Emscripten: Experimental -sPROXY_POSIX_SOCKETS support

...see
<https://emscripten.org/docs/porting/networking.html#full-posix-sockets-over-websocket-proxy-server>.

This requires
<4aff1f28b8>
"-sPROXY_POSIX_SOCKETS: Add websocket_proxy_poll".  When configured with
--disable-socketpair (which appears to have no negative consequences),
external/curl appears to only call poll(2) with socket-related file descriptors,
so we can use websocket_proxy_poll instead.

The URL on which the websocket_to_posix_proxy process listens must be specified
as Module.uno_websocket_to_posix_socket_url.

Change-Id: I4ad23098b5bbc0646fa50859c0aeb9870d1cc92a
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/172243
Reviewed-by: Stephan Bergmann <stephan.bergmann@allotropia.de>
Tested-by: Jenkins

config_host.mk.in

@@ -175,6 +175,7 @@ export ENABLE_DEBUG=@ENABLE_DEBUG@
 ENABLE_DOTNET=@ENABLE_DOTNET@
 SYSTEM_DRAGONBOX=@SYSTEM_DRAGONBOX@
 SYSTEM_FROZEN=@SYSTEM_FROZEN@
+export ENABLE_EMSCRIPTEN_PROXY_POSIX_SOCKETS=@ENABLE_EMSCRIPTEN_PROXY_POSIX_SOCKETS@
 export ENABLE_EPOXY=@ENABLE_EPOXY@
 export ENABLE_EOT=@ENABLE_EOT@
 export ENABLE_EVOAB2=@ENABLE_EVOAB2@

config_host/config_emscripten.h.in

@@ -0,0 +1,14 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4; fill-column: 100 -*- */
+/*
+ * This file is part of the LibreOffice project.
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ */
+
+#pragma once
+
+#define HAVE_EMSCRIPTEN_PROXY_POSIX_SOCKETS 0
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab cinoptions=b1,g0,N-s cinkeys+=0=break: */

configure.ac

@@ -2166,6 +2166,15 @@ AC_ARG_WITH(main-module,
         Default value is 'writer'.]),
 ,)
 
+if test "$_os" = Emscripten; then
+    AC_ARG_ENABLE(emscripten-proxy-posix-sockets,
+        AS_HELP_STRING([--enable-emscripten-proxy-posix-sockets],
+            [Enable experimental Emscripten support for full POSIX sockets over WebSocket proxy
+             server (-sPROXY_POSIX_SOCKETS).]))
+else
+    enable_emscripten_proxy_posix_sockets=
+fi
+
 AC_ARG_ENABLE(xmlhelp,
     AS_HELP_STRING([--disable-xmlhelp],
         [Disable XML help support]),
@@ -4238,6 +4247,14 @@ AC_SUBST(ENABLE_WASM_STRIP)
 AC_SUBST(ENABLE_WASM_STRIP_WRITER)
 AC_SUBST(ENABLE_WASM_STRIP_CALC)
 
+if test "$enable_emscripten_proxy_posix_sockets" = yes; then
+    ENABLE_EMSCRIPTEN_PROXY_POSIX_SOCKETS=TRUE
+    AC_DEFINE(HAVE_EMSCRIPTEN_PROXY_POSIX_SOCKETS)
+else
+    ENABLE_EMSCRIPTEN_PROXY_POSIX_SOCKETS=
+fi
+AC_SUBST(ENABLE_EMSCRIPTEN_PROXY_POSIX_SOCKETS)
+
 # Use -isystem (gcc) if possible, to avoid warnings in 3rd party headers.
 # NOTE: must _not_ be used for bundled external libraries!
 ISYSTEM=
@@ -15697,6 +15714,7 @@ AC_CONFIG_HEADERS([config_host/config_cairo_canvas.h])
 AC_CONFIG_HEADERS([config_host/config_cairo_rgba.h])
 AC_CONFIG_HEADERS([config_host/config_cxxabi.h])
 AC_CONFIG_HEADERS([config_host/config_dbus.h])
+AC_CONFIG_HEADERS([config_host/config_emscripten.h])
 AC_CONFIG_HEADERS([config_host/config_features.h])
 AC_CONFIG_HEADERS([config_host/config_feature_desktop.h])
 AC_CONFIG_HEADERS([config_host/config_feature_opencl.h])

desktop/source/app/app.cxx

@@ -18,6 +18,7 @@
  */
 
 #include <memory>
+#include <config_emscripten.h>
 #include <config_features.h>
 #include <config_feature_desktop.h>
 #include <config_feature_opencl.h>
@@ -150,6 +151,15 @@
 #define GETPID getpid
 #endif
 
