UK) Ltd.
+// This file is part of Parity.
+
+// Parity is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Parity is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Parity.  If not, see <http://www.gnu.org/licenses/>.
+
+pub mod les_request;
--- a/ethcore/src/client/client.rs
+++ b/ethcore/src/client/client.rs
@ -52,7 +52,7 @@ use blockchain::{BlockChain, BlockProvider, TreeRoute, ImportRoute};
 use client::{
 	BlockID, TransactionID, UncleID, TraceId, ClientConfig, BlockChainClient,
 	MiningBlockChainClient, TraceFilter, CallAnalytics, BlockImportError, Mode,
-	ChainNotify,
+	ChainNotify, PruningInfo, ProvingBlockChainClient,
 };
 use client::Error as ClientError;
 use env_info::EnvInfo;
@ -1286,6 +1286,13 @@ impl BlockChainClient for Client {
 		self.uncle(id)
 			.map(|header| self.engine.extra_info(&decode(&header)))
 	}
+
+	fn pruning_info(&self) -> PruningInfo {
+		PruningInfo {
+			earliest_chain: self.chain.read().first_block_number().unwrap_or(1),
+			earliest_state: self.state_db.lock().journal_db().earliest_era().unwrap_or(0),
+		}
+	}
 }

 impl MiningBlockChainClient for Client {
@ -1370,32 +1377,60 @@ impl MayPanic for Client {
 	}
 }

+impl ProvingBlockChainClient for Client {
+	fn prove_storage(&self, key1: H256, key2: H256, from_level: u32, id: BlockID) -> Vec<Bytes> {
+		self.state_at(id)
+			.and_then(move |state| state.prove_storage(key1, key2, from_level).ok())
+			.unwrap_or_else(Vec::new)
+	}

-#[test]
-fn should_not_cache_details_before_commit() {
-	use tests::helpers::*;
-	use std::thread;
-	use std::time::Duration;
-	use std::sync::atomic::{AtomicBool, Ordering};
+	fn prove_account(&self, key1: H256, from_level: u32, id: BlockID) -> Vec<Bytes> {
+		self.state_at(id)
+			.and_then(move |state| state.prove_account(key1, from_level).ok())
+			.unwrap_or_else(Vec::new)
+	}

-	let client = generate_dummy_client(0);
-	let genesis = client.chain_info().best_block_hash;
-	let (new_hash, new_block) = get_good_dummy_block_hash();
-
-	let go = {
-		// Separate thread uncommited transaction
-		let go = Arc::new(AtomicBool::new(false));
-		let go_thread = go.clone();
-		let another_client = client.reference().clone();
-		thread::spawn(move || {
-			let mut batch = DBTransaction::new(&*another_client.chain.read().db().clone());
-			another_client.chain.read().insert_block(&mut batch, &new_block, Vec::new());
-			go_thread.store(true, Ordering::SeqCst);
-		});
-		go
-	};
-
-	while !go.load(Ordering::SeqCst) { thread::park_timeout(Duration::from_millis(5)); }
-
-	assert!(client.tree_route(&genesis, &new_hash).is_none());
+	fn code_by_hash(&self, account_key: H256, id: BlockID) -> Bytes {
+		self.state_at(id)
+			.and_then(move |state| state.code_by_address_hash(account_key).ok())
+			.and_then(|x| x)
+			.unwrap_or_else(Vec::new)
+	}
 }
+
+#[cfg(test)]
+mod tests {
+
+	#[test]
+	fn should_not_cache_details_before_commit() {
+		use client::BlockChainClient;
+		use tests::helpers::*;
+
+		use std::thread;
+		use std::time::Duration;
+		use std::sync::Arc;
+		use std::sync::atomic::{AtomicBool, Ordering};
+		use util::kvdb::DBTransaction;
+
+		let client = generate_dummy_client(0);
+		let genesis = client.chain_info().best_block_hash;
+		let (new_hash, new_block) = get_good_dummy_block_hash();
+
+		let go = {
+			// Separate thread uncommited transaction
+			let go = Arc::new(AtomicBool::new(false));
+			let go_thread = go.clone();
+			let another_client = client.reference().clone();
+			thread::spawn(move || {
+				let mut batch = DBTransaction::new(&*another_client.chain.read().db().clone());
+				another_client.chain.read().insert_block(&mut batch, &new_block, Vec::new());
+				go_thread.store(true, Ordering::SeqCst);
+			});
+			go
+		};
+
+		while !go.load(Ordering::SeqCst) { thread::park_timeout(Duration::from_millis(5)); }
+
+		assert!(client.tree_route(&genesis, &new_hash).is_none());
+	}
+}
--- a/ethcore/src/client/mod.rs
+++ b/ethcore/src/client/mod.rs
@ -25,18 +25,21 @@ mod client;
 pub use self::client::*;
 pub use self::config::{Mode, ClientConfig, DatabaseCompactionProfile, BlockChainConfig, VMType};
 pub use self::error::Error;
-pub use types::ids::*;
 pub use self::test_client::{TestBlockChainClient, EachBlockWith};
+pub use self::chain_notify::ChainNotify;
+pub use self::traits::{BlockChainClient, MiningBlockChainClient, ProvingBlockChainClient};
+
+pub use types::ids::*;
 pub use types::trace_filter::Filter as TraceFilter;
+pub use types::pruning_info::PruningInfo;
+pub use types::call_analytics::CallAnalytics;
+
 pub use executive::{Executed, Executive, TransactOptions};
 pub use env_info::{LastHashes, EnvInfo};
-pub use self::chain_notify::ChainNotify;

