TCP support for Machnet, when non-machnet application connect a machnet application. #54

sarsanaee · 2026-02-08T23:27:44Z

This is not ready for merge, but it is a version where TCP is working here, addresses issue #53

TCP transport is important in any networking stack. Therefore, this is the first try to add this transport to Machnet. Signed-off-by: Alireza Sanaee <sarsanaee@gmail.com>

Signed-off-by: Alireza Sanaee <sarsanaee@gmail.com>

Copilot

Pull request overview

Adds an experimental TCP transport path to Machnet so non-Machnet applications (Linux TCP stack) can connect to Machnet applications, addressing issue #53 by introducing a TCP flow implementation and exposing protocol selection through the public API and bindings.

Changes:

Introduce TCP wire header + TcpFlow (handshake, framing/deframing, basic timers) and integrate TCP dispatch/listeners into MachnetEngine.
Extend the public C API (machnet_connect, machnet_listen) with a protocol selector and propagate it through examples and language bindings.
Add a standalone tcp_msg_gen app to interop with Machnet TCP framing.

Reviewed changes

Copilot reviewed 30 out of 30 changed files in this pull request and generated 12 comments.

Show a summary per file

File	Description
src/include/tcp_flow.h	New TCP flow implementation (state machine + framing over TCP).
src/include/tcp.h	New packed TCP header definition for parsing/construction.
src/include/packet.h	Add TCPv4 checksum offload helper.
src/include/machnet_engine.h	Add TCP listeners/flows, TCP control ops, and TCP RX/TX routing.
src/include/channel.h	Track active TCP flows per channel; add create/remove helpers.
src/ext/machnet_common.h	Add protocol constants and new TCP control-plane opcodes; fix STATUS macro semicolon.
src/ext/machnet.h	Extend public API: protocol parameter for connect/listen.
src/ext/machnet.c	Implement protocol-aware connect/listen opcodes in user library.
src/core/net/tcp.cc	Implement `Tcp::ToString()`.
src/core/drivers/shm/channel.cc	Implement `Channel::RemoveTcpFlow()`.
src/apps/tcp_msg_gen/main.cc	New Linux TCP tool speaking Machnet TCP framing.
src/apps/tcp_msg_gen/CMakeLists.txt	Build configuration for `tcp_msg_gen`.
src/apps/rocksdb_server/rocksdb_server.cc	Update call to new `machnet_listen(..., protocol)` signature.
src/apps/msg_gen/main.cc	Add `--protocol={udp,tcp}` flag and wire it into connect/listen.
src/apps/CMakeLists.txt	Add `tcp_msg_gen` subdirectory.
examples/sync.sh	Add rsync helper script for syncing a workspace to a remote machine.
examples/rust/src/main.rs	Update Rust example calls to include protocol argument.
examples/hello_world.cc	Update example calls to include protocol argument.
bindings/rust/src/lib.rs	Update Rust wrapper to pass protocol and adjust doc reference.
bindings/rust/src/bindings.rs	Update Rust FFI signatures for protocol argument.
bindings/rust/resources/machnet.h	Update bundled header used by Rust bindings with protocol parameter.
bindings/js/rocksdb_client.js	Update JS client to pass protocol argument.
bindings/js/machnet_shim.js	Update JS FFI signatures to include protocol argument.
bindings/js/latency.js	Update JS example to pass protocol argument.
bindings/js/hello_world.js	Update JS example to pass protocol argument.
bindings/go/msg_gen/main.go	Update Go example to pass protocol argument.
bindings/go/machnet/machnet.go	Update Go wrapper signatures to include protocol argument.
bindings/go/machnet/conversion.h	Update Go C shim signatures to include protocol argument.
bindings/csharp/HelloWorld/machnet_shim.cs	Update C# P/Invoke signatures to include protocol argument.
bindings/csharp/HelloWorld/Program.cs	Update C# example calls to pass protocol argument.

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Copilot · 2026-02-08T23:36:43Z

src/include/tcp_flow.h

+    tcph->set_header_length(sizeof(Tcp));  // 20 bytes, no options.
+    tcph->flags = flags;
+    tcph->window = be16_t(rcv_wnd_);
+    tcph->checksum = 0;
+    tcph->urgent_ptr = be16_t(0);


The receive window advertised in outgoing TCP headers is always rcv_wnd_ (initialized to 65535) and is never reduced when the channel runs out of MsgBufs. If MsgBufAlloc fails, data is dropped but we continue to advertise a large window, breaking TCP flow control and risking stream desynchronization. Consider tying rcv_wnd_ to actual available channel/buffer capacity and advertising a zero/smaller window under pressure.

