realm

Realm

A simple, high performance relay server written in rust.

Features

• Zero configuration. Setup and run in one command.
• Concurrency. Bidirectional concurrent traffic leads to high performance.
• Low resources cost.

Container

Realm can be run in a container with OCI (like Docker, Podman, Kubernetes, etc), see guides here.

Build

Install rust toolchain with rustup:

curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh

Clone this repository:

git clone https://github.com/zhboner/realm && cd realm

Build:

cargo build --release

You can also pass target_cpu=native to allow more possible optimizations:

RUSTFLAGS='-C target_cpu=native' cargo build --release

The realm binary will be available in target/release.

Build Options

• udp: enable udp relay builtin.
• tfo: enable tcp-fast-open deprecated.
• trust-dns: enable trust-dns's async dns resolver builtin.
• zero-copy: enable zero-copy on linux builtin.
• brutal-shutdown: see realm_io/brutal-shutdown.
• hook: see realm_hook.
• proxy: enable proxy-protocol.
• balance: enable load balance.
• transport: enable ws/tls/wss.
• transport-tls-ring: use ring as rustls backend.
• transport-tls-awslc: use aws-lc as rustls backend.
• batched-udp: enable more efficient udp on linux.
• multi-thread: enable tokio's multi-threaded IO scheduler.
• mi-malloc: custom memory allocator.
• jemalloc: custom memory allocator.
• page-alloc: custom memory allocator.

Default: proxy + balance + transport + transport-tls-awslc + batched-udp + brutal-shutdown + multi-thread.

Deafult-Slim: batched-udp + brutal-shutdown + multi-thread.

See also: Cargo.toml.

Examples:

# simple tcp
cargo build --release --no-default-features

# enable other options
cargo build --release --features 'jemalloc'

# fully customized
cargo build --release \
    --no-default-features \
    --features 'transport, multi-thread, jemalloc'

# (since v2.9) use ring as rustls backend
cargo build --release \
    --no-default-features \
    --features 'multi-thread, brutal-shutdown' \
    --features 'proxy, balance, batched-udp' \
    --features 'transport, transport-tls-ring'
# equals
cargo build --release --no-default-features --features default-ring

Cross Compile

Please refer to https://rust-lang.github.io/rustup/cross-compilation.html. You may need to install cross-compilers or other SDKs, and specify them when building the project.

Or have a look at Cross, it makes things easier.

Usage

…

Start from command line arguments:

realm -l 0.0.0.0:5000 -r 1.1.1.1:443

Start with config file:

# use toml
realm -c config.toml

# use json
realm -c config.json

# use configs in folder (since v2.6.2)
# all toml and json files are recursively included (e.g.: config/log.toml, config/node/n1.toml)
# hidden ones are recursively excluded (e.g.: config/.hidden_file, config/.hidden_dir/)
realm -c config/

Start with environment variables:

REALM_CONF='{"endpoints":[{"local":"127.0.0.1:5000","remote":"1.1.1.1:443"}]}' realm

# or
export REALM_CONF=`cat config.json | jq -c `
realm

Convert a legacy config file:

realm convert old.json

Configuration

TOML Example

[log]
level = "warn"
output = "realm.log"

[network]
no_tcp = false
use_udp = true

[[endpoints]]
listen = "0.0.0.0:5000"
remote = "1.1.1.1:443"

[[endpoints]]
listen = "0.0.0.0:10000"
remote = "www.google.com:443"

{
  "log": {
    "level": "warn",
    "output": "realm.log"
  },
  "network": {
    "no_tcp": false,
    "use_udp": true
  },
  "endpoints": [
    {
      "listen": "0.0.0.0:5000",
      "remote": "1.1.1.1:443"
    },
    {
      "listen": "0.0.0.0:10000",
      "remote": "www.google.com:443"
    }
  ]
}

See more examples here.

Overview

…

You should provide at least endpoint.listen and endpoint.remote, the left fields will take their default values.

Option priority: cmd override > endpoint config > global config.

endpoint

endpoint.listen: string

Local address, supported formats:

• ipv4:port
• ipv6:port

endpoint.remote: string

Remote address, supported formats:

• ipv4:port
• ipv6:port
• example.com:port

endpoint.extra_remotes: string array

Extra remote address, same as endpoint.remote above.

endpoint.balance: string

Require balance feature.

Load balance strategy and weights of remote peers.

Format:

$strategy: $weight1, $weight2, ...

Where remote is used as default backend server, and extra_remotes are used as backups.

Available algorithms (provided by realm_lb):

• iphash

• roundrobin

Example:

[[endpoints]]
remote = "a:443"
extra_remotes = ["b:443", "c:443"]
balance = "roundrobin: 4, 2, 1"

The weight of [a, b, c] is [4, 2, 1] in turn.

endpoint.through: string

TCP: Bind a specific ip before opening a connection.

