jwalanta/OpenWrt detect new device and send text message.md

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Detect new network devices connecting to OpenWrt and send text message

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OpenWrt detect new device and send text message.md

Add the following line in `/etc/dnsmasq.conf`

dhcp-script=/etc/detect_new_device.sh

Setup sendmail to send email to your text number.

Reference:

Create `/etc/detect_new_device.sh` with the following content

#!/bin/sh

# script to detect new dhcp lease

# this will be called by dnsmasq everytime a new device is connected
# with the following arguments
# $1 = add | old
# $2 = mac address
# $3 = ip address
# $4 = device name

notification_email="[email protected]"

if [ "$1" == "add" ]; then
  msg="New device on `uci get system.@system[0].hostname`.`uci get dhcp.@dnsmasq[0].domain` $*"
  echo `date` $msg >> /tmp/dhcpmasq.log

  # encode colon (:) and send email
  echo $msg | sed s/:/-/g | sendmail "$notification_email"
fi

Alternative script using whitelist

This script only sends alerts if the mac address is not in the list

#!/bin/sh

# script to detect new dhcp lease

# this will be called by dnsmasq everytime a new device is connected
# with the following arguments
# $1 = add | old
# $2 = mac address
# $3 = ip address
# $4 = device name

known_mac_addr="/etc/known_mac_addr"
notification_email="[email protected]"

# check if the mac is in known devices list
grep -q "$2" "$known_mac_addr"
unknown_mac_addr=$?

if [ "$1" == "add" ] && [ "$unknown_mac_addr" -ne 0 ]; then
  msg="New device on `uci get system.@system[0].hostname`.`uci get dhcp.@dnsmasq[0].domain` $*"
  echo `date` $msg >> /tmp/dhcpmasq.log

  # encode colon (:) and send email
  echo $msg | sed s/:/-/g | sendmail "$notification_email"
fi

When a new device is added, dnsmasq calls detect_new_device.sh with arguments add mac_addr ip_addr devicename. The script checks if the device is new (if the dhcp lease hasn't expired, it calls with old), then logs and emails (which eventually is a text message) the information.

alixyz commented May 10, 2023

@EnlightedBitFox, also confirming you did update the following:

The mailsend commands with your credentials.

notification_email="[email protected]"

lan="192.168.x." #Update subnets for the lan, guest, iot

guest="192.168.y."

iot="192.168.z."

Yes is did. I changed the ips matching mine. I doesnt have a subnet for guest and iot

Can you try removing the # in front of the following line ~11. So that it starts with echo. #echo $ACTION $MACADDR $IPADDR $HOSTNAME >>/tmp/detect
After doing so, connect a device with a new MAC address and see if you get anything in the /tmp/detect file.

About the subnets: Do i have to enter the subnet-ID or just the 3. octet?

Just the 3, since you're looking for a text pattern.

Uncommenting the lined mentioned earlier by removing the #, will post an entry in the /tmp/detect file upon the script being run, that will rule out any potential filtering issues.

Additionally, did you also follow the steps from the 1st post from the original author. Those steps are required to call this script.

EnlightedBitFox commented May 11, 2023

Hello,
I checked the system log and I found the following:
Thu May 11 06:26:22 2023 daemon.err dnsmasq[1]: failed to execute /etc/detect_new_device.sh: No such file or directory.
TBH i dont understand why. I placed the detect_new_device.sh script in /etc/

alixyz commented May 11, 2023

I checked mine and at some point I moved it to the following location and changed the name:
/etc/hotplug.d/dhcp/00-detect_new_device.sh

Don't recall why, but must have been due to an issue that came up, possibility with v22.xx.x

Also change the file permissions to make it executable using:
chmod +x /etc/hotplug.d/dhcp/00-detect_new_device.sh

EnlightedBitFox commented May 11, 2023

Ahh ok will try it out.
You changed it, because on the ujail permissions.
What about the dnsmasq.conf? I assume, the only thing to do is adjusting the path

alixyz commented May 11, 2023

Yes, its coming back to me :)

Actually the dnsmasq.conf file no longer has the entry, I have it commented out.

