B4

[русский язык]

Network packet processor for circumventing Deep Packet Inspection (DPI) systems.

Overview

B4 uses Linux netfilter to intercept and modify network packets in real-time, applying various techniques to bypass DPI systems used by ISPs and network administrators.

Prerequisites

• Linux-based system (desktop, server, or router)
• Root access (sudo)

That's it. The installer handles everything else.

Installation

Automated Installation

Note

In some systems you need to run sudo b4install.sh.

wget -O ~/b4install.sh https://raw.githubusercontent.com/DanielLavrushin/b4/main/install.sh && chmod +x ~/b4install.sh && ~/b4install.sh

If something went wrong try to run - this will diagnose the system

wget -O ~/b4install.sh https://raw.githubusercontent.com/DanielLavrushin/b4/main/install.sh && chmod +x ~/b4install.sh && ~/b4install.sh --sysinfo

Installer Options

./b4install.sh # perform installation of the B4 application

./b4install.sh -h # print help

# Show system information
./b4install.sh --sysinfo

# Install specific version
./b4install.sh v1.10.0

# Quiet mode
./b4install.sh --quiet

# Specify geosite source
./b4install.sh --geosite-src=https://example.com/geosite.dat --geosite-dst=/opt/etc/b4

# Update existing installation
./b4install.sh --update

# Uninstall
./b4install.sh --remove

Basic Usage

Starting B4

# Standard Linux (systemd)
sudo systemctl start b4
sudo systemctl enable b4  # Start on boot

# OpenWRT
/etc/init.d/b4 start # restart | stop

# Entware/MerlinWRT
/opt/etc/init.d/S99b4 start # restart | stop

Access Web Interface

Open your browser and navigate to:

http://your-device-ip:7000

Building from Source

# Clone repository
git clone https://github.com/daniellavrushin/b4.git
cd b4

# Build binary
make build

# Build for all architectures
make build-all

# Build for specific architecture
make linux-amd64
make linux-arm64
make linux-armv7

Command-Line Usage

# get help
b4  --help

# Basic usage with manual domains
sudo b4 --sni-domains youtube.com,netflix.com

# Using geosite categories
sudo b4 --geosite /etc/b4/geosite.dat --geosite-categories youtube,netflix

# Custom configuration
sudo b4 --queue-num 100 --threads 4 --web-port 8080

Configuration File

Usually a configuration file is located in /etc/b4/b4.json and is created automatically when missing. (the file can be redefined by passing the --config= argument):

Load with custom configuration:

sudo b4 --config /home/username/b4custom.json

Configuration Options

Network Configuration

Flag	Default	Description
--queue-num	537	Netfilter queue number
--threads	4	Number of worker threads
--mark	32768	Packet mark value
--connbytes-limit	19	TCP connection bytes limit
--seg2delay	0	Delay between segments (ms)
--ipv4	true	Enable IPv4 processing
--ipv6	false	Enable IPv6 processing

Domain Filtering

Flag	Default	Description
--sni-domains	[]	Comma-separated list of domains
--geosite	""	Path to geosite.dat file
--geosite-categories	[]	Categories to process

TCP Fragmentation

Flag	Default	Description
--frag	tcp	Fragmentation strategy: tcp/ip/none
--frag-sni-reverse	true	Reverse fragment order
--frag-middle-sni	true	Fragment in middle of SNI
--frag-sni-pos	1	SNI fragment position

Fake SNI Configuration

Flag	Default	Description
--fake-sni	true	Enable fake SNI packets
--fake-ttl	8	TTL for fake packets
--fake-strategy	pastseq	Strategy: ttl/randseq/pastseq/tcp_check/md5sum
--fake-seq-offset	10000	Sequence offset for fake packets
--fake-sni-len	1	Length of fake SNI sequence
--fake-sni-type	2	Payload type: 0=random, 1=custom, 2=default

UDP/QUIC Configuration

Flag	Default	Description
--udp-mode	fake	UDP handling: drop/fake
--udp-fake-seq-len	6	UDP fake packet sequence length
--udp-fake-len	64	UDP fake packet size (bytes)
--udp-faking-strategy	none	Strategy: none/ttl/checksum
--udp-dport-min	0	Minimum UDP destination port
--udp-dport-max	0	Maximum UDP destination port
--udp-filter-quic	parse	QUIC filtering: disabled/all/parse
--udp-filter-stun	true	Enable STUN filtering
--udp-conn-bytes-limit	8	UDP connection bytes limit

System Configuration

Flag	Default	Description
--skip-tables	false	Skip iptables/nftables setup
--tables-monitor-interval	10	Tables monitor interval (seconds, 0=disabled)
--web-port	7000	Web interface port (0=disabled)
--verbose	info	Log level: debug/trace/info/error/silent
--instaflush	true	Flush logs immediately
--syslog	false	Enable syslog output

Web Interface

The web interface is accessible at http://device-ip:7000 (default port, can be changed in the config file).

Geosite Integration

B4 supports v2ray/xray geosite.dat files from various sources:

# Loyalsoldier
wget https://github.com/Loyalsoldier/v2ray-rules-dat/releases/latest/download/geosite.dat

# RUNET Freedom
wget https://raw.githubusercontent.com/runetfreedom/russia-v2ray-rules-dat/release/geosite.dat

# Nidelon
wget https://github.com/Nidelon/ru-block-v2ray-rules/releases/latest/download/geosite.dat

Place the file in /etc/b4/geosite.dat and configure categories:

sudo b4 --geosite /etc/b4/geosite.dat --geosite-categories youtube,netflix,facebook

Tip

All these settings can be configured via the web interface.

Building and Development

Development Setup

# Clone repository
git clone https://github.com/daniellavrushin/b4.git
cd b4

# Install dependencies
cd ui && pnpm install

# Build and run
make build
sudo ./out/b4 --verbose debug

Build Requirements

• Go 1.25 or later
• Node.js 22+ and pnpm (for web UI)
• Make

Build Commands

First, build the UI (as the binary will require to have some assets in place before building it)

cd src/http/ui
pnpm install
pnpm build

Now, you can build the binary

# Build for current platform
make build

# Build for all platforms
make build-all

# Build for specific platform
make amd64
make arm64
make armv7

# Clean build artifacts
make clean

Contributing

Contributions are accepted through GitHub pull requests.

Credits

This project incorporates research and techniques from:

• youtubeUnblock - C-based DPI bypass
• GoodbyeDPI - Windows DPI circumvention
• zapret - Advanced DPI bypass techniques

License

This project is provided for educational purposes. Users are responsible for compliance with applicable laws and regulations. The authors are not responsible for misuse of this software.