feat: initial release - mDNS publisher and resolver for Termux

- mdns-publish.py: publishes movil.local:8022 via Zeroconf
- mdns-resolve: raw UDP mDNS resolver (RFC 6762)
- ssh-mdns-proxy: SSH ProxyCommand with mDNS/Tailscale/cache fallback
- install.sh: automated installer with boot integration

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

.gitignore

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+__pycache__/
+*.pyc

README.md

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+# termux-mdns
+
+mDNS publisher and resolver for Termux (Android).
+
+Publishes `movil.local` on the local network via Zeroconf so other machines can find the phone by hostname instead of dynamic DHCP IPs.
+
+## Components
+
+| Script | Purpose |
+|--------|---------|
+| `mdns-publish.py` | Publishes `movil.local:8022` as an SSH service via mDNS/Zeroconf |
+| `mdns-resolve` | Resolves `.local` hostnames via raw UDP multicast (RFC 6762) |
+| `ssh-mdns-proxy` | SSH ProxyCommand with mDNS → Tailscale → cache fallback chain |
+
+## Install
+
+```bash
+pkg install python
+pip install zeroconf
+./install.sh
+```
+
+## Usage
+
+From any machine on the LAN:
+```bash
+ssh -p 8022 movil.local
+```
+
+From the phone to other machines:
+```bash
+ssh dell   # resolves via mdns-resolve → ssh-mdns-proxy
+```
+
+## Boot
+
+The installer adds `mdns-publish.py` to `~/.termux/boot/start-services` so it starts automatically when Termux boots.
+
+## License
+
+MIT

install.sh

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+#!/data/data/com.termux/files/usr/bin/bash
+set -e
+
+BIN="$HOME/.local/bin"
+BOOT="$HOME/.termux/boot/start-services"
+
+mkdir -p "$BIN"
+
+cp mdns-publish.py mdns-resolve ssh-mdns-proxy "$BIN/"
+chmod +x "$BIN/mdns-publish.py" "$BIN/mdns-resolve" "$BIN/ssh-mdns-proxy"
+
+# Add to boot if not already there
+if ! grep -q "mdns-publish" "$BOOT" 2>/dev/null; then
+    sed -i "/^sshd$/a \\\n# Iniciar mDNS (publica movil.local)\nnohup python ~/.local/bin/mdns-publish.py > /dev/null 2>&1 &" "$BOOT"
+    echo "Added mdns-publish to boot script"
+fi
+
+# Start if not running
+if ! pgrep -f mdns-publish.py > /dev/null; then
+    nohup python "$BIN/mdns-publish.py" > /dev/null 2>&1 &
+    echo "mdns-publish started (PID: $!)"
+else
+    echo "mdns-publish already running"
+fi
+
+echo "Install complete"

mdns-publish.py

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+#!/data/data/com.termux/files/usr/bin/python
+"""Publica el servicio SSH como movil.local via mDNS/Zeroconf"""
+import socket
+import signal
+import sys
+from zeroconf import ServiceInfo, Zeroconf, IPVersion
+
+def get_local_ip():
+    """Obtiene la IP local del dispositivo"""
+    try:
+        s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
+        s.connect(('8.8.8.8', 80))
+        ip = s.getsockname()[0]
+        s.close()
+        return ip
+    except:
+        return '127.0.0.1'
+
+def main():
+    hostname = 'movil'
+    port = 8022
+    ip = get_local_ip()
+    
+    zc = Zeroconf(ip_version=IPVersion.V4Only)
+    
+    # Registrar servicio SSH
+    info = ServiceInfo(
+        '_ssh._tcp.local.',
+        f'{hostname}._ssh._tcp.local.',
+        addresses=[socket.inet_aton(ip)],
+        port=port,
+        properties={'description': 'Termux SSH'},
+        server=f'{hostname}.local.',
+    )
+    
+    print(f'Publicando {hostname}.local -> {ip}:{port}')
+    zc.register_service(info)
+    
+    def signal_handler(sig, frame):
+        print('Deteniendo mDNS...')
+        zc.unregister_service(info)
+        zc.close()
+        sys.exit(0)
+    
+    signal.signal(signal.SIGINT, signal_handler)
+    signal.signal(signal.SIGTERM, signal_handler)
+    
+    # Mantener corriendo
+    try:
+        signal.pause()
+    except:
+        while True:
+            import time
+            time.sleep(3600)
+
+if __name__ == '__main__':
+    main()

