# Rusnel
[](https://crates.io/crates/rusnel)
## Description
Rusnel is a fast TCP/UDP tunnel, transported over and encrypted using QUIC protocol. Single executable including both client and server. Written in Rust.
## Features
- Easy to use
- Single executable including both client and server.
- Uses QUIC protocol for fast and multiplexed communication.
- Encrypted connections using the QUIC protocol (TLS 1.3).
- Static forward tunneling (TCP, UDP)
- Static reverse tunneling (TCP, UDP)
- Dynamic tunneling (socks5, including UDP ASSOCIATE)
- Dynamic reverse tunneling (reverse socks5, including UDP ASSOCIATE)
- Layered peer authentication: insecure, fingerprint pinning, or full mTLS
(see [Authentication](#authentication)).
## Install
```bash
cargo install rusnel
```
### or
Clone the repository and build the project:
```bash
git clone https://github.com/guyte149/Rusnel.git
cd rusnel
cargo build --release
```
## Usage
```bash
$ rusnel --help
A fast tcp/udp tunnel
Usage: rusnel <COMMAND>
Commands:
server run Rusnel in server mode
client run Rusnel in client mode
cert generate certificates for use with --tls-* flags
help Print this message or the help of the given subcommand(s)
Options:
-h, --help Print help
-V, --version Print version
```
```bash
$ rusnel server --help
run Rusnel in server mode
Usage: rusnel server [OPTIONS]
Options:
--host <HOST> defines Rusnel listening host [default: 0.0.0.0]
-p, --port <PORT> defines Rusnel listening port [default: 8080]
--allow-reverse Allow clients to specify reverse port forwarding remotes
--allow-socks Allow clients to specify SOCKS5 remotes. `R:socks`
additionally requires `--allow-reverse`.
--insecure Disable all TLS authentication (testing only)
--tls-self-signed Persisted self-signed cert under --tls-state-dir
--tls-state-dir <DIR> Directory for persisted self-signed cert/key (default: ~/.rusnel)
--tls-cert <PATH> Server PEM cert (paired with --tls-key)
--tls-key <PATH> Server PEM key (paired with --tls-cert)
--tls-ca <PATH> Enable mTLS: require client certs signed by this CA
--congestion <CC> QUIC congestion controller: cubic (default) or bbr.
cubic wins on loopback / clean LANs; bbr wins on
high-BDP / lossy WAN links (≳25ms RTT or any loss).
-v, --verbose enable verbose logging
--debug enable debug logging
-h, --help Print help
```
```bash
$ rusnel client --help
run Rusnel in client mode
Usage: rusnel client [OPTIONS] <SERVER> <remote>...
Arguments:
<SERVER> defines the Rusnel server address (in form of host:port)
<remote>...
<remote>s are remote connections tunneled through the server, each which come in the form:
<local-host>:<local-port>:<remote-host>:<remote-port>/<protocol>
■ local-host defaults to 0.0.0.0 (all interfaces).
■ local-port defaults to remote-port.
■ remote-port is required*.
■ remote-host defaults to 0.0.0.0 (server localhost).
■ protocol defaults to tcp.
which shares <remote-host>:<remote-port> from the server to the client as <local-host>:<local-port>, or:
R:<local-host>:<local-port>:<remote-host>:<remote-port>/<protocol>
which does reverse port forwarding,
sharing <remote-host>:<remote-port> from the client to the server\'s <local-host>:<local-port>.
example remotes
1337
example.com:1337
1337:google.com:80
192.168.1.14:5000:google.com:80
socks
5000:socks
R:2222:localhost:22
R:socks
R:5000:socks
1.1.1.1:53/udp
[::1]:80
[::1]:5000:[2001:db8::1]:80
R:[::1]:2222:[::1]:22
IPv6 literals must be wrapped in [brackets] (same
convention as URLs and ssh -L).
When the Rusnel server has --allow-reverse enabled, remotes can be prefixed with R to denote that they are reversed.
Remotes can specify "socks" in place of remote-host and remote-port.
The default local host and port for a "socks" remote is 127.0.0.1:1080.
