Allow changing the Kademlia protocol name (#1118)

* Allow changing the Kademlia protocol name

* Expose the method to the behaviour

* Address review

protocols/kad/src/behaviour.rs

@@ -30,7 +30,7 @@ use libp2p_core::swarm::{ConnectedPoint, NetworkBehaviour, NetworkBehaviourActio
 use libp2p_core::{protocols_handler::ProtocolsHandler, Multiaddr, PeerId};
 use multihash::Multihash;
 use smallvec::SmallVec;
-use std::{error, marker::PhantomData, num::NonZeroUsize, time::Duration};
+use std::{borrow::Cow, error, marker::PhantomData, num::NonZeroUsize, time::Duration};
 use tokio_io::{AsyncRead, AsyncWrite};
 use wasm_timer::{Instant, Interval};
 
@@ -41,6 +41,9 @@ pub struct Kademlia<TSubstream> {
     /// Storage for the nodes. Contains the known multiaddresses for this node.
     kbuckets: KBucketsTable<KadHash, Addresses>,
 
+    /// If `Some`, we overwrite the Kademlia protocol name with this one.
+    protocol_name_override: Option<Cow<'static, [u8]>>,
+
     /// All the iterative queries we are currently performing, with their ID. The last parameter
     /// is the list of accumulated providers for `GET_PROVIDERS` queries.
     active_queries: FnvHashMap<QueryId, QueryState<QueryInfo, PeerId>>,
@@ -189,6 +192,16 @@ impl<TSubstream> Kademlia<TSubstream> {
         Self::new_inner(local_peer_id)
     }
 
+    /// The same as `new`, but using a custom protocol name.
+    ///
+    /// 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 with_protocol_name(local_peer_id: PeerId, name: impl Into<Cow<'static, [u8]>>) -> Self {
+        let mut me = Kademlia::new_inner(local_peer_id);
+        me.protocol_name_override = Some(name.into());
+        me
+    }
+
     /// Creates a `Kademlia`.
     ///
     /// Contrary to `new`, doesn't perform the initialization queries that store our local ID into
@@ -251,6 +264,7 @@ impl<TSubstream> Kademlia<TSubstream> {
 
         Kademlia {
             kbuckets: KBucketsTable::new(local_peer_id.into(), Duration::from_secs(60)),   // TODO: constant
+            protocol_name_override: None,
             queued_events: SmallVec::new(),
             active_queries: Default::default(),
             connected_peers: Default::default(),
@@ -386,7 +400,11 @@ where
     type OutEvent = KademliaOut;
 
     fn new_handler(&mut self) -> Self::ProtocolsHandler {
-        KademliaHandler::dial_and_listen()
+        let mut handler = KademliaHandler::dial_and_listen();
+        if let Some(name) = self.protocol_name_override.as_ref() {
+            handler = handler.with_protocol_name(name.clone());
+        }
+        handler
     }
 
     fn addresses_of_peer(&mut self, peer_id: &PeerId) -> Vec<Multiaddr> {

protocols/kad/src/handler.rs

@@ -32,7 +32,7 @@ use libp2p_core::protocols_handler::{
 };
 use libp2p_core::{upgrade, either::EitherOutput, InboundUpgrade, OutboundUpgrade, PeerId, upgrade::Negotiated};
 use multihash::Multihash;
-use std::{error, fmt, io, time::Duration};
+use std::{borrow::Cow, error, fmt, io, time::Duration};
 use tokio_io::{AsyncRead, AsyncWrite};
 use wasm_timer::Instant;
 
@@ -303,7 +303,6 @@ where
 {
     /// Create a `KademliaHandler` that only allows sending messages to the remote but denying
     /// incoming connections.
-    #[inline]
     pub fn dial_only() -> Self {
         KademliaHandler::with_allow_listening(false)
     }
@@ -312,7 +311,6 @@ where
     /// requests.
     ///
     /// The `Default` trait implementation wraps around this function.
-    #[inline]
     pub fn dial_and_listen() -> Self {
         KademliaHandler::with_allow_listening(true)
     }
@@ -326,6 +324,13 @@ where
             keep_alive: KeepAlive::Yes,
         }
     }
+
+    /// 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 {
+        self.config = self.config.with_protocol_name(name);
+        self
+    }
 }
 
 impl<TSubstream, TUserData> Default for KademliaHandler<TSubstream, TUserData>
@@ -355,7 +360,7 @@ where
     #[inline]
     fn listen_protocol(&self) -> SubstreamProtocol<Self::InboundProtocol> {
         if self.allow_listening {
-            SubstreamProtocol::new(self.config).map_upgrade(upgrade::EitherUpgrade::A)
+            SubstreamProtocol::new(self.config.clone()).map_upgrade(upgrade::EitherUpgrade::A)
         } else {
             SubstreamProtocol::new(upgrade::EitherUpgrade::B(upgrade::DeniedUpgrade))
         }
@@ -493,7 +498,7 @@ where
             let mut substream = self.substreams.swap_remove(n);
 
             loop {
-                match advance_substream(substream, self.config) {
+                match advance_substream(substream, self.config.clone()) {
                     (Some(new_state), Some(event), _) => {
                         self.substreams.push(new_state);
                         return Ok(Async::Ready(event));

protocols/kad/src/protocol.rs

@@ -34,7 +34,7 @@ use libp2p_core::{Multiaddr, PeerId};
 use libp2p_core::upgrade::{InboundUpgrade, OutboundUpgrade, UpgradeInfo, Negotiated};
 use multihash::Multihash;
 use protobuf::{self, Message};
-use std::convert::TryFrom;
+use std::{borrow::Cow, convert::TryFrom};
 use std::{io, iter};
 use tokio_codec::Framed;
 use tokio_io::{AsyncRead, AsyncWrite};
@@ -138,16 +138,34 @@ impl Into<proto::Message_Peer> for KadPeer {
 // TODO: if, as suspected, we can confirm with Protocol Labs that each open Kademlia substream does
 //       only one request, then we can change the output of the `InboundUpgrade` and
 //       `OutboundUpgrade` to be just a single message
-#[derive(Debug, Default, Copy, Clone)]
+#[derive(Debug, Clone)]
-pub struct KademliaProtocolConfig;
+pub struct KademliaProtocolConfig {
+    protocol_name: Cow<'static, [u8]>,
+}
+
+impl KademliaProtocolConfig {
+    /// 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 {
+        self.protocol_name = name.into();
+        self
+    }
+}
+
+impl Default for KademliaProtocolConfig {
+    fn default() -> Self {
+        KademliaProtocolConfig {
+            protocol_name: Cow::Borrowed(b"/ipfs/kad/1.0.0"),
+        }
+    }
+}
 
 impl UpgradeInfo for KademliaProtocolConfig {
-    type Info = &'static [u8];
+    type Info = Cow<'static, [u8]>;
     type InfoIter = iter::Once<Self::Info>;
 
-    #[inline]
     fn protocol_info(&self) -> Self::InfoIter {
-        iter::once(b"/ipfs/kad/1.0.0")
+        iter::once(self.protocol_name.clone())
     }
 }