feat(ffi): add async data plane API (#2321)

* feat(ffi): add async data plane API
* feat(ffi): add async data plane examples
* test(ffi): make async Go dataplane tests self-contained
* docs(ffi): document Go async dataplane API
* docs(android): document dataplane JNI API

easytier-contrib/easytier-ffi/examples/example_data_plane_async.c

@@ -0,0 +1,429 @@
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#define DATA_PLANE_OP_PENDING 0
+#define DATA_PLANE_OP_READY 1
+#define DATA_PLANE_OP_FAILED -1
+#define DATA_PLANE_OP_INVALID -2
+
+extern int run_network_instance(const char *cfg_str);
+extern void get_error_msg(const char **out);
+extern void free_string(const char *s);
+
+extern int data_plane_async_op_status(uint64_t op);
+extern int data_plane_async_op_wait(uint64_t op, uint64_t timeout_ms);
+extern int data_plane_async_op_cancel(uint64_t op);
+extern int data_plane_async_op_free(uint64_t op);
+extern void data_plane_free_bytes(const uint8_t *ptr, uint32_t len);
+
+extern uint64_t data_plane_tcp_connect_start(
+    const char *inst_name,
+    const char *dst_ip,
+    uint16_t dst_port,
+    uint64_t timeout_ms);
+extern uint64_t data_plane_tcp_connect_finish(
+    uint64_t op,
+    const char **out_local_ip,
+    uint16_t *out_local_port);
+extern uint64_t data_plane_tcp_bind_start(
+    const char *inst_name,
+    uint16_t local_port,
+    uint64_t timeout_ms);
+extern uint64_t data_plane_tcp_bind_finish(
+    uint64_t op,
+    const char **out_local_ip,
+    uint16_t *out_local_port);
+extern uint64_t data_plane_tcp_accept_start(uint64_t listener, uint64_t timeout_ms);
+extern uint64_t data_plane_tcp_accept_finish(
+    uint64_t op,
+    const char **out_local_ip,
+    uint16_t *out_local_port,
+    const char **out_peer_ip,
+    uint16_t *out_peer_port);
+extern uint64_t data_plane_tcp_read_start(
+    uint64_t stream,
+    uint32_t max_len,
+    uint64_t timeout_ms);
+extern int data_plane_tcp_read_finish(
+    uint64_t op,
+    const uint8_t **out_buf,
+    uint32_t *out_len);
+extern uint64_t data_plane_tcp_write_start(
+    uint64_t stream,
+    const uint8_t *buf,
+    uint32_t len,
+    uint64_t timeout_ms);
+extern int data_plane_tcp_write_finish(uint64_t op);
+extern int data_plane_tcp_close(uint64_t stream);
+extern int data_plane_tcp_listener_close(uint64_t listener);
+
+extern uint64_t data_plane_udp_bind_start(
+    const char *inst_name,
+    uint16_t local_port,
+    uint64_t timeout_ms);
+extern uint64_t data_plane_udp_bind_finish(
+    uint64_t op,
+    const char **out_local_ip,
+    uint16_t *out_local_port);
+extern uint64_t data_plane_udp_send_to_start(
+    uint64_t socket,
+    const char *dst_ip,
+    uint16_t dst_port,
+    const uint8_t *buf,
+    uint32_t len,
+    uint64_t timeout_ms);
+extern int data_plane_udp_send_to_finish(uint64_t op);
+extern uint64_t data_plane_udp_recv_from_start(
+    uint64_t socket,
+    uint32_t max_len,
+    uint64_t timeout_ms);
+extern int data_plane_udp_recv_from_finish(
+    uint64_t op,
+    const uint8_t **out_buf,
+    uint32_t *out_len,
+    const char **out_ip,
+    uint16_t *out_port);
+extern int data_plane_udp_close(uint64_t socket);
+
+static void print_last_error(const char *prefix) {
+    const char *err = NULL;
+    get_error_msg(&err);
+    if (err) {
+        fprintf(stderr, "%s: %s\n", prefix, err);
+        free_string(err);
+    } else {
+        fprintf(stderr, "%s\n", prefix);
+    }
+}
+
+static int parse_ip_port(const char *value, char *ip, size_t ip_len, uint16_t *port) {
