node:net: hookup the backlog parameter

packages/bun-types/bun.d.ts

@@ -5104,6 +5104,14 @@ declare module "bun" {
      * @default false
      */
     allowHalfOpen?: boolean;
+    /**
+     * Specifies the maximum length of the queue of pending connections. The actual length
+     * will be determined by the OS through sysctl settings such as `tcp_max_syn_backlog`
+     * and `somaxconn` on Linux.
+     *
+     * @default 511
+     */
+    backlog?: number;
   }
 
   interface TCPSocketListenOptions<Data = undefined> extends SocketOptions<Data> {

packages/bun-usockets/src/bsd.c

@@ -956,6 +956,7 @@ inline __attribute__((always_inline)) LIBUS_SOCKET_DESCRIPTOR bsd_bind_listen_fd
     struct addrinfo *listenAddr,
     int port,
     int options,
+    int backlog,
     int* error
 ) {
 
@@ -981,7 +982,7 @@ inline __attribute__((always_inline)) LIBUS_SOCKET_DESCRIPTOR bsd_bind_listen_fd
     }
 #endif
 
-    if (us_internal_bind_and_listen(listenFd, listenAddr->ai_addr, (socklen_t) listenAddr->ai_addrlen, 512, error)) {
+    if (us_internal_bind_and_listen(listenFd, listenAddr->ai_addr, (socklen_t) listenAddr->ai_addrlen, backlog, error)) {
         return LIBUS_SOCKET_ERROR;
     }
 
@@ -990,7 +991,7 @@ inline __attribute__((always_inline)) LIBUS_SOCKET_DESCRIPTOR bsd_bind_listen_fd
 
 // return LIBUS_SOCKET_ERROR or the fd that represents listen socket
 // listen both on ipv6 and ipv4
-LIBUS_SOCKET_DESCRIPTOR bsd_create_listen_socket(const char *host, int port, int options, int* error) {
+LIBUS_SOCKET_DESCRIPTOR bsd_create_listen_socket(const char *host, int port, int options, int backlog, int* error) {
     struct addrinfo hints, *result;
     memset(&hints, 0, sizeof(struct addrinfo));
 
@@ -1015,7 +1016,7 @@ LIBUS_SOCKET_DESCRIPTOR bsd_create_listen_socket(const char *host, int port, int
             }
 
             listenAddr = a;
-            if (bsd_bind_listen_fd(listenFd, listenAddr, port, options, error) != LIBUS_SOCKET_ERROR) {
+            if (bsd_bind_listen_fd(listenFd, listenAddr, port, options, backlog, error) != LIBUS_SOCKET_ERROR) {
                 freeaddrinfo(result);
                 return listenFd;
             }
@@ -1032,7 +1033,7 @@ LIBUS_SOCKET_DESCRIPTOR bsd_create_listen_socket(const char *host, int port, int
             }
 
             listenAddr = a;
-            if (bsd_bind_listen_fd(listenFd, listenAddr, port, options, error) != LIBUS_SOCKET_ERROR) {
+            if (bsd_bind_listen_fd(listenFd, listenAddr, port, options, backlog, error) != LIBUS_SOCKET_ERROR) {
                 freeaddrinfo(result);
                 return listenFd;
             }
@@ -1137,7 +1138,7 @@ static LIBUS_SOCKET_DESCRIPTOR bsd_create_unix_socket_address(const char *path,
     return 0;
 }
 
-static LIBUS_SOCKET_DESCRIPTOR internal_bsd_create_listen_socket_unix(const char* path, int options, struct sockaddr_un* server_address, size_t addrlen, int* error) {
+static LIBUS_SOCKET_DESCRIPTOR internal_bsd_create_listen_socket_unix(const char* path, int options, struct sockaddr_un* server_address, size_t addrlen, int backlog, int* error) {
     LIBUS_SOCKET_DESCRIPTOR listenFd = LIBUS_SOCKET_ERROR;
 
     listenFd = bsd_create_socket(AF_UNIX, SOCK_STREAM, 0, NULL);
@@ -1152,7 +1153,7 @@ static LIBUS_SOCKET_DESCRIPTOR internal_bsd_create_listen_socket_unix(const char
     unlink(path);
 #endif
 
