Parse inv messages, refactor inventory vectors.

This removes the inventory vector structs from `zebra-chain` (as they
are really part of the network protocol) and refactors them into a
single `InventoryHash` type.  This corresponds to Bitcoin's "inventory
vector" but with a different, better name (it's not a vector, it's just
a typed hash of some other item).

zebra-chain/src/types.rs

@@ -19,34 +19,6 @@ impl<'a> From<&'a [u8]> for Sha256dChecksum {
 #[derive(Copy, Clone, Debug, Eq, PartialEq)]
 pub struct BlockHeight(pub u32);
 
-/// InventoryType
-///
-/// [Bitcoin·reference](https://en.bitcoin.it/wiki/Protocol_documentation#Inventory_Vectors)
-#[derive(Copy, Clone, Debug, Eq, PartialEq)]
-#[repr(u8)]
-pub enum InventoryType {
-    /// Any data of with this number may be ignored.
-    Error = 0x00,
-
-    /// Hash is related to a transaction.
-    MsgTx = 0x01,
-
-    /// Hash is related to a data block.
-    MsgBlock = 0x02,
-
-    /// Hash of a block header, but only to be used in getdata
-    /// message. Indicates the reply should be a merkleblock message
-    /// rather than a block message; this only works if a bloom filter
-    /// has been set.
-    // XXX: Since we don't intend to include the bloom filter to
-    // start, do we need this?
-    MsgFilteredBlock = 0x03,
-}
-
-/// Inventory Vector
-#[derive(Copy, Clone, Debug, Eq, PartialEq)]
-pub struct InventoryVector(pub InventoryType, pub [u8; 32]);
-
 #[cfg(test)]
 mod tests {
     use super::*;

zebra-network/src/protocol.rs

@@ -3,3 +3,5 @@
 pub mod codec;
 pub mod message;
 pub mod types;
+
+pub mod inv;

zebra-network/src/protocol/codec.rs

@@ -9,7 +9,7 @@ use failure::Error;
 use tokio::codec::{Decoder, Encoder};
 
 use zebra_chain::{
-    serialization::{ReadZcashExt, WriteZcashExt, ZcashSerialize},
+    serialization::{ReadZcashExt, WriteZcashExt, ZcashDeserialize, ZcashSerialize},
     types::{BlockHeight, Sha256dChecksum},
 };
 
@@ -197,6 +197,12 @@ impl Codec {
             Pong(nonce) => {
                 writer.write_u64::<LittleEndian>(nonce.0)?;
             }
+            Inv(ref hashes) => {
+                writer.write_compactsize(hashes.len() as u64)?;
+                for hash in hashes {
+                    hash.zcash_serialize(&mut writer)?;
+                }
+            }
             Block { ref block } => {
                 block
                     .zcash_serialize(&mut writer)
@@ -395,9 +401,28 @@ impl Codec {
         bail!("unimplemented message type")
     }
 
-    fn read_inv<R: Read>(&self, mut _reader: R) -> Result<Message, Error> {
+    fn read_inv<R: Read>(&self, mut reader: R) -> Result<Message, Error> {
-        trace!("inv");
+        use super::inv::InventoryHash;
-        bail!("unimplemented message type")
+
+        let count = reader.read_compactsize()? as usize;
+        // Preallocate a buffer, performing a single allocation in the honest
+        // case. Although the size of the recieved data buffer is bounded by the
+        // codec's max_len field, it's still possible for someone to send a
+        // short message with a large count field, so if we naively trust
+        // the count field we could be tricked into preallocating a large
+        // buffer. Instead, calculate the maximum count for a valid message from
+        // the codec's max_len using ENCODED_INVHASH_SIZE.
+        //
+        // encoding: 4 byte type tag + 32 byte hash
+        const ENCODED_INVHASH_SIZE: usize = 4 + 32;
+        let max_count = self.builder.max_len / ENCODED_INVHASH_SIZE;
+        let mut hashes = Vec::with_capacity(std::cmp::min(count, max_count));
+
+        for _ in 0..count {
+            hashes.push(InventoryHash::zcash_deserialize(&mut reader)?);
+        }
+
+        Ok(Message::Inventory(hashes))
     }
 