+    const char *colon = strrchr(value, ':');
+    if (!colon || colon == value || !colon[1]) {
+        fprintf(stderr, "expected IPv4 target in IP:PORT form, got %s\n", value);
+        return -1;
+    }
+    size_t host_len = (size_t)(colon - value);
+    if (host_len >= ip_len) {
+        fprintf(stderr, "IP address is too long: %s\n", value);
+        return -1;
+    }
+    char *end = NULL;
+    long parsed_port = strtol(colon + 1, &end, 10);
+    if (!end || *end != '\0' || parsed_port < 0 || parsed_port > 65535) {
+        fprintf(stderr, "invalid port in %s\n", value);
+        return -1;
+    }
+    memcpy(ip, value, host_len);
+    ip[host_len] = '\0';
+    *port = (uint16_t)parsed_port;
+    return 0;
+}
+
+static int wait_op(uint64_t op, uint64_t timeout_ms) {
+    uint64_t waited = 0;
+    while (waited < timeout_ms) {
+        int status = data_plane_async_op_wait(op, 50);
+        if (status != DATA_PLANE_OP_PENDING) {
+            return status;
+        }
+        waited += 50;
+    }
+    return data_plane_async_op_status(op);
+}
+
+static int wait_or_cancel(uint64_t op, uint64_t timeout_ms, const char *what) {
+    int status = wait_op(op, timeout_ms);
+    if (status == DATA_PLANE_OP_READY || status == DATA_PLANE_OP_FAILED) {
+        return status;
+    }
+    if (status == DATA_PLANE_OP_PENDING) {
+        fprintf(stderr, "%s did not finish within %llu ms\n", what, (unsigned long long)timeout_ms);
+        data_plane_async_op_cancel(op);
+        data_plane_async_op_free(op);
+        return DATA_PLANE_OP_INVALID;
+    }
+    fprintf(stderr, "%s returned invalid op status %d\n", what, status);
+    return status;
+}
+
+static int async_tcp_read_once(uint64_t stream, uint64_t timeout_ms) {
+    uint64_t op = data_plane_tcp_read_start(stream, 512, timeout_ms);
+    if (!op) {
+        print_last_error("tcp read start failed");
+        return -1;
+    }
+    if (wait_or_cancel(op, timeout_ms + 1000, "tcp read") == DATA_PLANE_OP_INVALID) {
+        return -1;
+    }
+
+    const uint8_t *buf = NULL;
+    uint32_t len = 0;
+    int ret = data_plane_tcp_read_finish(op, &buf, &len);
+    if (ret < 0) {
+        print_last_error("tcp read finish failed");
+        return -1;
+    }
+    printf("tcp read %d bytes: %.*s\n", ret, ret, buf ? (const char *)buf : "");
+    data_plane_free_bytes(buf, len);
+    return 0;
+}
+
+static int async_tcp_write_all(uint64_t stream, const char *data, uint64_t timeout_ms) {
+    uint64_t op = data_plane_tcp_write_start(
+        stream,
+        (const uint8_t *)data,
+        (uint32_t)strlen(data),
+        timeout_ms);
+    if (!op) {
+        print_last_error("tcp write start failed");
+        return -1;
+    }
+    if (wait_or_cancel(op, timeout_ms + 1000, "tcp write") == DATA_PLANE_OP_INVALID) {
+        return -1;
+    }
+    int ret = data_plane_tcp_write_finish(op);
+    if (ret < 0) {
+        print_last_error("tcp write finish failed");
+        return -1;
+    }
+    printf("tcp wrote %d bytes\n", ret);
+    return 0;
+}
+
+static int run_tcp_connect_demo(const char *inst, const char *target) {
+    char ip[128];
+    uint16_t port = 0;
+    if (parse_ip_port(target, ip, sizeof(ip), &port) != 0) {
+        return -1;
+    }
+
+    uint64_t op = data_plane_tcp_connect_start(inst, ip, port, 30000);
+    if (!op) {
+        print_last_error("tcp connect start failed");
+        return -1;
+    }
+    if (wait_or_cancel(op, 31000, "tcp connect") == DATA_PLANE_OP_INVALID) {
+        return -1;
+    }
+
+    const char *local_ip = NULL;
