feat(udp): set SO_MARK for udp cnx

src/dns.rs

@@ -1,4 +1,4 @@
-use crate::{tcp};
+use crate::tcp;
 use anyhow::{anyhow, Context};
 use futures_util::{FutureExt, TryFutureExt};
 use hickory_resolver::config::{LookupIpStrategy, NameServerConfig, Protocol, ResolverConfig, ResolverOpts};

src/main.rs

@@ -991,8 +991,14 @@ async fn main() {
                                 port,
                             };
                             let connect_to_dest = |_| async {
-                                udp::connect(&tunnel.remote.0, tunnel.remote.1, cfg.timeout_connect, &cfg.dns_resolver)
+                                udp::connect(
-                                    .await
+                                    &tunnel.remote.0,
+                                    tunnel.remote.1,
+                                    cfg.timeout_connect,
+                                    cfg.socket_so_mark,
+                                    &cfg.dns_resolver,
+                                )
+                                .await
                             };
 
                             if let Err(err) =
@@ -1033,7 +1039,7 @@ async fn main() {
                                                 .map(|s| Box::new(s) as Box<dyn T>)
                                         }
                                         LocalProtocol::Udp { .. } => {
-                                            udp::connect(&remote.host, remote.port, timeout, dns_resolver)
+                                            udp::connect(&remote.host, remote.port, timeout, so_mark, dns_resolver)
                                                 .await
                                                 .map(|s| Box::new(s) as Box<dyn T>)
                                         }

src/tunnel/server.rs

@@ -60,6 +60,7 @@ async fn run_tunnel(
                 &remote.host,
                 remote.port,
                 timeout.unwrap_or(Duration::from_secs(10)),
+                server_config.socket_so_mark,
                 &server_config.dns_resolver,
             )
             .await?;

src/udp.rs

@@ -11,6 +11,7 @@ use std::net::{Ipv4Addr, Ipv6Addr, SocketAddr, SocketAddrV4, SocketAddrV6};
 use tokio::task::JoinSet;
 
 use log::warn;
+use socket2::SockRef;
 use std::pin::{pin, Pin};
 use std::sync::{Arc, Weak};
 use std::task::{ready, Poll};
@@ -323,6 +324,7 @@ pub async fn connect(
     host: &Host<String>,
     port: u16,
     connect_timeout: Duration,
+    so_mark: Option<u32>,
     dns_resolver: &DnsResolver,
 ) -> anyhow::Result<MyUdpSocket> {
     info!("Opening UDP connection to {}:{}", host, port);
@@ -354,6 +356,13 @@ pub async fn connect(
             }
         };
 
+        #[cfg(target_os = "linux")]
+        if let Some(so_mark) = so_mark {
+            SockRef::from(&socket)
+                .set_mark(so_mark)
+                .with_context(|| format!("cannot set SO_MARK on socket: {:?}", io::Error::last_os_error()))?;
+        }
+
         // Spawn the connection attempt in the join set.
         // We include a delay of ix * 250 milliseconds, as per RFC8305.
         // See https://datatracker.ietf.org/doc/html/rfc8305#section-5