-    if (us_internal_bind_and_listen(listenFd, (struct sockaddr *) server_address, (socklen_t) addrlen, 512, error)) {
+    if (us_internal_bind_and_listen(listenFd, (struct sockaddr *) server_address, (socklen_t) addrlen, backlog, error)) {
         #if defined(_WIN32)
           int shouldSimulateENOENT = WSAGetLastError() == WSAENETDOWN;
         #endif
@@ -1168,7 +1169,7 @@ static LIBUS_SOCKET_DESCRIPTOR internal_bsd_create_listen_socket_unix(const char
     return listenFd;
 }
 
-LIBUS_SOCKET_DESCRIPTOR bsd_create_listen_socket_unix(const char *path, size_t len, int options, int* error) {
+LIBUS_SOCKET_DESCRIPTOR bsd_create_listen_socket_unix(const char *path, size_t len, int options, int backlog, int* error) {
     int dirfd_linux_workaround_for_unix_path_len = -1;
     struct sockaddr_un server_address;
     size_t addrlen = 0;
@@ -1176,7 +1177,7 @@ LIBUS_SOCKET_DESCRIPTOR bsd_create_listen_socket_unix(const char *path, size_t l
         return LIBUS_SOCKET_ERROR;
     }
 
-    LIBUS_SOCKET_DESCRIPTOR listenFd = internal_bsd_create_listen_socket_unix(path, options, &server_address, addrlen, error);
+    LIBUS_SOCKET_DESCRIPTOR listenFd = internal_bsd_create_listen_socket_unix(path, options, &server_address, addrlen, backlog, error);
 
 #if defined(__linux__)
     if (dirfd_linux_workaround_for_unix_path_len != -1) {

packages/bun-usockets/src/context.c

@@ -361,14 +361,14 @@ void us_socket_context_free(int ssl, struct us_socket_context_t *context) {
     us_socket_context_unref(ssl, context);
 }
 
-struct us_listen_socket_t *us_socket_context_listen(int ssl, struct us_socket_context_t *context, const char *host, int port, int options, int socket_ext_size, int* error) {
+struct us_listen_socket_t *us_socket_context_listen(int ssl, struct us_socket_context_t *context, const char *host, int port, int options, int socket_ext_size, int backlog, int* error) {
 #ifndef LIBUS_NO_SSL
     if (ssl) {
-        return us_internal_ssl_socket_context_listen((struct us_internal_ssl_socket_context_t *) context, host, port, options, socket_ext_size, error);
+        return us_internal_ssl_socket_context_listen((struct us_internal_ssl_socket_context_t *) context, host, port, options, socket_ext_size, backlog, error);
     }
 #endif
 
-    LIBUS_SOCKET_DESCRIPTOR listen_socket_fd = bsd_create_listen_socket(host, port, options, error);
+    LIBUS_SOCKET_DESCRIPTOR listen_socket_fd = bsd_create_listen_socket(host, port, options, backlog, error);
 
     if (listen_socket_fd == LIBUS_SOCKET_ERROR) {
         return 0;
@@ -395,14 +395,14 @@ struct us_listen_socket_t *us_socket_context_listen(int ssl, struct us_socket_co
     return ls;
 }
 
-struct us_listen_socket_t *us_socket_context_listen_unix(int ssl, struct us_socket_context_t *context, const char *path, size_t pathlen, int options, int socket_ext_size, int* error) {
+struct us_listen_socket_t *us_socket_context_listen_unix(int ssl, struct us_socket_context_t *context, const char *path, size_t pathlen, int options, int socket_ext_size, int backlog, int* error) {
 #ifndef LIBUS_NO_SSL
     if (ssl) {
-        return us_internal_ssl_socket_context_listen_unix((struct us_internal_ssl_socket_context_t *) context, path, pathlen, options, socket_ext_size, error);
+        return us_internal_ssl_socket_context_listen_unix((struct us_internal_ssl_socket_context_t *) context, path, pathlen, options, socket_ext_size, backlog, error);
     }
 #endif
 