+    uint16_t local_port = 0;
+    uint64_t stream = data_plane_tcp_connect_finish(op, &local_ip, &local_port);
+    if (!stream) {
+        print_last_error("tcp connect finish failed");
+        return -1;
+    }
+    printf("tcp connected from %s:%u to %s:%u, handle=%llu\n",
+           local_ip,
+           local_port,
+           ip,
+           port,
+           (unsigned long long)stream);
+    free_string(local_ip);
+
+    int ret = async_tcp_read_once(stream, 10000);
+    data_plane_tcp_close(stream);
+    return ret;
+}
+
+static int run_tcp_listen_demo(const char *inst, const char *port_text) {
+    uint16_t port = (uint16_t)strtoul(port_text, NULL, 10);
+    uint64_t op = data_plane_tcp_bind_start(inst, port, 30000);
+    if (!op) {
+        print_last_error("tcp bind start failed");
+        return -1;
+    }
+    if (wait_or_cancel(op, 31000, "tcp bind") == DATA_PLANE_OP_INVALID) {
+        return -1;
+    }
+
+    const char *local_ip = NULL;
+    uint16_t local_port = 0;
+    uint64_t listener = data_plane_tcp_bind_finish(op, &local_ip, &local_port);
+    if (!listener) {
+        print_last_error("tcp bind finish failed");
+        return -1;
+    }
+    printf("tcp listening on %s:%u, handle=%llu\n",
+           local_ip,
+           local_port,
+           (unsigned long long)listener);
+    free_string(local_ip);
+
+    op = data_plane_tcp_accept_start(listener, 60000);
+    if (!op) {
+        print_last_error("tcp accept start failed");
+        data_plane_tcp_listener_close(listener);
+        return -1;
+    }
+    if (wait_or_cancel(op, 61000, "tcp accept") == DATA_PLANE_OP_INVALID) {
+        data_plane_tcp_listener_close(listener);
+        return -1;
+    }
+
+    const char *peer_ip = NULL;
+    uint16_t peer_port = 0;
+    local_ip = NULL;
+    local_port = 0;
+    uint64_t stream = data_plane_tcp_accept_finish(
+        op,
+        &local_ip,
+        &local_port,
+        &peer_ip,
+        &peer_port);
+    data_plane_tcp_listener_close(listener);
+    if (!stream) {
+        print_last_error("tcp accept finish failed");
+        return -1;
+    }
+    printf("tcp accepted %s:%u -> %s:%u, stream=%llu\n",
+           peer_ip,
+           peer_port,
+           local_ip,
+           local_port,
+           (unsigned long long)stream);
+    free_string(local_ip);
+    free_string(peer_ip);
+
+    int ret = async_tcp_read_once(stream, 10000);
+    if (ret == 0) {
+        ret = async_tcp_write_all(stream, "pong", 10000);
+    }
+    data_plane_tcp_close(stream);
+    return ret;
+}
+
+static int run_udp_demo(const char *inst, const char *target) {
+    char ip[128];
+    uint16_t port = 0;
+    if (parse_ip_port(target, ip, sizeof(ip), &port) != 0) {
+        return -1;
+    }
+
+    uint64_t op = data_plane_udp_bind_start(inst, 0, 30000);
+    if (!op) {
+        print_last_error("udp bind start failed");
+        return -1;
+    }
+    if (wait_or_cancel(op, 31000, "udp bind") == DATA_PLANE_OP_INVALID) {
+        return -1;
+    }
+
+    const char *local_ip = NULL;
+    uint16_t local_port = 0;
+    uint64_t socket = data_plane_udp_bind_finish(op, &local_ip, &local_port);
+    if (!socket) {
+        print_last_error("udp bind finish failed");
+        return -1;
+    }
+    printf("udp bound on %s:%u, handle=%llu\n",
+           local_ip,
+           local_port,
+           (unsigned long long)socket);
+    free_string(local_ip);
+
+    const char payload[] = "ping";
+    op = data_plane_udp_send_to_start(
+        socket,
+        ip,
+        port,
