qcp

The QUIC Copier (qcp) is an experimental high-performance remote file copy utility for long-distance internet connections.

📋 Features

• 🔧 Drop-in replacement for scp
• 🛡️ Similar security to scp, using existing, well-known mechanisms
• 🚀 Better throughput on congested networks

Platform support status

• Well tested: Debian and Ubuntu on x86_64, using OpenSSH
• Tested: Ubuntu on WSL; aarch64 (Raspbian)
• Untested: OSX/BSD family
• Not currently supported: Windows

🧰 Getting Started

• You must have ssh access to the target machine.
• Install the qcp binary on both machines. It needs to be in your PATH on the remote machine.
• Run qcp --help-buffers and follow its instructions.

Installing pre-built binaries

These can be found on the latest release.

• Debian/Ubuntu packages are provided.
• For other Linux x86_64: Use x86_64-unknown-linux-musl.tar.gz
• For other Linux aarch64: Use aarch64-unknown-linux-musl.tar.gz

The binaries are statically linked. Linux builds should work on all recent distributions, as long as you have selected the correct CPU architecture.

Installation from source

Prerequisite: You need to have capnpc installed. Your distribution likely packages this, or see https://capnproto.org/.

You can install the package from source using cargo:

cargo install --locked qcp

If you are new to Rust and don't have the tools installed

• Install the rustup tool via your package manager, or see Rust installation
• rustup toolchain install stable
• Proceed as above

⚙️ Usage

The basic syntax is the same as scp or rcp.

qcp [OPTIONS] <SOURCE> <DESTINATION>

The program has a comprehensive help message, accessed via qcp -h (brief) or qcp --help (long form).

For example:

$ qcp my-server:/tmp/testfile /tmp/
⠂ Transferring data                                                           2.1MB/s (last 1s)
testfile ████████████████████████████████████░░░░░░░░░░░░░░░░░░░░░░░░ 1s @ 6.71 MB/s [10.49 MB]

The program uses the ssh binary on your system to connect to the target machine. ssh will check the remote host key and prompt you for a password or passphrase in the usual way.

Tuning

By default qcp is tuned for a 100Mbit connection, with 300ms round-trip time to the target server.

Various network tuning options are available.

For example, if you have 300Mbit/s (37.5MB/s) download and 100Mbit/s (12.5MB/s) upload, you might use these options:

qcp my-server:/tmp/testfile /tmp/ --rx 37M --tx 12M

Performance tuning can be a tricky subject. See the performance documentation.

📖 How qcp works

The brief version:

1. We ssh to the remote machine and run qcp --server there
2. Both sides generate a TLS key and exchange self-signed certs over the ssh pipe between them
3. We use those certs to set up a QUIC session between the two
4. We transfer files over QUIC

The protocol documentation contains more detail and a discussion of its security properties.

⚖️ License

The initial release is made under the GNU Affero General Public License.

🧑‍🏭 Contributing

Feel free to report bugs via the bug tracker.

I'd particularly welcome performance reports from BSD/OSX users as that's not a platform I use regularly.

While suggestions and feature requests are welcome, please be aware that I mostly work on this project in my own time.

💸 Supporting the project

If you find this software useful and would like to say thank you, please consider buying me a coffee or ko-fi. Github sponsorship is also available.

If you're a business and need a formal invoice for your accountant, my freelancing company can issue the paperwork. For this, and any other commercial enquiries (alternative licensing, support, etc) please get in touch, to qcp@crazyscot.com.

Please also consider supporting the galaxy of projects this work builds upon. Most notably, Quinn is a pure-Rust implementation of the QUIC protocol, without which qcp simply wouldn't exist in its current form.

💡 Roadmap

Some ideas for the future, in no particular order:

• A local config mechanism, so you don't have to type out the network parameters every time
• Support for copying multiple files (e.g. shell globs or scp -r)
• Windows native support, at least for client mode
• Firewall/NAT traversal
• Interactive file transfer (akin to ftp)
• Smart file copy using the rsync protocol or similar (send only the sections you need to)
• Graphical interface for ftp mode
• Review the protocol and perhaps pivot to using capnp RPC
• Bind a daemon to a fixed port, for better firewall/NAT traversal properties but at the cost of having to implement user authentication.
• The same thing we do every night, Pinky. We try to take over the world!