+#if HAVE_EMSCRIPTEN_PROXY_POSIX_SOCKETS
+#include <stdexcept>
+#include <string>
+#include <emscripten/posix_socket.h>
+#include <emscripten/threading.h>
+#include <emscripten/val.h>
+#include <emscripten/websocket.h>
+#endif
+
 #include <strings.hxx>
 
 using namespace ::com::sun::star::awt;
@@ -547,6 +557,35 @@ void Desktop::Init()
         RequestHandler::Disable();
     }
     pSignalHandler = osl_addSignalHandler(SalMainPipeExchangeSignal_impl, nullptr);
+
+#if HAVE_EMSCRIPTEN_PROXY_POSIX_SOCKETS
+    {
+        auto const val = emscripten::val::module_property("uno_websocket_to_posix_socket_url");
+        if (val.isUndefined()) {
+            throw std::runtime_error("Module.uno_websocket_to_posix_socket_url is undefined");
+        } else {
+            auto const url = val.as<std::string>();
+            if (url.find('\0') != std::string::npos) {
+                throw std::runtime_error(
+                    "Module.uno_websocket_to_posix_socket_url contains embedded NUL");
+            }
+            SAL_INFO("desktop.app", "connecting to <" << url << ">");
+            static auto const socket = emscripten_init_websocket_to_posix_socket_bridge(
+                url.c_str());
+            // 0 is CONNECTING, 1 is OPEN, see
+            // <https://websockets.spec.whatwg.org/#websocket-ready-state>:
+            unsigned short readyState = 0;
+            do {
+                emscripten_websocket_get_ready_state(socket, &readyState);
+                emscripten_thread_sleep(100);
+            } while (readyState == 0);
+            if (readyState != 1) {
+                throw std::runtime_error("could not connect to <" + url + ">");
+            }
+            SAL_INFO("desktop.app", "connected to <" << url << ">");
+        }
+    }
+#endif
 }
 
 void Desktop::InitFinished()

external/curl/ExternalProject_curl.mk

@@ -65,6 +65,7 @@ $(call gb_ExternalProject_get_state_target,curl,build):
 			$(if $(filter MACOSX,$(OS)),--prefix=/@.__________________________________________________OOO) \
 			$(if $(filter MACOSX,$(OS)),CFLAGS='$(CFLAGS) \
 				-mmacosx-version-min=$(MACOSX_DEPLOYMENT_TARGET)') \
+			$(if $(ENABLE_EMSCRIPTEN_PROXY_POSIX_SOCKETS),--disable-socketpair) \
 			$(if $(filter -fsanitize=undefined,$(CC)),CC='$(CC) -fno-sanitize=function') \
 			CPPFLAGS='$(curl_CPPFLAGS)' \
 			CFLAGS="$(gb_CFLAGS) $(call gb_ExternalProject_get_build_flags,curl)" \

external/curl/UnpackedTarball_curl.mk

@@ -33,4 +33,10 @@ $(eval $(call gb_UnpackedTarball_add_patches,curl, \
 ))
 endif
 
+ifeq ($(ENABLE_EMSCRIPTEN_PROXY_POSIX_SOCKETS),TRUE)
+$(eval $(call gb_UnpackedTarball_add_patches,curl, \
+    external/curl/emscripten-proxy-poll.patch.0 \
+))
+endif
+
 # vim: set noet sw=4 ts=4:

external/curl/emscripten-proxy-poll.patch.0

@@ -0,0 +1,20 @@
+--- lib/select.c
++++ lib/select.c
+@@ -51,6 +51,8 @@
+ #include "curl_printf.h"
+ #include "curl_memory.h"
+ #include "memdebug.h"
++
++int websocket_proxy_poll(struct pollfd *fds, nfds_t nfds, int timeout);
+ 
+ /*
+  * Internal function used for waiting a specific amount of ms
+@@ -318,7 +320,7 @@
+     pending_ms = -1;
+   else
+     pending_ms = 0;
+-  r = poll(ufds, nfds, pending_ms);
++  r = websocket_proxy_poll(ufds, nfds, pending_ms);
+   if(r <= 0) {
+     if((r == -1) && (SOCKERRNO == EINTR))
+       /* make EINTR from select or poll not a "lethal" error */

solenv/gbuild/platform/EMSCRIPTEN_INTEL_GCC.mk

@@ -26,6 +26,10 @@ gb_EMSCRIPTEN_LDFLAGS += -sSTACK_SIZE=131072 -sDEFAULT_PTHREAD_STACK_SIZE=65536
 gb_EMSCRIPTEN_LDFLAGS += --bind -s FORCE_FILESYSTEM=1 -s WASM_BIGINT=1 -s ERROR_ON_UNDEFINED_SYMBOLS=1 -s FETCH=1 -s ASSERTIONS=1 -s EXIT_RUNTIME=0 -s EXPORTED_RUNTIME_METHODS=["UTF16ToString","stringToUTF16","UTF8ToString","ccall","cwrap","addOnPreMain","addOnPostRun","registerType","throwBindingError"$(if $(ENABLE_QT6),$(COMMA)"callMain"$(COMMA)"specialHTMLTargets")]
 gb_EMSCRIPTEN_QTDEFS := -DQT_NO_LINKED_LIST -DQT_NO_JAVA_STYLE_ITERATORS -DQT_NO_EXCEPTIONS -DQT_NO_DEBUG -DQT_WIDGETS_LIB -DQT_GUI_LIB -DQT_CORE_LIB
 
+ifeq ($(ENABLE_EMSCRIPTEN_PROXY_POSIX_SOCKETS),TRUE)
+gb_EMSCRIPTEN_LDFLAGS += -sPROXY_POSIX_SOCKETS -lwebsocket.js
+endif
+
 gb_Executable_EXT := .html
 gb_EMSCRIPTEN_EXCEPT = -fwasm-exceptions -s SUPPORT_LONGJMP=wasm