+        (const uint8_t *)payload,
+        (uint32_t)strlen(payload),
+        10000);
+    if (!op) {
+        print_last_error("udp send start failed");
+        data_plane_udp_close(socket);
+        return -1;
+    }
+    if (wait_or_cancel(op, 11000, "udp send") == DATA_PLANE_OP_INVALID) {
+        data_plane_udp_close(socket);
+        return -1;
+    }
+    int sent = data_plane_udp_send_to_finish(op);
+    if (sent < 0) {
+        print_last_error("udp send finish failed");
+        data_plane_udp_close(socket);
+        return -1;
+    }
+    printf("udp sent %d bytes to %s:%u\n", sent, ip, port);
+
+    op = data_plane_udp_recv_from_start(socket, 512, 30000);
+    if (!op) {
+        print_last_error("udp recv start failed");
+        data_plane_udp_close(socket);
+        return -1;
+    }
+    if (wait_or_cancel(op, 31000, "udp recv") == DATA_PLANE_OP_INVALID) {
+        data_plane_udp_close(socket);
+        return -1;
+    }
+
+    const uint8_t *buf = NULL;
+    uint32_t len = 0;
+    const char *peer_ip = NULL;
+    uint16_t peer_port = 0;
+    int ret = data_plane_udp_recv_from_finish(op, &buf, &len, &peer_ip, &peer_port);
+    if (ret < 0) {
+        print_last_error("udp recv finish failed");
+        data_plane_udp_close(socket);
+        return -1;
+    }
+    printf("udp received %d bytes from %s:%u: %.*s\n",
+           ret,
+           peer_ip,
+           peer_port,
+           ret,
+           buf ? (const char *)buf : "");
+    data_plane_free_bytes(buf, len);
+    free_string(peer_ip);
+    data_plane_udp_close(socket);
+    return 0;
+}
+
+static void print_usage(void) {
+    printf("Set EASYTIER_FFI_CONFIG and EASYTIER_FFI_INSTANCE to run the async data-plane demo.\n");
+    printf("Optional demos:\n");
+    printf("  EASYTIER_FFI_TARGET=10.0.0.2:22          async TCP connect/read\n");
+    printf("  EASYTIER_FFI_LISTEN_PORT=12345           async TCP bind/accept/read/write\n");
+    printf("  EASYTIER_FFI_UDP_TARGET=10.0.0.2:9000    async UDP bind/send_to/recv_from\n");
+}
+
+int main(void) {
+    const char *config = getenv("EASYTIER_FFI_CONFIG");
+    const char *instance = getenv("EASYTIER_FFI_INSTANCE");
+    if (!config || !instance) {
+        print_usage();
+        return 0;
+    }
+
+    if (run_network_instance(config) != 0) {
+        print_last_error("run_network_instance failed");
+        return 1;
+    }
+    printf("network instance started: %s\n", instance);
+
+    int failed = 0;
+    const char *target = getenv("EASYTIER_FFI_TARGET");
+    if (target) {
+        failed |= run_tcp_connect_demo(instance, target) != 0;
+    }
+
+    const char *listen_port = getenv("EASYTIER_FFI_LISTEN_PORT");
+    if (listen_port) {
+        failed |= run_tcp_listen_demo(instance, listen_port) != 0;
+    }
+
+    const char *udp_target = getenv("EASYTIER_FFI_UDP_TARGET");
+    if (udp_target) {
+        failed |= run_udp_demo(instance, udp_target) != 0;
+    }
+
+    if (!target && !listen_port && !udp_target) {
+        printf("No dataplane demo env var was set; nothing else to run.\n");
+        print_usage();
+    }
+
+    return failed ? 1 : 0;
+}

easytier-contrib/easytier-ffi/examples/go/README.md

@@ -3,6 +3,8 @@
 This demo wraps EasyTier FFI data-plane TCP as Go `net.Conn` and `net.Listener`.
 It can connect to an SSH server through EasyTier and read its banner, or accept a
 TCP connection from another EasyTier peer and run a small ping/pong exchange.
+The async op-handle wrapper is in `easytier_async.go`; the original synchronous
+wrapper stays in `easytier.go`.