-pub use types::call_analytics::CallAnalytics;
 pub use block_import_error::BlockImportError;
 pub use transaction_import::TransactionImportResult;
 pub use transaction_import::TransactionImportError;
-pub use self::traits::{BlockChainClient, MiningBlockChainClient};
 pub use verification::VerifierType;

 /// IPC interfaces
--- a/ethcore/src/client/test_client.rs
+++ b/ethcore/src/client/test_client.rs
@ -38,6 +38,7 @@ use evm::{Factory as EvmFactory, VMType, Schedule};
 use miner::{Miner, MinerService, TransactionImportResult};
 use spec::Spec;
 use types::mode::Mode;
+use types::pruning_info::PruningInfo;
 use views::BlockView;

 use verification::queue::QueueInfo;
@ -667,4 +668,11 @@ impl BlockChainClient for TestBlockChainClient {
 	fn mode(&self) -> Mode { Mode::Active }

 	fn set_mode(&self, _: Mode) { unimplemented!(); }
+
+	fn pruning_info(&self) -> PruningInfo {
+		PruningInfo {
+			earliest_chain: 1,
+			earliest_state: 1,
+		}
+	}
 }
--- a/ethcore/src/client/traits.rs
+++ b/ethcore/src/client/traits.rs
@ -39,6 +39,7 @@ use types::call_analytics::CallAnalytics;
 use types::blockchain_info::BlockChainInfo;
 use types::block_status::BlockStatus;
 use types::mode::Mode;
+use types::pruning_info::PruningInfo;

 #[ipc(client_ident="RemoteClient")]
 /// Blockchain database client. Owns and manages a blockchain and a block queue.
@ -250,10 +251,15 @@ pub trait BlockChainClient : Sync + Send {

 	/// Returns engine-related extra info for `UncleID`.
 	fn uncle_extra_info(&self, id: UncleID) -> Option<BTreeMap<String, String>>;
+
+	/// Returns information about pruning/data availability.
+	fn pruning_info(&self) -> PruningInfo;
 }

+impl IpcConfig for BlockChainClient { }
+
 /// Extended client interface used for mining
-pub trait MiningBlockChainClient : BlockChainClient {
+pub trait MiningBlockChainClient: BlockChainClient {
 	/// Returns OpenBlock prepared for closing.
 	fn prepare_open_block(&self,
 		author: Address,
@ -271,4 +277,23 @@ pub trait MiningBlockChainClient : BlockChainClient {
 	fn latest_schedule(&self) -> Schedule;
 }