Options:
--insecure Skip server cert verification (testing only)
--tls-fingerprint <SHA256> Pin server cert by SHA-256 fingerprint
--tls-ca <PATH> Verify server cert against this CA bundle
--tls-cert <PATH> Client PEM cert (mTLS; paired with --tls-key + --tls-ca)
--tls-key <PATH> Client PEM key (mTLS; paired with --tls-cert + --tls-ca)
--tls-server-name <NAME> Override SNI / verification name
--congestion <CC> QUIC congestion controller: cubic (default) or
bbr. cubic wins on loopback / clean LANs; bbr
wins on high-BDP / lossy WAN links.
--max-retry-count <N> Reconnect attempts after a disconnect or
failed connect. -1 = retry forever (default);
counter resets on every successful connect.
--max-retry-interval <S> Cap on the exponential reconnect backoff
(default 300s; starts at 200 ms and doubles).
--proxy <URL> Route the QUIC connection through a SOCKS5
proxy via UDP ASSOCIATE.
Form: socks5://[user:pass@]host:port.
-v, --verbose enable verbose logging
--debug enable debug logging
-h, --help Print help
```
The client survives both transient network drops and full server restarts
out of the box: on disconnect it logs the close reason (e.g.
`closed by peer: server received ^C (code 0)`), backs off, and tries every
resolved address in parallel using **RFC 8305 Happy Eyeballs** so v4-only
servers reachable via a v6-preferring resolver still connect within
~250 ms. Server-side resources (including reverse-tunnel listeners) are
released the moment the QUIC connection drops.
## Authentication
Both the server and the client require an explicit TLS-mode flag — there is
no silent insecure default. Three modes:
| Insecure | `--insecure` | `--insecure` |
| Fingerprint pin | `--tls-self-signed` (or `--tls-cert`/`--tls-key`) | `--tls-fingerprint sha256:...` |
| Full mTLS | `--tls-cert ... --tls-key ... --tls-ca ...` | `--tls-ca ... --tls-cert ... --tls-key ... [--tls-server-name ...]` |
Quickest path for a private/single-user setup — the server logs its
fingerprint at startup, the client pins it:
```bash
rusnel server --tls-self-signed
# server cert fingerprint: sha256:abcd...
rusnel client --tls-fingerprint sha256:abcd... 1.2.3.4:8080 1337
```
For full mTLS, generate a CA + server + client cert (no `openssl` required):
```bash
scripts/gen-certs.sh ./pki 1.2.3.4
rusnel server --tls-ca ./pki/ca.pem --tls-cert ./pki/server.pem --tls-key ./pki/server.key
rusnel client --tls-ca ./pki/ca.pem --tls-cert ./pki/client.pem --tls-key ./pki/client.key \
--tls-server-name 1.2.3.4 1.2.3.4:8080 1337
```
`rusnel cert --help` lists the underlying subcommands (`ca`, `server`,
`client`, `fingerprint`) for finer control.
### Embedded credentials (drop-and-run binaries)
For Sliver-style "drop the binary onto a host and have it just work" deployments,
Rusnel can bake credentials and a default server address into the binary at
**build time** via `RUSNEL_EMBED_*` env vars. The resulting binary runs in the
appropriate TLS mode with no flags required (CLI flags still override embedded
values when both are present).
```bash
# Pre-configured client: connects to 1.2.3.4:8080, fingerprint-pinned.
RUSNEL_EMBED_SERVER_ADDR=1.2.3.4:8080 \
RUSNEL_EMBED_FINGERPRINT=sha256:abcd... \
cargo build --release
./target/release/rusnel client 1337 # no --tls-* flags needed
# Pre-configured mTLS pair (CA + server cert/key on one binary, CA + client
# cert/key on the other). Both ends run in mTLS mode with no flags.
RUSNEL_EMBED_CA=./pki/ca.pem \
RUSNEL_EMBED_SERVER_CERT=./pki/server.pem \
RUSNEL_EMBED_SERVER_KEY=./pki/server.key \
cargo build --release # → server binary
RUSNEL_EMBED_CA=./pki/ca.pem \
RUSNEL_EMBED_CLIENT_CERT=./pki/client.pem \
RUSNEL_EMBED_CLIENT_KEY=./pki/client.key \
RUSNEL_EMBED_SERVER_NAME=1.2.3.4 \
cargo build --release # → client binary
```
Recognised vars: `RUSNEL_EMBED_SERVER_ADDR`, `RUSNEL_EMBED_CA`,
`RUSNEL_EMBED_FINGERPRINT`, `RUSNEL_EMBED_SERVER_NAME`,
`RUSNEL_EMBED_SERVER_CERT`, `RUSNEL_EMBED_SERVER_KEY`,
`RUSNEL_EMBED_CLIENT_CERT`, `RUSNEL_EMBED_CLIENT_KEY`. Path-style vars are
resolved at build time via `include_bytes!` (the file no longer needs to exist
on the deployment host); string-style vars are baked in as `&'static str`.