-    LIBUS_SOCKET_DESCRIPTOR listen_socket_fd = bsd_create_listen_socket_unix(path, pathlen, options, error);
+    LIBUS_SOCKET_DESCRIPTOR listen_socket_fd = bsd_create_listen_socket_unix(path, pathlen, options, backlog, error);
 
     if (listen_socket_fd == LIBUS_SOCKET_ERROR) {
         return 0;
@@ -961,4 +961,4 @@ void us_socket_context_on_handshake(int ssl, struct us_socket_context_t *context
         return;
     }
 #endif
-}
+}

packages/bun-usockets/src/crypto/openssl.c

@@ -857,7 +857,7 @@ create_ssl_context_from_options(struct us_socket_context_options_t options) {
 
   if (options.ssl_ciphers) {
     if (!SSL_CTX_set_cipher_list(ssl_context, options.ssl_ciphers)) {
-      unsigned long ssl_err = ERR_get_error(); 
+      unsigned long ssl_err = ERR_get_error();
       if (!(strlen(options.ssl_ciphers) == 0 && ERR_GET_REASON(ssl_err) == SSL_R_NO_CIPHER_MATCH)) {
         // TLS1.2 ciphers were deliberately cleared, so don't consider
         // SSL_R_NO_CIPHER_MATCH to be an error (this is how _set_cipher_suites()
@@ -1300,7 +1300,7 @@ SSL_CTX *create_ssl_context_from_bun_options(
 
   if (options.ssl_ciphers) {
     if (!SSL_CTX_set_cipher_list(ssl_context, options.ssl_ciphers)) {
-      unsigned long ssl_err = ERR_get_error(); 
+      unsigned long ssl_err = ERR_get_error();
       if (!(strlen(options.ssl_ciphers) == 0 && ERR_GET_REASON(ssl_err) == SSL_R_NO_CIPHER_MATCH)) {
         char error_msg[256];
         ERR_error_string_n(ERR_peek_last_error(), error_msg, sizeof(error_msg));
@@ -1308,7 +1308,7 @@ SSL_CTX *create_ssl_context_from_bun_options(
         // SSL_R_NO_CIPHER_MATCH to be an error (this is how _set_cipher_suites()
         // works). If the user actually sets a value (like "no-such-cipher"), then
         // that's actually an error.
-        *err = CREATE_BUN_SOCKET_ERROR_INVALID_CIPHERS;  
+        *err = CREATE_BUN_SOCKET_ERROR_INVALID_CIPHERS;
         free_ssl_context(ssl_context);
         return NULL;
       }
@@ -1579,21 +1579,27 @@ void us_internal_ssl_socket_context_free(
 }
 
 struct us_listen_socket_t *us_internal_ssl_socket_context_listen(
-    struct us_internal_ssl_socket_context_t *context, const char *host,
-    int port, int options, int socket_ext_size, int* error) {
-  return us_socket_context_listen(0, &context->sc, host, port, options,
-                                  sizeof(struct us_internal_ssl_socket_t) -
-                                      sizeof(struct us_socket_t) +
-                                      socket_ext_size, error);
+  struct us_internal_ssl_socket_context_t *context,
+  const char *host,
+  int port,
+  int options,
+  int socket_ext_size,
+  int backlog,
+  int* error
+) {
+  return us_socket_context_listen(0, &context->sc, host, port, options, sizeof(struct us_internal_ssl_socket_t) - sizeof(struct us_socket_t) + socket_ext_size, backlog, error);
 }
 
 struct us_listen_socket_t *us_internal_ssl_socket_context_listen_unix(
-    struct us_internal_ssl_socket_context_t *context, const char *path,
-    size_t pathlen, int options, int socket_ext_size, int* error) {
-  return us_socket_context_listen_unix(0, &context->sc, path, pathlen, options,
-                                       sizeof(struct us_internal_ssl_socket_t) -
-                                           sizeof(struct us_socket_t) +
-                                           socket_ext_size, error);
+  struct us_internal_ssl_socket_context_t *context,
+  const char *path,
+  size_t pathlen,
+  int options,
+  int socket_ext_size,
+  int backlog,
+  int* error
+) {
+  return us_socket_context_listen_unix(0, &context->sc, path, pathlen, options, sizeof(struct us_internal_ssl_socket_t) - sizeof(struct us_socket_t) + socket_ext_size, backlog, error);
 }
 
