Liyi Meng
f35530b523
Microsoft Remote Desktop for Mac was observed to garble Chinese text typed through its local Pinyin IME: the composed characters would land with pieces missing or extra characters deleted from the document. Root cause, confirmed with debug logging plus dbus-monitor on the live ibus session bus: the client forwards the raw pre-composition keystrokes over the normal RDP keyboard channel while composing (these reach XrdpIme's process-key-event handler and, since it never consumes anything, get typed into the document as literal ASCII), then once composition finishes sends a compensating burst of Backspace keystrokes sized to exactly undo them, interleaved with the final composed text arriving over the separate TS_UNICODE_KEYBOARD_EVENT side channel. The two channels have no ordering guarantee, so the side-channel commit could land in the middle of the client's own backspace cleanup and get partially deleted. Measured the backspace burst against the leaked raw-character count across several phrases (23-for-23, 29-for-29) - it's always exactly right, so this is a pure interleaving race, not a client miscount. That makes it fixable server-side: xrdp_input_queue_source_prepare/ _check now withhold a queued commit until raw key traffic on the engine has been quiet for XRDP_INPUT_COMMIT_QUIET_US (100ms), so the client's own cleanup has time to finish first, capped by XRDP_INPUT_COMMIT_MAX_WAIT_US (500ms) so back-to-back composition can't delay a commit indefinitely. This is an empirical mitigation tuned to observed client behaviour, not a protocol guarantee. Also fixes two latent data races found while reviewing this code against the cross-thread invariants already documented at the top of the file: g_engine and last_input_name are written by the IBus thread (engine enable/disable, an unexpected daemon disconnect) but were read and, for last_input_name, also written directly by xrdp_input_enable() on chansrv's own thread with no synchronization - unlike `bus`, which already gets this treatment. Both now follow the same publish/clear-under-state_mutex pattern as `bus`. Added IBUS-KEY/IBUS-COMMIT debug logging used to diagnose this. Verified live against a real Microsoft Remote Desktop for Mac client connected to an xrdp/ibus session: multiple Chinese phrases of varying length composed and committed cleanly with the debounce in place, after reliably reproducing the interleaved garbling without it. Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
xrdp - an open source RDP server
Overview
xrdp provides a graphical login to remote machines using Microsoft Remote Desktop Protocol (RDP). xrdp accepts connections from a variety of RDP clients:
- FreeRDP
- rdesktop
- KRDC
- NeutrinoRDP
- Windows MSTSC (Microsoft Terminal Services Client, aka
mstsc.exe) - Microsoft Remote Desktop (found on Microsoft Store, which is distinct from MSTSC)
Many of these work on some or all of Windows, Mac OS, iOS, and/or Android.
RDP transport is encrypted using TLS by default.
Features
Remote Desktop Access
- Connect to a Linux desktop using RDP from anywhere (requires xorgxrdp Xorg module)
- Reconnect to an existing session
- Session resizing (both on-connect and on-the-fly)
- RDP/VNC proxy (connect to another RDP/VNC server via xrdp)
Access to Remote Resources
- Two-way clipboard transfer (text, bitmap, file)
- Audio redirection (requires to build additional modules)
- Microphone redirection (requires to build additional modules)
- Drive redirection (mount local client drives on remote machine)
Supported Platforms
xrdp primarily targets GNU/Linux operating system. x86 (including x86-64) and ARM processors are most mature architecture to run xrdp on. See also Platform Support Tier.
Some components such as xorgxrdp and RemoteFX codec have special optimization for x86 using SIMD instructions. So running xrdp on x86 processors will get fully accelerated experience.
Quick Start
Most Linux distributions should distribute the latest release of xrdp in their repository. You would need xrdp and xorgxrdp packages for the best experience. It is recommended that xrdp depends on xorgxrdp, so it should be sufficient to install xrdp. If xorgxrdp is not provided, use Xvnc server.
xrdp listens on 3389/tcp. Make sure your firewall accepts connection to 3389/tcp from where you want to access.
Ubuntu / Debian
apt install xrdp
Fedora, RHEL and derivatives
If you're not running Fedora, make sure to enable EPEL packages first.
dnf install epel-release
(All systems) Install xrdp with:-
dnf install xrdp
Compiling
See also https://github.com/neutrinolabs/xrdp/wiki#building-from-sources
Prerequisites
To compile xrdp from the packaged sources, you need basic build tools - a compiler (gcc or clang) and the make program. Additionally, you would need openssl-devel, pam-devel, libX11-devel, libXfixes-devel, libXrandr-devel. More additional software would be needed depending on your configuration.
To compile xrdp from a checked out git repository, you would additionally need autoconf, automake, libtool and pkg-config.
Get the source and build it
If compiling from the packaged source, unpack the tarball and change to the resulting directory.
If compiling from a checked out repository, please make sure you've got the submodules
cloned too (use git clone --recursive https://github.com/neutrinolabs/xrdp)
Then run following commands to compile and install xrdp:
./bootstrap
./configure
make
sudo make install
If you want to use audio redirection, you need to build and install additional pulseaudio modules. The build instructions can be found at wiki.
Directory Structure
xrdp
├── common ······ common code
├── docs ········ documentation
├── fontutils ··· font handling utilities
├── genkeymap ··· keymap generator
├── instfiles ··· installable data file
├── keygen ······ xrdp RSA key pair generator
├── libpainter ·· painter library
├── librfxcodec · RFX codec library
├── libxrdp ····· core RDP protocol implementation
├── m4 ·········· Autoconf macros
├── mc ·········· media center module
├── neutrinordp · RDP client module for proxying RDP connections using NeutrinoRDP
├── pkgconfig ··· pkg-config configuration
├── scripts ····· build scripts
├┬─ sesman ······ session manager for xrdp
|├── chansrv ···· channel server for xrdp
|├── libsesman ·· Code common to sesman and its related executables
|└── tools ······ session management tools for sys admins
├── tests ······· tests for the code
├┬─ tools ······· tools
|└┬─ devel ······ development tools
| ├── gtcp_proxy GTK app that forwards TCP connections to a remote host
| └── tcp_proxy · CLI app that forwards TCP connections to a remote host
├── vnc ········· VNC client module for xrdp
├── vrplayer ···· QT player redirecting video/audio to clients over xrdpvr channel
├── xrdp ········ main server code
├── xrdpapi ····· virtual channel API
├── xrdpvr ······ API for playing media over RDP
└── xup ········· xorgxrdp client module