mirror of https://github.com/poanetwork/hbbft.git
465 lines
17 KiB
Rust
465 lines
17 KiB
Rust
use std::collections::BTreeMap;
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use std::sync::Arc;
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use byteorder::{BigEndian, ByteOrder};
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use hex_fmt::{HexFmt, HexList};
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use reed_solomon_erasure as rse;
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use reed_solomon_erasure::ReedSolomon;
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use super::merkle::{Digest, MerkleTree, Proof};
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use super::message::HexProof;
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use super::{Error, Message, Result};
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use fault_log::{Fault, FaultKind};
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use {DistAlgorithm, NetworkInfo, NodeIdT, Target};
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/// Broadcast algorithm instance.
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#[derive(Debug)]
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pub struct Broadcast<N> {
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/// Shared network data.
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netinfo: Arc<NetworkInfo<N>>,
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/// The ID of the sending node.
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proposer_id: N,
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data_shard_num: usize,
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coding: Coding,
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/// Whether we have already multicast `Echo`.
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echo_sent: bool,
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/// Whether we have already multicast `Ready`.
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ready_sent: bool,
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/// Whether we have already output a value.
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decided: bool,
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/// The proofs we have received via `Echo` messages, by sender ID.
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echos: BTreeMap<N, Proof<Vec<u8>>>,
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/// The root hashes we received via `Ready` messages, by sender ID.
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readys: BTreeMap<N, Vec<u8>>,
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}
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pub type Step<N> = ::Step<Broadcast<N>>;
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impl<N: NodeIdT> DistAlgorithm for Broadcast<N> {
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type NodeId = N;
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// TODO: Allow anything serializable and deserializable, i.e. make this a type parameter
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// T: Serialize + DeserializeOwned
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type Input = Vec<u8>;
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type Output = Self::Input;
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type Message = Message;
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type Error = Error;
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fn handle_input(&mut self, input: Self::Input) -> Result<Step<N>> {
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if *self.netinfo.our_id() != self.proposer_id {
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return Err(Error::InstanceCannotPropose);
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}
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// Split the value into chunks/shards, encode them with erasure codes.
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// Assemble a Merkle tree from data and parity shards. Take all proofs
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// from this tree and send them, each to its own node.
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let (proof, mut step) = self.send_shards(input)?;
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let our_id = &self.netinfo.our_id().clone();
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step.extend(self.handle_value(our_id, proof)?);
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Ok(step)
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}
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fn handle_message(&mut self, sender_id: &N, message: Self::Message) -> Result<Step<N>> {
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if !self.netinfo.is_node_validator(sender_id) {
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return Err(Error::UnknownSender);
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}
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match message {
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Message::Value(p) => self.handle_value(sender_id, p),
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Message::Echo(p) => self.handle_echo(sender_id, p),
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Message::Ready(ref hash) => self.handle_ready(sender_id, hash),
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}
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}
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fn terminated(&self) -> bool {
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self.decided
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}
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fn our_id(&self) -> &N {
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self.netinfo.our_id()
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}
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}
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impl<N: NodeIdT> Broadcast<N> {
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/// Creates a new broadcast instance to be used by node `our_id` which expects a value proposal
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/// from node `proposer_id`.
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pub fn new(netinfo: Arc<NetworkInfo<N>>, proposer_id: N) -> Result<Self> {
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let parity_shard_num = 2 * netinfo.num_faulty();
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let data_shard_num = netinfo.num_nodes() - parity_shard_num;
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let coding = Coding::new(data_shard_num, parity_shard_num)?;
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Ok(Broadcast {
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netinfo,
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proposer_id,
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data_shard_num,
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coding,
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echo_sent: false,
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ready_sent: false,
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decided: false,
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echos: BTreeMap::new(),
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readys: BTreeMap::new(),
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})
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}
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/// Breaks the input value into shards of equal length and encodes them --
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/// and some extra parity shards -- with a Reed-Solomon erasure coding
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/// scheme. The returned value contains the shard assigned to this
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/// node. That shard doesn't need to be sent anywhere. It gets recorded in
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/// the broadcast instance.
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fn send_shards(&mut self, mut value: Vec<u8>) -> Result<(Proof<Vec<u8>>, Step<N>)> {
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let data_shard_num = self.coding.data_shard_count();
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let parity_shard_num = self.coding.parity_shard_count();
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debug!(
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"Data shards: {}, parity shards: {}",
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self.data_shard_num, parity_shard_num
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);
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// Insert the length of `v` so it can be decoded without the padding.