 // https://github.com/oven-sh/bun/issues/16995

packages/bun-usockets/src/internal/internal.h

@@ -402,11 +402,11 @@ void us_internal_ssl_socket_context_on_socket_connect_error(
 
 struct us_listen_socket_t *us_internal_ssl_socket_context_listen(
     us_internal_ssl_socket_context_r context, const char *host,
-    int port, int options, int socket_ext_size, int* error);
+    int port, int options, int socket_ext_size, int backlog, int* error);
 
 struct us_listen_socket_t *us_internal_ssl_socket_context_listen_unix(
     us_internal_ssl_socket_context_r context, const char *path,
-    size_t pathlen, int options, int socket_ext_size, int* error);
+    size_t pathlen, int options, int socket_ext_size, int backlog, int* error);
 
 struct us_socket_t *us_internal_ssl_socket_context_connect(
     us_internal_ssl_socket_context_r context, const char *host,

packages/bun-usockets/src/internal/networking/bsd.h

@@ -219,9 +219,9 @@ int bsd_would_block();
 
 // return LIBUS_SOCKET_ERROR or the fd that represents listen socket
 // listen both on ipv6 and ipv4
-LIBUS_SOCKET_DESCRIPTOR bsd_create_listen_socket(const char *host, int port, int options, int* error);
+LIBUS_SOCKET_DESCRIPTOR bsd_create_listen_socket(const char *host, int port, int options, int backlog, int* error);
 
-LIBUS_SOCKET_DESCRIPTOR bsd_create_listen_socket_unix(const char *path, size_t pathlen, int options, int* error);
+LIBUS_SOCKET_DESCRIPTOR bsd_create_listen_socket_unix(const char *path, size_t pathlen, int options, int backlog, int* error);
 
 /* Creates an UDP socket bound to the hostname and port */
 LIBUS_SOCKET_DESCRIPTOR bsd_create_udp_socket(const char *host, int port, int options, int *err);

packages/bun-usockets/src/libusockets.h

@@ -310,10 +310,10 @@ void us_socket_context_close(int ssl, us_socket_context_r context);
 
 /* Listen for connections. Acts as the main driving cog in a server. Will call set async callbacks. */
 struct us_listen_socket_t *us_socket_context_listen(int ssl, us_socket_context_r context,
-    const char *host, int port, int options, int socket_ext_size, int* error);
+    const char *host, int port, int options, int socket_ext_size, int backlog, int* error);
 
 struct us_listen_socket_t *us_socket_context_listen_unix(int ssl, us_socket_context_r context,
-    const char *path, size_t pathlen, int options, int socket_ext_size, int* error);
+    const char *path, size_t pathlen, int options, int socket_ext_size, int backlog, int* error);
 
 /* listen_socket.c/.h */
 void us_listen_socket_close(int ssl, struct us_listen_socket_t *ls) nonnull_fn_decl;