Copilot · 2026-02-08T23:36:43Z

bindings/rust/src/lib.rs

+pub fn machnet_listen(channel: &mut MachnetChannel, local_ip: &str, local_port: u16, protocol: i32) -> i32 {
    unsafe {
        let channel_ptr = channel.get_ptr();
        let local_ip_cstr = CString::new(local_ip).unwrap();
-        bindings::machnet_listen(channel_ptr, local_ip_cstr.as_ptr(), local_port)
+        bindings::machnet_listen(channel_ptr, local_ip_cstr.as_ptr(), local_port, protocol)


The machnet_listen() signature was updated to include a protocol argument, but the Rustdoc examples above this function (and any other docs referencing machnet_listen) still show the old 3-arg call. Update the examples to include the protocol parameter so doctests/docs don’t mislead users.

Copilot · 2026-02-08T23:36:43Z

src/include/tcp_flow.h

+  void InitiateHandshake() {
+    CHECK(state_ == State::kClosed);
+    SendSyn();
+    state_ = State::kSynSent;
+    rto_active_ = true;
+    rto_remaining_ = rto_ticks_;
+  }


TcpFlow introduces a new TCP state machine, framing, and retransmission/timer behavior, but there are no accompanying unit/integration tests in this PR (contrast with existing flow/channel tests). Adding tests for handshake (active+passive open), framing/deframing across segment boundaries, and FIN/RST handling would help prevent regressions as this evolves.

Copilot · 2026-02-08T23:36:44Z

bindings/go/machnet/conversion.h

 int __machnet_connect_go(MachnetChannelCtx_t* ctx, uint32_t local_ip,
                         uint32_t remote_ip, uint16_t remote_port,
-                         MachnetFlow_t* flow) {
-  return machnet_connect(ctx, local_ip, remote_ip, remote_port, flow);
+                         MachnetFlow_t* flow, int protocol) {
+  return machnet_connect(ctx, local_ip, remote_ip, remote_port, flow, protocol);
 }

 int __machnet_listen_go(MachnetChannelCtx_t* ctx, uint32_t local_ip,
-                        uint16_t port) {
-  return machnet_listen(ctx, local_ip, port);
+                        uint16_t port, int protocol) {
+  return machnet_listen(ctx, local_ip, port, protocol);
 }


Go bindings now call machnet_connect()/machnet_listen() with uint32_t IPs, but the C API expects const char* IP strings. This will compile with warnings (C) but pass invalid pointers at runtime (likely crash). Update the Go wrapper to pass string IPs (and remove ipv4_str_to_uint32 usage) or introduce separate C APIs (e.g., machnet_connect_ipv4_u32 / machnet_listen_ipv4_u32) and expose those instead.

Copilot · 2026-02-08T23:36:44Z

examples/sync.sh

+REMOTE_USER="sarsanaee"
+REMOTE_HOST="asas-westus2-vm-0"
+LOCAL_PATH="/home/sarsanaee/machnet/"
+REMOTE_PATH="${REMOTE_USER}@${REMOTE_HOST}:/home/sarsanaee/machnet/"
+


This script hard-codes a specific username, host, and absolute home-directory path. Checking in personal deployment details is risky and makes the script unusable for others; it can also leak internal hostnames. Consider removing this file from the repo or parameterizing via env vars/CLI args and documenting usage generically.

Suggested change

REMOTE_USER="sarsanaee"

REMOTE_HOST="asas-westus2-vm-0"

LOCAL_PATH="/home/sarsanaee/machnet/"

REMOTE_PATH="${REMOTE_USER}@${REMOTE_HOST}:/home/sarsanaee/machnet/"

# Required: remote SSH username and host. Set these via environment variables.

: "${REMOTE_USER:?REMOTE_USER is not set. Please export REMOTE_USER before running this script.}"

: "${REMOTE_HOST:?REMOTE_HOST is not set. Please export REMOTE_HOST before running this script.}"

# Optional: override LOCAL_PATH and REMOTE_BASE_PATH via environment variables.

: "${LOCAL_PATH:=${HOME}/machnet/}"

: "${REMOTE_BASE_PATH:=/home/${REMOTE_USER}/machnet/}"

REMOTE_PATH="${REMOTE_USER}@${REMOTE_HOST}:${REMOTE_BASE_PATH}"

Copilot · 2026-02-08T23:36:45Z

src/include/tcp_flow.h

+    // Retransmit based on state.
+    switch (state_) {
+      case State::kSynSent:
+        LOG(INFO) << "TCP retransmitting SYN";
+        SendSyn();
+        break;
+      case State::kSynReceived:
+        LOG(INFO) << "TCP retransmitting SYN-ACK";
+        SendSynAck();
+        break;
+      default:
+        // For established connections, a full retransmission mechanism
+        // would require buffering sent data. For now, we just reset the timer.
+        break;
+    }


PeriodicCheck() does not retransmit any application data when RTO expires in established states (it only retransmits SYN/SYN-ACK). With any packet loss, the connection can hang indefinitely because lost bytes are never resent. Either implement buffering+retransmission for unacked data or fail the connection (RST/close) on RTO until retransmission support is added.

