Send IP to Telegram using Bot API as soon as internet connection established & make SSH tunnel

99-send-ip-to-telegram

#!/bin/sh

case "$reason" in
  BOUND|RENEW|STATIC)
    /usr/local/bin/send_ip_telegram.sh &
    ;;
esac

README.md

Files

send_ip_telegram.service => /etc/systemd/system/send_ip_telegram.service

send_ip_telegram.sh => /usr/local/bin/send_ip_telegram.sh

99-send-ip-to-telegram => /lib/dhcpcd/dhcpcd-hooks/99-send-ip-to-telegram

autossh-tunnel.service => /etc/systemd/system/autossh-tunnel.service

Configure server

sudo adduser --disabled-password --gecos "" tunneluser
sudo usermod -s /usr/sbin/nologin tunneluser
sudo mkdir /home/tunneluser/.ssh
sudo chown tunneluser:tunneluser /home/tunneluser/.ssh
sudo chmod 700 /home/tunneluser/.ssh
sudo chown tunneluser:tunneluser /home/tunneluser/.ssh/authorized_keys
sudo chmod 600 /home/tunneluser/.ssh/authorized_keys
sudo ufw allow 2222/tcp

/etc/ssh/sshd_config:

...
GatewayPorts yes
AllowTcpForwarding yes
...
...
Match User tunneluser
    ForceCommand /usr/bin/echo 'This account is restricted to port forwarding only.'
    AllowTcpForwarding yes

sudo systemctl restart sshd

Connect

[Optional; cause service used] From source (tunnel issuer) - Initiate tunnel:

autossh -N -R 2222:localhost:22 tunneluser@<hostname> -I <identityfile>

From user (not from server and tunnel issuer):

ssh sourceuser@<hostname> -I <identityfile> -p 2222

autossh-tunnel.service

[Unit]
Description=AutoSSH Tunnel Service
After=network-online.target
Wants=network-online.target

[Service]
User=pi
Environment="AUTOSSH_GATETIME=0"
ExecStart=/usr/bin/autossh -N -R 2222:localhost:22 tunneluser@<hostname> -I <identityfile>
Restart=always

[Install]
WantedBy=multi-user.target

send_ip_telegram.service

[Unit]
Description=Send IP to Telegram when internet is available
After=network-online.target
Wants=network-online.target

[Service]
Type=simple
ExecStart=/usr/local/bin/send_ip_telegram.sh
Restart=on-failure

[Install]
WantedBy=multi-user.target

send_ip_telegram.sh

#!/bin/bash

until curl -s --fail --head https://www.google.com -o /dev/null; do
    echo "Waiting for internet connection..."
    sleep 5
done

LAST_IP_FILE="/tmp/last_ip.txt"
CURRENT_TIME=$(date +%s)
THROTTLE_TIME=600  # 10 minutes

IP=$(hostname -I | awk '{print $1}')

if [ -f "$LAST_IP_FILE" ]; then
    read LAST_IP LAST_TIME < "$LAST_IP_FILE"
    if [ "$IP" = "$LAST_IP" ]; then
        ELAPSED=$(( CURRENT_TIME - LAST_TIME ))
        if [ $ELAPSED -lt $THROTTLE_TIME ]; then
            echo "IP unchanged and only $ELAPSED seconds since last notification. No message sent."
            exit 0
        fi
    fi
fi

BOT_TOKEN="..."
CHAT_ID="..."

MESSAGE="Device Local IP: $IP"

curl -s -X POST "https://api.telegram.org/bot${BOT_TOKEN}/sendMessage" \
     -d chat_id="${CHAT_ID}" \
     -d text="${MESSAGE}"

echo "Message sent: ${MESSAGE}"

echo "$IP $CURRENT_TIME" > "$LAST_IP_FILE"