fix tcp incoming failure when kcp proxy is enabled (#601)

easytier/src/gateway/kcp_proxy.rs

@@ -12,7 +12,12 @@ use kcp_sys::{
     packet_def::KcpPacket,
     stream::KcpStream,
 };
-use pnet::packet::{ip::IpNextHeaderProtocols, ipv4::Ipv4Packet};
+use pnet::packet::{
+    ip::IpNextHeaderProtocols,
+    ipv4::Ipv4Packet,
+    tcp::{TcpFlags, TcpPacket},
+    Packet as _,
+};
 use prost::Message;
 use tokio::{io::copy_bidirectional, task::JoinSet};
 
@@ -138,7 +143,6 @@ impl NatDstConnector for NatDstKcpConnector {
     }
 
     fn check_packet_from_peer_fast(&self, _cidr_set: &CidrSet, _global_ctx: &GlobalCtx) -> bool {
-        // if kcp is turned off, the filter will not be added to the pipeline
         true
     }
 
@@ -146,10 +150,11 @@ impl NatDstConnector for NatDstKcpConnector {
         &self,
         _cidr_set: &CidrSet,
         _global_ctx: &GlobalCtx,
-        _hdr: &PeerManagerHeader,
+        hdr: &PeerManagerHeader,
         _ipv4: &Ipv4Packet,
     ) -> bool {
-        true
+        // TODO: how to support net to net kcp proxy?
+        return hdr.from_peer_id == hdr.to_peer_id;
     }
 }
 
@@ -201,6 +206,19 @@ impl NicPacketFilter for TcpProxyForKcpSrc {
             return false;
         }
 
+        // if no connection is established, only allow SYN packet
+        let tcp_packet = TcpPacket::new(ip_packet.payload()).unwrap();
+        let is_syn = tcp_packet.get_flags() & TcpFlags::SYN != 0
+            && tcp_packet.get_flags() & TcpFlags::ACK == 0;
+        if !is_syn
+            && !self.0.is_tcp_proxy_connection(SocketAddr::new(
+                IpAddr::V4(my_ipv4.address()),
+                tcp_packet.get_source(),
+            ))
+        {
+            return false;
+        }
+
         zc_packet.mut_peer_manager_header().unwrap().to_peer_id = self.0.get_my_peer_id().into();
 
         true

easytier/src/gateway/tcp_proxy.rs

@@ -795,4 +795,8 @@ impl<C: NatDstConnector> TcpProxy<C> {
     pub fn get_peer_manager(&self) -> &Arc<PeerManager> {
         &self.peer_manager
     }
+
+    pub fn is_tcp_proxy_connection(&self, src: SocketAddr) -> bool {
+        self.syn_map.contains_key(&src) || self.addr_conn_map.contains_key(&src)
+    }
 }

easytier/src/instance/instance.rs

@@ -382,13 +382,6 @@ impl Instance {
 
         self.run_rpc_server().await?;
 
-        // run after tun device created, so listener can bind to tun device, which may be required by win 10
-        self.ip_proxy = Some(IpProxy::new(
-            self.get_global_ctx(),
-            self.get_peer_manager(),
-        )?);
-        self.run_ip_proxy().await?;
-
         if self.global_ctx.get_flags().enable_kcp_proxy {
             let src_proxy = KcpProxySrc::new(self.get_peer_manager()).await;
             src_proxy.start().await;
@@ -401,6 +394,13 @@ impl Instance {
             self.kcp_proxy_dst = Some(dst_proxy);
         }
 
+        // run after tun device created, so listener can bind to tun device, which may be required by win 10
+        self.ip_proxy = Some(IpProxy::new(
+            self.get_global_ctx(),
+            self.get_peer_manager(),
+        )?);
+        self.run_ip_proxy().await?;
+
         self.udp_hole_puncher.lock().await.run().await?;
 
         self.peer_center.init().await;

easytier/src/tests/three_node.rs

@@ -366,6 +366,7 @@ pub async fn subnet_proxy_three_node_test(
     #[values(true, false)] relay_by_public_server: bool,
     #[values(true, false)] enable_kcp_proxy: bool,
     #[values(true, false)] disable_kcp_input: bool,
+    #[values(true, false)] dst_enable_kcp_proxy: bool,
 ) {
     let insts = init_three_node_ex(
         proto,
@@ -374,6 +375,7 @@ pub async fn subnet_proxy_three_node_test(
                 let mut flags = cfg.get_flags();
                 flags.no_tun = no_tun;
                 flags.disable_kcp_input = disable_kcp_input;
+                flags.enable_kcp_proxy = dst_enable_kcp_proxy;
                 cfg.set_flags(flags);
                 cfg.add_proxy_cidr("10.1.2.0/24".parse().unwrap());
             }