UDP: Bind a specific ip or address before sending packet.

Supported formats:

• ipv4/ipv6 (tcp/udp)
• ipv4/ipv6:port (udp)

endpoint.interface: string

Bind to a specific interface for outgoing traffics.

endpoint.listen_interface: string

Bind to a specific interface for incoming traffics.

endpoint.listen_transport: string

Require transport feature.

See Kaminari Options.

endpoint.remote_transport: string

Require transport feature.

See Kaminari Options.

endpoint.network

The same as network, override global options.

log

log.level: string

values:

• off
• error
• warn
• info
• debug
• trace

default: off

log.output: string

values:

• stdout
• stderr
• path (e.g. /var/log/realm.log)

default: stdout

dns

Require trust-dns feature.

dns.mode: string

Dns resolve strategy.

values:

• ipv4_only
• ipv6_only
• ipv4_then_ipv6
• ipv6_then_ipv4
• ipv4_and_ipv6

default: ipv4_and_ipv6

dns.protocol: string

Dns transport protocol.

values:

• tcp
• udp
• tcp_and_udp

default: tcp_and_udp

dns.nameservers: string array

Custom upstream servers.

format: ["server1", "server2" ...]

default:

If on unix/windows, read from the default location.(e.g. /etc/resolv.conf).

Otherwise, use google's public dns(8.8.8.8:53, 8.8.4.4:53 and 2001:4860:4860::8888:53, 2001:4860:4860::8844:53).

dns.min_ttl: unsigned int

The minimum lifetime of a positive dns cache.

default: 0

dns.max_ttl: unsigned int

The maximum lifetime of a positive dns cache.

default: 86400 (1 day)

dns.cache_size: unsigned int

The maximum count of dns cache.

default: 32

network

network.no_tcp: bool

Do not start a tcp relay.

default: false

network.use_udp: bool

Require udp feature

Start listening on a udp endpoint and forward packets to the remote peer.

It will dynamically allocate local endpoints and establish udp associations. Once timeout, the endpoints will be deallocated and the association will be terminated. See also: network.udp_timeout.

Due to the receiver side not limiting access to the association, the relay works like a full-cone NAT.

default: false

network.ipv6_only: bool

Disable ipv4-mapped-ipv6 when binding to an ipv6 address.

E.g.: [::0]:port with (ipv6_only=false) binds to *:port

[::0]:port with (ipv6_only=true) binds to [::]:port

default: false

network.zero_copy: bool deprecated

Require zero-copy feature.

Use splice instead of send/recv while handing tcp connection. This will save a lot of memory copies and context switches.

default: false

network.fast_open: bool deprecated

Require fast-open feature.

It is not recommended to enable this option, see The Sad Story of TCP Fast Open.

default: false

network.tcp_timeout: unsigned int

This is connect timeout. An attempt to connect to a remote peer fails after waiting for a period of time.

To disable timeout, you need to explicitly set timeout value to 0.

default: 5

network.udp_timeout: unsigned int

Terminate udp association after timeout.

The timeout value must be properly configured in case of memory leak. Do not use a large timeout!

default: 30

network.tcp_keepalive: unsigned int

TCP Keepalive interval.

On Linux, this is equivalent to setting both net.ipv4.tcp_keepalive_time and net.ipv4.tcp_keepalive_intvl.

To use system's tcp keepalive interval, you need to explicitly set this option to 0.

default: 15

network.tcp_keepalive_probe: unsigned int

TCP Keepalive retries.

On Linux, this is equivalent to ipv4.tcp_keepalive_probes.

default: 3

network.send_mptcp: bool

Enable MPTCP outbound connections on Linux.

Requires a higher kernel version(>5.6) with net.mptcp.enabled=1.

See also Path Manager guidelines.

default: false

network.accept_mptcp: bool

Enable MPTCP inbound connections on Linux.

default: false

network.send_proxy: bool

Require proxy feature.

Send haproxy PROXY header once the connection established. Both v1 and v2 are supported, see send_proxy_version.

You should make sure the remote peer also speaks proxy-protocol.

default: false

network.send_proxy_version: unsigned int

Require proxy feature.

This option has no effect unless send_proxy is enabled.

value:

• 1
• 2

default: 2

network.accept_proxy: bool

Require proxy feature.

Wait for a PROXY header once the connection established.

If the remote sender does not send a v1 or v2 header before other contents, the connection will be closed.

default: false

network.accept_timeout: unsigned int

Require proxy feature.

Wait for a PROXY header within a period of time, otherwise close the connection.

default: 5.