mdns-resolve

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+#!/data/data/com.termux/files/usr/bin/python3
+"""
+Resuelve hostname.local via mDNS multicast.
+Uso: mdns-resolve <hostname.local>
+Retorna: IP address o exit 1
+"""
+import sys
+import socket
+import struct
+import select
+
+def build_mdns_query(hostname: str) -> bytes:
+    """Construye query DNS para hostname."""
+    # Header: ID=0, Flags=0, QDCOUNT=1, ANCOUNT=0, NSCOUNT=0, ARCOUNT=0
+    header = struct.pack('>HHHHHH', 0, 0, 1, 0, 0, 0)
+
+    # Question section
+    question = b''
+    for part in hostname.rstrip('.').split('.'):
+        question += bytes([len(part)]) + part.encode()
+    question += b'\x00'  # End of name
+    question += struct.pack('>HH', 1, 1)  # Type A, Class IN
+
+    return header + question
+
+def parse_mdns_response(data: bytes, hostname: str) -> str | None:
+    """Parsea respuesta mDNS y extrae IP."""
+    if len(data) < 12:
+        return None
+
+    # Skip header, find answers
+    qdcount = struct.unpack('>H', data[4:6])[0]
+    ancount = struct.unpack('>H', data[6:8])[0]
+
+    if ancount == 0:
+        return None
+
+    # Skip questions
+    offset = 12
+    for _ in range(qdcount):
+        while offset < len(data) and data[offset] != 0:
+            if data[offset] & 0xc0 == 0xc0:  # Compression
+                offset += 2
+                break
+            offset += data[offset] + 1
+        else:
+            offset += 1
+        offset += 4  # Type + Class
+
+    # Parse answers
+    for _ in range(ancount):
+        # Skip name (handle compression)
+        while offset < len(data):
+            if data[offset] & 0xc0 == 0xc0:
+                offset += 2
+                break
+            elif data[offset] == 0:
+                offset += 1
+                break
+            else:
+                offset += data[offset] + 1
+
+        if offset + 10 > len(data):
+            break
+
+        rtype, rclass, ttl, rdlength = struct.unpack('>HHIH', data[offset:offset+10])
+        offset += 10
+
+        # Type A (1) = IPv4 address
+        if rtype == 1 and rdlength == 4 and offset + 4 <= len(data):
+            ip = socket.inet_ntoa(data[offset:offset+4])
+            return ip
+
+        offset += rdlength
+
+    return None
+
+def resolve_mdns(hostname: str, timeout: float = 2.0) -> str | None:
+    """Resuelve hostname via mDNS multicast."""
+    if not hostname.endswith('.local'):
+        hostname += '.local'
+
+    MDNS_ADDR = '224.0.0.251'
+    MDNS_PORT = 5353
+
+    try:
+        sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
+        sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
+        sock.setblocking(False)
+
+        # Enviar query
+        query = build_mdns_query(hostname)
+        sock.sendto(query, (MDNS_ADDR, MDNS_PORT))
+
+        # Esperar respuesta
+        end_time = __import__('time').time() + timeout
+        while __import__('time').time() < end_time:
+            ready, _, _ = select.select([sock], [], [], 0.1)
+            if ready:
+                try:
+                    data, addr = sock.recvfrom(4096)
+                    ip = parse_mdns_response(data, hostname)
+                    if ip:
+                        sock.close()
+                        return ip
+                except:
+                    pass
+
+        sock.close()
+    except Exception as e:
+        pass
+
+    return None
+
+def main():
+    if len(sys.argv) < 2:
+        print("Uso: mdns-resolve <hostname.local>", file=sys.stderr)
+        sys.exit(1)
+
+    hostname = sys.argv[1]
+    timeout = float(sys.argv[2]) if len(sys.argv) > 2 else 2.0
+
+    ip = resolve_mdns(hostname, timeout)
+    if ip:
+        print(ip)
+        sys.exit(0)
+    else:
+        sys.exit(1)
+
+if __name__ == "__main__":
+    main()

ssh-mdns-proxy

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+#\!/data/data/com.termux/files/usr/bin/bash
+# ssh-mdns-proxy: Resolve .local via mDNS with fallbacks, then connect
+HOST="$1"
+PORT="${2:-22}"
+CACHE="$HOME/.ssh/mdns-cache"
+QUERY="${HOST%.local}"
+
+# Alias mapping (short name → mDNS hostname)
+declare -A ALIASES=(
+    [dell]="dell-latitude3400"
+    [lenovo]="lenovo-ideapad"
+)
+[[ -n "${ALIASES[$QUERY]}" ]] && QUERY="${ALIASES[$QUERY]}"
+
+# 1. mDNS resolution
+IP=$("$HOME/.local/bin/mdns-resolve" "${QUERY}.local" 2 2>/dev/null)
+
+# 2. Fallback: Tailscale DNS
+if [[ -z "$IP" ]]; then
+    IP=$(getent hosts "${QUERY}.tailb0bb74.ts.net" 2>/dev/null | awk "{print \$1}")
+fi
+
+# 3. Fallback: cached IP
+if [[ -z "$IP" && -f "$CACHE" ]]; then
+    IP=$(grep "^${QUERY} " "$CACHE" 2>/dev/null | awk "{print \$2}")
+fi
+
+if [[ -z "$IP" ]]; then
+    echo "Error: cannot resolve ${HOST}" >&2
+    exit 1
+fi
+
+# Save to cache
+mkdir -p "$(dirname "$CACHE")"
+grep -v "^${QUERY} " "$CACHE" > "${CACHE}.tmp" 2>/dev/null || true
+echo "${QUERY} ${IP}" >> "${CACHE}.tmp"
+mv "${CACHE}.tmp" "$CACHE"
+
+exec nc "$IP" "$PORT"