From 7775a19ffab7588c837a7a65b00df2696fd91de7 Mon Sep 17 00:00:00 2001
From: eyedeekay <hankhill19580@gmail.com>
Date: Mon, 26 May 2025 17:54:53 -0400
Subject: [PATCH] work on tcp lib

---
 tcp/listen.go      | 58 ++++++++++++++++++++++++++++------------------
 tcp/listen_test.go | 35 ++++++++++++++++++++++++++++
 2 files changed, 70 insertions(+), 23 deletions(-)

diff --git a/tcp/listen.go b/tcp/listen.go
index e302ebb..41d5111 100644
--- a/tcp/listen.go
+++ b/tcp/listen.go
@@ -35,7 +35,7 @@ const (
 func Listen(network, address string) (net.Listener, error) {
 	// Validate network parameter
 	if !isValidNetwork(network) {
-		return nil, fmt.Errorf("tcp.Listen: invalid network type %q, must be tcp, tcp4, or tcp6", network)
+		return nil, fmt.Errorf("tcp.Listen: invalid network type %q for addr %s, must be tcp, tcp4, or tcp6", network, address)
 	}
 
 	// Validate address format by attempting to resolve
@@ -77,33 +77,45 @@ func isValidNetwork(network string) bool {
 
 // configureSocket applies production-ready socket options to the TCP listener
 func configureSocket(listener *net.TCPListener) error {
-	// Get the underlying file descriptor for socket configuration
-	file, err := listener.File()
+	// Use SyscallConn to access the raw socket without duplicating the file descriptor
+	rawConn, err := listener.SyscallConn()
 	if err != nil {
-		return fmt.Errorf("failed to get listener file descriptor: %w", err)
-	}
-	defer file.Close()
-
-	fd := int(file.Fd())
-
-	// Enable SO_REUSEADDR to prevent "address already in use" errors
-	if err := syscall.SetsockoptInt(fd, syscall.SOL_SOCKET, syscall.SO_REUSEADDR, 1); err != nil {
-		return fmt.Errorf("failed to set SO_REUSEADDR: %w", err)
+		return fmt.Errorf("failed to get listener syscall connection: %w", err)
 	}
 
-	// Set receive buffer size for optimal throughput
-	if err := syscall.SetsockoptInt(fd, syscall.SOL_SOCKET, syscall.SO_RCVBUF, bufferSize); err != nil {
-		return fmt.Errorf("failed to set receive buffer size: %w", err)
-	}
+	// Apply socket options using the raw connection
+	var sockErr error
+	err = rawConn.Control(func(fd uintptr) {
+		// Enable SO_REUSEADDR to prevent "address already in use" errors
+		if err := syscall.SetsockoptInt(int(fd), syscall.SOL_SOCKET, syscall.SO_REUSEADDR, 1); err != nil {
+			sockErr = fmt.Errorf("failed to set SO_REUSEADDR: %w", err)
+			return
+		}
 
-	// Set send buffer size for optimal throughput
-	if err := syscall.SetsockoptInt(fd, syscall.SOL_SOCKET, syscall.SO_SNDBUF, bufferSize); err != nil {
-		return fmt.Errorf("failed to set send buffer size: %w", err)
-	}
+		// Set receive buffer size for optimal throughput
+		if err := syscall.SetsockoptInt(int(fd), syscall.SOL_SOCKET, syscall.SO_RCVBUF, bufferSize); err != nil {
+			sockErr = fmt.Errorf("failed to set receive buffer size: %w", err)
+			return
+		}
 
-	// Enable TCP_NODELAY to minimize latency (disable Nagle's algorithm)
-	if err := syscall.SetsockoptInt(fd, syscall.IPPROTO_TCP, syscall.TCP_NODELAY, 1); err != nil {
-		return fmt.Errorf("failed to set TCP_NODELAY: %w", err)
+		// Set send buffer size for optimal throughput
+		if err := syscall.SetsockoptInt(int(fd), syscall.SOL_SOCKET, syscall.SO_SNDBUF, bufferSize); err != nil {
+			sockErr = fmt.Errorf("failed to set send buffer size: %w", err)
+			return
+		}
+
+		// Enable TCP_NODELAY to minimize latency (disable Nagle's algorithm)
+		if err := syscall.SetsockoptInt(int(fd), syscall.IPPROTO_TCP, syscall.TCP_NODELAY, 1); err != nil {
+			sockErr = fmt.Errorf("failed to set TCP_NODELAY: %w", err)
+			return
+		}
+	})
+
+	if err != nil {
+		return fmt.Errorf("failed to access socket for configuration: %w", err)
+	}
+	if sockErr != nil {
+		return sockErr
 	}
 
 	return nil
diff --git a/tcp/listen_test.go b/tcp/listen_test.go
index fbfe08e..bdd6f53 100644
--- a/tcp/listen_test.go
+++ b/tcp/listen_test.go
@@ -258,3 +258,38 @@ func BenchmarkListen(b *testing.B) {
 		listener.Close()
 	}
 }
+
+func TestConfigureSocket_NoResourceLeak(t *testing.T) {
+	// Create a listener
+	listener, err := net.Listen("tcp", ":0")
+	if err != nil {
+		t.Fatalf("Failed to create base listener: %v", err)
+	}
+	defer listener.Close()
+
+	tcpListener := listener.(*net.TCPListener)
+
+	// Configure the socket - this should not invalidate the listener
+	err = configureSocket(tcpListener)
+	if err != nil {
+		t.Fatalf("Socket configuration failed: %v", err)
+	}
+
+	// Verify the listener is still usable by accepting a connection
+	addr := listener.Addr().String()
+
+	// Test connection in a goroutine
+	go func() {
+		conn, err := net.Dial("tcp", addr)
+		if err == nil {
+			conn.Close()
+		}
+	}()
+
+	// This should succeed if the listener wasn't invalidated
+	conn, err := listener.Accept()
+	if err != nil {
+		t.Fatalf("Listener became unusable after configuration: %v", err)
+	}
+	conn.Close()
+}