 
 ## 1.1. Build the FFI library
 
@@ -27,7 +29,6 @@ To use another library path, export `EASYTIER_FFI_LIB=/path/to/libeasytier_ffi.s
 ```sh
 export EASYTIER_FFI_CONFIG='instance_name = "default"
 ipv4 = "10.0.0.1"
-peers = ["tcp://123.123.123.123:11010"]
 
 [network_identity]
 network_name = "testnet"
@@ -35,6 +36,10 @@ network_secret = "mysecret"
 
 [flags]
 no_tun = true # disable tun device to avoid permission issues.
+bind_device = false # allow loopback peers in local examples.
+
+[[peer]]
+uri = "tcp://123.123.123.123:11010"
 '
 ```
 
@@ -53,7 +58,6 @@ test, use a separate instance name and config:
 ```sh
 export EASYTIER_FFI_LISTEN_CONFIG='instance_name = "listener"
 ipv4 = "10.0.0.3"
-peers = ["tcp://123.123.123.123:11010"]
 
 [network_identity]
 network_name = "testnet"
@@ -61,6 +65,10 @@ network_secret = "mysecret"
 
 [flags]
 no_tun = true
+bind_device = false
+
+[[peer]]
+uri = "tcp://123.123.123.123:11010"
 '
 export EASYTIER_FFI_LISTEN_INSTANCE=listener
 export EASYTIER_FFI_LISTEN_PORT=12345
@@ -68,14 +76,27 @@ export EASYTIER_FFI_LISTEN_PORT=12345
 
 ## 1.3. Run the demo
 
-`goffi` is built without cgo on Linux, so run the test with `CGO_ENABLED=0`:
+`goffi` is built without cgo on Linux, so run the tests with `CGO_ENABLED=0`:
 
 ```sh
 cd easytier-contrib/easytier-ffi/examples/go
 CGO_ENABLED=0 go test -v ./...
 ```
 
-Expected output includes an SSH banner similar to:
+The synchronous tests use the environment variables above. The async Go tests
+are self-contained: they start two local EasyTier instances in the same test
+process with `no_tun = true` and `bind_device = false`, then run TCP and UDP
+ping/pong over the async data-plane API.
+
+To run only the async tests:
+
+```sh
+cd easytier-contrib/easytier-ffi/examples/go
+CGO_ENABLED=0 go test -run 'TestAsync' -v ./...
+```
+
+When the SSH integration environment variables are set, expected synchronous
+test output includes an SSH banner similar to:
 
 ```text
 attempt 1: got banner "SSH-2.0-..."
@@ -85,3 +106,26 @@ PASS
 For `TestTCPListenIntegration`, connect from another EasyTier peer to the local
 EasyTier IPv4 address and `EASYTIER_FFI_LISTEN_PORT`, send `ping`, and expect
 `pong` in response.
+
+The async test output should include local TCP bind/connect log lines and finish
+with `PASS` without any extra environment variables.
+
+## 1.4. C async example
+
+The C async example is kept separate from the basic C example:
+
+```sh
+cargo build -p easytier-ffi --features ffi-dataplane
+cc -Wall -Wextra -pedantic \
+  ../example_data_plane_async.c \
+  -L ../../../../target/debug -leasytier_ffi \
+  -Wl,-rpath,../../../../target/debug \
+  -o /tmp/easytier_data_plane_async
+
+/tmp/easytier_data_plane_async
+```
+
+Without environment variables it prints usage and exits successfully. With
+`EASYTIER_FFI_CONFIG`, `EASYTIER_FFI_INSTANCE`, and one of
+`EASYTIER_FFI_TARGET`, `EASYTIER_FFI_LISTEN_PORT`, or `EASYTIER_FFI_UDP_TARGET`,
+it runs the corresponding async data-plane flow.