EnlightedBitFox commented May 11, 2023

Awesome!
Now it works 😁
Thank you ✌️

Green-m commented May 17, 2023

I upgrade my openwrt to 23, the dhcp script breaks. I figure it out and finally make it works again. Share my procedure to help others.

This is my dhcp script:

#!/bin/sh

# script to detect new dhcp lease

# this will be called by dnsmasq everytime a new device is connected
# with the following arguments
# $1 = add | old
# $2 = mac address
# $3 = ip address
# $4 = device name
#echo "$0" "My custom script called with $@"
#echo "$1 $2 $3 $4"
known_mac_addr="/etc/config/dhcp"

send_notification(){
    msg="$1"
    curl "https://<myhookapi>/WLAN_NEW_CLIENT_ALERT! $msg"
}

# check if the mac is in known devices list
/bin/grep -iq "$2" "$known_mac_addr"
unknown_mac_addr=$?

if [ "$ACTION" = add ] && [ "$unknown_mac_addr" -ne 0 ]; then
  msg="New device on $(uci get system.@system[0].hostname).$(uci get dhcp.@dnsmasq[0].domain) MAC=$2, IP=$3, NAME=$4"
  echo "$msg"

  send_notification "$3_$4"

fi

After I add it to config with uci set, the openwrt log shows:

...
grep: /etc/config/dhcp: No such file or directory
...
line 24: /bin/grep: not found

There are much logs like that. So I check the dnsmasq service script, thinking maybe the ujail restrict the command and file access, and the I modify the /etc/init.d/dnsmasq file.

DHCPSCRIPT="/usr/lib/dnsmasq/dhcp-script.sh"
DHCPSCRIPT_DEPENDS="/usr/share/libubox/jshn.sh /usr/bin/jshn /bin/ubus /bin/grep /usr/bin/curl /etc/config/dhcp"

I update the DHCPSCRIPT_DEPENDS to add the command and file needed in dhcp script. After that, everything works, and error log has gone.

It's a little nasty, if someone knows there is a more elegant way to change the DHCPSCRIPT_DEPENDS, please share.

ktomy commented Nov 4, 2023 •

edited

Loading

I extended it a bit to send tmessaged through a telegram bot

My script:

#!/bin/sh

# script to detect new dhcp lease

# this will be called by dnsmasq everytime a new device is connected
# with the following arguments
# $1 = add | old
# $2 = mac address
# $3 = ip address
# $4 = device name

# logger -p local0.info -t dhcp-join-notify "$0: My custom script called with $@"

known_mac_addr="/etc/config/dhcp"


BOT_TOKEN='<INSERT_TOKEN_HERE>'
CHAT_ID='<INSERT_GROUP_CHAT_ID>'


send_notification(){
    msg="$1"
    curl -ks https://api.telegram.org/bot$BOT_TOKEN/sendMessage -d chat_id=$CHAT_ID -d parse_mode=HTML -d text="$msg" >/dev/null
}
# check if the mac is in known devices list
/bin/grep -iq "$2" "$known_mac_addr"
unknown_mac_addr=$?

if [ "$1" = add ] && [ "$unknown_mac_addr" -ne 0 ]; then
  local_msg="New device detected: MAC=$2, IP=$3, NAME=$4"
msg="New device joined the home network:
Hostname: <b>$4</b>
IP Address: <b>$3</b>
MAC Address: <b>$2</b>"
  logger -p local0.info -t dhcp-join-notify "$local_msg"

  send_notification "$msg"

fi

The init script change:
DHCPSCRIPT_DEPENDS="/usr/share/libubox/jshn.sh /usr/bin/jshn /bin/ubus /bin/grep /usr/bin/curl /etc/config/dhcp /usr/bin/logger /sbin/uci /etc/ssl/certs/ca-certificates.crt"

