Fix bugs with connecting to localhost (#3758)

* Fix bugs with connecting to localhost

* Update uws

* More logs

* Allow not setting a hostname

* Make server.hostname & server.protocol faster

* Fixup

* normalize listening host

* Fix test

---------

Co-authored-by: Jarred Sumner <709451+Jarred-Sumner@users.noreply.github.com>

7 files changed, 71 insertions, 38 deletions

diff --git a/src/bun.js/api/bun/socket.zig b/src/bun.js/api/bun/socket.zig
index 2f35a48a5..ce43e3574 100644
--- a/src/bun.js/api/bun/socket.zig
+++ b/src/bun.js/api/bun/socket.zig
@@ -18,6 +18,14 @@ const ZigString = JSC.ZigString;
 const BoringSSL = bun.BoringSSL;
 const X509 = @import("./x509.zig");
 
+fn normalizeListeningHost(host: [:0]const u8) ?[*:0]const u8 {
+    if (host.len == 0 or strings.eqlComptime(host, "0.0.0.0")) {
+        return null;
+    }
+
+    return host.ptr;
+}
+
 // const Corker = struct {
 //     ptr: ?*[16384]u8 = null,
 //     holder: ?*anyopaque = null,
@@ -132,13 +140,6 @@ noinline fn getSSLException(globalThis: *JSC.JSGlobalObject, defaultMessage: []c
 }
 
 fn normalizeHost(input: anytype) @TypeOf(input) {
-    if (input.len == 0) {
-        return "localhost";
-    }
-
-    if (strings.eqlComptime(input, "localhost"))
-        return "127.0.0.1";
-
     return input;
 }
 const BinaryType = JSC.BinaryType;
@@ -650,7 +651,7 @@ pub const Listener = struct {
                     const socket = uws.us_socket_context_listen(
                         @intFromBool(ssl_enabled),
                         socket_context,
-                        normalizeHost(@as([:0]const u8, host)),
+                        normalizeListeningHost(host),
                         c.port,
                         socket_flags,
                         8,
diff --git a/src/bun.js/api/server.zig b/src/bun.js/api/server.zig
index 4da7c6300..801745aee 100644
--- a/src/bun.js/api/server.zig
+++ b/src/bun.js/api/server.zig
@@ -121,7 +121,7 @@ const BlobFileContentResult = struct {
 
 pub const ServerConfig = struct {
     port: u16 = 0,
-    hostname: [*:0]const u8 = "localhost",
+    hostname: ?[*:0]const u8 = null,
 
     // TODO: use webkit URL parser instead of bun's
     base_url: URL = URL{},
@@ -658,7 +658,7 @@ pub const ServerConfig = struct {
 
         var args = ServerConfig{
             .port = 3000,
-            .hostname = "0.0.0.0",
+            .hostname = null,
             .development = true,
         };
         var has_hostname = false;
@@ -874,7 +874,7 @@ pub const ServerConfig = struct {
             }
         } else {
             const hostname: string =
-                if (has_hostname and std.mem.span(args.hostname).len > 0) std.mem.span(args.hostname) else "0.0.0.0";
+                if (has_hostname and std.mem.span(args.hostname.?).len > 0) std.mem.span(args.hostname.?) else "0.0.0.0";
 
             const needsBrackets: bool = strings.isIPV6Address(hostname) and hostname[0] != '[';
 
@@ -4528,6 +4528,9 @@ pub fn NewServer(comptime ssl_enabled_: bool, comptime debug_mode_: bool) type {
         poll_ref: JSC.PollRef = .{},
         temporary_url_buffer: std.ArrayListUnmanaged(u8) = .{},
 
+        cached_hostname: bun.String = bun.String.empty,
+        cached_protocol: bun.String = bun.String.empty,
+
         flags: packed struct(u3) {
             deinit_scheduled: bool = false,
             terminated: bool = false,
@@ -4978,15 +4981,29 @@ pub fn NewServer(comptime ssl_enabled_: bool, comptime debug_mode_: bool) type {
         }
 
         pub fn getHostname(this: *ThisServer, globalThis: *JSGlobalObject) JSC.JSValue {
-            return ZigString.init(bun.span(this.config.hostname)).toValue(globalThis);
+            if (this.cached_hostname.isEmpty()) {
+                if (this.listener) |listener| {
+                    var buf: [1024]u8 = [_]u8{0} ** 1024;
+                    var len: i32 = 1024;
+                    listener.socket().remoteAddress(&buf, &len);
+                    if (len > 0) {
+                        this.cached_hostname = bun.String.create(buf[0..@as(usize, @intCast(len))]);
+                    }
+                }
+
+                if (this.cached_hostname.isEmpty())
+                    this.cached_hostname = bun.String.create(bun.span(this.config.hostname orelse "localhost"));
+            }
+
+            return this.cached_hostname.toJS(globalThis);
         }
 