easytier-contrib/easytier-ffi/examples/go/easytier_async_test.go

@@ -0,0 +1,360 @@
+package easytierffi
+
+import (
+	"context"
+	"fmt"
+	"io"
+	"net"
+	"os"
+	"strconv"
+	"testing"
+	"time"
+)
+
+const asyncLocalTestTimeout = 120 * time.Second
+
+func TestAsyncSymbolBinding(t *testing.T) {
+	n := openAsyncForTest(t)
+
+	status, err := n.opWaitStatus(0, 0)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if status != dataPlaneOpInvalid {
+		t.Fatalf("expected invalid status for op 0, got %d", status)
+	}
+}
+
+func TestAsyncLocalTwoNodeTCPAndUDP(t *testing.T) {
+	n := openAsyncForTest(t)
+	topology := startLocalAsyncTopology(t, n)
+
+	ctx, cancel := context.WithTimeout(context.Background(), asyncLocalTestTimeout)
+	defer cancel()
+
+	runAsyncTCPPingPong(t, ctx, n, topology)
+	runAsyncUDPPingPong(t, ctx, n, topology)
+}
+
+type localAsyncTopology struct {
+	dialerInstance   string
+	listenerInstance string
+	listenerIP       string
+}
+
+func openAsyncForTest(t *testing.T) *AsyncNative {
+	t.Helper()
+
+	libraryPath := defaultLibraryPath()
+	if _, err := os.Stat(libraryPath); err != nil {
+		if os.IsNotExist(err) {
+			t.Skipf("build easytier-ffi with ffi-dataplane before running async tests: %v", err)
+		}
+		t.Fatalf("stat async ffi library: %v", err)
+	}
+
+	n, err := OpenAsync(libraryPath)
+	if err != nil {
+		t.Fatalf("open async ffi library: %v", err)
+	}
+	t.Cleanup(func() {
+		if err := n.Close(); err != nil {
+			t.Errorf("close async native: %v", err)
+		}
+	})
+	return n
+}
+
+func startLocalAsyncTopology(t *testing.T, n *AsyncNative) localAsyncTopology {
+	t.Helper()
+
+	suffix := strconv.FormatInt(time.Now().UnixNano(), 10)
+	networkName := "ffi-async-" + suffix
+	networkSecret := "ffi-async-secret-" + suffix
+	listenerInstance := "ffi-async-listener-" + suffix
+	dialerInstance := "ffi-async-dialer-" + suffix
+	listenerIP := "10.251.1.2"
+	dialerIP := "10.251.1.1"
+	listenerPort := freeLocalTCPPort(t)
+	listenerEndpoint := fmt.Sprintf("tcp://127.0.0.1:%d", listenerPort)
+	t.Cleanup(func() {
+		if err := n.deleteNetworkInstances([]string{dialerInstance, listenerInstance}); err != nil {
+			t.Errorf("cleanup async test EasyTier instances: %v", err)
+		}
+	})
+
+	listenerConfig := localAsyncConfig(
+		listenerInstance,
+		listenerIP,
+		networkName,
+		networkSecret,
+		[]string{listenerEndpoint},
+		nil,
+	)
+	dialerConfig := localAsyncConfig(
+		dialerInstance,
+		dialerIP,
+		networkName,
+		networkSecret,
+		nil,
+		[]string{listenerEndpoint},
+	)
+
+	if err := n.RunNetworkInstance(listenerConfig); err != nil {
+		t.Fatalf("start listener instance: %v", err)
+	}
+	if err := n.RunNetworkInstance(dialerConfig); err != nil {
+		t.Fatalf("start dialer instance: %v", err)
+	}
+
+	return localAsyncTopology{
+		dialerInstance:   dialerInstance,
+		listenerInstance: listenerInstance,
+		listenerIP:       listenerIP,
+	}
+}
+
+func localAsyncConfig(instance, ipv4, networkName, networkSecret string, listeners, peers []string) string {
+	config := fmt.Sprintf(`instance_name = %s
+ipv4 = %s
+listeners = %s
+
+[network_identity]
+network_name = %s
+network_secret = %s
+
+[flags]
+no_tun = true
+bind_device = false
+`,
+		strconv.Quote(instance),
+		strconv.Quote(ipv4),
+		tomlStringList(listeners),
+		strconv.Quote(networkName),