     fn read_getdata<R: Read>(&self, mut _reader: R) -> Result<Message, Error> {

zebra-network/src/protocol/inv.rs

@@ -0,0 +1,74 @@
+//! Inventory items for the Bitcoin protocol.
+
+// XXX the exact optimal arrangement of all of these parts is a little unclear
+// until we have more pieces in place the optimal global arrangement of items is
+// a little unclear.
+
+use std::io::{Read, Write};
+
+use byteorder::{LittleEndian, ReadBytesExt, WriteBytesExt};
+
+use zebra_chain::serialization::{
+    ReadZcashExt, SerializationError, ZcashDeserialize, ZcashSerialize,
+};
+
+/// Stub-- delete later.
+#[derive(Copy, Clone, Debug, Eq, PartialEq)]
+pub struct TxHash(pub [u8; 32]);
+/// Stub-- delete later.
+#[derive(Copy, Clone, Debug, Eq, PartialEq)]
+pub struct BlockHash(pub [u8; 32]);
+
+/// An inventory hash which refers to some advertised or requested data.
+///
+/// Bitcoin calls this an "inventory vector" but it is just a typed hash, not a
+/// container, so we do not use that term to avoid confusion with `Vec<T>`.
+///
+/// [Bitcoin·reference](https://en.bitcoin.it/wiki/Protocol_documentation#Inventory_Vectors)
+#[derive(Copy, Clone, Debug, Eq, PartialEq)]
+pub enum InventoryHash {
+    /// An error.
+    ///
+    /// The Bitcoin wiki just says "Any data of with this number may be ignored",
+    /// so we don't include a typed hash.
+    Error,
+    /// A hash of a transaction.
+    Tx(TxHash),
+    /// A hash of a block.
+    Block(BlockHash),
+    /// A hash of a filtered block.
+    ///
+    /// The Bitcoin wiki says: Hash of a block header, but only to be used in
+    /// getdata message. Indicates the reply should be a merkleblock message
+    /// rather than a block message; this only works if a bloom filter has been
+    /// set.
+    FilteredBlock(BlockHash),
+}
+
+impl ZcashSerialize for InventoryHash {
+    fn zcash_serialize<W: Write>(&self, mut writer: W) -> Result<(), SerializationError> {
+        let (code, bytes) = match *self {
+            InventoryHash::Error => (0, [0; 32]),
+            InventoryHash::Tx(hash) => (1, hash.0),
+            InventoryHash::Block(hash) => (2, hash.0),
+            InventoryHash::FilteredBlock(hash) => (3, hash.0),
+        };
+        writer.write_u32::<LittleEndian>(code)?;
+        writer.write_all(&bytes)?;
+        Ok(())
+    }
+}
+
+impl ZcashDeserialize for InventoryHash {
+    fn zcash_deserialize<R: Read>(mut reader: R) -> Result<Self, SerializationError> {
+        let code = reader.read_u32::<LittleEndian>()?;
+        let bytes = reader.read_32_bytes()?;
+        match code {
+            0 => Ok(InventoryHash::Error),
+            1 => Ok(InventoryHash::Tx(TxHash(bytes))),
+            2 => Ok(InventoryHash::Block(BlockHash(bytes))),
+            3 => Ok(InventoryHash::FilteredBlock(BlockHash(bytes))),
+            _ => Err(SerializationError::ParseError("invalid inventory code")),
+        }
+    }
+}

zebra-network/src/protocol/message.rs

@@ -9,6 +9,7 @@ use zebra_chain::{transaction::Transaction, types::BlockHeight};
 
 use crate::meta_addr::MetaAddr;
 
+use super::inv::InventoryHash;
 use super::types::*;
 
 /// A Bitcoin-like network message for the Zcash protocol.
@@ -162,13 +163,7 @@ pub enum Message {
     // XXX the bitcoin reference above suggests this can be 1.8 MB in bitcoin -- maybe
     // larger in Zcash, since Zcash objects could be bigger (?) -- does this tilt towards
     // having serialization be async?
-    Inventory {
+    Inventory(Vec<InventoryHash>),
-        /// Number of inventory entries.
-        count: u64,
-
-        /// Inventory vectors.
-        inventory: Vec<zebra_chain::types::InventoryVector>,
-    },
 
     /// A `getdata` message.
     ///
@@ -177,25 +172,13 @@ pub enum Message {
     /// packet, after filtering known elements.
     ///
     /// [Bitcoin reference](https://en.bitcoin.it/wiki/Protocol_documentation#getdata)
-    GetData {
+    GetData(Vec<InventoryHash>),
-        /// Number of inventory entries.
-        count: u64,
-
-        /// Inventory vectors.
-        inventory: Vec<zebra_chain::types::InventoryVector>,
-    },
 
     /// A `notfound` message.
     ///
     /// [Bitcoin reference](https://en.bitcoin.it/wiki/Protocol_documentation#notfound)
     // See note above on `Inventory`.
-    NotFound {
+    NotFound(Vec<InventoryHash>),
-        /// Number of inventory entries.
-        count: u64,
-
-        /// Inventory vectors.
-        inventory: Vec<zebra_chain::types::InventoryVector>,
-    },
 
     /// A `tx` message.
     ///