packages/bun-uws/src/HttpContext.h

@@ -650,7 +650,7 @@ public:
     /* Listen to port using this HttpContext */
     us_listen_socket_t *listen(const char *host, int port, int options) {
         int error = 0;
-        auto socket = us_socket_context_listen(SSL, getSocketContext(), host, port, options, sizeof(HttpResponseData<SSL>), &error);
+        auto socket = us_socket_context_listen(SSL, getSocketContext(), host, port, options, sizeof(HttpResponseData<SSL>), 511, &error);
         // we dont depend on libuv ref for keeping it alive
         if (socket) {
           us_socket_unref(&socket->s);
@@ -661,7 +661,7 @@ public:
     /* Listen to unix domain socket using this HttpContext */
     us_listen_socket_t *listen_unix(const char *path, size_t pathlen, int options) {
         int error = 0;
-        auto* socket =  us_socket_context_listen_unix(SSL, getSocketContext(), path, pathlen, options, sizeof(HttpResponseData<SSL>), &error);
+        auto* socket =  us_socket_context_listen_unix(SSL, getSocketContext(), path, pathlen, options, sizeof(HttpResponseData<SSL>), 511, &error);
         // we dont depend on libuv ref for keeping it alive
         if (socket) {
             us_socket_unref(&socket->s);

src/bun.js/api/bun/socket/Handlers.zig

@@ -238,6 +238,7 @@ pub const SocketConfig = struct {
     allowHalfOpen: bool = false,
     reusePort: bool = false,
     ipv6Only: bool = false,
+    backlog: i32 = 511,
 
     /// Deinitializes everything and `unprotect`s `handlers`.
     pub fn deinit(this: *SocketConfig) void {

src/bun.js/api/bun/socket/Listener.zig

@@ -155,7 +155,7 @@ pub fn listen(globalObject: *jsc.JSGlobalObject, opts: JSValue) bun.JSError!JSVa
                 .namedPipe = WindowsNamedPipeListeningContext.listen(
                     globalObject,
                     pipe_name,
-                    511,
+                    socket_config.backlog,
                     ssl,
                     this,
                 ) catch return globalObject.throwInvalidArguments(
@@ -249,7 +249,7 @@ pub fn listen(globalObject: *jsc.JSGlobalObject, opts: JSValue) bun.JSError!JSVa
                 const host = bun.handleOom(bun.default_allocator.dupeZ(u8, c.host));
                 defer bun.default_allocator.free(host);
 
-                const socket = socket_context.listen(ssl_enabled, host.ptr, c.port, socket_flags, 8, &errno);
+                const socket = socket_context.listen(ssl_enabled, host.ptr, c.port, socket_flags, 8, socket_config.backlog, &errno);
                 // should return the assigned port
                 if (socket) |s| {
                     connection.host.port = @as(u16, @intCast(s.getLocalPort(ssl_enabled)));
@@ -259,7 +259,7 @@ pub fn listen(globalObject: *jsc.JSGlobalObject, opts: JSValue) bun.JSError!JSVa
             .unix => |u| {
                 const host = bun.handleOom(bun.default_allocator.dupeZ(u8, u));
                 defer bun.default_allocator.free(host);
-                break :brk socket_context.listenUnix(ssl_enabled, host, host.len, socket_flags, 8, &errno);
+                break :brk socket_context.listenUnix(ssl_enabled, host, host.len, socket_flags, 8, socket_config.backlog, &errno);
             },
             .fd => |fd| {
                 const err: bun.jsc.SystemError = .{

src/bun.js/api/bun/socket/SocketConfig.bindv2.ts

@@ -79,5 +79,6 @@ export const SocketConfig = b.dictionary(
       internalName: "unix_", // `unix` is a predefined C macro...
     },
     fd: b.i32.optional,
+    backlog: b.i32.nullable,
   },
 );

src/deps/uws/SocketContext.zig

@@ -208,12 +208,12 @@ pub const SocketContext = opaque {
         c.us_socket_context_free(@intFromBool(ssl), this);
     }
 
-    pub fn listen(this: *SocketContext, ssl: bool, host: ?[*:0]const u8, port: i32, options: i32, socket_ext_size: i32, err: *c_int) ?*ListenSocket {
-        return c.us_socket_context_listen(@intFromBool(ssl), this, host, port, options, socket_ext_size, err);
+    pub fn listen(this: *SocketContext, ssl: bool, host: ?[*:0]const u8, port: i32, options: i32, socket_ext_size: i32, backlog: i32, err: *c_int) ?*ListenSocket {
+        return c.us_socket_context_listen(@intFromBool(ssl), this, host, port, options, socket_ext_size, backlog, err);
     }
 
