DnsFilter

A fast local DNS filtering proxy for Android. Intercepts DNS queries via Android's VpnService, blocks ads and tracking domains using customizable blocklists, and forwards to multiple upstream servers concurrently for the fastest response.

Version: 1.8.0 | Package: com.deatrg.dnsfilter | minSdk: 29 (Android 10+)

Features

• Local VPN-based DNS Proxy — Routes only DNS traffic into the app via split-tunnel VPN, all other traffic goes through normally
• Domain Blocking — Filters against AdAway-format blocklists. Supports multiple lists, add/remove/toggle, and manual refresh
• Concurrent Multi-Server Queries — Sends DNS queries to all enabled upstream servers simultaneously, uses the fastest successful response
• DNS Response Caching — 16,384-entry LRU cache with bounded TTL (30s–60min), stale-while-revalidate, and popular-domain prefetch
• In-flight Query Deduplication — Concurrent requests for the same domain share a single upstream query
• UDP Socket Pooling — Reusable socket pool per upstream server (4 per server) reduces connection overhead
• Statistics — In-memory query counter with batched persistence (every 5s), live display (total, blocked, block rate, avg response time)
• Dashboard — Protection status, start/stop toggle, statistics grid
• DNS Server Management — Configure multiple upstream servers with enable/disable toggle
• Foreground Service — Runs as a foreground service with notification and stop action
• Low Overhead — Packet buffer recycling, lock-free cache, minimal allocations in hot path

Screens

• Dashboard — Status card with protection state, start/stop, 2×2 statistics (total queries, blocked, block rate, avg response)
• DNS Servers — Manage upstream plain DNS servers (add, enable/disable, delete, reset to defaults)
• Filters — Manage blocklists (add, enable/disable, delete, refresh, view last update time)

Build

./gradlew assembleRelease

APKs are output to app/build/outputs/apk/release/. The build generates split APKs per ABI (armeabi-v7a, arm64-v8a, x86, x86_64) plus a universal APK.

Debug Build

./gradlew assembleDebug

Tech Stack

Layer	Technology
Language	Kotlin 2.2
UI	Jetpack Compose + Material 3 + Navigation Compose
Architecture	MVVM with manual DI (ServiceLocator)
Async	Kotlin Coroutines + Flow
Networking	OkHttp (blocklist downloads), DatagramSocket (DNS queries)
Persistence	DataStore Preferences (settings, statistics), file cache (blocklists, 24h expiry)
Background	Foreground Service + AlarmManager (blocklist updates)
Build	Gradle 9.3 + AGP 9.2 + Kotlin DSL

Architecture

VPN Interface (split-tunnel, DNS only)
       │
       ▼
DnsVpnService — reads IP packets, parses IPv4/IPv6/UDP/DNS
       │
       ├─── DomainFilter — O(1) HashSet blocklist lookup
       ├─── DnsQueryExecutor — LRU cache → concurrent upstream queries
       └─── StatisticsBuffer — in-memory counter, batched DataStore writes

How It Works

1. Creates a local VPN interface routing only traffic to virtual DNS addresses (10.10.10.10, fd00::10)
2. Reads raw IP/UDP packets from the VPN interface
3. Parses the DNS question from each packet
4. Checks against loaded blocklists — blocked domains get an immediate NXDOMAIN response
5. Checks the local LRU cache — fresh entries skip the upstream query entirely
6. Forwards to all enabled upstream DNS servers concurrently via plain UDP
7. Returns the fastest successful response, caches it, patches back into the original packet

License

Apache 2.0