Add P2P beacon mode (#47)

P2P beacon mode allows for lightweight node instance to run, with only
purpose to coordinate other nodes' peer discovery. This is effectively
a special node in the network that bridges others.

crates/node/src/cli.rs

@@ -48,7 +48,7 @@ pub struct Config {
         long,
         long_help = "",
         env = "GEVULOT_P2P_DISCOVERY_ADDR",
-        default_value = "bootstrap.p2p.devnet.gevulot.com"
+        default_value = "34.88.251.176:9999"
     )]
     pub p2p_discovery_addrs: Vec<String>,
 
@@ -136,6 +136,25 @@ pub enum PeerCommand {
     },
 }
 
+#[derive(Debug, Args)]
+pub struct P2PBeaconConfig {
+    #[arg(
+        long,
+        long_help = "P2P listen address",
+        env = "GEVULOT_P2P_LISTEN_ADDR",
+        default_value = "127.0.0.1:9999"
+    )]
+    pub p2p_listen_addr: SocketAddr,
+
+    #[arg(
+        long,
+        long_help = "P2P PSK passphrase",
+        env = "GEVULOT_PSK_PASSPHRASE",
+        default_value = "Pack my box with five dozen liquor jugs."
+    )]
+    pub p2p_psk_passphrase: String,
+}
+
 #[derive(Debug, Subcommand)]
 pub enum GenerateCommand {
     NodeKey {
@@ -184,6 +203,12 @@ pub enum Command {
         op: PeerCommand,
     },
 
+    /// P2PBeacon is a run mode where only P2P code is executed. Used for coordinating other nodes in the network.
+    P2PBeacon {
+        #[command(flatten)]
+        config: P2PBeaconConfig,
+    },
+
     /// Run the node.
     Run {
         #[command(flatten)]

crates/node/src/main.rs

@@ -13,7 +13,10 @@ use std::{
 use asset_manager::AssetManager;
 use async_trait::async_trait;
 use clap::Parser;
-use cli::{Cli, Command, Config, GenerateCommand, NodeKeyOptions, PeerCommand, ShowCommand};
+use cli::{
+    Cli, Command, Config, GenerateCommand, NodeKeyOptions, P2PBeaconConfig, PeerCommand,
+    ShowCommand,
+};
 use eyre::Result;
 use gevulot_node::types;
 use libsecp256k1::{PublicKey, SecretKey};
@@ -87,6 +90,7 @@ async fn main() -> Result<()> {
                 db.acl_deny(&key).await
             }
         },
+        Command::P2PBeacon { config } => p2p_beacon(config).await,
         Command::Run { config } => run(Arc::new(config)).await,
         Command::Show { op } => match op {
             ShowCommand::PublicKey { key_file } => {
@@ -297,6 +301,28 @@ async fn run(config: Arc<Config>) -> Result<()> {
     }
 }
 
+/// p2p_beacon brings up P2P networking but nothing else. This function can be
+/// used for independent P2P network beacon that provides connectivity for
+/// others, while it doesn't participate in the Gevulot's operational side
+/// in any other way - i.e. this won't handle transactions in any way.
+async fn p2p_beacon(config: P2PBeaconConfig) -> Result<()> {
+    let p2p = Arc::new(
+        networking::P2P::new(
+            "gevulot-network",
+            config.p2p_listen_addr,
+            &config.p2p_psk_passphrase,
+        )
+        .await,
+    );
+
+    let p2p_addr = p2p.node().start_listening().await?;
+    tracing::info!("listening for p2p at {}", p2p_addr);
+
+    loop {
+        sleep(Duration::from_secs(1));
+    }
+}
+
 fn read_node_key(node_key_file: &PathBuf) -> Result<SecretKey> {
     let bs = match std::fs::read(node_key_file) {
         Ok(key_data) => key_data,