-        pub fn getProtocol(_: *ThisServer, globalThis: *JSGlobalObject) JSC.JSValue {
-            if (comptime ssl_enabled) {
-                return ZigString.init("https:").toValue(globalThis);
-            } else {
-                return ZigString.init("http:").toValue(globalThis);
+        pub fn getProtocol(this: *ThisServer, globalThis: *JSGlobalObject) JSC.JSValue {
+            if (this.cached_protocol.isEmpty()) {
+                this.cached_protocol = bun.String.create(if (ssl_enabled) "https" else "http");
             }
+
+            return this.cached_protocol.toJS(globalThis);
         }
 
         pub fn getDevelopment(
@@ -5064,6 +5081,17 @@ pub fn NewServer(comptime ssl_enabled_: bool, comptime debug_mode_: bool) type {
 
         pub fn deinit(this: *ThisServer) void {
             httplog("deinit", .{});
+            this.cached_hostname.deref();
+            this.cached_protocol.deref();
+
+            if (this.config.hostname) |host| {
+                bun.default_allocator.destroy(host);
+            }
+
+            if (this.config.base_url.href.len > 0) {
+                bun.default_allocator.free(this.config.base_url.href);
+            }
+
             this.app.destroy();
             const allocator = this.allocator;
             allocator.destroy(this);
@@ -5438,22 +5466,18 @@ pub fn NewServer(comptime ssl_enabled_: bool, comptime debug_mode_: bool) type {
 
                 this.app.get("/src:/*", *ThisServer, this, onSrcRequest);
             }
-
-            const hostname = bun.span(this.config.hostname);
-
-            // When "localhost" is specified, we omit the hostname entirely
-            // Otherwise, "curl http://localhost:3000" doesn't actually work due to IPV6 vs IPV4 issues
-            // This prints a spurious log si_destination_compare on macOS but only when debugger is connected
-            var host: [*:0]const u8 = undefined;
+            var host: ?[*:0]const u8 = null;
             var host_buff: [1024:0]u8 = undefined;
 
-            if (hostname.len == 0 or (!ssl_enabled and strings.eqlComptime(hostname, "localhost"))) {
-                host = "";
-            } else if (hostname.len > 2 and hostname[0] == '[') {
-                // remove "[" and "]" from hostname
-                host = std.fmt.bufPrintZ(&host_buff, "{s}", .{hostname[1 .. hostname.len - 1]}) catch unreachable;
-            } else {
-                host = this.config.hostname;
+            if (this.config.hostname) |existing| {
+                const hostname = bun.span(existing);
+
+                if (hostname.len > 2 and hostname[0] == '[') {
+                    // remove "[" and "]" from hostname
+                    host = std.fmt.bufPrintZ(&host_buff, "{s}", .{hostname[1 .. hostname.len - 1]}) catch unreachable;
+                } else {
+                    host = this.config.hostname;
+                }
             }
 
             this.ref();
diff --git a/src/deps/uws b/src/deps/uws
-Subproject f29c6e24c33483c342bbc83c41cc032f42fbf77
+Subproject 0e9ddbe6944c3ca6b6957e5938d77d8ed9a8181
diff --git a/src/deps/uws.zig b/src/deps/uws.zig
index 15e6eaa68..43711e696 100644
--- a/src/deps/uws.zig
+++ b/src/deps/uws.zig
@@ -285,6 +285,8 @@ pub fn NewSocketHandler(comptime is_ssl: bool) type {
             ctx: Context,
             comptime socket_field_name: []const u8,
         ) ?*Context {
+            debug("connect({s}, {d})", .{ host, port });
+
             var stack_fallback = std.heap.stackFallback(1024, bun.default_allocator);
             var allocator = stack_fallback.get();
             var host_ = allocator.dupeZ(u8, host) catch return null;
@@ -333,6 +335,7 @@ pub fn NewSocketHandler(comptime is_ssl: bool) type {
             socket_ctx: *SocketContext,
             ctx: *anyopaque,
         ) ?ThisSocket {
+            debug("connect(unix:{s})", .{path});
             var stack_fallback = std.heap.stackFallback(1024, bun.default_allocator);
             var allocator = stack_fallback.get();
             var path_ = allocator.dupeZ(u8, path) catch return null;
@@ -356,6 +359,7 @@ pub fn NewSocketHandler(comptime is_ssl: bool) type {
             socket_ctx: *SocketContext,
             ptr: *anyopaque,
         ) ?ThisSocket {
+            debug("connect({s}, {d})", .{ host, port });
             var stack_fallback = std.heap.stackFallback(1024, bun.default_allocator);
             var allocator = stack_fallback.get();
             var host_ = allocator.dupeZ(u8, host) catch return null;
@@ -952,9 +956,9 @@ extern fn us_socket_context_on_connect_error(ssl: i32, context: ?*SocketContext,
 extern fn us_socket_context_on_end(ssl: i32, context: ?*SocketContext, on_end: *const fn (*Socket) callconv(.C) ?*Socket) void;
 extern fn us_socket_context_ext(ssl: i32, context: ?*SocketContext) ?*anyopaque;
 
