cross-control

Status: 0.2.0-alpha — Phase 1 close-out. Two daemons on the same LAN discover each other via mDNS and the cursor crosses between machines — no static IP in the config required. Clipboard sync, multi-monitor, and Windows support are next (see DESIGN.md and the issues). Not yet a daily driver, but the core KVM works end-to-end on Linux.

Share your keyboard and mouse across machines. A modern, Rust-based virtual KVM that lets you seamlessly move your cursor between computers on the same network.

Website: cross-control.adjoint.uk · the landing page source lives in site/.

Why cross-control?

The software KVM space is stagnant. Barrier is unmaintained since 2022, Input Leap and Deskflow have broken Wayland support, Synergy went proprietary, and the Rust alternatives (RKVM, LAN Mouse) are either Linux-only or use incompatible protocols.

cross-control takes a different approach:

	Barrier	Input Leap	Synergy	RKVM	LAN Mouse	cross-control
Active	Dead (2022)	Slow	Yes	Yes	Yes	Yes
Wayland	No	Partial	Partial	Yes	Yes	Native
Windows	Yes	Yes	Yes	No	Yes	Planned
Protocol	Synergy v1	Synergy v1	Proprietary	Custom	Custom	QUIC
Encryption	Optional TLS	Optional TLS	TLS	TLS	None	TLS 1.3 (always)
Discovery	No	No	No	No	No	mDNS
License	GPL-2.0	GPL-2.0	Proprietary	GPL-3.0	GPL-3.0	MIT/Apache-2.0

Features

• QUIC transport - Multiplexed streams, built-in TLS 1.3, 0-RTT reconnection. No other KVM uses QUIC.
• Wayland-native - Works on Wayland from day one via evdev/uinput, with enhanced support for wlroots compositors.
• Zero-config discovery - Machines find each other automatically via mDNS/DNS-SD.
• Clipboard sharing - Text, HTML, and images synced when you switch machines.
• Position-based switching - Move your cursor to the screen edge to switch, just like macOS Universal Control.
• Certificate pinning - SSH-style trust-on-first-use authentication. No central authority needed.
• Multi-machine - Star topology supports any number of machines.
• Permissive license - MIT OR Apache-2.0. Use it anywhere.

Requirements

• Linux (x86_64 or aarch64) — Windows support is planned
• Rust 1.75+ (if building from source)
• User must be in the input group to access keyboard/mouse devices
• /dev/uinput must be accessible for virtual device emulation

Installation

Install script (recommended)

curl -fsSL https://raw.githubusercontent.com/Adjoint-uk/cross-control/main/install.sh | bash

Prebuilt binaries

Download the latest release from GitHub Releases.

Build from source

git clone https://github.com/Adjoint-uk/cross-control.git
cd cross-control
cargo install --path crates/cross-control-cli

Linux permissions setup

# Add your user to the input group (required for keyboard/mouse access)
sudo usermod -aG input $USER

# Ensure uinput is accessible
sudo modprobe uinput
echo 'KERNEL=="uinput", MODE="0660", GROUP="input"' | sudo tee /etc/udev/rules.d/99-uinput.rules
sudo udevadm control --reload-rules && sudo udevadm trigger

# Log out and back in for group changes to take effect

Quick Start

Set up two Linux machines on the same network:

1. Install on both machines

cargo install --path crates/cross-control-cli

2. Generate certificates on both machines

cross-control generate-cert --output ~/.config/cross-control/

Note the fingerprint printed for each machine.

3. Create configuration

Machine A (left workstation at 192.168.1.10):

# ~/.config/cross-control/config.toml
[identity]
name = "workstation"

[[screens]]
name = "laptop"
address = "192.168.1.20:24800"
position = "Right"
fingerprint = "SHA256:..."  # laptop's fingerprint

Machine B (right laptop at 192.168.1.20):

# ~/.config/cross-control/config.toml
[identity]
name = "laptop"

[[screens]]
name = "workstation"
address = "192.168.1.10:24800"
position = "Left"
fingerprint = "SHA256:..."  # workstation's fingerprint

4. Start the daemon on both machines

cross-control start

5. Use it

Move your cursor to the right edge of Machine A's screen. It will appear on Machine B. Move it back to the left edge to return.

