support socks5 proxy

usage: --socks5 12345

create an socks5 server on port 12345, can be used by socks5 client to access
virtual network.

easytier/src/easytier-core.rs

@@ -4,8 +4,6 @@
 mod tests;
 
 use std::{
-    backtrace,
-    io::Write as _,
     net::{Ipv4Addr, SocketAddr},
     path::PathBuf,
 };
@@ -274,6 +272,13 @@ struct Cli {
         default_value = "false"
     )]
     relay_all_peer_rpc: bool,
+
+    #[cfg(feature = "socks5")]
+    #[arg(
+        long,
+        help = t!("core_clap.socks5").to_string()
+    )]
+    socks5: Option<u16>,
 }
 
 rust_i18n::i18n!("locales");
@@ -492,6 +497,15 @@ impl From<Cli> for TomlConfigLoader {
             ));
         }
 
+        #[cfg(feature = "socks5")]
+        if let Some(socks5_proxy) = cli.socks5 {
+            cfg.set_socks5_portal(Some(
+                format!("socks5://0.0.0.0:{}", socks5_proxy)
+                    .parse()
+                    .unwrap(),
+            ));
+        }
+
         let mut f = cfg.get_flags();
         if cli.default_protocol.is_some() {
             f.default_protocol = cli.default_protocol.as_ref().unwrap().clone();