Add ping protocol to ensure connection is alive

Adds the ping behaviour to both ASB and CLI behaviour that periodically pings a connected party to ensure that the underlying network connection is still alive.
This fixes problems with long-running connections that become dead without a connection closure being reported back to the swarm.

CHANGELOG.md

@@ -7,6 +7,12 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Fixed
+
+- An issue where long-running connections are dead without a connection closure being reported back to the swarm.
+  Adding a periodic ping ensures that the connection is kept alive, and a broken connection is reported back resulting in a close event on the swarm.
+  This fixes the error of the ASB being unable to send a transfer proof to the CLI.
+
 ## [0.6.0] - 2021-05-24
 
 ### Added

Cargo.lock

@@ -1767,6 +1767,7 @@ dependencies = [
  "libp2p-dns",
  "libp2p-mplex",
  "libp2p-noise",
+ "libp2p-ping",
  "libp2p-request-response",
  "libp2p-swarm",
  "libp2p-swarm-derive",
@@ -1876,6 +1877,21 @@ dependencies = [
  "zeroize",
 ]
 
+[[package]]
+name = "libp2p-ping"
+version = "0.29.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "bf4bfaffac63bf3c7ec11ed9d8879d455966ddea7e78ee14737f0b6dce0d1cd1"
+dependencies = [
+ "futures",
+ "libp2p-core",
+ "libp2p-swarm",
+ "log 0.4.14",
+ "rand 0.7.3",
+ "void",
+ "wasm-timer",
+]
+
 [[package]]
 name = "libp2p-request-response"
 version = "0.11.0"

swap/Cargo.toml

@@ -29,7 +29,7 @@ ecdsa_fun = { git = "https://github.com/LLFourn/secp256kfun", features = [ "libs
 ed25519-dalek = "1"
 futures = { version = "0.3", default-features = false }
 itertools = "0.10"
-libp2p = { version = "0.38", default-features = false, features = [ "tcp-tokio", "yamux", "mplex", "dns-tokio", "noise", "request-response", "websocket" ] }
+libp2p = { version = "0.38", default-features = false, features = [ "tcp-tokio", "yamux", "mplex", "dns-tokio", "noise", "request-response", "websocket", "ping" ] }
 libp2p-async-await = { git = "https://github.com/comit-network/rust-libp2p-async-await" }
 miniscript = { version = "5", features = [ "serde" ] }
 monero = { version = "0.12", features = [ "serde_support" ] }

swap/src/protocol/alice/behaviour.rs

@@ -4,6 +4,7 @@ use crate::protocol::alice::event_loop::LatestRate;
 use crate::protocol::alice::{execution_setup, spot_price, State3};
 use crate::{env, monero};
 use anyhow::{anyhow, Error};
+use libp2p::ping::{Ping, PingEvent};
 use libp2p::request_response::{RequestId, ResponseChannel};
 use libp2p::{NetworkBehaviour, PeerId};
 use uuid::Uuid;
@@ -75,6 +76,11 @@ where
     pub execution_setup: execution_setup::Behaviour,
     pub transfer_proof: transfer_proof::Behaviour,
     pub encrypted_signature: encrypted_signature::Behaviour,
+
+    /// Ping behaviour that ensures that the underlying network connection is
+    /// still alive. If the ping fails a connection close event will be
+    /// emitted that is picked up as swarm event.
+    ping: Ping,
 }
 
 impl<LR> Behaviour<LR>
@@ -104,6 +110,13 @@ where
             execution_setup: Default::default(),
             transfer_proof: transfer_proof::alice(),
             encrypted_signature: encrypted_signature::alice(),
+            ping: Ping::default(),
         }
     }
 }
+
+impl From<PingEvent> for OutEvent {
+    fn from(_: PingEvent) -> Self {
+        OutEvent::Other
+    }
+}

swap/src/protocol/bob/behaviour.rs

@@ -4,6 +4,7 @@ use crate::protocol::bob;
 use crate::protocol::bob::{execution_setup, State2};
 use anyhow::{anyhow, Error, Result};
 use libp2p::core::Multiaddr;
+use libp2p::ping::{Ping, PingEvent};
 use libp2p::request_response::{RequestId, ResponseChannel};
 use libp2p::{NetworkBehaviour, PeerId};
 use std::time::Duration;
@@ -66,6 +67,11 @@ pub struct Behaviour {
     pub transfer_proof: transfer_proof::Behaviour,
     pub encrypted_signature: encrypted_signature::Behaviour,
     pub redial: redial::Behaviour,
+
+    /// Ping behaviour that ensures that the underlying network connection is
+    /// still alive. If the ping fails a connection close event will be
+    /// emitted that is picked up as swarm event.
+    ping: Ping,
 }
 
 impl Behaviour {
@@ -77,6 +83,7 @@ impl Behaviour {
             transfer_proof: transfer_proof::bob(),
             encrypted_signature: encrypted_signature::bob(),
             redial: redial::Behaviour::new(alice, Duration::from_secs(2)),
+            ping: Ping::default(),
         }
     }
 
@@ -88,3 +95,9 @@ impl Behaviour {
         self.encrypted_signature.add_address(&peer_id, address);
     }
 }
+
+impl From<PingEvent> for OutEvent {
+    fn from(_: PingEvent) -> Self {
+        OutEvent::Other
+    }
+}