rkvm-{server,client}: Remove dead peers quickly

I use rkvm on a machine which hangs multiple times a day, leaving no
TCP FIN or RSTs behind.

Previously, the UX got very confusing once I rebooted the machine, because
it captured inputs without forwarding them anywhere live.

It's unfortunate that the TCP settings aren't shared between the client
& server because keepalive settings should be consistent to avoid one
peer disconnecting and the other waiting longer before timing out.

Cargo.lock

@@ -778,6 +778,7 @@ dependencies = [
  "rkvm-net",
  "rustls-pemfile",
  "serde",
+ "socket2 0.5.3",
  "thiserror",
  "tokio",
  "tokio-rustls",
@@ -829,6 +830,7 @@ dependencies = [
  "rustls-pemfile",
  "serde",
  "slab",
+ "socket2 0.5.3",
  "thiserror",
  "tokio",
  "tokio-rustls",
@@ -970,6 +972,16 @@ dependencies = [
  "winapi",
 ]
 
+[[package]]
+name = "socket2"
+version = "0.5.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2538b18701741680e0322a2302176d3253a35388e2e62f172f64f4f16605f877"
+dependencies = [
+ "libc",
+ "windows-sys 0.48.0",
+]
+
 [[package]]
 name = "spin"
 version = "0.5.2"
@@ -1054,7 +1066,7 @@ dependencies = [
  "num_cpus",
  "pin-project-lite",
  "signal-hook-registry",
- "socket2",
+ "socket2 0.4.9",
  "tokio-macros",
  "windows-sys 0.48.0",
 ]

rkvm-client/Cargo.toml

@@ -19,6 +19,7 @@ clap = { version = "4.2.2", features = ["derive"] }
 thiserror = "1.0.40"
 tokio-rustls = "0.24.0"
 rustls-pemfile = "1.0.2"
+socket2 = { version = "0.5.3", features = ["all"] }
 
 [package.metadata.rpm]
 package = "rkvm-client"

rkvm-client/src/client.rs

@@ -3,9 +3,11 @@ use rkvm_net::auth::{AuthChallenge, AuthStatus};
 use rkvm_net::message::Message;
 use rkvm_net::version::Version;
 use rkvm_net::Update;
+use socket2::{SockRef, TcpKeepalive};
 use std::collections::hash_map::Entry;
 use std::collections::HashMap;
 use std::io;
+use std::time::Duration;
 use thiserror::Error;
 use tokio::io::{AsyncWriteExt, BufStream};
 use tokio::net::TcpStream;
@@ -43,6 +45,15 @@ pub async fn run(
     stream.set_linger(None).map_err(Error::Network)?;
     stream.set_nodelay(false).map_err(Error::Network)?;
 
+    SockRef::from(&stream)
+        .set_tcp_keepalive(
+            &TcpKeepalive::new()
+                .with_time(Duration::from_secs(1))
+                .with_interval(Duration::from_secs(10))
+                .with_retries(1),
+        )
+        .map_err(Error::Network)?;
+
     log::info!("Connected to server");
 
     let stream = connector

rkvm-server/Cargo.toml

@@ -21,6 +21,7 @@ rustls-pemfile = "1.0.2"
 thiserror = "1.0.40"
 slab = "0.4.8"
 rand = "0.8.5"
+socket2 = { version = "0.5.3", features = ["all"] }
 
 [package.metadata.rpm]
 package = "rkvm-server"

rkvm-server/src/server.rs

@@ -8,6 +8,7 @@ use rkvm_net::message::Message;
 use rkvm_net::version::Version;
 use rkvm_net::Update;
 use slab::Slab;
+use socket2::{SockRef, TcpKeepalive};
 use std::collections::{HashMap, HashSet, VecDeque};
 use std::ffi::CString;
 use std::io::{self, ErrorKind};
@@ -267,6 +268,13 @@ async fn client(
         stream.set_linger(None)?;
         stream.set_nodelay(false)?;
 
+        SockRef::from(&stream).set_tcp_keepalive(
+            &TcpKeepalive::new()
+                .with_time(Duration::from_secs(1))
+                .with_interval(Duration::from_secs(10))
+                .with_retries(1),
+        )?;
+
         let stream = acceptor.accept(stream).await?;
         log::info!("{}: TLS connected", addr);