Press Ctrl+Shift+Escape to immediately release input and return control to the local machine.

6. Check status

cross-control status

See docs/setup-guide.md for detailed setup instructions and troubleshooting.

Run as a service

To keep the daemon running across logins, install the systemd user unit:

mkdir -p ~/.config/systemd/user
cp systemd/cross-control.service ~/.config/systemd/user/
systemctl --user daemon-reload
systemctl --user enable --now cross-control
systemctl --user status cross-control     # check it's running
journalctl --user -u cross-control -f      # follow logs

The install script offers to do this for you. Two prerequisites, since input capture/emulation needs device access: your user must be in the input group, and /dev/uinput must be group-readable/writable (see Linux permissions setup above). To have the service start before you log in, enable lingering: sudo loginctl enable-linger $USER. The unit assumes the binary is on ~/.cargo/bin; if you installed elsewhere, adjust ExecStart with systemctl --user edit cross-control.

Try it on one machine

No second computer? The loopback example runs two daemons in one process and drives a full session — handshake, cursor crossing, input forwarding — end to end on 127.0.0.1:

cargo run -p cross-control-daemon --example loopback

On a Linux desktop with /dev/uinput access, add --features linux -- --real to have the receiving daemon inject into a real virtual device so you can watch the cursor move. This covers everything except the physical input ends (real evdev capture and a live compositor).

Architecture

Physical Input                                              Virtual Input
  (keyboard/mouse)                                           (on remote machine)
       |                                                          ^
       v                                                          |
  +-----------+    +------------+    +-------+    +------------+  +-----------+
  | Input     | -> | Protocol   | -> | QUIC  | -> | Protocol   |->| Input     |
  | Capture   |    | Serialize  |    | Wire  |    | Deserialize|  | Emulation |
  +-----------+    +------------+    +-------+    +------------+  +-----------+
  (evdev/RawInput)  (bincode v2)    (quinn)       (bincode v2)   (uinput/SendInput)
       |                                                          |
  +-----------+                                            +-----------+
  | Clipboard | <------------- Clipboard Sync ------------>| Clipboard |
  +-----------+                                            +-----------+
       |                                                          |
  +-----------+                                            +-----------+
  | Discovery | <------------- mDNS/DNS-SD --------------->| Discovery |
  +-----------+                                            +-----------+

The project is organised as a Cargo workspace with 8 crates:

Crate	Purpose
cross-control-types	Shared types: events, devices, screens, identifiers
cross-control-protocol	QUIC transport (quinn), wire format (bincode v2)
cross-control-input	Platform-abstracted input capture and emulation
cross-control-clipboard	Clipboard synchronisation
cross-control-discovery	mDNS/DNS-SD zero-config discovery
cross-control-daemon	Core state machine, barrier logic, event routing
cross-control-cli	User-facing binary
cross-control-certgen	TLS certificate generation

Configuration

Configuration lives at ~/.config/cross-control/config.toml:

[daemon]
port = 24800
discovery = true

[identity]
name = "my-workstation"

[[screens]]
name = "laptop"
address = "192.168.1.42:24800"
position = "Right"
fingerprint = "SHA256:..."

# For 3+ machines, define adjacency
[[screen_adjacency]]
screen = "laptop"
neighbor = "tablet"
position = "Right"

See examples/config.toml for all configuration options.

Development Status

cross-control is in early development. Current status:

• Phase 0: Workspace scaffold, shared types, trait definitions, CI
• Phase 1 (v0.2.0-alpha): Linux-to-Linux end-to-end — evdev capture, QUIC transport, multi-hop switching, mDNS discovery, TOFU pinning, 64 tests
• Phase 2 (v0.5.0-beta): Clipboard sharing, multi-monitor, reconnect, polished setup
• Phase 3 (v0.9.0): Windows + macOS input backends, distro packaging
• Phase 4 (1.0.0): Protocol freeze, ADRs, security model, fuzz testing

Contributing

See CONTRIBUTING.md for development guidelines.

Security

See SECURITY.md for the security policy and reporting vulnerabilities.

License

Licensed under either of:

• Apache License, Version 2.0 (LICENSE-APACHE)
• MIT license (LICENSE-MIT)

at your option.

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Built by Adjoint Ltd