I did not use /etc/hotplug... but installed the script through something like uci set dhcp.@dnsmasq[0].dhcpscript='/root/alert_dhcp_new_device.sh'

hillz2 commented Feb 7, 2024

I extended it a bit to send tmessaged through a telegram bot

My script:

#!/bin/sh

# script to detect new dhcp lease

# this will be called by dnsmasq everytime a new device is connected
# with the following arguments
# $1 = add | old
# $2 = mac address
# $3 = ip address
# $4 = device name

# logger -p local0.info -t dhcp-join-notify "$0: My custom script called with $@"

known_mac_addr="/etc/config/dhcp"


BOT_TOKEN='<INSERT_TOKEN_HERE>'
CHAT_ID='<INSERT_GROUP_CHAT_ID>'


send_notification(){
    msg="$1"
    curl -ks https://api.telegram.org/bot$BOT_TOKEN/sendMessage -d chat_id=$CHAT_ID -d parse_mode=HTML -d text="$msg" >/dev/null
}
# check if the mac is in known devices list
/bin/grep -iq "$2" "$known_mac_addr"
unknown_mac_addr=$?

if [ "$1" = add ] && [ "$unknown_mac_addr" -ne 0 ]; then
  local_msg="New device detected: MAC=$2, IP=$3, NAME=$4"
msg="New device joined the home network:
Hostname: <b>$4</b>
IP Address: <b>$3</b>
MAC Address: <b>$2</b>"
  logger -p local0.info -t dhcp-join-notify "$local_msg"

  send_notification "$msg"

fi

The init script change: DHCPSCRIPT_DEPENDS="/usr/share/libubox/jshn.sh /usr/bin/jshn /bin/ubus /bin/grep /usr/bin/curl /etc/config/dhcp /usr/bin/logger /sbin/uci /etc/ssl/certs/ca-certificates.crt"

I did not use /etc/hotplug... but installed the script through something like uci set dhcp.@dnsmasq[0].dhcpscript='/root/alert_dhcp_new_device.sh'

Do you have a script for when someone is disconnected from your wifi ? I've been trying to figure out how to do that, currently I only have a script that tells me when a new device is connected to wifi but not when it's disconnected

bjalek commented Feb 9, 2024

This is my variation that script (etc\hotplug.d\dhcp\99-detect_new_device_email.sh ).
I have Lan, Guest and IoT.
Router send me an alert when someone connect/disconnect. (lease time run out).
I disabled known/unknown hosts

#!/bin/sh

# script to detect new dhcp lease

# this will be called by dnsmasq everytime a new device is connected with the following arguments
# $1 = $ACTION = add | update
# $2 = $MACADDR = mac address
# $3 = $IPADDR = ip address
# $4 = $HOSTNAME = device name

# this will create log file 
echo "$ACTION     $HOSTNAME     $IPADDR     $MACADDR      `date`">>/tmp/detect.log

known_mac_addr="/etc/config/dhcp"
notification_email="[email protected]"
lan="192.168.2."       #Update subnets for the lan, guest, iot
guest="192.168.4."
iot="192.168.3."

# Convert MAC to uppercase if you want
# mac=$(echo "$MACADDR" | awk '{print toupper($0)}')

# check if the mac is in known devices list
grep -q "$mac" "$known_mac_addr"
unknown_mac_addr=$?

# && [ "$unknown_mac_addr" -ne 1 ]

if [ "$ACTION" == "add" ]; then

  if test "${IPADDR#*$lan}" != "$IPADDR"; then
      ( echo "Subject: $HOSTNAME    Connected"
        echo ""
        echo "NAME:  $HOSTNAME"
        echo ""
        echo "MAC:   $(echo "$MACADDR" | awk '{print toupper($0)}')"
        echo "IP:   $IPADDR" 
        echo ""
        echo "LAN") | sendmail "$notification_email"
  fi

