mdns-termux

mDNS + Tailscale hostname resolution for Termux (Android).

Termux runs on Android's Bionic libc, which does not resolve .local names and lacks getent. This repo ships small, dependency-light helpers that fix that — without root, and without a custom system resolver.

Works on any network: LAN via multicast, off-LAN via Tailscale MagicDNS.

---

What's in here

Script	Role
mdns-resolve	Resolve <host>.local via raw multicast UDP (pure Python, stdlib only).
mdns-publish.py	Publish this device on the LAN as movil.local using zeroconf.
ssh-mdns-proxy	SSH ProxyCommand: mDNS → Tailscale DNS → cached IP.
ssh-fallback	SSH ProxyCommand: Tailscale → LAN, for flaky Tailscale.
resolve	Generic resolver for any command (ping, curl, kubectl, nc…). Same order.

Install

git clone https://devops.ingeniumcodex.com/andresgarcia0313/mdns-termux.git
cd mdns-termux
bash install.sh          # or --dry-run first

Then follow the printed reminders (append bashrc.snippet, set your TAILSCALE_DOMAIN, optionally merge ssh_config.example).

Usage

Generic resolver — works in any command

resolve lenovo                       # -> 100.69.236.16
ping   $(resolve hp62a)
curl   "http://$(resolve dell):8080"
kubectl --server="https://$(resolve master):6443" get nodes

Environment knobs:

• TAILSCALE_DOMAIN — defaults to tailb0bb74.ts.net. Set to your own tailnet.
• MDNS_TIMEOUT — seconds waiting for multicast (default 1, keeps off-LAN snappy).

Shell helpers (from config/bashrc.snippet)

alias r='resolve'
pingr <host>              # ping -c 3 to resolved IP
curlr <host> [flags]      # curl http://<resolved-ip>
sshr  <host> [cmd...]     # ssh via resolved IP with correct HostKeyAlias

SSH by hostname (via ProxyCommand)

Drop config/ssh_config.example into ~/.ssh/config. Then:

ssh lenovo                # resolves via mDNS then Tailscale, connects
ssh lenovo.local          # forces mDNS-first path

Publishing this device as movil.local

python ~/.local/bin/mdns-publish.py                                # foreground
nohup python ~/.local/bin/mdns-publish.py >>~/.cache/mdns.log 2>&1 & disown

Behavior by network

Scenario	Path	Typical latency
On home LAN	mDNS multicast (1 s cap) → else Tailscale	< 100 ms
Mobile data / away	mDNS fails → Tailscale MagicDNS	< 200 ms
No Tailscale	Both fail → cached last-known IP	instant

Gotchas found the hard way

• getent doesn't exist on Termux. Scripts that shell out to it silently fail. This repo uses python -c "import socket; socket.gethostbyname(...)" as the portable fallback on Bionic.
• Shebang matters. #!/data/data/com.termux/files/usr/bin/bash is required for declare -A. A stray backslash (#\!) makes the kernel fall through to sh, which rejects bash-only syntax with Syntax error: "(" unexpected.
• mDNS off-LAN is a no-op. Multicast (224.0.0.251) does not cross networks. Over mobile data, only Tailscale resolves.
• zeroconf is not pkg-managed. After restoring Termux from a tar backup, re-run pip install zeroconf or mdns-publish.py will silently die with ModuleNotFoundError.
• Silent failures are the enemy. The .bashrc snippet deliberately logs to ~/.cache/mdns.log instead of /dev/null. Keep it that way.

Tailscale on Termux

Tailscale runs as the Android app, not as a Termux CLI — tailscale up inside a shell won't work. The app provides MagicDNS for *.<your-tailnet>.ts.net, which Bionic-libc resolves fine (it's just a regular DNS lookup).

Related

• claude-code-termux — Claude Code CLI setup for Termux. Uses this repo for SSH/host resolution.

License

MIT — see LICENSE.