+		strconv.Quote(networkSecret),
+	)
+	for _, peer := range peers {
+		config += fmt.Sprintf("\n[[peer]]\nuri = %s\n", strconv.Quote(peer))
+	}
+	return config
+}
+
+func tomlStringList(values []string) string {
+	if len(values) == 0 {
+		return "[]"
+	}
+
+	out := "["
+	for i, value := range values {
+		if i > 0 {
+			out += ", "
+		}
+		out += strconv.Quote(value)
+	}
+	return out + "]"
+}
+
+func freeLocalTCPPort(t *testing.T) int {
+	t.Helper()
+
+	listener, err := net.Listen("tcp", "127.0.0.1:0")
+	if err != nil {
+		t.Fatalf("allocate local tcp port: %v", err)
+	}
+	defer listener.Close()
+	return listener.Addr().(*net.TCPAddr).Port
+}
+
+func runAsyncTCPPingPong(t *testing.T, ctx context.Context, n *AsyncNative, topology localAsyncTopology) {
+	t.Helper()
+
+	listener, listenerAddr := eventuallyTCPListen(t, ctx, n, topology.listenerInstance)
+
+	tcpCtx, cancel := context.WithCancel(ctx)
+	accepted := make(chan error, 1)
+	defer waitForAsyncHelper(t, accepted, "tcp accept helper")
+	defer cancel()
+	defer listener.Close()
+	go func() {
+		conn, err := listener.Accept()
+		if err != nil {
+			accepted <- fmt.Errorf("accept tcp stream: %w", err)
+			return
+		}
+		defer conn.Close()
+		_ = conn.SetDeadline(time.Now().Add(30 * time.Second))
+
+		payload := make([]byte, len("ping"))
+		if _, err := io.ReadFull(conn, payload); err != nil {
+			accepted <- fmt.Errorf("read tcp ping: %w", err)
+			return
+		}
+		if string(payload) != "ping" {
+			accepted <- fmt.Errorf("expected tcp ping, got %q", string(payload))
+			return
+		}
+		if _, err := conn.Write([]byte("pong")); err != nil {
+			accepted <- fmt.Errorf("write tcp pong: %w", err)
+			return
+		}
+		accepted <- nil
+	}()
+
+	conn, err := eventuallyTCPDial(t, tcpCtx, n, topology.dialerInstance, topology.listenerIP, listenerAddr.Port)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer conn.Close()
+	_ = conn.SetDeadline(time.Now().Add(30 * time.Second))
+
+	if _, err := conn.Write([]byte("ping")); err != nil {
+		t.Fatalf("write tcp ping: %v", err)
+	}
+	payload := make([]byte, len("pong"))
+	if _, err := io.ReadFull(conn, payload); err != nil {
+		t.Fatalf("read tcp pong: %v", err)
+	}
+	if string(payload) != "pong" {
+		t.Fatalf("expected tcp pong, got %q", string(payload))
+	}
+}
+
+func eventuallyTCPListen(t *testing.T, ctx context.Context, n *AsyncNative, instance string) (net.Listener, *net.TCPAddr) {
+	t.Helper()
+
+	var lastErr error
+	for attempt := 1; ctx.Err() == nil; attempt++ {
+		attemptCtx, cancel := context.WithTimeout(ctx, 5*time.Second)
+		listener, err := n.ListenContext(attemptCtx, instance, "tcp", "0.0.0.0:0")
+		cancel()
+		if err == nil {
+			addr := listener.Addr().(*net.TCPAddr)
+			t.Logf("async tcp bind succeeded on attempt %d at %s", attempt, addr)
+			return listener, addr
+		}
+
+		lastErr = err
+		t.Logf("attempt %d: async tcp bind failed: %v", attempt, err)
+		waitForRetry(ctx, 500*time.Millisecond)
+	}
+	t.Fatalf("async tcp bind never succeeded: %v", lastErr)
+	panic("unreachable")
+}
+
+func eventuallyTCPDial(t *testing.T, ctx context.Context, n *AsyncNative, instance, ip string, port int) (net.Conn, error) {
+	t.Helper()
+
+	address := net.JoinHostPort(ip, strconv.Itoa(port))
+	var lastErr error
+	for attempt := 1; ctx.Err() == nil; attempt++ {
