Fix the sync causing proxy to freak out

proxy/manager_test.go

@@ -0,0 +1,87 @@
+package proxy
+
+import (
+	"context"
+	"net/netip"
+	"os"
+	"strings"
+	"testing"
+	"time"
+
+	"github.com/fosrl/newt/internal/telemetry"
+	"github.com/fosrl/newt/logger"
+	"golang.zx2c4.com/wireguard/tun/netstack"
+)
+
+// TestRemoveTargetStopsAcceptLoop verifies that removing a TCP target on a
+// netstack-backed ProxyManager causes the accept loop goroutine to actually
+// stop retrying, instead of spinning forever logging
+// "Error accepting TCP connection: ... endpoint is in invalid state".
+func TestRemoveTargetStopsAcceptLoop(t *testing.T) {
+	if _, err := telemetry.Init(context.Background(), telemetry.Config{ServiceName: "test"}); err != nil {
+		t.Fatalf("telemetry.Init: %v", err)
+	}
+
+	logFile, err := os.CreateTemp(t.TempDir(), "newt-proxy-test-*.log")
+	if err != nil {
+		t.Fatalf("CreateTemp: %v", err)
+	}
+	defer logFile.Close()
+	logger.SetOutput(logFile)
+	defer logger.SetOutput(os.Stdout)
+
+	_, tnet, err := netstack.CreateNetTUN(
+		[]netip.Addr{netip.MustParseAddr("100.64.0.1")},
+		[]netip.Addr{},
+		1420,
+	)
+	if err != nil {
+		t.Fatalf("CreateNetTUN: %v", err)
+	}
+
+	pm := NewProxyManager(tnet)
+	const listenIP = "100.64.0.1"
+	const port = 53405
+
+	if err := pm.AddTarget("tcp", listenIP, port, "127.0.0.1:9999"); err != nil {
+		t.Fatalf("AddTarget: %v", err)
+	}
+	if err := pm.Start(); err != nil {
+		t.Fatalf("Start: %v", err)
+	}
+
+	if err := pm.RemoveTarget("tcp", listenIP, port); err != nil {
+		t.Fatalf("RemoveTarget: %v", err)
+	}
+
+	// If the bug is present, the accept loop spins every 100ms logging an
+	// error forever. Sample the log twice, 400ms apart; a healthy accept
+	// loop logs the error/close message once (or zero times) and then goes
+	// silent, while the buggy loop keeps appending.
+	time.Sleep(200 * time.Millisecond)
+	countAt1 := countAcceptErrors(t, logFile.Name())
+
+	time.Sleep(400 * time.Millisecond)
+	countAt2 := countAcceptErrors(t, logFile.Name())
+
+	t.Logf("accept-error-ish log lines: at 200ms=%d, at 600ms=%d", countAt1, countAt2)
+
+	if countAt2 > countAt1 {
+		t.Fatalf("accept loop kept logging after RemoveTarget (200ms=%d, 600ms=%d) -- it is spinning forever on the closed netstack listener instead of exiting", countAt1, countAt2)
+	}
+}
+
+func countAcceptErrors(t *testing.T, path string) int {
+	t.Helper()
+	data, err := os.ReadFile(path)
+	if err != nil {
+		t.Fatalf("ReadFile: %v", err)
+	}
+	count := 0
+	for _, line := range strings.Split(string(data), "\n") {
+		if strings.Contains(line, "Error accepting TCP connection") {
+			count++
+		}
+	}
+	return count
+}