-pub extern fn us_socket_context_listen(ssl: i32, context: ?*SocketContext, host: [*c]const u8, port: i32, options: i32, socket_ext_size: i32) ?*ListenSocket;
+pub extern fn us_socket_context_listen(ssl: i32, context: ?*SocketContext, host: ?[*:0]const u8, port: i32, options: i32, socket_ext_size: i32) ?*ListenSocket;
 pub extern fn us_socket_context_listen_unix(ssl: i32, context: ?*SocketContext, path: [*c]const u8, options: i32, socket_ext_size: i32) ?*ListenSocket;
-pub extern fn us_socket_context_connect(ssl: i32, context: ?*SocketContext, host: [*c]const u8, port: i32, source_host: [*c]const u8, options: i32, socket_ext_size: i32) ?*Socket;
+pub extern fn us_socket_context_connect(ssl: i32, context: ?*SocketContext, host: ?[*:0]const u8, port: i32, source_host: [*c]const u8, options: i32, socket_ext_size: i32) ?*Socket;
 pub extern fn us_socket_context_connect_unix(ssl: i32, context: ?*SocketContext, path: [*c]const u8, options: i32, socket_ext_size: i32) ?*Socket;
 pub extern fn us_socket_is_established(ssl: i32, s: ?*Socket) i32;
 pub extern fn us_socket_close_connecting(ssl: i32, s: ?*Socket) ?*Socket;
@@ -1431,6 +1435,10 @@ pub fn NewApp(comptime ssl: bool) type {
                 }
                 return us_socket_local_port(ssl_flag, @as(*uws.Socket, @ptrCast(this)));
             }
+
+            pub fn socket(this: *@This()) NewSocketHandler(ssl) {
+                return .{ .socket = @ptrCast(this) };
+            }
         };
 
         pub fn get(
@@ -2015,7 +2023,7 @@ extern fn uws_app_listen_with_config(
 extern fn uws_constructor_failed(ssl: i32, app: *uws_app_t) bool;
 extern fn uws_num_subscribers(ssl: i32, app: *uws_app_t, topic: [*c]const u8, topic_length: usize) c_uint;
 extern fn uws_publish(ssl: i32, app: *uws_app_t, topic: [*c]const u8, topic_length: usize, message: [*c]const u8, message_length: usize, opcode: Opcode, compress: bool) bool;
-extern fn uws_get_native_handle(ssl: i32, app: *uws_app_t) ?*anyopaque;
+extern fn uws_get_native_handle(ssl: i32, app: *anyopaque) ?*anyopaque;
 extern fn uws_remove_server_name(ssl: i32, app: *uws_app_t, hostname_pattern: [*c]const u8) void;
 extern fn uws_add_server_name(ssl: i32, app: *uws_app_t, hostname_pattern: [*c]const u8) void;
 extern fn uws_add_server_name_with_options(ssl: i32, app: *uws_app_t, hostname_pattern: [*c]const u8, options: us_bun_socket_context_options_t) void;
diff --git a/src/feature_flags.zig b/src/feature_flags.zig
index 0a0c920a4..6c19df844 100644
--- a/src/feature_flags.zig
+++ b/src/feature_flags.zig
@@ -104,7 +104,7 @@ pub const disable_lolhtml = false;
 /// on macOS that specifically impacts localhost and not
 /// other ipv4 hosts. This is a workaround for that.
 /// "localhost" fails to connect.
-pub const hardcode_localhost_to_127_0_0_1 = true;
+pub const hardcode_localhost_to_127_0_0_1 = false;
 
 /// React doesn't do anything with jsxs
 /// If the "jsxs" import is development, "jsxs" isn't supported
diff --git a/test/js/bun/net/tcp-server.test.ts b/test/js/bun/net/tcp-server.test.ts
index 18fa29231..ef8026a6c 100644
--- a/test/js/bun/net/tcp-server.test.ts
+++ b/test/js/bun/net/tcp-server.test.ts
@@ -33,7 +33,7 @@ it("remoteAddress works", async () => {
       data() {},
     },
     port: 0,
-    hostname: "localhost",
+    hostname: "127.0.0.1",
   });
 
   await Bun.connect({
diff --git a/test/js/bun/websocket/websocket-server.test.ts b/test/js/bun/websocket/websocket-server.test.ts
index 191bb6f92..dfe23e57f 100644
--- a/test/js/bun/websocket/websocket-server.test.ts
+++ b/test/js/bun/websocket/websocket-server.test.ts
@@ -2,7 +2,7 @@ import { describe, it, expect, afterEach } from "bun:test";
 import type { Server, Subprocess, WebSocketHandler } from "bun";
 import { serve, spawn } from "bun";
 import { bunEnv, bunExe, nodeExe } from "harness";
-
+import { isIP } from "node:net";
 const strings = [
   {
     label: "string (ascii)",
@@ -219,7 +219,7 @@ describe("ServerWebSocket", () => {
   }));
   test("remoteAddress", done => ({
     open(ws) {
-      expect(ws.remoteAddress).toMatch(/^(?:[0-9]{1,3}\.){3}[0-9]{1,3}$/);
+      expect(isIP(ws.remoteAddress)).toBeGreaterThan(0);
       done();
     },
   }));