+		attemptCtx, cancel := context.WithTimeout(ctx, 5*time.Second)
+		conn, err := n.DialContext(attemptCtx, instance, "tcp", address)
+		cancel()
+		if err == nil {
+			t.Logf("async tcp connect succeeded on attempt %d to %s", attempt, address)
+			return conn, nil
+		}
+
+		lastErr = err
+		t.Logf("attempt %d: async tcp connect failed: %v", attempt, err)
+		waitForRetry(ctx, 500*time.Millisecond)
+	}
+	return nil, fmt.Errorf("async tcp connect never succeeded: %w", lastErr)
+}
+
+func runAsyncUDPPingPong(t *testing.T, ctx context.Context, n *AsyncNative, topology localAsyncTopology) {
+	t.Helper()
+
+	dialerSocket, err := n.UDPBindContext(ctx, topology.dialerInstance, 0)
+	if err != nil {
+		t.Fatalf("bind dialer udp socket: %v", err)
+	}
+
+	listenerSocket, err := n.UDPBindContext(ctx, topology.listenerInstance, 0)
+	if err != nil {
+		t.Fatalf("bind listener udp socket: %v", err)
+	}
+
+	udpCtx, cancel := context.WithCancel(ctx)
+	warmupDone := make(chan error, 1)
+	received := make(chan error, 1)
+	defer waitForAsyncHelper(t, received, "udp receive helper")
+	defer cancel()
+	defer listenerSocket.Close()
+	defer dialerSocket.Close()
+
+	go func() {
+		if _, err := listenerSocket.SendTo(udpCtx, []byte("warmup"), dialerSocket.LocalAddr()); err != nil {
+			err = fmt.Errorf("send udp warmup: %w", err)
+			warmupDone <- err
+			received <- err
+			return
+		}
+		warmupDone <- nil
+
+		payload, from, err := listenerSocket.RecvFrom(udpCtx, 512)
+		if err != nil {
+			received <- fmt.Errorf("recv udp ping: %w", err)
+			return
+		}
+		if string(payload) != "ping" {
+			received <- fmt.Errorf("expected udp ping, got %q", string(payload))
+			return
+		}
+		if _, err := listenerSocket.SendTo(udpCtx, []byte("pong"), from); err != nil {
+			received <- fmt.Errorf("send udp pong: %w", err)
+			return
+		}
+		received <- nil
+	}()
+
+	select {
+	case err := <-warmupDone:
+		if err != nil {
+			t.Fatal(err)
+		}
+	case <-udpCtx.Done():
+		t.Fatal(udpCtx.Err())
+	}
+
+	target := &net.UDPAddr{IP: net.ParseIP(topology.listenerIP), Port: listenerSocket.LocalAddr().Port}
+	if _, err := dialerSocket.SendTo(udpCtx, []byte("ping"), target); err != nil {
+		t.Fatalf("send udp ping: %v", err)
+	}
+	for {
+		payload, from, err := dialerSocket.RecvFrom(udpCtx, 512)
+		if err != nil {
+			t.Fatalf("recv udp pong: %v", err)
+		}
+		if string(payload) == "pong" {
+			if !from.IP.Equal(target.IP) || from.Port != target.Port {
+				t.Fatalf("expected udp pong from %s, got %s", target, from)
+			}
+			break
+		}
+		t.Logf("skipping udp datagram from %s: %q", from, string(payload))
+	}
+}
+
+func waitForAsyncHelper(t *testing.T, done <-chan error, name string) {
+	t.Helper()
+
+	select {
+	case err := <-done:
+		if err != nil {
+			t.Errorf("%s: %v", name, err)
+		}
+	case <-time.After(10 * time.Second):
+		t.Errorf("%s did not stop", name)
+	}
+}
+
+func waitForRetry(ctx context.Context, delay time.Duration) {
+	timer := time.NewTimer(delay)
+	defer timer.Stop()
+
+	select {
+	case <-timer.C:
+	case <-ctx.Done():
+	}
+}

easytier-contrib/easytier-ffi/examples/go/go.sum

@@ -0,0 +1,2 @@
+github.com/go-webgpu/goffi v0.4.1 h1:2hQH5XXloxTyTtIleYv+Rajlwzp6UOETURhSZ5+zJxU=
+github.com/go-webgpu/goffi v0.4.1/go.mod h1:wfoxNsJkU+5RFbV1kNN1kunhc1lFHuJKK3zpgx08/uM=