Set SO_REUSEPORT on listening sockets

While `tokio`'s `TcpListener::bind` sets `SO_REUSEADDR` by default, it
does *not* set `SO_REUSEPORT`, which means that rebinding exactly the
same addr/port tuple might still fail with OS err 98. Here, we set
`SO_REUSEPORT` on the `TcpSocket`, which however requires us to do the
listener setup manually, which we do in accordance to the `tokio` docs
(see https://docs.rs/exstd/latest/exstd/tokio/net/struct.TcpSocket.html)

Author: tnull

src/lib.rs

@@ -103,6 +103,7 @@ mod types;
 mod wallet;
 
 use std::default::Default;
+use std::net::SocketAddr;
 use std::net::ToSocketAddrs;
 use std::sync::{Arc, Mutex, RwLock};
 use std::time::{Duration, Instant, SystemTime, UNIX_EPOCH};
@@ -154,6 +155,7 @@ use payment::{
 use peer_store::{PeerInfo, PeerStore};
 use rand::Rng;
 use runtime::Runtime;
+use tokio::net::{TcpListener, TcpSocket};
 use types::{
 	Broadcaster, BumpTransactionEventHandler, ChainMonitor, ChannelManager, Graph, KeysManager,
 	OnionMessenger, PaymentStore, PeerManager, Router, Scorer, Sweeper, Wallet,
@@ -344,15 +346,12 @@ impl Node {
 
 			let logger = Arc::clone(&listening_logger);
 			let listeners = self.runtime.block_on(async move {
-				let mut listeners = Vec::new();
+				let mut listeners: Vec<TcpListener> = Vec::new();
 
 				// Try to bind to all addresses
 				for addr in &*bind_addrs {
-					match tokio::net::TcpListener::bind(addr).await {
-						Ok(listener) => {
-							log_trace!(logger, "Listener bound to {}", addr);
-							listeners.push(listener);
-						},
+					match setup_tcp_listener(*addr) {
+						Ok(listener) => listeners.push(listener),
 						Err(e) => {
 							log_error!(
 								logger,
@@ -1835,3 +1834,18 @@ pub(crate) fn total_anchor_channels_reserve_sats(
 			* anchor_channels_config.per_channel_reserve_sats
 	})
 }
+
+fn setup_tcp_listener(addr: SocketAddr) -> Result<TcpListener, tokio::io::Error> {
+	let socket = match addr {
+		SocketAddr::V4(_) => TcpSocket::new_v4()?,
+		SocketAddr::V6(_) => TcpSocket::new_v6()?,
+	};
+	socket.set_reuseaddr(true)?;
+	#[cfg(not(target_os = "windows"))]
+	socket.set_reuseport(true)?;
+	socket.bind(addr)?;
+
+	// The max number of pending connections. 1024 is the tokio default value.
+	const TCP_CONN_BACKLOG: u32 = 1024;
+	socket.listen(TCP_CONN_BACKLOG)
+}