Detect new network devices connecting to OpenWrt and send text message

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:

• https://wiki.openwrt.org/doc/howto/smtp.client
• https://fixmynix.com/send-mail-command-line-linux-openwrt/
• http://lifehacker.com/5506326/how-can-i-send-an-email-via-text-message

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.

“$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：

1. 当信号不是处处完美时，会出现大量的连接和断开
2. 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