Allow customizing the Kademlia maximum packet size (#1502)

* Allow customizing the Kademlia maximum packet size

* Address concern

protocols/kad/src/behaviour.rs

@@ -52,8 +52,8 @@ pub struct Kademlia<TStore> {
     /// The Kademlia routing table.
     kbuckets: KBucketsTable<kbucket::Key<PeerId>, Addresses>,
 
-    /// An optional protocol name override to segregate DHTs in the network.
+    /// Configuration of the wire protocol.
-    protocol_name_override: Option<Cow<'static, [u8]>>,
+    protocol_config: KademliaProtocolConfig,
 
     /// The currently active (i.e. in-progress) queries.
     queries: QueryPool<QueryInner>,
@@ -94,7 +94,7 @@ pub struct Kademlia<TStore> {
 pub struct KademliaConfig {
     kbucket_pending_timeout: Duration,
     query_config: QueryConfig,
-    protocol_name_override: Option<Cow<'static, [u8]>>,
+    protocol_config: KademliaProtocolConfig,
     record_ttl: Option<Duration>,
     record_replication_interval: Option<Duration>,
     record_publication_interval: Option<Duration>,
@@ -108,7 +108,7 @@ impl Default for KademliaConfig {
         KademliaConfig {
             kbucket_pending_timeout: Duration::from_secs(60),
             query_config: QueryConfig::default(),
-            protocol_name_override: None,
+            protocol_config: Default::default(),
             record_ttl: Some(Duration::from_secs(36 * 60 * 60)),
             record_replication_interval: Some(Duration::from_secs(60 * 60)),
             record_publication_interval: Some(Duration::from_secs(24 * 60 * 60)),
@@ -125,7 +125,7 @@ impl KademliaConfig {
     /// Kademlia nodes only communicate with other nodes using the same protocol name. Using a
     /// custom name therefore allows to segregate the DHT from others, if that is desired.
     pub fn set_protocol_name(&mut self, name: impl Into<Cow<'static, [u8]>>) -> &mut Self {
-        self.protocol_name_override = Some(name.into());
+        self.protocol_config.set_protocol_name(name);
         self
     }
 
@@ -228,6 +228,14 @@ impl KademliaConfig {
         self.connection_idle_timeout = duration;
         self
     }
+
+    /// Modifies the maximum allowed size of individual Kademlia packets.
+    ///
+    /// It might be necessary to increase this value if trying to put large records.
+    pub fn set_max_packet_size(&mut self, size: usize) -> &mut Self {
+        self.protocol_config.set_max_packet_size(size);
+        self
+    }
 }
 
 impl<TStore> Kademlia<TStore>
@@ -241,9 +249,7 @@ where
 
     /// Get the protocol name of this kademlia instance.
     pub fn protocol_name(&self) -> &[u8] {
-        self.protocol_name_override
+        self.protocol_config.protocol_name()
-            .as_ref()
-            .map_or(crate::protocol::DEFAULT_PROTO_NAME.as_ref(), AsRef::as_ref)
     }
 
     /// Creates a new `Kademlia` network behaviour with the given configuration.
@@ -267,7 +273,7 @@ where
         Kademlia {
             store,
             kbuckets: KBucketsTable::new(local_key, config.kbucket_pending_timeout),
-            protocol_name_override: config.protocol_name_override,
+            protocol_config: config.protocol_config,
             queued_events: VecDeque::with_capacity(config.query_config.replication_factor.get()),
             queries: QueryPool::new(config.query_config),
             connected_peers: Default::default(),
@@ -1064,13 +1070,8 @@ where
     type OutEvent = KademliaEvent;
 
     fn new_handler(&mut self) -> Self::ProtocolsHandler {
-        let mut protocol_config = KademliaProtocolConfig::default();
-        if let Some(name) = self.protocol_name_override.as_ref() {
-            protocol_config = protocol_config.with_protocol_name(name.clone());
-        }
-
         KademliaHandler::new(KademliaHandlerConfig {
-            protocol_config,
+            protocol_config: self.protocol_config.clone(),
             allow_listening: true,
             idle_timeout: self.connection_idle_timeout,
         })

protocols/kad/src/protocol.rs

@@ -141,21 +141,33 @@ impl Into<proto::message::Peer> for KadPeer {
 #[derive(Debug, Clone)]
 pub struct KademliaProtocolConfig {
     protocol_name: Cow<'static, [u8]>,
+    /// Maximum allowed size of a packet.
+    max_packet_size: usize,
 }
 
 impl KademliaProtocolConfig {
+    /// Returns the configured protocol name.
+    pub fn protocol_name(&self) -> &[u8] {
+        &self.protocol_name
+    }
+
     /// Modifies the protocol name used on the wire. Can be used to create incompatibilities
     /// between networks on purpose.
-    pub fn with_protocol_name(mut self, name: impl Into<Cow<'static, [u8]>>) -> Self {
+    pub fn set_protocol_name(&mut self, name: impl Into<Cow<'static, [u8]>>) {
         self.protocol_name = name.into();
-        self
+    }
+
+    /// Modifies the maximum allowed size of a single Kademlia packet.
+    pub fn set_max_packet_size(&mut self, size: usize) {
+        self.max_packet_size = size;
     }
 }
 
 impl Default for KademliaProtocolConfig {
     fn default() -> Self {
         KademliaProtocolConfig {
-            protocol_name: Cow::Borrowed(DEFAULT_PROTO_NAME)
+            protocol_name: Cow::Borrowed(DEFAULT_PROTO_NAME),
+            max_packet_size: 4096,
         }
     }
 }
@@ -179,7 +191,7 @@ where
 
     fn upgrade_inbound(self, incoming: C, _: Self::Info) -> Self::Future {
         let mut codec = UviBytes::default();
-        codec.set_max_len(4096);
+        codec.set_max_len(self.max_packet_size);
 
         future::ok(
             Framed::new(incoming, codec)
@@ -211,7 +223,7 @@ where
 
     fn upgrade_outbound(self, incoming: C, _: Self::Info) -> Self::Future {
         let mut codec = UviBytes::default();
-        codec.set_max_len(4096);
+        codec.set_max_len(self.max_packet_size);
 
         future::ok(
             Framed::new(incoming, codec)