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let payload_len = value.len() as u32;
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value.splice(0..0, 0..4); // Insert four bytes at the beginning.
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BigEndian::write_u32(&mut value[..4], payload_len); // Write the size.
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let value_len = value.len();
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// Size of a Merkle tree leaf value, in bytes.
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let shard_len = if value_len % data_shard_num > 0 {
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value_len / data_shard_num + 1
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} else {
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value_len / data_shard_num
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};
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// Pad the last data shard with zeros. Fill the parity shards with
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// zeros.
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value.resize(shard_len * (data_shard_num + parity_shard_num), 0);
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debug!("value_len {}, shard_len {}", value_len, shard_len);
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// Divide the vector into chunks/shards.
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let shards_iter = value.chunks_mut(shard_len);
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// Convert the iterator over slices into a vector of slices.
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let mut shards: Vec<&mut [u8]> = shards_iter.collect();
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debug!("Shards before encoding: {:?}", HexList(&shards));
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// Construct the parity chunks/shards
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self.coding
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.encode(&mut shards)
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.expect("the size and number of shards is correct");
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debug!("Shards: {:?}", HexList(&shards));
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// Create a Merkle tree from the shards.
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let mtree = MerkleTree::from_vec(shards.into_iter().map(|shard| shard.to_vec()).collect());
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// Default result in case of `proof` error.
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let mut result = Err(Error::ProofConstructionFailed);
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assert_eq!(self.netinfo.num_nodes(), mtree.values().len());
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let mut step = Step::default();
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// Send each proof to a node.
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for (index, id) in self.netinfo.all_ids().enumerate() {
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let proof = mtree.proof(index).ok_or(Error::ProofConstructionFailed)?;
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if *id == *self.netinfo.our_id() {
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// The proof is addressed to this node.
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result = Ok(proof);
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} else {
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// Rest of the proofs are sent to remote nodes.
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let msg = Target::Node(id.clone()).message(Message::Value(proof));
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step.messages.push_back(msg);
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}
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}
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result.map(|proof| (proof, step))
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}
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/// Handles a received echo and verifies the proof it contains.
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fn handle_value(&mut self, sender_id: &N, p: Proof<Vec<u8>>) -> Result<Step<N>> {
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// If the sender is not the proposer or if this is not the first `Value`, ignore.
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if *sender_id != self.proposer_id {
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info!(
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"Node {:?} received Value from {:?} instead of {:?}.",
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self.netinfo.our_id(),
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sender_id,
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self.proposer_id
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);
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let fault_kind = FaultKind::ReceivedValueFromNonProposer;
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return Ok(Fault::new(sender_id.clone(), fault_kind).into());
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}
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if self.echo_sent {
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info!("Node {:?} received multiple Values.", self.netinfo.our_id());
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// TODO: should receiving two Values from a node be considered
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// a fault? If so, return a `Fault` here. For now, ignore.
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return Ok(Step::default());
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}
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// If the proof is invalid, log the faulty node behavior and ignore.
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if !self.validate_proof(&p, &self.netinfo.our_id()) {
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return Ok(Fault::new(sender_id.clone(), FaultKind::InvalidProof).into());
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}
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// Otherwise multicast the proof in an `Echo` message, and handle it ourselves.
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self.send_echo(p)
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}
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/// Handles a received `Echo` message.
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fn handle_echo(&mut self, sender_id: &N, p: Proof<Vec<u8>>) -> Result<Step<N>> {
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// If the sender has already sent `Echo`, ignore.
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if self.echos.contains_key(sender_id) {
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info!(
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"Node {:?} received multiple Echos from {:?}.",
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self.netinfo.our_id(),
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sender_id,
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);
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return Ok(Step::default());
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}
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// If the proof is invalid, log the faulty-node behavior, and ignore.
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if !self.validate_proof(&p, sender_id) {
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return Ok(Fault::new(sender_id.clone(), FaultKind::InvalidProof).into());
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}
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let hash = *p.root_hash();
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// Save the proof for reconstructing the tree later.
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self.echos.insert(sender_id.clone(), p);
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if self.ready_sent || self.count_echos(&hash) < self.netinfo.num_correct() {
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return self.compute_output(&hash);
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}
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// Upon receiving `N - f` `Echo`s with this root hash, multicast `Ready`.