-impl IpcConfig for BlockChainClient { }
+/// Extended client interface for providing proofs of the state.
+pub trait ProvingBlockChainClient: BlockChainClient {
+	/// Prove account storage at a specific block id.
+	///
+	/// Both provided keys assume a secure trie.
+	/// Returns a vector of raw trie nodes (in order from the root) proving the storage query.
+	/// Nodes after `from_level` may be omitted.
+	/// An empty vector indicates unservable query.
+	fn prove_storage(&self, key1: H256, key2: H256, from_level: u32, id: BlockID) -> Vec<Bytes>;
+
+	/// Prove account existence at a specific block id.
+	/// The key is the keccak hash of the account's address.
+	/// Returns a vector of raw trie nodes (in order from the root) proving the query.
+	/// Nodes after `from_level` may be omitted.
+	/// An empty vector indicates unservable query.	
+	fn prove_account(&self, key1: H256, from_level: u32, id: BlockID) -> Vec<Bytes>;
+
+	/// Get code by address hash.
+	fn code_by_hash(&self, account_key: H256, id: BlockID) -> Bytes;
+}
--- a/ethcore/src/state/account.rs
+++ b/ethcore/src/state/account.rs
@ -436,6 +436,27 @@ impl Account {
 	}
 }

+// light client storage proof.
+impl Account {
+	/// Prove a storage key's existence or nonexistence in the account's storage
+	/// trie.
+	/// `storage_key` is the hash of the desired storage key, meaning
+	/// this will only work correctly under a secure trie.
+	/// Returns a merkle proof of the storage trie node with all nodes before `from_level`
+	/// omitted.
+	pub fn prove_storage(&self, db: &HashDB, storage_key: H256, from_level: u32) -> Result<Vec<Bytes>, Box<TrieError>> {
+		use util::trie::{Trie, TrieDB};
+		use util::trie::recorder::{Recorder, BasicRecorder as TrieRecorder};
+
+		let mut recorder = TrieRecorder::with_depth(from_level);
+
+		let trie = try!(TrieDB::new(db, &self.storage_root));
+		let _ = try!(trie.get_recorded(&storage_key, &mut recorder));
+
+		Ok(recorder.drain().into_iter().map(|r| r.data).collect())
+	}
+}
+
 impl fmt::Debug for Account {
 	fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
 		write!(f, "{:?}", PodAccount::from_account(self))
--- a/ethcore/src/state/mod.rs
+++ b/ethcore/src/state/mod.rs
@ -16,7 +16,7 @@

 use std::cell::{RefCell, RefMut};
 use std::collections::hash_map::Entry;
-use util::*;
+
 use receipt::Receipt;
 use engines::Engine;
 use env_info::EnvInfo;
@ -30,6 +30,9 @@ use types::state_diff::StateDiff;
 use transaction::SignedTransaction;
 use state_db::StateDB;

+use util::*;
+use util::trie::recorder::{Recorder, BasicRecorder as TrieRecorder};
+
 mod account;
 mod substate;