  if test "${IPADDR#*$guest}" != "$IPADDR"; then
      ( echo "Subject: $HOSTNAME    Connected"
        echo ""
        echo "NAME:  $HOSTNAME"
        echo ""
        echo "MAC:   $(echo "$MACADDR" | awk '{print toupper($0)}')"
        echo "IP:   $IPADDR" 
        echo ""
        echo "Guest") | sendmail "$notification_email"
  fi

  if test "${IPADDR#*$iot}" != "$IPADDR"; then
      ( echo "Subject: $HOSTNAME    Connected"
        echo ""
        echo "NAME:  $HOSTNAME"
        echo ""
        echo "MAC:   $(echo "$MACADDR" | awk '{print toupper($0)}')"
        echo "IP:   $IPADDR" 
        echo ""
        echo "IoT") | sendmail "$notification_email"
  fi
fi
if [ "$ACTION" == "remove" ]; then

  if test "${IPADDR#*$lan}" != "$IPADDR"; then
      ( echo "Subject: $HOSTNAME    Disconnected"
        echo ""
        echo "NAME:  $HOSTNAME"
        echo ""
        echo "MAC:   $(echo "$MACADDR" | awk '{print toupper($0)}')"
        echo "IP:   $IPADDR" 
        echo ""
        echo "LAN") | sendmail "$notification_email"
  fi

  if test "${IPADDR#*$guest}" != "$IPADDR"; then
      ( echo "Subject: $HOSTNAME    Disconnected"
        echo ""
        echo "NAME:  $HOSTNAME"
        echo ""
        echo "MAC:   $(echo "$MACADDR" | awk '{print toupper($0)}')"
        echo "IP:   $IPADDR" 
        echo ""
        echo "Guest") | sendmail "$notification_email"
  fi

  if test "${IPADDR#*$iot}" != "$IPADDR"; then
      ( echo "Subject: $HOSTNAME    Disconnected"
        echo ""
        echo "NAME:  $HOSTNAME"
        echo ""
        echo "MAC:   $(echo "$MACADDR" | awk '{print toupper($0)}')"
        echo "IP:   $IPADDR" 
        echo ""
        echo "IoT") | sendmail "$notification_email"
  fi
fi

hillz2 commented Feb 9, 2024

"$ACTION" == "remove"

This action doesn't work when someone's device disconnects from a wifi network, I have a workaround by pinging their device IP every minute and send me a notification when the ping fails but it's not very reliable, sometimes the ping fails when their device is still connected to my wifi

bjalek commented Feb 9, 2024

"$ACTION" == "remove"

This action doesn't work when someone's device disconnects from a wifi network, I have a workaround by pinging their device IP every minute and send me a notification when the ping fails but it's not very reliable, sometimes the ping fails when their device is still connected to my wifi

You have to wait til DHCP lease time run out. Set up lease time shorter. I have 30m (=30 minutes).
Check out log file (/tmp/detect.log).

hillz2 commented Feb 9, 2024

"$ACTION" == "remove"

This action doesn't work when someone's device disconnects from a wifi network, I have a workaround by pinging their device IP every minute and send me a notification when the ping fails but it's not very reliable, sometimes the ping fails when their device is still connected to my wifi

You have to wait til DHCP lease time run out. Set up lease time shorter. I have 30m (=30 minutes). Check out log file (/tmp/detect.log).

Correct me if I'm wrong here, if you set the lease time of 30 minutes doesn't that mean "$ACTION" == "remove" will always be triggered every 30 minutes ? And that doesn't even mean that a device is disconnected from wifi

bjalek commented Feb 9, 2024

"$ACTION" == "remove"

This action doesn't work when someone's device disconnects from a wifi network, I have a workaround by pinging their device IP every minute and send me a notification when the ping fails but it's not very reliable, sometimes the ping fails when their device is still connected to my wifi

You have to wait til DHCP lease time run out. Set up lease time shorter. I have 30m (=30 minutes). Check out log file (/tmp/detect.log).