Copilot · 2026-02-08T23:36:45Z

bindings/csharp/HelloWorld/Program.cs

            // Client
            MachnetFlow_t flow = new MachnetFlow_t();
-            ret = MachnetShim.machnet_connect(channel_ctx, options.LocalIp, options.RemoteIp, kHelloWorldPort, ref flow);
+            ret = MachnetShim.machnet_connect(channel_ctx, options.LocalIp, options.RemoteIp, kHelloWorldPort, ref flow, 0);


Replace this call with a call to managed code if possible.

Copilot · 2026-02-08T23:36:45Z

bindings/csharp/HelloWorld/Program.cs

        {
            Console.WriteLine("Waiting for message from client");
-            ret = MachnetShim.machnet_listen(channel_ctx, options.LocalIp, kHelloWorldPort);
+            ret = MachnetShim.machnet_listen(channel_ctx, options.LocalIp, kHelloWorldPort, 0);


Replace this call with a call to managed code if possible.

Copilot · 2026-02-08T23:36:45Z

bindings/csharp/HelloWorld/machnet_shim.cs


    [DllImport(libmachnet_shim_location, CallingConvention = CallingConvention.Cdecl)]
-    public static extern int machnet_connect(IntPtr channel_ctx, string local_ip, string remote_ip, UInt16 port, ref MachnetFlow_t flow);
+    public static extern int machnet_connect(IntPtr channel_ctx, string local_ip, string remote_ip, UInt16 port, ref MachnetFlow_t flow, int protocol);


Minimise the use of unmanaged code.

Copilot · 2026-02-08T23:36:45Z

bindings/csharp/HelloWorld/machnet_shim.cs


    [DllImport(libmachnet_shim_location, CallingConvention = CallingConvention.Cdecl)]
-    public static extern int machnet_listen(IntPtr channel_ctx, string local_ip, UInt16 port);
+    public static extern int machnet_listen(IntPtr channel_ctx, string local_ip, UInt16 port, int protocol);


Minimise the use of unmanaged code.

Tests and readme added to describe tests used for the project on TCP side. Signed-off-by: Alireza Sanaee <sarsanaee@gmail.com>

Add TCP transport to Machnet

1c4ad22

TCP transport is important in any networking stack. Therefore, this is the first try to add this transport to Machnet. Signed-off-by: Alireza Sanaee <sarsanaee@gmail.com>

Copilot AI review requested due to automatic review settings February 8, 2026 23:27

Copilot started reviewing on behalf of sarsanaee February 8, 2026 23:28 View session

TCP working version

5f07af2

Signed-off-by: Alireza Sanaee <sarsanaee@gmail.com>

sarsanaee force-pushed the tcp-7-02-2026 branch from a2574e7 to 5f07af2 Compare February 8, 2026 23:34

Copilot AI reviewed Feb 8, 2026

View reviewed changes

Adding TCP flow test

4837db8

Tests and readme added to describe tests used for the project on TCP side. Signed-off-by: Alireza Sanaee <sarsanaee@gmail.com>

sarsanaee force-pushed the tcp-7-02-2026 branch from 5257833 to 4837db8 Compare February 9, 2026 00:33

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TCP support for Machnet, when non-machnet application connect a machnet application. #54

TCP support for Machnet, when non-machnet application connect a machnet application. #54

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-REMOTE_USER="sarsanaee"
-REMOTE_HOST="asas-westus2-vm-0"
-LOCAL_PATH="/home/sarsanaee/machnet/"
-REMOTE_PATH="${REMOTE_USER}@${REMOTE_HOST}:/home/sarsanaee/machnet/"
+# Required: remote SSH username and host. Set these via environment variables.
+: "${REMOTE_USER:?REMOTE_USER is not set. Please export REMOTE_USER before running this script.}"
+: "${REMOTE_HOST:?REMOTE_HOST is not set. Please export REMOTE_HOST before running this script.}"
+# Optional: override LOCAL_PATH and REMOTE_BASE_PATH via environment variables.
+: "${LOCAL_PATH:=${HOME}/machnet/}"
+: "${REMOTE_BASE_PATH:=/home/${REMOTE_USER}/machnet/}"
+REMOTE_PATH="${REMOTE_USER}@${REMOTE_HOST}:${REMOTE_BASE_PATH}"

TCP support for Machnet, when non-machnet application connect a machnet application. #54

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TCP support for Machnet, when non-machnet application connect a machnet application. #54

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