@ -758,6 +761,53 @@ impl State {
 	}
 }

+// LES state proof implementations.
+impl State {
+	/// Prove an account's existence or nonexistence in the state trie.
+	/// Returns a merkle proof of the account's trie node with all nodes before `from_level`
+	/// omitted or an encountered trie error.
+	/// Requires a secure trie to be used for accurate results.
+	/// `account_key` == sha3(address)
+	pub fn prove_account(&self, account_key: H256, from_level: u32) -> Result<Vec<Bytes>, Box<TrieError>> {
+		let mut recorder = TrieRecorder::with_depth(from_level);
+		let trie = try!(TrieDB::new(self.db.as_hashdb(), &self.root));
+		let _  = try!(trie.get_recorded(&account_key, &mut recorder));
+
+		Ok(recorder.drain().into_iter().map(|r| r.data).collect())
+	}
+
+	/// Prove an account's storage key's existence or nonexistence in the state.
+	/// Returns a merkle proof of the account's storage trie with all nodes before
+	/// `from_level` omitted. Requires a secure trie to be used for correctness.
+	/// `account_key` == sha3(address)
+	/// `storage_key` == sha3(key)
+	pub fn prove_storage(&self, account_key: H256, storage_key: H256, from_level: u32) -> Result<Vec<Bytes>, Box<TrieError>> {
+		// TODO: probably could look into cache somehow but it's keyed by
+		// address, not sha3(address).
+		let trie = try!(TrieDB::new(self.db.as_hashdb(), &self.root));
+		let acc = match try!(trie.get(&account_key)) {
+			Some(rlp) => Account::from_rlp(&rlp),
+			None => return Ok(Vec::new()),
+		};
+
+		let account_db = self.factories.accountdb.readonly(self.db.as_hashdb(), account_key);
+		acc.prove_storage(account_db.as_hashdb(), storage_key, from_level)
+	}
+
+	/// Get code by address hash.
+	/// Only works when backed by a secure trie.
+	pub fn code_by_address_hash(&self, account_key: H256) -> Result<Option<Bytes>, Box<TrieError>> {
+		let trie = try!(TrieDB::new(self.db.as_hashdb(), &self.root));
+		let mut acc = match try!(trie.get(&account_key)) {
+			Some(rlp) => Account::from_rlp(&rlp),
+			None => return Ok(None),
+		};
+
+		let account_db = self.factories.accountdb.readonly(self.db.as_hashdb(), account_key);
+		Ok(acc.cache_code(account_db.as_hashdb()).map(|c| (&*c).clone()))
+	}
+}
+
 impl fmt::Debug for State {
 	fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
 		write!(f, "{:?}", self.cache.borrow())
--- a/ethcore/src/types/mod.rs.in
+++ b/ethcore/src/types/mod.rs.in
@ -34,3 +34,4 @@ pub mod block_import_error;
 pub mod restoration_status;
 pub mod snapshot_manifest;
 pub mod mode;
+pub mod pruning_info;
--- a/ethcore/src/types/pruning_info.rs
+++ b/ethcore/src/types/pruning_info.rs
@ -0,0 +1,30 @@
+// Copyright 2015, 2016 Ethcore (UK) Ltd.
+// This file is part of Parity.
+
+// Parity is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Parity is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Parity.  If not, see <http://www.gnu.org/licenses/>.
+
+//! Information about portions of the state and chain which the client may serve.
+//!
+//! Currently assumes that a client will store everything past a certain point
+//! or everything. Will be extended in the future to support a definition
+//! of which portions of the ancient chain and current state trie are stored as well.
+
+/// Client pruning info. See module-level docs for more details.
+#[derive(Debug, Clone, Binary)]
+pub struct PruningInfo {
+	/// The first block which everything can be served after.
+	pub earliest_chain: u64,
+	/// The first block where state requests may be served.
+	pub earliest_state: u64,
+}
--- a/util/src/trie/mod.rs
+++ b/util/src/trie/mod.rs
@ -97,11 +97,11 @@ pub trait Trie {
 	}

 	/// Query the value of the given key in this trie while recording visited nodes
-	/// to the given recorder. If the query fails, the nodes passed to the recorder are unspecified.
+	/// to the given recorder. If the query encounters an error, the nodes passed to the recorder are unspecified.
 	fn get_recorded<'a, 'b, R: 'b>(&'a self, key: &'b [u8], rec: &'b mut R) -> Result<Option<DBValue>>
 		where 'a: 'b, R: Recorder;

-	/// Returns an iterator over elements of trie.
+	/// Returns a depth-first iterator over the elements of trie.
 	fn iter<'a>(&'a self) -> Result<Box<TrieIterator<Item = TrieItem> + 'a>>;
 }

@ -241,5 +241,5 @@ impl TrieFactory {
 	}

 	/// Returns true iff the trie DB is a fat DB (allows enumeration of keys).
-	pub fn is_fat(&self) -> bool { self.spec == TrieSpec::Fat } 
+	pub fn is_fat(&self) -> bool { self.spec == TrieSpec::Fat }
 }
--- a/util/src/trie/recorder.rs
+++ b/util/src/trie/recorder.rs
@ -35,7 +35,6 @@ pub struct Record {
 /// These are used to record which nodes are visited during a trie query.
 /// Inline nodes are not to be recorded, as they are contained within their parent.
 pub trait Recorder {
-
 	/// Record that the given node has been visited.
 	///
 	/// The depth parameter is the depth of the visited node, with the root node having depth 0.
@ -58,6 +57,7 @@ impl Recorder for NoOp {

 /// A simple recorder. Does nothing fancy but fulfills the `Recorder` interface
 /// properly.
+#[derive(Debug)]
 pub struct BasicRecorder {
 	nodes: Vec<Record>,
 	min_depth: u32,