-    pub fn listenUnix(this: *SocketContext, ssl: bool, path: [*:0]const u8, pathlen: usize, options: i32, socket_ext_size: i32, err: *c_int) ?*ListenSocket {
-        return c.us_socket_context_listen_unix(@intFromBool(ssl), this, path, pathlen, options, socket_ext_size, err);
+    pub fn listenUnix(this: *SocketContext, ssl: bool, path: [*:0]const u8, pathlen: usize, options: i32, socket_ext_size: i32, backlog: i32, err: *c_int) ?*ListenSocket {
+        return c.us_socket_context_listen_unix(@intFromBool(ssl), this, path, pathlen, options, socket_ext_size, backlog, err);
     }
 
     pub fn loop(this: *SocketContext, ssl: bool) ?*Loop {
@@ -259,8 +259,8 @@ pub const c = struct {
     pub extern fn us_socket_context_ext(ssl: i32, context: *SocketContext) ?*anyopaque;
     pub extern fn us_socket_context_free(ssl: i32, context: *SocketContext) void;
     pub extern fn us_socket_context_get_native_handle(ssl: i32, context: *SocketContext) ?*anyopaque;
-    pub extern fn us_socket_context_listen(ssl: i32, context: *SocketContext, host: ?[*:0]const u8, port: i32, options: i32, socket_ext_size: i32, err: *c_int) ?*ListenSocket;
-    pub extern fn us_socket_context_listen_unix(ssl: i32, context: *SocketContext, path: [*:0]const u8, pathlen: usize, options: i32, socket_ext_size: i32, err: *c_int) ?*ListenSocket;
+    pub extern fn us_socket_context_listen(ssl: i32, context: *SocketContext, host: ?[*:0]const u8, port: i32, options: i32, socket_ext_size: i32, backlog: i32, err: *c_int) ?*ListenSocket;
+    pub extern fn us_socket_context_listen_unix(ssl: i32, context: *SocketContext, path: [*:0]const u8, pathlen: usize, options: i32, socket_ext_size: i32, backlog: i32, err: *c_int) ?*ListenSocket;
     pub extern fn us_socket_context_loop(ssl: i32, context: *SocketContext) ?*Loop;
     pub extern fn us_socket_context_on_close(ssl: i32, context: *SocketContext, on_close: ?*const fn (*us_socket_t, i32, ?*anyopaque) callconv(.c) ?*us_socket_t) void;
     pub extern fn us_socket_context_on_connect_error(ssl: i32, context: *SocketContext, on_connect_error: ?*const fn (*uws.ConnectingSocket, i32) callconv(.c) ?*uws.ConnectingSocket) void;

src/js/node/net.ts

@@ -2351,6 +2351,7 @@ Server.prototype[kRealListen] = function (
   contexts,
   _onListen,
   fd,
+  backlog,
 ) {
   if (path) {
     this._handle = Bun.listen({
@@ -2362,6 +2363,7 @@ Server.prototype[kRealListen] = function (
       exclusive: exclusive || this[bunSocketServerOptions]?.exclusive || false,
       socket: ServerHandlers,
       data: this,
+      backlog,
     });
   } else if (fd != null) {
     this._handle = Bun.listen({
@@ -2374,6 +2376,7 @@ Server.prototype[kRealListen] = function (
       exclusive: exclusive || this[bunSocketServerOptions]?.exclusive || false,
       socket: ServerHandlers,
       data: this,
+      backlog,
     });
   } else {
     this._handle = Bun.listen({
@@ -2386,6 +2389,7 @@ Server.prototype[kRealListen] = function (
       exclusive: exclusive || this[bunSocketServerOptions]?.exclusive || false,
       socket: ServerHandlers,
       data: this,
+      backlog,
     });
   }
 
@@ -2494,6 +2498,7 @@ function listenInCluster(
       contexts,
       onListen,
       fd,
+      backlog,
     );
     return;
   }
@@ -2524,6 +2529,7 @@ function listenInCluster(
       contexts,
       onListen,
       fd,
+      backlog,
     );
   });
 }