DNS Host Mapper VPN (Android)

DNS Host Mapper VPN is an Android app that acts like a mobile hosts file by intercepting DNS queries through a local VpnService.

It lets you:

• map custom domains to IPv4 addresses (for example hasan.local -> 192.168.6.5)
• use custom upstream DNS servers (for example 217.218.155.155)
• answer local mapped domains directly
• forward non-mapped domains to upstream DNS with fallback behavior
• announce .local entries over mDNS on the LAN

Why this app exists

Android does not provide a system-wide editable hosts file for normal apps.
This project provides a user-space alternative by:

1. creating a local VPN tunnel
2. capturing DNS packets sent by apps
3. responding locally for mapped domains
4. forwarding other domains to configured upstream resolvers

Key Features

• Add/Edit/Delete domain to IPv4 rules
• Rule persistence via SharedPreferences
• Custom DNS server management
• mDNS support for .local domains
• DNS response cache with TTL-aware behavior
• Upstream resolver cooldown/fallback logic
• Verbose DNS trace logging (DNS_HOST_MAP_TRACE)

Project Structure

• app/src/main/java/com/example/etc/MainActivity.kt : Main UI, rule/DNS management, VPN start/stop/state sync.
• app/src/main/java/com/example/etc/data/HostRuleStore.kt : Stores rules, custom DNS servers, and VPN running state.
• app/src/main/java/com/example/etc/vpn/HostsVpnService.kt : Core VPN tunnel loop and DNS packet handling.
• app/src/main/java/com/example/etc/vpn/UpstreamDnsResolver.kt : Upstream DNS querying, candidate selection, cooldown, caching.
• app/src/main/java/com/example/etc/vpn/MdnsLocalResponder.kt : mDNS listener/announcer for .local entries.
• app/src/main/java/com/example/etc/vpn/DnsPacketCodec.kt : DNS parse/build helpers (A/AAAA/PTR/HTTPS/etc).

Build

./gradlew :app:assembleDebug

Run

1. Install and open app.
2. Add mapping (example): : Domain: hasan.local : IPv4: 192.168.6.5
3. Optionally add custom DNS server: : 217.218.155.155
4. Tap START VPN.
5. Test from network tools/browser: : hasan.local, zarebin.ir, soft98.ir

Screenshots

Troubleshooting

• Ensure Android Private DNS is disabled if interception is bypassed.
• Keep VPN running while testing mapped domains.
• Check logcat tag: DNS_HOST_MAP_TRACE.
• If mapped .local fails on some clients, verify mDNS traffic on LAN and that multicast is available.

License

No license file is currently included in this repository.