Four Handy Open‑Source Tools That Solve Real‑World Pain Points

Rethink: Android firewall with DNS encryption

Project URL: https://github.com/celzero/rethink-app (⭐ 4.9k). Rethink combines an app‑level firewall, DNS over HTTPS, DNS over Tor, DNSCrypt, WireGuard proxy, and live connection tracking in a single Android app that works without root.

App‑level firewall: control per‑app network access and choose Wi‑Fi or cellular.

DNS over HTTPS / DNS over Tor: encrypt DNS queries.

DNSCrypt support: transmit DNS requests via an encrypted protocol.

WireGuard proxy: forward traffic through a WireGuard tunnel.

Live connection tracking: display which app connects to which IP, protocol, and port.

Install from Google Play or F‑Droid by searching “Rethink DNS”.

Pinta: Lightweight cross‑platform drawing software

Project URL: https://github.com/PintaProject/Pinta (⭐ 3.7k). Pinta is a GTK‑based drawing and image‑editing tool inspired by Paint.NET, running on Linux, macOS, and Windows.

Basic drawing tools: brush, shape, fill, text, selection.

Layer support: add, delete, merge layers; adjust order and opacity.

35+ filters and adjustments: blur, distortion, sharpen, curves, hue/saturation, etc.

Unlimited undo/redo.

Tile windows: multiple documents can be tiled for side‑by‑side comparison.

Installation commands:

# macOS
brew install --cask pinta
# Ubuntu/Debian
sudo snap install pinta
# Windows / other platforms
# Download from https://www.pinta-project.com/

Gecit: DPI‑bypass tool

Project URL: https://github.com/boratanrikulu/gecit (⭐ 315). Gecit modifies TCP handshake packets before they reach deep‑packet inspection devices, allowing traffic to evade DPI.

Linux: uses eBPF at the socket layer to alter MSS and other TCP parameters.

macOS/Windows: employs a TUN virtual network interface to intercept and modify traffic.

Operates without proxies, VPNs, or configuration files; only raw TCP features are changed.

Usage example:

# Linux (requires root)
sudo gecit run
# macOS/Windows
gecit run

Boss Agent CLI: AI‑powered job‑search assistant for BOSS Direct Hiring

Project URL: https://github.com/can4hou6joeng4/boss-agent-cli (⭐ 892). The CLI integrates with BOSS 直聘, using an AI agent to automate job search, resume submission, and recruiter communication.

Automatic job search: set keywords, city, salary range, and fetch matching positions.

Benefit filtering: select jobs with weekends off, five‑social‑insurance, no overtime.

Recruiter communication: auto‑greet HR, send resumes, schedule interviews.

Resume optimization: AI refines resume content for each target role.

MCP protocol support: provides a Model Context Protocol interface for custom AI workflows.

Simple usage example:

# Search Python developer jobs, salary >20k, weekends off
boss-agent search --query "Python 开发" --salary 20k
# Auto‑apply resumes
boss-agent apply --auto
# Start MCP service mode
boss-agent mcp

⚠️ Requires a BOSS 直聘 account; the tool uses Playwright to simulate a browser, which may trigger anti‑scraping defenses.