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self.send_ready(&hash)
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}
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/// Handles a received `Ready` message.
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fn handle_ready(&mut self, sender_id: &N, hash: &Digest) -> Result<Step<N>> {
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// If the sender has already sent a `Ready` before, ignore.
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if self.readys.contains_key(sender_id) {
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info!(
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"Node {:?} received multiple Readys from {:?}.",
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self.netinfo.our_id(),
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sender_id
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);
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return Ok(Step::default());
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}
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self.readys.insert(sender_id.clone(), hash.to_vec());
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let mut step = Step::default();
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// Upon receiving f + 1 matching Ready(h) messages, if Ready
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// has not yet been sent, multicast Ready(h).
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if self.count_readys(hash) == self.netinfo.num_faulty() + 1 && !self.ready_sent {
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// Enqueue a broadcast of a Ready message.
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step.extend(self.send_ready(hash)?);
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}
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step.extend(self.compute_output(hash)?);
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Ok(step)
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}
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/// Sends an `Echo` message and handles it. Does nothing if we are only an observer.
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fn send_echo(&mut self, p: Proof<Vec<u8>>) -> Result<Step<N>> {
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self.echo_sent = true;
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if !self.netinfo.is_validator() {
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return Ok(Step::default());
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}
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let echo_msg = Message::Echo(p.clone());
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let mut step: Step<_> = Target::All.message(echo_msg).into();
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let our_id = &self.netinfo.our_id().clone();
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step.extend(self.handle_echo(our_id, p)?);
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Ok(step)
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}
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/// Sends a `Ready` message and handles it. Does nothing if we are only an observer.
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fn send_ready(&mut self, hash: &Digest) -> Result<Step<N>> {
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self.ready_sent = true;
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if !self.netinfo.is_validator() {
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return Ok(Step::default());
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}
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let ready_msg = Message::Ready(*hash);
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let mut step: Step<_> = Target::All.message(ready_msg).into();
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let our_id = &self.netinfo.our_id().clone();
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step.extend(self.handle_ready(our_id, hash)?);
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Ok(step)
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}
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/// Checks whether the conditions for output are met for this hash, and if so, sets the output
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/// value.
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fn compute_output(&mut self, hash: &Digest) -> Result<Step<N>> {
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if self.decided
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|| self.count_readys(hash) <= 2 * self.netinfo.num_faulty()
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|| self.count_echos(hash) < self.coding.data_shard_count()
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{
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return Ok(Step::default());
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}
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// Upon receiving 2f + 1 matching Ready(h) messages, wait for N − 2f Echo messages.
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let mut leaf_values: Vec<Option<Box<[u8]>>> = self
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.netinfo
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.all_ids()
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.map(|id| {
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self.echos.get(id).and_then(|p| {
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if p.root_hash() == hash {
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Some(p.value().clone().into_boxed_slice())
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} else {
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None
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}
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})
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}).collect();
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if let Some(value) =
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decode_from_shards(&mut leaf_values, &self.coding, self.data_shard_num, hash)
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{
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self.decided = true;
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Ok(Step::default().with_output(value))
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} else {
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Ok(Step::default())
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}
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}
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/// Returns `true` if the proof is valid and has the same index as the node ID. Otherwise
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/// logs an info message.
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fn validate_proof(&self, p: &Proof<Vec<u8>>, id: &N) -> bool {
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if !p.validate(self.netinfo.num_nodes()) {
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info!(
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"Node {:?} received invalid proof: {:?}",
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self.netinfo.our_id(),
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HexProof(&p)
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);
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false
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} else if self.netinfo.node_index(id) != Some(p.index()) {
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info!(
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"Node {:?} received proof for wrong position: {:?}.",
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self.netinfo.our_id(),
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HexProof(&p)
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);
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false
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} else {
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true
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}
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}
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/// Returns the number of nodes that have sent us an `Echo` message with this hash.
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fn count_echos(&self, hash: &Digest) -> usize {
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self.echos
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.values()
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.filter(|p| p.root_hash() == hash)
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.count()
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}
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/// Returns the number of nodes that have sent us a `Ready` message with this hash.
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fn count_readys(&self, hash: &Digest) -> usize {
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self.readys
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.values()
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.filter(|h| h.as_slice() == hash)
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.count()
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}
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}
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/// A wrapper for `ReedSolomon` that doesn't panic if there are no parity shards.