See [`build.rs`](build.rs) for the full mapping.
## Performance
Rusnel (QUIC) vs [Chisel](https://github.com/jpillora/chisel) (SSH-over-WebSocket)
on loopback. Throughput is iperf3 over a tunneled TCP forward
(100 MB × 5 runs + warmup, median); latency is the round-trip time of a
64 B echo across the tunnel.
End-to-end HTTP request times through the tunnel across payload sizes
(median of 5 runs, error bars show min/max):
The benchmark harness also includes a `wan` profile that applies
`tc qdisc netem delay 25ms` to the loopback interface to approximate a
50 ms-RTT WAN. Reproduce everything with `./benchmark/run.sh`
(requires Docker; needs `--cap-add=NET_ADMIN` for netem profiles, which
the script adds for you). See [`benchmark/`](benchmark/) for tunables.
## TODO
### Reliability & UX
- [x] client reconnect with exponential backoff (configurable via `--max-retry-count` / `--max-retry-interval`)
- [x] proxy support for client: `--proxy socks5://[user:pass@]host:port` routes the QUIC connection through a SOCKS5 proxy via UDP ASSOCIATE (RFC 1928 §4). HTTP CONNECT is intentionally not supported in this release because it cannot carry UDP — see the WebSocket-fallback transport item under `Security & access control` for the path that would unlock HTTP/SOCKS-CONNECT proxies.
- [ ] `RUST_LOG`-style env filter for `tracing-subscriber` (per-module log levels)
### Protocol features
- [ ] add fake-backend http/3 feature to server (real HTTP/3 facade for active probes that open streams)
- [ ] skip the 1-RTT control handshake on static forwards (cache the parsed `RemoteRequest` server-side; saves ~1 RTT per accepted TCP connection on WAN)
- [ ] enable QUIC 0-RTT connection resumption (session-ticket cache; cuts the first request after `rusnel client` startup from ~3 RTT to ~1 RTT)
- [ ] UDP hole-punching / NAT traversal mode: introduce a `rusnel broker` role that observes each peer's reflexive address (optionally cross-checked against public STUN servers to detect symmetric NAT) and brokers a direct QUIC connection between two NATed peers à la libp2p DCUtR / Tailscale DERP, with relay fallback when punching fails. Lets two devices behind NAT talk without anyone running a publicly-reachable data-plane server.
### Security & access control
- [ ] server-side remote ACLs: `--allow` / `--deny` flags (and config-file equivalents) accepting wildcarded `RemoteRequest` patterns, e.g. `--allow socks`, `--allow R:2222:localhost:22`, `--deny tcp:*:*:169.254.169.254:*`. Default-deny dangerous targets like cloud instance-metadata endpoints. With mTLS, bind ACLs to the client cert subject / fingerprint so a contractor cert can be scoped to one tunnel.
- [ ] SSO / OIDC client auth via a `rusnel-issuer` daemon: client runs `rusnel client --sso https://issuer.corp.example`, completes a device-code flow against the org's IdP (Okta/Google/Auth0), and the issuer mints a short-lived (~8h) mTLS client cert with the user's email/groups in the SAN. Rusnel server only needs to trust the issuer's CA — no IdP knowledge in the data path. ACLs from the bullet above match on cert subject/groups.
### Operability
- [ ] server admin API + CLI + web UI:
- typed `ServerState` (DashMap of clients/tunnels with bytes-in/out counters) populated from the existing per-connection / per-tunnel handlers.
- HTTP admin API on a unix socket (filesystem-perm gated) or TCP+mTLS: `GET /clients`, `GET /clients/:id/tunnels`, `GET /tunnels`, `DELETE /clients/:id` (kick), `GET /metrics` (Prometheus).
- `rusnel ctl clients|tunnels|kick` subcommand consuming that API.
- tiny embedded web UI (single `include_str!`'d HTML file, no JS framework) with a client/tunnel dashboard and bandwidth sparklines off `/metrics`.
### Testing & CI
- [ ] run `./benchmark/run.sh` on a self-hosted runner per release tag and commit the result PNGs back, so perf regressions surface in PRs