node: Start implementing gossip subscriptions

Signed-off-by: Alexis Sellier <alexis@radicle.xyz>

node/src/protocol/filter.rs

@@ -0,0 +1,58 @@
+use std::io;
+use std::ops::{Deref, DerefMut};
+
+use bloomy::BloomFilter;
+
+use crate::identity::Id;
+use crate::protocol::wire;
+
+/// Size in bytes of subscription bloom filter.
+pub const FILTER_SIZE: usize = 1024 * 16;
+/// Number of hashes used for bloom filter.
+pub const FILTER_HASHES: usize = 2;
+
+/// Subscription filter.
+/// Nb. This filter doesn't currently support inserting public keys.
+#[derive(Clone, PartialEq, Eq)]
+pub struct Filter(BloomFilter<Id>);
+
+impl Deref for Filter {
+    type Target = BloomFilter<Id>;
+
+    fn deref(&self) -> &Self::Target {
+        &self.0
+    }
+}
+
+impl DerefMut for Filter {
+    fn deref_mut(&mut self) -> &mut Self::Target {
+        &mut self.0
+    }
+}
+
+impl Default for Filter {
+    fn default() -> Self {
+        Self(BloomFilter::with_size(FILTER_SIZE))
+    }
+}
+
+impl wire::Encode for Filter {
+    fn encode<W: io::Write + ?Sized>(&self, writer: &mut W) -> Result<usize, io::Error> {
+        let mut n = 0;
+
+        n += self.0.as_bytes().encode(writer)?;
+
+        Ok(n)
+    }
+}
+
+impl wire::Decode for Filter {
+    fn decode<R: std::io::Read + ?Sized>(reader: &mut R) -> Result<Self, wire::Error> {
+        let bytes: [u8; FILTER_SIZE] = wire::Decode::decode(reader)?;
+        let bf = BloomFilter::from(Vec::from(bytes));
+
+        debug_assert_eq!(bf.hashes(), FILTER_HASHES);
+
+        Ok(Self(bf))
+    }
+}

node/src/protocol/message.rs

@@ -5,6 +5,7 @@ use byteorder::{NetworkEndian, ReadBytesExt};
 use crate::crypto;
 use crate::git;
 use crate::identity::Id;
+use crate::protocol::filter::Filter;
 use crate::protocol::wire;
 use crate::protocol::{NodeId, Timestamp, PROTOCOL_VERSION};
 use crate::storage::refs::Refs;
@@ -33,6 +34,7 @@ pub enum MessageType {
     NodeAnnouncement = 2,
     InventoryAnnouncement = 4,
     RefsAnnouncement = 6,
+    Subscribe = 8,
 }
 
 impl From<MessageType> for u16 {
@@ -50,6 +52,7 @@ impl TryFrom<u16> for MessageType {
             2 => Ok(MessageType::NodeAnnouncement),
             4 => Ok(MessageType::InventoryAnnouncement),
             6 => Ok(MessageType::RefsAnnouncement),
+            8 => Ok(MessageType::Subscribe),
             _ => Err(other),
         }
     }
@@ -334,6 +337,10 @@ pub enum Message {
         git: git::Url,
     },
 
+    /// Subscribe to gossip messages matching the filter, that are newer than the given
+    /// timestamp.
+    Subscribe { filter: Filter, since: Timestamp },
+
     /// Node announcing its inventory to the network.
     /// This should be the whole inventory every time.
     InventoryAnnouncement {
@@ -404,6 +411,7 @@ impl Message {
     pub fn type_id(&self) -> u16 {
         match self {
             Self::Hello { .. } => MessageType::Hello,
+            Self::Subscribe { .. } => MessageType::Subscribe,
             Self::NodeAnnouncement { .. } => MessageType::NodeAnnouncement,
             Self::InventoryAnnouncement { .. } => MessageType::InventoryAnnouncement,
             Self::RefsAnnouncement { .. } => MessageType::RefsAnnouncement,
@@ -416,6 +424,7 @@ impl fmt::Debug for Message {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         match self {
             Self::Hello { id, .. } => write!(f, "Hello({})", id),
+            Self::Subscribe { since, .. } => write!(f, "Subscribe({})", since),
             Self::NodeAnnouncement { node, .. } => write!(f, "NodeAnnouncement({})", node),
             Self::InventoryAnnouncement { node, message, .. } => {
                 write!(
@@ -460,6 +469,10 @@ impl wire::Encode for Message {
                 n += addrs.as_slice().encode(writer)?;
                 n += git.encode(writer)?;
             }
+            Self::Subscribe { filter, since } => {
+                n += filter.encode(writer)?;
+                n += since.encode(writer)?;
+            }
             Self::RefsAnnouncement {
                 node,
                 message,
@@ -512,6 +525,12 @@ impl wire::Decode for Message {
                     git,
                 })
             }
+            Ok(MessageType::Subscribe) => {
+                let filter = Filter::decode(reader)?;
+                let since = Timestamp::decode(reader)?;
+
+                Ok(Self::Subscribe { filter, since })
+            }
             Ok(MessageType::NodeAnnouncement) => {
                 let node = NodeId::decode(reader)?;
                 let message = NodeAnnouncement::decode(reader)?;

node/src/protocol/peer.rs

@@ -230,6 +230,9 @@ impl Peer {
                 }
                 log::warn!("Node announcement handling is not implemented");
             }
+            (PeerState::Negotiated { .. }, Message::Subscribe { .. }) => {
+                log::warn!("Subscribe message handling is not implemented");
+            }
             (PeerState::Negotiated { .. }, Message::Hello { .. }) => {
                 debug!(
                     "Disconnecting peer {} for sending us a redundant handshake message",