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#[derive(Debug)]
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enum Coding {
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/// A `ReedSolomon` instance with at least one parity shard.
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ReedSolomon(Box<ReedSolomon>),
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/// A no-op replacement that doesn't encode or decode anything.
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Trivial(usize),
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}
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impl Coding {
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/// Creates a new `Coding` instance with the given number of shards.
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fn new(data_shard_num: usize, parity_shard_num: usize) -> Result<Self> {
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Ok(if parity_shard_num > 0 {
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let rs = ReedSolomon::new(data_shard_num, parity_shard_num)
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.map_err(Error::CodingNewReedSolomon)?;
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Coding::ReedSolomon(Box::new(rs))
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} else {
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Coding::Trivial(data_shard_num)
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})
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}
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/// Returns the number of data shards.
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fn data_shard_count(&self) -> usize {
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match *self {
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Coding::ReedSolomon(ref rs) => rs.data_shard_count(),
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Coding::Trivial(dsc) => dsc,
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}
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}
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/// Returns the number of parity shards.
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fn parity_shard_count(&self) -> usize {
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match *self {
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Coding::ReedSolomon(ref rs) => rs.parity_shard_count(),
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Coding::Trivial(_) => 0,
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}
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}
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/// Constructs (and overwrites) the parity shards.
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fn encode(&self, slices: &mut [&mut [u8]]) -> Result<()> {
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match *self {
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Coding::ReedSolomon(ref rs) => {
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rs.encode(slices).map_err(Error::CodingEncodeReedSolomon)?
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}
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Coding::Trivial(_) => (),
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}
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Ok(())
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}
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/// If enough shards are present, reconstructs the missing ones.
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fn reconstruct_shards(&self, shards: &mut [Option<Box<[u8]>>]) -> Result<()> {
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match *self {
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Coding::ReedSolomon(ref rs) => rs
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.reconstruct_shards(shards)
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.map_err(Error::CodingReconstructShardsReedSolomon)?,
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Coding::Trivial(_) => {
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if shards.iter().any(Option::is_none) {
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return Err(Error::CodingReconstructShardsTrivialReedSolomon(
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rse::Error::TooFewShardsPresent,
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));
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}
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}
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}
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Ok(())
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}
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}
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fn decode_from_shards(
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leaf_values: &mut [Option<Box<[u8]>>],
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coding: &Coding,
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data_shard_num: usize,
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root_hash: &Digest,
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) -> Option<Vec<u8>> {
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// Try to interpolate the Merkle tree using the Reed-Solomon erasure coding scheme.
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if let Err(err) = coding.reconstruct_shards(leaf_values) {
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error!("Shard reconstruction failed: {:?}", err); // Faulty proposer
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return None;
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}
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// Recompute the Merkle tree root.
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// Collect shards for tree construction.
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let shards: Vec<Vec<u8>> = leaf_values
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.iter()
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.filter_map(|l| l.as_ref().map(|v| v.to_vec()))
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.collect();
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debug!("Reconstructed shards: {:?}", HexList(&shards));
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// Construct the Merkle tree.
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let mtree = MerkleTree::from_vec(shards);
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// If the root hash of the reconstructed tree does not match the one
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// received with proofs then abort.
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if mtree.root_hash() != root_hash {
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None // The proposer is faulty.
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} else {
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// Reconstruct the value from the data shards.
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glue_shards(mtree, data_shard_num)
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}
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}
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/// Concatenates the first `n` leaf values of a Merkle tree `m` in one value of
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/// type `T`. This is useful for reconstructing the data value held in the tree
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/// and forgetting the leaves that contain parity information.
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fn glue_shards(m: MerkleTree<Vec<u8>>, n: usize) -> Option<Vec<u8>> {
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// Create an iterator over the shard payload, drop the index bytes.
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let mut bytes = m.into_values().into_iter().take(n).flatten();
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let payload_len = match (bytes.next(), bytes.next(), bytes.next(), bytes.next()) {
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(Some(b0), Some(b1), Some(b2), Some(b3)) => BigEndian::read_u32(&[b0, b1, b2, b3]) as usize,
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_ => return None, // The proposing node is faulty: no payload size.
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};
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let payload: Vec<u8> = bytes.take(payload_len).collect();
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debug!("Glued data shards {:?}", HexFmt(&payload));
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Some(payload)
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}
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