Correct me if I'm wrong here, if you set the lease time of 30 minutes doesn't that mean "$ACTION" == "remove" will always be triggered every 30 minutes ? And that doesn't even mean that a device is disconnected from wifi

Yes, Every 30 minutes will try DHCP add new lease or Update or remove lease. But you can specify every host own lease time or general lease time reduce to 2m (2 minutes).

I tried to use hostapd, but it was not ideal:

lots of connections and disconections when signal is not perfect everywhere
missing host IP in hostapd

If somebody have better soution please share it.

BackupMann commented Jan 15, 2025

Hello, Firstly thanks for the code sent me on the right path to achieving what I needed!

In regards to the final comment if you use a captive portal such as opennds you can simply place some email sending code in the custombinauth.sh file. Doing the below will allow you to receive a notification on clients authenticating and de-authenticating.

if [ $action = "auth" ]; then
	msg="New device on: `uci get system.@system[0].hostname`.`uci get dhcp.@dnsmasq[0].domain` $*"
	echo `date` $msg >> /tmp/dhcpmasq.log

	# Send email
	(echo "Status: connected"
	echo ""
	echo "MAC: $clientmac"
	echo ""
	echo "IP: $clientip"
	echo ""
	echo "<more details>") | mailsend <details here>
else
	msg="New device on: `uci get system.@system[0].hostname`.`uci get dhcp.@dnsmasq[0].domain` $*"
	echo `date` $msg >> /tmp/dhcpmasq.log

	# Send email
	(echo "Status: disconnected"
	echo ""
	echo "MAC: $clientmac"
	echo ""
	echo "IP: $clientip"
	echo ""
	echo "<more details>") | mailsend <details here>
fi

Hope that helps someone. Cheers.

tty228 commented Mar 31, 2025

“$ACTION”==“删除”

当某人的设备与 wifi 网络断开连接时，此操作不起作用，我有一个解决方法，即每分钟 ping 一次他们的设备 IP，并在 ping 失败时向我发送通知，但这不太可靠，有时当他们的设备仍连接到我的 wifi 时 ping 会失败

您必须等到 DHCP 租约时间用完。请将租约时间设置得短一些。我的租约时间是 30 分钟。请查看日志文件 (/tmp/detect.log)。

如果我错了，请纠正我，如果你设置了 30 分钟的租约时间，那不是意味着"$ACTION" == "remove"每 30 分钟就会触发一次吗？这甚至不意味着设备与 wifi 断开连接

是的，每 30 分钟会尝试 DHCP 添加新租约或更新或删除租约。但您可以指定每个主机自己的租约时间或将一般租约时间缩短至 2m（2 分钟）。

我尝试使用hostapd，但效果并不理想：

当信号不是处处完美时，会出现大量的连接和断开

hostapd 中缺少主机 IP

如果有人有更好的解决方案，请分享。

You might be able to use this plugin: luci-app-wechatpush

jwalanta/OpenWrt detect new device and send text message.md

Add the following line in /etc/dnsmasq.conf

Setup sendmail to send email to your text number.

Create /etc/detect_new_device.sh with the following content

Alternative script using whitelist

alixyz commented May 10, 2023

EnlightedBitFox commented May 11, 2023

alixyz commented May 11, 2023

EnlightedBitFox commented May 11, 2023

alixyz commented May 11, 2023

EnlightedBitFox commented May 11, 2023

Green-m commented May 17, 2023

ktomy commented Nov 4, 2023 • edited Loading

hillz2 commented Feb 7, 2024

bjalek commented Feb 9, 2024

hillz2 commented Feb 9, 2024

bjalek commented Feb 9, 2024

hillz2 commented Feb 9, 2024

bjalek commented Feb 9, 2024

BackupMann commented Jan 15, 2025

tty228 commented Mar 31, 2025

Add the following line in `/etc/dnsmasq.conf`

Create `/etc/detect_new_device.sh` with the following content

ktomy commented Nov 4, 2023 •

edited

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